Science.gov

Sample records for accelerated reference frame

  1. Independent Study Unit on Accelerated Reference Frames

    ERIC Educational Resources Information Center

    Poultney, S. K.

    1973-01-01

    Presents a list of topics, research areas, references, and laboratory equipment which is prepared to facilitate general-science students' understanding of physics aspects in accelerated reference frames after their study of circular motion and Galilean relativity in mechanics. (CC)

  2. Reference Frames and Relativity.

    ERIC Educational Resources Information Center

    Swartz, Clifford

    1989-01-01

    Stresses the importance of a reference frame in mechanics. Shows the Galilean transformation in terms of relativity theory. Discusses accelerated reference frames and noninertial reference frames. Provides examples of reference frames with diagrams. (YP)

  3. Quantum mechanics in noninertial reference frames: Relativistic accelerations and fictitious forces

    NASA Astrophysics Data System (ADS)

    Klink, W. H.; Wickramasekara, S.

    2016-06-01

    One-particle systems in relativistically accelerating reference frames can be associated with a class of unitary representations of the group of arbitrary coordinate transformations, an extension of the Wigner-Bargmann definition of particles as the physical realization of unitary irreducible representations of the Poincaré group. Representations of the group of arbitrary coordinate transformations become necessary to define unitary operators implementing relativistic acceleration transformations in quantum theory because, unlike in the Galilean case, the relativistic acceleration transformations do not themselves form a group. The momentum operators that follow from these representations show how the fictitious forces in noninertial reference frames are generated in quantum theory.

  4. Classical relativistic ideal gas in thermodynamic equilibrium in a uniformly accelerated reference frame

    NASA Astrophysics Data System (ADS)

    Louis-Martinez, Domingo

    2011-04-01

    A classical (non-quantum-mechanical) relativistic ideal gas in thermodynamic equilibrium in a uniformly accelerated frame of reference is studied using Gibbs's microcanonical and grand canonical formulations of statistical mechanics. Using these methods explicit expressions for the particle, energy and entropy density distributions are obtained, which are found to be in agreement with the well known results of the relativistic formulation of Boltzmann's kinetic theory. Explicit expressions for the total entropy, total energy and rest mass of the gas are obtained. The position of the center of mass of the gas in equilibrium is found. The non-relativistic and ultrarelativistic approximations are also considered. The phase space volume of the system is calculated explicitly in the ultrarelativistic approximation.

  5. Classical relativistic ideal gas in thermodynamic equilibrium in a uniformly accelerated reference frame

    NASA Astrophysics Data System (ADS)

    Louis-Martinez, Domingo J.

    2011-02-01

    A classical (non-quantum-mechanical) relativistic ideal gas in thermodynamic equilibrium in a uniformly accelerated frame of reference is studied using Gibbs's microcanonical and grand canonical formulations of statistical mechanics. Using these methods explicit expressions for the particle, energy and entropy density distributions are obtained, which are found to be in agreement with the well-known results of the relativistic formulation of Boltzmann's kinetic theory. Explicit expressions for the total entropy, total energy and rest mass of the gas are obtained. The position of the center of mass of the gas in equilibrium is found. The non-relativistic and ultrarelativistic approximations are also considered. The phase space volume of the system is calculated explicitly in the ultrarelativistic approximation.

  6. Reference frames and reference networks

    NASA Astrophysics Data System (ADS)

    Bosy, Jaroslaw; Krynski, Jan

    2015-12-01

    The summary of research activities concerning reference frames and reference networks performed in Poland in a period of 2011-2014 is presented. It contains the results of research on implementation of IUGG2011 and IAU2012 resolutions on reference systems, implementation of the ETRS89 in Poland, operational work of permanent IGS/ EUREF stations in Poland, operational work of ILRS laser ranging station in Poland, active GNSS station networks in Poland, maintenance of vertical control in Poland, maintenance and modernization of gravity control, and maintenance of magnetic control in Poland. The bibliography of the related works is given in references.

  7. Frames of Reference in the Classroom

    ERIC Educational Resources Information Center

    Grossman, Joshua

    2012-01-01

    The classic film "Frames of Reference" effectively illustrates concepts involved with inertial and non-inertial reference frames. In it, Donald G. Ivey and Patterson Hume use the cameras perspective to allow the viewer to see motion in reference frames translating with a constant velocity, translating while accelerating, and rotating--all with…

  8. Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.

    2013-09-01

    Concepts and Background: This paper gives an overview of modern celestial reference frames as realized at radio frequencies using the Very Long baseline Interferometry (VLBI) technique. We discuss basic celestial reference frame concepts, desired properties, and uses. We review the networks of antennas used for this work. We briefly discuss the history of the science of astrometry touching upon the discovery of precession, proper motion, nutation, and parallax, and the field of radio astronomy. Building Celestial Frames: Next, we discuss the multi-step process of building a celestial frame: First candidate sources are identified based on point-like properties from single dish radio telescopes surveys. Second, positions are refined using connected element interferometers such as the Very Large Array, and the ATCA. Third, positions of approximately milli-arcsecond (mas) accuracy are determined using intercontinental VLBI surveys. Fourth, sub-mas positions are determined by multiyear programs using intercontinental VLBI. These sub-mas sets of positions are then verified by multiple teams in preparation for release to non-specialists in the form of an official IAU International Celestial Reference Frame (ICRF). The process described above has until recently been largely restricted to work at S/X-band (2.3/8.4 GHz). However, in the last decade sub-mas work has expanded to include celestial frames at K-band (24 GHz), Ka-band (32 GHz), and Q-band (43 GHz). While these frames currently have the disadvantage of far smaller data sets, the astrophysical quality of the sources themselves improves at these higher frequencies and thus make these frequencies attractive for realizations of celestial reference frames. Accordingly, we review progress at these higher frequency bands. Path to the Future: We discuss prospects for celestial reference frames over the next decade. We present an example of an error budget for astrometric VLBI and discuss the budget's use as a tool for

  9. Transforming in-situ observations of CME-driven shock accelerated protons into the shock's reference frame.

    NASA Astrophysics Data System (ADS)

    Robinson, I. M.; Simnett, G. M.

    2005-07-01

    We examine the solar energetic particle event following solar activity from 14, 15 April 2001 which includes a "bump-on-the-tail" in the proton energy spectra at 0.99 AU from the Sun. We find this population was generated by a CME-driven shock which arrived at 0.99 AU around midnight 18 April. As such this population represents an excellent opportunity to study in isolation, the effects of proton acceleration by the shock. The peak energy of the bump-on-the-tail evolves to progressively lower energies as the shock approaches the observing spacecraft at the inner Lagrange point. Focusing on the evolution of this peak energy we demonstrate a technique which transforms these in-situ spectral observations into a frame of reference co-moving with the shock whilst making allowance for the effects of pitch angle scattering and focusing. The results of this transform suggest the bump-on-the-tail population was not driven by the 15 April activity but was generated or at least modulated by a CME-driven shock which left the Sun on 14 April. The existence of a bump-on-the-tail population is predicted by models in Rice et al. (2003) and Li et al. (2003) which we compare with observations and the results of our analysis in the context of both the 14 April and 15 April CMEs. We find an origin of the bump-on-the-tail at the 14 April CME-driven shock provides better agreement with these modelled predictions although some discrepancy exists as to the shock's ability to accelerate 100 MeV protons. Keywords. Solar physics, astrophysics and astronomy (Energetic particles; Flares and mass ejections) Space plasma physics (Transport processes)

  10. Ties Between Celestial And Planetary Reference Frames

    NASA Technical Reports Server (NTRS)

    Finger, Mark H.; Folkner, William M.

    1992-01-01

    Report presents new determination of relative orientation (or frame tie) between reference frame of extra-galactic radio sources and reference frame of planetary ephemeris. Method employed for improved frame-tie estimate relies on ability to measure orientation of Earth with respect to inertial reference frame. Improves orbit determination for interplanetary spacecraft.

  11. Astrophysics of Reference Frame Tie Objects

    NASA Technical Reports Server (NTRS)

    Johnston, Kenneth J.; Boboltz, David; Fey, Alan Lee; Gaume, Ralph A.; Zacharias, Norbert

    2004-01-01

    The Astrophysics of Reference Frame Tie Objects Key Science program will investigate the underlying physics of SIM grid objects. Extragalactic objects in the SIM grid will be used to tie the SIM reference frame to the quasi-inertial reference frame defined by extragalactic objects and to remove any residual frame rotation with respect to the extragalactic frame. The current realization of the extragalactic frame is the International Celestial Reference Frame (ICRF). The ICRF is defined by the radio positions of 212 extragalactic objects and is the IAU sanctioned fundamental astronomical reference frame. This key project will advance our knowledge of the physics of the objects which will make up the SIM grid, such as quasars and chromospherically active stars, and relates directly to the stability of the SIM reference frame. The following questions concerning the physics of reference frame tie objects will be investigated.

  12. Frames of Reference in the Classroom

    NASA Astrophysics Data System (ADS)

    Grossman, Joshua

    2012-12-01

    The classic film "Frames of Reference"1,2 effectively illustrates concepts involved with inertial and non-inertial reference frames. In it, Donald G. Ivey and Patterson Hume use the cameras perspective to allow the viewer to see motion in reference frames translating with a constant velocity, translating while accelerating, and rotating—all with respect to the Earth frame. The film is a classic for good reason, but today it does have a couple of drawbacks: 1) The film by nature only accommodates passive learning. It does not give students the opportunity to try any of the experiments themselves. 2) The dated style of the 50-year-old film can distract students from the physics content. I present here a simple setup that can recreate many of the movies demonstrations in the classroom. The demonstrations can be used to supplement the movie or in its place, if desired. All of the materials except perhaps the inexpensive web camera should likely be available already in most teaching laboratories. Unlike previously described activities, these experiments do not require travel to another location3 or an involved setup.4,5

  13. Egocentric and allocentric reference frames for catching a falling object.

    PubMed

    Le Séac'h, Anne Brec'hed; Senot, Patrice; McIntyre, Joseph

    2010-04-01

    When programming movement, one must account for gravitational acceleration. This is particularly important when catching a falling object because the task requires a precise estimate of time-to-contact. Knowledge of gravity's effects is intimately linked to our definition of 'up' and 'down'. Both directions can be described in an allocentric reference frame, based on visual and/or gravitational cues, or in an egocentric reference frame in which the body axis is taken as vertical. To test which frame humans use to predict gravity's effect, we asked participants to intercept virtual balls approaching from above or below with artificially controlled acceleration that could be congruent or not with gravity. To dissociate between these frames, subjects were seated upright (trunk parallel to gravity) or lying down (body axis orthogonal to the gravitational axis). We report data in line with the use of an allocentric reference frame and discuss its relevance depending on available gravity-related cues. PMID:20024651

  14. Spatial Reference Frame of Incidentally Learned Attention

    ERIC Educational Resources Information Center

    Jiang, Yuhong V.; Swallow, Khena M.

    2013-01-01

    Visual attention prioritizes information presented at particular spatial locations. These locations can be defined in reference frames centered on the environment or on the viewer. This study investigates whether incidentally learned attention uses a viewer-centered or environment-centered reference frame. Participants conducted visual search on a…

  15. Newton-Cartan Gravity in Noninertial Reference Frames

    NASA Astrophysics Data System (ADS)

    Rodriguez, Leo; St. Germaine-Fuller, James; Wickramasekara, Sujeev

    2015-03-01

    We study Newton-Cartan gravity under transformations into all noninertial, nonrelativistic reference frames. These transformations form an infinite dimensional Lie group, called the Galilean line group, which contains as a subgroup the Galilei group. The fictitious forces of noninertial reference frames are encoded in the Cartan connection transformed under the Galilean line group. These fictitious forces, which are coordinate effects, do not contribute to the Ricci tensor. Only the 00-component of the Ricci tensor is non-zero and equals (4 π times) the matter density in all reference frames. While the Ricci field equation and Gauss' law are fulfilled by the physical matter density in inertial and linearly accelerating reference frames, in rotating reference frames Gauss' law holds for an effective mass density that differs from the physical matter density. This effective density has its origin in the simulated magnetic field of rotating frames, highlighting a striking difference between linearly and rotationally accelerating frames. The equations governing the simulated fields have the same form as Maxwell's equations, a surprising result given that these equations obey special relativity (and U (1) -gauge symmetry), rather than Galilean symmetry. This work was supported in part by the HHMI Undergraduate Science Education Award 52006298 and the Grinnell College Academic Affairs' CSFS and MAP programs.

  16. Toward a generalized plate motion reference frame

    NASA Astrophysics Data System (ADS)

    Becker, T. W.; Schaeffer, A. J.; Lebedev, S.; Conrad, C. P.

    2015-05-01

    An absolute plate motion (APM) model is required to address issues such as the thermochemical evolution of Earth's mantle. All APM models have to rely on indirect inferences, including those based on hot spots and seismic anisotropy, each with their own set of uncertainties. Here, we explore a seafloor spreading-aligned reference frame. We show that this reference frame fits azimuthal seismic anisotropy in the uppermost mantle very well. The corresponding Euler pole is close to those of hot spot reference frames, ridge motion minimizing models, and geodynamic estimates of net rotation and predicts clear trench motion patterns. We conclude that a net rotation pole guided by the spreading-aligned model (at 64°E, 61°S, with moderate rotation of ˜ 0.2 … 0.3°/Myr) could indeed represent a standard, comprehensive reference frame for present-day plate motions with respect to the deep mantle.

  17. Relativistic Jets in the Radio Reference Frame Image Database. II. Blazar Jet Accelerations from the First 10 Years of Data (1994-2003)

    NASA Astrophysics Data System (ADS)

    Piner, B. G.; Pushkarev, A. B.; Kovalev, Y. Y.; Marvin, C. J.; Arenson, J. G.; Charlot, P.; Fey, A. L.; Collioud, A.; Voitsik, P. A.

    2012-10-01

    We analyze blazar jet apparent speeds and accelerations from the RDV series of astrometric and geodetic very long baseline interferometry (VLBI) experiments. From these experiments, we have produced and analyzed 2753 global VLBI images of 68 sources at 8 GHz with a median beam size of 0.9 milliarcseconds (mas) and a median of 43 epochs per source. From this sample, we analyze the motions of 225 jet components in 66 sources. The distribution of the fastest measured apparent speed in each source has a median of 8.3c and a maximum of 44c. Sources in the 2FGL Fermi LAT catalog display higher apparent speeds than those that have not been detected. On average, components farther from the core in a given source have significantly higher apparent speeds than components closer to the core; for example, for a typical source, components at ~3 mas from the core (~15 pc projected at z ~ 0.5) have apparent speeds about 50% higher than those of components at ~1 mas from the core (~5 pc projected at z ~ 0.5). We measure accelerations of components in orthogonal directions parallel and perpendicular to their average velocity vector. Parallel accelerations have significantly larger magnitudes than perpendicular accelerations, implying that observed accelerations are predominantly due to changes in the Lorentz factor (bulk or pattern) rather than projection effects from jet bending. Positive parallel accelerations are significantly more common than negative ones, so the Lorentz factor (bulk or pattern) tends to increase on the scales observed here. Observed parallel accelerations correspond to modest source frame increases in the bulk or pattern Lorentz factor.

  18. Physics of Non-Inertial Reference Frames

    NASA Astrophysics Data System (ADS)

    Kamalov, Timur F.

    2010-12-01

    Physics of non-inertial reference frames is a generalizing of Newton's laws to any reference frames. It is the system of general axioms for classical and quantum mechanics. The first, Kinematics Principle reads: the kinematic state of a body free of forces conserves and equal in absolute value to an invariant of the observer's reference frame. The second, Dynamics Principle extended Newton's second law to non-inertial reference frames and also contains additional variables there are higher derivatives of coordinates. Dynamics Principle reads: a force induces a change in the kinematic state of the body and is proportional to the rate of its change. It is mean that if the kinematic invariant of the reference frame is n-th derivative with respect the time, then the dynamics of a body being affected by the force F is described by the 2n-th differential equation. The third, Statics Principle reads: the sum of all forces acting a body at rest is equal to zero.

  19. Physics of Non-Inertial Reference Frames

    SciTech Connect

    Kamalov, Timur F.

    2010-12-22

    Physics of non-inertial reference frames is a generalizing of Newton's laws to any reference frames. It is the system of general axioms for classical and quantum mechanics. The first, Kinematics Principle reads: the kinematic state of a body free of forces conserves and equal in absolute value to an invariant of the observer's reference frame. The second, Dynamics Principle extended Newton's second law to non-inertial reference frames and also contains additional variables there are higher derivatives of coordinates. Dynamics Principle reads: a force induces a change in the kinematic state of the body and is proportional to the rate of its change. It is mean that if the kinematic invariant of the reference frame is n-th derivative with respect the time, then the dynamics of a body being affected by the force F is described by the 2n-th differential equation. The third, Statics Principle reads: the sum of all forces acting a body at rest is equal to zero.

  20. Ray Effect Mitigation Through Reference Frame Rotation

    DOE PAGESBeta

    Tencer, John

    2016-06-14

    The discrete ordinates method is a popular and versatile technique for solving the radiative transport equation, a major drawback of which is the presence of ray effects. Mitigation of ray effects can yield significantly more accurate results and enhanced numerical stability for combined mode codes. Moreover, when ray effects are present, the solution is seen to be highly dependent upon the relative orientation of the geometry and the global reference frame. It is an undesirable property. A novel ray effect mitigation technique of averaging the computed solution for various reference frame orientations is proposed.

  1. Multiple reference frames in haptic spatial processing

    NASA Astrophysics Data System (ADS)

    Volčič, R.

    2008-08-01

    The present thesis focused on haptic spatial processing. In particular, our interest was directed to the perception of spatial relations with the main focus on the perception of orientation. To this end, we studied haptic perception in different tasks, either in isolation or in combination with vision. The parallelity task, where participants have to match the orientations of two spatially separated bars, was used in its two-dimensional and three-dimensional versions in Chapter 2 and Chapter 3, respectively. The influence of non-informative vision and visual interference on performance in the parallelity task was studied in Chapter 4. A different task, the mental rotation task, was introduced in a purely haptic study in Chapter 5 and in a visuo-haptic cross-modal study in Chapter 6. The interaction of multiple reference frames and their influence on haptic spatial processing were the common denominators of these studies. In this thesis we approached the problems of which reference frames play the major role in haptic spatial processing and how the relative roles of distinct reference frames change depending on the available information and the constraints imposed by different tasks. We found that the influence of a reference frame centered on the hand was the major cause of the deviations from veridicality observed in both the two-dimensional and three-dimensional studies. The results were described by a weighted average model, in which the hand-centered egocentric reference frame is supposed to have a biasing influence on the allocentric reference frame. Performance in haptic spatial processing has been shown to depend also on sources of information or processing that are not strictly connected to the task at hand. When non-informative vision was provided, a beneficial effect was observed in the haptic performance. This improvement was interpreted as a shift from the egocentric to the allocentric reference frame. Moreover, interfering visual information presented

  2. Celestial Reference Frames at Multiple Radio Wavelengths

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.

    2012-01-01

    In 1997 the IAU adopted the International Celestial Reference Frame (ICRF) built from S/X VLBI data. In response to IAU resolutions encouraging the extension of the ICRF to additional frequency bands, VLBI frames have been made at 24, 32, and 43 gigahertz. Meanwhile, the 8.4 gigahertz work has been greatly improved with the 2009 release of the ICRF-2. This paper discusses the motivations for extending the ICRF to these higher radio bands. Results to date will be summarized including evidence that the high frequency frames are rapidly approaching the accuracy of the 8.4 gigahertz ICRF-2. We discuss current limiting errors and prospects for the future accuracy of radio reference frames. We note that comparison of multiple radio frames is characterizing the frequency dependent systematic noise floor from extended source morphology and core shift. Finally, given Gaia's potential for high accuracy optical astrometry, we have simulated the precision of a radio-optical frame tie to be approximately10-15 microarcseconds ((1-sigma) (1-standard deviation), per component).

  3. Cultural background shapes spatial reference frame proclivity

    PubMed Central

    Goeke, Caspar; Kornpetpanee, Suchada; Köster, Moritz; Fernández-Revelles, Andrés B.; Gramann, Klaus; König, Peter

    2015-01-01

    Spatial navigation is an essential human skill that is influenced by several factors. The present study investigates how gender, age, and cultural background account for differences in reference frame proclivity and performance in a virtual navigation task. Using an online navigation study, we recorded reaction times, error rates (confusion of turning axis), and reference frame proclivity (egocentric vs. allocentric reference frame) of 1823 participants. Reaction times significantly varied with gender and age, but were only marginally influenced by the cultural background of participants. Error rates were in line with these results and exhibited a significant influence of gender and culture, but not age. Participants’ cultural background significantly influenced reference frame selection; the majority of North-Americans preferred an allocentric strategy, while Latin-Americans preferred an egocentric navigation strategy. European and Asian groups were in between these two extremes. Neither the factor of age nor the factor of gender had a direct impact on participants’ navigation strategies. The strong effects of cultural background on navigation strategies without the influence of gender or age underlines the importance of socialized spatial cognitive processes and argues for socio-economic analysis in studies investigating human navigation. PMID:26073656

  4. On Translators' Cultural Frame of Functionist Reference

    ERIC Educational Resources Information Center

    Fu, Zhiyi

    2009-01-01

    A deep cognition with translators' cultural frame of functionist reference can help instructors and teachers adjust and extend patterns and schemes of translation and generate the optimal classroom conditions for acquisition of the target language. The author of the paper, in the perspectives of motivational, cognitive and communicative…

  5. Reference Frames in Earth Rotation Theories

    NASA Astrophysics Data System (ADS)

    Ferrándiz, José M.; Belda, Santiago; Heinkelmann, Robert; Getino, Juan; Schuh, Harald; Escapa, Alberto

    2015-04-01

    Nowadays the determination of the Earth Orientation Parameters (EOP) and the different Terrestrial Reference Frames (TRF) are not independent. The available theories of Earth rotation aims at providing the orientation of a certain reference system linked somehow to the Earth with respect to a given celestial system, considered as inertial. In the past years a considerable effort has been dedicated to the improvement of the TRF realizations, following the lines set up in the 1980's. However, the reference systems used in the derivation of the theories have been rather considered as something fully established, not deserving a special attention. In this contribution we review the definitions of the frames used in the main theoretical approaches, focusing on those used in the construction of IAU2000, and the extent to which their underlying hypotheses hold. The results are useful to determine the level of consistency of the predicted and determined EOP.

  6. Turbulence modeling in non-inertial frames of reference

    NASA Technical Reports Server (NTRS)

    Speziale, Charles G.

    1988-01-01

    The effect of an arbitrary change of frame on the structure of turbulence models is examined from a fundamental theoretical standpoint. It is proven, as a rigorous consequence of the Navier-Stokes equations, that turbulence models must be form invariant under arbitrary translational accelerations of the reference frame and should only be affected by rotations through the intrinsic mean vorticity. A direct application of the invariance property along with the Taylor-Proudman Theorem, material frame-indifference in the limit of two-dimensional turbulence and Rapid Distortion Theory is shown to yield powerful constraints on the allowable form of turbulence models. Most of the commonly used turbulence models are demonstrated to be in serious violation of these constraints and consequently are inconsistent with the Navier-Stokes equations in non-inertial frames. Alternative models with improved non-inertial properties are developed and some simple applications to rotating turbulent flows are considered.

  7. URAT and the celestial reference frame

    NASA Astrophysics Data System (ADS)

    Zacharias, Norbert

    2015-08-01

    The US Naval Observatory Robotic Astrometric Telescope (URAT) survey begun in April 2012 and the Northern Hemisphere program will be completed in 2015. Positions of over 228 million stars in the about R = 3 to 19 mag range were published with the URAT1 catalog release (CDS I/329) and positional accuracy near 10 mas per coordinate for mid-range magnitude objects.URAT directly observes Hipparcos stars as well as counterparts of extragalactic ICRF2 sources. The status of the current celestial reference frame is investigated with URAT data. The accuracy of Hipparcos positions at URAT epoch is analyzed. Radio-optical position differences are investigated for possible astrophysical offsets which would affect the Gaia to radio reference frame alignment accuracy.

  8. GAOUA realizations of the Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Yatskiv, Ya.; Bolotin, S.; Kur'yanova, A.

    2005-09-01

    Short overview of the activity of the Main Astronomical observatory of National Academy of Science of Ukraine for maintenance and extension of the International Celestial Reference Frame (ICRF) is presented. Special attention is paid on the time stabilities of positions of radio sources (RS) and on the selection of a subset of RS to be used for maintenance of the ICRF. It is shown that seven RS qualified by the IERS as defining sources are unstable.

  9. Frames of reference in spatial language acquisition.

    PubMed

    Shusterman, Anna; Li, Peggy

    2016-08-01

    Languages differ in how they encode spatial frames of reference. It is unknown how children acquire the particular frame-of-reference terms in their language (e.g., left/right, north/south). The present paper uses a word-learning paradigm to investigate 4-year-old English-speaking children's acquisition of such terms. In Part I, with five experiments, we contrasted children's acquisition of novel word pairs meaning left-right and north-south to examine their initial hypotheses and the relative ease of learning the meanings of these terms. Children interpreted ambiguous spatial terms as having environment-based meanings akin to north and south, and they readily learned and generalized north-south meanings. These studies provide the first direct evidence that children invoke geocentric representations in spatial language acquisition. However, the studies leave unanswered how children ultimately acquire "left" and "right." In Part II, with three more experiments, we investigated why children struggle to master body-based frame-of-reference words. Children successfully learned "left" and "right" when the novel words were systematically introduced on their own bodies and extended these words to novel (intrinsic and relative) uses; however, they had difficulty learning to talk about the left and right sides of a doll. This difficulty was paralleled in identifying the left and right sides of the doll in a non-linguistic memory task. In contrast, children had no difficulties learning to label the front and back sides of a doll. These studies begin to paint a detailed account of the acquisition of spatial terms in English, and provide insights into the origins of diverse spatial reference frames in the world's languages. PMID:27423134

  10. Flexibly weighted integration of tactile reference frames.

    PubMed

    Badde, Stephanie; Röder, Brigitte; Heed, Tobias

    2015-04-01

    To estimate the location of a tactile stimulus, the brain seems to integrate different types of spatial information such as skin-based, anatomical coordinates and external, spatiotopic coordinates. The aim of the present study was to test whether the use of these coordinates is fixed, or whether they are weighted according to the task context. Participants made judgments about two tactile stimuli with different vibration characteristics, one applied to each hand. First, they always performed temporal order judgments (TOJ) of the tactile stimuli with respect to the stimulated hands that were either crossed or uncrossed. The resulting crossing effect, that is, impaired performance in crossed compared to uncrossed conditions, was used as a measure of reference frame weighting and was compared across conditions. Second, in dual judgment conditions participants subsequently made judgments about the stimulus vibration characteristics, either with respect to spatial location or with respect to temporal order. Responses in the spatial secondary task either accented anatomical (Experiment 1) or external (Experiment 2) coding. A TOJ crossing effect emerged in all conditions, and secondary tasks did not affect primary task performance in the uncrossed posture. Yet, the spatial secondary task resulted in improved crossed hands performance in the primary task, but only if the secondary judgment stressed the anatomical reference frame (Experiment 1), rather than the external reference frames (Experiment 2). Like the anatomically coded spatial secondary task, the temporal secondary task improved crossed hand performance of the primary task. The differential influence of the varying secondary tasks implies that integration weights assigned to the anatomical and external reference frames are not fixed. Rather, they are flexibly adjusted to the context, presumably through top-down modulation. PMID:25447059

  11. Reference frame requirements and the MERIT campaign

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.; Zhu, S. Y.; Bock, Y.

    1982-01-01

    An analysis is given of how satellite, lunar laser, and very long base interferometry stations available during the MERIT Campaign in 1983/84 can contribute to the detection of short periodic variations in the rotational parameters of the earth, as well as the determination of the differences between the various Conventional Terrestrial and Inertial Reference Frames inherent in the above systems. Specific observational requirements are given both by objective and by country.

  12. Kinematics and dynamics in noninertial quantum frames of reference

    NASA Astrophysics Data System (ADS)

    Angelo, R. M.; Ribeiro, A. D.

    2012-11-01

    From the principle that there is no absolute description of a physical state, we advance the approach according to which one should be able to describe the physics from the perspective of a quantum particle. The kinematics seen from this frame of reference is shown to be rather unconventional. In particular, we discuss several subtleties emerging in the relative formulation of central notions, such as vector states, the classical limit, entanglement, uncertainty relations and the complementary principle. A Hamiltonian formulation is also derived which correctly encapsulates effects of fictitious forces associated with the accelerated motion of the frame. Our approach shows, therefore, how to formulate nonrelativistic quantum mechanics within noninertial reference frames which can be consistently described by the theory, with no appeal to classical elements.

  13. Mesoscopic mechanical resonators as quantum noninertial reference frames

    NASA Astrophysics Data System (ADS)

    Katz, B. N.; Blencowe, M. P.; Schwab, K. C.

    2015-10-01

    An atom attached to a micrometer-scale wire that is vibrating at a frequency ˜100 MHz and with displacement amplitude ˜1 nm experiences an acceleration magnitude ˜109ms -2 , approaching the surface gravity of a neutron star. As one application of such extreme noninertial forces in a mesoscopic setting, we consider a model two-path atom interferometer with one path consisting of the 100 MHz vibrating wire atom guide. The vibrating wire guide serves as a noninertial reference frame and induces an in principle measurable phase shift in the wave function of an atom traversing the wire frame. We furthermore consider the effect on the two-path atom wave interference when the vibrating wire is modeled as a quantum object, hence functioning as a quantum noninertial reference frame. We outline a possible realization of the vibrating wire, atom interferometer using a superfluid helium quantum interference setup.

  14. The equations of relative motion in the orbital reference frame

    NASA Astrophysics Data System (ADS)

    Casotto, Stefano

    2016-03-01

    The analysis of relative motion of two spacecraft in Earth-bound orbits is usually carried out on the basis of simplifying assumptions. In particular, the reference spacecraft is assumed to follow a circular orbit, in which case the equations of relative motion are governed by the well-known Hill-Clohessy-Wiltshire equations. Circular motion is not, however, a solution when the Earth's flattening is accounted for, except for equatorial orbits, where in any case the acceleration term is not Newtonian. Several attempts have been made to account for the J_2 effects, either by ingeniously taking advantage of their differential effects, or by cleverly introducing ad-hoc terms in the equations of motion on the basis of geometrical analysis of the J_2 perturbing effects. Analysis of relative motion about an unperturbed elliptical orbit is the next step in complexity. Relative motion about a J_2-perturbed elliptic reference trajectory is clearly a challenging problem, which has received little attention. All these problems are based on either the Hill-Clohessy-Wiltshire equations for circular reference motion, or the de Vries/Tschauner-Hempel equations for elliptical reference motion, which are both approximate versions of the exact equations of relative motion. The main difference between the exact and approximate forms of these equations consists in the expression for the angular velocity and the angular acceleration of the rotating reference frame with respect to an inertial reference frame. The rotating reference frame is invariably taken as the local orbital frame, i.e., the RTN frame generated by the radial, the transverse, and the normal directions along the primary spacecraft orbit. Some authors have tried to account for the non-constant nature of the angular velocity vector, but have limited their correction to a mean motion value consistent with the J_2 perturbation terms. However, the angular velocity vector is also affected in direction, which causes precession

  15. The celestial reference frame defined by VLBI

    NASA Technical Reports Server (NTRS)

    Ma, C.; Shaffer, D. B.

    1988-01-01

    VLBI currently produces the most accurate positions of celestial objects. From 1979 to 1987, 114 extragalactic radio sources have been observed with dual-frequency Mark III VLBI as part of the NASA Crustal Dynamics Project and the NGS POLARIS/IRIS program. The formal statistical errors of conventional celestial coordinates are as small as 0.3 milliarcseconds. The fundamental quantity measured by VLBI is the arc length between radio sources. Thus, it is suggested that VLBI be used to establish a coordinate reference frame based solely on radio positions, and that this system not necessarily be coupled to right ascension and declination.

  16. Modeling laser wakefield accelerators in a Lorentz boosted frame

    SciTech Connect

    Vay, J.-L.; Geddes, C.G.R.; Cormier-Michel, E.; Grotec, D. P.

    2010-06-15

    Modeling of laser-plasma wakefield accelerators in an optimal frame of reference is shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups requires mitigation of a high-frequency instability that otherwise limits effectiveness in addition to solutions for handling data input and output in a relativistically boosted frame of reference. The observed high-frequency instability is mitigated using methods including an electromagnetic solver with tunable coefficients, its extension to accomodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is shown that choosing the frame of the wake as the frame of reference allows for higher levels of filtering and damping than is possible in other frames for the same accuracy. Detailed testing also revealed serendipitously the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion, thus indicating that the observed instability may not be due primarily to Numerical Cerenkov as has been conjectured. The techniques developed for Cerenkov mitigation prove nonetheless to be very efficient at controlling the instability. Using these techniques, agreement at the percentage level is demonstrated between simulations using different frames of reference, with speedups reaching two orders of magnitude for a 0.1 GeV class stages. The method then allows direct and efficient full-scale modeling of deeply depleted laser-plasma stages of 10 GeV-1 TeV for the first time, verifying the scaling of plasma accelerators to very high energies. Over 4, 5 and 6 orders of magnitude speedup is achieved for the modeling of 10 GeV, 100 GeV and 1 TeV class stages, respectively.

  17. Modeling laser wakefield accelerators in a Lorentz boosted frame

    SciTech Connect

    Vay, J.-L.; Geddes, C.G.R.; Cormier-Michel, E.; Grote, D.P.

    2010-09-15

    Modeling of laser-plasma wakefield accelerators in an optimal frame of reference [1] is shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups requires mitigation of a high frequency instability that otherwise limits effectiveness in addition to solutions for handling data input and output in a relativistically boosted frame of reference. The observed high-frequency instability is mitigated using methods including an electromagnetic solver with tunable coefficients, its extension to accomodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is shown that choosing theframe of the wake as the frame of reference allows for higher levels of filtering and damping than is possible in other frames for the same accuracy. Detailed testing also revealed serendipitously the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion, thus indicating that the observed instability may not be due primarily to Numerical Cerenkov as has been conjectured. The techniques developed for Cerenkov mitigation prove nonetheless to be very efficient at controlling the instability. Using these techniques, agreement at the percentage level is demonstrated between simulations using different frames of reference, with speedups reaching two orders of magnitude for a 0.1 GeV class stages. The method then allows direct and efficient full-scale modeling of deeply depleted laser-plasma stages of 10 GeV-1 TeV for the first time, verifying the scaling of plasma accelerators to very high energies. Over 4, 5 and 6 orders of magnitude speedup is achieved for the modeling of 10 GeV, 100 GeV and 1 TeV class stages, respectively.

  18. Reference-frame-independent quantum key distribution

    SciTech Connect

    Laing, Anthony; Rarity, John G.; O'Brien, Jeremy L.; Scarani, Valerio

    2010-07-15

    We describe a quantum key distribution protocol based on pairs of entangled qubits that generates a secure key between two partners in an environment of unknown and slowly varying reference frame. A direction of particle delivery is required, but the phases between the computational basis states need not be known or fixed. The protocol can simplify the operation of existing setups and has immediate applications to emerging scenarios such as earth-to-satellite links and the use of integrated photonic waveguides. We compute the asymptotic secret key rate for a two-qubit source, which coincides with the rate of the six-state protocol for white noise. We give the generalization of the protocol to higher-dimensional systems and detail a scheme for physical implementation in the three-dimensional qutrit case.

  19. Convecting reference frames and invariant numerical models

    NASA Astrophysics Data System (ADS)

    Bihlo, Alexander; Nave, Jean-Christophe

    2014-09-01

    In the recent paper by Bernardini et al. [1] the discrepancy in the performance of finite difference and spectral models for simulations of flows with a preferential direction of propagation was studied. In a simplified investigation carried out using the viscous Burgers equation the authors attributed the poorer numerical results of finite difference models to a violation of Galilean invariance in the discretization and propose to carry out the computations in a reference frame moving with the bulk velocity of the flow. Here we further discuss this problem and relate it to known results on invariant discretization schemes. Non-invariant and invariant finite difference discretizations of Burgers equation are proposed and compared with the discretization using the remedy proposed by Bernardini et al.

  20. The Effect of Companions on the SIM Reference Frame

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.; Turyshev, Slava G.

    2000-01-01

    The Space Interferometry Mission (SIM) is a 10-m Michelson space-based optical interferometer designed for precision astrometry (4 microarcseconds, 3 microarcseconds/year) with better accuracy than before over a narrow field of view. One of the primary objectives of the SIM instrument is to determine accurately the directions to a grid of stars, together with their proper motions and parallax, improving a priori knowledge by nearly three orders of magnitude over Hipparcos and one order of magnitude over FAME's planned accuracy (Johnston, 2000). The instrument does not measure directly the angular separation between stars, but rather it measures the projection of each star's direction vector onto the interferometer baseline vector by measuring the pathlength delay of starlight as it passes through the two arms of the interferometer. The accuracy and stability of SIM's celestial reference frame is subject to degradation over the 5-year mission from the reflex motion induced by massive companions of the objects used to construct the celestial reference frame. The authors present the results of simulations that show the sensitivity of reference frame accuracy to companions as a function of mass and period. They assume that pre-launch ground surveys will eliminate all objects with RMS radial velocity greater than 10 m/s. They further assume that the standard astrometric parameters of position, parallax, and proper motion plus acceleration terms in right ascension and declination will be allowed to absorb reflex motion.

  1. Reference frames for reach planning in macaque dorsal premotor cortex.

    PubMed

    Batista, Aaron P; Santhanam, Gopal; Yu, Byron M; Ryu, Stephen I; Afshar, Afsheen; Shenoy, Krishna V

    2007-08-01

    When a human or animal reaches out to grasp an object, the brain rapidly computes a pattern of muscular contractions that can acquire the target. This computation involves a reference frame transformation because the target's position is initially available only in a visual reference frame, yet the required control signal is a set of commands to the musculature. One of the core brain areas involved in visually guided reaching is the dorsal aspect of the premotor cortex (PMd). Using chronically implanted electrode arrays in two Rhesus monkeys, we studied the contributions of PMd to the reference frame transformation for reaching. PMd neurons are influenced by the locations of reach targets relative to both the arm and the eyes. Some neurons encode reach goals using limb-centered reference frames, whereas others employ eye-centered reference fames. Some cells encode reach goals in a reference frame best described by the combined position of the eyes and hand. In addition to neurons like these where a reference frame could be identified, PMd also contains cells that are influenced by both the eye- and limb-centered locations of reach goals but for which a distinct reference frame could not be determined. We propose two interpretations for these neurons. First, they may encode reach goals using a reference frame we did not investigate, such as intrinsic reference frames. Second, they may not be adequately characterized by any reference frame. PMID:17581846

  2. Determination of an Infrared Reference Frame

    NASA Technical Reports Server (NTRS)

    Sutton, Edmund C.

    1998-01-01

    The mission of the European Space Agency's Hipparcos satellite was to provide high precision astrometric and photometric data for over 100,000 stars and somewhat lower precision data on over a million additional stars. These observations were made in the optical band (340 - 850 nm) and resulted in median precisions of better than 1 milli-arcsec (mas) in position and parallax and I mas/yr in proper motion. The Hipparcos frame is inertial within an estimated uncertainty of +/- 0.25 mas/yr. The other important wavelength band for astrometry has been the radio band. A reference frame has been defined based on absolute Very Long Baseline Interferometry (VLBI) positions of several hundreds of radio sources. There have been a number of projects to refine the link between the optical and radio reference frames. In recent years there has been increasing interest in the astrometry of infrared sources. For example, stars with circumstellar shells can be observed in both the optical and radio (e.g. SiO maser emission). The infrared emission from such sources is dominated by thermal dust emission. The spatial distribution of radiation in the three bands is expected to be quite different. In 1982 we proposed a number of infrared-selected sources (S(sub 10 micron) greater than or approx. equal to 100 J(sub y)) for inclusion in the Hipparcos Input Catalog. Most of those sources were observed, and in Sutton (1997) we report the optical astrometric results (position, proper motion, and parallax) for 87 such sources. These sources were selected to have reasonable agreement between infrared and optical positions, and so may be used as primary standards for future infrared astrometry. They are well distributed across the sky, but exhibit some bias towards the galactic plane and the northern hemisphere. We have also obtained a set of 1480 secondary standards (unpublished) A comparison between optical positions and 86 GHz SiO maser positions for 10 sources indicates coincidence at the 0

  3. Communication between inertial observers with partially correlated reference frames

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mehdi; Smith, Alexander R. H.; Dragan, Andrzej

    2015-12-01

    In quantum communication protocols the existence of a shared reference frame between two spatially separated parties is normally presumed. However, in many practical situations we are faced with the problem of misaligned reference frames. In this paper, we study communication between two inertial observers who have partial knowledge about the Lorentz transformation that relates their frames of reference. Since every Lorentz transformation can be decomposed into a pure boost followed by a rotation, we begin by analyzing the effects on communication when the parties have partial knowledge about the transformation relating their frames, when the transformation is either a rotation or a pure boost. This then enables us to investigate how the efficiency of communication is affected due to partially correlated inertial reference frames related by an arbitrary Lorentz transformation. Furthermore, we show how the results of previous studies where reference frames are completely uncorrelated are recovered from our results in appropriate limits.

  4. Spatial vision within egocentric and exocentric frames of reference

    NASA Technical Reports Server (NTRS)

    Howard, Ian P.

    1991-01-01

    It is remarkable that we are able to perceive a stable visual world and judge the directions, orientations, and movements of visual objects given that images move on the retina, the eyes move in the head, the head moves on the body, and the body moves in space. An understanding of the mechanisms underlying perceptual stability and spatial judgements requires precise definitions of relevant coordinate systems. An egocentric frame of reference is defined with respect to some part of the observer. There are four principal egocentric frames of reference, a station-point frame associated with the nodal point of the eye, an retinocentric frame associated with the retina, a headcentric frame associated with the head, and a bodycentric frame (torsocentric) associated with the torso. Additional egocentric frames can be identified with respect to any segment of the body. An egocentric task is one in which the position, orientation, or motion of an object is judged with respect to an egocentric frame of reference. A proprioceptive is a special kind of egocentric task in which the object being judged is also part of the body. An example of a proprioceptive task is that of directing the gaze toward the seen or unseen toe. An exocentric frame of reference is external to the observer. Geographical coordinates and the direction of gravity are examples of exocentric frames of reference. These various frames are listed in tabular form, together with examples of judgements of each type.

  5. The Period of a Swinging Rod in an Oscillating Frame of Reference

    ERIC Educational Resources Information Center

    Biezeveld, Hubert

    2012-01-01

    It was obvious long ago that for mechanical behavior a gravitational field and an accelerating frame of reference are equivalent. Or in other words: it is impossible to decide whether you are in an accelerating elevator or in a closed room on a planet with a different value of "g". In the first section of this article I will describe a simple…

  6. Celestial reference frame RSC (GAOUA) 98 C 01.

    NASA Astrophysics Data System (ADS)

    Molotaj, O. A.; Tel'Nyuk-Adamchuk, V. V.; Yatskiv, Ya. S.

    The celestial reference frame RSC (GAOUA) 98 C 01 was constructed by applying the Kiev arc method to five initial frames submitted to the IERS during 1997. The frame comprises positions of 631 radio sources. The frame axes are aligned to those of the ICRF with an accuracy of 0.02 mas using all 212 defining common radio sources. The internal standard errors of right ascension and declination for the defining sources are equal to 0.11 and 0.13 mas, respectively. Results of intercomparison between the ICRF, five initial frames, and the compiled frame are discussed.

  7. Tripartite entanglement of fermionic system in accelerated frames

    SciTech Connect

    Khan, Salman

    2014-09-15

    The dynamics of tripartite entanglement of fermionic system in noninertial frames through linear contraction criterion when one or two observers are accelerated is investigated. In one observer accelerated case the entanglement measurement is not invariant with respect to the partial realignment of different subsystems and for two observers accelerated case it is invariant. It is shown that the acceleration of the frame does not generate entanglement in any bipartite subsystems. Unlike the bipartite states, the genuine tripartite entanglement does not completely vanish in both one observer accelerated and two observers accelerated cases even in the limit of infinite acceleration. The degradation of tripartite entanglement is fast when two observers are accelerated than when one observer is accelerated. It is shown that tripartite entanglement is a better resource for quantum information processing than the bipartite entanglement in noninertial frames. - Highlights: • Tripartite entanglement of fermionic system in noninertial frames is studied. • Linear contraction criterion for quantifying tripartite entanglement is used. • Acceleration does not produce any bipartite entanglement. • The invariance of entanglement quantifier depends on accelerated observers. • The tripartite entanglement degrades against the acceleration, it never vanishes.

  8. Use of Reference Frames for Interplanetary Navigation at JPL

    NASA Technical Reports Server (NTRS)

    Heflin, Michael; Jacobs, Chris; Sovers, Ojars; Moore, Angelyn; Owen, Sue

    2010-01-01

    Navigation of interplanetary spacecraft is typically based on range, Doppler, and differential interferometric measurements made by ground-based telescopes. Acquisition and interpretation of these observations requires accurate knowledge of the terrestrial reference frame and its orientation with respect to the celestial frame. Work is underway at JPL to reprocess historical VLBI and GPS data to improve realizations of the terrestrial and celestial frames. Improvements include minimal constraint alignment, improved tropospheric modeling, better orbit determination, and corrections for antenna phase center patterns.

  9. Future National Reference Frames for the United States

    NASA Astrophysics Data System (ADS)

    Stone, W. A.

    2015-12-01

    The mission of the National Oceanic and Atmospheric Administration's National Geodetic Survey (NGS) is "to define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs." NSRS is the nation's system of latitude, longitude, elevation, and related geophysical and geodetic models and tools, which provides a consistent spatial reference framework for the broad spectrum of geoscientific applications and other positioning-related requirements. Technological developments - notably Global Navigation Satellite Systems (GNSS) - and user accuracy requirements necessitate that NGS endeavor to modernize the NSRS. Preparations are underway by NGS for a comprehensive NSRS makeover, to be completed in 2022 and delivered through a new generation of horizontal and vertical datums (reference frames), featuring unprecedented accuracy, repeatability, and efficiency of access. This evolution is outlined in the "National Geodetic Survey Ten-Year Strategic Plan, 2013-2023." This presentation will outline the motivation for this effort and the history, current status and planned evolution of NSRS. Fundamental to the delivery of the future reference frame paradigm are new geometric and geopotential (elevation) frameworks. The new geometric reference frame, realized through GNSS Continuously Operating Reference Stations (CORS), will replace the North American Datum of 1983 (NAD83) and will provide the nationwide framework for determination of latitude, longitude, and ellipsoid height. Designed to complement the new geometric reference frame, a corresponding geopotential reference frame - based on a national gravimetric geoid and replacing the North American Vertical Datum of 1988 (NAVD88) - will be developed and co-released. The gravimetric geoid - or definitional reference surface (zero elevation) - for the future geopotential reference frame will be built in part from airborne gravimetric data collected in

  10. Frames of reference and students' conceptual understanding of seasons

    NASA Astrophysics Data System (ADS)

    Chandra, Nalini Michelle

    This thesis focused on students' misconceptions in the topic of seasons. Its three investigations explored the central question of: How do frames of reference influence students' conceptual understanding of seasons? The results from these investigations found that some single frames of reference can limit students' understanding of seasons or confuse students, while additional frames of reference can enhance students' understanding. These three investigations were driven by the principles of design research methodology. They examined how frames of reference provided by: Starry Night(TM) software, 3D models and textbook diagrams influenced students' understanding of seasons. The first investigation compared two groups of students. One group, the Egocentric Group (n=15), used Starry Night(TM). The second group, the Egocentric Group (n=13), mainly used text diagrams and 3D models. This investigation isolated different frames of reference in students' explanations of seasons. The results from this first investigation revealed that different frames of reference limit students' explanations of seasons. The second investigation addressed findings from the first investigation and observed how sixteen, grade six students' explanations about seasons changed as they were exposed to different frames of reference over the course of seven days for two hours per day. Students gave written explanations to the same questions about seasons during the first, fourth and seventh days. The results in this investigation revealed that students' explanations of seasons changed gradually and incorporated their experiences as they were introduced to new frames of reference. The third investigation explored what was happening to the students' intuitive understanding of seasons as they moved between different frames of reference in a problem-solving situation. Qualitative discourse analysis from three pairs of students found that as students moved between different frames of reference they

  11. Are All Spatial Reference Frames Egocentric? Reinterpreting Evidence for Allocentric, Object-Centered, or World-Centered Reference Frames

    PubMed Central

    Filimon, Flavia

    2015-01-01

    The use and neural representation of egocentric spatial reference frames is well-documented. In contrast, whether the brain represents spatial relationships between objects in allocentric, object-centered, or world-centered coordinates is debated. Here, I review behavioral, neuropsychological, neurophysiological (neuronal recording), and neuroimaging evidence for and against allocentric, object-centered, or world-centered spatial reference frames. Based on theoretical considerations, simulations, and empirical findings from spatial navigation, spatial judgments, and goal-directed movements, I suggest that all spatial representations may in fact be dependent on egocentric reference frames. PMID:26696861

  12. Spatial vision within egocentric and exocentric frames of reference

    NASA Technical Reports Server (NTRS)

    Howard, Ian P.

    1989-01-01

    The extent to which perceptual judgements within egocentric and exocentric frames of reference are subject to illusory disturbances and long term modifications is discussed. It is argued that well known spatial illusions, such as the oculogyral illusion and induced visual motion have usually been discussed without proper attention being paid to the frame of reference within which they occur, and that this has led to the construction of inadequate theories and inappropriate procedures for testing them.

  13. Reference frames in learning from maps and navigation.

    PubMed

    Meilinger, Tobias; Frankenstein, Julia; Watanabe, Katsumi; Bülthoff, Heinrich H; Hölscher, Christoph

    2015-11-01

    In everyday life, navigators often consult a map before they navigate to a destination (e.g., a hotel, a room, etc.). However, not much is known about how humans gain spatial knowledge from seeing a map and direct navigation together. In the present experiments, participants learned a simple multiple corridor space either from a map only, only from walking through the virtual environment, first from the map and then from navigation, or first from navigation and then from the map. Afterwards, they conducted a pointing task from multiple body orientations to infer the underlying reference frames. We constructed the learning experiences in a way such that map-only learning and navigation-only learning triggered spatial memory organized along different reference frame orientations. When learning from maps before and during navigation, participants employed a map- rather than a navigation-based reference frame in the subsequent pointing task. Consequently, maps caused the employment of a map-oriented reference frame found in memory for highly familiar urban environments ruling out explanations from environmental structure or north preference. When learning from navigation first and then from the map, the pattern of results reversed and participants employed a navigation-based reference frame. The priority of learning order suggests that despite considerable difference between map and navigation learning participants did not use the more salient or in general more useful information, but relied on the reference frame established first. PMID:25416007

  14. Reference frame realized by RSC(GAOUA)97 C 01

    NASA Astrophysics Data System (ADS)

    Molotaj, O.; Tel'Nyuk-Adamchuk, V.; Yatskiv, Ya.

    The RSC(GAO UA)97 C 01 reference frame have been constructed using the method of arcs between the extragalactic radio sources developed by Yatskiv and Kuryanova. This continues the Kyiv series of compiled catalogues of radio source positions. The method enables to derive the uncertainty of source catalogues and to detect inconsistency of separate radio source position. A comparison between the catalogue constructed, on the one hand, and the reference frames RSC(IERS)95 C 02 and RSC(WGRF)95 R 02, on the other hand, has been carried out. Systematic differences and consistency of the frames mentioned are discussed.

  15. Modeling laser-plasma acceleration in the laboratory frame

    SciTech Connect

    2011-01-01

    A simulation of laser-plasma acceleration in the laboratory frame. Both the laser and the wakefield buckets must be resolved over the entire domain of the plasma, requiring many cells and many time steps. While researchers often use a simulation window that moves with the pulse, this reduces only the multitude of cells, not the multitude of time steps. For an artistic impression of how to solve the simulation by using the boosted-frame method, watch the video "Modeling laser-plasma acceleration in the wakefield frame."

  16. Gaia reference frame amid quasar variability and proper motion patterns in the data

    NASA Astrophysics Data System (ADS)

    Bachchan, R. K.; Hobbs, D.; Lindegren, L.

    2016-05-01

    Context. Gaia's very accurate astrometric measurements will allow the optical realisation of the International Celestial Reference System to be improved by a few orders of magnitude. Several sets of quasars are used to define a kinematically stable non-rotating reference frame with the barycentre of the solar system as its origin. Gaia will also observe a large number of galaxies. Although they are not point-like, it may be possible to determine accurate positions and proper motions for some of their compact bright features. Aims: The optical stability of the quasars is critical, and we investigate how accurately the reference frame can be recovered. Various proper motion patterns are also present in the data, the best known is caused by the acceleration of the solar system barycentre, presumably, towards the Galactic centre. We review some other less well-known effects that are not part of standard astrometric models. Methods: We modelled quasars and galaxies using realistic sky distributions, magnitudes, and redshifts. Position variability was introduced using a Markov chain model. The reference frame was determined using the algorithm developed for the Gaia mission, which also determines the acceleration of the solar system. We also tested a method for measuring the velocity of the solar system barycentre in a cosmological frame. Results: We simulated the recovery of the reference frame and the acceleration of the solar system and conclude that they are not significantly disturbed by quasar variability, which is statistically averaged. However, the effect of a non-uniform sky distribution of the quasars can result in a correlation between the parameters describing the spin components of the reference frame and the acceleration components, which degrades the solution. Our results suggest that an attempt should be made to astrometrically determine the redshift-dependent apparent drift of galaxies that is due to our velocity relative to the cosmic microwave

  17. Gaia reference frame amid quasar variability and proper motion patterns in the data

    NASA Astrophysics Data System (ADS)

    Bachchan, R. K.; Hobbs, D.; Lindegren, L.

    2016-04-01

    Context. Gaia's very accurate astrometric measurements will allow the optical realisation of the International Celestial Reference System to be improved by a few orders of magnitude. Several sets of quasars are used to define a kinematically stable non-rotating reference frame with the barycentre of the solar system as its origin. Gaia will also observe a large number of galaxies. Although they are not point-like, it may be possible to determine accurate positions and proper motions for some of their compact bright features. Aims: The optical stability of the quasars is critical, and we investigate how accurately the reference frame can be recovered. Various proper motion patterns are also present in the data, the best known is caused by the acceleration of the solar system barycentre, presumably, towards the Galactic centre. We review some other less well-known effects that are not part of standard astrometric models. Methods: We modelled quasars and galaxies using realistic sky distributions, magnitudes, and redshifts. Position variability was introduced using a Markov chain model. The reference frame was determined using the algorithm developed for the Gaia mission, which also determines the acceleration of the solar system. We also tested a method for measuring the velocity of the solar system barycentre in a cosmological frame. Results: We simulated the recovery of the reference frame and the acceleration of the solar system and conclude that they are not significantly disturbed by quasar variability, which is statistically averaged. However, the effect of a non-uniform sky distribution of the quasars can result in a correlation between the parameters describing the spin components of the reference frame and the acceleration components, which degrades the solution. Our results suggest that an attempt should be made to astrometrically determine the redshift-dependent apparent drift of galaxies that is due to our velocity relative to the cosmic microwave

  18. Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations

    NASA Astrophysics Data System (ADS)

    Klink, W. H.; Wickramasekara, S.

    2013-09-01

    This is the fourth in a series of papers on developing a formulation of quantum mechanics in non-inertial reference frames. This formulation is grounded in a class of unitary cocycle representations of what we have called the Galilean line group, the generalization of the Galilei group to include transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. In previous work, we have shown that there exist representations of the Galilean line group that uphold the non-relativistic equivalence principle as well as representations that violate the equivalence principle. In these previous studies, the focus was on linear accelerations. In this paper, we undertake an extension of the formulation to include rotational accelerations. We show that the incorporation of rotational accelerations requires a class of loop prolongations of the Galilean line group and their unitary cocycle representations. We recover the centrifugal and Coriolis force effects from these loop representations. Loops are more general than groups in that their multiplication law need not be associative. Hence, our broad theoretical claim is that a Galilean quantum theory that holds in arbitrary non-inertial reference frames requires going beyond groups and group representations, the well-established framework for implementing symmetry transformations in quantum mechanics.

  19. Asynchronous reference frame agreement in a quantum network

    NASA Astrophysics Data System (ADS)

    Islam, Tanvirul; Wehner, Stephanie

    2016-03-01

    An efficient implementation of many multiparty protocols for quantum networks requires that all the nodes in the network share a common reference frame. Establishing such a reference frame from scratch is especially challenging in an asynchronous network where network links might have arbitrary delays and the nodes do not share synchronised clocks. In this work, we study the problem of establishing a common reference frame in an asynchronous network of n nodes of which at most t are affected by arbitrary unknown error, and the identities of the faulty nodes are not known. We present a protocol that allows all the correctly functioning nodes to agree on a common reference frame as long as the network graph is complete and not more than t\\lt n/4 nodes are faulty. As the protocol is asynchronous, it can be used with some assumptions to synchronise clocks over a network. Also, the protocol has the appealing property that it allows any existing two-node asynchronous protocol for reference frame agreement to be lifted to a robust protocol for an asynchronous quantum network.

  20. Reference frames in virtual spatial navigation are viewpoint dependent

    PubMed Central

    Török, Ágoston; Nguyen, T. Peter; Kolozsvári, Orsolya; Buchanan, Robert J.; Nadasdy, Zoltan

    2014-01-01

    Spatial navigation in the mammalian brain relies on a cognitive map of the environment. Such cognitive maps enable us, for example, to take the optimal route from a given location to a known target. The formation of these maps is naturally influenced by our perception of the environment, meaning it is dependent on factors such as our viewpoint and choice of reference frame. Yet, it is unknown how these factors influence the construction of cognitive maps. Here, we evaluated how various combinations of viewpoints and reference frames affect subjects' performance when they navigated in a bounded virtual environment without landmarks. We measured both their path length and time efficiency and found that (1) ground perspective was associated with egocentric frame of reference, (2) aerial perspective was associated with allocentric frame of reference, (3) there was no appreciable performance difference between first and third person egocentric viewing positions and (4) while none of these effects were dependent on gender, males tended to perform better in general. Our study provides evidence that there are inherent associations between visual perspectives and cognitive reference frames. This result has implications about the mechanisms of path integration in the human brain and may also inspire designs of virtual reality applications. Lastly, we demonstrated the effective use of a tablet PC and spatial navigation tasks for studying spatial and cognitive aspects of human memory. PMID:25249956

  1. Transport equations of electrodiffusion processes in the laboratory reference frame.

    PubMed

    Garrido, Javier

    2006-02-23

    The transport equations of electrodiffusion processes use three reference frames for defining the fluxes: Fick's reference in diffusion, solvent-fixed reference in transference numbers, and laboratory fluxes in electric conductivity. The convenience of using only one reference frame is analyzed here from the point of view of the thermodynamics of irreversible processes. A relation between the fluxes of ions and solvent and the electric current density is deduced first from a mass and volume balance. This is then used to show that (i) the laboratory and Fick's diffusion coefficients are identical and (ii) the transference numbers of both the solvent and the ion in the laboratory reference frame are related. Finally, four experimental methods for the measurement of ion transference numbers are analyzed critically. New expressions for evaluating transference numbers for the moving boundary method and the chronopotentiometry technique are deduced. It is concluded that the ion transport equation in the laboratory reference frame plays a key role in the description of electrodiffusion processes. PMID:16494340

  2. Reference frame-induced errors in VLBI Earth rotation determinations

    NASA Astrophysics Data System (ADS)

    Heinkelmann, Robert; Karbon, Maria; Liu, Li; Lu, Cuixian; Mora-Diaz, Julian A.; Nilsson, Tobias J.; Raposo-Pulido, Virginia; Soja, Benedikt; Xu, Minghui; Schuh, Harald

    2014-05-01

    Earth Rotation is defined as the transformation between the Geocentric Celestial Reference System (GCRS) and the International Terrestrial Reference System (ITRS). It is a three-dimensional rotation which is described by the precession/nutation Q, the Earth rotation R, and the polar motion W matrices (IERS Coventions 2010): xGCRS = QRWxITRS. The actual determination of Earth Rotation by Very Long Baseline Interferometry (VLBI) is based on the reference frames involved in the VLBI analysis. VLBI is the only space-geodetic technique used for the realization of the International Celestial Reference System (ICRS), which is the geocentric celestial reference system (GCRS) practically realized to evaluate the above equation. Since the Earth Orientation Parameters (EOP) are obtained as 'session-wise parameters', they can suffer from any inconsistencies between session-wise TRF and CRF realizations. In this paper we assess the session-wise TRF and CRF differences by determining the respective transformation parameters of the adjusted terrestrial and celestial positions on a session basis to the catalogue coordinates, given by the International Terrestrial Reference Frame 2008 (ITRF2008) and the Second International Celestial Reference Frame (ICRF2).

  3. Connecting kinematic and dynamic reference frames by D-VLBI

    NASA Astrophysics Data System (ADS)

    Schuh, Harald; Plank, Lucia; Madzak, Matthias; Böhm, Johannes

    2012-08-01

    In geodetic and astrometric practice, terrestrial station coordinates are usually provided in the kinematic International Terrestrial Reference Frame (ITRF) and radio source coordinates in the International Celestial Reference Frame (ICRF), whereas measurements of space probes such as satellites and spacecrafts, or planetary ephemerides rest upon dynamical theories. To avoid inconsistencies and errors during measurement and calculation procedures, exact frame ties between quasi - inertial, kinematic and dynamic reference frames have to be secured. While the Earth Orientation Parameters (EOP), e.g. measured by VLBI, link the ITRF to the ICRF, the ties with the dynamic frames can be established with the differential Very Long Baseline Interferometry (D - VLBI) method. By observing space probes alternately t o radio sources, the relative position of the targets to each other on the sky can be determined with high accuracy. While D - VLBI is a common technique in astrophysics (source imaging) and deep space navigation, just recently there have been several effort s to use it for geodetic purposes. We present investigations concerning possible VLBI observations to satellites. This includes the potential usage of available GNNS satellites as well as specifically designed missions, as e.g. the GRASP mission proposed b y JPL/NASA and an international consortium, where the aspect of co - location in space of various techniques (VLBI, SLR, GNSS, DORIS) is the main focus.

  4. Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations

    SciTech Connect

    Klink, W.H.; Wickramasekara, S.

    2013-09-15

    This is the fourth in a series of papers on developing a formulation of quantum mechanics in non-inertial reference frames. This formulation is grounded in a class of unitary cocycle representations of what we have called the Galilean line group, the generalization of the Galilei group to include transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. In previous work, we have shown that there exist representations of the Galilean line group that uphold the non-relativistic equivalence principle as well as representations that violate the equivalence principle. In these previous studies, the focus was on linear accelerations. In this paper, we undertake an extension of the formulation to include rotational accelerations. We show that the incorporation of rotational accelerations requires a class of loop prolongations of the Galilean line group and their unitary cocycle representations. We recover the centrifugal and Coriolis force effects from these loop representations. Loops are more general than groups in that their multiplication law need not be associative. Hence, our broad theoretical claim is that a Galilean quantum theory that holds in arbitrary non-inertial reference frames requires going beyond groups and group representations, the well-established framework for implementing symmetry transformations in quantum mechanics. -- Highlights: •A formulation of Galilean quantum mechanics in non-inertial reference frames is presented. •The Galilei group is generalized to infinite dimensional Galilean line group. •Loop prolongations of Galilean line group contain central extensions of Galilei group. •Unitary representations of the loops are constructed. •These representations lead to terms in the Hamiltonian corresponding to fictitious forces, including centrifugal and Coriolis

  5. Work and energy in inertial and noninertial reference frames

    NASA Astrophysics Data System (ADS)

    Diaz, Rodolfo A.; Herrera, William J.; Manjarrés, Diego A.

    2009-03-01

    It is usual in introductory courses of mechanics to develop the work and energy formalism from Newton's laws. It has been shown how forces transform under a change of reference frame. No analogous study is usually done for the way in which work and energy transform under a change of reference frames. We analyze the behavior of energy and work under such transformations and explicitly show the expected invariance of the formalism under Galilean transformations for one particle and a system of particles. The case of noninertial systems is also analyzed and the fictitious work is characterized. In particular, we showed that the total fictitious work in the center of mass system vanishes even if the center of mass defines a noninertial frame. Some subtleties that arise from the formalism are illustrated by examples.

  6. The Bernoulli Equation in a Moving Reference Frame

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2011-01-01

    Unlike other standard equations in introductory classical mechanics, the Bernoulli equation is not Galilean invariant. The explanation is that, in a reference frame moving with respect to constrictions or obstacles, those surfaces do work on the fluid, constituting an extra term that needs to be included in the work-energy calculation. A…

  7. The GAOUA series of compiled celestial reference frames

    NASA Astrophysics Data System (ADS)

    Molotaj, O.; Tel'Nyuk-Adamchuk, V.; Yatskiv, Ya.

    2000-09-01

    The GAOUA series of compiled celestial reference frames is obtained by using the original Kyiv arc length approach for combination of initial RSC solutions which are yearly submitted to the IERS CB by various VLBI Analysis Centers. The presentation is concerned with an analysis of accuracies of these individual and combined solutions and that of the ICRF.

  8. Limited Aspects of Reality: Frames of Reference in Language Assessment

    ERIC Educational Resources Information Center

    Fulcher, Glenn; Svalberg, Agneta

    2013-01-01

    Language testers operate within two frames of reference: norm-referenced (NRT) and criterion-referenced testing (CRT). The former underpins the world of large-scale standardized testing that prioritizes variability and comparison. The latter supports substantive score meaning in formative and domain specific assessment. Some claim that the…

  9. Frames of Reference in African Proverbs on Disability.

    ERIC Educational Resources Information Center

    Devlieger, Patrick J.

    1999-01-01

    Fifty-five proverbs relating to disability were collected from sub-Saharan African countries and analyzed for larger frames of reference of personhood and cosmogony. Themes include warnings against laughing at a disabled person, personhood, existential insecurity, acceptance of what is, and the function and nature of disability. (DB)

  10. Cross-Sensory Transfer of Reference Frames in Spatial Memory

    ERIC Educational Resources Information Center

    Kelly, Jonathan W.; Avraamides, Marios N.

    2011-01-01

    Two experiments investigated whether visual cues influence spatial reference frame selection for locations learned through touch. Participants experienced visual cues emphasizing specific environmental axes and later learned objects through touch. Visual cues were manipulated and haptic learning conditions were held constant. Imagined perspective…

  11. Change of Reference Frame for Tactile Localization during Child Development

    ERIC Educational Resources Information Center

    Pagel, Birthe; Heed, Tobias; Roder, Brigitte

    2009-01-01

    Temporal order judgements (TOJ) for two tactile stimuli, one presented to the left and one to the right hand, are less precise when the hands are crossed over the midline than when the hands are uncrossed. This "crossed hand" effect has been considered as evidence for a remapping of tactile input into an external reference frame. Since late, but…

  12. Reference Frames during the Acquisition and Development of Spatial Memories

    ERIC Educational Resources Information Center

    Kelly, Jonathan W.; McNamara, Timothy P.

    2010-01-01

    Four experiments investigated the role of reference frames during the acquisition and development of spatial knowledge, when learning occurs incrementally across views. In two experiments, participants learned overlapping spatial layouts. Layout 1 was first studied in isolation, and Layout 2 was later studied in the presence of Layout 1. The…

  13. Intrinsic frames of reference in haptic spatial learning.

    PubMed

    Yamamoto, Naohide; Philbeck, John W

    2013-11-01

    It has been proposed that spatial reference frames with which object locations are specified in memory are intrinsic to a to-be-remembered spatial layout (intrinsic reference theory). Although this theory has been supported by accumulating evidence, it has only been collected from paradigms in which the entire spatial layout was simultaneously visible to observers. The present study was designed to examine the generality of the theory by investigating whether the geometric structure of a spatial layout (bilateral symmetry) influences selection of spatial reference frames when object locations are sequentially learned through haptic exploration. In two experiments, participants learned the spatial layout solely by touch and performed judgments of relative direction among objects using their spatial memories. Results indicated that the geometric structure can provide a spatial cue for establishing reference frames as long as it is accentuated by explicit instructions (Experiment 1) or alignment with an egocentric orientation (Experiment 2). These results are entirely consistent with those from previous studies in which spatial information was encoded through simultaneous viewing of all object locations, suggesting that the intrinsic reference theory is not specific to a type of spatial memory acquired by the particular learning method but instead generalizes to spatial memories learned through a variety of encoding conditions. In particular, the present findings suggest that spatial memories that follow the intrinsic reference theory function equivalently regardless of the modality in which spatial information is encoded. PMID:24007919

  14. Modeling laser-plasma acceleration in the wakefield frame

    SciTech Connect

    2011-01-01

    A simulation of laser-plasma acceleration in the boosted frame of the wake, moving at near lightspeed. Space has contracted and time has stretched, separating events in time. Relatively few time steps are needed to model them, requiring less computer time.

  15. Using quasar physics to improve the celestial reference frame

    NASA Astrophysics Data System (ADS)

    Shabala, Stanislav; Plank, Lucia; McCallum, Jamie; Boehm, Johannes

    2015-08-01

    Radio-loud quasars making up the International Celestial Reference Frame (ICRF) are dynamic objects with significant structure that changes on timescales of months and years. This is a problem for reference frame stability, as realised through the geodetic and astrometric Very Long Baseline Interferometry (VLBI) technique, which has so far largely treated quasars as point sources in analysis. I will describe the source structure simulator recently implemented in the Vienna VLBI Software (VieVS) package, and quantify the effects of various levels of source structure on the celestial and terrestrial reference frames, and Earth Orientation Parameters linking these two frames. We find that even relatively modest levels of quasar structure can produce systematic effects that affect derived quasar positions significantly in excess of the noise floor of the present ICRF realisation, ICRF2.I will also discuss the observed relationship between astrophysical properties of quasars, their structure and geodetic stability. By simulating quasar structure and evolution in VieVS, we have devised various quasar mitigation strategies. These include: (1) astrophysically-based quasar selection techniques; (2) scheduling sources by taking into account quasar structure; and (3) analyzing geodetic and astrometric VLBI observations using knowledge of quasar structure. I will describe our simulation results, and outline promising quasar structure mitigation strategies.

  16. Deriving a geocentric reference frame for satellite positioning and navigation

    NASA Technical Reports Server (NTRS)

    Malla, R. P.; Wu, S.-C.

    1988-01-01

    With the advent of Earth-orbiting geodetic satellites, nongeocentric datums or reference frames have become things of the past. Accurate geocentric three-dimensional positioning is now possible and is of great importance for various geodetic and oceanographic applications. While relative positioning accuracy of a few centimeters has become a reality using very long baseline interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be on the order of 1 meter. Satellite laser ranging (SLR), however, is capable of determining this offset to better than 10 cm, but this is possible only after years of measurements. Global Positioning System (GPS) measurements provide a powerful tool for an accurate determination of this origin offset. Two strategies are discussed. The first strategy utilizes the precise relative positions that were predetermined by VLBI to fix the frame orientation and the absolute scaling, while the offset from the geocenter is determined from GPS measurements. Three different cases are presented under this strategy. The reference frame thus adopted will be consistent with the VLBI coordinate system. The second strategy establishes a reference frame by holding only the longitude of one of the tracking sites fixed. The absolute scaling is determined by the adopted gravitational constant (GM) of the Earth; and the latitude is inferred from the time signature of the Earth rotation in the GPS measurements. The coordinate system thus defined will be a geocentric Earth-fixed coordinate system.

  17. Quantum image coding with a reference-frame-independent scheme

    NASA Astrophysics Data System (ADS)

    Chapeau-Blondeau, François; Belin, Etienne

    2016-07-01

    For binary images, or bit planes of non-binary images, we investigate the possibility of a quantum coding decodable by a receiver in the absence of reference frames shared with the emitter. Direct image coding with one qubit per pixel and non-aligned frames leads to decoding errors equivalent to a quantum bit-flip noise increasing with the misalignment. We show the feasibility of frame-invariant coding by using for each pixel a qubit pair prepared in one of two controlled entangled states. With just one common axis shared between the emitter and receiver, exact decoding for each pixel can be obtained by means of two two-outcome projective measurements operating separately on each qubit of the pair. With strictly no alignment information between the emitter and receiver, exact decoding can be obtained by means of a two-outcome projective measurement operating jointly on the qubit pair. In addition, the frame-invariant coding is shown much more resistant to quantum bit-flip noise compared to the direct non-invariant coding. For a cost per pixel of two (entangled) qubits instead of one, complete frame-invariant image coding and enhanced noise resistance are thus obtained.

  18. Quantum image coding with a reference-frame-independent scheme

    NASA Astrophysics Data System (ADS)

    Chapeau-Blondeau, François; Belin, Etienne

    2016-04-01

    For binary images, or bit planes of non-binary images, we investigate the possibility of a quantum coding decodable by a receiver in the absence of reference frames shared with the emitter. Direct image coding with one qubit per pixel and non-aligned frames leads to decoding errors equivalent to a quantum bit-flip noise increasing with the misalignment. We show the feasibility of frame-invariant coding by using for each pixel a qubit pair prepared in one of two controlled entangled states. With just one common axis shared between the emitter and receiver, exact decoding for each pixel can be obtained by means of two two-outcome projective measurements operating separately on each qubit of the pair. With strictly no alignment information between the emitter and receiver, exact decoding can be obtained by means of a two-outcome projective measurement operating jointly on the qubit pair. In addition, the frame-invariant coding is shown much more resistant to quantum bit-flip noise compared to the direct non-invariant coding. For a cost per pixel of two (entangled) qubits instead of one, complete frame-invariant image coding and enhanced noise resistance are thus obtained.

  19. Determination and Maintenance of the Galileo Terrestrial Reference Frame

    NASA Astrophysics Data System (ADS)

    Fritsche, Mathias

    2016-04-01

    A highly precise and stable Galileo Terrestrial Reference Frame (GTRF) is a crucial prerequisite for the provision of precise Galileo products and related services. The GTRF determination shall be compatible with the latest International Terrestrial Reference Frame (ITRF) providing the same level of accuracy, long-term stability, and reliability to the maximum extent possible. The connection to ITRF is realized and validated by stations of the International GNSS Service (IGS) and by geodetic local ties to stations equipped with other geodetic techniques. Primary GTRF input data are provided by the Orbit Validation Facility (OVF) including precise satellite orbit and clocks, ground tracking station coordinates and Earth rotation parameters. The OVF service is delivered by the GGSP consortium, a group of five European institutes having a strong geodetic background. In this presentation, we provide an up-to-date overview on the latest GTRF release and the current OVF status.

  20. Disentangling the External Reference Frames Relevant to Tactile Localization

    PubMed Central

    Backhaus, Jenny; Röder, Brigitte; Badde, Stephanie

    2016-01-01

    Different reference frames appear to be relevant for tactile spatial coding. When participants give temporal order judgments (TOJ) of two tactile stimuli, one on each hand, performance declines when the hands are crossed. This effect is attributed to a conflict between anatomical and external location codes: hand crossing places the anatomically right hand into the left side of external space. However, hand crossing alone does not specify the anchor of the external reference frame, such as gaze, trunk, or the stimulated limb. Experiments that used explicit localization responses, such as pointing to tactile stimuli rather than crossing manipulations, have consistently implicated gaze-centered coding for touch. To test whether crossing effects can be explained by gaze-centered coding alone, participants made TOJ while the position of the hands was manipulated relative to gaze and trunk. The two hands either lay on different sides of space relative to gaze or trunk, or they both lay on one side of the respective space. In the latter posture, one hand was on its "regular side of space" despite hand crossing, thus reducing overall conflict between anatomical and external codes. TOJ crossing effects were significantly reduced when the hands were both located on the same side of space relative to gaze, indicating gaze-centered coding. Evidence for trunk-centered coding was tentative, with an effect in reaction time but not in accuracy. These results link paradigms that use explicit localization and TOJ, and corroborate the relevance of gaze-related coding for touch. Yet, gaze and trunk-centered coding did not account for the total size of crossing effects, suggesting that tactile localization relies on additional, possibly limb-centered, reference frames. Thus, tactile location appears to be estimated by integrating multiple anatomical and external reference frames. PMID:27391805

  1. Disentangling the External Reference Frames Relevant to Tactile Localization.

    PubMed

    Heed, Tobias; Backhaus, Jenny; Röder, Brigitte; Badde, Stephanie

    2016-01-01

    Different reference frames appear to be relevant for tactile spatial coding. When participants give temporal order judgments (TOJ) of two tactile stimuli, one on each hand, performance declines when the hands are crossed. This effect is attributed to a conflict between anatomical and external location codes: hand crossing places the anatomically right hand into the left side of external space. However, hand crossing alone does not specify the anchor of the external reference frame, such as gaze, trunk, or the stimulated limb. Experiments that used explicit localization responses, such as pointing to tactile stimuli rather than crossing manipulations, have consistently implicated gaze-centered coding for touch. To test whether crossing effects can be explained by gaze-centered coding alone, participants made TOJ while the position of the hands was manipulated relative to gaze and trunk. The two hands either lay on different sides of space relative to gaze or trunk, or they both lay on one side of the respective space. In the latter posture, one hand was on its "regular side of space" despite hand crossing, thus reducing overall conflict between anatomical and external codes. TOJ crossing effects were significantly reduced when the hands were both located on the same side of space relative to gaze, indicating gaze-centered coding. Evidence for trunk-centered coding was tentative, with an effect in reaction time but not in accuracy. These results link paradigms that use explicit localization and TOJ, and corroborate the relevance of gaze-related coding for touch. Yet, gaze and trunk-centered coding did not account for the total size of crossing effects, suggesting that tactile localization relies on additional, possibly limb-centered, reference frames. Thus, tactile location appears to be estimated by integrating multiple anatomical and external reference frames. PMID:27391805

  2. 32 GHz Celestial Reference Frame Survey for Dec < -45 deg.

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Phillips, Chris; Jacobs, Christopher; Sotuela, Ioana; Garcia miro, Cristina

    2012-04-01

    We propose to conduct a LBA survey of compact radio sources at 32 GHz near the south pole region. This is the first attempt to fill the gap in the existing 32 GHz catalogue establish by NASA Deep Space Network toward completing the full sky celestial reference frame at 32 GHz. The catalogue will be used for future spacecraft navigation by NASA and other space agencies as well as for radio astronomical observations with southern radio telescope arrays such as ATCA and LBA.

  3. Global GPS reference frame solutions of unlimited size

    NASA Astrophysics Data System (ADS)

    Boomkamp, H.

    2010-07-01

    This paper reports on the Dancer project, which is one of three related projects initiated by working group 1 of the International Association of Geodesy. The Dancer project develops JAVA parameter estimation software that runs in the form of a distributed process on the internet, in such a way that each processing node handles the data of a single geodetic instrument. By exchanging a minimum amount of information among all processing nodes, the same global normal equation solution is found by all instruments. The result is a fully scalable least squares solution that has no practical limit to the number of GPS receivers or other tracking devices that may be included in a single reference frame realization. High-end GPS users will also be able to run a Dancer process for their own data, without contributing to the reference frame solution but taking full advantage of its global consistency. This offers direct access to precise International Terrestrial Reference Frame and UTC realizations, anywhere on Earth where there is an internet connection. Mission control centres of low satellites with GPS receivers can run a Dancer process on the incoming data from the orbiting receiver, to introduce strong ties with other techniques such as Satellite Laser Ranging.

  4. On the errors and stability of reference frames

    NASA Astrophysics Data System (ADS)

    Gubanov, V. S.; Kurdubov, S. L.

    2013-12-01

    The distribution of systematic errors in the coordinates of 1217 extragalactic radio sources included in the latest version of the ICRF2 (International Celestial Reference Frame) reference catalog has been mapped for the first time by processing VLBI observations from international astrometric and geodetic programs spanning the period 1980-2012. These errors are shown to reach ±1.0 mas (milliarcseconds). However, for a sample of 752 sources observed more than 100 times, these errors do not exceed ±0.2 mas, suggesting that ICRF2 is inhomogeneous. In addition, the individual stability of dozens of extragalactic radio sources and ground-based stations included in the latest version of the International Terrestrial Reference Frame, ITRF2005, has been investigated. Significant linear trends and anomalous shifts reaching ±20 µas (microarcseconds) have been detected for many of the sources. Significant systematic shifts have also been found for some of the reference stations. The results obtained stimulate a search for new methods of analyzing VLBI observations and ways of their global adjustment that would provide greater homogeneity and stability of the ICRF and ITRF. This is needed both to increase the accuracy of determining the astrometric, geodetic, and geodynamic parameters derived from these observations and to facilitate their physical interpretation. The work has been performed with the QUASAR multifunction software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences.

  5. Optical position meters analyzed in the noninertial reference frames

    SciTech Connect

    Tarabrin, Sergey P.; Seleznyov, Alexander A.

    2008-09-15

    In the framework of general relativity we develop a method for the analysis of the operation of the optical position meters in their photodetectors proper reference frames. These frames are noninertial in general due to the action of external fluctuative forces on meters test masses, including detectors. For comparison we also perform the calculations in the laboratory (globally inertial) reference frame and demonstrate that for certain optical schemes laboratory-based analysis results in unmeasurable quantities, in contrast to the detector-based analysis. We also calculate the response of the simplest optical meters to weak plane gravitational waves and fluctuative motions of their test masses. It is demonstrated that for the round-trip meter analysis in both the transverse-traceless (TT) and local Lorentz (LL) gauges produces equal results, while for the forward-trip meter corresponding results differ in accordance with different physical assumptions (e.g. procedure of clocks synchronization) implicitly underlying the construction of the TT and LL gauges.

  6. 32 GHz Celestial Reference Frame Survey for Dec. < -45 °

    NASA Astrophysics Data System (ADS)

    Horiuchi, S.; Jacobs, C. S.; Phillips, C.; Sotuela, I.; García-Miró, C.

    2012-12-01

    We have been developing a celestial reference frame at 32 GHz using the 34-m Beam Wave Guide antennas of NASA's Deep Space Network (DSN) to complement the current IAU standard ICRF2 at S/X-band. However, the DSN VLBI network alone can only cover a limited part of the full sky, missing the declination range from -45 to -90 degrees. To extend the 32 GHz frame, we recently initiated a project to survey candidate sources in the southern sky using Canberra's DSS-34 antenna in conjunction with two elements of the Australian Long Baseline Array (LBA) that can observe at 32 GHz: the Mopra Radio Relescope and the Australian Telescope Compact Array (ATCA).

  7. 32 GHz Celestial Reference Frame Survey for Dec < -45 deg

    NASA Astrophysics Data System (ADS)

    Horiuchi, S.; Phillips, C.; Sotuela, I.; Jacobs, Christopher S.; García-Miró, C.

    2012-03-01

    We have been developing a celestial reference frame at 32 GHz using the 34-m Beam Wave Guide antennas of NASA's Deep Space Network (DSN) to complement the current IAU standard ICRF2 at S/X-band. However, the DSN VLBI network alone can only cover a limited part of the full sky, missing the declination range from -45 to -90 degrees. To extend the 32 GHz frame, we recently initiated a project to survey candidate sources in the southern sky using Canberra's DSS-34 antenna in conjunction with two elements of the Australian Long Baseline Array (LBA) that can observe at 32 GHz: the Mopra Radio Relescope and the Australian Telescope Compact Array (ATCA).

  8. On the Assessment of Global Terrestrial Reference Frame Temporal Variations

    NASA Astrophysics Data System (ADS)

    Ampatzidis, Dimitrios; Koenig, Rolf; Zhu, Shengyuan

    2015-04-01

    Global Terrestrial Reference Frames (GTRFs) as the International Terrestrial Reference Frame (ITRF) provide reliable 4-D position information (3-D coordinates and their evolution through time). The given 3-D velocities play a significant role in precise position acquisition and are estimated from long term coordinate time series from the space-geodetic techniques DORIS, GNSS, SLR, and VLBI. GTRFs temporal evolution is directly connected with their internal stability: The more intense and inhomogeneous velocity field, the less stable TRF is derived. The assessment of the quality of the GTRF is mainly realized by comparing it to each individual technique's reference frame. E.g the comparison of GTRFs to SLR-only based TRF gives the sense of the ITRF stability with respect to the Geocenter and scale and their associated rates respectively. In addition, the comparison of ITRF to the VLBI-only based TRF can be used for the scale validation. However, till now there is not any specified methodology for the total assessment (in terms of origin, orientation and scale respectively) of the temporal evolution and GTRFs associated accuracy. We present a new alternative diagnostic tool for the assessment of GTRFs temporal evolution based on the well-known time-dependent Helmert type transformation formula (three shifts, three rotations and scale rates respectively). The advantage of the new methodology relies on the fact that it uses the full velocity field of the TRF and therefore all points not just the ones common to different techniques. It also examines simultaneously rates of origin, orientation and scale. The methodology is presented and implemented to the two existing GTRFs on the market (ITRF and DTRF which is computed from DGFI) , the results are discussed. The results also allow to compare directly each GTRF dynamic behavior. Furthermore, the correlations of the estimated parameters can also provide useful information to the proposed GTRFs assessment scheme.

  9. Distributions of Grain Boundary Normals in the Laboratory Reference Frame

    NASA Astrophysics Data System (ADS)

    Glowinski, Krzysztof; Rohrer, Gregory S.

    2016-06-01

    Distributions of grain boundary normals with their components expressed in the laboratory reference frame are obtained for yttria and austenitic steel based on three-dimensional electron backscatter diffraction data. The distributions exhibit various extrema that are attributed to the inaccuracy of the boundary surface reconstruction and to the discrete nature of the orientation data. We provide interpretation of the distributions with particular emphasis put on indicating the sources of these artifacts. Moreover, we verify the negligible impact of these issues on grain boundary plane and character distributions.

  10. Stability study of realization of the celestial reference frame

    NASA Astrophysics Data System (ADS)

    Yatskiv, Ya. S.; Bolotin, S. L.; Kur'yanova, A. N.

    2004-09-01

    We present a short overview of the activity of the IERS as well as the Main Astronomical Observatory (MAO) of the National Academy of Sciences of Ukraine for maintenance and extention of the International Celestial Reference Frame (ICRF). Special attention is given to the time stabilities of positions of radio sources (RS) and to the selection of a subset of RS to be used for maintenance of the ICRF. It is shown that seven RS qualified by the IERS as defining sources are unstable.

  11. Standardization of Observatories, Instruments and Reference Frames for Planetary Sciences

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Erard, S.; Le Sidaner, P.

    2015-10-01

    The recent developments on planetary science interoperability showed that a standardization of naming conventions was required for observatories (including ground based facilities and space mission), instruments (types and names) as well as reference frames used to describe planetary observations. A review of existing catalogs and naming for those entities is presented. We also report on the discussions that occurred within the IVOA (International Virtual Observatory Alliance), IPDA (International Planetary Data Alliance) and VESPA (Virtual European Solar and Planetary Access) working groups. A proposal for standard lists, possibly to be endorsed by IAU, is presented and discussed.

  12. Standardization of Observatories, Instruments and Reference Frames for Planetary Sciences

    NASA Astrophysics Data System (ADS)

    Cecconi, Baptiste; Erard, Stéphane; Le Sidaner, Pierre

    2015-08-01

    The recent developments on planetary science interoperability showed that a standardization of naming conventions was required for observatories (including ground based facilities and space mission), instruments (types and names) as well as reference frames used to describe planetary observations. A review of existing catalogs and naming for those entities is presented. We also report on the discussions that occurred within the IVOA (International Virtual Observatory Alliance), IPDA (International Planetary Data Alliance) and VESPA (Virtual European Solar and Planetary Access) working groups. A proposal for standard lists, possibly to be endorsed by IAU, is presented and discussed.

  13. Distributions of Grain Boundary Normals in the Laboratory Reference Frame

    NASA Astrophysics Data System (ADS)

    Glowinski, Krzysztof; Rohrer, Gregory S.

    2016-04-01

    Distributions of grain boundary normals with their components expressed in the laboratory reference frame are obtained for yttria and austenitic steel based on three-dimensional electron backscatter diffraction data. The distributions exhibit various extrema that are attributed to the inaccuracy of the boundary surface reconstruction and to the discrete nature of the orientation data. We provide interpretation of the distributions with particular emphasis put on indicating the sources of these artifacts. Moreover, we verify the negligible impact of these issues on grain boundary plane and character distributions.

  14. Inhibition within a Reference Frame during the Interpretation of Spatial Language

    ERIC Educational Resources Information Center

    Carlson, Laura A.; Van Deman, Shannon R.

    2008-01-01

    Spatial terms such as "right" are potentially ambiguous because they can refer to different regions of space when defined by competing reference frames (e.g., my "right" within a relative reference frame versus an object's "right" within an intrinsic reference frame). In such situations, previous research has suggested that multiple reference…

  15. Spatial Reasoning With Multiple Intrinsic Frames of Reference

    PubMed Central

    Tamborello, Franklin P; Sun, Yanlong; Wang, Hongbin

    2016-01-01

    Establishing and updating spatial relationships between objects in the environment is vital to maintaining situation awareness and supporting many socio-spatial tasks. In a complex environment, people often need to utilize multiple reference systems that are intrinsic to different objects (intrinsic frame of reference, IFOR), but these IFORs may conflict with each other in one or more ways. Current spatial cognition theories do not adequately address how people handle multi-IFOR reasoning problems. Two experiments manipulated relative orientations of two task-relevant objects with intrinsic axes of orientation as well as their relative task salience. Response times (RTs) decreased with increasing salience of the targeted IFOR. In addition, RTs increased as a consequence of intrinsic orientation conflict, but not by amount of orientation difference. The results suggest that people encounter difficulties when they have to process two conflicting IFOR representations, and that they seem to prioritize processing of each IFOR by salience. PMID:21768066

  16. Galileo Terrestrial Reference Frame realization and beyond: the GGSP project

    NASA Astrophysics Data System (ADS)

    Söhne, W.; Dach, R.; Springer, T.; Gendt, G.

    2009-04-01

    The GGSP prototype, a project funded by the 6th framework programme of the European Union and managed by the European GNSS Supervisory Authority (GSA), will be finished end of May this year. The main task of the GGSP prototype was the definition, realization and maintenance of the Galileo Terrestrial Reference Frame (GTRF) with the requirement to align the GTRF to the International Terrestrial Reference Frame (ITRF) within 3 cm (2 sigma) accuracy. With regard to the non-availability of Galileo signals in space the initialization and maintenance of the GTRF were realized with GPS observations only. Moreover, the GGSP prototype carried out orbit, clock and coordinate parameter estimation on a weekly basis, using a processing strategy known from the International GNSS Service (IGS). Beyond these activities, the consortium has been analysing the Galileo signals as transmitted by the two GIOVE spacecrafts. Since April 2008 the second test satellite GIOVE-B is in orbit while the first one, GIOVE-A, is transmitting the first Galileo signals for over three years now. A special feature of GIOVE-B is the onboard passive hydrogen maser (PHM). Known from terrestrial reference station, hydrogen masers are providing the highest short-term stability. It is expected that the PHM onboard GIOVE-B will show similar clock stability as terrestrial hydrogen masers. Using different sampling rates, the performance of the GIOVE-B onboard clock could be tested for different time intervals. We will use comparisons with onboard clocks of other GNSS as well as with clocks of terrestrial reference stations to illustrate the GIOVE-B clock behaviour. Moreover, some results of intersystem biases, between GPS and Galileo/GIOVE, will be presented.

  17. Reference-frame-independent quantum key distribution with source flaws

    NASA Astrophysics Data System (ADS)

    Wang, Can; Sun, Shi-Hai; Ma, Xiang-Chun; Tang, Guang-Zhao; Liang, Lin-Mei

    2015-10-01

    Compared with the traditional protocols of quantum key distribution (QKD), the reference-frame-independent (RFI)-QKD protocol has been generally proved to be very useful and practical, since its experimental implementation can be simplified without the alignment of a reference frame. In most RFI-QKD systems, the encoding states are always taken to be perfect, which, however, is not practical in realizations. In this paper, we consider the security of RFI QKD with source flaws based on the loss-tolerant method proposed by Tamaki et al. [Phys. Rev. A 90, 052314 (2014), 10.1103/PhysRevA.90.052314]. As the six-state protocol can be realized with four states, we show that the RFI-QKD protocol can also be performed with only four encoding states instead of six encoding states in its standard version. Furthermore, the numerical simulation results show that the source flaws in the key-generation basis (Z basis) will reduce the key rate but are loss tolerant, while the ones in X and Y bases almost have no effect and the key rate remains almost the same even when they are very large. Hence, our method and results will have important significance in practical experiments, especially in earth-to-satellite or chip-to-chip quantum communications.

  18. Relating the Planetary Ephemerides and the Radio Reference Frame

    NASA Technical Reports Server (NTRS)

    Niell, A. E.; Newhall, X. X.; Preston, R. A.; Berge, G. L.; Muhleman, D. O.; Rudy, D. J.; Campbell, J. K.; Esposito, P. B.; Standish, E. M.

    1985-01-01

    The positions of Venus, Mars, and Jupiter were obtained in the VLBI radio reference frame by measuring the position of a satellite (natural or artificial) of each planet relative to an extragalactic source in the radio catalogue. From the results for Mars and Venus it is concluded that the offset in right ascension of the radio frame from the dynamical equinox defined in DE200 is 0.00 sec +/- 0.04 sec. The observations for Jupiter imply a correction to its position from DE200 of -0.18 sec +/- 0.04 sec in right ascension and -0.06 +/- 0.05 sec in declination on 1983 April 29. The right ascension of Jupiter relative to the inner planets has been measured independently using Doppler tracking data near Jupiter encounter from Pioneers 10 and 11 and from Voyagers 1 and 2 by tying the tracking station positions, through previous spacecraft missions, to the DE200 ephemerides of the inner planets. This technique yielded a correction to Jupiter's right ascension of -0.22 +/- 0.05 sec, in good agreement with the results from the direct radio measurements.

  19. Reframing Student Affairs Leadership: An Analysis of Organizational Frames of Reference and Locus of Control

    ERIC Educational Resources Information Center

    Tull, Ashley; Freeman, Jerrid P.

    2011-01-01

    Examined in this study were the identified frames of reference and locus of control used by 478 student affairs administrators. Administrator responses were examined to identify frames of reference most commonly used and their preference order. Locus of control most commonly used and the relationship between frames of reference and locus of…

  20. Comparison of Realizations of the Terrestrial Reference Frame

    NASA Technical Reports Server (NTRS)

    Ma, C.; Macmillan, D.; Bolotin, S.; Le Bail, K.; Gordon, D.; Gipson, J.

    2015-01-01

    IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We compared the IGN and DGFI TRFs with a GSFC CALC/SOLVE TRF. WRMS position and velocity differences for the 40 most frequently observed sites were 2-3 mm and 0.3-0.4 mm/year. There was a scale difference of 0.39/0.09 ppb between the IGN/DGFI realizations and the GSFC solution. When we fixed positions and velocities to either the IGN or DGFI values in CALC/SOLVE solutions, the resulting EOP estimates were not significantly different from the estimates from a standard TRF solution.

  1. Galilei covariance and Einstein's equivalence principle in quantum reference frames

    NASA Astrophysics Data System (ADS)

    Pereira, S. T.; Angelo, R. M.

    2015-02-01

    The covariance of the Schrödinger equation under Galilei boosts and the compatibility of nonrelativistic quantum mechanics with Einstein's equivalence principle have been constrained for so long to the existence of a superselection rule which would prevent a quantum particle from being found in superposition states of different masses. In an effort to avoid this expedient, and thus allow nonrelativistic quantum mechanics to account for unstable particles, recent works have suggested that the usual Galilean transformations are inconsistent with the nonrelativistic limit implied by the Lorentz transformation. Here we approach the issue in a fundamentally different way. Using a formalism of unitary transformations and employing quantum reference frames rather than immaterial coordinate systems, we show that the Schrödinger equation, although form variant, is fully compatible with the aforementioned principles of relativity.

  2. 32 GHz Celestial Reference Frame Survey for Dec < -45 deg.

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Phillips, Chris; Stevens, Jamie; Jacobs, Christopher; Sotuela, Ioana; Garcia miro, Cristina

    2014-04-01

    (We resubmit this proposal to extend from the previous semester. The 24 hour blocks for ATCA and Mopra were granted in May 2012 but canceled because fringe test before the scheduled experiment failed although fringes were detected between Mopra and Tidbinbilla. During the last scheduled LBA session for this project we discovered ATCA/Mopra had an issue with frequency standard, which has now been resolved.) We propose to conduct a LBA survey of compact radio sources at 32 GHz near the south pole region. This is the first attempt to fill the gap in the existing 32 GHz catalogue establish by NASA Deep Space Network toward completing the full sky celestial reference frame at 32 GHz. The catalogue will be used for future spacecraft navigation by NASA and other space agencies as well as for radio astronomical observations with southern radio telescope arrays such as ATCA and LBA.

  3. 32 GHz Celestial Reference Frame Survey for Dec < -45 deg.

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Phillips, Chris; Stevens, Jamie; Jacobs, Christopher; Sotuela, Ioana; Garcia miro, Cristina

    2013-04-01

    (We resubmit this proposal to extend from the previous semester. The 24 hour blocks for ATCA and Mopra were granted in May 2012 but canceled because fringe test before the scheduled experiment failed although fringes were detected between Mopra and Tidbinbilla. As it turned out ATCA had an issue with frequency standard, which has now been resolved.) We propose to conduct a LBA survey of compact radio sources at 32 GHz near the south pole region. This is the first attempt to fill the gap in the existing 32 GHz catalogue establish by NASA Deep Space Network toward completing the full sky celestial reference frame at 32 GHz. The catalogue will be used for future spacecraft navigation by NASA and other space agencies as well as for radio astronomical observations with southern radio telescope arrays such as ATCA and LBA.

  4. KS variables in rotating reference frame. Application to cometary dynamics

    NASA Astrophysics Data System (ADS)

    Langner, K.; Breiter, S.

    2015-06-01

    The problem of Keplerian motion in the uniformly rotating reference frame has been solved in terms of the Kustaanheimo-Stiefel (KS) variables using canonical formalism. No recourse to the Cartesian variables or orbital elements has been required. The form of solution is well suited for the application as a part of symplectic integrator. The results show that the motion is actually the composition of four independent harmonic oscillations and of the rotation in two specific coordinate planes and their conjugate momenta planes. As an example of application, we use the KS symplectic integrator to study the motion of comet C/1997 J2 (Meunier-Dupuoy) under the action of Galactic tides. The comet is found to follow an orbit in commensurability with the Sun motion around the Galactic centre, but the perturbations are not qualified as a resonance.

  5. Accurate Realization of GPS Vertical Global Reference Frame

    NASA Technical Reports Server (NTRS)

    Elosegui, Pedro

    2005-01-01

    The goal of this project is to improve our current understanding of GPS error sources associated with estimates of radial velocities at global scales. An improvement in the accuracy of radial global velocities would have a very positive impact on a large number of geophysical studies of current general interest such as global sea-level and climate change, coastal hazards, glacial isostatic adjustment, atmospheric and oceanic loading, glaciology and ice mass variability, tectonic deformation and volcanic inflation, and geoid variability. A set of GPS error sources relevant to this project are those related to the combination of the positions and velocities of a set of globally distributed stations as determined &om the analysis of GPS data, including possible methods of combining and defining terrestrial reference frames. This is were our research activities during this reporting period have concentrated. During this reporting period, we have researched two topics: (1) The effect of errors on the GPS satellite antenna models (or lack thereof) on global GPS vertical position and velocity estimates; (2) The effect of reference W e definition and practice on estimates of the geocenter variations.

  6. The role of frames of reference in the development of responsiveness to shading information.

    PubMed

    Yonas, A; Kuskowski, M; Sternfels, S

    1979-06-01

    The use of frames of reference in interpreting shading information in pictures was studied with children from 3 to 8 years of age. After learning to discriminate tactually between a convexity and a concavity, the subjects were presented a photograph of the convexity and the concavity in which the only information for differential shape was provided by the relationship between the orientation of the shading on the shapes and the frames of reference. By changing the position of the subject's head, rotating the display, and changing the location of the source of illumination, the relevance of egocentric, environmental, and lighting-specified frames of reference was manipulated. Children in this age range were found to be sensitive to shading information for depth, both when that information was specified by only a single frame of reference and when all three frames of reference were relevant. Differences in the responsiveness to individual frames of reference were found: the egocentric (head-retina) frame of reference was most effective, followed by the environmental reference frame, and finally by the frame of reference based on the location of the light source in the space surrounding the photograph. Responsiveness to the environmental and lighting-based frames of reference increased with age, while responsiveness to the egocentric frame of reference was high for all age groups and did not increase with age. PMID:487887

  7. Realization of the International Celestial Reference Frame from VLBI Astrometry

    NASA Astrophysics Data System (ADS)

    Ma, C.

    1997-12-01

    The International Celestial Reference Frame (ICRF) has now been realized with compact extragalactic objects whose radio-frequency positions are measured at the submilliarcsecond level by VLBI (Very Long Baseline Interferometry). The ICRF replaces the FK5 as the defining realization of the celestial reference system as of 1 Jan 1998 according the resolution adopted by the IAU General Assembly in Kyoto. The ICRF catalog includes 212 defining sources, 294 candidate sources, and 102 other sources, the sum uniformly populating the celestial sphere. The majority are quasars with compact cores and many have optical counterparts. Because of the nature of the VLBI observations (precise angular measurements over a large portion of the sky in a 24-hr interval) and the absence of measurable real transverse motion of the objects, the ICRF can be constructed rigidly and with great precision using data of considerable temporal and geographic extent. The positions and uncertainties, typically <0.5 mas, represent the distillation of 1.6 million dual-frequency Mark III VLBI delay and delay rate observations acquired between August 1979 and July 1995 from various geodetic and astrometric observing programs using radio observatories on every continent. Following IAU resolutions, individual ICRF positions will evolve as more observations and improved models become available, but the orientation (axes) of the ICRF will be maintained by a statistical no-net-rotation condition between the catalog positions of successive realizations. Celestial positions are no longer referred to a system associated with the equator or the ecliptic. Further information about the ICRF can be found in Technical Note 23 of the International Earth Rotation Service.

  8. Gaia Reference frame determination: the AVU/GSR pipeline

    NASA Astrophysics Data System (ADS)

    Vecchiato, Alberto; Abbas, Ummi; Becciani, Ugo; Bianchi, Luca; Bucciarelli, Beatrice; Crosta, Mariateresa; Lattanzi, Mario G.

    2015-08-01

    The main goal of the Gaia ESA mission is the production of a 5 parameters astrometric catalog - i.e. including positions, parallaxes and the two components of the proper motions - of about 1 billion stars of our Galaxy at an accuracy level going from the few micro-arcseconds of the brightest objects to some ~100 micro-arcseconds of the faintests. This goal will be reached by means of high-precision astrometric measurements conducted by a satellite sweeping continuously the celestial sphere during its 5-years mission.A fundamental step toward the realization of this catalog is the so-called ''Sphere Reconstruction'', which determines the celestial reference frame using the observations of a subset of up to 100 million ''primary stars'' among those observed by Gaia.From a mathematical point of view, these observations translate into a large number of equations, linearized with respect to the unknown parameters around known initial values, whose solution in the least-squares sense eventually provides the catalog with its errors, and determines the Gaia reference frame.This represents an extremely challenging problem because of the high accuracy of the observations and of the large number of unknowns involved. The former issue implies that an adequately accurate relativistic astrometric model has to be used, while the huge number of unknowns and observations puts this task at the forefront of the High-Performance Computing problems.These challenges, and the absolute character of the Gaia measurements and results, calls for a careful scientific validation of the sphere reconstruction, as it was done for the previous HIPPARCOS mission. For these reasons the Gaia Data Processing and Analysis Consortium (DPAC) decided to replicate the baseline process, named AGIS (Astrometric Global Iterative Solution) with another independent solution, named GSR (Global Sphere Reconstruction) which uses a different astrometric model and different algorithms for the system solution

  9. Towards an All-Sky 32 GHz Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Horiuchi, S.; Phillips, C.; Jacobs, Christopher S.; Sotuela, I.; García-Miró, C.

    2012-07-01

    We have been developing a celestial reference frame catalogue at 32 GHz using 34m Beam Wave Guide antennas of NASA Deep Space Network to complement the current IAU standard S/X-band ICRF2. However, the DSN VLBI network alone can only cover limited part of the full sky, missing in the declination range from -45 to -90 degree. To extend the 32 GHz catalogue, we recently initiated a project to survey candidate catalogue sources in the southern sky using Canberra DSS-34 antenna in conjunction with two elements of LBA that can observe at 32 GHz, the Mopra telescope and ATCA. We formed a list of 144 new 32 GHz candidate catalogue sources at -90 < Dec. < -45 deg. as target sources of this pilot survey. We selected those sources as expected to be reasonably strong and compact for our purpose, considering estimated flux densities at 32 GHz based on the results of the ATCA 20 GHz (AT20G) survey with 8.6 GHz flux density measurements, as well as characteristics of the X-band unresolved components based on the RFC2011c version catalogue sources. The candidate list of 144 sources includes 46 ICRF2 sources with 29 "Defining" objects. This would allow cross-checking with the S/X results of ICRF2. The ultimate goal of our project is to establish a reference source catalogue at 32 GHz for the south polar cap region, which has never been covered in existing catalogues at that frequency. The catalogue can be used for future space navigation as well as astronomical and geodetic observations with southern radio telescope arrays such as ATCA and LBA.

  10. Spatial reference frame of attention in a large outdoor environment

    PubMed Central

    Jiang, Yuhong V.; Won, Bo-Yeong; Swallow, Khena M.; Mussack, Dominic M.

    2014-01-01

    A central question about spatial attention is whether it is referenced relative to the external environment or to the viewer. This question has received great interest in recent psychological and neuroscience research, with many but not all, finding evidence for a viewer-centered representation. However, these previous findings were confined to computer-based tasks that involved stationary viewers. Because natural search behaviors differ from computer-based tasks in viewer mobility and spatial scale, it is important to understand how spatial attention is coded in the natural environment. To this end, we created an outdoor visual search task in which participants searched a large (690 square feet), concrete, outdoor space to report which side of a coin on the ground faced up. They began search in the middle of the space and were free to move around. Attentional cuing by statistical learning was examined by placing the coin in one quadrant of the search space on 50% of the trials. As in computer-based tasks participants learned and used these regularities to guide search. However, cuing could be referenced to either the environment or the viewer. The spatial reference frame of attention shows greater flexibility in the natural environment than previously found in the lab. PMID:24842066

  11. GPS inferred geocentric reference frame for satellite positioning and navigation

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1989-01-01

    Accurate geocentric three-dimensional positioning is of great importance for various geodetic and oceanographic applications. While relative positioning accuracy of a few centimeters has become a reality using Very Long Baseline Interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be of the order of one meter. Satellite Laser Ranging (SLR) is capable of determining this offset to better than 10 cm, though, because of the limited number of satellites, this requires a long arc of data. The Global Positioning System (GPS) measurements provide a powerful alternative for an accurate determination of this origin offset in relatively short period of time. Two strategies are discussed, the first utilizes the precise relative positions predetermined by VLBI, whereas the second establishes a reference frame by holding only one of the tracking sites longitude fixed. Covariance analysis studies indicate that geocentric positioning to an accuracy of a few centimeters can be achieved with just one day of precise GPS pseudorange and carrier phase data.

  12. Spatial reference frame of attention in a large outdoor environment.

    PubMed

    Jiang, Yuhong V; Won, Bo-Yeong; Swallow, Khena M; Mussack, Dominic M

    2014-08-01

    A central question about spatial attention is whether it is referenced relative to the external environment or to the viewer. This question has received great interest in recent psychological and neuroscience research, with many but not all, finding evidence for a viewer-centered representation. However, these previous findings were confined to computer-based tasks that involved stationary viewers. Because natural search behaviors differ from computer-based tasks in viewer mobility and spatial scale, it is important to understand how spatial attention is coded in the natural environment. To this end, we created an outdoor visual search task in which participants searched a large (690 square ft), concrete, outdoor space to report which side of a coin on the ground faced up. They began search in the middle of the space and were free to move around. Attentional cuing by statistical learning was examined by placing the coin in 1 quadrant of the search space on 50% of the trials. As in computer-based tasks, participants learned and used these regularities to guide search. However, cuing could be referenced to either the environment or the viewer. The spatial reference frame of attention shows greater flexibility in the natural environment than previously found in the lab. PMID:24842066

  13. Displacements and rotations of a body moving about an arbitrary axis in a global reference frame

    SciTech Connect

    Hollerbach, K.; Hollister, A.

    1995-11-01

    Measurement of human joint motion frequently involves the use of markers to describe joint motion in a global reference frame. Results may be quite arbitrary if the reference frame is not properly chosen with respect to the joint`s rotational axis(es). In nature joint axes can exist at any orientation and location relative to an arbitrarily chosen global reference frame. An arbitrary axis is any axis that is not coincident with a reference coordinate. Calculations are made of the errors that result when joint motion occurs about an arbitrary axis in a global reference frame.

  14. Improved DORIS Reference Frame Solution from NASA GSFC

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank; Chinn, D. S.; Le Bail, K.; Zelensky, N. P.; Ray, R. D.; Beckley, B. D.; Beall, J. W.

    2012-01-01

    At GSFC, since 2008, we have been routinely processing data to DORIS and SLR satellites from 1993. A SINEX time series, based on processing of DORIS data from 1993 to 2008 (designated wd10) was included in the IDS combination for ITRF2008 (Le Bail et al., 2010; Valette et al., 2010). We have updated this series with the addition of new satellites Cryosat2 and Jason-2, and the new series (designated wd12) is routinely submitted to the IDS combination center for inclusion in the DORIS operational combination. In preparation for an eventual reprocessing of all the DORIS data for eventual inclusion in a new ITRF we are now updating our processing standards. As a first step, we update to the ITRF2008 reference frame as expressed through DPOD2008. In addition, we apply the GMF and GPT models for the troposphere, and we update the modeling for the change in pitch of SPOT-5 solar arrays after January 2008. Finally, we consider updated standards for static and time-variable gravity modeling. With this base series, we compute cumulative solution, expressed in ITRF2008, and examine the week-by-week station solution parameters, in particular scale, WRMS and Helmert transformation parameters. Finally we consider a joint solution with SLR, where the DORIS system is tied to SLR in two ways, first through the orbit computations using satellites tracked by both SLR and DORIS (e.g. TOPEX, Envisat, Jason-2, Cryosat2), and second through explicit ties at collocated sites. As one of the means of testing of these DORIS-only and SLR+DORIS solutions, we examine the vertical rates at sites in the vicinity of tide gauges.

  15. GPU accelerated processing of astronomical high frame-rate videosequences

    NASA Astrophysics Data System (ADS)

    Vítek, Stanislav; Švihlík, Jan; Krasula, Lukáš; Fliegel, Karel; Páta, Petr

    2015-09-01

    Astronomical instruments located around the world are producing an incredibly large amount of possibly interesting scientific data. Astronomical research is expanding into large and highly sensitive telescopes. Total volume of data rates per night of operations also increases with the quality and resolution of state-of-the-art CCD/CMOS detectors. Since many of the ground-based astronomical experiments are placed in remote locations with limited access to the Internet, it is necessary to solve the problem of the data storage. It mostly means that current data acquistion, processing and analyses algorithm require review. Decision about importance of the data has to be taken in very short time. This work deals with GPU accelerated processing of high frame-rate astronomical video-sequences, mostly originating from experiment MAIA (Meteor Automatic Imager and Analyser), an instrument primarily focused to observing of faint meteoric events with a high time resolution. The instrument with price bellow 2000 euro consists of image intensifier and gigabite ethernet camera running at 61 fps. With resolution better than VGA the system produces up to 2TB of scientifically valuable video data per night. Main goal of the paper is not to optimize any GPU algorithm, but to propose and evaluate parallel GPU algorithms able to process huge amount of video-sequences in order to delete all uninteresting data.

  16. Spatial properties of non-retinotopic reference frames in human vision.

    PubMed

    Noory, Babak; Herzog, Michael H; Ogmen, Haluk

    2015-08-01

    Many visual attributes of a target stimulus are computed according to dynamic, non-retinotopic reference frames. For example, the motion trajectory of a reflector on a bicycle wheel is perceived as orbital, even though it is in fact cycloidal in retinal, as well as spatial coordinates. We cannot perceive the cycloidal motion because the linear motion of the bike is discounted for. In other words, the linear motion common to all bicycle components serves as a non-retinotopic reference frame, with respect to which the residual (orbital) motion of the reflector is computed. Very little is known about the underlying mechanisms involved in formation and operation of non-retinotopic reference frames. Here, we investigate spatial properties of non-retinotopic reference frames. We show that reference frames are not restricted within the boundaries of moving stimuli but extend over space. By using a variation of the Ternus-Pikler paradigm, we show that the spatial extent of a non-retinotopic reference frame is independent of the size of the inducing elements and the target position near the object boundary. While dynamic reference-frames interact with each other significantly, a static reference-frame has no effect on a dynamic one. The magnitude of interactions between two neighboring dynamic reference-frames increases as the distance between them reduces. Finally, our results indicate that the reference-frame strength is significantly attenuated if the locus of attention is shifted to the elements of the neighboring reference instead of the main reference. We suggest that these results can be conceptualized as reference frames that act and interact as fields. PMID:26049040

  17. Mathematical analysis of errors resulting from choice of reference frame coordinates in measuring human joint motion

    SciTech Connect

    Hollerbach, K.; Hollister, A.

    1995-02-01

    Measurements of human joint motion frequently involve the use of opto-electronic and other motion analysis systems where some type of makers are used to establish joint motion within a global reference coordinate frame. Typically, this global reference coordinate frame is chosen to be most convenient for the person carrying out the experiment in which the joint motion is measured, and Euler angles are chosen as the measure of joint motion. Results, however, may be quite arbitrary and therefore rendered meaningless if the reference frame is not properly chosen with respect to the physical joint axis. In order to make a proper choice of coordinate axes in the reference frame, one must take into consideration both the location and the orientation of die physical joint axis relative to the reference frame`s axes. In nature, joint axes can exist at any orientation and location relative to an arbitrarily chosen global reference frame. An axis that is not properly aligned with the global reference frame is therefore called an arbitrary axis. We demonstrate that errors result when measurements and calculations are made in a global reference frame that is arbitrarily placed and oriented, with little regard for the physical axis. Slight offsets of global reference frame produce significant errors in recording rotations about the joint axis. We conclude that, in order to be able to reach valid conclusions from joint motion measurements, the reference frame with respect to which all are taken must be brought to the physical axis; furthermore, one of the reference axes must be aligned with the physical axis. Any other choice of reference axes will result in misleading an often erroneous results.

  18. ILC Reference Design Report: Accelerator Executive Summary

    SciTech Connect

    Phinney, Nan; /SLAC

    2007-12-14

    The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radiofrequency (SCRF) accelerating cavities. The use of the SCRF technology was recommended by the International Technology Recommendation Panel (ITRP) in August 2004 [1], and shortly thereafter endorsed by the International Committee for Future Accelerators (ICFA). In an unprecedented milestone in high-energy physics, the many institutes around the world involved in linear collider R&D united in a common effort to produce a global design for the ILC. In November 2004, the 1st International Linear Collider Workshop was held at KEK, Tsukuba, Japan. The workshop was attended by some 200 accelerator physicists from around the world, and paved the way for the 2nd ILC Workshop in August 2005, held at Snowmass, Colorado, USA, where the ILC Global Design Effort (GDE) was officially formed. The GDE membership reflects the global nature of the collaboration, with accelerator experts from all three regions (Americas, Asia and Europe). The first major goal of the GDE was to define the basic parameters and layout of the machine--the Baseline Configuration. This was achieved at the first GDE meeting held at INFN, Frascati, Italy in December 2005 with the creation of the Baseline Configuration Document (BCD). During the next 14 months, the BCD was used as the basis for the detailed design work and value estimate (as described in section 1.6) culminating in the completion of the second major milestone, the publication of the draft ILC Reference Design Report (RDR). The technical design and cost estimate for the ILC is based on two decades of world-wide Linear Collider R&D, beginning with the construction and operation of the SLAC Linear Collider (SLC). The SLC is acknowledged as a proof-of-principle machine for the linear collider concept. The ILC SCRF linac technology was pioneered by the TESLA collaboration*, culminating in

  19. Geometric Cues, Reference Frames, and the Equivalence of Experienced-Aligned and Novel-Aligned Views in Human Spatial Memory

    ERIC Educational Resources Information Center

    Kelly, Jonathan W.; Sjolund, Lori A.; Sturz, Bradley R.

    2013-01-01

    Spatial memories are often organized around reference frames, and environmental shape provides a salient cue to reference frame selection. To date, however, the environmental cues responsible for influencing reference frame selection remain relatively unknown. To connect research on reference frame selection with that on orientation via…

  20. Reynolds stress under a change of frame of reference.

    PubMed

    Huang, Y N; Durst, F

    2001-05-01

    In this paper, we study the characteristics of the Reynolds stress under a change of frame, as defined by the Euclidean group of transformation. We show that being subject to the dynamical processes induced from the mean Navier-Stokes equations, the invariance group of the fluctuating velocity and the Reynolds stress is no longer the Euclidean group of transformation, which is merely a kinematical aspect, but reduces to the extended Galilean group of transformation. As a consequence, in contrast to developing the constitutive equations for the Cauchy stress in continuum mechanics, wherein the principle of material frame-indifference is a guiding principle, the frame-dependent kinematical quantities, e.g., the mean spin tensor, may be allowed to play an effective role as the constitutive variable in turbulence modeling. PMID:11415004

  1. Conflict Management Styles Predicted by Managerial Frames of Reference.

    ERIC Educational Resources Information Center

    Van Epps, Pamela D.; Thompson, Bruce

    The measurement integrity of M. A. Rahim's Organizational Conflict Inventory (ROCI-II) and D. M. Roussel's Managerial Frames of Mind Survey (MFMS) was investigated, as was the relationship between scores on the two measures. Subjects were 369 managers from three types of organizations: (1) higher education; (2) not-for-profit public sector…

  2. The Inertial Property of Approximately Inertial Frames of Reference

    ERIC Educational Resources Information Center

    Chubykalo, Andrew E.; Espinoza, Augusto; Kosyakov, B. P.

    2011-01-01

    Is it possible to compare approximately inertial frames in the inertial property? If this is the case, the inertial property becomes a measurable quantity. We give a positive answer to this question, and discuss the general principle of design of devices for making the required measurements. This paper is intended for advanced undergraduate and…

  3. Tracking down abstract linguistic meaning: neural correlates of spatial frame of reference ambiguities in language.

    PubMed

    Janzen, Gabriele; Haun, Daniel B M; Levinson, Stephen C

    2012-01-01

    This functional magnetic resonance imaging (fMRI) study investigates a crucial parameter in spatial description, namely variants in the frame of reference chosen. Two frames of reference are available in European languages for the description of small-scale assemblages, namely the intrinsic (or object-oriented) frame and the relative (or egocentric) frame. We showed participants a sentence such as "the ball is in front of the man", ambiguous between the two frames, and then a picture of a scene with a ball and a man--participants had to respond by indicating whether the picture did or did not match the sentence. There were two blocks, in which we induced each frame of reference by feedback. Thus for the crucial test items, participants saw exactly the same sentence and the same picture but now from one perspective, now the other. Using this method, we were able to precisely pinpoint the pattern of neural activation associated with each linguistic interpretation of the ambiguity, while holding the perceptual stimuli constant. Increased brain activity in bilateral parahippocampal gyrus was associated with the intrinsic frame of reference whereas increased activity in the right superior frontal gyrus and in the parietal lobe was observed for the relative frame of reference. The study is among the few to show a distinctive pattern of neural activation for an abstract yet specific semantic parameter in language. It shows with special clarity the nature of the neural substrate supporting each frame of spatial reference. PMID:22363462

  4. Frames of reference utilized in the rehabilitation of individuals with eating disorders.

    PubMed

    Henderson, S

    1999-02-01

    An occupational therapist's role with clients diagnosed with eating disorders, both anorexia nervosa and bulimia nervosa, has been described throughout the literature. However, the frames of reference and treatment approaches that occupational therapists implement have not been clearly established or validated. This paper outlines the symptomatology of anorexia nervosa and bulimia nervosa, and critically reviews the current literature concerning the frames of reference and treatment approaches used by occupational therapists when intervening with this population. The literature reviewed indicates that therapists are using a variety of frames of reference and treatment approaches. There appears to be an emphasis on the psychoanalytical and cognitive-behavioural frames of reference, although there is a lack of empirical evidence in regards to all frames of reference and treatment approaches. Reasons for the lack of current research with this population, and possible future areas of research are suggested. PMID:10462881

  5. Realization of ETRF2000 as a New Terrestrial Reference Frame in Republic of Serbia

    NASA Astrophysics Data System (ADS)

    Blagojevic, D.; Vasilic, V.

    2012-12-01

    The International Earth Rotation and Reference Systems Service (IERS) is a joint service of the International Association of Geodesy (IAG) and the International Astronomical Union (IAU), which provides the scientific community with the means for computing the transformation from the International Celestial Reference System (ICRS) to the International Terrestrial Reference System (ITRS). It further maintains the realizations of these systems by appropriate coordinate sets called "frames". The densification of terrestrial frame usually serves as official frame for positioning and navigation tasks within the territory of particular country. One of these densifications was recently performed in order to establish new reference frame for Republic of Serbia. The paper describes related activities resulting in ETRF2000 as a new Serbian terrestrial reference frame.

  6. Allocentric and egocentric reference frames in the processing of three-dimensional haptic space

    PubMed Central

    Kappers, Astrid M. L.

    2008-01-01

    The main goal of our study is to gain insight into the reference frames involved in three-dimensional haptic spatial processing. Previous research has shown that two-dimensional haptic spatial processing is prone to large systematic deviations. A weighted average model that identifies the origin of the systematic error patterns in the biasing influence of an egocentric reference frame on the allocentric reference frame was proposed as an explanation of the results. The basis of the egocentric reference frame was linked either to the hand or to the body. In the present study participants had to construct a field of parallel bars that could be oriented in three dimensions. First, systematic error patterns were found also in this three-dimensional haptic parallelity task. Second, among the different models tested for their accuracy in explaining the error patterns, the Hand-centered weighted average model proved to most closely resemble the data. A participant-specific weighting factor determined the biasing influence of the hand-centered egocentric reference frame. A shift from the allocentric towards the egocentric frame of reference of approximately 20% was observed. These results support the hypothesis that haptic spatial processing is a product of the interplay of diverse, but synergistically operating frames of reference. PMID:18368397

  7. Frames of Reference in Spatial Memories Acquired From Language

    ERIC Educational Resources Information Center

    Mou, Weimin; Zhang, Kan; McNamara, Timothy P.

    2004-01-01

    Four experiments examined reference systems in spatial memories acquired from language. Participants read narratives that located 4 objects in canonical (front, back, left, right) or noncanonical (left front, right front, left back, right back) positions around them. Participants' focus of attention was first set on each of the 4 objects, and then…

  8. Resolving Ambiguity from Competing Spatial Frames of Reference.

    ERIC Educational Resources Information Center

    Codd, Judith; Bialystok, Ellen

    A 2-part investigation was conducted to examine the ways children resolve the inherent ambiguity of spatial descriptions in terms of cues indicated by the three constituents of spatial propositions: predicate, referent, and relatum. In the first study, it was hypothesized that certain objects, structural markers, and definite articles accompanying…

  9. Reference Frames and Coordinate Transformations for Advanced Post-Newtonian Theory of the Lunar Motion

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Kopeikin, S.

    2009-05-01

    We construct a set of reference frames for description of the orbital and rotational motion of the Moon. We use a scalar-tensor theory of gravity depending on two parameters of the parametrized post-Newtonian (PPN) formalism and utilize the concepts of the relativistic resolutions on reference frames adopted by the International Astronomical Union in 2000. We assume that the solar system is isolated and space-time is asymptotically flat. The primary reference frame has the origin at the solar-system barycentric (SSB) frame and spatial axes are going to infinity. The SSB frame is not rotating with respect to distant quasars. The secondary reference frame has the origin at the Earth-Moon barycenter (EMB). The EMB frame is local with its spatial axes spreading out to the orbits of Venus and Mars and not rotating dynamically in the sense that both the Coriolis and centripetal forces acting on a free-falling test particle, moving with respect to the EMB frame, are excluded. Two other local frames, the geocentric (GRS) and the selenocentric (SRS) frames, have the origin at the center of mass of the Earth and Moon respectively. They are both introduced in order to connect the coordinate description of the lunar motion, observer on the Earth, and a retro-reflector on the Moon to the observable quantities which are the proper time and the laser-ranging distance. We solve the gravity field equations and find the metric tensor and the scalar field in all frames. We also derive the post-Newtonian coordinate transformations between the frames and analyze the residual gauge freedom imposed by the scalar-tensor theory on the coordinate transformations.

  10. Atomic References for Measuring Small Accelerations

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Yu, Nan

    2009-01-01

    Accelerometer systems that would combine the best features of both conventional (e.g., mechanical) accelerometers and atom interferometer accelerometers (AIAs) have been proposed. These systems are intended mainly for use in scientific research aboard spacecraft but may also be useful on Earth in special military, geological, and civil-engineering applications. Conventional accelerometers can be sensitive, can have high dynamic range, and can have high frequency response, but they lack accuracy and long-term stability. AIAs have low frequency response, but they offer high sensitivity, and high accuracy for measuring small accelerations. In a system according to the proposal, a conventional accelerometer would be used to perform short-term measurements of higher-frequency components of acceleration, while an AIA would be used to provide consistent calibration of, and correction of errors in, the measurements of the conventional accelerometer in the lower-frequency range over the long term. A brief description of an AIA is prerequisite to a meaningful description of a system according to the proposal. An AIA includes a retroreflector next to one end of a cell that contains a cold cloud of atoms in an ultrahigh vacuum. The atoms in the cloud are in free fall. The retroreflector is mounted on the object, the acceleration of which is to be measured. Raman laser beams are directed through the cell from the end opposite the retroreflector, then pass back through the cell after striking the retroreflector. The Raman laser beams together with the cold atoms measure the relative acceleration, through the readout of the AIA, between the cold atoms and the retroreflector.

  11. Full-Frame Reference for Test Photo of Moon

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This pair of views shows how little of the full image frame was taken up by the Moon in test images taken Sept. 8, 2005, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The Mars-bound camera imaged Earth's Moon from a distance of about 10 million kilometers (6 million miles) away -- 26 times the distance between Earth and the Moon -- as part of an activity to test and calibrate the camera. The images are very significant because they show that the Mars Reconnaissance Orbiter spacecraft and this camera can properly operate together to collect very high-resolution images of Mars. The target must move through the camera's telescope view in just the right direction and speed to acquire a proper image. The day's test images also demonstrate that the focus mechanism works properly with the telescope to produce sharp images.

    Out of the 20,000-pixel-by-6,000-pixel full frame, the Moon's diameter is about 340 pixels, if the full Moon could be seen. The illuminated crescent is about 60 pixels wide, and the resolution is about 10 kilometers (6 miles) per pixel. At Mars, the entire image region will be filled with high-resolution information.

    The Mars Reconnaissance Orbiter, launched on Aug. 12, 2005, is on course to reach Mars on March 10, 2006. After gradually adjusting the shape of its orbit for half a year, it will begin its primary science phase in November 2006. From the mission's planned science orbit about 300 kilometers (186 miles) above the surface of Mars, the high resolution camera will be able to discern features as small as one meter or yard across.

    The Mars Reconnaissance Orbiter mission is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate. Lockheed Martin Space Systems, Denver, prime contractor for the project, built the spacecraft. Ball Aerospace & Technologies Corp., Boulder, Colo

  12. Four-Year-Olds Use a Mixture of Spatial Reference Frames.

    PubMed

    Negen, James; Nardini, Marko

    2015-01-01

    Keeping track of unseen objects is an important spatial skill. In order to do this, people must situate the object in terms of different frames of reference, including body position (egocentric frame of reference), landmarks in the surrounding environment (extrinsic frame reference), or other attached features (intrinsic frame of reference). Nardini et al. hid a toy in one of 12 cups in front of children, turned the array when they were not looking, and then asked them to point to the cup with the toy. This forced children to use the intrinsic frame (information about the array of cups) to locate the hidden toy. Three-year-olds made systematic errors by using the wrong frame of reference, 4-year-olds were at chance, and only 5- and 6-year-olds were successful. Can we better understand the developmental change that takes place at four years? This paper uses a modelling approach to re-examine the data and distinguish three possible strategies that could lead to the previous results at four years: (1) Children were choosing cups randomly, (2) Children were pointing between the egocentric/extrinsic-cued location and the correct target, and (3) Children were pointing near the egocentric/extrinsic-cued location on some trials and near the target on the rest. Results heavily favor the last possibility: 4-year-olds were not just guessing or trying to combine the available frames of reference. They were using the intrinsic frame on some trials, but not doing so consistently. These insights suggest that accounts of improving spatial performance at 4 years need to explain why there is a mixture of responses. Further application of the selected model also suggests that children become both more reliant on the correct frame and more accurate with any chosen frame as they mature. PMID:26133990

  13. From Laboratory to Practice: Neglected Issues in Implementing Frame-of-Reference Rate-Training.

    ERIC Educational Resources Information Center

    Hauenstein, Neil M. A.; Foti, Roseanne J.

    1989-01-01

    Data collected at two law enforcement agencies were used to address three specific issues concerning frame-of-reference rater training: (1) prototype-anchored rating system; (2) sensitivity and threshold analyses to identify idiosyncratic raters; and (3) areas of performance where supervisors and subordinates were likely to disagree on frame of…

  14. Report of the panel on earth rotation and reference frames, section 7

    NASA Technical Reports Server (NTRS)

    Dickey, Jean O.; Dickman, Steven R.; Eubanks, Marshall T.; Feissel, Martine; Herring, Thomas A.; Mueller, Ivan I.; Rosen, Richard D.; Schutz, Robert E.; Wahr, John M.; Wilson, Charles R.

    1991-01-01

    Objectives and requirements for Earth rotation and reference frame studies in the 1990s are discussed. The objectives are to observe and understand interactions of air and water with the rotational dynamics of the Earth, the effects of the Earth's crust and mantle on the dynamics and excitation of Earth rotation variations over time scales of hours to centuries, and the effects of the Earth's core on the rotational dynamics and the excitation of Earth rotation variations over time scales of a year or longer. Another objective is to establish, refine and maintain terrestrial and celestrial reference frames. Requirements include improvements in observations and analysis, improvements in celestial and terrestrial reference frames and reference frame connections, and improved observations of crustal motion and mass redistribution on the Earth.

  15. Children's Location of a Point in Space: Effects of Dimensionality and Salience of Frame of Reference.

    ERIC Educational Resources Information Center

    Allen, Deborah A.; Hennessey, Steve, Jr.

    1980-01-01

    Examines the effects of dimensionality and salience of frame of reference on children's location of a point in space. Subjects were eight boys and eight girls from each of first, second and third grades. (CM)

  16. Reference frames, gauge transformations and gravitomagnetism in the post-Newtonian theory of the lunar motion

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Kopeikin, Sergei

    2010-01-01

    We construct a set of reference frames for description of the orbital and rotational motion of the Moon. We use a scalar-tensor theory of gravity depending on two parameters of the parametrized post-Newtonian (PPN) formalism and utilize the concepts of the relativistic resolutions on reference frames adopted by the International Astronomical Union in 2000. We assume that the solar system is isolated and space-time is asymptotically flat. The primary reference frame has the origin at the solar-system barycenter (SSB) and spatial axes are going to infinity. The SSB frame is not rotating with respect to distant quasars. The secondary reference frame has the origin at the Earth-Moon barycenter (EMB). The EMB frame is local with its spatial axes spreading out to the orbits of Venus and Mars and not rotating dynamically in the sense that both the Coriolis and centripetal forces acting on a free-falling test particle, moving with respect to the EMB frame, are excluded. Two other local frames, the geocentric (GRF) and the selenocentric (SRF) frames, have the origin at the center of mass of the Earth and Moon respectively. They are both introduced in order to connect the coordinate description of the lunar motion, observer on the Earth, and a retro-reflector on the Moon to the observable quantities which are the proper time and the laser-ranging distance. We solve the gravity field equations and find the metric tensor and the scalar field in all frames. We also derive the post-Newtonian coordinate transformations between the frames and analyze the residual gauge freedom of the solutions of the field equations. We discuss the gravitomagnetic effects in the barycentric equations of the motion of the Moon and argue that they are beyond the current accuracy of lunar laser ranging (LLR) observations.

  17. Establishing a celestial VLBI reference frame. 1: Searching for VLBI sources

    NASA Technical Reports Server (NTRS)

    Preston, R. A.; Morabito, D. D.; Williams, J. G.; Slade, M. A.; Harris, A. W.; Finley, S. G.; Skjerve, L. J.; Tanida, L.; Spitzmesser, D. J.; Johnson, B.

    1978-01-01

    The Deep Space Network is currently engaged in establishing a new high-accuracy VLBI celestial reference frame. The present status of the task of finding suitable celestial radio sources for constructing this reference frame is discussed. To date, 564 VLBI sources were detected, with 166 of these lying within 10 deg of the ecliptic plane. The variation of the sky distribution of these sources with source strength is examined.

  18. Looking for systematic error in scale from terrestrial reference frames derived from DORIS data

    NASA Technical Reports Server (NTRS)

    Willis, Pascal; Soudarin, L.; Lemoine, F. G.

    2005-01-01

    The long-term stability of the scale of Terrestrial Reference Frames is directly linked with station height determination and is critical for several scientific studies, such as global mean sea level rise or ocean circulation with consequences on global warming studies. In recent International Terrestrial Reference Frame solutions, the DORIS technique was not sonsidered able to provide any useful information on scale. We have analyzed three different DORIS time series of coordinates performed independently using different software packages.

  19. The task of the relativistic oscillator in a non-inertial frame of reference

    NASA Astrophysics Data System (ADS)

    Perepelkin, E. E.; Sadovnikov, B. I.; Inozemtseva, N. G.

    2016-09-01

    The relativistic theory is one of the most difficult parts of theoretical physics to understand by high school students and scientists alike. In this paper, the important aspects from this theory are considered. The case of the non-inertial reference frame in which the space–time interval was presented for the Lorentz-like transformations, and the condition by which the transition to the inertial reference frame takes place, is shown.

  20. Reference coordinate systems and frames: Concepts and realization

    NASA Astrophysics Data System (ADS)

    Mueller, Ivan I.

    1985-06-01

    Geodynamics has become the subject of intensive international research during the last decade, involving plate tectonics, both on the intra-plate and inter-plate scale, i.e., the study of crustal movements, and the study of earth rotation and of other dynamic phenomena such as the tides. Interrelated are efforts improving our knowledge of the gravity and magnetic fields of the earth. A common requirement for all these investigations is the necessity for a well-defined reference coordinate system (or systems) to which all relevant observations can be referred and in which theories or models for the dynamic behavior of the earth can be formulated. In view of the unprecedented progress in the ability of geodetic observational systems to measure crustal movements and the rotation of the earth, as well as in theory and model development, there is a great need for the theoretical definition, practical realization, and international acceptance of suitable coordinate system(s) to facilitate such work. This article deals with certain aspects of the establishment and maintenance of such a coordinate system.

  1. A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging.

    PubMed

    Zhu, Xinhui; Wang, Ren; Sun, Fuping; Wang, Jinling

    2016-01-01

    Crustal movement is one of the main factors influencing the change of the Earth system, especially in its vertical direction, which affects people's daily life through the frequent occurrence of earthquakes, geological disasters, and so on. In order to get a better study and application of the vertical crustal movement,as well as its changes, the foundation and prerequisite areto devise and establish its reference frame; especially, a unified global reference frame is required. Since SLR (satellite laser ranging) is one of the most accurate space techniques for monitoring geocentric motion and can directly measure the ground station's geocentric coordinates and velocities relative to the centre of the Earth's mass, we proposed to take the vertical velocity of the SLR technique in the ITRF2008 framework as the reference frame of vertical crustal motion, which we defined as the SLR vertical reference frame (SVRF). The systematic bias between other velocity fields and the SVRF was resolved by using the GPS (Global Positioning System) and VLBI (very long baseline interferometry) velocity observations, and the unity of other velocity fields and SVRF was realized,as well. The results show that it is feasible and suitable to take the SVRF as a reference frame, which has both geophysical meanings and geodetic observations, so we recommend taking the SLR vertical velocity under ITRF2008 as the global reference frame of vertical crustal movement. PMID:26867197

  2. Frames of reference that address the impact of physical environments on occupational performance.

    PubMed

    Whedon, Caren A.

    2000-01-01

    A frame of reference is the mechanism for linking theory to practice. It may be the most practical and important tool a professional uses. As the practice of occupational therapy has evolved, so has the basis of information, or theories, on which it is grounded. From the theories, models have been developed that typically view occupational performance as a transaction between the person, occupation and environment. Occupational therapy practitioners use many frames of reference. Not all of them address all areas of occupational performance identified within this overarching model. Often the area of the environment does not receive attention. To do their jobs thoroughly, occupational therapy practitioners need frames of reference for thinking about the environment. The purpose of this paper is to identify and explore frames of reference that may be useful to occupational therapy practitioners when they are taking into consideration the physical environment. Included are the following frames of reference: ergonomics, industrial hygiene, environmental psychology, accessibility and feng shui. A case study is presented to illustrate the unique perspective of each frame of reference. PMID:12441533

  3. A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging

    PubMed Central

    Zhu, Xinhui; Wang, Ren; Sun, Fuping; Wang, Jinling

    2016-01-01

    Crustal movement is one of the main factors influencing the change of the Earth system, especially in its vertical direction, which affects people’s daily life through the frequent occurrence of earthquakes, geological disasters, and so on. In order to get a better study and application of the vertical crustal movement, as well as its changes, the foundation and prerequisite areto devise and establish its reference frame; especially, a unified global reference frame is required. Since SLR (satellite laser ranging) is one of the most accurate space techniques for monitoring geocentric motion and can directly measure the ground station’s geocentric coordinates and velocities relative to the centre of the Earth’s mass, we proposed to take the vertical velocity of the SLR technique in the ITRF2008 framework as the reference frame of vertical crustal motion, which we defined as the SLR vertical reference frame (SVRF). The systematic bias between other velocity fields and the SVRF was resolved by using the GPS (Global Positioning System) and VLBI (very long baseline interferometry) velocity observations, and the unity of other velocity fields and SVRF was realized, as well. The results show that it is feasible and suitable to take the SVRF as a reference frame, which has both geophysical meanings and geodetic observations, so we recommend taking the SLR vertical velocity under ITRF2008 as the global reference frame of vertical crustal movement. PMID:26867197

  4. The role of perspective taking in how children connect reference frames when explaining astronomical phenomena

    NASA Astrophysics Data System (ADS)

    Plummer, Julia D.; Bower, Corinne A.; Liben, Lynn S.

    2016-02-01

    This study investigates the role of perspective-taking skills in how children explain spatially complex astronomical phenomena. Explaining many astronomical phenomena, especially those studied in elementary and middle school, requires shifting between an Earth-based description of the phenomena and a space-based reference frame. We studied 7- to 9-year-old children (N = 15) to (a) develop a method for capturing how children make connections between reference frames and to (b) explore connections between perspective-taking skill and the nature of children's explanations. Children's explanations for the apparent motion of the Sun and stars and for seasonal changes in constellations were coded for accuracy of explanation, connection between frames of reference, and use of gesture. Children with higher spatial perspective-taking skills made more explicit connections between reference frames and used certain gesture-types more frequently, although this pattern was evident for only some phenomena. Findings suggest that children - particularly those with lower perspective-taking skills - may need additional support in learning to explicitly connect reference frames in astronomy. Understanding spatial thinking among children who successfully made explicit connections between reference frames in their explanations could be a starting point for future instruction in this domain.

  5. Numerical methods for instability mitigation in the modeling of laser wakefield accelerators in a Lorentz-boosted frame

    SciTech Connect

    Vay, J.-L.; Geddes, C.G.R.; Cormier-Michel, E.; Grote, D.P.

    2011-07-01

    Modeling of laser-plasma wakefield accelerators in an optimal frame of reference has been shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups required mitigation of a high-frequency instability that otherwise limits effectiveness. In this paper, methods are presented which mitigated the observed instability, including an electromagnetic solver with tunable coefficients, its extension to accommodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is observed that choosing the frame of the wake as the frame of reference allows for higher levels of filtering or damping than is possible in other frames for the same accuracy. Detailed testing also revealed the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion. A combination of the techniques presented in this paper prove to be very efficient at controlling the instability, allowing for efficient direct modeling of 10 GeV class laser plasma accelerator stages. The methods developed in this paper may have broader application, to other Lorentz-boosted simulations and Particle-In-Cell simulations in general.

  6. Accurate Realization of GPS Vertical Global Reference Frame

    NASA Technical Reports Server (NTRS)

    Elosegui, Pedro

    2004-01-01

    The few millimeter per year level accuracy of radial global velocity estimates with the Global Positioning System (GPS) is at least an order of magnitude poorer than the accuracy of horizontal global motions. An improvement in the accuracy of radial global velocities would have a very positive impact on a number of geophysical studies of current general interest such as global sea-level and climate change, coastal hazards, glacial isostatic adjustment, atmospheric and oceanic loading, glaciology and ice mass variability, tectonic deformation and volcanic inflation, and geoid variability. The goal of this project is to improve our current understanding of GPS error sources associated with estimates of radial velocities at global scales. GPS error sources relevant to this project can be classified in two broad categories: (1) those related to the analysis of the GPS phase observable, and (2) those related to the combination of the positions and velocities of a set of globally distributed stations as determined from the analysis of GPS data important aspect in the first category include the effect on vertical rate estimates due to standard analysis choices, such as orbit modeling, network geometry, ambiguity resolution, as well as errors in models (or simply the lack of models) for clocks, multipath, phase-center variations, atmosphere, and solid-Earth tides. The second category includes the possible methods of combining and defining terrestrial reference flames for determining vertical velocities in a global scale. The latter has been the subject of our research activities during this reporting period.

  7. Visual Experience Determines the Use of External Reference Frames in Joint Action Control

    PubMed Central

    Dolk, Thomas; Liepelt, Roman; Prinz, Wolfgang; Fiehler, Katja

    2013-01-01

    Vision plays a crucial role in human interaction by facilitating the coordination of one's own actions with those of others in space and time. While previous findings have demonstrated that vision determines the default use of reference frames, little is known about the role of visual experience in coding action-space during joint action. Here, we tested if and how visual experience influences the use of reference frames in joint action control. Dyads of congenitally-blind, blindfolded-sighted, and seeing individuals took part in an auditory version of the social Simon task, which required each participant to respond to one of two sounds presented to the left or right of both participants. To disentangle the contribution of external—agent-based and response-based—reference frames during joint action, participants performed the task with their respective response (right) hands uncrossed or crossed over one another. Although the location of the auditory stimulus was completely task-irrelevant, participants responded overall faster when the stimulus location spatially corresponded to the required response side than when they were spatially non-corresponding: a phenomenon known as the social Simon effect (SSE). In sighted participants, the SSE occurred irrespective of whether hands were crossed or uncrossed, suggesting the use of external, response-based reference frames. Congenitally-blind participants also showed an SSE, but only with uncrossed hands. We argue that congenitally-blind people use both agent-based and response-based reference frames resulting in conflicting spatial information when hands are crossed and, thus, canceling out the SSE. These results imply that joint action control functions on the basis of external reference frames independent of the presence or (transient/permanent) absence of vision. However, the type of external reference frames used for organizing motor control in joint action seems to be determined by visual experience. PMID

  8. Flexible Reference Frames for Grasp Planning in Human Parietofrontal Cortex(1,2,3).

    PubMed

    Leoné, Frank T M; Monaco, Simona; Henriques, Denise Y P; Toni, Ivan; Medendorp, W Pieter

    2015-01-01

    Reaching to a location in space is supported by a cortical network that operates in a variety of reference frames. Computational models and recent fMRI evidence suggest that this diversity originates from neuronal populations dynamically shifting between reference frames as a function of task demands and sensory modality. In this human fMRI study, we extend this framework to nonmanipulative grasping movements, an action that depends on multiple properties of a target, not only its spatial location. By presenting targets visually or somaesthetically, and by manipulating gaze direction, we investigate how information about a target is encoded in gaze- and body-centered reference frames in dorsomedial and dorsolateral grasping-related circuits. Data were analyzed using a novel multivariate approach that combines classification and cross-classification measures to explicitly aggregate evidence in favor of and against the presence of gaze- and body-centered reference frames. We used this approach to determine whether reference frames are differentially recruited depending on the availability of sensory information, and where in the cortical networks there is common coding across modalities. Only in the left anterior intraparietal sulcus (aIPS) was coding of the grasping target modality dependent: predominantly gaze-centered for visual targets and body-centered for somaesthetic targets. Left superior parieto-occipital cortex consistently coded targets for grasping in a gaze-centered reference frame. Left anterior precuneus and premotor areas operated in a modality-independent, body-centered frame. These findings reveal how dorsolateral grasping area aIPS could play a role in the transition between modality-independent gaze-centered spatial maps and body-centered motor areas. PMID:26464989

  9. Interaction between allocentric and egocentric reference frames in deaf and hearing populations.

    PubMed

    Zhang, Ming; Tan, Xinyi; Shen, Lu; Wang, Aijun; Geng, Shuang; Chen, Qi

    2014-02-01

    Spatial position of an object can be represented in the human brain based on two types of reference frames: allocentric and egocentric. The perception/action hypothesis of the ventral/dorsal visual stream proposed that allocentric reference frame codes object positions relative to another object/background subserving conscious perception of the external world while egocentric reference frame codes object positions relative to the observer's body/body parts subserving goal-directed actions towards the objects. In three experiments of the present study, by asking congenitally deaf participants and hearing controls to perform allocentric and egocentric judgment tasks on the same stimulus set and by using the spatial congruency effect between allocentric and egocentric positions of the same target object to indicate the extent of influences between the two frames, we aimed to investigate whether the two frames and the potential interaction between them are altered after early deafness. Our results suggested that deaf participants' responses were significantly slower in the egocentric tasks as compared to hearing controls while the two groups showed comparable task performance in the allocentric tasks, indicating that egocentric reference frame was impaired after early deafness. Moreover, the pattern of interaction between the two frames was different between deaf and hearing groups: irrelevant egocentric positions caused more interference to allocentric processing than vice versa in the hearing group while the two frames caused equivalent interference to each other in the deaf group. Further control experiments suggested that the above effects were not caused by the impaired sense of balance in the congenitally deaf participants (via open-loop pointing test), and was independent of whether the speed of allocentric and egocentric processing was equivalent or not in the hearing group. PMID:24361477

  10. Effects of adopting new precession, nutation and equinox corrections on the terrestrial reference frame

    NASA Technical Reports Server (NTRS)

    Zhu, S. Y.; Mueller, I. I.

    1982-01-01

    The effect of adopting definitive precession and equinox corrections on the terrestrial reference frame was investigated. It is noted that the effect on polar motion is a diurnal periodic term with an amplitude increasing linearly in time whole on UT1 it is a linear term: general principles are given to determine the effects of small rotations of the frame of a conventional inertial reference system (CIS) on the frame of the conventional terrestrial reference system (CTS); seven CTS options are presented, one of which is necessary to accommodate such rotation. Accommodating possible future changes in the astronomical nutation is discussed. The effects of differences which may exist between the various CTS's and CIS's on Earth rotation parameters (ERP) and how these differences can be determined are examined. It is shown that the CTS differences can be determined from observations made at the same site. The CIS differences by comparing the ERP's are determined by the different techniques during the same time period.

  11. A spatial reference frame model of Beijing based on spatial cognitive experiment

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Zhang, Jing; Liu, Yu

    2006-10-01

    Orientation relation in the spatial relation is very important in GIS. People can obtain orientation information by making use of map reading and the cognition of the surrounding environment, and then create the spatial reference frame. City is a kind of special spatial environment, a person with life experiences has some spatial knowledge about the city where he or she lives in. Based on the spatial knowledge of the city environment, people can position, navigate and understand the meaning embodied in the environment correctly. Beijing as a real geographic space, its layout is very special and can form a kind of new spatial reference frame. Based on the characteristics of the layout of Beijing city, this paper will introduce a new spatial reference frame of Beijing and use two psychological experiments to validate its cognitive plausibility.

  12. Influences of indigenous language on spatial frames of reference in Aboriginal English

    NASA Astrophysics Data System (ADS)

    Edmonds-Wathen, Cris

    2014-06-01

    The Aboriginal English spoken by Indigenous children in remote communities in the Northern Territory of Australia is influenced by the home languages spoken by themselves and their families. This affects uses of spatial terms used in mathematics such as `in front' and `behind.' Speakers of the endangered Indigenous Australian language Iwaidja use the intrinsic frame of reference in contexts where speakers of Standard Australian English use the relative frame of reference. Children speaking Aboriginal English show patterns of use that parallel the Iwaidja contexts. This paper presents detailed examples of spatial descriptions in Iwaidja and Aboriginal English that demonstrate the parallel patterns of use. The data comes from a study that investigated how an understanding of spatial frame of reference in Iwaidja could assist teaching mathematics to Indigenous language-speaking students. Implications for teaching mathematics are explored for teachers without previous experience in a remote Indigenous community.

  13. Terrestrial and Celestial Reference Frame Realization with Highly Elliptical Orbit - The ESA STE-QUEST Mission

    NASA Astrophysics Data System (ADS)

    Svehla, Drazen; Rothacher, Markus; Hugentobler, Urs; Nothnagel, Axel; Willis, Pascal; Biancale, Richard; Ziebart, Marek; Appleby, Graham; Schuh, Harald; Ádám, József; Iess, Luciano; Cacciapuoti, Luigi

    2014-05-01

    The Space-Time Explorer and QUantum Equivalence Principle Space Test (STE-QUEST) is a Medium Class fundamental physics mission pre-selected for the M3 slot of the ESA Cosmic Vision Programme to test Einstein's Equivalence Principle using atom interferometry and the general and special theory of relativity. Two secondary mission objectives are related to space geodesy: terrestrial and celestial reference frame of the Earth and relativistic geodesy aiming at the realization of unified reference frame for positioning, time, and temporal gravity. The highly elliptical orbit of the STE-QUEST satellite can be used for terrestrial reference frame realization by means of on board GNSS, SLR and VLBI radio source (STE-QUEST metrology link tracked by VLBI antenna - compatible with VLBI2010). By upgrading the on board GNSS receiver for DORIS tracking, the STE-QUEST mission will be similar to the GRASP mission proposal from JPL. Due to the highly elliptical orbit of STE-QUEST (apogee

  14. Experimental demonstration of genuine multipartite quantum nonlocality without shared reference frames

    NASA Astrophysics Data System (ADS)

    Wang, Zhao; Zhang, Chao; Huang, Yun-Feng; Liu, Bi-Heng; Li, Chuan-Feng; Guo, Guang-Can

    2016-03-01

    Multipartite quantum nonlocality is an important diagnostic tool and resource for both researches in fundamental quantum mechanics and applications in quantum information protocols. Shared reference frames among all parties are usually required for experimentally observing quantum nonlocality, which is not possible in many circumstances. Previous results have shown violations of bipartite Bell inequalities with approaching unit probability, without shared reference frames. Here we experimentally demonstrate genuine multipartite quantum nonlocality without shared reference frames, using the Svetlichny inequality. A significant violation probability of 0.58 is observed with a high-fidelity three-photon Greenberger-Horne-Zeilinger state. Furthermore, when there is one shared axis among all the parties, which is the usual case in fiber-optic or earth-satellite links, the experimental results demonstrate the genuine three-partite nonlocality with certainty. Our experiment will be helpful for applications in multipartite quantum communication protocols.

  15. On the dynamics of Armbruster Guckenheimer Kim galactic potential in a rotating reference frame

    NASA Astrophysics Data System (ADS)

    Elmandouh, A. A.

    2016-06-01

    In this article, we are interested in studying some dynamics aspects for the Armbruster Guckenheimer Kim galactic potential in a rotating reference frame. We introduce a non-integrability condition for this problem using Painlevé analysis. The equilibrium positions are given and their stability is studied. Furthermore, we prove the force resulting from the rotation of the reference frame can be used to stabilize the unstable maximum equilibrium positions. The periodic solutions near the equilibrium positions are constructed by applying Lyapunov method. The permitted region of motion is determined.

  16. A First Look at Terrestrial Reference Frame ITRF2013G Computed with Gipsy Software

    NASA Astrophysics Data System (ADS)

    Heflin, M. B.; Abbondanza, C.; Chin, M.; Gross, R. S.; Parker, J. W.; Wu, X.

    2014-12-01

    The ITRF2013 data set includes new sinex files from each of the four techniques DORIS, GPS, SLR, and VLBI. These files benefit from modeling upgrades implemented for reprocessing. In addition, five extra years of measurements have been acquired since 2008. We are developing GIPSY software tools to reduce the time and labor necessary to build the global reference frame. Automation is used to remove outliers and detect breaks before combining the files from each technique. All four techniques and ties are then combined to build the reference frame. We are specifically interested in the simplest configurations of sites and ties which can deliver long term accuracy at a sustainable cost.

  17. Interpretation versus Reference Framing: Assimilation and Contrast Effects in the Organizational Domain.

    PubMed

    Stapel; Koomen

    1998-11-01

    We examined conditions under which contextually activated information affects strategic decision-making and found that the subjective framing of organizational issues may be affected by variables other than semantic manipulation. Context information may be used as an interpretation frame (and lead to assimilation) or as a reference frame (and lead to contrast). Whether context information instigates assimilative interpretation or contrastive comparison processes may depend on the level of categorical context-target similarity. This is demonstrated in three experiments in which participants read an unambiguous business threat or opportunity scenario prior to judging an ambiguous, strategic issue. Findings are discussed in the light of previous judgment and decision-making studies of framing and context effects. Copyright 1998 Academic Press. PMID:9831519

  18. First Report of the Stable North America Reference Frame (SNARF) Working Group

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Bennett, R. A.; Calais, E.; Herring, T. A.; Larson, K. M.; Miller, M. M.; Sella, G.; Snay, R. A.; Tamisiea, M. E.

    2004-05-01

    We report on the first SNARF Workshop funded by NSF EarthScope, held on Jan 27, 2004. The initial SNARF Working Group membership was approved by the UNAVCO Board and is charged with producing a standard reference frame (for studies in North America) and specifying standard procedures to realize such a frame to meet the needs of EarthScope and the UNAVCO community. SNARF is an official IAG working group under the North America Reference Frame (NAREF) sub-commission. There is also a public service element to these activities in that one objective is for SNARF to become part of the definition of the legal reference frame used in the USA and Canada (NAD83), a natural spin-off demanded by society's increasingly sophisticated needs following on the heels of scientific progress. Through the first workshop, the SNARF WG has already begun to address the pressing needs for a North America-fixed reference frame that is stable at the sub-millimeter level, and what is involved in defining a frame with such stability. Velocity solutions from GPS networks covering the North America-Pacific plate boundary (including the Plate Boundary Observatory under construction) are most naturally expressed with respect to the stable interiors of either the North America or Pacific plates. As well as providing a common frame by which to compare results from different analysis groups, such a system makes it easier to interpret the data in terms of where the total budget of relative plate motion is accomodated, and how deep plate boundary dynamics penetrate into the plate interior. Defining a stable frame at the sub-millimeter level requires adequate characterization of kinematics at that level across a sufficiently broad expanse of what may be termed the "plate interior," which deforms due to GIA and other mantle processes, coupled with lithospheric heterogeneity. A dynamically defined velocity datum (as opposed to a purely kinematic choice) is preferable to add interpretive value to site

  19. Maintenance of the Geodetic Reference Frame in the Global Positioning System

    NASA Astrophysics Data System (ADS)

    Oria, A.; Brodsky, B. L.; Labrecque, J.; Miller, J. J.; Moreau, M.; Pearlman, M.; Nelson, R.

    2007-12-01

    In the Global Positioning System (GPS) measurements of the satellite coordinates and the underlying World Geodetic System 1984 (WGS 84) reference frame are derived from observables such as pseudorandom noise (PRN) signals, and carrier phase, which are referenced to on-board atomic clocks. Systematic errors exist in both the estimated satellite coordinates and the reference frame. The reference frame utilizes external inputs in the form of International Terrestrial Reference Frame (ITRF) coordinates and constrains the results to be compatible with the ITRF coordinates for a set of global reference stations. The ITRF is, in turn, obtained from the combined analysis of GPS, Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) data. The current realization of the reference frame could be described as circular in that an independent method of external verification is currently not available. To ensure the continued successful operation of the GPS it is necessary to have the capability of analyzing systematic errors by an independent means from current radiometric observables and data from foreign sources. In practice, accuracy of the standards used for measurement should be better than the expected, required operational measurement accuracy by a factor of ten to ensure that the desired requirement is met. Currently, the accuracy of both the ITRF and the WGS 84 is estimated to be on the order of 1 to 2 parts per billion, leading to expected drifts of 0.6 to 1.2 cm per year. The experience of the last three decades has indicated an approximate improvement by a factor of ten per decade. Therefore, while current accuracy of the ITRF and WGS 84 reference frames marginally meets civilian and military requirements, it is very likely that, within the lifetime of GPS III, the accuracy of the reference frames will be unable to meet the anticipated requirements. This report examines

  20. Does Changing the Reference Frame Affect Infant Categorization of the Spatial Relation BETWEEN?

    ERIC Educational Resources Information Center

    Quinn, Paul C.; Doran, Matthew M.; Papafragou, Anna

    2011-01-01

    Past research has shown that variation in the target objects depicting a given spatial relation disrupts the formation of a category representation for that relation. In the current research, we asked whether changing the orientation of the referent frame depicting the spatial relation would also disrupt the formation of a category representation…

  1. Operationalization of a Frame of Reference for Studying Organizational Culture in Middle Schools.

    ERIC Educational Resources Information Center

    Daniel, Larry G.

    A frame of reference for studying culture in middle schools was developed. Items for the Middle School Description Survey (MSDS), which was designed to test elements of the ideal middle school culture, were created based on middle school advocacy literature. The items were conceptually categorized according to E. H. Schein's (1985) cultural…

  2. Sometimes Losing Your Self in Space: Children's and Adults' Spontaneous Use of Multiple Spatial Reference Frames

    ERIC Educational Resources Information Center

    Surtees, Andrew D. R.; Noordzij, Matthijs L.; Apperly, Ian A.

    2012-01-01

    Two experiments tested 6- to 11-year-old children's and college students' use of different frames of reference when making judgments about descriptions of social and nonsocial scenes. In Experiment 1, when social and nonsocial scenes were mixed, both children and students (N = 144) showed spontaneous sensitivity to the intrinsic and the relative…

  3. Status Consistency of the Projected Frames of Reference of Rural Males.

    ERIC Educational Resources Information Center

    Pelham, John T.

    The specific research objective of this paper was to make racial comparisons on the consistency dimension of the projected frames of reference of adolescent males from the rural South. Data were obtained from a population of high school sophomores in 3 Texas and 2 Georgia counties. Complete data were available for 223 white and 192 Negro males.…

  4. Differential Developmental Trajectories for Egocentric, Environmental and Intrinsic Frames of Reference in Spatial Memory

    ERIC Educational Resources Information Center

    Nardini, Marko; Burgess, Neil; Breckenridge, Kate; Atkinson, Janette

    2006-01-01

    We studied the development of spatial frames of reference in children aged 3-6 years, who retrieved hidden toys from an array of identical containers bordered by landmarks under four conditions. By moving the child and/or the array between presentation and test, we varied the consistency of the hidden toy with (1) the body, and (2) the testing…

  5. The Second Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry

    NASA Astrophysics Data System (ADS)

    Fey, A. L.; Gordon, D.; Jacobs, C. S.; Ma, C.; Gaume, R. A.; Arias, E. F.; Bianco, G.; Boboltz, D. A.; Böckmann, S.; Bolotin, S.; Charlot, P.; Collioud, A.; Engelhardt, G.; Gipson, J.; Gontier, A.-M.; Heinkelmann, R.; Kurdubov, S.; Lambert, S.; Lytvyn, S.; MacMillan, D. S.; Malkin, Z.; Nothnagel, A.; Ojha, R.; Skurikhina, E.; Sokolova, J.; Souchay, J.; Sovers, O. J.; Tesmer, V.; Titov, O.; Wang, G.; Zharov, V.

    2015-08-01

    We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. ICRF2 contains precise positions of 3414 compact radio astronomical objects and has a positional noise floor of ∼40 μas and a directional stability of the frame axes of ∼10 μas. A set of 295 new “defining” sources was selected on the basis of positional stability and the lack of extensive intrinsic source structure. The positional stability of these 295 defining sources and their more uniform sky distribution eliminates the two greatest weaknesses of the first realization of the International Celestial Reference Frame (ICRF1). Alignment of ICRF2 with the International Celestial Reference System was made using 138 positionally stable sources common to both ICRF2 and ICRF1. The resulting ICRF2 was adopted by the International Astronomical Union as the new fundamental celestial reference frame, replacing ICRF1 as of 2010 January 1.

  6. The Effects of Frame of Reference on Responses to Questions about Sexual Assault Victimization and Perpetration

    ERIC Educational Resources Information Center

    Abbey, Antonia; Parkhill, Michele R.; Koss, Mary P.

    2005-01-01

    Self-reports of sexual assault are affected by a variety of factors including the number of questions, question phrasing, and context. Participants (307 women, 166 men) were randomly assigned to one of two forms of a questionnaire. One form had the tactics used to obtain forced sex as the initial frame of reference, whereas the other form had the…

  7. Aligning Body and World: Stable Reference Frames Improve Young Children's Search for Hidden Objects

    ERIC Educational Resources Information Center

    Perry, Lynn K.; Samuelson, Larissa K.; Spencer, John P.

    2009-01-01

    This study investigated how young children's increasingly flexible use of spatial reference frames enables accurate search for hidden objects by using a task that 3-year-olds have been shown to perform with great accuracy and 2-year-olds have been shown to perform inaccurately. Children watched as an object was rolled down a ramp, behind a panel…

  8. Spatial Mental Representations Derived from Survey and Route Descriptions: When Individuals Prefer Extrinsic Frame of Reference

    ERIC Educational Resources Information Center

    Meneghetti, Chiara; Pazzaglia, Francesca; De Beni, Rossana

    2011-01-01

    The present research investigates the role of individual differences in preference for adopting extrinsic frame of reference (EFR) in ability to represent mentally spatial information learned through survey and route descriptions. A sample of 191 participants (100 females and 91 males) was categorized as four groups with high (H-EFR), medium-high…

  9. Human Information and Argument Retrieval: Language Correlates and Attitudinal Frame of Reference; Rhetorical Invention: Attitudinally Bound.

    ERIC Educational Resources Information Center

    Skirde, Edward G.

    An act of rhetoric has attitudinal significance; that is, a part of rhetoric involves persuasion. Further, attitudinal frames of reference relate to and result from the retrieval of stored information (memory, etc.) and the generation of arguments. By studying the relative strength that subjects use in arguing an "issue-concept," the subjects'…

  10. The Reciprocal Internal/External Frame of Reference Model Using Grades and Test Scores

    ERIC Educational Resources Information Center

    Möller, Jens; Zimmermann, Friederike; Köller, Olaf

    2014-01-01

    Background: The reciprocal I/E model (RI/EM) combines the internal/external frame of reference model (I/EM) with the reciprocal effects model (REM). The RI/EM extends the I/EM longitudinally and the REM across domains. The model predicts that, within domains, mathematics and verbal achievement (VACH) and academic self-concept have positive effects…

  11. The NKG2008 GPS campaign - final transformation results and a new common Nordic reference frame

    NASA Astrophysics Data System (ADS)

    Häkli, P.; Lidberg, M.; Jivall, L.; Nørbech, T.; Tangen, O.; Weber, M.; Pihlak, P.; Aleksejenko, I.; Paršeliunas, E.

    2016-03-01

    The NKG 2008 GPS campaign was carried out in September 28 - October 4, 2008. The purpose was to establish a common reference frame in the Nordic- Baltic-Arctic region, and to improve and update the transformations from the latest global ITRF reference frame to the national ETRS89 realizations of the Nordic/Baltic countries. Postglacial rebound in the Fennoscandian area causes intraplate deformations up to about 10 mm/yr to the Eurasian tectonic plate which need to be taken into account in order to reach centimetre level accuracies in the transformations. We discuss some possible alternatives and present the most applicable transformation strategy. The selected transformation utilizes the de facto transformation recommended by the EUREF but includes additional intraplate corrections and a new common Nordic-Baltic reference frame to serve the requirements of the Nordic/Baltic countries. To correct for the intraplate deformations in the Nordic-Baltic areawe have used the commonNordic deformation model NKG RF03vel. The new common reference frame, NKG ETRF00, was aligned to ETRF2000 at epoch 2000.0 in order to be close to the national ETRS89 realizations and to coincide with the land uplift epoch of the national height systems. We present here the realization of the NKG ETRF00 and transformation formulae together with the parameters to transform from global ITRF coordinates to Nordic/Baltic realizations of the ETRS89.

  12. On multi-timescale variability of temperature in China in modulated annual cycle reference frame

    NASA Astrophysics Data System (ADS)

    Qian, Cheng; Wu, Zhaohua; Fu, Congbin; Zhou, Tianjun

    2010-09-01

    The traditional anomaly (TA) reference frame and its corresponding anomaly for a given data span changes with the extension of data length. In this study, the modulated annual cycle (MAC), instead of the widely used climatological mean annual cycle, is used as an alternative reference frame for computing climate anomalies to study the multi-timescale variability of surface air temperature (SAT) in China based on homogenized daily data from 1952 to 2004. The Ensemble Empirical Mode Decomposition (EEMD) method is used to separate daily SAT into a high frequency component, a MAC component, an interannual component, and a decadal-to-trend component. The results show that the EEMD method can reflect historical events reasonably well, indicating its adaptive and temporally local characteristics. It is shown that MAC is a temporally local reference frame and will not be altered over a particular time span by an extension of data length, thereby making it easier for physical interpretation. In the MAC reference frame, the low frequency component is found more suitable for studying the interannual to longer timescale variability (ILV) than a 13-month window running mean, which does not exclude the annual cycle. It is also better than other traditional versions (annual or summer or winter mean) of ILV, which contains a portion of the annual cycle. The analysis reveals that the variability of the annual cycle could be as large as the magnitude of interannual variability. The possible physical causes of different timescale variability of SAT in China are further discussed.

  13. The Role of Perspective Taking in How Children Connect Reference Frames When Explaining Astronomical Phenomena

    ERIC Educational Resources Information Center

    Plummer, Julia D.; Bower, Corinne A.; Liben, Lynn S.

    2016-01-01

    This study investigates the role of perspective-taking skills in how children explain spatially complex astronomical phenomena. Explaining many astronomical phenomena, especially those studied in elementary and middle school, requires shifting between an Earth-based description of the phenomena and a space-based reference frame. We studied 7- to…

  14. Layout Geometry in the Selection of Intrinsic Frames of Reference from Multiple Viewpoints

    ERIC Educational Resources Information Center

    Mou, Weimin; Zhao, Mintao; McNamara, Timothy P.

    2007-01-01

    Four experiments investigated the roles of layout geometry in the selection of intrinsic frames of reference in spatial memory. Participants learned the locations of objects in a room from 2 or 3 viewing perspectives. One view corresponded to the axis of bilateral symmetry of the layout, and the other view(s) was (were) nonorthogonal to the axis…

  15. Recovery of a geocentric reference frame using the present-day GPS system

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1990-01-01

    A geocentric reference frame adopts the center of mass of the earth as the origin of the coordinate axes. The center of mass of the earth is the natural and unambiguous origin of a geocentric satellite dynamical system. But in practice a kinematically obtained terrestrial reference frame may assume an origin other than the geocenter. The establishment of a geocentric reference frame, to which all relevant observations and results can be referred and in which geodynamic theories or models for the dynamic behavior of earth can be formulated, requires the ability to accurately recover a given coordinate frame origin offset from the geocenter. GPS measurements, because of their abundance and broad distribution, provide a powerful tool to obtain this origin offset in a short period of time. Two effective strategies have been devised. Data from the First Central And South America (Casa Uno) geodynamics experiment has been studied, in order to demonstrate the ability of recovering the geocenter location with present day GPS satellites and receivers.

  16. Myths, Misconceptions, and Misunderstandings: A Different Spin on Coriolis--Applying Frame of Reference

    ERIC Educational Resources Information Center

    DiSpezio, Michael A.

    2011-01-01

    This article addresses misconceptions surrounding the Coriolis force and describes how it should be presented as a function within inertial and noninertial frames of reference. Not only does this demonstrate the nature of science as it strives to best interpret the natural world (and presents alternative explanations), but it offers a rich…

  17. Ipsilateral wrist-ankle movements in the sagittal plane encoded in extrinsic reference frame.

    PubMed

    Muraoka, Tetsuro; Ishida, Yuki; Obu, Takashi; Crawshaw, Larry; Kanosue, Kazuyuki

    2013-04-01

    When performing oscillatory movements of two joints in the sagittal plane, there is a directional constraint for performing such movements. Previous studies could not distinguish whether the directional constraint reflected movement direction encoded in the extrinsic (outside the body) reference frame or in the intrinsic (the participants' torso/head) reference frame since participants performed coordinated movements in a sitting position where the torso/head was stationary relative to the external world. In order to discern the reference frame in the present study, participants performed paced oscillatory movements of the ipsilateral wrist and ankle in the sagittal plane in a standing position so that the torso/head moved relative to the external world. The coordinated movements were performed in one of two modes of coordination, moving the hand upward concomitant with either ankle plantarflexion or ankle dorsiflexion. The same directional mode relative to extrinsic space was more stable and accurate as compared with the opposite directional mode. When forearm position was changed from the pronated position to the supinated position, similar results were obtained, indicating that the results were independent of a particular coupling of muscles. These findings suggest that the directional constraint on ipsilateral joints movements in the sagittal plane reflects movement direction encoded in the extrinsic reference frame. PMID:23507257

  18. Location memory biases reveal the challenges of coordinating visual and kinesthetic reference frames

    PubMed Central

    Simmering, Vanessa R.; Peterson, Clayton; Darling, Warren; Spencer, John P.

    2008-01-01

    Five experiments explored the influence of visual and kinesthetic/proprioceptive reference frames on location memory. Experiments 1 and 2 compared visual and kinesthetic reference frames in a memory task using visually-specified locations and a visually-guided response. When the environment was visible, results replicated previous findings of biases away from the midline symmetry axis of the task space, with stability for targets aligned with this axis. When the environment was not visible, results showed some evidence of bias away from a kinesthetically-specified midline (trunk anterior–posterior [a–p] axis), but there was little evidence of stability when targets were aligned with body midline. This lack of stability may reflect the challenges of coordinating visual and kinesthetic information in the absence of an environmental reference frame. Thus, Experiments 3–5 examined kinesthetic guidance of hand movement to kinesthetically-defined targets. Performance in these experiments was generally accurate with no evidence of consistent biases away from the trunk a–p axis. We discuss these results in the context of the challenges of coordinating reference frames within versus between multiple sensori-motor systems. PMID:17703284

  19. An experimental Kalman filter approach to the International Terrestrial Reference Frame realization

    NASA Astrophysics Data System (ADS)

    Wu, X.; Abbondanza, C.; Altamimi, Z.; Chin, T.; Gross, R.; Heflin, M.

    2012-04-01

    To monitor global geophysical changes with realistic uncertainties using millimeter-precision geodesy, it is essential to define, realize and maintain the International Terrestrial Reference Frame (ITRF) consistently and accurately. Precise determinations of geocentric site positions and motions, satellite orbits, geocenter motion, Earth orientation and its variations, mean sea level rise, and polar ice mass changes at various time scales all depend critically on the accuracy and stability of the ITRF. By definition, the ITRF is a secular frame based on a linear model and consisting of mean epoch positions and velocities for a global set of stations. It is needed to serve as a standard reference frame in which geophysical results can be formulated and compared. The neglected up-to centimeter-level non-linear station motion can bias the linear station velocities, which can be significantly compounded for stations with short time-span. Here, we conceptually define an experimental reference frame with its origin at the nearly instantaneous center-of-mass (CM) of the total Earth system, by specifying the frame and combining different technique data weekly (daily for Earth orientation parameters). For co-located sites, available local ties are applied only once; but site motions are usually constrained to be the same. A Kalman filter and smoother algorithm has been developed and coupled to the ITRF/CATREF software to solve for geocentric coordinate time series, as well as a model of secular, periodical and stochastic motion components. Preliminary results using linear and linear plus sinusoidal motion models without stochastic components compare very favorably with the ITRF2005 solution. With only a subset of the ITRF2005 input data time series from 1996 onward, we have obtained reference frame solutions that differ from ITRF2005 in origin by 0.6 mm and 0.3 mm/yr. Filtering strategies and time series results will also be presented.

  20. Common Observables of Trench Migration and Plate Motion in Different Global Reference Frames

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.; Stegman, D. A.; Freeman, J.; Moresi, L.

    2007-12-01

    Plate velocities and trench migration velocities are commonly described in some sort of global "absolute" reference frame. From calculating such motions for all plates and subduction zones on Earth, one might obtain insight into the importance of various driving and resistive forces of plate tectonics and plate boundary migration. Trench migration velocities and plate velocities have been calculated for all subduction zones on Earth in eight global reference frames. The calculations show that such velocities can differ substantially between different global reference frames (up to 4 cm/yr), in particular between one Pacific hotspot reference frame (HS3- NUVEL1A) and all the others. In addition, this reference frame shows a bimodal distribution of trench velocities, while all the others show a Gaussian distribution. Nevertheless, some common features are observed irrespective of the reference frame. First, trench retreat always dominates over trench advance, with 62-78% of the trench segments retreating, while the mean and median trench velocities are always positive (retreating). Second, trench retreat is always slow in the middle of wide subduction zones, i.e. far (>2000 km) from lateral slab edges (<2 cm/yr in seven reference frames). Third, fast trench retreat (>6 cm/yr) is only found close (<1500 km) to lateral slab edges. Fourth, plates with a substantial percentage of their circumference attached to a subducting slab (Pacific, Nazca, Cocos, Philippine, Australia) move trenchward. These calculations are predicted by three-dimensional geodynamic models of free subduction with a variable slab width (300-7000 km), in which the slab to upper mantle viscosity ratio is low (100-200). This suggests that trench velocities and plate velocities are indeed primarily controlled by the negative buoyancy and width of subducting slabs. It further suggests that slab/upper mantle viscosity ratios in nature are 100-200, as the models show trench motion dominated by retreat, and

  1. Application of the reduction of scale range in a Lorentz boosted frame to the numerical simulation of particle acceleration devices.

    SciTech Connect

    Vay, J; Fawley, W M; Geddes, C G; Cormier-Michel, E; Grote, D P

    2009-05-05

    It has been shown that the ratio of longest to shortest space and time scales of a system of two or more components crossing at relativistic velocities is not invariant under Lorentz transformation. This implies the existence of a frame of reference minimizing an aggregate measure of the ratio of space and time scales. It was demonstrated that this translated into a reduction by orders of magnitude in computer simulation run times, using methods based on first principles (e.g., Particle-In-Cell), for particle acceleration devices and for problems such as: free electron laser, laser-plasma accelerator, and particle beams interacting with electron clouds. Since then, speed-ups ranging from 75 to more than four orders of magnitude have been reported for the simulation of either scaled or reduced models of the above-cited problems. In it was shown that to achieve full benefits of the calculation in a boosted frame, some of the standard numerical techniques needed to be revised. The theory behind the speed-up of numerical simulation in a boosted frame, latest developments of numerical methods, and example applications with new opportunities that they offer are all presented.

  2. Global, Regional and National Geodetic Reference Frames for Geodesy and Geodynamics

    NASA Astrophysics Data System (ADS)

    Bosy, Jaroslaw

    2014-06-01

    In July 2003 the International Association of Geodesy (IAG) established the Global Geodetic Observing System (GGOS). The GGOS is integrating the three basic components: geometry, the earth rotation and gravity. The backbone of this integration is the existing global ground network, based on the geodetic space techniques: very long baseline interferometry, satellite laser ranging, global navigation satellite systems and Doppler orbitography and radiopositioning integrated by satellite. These techniques have to operate as one global entity and in one global reference frame. The global reference frame in the GGOS is a realization of the International Terrestrial Reference System (ITRS). The ITRS is a world spatial reference system co-rotating with the Earth in its diurnal motion in the space. The IAG Subcommision for the European Reference Frame (EUREF) in 1991 recommended that the terrestrial reference system for Europe should be coincident with ITRS at the epoch t 0 = 1989.0 and fixed to the stable part of the Eurasian Plate. It was named the European Terrestrial Reference System 89 (ETRS89). On the 2nd of June 2008, the Head Office of Geodesy and Cartography in Poland commenced operating the ASG-EUPOS multifunctional precise satellite positioning system. The ASG-EUPOS network defines the European Terrestrial Reference System ETRS89 in Poland. A close connection between the ASG-EUPOS stations and 15 out of 18 Polish EUREF permanent network stations controls the realization of the ETRS89 on Polish territory. This paper is a review of the global ITRS, as well as a regional and a national geodetic reference systems ETRS89.

  3. The ICRF-3: Proposed Roadmap to the Next Generation International Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Arias, F.; Boboltz, D.; Boehm, J.; Bolotin, S.; Bourda, G.; Charlot, P.; de Witt, A.; Fey, A.; Gaume, R.; Gordon, D.; Heinkelmann, R.; Lambert, S.; Ma, C.; Malkin, Z.; Nothnagel, A.; Seitz, M.; Skurikhina, E.; Souchay, J.; Titov, O.

    2013-09-01

    We propose a 3rd generation radio-based International Celestial Reference Frame (ICRF- 3) to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverages relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames early enough to test the Gaia optical frame during its construction. Several specific actions are underway. A collaboration has been started to improve S/X-band precision of the 2000+ VLBA Calibrator Survey sources which are typically 5 times less precise than the rest of the ICRF-2. S/X-band southern precision improvements are planned from observations with southern antennas such as the AuScope and HartRAO, S. Africa. We seek to improve radio frequency coverage with X/Ka and K- band work. An X/Ka frame of 631 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which should strengthen the southern hemisphere in general. A K-band collaboration has formed with similar coverage and southern precision goals. On the analysis front, special attention will be given to combination techniques both of VLBI catalogs and of multiple data types (e.g. VLBI+GPS). Finally, work is underway to identify and pinpoint sources bright enough in both radio and optical to allow for a robust frame tie between VLBI and Gaia optical frames.

  4. KALREF - A Kalman filter approach to the International Terrestrial Reference Frame realization

    NASA Astrophysics Data System (ADS)

    Wu, X.; Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Gross, R. S.; Heflin, M. B.; Hurst, K. J.; Parker, J. W.

    2012-12-01

    To monitor global geophysical changes with realistic uncertainties using millimeter-precision geodesy, it is essential to define, realize and maintain the International Terrestrial Reference Frame (ITRF) consistently and accurately. Precise determinations of geocentric site positions and motions, satellite orbits, geocenter motion, Earth orientation and its variations, mean sea level rise, and polar ice mass changes at various time scales all depend critically on the accuracy and stability of the ITRF. Currently, the ITRF is a secular frame based on a linear model and consisting of mean epoch positions and velocities for a global set of stations. With higher accuracy and density geodetic data increasingly used for near real time geophysical change determinations, a research version of Terrestrial Reference Frame (TRF) realized by station time series is needed, which combines strengths of different geodetic techniques and unifies the different technique time series in the single frame. Here, we conceptually define an experimental reference frame with its origin at the nearly instantaneous center-of-mass (CM) of the total Earth system, by specifying the frame and combining different technique data weekly (daily for Earth orientation parameters). For co-located sites, available local ties are applied only once; but site motions are usually constrained to be the same. A Kalman filter and smoother algorithm has been developed and coupled to the ITRF/CATREF software to solve for geocentric coordinate time series with a model of secular, periodical and stochastic motion components. Results using linear and linear plus sinusoidal motion models without stochastic components compare very favorably with the ITRF2005 solution. Filtering strategies and time series results using ITRF2005 and ITRF2008 input data will be presented.

  5. The Gaia inertial reference frame and the tilting of the Milky Way disk

    SciTech Connect

    Perryman, Michael; Spergel, David N.; Lindegren, Lennart

    2014-07-10

    While the precise relationship between the Milky Way disk and the symmetry planes of the dark matter halo remains somewhat uncertain, a time-varying disk orientation with respect to an inertial reference frame seems probable. Hierarchical structure formation models predict that the dark matter halo is triaxial and tumbles with a characteristic rate of ∼2 rad H{sub 0}{sup −1} (∼30 μas yr{sup –1}). These models also predict a time-dependent accretion of gas, such that the angular momentum vector of the disk should be misaligned with that of the halo. These effects, as well as tidal effects of the LMC, will result in the rotation of the angular momentum vector of the disk population with respect to the quasar reference frame. We assess the accuracy with which the positions and proper motions from Gaia can be referred to a kinematically non-rotating system, and show that the spin vector of the transformation from any rigid self-consistent catalog frame to the quasi-inertial system defined by quasars should be defined to better than 1 μas yr{sup –1}. Determination of this inertial frame by Gaia will reveal any signature of the disk orientation varying with time, improve models of the potential and dynamics of the Milky Way, test theories of gravity, and provide new insights into the orbital evolution of the Sagittarius dwarf galaxy and the Magellanic Clouds.

  6. A Ka-band Celestial Reference Frame with Applications to Deep Space Navigation

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Clark, J. E.; García-Miró, C.; Horiuchi, S.; Sotuela, I.

    2011-10-01

    The Ka-band radio spectrum is now being used for a wide variety of applications. This paper highlights the use of Ka-band as a frequency for precise deep space navigation based on a set of reference beacons provided by extragalactic quasars which emit broadband noise at Ka-band. This quasar-based celestial reference frame is constructed using X/Ka-band (8.4/32 GHz) from fifty-five 24-hour sessions with the Deep Space Network antennas in California, Australia, and Spain. We report on observations which have detected 464 sources covering the full 24 hours of Right Ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the international standard S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of ~200 micro-arcsec (μas) in α cos δ and ~300 μas in δ. There is evidence for systematic errors at the 100 μas level. Known errors include limited SNR, lack of instrumental phase calibration, tropospheric refraction mis-modeling, and limited southern geometry. The motivation for extending the celestial reference frame to frequencies above 8 GHz is to access more compact source morphology for improved frame stability and to support spacecraft navigation for Ka-band based NASA missions.

  7. Using radio stars to link the Gaia and VLBI reference frames

    NASA Astrophysics Data System (ADS)

    Malkin, Zinovy

    2016-09-01

    A possible method for linking the optical Gaia Celestial Reference Frame (GCRF) to the VLBI-based International Celestial Reference Frame (ICRF) is to use radio stars in a manner similar to that in the linking of the Hipparcos Celestial Reference Frame (HCRF) to ICRF. In this work, an obtainable accuracy of the orientation angles between GCRF and ICRF frames was estimated by Monte Carlo simulation. If the uncertainties in the radio star positions obtained by VLBI are in the range of 0.1-4 mas and those obtained by Gaia are in the range of 0.005-0.4 mas, the orientation angle uncertainties are 0.018-0.72 mas if 46 radio stars are used, 0.013-0.51 mas if 92 radio stars are used, and 0.010-0.41 mas if 138 radio stars are used. The general conclusion from this study is that a properly organized VLBI programme for radio star observation with a reasonable load on the VLBI network can allow for the realization of GCRF-ICRF link with an error of about 0.1 mas.

  8. A Ka-Band Celestial Reference Frame with Applications to Deep Space Navigation

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.; Clark, J. Eric; Garcia-Miro, Cristina; Horiuchi, Shinji; Sotuela, Ioana

    2011-01-01

    The Ka-band radio spectrum is now being used for a wide variety of applications. This paper highlights the use of Ka-band as a frequency for precise deep space navigation based on a set of reference beacons provided by extragalactic quasars which emit broadband noise at Ka-band. This quasar-based celestial reference frame is constructed using X/Ka-band (8.4/32 GHz) from fifty-five 24-hour sessions with the Deep Space Network antennas in California, Australia, and Spain. We report on observations which have detected 464 sources covering the full 24 hours of Right Ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the international standard S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of approximately 200 micro-arcsec in alpha cos(delta) and approximately 300 micro-arcsec in delta. There is evidence for systematic errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of instrumental phase calibration, tropospheric refraction mis-modeling, and limited southern geometry. The motivation for extending the celestial reference frame to frequencies above 8 GHz is to access more compact source morphology for improved frame stability and to support spacecraft navigation for Ka-band based NASA missions.

  9. KALREF—A Kalman filter and time series approach to the International Terrestrial Reference Frame realization

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoping; Abbondanza, Claudio; Altamimi, Zuheir; Chin, T. Mike; Collilieux, Xavier; Gross, Richard S.; Heflin, Michael B.; Jiang, Yan; Parker, Jay W.

    2015-05-01

    The current International Terrestrial Reference Frame is based on a piecewise linear site motion model and realized by reference epoch coordinates and velocities for a global set of stations. Although linear motions due to tectonic plates and glacial isostatic adjustment dominate geodetic signals, at today's millimeter precisions, nonlinear motions due to earthquakes, volcanic activities, ice mass losses, sea level rise, hydrological changes, and other processes become significant. Monitoring these (sometimes rapid) changes desires consistent and precise realization of the terrestrial reference frame (TRF) quasi-instantaneously. Here, we use a Kalman filter and smoother approach to combine time series from four space geodetic techniques to realize an experimental TRF through weekly time series of geocentric coordinates. In addition to secular, periodic, and stochastic components for station coordinates, the Kalman filter state variables also include daily Earth orientation parameters and transformation parameters from input data frames to the combined TRF. Local tie measurements among colocated stations are used at their known or nominal epochs of observation, with comotion constraints applied to almost all colocated stations. The filter/smoother approach unifies different geodetic time series in a single geocentric frame. Fragmented and multitechnique tracking records at colocation sites are bridged together to form longer and coherent motion time series. While the time series approach to TRF reflects the reality of a changing Earth more closely than the linear approximation model, the filter/smoother is computationally powerful and flexible to facilitate incorporation of other data types and more advanced characterization of stochastic behavior of geodetic time series.

  10. A catalogue of QSOs and link stars for the HST link of the Hipparcos reference frame

    NASA Technical Reports Server (NTRS)

    White, Graeme L.; Jauncey, David L.; Reynolds, John E.; Malin, David; Argue, A. N.

    1990-01-01

    A list of bright (less than 17 mag) southern QSOs and bright (less than 11 mag) stars that may be suitable for the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the VLBI extragalactic frame is presented. The QSOs have been selected from various lists of radio objects and identifications. The stars have been selected from the Strasbourg (CDS) data base and from the Preliminary Second Cape Photographic Catalog, and supplemented with stars measured from the SERC IIIa-J Schmidt survey. These QSOs and stars have been included in the Hipparcos and HST schedule of observations.

  11. The Celestial Reference Frame at X/Ka-band: Status & Prospects for Improving the South

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Alonso, J.; Clark, J. E.; Gamborino, L.; García-Miró, C.; Horiuchi, S.; Lobo, J.; Maddè, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2012-10-01

    Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN).We discuss the construction of such a frame based on radio observations of AGN at X/Ka-band (8.4/32 GHz). Compared to S/Xband frames such as the international standard ICRF2, X/Ka-band allows access to more compact source morphology and reduced core shift. Both these effects allow for a more well-defined and stable reference frame at X/Ka. Using sixty-seven 24-hour sessions with NASA's Deep Space Network, we detected over 482 sources covering the full 24 hours of right ascension and declinations down to -45deg. There is evidence for systematic errors at the 100 µas level. Known errors include limited SNR, lack of phase calibration, troposphere mis-modelling, and limited southern geometry. We discuss our plans to address these errors with an emphasis on plans to use ESA's new 35-meter antenna in Malargüe, Argentina to greatly improve our southern hemisphere geometric coverage. We report successful fringe tests between ESA's 35-m antenna in Cebreros, Spain and the NASA 34-m in Robledo, Spain thereby validating the NASA-ESA interfaces and the portable VLBI recorder intended for use at Malargüe when that station is ready in the Fall of 2012. Allan variance tests on time scales of 1-1000 sec on the Cebreros-Robledo baseline were limited by tropospheric stability thus confirming that instrumental stability is not expected to be a limiting factor on these time scales once we go to Malargüe. In the next decade, we expect that ESA's optically based Gaia mission will produce a competitive frame. In anticipation of this development, we simulated a frame tie between our X/Ka frame and the Gaia frame. The simulation predicts a frame tie precision of 10-15 µas (1-sigma, per 3-D rotation component) with anticipated improvements in the radio reducing that to 5-10 µas per component by the time of Gaia's end of mission ca

  12. Age-related effects on spatial memory across viewpoint changes relative to different reference frames.

    PubMed

    Montefinese, Maria; Sulpizio, Valentina; Galati, Gaspare; Committeri, Giorgia

    2015-07-01

    Remembering object positions across different views is a fundamental competence for acting and moving appropriately in a large-scale space. Behavioural and neurological changes in elderly subjects suggest that the spatial representations of the environment might decline compared to young participants. However, no data are available on the use of different reference frames within topographical space in aging. Here we investigated the use of allocentric and egocentric frames in aging, by asking young and older participants to encode the location of a target in a virtual room relative either to stable features of the room (allocentric environment-based frame), or to an unstable objects set (allocentric objects-based frame), or to the viewer's viewpoint (egocentric frame). After a viewpoint change of 0° (absent), 45° (small) or 135° (large), participants judged whether the target was in the same spatial position as before relative to one of the three frames. Results revealed a different susceptibility to viewpoint changes in older than young participants. Importantly, we detected a worst performance, in terms of reaction times, for older than young participants in the allocentric frames. The deficit was more marked for the environment-based frame, for which a lower sensitivity was revealed as well as a worst performance even when no viewpoint change occurred. Our data provide new evidence of a greater vulnerability of the allocentric, in particular environment-based, spatial coding with aging, in line with the retrogenesis theory according to which cognitive changes in aging reverse the sequence of acquisition in mental development. PMID:25037856

  13. Evaluating seasonal loading models and their impact on global and regional reference frame alignment

    NASA Astrophysics Data System (ADS)

    Zou, Rong; Freymueller, Jeffrey T.; Ding, Kaihua; Yang, Shaomin; Wang, Qi

    2014-02-01

    Seasonal variations are observed in GPS time series, but are not included in the International Terrestrial Reference Frame (ITRF) models. Unmodeled seasonal variations at sites used for reference frame alignment are aliased into the reference frame parameters and bias all coordinates in the transformed solution. We augment ITRF2008 with seasonal loading models based either on Gravity Recovery and Climate Experiment (GRACE) measurements or a suite of models for atmospheric pressure, continental hydrology, and nontidal ocean loading. We model the seasonal components using either annual and semiannual terms or a nonparametric approach. When we include a seasonal variation model, the weighted root-mean-square misfit after seven-parameter transformation decreases for 70-90% of the daily GPS solutions depending on the network and seasonal model used, relative to a baseline case using ITRF2008. When seasonal variations are included in the reference frame solution, the observed seasonal variations are more consistent with the GRACE-based model at 80-85% of the GPS sites that were not used in the frame alignment. The suite of forward models performs nearly as well as the GRACE-based model for North America, but substantially worse for other parts of the world. We interpret these findings to mean that the use of ITRF2008 without seasonal terms causes the amplitude of seasonal variations in the coordinate time series to be damped down relative to the true loading deformation and that the observed GPS time series are more consistent with a TRF model that includes seasonal variations. At present, a seasonal model derived from GRACE captures seasonal variations more faithfully than one based on hydrologic models.

  14. Examining reference frame interaction in spatial memory using a distribution analysis.

    PubMed

    Street, Whitney N; Wang, Ranxiao Frances

    2016-02-01

    Previous research showed competition among reference frames in spatial attention and language. The present studies developed a new distribution analysis to examine reference frame interactions in spatial memory. Participants viewed virtual arrays of colored pegs and were instructed to remember them either from their own perspective or from the perspective aligned with the rectangular floor. Then they made judgments of relative directions from their respective encoding orientation. Those taking the floor-axis perspective showed systematic bias in the signed errors toward their egocentric perspective, while those taking their own perspective showed no systematic bias, both for random and symmetrical object arrays. The bias toward the egocentric perspective was observed when learning a real symmetric regular object array with strong environmental cues for the aligned axis. These results indicate automatic processing of the self reference while taking the floor-axis perspective but not vice versa, and suggest that research on spatial memory needs to consider the implications of competition effects in reference frame use. PMID:26032226

  15. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2010-01-01

    A celestial reference frame at X/Kaband (8.4/32 GHz) has been constructed using fiftyone 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec ( mu as) in alpha cos delta and 290 mu as in delta. There is evidence for zonal errors at the 100 mu as level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  16. The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Heflin, M. B.; Skjerve, L. J.; Sovers, O. J.; Garcia-Miro, C.; Moll, V. E.; Horiuchi, S.

    2011-01-01

    A celestial reference frame at X/Ka-band (8.4/32 GHz) has been constructed using fifty-one 24-hour sessions with the Deep Space Network. We report on observations which have detected 436 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of this X/Ka-band frame to the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 200 micro-arcsec in a cos delta and 290 micro-arcsec in delta. There is evidence for zonal errors at the 100 micro-arcsec level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. The motivations for extending the ICRF to frequencies above 8 GHz are to access more compact source morphology for improved frame stability, to provide calibrators for phase referencing, and to support spacecraft navigation at Ka-band.

  17. Modeling laser wakefield accelerator experiments with ultrafast particle-in-cell simulations in boosted frames

    SciTech Connect

    Martins, S. F.; Fonseca, R. A.; Vieira, J.; Silva, L. O.

    2010-05-15

    The development of new laser systems at the 10 Petawatt range will push laser wakefield accelerators to novel regimes, for which theoretical scalings predict the possibility to accelerate electron bunches up to tens of GeVs in meter-scale plasmas. Numerical simulations will play a crucial role in testing, probing, and optimizing the physical parameters and the setup of future experiments. Fully kinetic simulations are computationally very demanding, pushing the limits of today's supercomputers. In this paper, the recent developments in the OSIRIS framework [R. A. Fonseca et al., Lect. Notes Comput. Sci. 2331, 342 (2002)] are described, in particular the boosted frame scheme, which leads to a dramatic change in the computational resources required to model laser wakefield accelerators. Results from one-to-one modeling of the next generation of laser systems are discussed, including the confirmation of electron bunch acceleration to the energy frontier.

  18. Proof-of-principle experiment of reference-frame-independent quantum key distribution with phase coding

    PubMed Central

    Liang, Wen-Ye; Wang, Shuang; Li, Hong-Wei; Yin, Zhen-Qiang; Chen, Wei; Yao, Yao; Huang, Jing-Zheng; Guo, Guang-Can; Han, Zheng-Fu

    2014-01-01

    We have demonstrated a proof-of-principle experiment of reference-frame-independent phase coding quantum key distribution (RFI-QKD) over an 80-km optical fiber. After considering the finite-key bound, we still achieve a distance of 50 km. In this scenario, the phases of the basis states are related by a slowly time-varying transformation. Furthermore, we developed and realized a new decoy state method for RFI-QKD systems with weak coherent sources to counteract the photon-number-splitting attack. With the help of a reference-frame-independent protocol and a Michelson interferometer with Faraday rotator mirrors, our system is rendered immune to the slow phase changes of the interferometer and the polarization disturbances of the channel, making the procedure very robust. PMID:24402550

  19. The Relationship Between Global Mean Sea Level Rise and the Reference Frame

    NASA Technical Reports Server (NTRS)

    Lemoine, F.; Luthcke, S.; Zelensky, N.; Pavlis, E.; Beckley, B.; Ray, R.; Petrov, L.; Pavlis, D.; Rowlands, D.

    2006-01-01

    The Terrestrial Reference Frame is the fundamental means by which we relate observations in space and time. For example, in order to generate a homogeneous and consistent time series of geo-referenced altimeter measurements over the span of the Topex/Poseidon and Jason-1 missions, we must examine carefully the role of improvements in measurement modelling, force modelling, and improved reference frame realizations. In this paper, we quantify the effects of improvements in force modelling, for example the use of new GRACE-derived gravity models, the effect of time-variable gravity derived from GRACE on altimeter satellite orbits. In addition, we examine the effects of modelling geocenter in altimeteric satellite POD, and look at how the application of atmospheric loading might affect the time-series of precise orbits for Topex/Poseidon and Jason-1.

  20. Transfer of spatial reference frame using singlet states and classical communication

    NASA Astrophysics Data System (ADS)

    Bahder, Thomas B.

    2016-03-01

    A simple protocol is described for transferring spatial orientation from Alice to Bob (two spatially separated observers). The two observers are assumed to share quantum singlet states and classical communication. The protocol assumes that Alice and Bob have complete free will (measurement independence) and is based on maximizing the Shannon mutual information between Alice and Bob's measurement outcomes. Repeated use of this protocol for each spatial axis of Alice allows transfer of a complete three-dimensional reference frame, up to inversion of each of the axes. The technological complexity of this protocol is similar to that needed for BB84 quantum key distribution and hence is much simpler to implement than recently proposed schemes for transmission of reference frames. A second protocol based on a Bayesian formalism is also discussed.

  1. Research Activities for the DORIS Contribution to the Next International Terrestrial Reference Frame

    NASA Technical Reports Server (NTRS)

    Soudarin, L.; Moreaux, G.; Lemoine, F.; Willis, P.; Stepanek, P.; Otten, M.; Govind, R.; Kuzin, S.; Ferrage, P.

    2012-01-01

    For the preparation of ITRF2008, the IDS processed data from 1993 to 2008, including data from TOPEX/Poseidon, the SPOT satellites and Envisat in the weekly solutions. Since the development of ITRF2008, the IDS has been engaged in a number of efforts to try and improve the reference frame solutions. These efforts include (i) assessing the contribution of the new DORIS satellites, Jason-2 and Cryosat2 (2008-2011), (ii) individually analyzing the DORIS satellite contributions to geocenter and scale, and (iii) improving orbit dynamics (atmospheric loading effects, satellite surface force modeling. . . ). We report on the preliminary results from these research activities, review the status of the IDS combination which is now routinely generated from the contributions of the IDS analysis centers, and discuss the prospects for continued improvement in the DORIS contribution to the next international reference frame.

  2. Reference frames for reaching when decoupling eye and target position in depth and direction

    PubMed Central

    Bosco, A.; Breveglieri, R.; Hadjidimitrakis, K.; Galletti, C.; Fattori, P.

    2016-01-01

    Spatial representations in cortical areas involved in reaching movements were traditionally studied in a frontoparallel plane where the two-dimensional target location and the movement direction were the only variables to consider in neural computations. No studies so far have characterized the reference frames for reaching considering both depth and directional signals. Here we recorded from single neurons of the medial posterior parietal area V6A during a reaching task where fixation point and reaching targets were decoupled in direction and depth. We found a prevalent mixed encoding of target position, with eye-centered and spatiotopic representations differently balanced in the same neuron. Depth was stronger in defining the reference frame of eye-centered cells, while direction was stronger in defining that of spatiotopic cells. The predominant presence of various typologies of mixed encoding suggests that depth and direction signals are processed on the basis of flexible coordinate systems to ensure optimal motor response. PMID:26876496

  3. Killing horizons and dragging of the inertial frame about a uniformly accelerating particle

    SciTech Connect

    Farhoosh, H.; Zimmerman, R.L.

    1980-01-15

    The structure of Killing horizons in the static vacuum C metric which represents the gravitational field of a uniformly accelerating Schwarzschild-type particle is studied. It is shown that for A/sup 2/m/sup 2/<1/27 there exist two physically meaningful horizons. One horizon is analogous to the Schwarzschild surface and the other is similar to a flat surface in Euclidean space traveling at the speed of light along the axis of symmetry. This second surface is called the Rindler surface because of its analogy with the Rindler surface in the limit that geometry becomes Euclidean. As the acceleration increases, the Schwarzschild surface distorts from its original spherical shape. Its shape becomes teardroplike with the pointed end oriented in the direction of the acceleration. In the forward direction the Schwarzschild surface moves outward from the origin as the acceleration continues to increase in accordance with the principle of equivalence. In the backward direction the surface shrinks from its original Schwarzschild surface as the acceleration increases for relatively small values of the acceleration. This is also expected from the principle of equivalence. As the acceleration reaches A=1/..sqrt..54m the Schwarzschild surface in the backward direction reaches a minimum distance from the origin at r=..sqrt..3m and as the acceleration further increases it reverses its direction of motion and grows outward until it reaches the original Schwarzschild surface at r=2m. This behavior is an apparent violation of the principle of equivalence. As the acceleration increases, the Rindler surface moves inward approaching the Schwarzschild surface, and finally when A=1/..sqrt..27m the two surfaces unite and produce a naked singularity. Radial geodesic and nongeodesic motions are also investigated. It is shown that for small accelerations the results are in agreement with the principle of equivalence and the effects of dragging of the inertial frame due to the rectilinear

  4. Generalization of Dexterous Manipulation Is Sensitive to the Frame of Reference in Which It Is Learned.

    PubMed

    Marneweck, Michelle; Knelange, Elisabeth; Lee-Miller, Trevor; Santello, Marco; Gordon, Andrew M

    2015-01-01

    Studies have shown that internal representations of manipulations of objects with asymmetric mass distributions that are generated within a specific orientation are not generalizable to novel orientations, i.e., subjects fail to prevent object roll on their first grasp-lift attempt of the object following 180° object rotation. This suggests that representations of these manipulations are specific to the reference frame in which they are formed. However, it is unknown whether that reference frame is specific to the hand, the body, or both, because rotating the object 180° modifies the relation between object and body as well as object and hand. An alternative, untested explanation for the above failure to generalize learned manipulations is that any rotation will disrupt grasp performance, regardless if the reference frame in which the manipulation was learned is maintained or modified. We examined the effect of rotations that (1) maintain and (2) modify relations between object and body, and object and hand, on the generalizability of learned two-digit manipulation of an object with an asymmetric mass distribution. Following rotations that maintained the relation between object and body and object and hand (e.g., rotating the object and subject 180°), subjects continued to use appropriate digit placement and load force distributions, thus generating sufficient compensatory moments to minimize object roll. In contrast, following rotations that modified the relation between (1) object and hand (e.g. rotating the hand around to the opposite object side), (2) object and body (e.g. rotating subject and hand 180°), or (3) both (e.g. rotating the subject 180°), subjects used the same, yet inappropriate digit placement and load force distribution, as those used prior to the rotation. Consequently, the compensatory moments were insufficient to prevent large object rolls. These findings suggest that representations of learned manipulation of objects with asymmetric mass

  5. Generalization of Dexterous Manipulation Is Sensitive to the Frame of Reference in Which It Is Learned

    PubMed Central

    Marneweck, Michelle; Knelange, Elisabeth; Lee-Miller, Trevor; Santello, Marco; Gordon, Andrew M.

    2015-01-01

    Studies have shown that internal representations of manipulations of objects with asymmetric mass distributions that are generated within a specific orientation are not generalizable to novel orientations, i.e., subjects fail to prevent object roll on their first grasp-lift attempt of the object following 180° object rotation. This suggests that representations of these manipulations are specific to the reference frame in which they are formed. However, it is unknown whether that reference frame is specific to the hand, the body, or both, because rotating the object 180° modifies the relation between object and body as well as object and hand. An alternative, untested explanation for the above failure to generalize learned manipulations is that any rotation will disrupt grasp performance, regardless if the reference frame in which the manipulation was learned is maintained or modified. We examined the effect of rotations that (1) maintain and (2) modify relations between object and body, and object and hand, on the generalizability of learned two-digit manipulation of an object with an asymmetric mass distribution. Following rotations that maintained the relation between object and body and object and hand (e.g., rotating the object and subject 180°), subjects continued to use appropriate digit placement and load force distributions, thus generating sufficient compensatory moments to minimize object roll. In contrast, following rotations that modified the relation between (1) object and hand (e.g. rotating the hand around to the opposite object side), (2) object and body (e.g. rotating subject and hand 180°), or (3) both (e.g. rotating the subject 180°), subjects used the same, yet inappropriate digit placement and load force distribution, as those used prior to the rotation. Consequently, the compensatory moments were insufficient to prevent large object rolls. These findings suggest that representations of learned manipulation of objects with asymmetric mass

  6. Neural network simulations of the primate oculomotor system. II. Frames of reference.

    PubMed

    Moschovakis, A K

    1996-01-01

    Theories of motor control often assume that the location of visual stimuli is expressed in non retinotopic frames of reference. The saccadic system is known in enough detail for us to examine the evidential basis of this assumption. The organization of the neural circuit that controls saccades is first summarized. It is shown to consist of at least two interconnected modules. The first one is the burst generator, which resides in the reticular formation, and is entrusted with the tasks of impedance matching, synergist coactivation and reciprocal inhibition between antagonists. The second is a metric computer, which resides in the superior colliculus and the cerebral cortex, and computes the size and direction of the desired movement. Alternative models of the burst generator are presented and their "verisimilitude" is assessed in the light of evidence concerning saccadic trajectories, neuronal discharge patterns, interneuronal connections, as well as the results of lesion and stimulation experiments. Several models of the "metric computer" in the superior colliculus are then examined; their performance is again evaluated in the light of psychophysical, anatomical, physiological, and clinical evidence. It is demonstrated that the location of visual stimuli need not be expressed in nonretinotopic frames of reference for either the burst generator or the metric computer to issue appropriate commands to move the eyes. Instead, using information concerning intervening movements of the eyes to update the location of visual stimuli in a retinotopic frame of reference suffices for the planning and execution of correct saccades. More generally, it is proposed that the location of sensory stimuli need not be expressed in higher order frames of reference (e.g., centered in the body or even in extrapersonal space) provided that their location in a sensorium specific map is updated on the basis of effector movements. PMID:8886356

  7. Frames of reference for helicopter electronic maps - The relevance of spatial cognition and componential analysis

    NASA Technical Reports Server (NTRS)

    Harwood, Kelly; Wickens, Christopher D.

    1991-01-01

    Computer-generated map displays for NOE and low-level helicopter flight were formed according to prior research on maps, navigational problem solving, and spatial cognition in large-scale environments. The north-up map emphasized consistency of object location, wheareas, the track-up map emphasized map-terrain congruency. A component analysis indicates that different cognitive components, e.g., orienting and absolute object location, are supported to varying degrees by properties of different frames of reference.

  8. The Geodetic Reference Antenna in Space (GRASP) - A Mission to Enhance the Terrestrial Reference Frame

    NASA Astrophysics Data System (ADS)

    Nerem, R.; Bar-Sever, Y. E.; Grasp Team

    2011-12-01

    The Geodetic Reference Antenna in Space (GRASP) is a small satellite mission concept, currently being proposed to NASA's Earth Venture 2 (EV-2) announcement of opportunity, that is dedicated to the enhancement of all the space geodetic techniques, promising revolutionary improvements to the definition of the TRF, its densification, and accessibility. GRASP collocates GNSS, SLR, VLBI, and DORIS sensors on a supremely calibrated and modeled spacecraft, offering an innovative space-based approach to a heretofore intractable problem: establishing precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a solution to another difficult problem, namely, the consistent calibration of the myriad antennas used to transmit and receive the ubiquitous signals of the present and future Global Navigation Satellite Systems (GNSS). We will describe how errors in the TRF impact our ability to answer key science questions, such as mean sea level rise, and present new analysis of GRASP's capability to improve various aspects of the TRF. We will also discuss opportunities for the geodetic community to contribute, support, and enhance this mission.

  9. Effects of adopting new precession, nutation and equinox corrections on the terrestrial reference frame

    NASA Technical Reports Server (NTRS)

    Zhu, S. Y.; Mueller, I. I.

    1982-01-01

    The effects of adopting new definitive precession and equinox corrections on the terrestrial reference frame was investigated. It is noted that: (1) the effect on polar motion is a diurnal periodic term with an amplitude increasing linearly in time whole on UT1 it is a linear term; (2) general principles are given to determine the effects of small rotations of the frame of a conventional inertial reference system (CIS) on the frame of the conventional terrestrial reference system (CTS); (3) seven CTS options are presented, one of which is necessary to accommodate such rotation. Accommodating possible future changes in the astronomical nutation is discussed. The effects of differences which may exist between the various CTS's and CIS's on Earth rotation parameters (ERP) and how these differences can be determined are examined. It is shown that the CTS differences can be determined from observations made at the same site, while the CIS differences by comparing the ERP's determined by the different techniques during the same time period.

  10. New Observations Testing the Adopted HIPPARCOS Link to the International Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Stone, Ronald C.

    1998-10-01

    This paper tests the Hipparcos link to the extragalactic reference frame by using new data obtained after the release of the catalog, thereby providing an external check on the accuracy of the established link process. The new data consist of 689 positions of Hipparcos stars determined in the International Celestial Reference Frame (ICRF) from CCD observations taken with the Flagstaff Astrometric Scanning Transit Telescope (FASTT). A comparison of the FASTT and Hipparcos catalog star positions observed in common finds that the axial rotations between the Hipparcos and ICRF reference frames are, respectively, (εx, εy, εz) = (-2.2+/-3.3, -2.2+/-3.3, 3.3+/-2.9) (s.e.) mas at epoch 1996.5. All of these rotations are small and insignificant with respect to their errors (εx and εy are less than 1 σ detections whereas εz is only a 1.1 σ detection). Hence, this paper finds that the Hipparcos link to the ICRF was well determined and is not seriously degrading with time.

  11. The consistency of the current conventional celestial and terrestrial reference frames and the conventional EOP series

    NASA Astrophysics Data System (ADS)

    Heinkelmann, R.; Belda-Palazon, S.; Ferrándiz, J.; Schuh, H.

    2015-08-01

    For applications in Earth sciences, navigation, and astronomy the celestial (ICRF) and terrestrial (ITRF) reference frames as well as the orientation among them, the Earth orientation parameters (EOP), have to be consistent at the level of 1 mm and 0.1 mm/yr (GGOS recommendations). We assess the effect of unmodelled geophysical signals in the regularized coordinates and the sensitivity with respect to different a priori EOP and celestial reference frames. The EOP are determined using the same VLBI data but with station coordinates fixed on different TRFs. The conclusion is that within the time span of data incorporated into ITRF2008 (Altamimi, et al., 2011) the ITRF2008 and the IERS 08 C04 are consistent. This consistency involves that non-linear station motion such as unmodelled geophysical signals partly affect the IERS 08 C04 EOP. There are small but not negligible inconsistencies between the conventional celestial reference frame, ICRF2 (Fey, et al., 2009), the ITRF2008 and the conventional EOP that are quantified by comparing VTRF2008 (Böckmann, et al., 2010) and ITRF2008.

  12. Spatial scale, rather than nature of task or locomotion, modulates the spatial reference frame of attention

    PubMed Central

    Jiang, Yuhong V.; Won, Bo-Yeong

    2015-01-01

    Visuospatial attention is strongly biased to locations that frequently contained a search target before. However, the function of this bias depends on the reference frame in which attended locations are coded. Previous research has shown a striking difference between tasks administered on a computer monitor and in a large environment, with the former inducing viewer-centered learning and the latter environment-centered learning. Why does environment-centered learning fail on a computer? Here we tested three possibilities: differences in spatial scale, nature of task, and locomotion may influence the reference frame of attention. Participants searched for a target on a monitor placed flat on a stand. On each trial they stood at a different location around the monitor. The target was frequently located in a fixed area of the monitor, but changes in participants’ perspective rendered this area random relative to the participants. Under incidental learning conditions participants failed to acquire environment-centered learning even when (i) the task and display resembled the large-scale task, and (ii) the search task required locomotion. The difficulty in inducing environment-centered learning on a computer underscores the egocentric nature of visual attention. It supports the idea that spatial scale modulates the reference frame of attention. PMID:25867510

  13. Effects of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Dach, R.; Heflin, M. B.; Gross, R. S.; König, R.; Lemoine, F. G.; MacMillan, D. S.; Parker, J. W.; van Dam, T. M.; Wu, X.

    2013-12-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS global networks used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, the effect of non-tidal atmospheric loading (NTAL) corrections on the TRF is assessed adopting a Remove/Restore approach: (i) Focusing on the a-posteriori approach, the NTAL model derived from the National Center for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations. (ii) Adopting a Kalman-filter based approach, a linear TRF is estimated combining the 4 SG solutions free from NTAL displacements. (iii) Linear fits to the NTAL displacements removed at step (i) are restored to the linear reference frame estimated at (ii). The velocity fields of the (standard) linear reference frame in which the NTAL model has not been removed and the one in which the model has been removed/restored are compared and discussed.

  14. Quantum reference frames associated with noncompact groups: The case of translations and boosts and the role of mass

    NASA Astrophysics Data System (ADS)

    Smith, Alexander R. H.; Piani, Marco; Mann, Robert B.

    2016-07-01

    Quantum communication without a shared reference frame or the construction of a relational quantum theory requires the notion of a quantum reference frame. We analyze aspects of quantum reference frames associated with noncompact groups, specifically, the group of spatial translations and Galilean boosts. We begin by demonstrating how the usually employed group average, used to dispense of the notion of an external reference frame, leads to unphysical states when applied to reference frames associated with noncompact groups. However, we show that this average does lead naturally to a reduced state on the relative degrees of freedom of a system, which was previously considered by Angelo et al. [J. Phys. A: Math. Theor. 44, 145304 (2011), 10.1088/1751-8113/44/14/145304]. We then study in detail the informational properties of this reduced state for systems of two and three particles in Gaussian states.

  15. Modeling of Laser wakefield acceleration in the Lorentz boosted frame using UPIC-EMMA and OSIRIS

    NASA Astrophysics Data System (ADS)

    Yu, Peicheng; Xu, Xinlu; Decyk, Viktor; Tsung, Frank; Vieira, Jorge; Fonseca, Ricardo; Lu, Wei; Silva, Luis; Mori, Warren; UCLA Team; Tsinghua University Beijing Team; IST Portugal Team

    2014-10-01

    We present the capability of investigating physics of laser wakefield accelerator (LWFA) in nonlinear regimes using various approaches. This includes simulating the physics using OSIRIS 3D code in the lab and boosted frame. We also implemented hybrid 3D algorithm into OSIRIS which uses an algorithm with a PIC description in r-z and a gridless description in phi [A. F. Lifschitz et al., JCP. 228, 1803 (2009)]. This algorithm greatly reduce the computation load by describing the three-dimensional (3D) physics problem of laser-plasma interaction with essentially two-dimensional if the expansion is truncated. The hybrid 3D OSIRIS code can be used to simulate the nonlinear physics in LWFA in both lab and boosted frames. Combining the hybrid 3D and boosted frame approaches potentially provides unprecedented speedups. Furthermore, we can simulate the same problems in a boosted frame using the spectral EM-PIC code UPIC-EMMA which solves the Maxwell's equation in Fourier space. By applying a recipe to systematically reduce the numerical Cerenkov instability (NCI) in the spspectral code, we are able to conduct LWFA Lorentz boosted frame simulation at arbitrary gamma with no signs of NCI.

  16. The International Terrestrial Reference Frame: current status and future challenges (Vening Meinesz Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Altamimi, Zuheir

    2013-04-01

    The ability to assign accurate time-dependent coordinates to points on the Earth's surface is fundamental for many Earth observation applications. Also important is monitoring these coordinates over time in order to take into account all geophysical changes affecting the Earth's surface. Many areas of science, Earth observation, geo-referencing applications, and society at large, today depend on being able to determine positions to millimeter level precision. Point positions, to be meaningful and fully exploitable, have to be determined and expressed in a well-defined Terrestrial Reference Frame (TRF). All current global and regional reference frames rely on the availability of the International Terrestrial Reference Frame (ITRF), which is the most accurate realization of the International Terrestrial Reference System (ITRS). The positions of the thousands of geodetic stations distributed over the Earth's surface can now be determined with a precision at the level of a few millimeters and their variation over time at the level of, or better than, 1 mm/yr in a global geocentric frame. This performance is only possible as a result of the tremendous progress made in improving the hardware of the space geodetic techniques and in the high level algorithms, models, and scientific software packages developed by the analysis centers dealing with the geodetic observations accumulated over the last three decades. However, none of space geodetic techniques is able to provide all the parameters necessary to completely define a TRF (origin, scale and orientation). While satellite techniques are sensitive to the Earth center of mass (the point around which a satellite orbits; a natural TRF origin), VLBI is not (whose TRF origin is arbitrarily defined). The scale is dependent on the modeling of some physical parameters, and the absolute TRF orientation (unobservable by any technique) is arbitrary or conventionally defined through specific constraints. Therefore the value of the

  17. The Simon effect based on the egocentric and allocentric reference frame.

    PubMed

    Wang, Huan; Liu, Nan; Zou, Guiying; Li, Hui; Zeng, Hang; Chen, Jiedan; Chen, Qi

    2016-02-01

    The classic Simon effect refers to the phenomenon that responses are faster when the task-irrelevant egocentric stimulus location is on the same side as the response hand than when not. However, the spatial location of an object often varies according to which reference frame the object location was represented in, e.g., egocentric versus allocentric reference frame. It has been unknown, however, whether and how the Simon effect based on the egocentric and the allocentric reference interact, and whether the potential interaction between them is affected by task demands. To investigate these questions, we orthogonally crossed the stimulus-response compatibility induced by the egocentric and the allocentric positions during the Simon effect. Moreover, the irrelevant egocentric and allocentric positions were either explicitly represented via interleaving spatial and non-spatial tasks in Experiment 1 or not in Experiment 2. The results suggested that the Simon effect based on the egocentric locations occurred irrespective of whether the egocentric representations were explicitly coded based on current task demands or not. The Simon effect based on allocentric locations, however, seemed to occur only when the allocentric representations were explicitly induced. Moreover, the egocentric and allocentric Simon effect interacted in a similar way irrespective of task demands, with significantly delayed responses when both the egocentric and the allocentric locations were incongruent with the response code. PMID:26603042

  18. The role of the brain's frontal eye fields in constructing frame of reference.

    PubMed

    Wallentin, Mikkel

    2012-08-01

    Establishing contextual reference during discourse is a vital part of language function. Personal pronouns (e.g., he/she/it) are used to refer to previously experienced objects, utterances and events. These items, however, are often no longer present in the environment and have to be maintained and manipulated in working memory (WM). One aspect of this is the construction of a spatial frame of reference (e.g., "He was in front of it" where "he" is established as figure and "it" is the ground). The WM processes underlying this function may be different from those involved in establishing a non-spatial relation (e.g., "He was older than her"). The brain's frontal eye fields (FEFs), responsible for eye movement control, are known to be involved in processing spatial WM. This paper reviews both functional magnetic resonance imaging experiments and a subsequent behavioral interference study demonstrating a specific role for the FEFs and the brain's eye movement control system in manipulation of WM content for establishing object-centered spatial reference frames during verbally cued recall of recent visual and linguistic experiences. PMID:22806655

  19. Framing spatial cognition: Neural representations of proximal and distal frames of reference and their roles in navigation

    PubMed Central

    Knierim, James J.; Hamilton, Derek A.

    2011-01-01

    The most common behavioral test of hippocampus-dependent, spatial learning and memory is the Morris water task, and the most commonly studied behavioral correlate of hippocampal neurons is the spatial specificity of place cells. Despite decades of intensive research, it is not completely understood how animals solve the water task and how place cells generate their spatially specific firing fields. Based on early work, it has become the accepted wisdom in the general neuroscience community that distal spatial cues are the primary sources of information used by animals to solve the water task (and similar spatial tasks) and by place cells to generate their spatial specificity. More recent research, along with earlier studies that were overshadowed by the emphasis on distal cues, put this common view into question by demonstrating primary influences of local cues and local boundaries on spatial behavior and place-cell firing. This paper first reviews the historical underpinnings of the “standard” view from a behavioral perspective, and then reviews newer results demonstrating that an animal's behavior in such spatial tasks is more strongly controlled by a local-apparatus frame of reference than by distal landmarks. The paper then reviews similar findings from the literature on the neurophysiological correlates of place cells and other spatially-correlated cells from related brain areas. A model is proposed by which distal cues primarily set the orientation of the animal's internal spatial coordinate system, via the head direction cell system, whereas local cues and apparatus boundaries primarily set the translation and scale of that coordinate system. PMID:22013211

  20. The Influence of the Terrestrial Reference Frame on Studies of Sea Level Change

    NASA Astrophysics Data System (ADS)

    Nerem, R. S.; Bar-Sever, Y. E.; Haines, B. J.; Desai, S.; Heflin, M. B.

    2015-12-01

    The terrestrial reference frame (TRF) provides the foundation for the accurate monitoring of sea level using both ground-based (tide gauges) and space-based (satellite altimetry) techniques. For the latter, tide gauges are also used to monitor drifts in the satellite instruments over time. The accuracy of the terrestrial reference frame (TRF) is thus a critical component for both types of sea level measurements. The TRF is central to the formation of geocentric sea-surface height (SSH) measurements from satellite altimeter data. The computed satellite orbits are linked to a particular TRF via the assumed locations of the ground-based tracking systems. The manner in which TRF errors are expressed in the orbit solution (and thus SSH) is not straightforward, and depends on the models of the forces underlying the satellite's motion. We discuss this relationship, and provide examples of the systematic TRF-induced errors in the altimeter derived sea-level record. The TRF is also crucial to the interpretation of tide-gauge measurements, as it enables the separation of vertical land motion from volumetric changes in the water level. TRF errors affect tide gauge measurements through GNSS estimates of the vertical land motion at each tide gauge. This talk will discuss the current accuracy of the TRF and how errors in the TRF impact both satellite altimeter and tide gauge sea level measurements. We will also discuss simulations of how the proposed Geodetic Reference Antenna in SPace (GRASP) satellite mission could reduce these errors and revolutionize how reference frames are computed in general.

  1. Numerical methods for the weakly compressible Generalized Langevin Model in Eulerian reference frame

    NASA Astrophysics Data System (ADS)

    Azarnykh, Dmitrii; Litvinov, Sergey; Adams, Nikolaus A.

    2016-06-01

    A well established approach for the computation of turbulent flow without resolving all turbulent flow scales is to solve a filtered or averaged set of equations, and to model non-resolved scales by closures derived from transported probability density functions (PDF) for velocity fluctuations. Effective numerical methods for PDF transport employ the equivalence between the Fokker-Planck equation for the PDF and a Generalized Langevin Model (GLM), and compute the PDF by transporting a set of sampling particles by GLM (Pope (1985) [1]). The natural representation of GLM is a system of stochastic differential equations in a Lagrangian reference frame, typically solved by particle methods. A representation in a Eulerian reference frame, however, has the potential to significantly reduce computational effort and to allow for the seamless integration into a Eulerian-frame numerical flow solver. GLM in a Eulerian frame (GLMEF) formally corresponds to the nonlinear fluctuating hydrodynamic equations derived by Nakamura and Yoshimori (2009) [12]. Unlike the more common Landau-Lifshitz Navier-Stokes (LLNS) equations these equations are derived from the underdamped Langevin equation and are not based on a local equilibrium assumption. Similarly to LLNS equations the numerical solution of GLMEF requires special considerations. In this paper we investigate different numerical approaches to solving GLMEF with respect to the correct representation of stochastic properties of the solution. We find that a discretely conservative staggered finite-difference scheme, adapted from a scheme originally proposed for turbulent incompressible flow, in conjunction with a strongly stable (for non-stochastic PDE) Runge-Kutta method performs better for GLMEF than schemes adopted from those proposed previously for the LLNS. We show that equilibrium stochastic fluctuations are correctly reproduced.

  2. Transformation properties of dynamic subgrid-scale models in a frame of reference undergoing rotation

    NASA Astrophysics Data System (ADS)

    Horiuti, Kiyosi

    Theoretical consideration is presented for the transformation properties of the subgrid-scale (SGS) models for the SGS stress tensor in a non-inertial frame of reference undergoing rotation. As was previously shown (Speziale, C.G., Geophys. Astrophys. Fluid Dynamics 33, 199 (1985)), an extra correction term is yielded for the SGS stress tensor in the transformation of a rotating frame relative to an inertial framing. We derived the exact expression for the correction term for the spherical Gaussian filter function. Certain transformation rules are imposed on the SGS stress by the derived correction term, namely the SGS stress is not indifferent to a frame rotation, but the divergence of the SGS stress is frame indifferent. Conformity of the modelled SGS stress tensor estimated using the previous dynamic SGS models (the dynamic Smagorinsky, dynamic mixed and nonlinear models) with these transformation rules is examined. It is shown that values for certain model parameters contained in the mixed models can be theoretically determined by imposing these rules. We have conducted the a priori and a postepriori numerical assessments of the SGS models in decaying homogeneous turbulence which is subjected to rotation. All of the previous dynamic models were found to violate the rules except for the nonlinear model. The nonlinear model is form invariant, but the result obtained using the nonlinear model showed significant deviation from the DNS data. Failure of previous models was attributable to insufficient accuracy in approximating the modified cross term in the decomposition of the SGS stress tensor. A dynamic mixed model is proposed to eliminate the truncation error for the modelled correction term, in which multilevel filtering of the velocity field was utilized. The proposed model obeyed the transformation rules when the level of the multifiltering operation was large. It was shown that the defiltered model is derived in the limit of the infinite level of

  3. Frames of reference and categorical/coordinate spatial relations in a "what was where" task.

    PubMed

    Ruotolo, Francesco; Iachini, Tina; Ruggiero, Gennaro; van der Ham, Ineke J M; Postma, Albert

    2016-09-01

    The aim of this study was to explore how people use egocentric (i.e., with respect to their body) and allocentric (i.e., with respect to another element in the environment) references in combination with coordinate (metric) or categorical (abstract) spatial information to identify a target element. Participants were asked to memorize triads of 3D objects or 2D figures, and immediately or after a delay of 5 s, they had to verbally indicate what was the object/figure: (1) closest/farthest to them (egocentric coordinate task); (2) on their right/left (egocentric categorical task); (3) closest/farthest to another object/figure (allocentric coordinate task); (4) on the right/left of another object/figure (allocentric categorical task). Results showed that the use of 2D figures favored categorical judgments over the coordinate ones with either an egocentric or an allocentric reference frame, whereas the use of 3D objects specifically favored egocentric coordinate judgments rather than the allocentric ones. Furthermore, egocentric judgments were more accurate than allocentric judgments when the response was Immediate rather than delayed and 3D objects rather than 2D figures were used. This pattern of results is discussed in the light of the functional roles attributed to the frames of reference and spatial relations by relevant theories of visuospatial processing. PMID:27180248

  4. Impaired spatial working memory maintenance in schizophrenia involves both spatial coordinates and spatial reference frames.

    PubMed

    Mazhari, Shahrzad; Badcock, Johanna C; Waters, Flavie A; Dragović, Milan; Badcock, David R; Jablensky, Assen

    2010-10-30

    Spatial working memory (SWM) dysfunction is a central finding in schizophrenia; however, more evidence of impaired maintenance over time is required. Consequently, the present study examined SWM maintenance over short unfilled delays, and with encoding equated. The influence of a vertical reference frame to support maintenance was also investigated. The performance of 58 patients with schizophrenia and 50 healthy controls was assessed using the Visuo-Spatial Working Memory (VSWM) Test across three unfilled delays (0, 2, and 4s). Inaccuracy of direction and distance responses was examined at each delay duration. The results showed that performance was significantly less accurate for both distance and direction responses at 2 and 4s delays in schizophrenia, but was not significantly different from controls at the 0s delay. Patients showed a particularly marked loss of accuracy between the time interval of 0-2s. Furthermore, schizophrenia participants exhibited significantly greater response variability at the vertical axis of symmetry than controls at the 2 and 4s delays, but not at the 0s delay. These data clearly show both impaired maintenance over time and difficulty using a vertical frame of reference in schizophrenia. The latter findings may reflect, in part, dysfunctional reference-related inhibition. PMID:20493553

  5. Impact of seasonal and postglacial surface displacement on global reference frames

    NASA Astrophysics Data System (ADS)

    Krásná, Hana; Böhm, Johannes; King, Matt; Memin, Anthony; Shabala, Stanislav; Watson, Christopher

    2014-05-01

    The calculation of actual station positions requires several corrections which are partly recommended by the International Earth Rotation and Reference Systems Service (IERS) Conventions (e.g., solid Earth tides and ocean tidal loading) as well as other corrections, e.g. accounting for hydrology and atmospheric loading. To investigate the pattern of omitted non-linear seasonal motion we estimated empirical harmonic models for selected stations within a global solution of suitable Very Long Baseline Interferometry (VLBI) sessions as well as mean annual models by stacking yearly time series of station positions. To validate these models we compare them to displacement series obtained from the Gravity Recovery and Climate Experiment (GRACE) data and to hydrology corrections determined from global models. Furthermore, we assess the impact of the seasonal station motions on the celestial reference frame as well as on Earth orientation parameters derived from real and also artificial VLBI observations. In the second part of the presentation we apply vertical rates of the ICE-5G_VM2_2012 vertical land movement grid on vertical station velocities. We assess the impact of postglacial uplift on the variability in the scale given different sampling of the postglacial signal in time and hence on the uncertainty in the scale rate of the estimated terrestrial reference frame.

  6. Current global plate kinematics from GPS (1995-2007) with the plate-consistent reference frame

    NASA Astrophysics Data System (ADS)

    Kogan, Mikhail G.; Steblov, Grigory M.

    2008-04-01

    We present the vectors of rotation of 10 major lithospheric plates, estimated from continuous GPS observations at 192 globally distributed stations; 71 stations were selected as representing stable plate regions. All days for the period 1995.0-2007.0 were included in the analysis. In contrast to previous GPS plate models, our model is independent of international terrestrial reference frames (ITRF). The origin of our plate-consistent reference frame is the center of plate rotation (CP) rather than the center of mass of the entire Earth's system (CM) as in recent versions of ITRF. We estimate plate rotations and CP by minimizing the misfit between the horizontal velocities predicted by the plate model and the observed GPS velocities. If any version of ITRF is used as the reference frame, the drift of the ITRF origin relative to CP cannot be neglected in estimation of plate rotation vectors and plate-residual station velocities. The model of the plate kinematics presented here addresses the problem debated since the beginning of the space geodesy: how big are disagreements between the current plate motions and the motions averaged over several million years? We compare the vectors of relative plate rotations estimated here with the published vectors from GPS and geologic models. We also discuss the integrity of individual plates as exhibited by plate-residual station velocities. For seven largest plates, the RMS value of plate-residual station velocities in stable plate interiors is 0.5-0.9 mm/a; this value is an upper bound on deviation of real plates from infinite stiffness.

  7. Evidence for a reference frame transformation of vestibular signal contributions to voluntary reaching.

    PubMed

    Moreau-Debord, Ian; Martin, Christophe Z; Landry, Marianne; Green, Andrea M

    2014-05-01

    To contribute appropriately to voluntary reaching during body motion, vestibular signals must be transformed from a head-centered to a body-centered reference frame. We quantitatively investigated the evidence for this transformation during online reach execution by using galvanic vestibular stimulation (GVS) to simulate rotation about a head-fixed, roughly naso-occipital axis as human subjects made planar reaching movements to a remembered location with their head in different orientations. If vestibular signals that contribute to reach execution have been transformed from a head-centered to a body-centered reference frame, the same stimulation should be interpreted as body tilt with the head upright but as vertical-axis rotation with the head inclined forward. Consequently, GVS should perturb reach trajectories in a head-orientation-dependent way. Consistent with this prediction, GVS applied during reach execution induced trajectory deviations that were significantly larger with the head forward compared with upright. Only with the head forward were trajectories consistently deviated in opposite directions for rightward versus leftward simulated rotation, as appropriate to compensate for body vertical-axis rotation. These results demonstrate that vestibular signals contributing to online reach execution have indeed been transformed from a head-centered to a body-centered reference frame. Reach deviation amplitudes were comparable to those predicted for ideal compensation for body rotation using a biomechanical limb model. Finally, by comparing the effects of application of GVS during reach execution versus prior to reach onset we also provide evidence that spatially transformed vestibular signals contribute to at least partially distinct compensation mechanisms for body motion during reach planning versus execution. PMID:24523527

  8. Future global SLR network evolution and its impact on the terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Kehm, Alexander; Bloßfeld, Mathis; Pavlis, Erricos C.

    2016-04-01

    SLR is the unique technique that allows determining the geocentre with very high accuracy and contributes to the realization of the scale of a conventional reference frame. In addition, due to the high sensitivity of the SLR-tracked satellites on the Earth's gravitational field, SLR is a crucial technique for determining important geodetic parameters such as Earth Orientation Parameters (EOP) and low-degree spherical harmonics of the Earth's gravitational field model. So far, the distribution of SLR stations has been quite inhomogeneous, especially in the southern hemisphere, mostly due to the lack of land-masses. With the set-up of a new SLR station in Brasilia in 2014 and the transfer of the former TIGO observatory from Concepción (Chile) to La Plata (Argentina) - now known as AGGO Argentinian-German Geodetic Observatory -, the shape of SLR subnetwork in South America has changed significantly. Furthermore, additional SLR stations in India (Mount Abu and Ponmundi), as well as a new station in Hartebeesthoek, are scheduled to start operations in 2016 and they will further improve the global SLR network geometry. In this work, SLR data has been simulated in order to determine the influence of the changing SLR network geometry on the geodetic parameters such as a global terrestrial reference frame, EOP and the low-degree harmonics of the Earth's gravitational field. The simulations have been performed for different network geometries as well as different satellites. In this investigation, a special emphasis is placed on the improvement of the geocentric realization of a global SLR-derived reference frame.

  9. OPTICAL SPECTRA OF CANDIDATE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) FLAT-SPECTRUM RADIO SOURCES

    SciTech Connect

    Titov, O.; Stanford, Laura M.; Johnston, Helen M.; Hunstead, Richard W.; Pursimo, T.; Jauncey, David L.; Maslennikov, K.

    2013-07-01

    Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy and Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.

  10. Contribution of the Main Astronomical Observatory, Ukraine, to the Reference Frame Link

    NASA Astrophysics Data System (ADS)

    Kislyuk, V. S.; Rybka, S. P.; Yatsenko, A. I.; Kharchenko, N. V.; Yatskiv, Ya. S.

    1997-08-01

    Absolute proper motions of stars with respect to galaxies obtained within the KSZ programme were used in the determination of spin parameters of the Hipparcos catalogue system relative to the inertial reference frame. Solutions using bright, faint, blue, and red stars as well as the whole magnitude range of stars were found. `The faint KSZ stars' solution (omega_x = -0.27 +/- 0.80 mas/yr, omega_y = +0.15 +/- 0.60 mas/yr, omega_z = -1.07 +/- 0.80 mas/yr) is considered as the most reliable and is recommended for the correction of the Hipparcos catalogue system.

  11. POINTS - A global reference frame opportunity. [Precision Optical Interferometer in Space

    NASA Technical Reports Server (NTRS)

    Chandler, J. F.; Reasenberg, R. D.

    1990-01-01

    POINTS is a space-based optical astrometric interferometer capable of measuring the angular separation of two stars about 90 degrees apart with 5-microarcsec nominal accuracy . During the intended ten-year mission, a repeated survey of a few hundred targets over the whole sky, including a few bright quasars, establish a 'rigid' reference grid with 0.5 microarcsec position uncertainties. At that level, the grid is free of regional biases and tied to the extra-Galactic frame that is the present best candidate for an inertial frame. POINTS will also determine parallaxes and annual proper motions at about the same level. Further, the planetary ephemeris frame is tied through stellar aberration to the grid at about 300 microarcsec. Additional targets of interest, to a limiting magnitude of greater than 20, are observed relative to the grid, yielding determinations with uncertainties depending on the observing schedule. Measurement at the microarcsec/year level of the apparent relative velocities of quasars that are widely separated on the sky severely test the assumption of cosmological quasar distances and may also constrain models of the early universe.

  12. Celestial reference frames and the gauge freedom in the post-Newtonian mechanics of the Earth-Moon system

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei; Xie, Yi

    2010-11-01

    We introduce the Jacobi coordinates adopted to the advanced theoretical analysis of the relativistic Celestial Mechanics of the Earth-Moon system. Theoretical derivation utilizes the relativistic resolutions on reference frames adopted by the International Astronomical Union (IAU) in 2000. The resolutions assume that the Solar System is isolated and space-time is asymptotically flat at infinity and the primary reference frame covers the entire space-time, has its origin at the Solar System barycenter (SSB) with spatial axes stretching up to infinity. The SSB frame is not rotating with respect to a set of distant quasars that are assumed to be at rest on the sky forming the International Celestial Reference Frame (ICRF). The second reference frame has its origin at the Earth-Moon barycenter (EMB). The EMB frame is locally inertial and is not rotating dynamically in the sense that equation of motion of a test particle moving with respect to the EMB frame, does not contain the Coriolis and centripetal forces. Two other local frames—geocentric and selenocentric—have their origins at the center of mass of Earth and Moon respectively and do not rotate dynamically. Each local frame is subject to the geodetic precession both with respect to other local frames and with respect to the ICRF because of their relative motion with respect to each other. Theoretical advantage of the dynamically non-rotating local frames is in a more simple mathematical description of the metric tensor and relative equations of motion of the Moon with respect to Earth. Each local frame can be converted to kinematically non-rotating one after alignment with the axes of ICRF by applying the matrix of the relativistic precession as recommended by the IAU resolutions. The set of one global and three local frames is introduced in order to decouple physical effects of gravity from the gauge-dependent effects in the equations of relative motion of the Moon with respect to Earth.

  13. OPTICAL SPECTRA OF CANDIDATE SOUTHERN HEMISPHERE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) RADIO SOURCES

    SciTech Connect

    Titov, O.; Jauncey, D. L.; Johnston, H. M.; Hunstead, R. W.; Christensen, L.

    2011-11-15

    We present the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue as part of a very long baseline interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south. We made the observations with the 3.58 m European Southern Observatory New Technology Telescope. We obtained redshifts for 30 quasars and one radio galaxy, with a further seven objects being probable BL Lac objects with featureless spectra. Of the remainder, four were clear misidentifications with Galactic stars and five had low signal-to-noise spectra and could not be classified. These results, in combination with new VLBI data of the radio sources with redshifts more than 2, add significantly to the existing data needed to refine the distribution of source proper motions over the celestial sphere.

  14. Out of body, out of space: Impaired reference frame processing in eating disorders.

    PubMed

    Serino, Silvia; Dakanalis, Antonios; Gaudio, Santino; Carrà, Giuseppe; Cipresso, Pietro; Clerici, Massimo; Riva, Giuseppe

    2015-12-15

    A distorted body representation is a core symptom in eating disorders (EDs), though its mechanism is unclear. Allocentric lock theory, emphasising the role of reference frame processing in body image, suggests that ED patients may be (b)locked to an (allocentric) representation of their own body stored in long-term memory (e.g., my body is fat) that is not updated (modified) by the (real-time egocentric) perception-driven experience of the physical body. Employing a well-validated virtual reality-based procedure, relative to healthy controls, ED patients showed deficits in the ability to refer to and update a long-term stored (allocentric) representation with (egocentric) perceptual-driven inputs. PMID:26541204

  15. Unit Template Synchronous Reference Frame Theory Based Control Algorithm for DSTATCOM

    NASA Astrophysics Data System (ADS)

    Bangarraju, J.; Rajagopal, V.; Jayalaxmi, A.

    2014-04-01

    This article proposes new and simplified unit templates instead of standard phase locked loop (PLL) for Synchronous Reference Frame Theory Control Algorithm (SRFT). The extraction of synchronizing components (sinθ and cosθ) for parks and inverse parks transformation using standard PLL takes more execution time. This execution time in control algorithm delays the extraction of reference source current generation. The standard PLL not only takes more execution time but also increases the reactive power burden on the Distributed Static Compensator (DSTATCOM). This work proposes a unit template based SRFT control algorithm for four-leg insulated gate bipolar transistor based voltage source converter for DSTATCOM in distribution systems. This will reduce the execution time and reactive power burden on the DSTATCOM. The proposed DSTATCOM suppress harmonics, regulates the terminal voltage along with neutral current compensation. The DSTATCOM in distribution systems with proposed control algorithm is modeled and simulated using MATLAB using SIMULINK and Simpower systems toolboxes.

  16. Accelerating reconstruction of reference digital tomosynthesis using graphics hardware

    SciTech Connect

    Yan Hui; Ren Lei; Godfrey, Devon J.; Yin Fangfang

    2007-10-15

    The successful implementation of digital tomosynthesis (DTS) for on-board image guided radiation therapy (IGRT) requires fast DTS image reconstruction. Both target and reference DTS image sets are required to support an image registration application for IGRT. Target images are usually DTS image sets reconstructed from on-board projections, which can be accomplished quickly using the conventional filtered backprojection algorithm. Reference images are DTS image sets reconstructed from digitally reconstructed radiographs (DRRs) previously generated from conventional planning CT data. Generating a set of DRRs from planning CT is relatively slow using the conventional ray-casting algorithm. In order to facilitate DTS reconstruction within a clinically acceptable period of time, we implemented a high performance DRR reconstruction algorithm on a graphics processing unit of commercial PC graphics hardware. The performance of this new algorithm was evaluated and compared with that which is achieved using the conventional software-based ray-casting algorithm. DTS images were reconstructed from DRRs previously generated by both hardware and software algorithms. On average, the DRR reconstruction efficiency using the hardware method is improved by a factor of 67 over the software method. The image quality of the DRRs was comparable to those generated using the software-based ray-casting algorithm. Accelerated DRR reconstruction significantly reduces the overall time required to produce a set of reference DTS images from planning CT and makes this technique clinically practical for target localization for radiation therapy.

  17. Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

    NASA Astrophysics Data System (ADS)

    Soja, Benedikt; Nilsson, Tobias; Balidakis, Kyriakos; Glaser, Susanne; Heinkelmann, Robert; Schuh, Harald

    2016-06-01

    Terrestrial reference frames (TRF), such as the ITRF2008, are primary products of geodesy. In this paper, we present TRF solutions based on Kalman filtering of very long baseline interferometry (VLBI) data, for which we estimate steady station coordinates over more than 30 years that are updated for every single VLBI session. By applying different levels of process noise, non-linear signals, such as seasonal and seismic effects, are taken into account. The corresponding stochastic model is derived site-dependent from geophysical loading deformation time series and is adapted during periods of post-seismic deformations. Our results demonstrate that the choice of stochastic process has a much smaller impact on the coordinate time series and velocities than the overall noise level. If process noise is applied, tests with and without additionally estimating seasonal signals indicate no difference between the resulting coordinate time series for periods when observational data are available. In a comparison with epoch reference frames, the Kalman filter solutions provide better short-term stability. Furthermore, we find out that the Kalman filter solutions are of similar quality when compared to a consistent least-squares solution, however, with the enhanced attribute of being easier to update as, for instance, in a post-earthquake period.

  18. Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements

    NASA Astrophysics Data System (ADS)

    Maus, Stefan

    2015-12-01

    The orientation of a spacecraft in Low Earth Orbit can be determined accurately from either magnetic field measurements or star camera images. Ideally, the independently computed spacecraft attitudes should agree. However, we find that the German CHAMP and European Space Agency triple-satellite Swarm geomagnetic satellites exhibit consistent misalignments between the stellar and geomagnetic reference frames, which oscillate with the local time of the orbit. Having an amplitude of 20 arcsec, these oscillations are more than an order of magnitude larger than the stability of the optical bench, which cohosts the magnetometers and star cameras. The misalignments could originate either from the magnetometer or star camera measurements. On one hand, as-yet-unknown external magnetic field contributions could appear as a rotation of the geomagnetic reference frame. On the other hand, the observed misalignments agree in amplitude and phase with the effects of stellar aberration, caused by the movement of the star cameras relative to the light rays emitted by the stars. This is surprising because stellar aberration is allegedly already corrected for by the star image processing system. Resolving these mysterious misalignments is key to fulfilling the measurement accuracy requirements and science objectives of the ongoing Swarm mission. If caused by stellar aberration, fully correcting for this effect could significantly improve the attitude accuracy not only of CHAMP and Swarm, but also of several other past and ongoing scientific satellite missions.

  19. A reference frame formulation for the analysis and design of steady manufacturing processes

    NASA Astrophysics Data System (ADS)

    Balagangadhar, Dinesh

    A reference frame formulation for large deformation steady state processes is proposed. The displacement and material state variables appear as the primary response fields in this mixed formulation. Unlike displacement based Lagrangian formulations, our formulation does not require a transient analysis to simulate a quasi-steady process and yields results that are free of numerical oscillations and which require considerably less computational effort. And unlike velocity based Eulerian methods, our formulation does not require free surface corrections or streamline integration algorithms. An iterative design environment for quasi-steady forming processes is developed from the computationally efficient reference frame formulation. The direct differentiation method is used to efficiently evaluate the response sensitivities. Select forming response measures and their sensitivities are combined with nonlinear programming methods to optimize the process. Three example problems are presented to demonstrate the efficiency of the proposed formulations: a laser surface treatment process is analyzed, a drawing process is analyzed and optimized and a multi-pass rolling process is analyzed and designed.

  20. Impact of GPS Satellite Antenna Phase Center Variations and Modified Sidereal Filtering on Reference Frame Determination.

    NASA Astrophysics Data System (ADS)

    Owen, S. E.; Webb, F.

    2005-12-01

    Errors in the satellite and ground station antenna phase center variations are among the limiting sources of error in high precision GPS positioning. Recent determinations of phase-center variations (PCV) for both the transmitting satellite and receiving ground station antennas have shown promise for improving geodetic estimates of reference frame parameters, such as scale. While the PCV for the transmitting antennas is reasonably well determined and includes some variation from satellite to satellite, the apparent PCV at ground station antennas are likely to be site specific and dominated by local environmental effects, such as signal multipath. To mitigate these effects, we implement a modified sidereal filter (MSF). The MSF is applied as a correction to the phase and range data. The correction is based on stacking several days of phase and range residuals where each day is shifted by the actual orbital period of each satellite, rather than sidereal time. We will evaluate the effect of stacking several days to 1 month of residuals on such metrics as phase rms and point positioning repeatability. We will present an evaluation the impact of these PCV and MSF corrections on reference frame parameters. The corrections will be applied to several years of observations from a global set of IGS stations.

  1. Egocentric and geocentric frames of reference in memory of large-scale space.

    PubMed

    McNamara, Timothy P; Rump, Björn; Werner, Steffen

    2003-09-01

    This experiment investigated the frames of reference used in memory to represent the spatial structure of a large-scale outdoor environment. Participants learned the locations of eight objects in an unfamiliar city park by walking through the park on one of two prescribed paths that encircled a large rectangular building. The aligned path was oriented with the building; the misaligned path was rotated by 45 degrees. Later, participants pointed to target objects from imagined vantage points using their memories. Pointing accuracy was higher in the aligned than in the misaligned path group, and the patterns of results differed: In the aligned condition, accuracy was higher for imagined headings parallel to legs of the path and for an imagined heading oriented toward a nearby lake, a salient landmark. In the misaligned condition, pointing accuracy was highest for the imagined heading oriented toward the lake, and decreased monotonically with angular distance. These results indicated that locations of objects were mentally represented in terms of frames of reference defined by the environment but selected on the basis of egocentric experience. PMID:14620351

  2. Insight into others’ minds: spatio-temporal representations by intrinsic frame of reference

    PubMed Central

    Sun, Yanlong; Wang, Hongbin

    2014-01-01

    Recent research has seen a growing interest in connections between domains of spatial and social cognition. Much evidence indicates that processes of representing space in distinct frames of reference (FOR) contribute to basic spatial abilities as well as sophisticated social abilities such as tracking other’s intention and belief. Argument remains, however, that belief reasoning in social domain requires an innately dedicated system and cannot be reduced to low-level encoding of spatial relationships. Here we offer an integrated account advocating the critical roles of spatial representations in intrinsic frame of reference. By re-examining the results from a spatial task (Tamborello etal., 2012) and a false-belief task (Onishi and Baillargeon, 2005), we argue that spatial and social abilities share a common origin at the level of spatio-temporal association and predictive learning, where multiple FOR-based representations provide the basic building blocks for efficient and flexible partitioning of the environmental statistics. We also discuss neuroscience evidence supporting these mechanisms. We conclude that FOR-based representations may bridge the conceptual as well as the implementation gaps between the burgeoning fields of social and spatial cognition. PMID:24592226

  3. Co-Seismic Deformations Impact on Geodetic Time Series and Reference Frame Determination

    NASA Astrophysics Data System (ADS)

    Metivier, L.; Collilieux, X.; Lercier, D.; Altamimi, Z.; Beauducel, F.

    2014-12-01

    One of the major sources of error in reference frame determination comes from the undetected discontinuities in station position time series, particularly in GNSS data. Until now, discontinuities in station position time series due to large earthquakes were usually detected visually. Based on a geophysical modeling, we develop a method to predict the effect of co-seismic deformations on position series. Investigating a global network of GPS stations, we demonstrate that a systematic global modeling of co-seismic deformations helps greatly to detect discontinuities in GPS coordinate time series. We show that numerous discontinuities induced by earthquakes are too small to be visually detected because of seasonal variations and GPS noise that disturb their identification. However, not taking these discontinuities into account has a large impact on the station velocity estimation, considering today's precision requirements. Beyond time series discontinuities, we also investigate GPS station displacements induced by two decades of accumulated seismicity. We show here that the accumulation of very small co-seismic deformations may explain non-linear behaviors of GPS station position. It raises the unexpected question of the treatment of such station non-linear motions in reference frame elaboration.

  4. Global Plate Kinematics From GPS in Self-Consistent Reference Frame

    NASA Astrophysics Data System (ADS)

    Kogan, M. G.; Steblov, G. M.

    2007-12-01

    Our study is based on the vectors of rotation of ten major lithospheric plates, that we estimated from continuous GPS observations at 192 globally distributed stations; 71 stations were selected as representing stable plate regions. The time series in the analysis span all days in the interval 1995-2007. In contrast to previous GPS plate models, we estimate relative plate rotations and plate-residual station velocities independently of any reference frame of the ITRF series. We analyze the drift of several ITRF origins relative to the center of plate rotation and show that the drift cannot be neglected in estimating plate motions, especially if the most recent ITRF2005 is used. The solution presented here is obtained under the constraint of no-net translation imposed on plate- residual velocities. Actually, we introduce the reference frame self-consistent with the plate kinematics, with the frame origin at the center of the sphere whose outer shell contains lithospheric plates. The model of the plate kinematics presented here addresses the problem debated since the start of the space geodesy, How big are disagreements between the current and geologic plate motions? We compare the vectors of relative plate rotations in our model with the published vectors from GPS and geologic models for several plate pairs discussed for over a decade. We also analyze the integrity of individual plates as evidenced by plate- residual station velocities. For seven largest plates, the rms value of plate-residual station velocities in stable plate interiors is 0.5-0.9 mm/yr; this value can be regarded as an upper bound on deviation of real plates from infinite stiffness.

  5. Post-Newtonian Reference Frames for Advanced Theory of the Lunar Motion and a New Generation of Lunar Laser Ranging

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Kopeikin, Sergei

    2010-08-01

    We overview a set of post-Newtonian reference frames for a comprehensive study of the orbital dynamics and rotational motion of Moon and Earth by means of lunar laser ranging (LLR). We employ a scalar-tensor theory of gravity depending on two post-Newtonian parameters, and , and utilize the relativistic resolutions on reference frames adopted by the International Astronomical Union (IAU) in 2000. We assume that the solar system is isolated and space-time is asymptotically flat at infinity. The primary reference frame covers the entire space-time, has its origin at the solar-system barycenter (SSB) and spatial axes stretching up to infinity. The SSB frame is not rotating with respect to a set of distant quasars that are forming the International Celestial Reference Frame (ICRF). The secondary reference frame has its origin at the Earth-Moon barycenter (EMB). The EMB frame is locally-inertial and is not rotating dynamically in the sense that equation of motion of a test particle moving with respect to the EMB frame, does not contain the Coriolis and centripetal forces. Two other local frames geocentric (GRF) and selenocentric (SRF) have their origins at the center of mass of Earth and Moon respectively and do not rotate dynamically. Each local frame is subject to the geodetic precession both with respect to other local frames and with respect to the ICRF because of their relative motion with respect to each other. Theoretical advantage of the dynamically non-rotating local frames is in a more simple mathematical description. Each local frame can be aligned with the axes of ICRF after applying the matrix of the relativistic precession. The set of one global and three local frames is introduced in order to fully decouple the relative motion of Moon with respect to Earth from the orbital motion of the Earth-Moon barycenter as well as to connect the coordinate description of the lunar motion, an observer on Earth, and a retro-reflector on Moon to directly measurable

  6. Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame

    SciTech Connect

    Vay, J.-L.; Geddes, C. G. R.; Cormier-Michel, E.; Grote, D. P.

    2010-09-21

    Laser driven plasma accelerators promise much shorter particle accelerators but their development requires detailed simulations that challenge or exceed current capabilities. We report the first direct simulations of stages up to 1 TeV from simulations using a Lorentz boosted calculation frame resulting in a million times speedup, thanks to a frame boost as high as gamma = 1300. Effects of the hyperbolic rotation in Minkowski space resulting from the frame boost on the laser propagation in the plasma is shown to be key in the mitigation of a numerical instability that was limiting previous attempts.

  7. The modulated annual cycle: an alternative reference frame for climate anomalies

    NASA Astrophysics Data System (ADS)

    Wu, Zhaohua; Schneider, Edwin K.; Kirtman, Ben P.; Sarachik, E. S.; Huang, Norden E.; Tucker, Compton J.

    2008-12-01

    In climate science, an anomaly is the deviation of a quantity from its annual cycle. There are many ways to define annual cycle. Traditionally, this annual cycle is taken to be an exact repeat of itself year after year. This stationary annual cycle may not reflect well the intrinsic nonlinearity of the climate system, especially under external forcing. In this paper, we re-examine the reference frame for anomalies by re-examining the annual cycle. We propose an alternative reference frame for climate anomalies, the modulated annual cycle (MAC) that allows the annual cycle to change from year to year, for defining anomalies. In order for this alternative reference frame to be useful, we need to be able to define the instantaneous annual cycle: we therefore also introduce a new method to extract the MAC from climatic data. In the presence of a MAC, modulated in both amplitude and frequency, we can then define an alternative version of an anomaly, this time with respect to the instantaneous MAC rather than a permanent and unchanging AC. Based on this alternative definition of anomalies, we re-examine some familiar physical processes: in particular SST re-emergence and ENSO phase locking to the annual cycle. We find that the re-emergence mechanism may be alternatively interpreted as an explanation of the change of the annual cycle instead of an explanation of the interannual to interdecadal persistence of SST anomalies. We also find that the ENSO phase locking can largely be attributed to the residual annual cycle (the difference of the MAC and the corresponding traditional annual cycle) contained in the traditional anomaly, and, therefore, can be alternatively interpreted as a part of the annual cycle phase locked to the annual cycle itself. In addition to the examples of reinterpretation of physics of well known climate phenomena, we also present an example of the implications of using a MAC against which to define anomalies. We show that using MAC as a reference

  8. Coordinated turn-and-reach movements. II. Planning in an external frame of reference

    NASA Technical Reports Server (NTRS)

    Pigeon, Pascale; Bortolami, Simone B.; DiZio, Paul; Lackner, James R.

    2003-01-01

    The preceding study demonstrated that normal subjects compensate for the additional interaction torques generated when a reaching movement is made during voluntary trunk rotation. The present paper assesses the influence of trunk rotation on finger trajectories and on interjoint coordination and determines whether simultaneous turn-and-reach movements are most simply described relative to a trunk-based or an external reference frame. Subjects reached to targets requiring different extents of arm joint and trunk rotation at a natural pace and quickly in normal lighting and in total darkness. We first examined whether the larger interaction torques generated during rapid turn-and-reach movements perturb finger trajectories and interjoint coordination and whether visual feedback plays a role in compensating for these torques. These issues were addressed using generalized Procrustes analysis (GPA), which attempts to overlap a group of configurations (e.g., joint trajectories) through translations and rotations in multi-dimensional space. We first used GPA to identify the mean intrinsic patterns of finger and joint trajectories (i.e., their average shape irrespective of location and orientation variability in the external and joint workspaces) from turn-and-reach movements performed in each experimental condition and then calculated their curvatures. We then quantified the discrepancy between each finger or joint trajectory and the intrinsic pattern both after GPA was applied individually to trajectories from a pair of experimental conditions and after GPA was applied to the same trajectories pooled together. For several subjects, joint trajectories but not finger trajectories were more curved in fast than slow movements. The curvature of both joint and finger trajectories of turn-and-reach movements was relatively unaffected by the vision conditions. Pooling across speed conditions significantly increased the discrepancy between joint but not finger trajectories for

  9. Accuracy and Stability of a Terrestrial Reference Frame Realized from GPS Data

    NASA Astrophysics Data System (ADS)

    Haines, B. J.; Bertiger, W.; Desai, S. D.; Harvey, N. E.; Sibois, A.; Weiss, J. P.

    2012-12-01

    We describe new realizations of the terrestrial reference frame (TRF) based exclusively on GPS data. One of the historical weaknesses of the GPS technique is determination of scale at the level necessary to support the most demanding applications of the TRF (e.g., sea-level change). This weakness is linked primarily to uncertainties in the the antenna phase variations (APV) of the GPS satellite transmitters, which are designed to support navigation rather than mm-level geodesy. Building on our prior work, we characterize the APV of the GPS satellite transmitters using GPS data collected by satellites in low-Earth orbit (LEO). LEO data offer a number of substantial advantages for characterizing the APV of the GPS satellites. The perspective afforded by GPS receivers in orbit is unmatched in terms of both spatial and temporal coverage. In addition, there is no troposphere signal to confound interpretation of the GPS data. More important, however, the scale (mean height) of the precise orbit solutions is well determined (cm-level) from dynamical constraints. This scale knowledge translates into improved scale for the TRF, assuming the APV of the reference LEO antenna is well understood. For our latest APV solutions, the GPS antenna on the TOPEX/POSEIDON mission (1992-2005) serves as our reference LEO antenna. A choke-ring on a 4-m boom extending above the spacecraft, the antenna configuration is very favorable from the standpoint of phase multipath. In addition, the intrinsic APV of the choke-ring antenna assembly was measured before launch at the JPL test range. Since T/P observed only the legacy (Block II/IIA) GPS satellites, we use data from the GRACE mission (2002-pr.) to transfer the T/P reference to the replenishment (Block IIR) GPS satellites. We apply the resulting APV models in weekly network solutions in order to realize the terrestrial reference frame from GPS alone. Current comparisons of our GPS-based TRF (1999-2012) with ITRF2008 yield 0.2 mm

  10. Hybrid Envelope Model/Boosted-Frame Simulations of Laser Wakefield Accelerators

    NASA Astrophysics Data System (ADS)

    Higuera, Adam; Weichman, Kathleen; Abell, Dan; Cowan, Ben; Downer, Michael; Cary, John

    2015-11-01

    Laser wakefield accelerators use a high-intensity laser pulse to drive a wave in a plasma that traps, transports, and accelerates electrons. The Texas Petawatt Laser experiment measures different electron energies (2 GeV) than predicted (7 GeV) by computer simulations. We present and analyze a method for efficiently performing higher-fidelity 3-D, particle-in-cell simulations of laser wakefield acceleration. This method combines previous work on a Laser Envelope Model, which resolves electron self-injection, and boosted-frame simulation, which efficiently models beam propagation in the regime where the Envelope Model is no longer valid. This work is supported by the DOE under Grants No. DE-SC0011617 and DE-SC0012444, by DOE/NSF Grant No. DE-SC0012584, and used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  11. Interaction of Egocentric and World-Centered Reference Frames in the Rat Posterior Parietal Cortex

    PubMed Central

    Clark, Benjamin J.; Forster, Tyler C.; Tatsuno, Masami; McNaughton, Bruce L.

    2014-01-01

    Navigation requires coordination of egocentric and allocentric spatial reference frames and may involve vectorial computations relative to landmarks. Creation of a representation of target heading relative to landmarks could be accomplished from neurons that encode the conjunction of egocentric landmark bearings with allocentric head direction. Landmark vector representations could then be created by combining these cells with distance encoding cells. Landmark vector cells have been identified in rodent hippocampus. Given remembered vectors at goal locations, it would be possible to use such cells to compute trajectories to hidden goals. To look for the first stage in this process, we assessed parietal cortical neural activity as a function of egocentric cue light location and allocentric head direction in rats running a random sequence to light locations around a circular platform. We identified cells that exhibit the predicted egocentric-by-allocentric conjunctive characteristics and anticipate orienting toward the goal. PMID:24741034

  12. Temperature and solute-transport simulation in streamflow using a Lagrangian reference frame

    USGS Publications Warehouse

    Jobson, Harvey E.

    1980-01-01

    A computer program for simulating one-dimensional, unsteady temperature and solute transport in a river has been developed and documented for general use. The solution approach to the convective-diffusion equation uses a moving reference frame (Lagrangian) which greatly simplifies the mathematics of the solution procedure and dramatically reduces errors caused by numerical dispersion. The model documentation is presented as a series of four programs of increasing complexity. The conservative transport model can be used to route a single conservative substance. The simplified temperature model is used to predict water temperature in rivers when only temperature and windspeed data are available. The complete temperature model is highly accurate but requires rather complete meteorological data. Finally, the 10-parameter model can be used to route as many as 10 interacting constituents through a river reach. (USGS)

  13. Guaranteed violation of a Bell inequality without aligned reference frames or calibrated devices

    PubMed Central

    Shadbolt, Peter; Vértesi, Tamás; Liang, Yeong-Cherng; Branciard, Cyril; Brunner, Nicolas; O'Brien, Jeremy L.

    2012-01-01

    Bell tests — the experimental demonstration of a Bell inequality violation — are central to understanding the foundations of quantum mechanics, and are a powerful diagnostic tool for the development of quantum technologies. To date, Bell tests have relied on careful calibration of measurement devices and alignment of a shared reference frame between two parties — both technically demanding tasks. We show that neither of these operations are necessary, violating Bell inequalities (i) with certainty using unaligned, but calibrated, measurement devices, and (ii) with near-certainty using uncalibrated and unaligned devices. We demonstrate generic quantum nonlocality with randomly chosen measurements on a singlet state of two photons, implemented using a reconfigurable integrated optical waveguide circuit. The observed results demonstrate the robustness of our schemes to imperfections and statistical noise. This approach is likely to have important applications both in fundamental science and quantum technologies, including device-independent quantum key distribution. PMID:22737404

  14. Dynamical reference frames in the planetary and earth-moon systems

    NASA Technical Reports Server (NTRS)

    Standish, E. M.; Williams, G.

    1990-01-01

    Estimates of the accuracies of the ephemerides are reviewed using data for planetary and lunar systems to determine the efficacy of the inherent dynamical reference frame. The varied observational data are listed and given with special attention given to ephemeris improvements. The importance of ranging data is discussed with respect to the inner four planets and the moon, and the discrepancy of 1 arcsec/century between mean motions determined by optical observations versus ranging data is addressed. The Viking mission data provide inertial mean motions for the earth and Mars of 0.003 arcsec/century which will deteriorate to 0.01 arcsec after about 10 years. Uncertainties for other planets and the moon are found to correspond to approximately the same level of degradation. In general the data measurements and error estimates are improving the ephemerides, although refitting the data cannot account for changes in mean motion.

  15. Numerical Analysis of a Rotating Detonation Engine in the Relative Reference Frame

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2014-01-01

    A two-dimensional, computational fluid dynamic (CFD) simulation of a semi-idealized rotating detonation engine (RDE) is described. The simulation operates in the detonation frame of reference and utilizes a relatively coarse grid such that only the essential primary flow field structure is captured. This construction yields rapidly converging, steady solutions. Results from the simulation are compared to those from a more complex and refined code, and found to be in reasonable agreement. The performance impacts of several RDE design parameters are then examined. Finally, for a particular RDE configuration, it is found that direct performance comparison can be made with a straight-tube pulse detonation engine (PDE). Results show that they are essentially equivalent.

  16. Impact of A Priori Gradients on VLBI-Derived Terrestrial Reference Frames

    NASA Astrophysics Data System (ADS)

    Böhm, J.; Spicakova, H.; Urquhart, L.; Steigenberger, P.; Schuh, H.

    2011-07-01

    Tropospheric gradients are usually estimated in the analysis of space geodetic observations to account for the azimuthal asymmetry of troposphere delays. Whereas some analysis centres use a priori gradients for the analysis of Very Long Baseline Interferometry (VLBI) observations, no a priori information is generally applied in the analysis of Global Navigation Satellite Systems (GNSS) observations. We introduce a spherical harmonic expansion of total gradients derived from climatology data of the European Centre for Medium-Range Weather Forecasts (ECMWF), and we compare it to the gradients which have been determined for selected VLBI sites from data of the Data Assimilation Office (DAO) at Goddard Space Flight Center. The latter are usually applied in VLBI analysis. We show the effect of using both types of a priori gradients on the terrestrial and celestial reference frames which are determined from GNSS and VLBI analysis.

  17. Using Space Telescope to tie the HIPPARCOS and extragalactic reference frames together

    NASA Technical Reports Server (NTRS)

    Hemenway, P. D.; Duncombe, R. L.; Jefferys, W. H.; Shelus, P. J.

    1985-01-01

    Hubble Space Telescope observations will be made to tie the HIPPARCOS Instrumental System (HIS) to extragalactic objects, to determine the overall rotation of the HIS with respect to a set of extragalactic objects; to compare the HIS to an accurate radio reference frame; and to look for motions in the optical centroids of compact extragalactic objects at the level of 0.001 arcseconds per year. About 75 radio sources and extragalactic objects will be chosen from the initial group of 414 pairs. The egos will have their positions and proper motions determined relative to the HIPPARCOS Input Catalog stars. The candidate stars are being screened by ground based speckle interferometry to select a final set.

  18. Demonstration of free-space reference frame independent quantum key distribution

    NASA Astrophysics Data System (ADS)

    Wabnig, J.; Bitauld, D.; Li, H. W.; Laing, A.; O'Brien, J. L.; Niskanen, A. O.

    2013-07-01

    Quantum key distribution (QKD) is moving from research laboratories towards applications. As computing becomes more mobile, cashless as well as cardless payment solutions are introduced. A possible route to increase the security of wireless communications is to incorporate QKD in a mobile device. Handheld devices present a particular challenge as the orientation and the phase of a qubit will depend on device motion. This problem is addressed by the reference frame independent (RFI) QKD scheme. The scheme tolerates an unknown phase between logical states that vary slowly compared to the rate of particle repetition. Here we experimentally demonstrate the feasibility of RFI QKD over a free-space link in a prepare and measure scheme using polarization encoding. We extend the security analysis of the RFI QKD scheme to be able to deal with uncalibrated devices and a finite number of measurements. Together these advances are an important step towards mass production of handheld QKD devices.

  19. On the estimation of a celestial reference frame in the presence of source structure

    NASA Astrophysics Data System (ADS)

    Plank, L.; Shabala, S. S.; McCallum, J. N.; Krásná, H.; Petrachenko, B.; Rastorgueva-Foi, E.; Lovell, J. E. J.

    2016-01-01

    The spatial structure of sources making up the celestial reference frame (CRF) at radio frequencies is a systematic error source in very long baseline interferometry (VLBI) measurements. Using simulations, we investigate the effects of source structure on the CRF, determined by the actual observational programme of the International VLBI Service for Geodesy and Astrometry. This is done using the source structure simulator of the Vienna VLBI Software. Applying various mock two-component source models, systematic displacements of 10-80 μas in median source position offsets are found. These offsets are predominantly aligned with the direction of the jet. The simulations further show that slight changes in the source model can significantly change the estimated positions. We finally present a new parametrization of source positions in the analysis, namely along the jet direction and perpendicular to it, allowing us to significantly mitigate the effects of source structure on an estimated CRF.

  20. Geometry of the submanifolds of SEXn. I. The C-nonholonomic frame of reference

    NASA Astrophysics Data System (ADS)

    Chung, Kyung Tae; So, Keum Sook; Lee, Jong Woo

    1989-08-01

    A connection which is both Einstein and semisymmetric is called an SE connection. A generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by g λμ through an SE connection is called an n-dimensional SE manifold and denoted by SEXn. This paper is the introductory part of a systematic study of the submanifolds of SEXn. It introduces a new concept of the C-nonholonomic frame of references in SEXn at points of its submanifold and deals with its consequences. The second part will deal with the generalized fundamental equations on an SE hypersubmanifold of SEXn. The third part will be devoted to the theory of parallelism in SEXn and in its submanifold. Finally, the last part will study the curvature theory in a submanifold of SEXn.

  1. The Quest for Astronomical Verification of the First Geodetic Reference Frame in Norway

    NASA Astrophysics Data System (ADS)

    Pettersen, Bjørn R.

    2010-05-01

    The first geodetic reference frame in Norway was established between 1779 and 1806. Geographical circles were used to triangulate the periphery of Southern Norway, thus establishing a continuous geodetic arc along the Norwegian-Swedish border from Halden to Trondheim and then along the west and south coast of Norway to close the arc. The closure allows longitude differences between sites to be calculated by two different trajectories. At selected sites, astronomical observations were carried out to determine latitudes and longitudes for the purpose of verifying the derived geodetic coordinates. This activity was continued for a full century after the geodetic observations had been completed. We track these efforts and compare the results to investigate the improvements over time.

  2. Guaranteed violation of a Bell inequality without aligned reference frames or calibrated devices.

    PubMed

    Shadbolt, Peter; Vértesi, Tamás; Liang, Yeong-Cherng; Branciard, Cyril; Brunner, Nicolas; O'Brien, Jeremy L

    2012-01-01

    Bell tests - the experimental demonstration of a Bell inequality violation - are central to understanding the foundations of quantum mechanics, and are a powerful diagnostic tool for the development of quantum technologies. To date, Bell tests have relied on careful calibration of measurement devices and alignment of a shared reference frame between two parties - both technically demanding tasks. We show that neither of these operations are necessary, violating Bell inequalities (i) with certainty using unaligned, but calibrated, measurement devices, and (ii) with near-certainty using uncalibrated and unaligned devices. We demonstrate generic quantum nonlocality with randomly chosen measurements on a singlet state of two photons, implemented using a reconfigurable integrated optical waveguide circuit. The observed results demonstrate the robustness of our schemes to imperfections and statistical noise. This approach is likely to have important applications both in fundamental science and quantum technologies, including device-independent quantum key distribution. PMID:22737404

  3. Global Reference Frame Realization on National Level Based on the Integration of National CORS Networks

    NASA Astrophysics Data System (ADS)

    Kenyeres, A.; Caporali, A.; Horvath, T.; Baron, A.; Doncker, F. D.; Droscak, B.; Duret, A.; Franke, P.; Georgiev, I.; Gianniou, M.; Hansen, D.; Huisman, L.; Morozova, K.; Nagl, J.; Pihlak, P.; Stangl, G.; Valdes, M.; Ryczywolski, M.; Zurutuza, J.

    2015-12-01

    The national permanent GNSS networks are not only serving the general surveying practice in real-time mode, but they are deployed at reference frame maintenance and geodynamic studies relying on their homogeneously analyzed long-term data series. The ongoing EPN (EUREF Permanent Network) densification targets the integration of the national CORS networks and a homogeneous, dense position and velocity product is derived using the EPN as backbone infrastructure. The homogeneous cumulative solution relies on the national weekly SINEX products in order to minimize inconsistencies (e.g. site naming, discontinuities). The integration is done with the CATREF software (Altamimi et al, IGN) using the Minimum Constraint approach. The derived position and velocity product will be an essential material for various geokinematic studies (PGR, intraplate and plate boundary zone investigations), and also for the better realization of ETRS89 over tectonically active regions. This work is very well inline with the goals of other European initiatives as EPOS and EUPOS. The preparatory work is well in progress, several years of weekly SINEX files are already available and analyzed. The database contains more than 2000 stations stemming from 15 contributing Analysis Centres. A significant effort is devoted to the cleaning and organization of the station metadata and publish on the EPNCB website, which is necessary to improve the quality and reliabilty of the combination product.This presentation, beyond the publication of the state-of the-art combination results partly focuses on the analysis of existing reference frame realization issues caused by the GNSS antenna PCV updates not yet eliminated on the national CORS level.

  4. Dragging of inertial frames.

    PubMed

    Ciufolini, Ignazio

    2007-09-01

    The origin of inertia has intrigued scientists and philosophers for centuries. Inertial frames of reference permeate our daily life. The inertial and centrifugal forces, such as the pull and push that we feel when our vehicle accelerates, brakes and turns, arise because of changes in velocity relative to uniformly moving inertial frames. A classical interpretation ascribed these forces to acceleration relative to some absolute frame independent of the cosmological matter, whereas an opposite view related them to acceleration relative to all the masses and 'fixed stars' in the Universe. An echo and partial realization of the latter idea can be found in Einstein's general theory of relativity, which predicts that a spinning mass will 'drag' inertial frames along with it. Here I review the recent measurements of frame dragging using satellites orbiting Earth. PMID:17805287

  5. Application of the Reduction of Scale Range in a Lorentz Boosted Frame to the Numerical Simulation of Particle Acceleration Devices

    SciTech Connect

    Vay, J.-L.; Fawley, W.M.; Geddes, C.G.R.; Cormier-Michel, E.; Grote, D.P.

    2009-05-01

    It has been shown [1] that it may be computationally advantageous to perform computer simulations in a boosted frame for a certain class of systems: particle beams interacting with electron clouds, free electron lasers, and laser-plasma accelerators. However, even if the computer model relies on a covariant set of equations, it was also pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup [2] . In this paper, we focus on the analysis of the complication of data input and output in a Lorentz boosted frame simulation, and describe the procedures that were implemented in the simulation code Warp[3]. We present our most recent progress in the modeling of laser wakefield acceleration in a boosted frame, and describe briefly the potential benefits of calculating in a boosted frame for the modeling of coherent synchrotron radiation.

  6. Morphology of QSOs-the gridpoints of the Gaia Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Andrei, Alexandre Humberto; Souchay, Jean; Martins, Roberto Vieira; Anton, Sonia; Taris, Francois; Bouquillon, Sebastien; Assafin, Marcelo; Barache, Christophe; Camargo, Julio Ignacio Bueno; Coelho, Bruno; da Silva Neto, Dario Nepomuceno

    2012-08-01

    The acronym QSO refers to the particular time in the life of giant galaxies, often elliptic ones, when the nucleus becomes extremely active fueled by matter infalling onto the accretion disk feeding the massive central black hole. But the duration and intensity of such a phase make QSOs to be treated as a class of objects, and indeed a c lass of enhanced cosmologic, astrophysical and astrometric bearings. As a consequence, even in the optical domain, the morphology of a quasar can be understood as comprehending the domineering central source, the immediate surrounding regions, the jet basis and features along the jet, and a bright host galaxy which is likely to be intensely star forming and generally speaking a lively place in itself. Morphology, and its color dependent aspects, can thus inform on the physical processes at work on a given Q SO, for example what is likeness to exhibit different time scales of variability. The ESA Gaia mission will have its fundamental reference frame formed by quasars, which are desired to be as point like as can be gathered for the sake of ensuring maximum astrometric precision and accuracy. We will present how the morphology characteristic is indicated in the Gaia Initial QSO Catalog and the related investigations. We will also outline t he Gaia extended sources methods that will be applied to all QSOs observe d, and the vast amount of information that will be made available from the mission outcomes.

  7. VizieR Online Data Catalog: International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)

    NASA Astrophysics Data System (ADS)

    Ma, C.; Arias, F. E.; Bianco, G.; Boboltz, D. A.; Bolotin, S. L.; Charlot, P.; Engelhardt, G.; Fey, A. L.; Gaume, R. A.; Gontier, A.-M.; Heinkelmann, R.; Jacobs, C. S.; Kurdubov, S.; Lambert, S. B.; Malkin, Z. M.; Nothnagel, A.; Petrov, L.; Skurikhina, E.; Sokolova, J. R.; Souchay, J.; Sovers, O. J.; Tesmer, V.; Titov, O. A.; Wang, G.; Zharov, V. E.; Barache, C.; Bockmann, S.; Collioud, A.; Gipson, J. M.; Gordon, D.; Lytvyn, S. O.; MacMillan, D. S.; Ojha, R.; Fey, A. L.; Gordon, D.; Jacobs, C. S.

    2013-06-01

    This Technical Note describes the generation by an international team of the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry (VLBI) observations. ICRF2 contains precise positions of 3414 compact radio astronomical sources, more than five times the number as in the first ICRF, hereafter ICRF1. Further, the ICRF2 is found to have a noise floor of only 40μas, some 5-6 times better than ICRF1, and an axis stability of 10μas, nearly twice as stable as ICRF1. Alignment of ICRF2 with the International Celestial Reference System (ICRS) was made using 138 stable sources common to both ICRF2 and ICRF1-Ext2. Future maintenance of ICRF2 will be made using a set of 295 new "defining" sources selected on the basis of positional stability and the lack of extensive intrinsic source structure. The stability of these 295 defining sources, and their more uniform sky distribution eliminates the two largest weaknesses of ICRF1. (2 data files).

  8. A common frame of reference for learned and communicated vectors in honeybee navigation.

    PubMed

    Menzel, Randolf; Kirbach, Andreas; Haass, Wolf-Dieter; Fischer, Bernd; Fuchs, Jacqueline; Koblofsky, Miriam; Lehmann, Konstantin; Reiter, Lutz; Meyer, Hanno; Nguyen, Hai; Jones, Sarah; Norton, Philipp; Greggers, Uwe

    2011-04-26

    Humans draw maps when communicating about places or verbally describe routes between locations. Honeybees communicate places by encoding distance and direction in their waggle dances. Controversy exists not only about the structure of spatial memory but also about the efficiency of dance communication. Some of these uncertainties were resolved by studies in which recruits' flights were monitored using harmonic radar. We asked whether the two sources of vector information--the previously learned flight vector to a food source and the communicated vector--are represented in a common frame of spatial reference. We found that recruits redirect their outbound flights and perform novel shortcut flights between the communicated and learned locations in both directions. Guidance by beacons at the respective locations or by the panorama of the horizon was excluded. These findings indicate a spatial reference based on either large-scale vector integration or a common geocentric map-like spatial memory. Both models predict a memory structure that stores the spatial layout in such a way that decisions are made according to estimated distances and directions. The models differ with respect to the role of landmarks and the time of learning of spatial relations. PMID:21474313

  9. UTC(SU) and EOP(SU) - the only legal reference frames of Russian Federation

    NASA Astrophysics Data System (ADS)

    Koshelyaevsky, Nikolay B.; Blinov, Igor Yu; Pasynok, Sergey L.

    2015-08-01

    There are two legal time reference frames in Russian Federation. UTC(SU) deals with atomic time and play a role of reference for legal timing through the whole country. The other one, EOP(SU), deals with Earth's orientation parameters and provides the official EOP data for scientific, technical and metrological applications in Russia.The atomic time is based on two essential hardware components: primary Cs fountain standards and ensemble of continuously operating H-masers as a time unit/time scale keeper. Basing on H-maser intercomparison system data, regular H-maser frequency calibration against Cs standards and time algorithm autonomous TA(SU) time scale is maintained by the Main Metrological Center. Since 2013 time unit in TA(SU) is the second (SU) reproduced independently by VNIIFTRI Cs primary standards in accordance to it’s definition in the SI. UTC(SU) is relied on TA(SU) and steering to UTC basing on TWSTFT/GNSS time link data. As a result TA(SU) stability level relative to TT considerably exceeds 1×10-15 for sample time one month and more, RMS[UTC-UTC(SU)] ≤ 3 ns for the period of 2013-2015. UTC(SU) is broadcasted by different national means such as specialized radio and TV stations, NTP servers and GLONASS. Signals of Russian radio stations contains DUT1 and dUT1 values at 0.1s and 0.02s resolution respectively.The definitive EOP(SU) are calculated by the Main Metrological Center basing on composition of the eight independent individual EOP data streams delivered by four Russian analysis centers: VNIIFTRI, Institute of Applied Astronomy, Information-Analytical Center of Russian Space Agency and Analysis Center of Russian Space Agency. The accuracy of ultra-rapid EOP values for 2014 is estimated ≤ 0.0006" for polar motion, ≤ 70 microseconds for UT1-UTC and ≤ 0.0003" for celestial pole offsets respectively.The other VNIIFTRI EOP activities can be grouped in three basic directions:- arrangement and carrying out GNSS and SLR observations at five

  10. Non-singular expressions for the spherical harmonic synthesis of gravitational curvatures in a local north-oriented reference frame

    NASA Astrophysics Data System (ADS)

    Hamáčková, Eliška; Šprlák, Michal; Pitoňák, Martin; Novák, Pavel

    2016-03-01

    Third-order gradients of the gravitational potential (gravitational curvatures) have already found some applications in geosciences. Observability of these parameters, describing the Earth's gravitational field in a more complex way than any other currently available gravitational parameter, such as gravitational acceleration (first-order gradient) or gravitational (second-order) gradient, is currently discussed by physicists. Moreover, first designs of observational devices (sensors) have already been proposed. The spherical harmonic analysis and synthesis are the common tools used by geoscientists to study spectral properties of various functionals of the Earth's gravitational potential. However, the conventional spherical harmonic expansions of the gravitational curvatures in the local north-oriented reference frame have rather complicated forms that depend on the first-, second- and third-order derivatives of the associated Legendre functions. Moreover, some of these expansions also contain singular terms at the poles. In this paper, the conventional series are transformed to new simpler and non-singular forms based on relations between the associated Legendre functions and their derivatives. Numerical experiments demonstrate the applicability and correctness of the new expressions.

  11. An EPID based method for performing high accuracy calibration between an optical external marker tracking device and the LINAC reference frame

    PubMed Central

    Grelewicz, Zachary; Kang, Hyejoo; Wiersma, Rodney D.

    2012-01-01

    Purpose: With the increasing use of external 3D optical tracking cameras to guide modern radiation therapy procedures, it has become vitally important to have an accurate camera to linear accelerator (LINAC) reference frame calibration. To eliminate errors present in current calibration procedures based on the manual hand alignment of a device using the light field crosshairs and in room guidance lasers, a semiautomated quantitative calibration approach requiring only use of an electronic portal imaging device (EPID) was developed. Methods: A phantom comprised of seven highly IR reflective plastic BBs was placed on the LINAC treatment couch and imaged with both a 3D stereoscopic IR imager and the on board megavoltage (MV) EPID imager. Having knowledge of the optically determined 3D positions and projected EPID images of the BBs, simulated annealing was used to optimize the location of the BBs in the LINAC frame using four different optimization functions. Singular value decomposition was then used to calculate the transformation matrix between the camera and LINAC reference frames. Results were then compared to a traditional camera calibration method for overall accuracy. Results: Using modeled data, the simulated annealing process was able to determine the actual locations of the BBs with a RMSE of 0.23 mm. Using projection images acquired with an MV imager, the process was able to determine locations of BBs within .26 mm. The results depend on the choice of optimization function. Conclusions: Results show that the method can be used to provide highly accurate spatial registration between an external 3D imaging reference frame and the LINAC frame. The experimental MV imager results, while not as precise as the simulated results, exceed 1 mm accuracy and the current accepted AAPM TG-142 standard of ≤2 mm positioning accuracy. PMID:22559649

  12. Reference frames in allocentric representations are invariant across static and active encoding

    PubMed Central

    Chan, Edgar; Baumann, Oliver; Bellgrove, Mark A.; Mattingley, Jason B.

    2013-01-01

    An influential model of spatial memory—the so-called reference systems account—proposes that relationships between objects are biased by salient axes (“frames of reference”) provided by environmental cues, such as the geometry of a room. In this study, we sought to examine the extent to which a salient environmental feature influences the formation of spatial memories when learning occurs via a single, static viewpoint and via active navigation, where information has to be integrated across multiple viewpoints. In our study, participants learned the spatial layout of an object array that was arranged with respect to a prominent environmental feature within a virtual arena. Location memory was tested using judgments of relative direction. Experiment 1A employed a design similar to previous studies whereby learning of object-location information occurred from a single, static viewpoint. Consistent with previous studies, spatial judgments were significantly more accurate when made from an orientation that was aligned, as opposed to misaligned, with the salient environmental feature. In Experiment 1B, a fresh group of participants learned the same object-location information through active exploration, which required integration of spatial information over time from a ground-level perspective. As in Experiment 1A, object-location information was organized around the salient environmental cue. Taken together, the findings suggest that the learning condition (static vs. active) does not affect the reference system employed to encode object-location information. Spatial reference systems appear to be a ubiquitous property of spatial representations, and might serve to reduce the cognitive demands of spatial processing. PMID:24009595

  13. Spatial Frames of Reference in Traditional Negev Arabic: Language-to-Cognition Correlation.

    PubMed

    Cerqueglini, Letizia

    2015-09-01

    Linguistic and cognitive tasks on spatial Frames of Reference (FoRs) in Traditional Negev Arabic (TNA) show that TNA is a referentially promiscuous language, using Intrinsic, Relative and Absolute FoRs. FoRs are selected in context according to culture-specific features of the ground (G). TNA speakers exclusively use the Absolute FoR in cognitive tasks, similarly to Mesoamerican languages (Bohnemeyer et al. in Proceedings of the 36th Annual Conference of the Cognitive Science Society, Austin, 2014). Absolute FoR in TNA is anchored on the four cardinal directions. Nevertheless, in TNA and in other varieties of Nomadic Arabic, geocentric sub-types of the Absolute FoR are also observable. Indeed, as in other Absolute-framing systems worldwide, different anchoring strategies (geocentric and astronomic) tend to coexist. I define their coexistence "Absolute Referential Modularity" (ARM). ARM appears in TNA in cognitive referential tasks and in some lexical items, not in linguistic tasks (as elaborated by Levinson et al. in Space stimuli kit 1.2: November 1992. Max Planck Institute for Psycholinguistics, Nijmegen, pp 7-14, 1992). Cardinal directions across Nomadic Arabic varieties show great cultural salience. They are associated with concrete geographical elements and encode topological relations: east-west axis encodes the mountain-sea opposition, beside many symbolic meanings, and encodes the oppositions Up/Down and Inside (familiar)/Outside (foreign). The detection of cognitive and linguistic Absolute referential practices-characterized by Modularity-and the cultural salience of cardinal directions within the whole Nomadic Arabic linguistic group, support the bias for Absolute cognition in promiscuous systems and its antecedence with respect to later linguistic referential strategies (Bohnemeyer et al. 2014). TNA linguistic promiscuity represents an innovation with respect to the cognitive concepts and demonstrates that language first generates semantic structures

  14. Rotor reference frame models of a multiloop 2-phase motor drive in brushless DC and microstepping modes

    SciTech Connect

    Chen, J.E.

    1995-12-31

    This paper describes non-linear models of a 2-phase permanent magnet synchronous motor drive in brushless DC and microstepping modes. The models account for everything from the main power bus up to and including the mechanical load and velocity feedback loop. In particular, the models include the power electronics for each phase complete with their internal feedback loops. Classical state space averaged power electronics models are transformed to the rotor reference frame along with the usual electromechanical variables. Since SPICE linearizes the rotor reference frame model about shaft velocity, instead of shaft angle, frequency domain methods apply. The frequency domain analysis detects unstable interactions between torque angle and deliberate feedback within the drives. Time domain simulations using stator reference frame models confirm the results. All models are SPICE-compatible but were developed on Cadence`s Analog Workbench.

  15. The Realisation and Validation of the Galileo Terrestrial Reference Frame (GTRF)

    NASA Astrophysics Data System (ADS)

    Söhne, W.; Dach, R.; GTRF Team

    2008-12-01

    After a time of uncertainty the European Global Navigation Satellite System (GNSS) Galileo is going to be realized in the next years. Two test satellites - GIOVE A and B - have been placed in the orbit to validate various signals and component. One basic element of the overall Galileo system is the so-called Galileo Terrestrial Reference Frame (GTRF) as the basis for all Galileo products and services. The realization and maintenance of such a TRF has been given to an external consortium, named the Galileo Geodetic Service Provider (GGSP), which consists of seven institutions under the lead of GeoForschungsZentrum Potsdam. The project is funded within the sixth framework programme (FP6) of the European Union and managed by the European GNSS Supervisory Authority (GSA). It will last until May 2009. The GTRF will be a realisation of the International Terrestrial Reference Frame (ITRF) on a position precision level of 3 cm (2 sigma). Since the GTRF will already be required by the time when the first Galileo signals are going to be emitted during the In-Orbit-Validation (IOV) phase, an initial realisation of the GTRF has to be based on other positioning data, notably GPS. In addition to the GTRF, the GGSP will generate additional products and information, such as Earth Rotation Parameters, satellites orbits, clocks for satellites and stations. The presentation describes the strategy for the GTRF realisation following the "state of the art" TRF implementation. Since the Galileo tracking stations, named Galileo Sensor Stations (GSS), will form a sparse global network, it is necessary to densify the network with additional stations to get the highest possible precision and stability for the GTRF. The connection to the ITRF is realized and validated by IGS stations, which are part of the ITRF, and especially by local ties to other geodetic techniques like satellite laser ranging and VLBI. Results from the first analysis campaigns will be shown with special concern to the so

  16. Celestial Reference Frame at X/KA-Band (8.4/32 GHz) for Deep Space Navigation

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Clark, J. E.; García-Miró, C.; Horiuchi, S.; Romero-Wolf, A.; Snedeker, L. G.; Sotuela, I.

    2012-10-01

    Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN). These objects, which are found at extreme distances characterized by median redshifts of z = 1, are ideal for reference frame definition because they exhibit no measurable parallax or proper motion. They are thought to be powered by super massive black holes whose gravitational energy drives galactic sized relativistic jets. These jets produce synchrotron emissions which are detectable by modern radio techniques such as Very Long baseline Interferometry (VLBI). We have constructed a reference frame based on sixty seven X/Ka-band (8.4/32 GHz) VLBI observing sessions (2005 to present), each of ∼24 hours duration, using the intercontinental baselines of NASA's Deep Space Network (DSN): Goldstone, California to Madrid, Spain and Canberra, Australia. We detected 482 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of 460 X/Ka sources in common with the international standard ICRF2 at S/X-band (2.3/8.4 GHz) shows wRMS agreement of 180 μas in RA cos(dec) and 270 μas in Dec. There is evidence for systematic errors at the 100 μas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. Compared to S/X-band frames (e.g. ICRF2 (Ma et al, 2009)), X/Ka-band allows access to more compact source morphology and reduced core shift. Both these improvements allow for a more well-defined and stable reference frame at X/Ka-band. In the next decade, the optically-based Gaia mission (Lindegren, 2008) may produce a frame with competitive precision. By accurately registering radio frames with Gaia, we could study wavelength dependent systematic errors. A simulated frame tie between our X/Ka radio frame and the Gaia optical frame predicts a frame tie precision of 10-15 μas (1-σ, per 3-D rotation component) with

  17. A Celestial Reference Frame at X/ka-Band (8.4/32 Ghz) for Deep Space Navigation

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Clark, J. E.; Garcia-Miro, C.; Horiuchi, S.; Romero-Wolf, A.; Snedeker, L.; Sotuela, I.

    2012-01-01

    Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN). These objects, which are found at extreme distances characterized by median redshifts of z = 1, are ideal for reference frame definition because they exhibit no measurable parallax or proper motion. They are thought to be powered by super massive black holes whose gravitational energy drives galactic sized relativistic jets. These jets produce synchrotron emissions which are detectable by modern radio techniques such as Very Long baseline Interferometry (VLBI).

  18. International Celestial Reference Frame (ICRF): mantenimiento y extensión

    NASA Astrophysics Data System (ADS)

    Ma, C.; Arias, E. F.; Eubanks, T.; Fey, A. L.; Gontier, A.-M.; Jacobs, C. S.; Sovers, O. J.; Archinal, B. A.; Charlot, P.

    A partir de enero de 1998 el sistema de referencia celeste convencional está representado por el International Celestial Reference System (ICRS) y materializado a través de las coordenadas VLBI del conjunto de radiofuentes extragalácticas que conforman el International Celestial Reference Frame (ICRF). La primera realización del ICRF, fue elaborada en 1995 por un grupo de expertos designado por la IAU, la que encomendó al International Earth Rotation Service el mantenimiento del ICRS, del ICRF y del vínculo con marcos de referencia en otras frecuencias. Una primera extensión del ICRF se realizó entre abril y junio de 1999, con el objetivo primario de proveer posiciones de radiofuentes extragalácticas observadas a partir de julio de 1995 y de mejorar las posiciones de las fuentes ``candidatas" con la inclusión de observaciones adicionales. Objetivos secundarios fueron monitorear a las radiofuentes para verificar que siguen siendo adecuadas para realizar al ICRF y mejorar las técnicas de análisis de datos. Como resultado del nuevo análisis se obtuvo una solución a partir de la cual se construyó la primera extensión del ICRF, denominada ICRF - Ext.1. Ella representa al ICRS, sus fuentes de definición se mantienen con las mismas posiciones y errores que en la primera realización del ICRF; las demás radiofuentes tienen coordenadas mejor determinadas que en ICRF; el marco de referencia se densificó con el agregado de 59 nuevas radiofuentes.

  19. THE CELESTIAL REFERENCE FRAME AT 24 AND 43 GHz. II. IMAGING

    SciTech Connect

    Charlot, P.; Boboltz, D. A.; Fey, A. L.; Fomalont, E. B.; Geldzahler, B. J.; Gordon, D.; Ma, C.; Romney, J. D.; Sovers, O. J.

    2010-05-15

    We have measured the submilliarcsecond structure of 274 extragalactic sources at 24 and 43 GHz in order to assess their astrometric suitability for use in a high-frequency celestial reference frame (CRF). Ten sessions of observations with the Very Long Baseline Array have been conducted over the course of {approx}5 years, with a total of 1339 images produced for the 274 sources. There are several quantities that can be used to characterize the impact of intrinsic source structure on astrometric observations including the source flux density, the flux density variability, the source structure index, the source compactness, and the compactness variability. A detailed analysis of these imaging quantities shows that (1) our selection of compact sources from 8.4 GHz catalogs yielded sources with flux densities, averaged over the sessions in which each source was observed, of about 1 Jy at both 24 and 43 GHz, (2) on average the source flux densities at 24 GHz varied by 20%-25% relative to their mean values, with variations in the session-to-session flux density scale being less than 10%, (3) sources were found to be more compact with less intrinsic structure at higher frequencies, and (4) variations of the core radio emission relative to the total flux density of the source are less than 8% on average at 24 GHz. We conclude that the reduction in the effects due to source structure gained by observing at higher frequencies will result in an improved CRF and a pool of high-quality fiducial reference points for use in spacecraft navigation over the next decade.

  20. Deep mantle structure as a reference frame for movements in and on the Earth

    PubMed Central

    Torsvik, Trond H.; van der Voo, Rob; Doubrovine, Pavel V.; Burke, Kevin; Steinberger, Bernhard; Ashwal, Lewis D.; Trønnes, Reidar G.; Webb, Susan J.; Bull, Abigail L.

    2014-01-01

    Earth’s residual geoid is dominated by a degree-2 mode, with elevated regions above large low shear-wave velocity provinces on the core–mantle boundary beneath Africa and the Pacific. The edges of these deep mantle bodies, when projected radially to the Earth’s surface, correlate with the reconstructed positions of large igneous provinces and kimberlites since Pangea formed about 320 million years ago. Using this surface-to-core–mantle boundary correlation to locate continents in longitude and a novel iterative approach for defining a paleomagnetic reference frame corrected for true polar wander, we have developed a model for absolute plate motion back to earliest Paleozoic time (540 Ma). For the Paleozoic, we have identified six phases of slow, oscillatory true polar wander during which the Earth’s axis of minimum moment of inertia was similar to that of Mesozoic times. The rates of Paleozoic true polar wander (<1°/My) are compatible with those in the Mesozoic, but absolute plate velocities are, on average, twice as high. Our reconstructions generate geologically plausible scenarios, with large igneous provinces and kimberlites sourced from the margins of the large low shear-wave velocity provinces, as in Mesozoic and Cenozoic times. This absolute kinematic model suggests that a degree-2 convection mode within the Earth’s mantle may have operated throughout the entire Phanerozoic. PMID:24889632

  1. Force encoding in stick insect legs delineates a reference frame for motor control

    PubMed Central

    Schmitz, Josef; Chaudhry, Sumaiya; Büschges, Ansgar

    2012-01-01

    The regulation of forces is integral to motor control. However, it is unclear how information from sense organs that detect forces at individual muscles or joints is incorporated into a frame of reference for motor control. Campaniform sensilla are receptors that monitor forces by cuticular strains. We studied how loads and muscle forces are encoded by trochanteral campaniform sensilla in stick insects. Forces were applied to the middle leg to emulate loading and/or muscle contractions. Selective sensory ablations limited activities recorded in the main leg nerve to specific receptor groups. The trochanteral campaniform sensilla consist of four discrete groups. We found that the dorsal groups (Groups 3 and 4) encoded force increases and decreases in the plane of movement of the coxo-trochanteral joint. Group 3 receptors discharged to increases in dorsal loading and decreases in ventral load. Group 4 showed the reverse directional sensitivities. Vigorous, directional responses also occurred to contractions of the trochanteral depressor muscle and to forces applied at the muscle insertion. All sensory discharges encoded the amplitude and rate of loading or muscle force. Stimulation of the receptors produced reflex effects in the depressor motoneurons that could reverse in sign during active movements. These data, in conjunction with findings of previous studies, support a model in which the trochanteral receptors function as an array that can detect forces in all directions relative to the intrinsic plane of leg movement. The array could provide requisite information about forces and simplify the control and adaptation of posture and walking. PMID:22673329

  2. Effects of frame of reference and point of view on infantry wayfinding

    NASA Astrophysics Data System (ADS)

    Kumagai, Jason K.; Allard, Fran

    2003-09-01

    Two frames of reference (exocentric and egocentric) and two points of view (first-person and second-person) were contrasted in two experiments to measure their effect on wayfinding performance. Twelve male infantry soldiers used three helmet-mounted display designs (second-person exocentric, second-person egocentric, first-person egocentric) to locate bearings to waypoints. From a constant location, participants were required to face waypoints presented at offset bearings of 25°, 65° and 125°. The egocentric display supported faster performance times than the exocentric display, significantly faster at the largest offset. Faster times were attributed to fewer head misdirection errors and better display compatibility with expectations of spatial orientation. The second-person display supported significantly faster performance times than the first-person display at all offset levels. However, the time differences were not attributed to accuracy or head misdirection errors. Other display features, such as amount of information or field of view may have contributed to the differences. There were no qualitative differences between displays for ease of use, acceptance for land navigation, or mental demand. Implications for the design of helmet-mounted displays for land-based navigational tasks are discussed.

  3. Results from the Reanalysis of Global GPS Data in the IGS08 Reference Frame

    NASA Astrophysics Data System (ADS)

    Desai, S. D.; Bertiger, W.; Haines, B.; Harvey, N.; Selle, C.; Sibthorpe, A.; Weiss, J. P.

    2011-12-01

    We present results from a reanalysis of global GPS data from 1996-present for the determination of orbit and clock solutions for the GPS constellation using the recently released IGS08 reference frame and IERS2010 standards. The precision of these orbit and clock solutions improves by approximately 20-25% when compared to our previous IGS05-based solutions, primarily due to the use of IGS08-based antenna calibrations and improved models of the solar radiation pressure forces acting on the satellites. We show that when using these IGS08-based orbit and clock products the repeatability of precise point positioning solutions of terrestrial stations improves by 5-30%, particularly in the north component. The products from our reanalysis include information that enables single receiver ambiguity resolved positioning for the entire duration (1996-present). We show that average vertical and transverse station repeatability of 5 and 2 mm, respectively, is achieved when using this capability with the IGS08-based orbit and clock solutions for the GPS constellation. This represents an additional improvement of 5-10% in the vertical and north components, and more than 40% in the east component.

  4. Applicability of the "Frame of Reference" approach for environmental monitoring of offshore renewable energy projects.

    PubMed

    Garel, Erwan; Rey, Cibran Camba; Ferreira, Oscar; van Koningsveld, Mark

    2014-08-01

    This paper assesses the applicability of the Frame of Reference (FoR) approach for the environmental monitoring of large-scale offshore Marine Renewable Energy (MRE) projects. The focus is on projects harvesting energy from winds, waves and currents. Environmental concerns induced by MRE projects are reported based on a classification scheme identifying stressors, receptors, effects and impacts. Although the potential effects of stressors on most receptors are identified, there are large knowledge gaps regarding the corresponding (positive and negative) impacts. In that context, the development of offshore MRE requires the implementation of fit-for-purpose monitoring activities aimed at environmental protection and knowledge development. Taking European legislation as an example, it is suggested to adopt standardized monitoring protocols for the enhanced usage and utility of environmental indicators. Towards this objective, the use of the FoR approach is advocated since it provides guidance for the definition and use of coherent set of environmental state indicators. After a description of this framework, various examples of applications are provided considering a virtual MRE project located in European waters. Finally, some conclusions and recommendations are provided for the successful implementation of the FoR approach and for future studies. PMID:24768831

  5. The virtual hand illusion is moderated by context-induced spatial reference frames

    PubMed Central

    Zhang, Jing; Ma, Ke; Hommel, Bernhard

    2015-01-01

    The tendency to perceive an artificial effector as part of one’s own body is known to depend on temporal criteria, like the synchrony between stimulus events informing about the effector. The role of spatial factors is less well understood. Rather than physical distance, which has been manipulated in previous studies, we investigated the role of relative, context-induced distance between the participant’s real hand and an artificial hand stimulated synchronously or asynchronously with the real hand. We replicated previously reported distance effects in a virtual reality setup: the perception of ownership increased with decreased distance, and the impact of synchrony was stronger for short distances. More importantly, we found that ownership perception and impact of synchrony were affected by previous distance: the same, medium distance between real and artificial hand induced more pronounced ownership after having experienced a far-distance condition than after a near-distance condition. This suggests that subjective, context-induced spatial reference frames contribute to ownership perception, which does not seem to fit with the idea of fixed spatial criteria and/or permanent body representations as the sole determinants of perceived body ownership. PMID:26579042

  6. The IAU2000 Standards: The Newly Adopted Time, Coordinates, and Reference Frames.

    NASA Astrophysics Data System (ADS)

    Standish, E. M.

    2003-08-01

    Over the past dozen years or so, the IAU has been deluged with resolutions from Division I (Fundamental Astronomy) regarding dynamics, reference frames, fundamental time-scales, earth orientation, etc. Some of the resolutions are merely cosmetic in nature, detailing the basic foundations which have been used by serious researchers for many years. Some of the other resolutions, however, will have a direct affect upon a number of different fields of study. Sooner or later, these changes will actually be implemented, and they will affect anyone doing precision-type work in astronomy, geophysics, and related fields. As with most changes, there are pros and cons; these will be discussed. On a more practical level, the following questions will be addressed: What major areas of astrometry will be affected? What specific items will change? What does one need to know in order to survive the changes? What does one have to do in order to not be adversely affected? The research described in this publication was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  7. Deep mantle structure as a reference frame for movements in and on the Earth.

    PubMed

    Torsvik, Trond H; van der Voo, Rob; Doubrovine, Pavel V; Burke, Kevin; Steinberger, Bernhard; Ashwal, Lewis D; Trønnes, Reidar G; Webb, Susan J; Bull, Abigail L

    2014-06-17

    Earth's residual geoid is dominated by a degree-2 mode, with elevated regions above large low shear-wave velocity provinces on the core-mantle boundary beneath Africa and the Pacific. The edges of these deep mantle bodies, when projected radially to the Earth's surface, correlate with the reconstructed positions of large igneous provinces and kimberlites since Pangea formed about 320 million years ago. Using this surface-to-core-mantle boundary correlation to locate continents in longitude and a novel iterative approach for defining a paleomagnetic reference frame corrected for true polar wander, we have developed a model for absolute plate motion back to earliest Paleozoic time (540 Ma). For the Paleozoic, we have identified six phases of slow, oscillatory true polar wander during which the Earth's axis of minimum moment of inertia was similar to that of Mesozoic times. The rates of Paleozoic true polar wander (<1°/My) are compatible with those in the Mesozoic, but absolute plate velocities are, on average, twice as high. Our reconstructions generate geologically plausible scenarios, with large igneous provinces and kimberlites sourced from the margins of the large low shear-wave velocity provinces, as in Mesozoic and Cenozoic times. This absolute kinematic model suggests that a degree-2 convection mode within the Earth's mantle may have operated throughout the entire Phanerozoic. PMID:24889632

  8. Global apparent polar wander paths in a hot spot reference frame

    SciTech Connect

    Bocharova, N.Yu.; Scotese, C.R. . Dept. of Geology); Van Der Voo, R. . Dept. Geological Sciences)

    1992-01-01

    Paleomagnetic data provide the basis for plate tectonic reconstructions, especially for the Early mesozoic and Paleozoic. Nevertheless, paleomagnetic pole positions indicate only paleolatitudes of lithospheric blocks without any longitudinal control. If paleomagnetic data, however, are combined with plate motions predicted by the trajectory of hot spot tracks, it is possible to constrain both the latitudinal and longitudinal motion. Global apparent polar wander (GAPW) paths were calculated back to Devonian time (400 Ma), using the paleomagnetic pole summary of Van der Voo (1992) and the global plate tectonic model of the PALEOMAP Project. Only poles with reliability factor not less than 3 were used in the analysis. Individual paleomagnetic poles were rotated in the reference frames of North America, Europe, Siberia, Africa, india, and Australia, and mean poles were calculated at 10 million year intervals. The best results (alpha 95 = 5[degree]) were obtained for Early and Middle Permian. Good results (alpha 95 = 7[degree]) were obtained Early tertiary, Cretaceous, triassic and the Late Carboniferous. Global mean poles for the Early Carboniferous and Early and Middle Jurassic grouped poorly (alpha 95 = 9[degree]). The worst results were obtained for the Devonian (alpha 95 = 11[degree]) and Late Jurassic (alpha 95 = 15[degree]). As a final step, in order to combine the paleomagnetic information with the motions predicted from the hot spot trajectories, stage poles were calculated that fit both the improved GAWP paths and the trajectory of intraplate volcanic chains.

  9. THE CELESTIAL REFERENCE FRAME AT 24 AND 43 GHz. I. ASTROMETRY

    SciTech Connect

    Lanyi, G. E.; Jacobs, C. S.; Naudet, C. J.; Sovers, O. J.; Zhang, L. D.; Boboltz, D. A.; Fey, A. L.; Charlot, P.; Fomalont, E. B.; Geldzahler, B. J.; Gordon, D.; Romney, J. D.

    2010-05-15

    We present astrometric results for compact extragalactic objects observed with the Very Long Baseline Array at radio frequencies of 24 and 43 GHz. Data were obtained from ten 24 hr observing sessions made over a five-year period. These observations were motivated by the need to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies to enable improved deep space navigation after 2016 and to improve state-of-the-art astrometry. Source coordinates for 268 sources were estimated at 24 GHz and for 131 sources at 43 GHz. The median formal uncertainties of right ascension and declination at 24 GHz are 0.08 and 0.15 mas, respectively. Median formal uncertainties at 43 GHz are 0.20 and 0.35 mas, respectively. Weighted root-mean-square differences between the 24 and 43 GHz positions and astrometric positions based on simultaneous 2.3 and 8.4 GHz Very Long Baseline Interferometry observations, such as the ICRF, are less than about 0.3 mas in both coordinates. With observations over five years we have achieved a precision at 24 GHz approaching that of the ICRF but unaccounted systematic errors limit the overall accuracy of the catalogs.

  10. Deep Mantle Structure As a Reference Frame for Absolute Plate Motions

    NASA Astrophysics Data System (ADS)

    Torsvik, T. H.; Van Der Voo, R.; Doubrovine, P. V.; Burke, K. C.; Steinberger, B. M.; Domeier, M.

    2014-12-01

    Since the Pangea supercontinent formed some 320 million years ago, the majority of large igneous provinces and diamond-bearing rocks (kimberlites) near Earth's surface can be sourced to plumes erupting from the margins of two large thermochemical reservoirs at the core-mantle boundary. Using this surface to core-mantle boundary correlation to locate continents in longitude and a new iterative approach for defining a paleomagnetic reference frame corrected for true polar wander, we present a model for plate motion back to earliest Paleozoic time (540 Ma). We have identified six phases of slow, oscillatory true polar wander during the Paleozoic. True polar wander rates (<1 Degree/Myr) are compatible to those in the Mesozoic but plate velocities are on average twice as high. We show that a geologically reasonable model that reconstructs continents in longitude in such a way that large igneous provinces and kimberlites are positioned above the plume generation zones at the times of their formation can be successfully applied to the entire Phanerozoic. Our model is a kinematic model for only the continents. The next step in improving it will be developing a model for the entire lithosphere, including synthetic oceanic lithosphere. This is challenging, but we will demonstrate a full-plate model back to the Late Paleozoic (410 Ma).

  11. Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame

    NASA Technical Reports Server (NTRS)

    Jones, William T.; Nielsen, Eric J.; Lee-Rausch, Elizabeth M.; Acree, Cecil W.

    2014-01-01

    Optimization of tilt-rotor systems requires the consideration of performance at multiple design points. In the current study, an adjoint-based optimization of a tilt-rotor blade is considered. The optimization seeks to simultaneously maximize the rotorcraft figure of merit in hover and the propulsive efficiency in airplane-mode for a tilt-rotor system. The design is subject to minimum thrust constraints imposed at each design point. The rotor flowfields at each design point are cast as steady-state problems in a noninertial reference frame. Geometric design variables used in the study to control blade shape include: thickness, camber, twist, and taper represented by as many as 123 separate design variables. Performance weighting of each operational mode is considered in the formulation of the composite objective function, and a build up of increasing geometric degrees of freedom is used to isolate the impact of selected design variables. In all cases considered, the resulting designs successfully increase both the hover figure of merit and the airplane-mode propulsive efficiency for a rotor designed with classical techniques.

  12. Sequential Estimation of Terrestrial Reference Frame using Information Filter for a Singular System

    NASA Astrophysics Data System (ADS)

    Chin, T. M.; Wu, X.; Gross, R. S.; Heflin, M. B.; Abbondanza, C.; Parker, J. W.

    2013-12-01

    At present, the solution of the International Terrestrial Reference Frame (ITRF) is computed through direct inversion of a single large-scale normal equation. The merits of performing the inversion by an alternative, sequential computational method include: (i) shorter computation time, and (ii) flexibility to incorporate empirical stochastic models for station motion and time-dependent noise processes. KALREF, an ITRF-like formulation implemented using the Kalman filter and a newly developed formulas for the RTS smoother, has been shown to be able to perform a significant portion of the computation sequentially in time. In this presentation, we present a sequential algorithm based on the "information filter", a well-documented variant of the Kalman filter. Unlike the standard Kalman filter, the information filter is able to handle under-constrained state variables and is hence particularly suitable for the "long-term solution" stage of ITRF, where the normal equation remains rank-deficient until an appropriate amount of data is collected ("stacked") over time. However, the ITRF "internal/intrinsic constraint" applied to the Helmert transformation parameters leads to a singularity in temporal dynamics, requiring some significant modifications in the filtering algorithm to avoid numerical degeneracy. We will present such developments in computational algorithms as well as evaluation of their numerical performances using actual data.

  13. Synchronization of high speed framing camera and intense electron-beam accelerator

    NASA Astrophysics Data System (ADS)

    Cheng, Xin-Bing; Liu, Jin-Liang; Hong, Zhi-Qiang; Qian, Bao-Liang

    2012-06-01

    A new trigger program is proposed to realize the synchronization of high speed framing camera (HSFC) and intense electron-beam accelerator (IEBA). The trigger program which include light signal acquisition radiated from main switch of IEBA and signal processing circuit could provide a trigger signal with rise time of 17 ns and amplitude of about 5 V. First, the light signal was collected by an avalanche photodiode (APD) module, and the delay time between the output voltage of APD and load voltage of IEBA was tested, it was about 35 ns. Subsequently, the output voltage of APD was processed further by the signal processing circuit to obtain the trigger signal. At last, by combining the trigger program with an IEBA, the trigger program operated stably, and a delay time of 30 ns between the trigger signal of HSFC and output voltage of IEBA was obtained. Meanwhile, when surface flashover occurred at the high density polyethylene sample, the delay time between the trigger signal of HSFC and flashover current was up to 150 ns, which satisfied the need of synchronization of HSFC and IEBA. So the experiment results proved that the trigger program could compensate the time (called compensated time) of the trigger signal processing time and the inherent delay time of the HSFC.

  14. Synchronization of high speed framing camera and intense electron-beam accelerator

    SciTech Connect

    Cheng Xinbing; Liu Jinliang; Hong Zhiqiang; Qian Baoliang

    2012-06-15

    A new trigger program is proposed to realize the synchronization of high speed framing camera (HSFC) and intense electron-beam accelerator (IEBA). The trigger program which include light signal acquisition radiated from main switch of IEBA and signal processing circuit could provide a trigger signal with rise time of 17 ns and amplitude of about 5 V. First, the light signal was collected by an avalanche photodiode (APD) module, and the delay time between the output voltage of APD and load voltage of IEBA was tested, it was about 35 ns. Subsequently, the output voltage of APD was processed further by the signal processing circuit to obtain the trigger signal. At last, by combining the trigger program with an IEBA, the trigger program operated stably, and a delay time of 30 ns between the trigger signal of HSFC and output voltage of IEBA was obtained. Meanwhile, when surface flashover occurred at the high density polyethylene sample, the delay time between the trigger signal of HSFC and flashover current was up to 150 ns, which satisfied the need of synchronization of HSFC and IEBA. So the experiment results proved that the trigger program could compensate the time (called compensated time) of the trigger signal processing time and the inherent delay time of the HSFC.

  15. Facing the Sunrise: Cultural Worldview Underlying Intrinsic-Based Encoding of Absolute Frames of Reference in Aymara

    ERIC Educational Resources Information Center

    Nunez, Rafael E.; Cornejo, Carlos

    2012-01-01

    The Aymara of the Andes use absolute (cardinal) frames of reference for describing the relative position of ordinary objects. However, rather than encoding them in available absolute lexemes, they do it in lexemes that are intrinsic to the body: "nayra" ("front") and "qhipa" ("back"), denoting east and west, respectively. Why? We use different but…

  16. The Pivotal Role of Frames of Reference in Academic Self-Concept Formation: The "Big Fish-Little Pond" Effect.

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Craven, Rhonda G.

    This chapter examines how adolescents' self-concept beliefs are powerfully influenced by frame of reference effects, which involve students comparisons of their ability levels with those of other students in the immediate context as well as assessments of their own ability and academic accomplishments. Noting that academic self-concept is…

  17. Asymmetric Learning Transfer between Imagined Viewer- and Object-Rotations: Evidence of a Hierarchical Organization of Spatial Reference Frames

    ERIC Educational Resources Information Center

    Pellizzer, Giuseppe; Ba, Maryse Badan; Zanello, Adriano; Merlo, Marco C. G.

    2009-01-01

    Neural resources subserving spatial processing in either egocentric or allocentric reference frames are, at least partly, dissociated. However, it is unclear whether these two types of representations are independent or whether they interact. We investigated this question using a learning transfer paradigm. The experiment and material were…

  18. Flying over uneven moving terrain based on optic-flow cues without any need for reference frames or accelerometers.

    PubMed

    Expert, Fabien; Ruffier, Franck

    2015-04-01

    Two bio-inspired guidance principles involving no reference frame are presented here and were implemented in a rotorcraft, which was equipped with panoramic optic flow (OF) sensors but (as in flying insects) no accelerometer. To test these two guidance principles, we built a tethered tandem rotorcraft called BeeRotor (80 grams), which was tested flying along a high-roofed tunnel. The aerial robot adjusts its pitch and hence its speed, hugs the ground and lands safely without any need for an inertial reference frame. The rotorcraft's altitude and forward speed are adjusted via two OF regulators piloting the lift and the pitch angle on the basis of the common-mode and differential rotor speeds, respectively. The robot equipped with two wide-field OF sensors was tested in order to assess the performances of the following two systems of guidance involving no inertial reference frame: (i) a system with a fixed eye orientation based on the curved artificial compound eye (CurvACE) sensor, and (ii) an active system of reorientation based on a quasi-panoramic eye which constantly realigns its gaze, keeping it parallel to the nearest surface followed. Safe automatic terrain following and landing were obtained with CurvACE under dim light to daylight conditions and the active eye-reorientation system over rugged, changing terrain, without any need for an inertial reference frame. PMID:25717052

  19. Reference Frames and 3-D Shape Perception of Pictured Objects: On Verticality and Viewpoint-From-Above

    PubMed Central

    van Doorn, Andrea J.; Wagemans, Johan

    2016-01-01

    Research on the influence of reference frames has generally focused on visual phenomena such as the oblique effect, the subjective visual vertical, the perceptual upright, and ambiguous figures. Another line of research concerns mental rotation studies in which participants had to discriminate between familiar or previously seen 2-D figures or pictures of 3-D objects and their rotated versions. In the present study, we disentangled the influence of the environmental and the viewer-centered reference frame, as classically done, by comparing the performances obtained in various picture and participant orientations. However, this time, the performance is the pictorial relief: the probed 3-D shape percept of the depicted object reconstructed from the local attitude settings of the participant. Comparisons between the pictorial reliefs based on different picture and participant orientations led to two major findings. First, in general, the pictorial reliefs were highly similar if the orientation of the depicted object was vertical with regard to the environmental or the viewer-centered reference frame. Second, a viewpoint-from-above interpretation could almost completely account for the shears occurring between the pictorial reliefs. More specifically, the shears could largely be considered as combinations of slants generated from the viewpoint-from-above, which was determined by the environmental as well as by the viewer-centered reference frame. PMID:27433329

  20. Verbal and Math Self-Concepts: An Extension of the Internal/External Frame of Reference Model.

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Byrne, Barbara M.

    The internal/external (I/E) frame of reference model describes relations among Verbal self-concept (VSC), Math self-concept (MSC), and corresponding achievement scores (VACH, MACH). In support of the model Marsh (1986) found that: (1) VSC and MSC were nearly uncorrelated; (2) the effect of VACH on VSC, and of MACH on MSC, were positive; but (3)…

  1. Learning to Explain Astronomy across Moving Frames of Reference: Exploring the Role of Classroom and Planetarium-Based Instructional Contexts

    ERIC Educational Resources Information Center

    Plummer, Julia Diane; Kocareli, Alicia; Slagle, Cynthia

    2014-01-01

    Learning astronomy involves significant spatial reasoning, such as learning to describe Earth-based phenomena and understanding space-based explanations for those phenomena as well as using the relevant size and scale information to interpret these frames of reference. This study examines daily celestial motion (DCM) as one case of how children…

  2. Cognitive Ability, Academic Achievement and Academic Self-Concept: Extending the Internal/External Frame of Reference Model

    ERIC Educational Resources Information Center

    Chen, Ssu-Kuang; Hwang, Fang-Ming; Yeh, Yu-Chen; Lin, Sunny S. J.

    2012-01-01

    Background: Marsh's internal/external (I/E) frame of reference model depicts the relationship between achievement and self-concept in specific academic domains. Few efforts have been made to examine concurrent relationships among cognitive ability, achievement, and academic self-concept (ASC) within an I/E model framework. Aim: To simultaneously…

  3. Business vs. Cultural Frames of Reference in Group Decision Making: Interactions among Austrian, Finnish, and Swedish Business Students.

    ERIC Educational Resources Information Center

    Auer-Rizzi, Werner; Berry Michael

    2000-01-01

    Examines ways business and cultural frames of reference affect decision making in multicultural groups. Finds students' reactions to two class activities shows how "groupthink" arose in both exercises; cultural interference paralyzed group decision making in one group; and cultural interference demonstrated the importance of a cultural negotiation…

  4. Justifying Alternative Models in Learning Astronomy: A Study of K-8 Science Teachers' Understanding of Frames of Reference

    ERIC Educational Resources Information Center

    Shen, Ji; Confrey, Jere

    2010-01-01

    Understanding frames of reference is critical in describing planetary motion and learning astronomy. Historically, the geocentric and heliocentric models were defended and advocated against each other. Today, there are still many people who do not understand the relationship between the two models. This topic is not adequately treated in astronomy…

  5. Teachers' Interpretations of the Internet. An Applied Case Study for the Evaluation of Technological Frames of Reference

    ERIC Educational Resources Information Center

    Camilleri, Patrick

    2012-01-01

    In 1994 Orlikowski and Gash articulated Technological Frames of Reference as a systematic theoretical lens to examine technological developments in organisations. A decade later, in 2004, Davidson and Pai expressed concern that while the lens was widely cited in academic discourse, the incidence and adoption of the model as an analytical framework…

  6. Effector-Independent Motor Sequence Representations Exist in Extrinsic and Intrinsic Reference Frames

    PubMed Central

    Wiestler, Tobias; Waters-Metenier, Sheena

    2014-01-01

    Many daily activities rely on the ability to produce meaningful sequences of movements. Motor sequences can be learned in an effector-specific fashion (such that benefits of training are restricted to the trained hand) or an effector-independent manner (meaning that learning also facilitates performance with the untrained hand). Effector-independent knowledge can be represented in extrinsic/world-centered or in intrinsic/body-centered coordinates. Here, we used functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis to determine the distribution of intrinsic and extrinsic finger sequence representations across the human neocortex. Participants practiced four sequences with one hand for 4 d, and then performed these sequences during fMRI with both left and right hand. Between hands, these sequences were equivalent in extrinsic or intrinsic space, or were unrelated. In dorsal premotor cortex (PMd), we found that sequence-specific activity patterns correlated higher for extrinsic than for unrelated pairs, providing evidence for an extrinsic sequence representation. In contrast, primary sensory and motor cortices showed effector-independent representations in intrinsic space, with considerable overlap of the two reference frames in caudal PMd. These results suggest that effector-independent representations exist not only in world-centered, but also in body-centered coordinates, and that PMd may be involved in transforming sequential knowledge between the two. Moreover, although effector-independent sequence representations were found bilaterally, they were stronger in the hemisphere contralateral to the trained hand. This indicates that intermanual transfer relies on motor memories that are laid down during training in both hemispheres, but preferentially draws upon sequential knowledge represented in the trained hemisphere. PMID:24695723

  7. Supercontinent Pangea, Mantle Dynamics, and Reference Frame of Global Plate Motions

    NASA Astrophysics Data System (ADS)

    Zhong, S.; Rudolph, M. L.; Liu, X.

    2014-12-01

    Arguably the most important and challenging goal in geodynamics is to understand the two-way dynamics between tectonic plates and mantle convection. While it has long been recognized that the present-day degree-2 mantle structure as imaged seismically is closely related to the plate motions (Hager and O'Connell, 1981) and their history (<119 Ma) (Ricard et al., 1993; McNamara and Zhong, 2005), recent studies have expanded this concept, from two different perspectives, by seeking connections between Pangea assembly and breakup and mantle structure and dynamics. First, it has been proposed that the large igneous provinces (LIPs) and kimberlite volcanism erupted mainly along the edges of the two major seismically slow anomalies above the core-mantle boundary (often referred to as the Africa and Pacific LLSVPs) (Torsvik et al, 2010). This has led to the proposal that the present-day degree-2 mantle structure has existed for >500 Ma (Torsvik et al., 2014), although its statistical significance has been challenged (Austermann et al., 2013). The proposals of the spatially stable Africa and Pacific LLSVPs and of the LIP eruptions along their edges have also been exploited in attempts to build global plate motion models since the Pangea assembly by providing a plate motion reference frame or inferring true polar wander (TPW) corrections to the plate motions (Torsvik et al., 2014). Second, mantle dynamics studies indicate that degree-1 mantle convection, which is expected with realistic lithospheric and mantle viscosity, may be needed for assembly of a supercontinent (e.g., Pangea) (Zhong et al., 2007). This suggests that the present degree-2 mantle structure may have been formed only after the Pangea assembly from an initially degree-1 structure - a scenario that is consistent with convection calculations with a proxy plate motion model that considers Pangea process (Zhang et al., 2010). In this presentation, in addition to critically reviewing these arguments, we will

  8. Implications of a comprehensive, spreading-aligned plate motion reference frame in light of seismic anisotropy and global trench migration

    NASA Astrophysics Data System (ADS)

    Becker, T. W.; Schaeffer, A. J.; Lebedev, S.; Conrad, C. P.

    2015-12-01

    An absolute plate motion model is required to address issues such as the thermo-chemical evolution of Earth's mantle, yet all such models have to rely on indirect inferences. Given that azimuthal seismic anisotropy in the uppermost mantle appears to show fast axes parallel to seafloor spreading, we explore a new, spreading-aligned reference frame. We show that this reference frame indeed fits azimuthal seismic anisotropy from surface waves and SKS splitting very well. The corresponding Euler pole (at 64∘E, 61∘S, with rotation of ~0.25∘/Myr) is close to those of hot spot reference frames, as expected if hot spots were due to relatively stationary mantle plumes. The new Euler pole is also close to that of ridge motion minimizing models, and its amplitude broadly consistent with estimates of net rotation generation by mantle convection with strong continental keels and a weak asthenosphere. The finding that relative spreading aligns with absolute plate motions implies that ridges are passive and that transform faults weak, allowing for easy realignment of spreading centers during slab-driven plate reorganizations. We also explore the implications of our new reference frame for slabs where we find that all of the major eastern Pacific subduction zone trenches are rolling back (away from the overriding plate). Fast trench advance is only predicted in regions with strong corner flow and pivoting (Tonga), continental plate interactions (Sumatra and Caribbean), and most clearly in an ocean-ocean setting for the Philippine Sea Plate where double subduction, slab-slab interactions may explain the fast advance of the Marianas. We conclude that a net rotation pole guided by the spreading-aligned model could indeed represent a comprehensive reference frame for present-day plate motions with respect to the deep mantle.

  9. Some comments on multicomponent diffusion: negative main term diffusion coefficients, second law constraints, solvent choices, and reference frame transformations

    SciTech Connect

    Miller, D.G.; Vitagliano, V.; Sartorio, R.

    1986-04-10

    Some interesting aspects of multicomponent diffusion in liquids are discussed. These include the existence of a negative main term diffusion coefficient; the utility of taking different components as the solvent; the change-of-solvent transformation for Fick's law coefficients and Onsager coefficients; the validity of the Onsager reciprocal relations on changing solvents; and the calculation of partial molar volumes from diffusion data. Previous work is surveyed on the irreversible thermodynamic basis for macroscopic diffusion; the importance of reference frames and transformations among them; and second law conditions on the volume-fixed diffusion coefficient matrix. Certain diffusion descriptions in other reference frames do not preserve these second law conditions. 78 references, 5 tables.

  10. GPS derived ground motions (2005-2014) within the Gulf of Mexico region referred to a stable Gulf of Mexico reference frame

    NASA Astrophysics Data System (ADS)

    Yu, J.; Wang, G.

    2015-11-01

    This study investigates current ground motions derived from the GPS geodesy infrastructure in the Gulf of Mexico region. The positions and velocity vectors of 161 continuous GPS (CGPS) stations are presented with respect to a newly established local reference frame, the Stable Gulf of Mexico Reference Frame (SGOMRF). Thirteen long-term (> 5 years) CGPS are used to realize the local reference frame. The root-mean-square (RMS) of the velocities of the 13 SGOMRF reference stations achieves 0.2 mm yr-1 in the horizontal and 0.3 mm yr-1 in the vertical directions. GPS observations presented in this study indicate significant land subsidence in the coastal area of southeastern Louisiana, the greater Houston metropolitan area, and two cities in Mexico (Aguascalientes and Mexico City). The most rapid subsidence is recorded at the Mexico City International airport, which is up to 26.6 cm yr-1 (2008-2014). Significant spatial variation of subsidence rates is observed in both Mexico City and the Houston area. The overall subsidence rate in the Houston area is decreasing. GPS observations in southeastern Louisiana indicate minor (4.0-6.0 mm yr-1) but consistent subsidence over time and space. This poses a potential threat to the safety of costal infrastructure in the long-term.

  11. GPS-derived ground deformation (2005-2014) within the Gulf of Mexico region referred to a stable Gulf of Mexico reference frame

    NASA Astrophysics Data System (ADS)

    Yu, Jiangbo; Wang, Guoquan

    2016-07-01

    This study investigates current ground deformation derived from the GPS geodesy infrastructure in the Gulf of Mexico region. The positions and velocity vectors of 161 continuous GPS (CGPS) stations are presented with respect to a newly established local reference frame, the Stable Gulf of Mexico Reference Frame (SGOMRF). Thirteen long-term (> 5 years) CGPS are used to realize the local reference frame. The root mean square (RMS) of the velocities of the 13 SGOMRF reference stations achieves 0.2 mm yr-1 in the horizontal and 0.3 mm yr-1 in the vertical directions. GPS observations presented in this study indicate significant land subsidence in the coastal area of southeastern Louisiana, the greater Houston metropolitan area, and two cities in Mexico (Aguascalientes and Mexico City). The most rapid subsidence is recorded at the Mexico City International airport, which is up to 26.6 cm yr-1 (2008-2014). Significant spatial variation of subsidence rates is observed in both Mexico City and the Houston area. The overall subsidence rate in the Houston area is decreasing. The subsidence rate in southeastern Louisiana is relatively smaller (4.0-6.0 mm yr-1) but tends to be steady over time. This poses a potential threat to the safety of coastal infrastructure in the long-term.

  12. On the consistency of the ICRF and the reference frame realized by RSC(GAO UA)97 C 01

    NASA Astrophysics Data System (ADS)

    Molotaj, O.; Telnyuk-Adamchuk, V.; Yatskiv, Ya.

    Using the method of arcs between the radio sources (RS) developed by Yatskiv and Kuryanova, the Kyiv series of compiled catalogues of RS positions has been continued. This method provides the possibilities of deriving the uncertainty of source catalogues and of detecting inconsistencies in the separation of RS positions. A comparison between the constructed catalogue RSC(GAO UA)97 C 01, on the one hand, and the reference frames ICRF94 and RSC(WGRF)95 R 02, on the other hand, has been carried out. Systematic differences and the consistency of these frames are discussed.

  13. The ICRF-3: Status, Plans, and Multi-wavelength Progress on the next generation Celestial Reference Frame.

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher

    2015-08-01

    ICRF-3 seeks to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverage relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames that are ready for comparison with the Gaia optical frame.Several specific actions are underway. A collaboration to improve at S/X-band precision of the Very Long Baseline Array (VLBA) Calibrator Survey's ~2200 sources, which are typically 5 times less precise than the rest of the ICRF-2, is bearing fruit and is projected to yield a factor of 3 improvement in precision. S/X-band southern hemisphere precision improvements are underway with observations using southern antennas such as the AuScope, Warkworth, and HartRAO, South Africa.We also seek to improve radio frequency coverage with X/Ka-band and K-band work. An X/Ka frame of 660 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which is strengthening the southern hemisphere in general. The X/Ka-band frame's precision is now comparable to the ICRF-2 for the 530 sources in common. A K-band collaboration has formed with similar coverage and southern precision goals. By the time of this meeting, we expect K-band to complete full sky coverage with south polar cap observations and to improve spatial density north of -30 deg declination with VLBA observations.On the analysis front, special attention is being given to combination techniques both of Very Long Baseline Interferometry (VLBI) frames and of multiple data types. Consistency of the Celestial Reference Frame (CRF) with the Terrestrial Reference Frame (TRF) and Earth Oreintation Parameters (EOP) is another area of concern. Comparison of celestial frame solutions from various groups is underway in order to identify and correct systematic errors. We will discuss evidence emerging for 100 µas zonal errors in the ICRF2 in the declination range from 0 to -30 deg.Finally, work is underway to identify and

  14. A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Reynolds, J. E.; Jauncey, D. L.; De Vegt, C.; Zacharias, N.; Ma, C.; Fey, A. L.; Johnston, K. J.; Hindsley, R.; Hughes, J. A.

    1994-01-01

    We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

  15. Are OPERA neutrinos faster than light because of non-inertial reference frames?

    NASA Astrophysics Data System (ADS)

    Germanà, C.

    2012-02-01

    Context. Recent results from the OPERA experiment reported a neutrino beam traveling faster than light. The challenging experiment measured the neutrino time of flight (TOF) over a baseline from the CERN to the Gran Sasso site, concluding that the neutrino beam arrives ~60 ns earlier than a light ray would do. Because the result, if confirmed, has an enormous impact on science, it might be worth double-checking the time definitions with respect to the non-inertial system in which the neutrino travel time was measured. An observer with a clock measuring the proper time τ free of non-inertial effects is the one located at the solar system barycenter (SSB). Aims: Potential problems in the OPERA data analysis connected with the definition of the reference frame and time synchronization are emphasized. We aim to investigate the synchronization of non-inertial clocks on Earth by relating this time to the proper time of an inertial observer at SSB. Methods: The Tempo2 software was used to time-stamp events observed on the geoid with respect to the SSB inertial observer time. Results: Neutrino results from OPERA might carry the fingerprint of non-inertial effects because they are timed by terrestrial clocks. The CERN-Gran Sasso clock synchronization is accomplished by applying corrections that depend on special and general relativistic time dilation effects at the clocks, depending on the position of the clocks in the solar system gravitational well. As a consequence, TOF distributions are centered on values shorter by tens of nanoseconds than expected, integrating over a period from April to December, longer if otherwise. It is worth remarking that the OPERA runs have always been carried out from April/May to November. Conclusions: If the analysis by Tempo2 holds for the OPERA experiment, the excellent measurement by the OPERA collaboration will turn into a proof of the general relativity theory in a weak field approximation. The analysis presented here is falsifiable

  16. Enabling Lorentz boosted frame particle-in-cell simulations of laser wakefield acceleration in quasi-3D geometry

    NASA Astrophysics Data System (ADS)

    Yu, Peicheng; Xu, Xinlu; Davidson, Asher; Tableman, Adam; Dalichaouch, Thamine; Li, Fei; Meyers, Michael D.; An, Weiming; Tsung, Frank S.; Decyk, Viktor K.; Fiuza, Frederico; Vieira, Jorge; Fonseca, Ricardo A.; Lu, Wei; Silva, Luis O.; Mori, Warren B.

    2016-07-01

    When modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) algorithm in a Lorentz boosted frame, the plasma is drifting relativistically at βb c towards the laser, which can lead to a computational speedup of ∼ γb2 = (1 - βb2)-1. Meanwhile, when LWFA is modeled in the quasi-3D geometry in which the electromagnetic fields and current are decomposed into a limited number of azimuthal harmonics, speedups are achieved by modeling three dimensional (3D) problems with the computational loads on the order of two dimensional r - z simulations. Here, we describe a method to combine the speedups from the Lorentz boosted frame and quasi-3D algorithms. The key to the combination is the use of a hybrid Yee-FFT solver in the quasi-3D geometry that significantly mitigates the Numerical Cerenkov Instability (NCI) which inevitably arises in a Lorentz boosted frame due to the unphysical coupling of Langmuir modes and EM modes of the relativistically drifting plasma in these simulations. In addition, based on the space-time distribution of the LWFA data in the lab and boosted frame, we propose to use a moving window to follow the drifting plasma, instead of following the laser driver as is done in the LWFA lab frame simulations, in order to further reduce the computational loads. We describe the details of how the NCI is mitigated for the quasi-3D geometry, the setups for simulations which combine the Lorentz boosted frame, quasi-3D geometry, and the use of a moving window, and compare the results from these simulations against their corresponding lab frame cases. Good agreement is obtained among these sample simulations, particularly when there is no self-trapping, which demonstrates it is possible to combine the Lorentz boosted frame and the quasi-3D algorithms when modeling LWFA. We also discuss the preliminary speedups achieved in these sample simulations.

  17. Investigation of student ability to relate measurements of physical quantities made in different inertial reference frames*

    NASA Astrophysics Data System (ADS)

    Boudreaux, Andrew

    1999-05-01

    The Physics Education Group at the University of Washington has been examining student understanding of relative motion in one and two dimensions. We have found that many students in introductory physics treat some vector quantities as being frame-independent or have difficulty in transforming these quantities from one frame to another. Evidence will be presented from results of interviews and written questions. * This work has been funded in part by NSF Grants DUE 9354501 and DUE 9727648, which include support from other Divisions of EHR and the Physics Division of MPS.

  18. Learning to Explain Astronomy Across Moving Frames of Reference: Exploring the role of classroom and planetarium-based instructional contexts

    NASA Astrophysics Data System (ADS)

    Plummer, Julia Diane; Kocareli, Alicia; Slagle, Cynthia

    2014-05-01

    Learning astronomy involves significant spatial reasoning, such as learning to describe Earth-based phenomena and understanding space-based explanations for those phenomena as well as using the relevant size and scale information to interpret these frames of reference. This study examines daily celestial motion (DCM) as one case of how children learn to move between frames of reference in astronomy wherein one explains Earth-based descriptions of the Sun's, Moon's, and stars' apparent motion using the Earth's daily rotation. We analysed interviews with 8-9-year-old students (N = 99) who participated in one of four instructional conditions emphasizing: the space-based perspective; the Earth-based perspective in the planetarium; constructing explanations for the Earth-based observations; and a combination of the planetarium plus constructing explanations in the classroom. We used an embodied cognition framework to analyse outcomes while also considering challenges learners face due to the high cognitive demands of spatial reasoning. Results support the hypothesis that instruction should engage students in learning both the Earth-based observations and space-based explanations, as focusing on a single frame of reference resulted in less sophisticated explanations; however, few students were able to construct a fully scientific explanation after instruction.

  19. Differential School Contextual Effects for Math and English: Integrating the Big-Fish-Little-Pond Effect and the Internal/External Frame of Reference

    ERIC Educational Resources Information Center

    Parker, Philip D.; Marsh, Herbert W.; Ludtke, Oliver; Trautwein, Ulrich

    2013-01-01

    The internal/external frame of reference and the big-fish-little-pond effect are two major models of academic self-concept formation which have considerable theoretical and empirical support. Integrating the domain specific and compensatory processes of the internal/external frame of reference model with the big-fish-little-pond effect suggests a…

  20. The Reciprocal Internal/External Frame of Reference Model: An Integration of Models of Relations between Academic Achievement and Self-Concept

    ERIC Educational Resources Information Center

    Moller, Jens; Retelsdorf, Jan; Koller, Olaf; Marsh, Herb W.

    2011-01-01

    The reciprocal internal/external frame of reference model (RI/EM) combines the internal/external frame of reference model and the reciprocal effects model. The RI/EM predicts positive effects of mathematics and verbal achievement and academic self-concepts (ASC) on subsequent mathematics and verbal achievements and ASCs within domains and negative…

  1. Modeling of Laser wakefield accelerator in Lorentz boosted frame using EM-PIC code with spectral solver

    NASA Astrophysics Data System (ADS)

    Yu, Peicheng; Xu, Xinlu; Decyk, Viktor; An, Weiming; Vieira, Jorge; Tsung, Frank; Fonseca, Ricardo; Lu, Wei; Silva, Luis; Mori, Warren; UCLA Collaboration; Tsinghua University Collaboration; IST Portugal Collaboration

    2013-10-01

    Simulating laser wakefield acceleration (LWFA) in a Lorentz boosted frame can reduce the computational time over existing fully explicit methods tremendously. In these simulations the relativistic drifting plasma inevitably induces a high frequency numerical instability that contaminates the interested physics, which we mitigate by solve Maxwell equations in Fourier space (a spectral solver) plus using a low pass or ring filter in Fourier space. We describe the development of UPIC-EMMA that uses a spectral solver and that includes the ability to launch a laser using a moving antenna. We show that using UPIC-EMMA LWFA simulations in boosted frames with arbitrary γb can be conducted without any evidence on the numerical instability. We also benchmark the results with lab frame simulations using OSIRIS. These simulations include the modeling cases where there are no self-trapped electrons, and modeling the self-trapped regime. Detailed comparison among Lorentz boost ed frame results and lab frame results obtained from OSIRIS shows the feasibility of using UPIC-EMMA to conduct LWFA simulation at high γb.

  2. The particle production at the event horizon of a black hole as gravitational Fowler-Nordheim emission in uniformly accelerated frame, in the non-relativistic scenario

    NASA Astrophysics Data System (ADS)

    De, Sanchari; Ghosh, Sutapa; Chakrabarty, Somenath

    2015-11-01

    In the conventional scenario, the Hawking radiation is believed to be a tunneling process at the event horizon of the black hole. In the quantum field theoretic approach the Schwinger's mechanism is generally used to give an explanation of this tunneling process. It is the decay of quantum vacuum into particle anti-particle pairs near the black hole surface. However, in a reference frame undergoing a uniform accelerated motion in an otherwise flat Minkowski space-time geometry, in the non-relativistic approximation, the particle production near the event horizon of a black hole may be treated as a kind of Fowler-Nordheim field emission, which is the typical electron emission process from a metal surface under the action of an external electrostatic field. This type of emission from metal surface is allowed even at extremely low temperature. It has been noticed that in one-dimensional scenario, the Schrödinger equation satisfied by the created particle (anti-particle) near the event horizon, can be reduced to a differential form which is exactly identical with that obeyed by an electron immediately after the emission from the metal surface under the action of a strong electrostatic field. The mechanism of particle production near the event horizon of a black hole is therefore identified with Schwinger process in relativistic quantum field theory, whereas in the non-relativistic scenario it may be interpreted as Fowler-Nordheim emission process, when observed from a uniformly accelerated frame.

  3. Can space ties on board GNSS satellites replace terrestrial ties in the implementation of Terrestrial Reference Frames?

    NASA Astrophysics Data System (ADS)

    Bruni, Sara; Zerbini, Susanna; Altamimi, Zuheir; Rebischung, Paul; Errico, Maddalena; Santi, Efisio

    2016-04-01

    The realization of Terrestrial Reference Frames (TRFs) must be periodically updated in order to account for newly acquired observations and for upgrades in data analysis procedures and/or combination techniques. Any innovative computation strategy should ameliorate the definition of the frame physical parameters, upon which a number of scientific applications critically rely. On the basis of the requirements of scientific cutting edge studies, the geodetic community has estimated that the present day challenge in the determination of TRFs is to provide a frame that is accurate and long-term stable at the level of 1 mm and 0.1 mm/y respectively. This work aims at characterizing the frame realized by a combination of Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) observations via their co-location on board GNSS spacecrafts. In particular, it is established how such a frame compares to the traditional ITRF computation and what is the impact on the realization of the frame origin and scale. Four years of data from a global network encompassing about one hundred GNSS stations and all SLR sites have been analyzed. In order to ensure the highest possible consistency, the raw data of both techniques are treated with the same analysis Software (Bernese GNSS Software 5.2) following IERS2010 Conventions. Both weekly and long term solutions are carried out exploiting either the Bernese or the Combination and Analysis of Terrestrial Reference Frames (CATREF) Software packages. We present the results of a combination study involving GNSS data and SLR observations to the two LAGEOS and to the GNSS satellites equipped with retroreflector arrays. The latter type of measurements is currently not included in the computation of the official ITRF solutions. The assessment of the benefit that they could provide to the definition of the origin and scale of the ITRF is however worth investigating, as such data provide the potential for linking the GNSS and

  4. Multiple reference frames for saccadic planning in the human parietal cortex.

    PubMed

    Pertzov, Yoni; Avidan, Galia; Zohary, Ehud

    2011-01-19

    We apply functional magnetic resonance imaging and multivariate analysis methods to study the coordinate frame in which saccades are represented in the human cortex. Subjects performed a memory-guided saccade task in which equal-amplitude eye movements were executed from several starting points to various directions. Response patterns during the memory period for same-vector saccades were correlated in the frontal eye fields and the intraparietal sulcus (IPS), indicating a retinotopic representation. Interestingly, response patterns in the middle aspect of the IPS were also correlated for saccades made to the same destination point, even when their movement vector was different. Thus, this region also contains information about saccade destination in (at least) a head-centered coordinate frame. This finding may explain behavioral and neuropsychological studies demonstrating that eye movements are also anchored to an egocentric or an allocentric representation of space rather than strictly to the retinal visual input and that parietal cortex is involved in maintaining these representations of space. PMID:21248131

  5. Modular neuron-based body estimation: maintaining consistency over different limbs, modalities, and frames of reference.

    PubMed

    Ehrenfeld, Stephan; Herbort, Oliver; Butz, Martin V

    2013-01-01

    This paper addresses the question of how the brain maintains a probabilistic body state estimate over time from a modeling perspective. The neural Modular Modality Frame (nMMF) model simulates such a body state estimation process by continuously integrating redundant, multimodal body state information sources. The body state estimate itself is distributed over separate, but bidirectionally interacting modules. nMMF compares the incoming sensory and present body state information across the interacting modules and fuses the information sources accordingly. At the same time, nMMF enforces body state estimation consistency across the modules. nMMF is able to detect conflicting sensory information and to consequently decrease the influence of implausible sensor sources on the fly. In contrast to the previously published Modular Modality Frame (MMF) model, nMMF offers a biologically plausible neural implementation based on distributed, probabilistic population codes. Besides its neural plausibility, the neural encoding has the advantage of enabling (a) additional probabilistic information flow across the separate body state estimation modules and (b) the representation of arbitrary probability distributions of a body state. The results show that the neural estimates can detect and decrease the impact of false sensory information, can propagate conflicting information across modules, and can improve overall estimation accuracy due to additional module interactions. Even bodily illusions, such as the rubber hand illusion, can be simulated with nMMF. We conclude with an outlook on the potential of modeling human data and of invoking goal-directed behavioral control. PMID:24191151

  6. Modular neuron-based body estimation: maintaining consistency over different limbs, modalities, and frames of reference

    PubMed Central

    Ehrenfeld, Stephan; Herbort, Oliver; Butz, Martin V.

    2013-01-01

    This paper addresses the question of how the brain maintains a probabilistic body state estimate over time from a modeling perspective. The neural Modular Modality Frame (nMMF) model simulates such a body state estimation process by continuously integrating redundant, multimodal body state information sources. The body state estimate itself is distributed over separate, but bidirectionally interacting modules. nMMF compares the incoming sensory and present body state information across the interacting modules and fuses the information sources accordingly. At the same time, nMMF enforces body state estimation consistency across the modules. nMMF is able to detect conflicting sensory information and to consequently decrease the influence of implausible sensor sources on the fly. In contrast to the previously published Modular Modality Frame (MMF) model, nMMF offers a biologically plausible neural implementation based on distributed, probabilistic population codes. Besides its neural plausibility, the neural encoding has the advantage of enabling (a) additional probabilistic information flow across the separate body state estimation modules and (b) the representation of arbitrary probability distributions of a body state. The results show that the neural estimates can detect and decrease the impact of false sensory information, can propagate conflicting information across modules, and can improve overall estimation accuracy due to additional module interactions. Even bodily illusions, such as the rubber hand illusion, can be simulated with nMMF. We conclude with an outlook on the potential of modeling human data and of invoking goal-directed behavioral control. PMID:24191151

  7. Development of a cryogenic load frame for the neutron diffractometer at Takumi in Japan Proton Accelerator Research Complex

    SciTech Connect

    Jin, Xinzhe; Nakamoto, Tatsushi; Ogitsu, Toru; Yamamoto, Akira; Sugano, Michinaka; Harjo, Stefanus; Aizawa, Kazuya; Abe, Jun; Gong, Wu; Iwahashi, Takaaki; Hemmi, Tsutomu; Umeno, Takahiro

    2013-06-15

    To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an external driving machine is 50 kN. Using a Gifford-MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire.

  8. Development of a cryogenic load frame for the neutron diffractometer at Takumi in Japan Proton Accelerator Research Complex.

    PubMed

    Jin, Xinzhe; Nakamoto, Tatsushi; Harjo, Stefanus; Hemmi, Tsutomu; Umeno, Takahiro; Ogitsu, Toru; Yamamoto, Akira; Sugano, Michinaka; Aizawa, Kazuya; Abe, Jun; Gong, Wu; Iwahashi, Takaaki

    2013-06-01

    To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an external driving machine is 50 kN. Using a Gifford-MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire. PMID:23822332

  9. Assessing the impact of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, Claudio; Altamimi, Zuheir; Chin, Toshio; Collilieux, Xavier; Dach, Rolf; Gross, Richard; Heflin, Michael; König, Rolf; Lemoine, Frank; Macmillan, Dan; Parker, Jay; van Dam, Tonie; Wu, Xiaoping

    2014-05-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, we assess the impact of non-tidal atmospheric loading (NTAL) corrections on the TRF computation. Focusing on the a-posteriori approach, (i) the NTAL model derived from the National Centre for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations; (ii) adopting a Kalman-filter based approach, two distinct linear TRFs are estimated combining the 4 SG solutions with (corrected TRF solution) and without the NTAL displacements (standard TRF solution). Linear fits (offset and atmospheric velocity) of the NTAL displacements removed during step (i) are estimated accounting for the station position discontinuities introduced in the SG solutions and adopting different weighting strategies. The NTAL-derived (atmospheric) velocity fields are compared to those obtained from the TRF reductions during step (ii). The consistency between the atmospheric and the TRF-derived velocity fields is examined. We show how the presence of station position discontinuities in SG solutions degrades the agreement between the velocity fields and compare the effect of different weighting structure adopted while estimating the linear fits to the NTAL displacements. Finally, we evaluate the effect of restoring the atmospheric velocities determined through the linear fits of the NTAL displacements to the single-technique linear reference frames obtained by stacking the standard SG SINEX files

  10. Reference-frame-independent quantum-key-distribution server with a telecom tether for an on-chip client.

    PubMed

    Zhang, P; Aungskunsiri, K; Martín-López, E; Wabnig, J; Lobino, M; Nock, R W; Munns, J; Bonneau, D; Jiang, P; Li, H W; Laing, A; Rarity, J G; Niskanen, A O; Thompson, M G; O'Brien, J L

    2014-04-01

    We demonstrate a client-server quantum key distribution (QKD) scheme. Large resources such as laser and detectors are situated at the server side, which is accessible via telecom fiber to a client requiring only an on-chip polarization rotator, which may be integrated into a handheld device. The detrimental effects of unstable fiber birefringence are overcome by employing the reference-frame-independent QKD protocol for polarization qubits in polarization maintaining fiber, where standard QKD protocols fail, as we show for comparison. This opens the way for quantum enhanced secure communications between companies and members of the general public equipped with handheld mobile devices, via telecom-fiber tethering. PMID:24745397

  11. Dynamic (computer) modelling of the particulate environment: Transformations from the LDEF reference frame to decode geocentric and interplanetary populations

    NASA Technical Reports Server (NTRS)

    Mcdonnell, J. A. M.; Sullivan, K.

    1992-01-01

    The Long Duration Exposure Facility (LDEF) impact signature record and the size frequency distribution of craters and perforations offers a unique record of environmental data referenced conveniently to the geocentric reference frame. Chemical analysis of residues can offer only limited assistance. Hence, flux modeling has been developed to transform both geocentric orbital distributions and geocentrically unbounded interplanetary source distributions. This is applied to the foil and crater penetration records in the Ram (E), Trailing (W), and Space Pointing directions to offer the means of decoding the records. It shows that the mix of the components is size dependent. Parametric forms of the modeling transformations are presented for the orbital and unbounded populations.

  12. Dynamic (computer) modelling of the particulate environment: Transformations from the LDEF reference frame to decode geocentric and interplanetary populations

    NASA Technical Reports Server (NTRS)

    Mcdonnell, J. A. M.; Sullivan, K.

    1991-01-01

    The Long Duration Exposure Facility's impact signature record and the size frequency distribution of craters and perforations offers a unique record of environmental data referenced conveniently to the geocentric reference frame. Chemical analysis of residues can offer only limited assistance. Hence, flux modelling has been developed to transform from both geocentric orbital distributions and geocentrically unbounded interplanetary source distributions. This is applied to the foil and crater penetration records in the Ram (E), Trailing (W), and Space Pointing directions to offer the means of decoding the records. It shows that the mix of the components is size dependent. Parametric forms of the modelling transformations are presented for the orbital and unbound populations.

  13. Transformation from proper time on earth to coordinate time in solar system barycentric space-time frame of reference

    NASA Technical Reports Server (NTRS)

    Moyer, T. D.

    1976-01-01

    An expression was derived for the time transformation t - tau, where t is coordinate time in the solar system barycentric space-time frame of reference and tau is proper time obtained from a fixed atomic clock on earth. This transformation is suitable for use in the computation of high-precision earth-based range and Doppler observables of a spacecraft or celestial body located anywhere in the solar system; it can also be used in obtaining computed values of very long baseline interferometry data types. The formulation for computing range and Doppler observables, which is an explicit function of the transformation t - tau, is described briefly.

  14. A Multi-Componential Approach to Frame of Reference Acceptability in Tabletop Space

    ERIC Educational Resources Information Center

    Robinette, Laurie E.

    2010-01-01

    English spatial term assignment can involve some level of ambiguity, in that a single preposition may map onto a different area of space depending upon contextual issues involved in the assignment. For example, a located object can be said to be "above" a reference object in different ways: (1) according to properties of the environment, (2)…

  15. Differences in lower limb transverse plane joint moments during gait when expressed in two alternative reference frames.

    PubMed

    Schache, Anthony G; Baker, Richard; Vaughan, Christopher L

    2007-01-01

    When comparing previous studies that have measured the three-dimensional moments acting about the lower limb joints (either external moments or opposing internal joint moments) during able-bodied adult gait, significant variation is apparent in the profiles of the reported transverse plane moments. This variation cannot be explained on the basis of adopted convention (i.e. external versus internal joint moment) or inherent variability in gait strategies. The aim of the current study was to determine whether in fact the frame in which moments are expressed has a dominant effect upon transverse plane moments and thus provides a valid explanation for the observed inconsistency in the literature. Kinematic and ground reaction force data were acquired from nine able-bodied adult subjects walking at a self-selected speed. Three-dimensional hip, knee and ankle joint moments during gait were calculated using a standard inverse dynamics approach. In addition to calculating internal joint moments, the components of the external moment occurring in the transverse plane at each of the lower limb joints were calculated to determine their independent effects. All moments were expressed in both the laboratory frame (LF) as well as the anatomical frame (AF) of the distal segment. With the exception of the ankle rotation moment in the foot AF, lower limb transverse plane joint moments during gait were found to display characteristic profiles that were consistent across subjects. Furthermore, lower limb transverse plane joint moments during gait differed when expressed in the distal segment AF compared to the LF. At the hip, the two alternative reference frames produced near reciprocal joint moment profiles. The components of the external moment revealed that the external ground reaction force moment was primarily responsible for this result. Lower limb transverse plane joint moments during gait were therefore found to be highly sensitive to a change in reference frame. These

  16. Time-Dependent Selection of an Optimal Set of Sources to Define a Stable Celestial Reference Frame

    NASA Technical Reports Server (NTRS)

    Le Bail, Karine; Gordon, David

    2010-01-01

    Temporal statistical position stability is required for VLBI sources to define a stable Celestial Reference Frame (CRF) and has been studied in many recent papers. This study analyzes the sources from the latest realization of the International Celestial Reference Frame (ICRF2) with the Allan variance, in addition to taking into account the apparent linear motions of the sources. Focusing on the 295 defining sources shows how they are a good compromise of different criteria, such as statistical stability and sky distribution, as well as having a sufficient number of sources, despite the fact that the most stable sources of the entire ICRF2 are mostly in the Northern Hemisphere. Nevertheless, the selection of a stable set is not unique: studying different solutions (GSF005a and AUG24 from GSFC and OPA from the Paris Observatory) over different time periods (1989.5 to 2009.5 and 1999.5 to 2009.5) leads to selections that can differ in up to 20% of the sources. Observing, recording, and network improvement are some of the causes, showing better stability for the CRF over the last decade than the last twenty years. But this may also be explained by the assumption of stationarity that is not necessarily right for some sources.

  17. The visible ground surface as a reference frame for scaling binocular depth of a target in midair.

    PubMed

    Wu, Jun; Zhou, Liu; Shi, Pan; He, Zijiang J; Ooi, Teng Leng

    2015-02-01

    The natural ground surface carries texture information that extends continuously from one's feet to the horizon, providing a rich depth resource for accurately locating an object resting on it. Here, we showed that the ground surface's role as a reference frame also aids in locating a target suspended in midair based on relative binocular disparity. Using real world setup in our experiments, we first found that a suspended target is more accurately localized when the ground surface is visible and the observer views the scene binocularly. In addition, the increased accuracy occurs only when the scene is viewed for 5 s rather than 0.15 s, suggesting that the binocular depth process takes time. Second, we found that manipulation of the configurations of the texture-gradient and/or linear-perspective cues on the visible ground surface affects the perceived distance of the suspended target in midair. Third, we found that a suspended target is more accurately localized against a ground texture surface than a ceiling texture surface. This suggests that our visual system uses the ground surface as the preferred reference frame to scale the distance of a suspended target according to its relative binocular disparity. PMID:25384237

  18. The statistical mapping of magnetosheath plasma properties based on THEMIS measurements in the magnetosheath interplanetary medium reference frame

    NASA Astrophysics Data System (ADS)

    Dimmock, A. P.; Nykyri, K.

    2013-08-01

    The magnetosheath operates as a natural filter between the solar wind and the magnetospheric plasma. As a result of this, the magnetosheath plays a crucial role in the plasma momentum and energy transport from the interplanetary medium into the magnetosphere. Statistical studies of the magnetosheath are difficult due to the dynamic nature of the terrestrial bow shock and the magnetopause. As a result of this, the spatial and temporal dependence of magnetosheath plasma properties under varying solar wind conditions is still not completely understood. We present a study of magnetosheath plasma properties using 5 years of THEMIS and OMNI data to produce statistical maps of fundamental magnetosheath plasma properties. The magnetosheath interplanetary medium reference frame is applied to present data in a normalized reference frame which accounts for both boundary and orbital motion. The statistical maps are compared with the MHD runs from the CCMC-BATS-R-US model which agree favorably. The results are also used to investigate the presence of any magnetosheath plasma parameter asymmetries and their possible causes.

  19. Judging beforehand the possibility of passing under obstacles without motion: the influence of egocentric and geocentric frames of reference.

    PubMed

    Bringoux, L; Robic, G; Gauthier, G M; Vercher, J L

    2008-03-01

    Previous studies have shown that the perception of the earth-based visual horizon, also named Gravity Referenced Eye Level (GREL), is modified by body tilt around a trans-ocular axis. Here, we investigated whether estimates of the elevation of a luminous horizontal line presented on a screen in otherwise darkness and estimates of the possibility of passing under are identically related to body tilt in absence of motion. Results showed that subjects overestimated the elevation of the projected line, whatever their body orientation. In the same way, subjects also overestimated their capacity of passing under the line. Both estimates appeared as a linear function of body tilt, that is, forward body tilt yielded increased overestimations, and backward body tilt yielded decreased overestimations. More strikingly, the linear effect of body tilt upon these estimates is comparable to that previously observed for direct GREL judgements. Overall, these data strongly suggest that the perception of the elevation of a visible obstacle and the perception of the ability of passing under in otherwise darkness shared common processes which are intimately linked to the GREL perception. The effect of body tilt upon these perceptions may illustrate an egocentric influence upon the semi-geocentric frame of reference required to perform the task. Possible interactions between egocentric and geocentric frames of reference are discussed. PMID:17989965

  20. Validation of reference materials for uranium radiochronometry in the frame of nuclear forensic investigations.

    PubMed

    Varga, Z; Mayer, K; Bonamici, C E; Hubert, A; Hutcheon, I; Kinman, W; Kristo, M; Pointurier, F; Spencer, K; Stanley, F; Steiner, R; Tandon, L; Williams, R

    2015-08-01

    The results of a joint effort by expert nuclear forensic laboratories in the area of age dating of uranium, i.e. the elapsed time since the last chemical purification of the material are presented and discussed. Completely separated uranium materials of known production date were distributed among the laboratories, and the samples were dated according to routine laboratory procedures by the measurement of the (230)Th/(234)U ratio. The measurement results were in good agreement with the known production date showing that the concept for preparing uranium age dating reference material based on complete separation is valid. Detailed knowledge of the laboratory procedures used for uranium age dating allows the identification of possible improvements in the current protocols and the development of improved practice in the future. The availability of age dating reference materials as well as the evolvement of the age dating best-practice protocol will increase the relevance and applicability of age dating as part of the tool-kit available for nuclear forensic investigations. PMID:26043276

  1. Modeling of laser wakefield acceleration in Lorentz boosted frame using EM-PIC code with spectral solver

    NASA Astrophysics Data System (ADS)

    Yu, Peicheng; Xu, Xinlu; Decyk, Viktor K.; An, Weiming; Vieira, Jorge; Tsung, Frank S.; Fonseca, Ricardo A.; Lu, Wei; Silva, Luis O.; Mori, Warren B.

    2014-06-01

    Simulating laser wakefield acceleration (LWFA) in a Lorentz boosted frame in which the plasma drifts towards the laser with vb can speed up the simulation by factors of γb2=(1. In these simulations the relativistic drifting plasma inevitably induces a high frequency numerical instability that contaminates the interesting physics. Various approaches have been proposed to mitigate this instability. One approach is to solve Maxwell equations in Fourier space (a spectral solver) as this has been shown to suppress the fastest growing modes of this instability in simple test problems using a simple low pass or "ring" or "shell" like filters in Fourier space. We describe the development of a fully parallelized, multi-dimensional, particle-in-cell code that uses a spectral solver to solve Maxwell's equations and that includes the ability to launch a laser using a moving antenna. This new EM-PIC code is called UPIC-EMMA and it is based on the components of the UCLA PIC framework (UPIC). We show that by using UPIC-EMMA, LWFA simulations in the boosted frames with arbitrary γb can be conducted without the presence of the numerical instability. We also compare the results of a few LWFA cases for several values of γb, including lab frame simulations using OSIRIS, an EM-PIC code with a finite-difference time domain (FDTD) Maxwell solver. These comparisons include cases in both linear and nonlinear regimes. We also investigate some issues associated with numerical dispersion in lab and boosted frame simulations and between FDTD and spectral solvers.

  2. Perspective taking in referring to objects behind versus in front of an observer: Frames of reference, intraindividual consistency, and response latencies.

    PubMed

    Beller, Sieghard; Bohlen, Judith; Hüther, Lisa; Bender, Andrea

    2016-07-01

    Speakers of English and German typically adopt the reflection variant of the relative frame of reference (FoR) in order to describe how nonoriented objects that are located in front of them are related to one another. Little is known, however, about how they proceed in dorsal settings, with objects located in their back. In this article, we explore the turn hypothesis, which assumes a (mental) 180° turn of the observer to face the objects, converting the dorsal into a frontal situation, so that the preferred FoR variant for frontal settings can be applied. To elicit spatial references, we used photographs that showed an observer and two objects either in the observer's visual field (frontal condition) or in the observer's back (dorsal condition). The observer was looking either in the same direction as the referencing individual (aligned perspectives) or in the opposite direction (vis-à-vis perspective). Data from two experiments show that while participants do adopt the observer's perspective, their references in dorsal settings are incompatible with the turn hypothesis. Analyses of response latencies indicate additional cognitive costs for establishing a FoR for the very first item in the dorsal condition as compared to the frontal condition, but fast adaption for subsequent items, and high intraindividual consistency in FoR choice in both conditions. Maintaining the assumption that references in dorsal settings should be compatible with the variant of the relative FoR adopted in frontal settings, participants' references can be explained by assuming a backward projection that gets by without a (mental) turn of the observer. PMID:26393674

  3. Investigations on the hierarchy of reference frames in geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Grafarend, E. W.; Mueller, I. I.; Papo, H. B.; Richter, B.

    1979-01-01

    Problems related to reference directions were investigated. Space and time variant angular parameters are illustrated in hierarchic structures or towers. Using least squares techniques, model towers of triads are presented which allow the formation of linear observation equations. Translational and rotational degrees of freedom (origin and orientation) are discussed along with and the notion of length and scale degrees of freedom. According to the notion of scale parallelism, scale factors with respect to a unit length are given. Three-dimensional geodesy was constructed from the set of three base vectors (gravity, earth-rotation and the ecliptic normal vector). Space and time variations are given with respect to a polar and singular value decomposition or in terms of changes in translation, rotation, deformation (shear, dilatation or angular and scale distortions).

  4. Accelerating seismic interpolation with a gradient projection method based on tight frame property of curvelet

    NASA Astrophysics Data System (ADS)

    Cao, Jingjie; Wang, Yanfei; Wang, Benfeng

    2015-08-01

    Seismic interpolation, as an efficient strategy of providing reliable wavefields, belongs to large-scale computing problems. The rapid increase of data volume in high dimensional interpolation requires highly efficient methods to relieve computational burden. Most methods adopt the L1 norm as a sparsity constraint of solutions in some transformed domain; however, the L1 norm is non-differentiable and gradient-type methods cannot be applied directly. On the other hand, methods for unconstrained L1 norm optimisation always depend on the regularisation parameter which needs to be chosen carefully. In this paper, a fast gradient projection method for the smooth L1 problem is proposed based on the tight frame property of the curvelet transform that can overcome these shortcomings. Some smooth L1 norm functions are discussed and their properties are analysed, then the Huber function is chosen to replace the L1 norm. The novelty of the proposed method is that the tight frame property of the curvelet transform is utilised to improve the computational efficiency. Numerical experiments on synthetic and real data demonstrate the validity of the proposed method which can be used in large-scale computing.

  5. The first privately produced map in Norway with a geodetic reference frame

    NASA Astrophysics Data System (ADS)

    Pettersen, B. R.

    2009-04-01

    A map of the district surrounding lake Mjøsa in Norway was published in 1796 by the Topographical Society of Norway. Their members contributed private funds for this unique map and for the publication of the Topographical Journal, containing multidisciplinary descriptions, including environmental, of many regions of the country. The map was produced by Niels S. Darre, an army surveyor and cartographer, as a private undertaking in his own home district. The geodetic reference point of the map is the church at Vang, the position of which had been determined by repeated astronomical observations by its vicar, Abraham Pihl. He had been trained as an astronomical observer by professor Thomas Bugge at the Round Tower Observatory in Copenhagen. A supporting latitude determination near Lillehammer is also noted on the map, obtained by Maximillian Hell in 1769 on his return from Vardø in North-Norway to Vienna after a successful observation of the transit of Venus. The observed magnetic deviation from astronomically determined north is given. The map also identifies a marker of the great flood of the river Glomma in 1789, causing environmental and social devastation.

  6. Quantum frames

    NASA Astrophysics Data System (ADS)

    Brown, Matthew J.

    2014-02-01

    The framework of quantum frames can help unravel some of the interpretive difficulties i the foundation of quantum mechanics. In this paper, I begin by tracing the origins of this concept in Bohr's discussion of quantum theory and his theory of complementarity. Engaging with various interpreters and followers of Bohr, I argue that the correct account of quantum frames must be extended beyond literal space-time reference frames to frames defined by relations between a quantum system and the exosystem or external physical frame, of which measurement contexts are a particularly important example. This approach provides superior solutions to key EPR-type measurement and locality paradoxes.

  7. Coupled finite-element/state-space modeling of turbogenerators in the ABC frame of reference -- The no-load case

    SciTech Connect

    Chaudhry, S.R.; Ahmed-Zaid, S.; Demerdash, N.A.

    1995-03-01

    This first of two companion papers centers on applying a coupled finite-element/state-space technique to the determination of self and mutual winding inductances of a 733-MVA turbogenerator and computing its open-circuit characteristic, in the natural ABC frame of reference. In this method, the apparent self anti-mutual inductance profiles of the armature and field windings, expressed as functions of rotor position angle, are computed from a series of magnetic field solutions performed at uniformly-distributed samples of rotor positions covering the entire 360{degree} electrical cycle, using the energy perturbation method. These inductances, which are obtained at no-load for three different excitation levels, include the full effect of space harmonics introduced by the magnetic circuit geometry, winding layouts and magnetic circuit saturation. The ABC-frame/finite-element computed open-circuit characteristic is in excellent agreement with the test results. This computed no-load set of parameters forms the initial data for simulation of the full-load performance given in the companion paper, including the full impact of space harmonics and saturation on the flux linkage, current and voltage waveforms, and other performance parameters.

  8. Terrestrial reference frame solution with the Vienna VLBI Software VieVS and implication of tropospheric gradient estimation

    NASA Astrophysics Data System (ADS)

    Spicakova, H.; Plank, L.; Nilsson, T.; Böhm, J.; Schuh, H.

    2011-07-01

    The Vienna VLBI Software (VieVS) has been developed at the Institute of Geodesy and Geophysics at TU Vienna since 2008. In this presentation, we present the module Vie_glob which is the part of VieVS that allows the parameter estimation from multiple VLBI sessions in a so-called global solution. We focus on the determination of the terrestrial reference frame (TRF) using all suitable VLBI sessions since 1984. We compare different analysis options like the choice of loading corrections or of one of the models for the tropospheric delays. The effect of atmosphere loading corrections on station heights if neglected at observation level will be shown. Time series of station positions (using a previously determined TRF as a priori values) are presented and compared to other estimates of site positions from individual IVS (International VLBI Service for Geodesy and Astrometry) Analysis Centers.

  9. PHOTOMETRIC OBSERVATIONS OF SELECTED, OPTICALLY BRIGHT QUASARS FOR SPACE INTERFEROMETRY MISSION AND OTHER FUTURE CELESTIAL REFERENCE FRAMES

    SciTech Connect

    Ojha, Roopesh E-mail: nz@usno.navy.mil E-mail: rgaume@usno.navy.mil

    2009-09-15

    Photometric observations of 235 extragalactic objects that are potential targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R, I magnitudes at the 5% level are obtained at 1-4 epochs between 2005 and 2007 using the 1 m telescopes at Cerro Tololo Inter-American Observatory and the Naval Observatory Flagstaff Station. Of the 134 sources that have V magnitudes in the Veron and Veron-Cetty catalog, a difference of over 1.0 mag is found for the observed-catalog magnitudes for about 36% of the common sources, and 10 sources show over 3 mag difference. Our first set of observations presented here form the basis of a long-term photometric variability study of the selected reference frame sources to assist in mission target selection and to support QSO multicolor photometric variability studies in general.

  10. Adjoint-Based Design of Rotors Using the Navier-Stokes Equations in a Noninertial Reference Frame

    NASA Technical Reports Server (NTRS)

    Nielsen, Eric J.; Lee-Rausch, Elizabeth M.; Jones, William T.

    2010-01-01

    Optimization of rotorcraft flowfields using an adjoint method generally requires a time-dependent implementation of the equations. The current study examines an intermediate approach in which a subset of rotor flowfields are cast as steady problems in a noninertial reference frame. This technique permits the use of an existing steady-state adjoint formulation with minor modifications to perform sensitivity analyses. The formulation is valid for isolated rigid rotors in hover or where the freestream velocity is aligned with the axis of rotation. Discrete consistency of the implementation is demonstrated by using comparisons with a complex-variable technique, and a number of single- and multipoint optimizations for the rotorcraft figure of merit function are shown for varying blade collective angles. Design trends are shown to remain consistent as the grid is refined.

  11. Adjoint-Based Design of Rotors using the Navier-Stokes Equations in a Noninertial Reference Frame

    NASA Technical Reports Server (NTRS)

    Nielsen, Eric J.; Lee-Rausch, Elizabeth M.; Jones, William T.

    2009-01-01

    Optimization of rotorcraft flowfields using an adjoint method generally requires a time-dependent implementation of the equations. The current study examines an intermediate approach in which a subset of rotor flowfields are cast as steady problems in a noninertial reference frame. This technique permits the use of an existing steady-state adjoint formulation with minor modifications to perform sensitivity analyses. The formulation is valid for isolated rigid rotors in hover or where the freestream velocity is aligned with the axis of rotation. Discrete consistency of the implementation is demonstrated using comparisons with a complex-variable technique, and a number of single- and multi-point optimizations for the rotorcraft figure of merit function are shown for varying blade collective angles. Design trends are shown to remain consistent as the grid is refined.

  12. Vehicle-track interaction at high frequencies - Modelling of a flexible rotating wheelset in non-inertial reference frames

    NASA Astrophysics Data System (ADS)

    Guiral, A.; Alonso, A.; Giménez, J. G.

    2015-10-01

    Vehicle-track interaction in the mid- and high-frequency range has become an important issue for rolling-stock manufacturers, railway operators and administrations. Previous modelling approaches have been focused on the development of flexible wheelset-track systems based on the assumption that the unsprung masses are decoupled from the high-frequency dynamic behaviour of carbody and bogies. In this respect, the available flexible wheelset models account for gyroscopic and inertial effects due to the main rotation but are, in general, developed from the viewpoint of inertial spaces and consequently restricted to the study of tangent layouts. The aim of this paper is to present the formulation of a flexible rotating wheelset derived within the framework of a non-inertial vehicle moving reference frame. This brings a double advantage; on the one hand, the formulation is not restricted to tangent tracks, but is also suitable for the study of transition curves and curve negotiation. On the other hand, the use of a vehicle moving reference frame allows the introduction of the hypothesis of small displacement for the degrees of freedom of the wheelset. This hypothesis is not applied to the pitch angle, as it is associated with the main axis of rotation. In addition, unlike previous flexible wheelset models that only consider the rotation around the main axis, all the degrees of freedom will be considered when developing the dynamic equations of motion. Results for the proposed model will be presented and the influence of the inertial and gyroscopic terms not taken into account in previous derived formulations will be evaluated.

  13. Updating of the spatial reference frame of head direction cells in response to locomotion in the vertical plane

    PubMed Central

    Wang, Sarah S.; Kim, Stanley Y.; Frohardt, Russell J.

    2013-01-01

    Many species navigate in three dimensions and are required to maintain accurate orientation while moving in an Earth vertical plane. Here we explored how head direction (HD) cells in the rat anterodorsal thalamus responded when rats locomoted along a 360° spiral track that was positioned vertically within the room at the N, S, E, or W location. Animals were introduced into the vertical plane either through passive placement (experiment 1) or by allowing them to run up a 45° ramp from the floor to the vertically positioned platform (experiment 2). In both experiments HD cells maintained direction-specific firing in the vertical plane with firing properties that were indistinguishable from those recorded in the horizontal plane. Interestingly, however, the cells' preferred directions were linked to different aspects of the animal's environment and depended on how the animal transitioned into the vertical plane. When animals were passively placed onto the vertical surface, the cells switched from using the room (global cues) as a reference frame to using the vertically positioned platform (local cues) as a reference frame, independent of where the platform was located. In contrast, when animals self-locomoted into the vertical plane, the cells' preferred directions remained anchored to the three-dimensional room coordinates and their activity could be accounted for by a simple 90° rotation of the floor's horizontal coordinate system to the vertical plane. These findings highlight the important role that active movement signals play for maintaining and updating spatial orientation when moving in three dimensions. PMID:23114216

  14. Construction of spherical harmonic series for the potential derivatives of arbitrary orders in the geocentric Earth-fixed reference frame

    NASA Astrophysics Data System (ADS)

    Petrovskaya, M. S.; Vershkov, A. N.

    2010-03-01

    The derivatives of the Earth gravitational potential are considered in the global Cartesian Earth-fixed reference frame. Spherical harmonic series are constructed for the potential derivatives of the first and second orders on the basis of a general expression of Cunningham (Celest Mech 2:207-216, 1970) for arbitrary order derivatives of a spherical harmonic. A common structure of the series for the potential and its first- and second-order derivatives allows to develop a general procedure for constructing similar series for the potential derivatives of arbitrary orders. The coefficients of the derivatives are defined by means of recurrence relations in which a coefficient of a certain order derivative is a linear function of two coefficients of a preceding order derivative. The coefficients of the second-order derivatives are also presented as explicit functions of three coefficients of the potential. On the basis of the geopotential model EGM2008, the spherical harmonic coefficients are calculated for the first-, second-, and some third-order derivatives of the disturbing potential T, representing the full potential V, after eliminating from it the zero- and first-degree harmonics. The coefficients of two lowest degrees in the series for the derivatives of T are presented. The corresponding degree variances are estimated. The obtained results can be applied for solving various problems of satellite geodesy and celestial mechanics.

  15. On Being the Same in Different Places: Evaluating Frame-of-Reference Effects Across Two Social Contexts.

    PubMed

    Kurtz, John E; Palfrey, Amy Pastva

    2016-02-01

    Frame-of-reference (FOR) effects in personality assessment are demonstrated when self-rated items oriented to specific contexts (e.g., workplace) show better predictive validity than noncontextualized items. Empirical support of FOR effects typically relies on job performance ratings or academic grades for criteria. The current study evaluates FOR effects using ratings of personality provided by informants from the home or school context. Items from the NEO Five-Factor Inventory (NEO-FFI; Costa & McCrae, 1992) were contextualized to the home and school contexts to create NEO-Home and NEO-School versions. One hundred fifty-eight college students completed the NEO-Home and NEO-School questionnaires, and 161 college students completed the standard, noncontextualized NEO-FFI. All participants recruited one peer from college and at least one parent to complete standard rater versions of the NEO-FFI. Contextualized self-ratings did not show FOR effects. NEO-Home self-ratings did not correlate higher with parent ratings than with peer ratings, and NEO-School self-ratings did not correlate higher with peer ratings than with parent ratings. Standard NEO-FFI self-ratings generally showed higher self-informant agreement with both types of informants than contextualized self-ratings. The pattern of correlations suggests that validity is enhanced more by specific trait-informant combinations than by the contextualization of items to social contexts. PMID:25329358

  16. A Logarithmic Complexity Floating Frame of Reference Formulation with Interpolating Splines for Articulated Multi-Flexible-Body Dynamics

    PubMed Central

    Ahn, W.; Anderson, K.S.; De, S.

    2013-01-01

    An interpolating spline-based approach is presented for modeling multi-flexible-body systems in the divide-and-conquer (DCA) scheme. This algorithm uses the floating frame of reference formulation and piecewise spline functions to construct and solve the non-linear equations of motion of the multi-flexible-body system undergoing large rotations and translations. The new approach is compared with the flexible DCA (FDCA) that uses the assumed modes method [1]. The FDCA, in many cases, must resort to sub-structuring to accurately model the deformation of the system. We demonstrate, through numerical examples, that the interpolating spline-based approach is comparable in accuracy and superior in efficiency to the FDCA. The present approach is appropriate for modeling flexible mechanisms with thin 1D bodies undergoing large rotations and translations, including those with irregular shapes. As such, the present approach extends the current capability of the DCA to model deformable systems. The algorithm retains the theoretical logarithmic complexity inherent in the DCA when implemented in parallel. PMID:24124265

  17. Indirect check of the stability of the reference ion chamber used for accelerator output calibration

    NASA Astrophysics Data System (ADS)

    Kang, Sei-Kwon; Yoon, Jai-Woong; Park, Soah; Hwang, Taejin; Cheong, Kwang-Ho; Han, Tae Jin; Kim, Haeyoung; Lee, Me-Yeon; Kim, Kyoung Ju; Bae, Hoonsik

    2014-11-01

    A linear accelerator's output is periodically checked by using a reference ion chamber which is also periodically calibrated at the accredited standard dosimetry laboratories. We suggest a simple procedure for checking the chamber's stability between calibrations by comparison with another ion chamber. To identify the long-term stability of chambers, we collected and assessed the dose-to-water conversion factors provided by standard laboratories for three chambers during a period of four years. To develop the chamber constancy check program, we used one Farmer-type reference ion chamber FC65-G, two ion chambers (CC13a and CC13b) and one CC01 ion chamber (IBA). Under the accelerator, each chamber was placed inside the solid phantom and irradiated; the experimental configurations were identical. To check the variation in charge collection of the reference chamber, we monitored the ratios of the FC65-G values over each chamber reading. Based on the error propagation of the two chamber ratios, we estimated the uncertainty of the output calibration from the chamber variation. The calibration factors provided for the three chambers showed 0.04 ˜ 0.12% standard deviations during four years. For procedure development, the reading ratios of FC65-G over CCxx showed very good stability; the ratios of FC65-G over CC13a, CC13b and CC01 varied less than 0.059, 0.087 and 0.248%, respectively, over five measurements. By ascribing possible uncertainties of the ratio to the reference chamber alone, we could conservatively check the stability of the reference chamber for treatment safety. An extension of the chamber calibration period was also evaluated. In conclusion, we designed a stability check procedure for the reference chamber based on a reading ratio of two chambers. This could help the user assess the chamber stability between periodic chamber calibration, and the associated patient treatment could be carried out with enhanced safety.

  18. Effect of general relativity on a near-Earth satellite in the geocentric and barycentric reference frames

    NASA Technical Reports Server (NTRS)

    Ries, J. C.; Huang, C.; Watkins, M. M.

    1988-01-01

    Whether one uses a solar-system barycentric frame or a geocentric frame when including the general theory of relativity in orbit determinations for near-Earth satellites, the results should be equivalent to some limiting accuracy. The purpose of this paper is to clarify the effects of relativity in each frame and to demonstrate their equivalence through the analysis of real laser-tracking data. A correction to the conventional barycentric equations of motion is shown to be required.

  19. Effect of general relativity on a near-Earth satellite in the geocentric and barycentric reference frames

    SciTech Connect

    Ries, J.C.; Huang, C.; Watkins, M.M.

    1988-08-22

    Whether one uses a solar-system barycentric frame or a geocentric frame when including the general theory of relativity in orbit determination for near-Earth satellites, the results should be equivalent to some limiting accuracy. The purpose of this paper is to clarify the effects of relativity in each frame and to demonstrate their equivalence through the analysis of real laser tracking data. A correction to the conventional barycentric equations of motion is shown to be required.

  20. Selective role of lingual/parahippocampal gyrus and retrosplenial complex in spatial memory across viewpoint changes relative to the environmental reference frame.

    PubMed

    Sulpizio, Valentina; Committeri, Giorgia; Lambrey, Simon; Berthoz, Alain; Galati, Gaspare

    2013-04-01

    Remembering object locations across different views is a fundamental competence for keeping oriented in large-scale space. Here we investigated such ability by comparing encoding and retrieval of locations across viewpoint changes relative to different spatial frames of reference. We acquired functional magnetic resonance images while subjects detected target displacements across consecutive views of a familiar virtual room, reporting changes in the target absolute position in the room (stable environmental frame), changes in its position relative to a set of movable objects (unstable object-based frame), and changes relative to their point of view (control viewer-centered frame). Behavioral costs were higher for the stable environmental frame, and a cortical network including the lingual/parahippocampal gyrus (LPHG) and the retrosplenial complex (RSC) selectively encoded spatial locations relative to this frame. Several regions, including the dorsal fronto-parietal cortex and the LPHG, were modulated by the amount of experienced viewpoint change, but only the RSC was selectively modulated by the amount of viewpoint change relative to the environmental frame, thus showing a special role in coding one's own position and heading in familiar environments. PMID:23274842

  1. High Speed Video Data Acquisition System (VDAS) for H. E. P. , including Reference Frame Subtractor, Data Compactor and 16 megabyte FIFO

    SciTech Connect

    Knickerbocker, K.L.; Baumbaugh, A.E.; Ruchti, R.; Baumbaugh, B.W.

    1987-02-01

    A Video-Data-Acquisition-System (VDAS) has been developed to record image data from a scintillating glass fiber-optic target developed for High Energy Physics. VDAS consists of a combination flash ADC, reference frame subtractor, high speed data compactor, an N megabyte First-In-First-Out (FIFO) memory (where N is a multiple of 4), and a single board computer as a control processor. System data rates are in excess of 30 megabytes/second. The reference frame subtractor, in conjunction with the data compactor, records only the differences from a standard frame. This greatly reduces the amount of data needed to record an image. Typical image sizes are reduced by as much as a factor of 20. With the exception of the ECL ADC board, the system uses standard TTL components to minimize power consumption and cost. VDAS operation as well as enhancements to the original system are discussed.

  2. Understanding hippocampal activity by using purposeful behavior: Place navigation induces place cell discharge in both task-relevant and task-irrelevant spatial reference frames

    PubMed Central

    Zinyuk, L.; Kubik, S.; Kaminsky, Yu.; Fenton, A. A.; Bures, J.

    2000-01-01

    Continuous rotation of an arena in a cue-rich room dissociates the stationary room-bound information from the rotating arena-bound information. This disrupted spatial discharge in the majority of place cells from rats trained to collect randomly scattered food. In contrast, most place cell firing patterns recorded from rats trained to solve a navigation task on the rotating arena were preserved during the rotation. Spatial discharge was preserved in both the task-relevant stationary and the task-irrelevant rotating reference frames, but firing was more organized in the task-relevant frame. It is concluded that, (i) the effects of environmental manipulations can be understood with confidence only when the rat's purposeful behavior is used to formulate interpretations of the data, and (ii) hippocampal place cell activity is organized in multiple overlapping spatial reference frames. PMID:10716713

  3. Explaining as Mediated Action: An Analysis of Pre-Service Teachers' Account of Forces of Inertia in Non-Inertial Frames of Reference

    ERIC Educational Resources Information Center

    de Pereira, Alexsandro Pereira; Lima Junior, Paulo; Rodrigues, Renato Felix

    2016-01-01

    Explaining is one of the most important everyday practices in science education. In this article, we examine how scientific explanations could serve as cultural tools for members of a group of pre-service physics teachers. Specifically, we aim at their use of explanations about forces of inertia in non-inertial frames of reference. A basic…

  4. Frame-of-Reference Training Effectiveness: Effects of Goal Orientation and Self-Efficacy on Affective, Cognitive, Skill-Based, and Transfer Outcomes

    ERIC Educational Resources Information Center

    Dierdorff, Erich C.; Surface, Eric A.; Brown, Kenneth G.

    2010-01-01

    Empirical evidence supporting frame-of-reference (FOR) training as an effective intervention for calibrating raters is convincing. Yet very little is known about who does better or worse in FOR training. We conducted a field study of how motivational factors influence affective, cognitive, and behavioral learning outcomes, as well as near transfer…

  5. The Internal/External Frame of Reference Model of Self-Concept and Achievement Relations: Age-Cohort and Cross-Cultural Differences

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Abduljabbar, Adel Salah; Parker, Philip D.; Morin, Alexandre J. S.; Abdelfattah, Faisal; Nagengast, Benjamin; Möller, Jens; Abu-Hilal, Maher M.

    2015-01-01

    The internal/external frame of reference (I/E) model and dimensional comparison theory posit paradoxical relations between achievement (ACH) and self-concept (SC) in mathematics (M) and verbal (V) domains; ACH in each domain positively affects SC in the matching domain (e.g., MACH to MSC) but negatively in the nonmatching domain (e.g., MACH to…

  6. The Immediate Affect of Information in a Delayed Choice on a Distant Distribution as Seen in Different Inertial Reference Frames: The ``Effect'' May Occur Before the ``Cause''

    NASA Astrophysics Data System (ADS)

    Snyder, Douglas

    2015-03-01

    An experiment is described in the laboratory reference frame that relies on delayed choices for idler photons that immediately affects the distribution of signal photons with which the idler photons are initially entangled. The delayed choices on the idler photons concern whether to maintain or instead eliminate the entanglement between the paired idler and signal photons before any measurements are made. Eliminating the entanglement is done through eliminating the which-way information carried by the idler photon. If the entanglement is maintained, the result is which-way information in the distribution of the signal photons. If the entanglement is instead eliminated, the result is the elimination of which-way information and the presence of interference in the distribution of the signal photons. In other inertial reference frames, the change in state in the signal photon may occur before the delayed choice on the paired idler photon is made. A Minkowski diagram depicts the situation for the laboratory reference frame and another inertial reference frame where the change in state in the signal photon occurs before the delayed choice on the paired idler photon.

  7. Extension of the Internal/External Frame of Reference Model of Self-Concept Formation: Importance of Native and Nonnative Languages for Chinese Students.

    ERIC Educational Resources Information Center

    Hau, Kit-Tai; Kong, Chit-Kwong; Marsh, Herbert W.; Cheng, Zi-Juan

    The internal/external frame of reference (I/E) model of self-concept formation was extended by relating Chinese, English, and mathematics achievement to Chinese, English, and mathematics self-concepts in a 5-year longitudinal study based on a large (N=9,482) representative sample of Hong Kong high school students. Tests of the I/E model are…

  8. Changes in Frame of Reference Use across the Preschool Years: A Longitudinal Study of the Gestures and Speech Produced during Route Descriptions

    ERIC Educational Resources Information Center

    Sekine, Kazuki

    2009-01-01

    This study longitudinally investigated developmental changes in the frame of reference used by children in their gestures and speech. Fifteen children, between 4 and 6 years of age, were asked once a year to describe their route home from their nursery school. When the children were 4 years old, they tended to produce gestures that directly and…

  9. Accelerating plant DNA barcode reference library construction using herbarium specimens: improved experimental techniques.

    PubMed

    Xu, Chao; Dong, Wenpan; Shi, Shuo; Cheng, Tao; Li, Changhao; Liu, Yanlei; Wu, Ping; Wu, Hongkun; Gao, Peng; Zhou, Shiliang

    2015-11-01

    A well-covered reference library is crucial for successful identification of species by DNA barcoding. The biggest difficulty in building such a reference library is the lack of materials of organisms. Herbarium collections are potentially an enormous resource of materials. In this study, we demonstrate that it is likely to build such reference libraries using the reconstructed (self-primed PCR amplified) DNA from the herbarium specimens. We used 179 rosaceous specimens to test the effects of DNA reconstruction, 420 randomly sampled specimens to estimate the usable percentage and another 223 specimens of true cherries (Cerasus, Rosaceae) to test the coverage of usable specimens to the species. The barcode rbcLb (the central four-sevenths of rbcL gene) and matK was each amplified in two halves and sequenced on Roche GS 454 FLX+. DNA from the herbarium specimens was typically shorter than 300 bp. DNA reconstruction enabled amplification fragments of 400-500 bp without bringing or inducing any sequence errors. About one-third of specimens in the national herbarium of China (PE) were proven usable after DNA reconstruction. The specimens in PE cover all Chinese true cherry species and 91.5% of vascular species listed in Flora of China. It is very possible to build well-covered reference libraries for DNA barcoding of vascular species in China. As exemplified in this study, DNA reconstruction and DNA-labelled next-generation sequencing can accelerate the construction of local reference libraries. By putting the local reference libraries together, a global library for DNA barcoding becomes closer to reality. PMID:25865498

  10. How coordinate and categorical spatial relations combine with egocentric and allocentric reference frames in a motor task: effects of delay and stimuli characteristics.

    PubMed

    Ruotolo, Francesco; van der Ham, Ineke; Postma, Albert; Ruggiero, Gennaro; Iachini, Tina

    2015-05-01

    This study explores how people represent spatial information in order to accomplish a visuo-motor task. To this aim we combined two fundamental components of the human visuo-spatial system: egocentric and allocentric frames of reference and coordinate and categorical spatial relations. Specifically, participants learned the position of three objects and then had to judge the distance (coordinate information) and the relation (categorical information) of a target object with respect to themselves (egocentric frame) or with respect to another object (allocentric frame). They gave spatial judgments by reaching and touching the exact position or the side previously occupied by the target object. The possible influence of stimuli characteristics (3D objects vs. 2D images) and delay between learning phase and testing phase (1.5 vs. 5s) was also assessed. Results showed an advantage of egocentric coordinate judgments over the allocentric coordinate ones independently from the kind of stimuli used and the temporal parameters of the response, whereas egocentric categorical judgments were more accurate than allocentric categorical ones only with 3D stimuli and when an immediate response was requested. This pattern of data is discussed in the light of the "perception-action" model by Milner and Goodale [13] and of neuroimaging evidence about frames of reference and spatial relations. PMID:25698602

  11. Orbital motions of astronomical bodies and their centre of mass from different reference frames: a conceptual step between the geocentric and heliocentric models

    NASA Astrophysics Data System (ADS)

    Guerra, André G. C.; Simeão Carvalho, Paulo

    2016-09-01

    The motion of astronomical bodies and the centre of mass of the system is not always well perceived by students. One of the struggles is the conceptual change of reference frame, which is the same that held back the acceptance of the Heliocentric model over the Geocentric one. To address the question, the notion of centre of mass, motion equations (and their numerical solution for a system of multiple bodies), and change of frame of reference is introduced. The discussion is done based on conceptual and real world examples, using the solar system. Consequently, through the use of simple ‘do it yourself’ methods and basic equations, students can debate complex motions, and have a wider and potentially effective understanding of physics.

  12. A radio optical reference frame. I - Precise radio source positions determined by Mark III VLBI - Observations from 1979 to 1988 and a tie to the FK5

    NASA Technical Reports Server (NTRS)

    Ma, C.; Shaffer, D. B.; De Vegt, C.; Johnston, K. J.; Russell, J. L.

    1990-01-01

    Observations from 600 Mark III VLBI experiments from 1979 to 1988, resulting in 237,681 acceptable pairs of group delay and phase delay rate observations, have been used to derive positions of 182 extragalactic radio sources with typical formal standard errors less than 1 mas. The sources are distributed fairly evenly above delta = -30 deg, and 70 sources have delta greater than 0 deg. Analysis with different troposphere models, as well as internal and external comparisons, indicates that a coordinate frame defined by this set of radio sources should be reliable at the 1 mas level. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Because of known defects in the knowledge of astronomical constants, daily nutation offsets in longitude and obliquity were determined relative to an arbitrary reference day in the set of experiments.

  13. Acceleration of iterative tomographic image reconstruction by reference-based back projection

    NASA Astrophysics Data System (ADS)

    Cheng, Chang-Chieh; Li, Ping-Hui; Ching, Yu-Tai

    2016-03-01

    The purpose of this paper is to design and implement an efficient iterative reconstruction algorithm for computational tomography. We accelerate the reconstruction speed of algebraic reconstruction technique (ART), an iterative reconstruction method, by using the result of filtered backprojection (FBP), a wide used algorithm of analytical reconstruction, to be an initial guess and the reference for the first iteration and each back projection stage respectively. Both two improvements can reduce the error between the forward projection of each iteration and the measurements. We use three methods of quantitative analysis, root-mean-square error (RMSE), peak signal to noise ratio (PSNR), and structural content (SC), to show that our method can reduce the number of iterations by more than half and the quality of the result is better than the original ART.

  14. The Influence of Application a Simplified Transformation Model Between Reference Frames ECEF and ECI onto Prediction Accuracy of Position and Velocity of GLONASS Satellites

    NASA Astrophysics Data System (ADS)

    Krzyżek, Robert; Skorupa, Bogdan

    2015-12-01

    In computational tasks of satellite geodesy there is a need for transformation of coordinates between reference frames ECEF - Earth Centered, Earth Fixed and ECI - Earth Centered, Inertial. Strict and simplified transformation models, which can be used in case of the position and velocity short-term predictions of GLONASS satellites, have been presented in this study. Comparison of the results of state vector components predictions of the GLONASS satellites, in dependence of the used transformation model, have also been presented. Accuracy of the prediction has been determined on the basis of the analyse of deviations of the predicted positions and velocities of GLONASS satellites from their values given in broadcast ephemeris.

  15. Precise optical positions of radio sources in the FK 4-system. II - Results from 28 sources on the northern hemisphere and a preliminary comparison of the optical-radio reference frame

    NASA Astrophysics Data System (ADS)

    de Vegt, C.; Gehlich, U. K.

    1982-09-01

    Precise optical positions of 28 optical counterparts of extragalactic radio sources in the northern hemisphere have been derived using different long focus telescopes. The source positions are referred to the FK 4-system by the AGK 3 RN reference star catalogue as a primary reference frame; a system of secondary reference stars of intermediate brightness mυ = 12-14 has been obtained from the 23-cm astrograph of the Hamburg Observatory. A preliminary comparison of the optical and quasi absolute radio reference frame has been performed using a provisional averaged catalogue of radio positions. Significant systematic differences with local amplitudes up to 0".2 have been found, mainly in declination.

  16. Non-singular spherical harmonic expressions of geomagnetic vector and gradient tensor fields in the local north-oriented reference frame

    NASA Astrophysics Data System (ADS)

    Du, J.; Chen, C.; Lesur, V.; Wang, L.

    2015-07-01

    General expressions of magnetic vector (MV) and magnetic gradient tensor (MGT) in terms of the first- and second-order derivatives of spherical harmonics at different degrees/orders are relatively complicated and singular at the poles. In this paper, we derived alternative non-singular expressions for the MV, the MGT and also the third-order partial derivatives of the magnetic potential field in the local north-oriented reference frame. Using our newly derived formulae, the magnetic potential, vector and gradient tensor fields and also the third-order partial derivatives of the magnetic potential field at an altitude of 300 km are calculated based on a global lithospheric magnetic field model GRIMM_L120 (GFZ Reference Internal Magnetic Model, version 0.0) with spherical harmonic degrees 16-90. The corresponding results at the poles are discussed and the validity of the derived formulas is verified using the Laplace equation of the magnetic potential field.

  17. Coupled finite-element/state-space modeling of turbogenerators in the ABC frame of reference -- The short-circuit and load cases including saturated parameters

    SciTech Connect

    Chaudhry, S.R.; Ahmed-Zaid, S.; Demerdash, N.A.

    1995-03-01

    In this paper, a coupled finite-element/state-space modeling technique is applied in the determination of the steady-state parameters of a 733-MVA turbogenerator in the abc frame of reference. In this modeling environment, the forward rotor stepping-finite element procedure described in a companion paper is used to obtain the various machine self and mutual inductances under short-circuit and load conditions. A fourth-order state-space model of the armature and field winding flux linkages in the ABC frame of reference is then used to obtain the next set of flux linkages and forcing function currents for the finite-element model. In this process, one iterates between the finite-element and state-space techniques until the terminal conditions converge to specified values. This method is applied to the determination of the short-circuit, and reduced and rated-voltage load characteristics, and the corresponding machine inductances. The spatial harmonics of these inductances are analyzed via Fourier analysis to reveal the impact of machine geometry and stator-to-rotor relative motion, winding layout, magnetic saturation, and other effects. In the full-load infinite-bus case, it is found that, while the three-phase terminal voltages are pure sinusoidal waveforms, the steady-state armature phase currents are non-sinusoidal and contain a substantial amount of odd harmonics which cannot be obtained using the traditional two-axis analysis.

  18. Accelerating the Academic Achievement of Students Referred to Developmental Education. CCRC Working Paper No. 30

    ERIC Educational Resources Information Center

    Edgecombe, Nikki

    2011-01-01

    Acceleration, which involves the reorganization of instruction and curricula in ways that facilitate the completion of academic requirements in an expedited manner, is an increasingly popular strategy at community colleges for improving the outcomes of developmental education students. This paper reviews the literature on acceleration and…

  19. Potential reference measurement procedures for PBDE in surface water at levels required by the EU Water Frame Directive.

    PubMed

    Swart, Claudia; Gantois, Fanny; Petrov, Panayot; Entwisle, John; Goenaga-Infante, Heidi; Nousiainen, Marjaana; Bílsel, Mine; Binici, Burcu; Gonzalez-Gago, Adriana; Pröfrock, Daniel; Gören, Ahmet C

    2016-05-15

    Polybrominated diphenylethers (PBDE), used as flame retardants, are named as priority substances in the Directive 2000/60/EC of the European parliament and of the council establishing a framework for Community action in the field of water policy. An annual average environmental quality standard (EQS) for inland surface waters of 0.0005 µg/L (0.0002 µg/L for other surface waters) for PBDE congeners involved in the technical penta-PBDE mixtures containing PBDE with five bromine atoms has been established. The directives focus especially on the congeners PBDE 28, 47, 99, 100, 153 and 154 contained in the penta-PBDE mixture. Up to now, no reference measurement procedures have been established reaching the limits of quantification (LOQs) and the associated uncertainties as defined in the directives with results traceable to the SI. Within a recent European project on metrology, different approaches for the traceable quantification of PBDE, based on liquid/liquid or solid phase extraction followed by the detection with gas chromatography coupled to either inductively coupled plasma mass spectrometry or triple quadrupole mass spectrometry, were investigated and the related LOQs and expanded uncertainties of the results were compared. A complete uncertainty budget for each method was estimated according to the Guide to the Expression of Uncertainty in Measurement (GUM). All presented analytical procedures can serve as reference measurement procedures regarding the LOQs and their associated expanded uncertainties for monitoring the six priority PBDEs named above. LOQs as low as 0.026 ng/kg with an associated expanded uncertainty of 0.002 ng/kg could be achieved. PMID:26992518

  20. Tilted frames of reference have similar effects on the perception of gravitational vertical and the planning of vertical saccadic eye movements.

    PubMed

    Morgan, Michael; Grant, Simon; Melmoth, Dean; Solomon, Joshua A

    2015-07-01

    We investigated the effects of a tilted reference frame (i.e., allocentric visual context) on the perception of the gravitational vertical and saccadic eye movements along a planned egocentric vertical path. Participants (n = 5) in a darkened room fixated a point in the center of a circle on an LCD display and decided which of two sequentially presented dots was closer to the unmarked '6 o'clock' position on that circle (i.e., straight down toward their feet). The slope of their perceptual psychometric functions showed that participants were able to locate which dot was nearer the vertical with a precision of 1°-2°. For three of the participants, a square frame centered at fixation and tilted (in the roll direction) 5.6° from the vertical caused a strong perceptual bias, manifest as a shift in the psychometric function, in the direction of the traditional 'rod-and-frame' effect, without affecting precision. The other two participants showed negligible or no equivalent biases. The same subjects participated in the saccade version of the task, in which they were instructed to shift their gaze to the 6 o'clock position as soon as the central fixation point disappeared. The participants who showed perceptual biases showed biases of similar magnitude in their saccadic endpoints, with a strong correlation between perceptual and saccadic biases across all subjects. Tilting of the head 5.6° reduced both perceptual and saccadic biases in all but one observer, who developed a strong saccadic bias. Otherwise, the overall pattern and significant correlations between results remained the same. We conclude that our observers' saccades-to-vertical were dominated by perceptual input, which outweighed any gravitational or head-centered input. PMID:25921228

  1. Mental rotation of letters, body parts and scenes during whole-body tilt: role of a body-centered versus a gravitational reference frame.

    PubMed

    Bock, Otmar L; Dalecki, Marc

    2015-04-01

    It is known that in mental-rotation tasks, subjects mentally transform the displayed material until it appears "upright" and then make a judgment. Here we evaluate, by using three typical mental rotation tasks with different degrees of embodiment, whether "upright" is coded to a gravitational or egocentric reference frame, or a combination of both. Observers stood erect or were whole-body tilted by 60°, with their left ear down. In either posture, they saw stimuli presented at different orientation angles in their frontal plane: in condition LETTER, they judged whether the stimuli were normal or mirror-reversed letters, in condition HAND whether they represented a left or a right hand, and in condition SCENE whether a weapon laid left or right in front of a displayed person. Data confirm that reaction times are modulated by stimulus orientation angle, and the modulation curve in LETTER and HAND differs from that in SCENE. More importantly, during 60° body tilt, the modulation curve shifted 12° away from the gravitational towards the egocentric vertical reference; this shift was comparable in all three conditions and independent of the degree of embodiment. We conclude that mental rotation in all conditions relied on a similar spatial reference, which seems to be a weighted average of the gravitational and the egocentric vertical, with a higher weight given to the former. PMID:25682375

  2. Frame-of-reference training effectiveness: effects of goal orientation and self-efficacy on affective, cognitive, skill-based, and transfer outcomes.

    PubMed

    Dierdorff, Erich C; Surface, Eric A; Brown, Kenneth G

    2010-11-01

    Empirical evidence supporting frame-of-reference (FOR) training as an effective intervention for calibrating raters is convincing. Yet very little is known about who does better or worse in FOR training. We conducted a field study of how motivational factors influence affective, cognitive, and behavioral learning outcomes, as well as near transfer indexed by achieving professional certification. Relying on goal orientation theory, we hypothesized effects for 3 goal orientations: learning, prove performance, and avoid performance. Results were generally supportive across learning outcomes and transfer. Findings further supported a hypothesized interaction between learning self-efficacy and avoid performance goal orientation, such that higher levels of learning self-efficacy mitigated the negative effects of higher performance avoid tendencies. PMID:20853944

  3. Non-singular spherical harmonic expressions of geomagnetic vector and gradient tensor fields in the local north-oriented reference frame

    NASA Astrophysics Data System (ADS)

    Du, J.; Chen, C.; Lesur, V.; Wang, L.

    2014-12-01

    General expressions of magnetic vector (MV) and magnetic gradient tensor (MGT) in terms of the first- and second-order derivatives of spherical harmonics at different degrees and orders, are relatively complicated and singular at the poles. In this paper, we derived alternative non-singular expressions for the MV, the MGT and also the higher-order partial derivatives of the magnetic field in local north-oriented reference frame. Using our newly derived formulae, the magnetic potential, vector and gradient tensor fields at an altitude of 300 km are calculated based on a global lithospheric magnetic field model GRIMM_L120 (version 0.0) and the main magnetic field model of IGRF11. The corresponding results at the poles are discussed and the validity of the derived formulas is verified using the Laplace equation of the potential field.

  4. A new velocity field for Africa from combined GPS and DORIS space geodetic Solutions: Contribution to the definition of the African reference frame (AFREF)

    NASA Astrophysics Data System (ADS)

    Saria, E.; Calais, E.; Altamimi, Z.; Willis, P.; Farah, H.

    2013-04-01

    We analyzed 16 years of GPS and 17 years of Doppler orbitography and radiopositioning integrated by satellite (DORIS) data at continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. The resulting velocity field describes horizontal and vertical motion at 133 GPS sites and 9 DORIS sites. Horizontal velocities at sites located on stable Nubia fit a single plate model with a weighted root mean square residual of 0.6 mm/yr (maximum residual 1 mm/yr), an upper bound for plate-wide motions and for regional-scale deformation in the seismically active southern Africa and Cameroon volcanic line. We confirm significant southward motion ( ˜ 1.5 mm/yr) in Morocco with respect to Nubia, consistent with earlier findings. We propose an updated angular velocity for the divergence between Nubia and Somalia, which provides the kinematic boundary conditions to rifting in East Africa. We update a plate motion model for the East African Rift and revise the counterclockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. Vertical velocities range from - 2 to +2 mm/yr, close to their uncertainties, with no clear geographic pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). Except for a few regions, the African continent remains largely under-sampled by continuous space geodetic data. Efforts are needed to augment the geodetic infrastructure and openly share existing data sets so that the objectives of AFREF can be fully reached.

  5. Medium to Long Range Kinematic GPS Positioning with Position-Velocity-Acceleration Model Using Multiple Reference Stations

    PubMed Central

    Hong, Chang-Ki; Park, Chi Ho; Han, Joong-hee; Kwon, Jay Hyoun

    2015-01-01

    In order to obtain precise kinematic global positioning systems (GPS) in medium to large scale networks, the atmospheric effects from tropospheric and ionospheric delays need to be properly modeled and estimated. It is also preferable to use multiple reference stations to improve the reliability of the solutions. In this study, GPS kinematic positioning algorithms are developed for the medium to large-scale network based on the position-velocity-acceleration model. Hence, the algorithm can perform even in cases where the near-constant velocity assumption does not hold. In addition, the estimated kinematic accelerations can be used for the airborne gravimetry. The proposed algorithms are implemented using Kalman filter and are applied to the in situ airborne GPS data. The performance of the proposed algorithms is validated by analyzing and comparing the results with those from reference values. The results show that reliable and comparable solutions in both position and kinematic acceleration levels can be obtained using the proposed algorithms. PMID:26184215

  6. Medium to Long Range Kinematic GPS Positioning with Position-Velocity-Acceleration Model Using Multiple Reference Stations.

    PubMed

    Hong, Chang-Ki; Park, Chi Ho; Han, Joong-hee; Kwon, Jay Hyoun

    2015-01-01

    In order to obtain precise kinematic global positioning systems (GPS) in medium to large scale networks, the atmospheric effects from tropospheric and ionospheric delays need to be properly modeled and estimated. It is also preferable to use multiple reference stations to improve the reliability of the solutions. In this study, GPS kinematic positioning algorithms are developed for the medium to large-scale network based on the position-velocity-acceleration model. Hence, the algorithm can perform even in cases where the near-constant velocity assumption does not hold. In addition, the estimated kinematic accelerations can be used for the airborne gravimetry. The proposed algorithms are implemented using Kalman filter and are applied to the in situ airborne GPS data. The performance of the proposed algorithms is validated by analyzing and comparing the results with those from reference values. The results show that reliable and comparable solutions in both position and kinematic acceleration levels can be obtained using the proposed algorithms. PMID:26184215

  7. Frame of Reference: Special Collections

    ERIC Educational Resources Information Center

    Goetsch, Lori A.

    2010-01-01

    Rare, distinctive, unique--academic libraries are exploring new ways to describe and define what they've traditionally called special collections: incunabula, manuscripts, rare books, cultural artifacts and more. These valuable, historically important, and often one-of-a-kind artifacts can be a treasure trove for scholars and students. Technology…

  8. Kinematics of Mid-Ocean Ridge Relative Motions in the Indo-Atlantic Frame of Reference: Passive and Active Spreading Ridges

    NASA Astrophysics Data System (ADS)

    Rowan, C. J.; Rowley, D. B.; Forte, A. M.

    2011-12-01

    A kinematic analysis of the motions of mid-ocean ridges is presented in the Indo-Atlantic hotspot frame of reference. Relative motions of all major divergent plate boundaries are computed, including an assessment of uncertainties in their motions, back to 83 Ma (C34ny). As is expected from the general assumption that ridges are passive components of the plate boundary and mantle convective system, most ridges migrate across the underlying mantle along simple paths, largely perpendicular to the trend of the ridge. In the Indo-Atlantic reference frame, the Nansen-Gakkel ridge has migrated away from Europe by ~800 km along a NE trajectory. The Mid Atlantic Ridge (MAR) just north of the Azores triple junction (TJ) has moved away from Europe by ~1800km towards the WNW. South of the Azores TJ the MAR has moved away from Africa by ~1600 km towards the W. The slow to ultraslow spreading Southwest Indian Ridge has migrated slightly away from Antarctica, with a considerable fraction of the motion approximately parallel to the ridge trend. The Carlsberg Ridge has moved ~3400 km away from Africa towards the NNE in the past 65 Ma, while the Mid-Indian Ridge has migrated to the NNE away from Africa by ~3950 km over 83 Ma. The Southeast Indian Ridge, west of the 90°E ridge (Capricorn-Australia-East Antarctica TJ), has migrated ~3950 km to the NE away from Antarctica. Farther east, divergence between Australia and Antarctica has resulted in ~1800 km of northward motion of the ridge away from Antarctica. The Southwest Pacific Ridge, between the Pacific and West Antarctic plates has migrated ~1500 km to the NW away from west Antarctica. These motions are entirely consistent with intuition, given that Africa and Antarctica are largely surrounded by spreading systems. In contrast to the rest of the global ridge system, despite its high spreading rate the East Pacific Ridge has undergone essentially no (<±500 km) ridge perpendicular (E-W) migration in the past 80 Ma, and neglible

  9. Examining the External Training Load of an English Premier League Football Team With Special Reference to Acceleration.

    PubMed

    Akenhead, Richard; Harley, Jamie A; Tweddle, Simon P

    2016-09-01

    Akenhead, R, Harley, J, and Tweddle, S. Examining the external training load of an English Premier League football team with special reference to acceleration. J Strength Cond Res 30(9): 2424-2432, 2016-Practitioners and coaches often use external training load variables such as distance run and the number of high-speed running (HSR) activities to quantify football training. However, an important component of the external load may be overlooked when acceleration activities are not considered. The aim of this study was to describe the within-microcycle distribution of external load, including acceleration, during in-season 1-game weeks in an elite football team. Global Positioning System technology was used to collect time-motion data from 12 representative 7-day microcycles across a competitive season (48 training days, 295 data sets). Training time, total distance (TD), high-speed running (HSR) distance (>5.8 m·s), sprint running distance (>6.7 m·s) and acceleration variables were recorded during each training session. Data were analysed for interday and interposition differences using mixed linear modeling. The distribution of external load was characterized by the second training day of the microcycle (5 days prematch) exhibiting the highest values for all variables of training load, with the fourth day (1 day prematch) exhibiting the lowest values. Central midfield players covered ∼8-16% greater TD than other positions excluding wide midfielders (p ≤ 0.03, d = 0.2-0.4) and covered ∼17% greater distance accelerating 1-2 m·s than central defenders (p = 0.03, d = 0.7). When expressed relative to training duration and TD, the magnitude of interday and interposition differences were markedly reduced (p = 0.03, d = 0.2-0.3). When managing the distribution of training load, practitioners should be aware of the intensity of training sessions and consider the density of external load within sessions. PMID:26817740

  10. Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation.

    PubMed

    Slaba, Tony C; Blattnig, Steve R; Norbury, John W; Rusek, Adam; La Tessa, Chiara

    2016-02-01

    The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities and possible biological considerations. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, a preliminary approach for selecting beams at NSRL to simulate the designated reference field is presented. This approach is not a final design for the GCR simulator, but rather a single step within a broader design strategy. It is shown that the beam selection methodology is tied directly to the reference environment, allows facility constraints to be incorporated, and may be adjusted to account for additional constraints imposed by biological or animal care considerations. The major biology questions are not addressed herein but are discussed in a companion paper published in the present issue of this journal. Drawbacks of the proposed methodology are discussed

  11. Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation

    NASA Astrophysics Data System (ADS)

    Slaba, Tony C.; Blattnig, Steve R.; Norbury, John W.; Rusek, Adam; La Tessa, Chiara

    2016-02-01

    The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities and possible biological considerations. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, a preliminary approach for selecting beams at NSRL to simulate the designated reference field is presented. This approach is not a final design for the GCR simulator, but rather a single step within a broader design strategy. It is shown that the beam selection methodology is tied directly to the reference environment, allows facility constraints to be incorporated, and may be adjusted to account for additional constraints imposed by biological or animal care considerations. The major biology questions are not addressed herein but are discussed in a companion paper published in the present issue of this journal. Drawbacks of the proposed methodology are discussed

  12. 2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: A progress report

    NASA Astrophysics Data System (ADS)

    Bennett, G. R.; Smith, I. C.; Shores, J. E.; Sinars, D. B.; Robertson, G.; Atherton, B. W.; Jones, M. C.; Porter, J. L.

    2008-10-01

    When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26MA Z Accelerator, the terawatt-class, multikilojoule, 526.57nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151keV (1s2-1s2p triplet line of He-like Mn) curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004); G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)], is capable of providing a high quality x radiograph per Z shot for inertial confinement fusion (ICF), complex hydrodynamics, and other high-energy-density physics experiments. For example, this diagnostic has recently afforded microgram-scale mass perturbation measurements on an imploding ignition-scale 1mg ICF capsule [G. R. Bennett et al., Phys. Rev. Lett. 99, 205003 (2007)], where the perturbation was initiated by a surrogate deuterium-tritium (DT) fuel fill tube. Using an angle-time multiplexing technique, ZBL now has the capability to provide two spatially and temporally separated foci in the Z chamber, allowing "two-frame" imaging to be performed, with an interframe time range of 2-20ns. This multiplexing technique allows the full area of the four-pass amplifiers to be used for the two pulses, rather than split the amplifiers effectively into two rectangular sections, with one leg delayed with respect to the other, which would otherwise double the power imposed onto the various optics thereby halving the damage threshold, for the same irradiance on target. The 6.151keV two frame technique has recently been used to image imploding wire arrays, using a 7.3ns interframe time. The diagnostic will soon be converted to operate with p-rather than s-polarized laser light for enhanced laser absorption in the Mn foil, plus other changes (e.g., operation at the possibly brighter 6.181keV Mn 1s2-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast (1ns gate time

  13. 2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: A progress report

    SciTech Connect

    Bennett, G. R.; Smith, I. C.; Shores, J. E.; Sinars, D. B.; Robertson, G.; Atherton, B. W.; Jones, M. C.; Porter, J. L.

    2008-10-15

    When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26 MA Z Accelerator, the terawatt-class, multikilojoule, 526.57 nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151 keV (1s{sup 2}-1s2p triplet line of He-like Mn) curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004); G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)], is capable of providing a high quality x radiograph per Z shot for inertial confinement fusion (ICF), complex hydrodynamics, and other high-energy-density physics experiments. For example, this diagnostic has recently afforded microgram-scale mass perturbation measurements on an imploding ignition-scale 1 mg ICF capsule [G. R. Bennett et al., Phys. Rev. Lett. 99, 205003 (2007)], where the perturbation was initiated by a surrogate deuterium-tritium (DT) fuel fill tube. Using an angle-time multiplexing technique, ZBL now has the capability to provide two spatially and temporally separated foci in the Z chamber, allowing 'two-frame' imaging to be performed, with an interframe time range of 2-20 ns. This multiplexing technique allows the full area of the four-pass amplifiers to be used for the two pulses, rather than split the amplifiers effectively into two rectangular sections, with one leg delayed with respect to the other, which would otherwise double the power imposed onto the various optics thereby halving the damage threshold, for the same irradiance on target. The 6.151 keV two frame technique has recently been used to image imploding wire arrays, using a 7.3 ns interframe time. The diagnostic will soon be converted to operate with p-rather than s-polarized laser light for enhanced laser absorption in the Mn foil, plus other changes (e.g., operation at the possibly brighter 6.181 keV Mn 1s{sup 2}-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast

  14. 2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: a progress report.

    PubMed

    Bennett, G R; Smith, I C; Shores, J E; Sinars, D B; Robertson, G; Atherton, B W; Jones, M C; Porter, J L

    2008-10-01

    When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26 MA Z Accelerator, the terawatt-class, multikilojoule, 526.57 nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151 keV (1s(2)-1s2p triplet line of He-like Mn) curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004); G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)], is capable of providing a high quality x radiograph per Z shot for inertial confinement fusion (ICF), complex hydrodynamics, and other high-energy-density physics experiments. For example, this diagnostic has recently afforded microgram-scale mass perturbation measurements on an imploding ignition-scale 1 mg ICF capsule [G. R. Bennett et al., Phys. Rev. Lett. 99, 205003 (2007)], where the perturbation was initiated by a surrogate deuterium-tritium (DT) fuel fill tube. Using an angle-time multiplexing technique, ZBL now has the capability to provide two spatially and temporally separated foci in the Z chamber, allowing "two-frame" imaging to be performed, with an interframe time range of 2-20 ns. This multiplexing technique allows the full area of the four-pass amplifiers to be used for the two pulses, rather than split the amplifiers effectively into two rectangular sections, with one leg delayed with respect to the other, which would otherwise double the power imposed onto the various optics thereby halving the damage threshold, for the same irradiance on target. The 6.151 keV two frame technique has recently been used to image imploding wire arrays, using a 7.3 ns interframe time. The diagnostic will soon be converted to operate with p-rather than s-polarized laser light for enhanced laser absorption in the Mn foil, plus other changes (e.g., operation at the possibly brighter 6.181 keV Mn 1s(2)-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast (1 ns

  15. Vombat: an open source proof-of-concept for the use of Digital outcrop models as reference frame for stratigraphic observations

    NASA Astrophysics Data System (ADS)

    Penasa, Luca; Franceschi, Marco; Preto, Nereo; Girardeau-Montaut, Daniel

    2015-04-01

    passive remote sensing devices). This information requires to be merged with geological data collected in the field, in a consistent and reproducible way. We present Vombat, a proof-of-concept of open-source software to illustrate some of the possibilities in terms of information storage, visualization and exploitation of outcrop stratigraphic information. Our solution integrates with CloudCompare, a software that permits to visualize and edit point clouds. A dedicated algorithm estimates stratigraphic attitudes from point cloud data, without the need of exposed planar bedding surfaces. These attitudes can be used to define a virtual stratigraphic section. Composite sections can then be realized defining stratigraphic constraints between different reference frames. Any observation can be displayed in a stratigraphic framework that is directly generated from a VOM. The virtual outcrop, the samples and the stratigraphic reference frames can be saved into an XML file. In the future, the adoption of a standard format (e.g. GeoSciML) will permit easier exchange of stratigraphic data among researchers. The software constitutes a first step towards the full exploitation of VOMs in stratigraphy, is stored at http://github.com/luca-penasa/vombat‏ and is open source. Comments and suggestions are most welcome and will help focusing and refining the software and its tools.

  16. Long-term R and V-band monitoring of some suitable targets for the link between ICRF and the future Gaia celestial reference frame

    NASA Astrophysics Data System (ADS)

    Taris, F.; Andrei, A.; Roland, J.; Klotz, A.; Vachier, F.; Souchay, J.

    2016-03-01

    Context. The Gaia astrometric mission of the European Space Agency was launched on December 2013. It will provide a catalog of 500 000 quasars. Some of these targets will be chosen to build an optical reference system that will be linked to the International Celestial Reference Frame (ICRF). The astrometric coordinates of these sources will have roughly the same uncertainty at both optical and radio wavelengths, and it is then mandatory to observe a common set of targets to build the link. In the ICRF, some targets have been chosen because of their pointlikeness. They are quoted as defining sources, and they ensure very good uncertainty about their astrometric coordinates. At optical wavelengths, a comparable uncertainty could be achieved for targets that do not exhibit strong astrophysical phenomena, which is a potential source of photocenter flickering. A signature of these phenomena is a magnitude variation at optical wavelengths. Aims: The goal of this work is to present the time series of 14 targets suitable for the link between the ICRF and the future Gaia Celestial Reference Frame. The observations have been done systematically by robotic telescopes in France and Chile once every two nights since 2011 and in two filters. These time series are analyzed to search for periodic or quasi-periodic phenomena that must be taken into account when computing the uncertainty about the astrometric coordinates. Methods: Two independent methods were used in this work to analyze the time series. We used the CLEAN algorithm to compare the frequency obtained to those given by the Lomb-Scargle method. It avoids misinterpreting the frequency peaks given in the periodograms. Results: For the 14 targets we determine some periods with a confidence level above 90% in each case. Some of the periods found in this work were not previously known. For the others, we did a comparative study of the periods previously studied by others and always confirm their values. All the periods given

  17. Plasma physics in noninertial frames

    SciTech Connect

    Thyagaraja, A.; McClements, K. G.

    2009-09-15

    Equations describing the nonrelativistic motion of a charged particle in an arbitrary noninertial reference frame are derived from the relativistically invariant form of the particle action. It is shown that the equations of motion can be written in the same form in inertial and noninertial frames, with the effective electric and magnetic fields in the latter modified by inertial effects associated with centrifugal and Coriolis accelerations. These modifications depend on the particle charge-to-mass ratio, and also the vorticity, specific kinetic energy, and compressibility of the frame flow. The Newton-Lorentz, Vlasov, and Fokker-Planck equations in such a frame are derived. Reduced models such as gyrokinetic, drift-kinetic, and fluid equations are then derivable from these equations in the appropriate limits, using standard averaging procedures. The results are applied to tokamak plasmas rotating about the machine symmetry axis with a nonrelativistic but otherwise arbitrary toroidal flow velocity. Astrophysical applications of the analysis are also possible since the power of the action principle is such that it can be used to describe relativistic flows in curved spacetime.

  18. Explaining as Mediated Action. An Analysis of Pre-service Teachers' Account of Forces of Inertia in Non-inertial Frames of Reference

    NASA Astrophysics Data System (ADS)

    de Pereira, Alexsandro Pereira; Lima Junior, Paulo; Rodrigues, Renato Felix

    2016-05-01

    Explaining is one of the most important everyday practices in science education. In this article, we examine how scientific explanations could serve as cultural tools for members of a group of pre-service physics teachers. Specifically, we aim at their use of explanations about forces of inertia in non-inertial frames of reference. A basic assumption of our study is that explanatory tools (e.g., typical explanations learned) shape the ways we think and speak about the world. Drawing on the theory of mediated action, analysis illustrates three major claims on scientific explanations: (1) explaining is an act of actively responding to explanations presented by others (and not only to evidence itself); (2) the actual experience of explaining involves the enactment of power and authority; (3) resistance (not acknowledging an explanation as one's own) might be a constitutive part of learning how to explain (hence, teachers could approach scientific explanation in a less dogmatic way). These assertions expand the possibilities of dialogue between studies of scientific explanations and the social sciences. Implications for science teaching and research in science education are presented.

  19. Effects of visual reference on adaptation to motion sickness and subjective responses evoked by graded cross-coupled angular accelerations. [vestibular oculogravic effect in human acceleration adaptation

    NASA Technical Reports Server (NTRS)

    Reason, J. T.; Diaz, E.

    1973-01-01

    Three groups of 10 subjects each were exposed to stepwise increments of cross coupled angular accelerations in three visual modes: internal visual reference (IVR), external visual reference (EVR), and vision absent (VA). The subjects in the IVR condition required significantly greater amounts of stimulus exposure to neutralize their illusory subjective reactions. They also suffered a greater loss of well-being and a more marked incidence of motion sickness than did subjects in the EVR and VA conditions. The same 30 subjects were reexposed to the same graded cross coupled stimulation 1 week later. This time, however, all the subjects were tested under only the IVR condition. All three groups showed some positive transfer of adaptation, but only the IVR-IVR combination required significantly fewer head motions to achieve the same level of adaptation on the second occasion. Taken overall, however, the most efficient and least disturbing route to adaptation at the completion of the second test was via the VA-IVR combination.

  20. [Senescence-accelerated mouse (SAM): with special reference to age-associated pathologies and their modulation].

    PubMed

    Takeda, T

    1996-07-01

    The senescence-accelerated mouse (SAM) has been under development by our research team at Kyoto University since 1970 through selective inbreeding of the AKR/J strain of mice donated by the Jackson Laboratory in 1968, based on the data of the grading score of senescence, life span, and pathologic phenotypes. At present, there are 12 lines of SAM; the 9 senescence-prone inbred strains (SAMP) include SAMP1, SAMP2, SAMP3, SAMP6, SAMP7, SAMP8, SAMP9, SAMP10 and SAMP11, and the 3 senescence-resistant inbred strains (SAMR) SAMR1, SANR4 and SAMR5. Data from survival curves, the Gompertzian function and the grading score of senescence, together with growth patterns of body weight of these SAMP and SAMR mice revealed that the characteristic feature of aging common to all SAMP mice is "accelerated senescence": early onset and irreversible advance of senescence manifested by several signs and gross lesions such as the loss of normal behavior, various skin lesions, increased lordokyphosis, etc., after a period of normal development. Routine postmortem examinations and the pathobiological features revealed by systematically designed studies have shown several pathologic phenotypes, which are often characteristic enough to differentiate among the various SAM strains: senile amyloidosis in SAMP1, -P2, -P7, -P9, -P10 and -P11, secondary amyloidosis in SAMP2 and -P6, contracted kidney in SAMP1, -P2, -P10, -P11, immunoblastic lymphoma in SAMR1 and -R4, histiocytic sarcoma in SAMR1 and -R4, ovarian cysts in SAMR1, impaired immune response in SAMP1, -P2 and -P8, hyperinflation of the lungs in SAMP1, hearing impairment in SAMP1, degenerative temporomandibular joint disease in SAMP3, senile osteoporosis in SAMP6, deficits in learning and memory in SAMP8 and -P10, emotional disorders in SAMP8 and -P10, cataracts in SAMP9, and brain atrophy in SAMP10. These are all age-associated pathologies, the incidence and severity of which increase with advancing age. The SAM model in which these

  1. The Longitudinal Interplay of Students' Academic Self-Concepts and Achievements within and across Domains: Replicating and Extending the Reciprocal Internal/External Frame of Reference Model

    ERIC Educational Resources Information Center

    Niepel, Christoph; Brunner, Martin; Preckel, Franzis

    2014-01-01

    Students' cognitive and motivational profiles have a large impact on their academic careers. The development of such profiles can partly be explained by the reciprocal internal/external frame of reference model (RI/E model). The RI/E model predicts positive and negative longitudinal effects between academic self-concepts and achievements…

  2. Identification and Estimation of Postseismic Deformation: Implications for Plate Motion Models, Models of the Earthquake Cycle, and Terrestrial Reference Frame Definition

    NASA Astrophysics Data System (ADS)

    Kedar, S.; Bock, Y.; Moore, A. W.; Argus, D. F.; Fang, P.; Liu, Z.; Haase, J. S.; Su, L.; Owen, S. E.; Goldberg, D.; Squibb, M. B.; Geng, J.

    2015-12-01

    Postseismic deformation indicates a viscoelastic response of the lithosphere. It is critical, then, to identify and estimate the extent of postseismic deformation in both space and time, not only for its inherent information on crustal rheology and earthquake physics, but also since it must considered for plate motion models that are derived geodetically from the "steady-state" interseismic velocities, models of the earthquake cycle that provide interseismic strain accumulation and earthquake probability forecasts, as well as terrestrial reference frame definition that is the basis for space geodetic positioning. As part of the Solid Earth Science ESDR System) SESES project under a NASA MEaSUREs grant, JPL and SIO estimate combined daily position time series for over 1800 GNSS stations, both globally and at plate boundaries, independently using the GIPSY and GAMIT software packages, but with a consistent set of a prior epoch-date coordinates and metadata. The longest time series began in 1992, and many of them contain postseismic signals. For example, about 90 of the global GNSS stations out of more than 400 that define the ITRF have experienced one or more major earthquakes and 36 have had multiple earthquakes; as expected, most plate boundary stations have as well. We quantify the spatial (distance from rupture) and temporal (decay time) extent of postseismic deformation. We examine parametric models (log, exponential) and a physical model (rate- and state-dependent friction) to fit the time series. Using a PCA analysis, we determine whether or not a particular earthquake can be uniformly fit by a single underlying postseismic process - otherwise we fit individual stations. Then we investigate whether the estimated time series velocities can be directly used as input to plate motion models, rather than arbitrarily removing the apparent postseismic portion of a time series and/or eliminating stations closest to earthquake epicenters.

  3. A time stepping coupled finite element-state space modeling environment for synchronous machine performance and design analysis in the ABC frame of reference

    NASA Astrophysics Data System (ADS)

    Deng, Fang

    iteratively used in obtaining inductance parameters prior to another round of SS computation of the steady-state current profiles. Again, the model is iterative in nature, in which the user continues cycling through the two sections, namely the FE and SS sections of the CFE-SS modeling environment, until the desired degree of convergence is achieved. The CFE-SS approach uses only design data such as physical dimensions, magnetic circuit geometry, magnetic material characteristics, winding particulars and layouts, and hence does not depend on the existence of actual hardware. The modeling environment is totally within the ABC frame of reference, therefore no approximating assumptions such as sinusoidally distributed mmf's or current sheets were made.

  4. Behavior of infilled frames

    SciTech Connect

    Flanagan, R.D.; Tenbus, M.A.; Bennett, R.M.; Jamal, B.D.

    1992-09-21

    A review of current analytical methods for infilled frame behavior is conducted. A subset of these methods are applied to experimental results. Parametric studies are used to find the sensitivity of the behavior to various parameters. In-plane loading, out-of-plane inertial loading, out-of-plane interstory drift loading, and combined loadings are examined. Particular reference is made to clay tile infilled frames, and the behavior of clay tile in compression.

  5. Mechanisms of homing in the fiddler crab Uca rapax. 2. Information sources and frame of reference for a path integration system.

    PubMed

    Layne, John E; Barnes, W Jon P; Duncan, Lindsey M J

    2003-12-01

    Fiddler crabs Uca rapax are central-place foragers, making feeding excursions of up to several meters from their burrows. This study investigates the sources of directional and distance information used by these crabs when returning to their burrows. We tested the spatial frame of reference (egocentric or exocentric), and the source of spatial information (idiothetic or allothetic) used during homing. We also tested which components of their locomotion they integrated (only voluntary, or voluntary plus reflexive). Fiddler crabs in their natural mudflat habitat were passively rotated during normal foraging behavior using experimenter-controlled disks, before they returned home. Crabs resisted passive rotations on the disk by counter-rotating when the disk turned, which was a compensatory response to unintended movement. Crabs were usually situated eccentrically on the disk, and therefore were also subjected to a translation when the disk rotated. No crab actively compensated for this translation. Crabs that fully compensated for disk rotation made no directional homing error. Crabs that did not fully compensate homed in a direction that reflected their new body orientation. In other words, if we succeeded in reorienting a crab (i.e. it undercompensated for disk rotation), its homing error was equal to the angle by which it had been reoriented, regardless of the magnitude of the optomotor compensation. Computer-modelled crabs, each equipped with a path integrator utilizing different combinations of external (allothetic) and path-related (idiothetic) input, traversed the digitized paths of the real crabs. The home vector computed by the model crab was then compared to the homing direction observed in the real crab. The model home vector that most closely matched that of the real crab was taken to comprise the path integration mechanism employed by fiddler crabs. The model that best matched the real crab gained direction and distance idiothetically (from internal

  6. Optical variability of extragalactic objects used to tie the HIPPARCOS reference frame to an extragalactic system using Hubble space telescope observations

    NASA Technical Reports Server (NTRS)

    Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel

    1990-01-01

    Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65 percent are optical variables beyond a 0.2 mag limit. To ensure proper exposure times, accurate mean magnitudes are necessary. In many cases, the average magnitudes listed in the literature were not adequate. The literature was searched for all relevant photometric information for the EGOs, and photometric parameters were derived, including mean magnitude, maximum range, and timescale of variability. This paper presents the results of that search and the parameters derived. The results will allow exposure times to be estimated such that an observed magnitude different from the tabular magnitude by 0.5 mag in either direction will not degrade the astrometric centering ability on a Planetary Camera CCD frame.

  7. Earth conical shadow modeling for LEO satellite using reference frame transformation technique: A comparative study with existing earth conical shadow models

    NASA Astrophysics Data System (ADS)

    Srivastava, V. K.; Yadav, S. M.; Ashutosh; Kumar, J.; Kushvah, B. S.; Ramakrishna, B. N.; Ekambram, P.

    2015-03-01

    In this article, we propose an Earth conical shadow model predicting umbra and penumbra states for the low Earth orbiting satellite considering the spherical shape of the Earth. The model is described using the umbra and penumbra cone geometries of the Earth's shadow and the geometrical equations of these conical shadow regions into a Sun centered frame. The proposed model is simulated for three polar Sun-synchronous Indian Remote Sensing satellites: Cartosat-2A, Resourcesat-2 and Oceansat-2. The proposed model compares well with the existing spherical Earth conical shadow models such as those given by Vallado (2013), Wertz (2002), Hubaux et al. (2012), and Srivastava et al. (2013, 2014). An assessment is carried out of the existing Earth conical shadow models with Systems Tool Kit (STK), a high fidelity commercial software package of Analytic Graphic Inc., and the real time telemetry data.

  8. Pseudo-entanglement evaluated in noninertial frames

    SciTech Connect

    Mehri-Dehnavi, Hossein; Mirza, Behrouz; Mohammadzadeh, Hosein; Rahimi, Robabeh

    2011-05-15

    Research Highlights: > We study pseudo-entanglement in noninertial frames. > We examine different measures of entanglement and nonclassical correlation for the state. > We find the threshold for entanglement is changed in noninertial frames. > We also describe the behavior of local unitary classes of states in noninertial frames. - Abstract: We study quantum discord, in addition to entanglement, of bipartite pseudo-entanglement in noninertial frames. It is shown that the entanglement degrades from its maximum value in a stationary frame to a minimum value in an infinite accelerating frame. There is a critical region found in which, for particular cases, entanglement of states vanishes for certain accelerations. The quantum discord of pseudo-entanglement decreases by increasing the acceleration. Also, for a physically inaccessible region, entanglement and nonclassical correlation are evaluated and shown to match the corresponding values of the physically accessible region for an infinite acceleration.

  9. Exploring laser-wakefield-accelerator regimes for near-term lasers using particle-in-cell simulation in Lorentz-boosted frames

    NASA Astrophysics Data System (ADS)

    Martins, S. F.; Fonseca, R. A.; Lu, W.; Mori, W. B.; Silva, L. O.

    2010-04-01

    Plasma-based acceleration offers compact accelerators with potential applications for high-energy physics and photon sources. The past five years have seen an explosion of experimental results with monoenergetic electron beams up to 1GeV on a centimetre-scale, using plasma waves driven by intense lasers. The next decade will see tremendous increases in laser power and energy, permitting beam energies beyond 10GeV. Leveraging on the Lorentz transformations to bring the laser and plasma spatial scales together, we have reduced the computational time for modelling laser-plasma accelerators by several orders of magnitude, including all the relevant physics. This scheme enables the first one-to-one particle-in-cell simulations of the next generation of accelerators at the energy frontier. Our results demonstrate that, for a given laser energy, choices in laser and plasma parameters strongly affect the output electron beam energy, charge and quality, and that all of these parameters can be optimized.

  10. Mixed quantum/classical theory for inelastic scattering of asymmetric-top-rotor + atom in the body-fixed reference frame and application to the H2O + He system

    NASA Astrophysics Data System (ADS)

    Semenov, Alexander; Dubernet, Marie-Lise; Babikov, Dmitri

    2014-09-01

    The mixed quantum/classical theory (MQCT) for inelastic molecule-atom scattering developed recently [A. Semenov and D. Babikov, J. Chem. Phys. 139, 174108 (2013)] is extended to treat a general case of an asymmetric-top-rotor molecule in the body-fixed reference frame. This complements a similar theory formulated in the space-fixed reference-frame [M. Ivanov, M.-L. Dubernet, and D. Babikov, J. Chem. Phys. 140, 134301 (2014)]. Here, the goal was to develop an approximate computationally affordable treatment of the rotationally inelastic scattering and apply it to H2O + He. We found that MQCT is somewhat less accurate at lower scattering energies. For example, below E = 1000 cm-1 the typical errors in the values of inelastic scattering cross sections are on the order of 10%. However, at higher scattering energies MQCT method appears to be rather accurate. Thus, at scattering energies above 2000 cm-1 the errors are consistently in the range of 1%-2%, which is basically our convergence criterion with respect to the number of trajectories. At these conditions our MQCT method remains computationally affordable. We found that computational cost of the fully-coupled MQCT calculations scales as n2, where n is the number of channels. This is more favorable than the full-quantum inelastic scattering calculations that scale as n3. Our conclusion is that for complex systems (heavy collision partners with many internal states) and at higher scattering energies MQCT may offer significant computational advantages.

  11. A review of trend models applied to sea level data with reference to the "acceleration-deceleration debate"

    NASA Astrophysics Data System (ADS)

    Visser, Hans; Dangendorf, Sönke; Petersen, Arthur C.

    2015-06-01

    Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. This has motivated a number of authors to search for already existing accelerations in observations, which would be, if present, vital for coastal protection planning purposes. No scientific consensus has been reached yet as to how a possible acceleration could be separated from intrinsic climate variability in sea level records. This has led to an intensive debate on its existence and, if absent, also on the general validity of current future projections. Here we shed light on the controversial discussion from a methodological point of view. To do so, we provide a comprehensive review of trend methods used in the community so far. This resulted in an overview of 30 methods, each having its individual mathematical formulation, flexibilities, and characteristics. We illustrate that varying trend approaches may lead to contradictory acceleration-deceleration inferences. As for statistics-oriented trend methods, we argue that checks on model assumptions and model selection techniques yield a way out. However, since these selection methods all have implicit assumptions, we show that good modeling practices are of importance too. We conclude at this point that (i) several differently characterized methods should be applied and discussed simultaneously, (ii) uncertainties should be taken into account to prevent biased or wrong conclusions, and (iii) removing internally generated climate variability by incorporating atmospheric or oceanographic information helps to uncover externally forced climate change signals.

  12. The Mediterranean Plio-Pleistocene: A reference frame for astronomically paced low and high latitude climate changes (Jean Baptiste Lamarck Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Lourens, Lucas

    2016-04-01

    The astronomical theory of climate has revolutionized our understanding of past climate change and the development of highly accurate geologic time scales for the entire Cenozoic. Most of this understanding has started with the construction of high-resolution stable oxygen isotope (18O) records from planktonic and benthic foraminifera of open ocean deep marine sediments explored by the international drilling operations of DSDP, ODP and IODP. These efforts culminated into global ocean isotopic stacked records, which give a clear picture of the evolution of the climate state through time. Fundamental for these reconstructions are the assumptions made between the astronomical forcing and the tuned time series and the accuracy of the astronomical solution. In the past decades, an astronomically calibrated time scale for the Pliocene and Pleistocene of the Mediterranean has been developed, which has become the reference for the standard Geologic Time Scale. Characteristic of the studied marine sediments are the cyclic lithological alternations, reflecting the interference between obliquity and precession-paced low latitude climate variability. These interference patterns allowed to evaluate the accuracy of astronomical solutions and to constrain the dynamical ellipticity of the Earth and tidal dissipation by the Sun and the Moon, which in turn provided the backbone for the widely applied LR04 open ocean benthic isotope stack of the past 5 Myr. So far, the assumed time lags between orbital forcing and the global climate response as reflected in LR04 have not been tested, while these assumptions hark back to SPECMAP, using simple ice sheet models and a limited number of radiometric dates. In addition, LR04 adopted a shorter response time for the smaller ice caps during the Pliocene. Here I present the first benthic 18O record of the Mediterranean reference scale, which strikingly mirrors the LR04. I will use this record to discuss the assumed phase relations and its

  13. Frame by Frame II: A Filmography of the African American Image, 1978-1994.

    ERIC Educational Resources Information Center

    Klotman, Phyllis R.; Gibson, Gloria J.

    A reference guide on African American film professionals, this book is a companion volume to the earlier "Frame by Frame I." It focuses on giving credit to African Americans who have contributed their talents to a film industry that has scarcely recognized their contributions, building on the aforementioned "Frame by Frame I," which included…

  14. Extending the X/Ka Celestial Reference Frame over the South Polar Cap: Results from combined NASA-ESA Deep Space Network baselines to Malargüe, Argentina

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; de Vicente, J.; Dugast, M.; García-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Maddè, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2013-03-01

    In order to extend the X/Ka-band (8.4/32 GHz) Celestial Reference Frame coverage over the south polar cap region of declinations -45 to -90 deg, we developed a collaboration between the NASA and ESA Deep Space Networks. In particular ESA's new 35-meter X/Ka-band antenna in Malargüe, Argentina which became operational in January 2013 is now available for X/Ka VLBI baselines to NASA's antennas in Tidbinbilla, Australia; Goldstone, California; and Robledo, Spain. We report first fringes on baselines from Malargüe to Tidbinbilla, Goldstone, and Robledo using a semi-portable digital backend recording at 256 Mbps. To the best of our knowledge the Giga-lambda Malargüe-Tidbinbilla baseline is producing the highest resolution interferometry ever achieved over the south polar cap. We will present the distribution of Ka-band sources detected on this all-southern baseline. Lastly, we will discuss the prospects for using these new baselines to improve the astrometric accuracy of the X/Ka frame in the southern hemisphere.

  15. Effects of chemical reaction on MHD free convection and mass transfer flow of a micropolar fluid with oscillatory plate velocity and constant heat source in a rotating frame of reference

    NASA Astrophysics Data System (ADS)

    Bakr, A. A.

    2011-02-01

    This paper concerns with studying the steady and unsteady MHD micropolar flow and mass transfers flow with constant heat source in a rotating frame of reference in the presence chemical reaction of the first-order, taking an oscillatory plate velocity and a constant suction velocity at the plate. The plate velocity is assumed to oscillate in time with a constant frequency; it is thus assumed that the solutions of the boundary layer are the same oscillatory type. The governing dimensionless equations are solved analytically after using small perturbation approximation. The effects of the various flow parameters and thermophysical properties on the velocity and temperature fields across the boundary layer are investigated. Numerical results of velocity profiles of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. The results show that there exists completely oscillating behavior in the velocity distribution.

  16. Mixed quantum/classical theory for inelastic scattering of asymmetric-top-rotor + atom in the body-fixed reference frame and application to the H{sub 2}O + He system

    SciTech Connect

    Semenov, Alexander; Dubernet, Marie-Lise; Babikov, Dmitri

    2014-09-21

    The mixed quantum/classical theory (MQCT) for inelastic molecule-atom scattering developed recently [A. Semenov and D. Babikov, J. Chem. Phys. 139, 174108 (2013)] is extended to treat a general case of an asymmetric-top-rotor molecule in the body-fixed reference frame. This complements a similar theory formulated in the space-fixed reference-frame [M. Ivanov, M.-L. Dubernet, and D. Babikov, J. Chem. Phys. 140, 134301 (2014)]. Here, the goal was to develop an approximate computationally affordable treatment of the rotationally inelastic scattering and apply it to H{sub 2}O + He. We found that MQCT is somewhat less accurate at lower scattering energies. For example, below E = 1000 cm{sup −1} the typical errors in the values of inelastic scattering cross sections are on the order of 10%. However, at higher scattering energies MQCT method appears to be rather accurate. Thus, at scattering energies above 2000 cm{sup −1} the errors are consistently in the range of 1%–2%, which is basically our convergence criterion with respect to the number of trajectories. At these conditions our MQCT method remains computationally affordable. We found that computational cost of the fully-coupled MQCT calculations scales as n{sup 2}, where n is the number of channels. This is more favorable than the full-quantum inelastic scattering calculations that scale as n{sup 3}. Our conclusion is that for complex systems (heavy collision partners with many internal states) and at higher scattering energies MQCT may offer significant computational advantages.

  17. Senescence-accelerated mouse (SAM) with special references to neurodegeneration models, SAMP8 and SAMP10 mice.

    PubMed

    Takeda, Toshio

    2009-04-01

    The SAM strains, a group of related inbred strains consisting of senescence-prone inbred strains (SAMP) and senescence-resistant inbred strains (SAMR), have been successfully developed by selective inbreeding of the AKR/J strain of mice donated by the Jackson laboratory in 1968. The characteristic feature of aging common to the SAMP and SAMR is accelerated senescence and normal aging, respectively. Furthermore, SAMP and SAMR strains of mice manifest various pathobiological phenotypes spontaneously. Among SAMP strains, SAMP8 and SAMP10 mice show age-related behavioral deterioration such as deficits in learning and memory, emotional disorders (reduced anxiety-like behavior and depressive behavior) and altered circadian rhythm associated with certain pathological, biochemical and pharmacological changes. Here, the previous and recent literature on SAM mice are reviewed with an emphasis on SAMP8 and SAMP10 mice. A spontaneous model like SAM with distinct advantages over the gene-modified model is hoped by investigators to be used more widely as a biogerontological resource to explore the etiopathogenesis of accelerated senescence and neurodegenerative disorders. PMID:19199030

  18. Non-Syntactic Antecedents and Frame Semantics.

    ERIC Educational Resources Information Center

    Gensler, Orin

    A polemic is made for frame semantics and the linguistic phenomenon of anaphoric reference without noun phrase (NP) antecedent is examined within this frame. Non-syntactic anaphora is that which does not point out into the real world but rather points back into the discourse in a frame which has been built up between the speaker and hearer in a…

  19. Novel frame-shift mutation in Slc5a2 encoding SGLT2 in a strain of senescence-accelerated mouse SAMP10.

    PubMed

    Unno, Keiko; Yamamoto, Hiroyuki; Toda, Masateru; Hagiwara, Shiori; Iguchi, Kazuaki; Hoshino, Minoru; Takabayashi, Fumiyo; Hasegawa-Ishii, Sanae; Shimada, Atsuyoshi; Hosokawa, Masanori; Higuchi, Keiichi; Mori, Masayuki

    2014-11-01

    The senescence-accelerated mouse prone10 (SAMP10) strain, a model of aging, exhibits cognitive impairments and cerebral atrophy. We noticed that SAMP10/TaSlc mice, a SAMP10 substrain, have developed persistent glucosuria over the past few years. In the present study, we characterized SAMP10/TaSlc mice and further identified a spontaneous mutation in the Slc5a2 gene encoding sodium-glucose co-transporter (SGLT) 2. The mean concentration of urine glucose was high in SAMP10/TaSlc mice and increased further with advancing age, whereas other strains of senescence-accelerated mice, including SAMP1/SkuSlc, SAMP6/TaSlc and SAMP8/TaSlc or normal aging control SAMR1/TaSlc mice, exhibited no detectable glucose in urine. SAMP10/TaSlc mice consumed increasing amounts of food and water compared to SAMR1/TaSlc mice, suggesting the compensation of polyuria and the loss of glucose. Oral glucose tolerance tests showed decreased glucose reabsorption in the kidney of SAMP10/TaSlc mice. In addition, blood glucose levels decreased in an age-dependent fashion. The kidney was innately larger than that of control mice with no histological alterations. We examined the expression levels of glucose transporters in the kidney. Among SGLT1, SGLT2, glucose transporter (GLUT) 1 and GLUT2, we found a significant decrease only in the level of SGLT2. DNA sequencing of SGLT2 in SAMP10/TaSlc mice revealed a single nucleotide deletion of guanine at 1236, which resulted in a frameshift mutation that produced a truncated protein. We designate this strain as SAMP10/TaSlc-Slc5a2(slc) (SAMP10-ΔSglt2). Recently, SGLT2 inhibitors have been demonstrated to be effective for the treatment of patients with type 2 diabetes (T2D). SAMP10-ΔSglt2 mice may serve as a unique preclinical model to study the link between aging-related neurodegenerative disorders and T2D. PMID:25450362

  20. On the Energy and Momentum of an Accelerated Charged Particle and the Sources of Radiation

    ERIC Educational Resources Information Center

    Eriksen, Erik; Gron, Oyvind

    2007-01-01

    We give a systematic development of the theory of the radiation field of an accelerated charged particle with reference to an inertial reference frame in flat spacetime. Special emphasis is given to the role of the Schott energy and momentum in the energy-momentum balance of the charge and its field. It is shown that the energy of the radiation…

  1. A-frame model for metaphor

    SciTech Connect

    Kilpatrick, W.

    1982-01-01

    While literal language is successfully being subjected to automatic analysis, metaphors remain intractable. Using Minsky's frame theory the metaphoric process is viewed as a copying of stereotypic terminal clusters from the frames of the 1 degrees and 2 degrees terms of the metaphor. Stereotypic values from the two original frames share equal status in this new frame, while non-stereotypic values from the two will be kept separate for possible use in metaphoric extension. The a-frame analysis is illustrated by application to non-literary novel metaphors. Frames provide the quantity of information needed for interpretation. Certain frame values are marked as stereotypic. Creativity is realized by the construction of a new a-frame, and the tension is realized by the presence in a single a-frame of both shared stereotypic and discrete non-stereotypic values. 10 references.

  2. Inflight observability of gyro reference frame misalignment

    NASA Technical Reports Server (NTRS)

    Huang, W. H.

    1986-01-01

    The effect of gyro misalignment on the attitude knowledge error (AKE) in a strapdown environment is analyzed. The subject attitude knowledge is defined, and the equation of motion is derived considering only the initial AKE and the misalignment. These two error sources are shown to be different. The closed-form solution to the equation of motion is presented, and an important theorem concerning the error induced by the initial AKE and misalignment is proven. The observability of misalignment in an ideal update environment where three cases of AKE can be measured simultaneously is examined. The misalignment observability in an infinitesimal field of view line of sight sensor update design is discussed. It is concluded that attitude error in a strapdown gyro application due to gyro misalignment is a conservative function of the attitude only.

  3. On the orientation of ephemeris reference frames

    NASA Technical Reports Server (NTRS)

    Standish, E. M., Jr.

    1985-01-01

    Precession corrections, equinox motions and locations, and obliquities for the FK4 are determined from laser-ranging data only by the ephemeris-fitting method of Standish (1982) and compared with those calculated by Fricke (1971 and 1982) from optical observations. The theoretical basis of the comparison is explained, and the results are presented in a table. No significant differences are found in the equinox offset and equinox motion values, and good agreement is found in the equinox location. The ephemeris-fitting obliquity values are shown to be consistent to within 10 marcsec and to be about 20 marcsec lower than the optical values.

  4. Frames of reference and motion aftereffects.

    PubMed

    Swanston, M T

    1994-01-01

    Evidence concerning the origin of the motion aftereffect (MAE) is assessed in terms of a model of levels of representation in visual motion perception proposed by Wade and Swanston. Very few experiments have been designed so as to permit unambiguous conclusions to be drawn. The requirements for such experiments are identified. Whereas retinocentric motion could in principle give rise to the MAE, data are not available which would enable a conclusion to be drawn. There is good evidence for a patterncentric origin, indicating that the MAE is primarily the result of adaptation in the systems responsible for detecting relative visual motion. There is evidence for a further contribution from the process that compensates retinocentric motion for eye movements, in the form of nonveridical information for eye movements. There may also be an effect at the level at which perceived distance and self-movement information are combined with egocentric motion to give a geocentric representation which provides the basis for reports of phenomenal experience. It is concluded that the MAE can be caused by changes in activity at more than one level of representation, and cannot be ascribed to a single underlying process. PMID:7899042

  5. Reduction of Acceleration to Effectively Microgravity Levels

    NASA Technical Reports Server (NTRS)

    Downey, James Patton

    2000-01-01

    Pressure gradients, i.e. pressure head, and buoyancy driven convection can be greatly decreased in experimental systems by acceleration of the laboratory reference frame at a rate consistent with the acceleration due to gravity. This may be done in a number of ways, the best known of which is the use of orbiting spacecraft. Other techniques include the use of aircraft following an appropriate parabolic trajectory or drop towers. The result is an experimental condition in which fluids experience virtually no outside forces relative to the laboratory reference frame. Such conditions are appropriate for the study of processes with diffusion dominated heat and/or mass Under, the study of phase transitions in the absence of pressure gradients, the study of solutal or thermal capillary convection, or containerless processes. Ways of achieving these conditions and complexities that arise in performing experiments in this environment are discussed.

  6. Accelerated construction of a regional DNA-barcode reference library: Caddisflies (Trichoptera) in the Great Smoky Mountains National Park

    USGS Publications Warehouse

    Zhou, X.; Robinson, J.L.; Geraci, C.J.; Parker, C.R.; Flint, O.S., Jr.; Etnier, D.A.; Ruiter, D.; DeWalt, R.E.; Jacobus, L.M.; Hebert, P.D.N.

    2011-01-01

    Deoxyribonucleic acid (DNA) barcoding is an effective tool for species identification and lifestage association in a wide range of animal taxa. We developed a strategy for rapid construction of a regional DNA-barcode reference library and used the caddisflies (Trichoptera) of the Great Smoky Mountains National Park (GSMNP) as a model. Nearly 1000 cytochrome c oxidase subunit I (COI) sequences, representing 209 caddisfly species previously recorded from GSMNP, were obtained from the global Trichoptera Barcode of Life campaign. Most of these sequences were collected from outside the GSMNP area. Another 645 COI sequences, representing 80 species, were obtained from specimens collected in a 3-d bioblitz (short-term, intense sampling program) in GSMNP. The joint collections provided barcode coverage for 212 species, 91% of the GSMNP fauna. Inclusion of samples from other localities greatly expedited construction of the regional DNA-barcode reference library. This strategy increased intraspecific divergence and decreased average distances to nearest neighboring species, but the DNA-barcode library was able to differentiate 93% of the GSMNP Trichoptera species examined. Global barcoding projects will aid construction of regional DNA-barcode libraries, but local surveys make crucial contributions to progress by contributing rare or endemic species and full-length barcodes generated from high-quality DNA. DNA taxonomy is not a goal of our present work, but the investigation of COI divergence patterns in caddisflies is providing new insights into broader biodiversity patterns in this group and has directed attention to various issues, ranging from the need to re-evaluate species taxonomy with integrated morphological and molecular evidence to the necessity of an appropriate interpretation of barcode analyses and its implications in understanding species diversity (in contrast to a simple claim for barcoding failure).

  7. Hamiltonian approach to frame dragging

    NASA Astrophysics Data System (ADS)

    Epstein, Kenneth J.

    2008-07-01

    A Hamiltonian approach makes the phenomenon of frame dragging apparent “up front” from the appearance of the drag velocity in the Hamiltonian of a test particle in an arbitrary metric. Hamiltonian (1) uses the inhomogeneous force equation (4), which applies to non-geodesic motion as well as to geodesics. The Hamiltonian is not in manifestly covariant form, but is covariant because it is derived from Hamilton’s manifestly covariant scalar action principle. A distinction is made between manifest frame dragging such as that in the Kerr metric, and hidden frame dragging that can be made manifest by a coordinate transformation such as that applied to the Robertson-Walker metric in Sect. 2. In Sect. 3 a zone of repulsive gravity is found in the extreme Kerr metric. Section 4 treats frame dragging in special relativity as a manifestation of the equivalence principle in accelerated frames. It answers a question posed by Bell about how the Lorentz contraction can break a thread connecting two uniformly accelerated rocket ships. In Sect. 5 the form of the Hamiltonian facilitates the definition of gravitomagnetic and gravitoelectric potentials.

  8. Three-Corner Hat for the assessment of the uncertainty of non-linear residuals of space-geodetic time series in the context of terrestrial reference frame analysis

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Gross, R. S.; Heflin, M. B.; Parker, J. W.; Wu, X.

    2015-04-01

    We discuss the application of the Three-Corner Hat (TCH) to time series of space-geodetic station position residuals with the purpose of characterizing the uncertainties of GPS, VLBI, SLR, DORIS for the International Terrestrial Reference Frame (ITRF) determination. Adopting simulations, we show that, in the absence of time-correlated errors, TCH is able to fully recover the nominal uncertainties of groups of observations whose intrinsic precisions are remarkably dissimilar to one another, as is the case for the space-geodetic techniques. When time-correlated errors are predominant, as it happens with GPS, TCH is affected by the increased variance of the observations and its estimates are positively biased. TCH applied to 16 ITRF co-located sites confirms that GPS, albeit affected by time-correlated errors, is the most precise of the space-geodetic techniques. GPS median uncertainties are 1.1, 1.2 and 2.8 mm, for the north, east and height component, respectively. VLBI performs particularly well in the horizontal component, the median uncertainties being mm. The height component is times larger than the GPS one. SLR and DORIS median uncertainties exceed by far the 7 mm level on all of the three components. Comparing TCH results with station position repeatabilities, we find that the two metrics are in striking agreement for VLBI and DORIS, but not for SLR and GPS. The inconsistencies between TCH and station repeatabilities for co-located GPS and SLR point to the presence of either specific station-dependent biases or low-quality co-locations. Scaling factors derived adopting the ratio between TCH and median formal errors on the positions suggest the station position covariances have to be up-scaled for VLBI, SLR, DORIS and down-scaled for GPS.

  9. Technological Frame Incongruence, Diffusion, and Noncompliance

    NASA Astrophysics Data System (ADS)

    Sobreperez, Polly

    The technological frames of reference strand of social shaping of technology theory is used to overlay the issues arising from a case study looking at noncompliance with information systems. A recent review of the theory suggests that although frame content is often addressed, frame structure, the process of framing, and the characteristics and outcomes of frames are largely overlooked. This paper attempts to address this shortfall by applying the indicators identified by case study research to the frames of different groups and using them to highlight differing perceptions and attitudes. In this way, the author suggests that issues surrounding noncompliance should not be dismissed as resistance but instead should be further studied by managers and developers, leading to accommodation of differing views. Further examination of frame incongruence reveals dependence on inefficient or ineffective organizational situations and thus these indicators can be useful in future studies to identify and address procedural, acceptance and cultural issues leading to acts of noncompliance.

  10. Thirty Frames per Second

    ERIC Educational Resources Information Center

    Kelly, Bruce

    2006-01-01

    Analyzing real motion with frame-by-frame precision can be conducted using modestly priced digital-video camcorders. Although well below the 1,000 frames-per-second threshold of high-speed cameras, commercially available camcorders grab 30 frames per second. A replay dissected at this lower frequency is fun to watch, challenges students'…

  11. Classroom Discourse Frames.

    ERIC Educational Resources Information Center

    Pennington, Martha C.

    An analysis of classroom discourse proposes four frames, modeled as concentric circles. The inner most circle is the lesson frame, removed or sheltered from outside influences and most likely, in a language class, to maintain second-language usage. The next frame from the center is the lesson-support frame, an intermediate layer of classroom…

  12. Automating Frame Analysis

    SciTech Connect

    Sanfilippo, Antonio P.; Franklin, Lyndsey; Tratz, Stephen C.; Danielson, Gary R.; Mileson, Nicholas D.; Riensche, Roderick M.; McGrath, Liam

    2008-04-01

    Frame Analysis has come to play an increasingly stronger role in the study of social movements in Sociology and Political Science. While significant steps have been made in providing a theory of frames and framing, a systematic characterization of the frame concept is still largely lacking and there are no rec-ognized criteria and methods that can be used to identify and marshal frame evi-dence reliably and in a time and cost effective manner. Consequently, current Frame Analysis work is still too reliant on manual annotation and subjective inter-pretation. The goal of this paper is to present an approach to the representation, acquisition and analysis of frame evidence which leverages Content Analysis, In-formation Extraction and Semantic Search methods to provide a systematic treat-ment of a Frame Analysis and automate frame annotation.

  13. VIRTUAL FRAME BUFFER INTERFACE

    NASA Technical Reports Server (NTRS)

    Wolfe, T. L.

    1994-01-01

    Large image processing systems use multiple frame buffers with differing architectures and vendor supplied user interfaces. This variety of architectures and interfaces creates software development, maintenance, and portability problems for application programs. The Virtual Frame Buffer Interface program makes all frame buffers appear as a generic frame buffer with a specified set of characteristics, allowing programmers to write code which will run unmodified on all supported hardware. The Virtual Frame Buffer Interface converts generic commands to actual device commands. The virtual frame buffer consists of a definition of capabilities and FORTRAN subroutines that are called by application programs. The virtual frame buffer routines may be treated as subroutines, logical functions, or integer functions by the application program. Routines are included that allocate and manage hardware resources such as frame buffers, monitors, video switches, trackballs, tablets and joysticks; access image memory planes; and perform alphanumeric font or text generation. The subroutines for the various "real" frame buffers are in separate VAX/VMS shared libraries allowing modification, correction or enhancement of the virtual interface without affecting application programs. The Virtual Frame Buffer Interface program was developed in FORTRAN 77 for a DEC VAX 11/780 or a DEC VAX 11/750 under VMS 4.X. It supports ADAGE IK3000, DEANZA IP8500, Low Resolution RAMTEK 9460, and High Resolution RAMTEK 9460 Frame Buffers. It has a central memory requirement of approximately 150K. This program was developed in 1985.

  14. Quantum decoherence in noninertial frames

    NASA Astrophysics Data System (ADS)

    Wang, Jieci; Jing, Jiliang

    2010-09-01

    Quantum decoherence, which appears when a system interacts with its environment in an irreversible way, plays a fundamental role in the description of quantum-to-classical transitions and has been successfully applied in some important experiments. Here, we study the decoherence in noninertial frames. It is shown that the decoherence and loss of the entanglement generated by the Unruh effect will influence each other remarkably. It is interesting to note that, in the case of the total system under decoherence, the sudden death of entanglement may appear for any acceleration. However, in the case of only Rob’s qubit undergoing decoherence, sudden death may only occur when the acceleration parameter is greater than a “critical point.”

  15. Quantum decoherence in noninertial frames

    SciTech Connect

    Wang Jieci; Jing Jiliang

    2010-09-15

    Quantum decoherence, which appears when a system interacts with its environment in an irreversible way, plays a fundamental role in the description of quantum-to-classical transitions and has been successfully applied in some important experiments. Here, we study the decoherence in noninertial frames. It is shown that the decoherence and loss of the entanglement generated by the Unruh effect will influence each other remarkably. It is interesting to note that, in the case of the total system under decoherence, the sudden death of entanglement may appear for any acceleration. However, in the case of only Rob's qubit undergoing decoherence, sudden death may only occur when the acceleration parameter is greater than a 'critical point'.

  16. Frame independent cosmological perturbations

    SciTech Connect

    Prokopec, Tomislav; Weenink, Jan E-mail: j.g.weenink@uu.nl

    2013-09-01

    We compute the third order gauge invariant action for scalar-graviton interactions in the Jordan frame. We demonstrate that the gauge invariant action for scalar and tensor perturbations on one physical hypersurface only differs from that on another physical hypersurface via terms proportional to the equation of motion and boundary terms, such that the evolution of non-Gaussianity may be called unique. Moreover, we demonstrate that the gauge invariant curvature perturbation and graviton on uniform field hypersurfaces in the Jordan frame are equal to their counterparts in the Einstein frame. These frame independent perturbations are therefore particularly useful in relating results in different frames at the perturbative level. On the other hand, the field perturbation and graviton on uniform curvature hypersurfaces in the Jordan and Einstein frame are non-linearly related, as are their corresponding actions and n-point functions.

  17. Effect of relativistic acceleration on localized two-mode Gaussian quantum states

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mehdi; Lorek, Krzysztof; Checińska, Agata; Smith, Alexander R. H.; Mann, Robert B.; Dragan, Andrzej

    2016-06-01

    We study how an arbitrary Gaussian state of two localized wave packets, prepared in an inertial frame of reference, is described by a pair of uniformly accelerated observers. We explicitly compute the resulting state for arbitrarily chosen proper accelerations of the observers and independently tuned distance between them. To do so, we introduce a generalized Rindler frame of reference and analytically derive the corresponding state transformation as a Gaussian channel. Our approach provides several new insights into the phenomenon of vacuum entanglement such as the highly nontrivial effect of spatial separation between the observers including sudden death of entanglement. We also calculate the fidelity of the two-mode channel for nonvacuum Gaussian states and obtain bounds on classical and quantum capacities of a single-mode channel. Our framework can be directly applied to any continuous variable quantum information protocol in which the effects of acceleration or gravity cannot be neglected.

  18. GENERAL RELATIVITY DERIVATION OF BEAM REST-FRAME HAMILTONIAN.

    SciTech Connect

    WEI,J.

    2001-06-18

    Analysis of particle interaction in the laboratory frame of storage rings is often complicated by the fact that particle motion is relativistic, and that reference particle trajectory is curved. Rest frame of the reference particle is a convenient coordinate system to work with, within which particle motion is non-relativistic. We have derived the equations of motion in the beam rest frame from the general relativity formalism, and have successfully applied them to the analysis of crystalline beams [1].

  19. Reduction of Effective Acceleration to Microgravity Levels

    NASA Technical Reports Server (NTRS)

    Downey, James P.

    2000-01-01

    Acceleration due to earth's gravity causes buoyancy driven convection and sedimentation in solutions. In addition. pressure gradients occur as a function of the height within a liquid column. Hence gravity effects both equilbria conditions and phase transitions as a result of hydrostatic pressure gradients. The affect of gravity on the rate of heat and man transfer in solutal processes can be particularly important in polymer processing due to the high sensitivity of polymeric materials to processing conditions. The term microgravity has been coined to describe an environment in which the affects of gravitational acceleration am greatly reduced. It may seem odd to talk in term of reducing the effects of gravitational acceleration since gravitational attraction is a basic property of matter. However, die presence of gravity on in situ processing or measurements can be negated by achieving conditions in which the laboratory, or more specifically the container of the experimental materials, a subjected to the same acceleration as the materials themselves. With regard to the laboratory reference frame, there is virtually no force on the experimental solutions. This is difficult to achieve but can be done. A short review of Newtonian physics provides an explanation on both how processes we affected by gravity and how microgravity conditions are achieved. The fact that fluids deform when subject to a force bid solids do not indicates that solids have a structure able to exert an opposing force that negates an externally applied force. Liquids deform when a force is applied, indicating that a liquid structure cannot completely negate an applied force. Just how easily a liquid resists deformation is related to its viscosity. Spaceflight provides an environment in which the laboratory reference frame i.e. the spacecraft and all the equipment therein an experiencing virtually identical forces. There is no solid foundation underneath such a laboratory, so the laboratory

  20. Modern Steel Framed Schools.

    ERIC Educational Resources Information Center

    American Inst. of Steel Construction, Inc., New York, NY.

    In view of the cost of structural framing for school buildings, ten steel-framed schools are examined to review the economical advantages of steel for school construction. These schools do not resemble each other in size, shape, arrangement or unit cost; some are original in concept and architecture, and others are conservative. Cost and…

  1. Quantum accelerometer: Distinguishing inertial Bob from his accelerated twin Rob by a local measurement

    SciTech Connect

    Dragan, Andrzej; Fuentes, Ivette; Louko, Jorma

    2011-04-15

    A single quantum system, such as the Unruh-DeWitt detector, can be used to determine absolute acceleration by local measurements on a quantum field. To show this, we consider two kinematically indistinguishable scenarios: an inertial observer, Bob, measuring the field of a uniformly accelerated cavity, and his noninertial twin, Rob, accelerating and making measurements in a stationary cavity. We find that these scenarios can be distinguished in the nonrelativistic regime only by measurements on highly excited massive fields, allowing one to detect the noninertialness of the reference frame.

  2. Quantum accelerometer: Distinguishing inertial Bob from his accelerated twin Rob by a local measurement

    NASA Astrophysics Data System (ADS)

    Dragan, Andrzej; Fuentes, Ivette; Louko, Jorma

    2011-04-01

    A single quantum system, such as the Unruh-DeWitt detector, can be used to determine absolute acceleration by local measurements on a quantum field. To show this, we consider two kinematically indistinguishable scenarios: an inertial observer, Bob, measuring the field of a uniformly accelerated cavity, and his noninertial twin, Rob, accelerating and making measurements in a stationary cavity. We find that these scenarios can be distinguished in the nonrelativistic regime only by measurements on highly excited massive fields, allowing one to detect the noninertialness of the reference frame.

  3. Entangled light in moving frames

    SciTech Connect

    Gingrich, Robert M.; Bergou, Attila J.; Adami, Christoph

    2003-10-01

    We calculate the entanglement between a pair of polarization-entangled photon beams as a function of the reference frame, in a fully relativistic framework. We find the transformation law for helicity basis states and show that, while it is frequency independent, a Lorentz transformation on a momentum-helicity eigenstate produces a momentum-dependent phase. This phase leads to changes in the reduced polarization density matrix, such that entanglement is either decreased or increased, depending on the boost direction, the rapidity, and the spread of the beam.

  4. DC-like Phase Space Manipulation and Particle Acceleration Using Chirped AC Fields

    SciTech Connect

    P.F. Schmit and N.J. Fisch

    2009-06-17

    Waves in plasmas can accelerate particles that are resonant with the wave. A DC electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. We investigate the effect on a Hamiltonian distribution of an accelerating potential waveform, which could, for example, represent the average ponderomotive effect of two counterpropagating electromagnetic waves. In particular, we examine the apparent DC-like time-asymptotic response of the distribution in regimes where the potential structure is accelerated adiabatically. A highly resonant population within the distribution is always present, and we characterize its nonadiabatic response during wave-particle resonance using an integral method in the noninertial reference frame moving with the wave. Finally, we show that in the limit of infinitely slow acceleration of the wave, these highly resonant particles disappear and the response

  5. The Kepler Full Frame Images

    NASA Astrophysics Data System (ADS)

    Dotson, Jessie L.; Batalha, N.; Bryson, S.; Caldwell, D. A.; Clarke, B.; Haas, M. R.; Jenkins, J.; Kolodziejczak, J.; Quintana, E.; Van Cleve, J.; Kepler Team

    2010-01-01

    NASA's exoplanet discovery mission Kepler provides uninterrupted 1-min and 30-min optical photometry of a 100 square degree field over a 3.5 yr nominal mission. Downlink bandwidth is filled at these short cadences by selecting only detector pixels specific to 105 preselected stellar targets. The majority of the Kepler field, comprising 4 x 106 mv < 20 sources, is sampled at much lower 1-month cadence in the form of a full-frame image. The Full Frame Images (FFIs) are calibrated by the Science Operations Center at NASA Ames Research Center. The Kepler Team employ these images for astrometric and photometric reference but make the images available to the astrophysics community through the Multimission Archive at STScI (MAST). The full-frame images provide a resource for potential Kepler Guest Observers to select targets and plan observing proposals, while also providing a freely-available long-cadence legacy of photometric variation across a swathe of the Galactic disk. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.

  6. The Kepler Full Frame Images

    NASA Technical Reports Server (NTRS)

    Dotson, Jessie L.; Batalha, Natalie; Bryson, Stephen T.; Caldwell, Douglas A.; Clarke, Bruce D.

    2010-01-01

    NASA's exoplanet discovery mission Kepler provides uninterrupted 1-min and 30-min optical photometry of a 100 square degree field over a 3.5 yr nominal mission. Downlink bandwidth is filled at these short cadences by selecting only detector pixels specific to 105 preselected stellar targets. The majority of the Kepler field, comprising 4 x 10(exp 6) m_v < 20 sources, is sampled at much lower 1-month cadence in the form of a full-frame image. The Full Frame Images (FFIs) are calibrated by the Science Operations Center at NASA Ames Research Center. The Kepler Team employ these images for astrometric and photometric reference but make the images available to the astrophysics community through the Multimission Archive at STScI (MAST). The full-frame images provide a resource for potential Kepler Guest Observers to select targets and plan observing proposals, while also providing a freely-available long-cadence legacy of photometric variation across a swathe of the Galactic disk.

  7. Complex equiangular tight frames

    NASA Astrophysics Data System (ADS)

    Tropp, Joel A.

    2005-08-01

    A complex equiangular tight frame (ETF) is a tight frame consisting of N unit vectors in Cd whose absolute inner products are identical. One may view complex ETFs as a natural geometric generalization of an orthonormal basis. Numerical evidence suggests that these objects do not arise for most pairs (d, N). The goal of this paper is to develop conditions on (d, N) under which complex ETFs can exist. In particular, this work concentrates on the class of harmonic ETFs, in which the components of the frame vectors are roots of unity. In this case, it is possible to leverage field theory to obtain stringent restrictions on the possible values for (d, N).

  8. Informative-frame filtering in endoscopy videos

    NASA Astrophysics Data System (ADS)

    An, Yong Hwan; Hwang, Sae; Oh, JungHwan; Lee, JeongKyu; Tavanapong, Wallapak; de Groen, Piet C.; Wong, Johnny

    2005-04-01

    Advances in video technology are being incorporated into today"s healthcare practice. For example, colonoscopy is an important screening tool for colorectal cancer. Colonoscopy allows for the inspection of the entire colon and provides the ability to perform a number of therapeutic operations during a single procedure. During a colonoscopic procedure, a tiny video camera at the tip of the endoscope generates a video signal of the internal mucosa of the colon. The video data are displayed on a monitor for real-time analysis by the endoscopist. Other endoscopic procedures include upper gastrointestinal endoscopy, enteroscopy, bronchoscopy, cystoscopy, and laparoscopy. However, a significant number of out-of-focus frames are included in this type of videos since current endoscopes are equipped with a single, wide-angle lens that cannot be focused. The out-of-focus frames do not hold any useful information. To reduce the burdens of the further processes such as computer-aided image processing or human expert"s examinations, these frames need to be removed. We call an out-of-focus frame as non-informative frame and an in-focus frame as informative frame. We propose a new technique to classify the video frames into two classes, informative and non-informative frames using a combination of Discrete Fourier Transform (DFT), Texture Analysis, and K-Means Clustering. The proposed technique can evaluate the frames without any reference image, and does not need any predefined threshold value. Our experimental studies indicate that it achieves over 96% of four different performance metrics (i.e. precision, sensitivity, specificity, and accuracy).

  9. Electrodynamics of hyperbolically accelerated charges V. The field of a charge in the Rindler space and the Milne space

    NASA Astrophysics Data System (ADS)

    Eriksen, E.; Grøn, Ø.

    2004-09-01

    We describe the electromagnetic field of a uniformly accelerated charge in its co-moving Rindler frame. It is shown that the electrical field lines coincide with the trajectories of photons. The self force of a charged particle at rest in Rindler space, and the increase of its weight due to its charge, is calculated. The general case of an accelerated charge in Rindler space is also considered. It is shown that the electrical field inside a uniformly charged spherical shell can be used as a measure of it 4-acceleration. A result that has earlier been deduced in a different way by Fugmann and Kretzschmar is confirmed, namely that the intensity of radiation from a point charge instantaneously at rest in an accelerated frame is proportional to the square of the relative acceleration of the charge and the observer. In particular it is shown that a freely falling charge in Rindler space radiates in accordance with Larmor's formula. In this case the radiation energy is taken from the Schott energy. The energy of the electromagnetic field is analysed from the point of view of the Hirayama-separation, which generalizes the Teitelboim-separation to non-inertial frames, of the field in a bound part and an unbound part. A detailed account, with reference to the Rindler frame, of the field energy and particle energy is given for the case of a charge entering and leaving a region with hyperbolic motion. We also consider the electromagnetic field of a uniformly accelerated charge with reference to the Milne frame, which covers a different part of spacetime than the Rindler frame. The radiating part of the electromagnetic field is found in the Milne sector of spacetime.

  10. Implications of an Absolute Simultaneity Theory for Cosmology and Universe Acceleration

    PubMed Central

    Kipreos, Edward T.

    2014-01-01

    An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centered non-rotating inertial reference frame, with the inference that in an ALT framework, preferred reference frames are associated with centers of gravitational mass. Applying this theoretical framework to cosmological data produces a scenario of universal time contraction in the past. In this scenario, past time contraction would be associated with increased levels of blueshifted light emissions from cosmological objects when viewed from our current perspective. The observation that distant Type Ia supernovae are dimmer than predicted by linear Hubble expansion currently provides the most direct evidence for an accelerating universe. Adjusting for the effects of time contraction on a redshift–distance modulus diagram produces a linear distribution of supernovae over the full redshift spectrum that is consistent with a non-accelerating universe. PMID:25536116

  11. Implications of an absolute simultaneity theory for cosmology and universe acceleration.

    PubMed

    Kipreos, Edward T

    2014-01-01

    An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centered non-rotating inertial reference frame, with the inference that in an ALT framework, preferred reference frames are associated with centers of gravitational mass. Applying this theoretical framework to cosmological data produces a scenario of universal time contraction in the past. In this scenario, past time contraction would be associated with increased levels of blueshifted light emissions from cosmological objects when viewed from our current perspective. The observation that distant Type Ia supernovae are dimmer than predicted by linear Hubble expansion currently provides the most direct evidence for an accelerating universe. Adjusting for the effects of time contraction on a redshift-distance modulus diagram produces a linear distribution of supernovae over the full redshift spectrum that is consistent with a non-accelerating universe. PMID:25536116

  12. APT/LEDA RFQ and support frame structural analysis

    SciTech Connect

    Ellis, S.

    1997-04-01

    This report documents structural analysis of the Accelerator Production of Tritium Low Energy Demonstration Accelerator (APT/LEDA) Radio Frequency Quadrupole (RFQ) accelerator structure and its associated support frame. This work was conducted for the Department of Energy in support of the APT/LEDA. Structural analysis of the RFQ was performed to quantify stress levels and deflections due to both vacuum loading and gravity loading. This analysis also verified the proposed support scheme geometry and quantified interface loads. This analysis also determined the necessary stiffness and strength requirements of the RFQ support frame verifying the conceptual design geometry and allowing specification of individual frame elements. Complete structural analysis of the frame was completed subsequently. This report details structural analysis of the RFQ assembly with regard to gravity and vacuum loads only. Thermally induced stresses from the Radio Frequency (RF) surface resistance heating were not considered.

  13. Building Trades. Block III. Floor Framing.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Vocational Instructional Services.

    This document contains three units of a course on floor framing to be used as part of a building trades program. Each unit consists, first, of an informational lesson, with complete lesson plan for the teacher's use. Included in each lesson plan are the lesson aim; lists of teaching aids, materials, references, and prerequisites for students;…

  14. Emergent Bilinguals: Framing Students as Statistical Data?

    ERIC Educational Resources Information Center

    Koyama, Jill; Menken, Kate

    2013-01-01

    Immigrant youth who are designated as English language learners in American schools--whom we refer to as "emergent bilinguals"--are increasingly framed by numerical calculations. Utilizing the notion of assemblage from actor-network theory (ANT), we trace how emergent bilinguals are discursively constructed by officials, administrators,…

  15. Design, Simulation and Testing of a Precision Alignment Frame for the Next Linear Collider

    SciTech Connect

    Fitsos, P

    2004-06-18

    An alignment frame is developed to support 3 Beam Position Monitors (BPM's) for detecting and ultimately aligning the electron beam from a linear accelerator. This report discusses the design details, preliminary modal analysis of the alignment frame as well as the addition of a metrology frame in the final phase of development.

  16. The International Celestial Reference System

    NASA Astrophysics Data System (ADS)

    Fomalont, E.

    2016-05-01

    The International Celestial Reference System (ICRS) is a set of prescriptions, conventions, observational techniques and modeling required to define an celestial inertial frame. The origin of the frame is the solar-system barycenter. The ICRS was adopted by the International Astronomical Union in 1997 as the replacement of the FK5 system. The frame is called the International Celestial Reference Frame (ICRF), and is realized (defined) by the accurate position of 295 radio sources, distributed over the sky, and the accuracy of the frame orientation is about 10 microarcsec. This review will cover: the history of the development of the ICRS; the basics of the major observational technique of Very Long Baseline Interferometry; the use of the fundamental observable, the group delay; experimental strategies to optimize the accuracy; the computational methods for analyzing the large data base; the two major error limitations; and the possible of ICRS/Gaia interactions.

  17. Framing Evolution Discussion Intellectually

    ERIC Educational Resources Information Center

    Oliveira, Alandeom W.; Cook, Kristin; Buck, Gayle A.

    2011-01-01

    This study examines how a first-year biology teacher facilitates a series of whole-class discussions about evolution during the implementation of a problem-based unit. A communicative theoretical perspective is adopted wherein evolution discussions are viewed as social events that the teacher can frame intellectually (i.e., present or organize as…

  18. Target activated frame capture

    NASA Astrophysics Data System (ADS)

    Roberts, G. Marlon; Fitzgerald, James; McCormack, Michael; Steadman, Robert

    2008-04-01

    Over the past decade, technological advances have enabled the use of increasingly intelligent systems for battlefield surveillance. These systems are triggered by a combination of external devices including acoustic and seismic sensors. Such products are mainly used to detect vehicles and personnel. These systems often use infra-red imagery to record environmental information, but Textron Defense Systems' Terrain Commander is one of a small number of systems which analyze these images for the presence of targets. The Terrain Commander combines acoustic, infrared, magnetic, seismic, and visible spectrum sensors to detect nearby targets in military scenarios. When targets are detected by these sensors, the cameras are triggered and images are captured in the infrared and visible spectrum. In this paper we discuss a method through which such systems can perform target tracking in order to record and transmit only the most pertinent surveillance images. This saves bandwidth which is crucial because these systems often use communication systems with throughputs below 2400bps. This method is expected to be executable on low-power processors at frame rates exceeding 10HZ. We accomplish this by applying target activated frame capture algorithms to infra-red video data. The target activated frame capture algorithms combine edge detection and motion detection to determine the best frames to be transmitted to the end user. This keeps power consumption and bandwidth requirements low. Finally, the results of the algorithm are analyzed.

  19. Aluminum space frame technology

    SciTech Connect

    Birch, S.

    1994-01-01

    This article examines the increased application of aluminum to the construction of automobile frames. The topics of the article include a joint venture between Audi and Alcoa, forms in which aluminum is used, new alloys and construction methods, meeting rigidity and safety levels, manufacturing techniques, the use of extrusions, die casting, joining techniques, and pollution control during manufacturing.

  20. Frame dragging and superenergy

    SciTech Connect

    Herrera, L.; Di Prisco, A.; Carot, J.

    2007-08-15

    We show that the vorticity appearing in stationary vacuum spacetimes is always related to the existence of a flow of superenergy on the plane orthogonal to the vorticity vector. This result, together with the previously established link between vorticity and superenergy in radiative (Bondi-Sachs) spacetimes, strengthens further the case for this latter quantity as the cause of frame dragging.

  1. Framing for Scientific Argumentation

    ERIC Educational Resources Information Center

    Berland, Leema K.; Hammer, David

    2012-01-01

    In recent years, research on students' scientific argumentation has progressed to a recognition of nascent resources: Students can and do argue when they experience the need and possibility of persuading others who may hold competing views. Our purpose in this article is to contribute to this progress by applying the perspective of framing to the…

  2. Popcorn Story Frames.

    ERIC Educational Resources Information Center

    DiLella, Carol Ann

    This paper presents "popcorn story frames"--holistic outlines that facilitate comprehension when reading and writing stories, useful for outlining stories read and for creating outlines for original student stories--that are particularly useful for elementary and intermediate school students. "Popcorn" pops in a horizontal manner rather than in a…

  3. Framing Leadership: Contributions and Impediments to Educational Change.

    ERIC Educational Resources Information Center

    Retallick, John; Fink, Dean

    2002-01-01

    Discusses results of 3-year study of the leadership of the principals of 4 Ontario secondary school involved in the Change Frames project, requiring each school to initiate change using each of 7 frames--purpose, emotions, politics, structure, culture, learning, and leadership. (Contains 18 references.) (PKP)

  4. Promotional Frames' Influence on Price Perceptions of Two Apparel Products.

    ERIC Educational Resources Information Center

    Stanforth, Nancy; Lennon, Sharron; Shin, Jung Im

    2001-01-01

    A study explored the differences in price perceptions of two apparel products when promotions were framed as either a price discount or a gift-with-purchase. The majority preferred the discount. Results illustrate the importance of promotional framing in forming consumer price perceptions. (Contains 30 references.) (Author/JOW)

  5. Nonexistence of the self-accelerating dipole and related questions

    NASA Astrophysics Data System (ADS)

    Steane, Andrew M.

    2014-06-01

    We calculate the self-force of a constantly accelerating electric dipole, showing, in particular, that classical electromagnetism does not predict that an electric dipole could self-accelerate, nor could it levitate in a gravitational field. We also resolve a paradox concerning the inertial mass of a longitudinally accelerating dipole, showing that the combined system of dipole plus field can be assigned a well-defined energy-momentum four-vector, so that the principle of relativity is satisfied. We then present some general features of electromagnetic phenomena in a reference frame described by the Rindler metric, showing in particular that an observer fixed in a gravitational field described everywhere by the Rindler metric will find any charged object supported in the gravitational field to possess an electromagnetic self-force equal to that observed by an inertial observer relative to which the body undergoes rigid hyperbolic motion. It follows that the principle of equivalence is satisfied by these systems.

  6. Solid-state framing camera with multiple time frames

    SciTech Connect

    Baker, K. L.; Stewart, R. E.; Steele, P. T.; Vernon, S. P.; Hsing, W. W.; Remington, B. A.

    2013-10-07

    A high speed solid-state framing camera has been developed which can operate over a wide range of photon energies. This camera measures the two-dimensional spatial profile of the flux incident on a cadmium selenide semiconductor at multiple times. This multi-frame camera has been tested at 3.1 eV and 4.5 keV. The framing camera currently records two frames with a temporal separation between the frames of 5 ps but this separation can be varied between hundreds of femtoseconds up to nanoseconds and the number of frames can be increased by angularly multiplexing the probe beam onto the cadmium selenide semiconductor.

  7. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  8. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  9. Nanosecond frame cameras

    SciTech Connect

    Frank, A M; Wilkins, P R

    2001-01-05

    The advent of CCD cameras and computerized data recording has spurred the development of several new cameras and techniques for recording nanosecond images. We have made a side by side comparison of three nanosecond frame cameras, examining them for both performance and operational characteristics. The cameras include; Micro-Channel Plate/CCD, Image Diode/CCD and Image Diode/Film; combinations of gating/data recording. The advantages and disadvantages of each device will be discussed.

  10. Recursive adaptive frame integration limited

    NASA Astrophysics Data System (ADS)

    Rafailov, Michael K.

    2006-05-01

    Recursive Frame Integration Limited was proposed as a way to improve frame integration performance and mitigate issues related to high data rate needed for conventional frame integration. The technique applies two thresholds - one tuned for optimum probability of detection, the other to manage required false alarm rate - and allows a non-linear integration process that, along with Signal-to-Noise Ratio (SNR) gain, provides system designers more capability where cost, weight, or power considerations limit system data rate, processing, or memory capability. However, Recursive Frame Integration Limited may have performance issues when single frame SNR is really low. Recursive Adaptive Frame Integration Limited is proposed as a means to improve limited integration performance with really low single frame SNR. It combines the benefits of nonlinear recursive limited frame integration and adaptive thresholds with a kind of conventional frame integration.

  11. Frame for a firearm

    DOEpatents

    Crandall, David L.; Watson, Richard W.

    2008-03-04

    A firearm frame which is adapted to be disposed in operative relationship as a component part of a firearm, the firearm having disposed in operative relationships each with one or more of the others, a barrel, a receiver, and at least one firing mechanism; wherein the barrel and receiver form operative parts of a movable assembly and the at least one firing mechanism is disposed in a substantially stationary operative relationship therewith; the firearm frame including at least one elongated support structure discrete from the barrel and receiver, the elongated support structure being adapted to directly support the movable assembly in an operative movable relationship therewith; whereby at least one of the barrel and receiver is in direct contact with and movable on the elongated support structure; and, a firing mechanism support structure connected to the at least one elongated support structure, the firing mechanism support structure being adapted to have the firing mechanism connected thereto; the firearm frame also directly supporting the movable assembly and the firing mechanism in corresponding movable and stationary operative relationships each with the other.

  12. The Virtual Reference Librarian's Handbook.

    ERIC Educational Resources Information Center

    Lipow, Anne Grodzins

    This book is a practical guide to librarians and their administrators who are thinking about or in the early stages of providing virtual reference service. Part 1, "The Decision to Go Virtual," provides a context for thinking about virtual reference, including the benefits and problems, getting in the virtual frame of mind, and shopping for…

  13. Electrically insulating and sealing frame

    DOEpatents

    Guthrie, Robin J.

    1983-11-08

    A combination gas seal and electrical insulator having a closed frame shape interconnects a fuel cell stack and a reactant gas plenum of a fuel cell generator. The frame can be of rectangular shape including at least one slidable spline connection in each side to permit expansion or contraction consistent with that of the walls of the gas plenum and fuel cell stack. The slidable spline connections in the frame sides minimizes lateral movement between the frame side members and sealing material interposed between the frame and the fuel cell stack or between the frame and the reactant gas plenum.

  14. Framing Vision: An Examination of Framing, Sensegiving, and Sensemaking during a Change Initiative

    ERIC Educational Resources Information Center

    Hamilton, William

    2016-01-01

    The purpose of this short article is to review the findings from an instrumental case study that examines how a college president used what this article refers to as "frame alignment processes" to mobilize internal and external support for a college initiative--one that achieved success under the current president. Specifically, I…

  15. Conformal frame dependence of inflation

    NASA Astrophysics Data System (ADS)

    Domènech, Guillem; Sasaki, Misao

    2015-04-01

    Physical equivalence between different conformal frames in scalar-tensor theory of gravity is a known fact. However, assuming that matter minimally couples to the metric of a particular frame, which we call the matter Jordan frame, the matter point of view of the universe may vary from frame to frame. Thus, there is a clear distinction between gravitational sector (curvature and scalar field) and matter sector. In this paper, focusing on a simple power-law inflation model in the Einstein frame, two examples are considered; a super-inflationary and a bouncing universe Jordan frames. Then we consider a spectator curvaton minimally coupled to a Jordan frame, and compute its contribution to the curvature perturbation power spectrum. In these specific examples, we find a blue tilt at short scales for the super-inflationary case, and a blue tilt at large scales for the bouncing case.

  16. VIOLENT FRAMES IN ACTION

    SciTech Connect

    Sanfilippo, Antonio P.; McGrath, Liam R.; Whitney, Paul D.

    2011-11-17

    We present a computational approach to radical rhetoric that leverages the co-expression of rhetoric and action features in discourse to identify violent intent. The approach combines text mining and machine learning techniques with insights from Frame Analysis and theories that explain the emergence of violence in terms of moral disengagement, the violation of sacred values and social isolation in order to build computational models that identify messages from terrorist sources and estimate their proximity to an attack. We discuss a specific application of this approach to a body of documents from and about radical and terrorist groups in the Middle East and present the results achieved.

  17. The Levels of Visual Framing

    ERIC Educational Resources Information Center

    Rodriguez, Lulu; Dimitrova, Daniela V.

    2011-01-01

    While framing research has centered mostly on the evaluations of media texts, visual news discourse has remained relatively unexamined. This study surveys the visual framing techniques and methods employed in previous studies and proposes a four-tiered model of identifying and analyzing visual frames: (1) visuals as denotative systems, (2) visuals…

  18. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  19. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  20. Extension of the Optical Reference Frame: Space Based

    NASA Astrophysics Data System (ADS)

    Röser, S.

    The author presents a brief overview of currently planned astrometry space missions. These include GAIA (Global Astrometric Interferometer for Astrophysics), FAME (Fizeau Astrometric Mapping Explorer), LIGHT (Light Interferometer satellite for the study of Galactic Halo Tracers), and DIVA (Double Interferometer for Visual Astrometry).

  1. Modern Science Fiction and Fantasy: A Frame of Reference

    ERIC Educational Resources Information Center

    Green, Roland J.

    1977-01-01

    This article reviews the development of the literature of science fiction and fantasy since the mid-19th century. Diversity of topics is a remarkable characteristic of this writing. An annotated reading list is included. (GC)

  2. Biological and cognitive determination of the gravitational reference frame

    NASA Astrophysics Data System (ADS)

    Tittmar, Heinz-Gunther

    It is argued that space sickness is not so much a physiological problem, but a psychological one, having its roots in the perception of the environment, and its associated cognitive processing. This cognitive processing is argued to be that of field dependence and field independence, for which exist psychobiological and cognitive assessment tests. Since there is an obvious economic advantage in the use of cognite testing, it is recommended that this could be used as an initial screening when selecting for astronauts.

  3. Successful or Not: It Depends on Your Frame of Reference

    ERIC Educational Resources Information Center

    Owen, John M.

    2010-01-01

    This article describes an evaluation that was judged to be unsuccessful from the point of view of key program stakeholders. This was due to the fact that the evaluation did not support program advocates who had much to gain from positive evaluation findings. We argue that, although the knowledge needs of stakeholders must be taken into account,…

  4. Frame of Reference: Open Access Starts with You

    ERIC Educational Resources Information Center

    Goetsch, Lori A.

    2010-01-01

    Federal legislation now requires the deposit of some taxpayer-funded research in "open-access" repositories--that is, sites where scholarship and research are made freely available over the Internet. The institutions whose faculty produce the research have begun to see the benefit of open-access publication as well. From the perspective of faculty…

  5. Neuronal reference frames for social decisions in primate frontal cortex

    PubMed Central

    Chang, Steve W. C.; Gariépy, Jean-Francois; Platt, Michael L.

    2012-01-01

    Social decisions play a crucial role in the success of individuals and the groups they compose. Group members respond vicariously to benefits obtained by others, and impairments in this capacity contribute to neuropsychiatric disorders like autism and sociopathy. We studied how neurons in three frontal cortical areas encode the outcomes of social decisions as monkeys performed a reward-allocation task. Neurons in the orbitofrontal cortex (OFC) predominantly encoded rewards delivered to oneself. Neurons in the anterior cingulate gyrus (ACCg) encoded reward allocations to the other monkey, reward allocations to oneself, or both. Neurons in the anterior cingulate sulcus (ACCs) signaled reward allocations to the other monkey or no one. Within this network of received (OFC) and foregone (ACCs) reward signaling, ACCg emerges as a key nexus for the computation of shared experience and social reward. Individual and species-specific variations in social decision-making might result from the relative activation and influence of these areas. PMID:23263442

  6. Intrinsic Frames of Reference and Egocentric Viewpoints in Scene Recognition

    ERIC Educational Resources Information Center

    Mou, Weimin; Fan, Yanli; McNamara, Timothy P.; Owen, Charles B.

    2008-01-01

    Three experiments investigated the roles of intrinsic directions of a scene and observer's viewing direction in recognizing the scene. Participants learned the locations of seven objects along an intrinsic direction that was different from their viewing direction and then recognized spatial arrangements of three or six of these objects from…

  7. ``Meta''-rigid motions and frames of reference

    NASA Astrophysics Data System (ADS)

    Bel, Lluís; Llosa, Josep

    1995-10-01

    We define the “meta”-rigid motions as particular classes of time-like congruences which are solutions of intrinsically defined partial differential equations that generalize Born's conditions. We consider in particular two hierarchies of such congruences. The first one is a geometrically motivated direct generalization of the symmetry concept inherent in Born congruences. The second one is an indirect generalization based on the conditions which guarantee the existence of a particular class of adapted coordinates of space, named quo-harmonic coordinates, whose definition is akin to the definition of harmonic coordinates but which differs from it in an essential point.

  8. Lattice Kinetic Theory in a Comoving Galilean Reference Frame.

    PubMed

    Frapolli, N; Chikatamarla, S S; Karlin, I V

    2016-07-01

    We prove that the fully discrete lattice Boltzmann method is invariant with respect to Galilean transformation. Based on this finding, a novel class of shifted lattices is proposed which dramatically increases the operating range of lattice Boltzmann simulations, in particular, for gas dynamics applications. A simulation of vortex-shock interaction is used to demonstrate the accuracy and efficiency of the proposed lattices. With one single algorithm it is now possible to simulate a broad range of applications, from low Mach number flows to transonic and supersonic flow regimes. PMID:27419555

  9. Lattice Kinetic Theory in a Comoving Galilean Reference Frame

    NASA Astrophysics Data System (ADS)

    Frapolli, N.; Chikatamarla, S. S.; Karlin, I. V.

    2016-07-01

    We prove that the fully discrete lattice Boltzmann method is invariant with respect to Galilean transformation. Based on this finding, a novel class of shifted lattices is proposed which dramatically increases the operating range of lattice Boltzmann simulations, in particular, for gas dynamics applications. A simulation of vortex-shock interaction is used to demonstrate the accuracy and efficiency of the proposed lattices. With one single algorithm it is now possible to simulate a broad range of applications, from low Mach number flows to transonic and supersonic flow regimes.

  10. Childhood PTSD in Israel: A Cross Cultural Frame of Reference.

    ERIC Educational Resources Information Center

    Milgram, Noach Norman

    There is considerable awareness among Israeli mental health workers and citizens of the importance of differentiating between acute or chronic reactions to severely stressful life situations and manifestations of mental illness and anxiety, or developmental and adjustment disorders. Israeli mental health workers have become expert and are heavily…

  11. The Second International Celestial Reference Frame (ICRF2)

    NASA Technical Reports Server (NTRS)

    Ma, Chopo

    2010-01-01

    The ICRF2 catalog was constructed by the IERS/IVS Working Group with oversight by the IAU Working Group. Derived using data from August 1979 through March 2009, it is a great improvement over the original ICRF with 3414 extragalactic radio source positions, a noise floor of 40 microarcsec, and axis stability of 10 microarcsec. Significant refinements were made in the selection of defining sources, modeling, and the integration of CRF, TRF, and EOP. The adoption of the ICRF2 was approved by the IAU in Resolution B3 at the XXVII IAU General Assembly and became effective 1 January 2010.

  12. Cognitive framing in action.

    PubMed

    Huhn, John M; Potts, Cory Adam; Rosenbaum, David A

    2016-06-01

    Cognitive framing effects have been widely reported in higher-level decision-making and have been ascribed to rules of thumb for quick thinking. No such demonstrations have been reported for physical action, as far as we know, but they would be expected if cognition for physical action is fundamentally similar to cognition for higher-level decision-making. To test for such effects, we asked participants to reach for a horizontally-oriented pipe to move it from one height to another while turning the pipe 180° to bring one end (the "business end") to a target on the left or right. From a physical perspective, participants could have always rotated the pipe in the same angular direction no matter which end was the business end; a given participant could have always turned the pipe clockwise or counter-clockwise. Instead, our participants turned the business end counter-clockwise for left targets and clockwise for right targets. Thus, the way the identical physical task was framed altered the way it was performed. This finding is consistent with the hypothesis that cognition for physical action is fundamentally similar to cognition for higher-level decision-making. A tantalizing possibility is that higher-level decision heuristics have roots in the control of physical action, a hypothesis that accords with embodied views of cognition. PMID:26970853

  13. Toward a Direct Measurement of the Cosmic Acceleration

    NASA Astrophysics Data System (ADS)

    Darling, Jeremiah K.

    2013-01-01

    We present precise redshift measurements and place model-free constraints on cosmic acceleration and the acceleration of the Solar System in a universal context. HI 21 cm absorption lines observed over multiple epochs can constrain the secular redshift drift or the proper acceleration, Δv/Δto, with high precision. A comparison of literature analog spectra to contemporary digital spectra shows significant acceleration almost certainly attributable to systematic instrumental or calibration errors. However, robust constraints have been obtained by using digital data from a single telescope, the Green Bank Telescope. An ensemble of 10 objects spanning z = 0.09-0.69 observed over 13.5 years show Δz/Δto = (-1.8 ± 1.2) × 10-8 yr-1 or Δv/Δto = -4.0 ± 3.0 m s-1 yr-1. The best constraint from a single object, 3C286 at = 0.692153275(85), is dz/dto = (1.5 ± 4.7) × 10-8 yr-1 or Δv/Δto = 2.7 ± 8.4 m s-1 yr-1. These measurements are three orders of magnitude larger than the expected acceleration in the concordance dark energy cosmology at z=0.5, Δz/Δto = 2 × 10-11 yr-1 or Δv/Δto = 0.3 cm s-1 yr-1, but they demonstrate a lack of secular redshift drift in absorption line systems and the long-term frequency stability of modern radio telescopes. This measurement likewise constrains the barycentric proper acceleration in a cosmological reference frame (as opposed to the Galactic pulsar-defined reference frame), but currently lacks the precision of quasar proper motion observations. A comparison of rest-frame UV metal absorption lines to the HI 21 cm line places improved constraints on the cosmic variation of physical constants: Δ(α2 gp μ)/(α2 gp μ) = (-3.5 ± 1.4) × 10-6 in the redshift range z=0.24-2.04, consistent with no variation. We estimate that the cosmic acceleration could be directly measured with this technique in about 300 years using modern telescopes or in about 12 years using a Square Kilometer Array, provided that new systematic effects do

  14. Frame architecture for video servers

    NASA Astrophysics Data System (ADS)

    Venkatramani, Chitra; Kienzle, Martin G.

    1999-11-01

    Video is inherently frame-oriented and most applications such as commercial video processing require to manipulate video in terms of frames. However, typical video servers treat videos as byte streams and perform random access based on approximate byte offsets to be supplied by the client. They do not provide frame or timecode oriented API which is essential for many applications. This paper describes a frame-oriented architecture for video servers. It also describes the implementation in the context of IBM's VideoCharger server. The later part of the paper describes an application that uses the frame architecture and provides fast and slow-motion scanning capabilities to the server.

  15. Scarcity frames value.

    PubMed

    Shah, Anuj K; Shafir, Eldar; Mullainathan, Sendhil

    2015-04-01

    Economic models of decision making assume that people have a stable way of thinking about value. In contrast, psychology has shown that people's preferences are often malleable and influenced by normatively irrelevant contextual features. Whereas economics derives its predictions from the assumption that people navigate a world of scarce resources, recent psychological work has shown that people often do not attend to scarcity. In this article, we show that when scarcity does influence cognition, it renders people less susceptible to classic context effects. Under conditions of scarcity, people focus on pressing needs and recognize the trade-offs that must be made against those needs. Those trade-offs frame perception more consistently than irrelevant contextual cues, which exert less influence. The results suggest that scarcity can align certain behaviors more closely with traditional economic predictions. PMID:25676256

  16. Automatic frame-centered object representation and integration revealed by iconic memory, visual priming, and backward masking

    PubMed Central

    Lin, Zhicheng; He, Sheng

    2012-01-01

    Object identities (“what”) and their spatial locations (“where”) are processed in distinct pathways in the visual system, raising the question of how the what and where information is integrated. Because of object motions and eye movements, the retina-based representations are unstable, necessitating nonretinotopic representation and integration. A potential mechanism is to code and update objects according to their reference frames (i.e., frame-centered representation and integration). To isolate frame-centered processes, in a frame-to-frame apparent motion configuration, we (a) presented two preceding or trailing objects on the same frame, equidistant from the target on the other frame, to control for object-based (frame-based) effect and space-based effect, and (b) manipulated the target's relative location within its frame to probe frame-centered effect. We show that iconic memory, visual priming, and backward masking depend on objects' relative frame locations, orthogonal of the retinotopic coordinate. These findings not only reveal that iconic memory, visual priming, and backward masking can be nonretinotopic but also demonstrate that these processes are automatically constrained by contextual frames through a frame-centered mechanism. Thus, object representation is robustly and automatically coupled to its reference frame and continuously being updated through a frame-centered, location-specific mechanism. These findings lead to an object cabinet framework, in which objects (“files”) within the reference frame (“cabinet”) are orderly coded relative to the frame. PMID:23104817

  17. Semiclassical framed BPS states

    NASA Astrophysics Data System (ADS)

    Moore, Gregory W.; Royston, Andrew B.; Van den Bleeken, Dieter

    2016-07-01

    We provide a semiclassical description of framed BPS states in four-dimensional {N}=2 super Yang-Mills theories probed by 't Hooft defects, in terms of a supersymmetric quantum mechanics on the moduli space of singular monopoles. Framed BPS states, like their ordinary counterparts in the theory without defects, are associated with the L 2 kernel of certain Dirac operators on moduli space, or equivalently with the L 2 cohomology of related Dolbeault operators. The Dirac/Dolbeault operators depend on two Cartan-valued Higgs vevs. We conjecture a map between these vevs and the Seiberg-Witten special coordinates, consistent with a one-loop analysis and checked in examples. The map incorporates all perturbative and nonperturbative corrections that are relevant for the semiclassical construction of BPS states, over a suitably defined weak coupling regime of the Coulomb branch. We use this map to translate wall crossing formulae and the no-exotics theorem to statements about the Dirac/Dolbeault operators. The no-exotics theorem, concerning the absence of nontrivial SU(2) R representations in the BPS spectrum, implies that the kernel of the Dirac operator is chiral, and further translates into a statement that all L 2 cohomology of the Dolbeault operator is concentrated in the middle degree. Wall crossing formulae lead to detailed predictions for where the Dirac operators fail to be Fredholm and how their kernels jump. We explore these predictions in nontrivial examples. This paper explains the background and arguments behind the results announced in the short note [1].

  18. Frame-based cranial reconstruction.

    PubMed

    Hochfeld, Mascha; Lamecker, Hans; Thomale, Ulrich-W; Schulz, Matthias; Zachow, Stefan; Haberl, Hannes

    2014-03-01

    The authors report on the first experiences with the prototype of a surgical tool for cranial remodeling. The device enables the surgeon to transfer statistical information, represented in a model, into the disfigured bone. The model is derived from a currently evolving databank of normal head shapes. Ultimately, the databank will provide a set of standard models covering the statistical range of normal head shapes, thus providing the required template for any standard remodeling procedure as well as customized models for intended overcorrection. To date, this technique has been used in the surgical treatment of 14 infants (age range 6-12 months) with craniosynostosis. In all 14 cases, the designated esthetic result, embodied by the selected model, has been achieved, without morbidity or mortality. Frame-based reconstruction provides the required tools to precisely realize the surgical reproduction of the model shape. It enables the establishment of a self-referring system, feeding back postoperative growth patterns, recorded by 3D follow-up, into the model design. PMID:24437987

  19. Optimization of a space spectrograph main frame and frequency response analysis of the frame

    NASA Astrophysics Data System (ADS)

    Zhang, Xin-yu; Chen, Zhi-yuan; Yang, Shi-mo

    2009-07-01

    A space spectrograph main structure is optimized and examined in order to satisfy the space operational needs. The space spectrograph will be transported into its operational orbit by the launch vehicle and it will undergo dynamic environment in the spacecraft injection period. The unexpected shocks may cause declination of observation accuracy and even equipment damages. The main frame is one of the most important parts because its mechanical performance has great influence on the operational life of the spectrograph, accuracy of observation, etc. For the reason of cost reduction and stability confirming, lower weight and higher structure stiffness of the frame are simultaneously required. Structure optimization was conducted considering the initial design modal analysis results. The base modal frequency raised 10.34% while the whole weight lowered 8.63% compared to the initial design. The purpose of this study is to analyze the new design of main frame mechanical properties and verify whether it can satisfy strict optical demands under the dynamic impact during spacecraft injection. For realizing and forecasting the frequency response characteristics of the main structure in mechanical environment experiment, dynamic analysis of the structure should be performed simulating impulse loads from the bottom base. Therefore, frequency response analysis (FRA) of the frame was then performed using the FEA software MSC.PATRAN/NASTRAN. Results of shock response spectrum (SRS) responses from the base excitations were given. Stress and acceleration dynamic responses of essential positions in the spacecraft injection course were also calculated and spectrometer structure design was examined considering stiffness / strength demands. In this simulation, maximum stresses of Cesic material in two acceleration application cases are 45.1 and 74.1 MPa, respectively. They are all less than yield strengths. As is demonstrated from the simulation, strength reservation of the frame is

  20. Modeling of 10 GeV-1 TeV laser-plasma accelerators using Lorentz boosted simulations

    SciTech Connect

    Vay, J.-L.; Geddes, C. G. R.; Esarey, E.; Schroeder, C. B.; Leemans, W. P.; Cormier-Michel, E.; Grote, D. P.

    2011-12-15

    Modeling of laser-plasma wakefield accelerators in an optimal frame of reference [J.-L. Vay, Phys. Rev. Lett. 98, 130405 (2007)] allows direct and efficient full-scale modeling of deeply depleted and beam loaded laser-plasma stages of 10 GeV-1 TeV (parameters not computationally accessible otherwise). This verifies the scaling of plasma accelerators to very high energies and accurately models the laser evolution and the accelerated electron beam transverse dynamics and energy spread. Over 4, 5, and 6 orders of magnitude speedup is achieved for the modeling of 10 GeV, 100 GeV, and 1 TeV class stages, respectively. Agreement at the percentage level is demonstrated between simulations using different frames of reference for a 0.1 GeV class stage. Obtaining these speedups and levels of accuracy was permitted by solutions for handling data input (in particular, particle and laser beams injection) and output in a relativistically boosted frame of reference, as well as mitigation of a high-frequency instability that otherwise limits effectiveness.