GAOUA realizations of the Celestial Reference Frame
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.
Celestial Reference Frames at Multiple Radio Wavelengths
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).
Radio and optical realizations of celestial reference frames
Lambert, S B; Le Poncin-Lafitte, C; Barache, C; Souchay, J
2006-01-01
The International Celestial Reference Frame (ICRF, Ma et al. 1998) is currently the best realization of a quasi-inertial reference system. It is based on more than 10 years of cumulated geodetic and astrometric VLBI observations of compact extragalactic objects at centimetric wavelengths. In the perspective of the realization of an accurate optical counterpart of the ICRF using future space astrometry missions like GAIA or SIM, this paper investigates the consistency of celestial reference frames realized through the same subset of compact extragalactic radio sources at optical wavelengths. Celestial reference frames realized in radio wavelengths with the VLBA Calibrator Survey (VCS) data and in optical wavelengths with the Sloan Digital Sky Survey (SDSS) data (DR3 quasar catalogue and DR5) are compared in terms of radio-optical distances between the common sources, global rotation of the axes and offset of the equator.
Celestial reference frame RSC (GAOUA) 98 C 01.
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.
The GAOUA series of compiled celestial reference frames
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.
Stability study of realization of the celestial reference frame
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.
Interaction Between the Celestial and the Terrestrial Reference Frames
Gordon, David; MacMillan, Dan; Bolotin, Sergei; Le Bail, Karine; Gipson, John; Ma, Chopo
2010-01-01
Effects of International Celestial Reference Frame (ICRF2) on the Terrestrial Reference Frames (TRF), CRF and EOP's, The ICRF2 became official on Jan. 1, 2010. It includes positions of 3414 compact radio astronomical sources observed with VLBI, a fivefold increase from the first ICRF. Numerous new VLBI models were used and the most unstable sources were treated as arc parameters to avoid distortions of the frame. The ICRF2 has a noise floor of 40 micro-arc-seconds and an axis stability of 10 micro-arc-seconds. It was aligned with the ICRS using 138 stable sources common to ICRF2 and ICRF-Ext2. Maintenance of ICRF2 is to be made using 295 defining sources chosen for their historical positional stability, minimal source structure, and sky distribution. Their stability and their more uniform sky distribution eliminate the two largest weaknesses of ICRF I. The switchover to ICRF2 has some small effects on the TRF, CRF and Earth Orientation Parameters (EOP). A CRF based on ICRF2 shows a relative rotation of 40 micro-arc-seconds, mostly about the Y-axis. Small shifts are also seen in the EOP's, the largest being 11 micro-arc-seconds in X-pole. Some small but insignificant differences are also seen in the TRF. These results will be presented and discussed.
Malkin, Z; Arias, F; Boboltz, D; Boehm, J; Bolotin, S; Bourda, G; Charlot, P; De Witt, A; Fey, A; Gaume, R; Heinkelmann, R; Lambert, S; Ma, C; Nothnagel, A; Seitz, M; Gordon, D; Skurikhina, E; Souchay, J; Titov, O
2015-01-01
The goal of this presentation is to report the latest progress in creation of the next generation of VLBI-based International Celestial Reference Frame, ICRF3. Two main directions of ICRF3 development are improvement of the S/X-band frame and extension of the ICRF to higher frequencies. Another important task of this work is the preparation for comparison of ICRF3 with the new generation optical frame GCRF expected by the end of the decade as a result of the Gaia mission.
Titov, O.; Stanford, Laura M. [Geoscience Australia, P.O. Box 378, Canberra, ACT 2601 (Australia); Johnston, Helen M.; Hunstead, Richard W. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Pursimo, T. [Nordic Optical Telescope, Nordic Optical Telescope Apartado 474E-38700 Santa Cruz de La Palma, Santa Cruz de Tenerife (Spain); Jauncey, David L. [CSIRO Astronomy and Space Science, ATNF and Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Maslennikov, K. [Central Astronomical Observatory at Pulkovo, Pulkovskoye Shosse, 65/1, 196140, St. Petersburg (Russian Federation); Boldycheva, A., E-mail: oleg.titov@ga.gov.au [Ioffe Physical Technical Institute, 26 Polytekhnicheskaya, St. Petersburg, 194021 (Russian Federation)
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.
The adoption of the International Celestial Reference System (ICRS), based on Very Long Baseline Interferometry (VLBI) observations of extragalactic radiosources by the International Astronomical Union (IAU) since 1998 January 1, opened a new era for astronomy. The ICRS and the corresponding frame, the International Celestial Reference Frame (ICRF), replaced the Fundamental Catalog (FK5) based on positions and proper motions of bright stars, with the Hipparcos catalog being adopted as the primary realization of the ICRS in optical wavelengths. According to its definition, the ICRS is such that the barycentric directions of distant extragalactic objects show no global rotation with respect to these objects; this provides a quasi-inertial reference for measuring the positions and angular motions of the celestial objects. Other resolutions on reference systems were passed by the IAU in 2000 and 2006 and endorsed by the International Union of Geodesy and Geophysics (IUGG) in 2003 and 2007, respectively. These especially concern the definition and realization of the astronomical reference systems in the framework of general relativity and transformations between them. First, the IAU 2000 resolutions refined the concepts and definition of the astronomical reference systems and parameters for Earth's rotation, and adopted the IAU 2000 precession-nutation. Then, the IAU 2006 resolutions adopted a new precession model that is consistent with dynamical theories; they also addressed definition, terminology or orientation issues relative to reference systems and time scales that needed to be specified after the adoption of the IAU 2000 resolutions. An additional IUGG 2007 resolution defined the International Terrestrial Reference System (ITRS) so that it strictly complies with the IAU recommendations. Finally, the IAU 2009 resolutions adopted a new system of astronomical constants and an improved realization of the ICRF. These fundamental changes have led to significant
Nicole Capitaine
2012-01-01
The adoption of the International Celestial Reference System (ICRS),based on Very Long Baseline Interferometry (VLBI) observations of extragalactic radiosources by the International Astronomical Union (IAU) since 1998 January 1,opened a new era for astronomy.The ICRS and the corresponding frame,the International Celestial Reference Frame (ICRF),replaced the Fundamental Catalog (FK5) based on positions and proper motions of bright stars,with the Hipparcos catalog being adopted as the primary realization of the ICRS in optical wavelengths.According to its definition,the ICRS is such that the barycentric directions of distant extragalactic objects show no global rotation with respect to these objects; this provides a quasi-inertial reference for measuring the positions and angular motions of the celestial objects.Other resolutions on reference systems were passed by the IAU in 2000 and 2006 and endorsed by the International Union of Geodesy and Geophysics (IUGG) in 2003 and 2007,respectively.These especially concern the definition and realization of the astronomical reference systems in the framework of general relativity and transformations between them.First,the IAU 2000 resolutions refined the concepts and definition of the astronomical reference systems and parameters for Earth's rotation,and adopted the IAU 2000 precession-nutation.Then,the IAU 2006 resolutions adopted a new precession model that is consistent with dynamical theories; they also addressed definition,terminology or orientation issues relative to reference systems and time scales that needed to be specified after the adoption of the IAU 2000 resolutions.An additional IUGG 2007 resolution defined the International Terrestrial Reference System (ITRS) so that it strictly complies with the IAU recommendations.Finally,the IAU 2009 resolutions adopted a new system of astronomical constants and an improved realization of the ICRF.These fundamental changes have led to significant improvements in the fields
Densification of the International Celestial Reference Frame: Results of EVN Observations
Charlot, P; Jacobs, C S; Ma, C; Sovers, O J; Baudry, A
2004-01-01
The current realization of the International Celestial Reference Frame (ICRF) comprises a total of 717 extragalactic radio sources distributed over the entire sky. An observing program has been developed to densify the ICRF in the northern sky using the European VLBI network (EVN) and other radio telescopes in Spitsbergen, Canada and USA. Altogether, 150 new sources selected from the Jodrell Bank-VLA Astrometric Survey were observed during three such EVN+ experiments conducted in 2000, 2002 and 2003. The sources were selected on the basis of their sky location in order to fill the "empty" regions of the frame. A secondary criterion was based on source compactness to limit structural effects in the astrometric measurements. All 150 new sources have been successfully detected and the precision of the estimated coordinates in right ascension and declination is better than 1 milliarcsecond (mas) for most of them. A comparison with the astrometric positions from the Very Long baseline Array Calibrator Survey for 1...
Sokolova, Yulia
2014-01-01
In this study, we compared results of determination of the orientation angles between celestial reference frames realized by radio source position catalogues using three methods of accounting for correlation information: using the position errors only, using additionally the correlations be-tween the right ascension and declination (RA/DE correlations) reported in radio source position catalogues published in the IERS format, and using the full covariance matrix. The computations were performed with nine catalogues computed at eight analysis centres. Our analysis has shown that using the RA/DE correlations only slightly influences the computed rotational angles, whereas using the full correlation matrices leads to substantial change in the orientation parameters be-tween the compared catalogues.
International Celestial Reference Frame (ICRF): mantenimiento y extensión
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.
Malkin, Zinovy; Ma, Chopo; Lambert, Sebastien
2014-01-01
In this paper we outline several problems related to the realization of the international celestial and terrestrial reference frames ICRF and ITRF at the millimeter level of accuracy, with emphasis on ICRF issues. The main topics considered are: analysis of the current status of the ICRF, mutual impact of ICRF and ITRF, and some considerations for future ICRF realizations.
The effects of frequency-dependent quasar evolution on the celestial reference frame
Shabala, Stanislav; McCallum, Jamie; Titov, Oleg; Blanchard, Jay; Lovell, Jim; Watson, Christopher
2013-01-01
We examine the relationship between source position stability and astrophysical properties of radio-loud quasars making up the International Celestial Reference Frame. We construct light curves for 95 most frequently observed ICRF2 quasars at both the geodetic VLBI observing bands. Because the appearance of new quasar components corresponds to an increase in quasar flux density, these light curves allow us to probe source structure on sub-100 microarcsecond scales, much smaller than conventional VLBI imaging. Flux density monitoring also allows us to trace the evolution of quasar structure. We test how source position stability depends on three astrophysical parameters: (1) Flux density variability at X-band; (2) Time lag between S and X-band light curves; (3) Spectral index rms, defined as the variability in the ratio between S and X-band flux densities. We find that small (<0.15 years) time lags between S and X-band light curves and low (<0.10) spectral index variability are excellent indicators of po...
Sobre as Bases de Referência Celeste (On the Celestial Reference Frames)
Martin, Vera A. F.; Poppe, Paulo C. R.
2003-05-01
Ao longo deste artigo, apresentamos, como continuidade à discussão apresentada no trabalho anterior, uma primeira discussão sobre algumas das principais bases de referência utilizadas em Astronomia. Da mesma forma, esperamos que o presente texto possa ser utilizado ao longo dos cursos de Introdução à Astronomia das atuais graduações de Física e áreas afins.
On the implications of the Galactic aberration in proper motions for celestial reference frame
Malkin, Zinovy
2014-01-01
During the last years, much attention has been paid to the astrometric implications of the galactic aberration in proper motions (GA). This effect causes systematic errors in astrometric measurements at a microarcsecond level. Some authors consider it so serious that it requires redefinition of the celestial reference system (CRF). We argue that such attention to the GA is too much exaggerated. It is just a small astrometric correction that must be taken into account during highly accurate astrometric and geodetic data processing. The accuracy of this correction depends on accuracy of the Galactic rotation parameters and, for most application, on the accuracy of the rotation matrix between Galactic and equatorial systems. Our analysis has shown that our today knowledge of these two factors is sufficient to compute the GA correction with accuracy of better than 10%. The remaining effect at a level of few tenths microarcsecond/yr is negligible nowadays. Another consequence of introducing the GA correction is ne...
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.
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
Global Vertical Reference Frame
Burša, Milan; Kenyon, S.; Kouba, J.; Šíma, Zdislav; Vatrt, V.; Vojtíšková, M.
-, č. 5 (2009), s. 53-63. ISSN 1801-8483 R&D Projects: GA ČR GA205/08/0328 Institutional research plan: CEZ:AV0Z10030501 Keywords : sea surface topography * satellite altimetry * vertical frames Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
X/Ka Celestial Frame Improvements: Vision to Reality
Jacobs, C. S.; Bagri, D. S.; Britcliffe, M. J.; Clark, J. E.; Franco, M. M.; Garcia-Miro, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Moll, V. E.; Navarro, R.; Rogstad, S. P.; Proctor, R. C.; Sigman, E. H.; Skjerve, L. J.; Soriano, M. A.; Sovers, O. J.; Tucker, B. C.; Wang, D.; White, L. A.
2010-01-01
In order to extend the International Celestial Reference Frame from its S/X-band (2.3/8.4 GHz) basis to a complementary frame at X/Ka-band (8.4/32 GHz), we began in mid-2005 an ongoing series of X/Ka observations using NASA s Deep Space Network (DSN) radio telescopes. Over the course of 47 sessions, we have detected 351 extra-galactic radio sources covering the full 24 hours of right ascension and declinations down to -45 degrees. Angular source position accuracy is at the part-per-billion level. We developed an error budget which shows that the main errors arise from limited sensitivity, mismodeling of the troposphere, uncalibrated instrumental effects, and the lack of a southern baseline. Recent work has improved sensitivity by improving pointing calibrations and by increasing the data rate four-fold. Troposphere calibration has been demonstrated at the mm-level. Construction of instrumental phase calibrators and new digital baseband filtering electronics began in recent months. We will discuss the expected effect of these improvements on the X/Ka frame.
Changing quantum reference frames
Palmer, Matthew C; Girelli, Florian; Bartlett, Stephen D.
2013-01-01
We consider the process of changing reference frames in the case where the reference frames are quantum systems. We find that, as part of this process, decoherence is necessarily induced on any quantum system described relative to these frames. We explore this process with examples involving reference frames for phase and orientation. Quantifying the effect of changing quantum reference frames serves as a first step in developing a relativity principle for theories in which all objects includ...
Astrophysics of Reference Frame Tie Objects
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.
Van Enk, S J
2004-01-01
We define a new quantity called refbit, which allows one to quantify the resource of sharing a reference frame in quantum communication protocols. By considering various protocols we find relations between refbits and other resources such as cbits, ebits, cobits, and qubits. We also consider the same resources in encoded, reference-frame independent, form. This allows one to rephrase and unify previous work on phase references, reference frames, and superselection rules.
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.
Use of Reference Frames for Interplanetary Navigation at JPL
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.
Earth Orientation Catalogue - an improved reference frame
Vondrák, Jan; Ron, Cyril
Washington : US Naval observatory, 2006 - (Gaume, R.; McCarthy, D.; Souchay, J.), s. 112-119 [General Assembly of the IAU /25./, Joint Discussion /16./. Sydney (AU), 22.07.2003-22.07.2003] R&D Projects: GA AV ČR IAA3003205 Institutional research plan: CEZ:AV0Z1003909 Keywords : reference frame * Earth orientation * astrometry Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Reference frame for Product Configuration
Ladeby, Klaes Rohde; Oddsson, Gudmundur Valur
2011-01-01
This paper presents a reference frame for configuration. The reference frame is established by review of existing literature, and consequently it is a theoretical frame of reference. The review of literature shows a deterioration of the understanding of configuration. Most recent literature reports...
On transformation between international celestial and terrestrial reference systems
Bretagnon, P.; Brumberg, V. A.
2003-09-01
Based on the current IAU hierarchy of the relativistic reference systems, practical formulae for the transformation between barycentric (BCRS) and geocentric (GCRS) celestial reference systems are derived. BCRS is used to refer to ICRS, International Celestial Reference System. This transformation is given in four versions, dependent on the time arguments used for BCRS (TCB or TDB) and for GCRS (TCG or TT). All quantities involved in these formulae have been tabulated with the use of the VSOP theories (IMCCE theories of motion of the major planets). In particular, these formulae may be applied to account for the indirect relativistic third-body perturbations in motion of Earth's satellites and Earth's rotation problem. We propose to use the SMART theory (IMCCE theory of Earth's rotation) in constructing the Newtonian three-dimensional spatial rotation transformation between GCRS and ITRS, the International Terrestrial Reference System. This transformation is compared with two other versions involving extra angular variables currently used by IERS, the International Earth Rotation Service. It is shown that the comparison of these three forms of the same transformation may be greatly simplified by using the proposed composite rotation formula. Tables 1-20 of Appendix B containing the initial terms of the VSOP-based series for the BCRSGCRS transformation are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/408/387. The work on ICRSGCRS transformation with the use of VSOP theories was done in February-March 2002 during the stay of the second author in IMCCE. The authors hoped to complete the second part concerning GCRSITRS transformation with the use of SMART theory in September 2002 during the visit of the first author to IAA. The grave disease of Pierre Bretagnon which tragically resulted in his death on November 17, 2002, did not permit us to complete this work
Using radio stars to link ICRF and GCRF reference frames
Malkin, Zinovy
2016-01-01
One of the possible strategies for linking the optical Gaia Celestial Reference Frame (GCRF) to the VLBI-based International Celestial Reference Frame (ICRF) is using radio stars in a manner similar to that used for linking HIPPARCOS Celestial Reference System (HCRF) to ICRF. A reachable precision of the orientation angles between GCRF and ICRF frames was estimated through Monte Carlo simulation. Supposing the radio stars position uncertainty obtained by VLBI in the range of 0.1 to 4 mas, and Gaia position uncertainty in the range of 0.055 to 0.4 mas, depending in the first place on the brightness of radio star in radio and optics and number of VLBI observations, the orientation angles uncertainty will be 0.02 to 0.66 mas for 46 radio stars used, and 0.01 to 0.39 mas for 138 radio stars used. Properly organized VLBI observing program on radio stars observations can allow to tie GCRF to ICRF with the accuracy better than 0.1 mas.
Inertial reference frames and gravitational forces
The connection between different definitions of inertial, i.e. fundamental, reference frames and the corresponding characterisation of gravitational fields by gravitational forces are considered from the point of view of their possible interpretation in university introductory courses. The introduction of a special class of reference frames, denoted 'mixed reference frames' is proposed and discussed. (author)
Physics of Non-Inertial Reference Frames
Kamalov, Timur F.
2007-01-01
Physics of non-inertial reference frames is a generalizing of Newton's laws to any reference frames. The first, Law of Kinematic in non-inertial reference frames reads: the kinematic state of a body free of forces conserves and determinates a constant n-th order derivative with respect to time being equal in absolute value to an invariant of the observer's reference frame. The second, Law of Dynamic extended Newton's second law to non-inertial reference frames and also contains additional var...
Degradation of a quantum reference frame
Bartlett, S D; Spekkens, R W; Turner, P S; Bartlett, Stephen D.; Rudolph, Terry; Spekkens, Robert W.; Turner, Peter S.
2006-01-01
We investigate the degradation of reference frames, treated as dynamical quantum systems, and quantify their longevity as a resource for performing tasks in quantum information processing. We adopt an operational measure of a reference frame's longevity, namely, the number of measurements that can be made against it with a certain error tolerance. We investigate two distinct types of reference frame: a reference direction, realized by a spin-j system, and a phase reference, realized by an oscillator mode with bounded energy. For both cases, we show that our measure of longevity increases quadratically with the size of the reference system and is therefore non-additive. Our results quantify the extent to which microscopic or mesoscopic reference frames may be used for repeated, high-precision measurements, without needing to be reset -- a question that is important for some implementations of quantum computing. We illustrate our results using the proposed single-spin measurement scheme of magnetic resonance fo...
Spatial reference frame agreement in quantum networks
In order to communicate information in a quantum network effectively, all network nodes should share a common reference frame. Here, we propose to study how well m nodes in a quantum network can establish a common spatial reference frame from scratch, even though t of them may be arbitrarily faulty. We present a protocol that allows all correctly functioning nodes to agree on a common reference frame as long as they are fully connected and not more than t
Physics within a quantum reference frame
We investigate the physics of quantum reference frames. Specifically, we study several simple scenarios involving a small number of quantum particles, whereby we promote one of these particles to the role of a quantum observer and ask what is the description of the rest of the system, as seen by this observer? We highlight the interesting aspects of such questions by presenting a number of apparent paradoxes. By unravelling these paradoxes, we obtain a better understanding of the physics of quantum reference frames.
Quantum communication, reference frames and gauge theory
van Enk, S. J.
2006-01-01
We consider quantum communication in the case that the communicating parties not only do not share a reference frame but use imperfect quantum communication channels, in that each channel applies some fixed but unknown unitary rotation to each qubit. We discuss similarities and differences between reference frames within that quantum communication model and gauge fields in gauge theory. We generalize the concept of refbits and analyze various quantum communication protocols within the communi...
Quantum communication, reference frames, and gauge theory
We consider quantum communication in the case that the communicating parties not only do not share a reference frame but use imperfect quantum communication channels, in that each channel applies some fixed but unknown unitary rotation to each qubit. We discuss similarities and differences between reference frames within that quantum communication model and gauge fields in gauge theory. We generalize the concept of refbits and analyze various quantum communication protocols within the communication model
Relativistic Reference Frames for Astrometry and Navigation in the Solar System
Kopeikin, S
2007-01-01
Astrophysical space missions deliver invaluable information about our universe, stellar dynamics of our galaxy, and motion of celestial bodies in the solar system. Astrometric space missions SIM and Gaia will determine distances to stars and cosmological objects as well as their physical characteristics and positions on the celestial sphere with microarcsecond precision. These and other space missions dedicated to exploration of the solar system are invaluable for experimental testing of general relativity. Permanently growing accuracy of space and ground-based astronomical observations require corresponding development of relativistic theory of reference frames, motion of celestial bodies, and propagation of light/radio signals from a source of light/radio to observer. Such theory must be based on Einstein's general relativity and account for various relativistic effects both in the solar system and outside of its boundary. We describe a hierarchy of the relativistic frames adopted by the International Astro...
Physics of Non-Inertial Reference Frames
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.
On Translators' Cultural Frame of Functionist Reference
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…
Frames of Reference in the Classroom
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
Improved optical reference frames for determining Earth orientation parameters in 20th century
Vondrák, Jan; Štefka, Vojtěch; Ron, Cyril
Kiev : Akademperiodika, 2010 - (Yatskiv, Y.), s. 64-71 ISBN 978-966-360-145-8. [The Study of the Earth as a Planet by Methods of Geophysics, Godesy and Astronomy. Kiev (UA), 22.06.2009-24.06.2009] R&D Projects: GA MŠk(CZ) LC506 Institutional research plan: CEZ:AV0Z10030501 Keywords : reference frames * astrometry * Earth rotation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Classical electromagnetic radiation in noninertial reference frames
Customarily electromagnetic radiation is defined with reference to some inertial laboratory frame. But such a definiton is too narrow to be applicable to questions concerning accelerated observers, e.g. why an accelerated observer does not receive radiation from a co-accelerating charge. It is shown in this paper that a radiation concept introduced for inertial observers by Rohrlich and Teitelboim allows an extension to noninertial (accelerating and rotating) reference frames in a natural way. The generalized concept is explicitly dependent on the proper acceleration and the rotation of the observer's laboratory frame. The case of radiation due to an accelerated point charge is treated in full detail. Roughly speaking, radiation from a point charge is observed, when the relative acceleration (in a well-defined sense) between charge and observer is nonvanishing. The analysis of this paper requires a detailed study of the general properties of noninertial laboratory frames. The necessary mathematical framework has been developed in an earlier paper, using ideas introduced by DeFacio, Dennis and Retzloff
Relativistic physics in arbitrary reference frames
Mitskievich, N V
1996-01-01
In this paper we give a review of the most general approach to description of reference frames, the monad formalism. This approach is explicitly general covariant at each step, permitting to use abstract representation of tensor quantities; it is applicable also to special relativity when non-inertial effects are considered in its context; moreover, it involves no hypotheses whatsoever thus being a completely natural one. For the sake of the reader's convenience, a synopsis of tensor calculus in pseudo-Riemannian space-time precedes discussion of the subject, containing expressions rarely encountered in literature but essentially facilitating the consideration. We give also a comparison of the monad formalism with the other approaches to description of reference frames in general relativity. In three chapters we consider applications of the monad formalism to general relativistic mechanics, electromagnetic and gravitational fields theory. Alongside of the general theory, which includes the monad representatio...
An Autonomous Reference Frame for Relativistic GNSS
Kostić, Uroš; Carloni, Sante; Delva, Pacôme; Gomboc, Andreja
2014-01-01
Current GNSS systems rely on global reference frames which are fixed to the Earth (via the ground stations) so their precision and stability in time are limited by our knowledge of the Earth dynamics. These drawbacks could be avoided by giving to the constellation of satellites the possibility of constituting by itself a primary and autonomous positioning system, without any a priori realization of a terrestrial reference frame. Our work shows that it is possible to construct such a system, an Autonomous Basis of Coordinates, via emission coordinates. Here we present the idea of the Autonomous Basis of Coordinates and its implementation in the perturbed space-time of Earth, where the motion of satellites, light propagation, and gravitational perturbations are treated in the formalism of general relativity.
Relativistic Physics in Arbitrary Reference Frames
Mitskievich, Nikolai V.
1996-01-01
In this paper we give a review of the most general approach to description of reference frames, the monad formalism. This approach is explicitly general covariant at each step, permitting to use abstract representation of tensor quantities; it is applicable also to special relativity when non-inertial effects are considered in its context; moreover, it involves no hypotheses whatsoever thus being a completely natural one. For the sake of the reader's convenience, a synopsis of tensor calculus...
Frames of reference in spatial language acquisition.
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
Physics within a quantum reference frame
Angelo, Renato M.; Brunner, Nicolas; Popescu, Sandu; Short, Anthony J.; Skrzypczyk, Paul
2010-01-01
We investigate the physics of quantum reference frames. Specifically, we study several simple scenarios involving a small number of quantum particles, whereby we promote one of these particles to the role of a quantum observer and ask what is the description of the rest of the system, as seen by this observer? We highlight the interesting aspects of such questions by presenting a number of apparent paradoxes. By unravelling these paradoxes we get a better understanding of the physics of quant...
Sébastien Viel
Full Text Available BACKGROUND: In order to test how gravitational information would affect the choice of stable reference frame used to control posture and voluntary movement, we have analysed the forearm stabilisation during sit to stand movement under microgravity condition obtained during parabolic flights. In this study, we hypothesised that in response to the transient loss of graviceptive information, the postural adaptation might involve the use of several strategies of segmental stabilisation, depending on the subject's perceptual typology (dependence--independence with respect to the visual field. More precisely, we expected a continuum of postural strategies across subjects with 1 at one extreme the maintaining of an egocentric reference frame and 2 at the other the re-activation of childhood strategies consisting in adopting an egocentric reference frame. METHODOLOGY/PRINCIPAL FINDINGS: To check this point, a forearm stabilisation task combined with a sit to stand movement was performed with eyes closed by 11 subjects during parabolic flight campaigns. Kinematic data were collected during 1-g and 0-g periods. The postural adaptation to microgravity's constraint may be described as a continuum of strategies ranging from the use of an exo- to an egocentric reference frame for segmental stabilisation. At one extremity, the subjects used systematically an exocentric frame to control each of their body segments independently, as under normogravity conditions. At the other, the segmental stabilisation strategies consist in systematically adopting an egocentric reference frame to control their forearm's stabilisation. A strong correlation between the mode of segmental stabilisation used and the perceptual typology (dependence--independence with respect to the visual field of the subjects was reported. CONCLUSION: The results of this study show different subjects' typologies from those that use the forearm orientation in a mainly exocentric reference frame to
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…
The Gaia reference frame amid quasar variability and proper motion patterns in the data
Bachchan, R K; Lindegren, L
2015-01-01
Gaia's very accurate astrometric measurements will allow the International Celestial Reference Frame (ICRF) to be improved by a few orders of magnitude in the optical. 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 which could obtain accurate positions and proper motions although they are not point-like. 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. We model quasars and galaxies using realistic sky distributions, magnitudes and redshifts. Position variability is introduced using a Markov chain model. The reference fr...
Gaia Reference frame determination: the AVU/GSR pipeline
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
Terrestrial Reference Frame from GPS and SLR
Weiss, Jan; Bertiger, Willy; Desai, Shailen; Haines, Bruce; Sibois, Aurore
2015-04-01
We present strategies for realizing the terrestrial reference frame (TRF) using tracking data from terrestrial GPS receivers alone and in tandem with the GRACE and LAGEOS satellites. We generate solutions without apriori ties to the International Terrestrial Reference Frame (ITRF). Our approach relies on processing multi-day orbit arcs to take advantage of the satellite dynamics, GPS receiver and transmitter calibrations derived from low-Earth orbiter (LEO) data, and estimation strategies tuned for realizing a stable and accurate TRF. We furthermore take advantage of the geometric diversity provided by GPS tracking from GRACE, and explore the impacts of including ground-based satellite laser range (SLR) measurements to LAGEOS-1 and -2 with local ties relating the two geodetic techniques. We process data from 2003-2014 and compute Helmert transformations relative to ITRF/IGb08. With GPS alone we achieve a 3D origin offset and rate of global solutions. Scale bias and rate are 3.1 ppb and 0.01 ppb/yr in either solution. Including SLR tracking from 11 ground stations to the LAGEOS satellites from 2012-2014 yields a reduction in scale bias of 0.5-1.0 ppb depending on the weight assigned to the SLR measurements. However, scatter is increased due to the relatively sparse SLR tracking network. We conclude with approaches for improving the TRF realized from GPS and SLR combined at the measurement level.
Astronomical reference frame, Hipparcos and Earth orientation
Vondrák, Jan
Belgrad : Faculty of mathematic , 2000 - (Bokan, N.), s. 13-28 [Symposium on contemporary mathematic s. Belgrad (YU), 18.12.1998-20.12.1998] R&D Projects: GA ČR GA205/98/1104 Institutional research plan: CEZ:AV0Z1003909 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Contribution of X/Ka VLBI to Multi-Wavelength Celestial Frame Studies
Jacobs, C. S.; Clark, J. E.; Garcia-Miro, C.; Horiuchi, S.; Sotuela, I.
2011-01-01
This paper is an update of Sotuela et al. (2011) which improves their simulated Gaia frame tie precision by approximately 10% by adding three additional VLBI observing sessions. Astrometry at X/Ka-band (8.4/32 GHz) using NASAs Deep Space Network has detected 466 quasars with accuracies of 200-300 micro-arc seconds. A program is underway to reduce errors by a factor of 2-3. From our sample, 245 sources have optical magnitudes V less than 20 and should also be detectable by Gaia. A covariance study using existing X/Ka data and simulated Gaia uncertainties for the 345 objects yields a frame tie precision of 10-15 micro-arc seconds (1 - sigma). The characterization of wavelength dependent systematic from extended source morphology and core shift should benefit greatly from adding X/Ka-band measurements to S/X-band (2.3/8.4 GHz) measurements thus helping to constrain astrophysical models of the wavelength dependence of positions.
Theory of Relativistic Reference Frames for High-Precision Astrometric Space Missions
Kopeikin, S M
2000-01-01
Recent modern space missions deliver invaluable information about origin of our universe, physical processes in the vicinity of black holes and other exotic astrophysical objects, stellar dynamics of our galaxy, etc. On the other hand, space astrometric missions make it possible to determine with unparalleled precision distances to stars and cosmological objects as well as their physical characteristics and positions on the celestial sphere. Permanently growing accuracy of space astronomical observations and the urgent need for adequate data processing algorithms require corresponding development of an adequate theory of reference frames along with unambiguous description of propagation of light rays from a source of light to observer. Such a theory must be based on the Einstein's general relativity and account for numerous relativistic effects both in the solar system and outside of its boundary. The main features of the relativistic theory of reference frames are presented in this work. A hierarchy of the f...
Communication between inertial observers with partially correlated reference frames
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.
Flexible reference frames for grasp planning in human parietofrontal cortex
Léoné, F.T.M.; Monaco, S.; Henriques, D.Y.P.; Toni, I.; Medendorp, W.P.
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 demand
Gaia reference frame amid quasar variability and proper motion patterns in the data
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
The proper characteristics of frame reference as a 4-invariants
Voytik, V V
2015-01-01
The paper derived 4-dimensional equation for the proper characteristics of the rigid frame of reference. From these conditions it follows the laws of motion of its proper tetrad and inverse kinematics equation, i. e., differential equations, which solves the problem of recovering the parameters of the motion of rigid frame of reference for their proper acceleration and angular velocity. In particular it is shown that the commission boost the moving frame of reference having Thomas precession for a new laboratory system will have a combination of two rotations: a new self-Thomas precession and rotation Wigner, which combine to give an initial frequency of the Thomas precession.
Egocentric and allocentric reference frames for catching a falling object.
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
Future National Reference Frames for the United States
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
Newton-Cartan Gravity in Noninertial Reference Frames
Rodriguez, Leo; Wickramasekara, Sujeev
2014-01-01
We study properties of Newton-Cartan gravity under transformations into all noninertial, nonrelativistic reference frames. The set of these transformations has the structure of an infinite dimensional Lie group, called the Galilean line group, which contains as a subgroup the Galilei group. We show that the fictitious forces of noninertial reference frames are naturally encoded in the Cartan connection transformed under the Galilean line group. These noninertial forces, which are coordinate effects, do not contribute to the Ricci tensor which describes the curvature of Newtonian spacetime. We show that only the $00$-component of the Ricci tensor is non-zero and equal to ($4\\pi$ times) the matter density in any inertial or noninetial reference frame and that it leads to what may be called Newtonian ADM mass. While the Ricci field equation and Gauss law are both fulfilled by the same physical matter density in inertial and linearly accelerating reference frames, there appears a discrepancy between the two in ro...
Newton-Cartan Gravity in Noninertial Reference Frames
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.
Reference frames in learning from maps and navigation.
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
Reference frame realized by RSC(GAOUA)97 C 01
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.
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. We employ a scalar-tensor theory of gravity depending on two post-Newtonian parameters, and utilize 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 at infinity. The primary reference frame covers the entire space-time, has its origin at the solar-system barycenter and spatial axes stretching up to infinity. The solar-system barycenter frame is not rotating with respect to a set of distant quasars that are forming the International Celestial Reference Frame. The secondary reference frame has its origin at the Earth-Moon barycenter. The Earth-Moon barycenter 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 Earth-Moon barycenter frame, does not contain the Coriolis and centripetal forces. Two other local frames-geocentric and seleno centric-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 International Celestial Reference Frame 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 International Celestial Reference Frame 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
Reference frames in virtual spatial navigation are viewpoint dependent
Ágoston eTörök
2014-09-01
Full Text Available 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 (i ground perspective was associated with egocentric frame of reference, (ii aerial perspective was associated with allocentric frame of reference, (iii there was no appreciable performance difference between first and third person egocentric viewing positions and (iv 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.
Jerk and Hyperjerk in a Rotating Frame of Reference
Sparavigna, Amelia Carolina
2015-01-01
Jerk is the derivative of acceleration with respect to time and then it is the third order derivative of the position vector. Hyperjerks are the n-th order derivatives with n>3. This paper describes the relations, for jerks and hyperjerks, between the quantities measured in an inertial frame of reference and those observed in a rotating frame. These relations can be interesting for teaching purposes.
Perception of space by multiple intrinsic frames of reference.
Yanlong Sun
Full Text Available It has been documented that when memorizing a physical space, the person's mental representation of that space is biased with distortion and segmentation. Two experiments reported here suggest that distortion and segmentation arise due to a hierarchical organization of the spatial representation. The spatial relations associated with salient landmarks are more strongly encoded and easier to recall than those associated with non-salient landmarks. In the presence of multiple salient landmarks, multiple intrinsic frames of reference are formed and spatial relations are anchored to each individual frame of reference. Multiple such representations may co-exist and interactively determine a person's spatial performance.
The equations of relative motion in the orbital reference frame
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
Developing a Frame of Reference for understanding configuration systems
Ladeby, Klaes Rohde; Edwards, Kasper
This paper uses the theory of technical systems to develop a frame of reference of product configuration systems. Following a definition of the configuration task, product model and product configuration system the theory of technical systems are presented. Configuration systems are then related ...
The Bernoulli Equation in a Moving Reference Frame
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…
Frames of Reference in African Proverbs on Disability.
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)
Reference Frames during the Acquisition and Development of Spatial Memories
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…
Quantum image coding with a reference-frame-independent scheme
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.
Quantum image coding with a reference-frame-independent scheme
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.
Determination and Maintenance of the Galileo Terrestrial Reference Frame
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.
An absolute reference frame for clumped isotope thermometry
Eiler, John M.; Dennis, Kate; Affek, Hagit P.; Passey, Ben; Schrag, Dan
2011-01-01
Analysis of multiply substituted isotopologues of molecules (‘clumped isotope geochemistry’) presents special challenges to both precision and accuracy. Previous discussions have focused on mass spectrometric precision for these rare species and intralaboratory reference frames. This discipline has spread, demanding interlaboratory standardization. We present a four-laboratory study of the calibration of mass-47 anomalies (Δ_(47) values) in CO_2 (especially extracted f...
Reference frames in virtual spatial navigation are viewpoint dependent
Ágoston eTörök; Peter eNguyen; Orsolya eKolozsvári; Robert Joseph Buchanan; Zoltan eNadasdy
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 combin...
Quantum communication using a bounded-size quantum reference frame
Typical quantum communication schemes are such that to achieve perfect decoding the receiver must share a reference frame (RF) with the sender. Indeed, if the receiver only possesses a bounded-size quantum token of the sender's RF, then the decoding is imperfect, and we can describe this effect as a noisy quantum channel. We seek here to characterize the performance of such schemes, or equivalently, to determine the effective decoherence induced by having a bounded-size RF. We assume that the token is prepared in a special state that has particularly nice group-theoretic properties and that is near-optimal for transmitting information about the sender's frame. We present a decoding operation, which can be proven to be near-optimal in this case, and we demonstrate that there are two distinct ways of implementing it (corresponding to two distinct Kraus decompositions). In one, the receiver measures the orientation of the RF token and reorients the system appropriately. In the other, the receiver extracts the encoded information from the virtual subsystems that describe the relational degrees of freedom of the system and token. Finally, we provide explicit characterizations of these decoding schemes when the system is a single qubit and for three standard kinds of RF: a phase reference, a Cartesian frame (representing an orthogonal triad of spatial directions), and a reference direction (representing a single spatial direction).
The Cosmological Constant Problem and Quantum Spacetime Reference Frame
Luo, M J
2015-01-01
This paper is a generalization of earlier papers [ Nucl. Phys. B 884, 344 (2014) (arXiv:1312.2759) and JHEP 6, 63 (2015) (arXiv:1401.2488) ]. Since space and time should be put on an equal footing, we generalize the idea of quantum clock time to a quantum spacetime reference frame via a physical realization of a reference system by quantum rulers and clocks. Omitting the internal degrees of freedoms (e.g. spin) of the physical rulers and clocks, only considering their metric properties, the spacetime reference frame is described by a bosonic non-linear sigma model. We study the quantum behavior of the system under given approximations, and obtain (1) a cosmological constant $(2/\\pi)\\rho_{c}$ ($\\rho_{c}$ the critical density) very close to current observational value; (2) an Einstein-Hilbert term in the quantum effective action; (3) the ratio of variance to mean-squared of spacetime distance tends to a universal constant $(2/\\pi)\\hbar^{2}$ in the infrared region. This effect is testable by observing the linear...
On the Assessment of Global Terrestrial Reference Frame Temporal Variations
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.
Relativistic Electrodynamics without Reference Frames. Clifford Algebra Formulation
Ivezic, Tomislav
2002-01-01
In the usual Clifford algebra formulation of electrodynamics the Faraday bivector field $F$ is expressed in terms of \\QTR{em}{the observer dependent} relative vectors $\\QTR{bf}{E}$ and $\\QTR{bf}{B.}$ In this paper we present \\QTR{em}{the observer independent}decomposition of $F$ by using the vectors (grade-1) of electric $E$ and magnetic $B$ fields and we develop the formulation of relativistic electrodynamics which is independent of the reference frame and of the chosen coordinatization. We ...
International Terrestrial Reference Frame for Global Change Monitoring
Wu, Xiaoping; Altamimi, Zuheir; Chin, T. Mike; Gross, Richard
2010-05-01
Most geodetic and many geophysical quantities measured and used depend on the definition, realization and stability of the International Terrestrial Reference Frame (ITRF). These include geocentric site coordinates and motions, satellite orbits, geocenter motion, Earth orientation and its variations, mean sea level rise, and polar ice mass changes. In some cases, the dependences may be implicit and not obvious. As we are approaching the stage of millimeter-precision geodesy and near real time global change monitoring with a multitude of space and time scales, it is critical to have a modern and stable infrastructure for the maintenance and improvement of the ITRF. It is also essential to improve the concepts, understanding, methodology, and products of ITRF to be consistent with the higher precision and ever-changing nature of the Earth. With these in mind and from the viewpoint of users interested in studying surface mass load, we will review and discuss certain limitations and difficulties of the current ITRF status and approach, including the sparseness of data, linear motion model, and multi-yearly updates. New perspectives on reference frame research and progress on our new experimental approach to a weekly ITRF realization will also be reported.
Reference-frame-independent quantum key distribution with source flaws
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.
An improve optical reference frame for long-term Earth rotation studies
Vondrák, Jan; Ron, Cyril
Bucharest: Astronomical Institute of the Romanian Academy, 2003, s. 49-55. [Journées 2002 - Systemes de reference spatio-temporels. Bucharest (RO), 25.09.2002-28.09.2002] R&D Projects: GA AV ČR IAA3003205 Institutional research plan: CEZ:AV0Z1003909 Keywords : Earth orientation * star catalogue Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
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…
Quantum cosmology with effects of a preferred reference frame
Recently, we presented a gravity model by generalizing the Brans-Dicke theory which is suitable for studying the metric signature transition dynamics without using an imaginary time parameter. Adding a suitable scalar potential described in terms of the Brans-Dicke scalar field 'Φ-tilde, this alternative theory is used to study the Wheeler-DeWitt approach of quantum cosmology. We assumed that the universe is defined in a flat Robertson-Walker metric with Lorentzian signature. In that case, the Wheeler-DeWitt wavefunctional is obtained as two-dimensional quantum harmonic oscillator convergent polynomials for both of the choices of positive and negative values of the Brans-Dicke parameter. Here we choose a preferred reference frame with a time coordinate of 'γ' which relates to time of cosmological free falling observer 't' as 'dt= Φ-tilde(γ)dγ'.
Tetrad formalism and frames of reference in general relativity
The review is devoted to problems of defining the frames of reference in the tetrad formalism of General Relativity. The tetrads are the decomposition coefficients of components of orthogonal basis over the differentials of a coordinate space. The Hamiltonian cosmological perturbation theory is presented in the terms of these invariant differential forms, and this theory doesn't contain the double counting of variable of spatial metric determinant in contrast to the standard Lifshits cosmological perturbation theory. The Lorentz transformations of components of orthogonal basis are given. Possible observational consequences of the Hamiltonian cosmological perturbation theory are discussed including quantum anomaly of geometrical interval and a shift of the coordinate origin in the process of the Universe evolution as a source of anisotropy of CMBR
Topos Theoretical Reference Frames on the Category of Quantum Observables
Zafiris, E
2002-01-01
An observable effects a schematization of the Quantum event structure by correlating Boolean algebras picked by measurements with the Borel algebra of the real line. In a well-defined sense Boolean observables play the role of coordinatizing objects in the Quantum world, by picking Boolean figures and subsequently opening Boolean windows for the perception of the latter, interpreted as local measurement charts. A mathematical scheme for the implementation of this thesis is being proposed based on Category theoretical methods. The scheme leads to a manifold representation of Quantum structure in terms of topos-theoretical Boolean reference frames. The coordinatizing objects give rise to structure preserving maps with the modeling objects as their domains, effecting finally an isomorphism between quantum event algebra objects and Boolean localization systems for the masurement of observables.
Crosta, Mariateresa
2009-01-01
The high accuracy of modern space astrometry requires the use of General Relativity to model the propagation of stellar light through the gravitational field encountered from a source to a given observer inside the Solar System. In this sense relativistic astrometry is part of fundamental physics. The general relativistic definition of astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU Resolutions (2000), which fix the celestial coordinate system. A consistent definition of the astrometric observables in the context of General Relativity is also essential to find uniquely the stellar coordinates and proper motion, this being the main physical task of the inverse ray tracing problem. Aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to garantee a physically correct definition of light direction to a star, an essential item for deducing ...
Lachièze-Rey, Marc; Luminet, Jean-Pierre
2001-07-01
Throughout history, the mysterious dark skies have inspired our imaginations in countless ways, influencing our endeavors in science and philosophy, religion, literature, and art. Filled with 380 full-color illustrations, Celestial Treasury shows the influence of astronomical theories and the richness of illustrations in Western civilization through the ages. The authors explore the evolution of our understanding of astronomy and weave together ancient and modern theories in a fascinating narrative. They incorporate a wealth of detail from Greek verse, medieval manuscripts and Victorian poetry with contemporary spacecraft photographs and computer-generated star charts. Celestial Treasury is more than a beautiful book: it answers a variety of questions that have intrigued scientists and laymen for centuries. -- How did philosophers and scientists try to explain the order that governs celestial motion? -- How did geometers and artists measure and map the skies? -- How many different answers have been proposed for the most fundamental of all questions: When and how did Earth come about? -- Who inhabits the heavens--gods, angels or extraterrestrials? No other book recounts humankind's fascination with the heavens as compellingly as Celestial Treasury. Marc Lachièze-Rey is a director of research at the Centre National pour la Récherche Scientifique and astrophysicist at the Centre d'Etudes de Saclay. He is the author of The Cosmic Background Radiation (Cambridge, 1999), and and The Quest for Unity, (Oxford, 1999 ), as well as many books in French. Jean-Pierre Luminet is a research director of the Centre National pour la Rechérche Scientifique, based at the Paris-Meudon observatory. He is the author of Black Holes, (Cambridge 1992), as well as science documentaries for television.
UTC(SU) and EOP(SU) - the only legal reference frames of Russian Federation
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
Electrodynamics in Arbitrary Reference Frames and in Arbitrary Material Media
Full text: The investigation of electromagnetic phenomena in material media still belongs to the most difficult tasks of electrodynamics. Complexity and variability of material media practically exclude effective applications of methods and computational techniques elaborated in the framework of standard microscopic electrodynamics with classical vacuum as a ground state. In order to obtain satisfactorily exact descriptions of electromagnetic properties of complex material media one is enforced to use methods and approximations which are difficult to control. Moreover, they usually break covariance properties and the results obtained are valid in one reference frame which choice remains subjective and model dependent. Some time ago we have proposed a reformulation of Maxwell electrodynamics which opens new ways in study of electromagnetic processes in material media. The formalism gets rid of assumptions characteristic for vacuum electrodynamics only and it avoids the usage of constitutive relations as primary relations put on quantities needed for a complete description of an electromagnetic system. Fundamental properties of all electromagnetic quantities are their uniquely defined transformation rules and their analysis allows to determine the possible relations between them. Within such a scheme it is possible to introduce constitutive relations which do not have analogies in macroscopic classical electrodynamics. They may be used in description of microscopic electromagnetic processes in a different way than it is done in the framework of quantum electrodynamics. (author)
Causality, relativity and quantum correlation experiments with moving reference frames
H Zbinden; J Brendel; W Tittel; N Gisin
2001-02-01
Entanglement, one of the most important features of quantum mechanics, is at the core of the famous Einstein–Bohr philosophical debate [1] and is the principal resource for quantum information processing [2]. We report on new experimental investigations of the properties of entangled photon pairs with emphasis on the tension between quantum mechanics and relativity [3,4]. Entangled photons are sent via an optical ﬁber network to two villages near Geneva, separated by more than 10 km where they are analyzed by interferometers [5]. The photon pair source is set as precisely as possible in the center so that the two photons arrive at the detectors within a time interval of less than 5 ps (corresponding to a path length difference of less than 1 mm). This sets a lower bound on the ‘speed of quantum information’ to 107 times the speed of light. Next, one detector is set in motion [6] so that both detectors, each in its own inertial reference frame, are ﬁrst to do the measurement! The data always reproduces the quantum correlations.
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
Spatial properties of non-retinotopic reference frames in human vision.
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
YUQIAN
2004-01-01
Celestial burial is worshipped in Tibet as the highest pursuit of life. Of three elements indispensable for celestial burial-celestial rock (also known as altar), cinereous vultures, and masters of celestial burial, celestial burial masters are the most mysteriously important.
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…
The state of non-relativistic quantum system in a relativistic reference frame
Deliyergiyev, M A; Merkotan, K K; Podoliian, N O; Potiyenko, O S; Ptashynskyy, D A; Rusov, V D; Sharph, I V; Sokhrannyi, G O; Tykhonov, A V; Volkotrub, Yu V
2013-01-01
Let us consider the problem of internal particle state transformation, which is a bound state of several particles, from the rest frame of a composite particle to the system in which it is relativistic. We also suppose that in the rest frame of the composite particle, its internal state could be considered in the relativistic approximation. It has been shown, that this internal state is unchanged during the transition from one reference frame to another. That is, the spherical symmetric particle in the rest frame stays in this state and resists, in any other reference frame, the Lorentz contraction along the movement direction of the arbitrary reference frame relative to the rest frame. It is discussed the possible application of the work results for hadrons scattering processes description like bound states of quarks.
Electrodynamics in rotating and other accelerated frames of reference
A systematic description of the various aspects of electrodynamics in accelerated frames, with a special emphasis to that in frames rotating about a fixed axis, at a constant rate, is attempted here. The related basic problems and controversies are of such nature that these can not be covered briefly in books on classical electrodynamics. For this reason all authors of such books avoid any presentation of this electrodynamics, even for very small rotational velocities. These problems have been clearly exposed here. (author). 10 refs
Fields of Iterated Quantum Reference Frames based on Gauge Transformations of Rational String States
Benioff, Paul
2006-01-01
This work is based on a description of quantum reference frames that seems more basic than others in the literature. Here a frame is based on a set of real and of complex numbers and a space time as a 4-tuple of the real numbers. There are many isomorphic frames as there are many isomorphic sets of real numbers. Each frame is suitable for construction of all physical theories as mathematical structures over the real and complex numbers. The organization of the frames into a field of frames is...
Methods of celestial mechanics
Brouwer, Dirk
2013-01-01
Methods of Celestial Mechanics provides a comprehensive background of celestial mechanics for practical applications. Celestial mechanics is the branch of astronomy that is devoted to the motions of celestial bodies. This book is composed of 17 chapters, and begins with the concept of elliptic motion and its expansion. The subsequent chapters are devoted to other aspects of celestial mechanics, including gravity, numerical integration of orbit, stellar aberration, lunar theory, and celestial coordinates. Considerable chapters explore the principles and application of various mathematical metho
Janzen, G.; Haun, D.B.M.; Levinson, S.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 obje
Gabriele Janzen
Full Text Available 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.
Electromagnetic Forces and Fields in a Rotating Reference Frame
Arendt, Jr., P. N.
1998-01-01
Maxwell's equations and the equations governing charged particle dynamics are presented for a rotating coordinate system with the global time coordinate of an observer on the rotational axis. Special care is taken in defining the relevant entities in these equations. Ambiguities in the definitions of the electromagnetic fields are pointed out, and in fact are shown to be essential in such a system of coordinates. The Lorentz force is found to have an extra term in this frame, which has its or...
Calibration of Robot Reference Frames for Enhanced Robot Positioning Accuracy
Cheng, Frank Shaopeng
2008-01-01
This chapter discussed the importance and methods of conducting robot workcell calibration for enhancing the accuracy of the robot TCP positions in industrial robot applications. It shows that the robot frame transformations define the robot geometric parameters such as joint position variables, link dimensions, and joint offsets in an industrial robot system. The D-H representation allows the robot designer to model the robot motion geometry with the four standard D-H parameters. The robot k...
Electromagnetic Forces and Fields in a Rotating Reference Frame
Arendt, P N
1998-01-01
Maxwell's equations and the equations governing charged particle dynamics are presented for a rotating coordinate system with the global time coordinate of an observer on the rotational axis. Special care is taken in defining the relevant entities in these equations. Ambiguities in the definitions of the electromagnetic fields are pointed out, and in fact are shown to be essential in such a system of coordinates. The Lorentz force is found to have an extra term in this frame, which has its origins in relativistic mass. A related term in the energy equation, which allows inertia to be gained even during strict corotation, suggests ways existing pulsar magnetosphere models may be modified to match observed `braking indices' more closely.
CHEN Tong; WU Ning; YU Yue
2011-01-01
We have developed a path integral formalism of the quantum mechanics in the rotating frame of reference, and proposed a path integral description of spin degrees of freedom, which is connected to the Schwinger bosons realization of the angular momenta. We
Xie, Yi
2009-01-01
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) an...
Medina, Jared; Kannan, Vijay; Pawlak, Mikolaj A.; Kleinman, Jonathan T.; Newhart, Melissa; Davis, Cameron; Heidler-Gary, Jennifer E.; Herskovits, Edward H; Hillis, Argye E.
2009-01-01
There is evidence for different levels of visuospatial processing with their own frames of reference: viewer-centered, stimulus-centered, and object-centered. The neural locus of these levels can be explored by examining lesion location in subjects with unilateral spatial neglect (USN) manifest in these reference frames. Most studies regarding the neural locus of USN have treated it as a homogenous syndrome, resulting in conflicting results. In order to further explore the neural locus of vis...
On the relation of Thomas rotation and angular velocity of reference frames
Matolcsi, T.; Matolcsi, M.; Tasnádi, T.
2006-01-01
In the extensive literature dealing with the relativistic phenomenon of Thomas rotation several methods have been developed for calculating the Thomas rotation angle of a gyroscope along a circular world line. One of the most appealing concepts, introduced in \\cite{rindler}, is to consider a rotating reference frame co-moving with the gyroscope, and relate the precession of the gyroscope to the angular velocity of the reference frame. A recent paper \\cite{herrera}, however, applies this princ...
Optimal state for keeping reference frames aligned and the Platonic solids
Kolenderski, Piotr; Demkowicz-Dobrzanski, Rafal
2008-01-01
The optimal N qubit states featuring highest sensitivity to small misalignment of cartesian reference frames are found using the Quantum Cramer-Rao bound. It is shown that the optimal states are supported on the symmetric subspace and hence are mathematically equivalent to a single spin J=N/2. Majorana representation of spin states is used to reveal a beautiful connection between the states optimal for aligning reference frames and the platonic solids.
Leman, Marc; Naveda, Luiz Alberto
2010-01-01
THE GOAL OF THE PRESENT STUDY IS TO GAIN BETTER insight into how dancers establish, through dancing, a spatiotemporal reference frame in synchrony with musical cues. With the aim of achieving this, repetitive dance patterns of samba and Charleston were recorded using a three-dimensional motion capture system. Geometric patterns then were extracted from each joint of the dancer's body. The method uses a body-centered reference frame and decomposes the movement into non-orthogonal periodicities...
A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging
Xinhui Zhu
2016-02-01
Full Text Available 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.
A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging.
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
A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging
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
Frames of reference that address the impact of physical environments on occupational performance.
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
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.
Examining egocentric and allocentric frames of reference in virtual space systems
FRIEDMAN, A.
2005-01-01
The aim of this paper is to examine the egocentric and allocentric frames of reference, through evidence from both gesture and linguistic communication. The action of frames of reference, helps the user refer to the agent as a base for movement or to the object as a guiding point. We will show that although each uses different methods to convey movement in virtual reality, both have a distinct ability to refer to the path’s intrinsic value, but both handle objects with a different number of a...
A reference frame for blood volume in children and adolescents
Donckerwolcke Raymond
2006-02-01
Full Text Available Abstract Background Our primary purpose was to determine the normal range and variability of blood volume (BV in healthy children, in order to provide reference values during childhood and adolescence. Our secondary aim was to correlate these vascular volumes to body size parameters and pubertal stages, in order to determine the best normalisation parameter. Methods Plasma volume (PV and red cell volume (RCV were measured and F-cell ratio was calculated in 77 children with idiopathic nephrotic syndrome in drug-free remission (mean age, 9.8 ± 4.6 y. BV was calculated as the sum of PV and RCV. Due to the dependence of these values on age, size and sex, all data were normalised for body size parameters. Results BV normalised for lean body mass (LBM did not differ significantly by sex (p Conclusion LBM was the anthropometric index most closely correlated to vascular fluid volumes, independent of age, gender and pubertal stage.
Accurate Realization of GPS Vertical Global Reference Frame
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.
Flexible Reference Frames for Grasp Planning in Human Parietofrontal Cortex(1,2,3).
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
Field, J H.
2005-01-01
The force due to electromagnetic induction on a test charge is calculated in different reference frames. The Faraday-Lenz Law and different formulae for the fields of a uniformly moving charge are used. The classical Heaviside formula for the electric field of a moving charge predicts that, for the particular spatial configuration considered, the inductive force vanishes in the frame in which the magnet is in motion and the test charge at rest. In contrast, consistent results, in different fr...
Interaction between allocentric and egocentric reference frames in deaf and hearing populations.
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
Thermodynamic Properties of Spherically-Symmetric, Uniformly-Accelerated Reference Frames
ZHANG Jian-Bao; HUANG Chao-Guang; LIU Zeng-Rong; SUN Jia-Rui; LI Ying
2008-01-01
We aim to study the thermodynamic properties of the spherically symmetric reference frames with uniform acceleration, including the spherically symmetric generalization of Rindler reference frame and the new kind of uniformly accelerated reference frame. We find that, unlike the general studies about the horizon thermodynamics, one cannot obtain the laws of thermodynamics for their horizons in the usual approaches, despite that one can formally define an area entropy (Bekenstein-Hawking entropy). In fact, the common horizon for a set of uniformly accelerated observers does not always exist, even though the Hawking-Unruh temperature is still well-defined. This result indicates that the Hawking-Unruh temperature is only a kinematic effect, and to gain the laws of thermodynamics for the horizon, one needs the help of dynamics. Our result is in accordance with those from the various studies about the acoustic black holes.
Influences of indigenous language on spatial frames of reference in Aboriginal English
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.
A spatial reference frame model of Beijing based on spatial cognitive experiment
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.
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.
Quantum mechanics in noninertial reference frames: Relativistic accelerations and fictitious forces
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.
A First Look at Terrestrial Reference Frame ITRF2013G Computed with Gipsy Software
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.
The task of the relativistic oscillator in a non-inertial frame of reference
Perepelkin, E E; Inozemtseva, N G
2016-01-01
In this paper the analogues of the Lorentz transformations for non-inertial reference frames have been obtained. A common case when the movement speed of one coordinate frame in relation to another one can have time derivatives of higher orders. The obtained transformations conserve invariance of the space-time interval, and in the particular case of inertial frames become the well-known Lorentz transformations. It is shown that the transition from classical mechanics to the theory of relativity is analogous to the consideration of the vibrating system described by the equation of the sine-Gordon type. In this case, if the amplitude of the elliptic functions is $k\\to 0$ the fluctuations can be considered small, and that leads to classical mechanics. With $k\\to 1$ time depends on the vibration amplitude, which leads to the theory of relativity. In the case of inertial frames the amplitude is $k=\\beta ={v}/{c}\\;$.
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
First Report of the Stable North America Reference Frame (SNARF) Working Group
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
Computation of Fluid Flows in Non-inertial Contracting, Expanding, and Rotating Reference Frames
Poludnenko, A Y
2005-01-01
We present the method for computation of fluid flows characterized by the large degree of expansion/contraction and in which the fluid velocity is dominated by the bulk component associated with the expansion/contraction and/or rotation of the flow. We consider the formulation of Euler equations of fluid dynamics in a homologously expanding/contracting and/or rotating reference frame. The frame motion is adjusted to minimize local fluid velocities. Such approach allows to accommodate very efficiently large degrees of change in the flow extent. Moreover, it eliminates the high Mach number problem in the flows of interest and allows for significantly larger time steps compared to the traditional moving mesh techniques. This dramatically decreases the error in pressure as well as numerical dissipation in the calculations. We also consider in detail equation invariance and existence of conservative formulation of equations for special classes of expanding/contracting reference frames. Special emphasis is placed o...
Binocular perception of slant about oblique axes relative to a visual frame of reference
Van Ee, R.; Erkelens, Casper J.
2001-01-01
From the literature it is known that the processing of disparity for slant is different in the presence and in the absence of a visual frame of reference. We elaborate the experimental finding that vertical disparity is not processed for slant perception in the presence of a visual reference. This theoretical analysis results in a reduction of the thre basic first-order transformations between the retinal half-images (Koen derink's divergence, rotation and deformation) to only two basic ortho...
Adaptive control of an induction rotor-flux oriented reference frame induction motor drive
In this paper, simultaneous estimation of the rotor speed and time constant estimation for a voltage source inverter-fed induction motor drive is discussed. Application of the Model Reference Adaptive System on the vector controlling of an induction motor drive in the rotor-flux-oriented reference frame is examined. Furthermore, to eliminate the offset error caused by the change in the stator resistance, a fuzzy resistance is also designed
Mental Accounting and Changes in Price: The Frame Dependence of Reference Dependence.
Heath, Timothy B; Chatterjee, Subimal; France, Karen Russo
1995-01-01
Mental accounting principles for multiple events were replicated and then extended to pricing situations that were designed to moderate these principles if reference dependence is proportional (i.e., if consumers evaluate events in terms of proportional deviations from reference states rather than raw deviations). Prices were stated with or without popular percentage-based pricing frames such as "33 percent off." Mental accounting principles generally prevailed in the absence of percentage-ba...
The Reciprocal Internal/External Frame of Reference Model Using Grades and Test Scores
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…
Spin Path Integral And Quantum Mechanics In Rotating Reference of Frame
Chern, Tong; Ning, Wu; Yue, YU
2011-01-01
We developed a path integral formalism for the quantum mechanics in a rotating reference of frame, and proposed a spin path integral description for the spin degrees of freedom in it. We have also give some examples for the applications of our foramlism.
A robust WENO scheme for nonlinear waves in a moving reference frame
Kontos, Stavros; Bingham, Harry B.; Lindberg, Ole;
2016-01-01
For robust nonlinear wave simulation in a moving reference frame, we recast the free surface problem in Hamilton-Jacobi form and propose a Weighted Essentially Non-Oscillatory (WENO) scheme to automatically handle the upwinding of the convective term. A new automatic procedure for deriving the...
On multi-timescale variability of temperature in China in modulated annual cycle reference frame
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.
Klink, W.H. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Wickramasekara, S., E-mail: wickrama@grinnell.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Department of Physics, Grinnell College, Grinnell, IA 50112 (United States)
2014-01-15
In previous work we have developed 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 that includes transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as is the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. A special feature of these previously constructed representations is that they all respect the non-relativistic equivalence principle, wherein the fictitious forces associated with linear acceleration can equivalently be described by gravitational forces. In this paper we exhibit a large class of cocycle representations of the Galilean line group that violate the equivalence principle. Nevertheless the classical mechanics analogue of these cocycle representations all respect the equivalence principle. -- Highlights: •A formulation of Galilean quantum mechanics in non-inertial reference frames is given. •The key concept is the Galilean line group, an infinite dimensional group. •A large class of general cocycle representations of the Galilean line group is constructed. •These representations show violations of the equivalence principle at the quantum level. •At the classical limit, no violations of the equivalence principle are detected.
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…
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…
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…
The NKG2008 GPS campaign - final transformation results and a new common Nordic reference frame
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.
Accuracy of the International Terrestrial Reference Frame origin and Earth expansion
Wu, X.; Collilieux, X.; Altamimi, Z.; Vermeersen, L.L.A.; Gross, R.S.; Fukumori, I.
2011-01-01
The International Terrestrial Reference Frame (ITRF) is a fundamental datum for high‐precision orbit tracking, navigation, and global change monitoring. Accurately realizing and maintaining ITRF origin at the mean Earth system center of mass (CM) is critical to surface and spacecraft based geodetic
An experimental Kalman filter approach to the International Terrestrial Reference Frame realization
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.
Post-Newtonian relativistic theory of astronomical reference frames based on Einstein's general theory of relativity was adopted by General Assembly of the International Astronomical Union in 2000. This theory is extended in the present paper by taking into account all relativistic effects caused by the presumable existence of a scalar field and parametrized by two parameters, β and γ, of the parametrized post-Newtonian (PPN) formalism. We use a general class of the scalar-tensor (Brans-Dicke type) theories of gravitation to work out PPN concepts of global and local reference frames for an astronomical N-body system. The global reference frame is a standard PPN coordinate system. A local reference frame is constructed in the vicinity of a weakly self-gravitating body (a sub-system of the bodies) that is a member of the astronomical N-body system. Such local inertial frame is required for unambiguous derivation of the equations of motion of the body in the field of other members of the N-body system and for construction of adequate algorithms for data analysis of various gravitational experiments conducted in ground-based laboratories and/or on board of spacecrafts in the solar system.We assume that the bodies comprising the N-body system have weak gravitational field and move slowly. At the same time we do not impose any specific limitations on the distribution of density, velocity and the equation of state of the body's matter. Scalar-tensor equations of the gravitational field are solved by making use of the post-Newtonian approximations so that the metric tensor and the scalar field are obtained as functions of the global and local coordinates. A correspondence between the local and global coordinate frames is found by making use of asymptotic expansion matching technique. This technique allows us to find a class of the post-Newtonian coordinate transformations between the frames as well as equations of translational motion of the origin of the local frame
Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations
Klink, W.H., E-mail: william-klink@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Wickramasekara, S., E-mail: wickrama@grinnell.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Department of Physics, Grinnell College, Grinnell, IA 50112 (United States)
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
Sato, Masanori
2006-01-01
We show the compatibility of the theory of special relativity with the absolute reference frame with a longitudinal Doppler shift. Using two absolute velocities vA and vS, the relative velocity u is derived. Thereafter the Doppler frequency is derived using the relative velocity u. We also show the method for detecting the absolute reference frame. The representation of the theory of special relativity using the absolute reference frame appears more intuitive than an orthodox interpretation.
On reference frames and the definition of space in a general spacetime
Arminjon, Mayeul
2013-01-01
First, we review local concepts defined previously. A (local) reference frame $\\mathrm{F}$ can be defined as an equivalence class of admissible spacetime charts (coordinate systems) having a common domain $\\mathrm{U}$ and exchanging by a spatial coordinate change. The associated (local) physical space is made of the world lines having constant space coordinates in any chart of the class. Second, we introduce new, global concepts. The data of a non-vanishing global vector field $\\,v\\,$ defines a global "reference fluid". The associated global physical space is made of the maximal integral curves of that vector field. Assume that, in any of the charts which make some reference frame $\\mathrm{F}$: (i) any of those integral curves $l$ has constant space coordinates $x^j$, and (ii) the mapping $l\\mapsto (x^j)$ is one-to-one. In that case, the local space can be identified with a part (an open subset) of the global space.
KALREF - A Kalman filter approach to the International Terrestrial Reference Frame realization
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.
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.
The Gaia inertial reference frame and the tilting of the Milky Way disk
Perryman, Michael; Spergel, David N. [Department of Astrophysical Sciences, Peyton Hall, Princeton, NJ 08544 (United States); Lindegren, Lennart, E-mail: mac.perryman@gmail.com [Lund Observatory, Box 43, SE-22100 Lund (Sweden)
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.
Examining reference frame interaction in spatial memory using a distribution analysis.
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
DQ reference frame modeling and control of single-phase active power decoupling circuits
Tang, Yi; Qin, Zian; Blaabjerg, Frede; Loh, Poh Chiang
Power decoupling circuits can compensate the inherent double line frequency ripple power in single-phase systems and greatly facilitate their dc-link capacitor design. Example applications of power decoupling circuit include photovoltaic, light-emitting diode, fuel cell, and motor drive systems....... This paper presents the dq synchronous reference frame modeling of single-phase power decoupling circuits and a complete model describing the dynamics of dc-link ripple voltage is presented. The proposed model is universal and valid for both inductive and capacitive decoupling circuits, and the input...... of decoupling circuits can be either dependent or independent of its front-end converters. Based on this model, a dq synchronous reference frame controller is designed which allows the decoupling circuit to operate in two different modes because of the circuit symmetry. Simulation and experimental...
The Relationship Between Global Mean Sea Level Rise and the Reference Frame
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.
Transfer of spatial reference frame using singlet states and classical communication
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.
Research Activities for the DORIS Contribution to the Next International Terrestrial Reference Frame
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.
Wallentin, Mikkel; Kristensen, Line Burholt; Olsen, Jacob Hedeager;
2011-01-01
The brain's frontal eye fields (FEF), responsible for eye movement control, are known to be involved in spatial working memory (WM). In a previous fMRI experiment (Wallentin, Roepstorff & Burgess, Neuropsychologia, 2008) it was found that FEF activation was primarily related to the formation...... of an object-centered, rather than egocentric, spatial reference frame. In this behavioral experiment we wanted to demonstrate a causal relationship between eye movement control and manipulation of spatial reference frames. Sixty two participants recalled either spatial ("Was X in front of Y?") or non......-spatial ("Was X darker than Y?") relations in a previously shown image containing two to four objects, each with an intrinsic orientation and unique luminance. During half of all recall trials a moving visual stimulus was presented, which participants had to ignore, thus suppressing eye movement. Response times...
Frontal eye fields involved in shifting frame of reference within working memory for scenes
Wallentin, Mikkel; Roepstorff, Andreas; Burgess, Neil
2008-01-01
during shifting reference frames in representational space. Analysis of actual eye movements in 3 subjects revealed no difference between egocentric and allocentric recall tasks where visual stimuli were also absent. Thus, the FEF machinery for directing eye movements may also be involved in changing...... shorter response time and more correct responses than poor performers in both tasks. These behavioural variables were entered into a principal component analysis. The first component reflected generalised performance level. We found that the frontal eye fields (FEF), bilaterally, had a higher BOLD...... response during recall involving allocentric compared to egocentric spatial reference frames, and that this difference was larger in good performers than in poor performers as measured by the first behavioural principal component. The frontal eye fields may be used when subjects move their internal gaze...
Insight into Others’ Minds: Spatio-Temporal Representations by Intrinsic Frame of Reference
Yanlong Sun
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 rela...
Insight into others’ minds: spatio-temporal representations by intrinsic frame of reference
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 rela...
Neural network simulations of the primate oculomotor system. II. Frames of reference.
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
Communication between general-relativistic observers without a shared reference frame
Checińska, Agata; Dragan, Andrzej
2015-07-01
We show how to reliably encode quantum information and send it between two arbitrary general-relativistic observers without a shared reference frame. Information stored in a quantum field will inevitably be destroyed by an unknown Bogoliubov transformation relating the observers. However, certain quantum correlations between different, independent fields will be preserved, no matter what transformation is applied. We show how to efficiently use these correlations in communication between arbitrary observers.
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.
A Frame of Reference for Research of Integrated Governance, Risk and Compliance (GRC)
Racz, Nicolas; Weippl, Edgar; Seufert, Andreas
2010-01-01
International audience Governance, Risk and Compliance (GRC) is an emerging topic in the business and information technology world. However to this day the concept behind the acronym has neither been adequately researched, nor is there a common understanding among professionals. The research at hand provides a frame of reference for research of integrated GRC that was derived from the first scientifically grounded definition of the term. By means of a literature review the authors merge ob...
Louis-Martinez, Domingo J.
2010-01-01
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 fo...
Accuracy of the International Terrestrial Reference Frame origin and Earth expansion
Wu, X; Collilieux, X.; Altamimi, Z.; L. L. A. Vermeersen; Gross, R.S.; Fukumori, I.
2011-01-01
The International Terrestrial Reference Frame (ITRF) is a fundamental datum for high‐precision orbit tracking, navigation, and global change monitoring. Accurately realizing and maintaining ITRF origin at the mean Earth system center of mass (CM) is critical to surface and spacecraft based geodetic measurements including those of sea level rise and its sources. Although ITRF combines data from satellite laser ranging (SLR), Very Long Baseline Interferometry (VLBI), Global Positioning System (...
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.
Extended intrinsic mean spin tensor for turbulence modelling in non-inertial frame of reference
HUANG Yu-ning; MA Hui-yang
2008-01-01
We investigate the role of extended intrinsic mean spin tensor introduced in this work for turbulence modelling in a non-inertial frame of reference.It is described by the Euclidean group of transformations and,in particular,its significance and importance in the approach of the algebraic Reynolds stress modelling,such as in a nonlinear K-εmodel.To this end and for illustration of the effect of extended intrinsic spin tensor on turbulence modelling,we examine several recently developed nonlinear K-ε models and compare their performance in predicting the homogeneous turbulent shear flow in a rotating frame of reference with LES data.Our results and analysis indicate that,only if the deficiencies of these models and the like be well understood and properly corrected,may in the near future,more sophisticated nonlinear K-ε models be 0eveloped to better predict complex turbulent flows in a non-inertial frame of reference.
Ettore Ambrosini
Full Text Available BACKGROUND: Several psychophysical experiments found evidence for the involvement of gaze-centered and/or body-centered coordinates in arm-movement planning and execution. Here we aimed at investigating the frames of reference involved in the visuomotor transformations for reaching towards visual targets in space by taking target eccentricity and performing hand into account. METHODOLOGY/PRINCIPAL FINDINGS: We examined several performance measures while subjects reached, in complete darkness, memorized targets situated at different locations relative to the gaze and/or to the body, thus distinguishing between an eye-centered and a body-centered frame of reference involved in the computation of the movement vector. The errors seem to be mainly affected by the visual hemifield of the target, independently from its location relative to the body, with an overestimation error in the horizontal reaching dimension (retinal exaggeration effect. The use of several target locations within the perifoveal visual field allowed us to reveal a novel finding, that is, a positive linear correlation between horizontal overestimation errors and target retinal eccentricity. In addition, we found an independent influence of the performing hand on the visuomotor transformation process, with each hand misreaching towards the ipsilateral side. CONCLUSIONS: While supporting the existence of an internal mechanism of target-effector integration in multiple frames of reference, the present data, especially the linear overshoot at small target eccentricities, clearly indicate the primary role of gaze-centered coding of target location in the visuomotor transformation for reaching.
Effects of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame
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.
Different effects of numerical magnitude on visual and proprioceptive reference frames
Elvio eBlini
2013-04-01
Full Text Available This study assessed whether numerical magnitude affects the setting of basic spatial coordinates and reference frames, namely the subjective straight ahead. Three tasks were given to 24 right-handed healthy participants: a proprioceptive and a visuo-proprioceptive task, requiring pointing to the subjective straight ahead, and a visual task, requiring a perceptual judgment about the straight ahead position of a light moving left-to-right, or right-to-left. A control task, requiring the bisection of rods of different lengths, was also given. The four tasks were performed under conditions of passive auditory numerical (i.e., listening to small, 2, and large, 8, numbers, and neutral auditory-verbal (blah stimulation. Numerical magnitude modulates the participants’ deviations in the visual straight ahead task, when the movement of the light is from left to right, with the small number bringing about a leftward deviation, the large number a rightward deviation. This result suggests that the spatial effects induced by the activation of the mental number line extend to an egocentric frame of reference. A similar directional modulation was found in the rod bisection task, in line with previous evidence. No effects of numerical magnitude were found on the proprioceptive and visuo-proprioceptive straight ahead tasks. These results suggest that the spatial effects induced by the activation of the mental number line extend to an egocentric frame of reference but only when a portion of horizontal space has to be actively explored.
Monfared, Mohammad; Golestan, Saeed; Guerrero, Josep M.
2014-01-01
Control of three-phase power converters in the synchronous reference frame is now a mature and well developed research topic. However, for single-phase converters, it is not as well-established as three-phase applications. This paper deals with the design of a synchronous reference frame multi...
Rodriguez, Pedro; Alloza, Alvaro Luna; Teodorescu, Remus; Iov, Florin; Blaabjerg, Frede
2007-01-01
This work exploits the Decoupled Double Synchronous Reference Frame PLL (DDSRF-PLL) as an effective method for grid synchronization of WT's power converters in the presence of transient faults in the grid. The DDSRF-PLL uses a dual synchronous reference frame and a decoupling network to effectively...
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.
Burnham, Robert
1978-01-01
Volume II of a comprehensive three-part guide to celestial objects outside our solar system ranges from Chamaeleon to Orion. Features coordinates, classifications, physical descriptions, hundreds of visual aids. 1977 edition.
Mesopotamian Celestial Divination
Verderame, Lorenzo
Celestial divination was an important aspect of scholarly activity in Mesopotamia. Several hundred cuneiform tablets attest to its practice and provide details of the different types of omens that were drawn from observations of the sky. This chapter outlines the sources of celestial divination in Mesopotamia and traces the development of the divinatory tradition from the late third millennium BC down to the end of the first millennium BC.
Celestial mechanics and astrodynamics theory and practice
Gurfil, Pini
2016-01-01
This volume is designed as an introductory text and reference book for graduate students, researchers and practitioners in the fields of astronomy, astrodynamics, satellite systems, space sciences and astrophysics. The purpose of the book is to emphasize the similarities between celestial mechanics and astrodynamics, and to present recent advances in these two fields so that the reader can understand the inter-relations and mutual influences. The juxtaposition of celestial mechanics and astrodynamics is a unique approach that is expected to be a refreshing attempt to discuss both the mechanics of space flight and the dynamics of celestial objects. “Celestial Mechanics and Astrodynamics: Theory and Practice” also presents the main challenges and future prospects for the two fields in an elaborate, comprehensive and rigorous manner. The book presents homogenous and fluent discussions of the key problems, rendering a portrayal of recent advances in the field together with some basic concepts and essential in...
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
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
Contribution of the Main Astronomical Observatory, Ukraine, to the Reference Frame Link
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.
Quantum reverse-engineering and reference frame alignment without non-local correlations
Bagán, E; Muñoz-Tàpia, R
2004-01-01
Estimation of unknown qubit elementary gates and alignment of reference frames are formally the same problem. Using quantum states made out of $N$ qubits, we show that the theoretical precision limit for both problems, which behaves as $1/N^{2}$, can be asymptotically attained with a covariant protocol that exploits the quantum correlation of internal degrees of freedom instead of the more fragile entanglement between distant parties. This cuts by half the number of qubits needed to achieve the precision of the dense covariant coding protocol.
Out of body, out of space: Impaired reference frame processing in eating disorders.
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
Back action evading quantum measurement of motion in a negative mass reference frame
Møller, Christoffer B; Vasilakis, Georgios; Zeuthen, Emil; Tsaturyan, Yeghishe; Jensen, Kasper; Schliesser, Albert; Hammerer, Klemens; Polzik, Eugene S
2016-01-01
Quantum mechanics dictates that a measurement without perturbation is not possible. A textbook example is the observation of the position of an object, which imposes a random back action perturbation on the momentum. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion. Here we demonstrate that the back action on an oscillator measured in a reference frame of another oscillator with an effective negative mass can be evaded in both position and momentum variables simultaneously. The mechanical oscillator is a millimeter-sized membrane and the reference negative mass oscillator is the collective spin of an atomic ensemble precessing in a magnetic field. Laser light transmitted through the hybrid system of these two disparate oscillators serves as the meter. We first observe the quantum measurement back action on each oscillator. We then demonstrate that back action at the single noise photon level is efficiently suppressed or enh...
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.
Relativistic Celestial Mechanics of the Solar System
Kopeikin, Sergei; Efroimsky, Michael; Kaplan, George
2011-09-01
The general theory of relativity was developed by Einstein a century ago. Since then, it has become the standard theory of gravity, especially important to the fields of fundamental astronomy, astrophysics, cosmology, and experimental gravitational physics. Today, the application of general relativity is also essential for many practical purposes involving astrometry, navigation, geodesy, and time synchronization. Numerous experiments have successfully tested general relativity to a remarkable level of precision. Exploring relativistic gravity in the solar system now involves a variety of high-accuracy techniques, for example, very long baseline radio interferometry, pulsar timing, spacecraft Doppler tracking, planetary radio ranging, lunar laser ranging, the global positioning system (GPS), torsion balances and atomic clocks. Over the last few decades, various groups within the International Astronomical Union have been active in exploring the application of the general theory of relativity to the modeling and interpretation of high-accuracy astronomical observations in the solar system and beyond. A Working Group on Relativity in Celestial Mechanics and Astrometry was formed in 1994 to define and implement a relativistic theory of reference frames and time scales. This task was successfully completed with the adoption of a series of resolutions on astronomical reference systems, time scales, and Earth rotation models by the 24th General Assembly of the IAU, held in Manchester, UK, in 2000. However, these resolutions only form a framework for the practical application of relativity theory, and there have been continuing questions on the details of the proper application of relativity theory to many common astronomical problems. To ensure that these questions are properly addressed, the 26th General Assembly of the IAU, held in Prague in August 2006, established the IAU Commission 52, "Relativity in Fundamental Astronomy". The general scientific goals of the new
Burnham, Robert
1978-01-01
Volume III of this three-part comprehensive guide to the thousands of celestial objects outside our solar system concludes with listings from Pavo through Vulpecula. Objects are grouped according to constellation, and their definitions feature names, coordinates, classifications, and physical descriptions. Additional notes offer fascinating historical information. Hundreds of visual aids. 1977 edition.
Burnham, Robert
1978-01-01
Volume I of this comprehensive three-part guide to the thousands of celestial objects outside our solar system ranges from Andromeda through Cetus. Objects are grouped according to constellation, and their definitions feature names, coordinates, classifications, and physical descriptions. Additional notes offer fascinating historical information. Hundreds of visual aids. 1977 edition.
Numerical Analysis of a Rotating Detonation Engine in the Relative Reference Frame
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.
Demonstration of free-space reference frame independent quantum key distribution
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. (paper)
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.
Positional priming of visual pop-out search is supported by multiple spatial reference frames
Ahu eGokce
2015-06-01
Full Text Available The present study investigates the representations(s underlying positional priming of visual ‘pop-out’ search (Maljkovic & Nakayama, 1996. Three search items (1 target and 2 distractors were presented at different locations, in invariant (Experiment 1 or random (Experiment 2 cross-trial sequences. By these manipulations it was possible to disentangle retinotopic, spatiotopic, and object-centered priming representations. Two forms of priming were tested: target location facilitation (i.e., faster reaction times – RTs– when the trial n target is presented at a trial n-1 target relative to n-1 blank location and distractor location inhibition (i.e., slower RTs for n targets presented at n-1 distractor compared to n-1 blank locations. It was found that target locations were coded in positional short-term memory with reference to both spatiotopic and object-centered representations (Experiment 1 vs. 2. In contrast, distractor locations were maintained in an object-centered reference frame (Experiments 1 and 2. We put forward the idea that the uncertainty induced by the experiment manipulation (predictable versus random cross-trial item displacements modulates the transition from object- to space-based representations in cross-trial memory for target positions.
In the frame of the decommissioning of two particle accelerators, one linear (700 MeV, electrons) and one synchrotron (3 GeV, protons), the CEA has set up a reference zoning of the radioactive waste and has looked for some elimination networks. That zoning has been established following an analytic process which has taken into account the installations' design, their running rules, and their history, in order to determine the possible presence of added radioactivity. We have used the following methodology: Identification of the sectors and elements, and within them of the main materials, where interactions between beam and matter may have happened; Characterisation of the radiation fields; Identification of the radio-elements representative of the potential activation of the materials; Evaluation of their mass activity, by semi empirical calculation or Monte Carlo simulation method, whether significant or not, compared with the reference values (Instruction 96/29/Euratom); Verification of the radiological state of the zones through radioactivity measures made on samples and through cartographies of the absorbed dose rates; Standard spectrums and transfer functions to assess the activity levels of the waste have then been calculated to allow the setting up of a control, of a selection and of a rigorous management of the waste coming from the concerned nuclear installations
HUANG YuNing; MA HuiYang; XU JingLei
2008-01-01
Modelling the turbulent flows in non-inertial frames of reference has long been a challenging task. Recently we introduced the notion of the "extended intrinsic mean spin tensor" for turbulence modelling and pointed out that, when applying the Reynolds stress models developed in the inertial frame of reference to model-ling the turbulence in a non-inertial frame of reference, the mean spin tensor should be replaced by the extended intrinsic mean spin tensor to correctly account for the rotation effects induced by the non-inertial frame of reference, to conform in phys-ics with the Reynolds stress transport equation. To exemplify the approach, we conducted numerical simulations of the fully developed turbulent channel flow in a rotating frame of reference by employing four non-linear K-εmodels. Our numerical results based on this approach at a wide range of Reynolds and Rossby numbers evince that, among the models tested, the non-linear K-ε model of Huang and Ma and the non-linear K-ε model of Craft, Launder and Suga can better capture the rotation effects and the resulting influence on the structures of turbulence, and therefore are satisfactorily applied to dealing with the turbulent flows of practical interest in engineering. The general approach worked out in this paper is also ap-plied to the second-moment closure and the large-eddy simulation of turbulence.
Kopeikin, Sergei; Xie, Yi
2009-01-01
We construct a set of post-Newtonian reference frames for a comprehensive study of the orbital dynamics and rotational motion of the Moon and Earth by means of lunar laser ranging (LLR) with the precision of one millimeter. We also derive the post-Newtonian coordinate transformations between the frames and analyze the residual gauge freedom, which is used for removing spurious post-Newtonian effects from the equations of motion of the solar system bodies.
Spatial Frames of Reference in Traditional Negev Arabic: Language-to-Cognition Correlation.
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
Paul Dassonville
2015-03-01
Full Text Available Several studies have demonstrated a dissociation of the effects of illusion on perception and action, with perception generally reported to be susceptible to illusions, while actions are seemingly immune. These findings have been interpreted to support Milner and Goodale's Two Visual Systems model, which proposes the existence of separate visual processing streams for perception and action. However, an alternative interpretation suggests that this type of behavioral dissociation will occur for any illusion that is caused by a distortion of the observer's egocentric reference frame, without requiring the existence of separate perception and action systems that are differently affected by the illusion. In this scenario, movements aimed at illusory targets will be accurate if they are guided within the same distorted reference frame used for target encoding, since the error of motor guidance will cancel with the error of encoding (hence, for actions, two wrongs do make a right. We further test this Two-Wrongs model by examining two illusions for which the hypothesis makes very different predictions: the rod-and-frame illusion (which affects perception but not actions and the simultaneous-tilt illusion (which affects perception and actions equally. We demonstrate that the rod-and-frame illusion is caused by a distortion of the observer's egocentric reference frame suitable for the cancellation of errors predicted by the Two-Wrongs model. In contrast, the simultaneous-tilt illusion is caused by local interactions between stimulus elements within an undistorted reference frame, precluding the cancellation of errors associated with the Two-Wrongs model such that the illusion is reflected in both perception and actions. These results provide evidence for a class of illusions that lead to dissociations of perception and action through distortions of the observer's spatial reference frame, rather than through the actions of functionally separate visual
Štefka, Vojtěch; Kostelecký, J.; Pešek, I.
2009-01-01
Roč. 6, č. 3 (2009), s. 239-246. ISSN 1214-9705. [Czech-Polish Workshop On recent geodynamics of the Sudety Mts. and adjacent areas /9./. Náchod, 12.11.2008-15.11.2008] R&D Projects: GA MŠk(CZ) LC506 Institutional research plan: CEZ:AV0Z10030501 Keywords : Earth orientation parameters * combination of space geodesy techniques * ITRF 2005 * station coordinates Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.275, year: 2009
The space time DoF surface density as a phase-space of accelerating reference frames
Hadad, Merav
2016-01-01
Padmanabhan found a definition for the surface density of space time degrees of freedom. We prove that this density can be constructed from a phase space which is derived with respect to a special space like direction: the direction of the acceleration of an accelerating reference frame. We show that in the Euclidean limit the projection of this phase space along (an accelerating) velocity vector generates Padmanabhan's density. This suggests that Padmanabhan's density may be regarded as the space time degrees of freedom of accelerating reference frames.
The selection and application of coordinate systems is an important issue in physics. However, considering different frames of references in a given problem sometimes seems un-intuitive and is difficult for students. We present a concrete problem of projectile motion which vividly demonstrates the value of considering different frames of references. We use this example to explore the effectiveness of video-based motion analysis (VBMA) as an instructional technique at university level in enhancing students’ understanding of the abstract concept of coordinate systems. A pilot study with 47 undergraduate students indicates that VBMA instruction improves conceptual understanding of this issue. (paper)
Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame
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.
Generalized Lorentzian Adjustment of Reference Frames and Waves of Transformation of Spacetime
Pinelis, I
1998-01-01
It is demonstrated that any two reference frames (RFs), which are uniformly and rectilinearly moving relative to each other, can be adjusted via (possibly anisotropic) rescaling and re-synchronization so that the resulting pair of RFs is Lorentzian; this statement remains true if the word "Lorentzian" is replaced by "Galilean" or "Riemannian", i.e., if a finite positive value of $c^2$ is replaced by $\\infty$ or by a negative real number. In this particular sense, the Lorentzian, as well as Galilean or Riemannian, phenomenon turns out to be merely a matter of an arbitrary choice of appropriate rescaling and re-synchronization of any given pair of RFs. Generalizations and refinements of this result are obtained, including universal generalized Lorentzian adjustment via rescaling and re-synchronization of arbitrarily large families of RFs. Alternatively, the generalized Lorentzian property of a pair of RFs is shown to be a consequence of reciprocity and isotropy, with no adjustment needed in this case. The unive...
The virtual hand illusion is moderated by context-induced spatial reference frames
Jing eZhang
2015-10-01
Full Text Available 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 are the sole determinants of perceived body ownership.
Sequential Estimation of Terrestrial Reference Frame using Information Filter for a Singular System
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.
IAEA activities related to safety indicators, time frames and reference scenarios
The fundamental principles for the safe management of radioactive waste have been agreed internationally and form the basis for the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management that entered into force in June 2001. Protection of human health and the environment and safety of facilities (including radioactive waste disposal facilities) are widely recognised principles to be followed and demonstrated in post-closure safety assessment of waste repositories. Dose and risk are at present internationally agreed safety criteria, used for judging the acceptability of such facilities. However, there have been a number of activities initiated and co-ordinated by the International Atomic Energy Agency (IAEA) which have provided an international forum for discussion and consensus building on the use safety indicators which are complementary to dose and risk. The Agency has been working on the definition of other safety indicators, such as flux, time, environmental concentration, etc.; the desired characteristics, and use of these indicators in different time frames. The IAEA has focused on safety indicators related to geological disposal, exploring their role in the development of a safety case, evaluating the advantages and disadvantages of using other safety indicators and how they complement the dose and risk indicators. The use of these indicators have been discussed also from regulatory perspective, mainly in terms of achieving reasonable assurance and confidence in safety assessments for waste repositories and decision making in the presence of uncertainty in the context of disposal of long-lived waste. Considerable effort has also been expended by the Agency on the development and application of principles for defining critical groups and biospheres for deep geological repositories. One of the important and successful IAEA programmes in this field is the Biosphere Modelling and Assessment (BIOMASS) project
Adventures in Celestial Mechanics
Szebehely, Victor G
1998-01-01
A fascinating introduction to the basic principles of orbital mechanics. It has been three hundred years since Isaac Newton first formulated laws to explain the orbits of the Moon and the planets of our solar system. In so doing he laid the groundwork for modern science's understanding of the workings of the cosmos and helped pave the way to the age of space exploration. Adventures in Celestial Mechanics offers students an enjoyable way to become acquainted with the basic principles involved in the motions of natural and human-made bodies in space. Packed with examples in which these principle
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…
Ciobotaru, Mihai; Iov, Florin; Zanchetta, P.;
2008-01-01
natural reference frame controller, based on proportional-resonant (PR) technique, for a multi-level H-bridge power converter for Universal and Flexible Power Management in Future Electricity Network. The proposed method is tested in terms of harmonic content in the Point of Common Coupling (PCC), voltage...
The evaluation of a frame-of-reference training programme for intern psychometrists
Gerdi Mulder
2013-01-01
Full Text Available Orientation: The use of assessment centres (ACs has drastically increased over the past decade. However, ACs are constantly confronted with the lack of construct validity. One aspect of ACs that could improve the construct validity significantly is that of assessor training. Unfortunately untrained or poorly trained assessors are often used in AC processes. Research purpose: The purpose of this research was to evaluate a frame-of-reference (FOR programme to train intern psychometrists as assessors at an assessment centre. Motivation of study: The role of an assessor is important in an AC; therefore it is vital for an assessor to be able to evaluate and observe candidates’ behaviour adequately. Commencing with this training in a graduate psychometrist programme gives the added benefit of sending skilled psychometrists to the workplace. Research design, approach and method: A quantitative research approach was implemented, utilising a randomised pre-test-post-test comparison group design. Industrial Psychology postgraduate students (N = 22 at a South African university were used and divided into an experimental group (n = 11 and control group (n = 11. Three typical AC simulations were utilised as pre- and post-tests, and the ratings obtained from both groups were statistically analysed to determine the effect of the FOR training programme. Main findings: The data indicated that there was a significant increase in the familiarity of the participants with the one-on-one simulation and the group discussion simulation. Practical/managerial implications: Training intern psychometrists in a FOR programme could assist organisations in the appointment of more competent assessors. Contribution/value-add: To design an assessor training programme using FOR training for intern psychometrists in the South African context, specifically by incorporating this programme into the training programme for Honours students at universities.
Frontiers in relativistic celestial mechanics
2014-01-01
Relativistic celestial mechanics – investigating the motion celestial bodies under the influence of general relativity – is a major tool of modern experimental gravitational physics. With a wide range of prominent authors from the field, this two-volume series consists of reviews on a multitude of advanced topics in the area of relativistic celestial mechanics – starting from more classical topics such as the regime of asymptotically-flat spacetime, light propagation and celestial ephemerides, but also including its role in cosmology and alternative theories of gravity as well as modern experiments in this area.
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.
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.
On the consistency of the ICRF and the reference frame realized by RSC(GAO UA)97 C 01
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.
The geometry of celestial mechanics
Geiges, Hansjörg
2016-01-01
Celestial mechanics is the branch of mathematical astronomy devoted to studying the motions of celestial bodies subject to the Newtonian law of gravitation. This mathematical introductory textbook reveals that even the most basic question in celestial mechanics, the Kepler problem, leads to a cornucopia of geometric concepts: conformal and projective transformations, spherical and hyperbolic geometry, notions of curvature, and the topology of geodesic flows. For advanced undergraduate and beginning graduate students, this book explores the geometric concepts underlying celestial mechanics and is an ideal companion for introductory courses. The focus on the history of geometric ideas makes it perfect supplementary reading for students in elementary geometry and topology. Numerous exercises, historical notes and an extensive bibliography provide all the contextual information required to gain a solid grounding in celestial mechanics.
Reconstruction of the celestial globe of the Ming Dynasty.
Xu, Zhengtao; Ling, Rongfu
1997-09-01
Four big bronze instruments were made in the seventh year of the Zhengtong reign of the Ming Dynasty (AD 1442). They are the Armillary Sphere, Abridged Armilla, Gnomon and Celestial Globe. The first three ones are well presented in the Purple Mountain Observatory. But the Celestial Globe was destroyed in the early period of the Qing Dynasty. According to the astronomical treatises of the Yuan and Ming Dynasty and related references the authors reconstructed this instrument in original size.
Degobert, P.; Hautier, J.P. [Laboratoire d' Electrotechnique et d' Electronique de Puissance de Lille, Lille (France)
2000-08-01
An original and perform method is proposed for the synthesis and the torque control of electrical machine in two-phases fictitious reference frame. For studied this method, linear modelling of the Synchronous Motor was used, but this will be applied to a saturated machine. For au optimal control of alternating currents, we used a new type of controllers called 'resonating controller'. (orig.)
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…
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…
Celestial data routing network
Bordetsky, Alex
2000-11-01
Imagine that information processing human-machine network is threatened in a particular part of the world. Suppose that an anticipated threat of physical attacks could lead to disruption of telecommunications network management infrastructure and access capabilities for small geographically distributed groups engaged in collaborative operations. Suppose that small group of astronauts are exploring the solar planet and need to quickly configure orbital information network to support their collaborative work and local communications. The critical need in both scenarios would be a set of low-cost means of small team celestial networking. To the geographically distributed mobile collaborating groups such means would allow to maintain collaborative multipoint work, set up orbital local area network, and provide orbital intranet communications. This would be accomplished by dynamically assembling the network enabling infrastructure of the small satellite based router, satellite based Codec, and set of satellite based intelligent management agents. Cooperating single function pico satellites, acting as agents and personal switching devices together would represent self-organizing intelligent orbital network of cooperating mobile management nodes. Cooperative behavior of the pico satellite based agents would be achieved by comprising a small orbital artificial neural network capable of learning and restructing the networking resources in response to the anticipated threat.
An introduction to celestial mechanics
Moulton, Forest Ray
1984-01-01
An unrivaled text in the field of celestial mechanics, Moulton's theoretical work on the prediction and interpretation of celestial phenomena has not been superseded. By providing a general account of all parts of celestial mechanics without an over-full treatment of any single aspect, by stating all the problems in advance, and, where the transformations are long, giving an outline of the steps which must be made, and by noting all the places where assumptions have been introduced or unjustified methods employed, Moulton has insured that his work will be valuable to all who are interested in
New Perspectives on the Relativistically Rotating Disk and Non-time-orthogonal Reference Frames
Klauber, R D
1998-01-01
The rotating disk problem is analyzed on the premise that proper interpretation of experimental evidence leads to the conclusion that the postulates upon which relativity theory is based, particularly the invariance of the speed of light, are not applicable to rotating frames. Different postulates based on the Sagnac experiment are proposed, and from these postulates a new relativistic theory of rotating frames is developed following steps similar to those initially followed by Einstein for rectilinear motion. The resulting theory agrees with all experiments, resolves problems with the traditional approach to the rotating disk, and exhibits both traditionally relativistic and non-relativistic characteristics. Of particular note, no Lorentz contraction exists on the rotating disk circumference, and the disk surface, contrary to the assertions of Einstein and others, is found to be Riemann flat. The variable speed of light found in the Sagnac experiment is then shown to be characteristic of non-time-orthogonal ...
Personality measures as predictors of job satisfaction from a frame-of-reference perspective
Lättman, Katrin
2012-01-01
Extending previous research by Bowling and Burns (2010), a comparison of work personality to general personality indicate that work personality has a stronger relationship with job satisfaction (work-criteria) than does general personality, and, contrary to the above study, general personality has a stronger relationship with life satisfaction (general criteria) than does work personality. Work personality is defined as the personality in the context of work, by promoting the use of a frame-o...
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
We study geometric quantum phases in the relativistic and non-relativistic quantum dynamics of a neutral particle with a permanent magnetic dipole moment interacting with two distinct field configurations in a cosmic string spacetime. We consider the local reference frames of the observers are transported via Fermi-Walker transport and study the influence of the non-inertial effects on the phase shift of the wave function of the neutral particle due to the choice of this local frame. We show that the wave function of the neutral particle acquires non-dispersive relativistic and non-relativistic quantum geometric phases due to the topology of the spacetime, the interaction between the magnetic dipole moment with external fields and the spin-rotation coupling. However, due to the Fermi-Walker reference frame, no phase shift associated to the Sagnac effect appears in the quantum dynamics of a neutral particle. We show that in the absence of topological defect, the contribution to the quantum phase due to the spin-rotation coupling is equivalent to the Mashhoon effect in non-relativistic dynamics. (orig.)
Hybrid state‐space time integration in a rotating frame of reference
Krenk, Steen; Nielsen, Martin Bjerre
2011-01-01
terms, while the centrifugal forces are represented implicitly via the hybrid state‐space format. An angular momentum and energy conserving algorithm is developed, in which the angular velocity of the frame is represented by its mean value. A consistent algorithmic damping scheme is identified by...... applying the conservative algorithm to a decaying response, which is rendered stationary by an increasing exponential factor that compensates the decay. The algorithmic damping is implemented by introducing forward weighting of the mean values appearing in the algorithm. Numerical examples illustrate the...
W production at LHC: lepton angular distributions and reference frames for probing hard QCD
Richter-Was, E
2016-01-01
Precision tests of the Standard Model in the Strong and Electroweak sectors play an important role, among the physics goals of LHC experiments. Because of the nature of proton-proton processes, observables based on the measurement of the direction and energy of leptons provide the most precise signatures. In the present paper, we concentrate on the angular distribution of leptons from W to l nu decays in the lepton-pair rest-frame. The vector nature of the intermediate state imposes that distributions are to a good precision described by spherical polynomials of at most second order. We argue, that contrary to general belief often expressed in the literature, the full set of angular coefficients can be measured experimentally, despite the presence in the final state of neutrino escaping detection. There is thus no principle difference with respect to the phenomenology of the Z/gamma to l^+ l^- Drell-Yan process. We show also, that with the proper choice of the coordinate frames, only one coefficient in this p...
Multiple reference frames for saccadic planning in the human parietal cortex.
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
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
M. V. Mackern
2009-12-01
Full Text Available Satellite positioning systems allow the fixing of the location of a point on the Earth's surface with very good precision and accuracy. To do this, however, it is necessary to determine the point coordinates taking account the reference system and the movements that affect them because of tectonic plate movements. These reference systems are materialized by a significant number of continuous measurement stations in South America. In SIRGAS (Sistema de Referencia Geocéntrico para las Américas, there are four Analysis Centers that process the data collected from satellites of the Global Navigation Satellite Systems (GNSS, with the primary purpose to maintain the international terrestrial reference frame through calculation of the coordinates and velocities of the continuous GNSS stations of the SIRGAS-CON Network.
In this work, we demonstrate the quality of the solutions from CIMA, one of the SIRGAS official processing centers operating in Mendoza, Argentina, in comparison with other South American processing centers. The importance of precise calculations of coordinates and velocities in a global frame is also shown. Finally, we give estimations of velocities from stations located within deformation zones in the Central Andes.
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
Vasquez, Juan Carlos; Guerrero, Josep M.; Savaghebi, Mehdi;
2011-01-01
the VSIs were based on the stationary reference frame. A hierarchical control for the paralleled VSI system was developed based on three levels. The primary control includes the droop method and the virtual impedance loops, in order to share active and reactive power. The secondary control restores...... the frequency and amplitude deviations produced by the primary control. And the tertiary control regulates the power flow between the grid and the microgrid. Also, a synchronization algorithm is presented in order to connect the microgrid to the grid. The evaluation of the hierarchical control is......-grid interactivity, and to manage power flows between the main grid and the VSIs....
Fixing the Reference Frame for PPMXL Proper Motions Using Extragalactic Sources
Grabowski, Kathleen; Newberg, Heidi Jo; Beers, Timothy C; Chen, Li; Deng, Licai; Grillmair, Carl J; Guhathakurta, Puragra; Hou, Jinliang; Lepine, Sebastien; Liu, Chao; Liu, Xiaowei; Luo, A-Li; Smith, Martin C; Yanny, Brian; Zhang, Haotong; Zheng, Zheng
2014-01-01
We quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Veron-Cetty & Veron Catalog of Quasars. Although the majority of the sources are from the Veron catalog, LAMOST makes important contributions in regions that are not well-sampled by previous catalogs, particularly at low Galactic latitudes and in the south Galactic cap. We show that quasars in PPMXL have measureable and significant proper motions, which reflect the systematic zero-point offsets present in the catalog. We confirm the global proper motion shifts seen by Wu, Ma, & Zhou (2011), and additionally find smaller-scale fluctuations of the QSO-derived corrections to an absolute frame. We average the proper motions of 158,106 extragalactic objects in bins of 3x3 degrees and present a table of proper motion corrections.
de Abreu, Rodrigo
2002-01-01
We begin by admitting the following: (i) there is a frame of reference where the speed of light is the same in any direction (that speed is c) (ii) the average speed of light on a two-way journey is c in every frame of reference. From this two premises we obtain an expression for the speed of light which implies the speed of light depends on the motion of the frame of reference. Also from this two premises solely we deduct Lorentz Transformation.
Stephan eEhrenfeld
2013-10-01
Full Text Available This paper addresses the question of how the brain may maintain 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 overal 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.
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
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 230Th/234U 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. - Highlights: • A methodology for preparing uranium age dating reference material was validated. • Detailed laboratory procedures for uranium age dating are summarized. • The difficulties and further developments of uranium age dating are demonstrated
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.
Sami Chalhoub
2009-12-01
Full Text Available Various astronomy subjects arose from scientific, social, and religious circumstances which were ruling in Islamic Arabic Civilized Age. These circumstances played basic role in directing this science and branching it into suitable branches. One of the plenty subjects which this science discuss it in Islamic, Arabic civilization is planet figure science which describe celestial figure and pinpoint the location of stars in length and width. The importance of this research comes out that it will study the relation between this branch of astrology's branches and astronomy through studying celestial figures in sign of the zodiac in the Comprehensive Reference to Rules in Ibn Hibinta's Manuscript of Astrology (Al-Mughni Fi Ahkam Al- Nujum to support studied Arabic astrological texts which is till nowadays still very few.
Hilderley, Alicia J; Leonard, Julia A; Green, Andrea; Ouckama, Ryan; Stapley, Paul J
2015-01-01
We investigated whether target position relative to the body modifies the postural adjustments produced when reaching movements are perturbed by unexpected displacements of the support surface. Eleven healthy participants reached to a target located at their midline, acromion height and at 130% their outstretched arm length. They stood on two force plates mounted on a moveable platform, capable of delivering horizontal forward ramp-and-hold perturbations. Three types of trial were given: reach only (R), perturbations only (P) and reaching movements during which a perturbation was given at a random delay after reach onset (RP). The target could be mounted either on a frame suspended from the ceiling such that it remained world-fixed (exocentric target, RP/X) or at an equivalent position on the moving platform so that it moved with the body (egocentric target, RP/E). Arm and body 3D kinematics and muscle activity from the right tibialis anterior (rTA) and soleus (rSOL) muscles were recorded. Normalised rTA activity was significantly lower in RP than in P trials. Furthermore, long-latency rTA muscle activity was lower in RP/E than in RP/X conditions when perturbations were given during either the arm deceleration phase of reaching. The rSOL muscle activity was lowest for the RP/E (arm deceleration) condition. When balance is perturbed during reaching, the manner in which the target moves relative to the body determines the muscle activity produced in the lower-limb muscles. Furthermore, a target that moves with the body requires a different regulation of muscle activity compared with one that moves independently of the body. PMID:25294498
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
Celestial navigation in a nutshell
Schlereth, Hewitt
2000-01-01
Celestial Navigation in a Nutshell demonstrates how to take sights by the sun, moon, stars, and planets, discussing the advantages and disadvantages of each method. The reader is taken carefully through several examples and situational illustrations, making this a most effective self-teaching guide. Common errors are reviewed and several tips on how to improve accuracy are given.
Celestial mechanics with geometric algebra
Hestenes, D.
1983-01-01
Geometric algebra is introduced as a general tool for Celestial Mechanics. A general method for handling finite rotations and rotational kinematics is presented. The constants of Kepler motion are derived and manipulated in a new way. A new spinor formulation of perturbation theory is developed.
From Work to Frame in Intermedial References: Joseph Beuys in Three Contemporary German Poems
Noël Reumkens
2009-07-01
Full Text Available Dans cet article, nous nous interrogeons sur ce qui se produit dans les textes littéraires se référant aux œuvres des arts visuels, qui en premier ressort ne sont pas visuels mais plutôt conceptuels et abstraits. L’œuvre conceptuelle de l’artiste allemand Joseph Beuys (1921-1986 s’appuie sur un cadre conceptuel résumé par le terme de “sculpture sociale”. Notre but est de rechercher comment trois poètes allemands contemporains, Thomas Kling, Durs Grünbein et Ulrike Draesner se rapprochent de cette “sculpture sociale” dans leurs poèmes.This article deals with about what happens in literary texts that refer to visual art works, that in the first place are not visual but rather conceptual and abstract. The conceptual work of the German artist Joseph Beuys (1921-1986 is founded on a conceptual framework that can be summed up under the term “social sculpture”. It is our goal to research exactly how three German contemporary poets, Thomas Kling, Durs Grünbein and Ulrike Draesner approach this “social sculpture” in their poems.En este artículo nos planteamos la cuestión de saber qué sucede con los textos literarios que remiten a obras de artes visuales que en primera instancia no son visuales, sino no más bien conceptuales y abstractos. La obra conceptual del artista alemán José Beuys (1921-1986 se fundamente en un marco conceptual sintetizado con el término de "escultura social ". Nuestro fin es ver cómo tres poetas alemanes contemporáneos, Thomás Kling, Durs Grünbein y Ulrike Draesner, se enfrentan en sus poemas a esta "escultura social".
Adjoint-Based Design of Rotors Using the Navier-Stokes Equations in a Noninertial Reference Frame
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.