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Sample records for 3d reference frame

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

    PubMed Central

    van Doorn, Andrea J.; Wagemans, Johan

    2016-01-01

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

  2. Development and reproducibility of a 3D stereophotogrammetric reference frame for facial soft tissue growth of babies and young children with and without orofacial clefts.

    PubMed

    Brons, S; van Beusichem, M E; Maal, T J J; Plooij, J M; Bronkhorst, E M; Bergé, S J; Kuijpers-Jagtman, A M

    2013-01-01

    The aim of this study was to develop a reference frame for three dimensional (3D) facial soft tissue growth analysis in children and to determine its reproducibility. Two observers twice placed the reference frame on 39 3D-stereophotogrammetry facial images of children with orofacial clefts and control children. The observers' performances were analyzed by calculating mean distance, distance variability, and P95 between the same facial surfaces at two different time points. Correlations between observers were analyzed with Pearson's correlation coefficient. The influence of presence of a cleft, absence of one ear in the photograph, and age on the reproducibility of the reference frame was checked using Student's t test. Results of intraobserver comparisons showed a mean distance of <0.40 mm, distance variability of <0.51 mm, and P95 of <0.80 mm. For interobserver reliability, the mean distance was <0.52 mm, distance variability was <0.53 mm, and P95 was <1.10 mm. Presence of a cleft, age, and absence of one ear on the 3D photograph did not have a significant influence on the reproducibility of placing the reference frame. The children's reference frame is a reproducible method to superimpose on 3D soft tissue stereophotogrammetry photographs of growing individuals with and without orofacial clefts.

  3. Mixed Body/Hand Reference Frame for Reaching in 3D Space in Macaque Parietal Area PEc.

    PubMed

    Piserchia, Valentina; Breveglieri, Rossella; Hadjidimitrakis, Kostas; Bertozzi, Federica; Galletti, Claudio; Fattori, Patrizia

    2017-03-01

    The neural correlates of coordinate transformations from vision to action are expressed in the activity of posterior parietal cortex (PPC). It has been demonstrated that among the medial-most areas of the PPC, reaching targets are represented mainly in hand-centered coordinates in area PE, and in eye-centered, body-centered, and mixed body/hand-centered coordinates in area V6A. Here, we assessed whether neurons of area PEc, located between V6A and PE in the medial PPC, encode targets in body-centered, hand-centered, or mixed frame of reference during planning and execution of reaching. We studied 104 PEc cells in 3 Macaca fascicularis. The animals performed a reaching task toward foveated targets located at different depths and directions in darkness, starting with the hand from 2 positions located at different depths, one next to the trunk and the other far from it. We show that most PEc neurons encoded targets in a mixed body/hand-centered frame of reference. Although the effect of hand position was often rather strong, it was not as strong as reported previously in area PE. Our results suggest that area PEc represents an intermediate node in the gradual transformation from vision to action that takes place in the reaching network of the dorsomedial PPC. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  4. Reference Frames and Relativity.

    ERIC Educational Resources Information Center

    Swartz, Clifford

    1989-01-01

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

  5. Reference Frames and Relativity.

    ERIC Educational Resources Information Center

    Swartz, Clifford

    1989-01-01

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

  6. Reliable measurement of 3D foot bone angles based on the frame-of-reference derived from a sole of the foot

    NASA Astrophysics Data System (ADS)

    Kim, Taeho; Lee, Dong Yeon; Park, Jinah

    2016-03-01

    Clinical management of foot pathology requires accurate and robust measurement of the anatomical angles. In order to measure a 3D angle, recent approaches have adopted a landmark-based local coordinate system to establish bone angles used in orthopedics. These measurement methods mainly assess the relative angle between bones using a representative axis derived from the morphological feature of the bone and therefore, the results can be affected by bone deformities. In this study, we propose a method of deriving a global frame-of-reference to acquire consistent direction of the foot by extracting the undersurface of the foot from the CT image data. The two lowest positions of the foot skin are identified from the surface to define the base plane, and the direction from the hallux to the fourth toe is defined together to construct the global coordinate system. We performed the experiment on 10 volumes of foot CT images of healthy subjects to verify that the proposed method provides reliable measurements. We measured 3D angles for talus-calcaneus and talus-navicular using facing articular surfaces of paired bones. The angle was reported in 3 projection angles based on both coordinate systems defined by proposed global frame-of-reference and by CT image planes (saggital, frontal, and transverse). The result shows that the quantified angle using the proposed method considerably reduced the standard deviation (SD) against the angle using the conventional projection planes, and it was also comparable with the measured angles obtained from local coordinate systems of the bones. Since our method is independent from any individual local shape of a bone, unlike the measurement method using the local coordinate system, it is suitable for inter-subject comparison studies.

  7. The accuracy of 3D image navigation with a cutaneously fixed dynamic reference frame in minimally invasive transforaminal lumbar interbody fusion.

    PubMed

    Cho, Ji Young; Chan, Chee Keong; Lee, Sang-Ho; Lee, Ho-Yeon

    2012-01-01

    In contrast to preoperative image-based 3D navigation systems, which require surgeon-dependent registration, an intraoperative cone-beam computed tomography (cb-CT) image-based 3D navigation system allows automatic registration during the acquisition of 3D images intraoperatively. Thus, the need for spinal exposure for point matching is obviated, making a cb-CT image-based navigation system ideal for use in minimally invasive spinal procedures. Conventionally, the dynamic reference frame (DRF) is mounted to an adjacent spinous process or iliac bone through a separate incision. However, the close proximity of the DRF to the surgical area may result in its interfering with the surgical procedure or causing streak artifacts on the navigation images. Cutaneous placement of the DRF overlying the sacral hiatus is one possible solution to these problems, but such a placement does not provide a solid bony fixation point and is distant from the surgical area, both of which factors may hinder the accuracy of the navigation. The purpose of this study was to evaluate the accuracy of a novel idea for DRF placement in a series of mini-open transforaminal lumbar interbody fusion (TLIF) procedures performed with intraoperative cb-CT image-based 3D navigation. From June 2009 to December 2009, 20 patients underwent mini-open TLIF for a total 82 pedicle screws placed in the lumbar spine with cutaneous placement of the DRF overlying the sacral hiatus. The pedicle screws were inserted under navigational guidance using cb-CT data acquired intraoperatively with a Medtronic O-arm. Screw positions were subsequently checked with a final intraoperative cb-CT scan. Nineteen patients underwent single-level fusion (8 at L4-5, 6 at L5-S1, 4 at L3-4, and 1 at L2-3) and one patient underwent two-level fusion (from L3-5). There were 4 (4.9%) pedicle perforations greater than 2 mm out of the 82 pedicle screw insertions in the 20 patients. Two of these breached screws were repositioned and

  8. Celestial Reference Frames

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.

    2013-03-01

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

  9. Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.

    2013-09-01

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

  10. Frames-Based Denoising in 3D Confocal Microscopy Imaging.

    PubMed

    Konstantinidis, Ioannis; Santamaria-Pang, Alberto; Kakadiaris, Ioannis

    2005-01-01

    In this paper, we propose a novel denoising method for 3D confocal microscopy data based on robust edge detection. Our approach relies on the construction of a non-separable frame system in 3D that incorporates the Sobel operator in dual spatial directions. This multidirectional set of digital filters is capable of robustly detecting edge information by ensemble thresholding of the filtered data. We demonstrate the application of our method to both synthetic and real confocal microscopy data by comparing it to denoising methods based on separable 3D wavelets and 3D median filtering, and report very encouraging results.

  11. 3D Frame Buffers For Interactive Analysis Of 3D Data

    NASA Astrophysics Data System (ADS)

    Hunter, Gregory M.

    1984-10-01

    Two-dimensional data such as photos, X rays, various types of satellite images, sonar, radar, seismic plots, etc., in many cases must be analyzed using frame buffers for purposes of medical diagnoses, crop estimates, mineral exploration, and so forth. In many cases the same types of sensors used to gather such samples in two dimensions can gather 3D data for even more effective analysis. Just as 2D arrays of data can be analyzed using frame buffers, three-dimensional data can be analyzed using SOLIDS-BUFFEPmemories. Image processors deal with samples from two-dimensional arrays, and are based on frame buffers. The SOLIDS PROCESSOR system, deals with samples from a three-dimensional volume, or solid, and is based on a 3D frame buffer. This paper focuses upon the SOLIDS-BUFFER system, as used in the INSIGHT SOLIDS-PROCESSOR system from Phoenix Data Systems.

  12. 3D Face Hallucination from a Single Depth Frame

    PubMed Central

    Liang, Shu; Kemelmacher-Shlizerman, Ira; Shapiro, Linda G.

    2015-01-01

    We present an algorithm that takes a single frame of a person’s face from a depth camera, e.g., Kinect, and produces a high-resolution 3D mesh of the input face. We leverage a dataset of 3D face meshes of 1204 distinct individuals ranging from age 3 to 40, captured in a neutral expression. We divide the input depth frame into semantically significant regions (eyes, nose, mouth, cheeks) and search the database for the best matching shape per region. We further combine the input depth frame with the matched database shapes into a single mesh that results in a highresolution shape of the input person. Our system is fully automatic and uses only depth data for matching, making it invariant to imaging conditions. We evaluate our results using ground truth shapes, as well as compare to state-of-the-art shape estimation methods. We demonstrate the robustness of our local matching approach with high-quality reconstruction of faces that fall outside of the dataset span, e.g., faces older than 40 years old, facial expressions, and different ethnicities. PMID:26280021

  13. The 3D Reference Earth Model (REM-3D): Update and Outlook

    NASA Astrophysics Data System (ADS)

    Lekic, V.; Moulik, P.; Romanowicz, B. A.; Dziewonski, A. M.

    2016-12-01

    Elastic properties of the Earth's interior (e.g. density, rigidity, compressibility, anisotropy) vary spatially due to changes in temperature, pressure, composition, and flow. In the 20th century, seismologists have constructed reference models of how these quantities vary with depth, notably the PREM model of Dziewonski and Anderson (1981). These 1D reference earth models have proven indispensable in earthquake location, imaging of interior structure, understanding material properties under extreme conditions, and as a reference in other fields, such as particle physics and astronomy. Over the past three decades, more sophisticated efforts by seismologists have yielded several generations of models of how properties vary not only with depth, but also laterally. Yet, though these three-dimensional (3D) models exhibit compelling similarities at large scales, differences in the methodology, representation of structure, and dataset upon which they are based, have prevented the creation of 3D community reference models. We propose to overcome these challenges by compiling, reconciling, and distributing a long period (>15 s) reference seismic dataset, from which we will construct a 3D seismic reference model (REM-3D) for the Earth's mantle, which will come in two flavors: a long wavelength smoothly parameterized model and a set of regional profiles. Here, we summarize progress made in the construction of the reference long period dataset, and present preliminary versions of the REM-3D in order to illustrate the two flavors of REM-3D and their relative advantages and disadvantages. As a community reference model and with fully quantified uncertainties and tradeoffs, REM-3D will facilitate Earth imaging studies, earthquake characterization, inferences on temperature and composition in the deep interior, and be of improved utility to emerging scientific endeavors, such as neutrino geoscience. In this presentation, we outline the outlook for setting up advisory community

  14. Astrophysics of Reference Frame Tie Objects

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  15. Frames of Reference in the Classroom

    ERIC Educational Resources Information Center

    Grossman, Joshua

    2012-01-01

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

  16. Frames of Reference in the Classroom

    ERIC Educational Resources Information Center

    Grossman, Joshua

    2012-01-01

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

  17. KB3D Reference Manual. Version 1.a

    NASA Technical Reports Server (NTRS)

    Munoz, Cesar; Siminiceanu, Radu; Carreno, Victor A.; Dowek, Gilles

    2005-01-01

    This paper is a reference manual describing the implementation of the KB3D conflict detection and resolution algorithm. The algorithm has been implemented in the Java and C++ programming languages. The reference manual gives a short overview of the detection and resolution functions, the structural implementation of the program, inputs and outputs to the program, and describes how the program is used. Inputs to the program can be rectangular coordinates or geodesic coordinates. The reference manual also gives examples of conflict scenarios and the resolution outputs the program produces.

  18. The Effect of Frame Rate on 3D Video Quality and Bitrate

    NASA Astrophysics Data System (ADS)

    Banitalebi-Dehkordi, Amin; Pourazad, Mahsa T.; Nasiopoulos, Panos

    2015-03-01

    Increasing the frame rate of a 3D video generally results in improved Quality of Experience (QoE). However, higher frame rates involve a higher degree of complexity in capturing, transmission, storage, and display. The question that arises here is what frame rate guarantees high viewing quality of experience given the existing/required 3D devices and technologies (3D cameras, 3D TVs, compression, transmission bandwidth, and storage capacity). This question has already been addressed for the case of 2D video, but not for 3D. The objective of this paper is to study the relationship between 3D quality and bitrate at different frame rates. Our performance evaluations show that increasing the frame rate of 3D videos beyond 60 fps may not be visually distinguishable. In addition, our experiments show that when the available bandwidth is reduced, the highest possible 3D quality of experience can be achieved by adjusting (decreasing) the frame rate instead of increasing the compression ratio. The results of our study are of particular interest to network providers for rate adaptation in variable bitrate channels.

  19. Functional influences on orienting a reference frame.

    PubMed

    Carlson-Radvansky, L A; Tang, Z

    2000-07-01

    Spatial relational terms like above are defined with respect to a reference frame. Reference frames are imposed on reference objects and define the space in which to search for a located object. Reference frames have a number of parameters that must be set during spatial term assignment, including origin, scale, and orientation. Previous research has shown that a functional relationship between objects in the scene influences the selection of a reference frame (Carlson-Radvansky & Radvansky, 1996). However, because this work operated at the level of the reference frame, generalizing across various spatial terms, it is unclear how function had its influence. One possibility is that function influences how the parameters of a reference frame are set. Consistent with this idea, Carlson-Radvansky, Covey, and Lattanzi (1999) showed an influence of function on where the origin of a reference frame was imposed. The present paper demonstrates that function also influences how the orientation of the axes of a reference frame is set. The implications for setting multiple parameters of a reference frame are discussed.

  20. Handheld camera 3D modeling system using multiple reference panels

    NASA Astrophysics Data System (ADS)

    Fujimura, Kouta; Oue, Yasuhiro; Terauchi, Tomoya; Emi, Tetsuichi

    2002-03-01

    A novel 3D modeling system in which a target object is easily captured and modeled by using a hand-held camera with several reference panels is presented in this paper. The reference panels are designed to be able to obtain the camera position and discriminate between each other. A conventional 3D modeling system using a reference panel has several restrictions regarding the target object, specifically the size and its location. Our system uses multiple reference panels, which are set around the target object to remove these restrictions. The main features of this system are as follows: 1) The whole shape and photo-realistic textures of the target object can be digitized based on several still images or a movie captured by using a hand-held camera; as well as each location of the camera that can be calculated using the reference panels. 2) Our system can be provided as a software product only. That means there are no special requirements for hardware; even the reference panels , because they can be printed from image files or software. 3) This system can be applied to digitize a larger object. In the experiments, we developed and used an interactive region selection tool to detect the silhouette on each image instead of using the chroma -keying method. We have tested our system with a toy object. The calculation time is about 10 minutes (except for the capturing the images and extracting the silhouette by using our tool) on a personal computer with a Pentium-III processor (600MHz) and 320MB memory. However, it depends on how complex the images are and how many images you use. Our future plan is to evaluate the system with various kind of objects, specifically, large ones in outdoor environments.

  1. Mechanical Energy Change in Inertial Reference Frames

    ERIC Educational Resources Information Center

    Ghanbari, Saeed

    2016-01-01

    The mechanical energy change of a system in an inertial frame of reference equals work done by the total nonconservative force in the same frame. This relation is covariant under the Galilean transformations from inertial frame S to S', where S' moves with constant velocity relative to S. In the presence of nonconservative forces, such as normal…

  2. Mechanical Energy Change in Inertial Reference Frames

    ERIC Educational Resources Information Center

    Ghanbari, Saeed

    2016-01-01

    The mechanical energy change of a system in an inertial frame of reference equals work done by the total nonconservative force in the same frame. This relation is covariant under the Galilean transformations from inertial frame S to S', where S' moves with constant velocity relative to S. In the presence of nonconservative forces, such as normal…

  3. Independent Study Unit on Accelerated Reference Frames

    ERIC Educational Resources Information Center

    Poultney, S. K.

    1973-01-01

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

  4. Spatial Reference Frame of Incidentally Learned Attention

    ERIC Educational Resources Information Center

    Jiang, Yuhong V.; Swallow, Khena M.

    2013-01-01

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

  5. Space VLBI and the Radio Reference Frame

    NASA Astrophysics Data System (ADS)

    Charlot, P.

    2009-08-01

    The current radio reference frame is defined by the VLBI positions of several hundreds of extragalactic sources measured with sub-milliarcsecond accuracy. We discuss whether space VLBI can be used to improve the accuracy of the frame, either directly by conducting absolute astrometric observations using space VLBI baselines, or in an indirect way by making available VLBI images of the reference frame sources with increased angular resolution. The VSOP-2 project, in its present state, is found to have the necessary capabilities for accurate absolute astrometry although there may be limitations due to scheduling constraints. Space VLBI images are essential for pinpointing accurately a stable reference feature within the extended structure of each source. In this respect, the VSOP-2 project may have a significant impact on the definition of the radio reference frame if targeting such reference frame sources on a regular basis.

  6. Concepts in Geodetic Reference Frames.

    DTIC Science & Technology

    1979-10-01

    Heiskanen and Moritz, 1967, sec. 2-21). However, such an empirically determined mean earth ellipsoid would not be suitable as a reference ellipsoid...magnitude of V/c 2 ? The gravity potential W at the surface of the earth is approximately W = 6.3 x 107 mIs - Z cf. the value U0 given in ( Heiskanen and...addition theorem for Legendre polynomials ( Heiskanen and Moritz, 1967, p. 33) gives Pz (cos z) = Pz (cosW) P2 (cos 8) + + l/3[R1 (6, hG)R,(e.) + s21(6, hG

  7. Realizing a terrestrial reference frame using the Global Positioning System

    NASA Astrophysics Data System (ADS)

    Haines, Bruce J.; Bar-Sever, Yoaz E.; Bertiger, Willy I.; Desai, Shailen D.; Harvey, Nate; Sibois, Aurore E.; Weiss, Jan P.

    2015-08-01

    We describe a terrestrial reference frame (TRF) realization based on Global Positioning System (GPS) data alone. Our approach rests on a highly dynamic, long-arc (9 day) estimation strategy and on GPS satellite antenna calibrations derived from Gravity Recovery and Climate Experiment and TOPEX/Poseidon low Earth orbit receiver GPS data. Based on nearly 17 years of data (1997-2013), our solution for scale rate agrees with International Terrestrial Reference Frame (ITRF)2008 to 0.03 ppb yr-1, and our solution for 3-D origin rate agrees with ITRF2008 to 0.4 mm yr-1. Absolute scale differs by 1.1 ppb (7 mm at the Earth's surface) and 3-D origin by 8 mm. These differences lie within estimated error levels for the contemporary TRF.

  8. Diffeomorphic Multi-Frame Non-Rigid Registration of Cell Nuclei in 2D and 3D Live Cell Images.

    PubMed

    Tektonidis, Marco; Rohr, Karl

    2017-03-01

    To gain a better understanding of cellular and molecular processes, it is important to quantitatively analyze the motion of subcellular particles in live cell microscopy image sequences. Since, generally, the subcellular particles move and cell nuclei move as well as deform, it is important to decouple the movement of particles from that of the cell nuclei using non-rigid registration methods. We have developed a diffeomorphic multi-frame approach for non-rigid registration of cell nuclei in 2D and 3D live cell fluorescence microscopy images. Our non-rigid registration approach is based on local optic flow estimation, exploits information from multiple consecutive image frames, and determines diffeomorphic transformations in the log-domain, which allows efficient computation of the inverse transformations. To register single images of an image sequence to a reference image, we use a temporally weighted mean image, which is constructed based on inverse transformations and multiple consecutive frames. Using multiple consecutive frames improves the registration accuracy compared to pairwise registration, and using a temporally weighted mean image significantly reduces the computation time compared with previous work. In addition, we use a flow boundary preserving method for regularization of computed deformation vector fields, which prevents from over-smoothing compared to standard Gaussian filtering. Our approach has been successfully applied to 2D and 3D synthetic as well as real live cell microscopy image sequences, and an experimental comparison with non-rigid pairwise, multi-frame, and temporal groupwise registration has been carried out.

  9. Physics of Non-Inertial Reference Frames

    SciTech Connect

    Kamalov, Timur F.

    2010-12-22

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

  10. Lorentz boosted frame simulation of Laser wakefield acceleration in quasi-3D geometry

    NASA Astrophysics Data System (ADS)

    Yu, Peicheng; Xu, Xinlu; Davidson, Asher; Tableman, Adam; Meyers, Michael; Dalichaouch, Thamine; Tsung, Frank; Decyk, Viktor; Fiuza, Frederico; Vieira, Jorge; Fonseca, Ricardo; Lu, Wei; Silva, Luis; Mori, Warren

    2015-11-01

    We present results on a systematic study of Particle-In-Cell simulation of Laser Wakefield Acceleration (LWFA) by combining the Lorentz boosted frame technique with the quasi-3D algorithm, in which fields are expanded into azimuthal harmonics and solved on an r - z PIC grid keeping only a few harmonics. The studies emphasize on LWFA in the nonlinear blowout regime, which is more challenging from a computational standpoint. We first discuss strategies for eliminating the numerical Cerenkov instability (NCI) that inevitably arises due to the presence of plasma drifting across the grid with relativistic speeds in quasi-3D geometry. These strategies work for FFT based Maxwell solvers. We have incorporated these mitigation strategies into our PIC code OSIRIS by adding a new hybrid Yee-FFT Maxwell solver. With these strategies, OSIRIS can now be used to combine the quasi-3D algorithm and Lorentz boosted frame technique, and carry out high fidelity LWFA boosted frame simulation with no evidence of the NCI in the quasi-3D geometry, leading to unprecedented speedups. Work supported by NSF and DOE.

  11. A 3D radiative transfer framework . VII. Arbitrary velocity fields in the Eulerian frame

    NASA Astrophysics Data System (ADS)

    Seelmann, A. M.; Hauschildt, P. H.; Baron, E.

    2010-11-01

    Aims: A solution of the radiative-transfer problem in 3D with arbitrary velocity fields in the Eulerian frame is presented. The method is implemented in our 3D radiative transfer framework and used in the PHOENIX/3D code. It is tested by comparison to our well-tested 1D co-moving frame radiative transfer code, where the treatment of a monotonic velocity field is implemented in the Lagrangian frame. The Eulerian formulation does not need much additional memory and is useable on state-of-the-art computers, even large-scale applications with 1000's of wavelength points are feasible. Methods: In the Eulerian formulation of the problem, the photon is seen by the atom at a Doppler-shifted wavelength depending on its propagation direction, which leads to a Doppler-shifted absorption and emission. This leads to a different source function and a different Λ^* operator in the radiative transfer equations compared to the static case. Results: The results of the Eulerian 3D spherical calculations are compared to our well-tested 1D Lagrangian spherical calculations, the agreement is, up to vmax = 1 × 103 km s-1 very good. Test calculation in other geometries are also shown.

  12. Ray Effect Mitigation Through Reference Frame Rotation

    DOE PAGES

    Tencer, John

    2016-05-01

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

  13. Ray Effect Mitigation Through Reference Frame Rotation

    SciTech Connect

    Tencer, John

    2016-05-01

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

  14. Celestial Reference Frames at Multiple Radio Wavelengths

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.

    2012-01-01

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

  15. Multiple reference frames in haptic spatial processing

    NASA Astrophysics Data System (ADS)

    Volčič, R.

    2008-08-01

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

  16. Global analyses of historical masonry buildings: Equivalent frame vs. 3D solid models

    NASA Astrophysics Data System (ADS)

    Clementi, Francesco; Mezzapelle, Pardo Antonio; Cocchi, Gianmichele; Lenci, Stefano

    2017-07-01

    The paper analyses the seismic vulnerability of two different masonry buildings. It provides both an advanced 3D modelling with solid elements and an equivalent frame modelling. The global structural behaviour and the dynamic properties of the compound have been evaluated using the Finite Element Modelling (FEM) technique, where the nonlinear behaviour of masonry has been taken into account by proper constitutive assumptions. A sensitivity analysis is done to evaluate the effect of the choice of the structural models.

  17. On Translators' Cultural Frame of Functionist Reference

    ERIC Educational Resources Information Center

    Fu, Zhiyi

    2009-01-01

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

  18. Cultural background shapes spatial reference frame proclivity

    PubMed Central

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

    2015-01-01

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

  19. A semi-automatic 2D-to-3D video conversion with adaptive key-frame selection

    NASA Astrophysics Data System (ADS)

    Ju, Kuanyu; Xiong, Hongkai

    2014-11-01

    To compensate the deficit of 3D content, 2D to 3D video conversion (2D-to-3D) has recently attracted more attention from both industrial and academic communities. The semi-automatic 2D-to-3D conversion which estimates corresponding depth of non-key-frames through key-frames is more desirable owing to its advantage of balancing labor cost and 3D effects. The location of key-frames plays a role on quality of depth propagation. This paper proposes a semi-automatic 2D-to-3D scheme with adaptive key-frame selection to keep temporal continuity more reliable and reduce the depth propagation errors caused by occlusion. The potential key-frames would be localized in terms of clustered color variation and motion intensity. The distance of key-frame interval is also taken into account to keep the accumulated propagation errors under control and guarantee minimal user interaction. Once their depth maps are aligned with user interaction, the non-key-frames depth maps would be automatically propagated by shifted bilateral filtering. Considering that depth of objects may change due to the objects motion or camera zoom in/out effect, a bi-directional depth propagation scheme is adopted where a non-key frame is interpolated from two adjacent key frames. The experimental results show that the proposed scheme has better performance than existing 2D-to-3D scheme with fixed key-frame interval.

  20. Dense 3D Reconstruction from High Frame-Rate Video Using a Static Grid Pattern.

    PubMed

    Sagawa, Ryusuke; Furukawa, Ryo; Kawasaki, Hiroshi

    2014-09-01

    Dense 3D reconstruction of fast moving objects could contribute to various applications such as body structure analysis, accident avoidance, and so on. In this paper, we propose a technique based on a one-shot scanning method, which reconstructs 3D shapes for each frame of a high frame-rate video capturing the scenes projected by a static pattern. To avoid instability of image processing, we restrict the number of colors used in the pattern to less than two. The proposed technique comprises (1) an efficient algorithm to eliminate ambiguity of projected parallel-line patterns by using intersection points, (2) a batch reconstruction algorithm of multiple frames by using spatio-temporal constraints, and (3) an efficient detection method of color-encoded grid pattern based on de Bruijn sequence. In the experiments, the line detection algorithm worked effectively and the dense reconstruction algorithm produces accurate and robust results. We also show the improved results by using temporal constraints. Finally, the dense reconstructions of fast moving objects in a high frame-rate video are presented.

  1. Frames of Reference in the Classroom

    NASA Astrophysics Data System (ADS)

    Grossman, Joshua

    2012-12-01

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

  2. Double-frame 3D-PTV using a tomographic predictor

    NASA Astrophysics Data System (ADS)

    Fuchs, Thomas; Hain, Rainer; Kähler, Christian J.

    2016-11-01

    Thanks to the technological progress, 3D velocimetry techniques are becoming more popular. In particular, the time-resolved flow analysis by means of particle tracking is very attractive. Compared to double-frame recordings, higher seeding concentrations are feasible, yielding high spatial resolution results without bias errors due to strong velocity gradients. However, hardware restrictions still limit time-resolved measurements to rather small flow velocities and low magnifications. In aerodynamics, especially, this is a drawback, since often higher flow velocities are of interest. To conduct reliable 3D-PTV measurements from double-frame recordings, the well-established techniques tomographic particle imaging and 3D-PTV are employed for a novel processing approach. In this combined approach, the tomographic reconstruction is used as a predictor for the sensor locations of the corresponding particle images of the reconstructed particles. Furthermore, the reconstruction helps to identify and reject non-corresponding sets of particle images, reducing the amount of ghost particles to a minimum. A probabilistic tracking algorithm is then applied to estimate the flow field.

  3. URAT and the celestial reference frame

    NASA Astrophysics Data System (ADS)

    Zacharias, Norbert

    2015-08-01

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

  4. Experimental bilocality violation without shared reference frames

    NASA Astrophysics Data System (ADS)

    Andreoli, Francesco; Carvacho, Gonzalo; Santodonato, Luca; Bentivegna, Marco; Chaves, Rafael; Sciarrino, Fabio

    2017-06-01

    Nonclassical correlations arising in complex quantum networks are attracting growing interest, both from a fundamental perspective and for potential applications in information processing. In particular, in an entanglement swapping scenario a new kind of correlations arise, the so-called nonbilocal correlations that are incompatible with local realism augmented with the assumption that the sources of states used in the experiment are independent. In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to the presence of shared reference frames between the parties. Here, we experimentally address this point showing that false positive nonbilocal quantum correlations can be observed even though the sources of states are independent. To overcome this problem, we propose and demonstrate a scheme for the violation of bilocality that does not require shared reference frames and thus constitutes an important building block for future investigations of quantum correlations in complex networks.

  5. Seismic Response of 3D Steel Buildings considering the Effect of PR Connections and Gravity Frames

    PubMed Central

    Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J. Luz

    2014-01-01

    The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system. PMID:24995357

  6. Seismic response of 3D steel buildings considering the effect of PR connections and gravity frames.

    PubMed

    Reyes-Salazar, Alfredo; Bojórquez, Edén; Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J Luz

    2014-01-01

    The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system.

  7. Frames of reference in spatial language acquisition.

    PubMed

    Shusterman, Anna; Li, Peggy

    2016-08-01

    Languages differ in how they encode spatial frames of reference. It is unknown how children acquire the particular frame-of-reference terms in their language (e.g., left/right, north/south). The present paper uses a word-learning paradigm to investigate 4-year-old English-speaking children's acquisition of such terms. In Part I, with five experiments, we contrasted children's acquisition of novel word pairs meaning left-right and north-south to examine their initial hypotheses and the relative ease of learning the meanings of these terms. Children interpreted ambiguous spatial terms as having environment-based meanings akin to north and south, and they readily learned and generalized north-south meanings. These studies provide the first direct evidence that children invoke geocentric representations in spatial language acquisition. However, the studies leave unanswered how children ultimately acquire "left" and "right." In Part II, with three more experiments, we investigated why children struggle to master body-based frame-of-reference words. Children successfully learned "left" and "right" when the novel words were systematically introduced on their own bodies and extended these words to novel (intrinsic and relative) uses; however, they had difficulty learning to talk about the left and right sides of a doll. This difficulty was paralleled in identifying the left and right sides of the doll in a non-linguistic memory task. In contrast, children had no difficulties learning to label the front and back sides of a doll. These studies begin to paint a detailed account of the acquisition of spatial terms in English, and provide insights into the origins of diverse spatial reference frames in the world's languages. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  8. Time Contraction Within Lightweight Reference Frames

    NASA Astrophysics Data System (ADS)

    Savi, Matheus F.; Angelo, Renato M.

    2017-06-01

    The special theory of relativity teaches us that, although distinct inertial frames perceive the same dynamical laws, space and time intervals differ in value. We revisit the problem of time contraction using the paradigmatic model of a fast-moving laboratory within which a photon is emitted and posteriorly absorbed. In our model, however, the laboratory is composed of two independent parallel plates, each of which allowed to be sufficiently light so as to get kickbacks upon emission and absorption of light. We show that the lightness of the laboratory accentuates the time contraction. We also discuss how the photon frequency shifts upon reflection in a light moving mirror. Although often imperceptible, these effects will inevitably exist whenever realistic finite-mass bodies are involved. More fundamentally, they should necessarily permeate any eventual approach to the problem of relativistic quantum frames of reference.

  9. The celestial reference frame defined by VLBI

    NASA Technical Reports Server (NTRS)

    Ma, C.; Shaffer, D. B.

    1988-01-01

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

  10. Fabrication of Orientation-Controlled 3D Tissues Using a Layer-by-Layer Technique and 3D Printed a Thermoresponsive Gel Frame.

    PubMed

    Tsukamoto, Yoshinari; Akagi, Takami; Shima, Fumiaki; Akashi, Mitsuru

    2017-06-01

    Herein, we report the fabrication of orientation-controlled tissues similar to heart and nerve tissues using a cell accumulation and three-dimensional (3D) printing technique. We first evaluated the 3D shaping ability of hydroxybutyl chitosan (HBC), a thermoresponsive polymer, by using a robotic dispensing 3D printer. HBC polymer could be laminated to a height of 1124 ± 14 μm. Based on this result, we fabricated 3D gel frames of various shapes, such as square, triangular, rectangular, and circular, for shape control of 3D tissue and then normal human cardiac fibroblasts (NHCFs) coated with extracellular matrix nanofilms were seeded in the frames. Observation of shape-controlled tissues after 1 day of cultivation showed that the orientation of fibroblasts was in one direction when a short-sided, thin, rectangular-shaped frame was used. Next, we tried to fabricate orientation-controlled tissue with a vascular network by coculturing NHCF and normal human cardiac microvascular endothelial cells. As a consequence of cultivation for 4 days, observation of cocultured tissue confirmed aligned cells and blood capillaries in orientation-controlled tissue. Our results clearly demonstrated that it would be possible to control the cell orientation by controlling the shape of the tissues by combining a cell accumulation technique and a 3D printing system. The results of this study suggest promising strategies for the fabrication of oriented 3D tissues in vitro. These tissues, mimicking native organ structures, such as muscle and nerve tissue with a cell alignment structure, would be useful for tissue engineering, regenerative medicine, and pharmaceutical applications.

  11. Development of high-frame-rate LED panel and its applications for stereoscopic 3D display

    NASA Astrophysics Data System (ADS)

    Yamamoto, H.; Tsutsumi, M.; Yamamoto, R.; Kajimoto, K.; Suyama, S.

    2011-03-01

    In this paper, we report development of a high-frame-rate LED display. Full-color images are refreshed at 480 frames per second. In order to transmit such a high frame-rate signal via conventional 120-Hz DVI, we have introduced a spatiotemporal mapping of image signal. A processor of LED image signal and FPGAs in LED modules have been reprogrammed so that four adjacent pixels in the input image are converted into successive four fields. The pitch of LED panel is 20 mm. The developed 480-fps LED display is utilized for stereoscopic 3D display by use of parallax barrier. The horizontal resolution of a viewed image decreases to one-half by the parallax barrier. This degradation is critical for LED because the pitch of LED displays is as large as tens of times of other flat panel displays. We have conducted experiments to improve quality of the viewed image through the parallax barrier. The improvement is based on interpolation by afterimages. It is shown that the HFR LED provides detailed afterimages. Furthermore, the HFR LED has been utilized for unconscious imaging, which provide a sensation of discovery of conscious visual information from unconscious images.

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

    NASA Astrophysics Data System (ADS)

    Ampatzidis, Dimitrios; Koenig, Rolf; Zhu, Shengyuan

    2015-04-01

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

  13. The use of custom 3D printed stereotactic frames for laser interstitial thermal ablation: technical note.

    PubMed

    Brandmeir, Nicholas J; McInerney, James; Zacharia, Brad E

    2016-10-01

    Over the last several years, laser interstitial thermotherapy (LITT) has gained wide acceptance for the treatment of a myriad of cranial lesions. A wide variety of techniques for placement of the laser fiber have been reported with a spectrum of perceived benefits and drawbacks. The authors present the first report of a customized 3D printed stereotactic frame for LITT. Approximately 1 week prior to surgery, 3-4 skull fiducials were placed after each of 5 patients received a local anesthetic as an outpatient. Radiographs with these fiducials were then used to create a trajectory to the lesion that would be treated with LITT. After the plan was completed, software was used to render a customized frame. On the day of surgery, the frame was attached to the implanted skull fiducials and the LITT catheter was placed. This procedure was carried out in 5 consecutive patients. In 2 patients, a needle biopsy was also performed. Intraoperative and postoperative imaging studies confirmed the accurate placement of the LITT catheter and the lesion created. Mean operating room time for all patients was 45 minutes but only 26 minutes when excluding the cases in which a biopsy was performed. To the best of the authors' knowledge, this is the first report of the use of a specific system, the STarFix microTargeting system, for use with LITT and brain biopsy. This system offers several advantages including fast operating times, extensive preoperative planning, no need for cranial fixation, and no need for frame or fiducial placement on the day of surgery. The accuracy of the system combined with these advantages may make this a preferred stereotactic method for LITT, especially in centers where LITT is performed in a diagnostic MRI suite.

  14. Reference-frame-independent quantum key distribution

    SciTech Connect

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

    2010-07-15

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

  15. Corrections to the FK5 reference frame

    NASA Astrophysics Data System (ADS)

    Jordi, C.; Rossello, G.

    1987-04-01

    Corrections to the equinox and equator of the FK5 reference frame have been obtained from an analysis of lunar occultations of stars made in the period AD 1800 to 1980. The ephemeris DE200/LE200 was used to reduce the data. The results show that the FK5 and dynamical equinox (defined by the ephemeris) agree closely at J2000.0; but they show that the equinox of the FK5 has a motion of -0.226±0.028 arcsec cy-1 with respect to the dynamical equinox. The equator of the FK5 differs from the dynamical equator by -0.099±0.006 arcsec at J2000.0 and has a motion of -0.150±0.009 arcsec cy-1 with respect to the dynamical equator.

  16. Convecting reference frames and invariant numerical models

    NASA Astrophysics Data System (ADS)

    Bihlo, Alexander; Nave, Jean-Christophe

    2014-09-01

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

  17. Polarization rotation, reference frames, and Mach's principle

    NASA Astrophysics Data System (ADS)

    Brodutch, Aharon; Terno, Daniel R.

    2011-12-01

    Polarization of light rotates in a gravitational field. The accrued phase is operationally meaningful only with respect to a local polarization basis. In stationary space-times, we construct local reference frames that allow us to isolate the Machian gravimagnetic effect from the geodetic (mass) contribution to the rotation. The Machian effect is supplemented by the geometric term that arises from the choice of standard polarizations. The phase accrued along a close trajectory is gauge-independent and is zero in the Schwarzschild space-time. The geometric term may give a dominant contribution to the phase. We calculate polarization rotation for several trajectories and find it to be more significant than is usually believed, pointing to its possible role as a future gravity probe.

  18. Spatial priming in ecologically relevant reference frames.

    PubMed

    Tower-Richardi, Sarah M; Leber, Andrew B; Golomb, Julie D

    2016-01-01

    In recent years, researchers have observed many phenomena demonstrating how the visual system exploits spatial regularities in the environment in order to benefit behavior. In this paper, we question whether spatial priming can be considered one such phenomenon. Spatial priming is defined as a response time facilitation to a visual search target when its spatial position has been repeated in recent trials (Maljkovic & Nakayama, 1996, Perception & Psychophysics, 58, 977-991). Does this priming serve a behaviorally adaptive role or is it merely a byproduct of ongoing visual processing? Critically, an adaptive priming mechanism must actively transform visual inputs from native retinotopic (eye-centered) coordinates into ecologically relevant coordinates, e.g., spatiotopic (world-centered) and/or object-centered. In Experiment 1, we tested this hypothesis by having participants move their eyes between trials, which dissociated retinotopic and spatiotopic frames of reference. Results showed only weak retinotopic priming, but robust spatiotopic priming. The second experiment again had participants move their eyes between trials but also manipulated the placement of a grouped array of display objects from trial to trial. This allowed us to measure not just retinotopic and spatiotopic priming, but object-centered priming as well. Results from this experiment did not yield retinotopic priming but showed robust spatiotopic and object-centered priming. These findings demonstrate that spatial priming operates within ecologically relevant coordinate systems, and the findings support the notion that spatial priming serves an adaptive role in human behavior.

  19. 3D-profile measurement of advanced semiconductor features by reference metrology

    NASA Astrophysics Data System (ADS)

    Takamasu, Kiyoshi; Iwaki, Yuuki; Takahashi, Satoru; Kawada, Hiroki; Ikota, Masami; Lorusso, Gian F.; Horiguchi, Naoto

    2016-03-01

    A method of sub-nanometer uncertainty for the 3D-profile measurement using TEM (Transmission Electron Microscope) images is proposed to standardize 3D-profile measurement through reference metrology. The proposed method has been validated for profiles of Si lines, photoresist features and advanced-FinFET (Fin-shaped Field-Effect Transistor) features in our previous investigations. However, efficiency of 3D-profile measurement using TEM is limited by measurement time including processing of the sample. In this article, we demonstrate a novel on-wafer 3D-profile metrology as "FIB-to-CDSEM method" with FIB (Focused Ion Beam) slope cut and CD-SEM (Critical Dimension Secondary Electron Microscope) measuring. Using the method, a few micrometer wide on a wafer is coated and cut by 45 degree slope using FIB tool. Then, the wafer is transferred to CD-SEM to measure the cross section image by top down CD-SEM measurement. We apply FIB-to-CDSEM method to CMOS sensor device. 3D-profile and 3D-profile parameters such as top line width and side wall angles of CMOS sensor device are evaluated. The 3D-profile parameters also are measured by TEM images as reference metrology. We compare the 3D-profile parameters by TEM method and FIB-to-CDSEM method. The average values and correlations on the wafer are agreed well between TEM and FIB-to- CDSEM methods.

  20. Real-time 3D ultrasound fetal image enhancment techniques using motion-compensated frame rate up-conversion

    NASA Astrophysics Data System (ADS)

    Lee, Gun-Ill; Park, Rae-Hong; Song, Young-Seuk; Kim, Cheol-An; Hwang, Jae-Sub

    2003-05-01

    In this paper, we present a motion compensated frame rate up-conversion method for real-time three-dimensional (3-D) ultrasound fetal image enhancement. The conventional mechanical scan method with one-dimensional (1-D) array converters used for 3-D volume data acquisition has a slow frame rate of multi-planar images. This drawback is not an issue for stationary objects, however in ultrasound images showing a fetus of more than about 25 weeks, we perceive abrupt changes due to fast motions. To compensate for this defect, we propose the frame rate up-conversion method by which new interpolated frames are inserted between two input frames, giving smooth renditions to human eyes. More natural motions can be obtained by frame rate up-conversion. In the proposed algorithm, we employ forward motion estimation (ME), in which motion vectors (MVs) ar estimated using a block matching algorithm (BMA). To smooth MVs over neighboring blocks, vector median filtering is performed. Using these smoothed MVs, interpolated frames are reconstructed by motion compensation (MC). The undesirable blocking artifacts due to blockwise processing are reduced by block boundary filtering using a Gaussian low pass filter (LPF). The proposed method can be used in computer aided diagnosis (CAD), where more natural 3-D ultrasound images are displayed in real-time. Simulation results with several real test sequences show the effectiveness of the proposed algorithm.

  1. Diverse spatial reference frames of vestibular signals in parietal cortex

    PubMed Central

    Chen, Xiaodong; DeAngelis, Gregory C; Angelaki, Dora E

    2013-01-01

    Summary Reference frames are important for understanding how sensory cues from different modalities are coordinated to guide behavior, and the parietal cortex is critical to these functions. We compare reference frames of vestibular self-motion signals in the ventral intraparietal area (VIP), parietoinsular vestibular cortex (PIVC), and dorsal medial superior temporal area (MSTd). Vestibular heading tuning in VIP is invariant to changes in both eye and head positions, indicating a body (or world)-centered reference frame. Vestibular signals in PIVC have reference frames that are intermediate between head- and body-centered. In contrast, MSTd neurons show reference frames between head- and eye-centered, but not body-centered. Eye and head position gain fields were strongest in MSTd and weakest in PIVC. Our findings reveal distinct spatial reference frames for representing vestibular signals, and pose new challenges for understanding the respective roles of these areas in potentially diverse vestibular functions. PMID:24239126

  2. Intuitive presentation of clinical forensic data using anonymous and person-specific 3D reference manikins.

    PubMed

    Urschler, Martin; Höller, Johannes; Bornik, Alexander; Paul, Tobias; Giretzlehner, Michael; Bischof, Horst; Yen, Kathrin; Scheurer, Eva

    2014-08-01

    The increasing use of CT/MR devices in forensic analysis motivates the need to present forensic findings from different sources in an intuitive reference visualization, with the aim of combining 3D volumetric images along with digital photographs of external findings into a 3D computer graphics model. This model allows a comprehensive presentation of forensic findings in court and enables comparative evaluation studies correlating data sources. The goal of this work was to investigate different methods to generate anonymous and patient-specific 3D models which may be used as reference visualizations. The issue of registering 3D volumetric as well as 2D photographic data to such 3D models is addressed to provide an intuitive context for injury documentation from arbitrary modalities. We present an image processing and visualization work-flow, discuss the major parts of this work-flow, compare the different investigated reference models, and show a number of cases studies that underline the suitability of the proposed work-flow for presenting forensically relevant information in 3D visualizations.

  3. On excitation of Earth's free wobble and reference frames

    NASA Technical Reports Server (NTRS)

    Chao, B. F.

    1983-01-01

    The excitation of the Earth's polar motion in connection with problems that are associated with the diversity of reference frames involved in observations and theoretical computations is studied. Following the dynamics of the Earth's polar motion, the kinematics that relates observations from different reference frames is developed. The conventional procedures of studying the seismic excitation of polar motion are re-examined, subject to the question: relative to what reference frame? It is concluded that an inconsistency in reference frames has prevailed in the literature. While this inconsistency is indeed far from trivial, the resultant discrepancy, however, is small for all practical purposes.

  4. Communication between inertial observers with partially correlated reference frames

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  5. Robustness of reference-frame-independent quantum key distribution against the relative motion of the reference frames

    NASA Astrophysics Data System (ADS)

    Pramanik, Tanumoy; Park, Byung Kwon; Cho, Young-Wook; Han, Sang-Wook; Kim, Yong-Su; Moon, Sung

    2017-08-01

    Reference-Frame-Independent quantum key distribution (RFI-QKD) is known to be robust against slowly varying reference frames. However, other QKD protocols such as BB84 can also provide secrete keys if the speed of the relative motion of the reference frames is slow enough. While there has been a few studies to quantify the speed of the relative motion of the reference frames in RFI-QKD, it is not yet clear if RFI-QKD provides better performance than other QKD protocols under this condition. Here, we analyze and compare the security of RFI-QKD and BB84 protocol in the presence of the relative motion of the reference frames. In order to compare their security in real world implementation, we also consider the QKD protocols with decoy state method. Our analysis shows that RFI-QKD provides more robustness than BB84 protocol against the relative motion of the reference frames.

  6. Spatial vision within egocentric and exocentric frames of reference

    NASA Technical Reports Server (NTRS)

    Howard, Ian P.

    1991-01-01

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

  7. Analysis of 3D face forms for proper sizing and CAD of spectacle frames.

    PubMed

    Kouchi, Makiko; Mochimaru, Masaaki

    2004-11-01

    Three-dimensional morphological variations in the human face were analysed using digital models of the human face, and the usefulness of such analysis in designing industrial products was demonstrated by validating spectacle frame designs based on an original sizing system developed based on the analysis. A normalized model of the three-dimensional face form was made for each of 56 young adult Japanese males. The morphological distances between subjects were defined, and subjects were divided into four groups based on analysis of the distance matrix. A prototype spectacle frame was designed for the average form of each of the four groups. Tightening force of the prototype frames was adjusted using the materialized average forms with soft material placed at the nasal bridge and side of the head. Four prototype frames as well as a conventional frame were evaluated using sensory evaluation and physical measurement of the pressure and slip in 38 young adult male subjects. For each of the 38 subjects, prototype frames were ranked according to the morphological similarity of the subjects and the average form of the four groups: the frame designed for the average form of the group most similar to the subject was #1, the frame designed for the average form of the next most similar group was #2, and so on. For the groups with smaller or narrower faces, new frame #1 was most preferred and had the best overall fit, smallest slip sensation and largest pressure sensation. The groups with larger or wider faces preferred tighter frames than new frame #1, because they were concerned that the frames might slip, although the frames did not. Most of the subjects habitually wore spectacles, and the reason that groups with larger or wider faces preferred tighter frames was thought to be that they were accustomed to tighter fitting frames.

  8. Interaction between Reference Frames, A Concern in Embedded Training?

    DTIC Science & Technology

    2009-10-01

    RTO-MP-HFM-169 8 - 1 Interaction between Reference Frames, A Concern in Embedded Training? PMB Sandor 1,2 MD-PhD, D Hartnagel 1 PhD, L...Lepecq JC, Sandor PMB, Pergandi JM, Mestre D (2009). Interaction between reference frames during subjective vertical estimates in a tilted immersive

  9. The Dirac oscillator in a rotating frame of reference

    NASA Astrophysics Data System (ADS)

    Strange, P.; Ryder, L. H.

    2016-10-01

    The Dirac equation in a rotating frame of reference is derived from first principles within a linear approximation. This equation is employed to exhibit an equivalence between a particle in a Dirac oscillator potential and a free particle in a rotating frame of reference. A zero-point contribution to the energy of the particle, resulting from its spin, is also noted.

  10. Object-centered reference frames in depth as revealed by induced motion.

    PubMed

    Léveillé, Jasmin; Myers, Emma; Yazdanbakhsh, Arash

    2014-03-11

    An object-centric reference frame is a spatial representation in which objects or their parts are coded relative to others. The existence of object-centric representations is supported by the phenomenon of induced motion, in which the motion of an inducer frame in a particular direction induces motion in the opposite direction in a target dot. We report on an experiment made with an induced motion display where a degree of slant is imparted to the inducer frame using either perspective or binocular disparity depth cues. Critically, the inducer frame oscillates perpendicularly to the line of sight, rather than moving in depth. Participants matched the perceived induced motion of the target dot in depth using a 3D rotatable rod. Although the frame did not move in depth, we found that subjects perceived the dot as moving in depth, either along the slanted frame or against it, when depth was given by perspective and disparity, respectively. The presence of induced motion is thus not only due to the competition among populations of planar motion filters, but rather incorporates 3D scene constraints. We also discuss this finding in the context of the uncertainty related to various depth cues, and to the locality of representation of reference frames.

  11. Frame-like gauge-invariant description of massive fermionic higher spins in 3D

    NASA Astrophysics Data System (ADS)

    Permiakova, M. Yu.; Snegirev, T. V.

    2017-03-01

    We give the frame-like gauge-invariant Lagrangian description for massive fermionic arbitrary spin fields in three-dimensional AdS space. The Lagrangian, complete set of gauge transformations and gauge-invariant curvatures are obtained.

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

    PubMed

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

    2010-04-01

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

  13. Use of Reference Frames for Interplanetary Navigation at JPL

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  14. 3D Mandibular Superimposition: Comparison of Regions of Reference for Voxel-Based Registration

    PubMed Central

    Ruellas, Antonio Carlos de Oliveira; Yatabe, Marilia Sayako; Souki, Bernardo Quiroga; Benavides, Erika; Nguyen, Tung; Luiz, Ronir Raggio; Franchi, Lorenzo; Cevidanes, Lucia Helena Soares

    2016-01-01

    Introduction The aim was to evaluate three regions of reference (Björk, Modified Björk and mandibular Body) for mandibular registration testing them in a patients’ CBCT sample. Methods Mandibular 3D volumetric label maps were built from CBCTs taken before (T1) and after treatment (T2) in a sample of 16 growing subjects and labeled with eight landmarks. Registrations of T1 and T2 images relative to the different regions of reference were performed, and 3D surface models were generated. Seven mandibular dimensions were measured separately for each time-point (T1 and T2) in relation to a stable reference structure (lingual cortical of symphysis), and the T2-T1 differences were calculated. These differences were compared to differences measured between the superimposed T2 (generated from different regions of reference: Björk, Modified Björk and Mandibular Body) over T1 surface models. ICC and the Bland-Altman method tested the agreement of the changes obtained by nonsuperimposition measurements from the patients’ sample, and changes between the overlapped surfaces after registration using the different regions of reference. Results The Björk region of reference (or mask) did work properly only in 2 of 16 patients. Evaluating the two other masks (Modified Björk and Mandibular body) on patients’ scans registration, the concordance and agreement of the changes obtained from superimpositions (registered T2 over T1) compared to results obtained from non superimposed T1 and T2 separately, indicated that Mandibular Body mask displayed more consistent results. Conclusions The mandibular body mask (mandible without teeth, alveolar bone, rami and condyles) is a reliable reference for 3D regional registration. PMID:27336366

  15. Future National Reference Frames for the United States

    NASA Astrophysics Data System (ADS)

    Stone, W. A.

    2015-12-01

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

  16. Newton-Cartan Gravity in Noninertial Reference Frames

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed Central

    Filimon, Flavia

    2015-01-01

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

  18. Astrometric microlensing and rotation of extragalactic reference frame

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. I.; Alexandrov, A. N.; Fedorova, E. V.

    Gravitational field of foreground stars of the Galaxy causes additional motion of images of extragalactic sources. We estimate characteristics of stochastic and average motions of these images. The probability distribution for the image motions and their changes is obtained for general spatial density of microlenses. We show that collective motion of stars induces small nonzero dragging velocity of the reference frame. The results obtained are compared to the other relativistic effects in optical satellite-oriented reference frame.

  19. Spatial vision within egocentric and exocentric frames of reference

    NASA Technical Reports Server (NTRS)

    Howard, Ian P.

    1989-01-01

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

  20. Reference frames in learning from maps and navigation.

    PubMed

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

    2015-11-01

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

  1. PRISM3D: a preliminary 3D reference seismic model of the crust and upper mantle beneath Iberia

    NASA Astrophysics Data System (ADS)

    Arroucau, Pierre; Custódio, Susana; Civiero, Chiara; Dias, Nuno A.; Silveira, Graça

    2017-04-01

    Earthquake location and moment tensor inversion are usually performed assuming one-dimensional (1D), radially symmetric models of the Earth's seismic velocity field. In a region such as Iberia, that hypothesis may no longer be valid: its location combining a plate boundary context with a passive margin environment indeed results in the presence of mountain ranges and abyssal plains, and juxtaposes sedimentary basins, thickened, normal and thinned continental crust, oceanic material, and even, locally, exhumed mantle. Furthermore, earthquakes in the Gulf of Cadiz and in the Alboran Sea, respectively west and east of Gibraltar Strait, are known to occur in the upper mantle, which also presents lateral velocity variations. A three-dimensional (3D) seismic velocity model of the crust and upper mantle beneath Iberia therefore appears necessary for accurate travel time and waveform modeling, in order to account for lateral variations of topography, Moho depth and lithology, and improve earthquake location and source inversion. Here, we present a new 3D P- and S-wave velocity model for Iberia. The model spans a region ranging from 17W to 6E in longitude and 28N to 47N in latitude, and from 7km above to 250 km below sea level in depth, with a grid node spacing of 10 km in longitude and latitude, and 0.5 km in depth. It results from the compilation of existing -published and unpublished - local earthquake and teleseismic body wave tomographic models, earthquake and ambient noise surface wave as well as receiver function inversion studies, and active source seismic experiments. Moho depth is estimated by interpolation of results from receiver function and deep seismic sounding using the reversible jump algorithm. Crust and mantle velocity field are then obtained separately by weighted average of the compiled models. This new 3D model, which combines the most recent seismic structure studies in Iberia and its surroundings, forms a reliable basis for earthquake location and

  2. Estimation and Analysis of Parameters for Reference Frame Transformation

    NASA Astrophysics Data System (ADS)

    Yang, T. G.; Gao, Y. P.; Tong, M. L.; Zhao, C. S.; Gao, F.

    2016-07-01

    Based on the estimation method of parameters for reference frame transformation, the parameters used for transformation between different modern DE (Develop-ment Ephemeris) ephemeris pairs are derived using the data of heliocentric coordinates of Earth-Moon barycenter from DE ephemeris pairs, and the transformation parameters between DE ephemeris dynamic reference frame and ICRF (International Celestial Reference Frame) are estimated by using the timing data and VLBI (Very Long Baseline Interferometry) observation results of millisecond pulsars. The estimated parameters for the reference frame transformation include three rotational angles of rotational matrix and their derivatives of time. The reference epoch of estimated parameters for the reference frame transformation is MJD51545, that is J2000.0. Our results show that the absolute maximum value of rotational angles for the transformation of DE200 to DE405 ephemeris is 13 mas, and its derivative of time is -0.0007 mas/d. No absolute value of rotational angles is larger than 0.1 mas for the transformation of DE414 to DE421 ephemeris. The absolute maximum value of rotational angles of rotation matrix for the transformation of DE421 ephemeris to ICRF is 3 mas, and the time derivatives of three rotational angles are also necessarily included.

  3. Turbulence Modeling in Non-Inertial Frames of Reference,

    DTIC Science & Technology

    1988-03-01

    40-R193 962 TURBULENCE MODELING IN NON-INERTIAL FRAMES OF REFERENCE 1Iii (U) INSTITUTE FOR COMPUTER APLICATIONS IN SCIENCE AND ENGINERIN C G MPEZIALE...0ICASE r TURBULENCE MODELING IN NON-INE&TIAL ~ FRANKS OF REFERENCE D1C SELECD Charles G. Spezial* APR0 81D Contract No. NASI-18107 March 1988 Vr oum

  4. Using Hyperspectral Frame Images from Unmanned Airborne Vehicle for Detailed Measurement of Boreal Forest 3D Structure

    NASA Astrophysics Data System (ADS)

    de Oliveira, Raquel A.; Tommaselli, Antonio M. G.; Honkavaara, Eija

    2016-10-01

    Objective of this work was to investigate the feasibility of using multi-image matching and information extracted from image classification to improve strategies in generation of point clouds of 3D forest scene. Image data sets were collected by a Fabry-Pérot interferometer (FPI) based hyperspectral frame camera on-board a UAV in a boreal forest area. The results of the new method are analysed and compared with commercial software and LiDAR data. Experiments showed that the point clouds generated with the proposed algorithm fitted better with the LiDAR data at the ground level, which is favourable for digital terrain model (DTM) extraction.

  5. REM-3D Reference Dataset: Reconciling 100 million surface-wave observations

    NASA Astrophysics Data System (ADS)

    Moulik, P.; Lekic, V.; Romanowicz, B. A.

    2016-12-01

    A three-dimensional Reference Earth model (REM-3D) should ideally represent the consensus view of large-scale heterogeneity in the Earth's mantle. This necessitates identification of the robust aspects of mantle structure through the joint modeling of large and diverse seismological datasets. An important goal of REM-3D is to provide a comprehensive and consistent set of long-period observations that would allow identification of outliers and assist in more detailed studies of heterogeneity. We present results from ongoing work with datasets contributed by the community analyzed in consultation with a Reference Dataset Working Group. The community response to data solicitation has been enthusiastic with several groups across the world contributing recent measurements of normal modes, surface waves and body waves. For example, eight groups contributed dispersion measurements of fundamental-mode surface waves, a key constraint for upper-mantle structure. The current compilation includes 100 million measurements of fundamental-mode surface waves and overtones up to the sixth branch. We have formulated a procedure for reconciling surface wave observations that includes, (1) quality control for salvaging missing metadata, and (2) identification of and reasons for discrepant measurements. In consultation with the Reference Dataset Working Group, we provided several guidelines for the metadata that would facilitate easy storage and reproducibility. However, some of the legacy compilations did not record all of the needed source/station information and other metadata; therefore, we have had to exclude as much as 25% of measurements in these cases. We find strong agreement between the dispersion measurements of fundamental-mode Rayleigh waves made using techniques that involve human supervision. A half-cycle band of discrepancies observed is inter-dataset comparisons is found to be associated primarily with reversed instrument polarities at a specific set of stations, which

  6. Reference frames in virtual spatial navigation are viewpoint dependent

    PubMed Central

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

    2014-01-01

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

  7. Testing Absolute Plate Reference Frames and the Implications for the Generation of Geodynamic Mantle Heterogeneity Structure

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Bunge, H.; Schuberth, B. S.; Müller, D.; Talsma, A.; Moder, C.

    2010-12-01

    Several absolute reference frames for Cretaceous-Tertiary plate tectonic reconstructions have been proposed over the last decade. They include reference frames based on hotspot tracks displaying age progression, and assuming either fixed or moving hotspots, as well as palaeomagnetically-based reference frames, a subduction reference frame and hybrid reference frames. All these alternative reference frames imply a particular history of the location of subduction zones through time, the associated subduction history, and the evolution of mantle heterogeneity via the mixing of subducted slab material with the mantle. Therefore it is possible to evaluate the observed distribution of subducted slab material in the mantle versus that predicted by a forward geodynamic model in which the plate kinematic history given by a particular absolute plate is coupled with a mantle convection model. We present a comparison of five alternative absolute plate motion models in terms of their consequences for global deep mantle structure by utilizing the 3-D spherical finite element mantle convection code TERRA, coupled with the global plate tectonic reconstruction software GPlates. We impose global palaeo-plate boundaries and plate velocities back to 140 Ma as surface boundary conditions for each absolute rotation model and forward model the associated subduction history. The correlation of seismic tomography with the predicted present-day mantle structure from each of plate models is then assessed using well-imaged slabs. We will present and discuss a comparison of geodynamically predicted mantle heterogeneity and seismic tomography to infer the robustness of each absolute reference frame through time, thus providing additional constraints for the integration of plate tectonics and mantle dynamics.

  8. Improved grid-noise removal in single-frame digital moiré 3D shape measurement

    NASA Astrophysics Data System (ADS)

    Mohammadi, Fatemeh; Kofman, Jonathan

    2016-11-01

    A single-frame grid-noise removal technique was developed for application in single-frame digital-moiré 3D shape measurement. The ability of the stationary wavelet transform (SWT) to prevent oscillation artifacts near discontinuities, and the ability of the Fourier transform (FFT) applied to wavelet coefficients to separate grid-noise from useful image information, were combined in a new technique, SWT-FFT, to remove grid-noise from moiré-pattern images generated by digital moiré. In comparison to previous grid-noise removal techniques in moiré, SWT-FFT avoids the requirement for mechanical translation of optical components and capture of multiple frames, to enable single-frame moiré-based measurement. Experiments using FFT, Discrete Wavelet Transform (DWT), DWT-FFT, and SWT-FFT were performed on moiré-pattern images containing grid noise, generated by digital moiré, for several test objects. SWT-FFT had the best performance in removing high-frequency grid-noise, both straight and curved lines, minimizing artifacts, and preserving the moiré pattern without blurring and degradation. SWT-FFT also had the lowest noise amplitude in the reconstructed height and lowest roughness index for all test objects, indicating best grid-noise removal in comparison to the other techniques.

  9. Evaluation of Bogie Frame Safety of Shanghai Metro Line 1 by 3D FEM Analysis

    NASA Astrophysics Data System (ADS)

    Xiongyao, Xie; Guolong, Jin; Rulu, Wang

    2010-05-01

    The vehicle bogies of Shanghai metro line 1 began to crack just in the third year after the trains operated. More than 50 cracks occurred in the succeeding six year during the train operation. This paper evaluated the safety of the motorized bogies. First, the loading conditions imposed on the vehicle structure were calculated based on the measured data in service of the train, and compared with the original design load. Then, this paper calculated simulated the stress of the vehicle bogie by 3D FEM, and presented the distribution of every stress concentration point in Goodman fatigue diagram. The computational locations of the strength less than the safety are agreed with where cracks have happened. Finally, this paper calculated the fatigue life of the motor bracket of the bogie through S-N curve based on revised Miner theory. In conclusion, this paper think that the bogie cracks of Shanghai metro line 1 are contributed by the overburden fatigue load, and ignoring the lateral vibration load in the design of the vehicle bogie is the important cause that bogie cracks occurred far earlier than in the designed time.

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

    PubMed

    Garrido, Javier

    2006-02-23

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

  11. A Gauss-Seidel Iteration Scheme for Reference-Free 3-D Histological Image Reconstruction

    PubMed Central

    Daum, Volker; Steidl, Stefan; Maier, Andreas; Köstler, Harald; Hornegger, Joachim

    2015-01-01

    Three-dimensional (3-D) reconstruction of histological slice sequences offers great benefits in the investigation of different morphologies. It features very high-resolution which is still unmatched by in-vivo 3-D imaging modalities, and tissue staining further enhances visibility and contrast. One important step during reconstruction is the reversal of slice deformations introduced during histological slice preparation, a process also called image unwarping. Most methods use an external reference, or rely on conservative stopping criteria during the unwarping optimization to prevent straightening of naturally curved morphology. Our approach shows that the problem of unwarping is based on the superposition of low-frequency anatomy and high-frequency errors. We present an iterative scheme that transfers the ideas of the Gauss-Seidel method to image stacks to separate the anatomy from the deformation. In particular, the scheme is universally applicable without restriction to a specific unwarping method, and uses no external reference. The deformation artifacts are effectively reduced in the resulting histology volumes, while the natural curvature of the anatomy is preserved. The validity of our method is shown on synthetic data, simulated histology data using a CT data set and real histology data. In the case of the simulated histology where the ground truth was known, the mean Target Registration Error (TRE) between the unwarped and original volume could be reduced to less than 1 pixel on average after 6 iterations of our proposed method. PMID:25312918

  12. A Gauss-Seidel iteration scheme for reference-free 3-D histological image reconstruction.

    PubMed

    Gaffling, Simone; Daum, Volker; Steidl, Stefan; Maier, Andreas; Kostler, Harald; Hornegger, Joachim

    2015-02-01

    Three-dimensional (3-D) reconstruction of histological slice sequences offers great benefits in the investigation of different morphologies. It features very high-resolution which is still unmatched by in vivo 3-D imaging modalities, and tissue staining further enhances visibility and contrast. One important step during reconstruction is the reversal of slice deformations introduced during histological slice preparation, a process also called image unwarping. Most methods use an external reference, or rely on conservative stopping criteria during the unwarping optimization to prevent straightening of naturally curved morphology. Our approach shows that the problem of unwarping is based on the superposition of low-frequency anatomy and high-frequency errors. We present an iterative scheme that transfers the ideas of the Gauss-Seidel method to image stacks to separate the anatomy from the deformation. In particular, the scheme is universally applicable without restriction to a specific unwarping method, and uses no external reference. The deformation artifacts are effectively reduced in the resulting histology volumes, while the natural curvature of the anatomy is preserved. The validity of our method is shown on synthetic data, simulated histology data using a CT data set and real histology data. In the case of the simulated histology where the ground truth was known, the mean Target Registration Error (TRE) between the unwarped and original volume could be reduced to less than 1 pixel on average after six iterations of our proposed method.

  13. Symmetric construction of reference-frame-free qudits

    NASA Astrophysics Data System (ADS)

    Suzuki, Jun; Tabia, Gelo Noel Macuja; Englert, Berthold-Georg

    2008-11-01

    By exploiting a symmetric scheme for coupling N spin- 1/2 constituents (the physical qubits) to states with total angular momentum N/2-1 , we construct rotationally invariant logical qudits of dimension d=N-1 . One can encode all qudit states, and realize all qudit measurements, by this construction. The rotational invariance of all relevant objects enables one to transmit quantum information without having aligned reference frames between the parties that exchange the qudits. We illustrate the method by explicit constructions of reference-frame-free qubits and qutrits and, for the qubit case, comment on possible experimental implementations.

  14. Overall properties of the Gaia DR1 reference frame

    NASA Astrophysics Data System (ADS)

    Liu, N.; Zhu, Z.; Liu, J.-C.; Ding, C.-Y.

    2017-03-01

    Aims: The first Gaia data release (Gaia DR1) provides 2191 ICRF2 sources with their positions in the auxiliary quasar solution and five astrometric parameters - positions, parallaxes, and proper motions - for stars in common between the Tycho-2 catalogue and Gaia in the joint Tycho-Gaia astrometric solution (TGAS). We aim to analyze the overall properties of Gaia DR1 reference frame. Methods: We compare quasar positions of the auxiliary quasar solution with ICRF2 sources using different samples and evaluate the influence on the Gaia DR1 reference frame owing to the Galactic aberration effect over the J2000.0-J2015.0 period. Then we estimate the global rotation between TGAS with Tycho-2 proper motion systems to investigate the property of the Gaia DR1 reference frame. Finally, the Galactic kinematics analysis using the K-M giant proper motions is performed to understand the property of Gaia DR1 reference frame. Results: The positional comparison between the auxiliary quasar solution and ICRF2 shows negligible orientation and validates the declination bias of -0.1mas in Gaia quasar positions with respect to ICRF2. Galactic aberration effect is thought to cause an offset 0.01mas of the Z axis direction of Gaia DR1 reference frame. The global rotation between TGAS and Tycho-2 proper motion systems, obtained by different samples, shows a much smaller value than the claimed value 0.24mas yr-1. For the Galactic kinematics analysis of the TGAS K-M giants, we find possible non-zero Galactic rotation components beyond the classical Oort constants: the rigid part ωYG = -0.38±0.15mas yr-1 and the differential part ω^primeYG = -0.29±0.19mas yr-1 around the YG axis of Galactic coordinates, which indicates possible residual rotation in Gaia DR1 reference frame or problems in the current Galactic kinematical model. Conclusions: The Gaia DR1 reference frame is well aligned to ICRF2, and the possible influence of the Galactic aberration effect should be taken into consideration

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. Turbulence modeling in non-inertial frames of reference

    NASA Technical Reports Server (NTRS)

    Speziale, Charles G.

    1988-01-01

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

  17. Global reference frame: Intercomparison of results (SLR, VLBI and GPS)

    NASA Technical Reports Server (NTRS)

    Ma, Chopo; Watkins, Michael M.; Heflin, M.

    1994-01-01

    The terrestrial reference frame (TRF) is realized by a set of positions and velocities derived from a combination of the three space geodetic techniques, SLR, VLBI and GPS. The standard International TRF is constructed by the International Earth Rotation Service in such a way that it is stable with time and the addition of new data. An adopted model for overall plate motion, NUVEL-1 NNR, defines the conceptual reference frame in which all the plates are moving. In addition to the measurements made between reference points within the space geodetic instruments, it is essential to have accurate, documented eccentricity measurements from the instrument reference points to ground monuments. Proper local surveys between the set of ground monuments at a site are also critical for the use of the space geodetic results. Eccentricities and local surveys are, in fact, the most common and vexing sources of error in the use of the TRF for such activities as collocation and intercomparison.

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

    NASA Astrophysics Data System (ADS)

    Casotto, Stefano

    2016-03-01

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

  19. Mesoscopic mechanical resonators as quantum noninertial reference frames

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  20. Deriving a unique reference frame for GPS measurements

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1988-01-01

    Two strategies for deriving a unique reference frame for GPS (Global Positioning System) measurements are discussed. The first strategy utilizes the precise relative positions which have been predetermined by VLBI (very long baseline interferometry) to fix the frame orientation and the absolute scaling, while the offset from the geocenter is determined from GPS measurements. Three different cases are presented under this strategy. The second strategy establishes a reference frame by holding only the longitudinal of one of the tracking sites fixed. The absolute scaling is determined by the adopted gravitational constant (GM) of the earth; and the latitude is inferred from the time signature of the earth's rotation in the GPS measurements. The coordinate system thus defined will be a geocentric earth fixed coordinate system. A covariance analysis shows that geometric positioning to an accuracy of a few centimeters can be achieved with just one day of precise GPS pseudorange and carrier phase data.

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

    ERIC Educational Resources Information Center

    Kelly, Jonathan W.; Avraamides, Marios N.

    2011-01-01

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

  2. Temporal dynamics of object location processing in allocentric reference frame.

    PubMed

    Török, Ágoston; Kóbor, Andrea; Persa, György; Galambos, Péter; Baranyi, Péter; Csépe, Valéria; Honbolygó, Ferenc

    2017-09-01

    The spatial location of objects is processed in egocentric and allocentric reference frames, the early temporal dynamics of which have remained relatively unexplored. Previous experiments focused on ERP components related only to egocentric navigation. Thus, we designed a virtual reality experiment to see whether allocentric reference frame-related ERP modulations can also be registered. Participants collected reward objects at the end of the west and east alleys of a cross maze, and their ERPs to the feedback objects were measured. Participants made turn choices from either the south or the north alley randomly in each trial. In this way, we were able to discern place and response coding of object location. Behavioral results indicated a strong preference for using the allocentric reference frame and a preference for choosing the rewarded place in the next trial, suggesting that participants developed probabilistic expectations between places and rewards. We also found that the amplitude of the P1 was sensitive to the allocentric place of the reward object, independent of its value. We did not find evidence for egocentric response learning. These results show that early ERPs are sensitive to the location of objects during navigation in an allocentric reference frame. © 2017 Society for Psychophysiological Research.

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

    ERIC Educational Resources Information Center

    Pagel, Birthe; Heed, Tobias; Roder, Brigitte

    2009-01-01

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

  4. The Bernoulli Equation in a Moving Reference Frame

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Kelly, Jonathan W.; McNamara, Timothy P.

    2010-01-01

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

  6. The Bernoulli Equation in a Moving Reference Frame

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Fulcher, Glenn; Svalberg, Agneta

    2013-01-01

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

  8. The IASPEI Reference Event List to Support 3D Velocity Model Validation Studies

    NASA Astrophysics Data System (ADS)

    Bondar, I.; Storchak, D. A.

    2013-05-01

    The IASPEI Reference Event List (Ground Truth database) maintained and hosted by the International Seismological Centre (ISC) on behalf of the IASPEI became an indispensable tool for the validation of 3D seismic velocity models. The Ground Truth database is regularly updated and currently consists of some 7,600 GT0-5 events (earthquakes, chemical and nuclear explosions). Recently the CTBTO has launched a global initiative to facilitate the development of the Regional Seismic Travel Time (RSTT) velocity model on a global scale by forming regional expert groups. We make a concentrated effort to increase the number and the coverage of ground truth events in Latin America. To further support the RSTT development and validation studies, the ISC has developed a version of its location software to accommodate local and regional travel-time predictions provided by the RSTT software package. The RSTT-enabled ISC locator is made available through the ISC website.

  9. Using quasar physics to improve the celestial reference frame

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Chapeau-Blondeau, François; Belin, Etienne

    2016-07-01

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

  11. Pushing the frames of reference in traumatic brain injury rehabilitation.

    PubMed

    Diller, Leonard

    2005-06-01

    Cognitive rehabilitation is an empirically based field driven by multiple sources of activities and knowledge bases. Drawing on frames of reference provided by rehabilitation, neuropsychology, and rehabilitation psychology, cognitive rehabilitation has evolved to a point where studies have been generated to qualify for consideration in tables of evidence. At the center of cognitive rehabilitation is the effort to teach people to overcome or adapt to limitations. While rehabilitation has traditionally been focused on activity, a recent trend in the literature is to incorporate the individuals experience into a frame of reference for rehabilitation. Emphasizing the experience of the person in the situation fits into cognitive rehabilitation and raises the bar for rehabilitation not only in viewing rehabilitation as an activity to relieve burdens but also in terms of how rehabilitants come to grips with limitations. Dealing with limitations is an important indicator of mental health.

  12. 3D dentofacial photogrammetry reference values: a novel approach to orthodontic diagnosis.

    PubMed

    Masoud, Mohamed I; Bansal, Neetu; C Castillo, Jose; Manosudprasit, Amornrut; Allareddy, Veerasathpurush; Haghi, Arshan; Hawkins, Hannah C; Otárola-Castillo, Erik

    2017-04-01

    Orthodontic diagnostic standards generally use the cranial base as a reference and rely on samples selected by orthodontists. The purpose of this study was to provide male and female standards for a novel non-radiographic approach for orthodontic diagnosis that utilizes 3D dentofacial photogrammetry using the eyes and natural head orientation as references instead of the cranial base. One hundred and eighty females and 200 males between the ages of 18 and 35 years from 2 modeling agencies were orthodontically screened for near ideal occlusion. Subjects that met the inclusion criteria were rated by a sample of 40 lay people for attractiveness on a visual analogue scale. The final sample that had 3D facial and dental imaging included 49 subjects 25 males and 24 females with near ideal occlusion and considered attractive by the public. Inter and Intra-examiner ICC were greater than 0.8 for both landmarking and indexing. Relative to a coronal plane contacting the pupils (MC), the mean sagittal position of the alar curvature (representing the nasomaxillary complex) was 14.36 ± 3.08 mm in males and 12.4 ± 3.58 mm in females. The sagittal position of soft tissue pogonion relative to the pupils was 14.84 ± 3.63 mm in males and 12.78 ± 5.68 mm in females. The angle between the alar curvature and pogonion relative to the pupils was 9° in males and 10° in females. With the exception of the occlusal plane which was steeper in females, no ratios or angular facial measurements showed a significant gender difference. Relative to MC, males had more proclined upper incisors (20° vs 16°) and more retroclined Lower incisors (27° vs 31°; P > 0.05). A Procrustes ANOVA and permutation test showed that the shapes of males and females are different enough to be considered two distinct populations. 1. When using the proposed method for orthodontic diagnosis, male and female patients should be compared to their respective dentofacial standards. 2. Validation of the proposed method

  13. An improved celestial radio reference frame: JPL 1982-4

    NASA Technical Reports Server (NTRS)

    Fanselow, J. L.; Sovers, O. J.; Thomas, J. B.; Purcell, G. J., Jr.

    1983-01-01

    In the development of a celestial radio reference frame, there are now over 100 sources whose relative positions are known with an average uncertainty less than 5 milliarcseconds. These sources are fairly uniformly distributed over the celestial sphere north of -40 deg declination. Their positions are expressed in the new IAU system. This presentation describes the analysis involved in obtaining these results, as well as future plans for linking this system to the JPL planetary ephemerides.

  14. Disentangling the External Reference Frames Relevant to Tactile Localization

    PubMed Central

    Backhaus, Jenny; Röder, Brigitte; Badde, Stephanie

    2016-01-01

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

  15. The Effect of Companions on the SIM Reference Frame

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.; Turyshev, Slava G.

    2000-01-01

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

  16. Global GPS reference frame solutions of unlimited size

    NASA Astrophysics Data System (ADS)

    Boomkamp, H.

    2010-07-01

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

  17. Specular vision-touch synaesthesia: two reference frames.

    PubMed

    White, Rebekah C; Aimola Davies, Anne M

    2012-01-01

    Two subtypes of vision-touch synaesthesia (VTS) have been identified. For anatomical VTS, sight of touch on another person elicits synaesthetic tactile sensation at the same location on the observer's own body (e.g., viewed touch on the left cheek elicits sensation on the observer's left cheek). For specular VTS, sight of touch on another person elicits synaesthetic tactile sensation at the mirror-reflected location (e.g., viewed touch on the left cheek elicits sensation on the observer's right cheek). Here we report two distinctly different patterns of sensation within the specular subtype. Both participants experienced synaesthetic tactile sensation on their right hand when they viewed unidirectional brushstrokes administered to a prosthetic left hand (positioned with fingers pointing toward the participant), but the direction of sensation matched the viewed touch in a hand-centred (spatial) reference frame for RS and in an external (viewer-centred) reference frame for NC. Competing reference frames affect how individuals with specular VTS experience synaesthetic tactile sensation.

  18. On the transition towards slow manifold in shallow-water and 3D Euler equations in a rotating frame

    NASA Technical Reports Server (NTRS)

    Mahalov, A.

    1994-01-01

    The long-time, asymptotic state of rotating homogeneous shallow-water equations is investigated. Our analysis is based on long-time averaged rotating shallow-water equations describing interactions of large-scale, horizontal, two-dimensional motions with surface inertial-gravity waves field for a shallow, uniformly rotating fluid layer. These equations are obtained in two steps: first by introducing a Poincare/Kelvin linear propagator directly into classical shallow-water equations, then by averaging. The averaged equations describe interaction of wave fields with large-scale motions on time scales long compared to the time scale 1/f(sub o) introduced by rotation (f(sub o)/2-angular velocity of background rotation). The present analysis is similar to the one presented by Waleffe (1991) for 3D Euler equations in a rotating frame. However, since three-wave interactions in rotating shallow-water equations are forbidden, the final equations describing the asymptotic state are simplified considerably. Special emphasis is given to a new conservation law found in the asymptotic state and decoupling of the dynamics of the divergence free part of the velocity field. The possible rising of a decoupled dynamics in the asymptotic state is also investigated for homogeneous turbulence subjected to a background rotation. In our analysis we use long-time expansion, where the velocity field is decomposed into the 'slow manifold' part (the manifold which is unaffected by the linear 'rapid' effects of rotation or the inertial waves) and a formal 3D disturbance. We derive the physical space version of the long-time averaged equations and consider an invariant, basis-free derivation. This formulation can be used to generalize Waleffe's (1991) helical decomposition to viscous inhomogeneous flows (e.g. problems in cylindrical geometry with no-slip boundary conditions on the cylinder surface and homogeneous in the vertical direction).

  19. Multiple 3D reference system analyses for Phobos grooves, a novel approach

    NASA Astrophysics Data System (ADS)

    Simioni, Emanuele; Pajola, Maurizio; Massironi, Matteo; Cremonese, Gabriele

    2015-04-01

    Grooves analysis has represented in the last decade a robust method for geomorphological study of small bodies, as is the case for asteroids 951 Gaspra (Veverka et al., 1994), 243 Ida (Belton et al., 1994), 433 Eros (Thomas et al., (2002), Buczkowski et al., 2008), 21 Lutetia (Massironi et al., 2011, *Besse et al., 2014*) and 4 Vesta (Buczkowski et al., 2*012). Hence, such source of information can be deeper used for a novel approach presented on Phobos with the aim of providing more hints on its harshly debated origin. Stereo-plots and cyclographs represent two methods, unified under the name of stereographic projections, commonly used to describe the statistic of the orientations (dip-angle and dip-direction) of different planes with respect to cardinal points and a reference horizontal plane (Bucher, 1944; Phillips, 1954; Ragan, 1985). However this reference system is ambiguous for any applications on small irregular bodies such as asteroids or comets since it does not permit to highlight systems of parallel anisotropies and to have an idea of their distribution with respect to a given surface feature (for example an impact crater). In this work we show a novel approach for stereographic projections focusing to a multi-reference system. The multi-reference system can be centered on a specific surface feature such as a crater and can alternatively use an absolute reference plane containing the center of figure of the body (to retrieve systems of parallel anisotropies) or a relative horizontal plane (to understand the distribution of the anisotropies with respect to the central feature). In this way we are able to well define the distribution of the grooves expected to be originated from a impact cratering event in a small body. Following this methodology, we have extracted 352 3D fracture planes from the attitudes of the grooves over the surface topography of Phobos and, for each plane, the local surface versor has been defined. Consequently, stereo-plots on

  20. Fixing a Reference Frame to a Moving and Deforming Continent

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Kreemer, C.; Hammond, W. C.

    2016-12-01

    The U.S. National Spatial Reference System will be modernized in 2022. A foundational component will be a geocentric reference frame fixed to the North America tectonic plate. Here we address challenges of fixing a reference frame to a moving and deforming continent. Scientific applications motivate that we fix the frame with a scale consistent with the SI system, an origin that coincides with the Earth system's center of mass, and with axes attached to the rigidly rotating interior of the North America plate. Realizing the scale and origin is now achieved to < 0.5 mm/yr by combining space-geodetic techniques (SLR, VLBI, GPS, and DORIS) in the global system, ITRS. To realize the no-net rotation condition, the complexity of plate boundary deformation demands that we only select GPS stations far from plate boundaries. Another problem is that velocity uncertainties in models of glacial isostatic adjustment (GIA) are significant compared to uncertainties in observed velocities. GIA models generally agree that far-field horizontal velocities tend to be directed toward/away from Hudson Bay, depending on mantle viscosity, with uncertain sign and magnitude of velocity. Also in the far field, strain rates tend to be small beyond the peripheral bulge ( US-Canada border). Thus the Earth's crust in the US east of the Rockies may appear to be rigid, even if this region moves relative to plate motion. This can affect Euler vector estimation, with implications (pros and cons) on scientific interpretation. Our previous approach [ref. 1] in defining the NA12 frame was to select a core set of 30 stations east of the Rockies and south of the U.S.-Canada border that satisfy strict criteria on position time series quality. The resulting horizontal velocities have an RMS of 0.3 mm/yr, quantifying a combination of plate rigidity and accuracy. However, this does not rule out possible common-mode motion arising from GIA. For the development of new frame NA16, we consider approaches to this

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  3. Quantum communication complexity of establishing a shared reference frame.

    PubMed

    Rudolph, Terry; Grover, Lov

    2003-11-21

    We discuss the aligning of spatial reference frames from a quantum communication complexity perspective. This enables us to analyze multiple rounds of communication and give several simple examples demonstrating tradeoffs between the number of rounds and the type of communication. Using a distributed variant of a quantum computational algorithm, we give an explicit protocol for aligning spatial axes via the exchange of spin-1/2 particles which makes no use of either exchanged entangled states, or of joint measurements. This protocol achieves a worst-case fidelity for the problem of "direction finding" that is asymptotically equivalent to the optimal average case fidelity achievable via a single forward communication of entangled states.

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

    ERIC Educational Resources Information Center

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  6. X/Ka Celestial Reference Frame Improvements: Vision to Reality

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Bagri, D. S.; Brticliffe, M. J.; Clark, J. E.; Franco, M. M.; García-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Moll, V. E.; Navarro, R.; Rogstad, S. P.; Proctor, R. C.; Skjerve, L. J.; Soriano, M. A.; Sovers, O. J.; Tucker, B. C.; Wang, D.; White, L. A.

    2010-12-01

    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.

  7. Spatial reasoning with multiple intrinsic frames of reference.

    PubMed

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

    2012-01-01

    Establishing and updating spatial relationships between objects in the environment is vital to maintaining situation awareness and supporting many socio-spatial tasks. In a complex environment, people often need to utilize multiple reference systems that are intrinsic to different objects (intrinsic frame of reference, IFOR), but these IFORs may conflict with each other in one or more ways. Current spatial cognition theories do not adequately address how people handle multi-IFOR reasoning problems. Two experiments manipulated relative orientations of two task-relevant objects with intrinsic axes of orientation as well as their relative task salience. Response times (RTs) decreased with increasing salience of the targeted IFOR. In addition, RTs increased as a consequence of intrinsic orientation conflict, but not by amount of orientation difference. The results suggest that people encounter difficulties when they have to process two conflicting IFOR representations, and that they seem to prioritize processing of each IFOR by salience. © 2012 Hogrefe Publishing

  8. International Terrestrial Reference Frame for Global Change Monitoring

    NASA Astrophysics Data System (ADS)

    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.

  9. Estimating the Celestial Reference Frame via Intra-Technique Combination

    NASA Astrophysics Data System (ADS)

    Iddink, Andreas; Artz, Thomas; Halsig, Sebastian; Nothnagel, Axel

    2016-12-01

    One of the primary goals of Very Long Baseline Interferometry (VLBI) is the determination of the International Celestial Reference Frame (ICRF). Currently the third realization of the internationally adopted CRF, the ICRF3, is under preparation. In this process, various optimizations are planned to realize a CRF that does not benefit only from the increased number of observations since the ICRF2 was published. The new ICRF can also benefit from an intra-technique combination as is done for the Terrestrial Reference Frame (TRF). Here, we aim at estimating an optimized CRF by means of an intra-technique combination. The solutions are based on the input to the official combined product of the International VLBI Service for Geodesy and Astrometry (IVS), also providing the radio source parameters. We discuss the differences in the setup using a different number of contributions and investigate the impact on TRF and CRF as well as on the Earth Orientation Parameters (EOPs). Here, we investigate the differences between the combined CRF and the individual CRFs from the different analysis centers.

  10. Flexible conceptual projection of time onto spatial frames of reference.

    PubMed

    Torralbo, Ana; Santiago, Julio; Lupiáñez, Juan

    2006-07-08

    Flexibility in conceptual projection constitutes one of the most challenging issues in the embodiment and conceptual metaphor literatures. We sketch a theoretical proposal that places the burden of the explanation on attentional dynamics in interaction with mental models in working memory that are constrained to be maximally coherent. A test of this theory is provided in the context of the conceptual projection of time onto the domain of space. Participants categorized words presented at different spatial locations (back-front, left-right) as referring to the past or to the future. Responses were faster when the irrelevant word location was congruent with the back-past, front-future metaphoric mapping. Moreover, when a new highly task-relevant spatial frame of reference was introduced, it changed the projection of past and future onto space in a way that was congruent with the new frame (past was now projected to left space and future to right space), as predicted by the theory. This study shows that there is substantial flexibility in conceptual projection and opens a venue to study metaphoric variation across tasks, individuals, and cultures as the result of attentional dynamics.

  11. Lift-Off: Using Reference Imagery and Freehand Sketching to Create 3D Models in VR.

    PubMed

    Jackson, Bret; Keefe, Daniel F

    2016-04-01

    Three-dimensional modeling has long been regarded as an ideal application for virtual reality (VR), but current VR-based 3D modeling tools suffer from two problems that limit creativity and applicability: (1) the lack of control for freehand modeling, and (2) the difficulty of starting from scratch. To address these challenges, we present Lift-Off, an immersive 3D interface for creating complex models with a controlled, handcrafted style. Artists start outside of VR with 2D sketches, which are then imported and positioned in VR. Then, using a VR interface built on top of image processing algorithms, 2D curves within the sketches are selected interactively and "lifted" into space to create a 3D scaffolding for the model. Finally, artists sweep surfaces along these curves to create 3D models. Evaluations are presented for both long-term users and for novices who each created a 3D sailboat model from the same starting sketch. Qualitative results are positive, with the visual style of the resulting models of animals and other organic subjects as well as architectural models matching what is possible with traditional fine art media. In addition, quantitative data from logging features built into the software are used to characterize typical tool use and suggest areas for further refinement of the interface.

  12. Terrestrial Reference Systems and Frames. A review of current activities

    NASA Astrophysics Data System (ADS)

    Boucher, C. C.

    2009-12-01

    Terrestrial Reference Systems (TRS) refer to an important domain of Geodesy, involving both theoretical and applied aspects, as well as deep connections with Astronomy, Earth Sciences and Geo-information. The concept of TRS implies several visions : - An astronomical vision, using TRS to study translational and rotational motion of the Earth in inertial space - An Earth Science vision, using TRS to build physical models of the Earth system, and its various components (solid earth, oceans, atmosphere, hydrosphere) - A metrological vision, using TRS together with suitable coordinate systems (geographical coordinates, map projections…) to define geographical position of objects in the Earth’s vicinity A survey of current activities in this area is presented, referring to works done by the International Association of Geodesy (IAG) and more specifically its Commission 1, GGOS and IERS. A focus is done on concepts and terminology, as well as progresses to get a wide acceptance on the International Terrestrial Reference System (ITRS) and its system of realizations through global, regional and national frames, as well as through specific systems such as satellite navigation systems.

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

    ERIC Educational Resources Information Center

    Tull, Ashley; Freeman, Jerrid P.

    2011-01-01

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

  14. 3D echocardiographic reference ranges for normal left ventricular volumes and strain: results from the EACVI NORRE study.

    PubMed

    Bernard, Anne; Addetia, Karima; Dulgheru, Raluca; Caballero, Luis; Sugimoto, Tadafumi; Akhaladze, Natela; Athanassopoulos, George D; Barone, Daniele; Baroni, Monica; Cardim, Nuno; Hagendorff, Andreas; Hristova, Krasimira; Ilardi, Federica; Lopez, Teresa; de la Morena, Gonzalo; Popescu, Bogdan A; Penicka, Martin; Ozyigit, Tolga; David Rodrigo Carbonero, Jose; van de Veire, Nico; Stephan Von Bardeleben, Ralph; Vinereanu, Dragos; Luis Zamorano, Jose; Martinez, Christophe; Magne, Julien; Cosyns, Bernard; Donal, Erwan; Habib, Gilbert; Badano, Luigi P; Lang, Roberto M; Lancellotti, Patrizio

    2017-04-01

    To obtain the normal ranges for 3D echocardiography (3DE) measurement of left ventricular (LV) volumes, function, and strain from a large group of healthy volunteers. A total of 440 (mean age: 45 ± 13 years) out of the 734 healthy subjects enrolled at 22 collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study had good-quality 3DE data sets that have been analysed with a vendor-independent software package allowing homogeneous measurements regardless of the echocardiographic machine used to acquire the data sets. Upper limits of LV end-diastolic and end-systolic volumes were larger in men (97 and 42 mL/m2) than in women (82 and 35 mL/m2; P < 0.0001). Conversely, lower limits of LV ejection fraction were higher in women than in men (51% vs. 50%; P < 0.01). Similarly, all strain components were higher in women than in men. Lower range was -18.6% in men and -19.5% in women for 3D longitudinal strain, -27.0% and -27.6% for 3D circumferential strain, -33.2% and -34.4% for 3D tangential strain and 38.8% and 40.7% for 3D radial strain, respectively. LV volumes decreased with age in both genders (P < 0.0001), whereas LV ejection fraction increased with age only in men. Among 3DE LV strain components, the only one, which did not change with age was longitudinal strain. The NORRE study provides applicable 3D echocardiographic reference ranges for LV function assessment. Our data highlight the importance of age- and gender-specific reference values for both LV volumes and strain.

  15. Registration uncertainties between 3D cone beam computed tomography and different reference CT datasets in lung stereotactic body radiation therapy.

    PubMed

    Oechsner, Markus; Chizzali, Barbara; Devecka, Michal; Combs, Stephanie Elisabeth; Wilkens, Jan Jakob; Duma, Marciana Nona

    2016-10-26

    The aim of this study was to analyze differences in couch shifts (setup errors) resulting from image registration of different CT datasets with free breathing cone beam CTs (FB-CBCT). As well automatic as manual image registrations were performed and registration results were correlated to tumor characteristics. FB-CBCT image registration was performed for 49 patients with lung lesions using slow planning CT (PCT), average intensity projection (AIP), maximum intensity projection (MIP) and mid-ventilation CTs (MidV) as reference images. Both, automatic and manual image registrations were applied. Shift differences were evaluated between the registered CT datasets for automatic and manual registration, respectively. Furthermore, differences between automatic and manual registration were analyzed for the same CT datasets. The registration results were statistically analyzed and correlated to tumor characteristics (3D tumor motion, tumor volume, superior-inferior (SI) distance, tumor environment). Median 3D shift differences over all patients were between 0.5 mm (AIPvsMIP) and 1.9 mm (MIPvsPCT and MidVvsPCT) for the automatic registration and between 1.8 mm (AIPvsPCT) and 2.8 mm (MIPvsPCT and MidVvsPCT) for the manual registration. For some patients, large shift differences (>5.0 mm) were found (maximum 10.5 mm, automatic registration). Comparing automatic vs manual registrations for the same reference CTs, ∆AIP achieved the smallest (1.1 mm) and ∆MIP the largest (1.9 mm) median 3D shift differences. The standard deviation (variability) for the 3D shift differences was also the smallest for ∆AIP (1.1 mm). Significant correlations (p < 0.01) between 3D shift difference and 3D tumor motion (AIPvsMIP, MIPvsMidV) and SI distance (AIPvsMIP) (automatic) and also for 3D tumor motion (∆PCT, ∆MidV; automatic vs manual) were found. Using different CT datasets for image registration with FB-CBCTs can result in different 3D couch shifts. Manual registrations

  16. Reference frame selection in dialog: priming or preference?

    PubMed Central

    Johannsen, Katrin; Ruiter, Jan P. De

    2013-01-01

    We investigate effects of priming and preference on frame of reference (FOR) selection in dialog. In a first study, we determine FOR preferences for specific object configurations to establish a baseline. In a second study, we focus on the selection of the relative or the intrinsic FOR in dialog using the same stimuli and addressing the questions whether (a) interlocutors prime each other to use the same FOR consistently or (b) the preference for the intrinsic FOR predominates priming effects. Our results show effects of priming (more use of the relative FOR) and a decreased preference for the intrinsic FOR. However, as FOR selection did not have an effect on target trial accuracy, neither effect alone represents the key to successful communication in this domain. Rather, we found that successful communication depended on the adaptation of strategies between interlocutors: the more the interlocutors adapted to each other's strategies, the more successful they were. PMID:24137122

  17. Comparison of Realizations of the Terrestrial Reference Frame

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  18. A Global Moving Hotspot Reference Frame: How well it fits?

    NASA Astrophysics Data System (ADS)

    Doubrovine, P. V.; Steinberger, B.; Torsvik, T. H.

    2010-12-01

    Since the early 1970s, when Jason Morgan proposed that hotspot tracks record motion of lithosphere over deep-seated mantle plumes, the concept of fixed hotspots has dominated the way we think about absolute plate reconstructions. In the last decade, with compelling evidence for southward drift of the Hawaiian hotspot from paleomagnetic studies, and for the relative motion between the Pacific and Indo-Atlantic hotspots from refined plate circuit reconstructions, the perception changed and a global moving hotspot reference frame (GMHRF) was introduced, in which numerical models of mantle convection and advection of plume conduits in the mantle flow were used to estimate hotspot motion. This reference frame showed qualitatively better performance in fitting hotspot tracks globally, but the error analysis and formal estimates of the goodness of fitted rotations were lacking in this model. Here we present a new generation of the GMHRF, in which updated plate circuit reconstructions and radiometric age data from the hotspot tracks were combined with numerical models of plume motion, and uncertainties of absolute plate rotations were estimated through spherical regression analysis. The overall quality of fit was evaluated using a formal statistical test, by comparing misfits produced by the model with uncertainties assigned to the data. Alternative plate circuit models linking the Pacific plate to the plates of Indo-Atlantic hemisphere were tested and compared to the fixed hotspot models with identical error budgets. Our results show that, with an appropriate choice of the Pacific plate circuit, it is possible to reconcile relative plate motions and modeled motions of mantle plumes globally back to Late Cretaceous time (80 Ma). In contrast, all fixed hotspot models failed to produce acceptable fits for Paleogene to Late Cretaceous time (30-80 Ma), highlighting significance of relative motion between the Pacific and Indo-Atlantic hotspots during this interval. The

  19. Accurate Realization of GPS Vertical Global Reference Frame

    NASA Technical Reports Server (NTRS)

    Elosegui, Pedro

    2005-01-01

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

  20. Learning to Provide 3D Virtual Reference: A Library Science Assignment

    ERIC Educational Resources Information Center

    Johnson, Megan; Purpur, Geraldine; Abbott, Lisa T.

    2009-01-01

    In spring semester 2009, two of the authors taught LIB 5020--Information Sources & Services to graduate library science students at Appalachian State University. The course covers information seeking patterns and provides an overview of reference services. The course is also designed to examine and evaluate library reference materials and…

  1. Improvements in the Global Reference Atmospheric Model and comparisons with a global 3-D numerical model

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; Alyea, F. N.; Chimonas, George; Cunnold, D. M.

    1989-01-01

    The status of the Global Reference Atmospheric Model (GRAM) and the Mars Global Reference Atmospheric Model (MARS-GRAM) is reviewed. The wavelike perturbations observed in the Viking 1 and 2 surface pressure data, in the Mariner 9 IR spectroscopy data, and in the Viking 1 and 2 lander entry profiles were studied and the results interpreted.

  2. Learning to Provide 3D Virtual Reference: A Library Science Assignment

    ERIC Educational Resources Information Center

    Johnson, Megan; Purpur, Geraldine; Abbott, Lisa T.

    2009-01-01

    In spring semester 2009, two of the authors taught LIB 5020--Information Sources & Services to graduate library science students at Appalachian State University. The course covers information seeking patterns and provides an overview of reference services. The course is also designed to examine and evaluate library reference materials and…

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  4. Spatial frames of reference and somatosensory processing: a neuropsychological perspective.

    PubMed Central

    Vallar, G

    1997-01-01

    In patients with lesions in the right hemisphere, frequently involving the posterior parietal regions, left-sided somatosensory (and visual and motor) deficits not only reflect a disorder of primary sensory processes, but also have a higher-order component related to a defective spatial representation of the body. This additional factor, related to right brain damage, is clinically relevant: contralesional hemianaesthesia (and hemianopia and hemiplegia) is more frequent in right brain-damaged patients than in patients with damage to the left side of the brain. Three main lines of investigation suggest the existence of this higher-order pathological factor. (i) Right brain-damaged patients with left hemineglect may show physiological evidence of preserved processing of somatosensory stimuli, of which they are not aware. Similar results have been obtained in the visual domain. (ii) Direction-specific vestibular, visual optokinetic and somatosensory or proprioceptive stimulations may displace spatial frames of reference in right brain-damaged patients with left hemineglect, reducing or increasing the extent of the patients' ipsilesional rightward directional error, and bring about similar directional effects in normal subjects. These stimulations, which may improve or worsen a number of manifestations of the neglect syndrome (such as extrapersonal and personal hemineglect), have similar effects on the severity of left somatosensory deficits (defective detection of tactile stimuli, position sense disorders). However, visuospatial hemineglect and the somatosensory deficits improved by these stimulations are independent, albeit related, disorders. (iii) The severity of left somatosensory deficits is affected by the spatial position of body segments, with reference to the midsagittal plane of the trunk. A general implication of these observations is that spatial (non-somatotopic) levels of representation contribute to corporeal awareness. The neural basis of these spatial

  5. Electron Microscopy: From 2D to 3D Images with Special Reference to Muscle

    PubMed Central

    2015-01-01

    This is a brief and necessarily very sketchy presentation of the evolution in electron microscopy (EM) imaging that was driven by the necessity of extracting 3-D views from the essentially 2-D images produced by the electron beam. The lens design of standard transmission electron microscope has not been greatly altered since its inception. However, technical advances in specimen preparation, image collection and analysis gradually induced an astounding progression over a period of about 50 years. From the early images that redefined tissues, cell and cell organelles at the sub-micron level, to the current nano-resolution reconstructions of organelles and proteins the step is very large. The review is written by an investigator who has followed the field for many years, but often from the sidelines, and with great wonder. Her interest in muscle ultrastructure colors the writing. More specific detailed reviews are presented in this issue. PMID:26913146

  6. Geodetic Reference System Transformations of 3d Archival Geospatial Data Using a Single SSC Terrasar-X Image

    NASA Astrophysics Data System (ADS)

    Vassilaki, D. I.; Stamos, A. A.

    2016-06-01

    Many older maps were created using reference coordinate systems which are no longer available, either because no information to a datum was taken in the first place or the reference system is forgotten. In other cases the relationship between the map's coordinate system is not known with precision, meaning that its absolute error is much larger than its relative error. In this paper the georeferencing of medium-scale maps is computed using a single TerraSAR-X image. A single TerraSAR-X image has high geolocation accuracy but it has no 3D information. The map, however, provides the missing 3D information, and thus it is possible to compute the georeferencing of the map using the TerraSAR-X geolocation information, assembling the information of both sources to produce 3D points in the reference system of the TerraSAR-X image. Two methods based on this concept are proposed. The methods are tested with real world examples and the results are promising for further research.

  7. Making Inexpensive 3-D Models

    ERIC Educational Resources Information Center

    Manos, Harry

    2016-01-01

    Visual aids are important to student learning, and they help make the teacher's job easier. Keeping with the "TPT" theme of "The Art, Craft, and Science of Physics Teaching," the purpose of this article is to show how teachers, lacking equipment and funds, can construct a durable 3-D model reference frame and a model gravity…

  8. Making Inexpensive 3-D Models

    ERIC Educational Resources Information Center

    Manos, Harry

    2016-01-01

    Visual aids are important to student learning, and they help make the teacher's job easier. Keeping with the "TPT" theme of "The Art, Craft, and Science of Physics Teaching," the purpose of this article is to show how teachers, lacking equipment and funds, can construct a durable 3-D model reference frame and a model gravity…

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

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1989-01-01

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

  10. Reference frame congruency in search-and-rescue tasks.

    PubMed

    Pavlovic, Nada J; Keillor, Jocelyn; Hollands, Justin G; Chignell, Mark H

    2009-04-01

    Our aim was to investigate how the congruency between visual displays and auditory cues affects performance on various spatial tasks. Previous studies have demonstrated that spatial auditory cues, when combined with visual displays, can enhance performance and decrease workload. However, this facilitation was achieved only when auditory cues shared a common reference frame (RF) with the visual display. In complex and dynamic environments, such as airborne search and rescue (SAR), it is often difficult to ensure such congruency. In a simulated SAR operation, participants performed three spatial tasks: target search, target localization, and target recall. The interface consisted of the camera view of the terrain from the aircraft-mounted sensor, a map of the area flown over, a joystick that controlled the sensor, and a mouse. Auditory cues were used to indicate target location. While flying in the scenario, participants searched for targets, identified their locations in one of two coordinate systems, and memorized their location relative to the terrain layout. Congruent cues produced the fastest and most accurate performance. Performance advantages were observed even with incongruent cues relative to neutral cues, and egocentric cues were more effective than exocentric cues. Although the congruent cues are most effective, in cases in which the same cue is used across spatial tasks, egocentric cues are a better choice than exocentric cues. Egocentric auditory cues should be used in display design for tasks that involve RF transformations, such as SAR, air traffic control, and unmanned aerial vehicle operations.

  11. Quantum Reference Frames in Flat Space-Time and Gravity

    NASA Astrophysics Data System (ADS)

    Mayburov, S.

    2002-12-01

    It was argued recently that in Quantum Mechanics (QM) the correct definition of physical reference frame (RF) must differ principally from universally accepted one. [1]. The reason is that in exact theory the quantum properties of any massive object M1 with which physical RF F1 associated must be taken into account, despite their possible smallness in laboratory conditions. Consequently F1 evolution must obey to Schrodinger equation, and its free state relative to external observer at rest F0 is the localizable wave packet Ψ(x1,t), not the classical trajectory. As the example F1 can be rocket in outer space and F0 earth, M0 → ∞. If F1 localized state Ψ(x,t0) ~ δ(x) prepared by F0 it will smear in space unrestrictedly with the time σx ~ t1/2. This smearing introduces additional uncertainty into the measurement of particles mi space coordinates by F1 xi1 = xi-x1 in F1, because x1 is also operator, mi states transformations between two such quantum RFs includes quantum corrections to Galilean transformations, which depends on RFs states vectors [1]. Consistent nonrelativistic quantization in such RFs of free particles mi and other quantum systems in two alternative formalisms was proposed [2]...

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-08-01

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

  14. Are allocentric spatial reference frames compatible with theories of Enactivism?

    PubMed

    König, Sabine U; Goeke, Caspar; Meilinger, Tobias; König, Peter

    2017-08-02

    Theories of Enactivism propose an action-oriented approach to understand human cognition. So far, however, empirical evidence supporting these theories has been sparse. Here, we investigate whether spatial navigation based on allocentric reference frames that are independent of the observer's physical body can be understood within an action-oriented approach. Therefore, we performed three experiments testing the knowledge of the absolute orientation of houses and streets towards north, the relative orientation of two houses and two streets, respectively, and the location of houses towards each other in a pointing task. Our results demonstrate that under time pressure, the relative orientation of two houses can be retrieved more accurately than the absolute orientation of single houses. With infinite time for cognitive reasoning, the performance of the task using house stimuli increased greatly for the absolute orientation and surpassed the slightly improved performance in the relative orientation task. In contrast, with streets as stimuli participants performed under time pressure better in the absolute orientation task. Overall, pointing from one house to another house yielded the best performance. This suggests, first, that orientation and location information about houses are primarily coded in house-to-house relations, whereas cardinal information is deduced via cognitive reasoning. Second, orientation information for streets is preferentially coded in absolute orientations. Thus, our results suggest that spatial information about house and street orientation is coded differently and that house orientation and location is primarily learned in an action-oriented way, which is in line with an enactive framework for human cognition.

  15. Method of multiple references for 3D imaging with Fourier transform interferometry.

    PubMed

    Lally, Evan; Gong, Jianmin; Wang, Anbo

    2010-08-16

    This letter presents an improved phase referencing technique, called Method of Multiple References, for optical profilometry. Based on a lookup table, the method eliminates several major drawbacks of single-reference Fourier Transform Interferometry by enabling surface error correction for steep slopes and step discontinuities, and by allowing mapping of multiple discrete objects using a single image set. The algorithm is tested using a fiber optic coupler-based FTI system and shown to have RMS surface error less than 0.03 mm.

  16. Form finding and analysis of extensible membranes attached to 2-D and 3-D frames intended for micro air vehicles via experimentally validated finite element methods

    NASA Astrophysics Data System (ADS)

    Abudaram, Yaakov Jack

    This work is concerned with a new method to apply consistent and known pretension to silicone rubber membranes intended for micro air vehicles as well as an understanding in the science of developed pre-tension in membranes constrained by 2- D and 3-D frames and structures. Pre-tension has a marked effect on the static and dynamic response of membrane wings and controls the overall deflections, as such control and measurement of the membrane pre-tension is important. Two different 2-D frame geometries were fabricated to evaluate the technique. For open-cell frames, the pretension was not uniform, whereas it was for closed-cell frames. Results show developed full-field stress and strain fields as a function of membrane attachment temperature and frame geometry along with experimental iterations to prove repeatability. The membranes can be stretched to a specific pretension according to the temperature at which it adheres to frames. Strain fields in membranes attached to 3-D frames at various temperatures are modeled through FEA utilizing Abaqus to be able to predict the developed membrane deformations, stresses, and strains. Rigid frames with various curvatures are built via appropriate molds and then adhered to silicone rubber membranes and elevated to various temperatures to achieve different pre-strains for experimental validation. Additional experiments are conducted for more complex frame geometries involving both convex and concave topologies embedded within frames. Results are then compared with the Abaqus outputs to validate the accuracy of the FEA model. Highly compliant wings have been used for MAV platforms, where the wing structure is determined by some combination of carbon fiber composites and a membrane skin, adhered in between the layers of composite material. Another new technique of attaching membranes firmly on wing structures is introduced, which involves the application of a technology known as corona treatment coupled with another method of

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

    SciTech Connect

    Hollerbach, K.; Hollister, A.

    1995-11-01

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

  18. Goce Gradients In Various Reference Frames and Their Accuracies

    NASA Astrophysics Data System (ADS)

    Müller, J.; Oberndorfer, H.

    The objective of GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) is the determination of the Earth's gravity field with high spatial resolution. The main sensor is a gradiometer which measures gravity gradients, i.e. the matrix of the sec- ond derivatives of the gravitational potential. Some of them (the diagonal compo- nents of the gravity tensor) are observed with highest accuracy of about 3 mE/ (Hz), whereas the others are determined less accurate. The gradients will be observed in the instrument frame, which approximates the satellite frame (beside some misalign- ments). Some users, however, need the gradients in more convenient frames for further processing. For the transformation of the gradients in other frames (e.g.in the nominal orbital frame or a terrestrial frame), the transformation parameters (orientation angles) and the single components of the gravity tensor have to be known with sufficient ac- curacy. As the accuracy of both quantities is restricted because of conceptual reasons, the resulting gradients in the new frames have only a reduced accuracy. We show how the elements of the gravity tensor and their accuracies look like in the various frames as well as their spectral behaviour.

  19. Global GPS Solution for Station Velocities Without Conventional Reference Frame

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    Meaningful GPS station velocities should not depend on the choice of a specific reference frame since the origin translation rate (OTR) can be estimated from velocities in stable plate interiors, and an appropriate correction can be applied (R.W. King, private communication). A conventional approach is to translate and rotate the initial, loosely constrained geodetic solution in order to best fit the velocities of official ITRF2000. A very different approach used in this study consists of following steps: (1) Assume that tectonic plates do not move with respect to each other and that they are perfectly rigid. This assumption is equivalent to setting all a priori velocities to zero. (2) Translate and rotate the loose geodetic solution to best fit the zero velocities at stations uniformly distributed over the whole network. (3) Evaluate OTR from station velocities in stable plate interiors, obtained in step 2. (4) Correct the velocities for OTR and estimate plate rotation vectors. (5) Repeat steps 1-4 as many times as required, typically four iterations is adequate. Such approach was realized in recent versions of the GAMIT/GLOBK software which we used. We tested at step 1 various starting reference frames with nonzero a priori velocities, such as ITRF2000 and NUVEL1-A, with no change in the final solution at step 5. Our database included: all daily GAMIT solutions for positions of the IGS network performed at SOPAC in interval 1995.0 - 2005.5; our daily GAMIT solutions from observations of several tens of continuous and survey mode stations on the Eurasian, North American, and Pacific plates. We then combined by GLOBK (Kalman filter) all daily solutions in the database and produced a multiyear loose solution for positions and velocities. By iteratively applying procedure 1-5, we came to the constrained solution in terms of plate-residual velocities for all stations and a set of rotation vectors for eight major plates. 76 sites with zero velocity chosen for initial

  20. Trajectory models and reference frames for crustal motion geodesy

    NASA Astrophysics Data System (ADS)

    Bevis, Michael; Brown, Abel

    2014-03-01

    We sketch the evolution of station trajectory models used in crustal motion geodesy over the last several decades, and describe some recent generalizations of these models that allow geodesists and geophysicists to parameterize accelerating patterns of displacement in general, and postseismic transient deformation in particular. Modern trajectory models are composed of three sub-models that represent secular trends, annual oscillations, and instantaneous jumps in coordinate time series. Traditionally the trend model invoked constant station velocity. This can be generalized by assuming that position is a polynomial function of time. The trajectory model can also be augmented as needed, by including one or more logarithmic transients in order to account for typical multi-year patterns of postseismic transient motion. Many geodetic and geophysical research groups are using general classes of trajectory model to characterize their crustal displacement time series, but few if any of them are using these trajectory models to define and realize the terrestrial reference frames (RFs) in which their time series are expressed. We describe a global GPS reanalysis program in which we use two general classes of trajectory model, tuned on a station by station basis. We define the network trajectory model as the set of station trajectory models encompassing every station in the network. We use the network trajectory model from the each global analysis to assign prior position estimates for the next round of GPS data processing. We allow our daily orbital solutions to relax so as to maintain their consistency with the network polyhedron. After several iterations we produce GPS time series expressed in a RF similar to, but not identical with ITRF2008. We find that each iteration produces an improvement in the daily repeatability of our global time series and in the predictive power of our trajectory models.

  1. Improved DORIS Reference Frame Solution from NASA GSFC

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  2. Concepts for reference frames in geodesy and geodynamics - The reference directions

    NASA Technical Reports Server (NTRS)

    Grafarend, E. W.; Richter, B.; Mueller, I. I.; Papo, H. B.

    1979-01-01

    The paper discusses a study that establishes a reference frame, moving with the earth (in some average sense), in which the geometric and dynamical behavior of the earth can be monitored, and whose motion with respect to inertial space can also be determined. Emphasis is placed on the fact that the reference directions at an observation point on the earth surface, are defined by fundamental vectors for both space and time. The interrelationships between this space- and time-variant angular parameter are illustrated in a commutative diagram and tower of triads. Although the model tower is also space- and time-variant, its variations are described by adopted parameters using our current knowledge of the earth.

  3. An Automated Reference Frame Selection (ARFS) Algorithm for Cone Imaging with Adaptive Optics Scanning Light Ophthalmoscopy

    PubMed Central

    Salmon, Alexander E.; Cooper, Robert F.; Langlo, Christopher S.; Baghaie, Ahmadreza; Dubra, Alfredo; Carroll, Joseph

    2017-01-01

    Purpose To develop an automated reference frame selection (ARFS) algorithm to replace the subjective approach of manually selecting reference frames for processing adaptive optics scanning light ophthalmoscope (AOSLO) videos of cone photoreceptors. Methods Relative distortion was measured within individual frames before conducting image-based motion tracking and sorting of frames into distinct spatial clusters. AOSLO images from nine healthy subjects were processed using ARFS and human-derived reference frames, then aligned to undistorted AO-flood images by nonlinear registration and the registration transformations were compared. The frequency at which humans selected reference frames that were rejected by ARFS was calculated in 35 datasets from healthy subjects, and subjects with achromatopsia, albinism, or retinitis pigmentosa. The level of distortion in this set of human-derived reference frames was assessed. Results The average transformation vector magnitude required for registration of AOSLO images to AO-flood images was significantly reduced from 3.33 ± 1.61 pixels when using manual reference frame selection to 2.75 ± 1.60 pixels (mean ± SD) when using ARFS (P = 0.0016). Between 5.16% and 39.22% of human-derived frames were rejected by ARFS. Only 2.71% to 7.73% of human-derived frames were ranked in the top 5% of least distorted frames. Conclusion ARFS outperforms expert observers in selecting minimally distorted reference frames in AOSLO image sequences. The low success rate in human frame choice illustrates the difficulty in subjectively assessing image distortion. Translational Relevance Manual reference frame selection represented a significant barrier to a fully automated image-processing pipeline (including montaging, cone identification, and metric extraction). The approach presented here will aid in the clinical translation of AOSLO imaging. PMID:28392976

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We have constructed an X/Ka-band (8.4/32 GHz) celestial reference frame using over seventy ~24-hour sessions with the Deep Space Network. We detected 646 sources covering the full 24 hours of right ascension and the full range of declinations. Comparison of 520 X/Ka sources in common with the S/X-band (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 167 micro-arcsec μas in RA cos(dec) and 219 μas in Dec. There is evidence for systematic errors at the 100 μas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling. We recently began a collaboration with ESA using their Malargüe, Argentina antenna. This site greatly improves our geometry in the south. Compared to X-band, Ka-band allows access to more compact source morphology and reduced core shift. Existing X/Ka data and simulated Gaia data predict a frame tie precision of 7 μas (1-sigma, per 3-D rotation component) with anticipated improvements reducing that to ~5 μas per component.

  5. 3D phase unwrapping using global expected phase as a reference: application to MRI global shimming.

    PubMed

    Liu, Wentao; Tang, Xin; Ma, Yajun; Gao, Jia-Hong

    2013-07-01

    MRI phase data often suffers from phase wrapping (i.e., phase may be discontinuous by 2π jumps). Numerous MRI phase unwrapping strategies were developed in the past using a criterion based on phase information of local or neighboring voxels. In this study, an alternative and novel three dimensional phase unwrapping strategy is introduced. This method considers the global character of the phase distribution and utilizes continuous trigonometric functions to construct an expected phase map as an unwrapping reference, which is then used to guide the phase correction of every individual voxel. The original phase is estimated by analyzing the derivative of the wrapped phase image. Simulations of various phase wrapped situations were performed and this new method was also used for an in vivo application (i.e., MRI automatic global shimming). Both simulated and experimental results demonstrate that our proposed method is more reliable and robust than traditional algorithms at obtaining correct phase maps, especially in regions of low-signal and air cavities, such as the abdomen and pelvis.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

  9. Pose-invariant face-head identification using a bank of neural networks and the 3D neck reference point

    NASA Astrophysics Data System (ADS)

    Hild, Michael; Yoshida, Kazunobu; Hashimoto, Motonobu

    2003-03-01

    A method for recognizing faces in relativley unconstrained environments, such as offices, is described. It can recognize faces occurring over an extended range of orientations and distances relative to the camera. As the pattern recognition mechanism, a bank of small neural networks of the multilayer perceptron type is used, where each perceptron has the task of recognizing only a single person's face. The perceptrons are trained with a set of nine face images representing the nine main facial orientations of the person to be identified, and a set face images from various other persons. The center of the neck is determined as the reference point for face position unification. Geometric normalization and reference point determination utilizes 3-D data point measurements obtained with a stereo camera. The system achieves a recognition rate of about 95%.

  10. DT-CWT Robust Filtering Algorithm for The Extraction of Reference and Waviness from 3-D Nano Scalar Surfaces

    NASA Astrophysics Data System (ADS)

    Ren, Zhi Ying.; Gao, ChengHui.; Han, GuoQiang.; Ding, Shen; Lin, JianXing.

    2014-04-01

    Dual tree complex wavelet transform (DT-CWT) exhibits superiority of shift invariance, directional selectivity, perfect reconstruction (PR), and limited redundancy and can effectively separate various surface components. However, in nano scale the morphology contains pits and convexities and is more complex to characterize. This paper presents an improved approach which can simultaneously separate reference and waviness and allows an image to remain robust against abnormal signals. We included a bilateral filtering (BF) stage in DT-CWT to solve imaging problems. In order to verify the feasibility of the new method and to test its performance we used a computer simulation based on three generations of Wavelet and Improved DT-CWT and we conducted two case studies. Our results show that the improved DT-CWT not only enhances the robustness filtering under the conditions of abnormal interference, but also possesses accuracy and reliability of the reference and waviness from the 3-D nano scalar surfaces.

  11. Connection Between the ICRF and the Dynamical Reference Frame for the Outer Planets

    NASA Astrophysics Data System (ADS)

    da Silva Neto, D. N.; Assafin, M.; Andrei, A. H.; Vieira Martins, R.

    2005-01-01

    This work brings an approach intending to improve the connection between the Dynamical Reference Frame and the Extragalactic Reference Frame. For that, close encounters of outer Solar System objects and quasars are used. With this goal, Uranus, Neptune and two quasars were observed at Laborat´orio Nacional de Astrof´ısica (LNA), Brazil. The optical reference frame is the HCRF, as given by the UCAC2 catalogue. The first results show an accuracy of 45 mas - 50 mas in the optical positions. The optical minus radio offsets give the local orientation between the catalogue and radio frame. From this, it is possible to place the optical planet coordinates on the extragalactic frame. A comparison between the new corrected optical coordinates and the respective DE ephemeris to these planets can give the instant orientations of the Dynamical Reference Frame with regard to the ICRS, for this zone of outer Solar System.

  12. The Inertial Property of Approximately Inertial Frames of Reference

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  13. The Inertial Property of Approximately Inertial Frames of Reference

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  14. Second-Order Inelastic Dynamic Analysis of 3D Semi-Rigid Steel Frames Under Earthquake Loads with Three Components

    SciTech Connect

    Ozakgul, Kadir

    2008-07-08

    In this study, it has been presented an algorithm for second-order elastoplastic dynamic time-history analysis of three dimensional frames that have steel members with semirigid joints. The proposed analysis accounts for material, geometric and connection nonlinearities. Material nonlinearity have been modeled by the Ramberg-Osgood relation. While the geometric nonlinearity caused by axial force has been described by the use of the geometric stiffness matrix, the nonlinearity caused by the interaction between the axial force and bending moment has been also described by the use of the stability functions. The independent hardening model has been used to describe the nonlinear behaviour of semi-rigid connections. Dynamic equation of motion has been solved by Newmark's constant acceleration method in time history domain.

  15. A Stable Reference Frame for Landslides Study in the Puerto Rico and Virgin Islands Region

    NASA Astrophysics Data System (ADS)

    Wang, G.

    2013-05-01

    In this study, we define a stable reference frame using 5-year continuous GPS data from 15 permanent stations located within a 100 km by 400 km area covering the Puerto Rico and Virgin Islands region. The local reference frame will be critical to accurate landslides monitoring in this region. The realization of the Stable Puerto Rico and Virgin Islands Reference Frame (SPRVIRF) is defined in terms of a 14-parameter similarity transformation from IGS08 to the local reference frame. The precise point positioning (PPP) with single receiver phase ambiguity resolution employed by the GIPSY/OASIS software package (V6.1.2) will be used in calculating coordinates within the International GNSS Service reference frame of 2008 (IGS08) in this study.

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

    NASA Astrophysics Data System (ADS)

    Blagojevic, D.; Vasilic, V.

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  18. Full-frame, high-speed 3D shape and deformation measurements using stereo-digital image correlation and a single color high-speed camera

    NASA Astrophysics Data System (ADS)

    Yu, Liping; Pan, Bing

    2017-08-01

    Full-frame, high-speed 3D shape and deformation measurement using stereo-digital image correlation (stereo-DIC) technique and a single high-speed color camera is proposed. With the aid of a skillfully designed pseudo stereo-imaging apparatus, color images of a test object surface, composed of blue and red channel images from two different optical paths, are recorded by a high-speed color CMOS camera. The recorded color images can be separated into red and blue channel sub-images using a simple but effective color crosstalk correction method. These separated blue and red channel sub-images are processed by regular stereo-DIC method to retrieve full-field 3D shape and deformation on the test object surface. Compared with existing two-camera high-speed stereo-DIC or four-mirror-adapter-assisted singe-camera high-speed stereo-DIC, the proposed single-camera high-speed stereo-DIC technique offers prominent advantages of full-frame measurements using a single high-speed camera but without sacrificing its spatial resolution. Two real experiments, including shape measurement of a curved surface and vibration measurement of a Chinese double-side drum, demonstrated the effectiveness and accuracy of the proposed technique.

  19. 3D mapping of existing observing capabilities in the frame of GAIA-CLIM H2020 project

    NASA Astrophysics Data System (ADS)

    Emanuele, Tramutola; Madonna, Fabio; Marco, Rosoldi; Francesco, Amato

    2017-04-01

    The aim of the Gap Analysis for Integrated Atmospheric ECV CLImate Monitoring (GAIA-CLIM) project is to improve our ability to use ground-based and sub-orbital observations to characterise satellite observations for a number of atmospheric Essential Climate Variables (ECVs). The key outcomes will be a "Virtual Observatory" (VO) facility of co-locations and their uncertainties and a report on gaps in capabilities or understanding, which shall be used to inform subsequent Horizon 2020 activities. In particular, Work Package 1 (WP1) of the GAIA-CLIM project is devoted to the geographical mapping of existing non-satellite measurement capabilities for a number of ECVs in the atmospheric, oceanic and terrestrial domains. The work carried out within WP1 has allowed to provide the users with an up-to-date geographical identification, at the European and global scales, of current surface-based, balloon-based and oceanic (floats) observing capabilities on an ECV by ECV basis for several parameters which can be obtained using space-based observations from past, present and planned satellite missions. Having alighted on a set of metadata schema to follow, a consistent collection of discovery metadata has been provided into a common structure and will be made available to users through the GAIA-CLIM VO in 2018. Metadata can be interactively visualized through a 3D Graphical User Interface. The metadataset includes 54 plausible networks and 2 aircraft permanent infrastructures for EO Characterisation in the context of GAIA-CLIM currently operating on different spatial domains and measuring different ECVs using one or more measurement techniques. Each classified network has in addition been assessed for suitability against metrological criteria to identifyy those with a level of maturity which enables closure on a comparison with satellite measurements. The metadata GUI is based on Cesium, a virtual globe freeware and open source written in Javascript. It allows users to apply

  20. Concurrent use of somatotopic and external reference frames in a tactile mislocalization task.

    PubMed

    Tamè, Luigi; Wühle, Anja; Petri, Caroline D; Pavani, Francesco; Braun, Christoph

    2017-02-01

    Localizing tactile stimuli on our body requires sensory information to be represented in multiple frames of reference along the sensory pathways. These reference frames include the representation of sensory information in skin coordinates, in which the spatial relationship of skin regions is maintained. The organization of the primary somatosensory cortex matches such somatotopic reference frame. In contrast, higher-order representations are based on external coordinates, in which body posture and gaze direction are taken into account in order to localise touch in other meaningful ways according to task demands. Dominance of one representation or the other, or the use of multiple representations with different weights, is thought to depend on contextual factors of cognitive and/or sensory origins. However, it is unclear under which situations a reference frame takes over another or when different reference frames are jointly used at the same time. The study of tactile mislocalizations at the fingers has shown a key role of the somatotopic frame of reference, both when touches are delivered unilaterally to a single hand, and when they are delivered bilaterally to both hands. Here, we took advantage of a well-established tactile mislocalization paradigm to investigate whether the reference frame used to integrate bilateral tactile stimuli can change as a function of the spatial relationship between the two hands. Specifically, supra-threshold interference stimuli were applied to the index or little fingers of the left hand 200ms prior to the application of a test stimulus on a finger of the right hand. Crucially, different hands postures were adopted (uncrossed or crossed). Results show that introducing a change in hand-posture triggered the concurrent use of somatotopic and external reference frames when processing bilateral touch at the fingers. This demonstrates that both somatotopic and external reference frames can be concurrently used to localise tactile

  1. Experimentally demonstrating reference-frame-independent violations of Bell inequalities

    NASA Astrophysics Data System (ADS)

    Palsson, Matthew S.; Wallman, Joel J.; Bennet, Adam J.; Pryde, Geoff J.

    2012-09-01

    We experimentally demonstrate, using qubits encoded in photon polarization, that two parties who share a single reference direction and use locally orthogonal measurements will always violate a Bell inequality, up to experimental deficiencies. This contrasts with the standard view of Bell inequalities, in which the parties need to completely align their measurements. Furthermore, we experimentally demonstrate that as the reference direction degrades the probability of the observers randomly choosing measurements that violate a Bell inequality decreases gradually and smoothly to 39.7%±0.1% in the limiting case that the observers do not share a reference direction. This result promises simplified distribution of entanglement between separated parties, with applications in fundamental investigations of quantum physics and tasks such as quantum communication.

  2. Full-Frame Reference for Test Photo of Moon

    NASA Technical Reports Server (NTRS)

    2005-01-01

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

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

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

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

  3. Full-Frame Reference for Test Photo of Moon

    NASA Technical Reports Server (NTRS)

    2005-01-01

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

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

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

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  5. Sensory transformations and the use of multiple reference frames for reach planning.

    PubMed

    McGuire, Leah M M; Sabes, Philip N

    2009-08-01

    The sensory signals that drive movement planning arrive in a variety of 'reference frames', and integrating or comparing them requires sensory transformations. We propose a model in which the statistical properties of sensory signals and their transformations determine how these signals are used. This model incorporates the patterns of gaze-dependent errors that we found in our human psychophysics experiment when the sensory signals available for reach planning were varied. These results challenge the widely held ideas that error patterns directly reflect the reference frame of the underlying neural representation and that it is preferable to use a single common reference frame for movement planning. We found that gaze-dependent error patterns, often cited as evidence for retinotopic reach planning, can be explained by a transformation bias and are not exclusively linked to retinotopic representations. Furthermore, the presence of multiple reference frames allows for optimal use of available sensory information and explains task-dependent reweighting of sensory signals.

  6. Education for Scientific Literacy: A Conceptual Frame of Reference and Some Applications

    ERIC Educational Resources Information Center

    Agin, Michael L.

    1974-01-01

    Presented is one individual's perception of the need for a scientifically literate population. A conceptual frame of reference for his position is described and some applications for curriculum development and science teaching are presented. (PEB)

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed

    Whedon, Caren A.

    2000-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  11. The visual system encodes others' direction of gaze in a first-person frame of reference.

    PubMed

    Palmer, Colin J; Clifford, Colin W G

    2017-11-01

    The primate visual system contains specialised neural mechanisms for encoding the direction of others' gaze. A foundational question that we can ask in this domain concerns the frame of reference in which another person's gaze is represented. Electrophysiological recordings in macaque monkeys suggest that direction of gaze might be encoded relative to the observer (i.e., in a first person reference frame) or relative to the head or body of the stimulus (i.e., in a second person reference frame). Here we use sensory adaptation to gaze direction as a psychophysical tool to probe how this property of the environment is represented in the human visual system. We find that strong perceptual aftereffects occur following adaptation to images that share a common direction of gaze in the first person reference frame, but vary in their direction of gaze in the second person reference frame. In contrast, sensory aftereffects do not occur following adaptation to images that share a common direction of gaze in the second person reference frame. These findings suggest that the adaptive coding of gaze direction in the human visual system occurs primarily in a first-person coordinate system. These data also provide strong support for perceptual constancy in the context of perceived gaze direction, implying that the direction of others' attention is represented in the brain as a higher-level perceptual property abstracted from lower-level cues (e.g., iris position and head rotation). Copyright © 2017 Elsevier B.V. All rights reserved.

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

    PubMed

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

    2016-02-08

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  14. Post-trial anatomical frame alignment procedure for comparison of 3D joint angle measurement from magnetic/inertial measurement units and camera-based systems.

    PubMed

    Li, Qingguo; Zhang, Jun-Tian

    2014-11-01

    Magnetic and inertial measurement units (MIMUs) have been widely used as an alternative to traditional camera-based motion capture systems for 3D joint kinematics measurement. Since these sensors do not directly measure position, a pre-trial anatomical calibration, either with the assistance of a special protocol/apparatus or with another motion capture system is required to establish the transformation matrices between the local sensor frame and the anatomical frame (AF) of each body segment on which the sensors are attached. Because the axes of AFs are often used as the rotational axes in the joint angle calculation, any difference in the AF determination will cause discrepancies in the calculated joint angles. Therefore, a direct comparison of joint angles between MIMU systems and camera-based systems is less meaningful because the calculated joint angles contain a systemic error due to the differences in the AF determination. To solve this problem a new post-trial AF alignment procedure is proposed. By correcting the AF misalignments, the joint angle differences caused by the difference in AF determination are eliminated and the remaining discrepancies are mainly from the measurement accuracy of the systems themselves. Lower limb joint angles from 30 walking trials were used to validate the effectiveness of the proposed AF alignment procedure. This technique could serve as a new means for calibrating magnetic/inertial sensor-based motion capture systems and correcting for AF misalignment in scenarios where joint angles are compared directly.

  15. Correlating Intravital Multi-Photon Microscopy to 3D Electron Microscopy of Invading Tumor Cells Using Anatomical Reference Points

    PubMed Central

    Karreman, Matthia A.; Mercier, Luc; Schieber, Nicole L.; Shibue, Tsukasa; Schwab, Yannick; Goetz, Jacky G.

    2014-01-01

    Correlative microscopy combines the advantages of both light and electron microscopy to enable imaging of rare and transient events at high resolution. Performing correlative microscopy in complex and bulky samples such as an entire living organism is a time-consuming and error-prone task. Here, we investigate correlative methods that rely on the use of artificial and endogenous structural features of the sample as reference points for correlating intravital fluorescence microscopy and electron microscopy. To investigate tumor cell behavior in vivo with ultrastructural accuracy, a reliable approach is needed to retrieve single tumor cells imaged deep within the tissue. For this purpose, fluorescently labeled tumor cells were subcutaneously injected into a mouse ear and imaged using two-photon-excitation microscopy. Using near-infrared branding, the position of the imaged area within the sample was labeled at the skin level, allowing for its precise recollection. Following sample preparation for electron microscopy, concerted usage of the artificial branding and anatomical landmarks enables targeting and approaching the cells of interest while serial sectioning through the specimen. We describe here three procedures showing how three-dimensional (3D) mapping of structural features in the tissue can be exploited to accurately correlate between the two imaging modalities, without having to rely on the use of artificially introduced markers of the region of interest. The methods employed here facilitate the link between intravital and nanoscale imaging of invasive tumor cells, enabling correlating function to structure in the study of tumor invasion and metastasis. PMID:25479106

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2012-05-01

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

  18. Accurate Realization of GPS Vertical Global Reference Frame

    NASA Technical Reports Server (NTRS)

    Elosegui, Pedro

    2004-01-01

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

  19. Disentangling gravitational, environmental, and egocentric reference frames in spatial neglect.

    PubMed

    Karnath, H O; Fetter, M; Niemeier, M

    1998-11-01

    gravity-based reference system.

  20. A Reference Frame for PBO: What do we Have; What do we Need?

    NASA Astrophysics Data System (ADS)

    Blewitt, G.

    2003-12-01

    By definition, the Plate Boundary Observatory (PBO) will investigate the mechanics associated with the boundary between the North America and Pacific plates. A natural frame of reference to describe crustal deformation between these two plates would be one in which the far field appears to be stationary, which leads to two possibilities: the "stable North America frame" or the "stable Pacific frame." The theory of plate tectonics pre-supposes the existence of such entities. Within such a framework the sum of deformations across contiguous regions of the plate boundary zone are constrained by the known relative far-field plate motion. However both theory and observation complicate this simplified framework. Are "stable plate interiors" a meaningful concept at the level of anticipated geodetic accuracy? Observational evidence suggests that most of the North America and Pacific Plates appear to be horizontally stable at the level of 1--2 mm/yr over plate-wide distance scales, which is not a very stringent constraint given current and anticipated station velocity accuracies at <1 mm/yr. Where do these stable plate interiors end, and the plate boundary zones begin? The Pacific-North America plate boundary zone is so broad that gravitational potential energy and mantle dynamics must play an important role - how deep into the plates do these dynamics have a measurable effect? How should we account for glacial isostatic adjustment in the definition of a plate-fixed frame? How should we define a "vertical datum" that is theoretically useful and can be realized in practice? In this presentation I review the current status of reference frame theory and actual practice, and I outline current thinking on the reference frame needs for PBO that derives from the working group on the "Stable North America Reference Frame" (SNARF), recently formed under the auspices of UNAVCO and the IAG sub-commission on the North America Reference Frame (NAREF).

  1. Flexible Reference Frames for Grasp Planning in Human Parietofrontal Cortex1,2,3

    PubMed Central

    Leoné, Frank T. M.; Monaco, Simona; Henriques, Denise Y. P.; Toni, Ivan

    2015-01-01

    Abstract 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

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

    PubMed

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

    2015-01-01

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

  3. Current control of PMSM based on maximum torque control reference frame

    NASA Astrophysics Data System (ADS)

    Ohnuma, Takumi

    2017-07-01

    This study presents a new method of current controls of PMSMs (Permanent Magnet Synchronous Motors) based on a maximum torque control reference frame, which is suitable for high-performance controls of the PMSMs. As the issues of environment and energy increase seriously, PMSMs, one of the AC motors, are becoming popular because of their high-efficiency and high-torque density in various applications, such as electric vehicles, trains, industrial machines, and home appliances. To use the PMSMs efficiently, a proper current control of the PMSMs is necessary. In general, a rotational coordinate system synchronizing with the rotor is used for the current control of PMSMs. In the rotating reference frame, the current control is easier because the currents on the rotating reference frame can be expressed as a direct current in the controller. On the other hand, the torque characteristics of PMSMs are non-linear and complex; the PMSMs are efficient and high-density though. Therefore, a complicated control system is required to involve the relation between the torque and the current, even though the rotating reference frame is adopted. The maximum torque control reference frame provides a simpler way to control efficiently the currents taking the torque characteristics of the PMSMs into consideration.

  4. The X/Ka Celestial Reference Frame: Results from combined NASA-ESA baselines including Malargüe, Argentina

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Clark, J. E.; Garcí-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Madde, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2014-03-01

    An X/Ka-band (8.4/32 GHz) celestial reference frame has been constructed using a combined NASA and ESA Deep Space Network. Observations at X/Ka-band are motivated by their ability to access more compact source morphology and reduced core shift relative to observations at the historically standard S/X-band. In 86 observing sessions we detected 631 sources covering the full 24 hours of right ascension and the full range of declinations. The collaboration between NASA and ESA's deep space antenna in Malargüe, Argentina was created with an emphasis on addressing weaknesses in the southern hemisphere. The accuracy of the resulting CRF was quantified by comparison of 520 X/Ka sources in common with the S/X-band (2.3/8.4 GHz) ICRF2 producing wRMS agreement of 175 μas in RA cos(dec) and 220 μas in Declination. There is evidence for systematic errors at the ~100 μas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and terrestrial frame distortions. Actions are underway to reduce all of these errors. The recent successful launch of the Gaia optical astrometric satellite motivates work to tie the radio and optical frames. Existing X/Ka data and simulated Gaia data predict a frame tie precision of ~10 μas (1-sigma, per 3-D rotation component) with anticipated improvements having the potential to produce a tie of 5 μas per component. If XKa precision can be pushed below 100 µas, the XKa frame has potential to produce a tie to Gaia that is superior to S/X due to reduced astrophysical systematics at X/Ka relative to S/X.

  5. Aligning VLBI and Gaia Extragalactic Celestial Reference Frames: source selection scenario

    NASA Astrophysics Data System (ADS)

    Bourda, Geraldine; Charlot, Patrick; Collioud, Arnaud

    2015-08-01

    The European space astrometry mission Gaia will construct a dense optical celestial reference frame based on Quasi Stellar Objects. Accordingly, by 2020, two extragalactic celestial reference frames will coexist: the VLBI frame (Very Long Baseline Interferometry) in the radio domain, currently adopted by the IAU as the fundamental one, and the Gaia frame determined from direct optical observations of quasars by the satellite.For consistency between optical and radio positions of any celestial targets, it will be fundamental to align the Gaia and VLBI frames with the highest accuracy. This issue is also important in the framework of astrophysics, for example to probe properly the jets properties and the physics of the Active Galactic Nuclei.In this paper, based on the ICRF2 catalogue (International Celestial Reference Frame) and specific dedicated VLBI projects (e.g. designed to observe additional weaker extragalactic radio sources), we will discuss the selection of the VLBI-Gaia transfer sources, present our initiatives to reach this alignment, review the status of the various projects in question and draw plans for the future.

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

    NASA Astrophysics Data System (ADS)

    Edmonds-Wathen, Cris

    2014-06-01

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

  7. Impact of the VLBA on reference frames and earth orientation studies

    NASA Astrophysics Data System (ADS)

    Gordon, David

    2016-09-01

    The geodetic VLBI community began using VLBA antennas in 1989 for geodesy and astrometry. We examine how usage of the VLBA has improved the celestial reference frame, the terrestrial reference frame, and Earth orientation parameters. Without the VLBA, ICRF2 would have had only 1011 sources instead of 3414. ICRF3 will contain at least 4121 sources, with approximately 70 % or more coming exclusively from VLBA astrometry and geodesy sessions. The terrestrial reference frame is also more stable and precise due to VLBA geodesy sessions. Approximately two dozen geodesy stations that have participated in VLBA sessions show average position formal errors that are ˜ 13-14 % better in the horizontal components and ˜ 5 % better in the vertical component than would be expected solely from the increased number of observations. Also the Earth orientation parameters obtained from the RDV sessions represent the most accurate EOP series of any of the long-term VLBI session types.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  9. Impact of the VLBA on reference frames and earth orientation studies

    NASA Astrophysics Data System (ADS)

    Gordon, David

    2017-07-01

    The geodetic VLBI community began using VLBA antennas in 1989 for geodesy and astrometry. We examine how usage of the VLBA has improved the celestial reference frame, the terrestrial reference frame, and Earth orientation parameters. Without the VLBA, ICRF2 would have had only 1011 sources instead of 3414. ICRF3 will contain at least 4121 sources, with approximately 70 % or more coming exclusively from VLBA astrometry and geodesy sessions. The terrestrial reference frame is also more stable and precise due to VLBA geodesy sessions. Approximately two dozen geodesy stations that have participated in VLBA sessions show average position formal errors that are ˜ 13-14 % better in the horizontal components and ˜ 5 % better in the vertical component than would be expected solely from the increased number of observations. Also the Earth orientation parameters obtained from the RDV sessions represent the most accurate EOP series of any of the long-term VLBI session types.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  11. Compared to what? The effects of a frame of reference on older adults' subjective memory.

    PubMed

    Lineweaver, Tara T; Horhota, Michelle; Hull, Rose; McRoberts, Sarah M; Fishbaugh, Megan E

    2016-01-01

    It is often unclear what comparisons older adults make when evaluating their own memory. If thinking about their memory relative to others, they may assess their own abilities differently than if comparing it to their past capabilities. To test the effect of reference frames on memory assessments and memory performance, we randomly assigned 120 older adults to one of three conditions in which we manipulated frames of reference (control, past-self comparison, or other adults comparison) on a memory self-efficacy questionnaire. Participants also completed general and specific memory predictions and an objective memory test. Participants in the past-self condition reported significantly lower global memory self-efficacy compared with the other adults and control conditions. No condition differences emerged for memory predictions, objective memory, or the likelihood of over- or underpredicting memory performance. These findings suggest that reference frames impact global memory self-efficacy, but do not influence the accuracy of subjective memory judgments.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  14. Motion-based nearest vector metric for reference frame selection in the perception of motion.

    PubMed

    Agaoglu, Mehmet N; Clarke, Aaron M; Herzog, Michael H; Ögmen, Haluk

    2016-05-01

    We investigated how the visual system selects a reference frame for the perception of motion. Two concentric arcs underwent circular motion around the center of the display, where observers fixated. The outer (target) arc's angular velocity profile was modulated by a sine wave midflight whereas the inner (reference) arc moved at a constant angular speed. The task was to report whether the target reversed its direction of motion at any point during its motion. We investigated the effects of spatial and figural factors by systematically varying the radial and angular distances between the arcs, and their relative sizes. We found that the effectiveness of the reference frame decreases with increasing radial- and angular-distance measures. Drastic changes in the relative sizes of the arcs did not influence motion reversal thresholds, suggesting no influence of stimulus form on perceived motion. We also investigated the effect of common velocity by introducing velocity fluctuations to the reference arc as well. We found no effect of whether or not a reference frame has a constant motion. We examined several form- and motion-based metrics, which could potentially unify our findings. We found that a motion-based nearest vector metric can fully account for all the data reported here. These findings suggest that the selection of reference frames for motion processing does not result from a winner-take-all process, but instead, can be explained by a field whose strength decreases with the distance between the nearest motion vectors regardless of the form of the moving objects.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    The International Celestial Reference Frame's current realization, the ICRF-2 (Ma et al, 2009), has the potential to be improved in several ways. In order to achieve this potential in time for comparisons with ESA's optical Gaia mission, the IAU has formed the ICRF-3 working group with the goal of producing the next generation ICRF by its 2018 General Assembly. With Gaia aiming for sub-100 μas precision for quasars in its frame, our goal for the ICRF-3 is to achieve sub-100 μas precision in the radio for as many sources at as many observing bands as possible. This talk will review the intiatives underway which collectively form our roadmap for achieving these goals. VCS-II: Noting that ~2/3 of the ICRF-2's 3414 sources have been observed in only 1 or 2 sessions (mostly the VLBA Calibrator Survey (VCS)) which produced median precisions of 620/ 1120 μas in RAcosDec/ Dec, respectively, we have instigated a collaboration to re-observe the VCS sources using modern systems which are 5 times more sensitive than the original VCS system. This will allow the VCS sources to have precision more nearly comparable to the other ICRF sources. High Frequency radio: Noting that comparison of radio frame to the Gaia optical frame will require an accurate undersanding of frequency dependent changes in source morphology (source structure) and frequency dependent opacity effects (core shift), we are encouraging the construction of 100 μas precision radio frames at multple radio frequencies such as X/Ka (8.4/32 Ghz), K-band (~24 GHz) and Q-band (43 GHz). Southern coverage: Noting that all current radio frames have poorer spatial covereage and precision in the southern hemisphere, we are encouraging increased astrometric observations from the southern hemisphere. Observations using stations from Australia, South Africa, and Argentina are currently being organized. Frame consistency: Noting that Celestial Reference Frames are often used in combination with other frames such as the

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

    SciTech Connect

    Klink, W.H.; Wickramasekara, S.

    2016-06-15

    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.

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

    NASA Astrophysics Data System (ADS)

    Elmandouh, A. A.

    2016-06-01

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

  19. Comparison of Weekly and Daily IGS Reference Frames: The First Year

    NASA Astrophysics Data System (ADS)

    Clarke, P. J.

    2013-12-01

    In August 2012, the IGS analysis centers switched from publishing weekly realizations of the GNSS reference frame to publishing these on a daily basis. Based on Newcastle GNAAC and official IGS combinations in the year following the changes, compared with previous data, I analyze the impact that this change has had on the quality of reference frame and site coordinate time series. Despite an expected increase in high-frequency noise, the daily solutions offer advantages for the detection of short-period and transient signals.

  20. A survey of clearing techniques for 3D imaging of tissues with special reference to connective tissue.

    PubMed

    Azaripour, Adriano; Lagerweij, Tonny; Scharfbillig, Christina; Jadczak, Anna Elisabeth; Willershausen, Brita; Van Noorden, Cornelis J F

    2016-08-01

    For 3-dimensional (3D) imaging of a tissue, 3 methodological steps are essential and their successful application depends on specific characteristics of the type of tissue. The steps are 1° clearing of the opaque tissue to render it transparent for microscopy, 2° fluorescence labeling of the tissues and 3° 3D imaging. In the past decades, new methodologies were introduced for the clearing steps with their specific advantages and disadvantages. Most clearing techniques have been applied to the central nervous system and other organs that contain relatively low amounts of connective tissue including extracellular matrix. However, tissues that contain large amounts of extracellular matrix such as dermis in skin or gingiva are difficult to clear. The present survey lists methodologies that are available for clearing of tissues for 3D imaging. We report here that the BABB method using a mixture of benzyl alcohol and benzyl benzoate and iDISCO using dibenzylether (DBE) are the most successful methods for clearing connective tissue-rich gingiva and dermis of skin for 3D histochemistry and imaging of fluorescence using light-sheet microscopy. Copyright © 2016 The Authors. Published by Elsevier GmbH.. All rights reserved.

  1. Testing nonlocality of a single photon without a shared reference frame

    NASA Astrophysics Data System (ADS)

    Brask, Jonatan Bohr; Chaves, Rafael; Brunner, Nicolas

    2013-07-01

    The question of testing the nonlocality of a single photon has raised much debate over the last years. The controversy is intimately related to the issue of providing a common reference frame for the observers to perform their local measurements. Here we address this point by presenting a simple scheme for demonstrating the nonlocality of a single photon which does not require a shared reference frame. Specifically, Bell inequality violation can be obtained with certainty with unaligned devices, even if the relative frame fluctuates between each experimental run of the Bell test. Our scheme appears feasible with current technology and may simplify the realization of quantum communication protocols based on single-photon entanglement.

  2. On the consistency of the current conventional EOP series and the celestial and terrestrial reference frames

    NASA Astrophysics Data System (ADS)

    Belda, Santiago; Heinkelmann, Robert; Ferrándiz, José M.; Nilsson, Tobias; Schuh, Harald

    2016-08-01

    Precise transformation between the celestial reference frames (CRF) and terrestrial reference frames (TRF) is needed for many purposes in Earth and space sciences. According to the Global Geodetic Observing System (GGOS) recommendations, the accuracy of positions and stability of reference frames should reach 1 mm and 0.1 mm year^{-1} , and thus, the Earth Orientation Parameters (EOP) should be estimated with similar accuracy. Different realizations of TRFs, based on the combination of solutions from four different space geodetic techniques, and CRFs, based on a single technique only (VLBI, Very Long Baseline Interferometry), might cause a slow degradation of the consistency among EOP, CRFs, and TRFs (e.g., because of differences in geometry, orientation and scale) and a misalignment of the current conventional EOP series, IERS 08 C04. We empirically assess the consistency among the conventional reference frames and EOP by analyzing the record of VLBI sessions since 1990 with varied settings to reflect the impact of changing frames or other processing strategies on the EOP estimates. Our tests show that the EOP estimates are insensitive to CRF changes, but sensitive to TRF variations and unmodeled geophysical signals at the GGOS level. The differences between the conventional IERS 08 C04 and other EOP series computed with distinct TRF settings exhibit biases and even non-negligible trends in the cases where no differential rotations should appear, e.g., a drift of about 20 μ as year^{-1 } in y_{pol } when the VLBI-only frame VTRF2008 is used. Likewise, different strategies on station position modeling originate scatters larger than 150 μ as in the terrestrial pole coordinates.

  3. On the consistency of the current conventional EOP series and the celestial and terrestrial reference frames

    NASA Astrophysics Data System (ADS)

    Belda, Santiago; Heinkelmann, Robert; Ferrándiz, José M.; Nilsson, Tobias; Schuh, Harald

    2017-02-01

    Precise transformation between the celestial reference frames (CRF) and terrestrial reference frames (TRF) is needed for many purposes in Earth and space sciences. According to the Global Geodetic Observing System (GGOS) recommendations, the accuracy of positions and stability of reference frames should reach 1 mm and 0.1 mm year^{-1}, and thus, the Earth Orientation Parameters (EOP) should be estimated with similar accuracy. Different realizations of TRFs, based on the combination of solutions from four different space geodetic techniques, and CRFs, based on a single technique only (VLBI, Very Long Baseline Interferometry), might cause a slow degradation of the consistency among EOP, CRFs, and TRFs (e.g., because of differences in geometry, orientation and scale) and a misalignment of the current conventional EOP series, IERS 08 C04. We empirically assess the consistency among the conventional reference frames and EOP by analyzing the record of VLBI sessions since 1990 with varied settings to reflect the impact of changing frames or other processing strategies on the EOP estimates. Our tests show that the EOP estimates are insensitive to CRF changes, but sensitive to TRF variations and unmodeled geophysical signals at the GGOS level. The differences between the conventional IERS 08 C04 and other EOP series computed with distinct TRF settings exhibit biases and even non-negligible trends in the cases where no differential rotations should appear, e.g., a drift of about 20 μ as year^{-1 }in y_{pol } when the VLBI-only frame VTRF2008 is used. Likewise, different strategies on station position modeling originate scatters larger than 150 μ as in the terrestrial pole coordinates.

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

    ERIC Educational Resources Information Center

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

    2009-01-01

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

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

    ERIC Educational Resources Information Center

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

    2016-01-01

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

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

    ERIC Educational Resources Information Center

    DiSpezio, Michael A.

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Biezeveld, Hubert

    2012-01-01

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

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

    ERIC Educational Resources Information Center

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

    2009-01-01

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

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

    ERIC Educational Resources Information Center

    DiSpezio, Michael A.

    2011-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

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

    2005-01-01

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

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

    ERIC Educational Resources Information Center

    Möller, Jens; Zimmermann, Friederike; Köller, Olaf

    2014-01-01

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

  13. The Generalized Internal/External Frame of Reference Model: An Extension to Dimensional Comparison Theory

    ERIC Educational Resources Information Center

    Möller, Jens; Müller-Kalthoff, Hanno; Helm, Friederike; Nagy, Nicole; Marsh, Herb W.

    2016-01-01

    The dimensional comparison theory (DCT) focuses on the effects of internal, dimensional comparisons (e.g., "How good am I in math compared to English?") on academic self-concepts with widespread consequences for students' self-evaluation, motivation, and behavioral choices. DCT is based on the internal/external frame of reference model…

  14. The relativistic blackbody spectrum in inertial and non-inertial reference frames

    NASA Astrophysics Data System (ADS)

    Lee, Jeffrey S.; Cleaver, Gerald B.

    2017-04-01

    By invoking inverse temperature as a van Kampen-Israel future-directed timelike 4-vector, this paper derives the Relativistic Blackbody Spectrum, the Relativistic Wien's Displacement Law, and the Relativistic Stefan-Boltzmann Law in inertial and non-inertial reference frames.

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

    ERIC Educational Resources Information Center

    Biezeveld, Hubert

    2012-01-01

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

  16. Frame of Reference Rater Training Issues: Recall, Time and Behavior Observation Training.

    ERIC Educational Resources Information Center

    Roch, Sylvia G.; O'Sullivan, Brian J.

    2003-01-01

    Graduate students were trained as raters either using frame of reference (FOR, n=220, behavior observation training (BOT, n=21), or performance appraisal (controls, n=21). They rated videotaped lecturers twice. FOR increased number of behaviors recalled; FOR and BOT improved recall quality. FOR improved rating accuracy even after 2 weeks.…

  17. Understanding Frame-of-Reference Training Success: A Social Learning Theory Perspective

    ERIC Educational Resources Information Center

    Sulsky, Lorne M.; Kline, Theresa J. B.

    2007-01-01

    Employing the social learning theory (SLT) perspective on training, we analysed the effects of alternative frame-of-reference (FOR) training protocols on various criteria of training effectiveness. Undergraduate participants (N = 65) were randomly assigned to one of four FOR training conditions and a control condition. Training effectiveness was…

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

    ERIC Educational Resources Information Center

    Möller, Jens; Zimmermann, Friederike; Köller, Olaf

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1990-01-01

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

  20. Mechanisms of Reference Frame Selection in Spatial Term Use: Computational and Empirical Studies

    ERIC Educational Resources Information Center

    Schultheis, Holger; Carlson, Laura A.

    2017-01-01

    Previous studies have shown that multiple reference frames are available and compete for selection during the use of spatial terms such as "above." However, the mechanisms that underlie the selection process are poorly understood. In the current paper we present two experiments and a comparison of three computational models of selection…

  1. Antecedents of Academic Emotions: Testing the Internal/External Frame of Reference Model for Academic Enjoyment

    ERIC Educational Resources Information Center

    Goetz, Thomas; Frenzel, Anne C.; Hall, Nathan C.; Pekrun, Reinhard

    2008-01-01

    The present study focused on students' academic enjoyment as predicted by achievement in multiple academic domains. Assumptions were based on Marsh's internal/external (I/E) frame of reference model and Pekrun's control-value theory of achievement emotions, and were tested in a sample of 1380 German students from grades 5 to 10. Students' academic…

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

    ERIC Educational Resources Information Center

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

    2016-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

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

    2012-01-01

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

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

    ERIC Educational Resources Information Center

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

    2007-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Daniel, Larry G.

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

  8. Frame of Reference Rater Training Issues: Recall, Time and Behavior Observation Training.

    ERIC Educational Resources Information Center

    Roch, Sylvia G.; O'Sullivan, Brian J.

    2003-01-01

    Graduate students were trained as raters either using frame of reference (FOR, n=220, behavior observation training (BOT, n=21), or performance appraisal (controls, n=21). They rated videotaped lecturers twice. FOR increased number of behaviors recalled; FOR and BOT improved recall quality. FOR improved rating accuracy even after 2 weeks.…

  9. Adjustment of Sonar and Laser Acquisition Data for Building the 3D Reference Model of a Canal Tunnel †

    PubMed Central

    Moisan, Emmanuel; Charbonnier, Pierre; Foucher, Philippe; Grussenmeyer, Pierre; Guillemin, Samuel; Koehl, Mathieu

    2015-01-01

    In this paper, we focus on the construction of a full 3D model of a canal tunnel by combining terrestrial laser (for its above-water part) and sonar (for its underwater part) scans collected from static acquisitions. The modeling of such a structure is challenging because the sonar device is used in a narrow environment that induces many artifacts. Moreover, the location and the orientation of the sonar device are unknown. In our approach, sonar data are first simultaneously denoised and meshed. Then, above- and under-water point clouds are co-registered to generate directly the full 3D model of the canal tunnel. Faced with the lack of overlap between both models, we introduce a robust algorithm that relies on geometrical entities and partially-immersed targets, which are visible in both the laser and sonar point clouds. A full 3D model, visually promising, of the entrance of a canal tunnel is obtained. The analysis of the method raises several improvement directions that will help with obtaining more accurate models, in a more automated way, in the limits of the involved technology. PMID:26690444

  10. Adjustment of Sonar and Laser Acquisition Data for Building the 3D Reference Model of a Canal Tunnel.

    PubMed

    Moisan, Emmanuel; Charbonnier, Pierre; Foucher, Philippe; Grussenmeyer, Pierre; Guillemin, Samuel; Koehl, Mathieu

    2015-12-11

    In this paper, we focus on the construction of a full 3D model of a canal tunnel by combining terrestrial laser (for its above-water part) and sonar (for its underwater part) scans collected from static acquisitions. The modeling of such a structure is challenging because the sonar device is used in a narrow environment that induces many artifacts. Moreover, the location and the orientation of the sonar device are unknown. In our approach, sonar data are first simultaneously denoised and meshed. Then, above- and under-water point clouds are co-registered to generate directly the full 3D model of the canal tunnel. Faced with the lack of overlap between both models, we introduce a robust algorithm that relies on geometrical entities and partially-immersed targets, which are visible in both the laser and sonar point clouds. A full 3D model, visually promising, of the entrance of a canal tunnel is obtained. The analysis of the method raises several improvement directions that will help with obtaining more accurate models, in a more automated way, in the limits of the involved technology.

  11. Consistent Feature Extraction From Vector Fields: Combinatorial Representations and Analysis Under Local Reference Frames

    SciTech Connect

    Bhatia, Harsh

    2015-05-01

    This dissertation presents research on addressing some of the contemporary challenges in the analysis of vector fields—an important type of scientific data useful for representing a multitude of physical phenomena, such as wind flow and ocean currents. In particular, new theories and computational frameworks to enable consistent feature extraction from vector fields are presented. One of the most fundamental challenges in the analysis of vector fields is that their features are defined with respect to reference frames. Unfortunately, there is no single “correct” reference frame for analysis, and an unsuitable frame may cause features of interest to remain undetected, thus creating serious physical consequences. This work develops new reference frames that enable extraction of localized features that other techniques and frames fail to detect. As a result, these reference frames objectify the notion of “correctness” of features for certain goals by revealing the phenomena of importance from the underlying data. An important consequence of using these local frames is that the analysis of unsteady (time-varying) vector fields can be reduced to the analysis of sequences of steady (timeindependent) vector fields, which can be performed using simpler and scalable techniques that allow better data management by accessing the data on a per-time-step basis. Nevertheless, the state-of-the-art analysis of steady vector fields is not robust, as most techniques are numerical in nature. The residing numerical errors can violate consistency with the underlying theory by breaching important fundamental laws, which may lead to serious physical consequences. This dissertation considers consistency as the most fundamental characteristic of computational analysis that must always be preserved, and presents a new discrete theory that uses combinatorial representations and algorithms to provide consistency guarantees during vector field analysis along with the uncertainty

  12. Extrinsic reference frames modify the neural substrates of object-location representations.

    PubMed

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

    2013-04-01

    The ability to form spatial representations of object locations is an important component of successful spatial navigation. Evidence from behavioral studies suggests that environmental features that have a salient coordinate axis (e.g., a rectangular building or a geometrical room) may provide a reference frame for the encoding of object-location information. Here we used functional magnetic resonance imaging (fMRI) to determine the brain networks engaged when object-location representations are stored with respect to an extrinsic reference frame. Participants learned the layout of an object array in an active, virtual-navigation paradigm. A square mat positioned on the floor of the virtual arena acted as the extrinsic reference frame. Knowledge of the spatial arrangement of the object array was probed while participants underwent fMRI, using a spatial judgment task that required them to imagine orientations of the learned array that were either aligned or misaligned with the geometry of the mat. Consistent with previous findings, participants responded faster and were more accurate when the imagined orientation was aligned, as opposed to misaligned, with the extrinsic reference frame. Analysis of the fMRI data revealed important differences in brain activity between the two conditions. Significantly greater activity was observed in the aligned condition compared with the misaligned condition across a bilateral network of brain areas that included the inferior occipital gyri, inferior and middle temporal gyri, and fusiform gyri. By contrast, activity in the misaligned condition was significantly greater than in the aligned condition in bilateral dorsolateral prefrontal and anterior cingulate cortex, and in the right anterior prefrontal and anterior insular cortex. These results suggest that retrieval of spatial locations that are aligned with an extrinsic reference frame involve direct access to detailed and accurate representations within the ventral visual

  13. Making Inexpensive 3-D Models

    NASA Astrophysics Data System (ADS)

    Manos, Harry

    2016-03-01

    Visual aids are important to student learning, and they help make the teacher's job easier. Keeping with the TPT theme of "The Art, Craft, and Science of Physics Teaching," the purpose of this article is to show how teachers, lacking equipment and funds, can construct a durable 3-D model reference frame and a model gravity well tailored to specific class lessons. Most of the supplies are readily available in the home or at school: rubbing alcohol, a rag, two colors of spray paint, art brushes, and masking tape. The cost of these supplies, if you don't have them, is less than 20.

  14. The ICRF3 Roadmap to the next generation International Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Arias, F.; Boboltz, D.; Boehm, J.; Bolotin, S.; Bourda, G.; Charlot, P.; de Witt, A.; Fey, A.; Gaume, R.; Gordon, D.; Heinkelmann, R.; Lambert, S.; Ma, C.; Malkin, Z.; Nothnagel, A.; Seitz, M.; Skurikhina, E.; Souchay, J.; Titov, O.; ICRF-3 working Group

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    SciTech Connect

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

    2014-07-10

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

  18. The African Reference Frame (AFREF) project: a fundamental geodetic tool for Africa

    NASA Astrophysics Data System (ADS)

    Farah, H.

    2009-04-01

    AFREF has as objective the establishment and maintenance of a unified geodetic reference frame for Africa, which will support and facilitate fundamental scientific and technical projects. The installation of observation systems all over Africa will provide important data that can be used in many different scientific fields (e.g., geodynamics, meteorological). Furthermore, AFREF will create an uniform frame that will support development projects, uniform environmental and mapping programmes as well as aid in resolving current and future international boundary disputes. This reference frame will be based on the International Terrestrial Reference Frame (ITRF) and will be realised through the establishment of a network of permanent Global Navigation Satellite System (GNSS) receivers. In close collaboration with several institutional role players, AFREF is an initiative of the United Nations Economic Commission for Africa (UNECA) Committee on Development Information (CODI). A steering committee is currently responsible for the over-all management and coordination of the implementation of AFREF. Implementation of AFREF is envisaged to be at national level in collaboration with National Mapping Organizations. Furthermore, many scientific Institutions are contributing for the densification of the network. The current status of the AFREF network will be discussed in detail. Several CORS systems have been installed to support AFREF specifically. In addition, most or all of the IGS stations located in Africa will automatically qualify as AFREF core stations. Furthermore, we will show examples of interaction between specific projects and AFREF that are contributing for the development of science in Africa.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  20. Contribution of reference frames for movement planning in peripersonal space representation.

    PubMed

    Ghafouri, Mohammad; Lestienne, Francis G

    2006-02-01

    The principal goal of our study is to gain an insight into the representation of peripersonal space. Two different experiments were conducted in this study. In the first experiment, subjects were asked to represent principal anatomical reference planes by drawing ellipses in the sagittal, frontal and horizontal planes. The three-dimensional hand-drawing movements, which were achieved with and without visual guidance, were considered as the expression of a cognitive process per se: the peripersonal space representation for action. We measured errors in the spatial orientation of ellipses with regard to the requested reference planes. For ellipses drawn without visual guidance, with eyes open and eyes closed, orientation errors were related to the reference planes. Errors were minimal for sagittal and maximal for horizontal plane. These disparities in errors were considerably reduced when subjects drew using a visual guide. These findings imply that different planes are centrally represented, and are characterized, by different errors when subjects use a body-centered frame for performing the movement and suggest that the representation of peripersonal space may be anisotropic. However, this representation can be modified when subjects use an environment-centered reference frame to produce the movement. In the second experiment, subjects were instructed to represent, with eyes open and eyes closed, sagittal, frontal and horizontal planes by pointing to virtual targets located in these planes. Disparities in orientation errors measured for pointing were similar to those found for drawing, implying that the sensorimotor representation of reference planes was not constrained by the type of motor tasks. Moreover, arm postures measured at pointing endpoints and at comparable spatial locations in drawing are strongly correlated. These results suggest that similar patterns of errors and arm posture correlation, for drawing and pointing, can be the consequence of using a

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    PubMed

    Street, Whitney N; Wang, Ranxiao Frances

    2016-02-01

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

  6. Determining sex with the clavicle in a contemporary Spanish reference collection: A study on 3D images.

    PubMed

    Mediavilla, Elena Ruiz; Pérez, Bernardo Perea; González, Elena Labajo; Sánchez, José Antonio Sánchez; Fernández, Enrique Dorado; Sáez, Andrés Santiago

    2016-04-01

    Sexual dimorphism of the clavicle based on metric studies has been determined among different populations from different eras. Due to the need to know about sexual dimorphism in the Spanish population in order to apply the results to the field of Forensic Anthropology, a study has been carried out on a sample in the contemporary Spanish population, made up of the right and left clavicles of 50 males and 50 females. A metric, volumetric and curvature study was performed. To do so, 3D scanning was completed on the entire sample using the Picza 3D Laser Scanner, and the study was performed using reproductions. There were taken 6 metric measurements and 4 volumetric measurements using the Geomagic software, and for the study of curves, an index was calculated which related the direct length of the clavicle and its length as cast onto a surface. The data are presented for all of the variables, distinguishing between the right and left side, and there were processed using the statistical program PASW Statistics 18. The results show that the classification functions which best categorize the sample with an unique variable are volumetric, which classify the sample correctly in 94% of cases based on diaphysis volume, followed by total volume, which provides an accurate classification in 92% of all cases. The sagittal diameter at midshaft provides an accurate classification in 90% of cases and the maximum length in 88% of cases. The curvature index shows that there are no statistically significant differences by side and the only curvature index that shows significant differences by sex is the total anterior curve of the left clavicle being the males curve more pronounced. The validation study performed on a sample of 20 individuals confirms the high discriminatory power of the volume obtaining an accurate classification rate of 85-100% depending on the variable studied.

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

    NASA Astrophysics Data System (ADS)

    Bahder, Thomas B.

    2016-03-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2014-01-09

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  12. Research activities for the DORIS contribution to the next International Terrestrial Reference Frame

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  13. A reinvestigation of the reference frame of the tilt-adaptation aftereffect

    PubMed Central

    Mathôt, Sebastiaan; Theeuwes, Jan

    2013-01-01

    The tilt-adaptation aftereffect (TAE) is the phenomenon that prolonged perception of a tilted ‘adapter’ stimulus affects the perceived tilt of a subsequent ‘tester’ stimulus. Although it is clear that TAE is strongest when adapter and tester are presented at the same location, the reference frame of the effect is debated. Some authors have reported that TAE is spatiotopic (world centred): It occurs when adapter and tester are presented at the same display location, even when this corresponds to different retinal locations. Others have reported that TAE is exclusively retinotopic (eye centred): It occurs only when adapter and tester are presented at the same retinal location, even when this corresponds to different display locations. Because this issue is crucial for models of transsaccadic perception, we reinvestigated the reference frame of TAE. We report that TAE is exclusively retinotopic, supporting the notion that there is no transsaccadic integration of low-level visual information. PMID:23359857

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  15. Tomographic Approach in Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution

    NASA Astrophysics Data System (ADS)

    Fang, Xi; Wang, Chao; Han, Yun-Guang; Yin, Zhen-Qiang; Chen, Wei; Han, Zheng-Fu

    2016-11-01

    Recently, a novel reference-frame-independent measurement-device-independent quantum key distribution protocol was proposed, which can remove all detector side channels as well as tolerate unknown and slow variance of reference frame without active alignment. In this paper, we propose a new tomographic method to estimate the key rate in that protocol. We estimate the key rate using conventional method and tomographic method respectively and compare the two methods by numerical simulation. The numerical simulation results show that tomographic approach is equivalent to the conventional approach, which can be used as an alternative method. Supported by the National Basic Research Program of China under Grant Nos. 2011CBA00200 and 2011CB921200, the National Natural Science Foundation of China under Grant Nos. 61475148, 61575183, and the “Strategic Priority Research Program (B)” of the Chinese Academy of Sciences under Grant Nos. XDB01030100, XDB01030300

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  17. Frames of Reference: A Metaphor for Analyzing and Interpreting Attitudes of Environmental Policy Makers and Policy Influencers

    PubMed

    Swaffield

    1998-07-01

    / The concept of frame of reference offers a potentially useful analytical metaphor in environmental management. This is illustrated by a case study in which attitudes of individuals involved in the management of trees in the New Zealand high country are classified into seven distinctive frames of reference. Some practical and theoretical implications of the use of the frame metaphor are explored, including its potential contribution to the emerg- ing field of communicative planning. KEY WORDS: Frames of reference; Environmental policy analysis; Metaphor; New Zealand high country

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

    NASA Technical Reports Server (NTRS)

    Harwood, Kelly; Wickens, Christopher D.

    1991-01-01

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

  19. From a Somatotopic to a Spatiotopic Frame of Reference for the Localization of Nociceptive Stimuli

    PubMed Central

    De Paepe, Annick L.; Crombez, Geert; Legrain, Valéry

    2015-01-01

    To react efficiently to potentially threatening stimuli, we have to be able to localize these stimuli in space. In daily life we are constantly moving so that our limbs can be positioned at the opposite side of space. Therefore, a somatotopic frame of reference is insufficient to localize nociceptive stimuli. Here we investigated whether nociceptive stimuli are mapped into a spatiotopic frame of reference, and more specifically a peripersonal frame of reference, which takes into account the position of the body limbs in external space, as well as the occurrence of external objects presented near the body. Two temporal order judgment (TOJ) experiments were conducted, during which participants had to decide which of two nociceptive stimuli, one applied to either hand, had been presented first while their hands were either uncrossed or crossed over the body midline. The occurrence of the nociceptive stimuli was cued by uninformative visual cues. We found that the visual cues prioritized the perception of nociceptive stimuli applied to the hand laying in the cued side of space, irrespective of posture. Moreover, the influence of the cues was smaller when they were presented far in front of participants’ hands as compared to when they were presented in close proximity. Finally, participants’ temporal sensitivity was reduced by changing posture. These findings are compatible with the existence of a peripersonal frame of reference for the localization of nociceptive stimuli. This allows for the construction of a stable representation of our body and the space closely surrounding our body, enabling a quick and efficient reaction to potential physical threats. PMID:26317671

  20. From a Somatotopic to a Spatiotopic Frame of Reference for the Localization of Nociceptive Stimuli.

    PubMed

    De Paepe, Annick L; Crombez, Geert; Legrain, Valéry

    2015-01-01

    To react efficiently to potentially threatening stimuli, we have to be able to localize these stimuli in space. In daily life we are constantly moving so that our limbs can be positioned at the opposite side of space. Therefore, a somatotopic frame of reference is insufficient to localize nociceptive stimuli. Here we investigated whether nociceptive stimuli are mapped into a spatiotopic frame of reference, and more specifically a peripersonal frame of reference, which takes into account the position of the body limbs in external space, as well as the occurrence of external objects presented near the body. Two temporal order judgment (TOJ) experiments were conducted, during which participants had to decide which of two nociceptive stimuli, one applied to either hand, had been presented first while their hands were either uncrossed or crossed over the body midline. The occurrence of the nociceptive stimuli was cued by uninformative visual cues. We found that the visual cues prioritized the perception of nociceptive stimuli applied to the hand laying in the cued side of space, irrespective of posture. Moreover, the influence of the cues was smaller when they were presented far in front of participants' hands as compared to when they were presented in close proximity. Finally, participants' temporal sensitivity was reduced by changing posture. These findings are compatible with the existence of a peripersonal frame of reference for the localization of nociceptive stimuli. This allows for the construction of a stable representation of our body and the space closely surrounding our body, enabling a quick and efficient reaction to potential physical threats.

  1. Brownian motion of a harmonic oscillator in a noninertial reference frame.

    PubMed

    Jiménez-Aquino, J I; Romero-Bastida, M

    2013-08-01

    The Brownian motion of a charged harmonic oscillator in the presence of additional force fields, such as a constant magnetic field and arbitrary time-dependent electric and mechanical forces, is studied in a rotational reference frame under uniform motion. By assuming an isotropic surrounding medium (a scalar friction constant), we solve explicitly the Smoluchowski equation associated with the Langevin equation for the charged harmonic oscillator and calculate the mean square displacements along and orthogonal to the rotation axis.

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

    NASA Technical Reports Server (NTRS)

    Harwood, Kelly; Wickens, Christopher D.

    1991-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  5. FOOT PLACEMENT IN A BODY REFERENCE FRAME DURING WALKING AND ITS RELATIONSHIP TO HEMIPARETIC WALKING PERFORMANCE

    PubMed Central

    Balasubramanian, Chitralakshmi K.; Neptune, Richard R.; Kautz, Steven A.

    2010-01-01

    Background Foot placement during walking is closely linked to the body position, yet it is typically quantified relative to the other foot. The purpose of this study was to quantify foot placement patterns relative to body post-stroke and investigate its relationship to hemiparetic walking performance. Methods Thirty-nine participants with hemiparesis walked on a split-belt treadmill at their self-selected speeds and twenty healthy participants walked at matched slow speeds. Anterior-posterior and medial-lateral foot placements (foot center-of-mass) relative to body (pelvis center-of-mass) quantified stepping in body reference frame. Walking performance was quantified using step length asymmetry ratio, percent of paretic propulsion and paretic weight support. Findings Participants with hemiparesis placed their paretic foot further anterior than posterior during walking compared to controls walking at matched slow speeds (p < .05). Participants also placed their paretic foot further lateral relative to pelvis than non-paretic (p < .05). Anterior-posterior asymmetry correlated with step length asymmetry and percent paretic propulsion but some persons revealed differing asymmetry patterns in the translating reference frame. Lateral foot placement asymmetry correlated with paretic weight support (r = .596; p < .001), whereas step widths showed no relation to paretic weight support. Interpretation Post-stroke gait is asymmetric when quantifying foot placement in a body reference frame and this asymmetry related to the hemiparetic walking performance and explained motor control mechanisms beyond those explained by step lengths and step widths alone. We suggest that biomechanical analyses quantifying stepping performance in impaired populations should investigate foot placement in a body reference frame. PMID:20193972

  6. The Large Quasar Reference Frame (LQRF). An Optical Representation of the ICRS

    DTIC Science & Technology

    2009-10-01

    A&A 505, 385–404 (2009) DOI: 10.1051/0004-6361/200912041 c© ESO 2009 Astronomy & Astrophysics The large quasar reference frame (LQRF) An optical...RJ, Brasil Received 12 March 2009 / Accepted 20 May 2009 ABSTRACT Context. The large number and all-sky distribution of quasars from different...surveys, along with their presence in large , deep astro- metric catalogs, enables us to build of an optical materialization of the International Celestial

  7. Geometric cues, reference frames, and the equivalence of experienced-aligned and novel-aligned views in human spatial memory.

    PubMed

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

    2013-03-01

    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 environmental shape, we explored the extent to which geometric cues were incidentally encoded and represented in memory by evaluating their influence on reference frame selection. Using a virtual environment equipped with a head-mounted-display, we presented participants with to-be-remembered object arrays. We manipulated whether the experienced viewpoint was aligned or misaligned with global (i.e., the principal axis of space) or local (i.e., wall orientations) geometric cues. During subsequent judgments of relative direction (i.e., participants imagined standing at one object, facing a second object, and pointed toward a third object), we show that performance was best when imagining perspectives aligned with these geometric cues; moreover, global geometric cues were sufficient for reference frame selection, global and local geometric cues were capable of exerting differential influence on reference frame selection, and performance from experienced-imagined perspectives was equivalent to novel-imagined perspectives aligned with geometric cues. These results explicitly connect theory regarding spatial reference frame selection and spatial orientation via environmental shape and indicate that spatial memories are organized around fundamental geometric properties of space. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. The Multi-Disciplinary Graduate Program in Educational Research. Final Report, Part V; The Frame of Reference Study.

    ERIC Educational Resources Information Center

    Lazarsfeld, Paul F., Ed.

    This "Frame of Reference Study" consists of the fifth section of the final report of the Multi-Disciplinary Graduate Program in Educational Research of the University of Pittsburgh. The term, "frames of reference," is used to mean the context of assumptions, procedures, rules, cognitive models, and conceptions of the nature of…

  9. Modality-switching in the Simon task: The clash of reference frames.

    PubMed

    Ruzzoli, Manuela; Soto-Faraco, Salvador

    2017-10-01

    The representation of spatial information related to an event can influence behavior even when location is task-irrelevant, as in the case of Stimulus-Response (S-R) compatibility effects on the Simon task. However, unlike single-modality situations, which are often used to study the Simon effect, in real-life scenarios various sensory modalities provide spatial information coded in different coordinate systems. Here, we address the expression of S-R compatibility effects in mixed-modality contexts, where events can occur in 1 of various sensory modalities (i.e., vision, touch or audition). The results confirm that, in single-modality cases, Simon effects in vision are expressed in an external spatial frame of reference, while touch information is coded anatomically. Remarkably, when mixing visual and tactile trials in an unpredictable way, the Simon effect disappeared in vision whereas tactile Simon effects remained expressed in their own (anatomical) frame of reference. Mixing visual and auditory stimuli did not obliterate the visual Simon effect and S-R compatibility effects in an external reference frame were evident for both modalities. The extinction of visual Simon effects as a result of mixing visual and tactile modalities can be interpreted as a consequence of the dynamic reorganization of the weights associated to the different sources of spatial information at play. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  10. Behavioral Investigation on the Frames of Reference Involved in Visuomotor Transformations during Peripheral Arm Reaching

    PubMed Central

    Pelle, Gina; Perrucci, Mauro Gianni; Galati, Gaspare; Fattori, Patrizia; Galletti, Claudio; Committeri, Giorgia

    2012-01-01

    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. PMID:23272180

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

    NASA Astrophysics Data System (ADS)

    Stone, Ronald C.

    1998-10-01

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

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

    PubMed Central

    Jiang, Yuhong V.; Won, Bo-Yeong

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-Yuan; Mueller, Ivan I.

    1983-03-01

    First, the paper is devoted to the effects of adopting new definitive precession and equinox corrections on the terrestrial reference frame: The effect on polar motion is a diurnal periodic term with an amplitude increasing linearly in time; on UT1 it is a linear term. Second, general principles are given the use of which can determine the effects of small rotations (such as precession, nutation or equinox corrections) of the frame of a Conventional Inertial Reference System (CIS) on the frame of the Conventional Terrestrial Reference System (CTS). Next, seven CTS options are presented, one of which is necessary to accommodate such rotations (corrections). The last of these options requiring no changes in the origin of terrestrial longitudes and in UT1 is advocated; this option would be maintained by eventually referencing the Greenwich Mean Sidereal Time to a fixed point on the equator, instead of to the mean equinox of date, the current practice. Accommodating possible future changes in the astronomical nutation is discussed in the last section. The Appendix deals with the effects of differences which may exist between the various CTS's and CIS's (inherent in the various observational techniques) on earth rotation parameters (ERP) and how these differences can be determined. It is shown that the CTS differences can be determined from observations made at the same site, while the CIS differences by comparing the ERP's determined by the different techniques during the same time period.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  16. Environmentally defined frames of reference: their time course and sensitivity to spatial cues and attention.

    PubMed

    Danziger, S; Kingstone, A; Ward, R

    2001-04-01

    In a Simon task the effects of spatial cues and attention on spatial stimulus coding were explored. Participants made speeded responses corresponding to the direction of target arrows that were preceded by peripherally presented cues. Cue validity varied across experiments as did the percentage of trials on which the target appeared peripherally or centrally. The data indicate (a) that targets are coded relative to multiple reference frames, (b) that spatial coding of a target is not affected when attention is shifted to the target, and (c) that an object serves as a referent for spatial coding of other objects even after its spatial code no longer activates responses.

  17. The scientific implications of the re-reductions in Hipparcos reference frame for Earth rotation studies.

    NASA Astrophysics Data System (ADS)

    Capitaine, N.

    After recalling the present knowledge in Earth rotation and the precision which is presently achieved on the Earth Rotation parameters (ERP) by the new techniques such as VLBI or satellite and lunar laser ranging, this paper investigates what will be the scientific implications of the re-reduction of the existing astrometric data which will be performed by the IAU Working Group "Earth Rotation in the Hipparcos Reference Frame". One of the main advantages of such a re-reduction over previous reductions is to refer to a much better realization of the optical Celestial Reference System as well as to an improved realization of the Terrestrial Reference System using corrections for the deviation of the vertical and for plate motions. An other advantage of the planned re-reduction is to use very long series of observations as compared to similar series obtained by the new techniques.

  18. Human fronto-parietal and parieto-hippocampal pathways represent behavioral priorities in multiple spatial reference frames

    PubMed Central

    Szczepanski, Sara M; Saalmann, Yuri B

    2013-01-01

    We represent behaviorally relevant information in different spatial reference frames in order to interact effectively with our environment. For example, we need an egocentric (e.g., body-centered) reference frame to specify limb movements and an allocentric (e.g., world-centered) reference frame to navigate from one location to another. Posterior parietal cortex (PPC) is vital for performing transformations between these different coordinate systems. Here, we review evidence for multiple pathways in the human brain, from PPC to motor, premotor, and supplementary motor areas, as well as to structures in the medial temporal lobe. These connections are important for transformations between egocentric reference frames to facilitate sensory-guided action, or from egocentric to allocentric reference frames to facilitate spatial navigation. PMID:24322829

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  20. Evaluation of local electric fields generated by transcranial direct current stimulation with an extracephalic reference electrode based on realistic 3D body modeling

    NASA Astrophysics Data System (ADS)

    Im, Chang-Hwan; Park, Ji-Hye; Shim, Miseon; Chang, Won Hyuk; Kim, Yun-Hee

    2012-04-01

    In this study, local electric field distributions generated by transcranial direct current stimulation (tDCS) with an extracephalic reference electrode were evaluated to address extracephalic tDCS safety issues. To this aim, we generated a numerical model of an adult male human upper body and applied the 3D finite element method to electric current conduction analysis. In our simulations, the active electrode was placed over the left primary motor cortex (M1) and the reference electrode was placed at six different locations: over the right temporal lobe, on the right supraorbital region, on the right deltoid, on the left deltoid, under the chin, and on the right buccinator muscle. The maximum current density and electric field intensity values in the brainstem generated by the extracephalic reference electrodes were comparable to, or even less than, those generated by the cephalic reference electrodes. These results suggest that extracephalic reference electrodes do not lead to unwanted modulation of the brainstem cardio-respiratory and autonomic centers, as indicated by recent experimental studies. The volume energy density was concentrated at the neck area by the use of deltoid reference electrodes, but was still smaller than that around the active electrode locations. In addition, the distributions of elicited cortical electric fields demonstrated that the use of extracephalic reference electrodes might allow for the robust prediction of cortical modulations with little dependence on the reference electrode locations.

  1. Evaluation of local electric fields generated by transcranial direct current stimulation with an extracephalic reference electrode based on realistic 3D body modeling.

    PubMed

    Im, Chang-Hwan; Park, Ji-Hye; Shim, Miseon; Chang, Won Hyuk; Kim, Yun-Hee

    2012-04-21

    In this study, local electric field distributions generated by transcranial direct current stimulation (tDCS) with an extracephalic reference electrode were evaluated to address extracephalic tDCS safety issues. To this aim, we generated a numerical model of an adult male human upper body and applied the 3D finite element method to electric current conduction analysis. In our simulations, the active electrode was placed over the left primary motor cortex (M1) and the reference electrode was placed at six different locations: over the right temporal lobe, on the right supraorbital region, on the right deltoid, on the left deltoid, under the chin, and on the right buccinator muscle. The maximum current density and electric field intensity values in the brainstem generated by the extracephalic reference electrodes were comparable to, or even less than, those generated by the cephalic reference electrodes. These results suggest that extracephalic reference electrodes do not lead to unwanted modulation of the brainstem cardio-respiratory and autonomic centers, as indicated by recent experimental studies. The volume energy density was concentrated at the neck area by the use of deltoid reference electrodes, but was still smaller than that around the active electrode locations. In addition, the distributions of elicited cortical electric fields demonstrated that the use of extracephalic reference electrodes might allow for the robust prediction of cortical modulations with little dependence on the reference electrode locations.

  2. Examination of global correlations in ground deformation for terrestrial reference frame estimation

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    The KALman filter for REFerence frames (KALREF, Wu et al. 2015) has been developed to produce terrestrial reference frame (TRF) solutions. TRFs consist of precise position coordinates and velocity vectors of terrestrial reference sites (with the geocenter as the origin) along with the Earth orientation parameters, and they are produced by combining decades worth of space geodetic data using site tie data. To perform the combination, KALREF relies on stochastic models of the geophysical processes that are causing the Earth's surface to deform and reference sites to be displaced. We are investigating application of the GRACE data to improve the KALREF stochastic models by determining spatial statistics of the deformation of the Earth's surface caused by mass loading. A potential target of improvement is the non-uniform distribution of the geodetic observation sites, which can introduce bias in TRF estimates of the geocenter. The global and relatively uniform coverage of the GRACE measurements is expected to be free of such bias and allow us to improve physical realism of the stochastic model. For such a goal, we examine the spatial correlations in ground deformation derived from several GRACE data sets.[Wu et al. 2015: Journal of Geophysical Research (Solid Earth) 120:3775-3802

  3. Accurate registration of random radiographic projections based on three spherical references for the purpose of few-view 3D reconstruction

    SciTech Connect

    Schulze, Ralf; Heil, Ulrich; Weinheimer, Oliver; Gross, Daniel; Bruellmann, Dan; Thomas, Eric; Schwanecke, Ulrich; Schoemer, Elmar

    2008-02-15

    Precise registration of radiographic projection images acquired in almost arbitrary geometries for the purpose of three-dimensional (3D) reconstruction is beset with difficulties. We modify and enhance a registration method [R. Schulze, D. D. Bruellmann, F. Roeder, and B. d'Hoedt, Med. Phys. 31, 2849-2854 (2004)] based on coupling a minimum amount of three reference spheres in arbitrary positions to a rigid object under study for precise a posteriori pose estimation. Two consecutive optimization procedures (a, initial guess; b, iterative coordinate refinement) are applied to completely exploit the reference's shadow information for precise registration of the projections. The modification has been extensive, i.e., only the idea of using the sphere shadows to locate each sphere in three dimensions from each projection was retained whereas the approach to extract the shadow information has been changed completely and extended. The registration information is used for subsequent algebraic reconstruction of the 3D information inherent in the projections. We present a detailed mathematical theory of the registration process as well as simulated data investigating its performance in the presence of error. Simulation of the initial guess revealed a mean relative error in the critical depth coordinate ranging between 2.1% and 4.4%, and an evident error reduction by the subsequent iterative coordinate refinement. To prove the applicability of the method for real-world data, algebraic 3D reconstructions from few ({<=}9) projection radiographs of a human skull, a human mandible and a teeth-containing mandible segment are presented. The method facilitates extraction of 3D information from only few projections obtained from off-the-shelf radiographic projection units without the need for costly hardware. Technical requirements as well as radiation dose are low.

  4. 3D nondestructive testing system with an affordable multiple reference optical-delay-based optical coherence tomography.

    PubMed

    Dsouza, Roshan; Subhash, Hrebesh M; Neuhaus, Kai; Hogan, Josh; Wilson, Carol; Leahy, Martin

    2015-06-20

    Optical coherence tomography (OCT) is emerging as a powerful noncontact imaging technique, allowing high-quality cross-sectional imaging of scattering specimens nondestructively. However, the complexity and cost of current embodiments of an OCT system limit its use in various nondestructive testing (NDT) applications at resource-limited settings. In this paper, we demonstrate the feasibility of a novel low-cost OCT system for a range of nondestructive testing (NDT) applications. The proposed imaging system is based on an enhanced time-domain OCT system with a low cost and small form factor reference arm optical delay, called multiple reference OCT (MR-OCT), which uses a miniature voice coil actuator and a partial mirror for extending the axial scan range. The proposed approach is potentially a low-cost, compact, and unique optical imaging modality for a range of NDT applications in a low-resource setting. Using this method, we demonstrated the capability of MR-OCT to perform cross-sectional and volumetric imaging at 1200 A-scans per second.

  5. A Computational Model for Spatial Navigation Based on Reference Frames in the Hippocampus, Retrosplenial Cortex, and Posterior Parietal Cortex.

    PubMed

    Oess, Timo; Krichmar, Jeffrey L; Röhrbein, Florian

    2017-01-01

    Behavioral studies for humans, monkeys, and rats have shown that, while traversing an environment, these mammals tend to use different frames of reference and frequently switch between them. These frames represent allocentric, egocentric, or route-centric views of the environment. However, combinations of either of them are often deployed. Neurophysiological studies on rats have indicated that the hippocampus, the retrosplenial cortex, and the posterior parietal cortex contribute to the formation of these frames and mediate the transformation between those. In this paper, we construct a computational model of the posterior parietal cortex and the retrosplenial cortex for spatial navigation. We demonstrate how the transformation of reference frames could be realized in the brain and suggest how different brain areas might use these reference frames to form navigational strategies and predict under what conditions an animal might use a specific type of reference frame. Our simulated navigation experiments demonstrate that the model's results closely resemble behavioral findings in humans and rats. These results suggest that navigation strategies may depend on the animal's reliance in a particular reference frame and shows how low confidence in a reference frame can lead to fluid adaptation and deployment of alternative navigation strategies. Because of its flexibility, our biologically inspired navigation system may be applied to autonomous robots.

  6. A Computational Model for Spatial Navigation Based on Reference Frames in the Hippocampus, Retrosplenial Cortex, and Posterior Parietal Cortex

    PubMed Central

    Oess, Timo; Krichmar, Jeffrey L.; Röhrbein, Florian

    2017-01-01

    Behavioral studies for humans, monkeys, and rats have shown that, while traversing an environment, these mammals tend to use different frames of reference and frequently switch between them. These frames represent allocentric, egocentric, or route-centric views of the environment. However, combinations of either of them are often deployed. Neurophysiological studies on rats have indicated that the hippocampus, the retrosplenial cortex, and the posterior parietal cortex contribute to the formation of these frames and mediate the transformation between those. In this paper, we construct a computational model of the posterior parietal cortex and the retrosplenial cortex for spatial navigation. We demonstrate how the transformation of reference frames could be realized in the brain and suggest how different brain areas might use these reference frames to form navigational strategies and predict under what conditions an animal might use a specific type of reference frame. Our simulated navigation experiments demonstrate that the model’s results closely resemble behavioral findings in humans and rats. These results suggest that navigation strategies may depend on the animal’s reliance in a particular reference frame and shows how low confidence in a reference frame can lead to fluid adaptation and deployment of alternative navigation strategies. Because of its flexibility, our biologically inspired navigation system may be applied to autonomous robots. PMID:28223931

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

    PubMed Central

    Knierim, James J.; Hamilton, Derek A.

    2011-01-01

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

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

    SciTech Connect

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  10. Formal structures, the concepts of covariance, invariance, equivalent reference frames, and the principle Relativity

    NASA Astrophysics Data System (ADS)

    Rodrigues, W. A.; Scanavini, M. E. F.; de Alcantara, L. P.

    1990-02-01

    In this paper a given spacetime theory T is characterized as the theory of a certain species of structure in the sense of Bourbaki [1]. It is then possible to clarify in a rigorous way the concepts of passive and active covariance of T under the action of the manifold mapping group G M . For each T, we define also an invariance group G I T and, in general, G I T ≠ G M . This group is defined once we realize that, for each τ ∈ ModT, each explicit geometrical object defining the structure can be classified as absolute or dynamical [2]. All spacetime theories possess also implicit geometrical objects that do not appear explicitly in the structure. These implicit objects are not absolute nor dynamical. Among them there are the reference frame fields, i.e., “timelike” vector fields X ∈ TU,U subseteq M M, where M is a manifold which is part of ST, a substructure for each τ ∈ ModT, called spacetime. We give a physically motivated definition of equivalent reference frames and introduce the concept of the equivalence group of a class of reference frames of kind X according to T, G X T. We define that T admits a weak principle of relativity (WPR) only if G X T ≠ identity for some X. If G X T = G I T for some X, we say that T admits a strong principle of relativity (PR). The results of this paper generalize and clarify several results obtained by Anderson [2], Scheibe [3], Hiskes [4], Recami and Rodrigues [5], Friedman [6], Fock [7], and Scanavini [8]. Among the novelties here, there is the realization that the definitions of G I T and G X T can be given only when certain boundary conditions for the equations of motion of T can be physically realizable in the domain U U subseteq M M, where a given reference frame is defined. The existence of physically realizable boundary conditions for each τ ∈ ModT (in ∂ U), in contrast with the mathematically possible boundary condition, is then seen to be essential for the validity of a principle of relativity for T

  11. Evaluation of reproducibility and reliability of 3D soft tissue analysis using 3D stereophotogrammetry.

    PubMed

    Plooij, J M; Swennen, G R J; Rangel, F A; Maal, T J J; Schutyser, F A C; Bronkhorst, E M; Kuijpers-Jagtman, A M; Bergé, S J

    2009-03-01

    In 3D photographs the bony structures are neither available nor palpable, therefore, the bone-related landmarks, such as the soft tissue gonion, need to be redefined. The purpose of this study was to determine the reproducibility and reliability of 49 soft tissue landmarks, including newly defined 3D bone-related soft tissue landmarks with the use of 3D stereophotogrammetric images. Two observers carried out soft-tissue analysis on 3D photographs twice for 20 patients. A reference frame and 49 landmarks were identified on each 3D photograph. Paired Student's t-test was used to test the reproducibility and Pearson's correlation coefficient to determine the reliability of the landmark identification. Intra- and interobserver reproducibility of the landmarks were high. The study showed a high reliability coefficient for intraobserver (0.97 (0.90 - 0.99)) and interobserver reliability (0.94 (0.69 - 0.99)). Identification of the landmarks in the midline was more precise than identification of the paired landmarks. In conclusion, the redefinition of bone-related soft tissue 3D landmarks in combination with the 3D photograph reference system resulted in an accurate and reliable 3D photograph based soft tissue analysis. This shows that hard tissue data are not needed to perform accurate soft tissue analysis.

  12. Effects of tectonic plate deformation on the geodetic reference frame of Mexico

    NASA Astrophysics Data System (ADS)

    Gonzalez Franco, G. A.; Avalos, D.; Esquivel, R.

    2013-05-01

    Positioning for geodetic applications is commonly determined at one observation epoch, but tectonic drift and tectonic deformation cause the coordinates to be different for any other epoch. Finding the right coordinates at a different epoch from that of the observation time is necessary in Mexico in order to comply the official reference frame, which requires all coordinates to be referred to the standard epoch 2010.0. Available models of horizontal movement in rigid tectonic plates are used to calculate the displacement of coordinates; however for a portion of Mexico these models fail because of miss-modeled regional deformation, decreasing the quality of users' data transformed to the standard epoch. In this work we present the progress achieved in measuring actual horizontal motion towards an improved modeling of horizontal displacements for some regions. Miss-modeled velocities found are as big as 23mm/a, affecting significantly applications like cadastral and geodetic control. Data from a large set of GNSS permanent stations in Mexico is being analyzed to produce the preliminary model of horizontal crustal movement that will be used to minimize distortions of the reference frame.

  13. The role of spatial memory and frames of reference in the precision of angular path integration.

    PubMed

    Arthur, Joeanna C; Philbeck, John W; Kleene, Nicholas J; Chichka, David

    2012-09-01

    Angular path integration refers to the ability to maintain an estimate of self-location after a rotational displacement by integrating internally-generated (idiothetic) self-motion signals over time. Previous work has found that non-sensory inputs, namely spatial memory, can play a powerful role in angular path integration (Arthur et al., 2007, 2009). Here we investigated the conditions under which spatial memory facilitates angular path integration. We hypothesized that the benefit of spatial memory is particularly likely in spatial updating tasks in which one's self-location estimate is referenced to external space. To test this idea, we administered passive, non-visual body rotations (ranging 40°-140°) about the yaw axis and asked participants to use verbal reports or open-loop manual pointing to indicate the magnitude of the rotation. Prior to some trials, previews of the surrounding environment were given. We found that when participants adopted an egocentric frame of reference, the previously-observed benefit of previews on within-subject response precision was not manifested, regardless of whether remembered spatial frameworks were derived from vision or spatial language. We conclude that the powerful effect of spatial memory is dependent on one's frame of reference during self-motion updating.

  14. The Role of Spatial Memory and Frames of Reference in the Precision of Angular Path Integration

    PubMed Central

    Arthur, Joeanna C.; Philbeck, John W.; Kleene, Nicholas J.; Chichka, David

    2012-01-01

    Angular path integration refers to the ability to maintain an estimate of self-location after a rotational displacement by integrating internally-generated (idiothetic) self-motion signals over time. Previous work has found that non-sensory inputs, namely spatial memory, can play a powerful role in angular path integration (Arthur et al., 2007, 2009). Here we investigated the conditions under which spatial memory facilitates angular path integration. We hypothesized that the benefit of spatial memory is particularly likely in spatial updating tasks in which one’s self-location estimate is referenced to external space. To test this idea, we administered passive, nonvisual body rotations (ranging 40° – 140°) about the yaw axis and asked participants to use verbal reports or open-loop manual pointing to indicate the magnitude of the rotation. Prior to some trials, previews of the surrounding environment were given. We found that when participants adopted an egocentric frame of reference, the previously-observed benefit of previews on within-subject response precision was not manifested, regardless of whether remembered spatial frameworks were derived from vision or spatial language. We conclude that the powerful effect of spatial memory is dependent on one’s frame of reference during self-motion updating. PMID:22885073

  15. ``Frames of Reference" as an Element in the Learning of Astronomy Concepts

    NASA Astrophysics Data System (ADS)

    Percy, J. R.; Chandra, N. R.; Kalchman, M.; Mutlak, H.; Woodruff, E.; Yoon, S.

    2000-12-01

    Pre-service elementary and middle school teachers possess large gaps in conceptual knowledge between what they understand about astronomy, and what they are required to teach according to the national standards for science education (Percy et al. 1999, BAAS, 31, 1520). The topics involved are not esoteric or trivial, and the knowledge gaps are very resistant to change. Thus, there is a need to understand the thinking processes involved in learning astronomy in order to identify, develop, and test professional development strategies that focus on issues around conceptual change. Our data suggest that teachers often try to change their frame of reference or perspective as they attempt to make sense of a concept. Detailed analyses on preservice teachers' performance on the astronomy self-assessment instrument, their audio- or videotaped discourse during relevant hands-on workshops, and their responses to an oral post-test interview allow us to identify (i) problems that require a ``frame of reference" approach, (ii) thinking processes which preservice teachers use during collaborative learning sessions, and (iii) strategies which distinguish successful from less successful learners. The results support our conjecture that the idea of frames of reference in thinking processes may support the learning of astronomy concepts. Indeed, our findings help to extend our view of knowledge gaps, and to identify thinking processes which may facilitate conceptual change. We believe that these insights apply to the learning of astronomy at the college and pre-college level, as well as in teacher education. Supported in part by SSHRC Canada, and the Ministry of Education, Ontario.

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

    SciTech Connect

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

    2013-07-01

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

  17. Mapping nociceptive stimuli in a peripersonal frame of reference: evidence from a temporal order judgment task.

    PubMed

    De Paepe, Annick L; Crombez, Geert; Spence, Charles; Legrain, Valéry

    2014-04-01

    The ability to localize nociceptive stimuli on the body surface is essential for an organism to respond appropriately to potential physical threats. This ability not only requires a representation of the space of the observer׳s body, but also of the external space with respect to their body. Therefore, localizing nociceptive stimuli requires coordinating multiple senses into an integrated frame of reference. The peripersonal frame of reference allows for the coding of the position of somatosensory stimuli on the body surface and the position of stimuli occurring close to the body (e.g., visual stimuli). Intensively studied for touch, this topic has been largely ignored when it comes to nociception. Here, we investigated, using a temporal order judgment task, whether the spatial perception of nociceptive stimuli is coordinated with that of proximal visual stimuli into an integrated representation of peripersonal space. Participants judged which of two nociceptive stimuli, one presented to either hand, had been presented first. Each pair of nociceptive stimuli was preceded by lateralized visual cues presented either unilaterally or bilaterally, and either close to, or far from, the participant׳s body. The perception of nociceptive stimuli was biased in favor of the stimulus delivered on the hand adjacent to the unilateral visual cue, especially when the cue was presented near the participant׳s hand. These results therefore suggest that a peripersonal frame of reference is used to map the position of nociceptive stimuli in multisensory space. We propose that peripersonal space constitutes a kind of margin of safety around the body to alert an organism to possible threats. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2014-05-01

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

  19. Radio optical reference frame. 6: Additional source positions in the northern hemisphere

    NASA Technical Reports Server (NTRS)

    Fey, A. L.; Russell, J. L.; De Vegt, C.; Zacharias, N.; Johnston, K. J.; Ma, C.; Hall, D. M.; Holdenried, E. R.

    1994-01-01

    Radio and optical positions for northern hemisphere extragalactic sources are reported. Milliarcsecond (mas) accurate radio positions of 106 sources north of -2 deg declination are derived from Mark III Very Long Baseline Interferometry (VLBI) observations taken during ten experiments from 1990 January through 1990 October. The results presented supplement an ongoing project to define and maintain an all-sky radio/optical reference frame of 400 or more extragalactic sources with mas accurate radio and optical positions. Radio positions for 34 new sources are presented along with improved radio positions for 72 sources already in the reference frame catalog. An additional nine sources have been determined to be unsuitable reference frame objects. Radio observations of nine calibration sources tie the new positions to the existing catalogue. The radio positions of the new sources have formal mean errors of approximately 0.7 mas in right ascension and approximately 1.0 mas in declination. Sources for which we report improved radio positions now have formal mean errors of approximately 0.5 mas in both coordinates, an improvement in some cases by as much as 75%. Positions in the FK5 system have also been obtained for the optical counterparts of an additional five northern hemisphere radio sources using prime focus plates from the Kitt Peak National Observatory's 4 m telescope and a Ritchey-Chretien focus plate from the Calar Alto 2.2 m telescope. The optical positions have internal accuracies of about 0.03 sec and differ from the radio positions by about 0.07 sec on the average.

  20. Antarctic VLNDEF Network for Regional Deformation Control in Absolute Reference Frame: Problems and Possible Solution.

    NASA Astrophysics Data System (ADS)

    Capra, A.; Gandolfi, S.; Mancini, F.; Negusini, M.; Vittuari, L.

    2004-05-01

    VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal deformation control of the Northern Victoria Land (Antarctica) by means of geodetic GPS measurements. The project is within the activity of GIANT (Geodetic Infrastructure of Antarctica) SCAR Program and was established within the actions of ANTEC (ANTarctic NeoTECtonics) Group of Specialists. During 1999-2000 and 2000-2001 Italian expeditions a network of 27 stations was established and completely surveyed over an area extending from the southernmost points at 70 degrees latitude south to the Oates Coast region at 76°S, corresponding to a wideness of 700 km along the south-north and 300 km in the west to east directions. The average distance between stations is about of 70-80 km. During the field activities in the 2002-03 expedition the whole network was surveyed. During those expeditions long time sessions of connection between VLNDEF and TAMDEF networks performed. TAMDEF is a USA NSF program for crustal deformation control on southern Victoria Land. The dataset has been processed using different package such as Bernese and Gipsy in order to compare solutions and fix the better approach for the transition between reference frame. The first solution was initially constrained in the ITRF97 solution using the TNB1 GPS permanent station coordinate provided by the SCAR GPS Epoch solution. The approach to crustal deformation determination is relevant in terms of relative regional deformation, among the network stations, and the absolute deformation study, through the connection to international reference frame. Particularly important is the study of for VLNDEF in order to integrated evaluation with other continental and regional networks, as SCAR GPS Epoch and TAMDEF.Some aspects related to the data processing in the Antarctic region and the use of the ITRF2000 as reference frame will be discussed in the paper in addition to the analysis of the deformation in the area.

  1. Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III.

    NASA Astrophysics Data System (ADS)

    Titov, O.; Pursimo, T.; Johnston, Helen M.; Stanford, Laura M.; Hunstead, Richard W.; Jauncey, David L.; Zenere, Katrina A.

    2017-04-01

    In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ˜160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.

  2. Contribution to defining a geodetic reference frame for Africa (AFREF): Geodynamics implications

    NASA Astrophysics Data System (ADS)

    Saria, Elifuraha E.

    African Reference Frame (AFREF) is the proposed regional three-dimensional standard frame, which will be used to reference positions and velocities for geodetic sites in Africa and surrounding. This frame will play a crucial role in scientific application for example plate motion and crustal deformation studies, and also in mapping when it involves for example national boundary surveying, remote sensing, GIS, engineering projects and other development programs in Africa. To contribute to the definition of geodetic reference frame for Africa and provide the first continent-wide position/velocity solution for Africa, we processed and analyzed 16 years of GPS and 17 years of DORIS data at 133 GPS sites and 9 DORIS sites continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. We use the resulting horizontal velocities to determine the level of rigidity of Nubia and updated a plate motion model for the East African Rift and revise the counter clockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. The vertical velocity ranges from -2 to +2 mm/yr, close to their uncertainties with no clear geographical pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). In the next step we used the substantial increase in the geologic, geophysical and geodetic data in Africa to improve our understanding of the rift geometry and the block kinematics of the EAR. We determined the best-fit fault structure of the rift in terms of the locking depth and dip angle and use a block modeling approach where observed velocities are described as the contribution of rigid block rotation and strain accumulation on locked faults. Our results

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  4. Selective frame dropping based on hypothetical reference decoder buffer model for initial buffering delay reduction

    NASA Astrophysics Data System (ADS)

    Deshpande, Sachin

    2008-02-01

    We propose a method for selective frame dropping based on hypothetical reference decoder buffer model for initial buffering delay reduction. The client side buffering consists of two logical buffers: a de-jitter buffer and a pre-decoder buffer. To playback an encoded bit-stream without underflow the client must do a minimum initial buffering. This minimum initial buffering is a property of the bit-stream. The minimum initial buffering relates to the pre-decoder buffer. In addition the client can do additional initial buffering to handle network jitter and other bandwidth variations. Our proposed approach relates to reducing the minimum initial buffering delay for an already encoded bit-stream. We propose a method for selectively dropping frames to reduce the amount of initial buffering the client needs to do to avoid underflow during the streaming. Our proposed method is especially applicable to pre-stored content. The method is also particularly useful for variable bit-rate (VBR) encoded media. The method can be used by a streaming server. Alternatively the method can be implemented by a trans-rater/ transcoder. In a preferred embodiment our method can be applied in advance on a pre-stored bit-stream to decide which frames to drop to reduce the required minimum initial buffering.

  5. W production at LHC: lepton angular distributions and reference frames for probing hard QCD

    NASA Astrophysics Data System (ADS)

    Richter-Was, E.; Was, Z.

    2017-02-01

    Precision tests of the Standard Model in the Strong and Electroweak sectors play a crucial role, among the physics program of LHC experiments. Because of the nature of proton-proton processes, observables based on the measurement of the direction and energy of final state leptons provide the most precise probes of such processes. In the present paper, we concentrate on the angular distribution of leptons from W → ℓ ν 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 harmonics 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 of escaping detection neutrino in the final state. There is thus no principle difference with respect to the phenomenology of the Z/γ → ℓ ^+ ℓ ^- Drell-Yan process. We show also, that with the proper choice of the reference frames, only one coefficient in this polynomial decomposition remains sizable, even in the presence of one or more high p_T jets. The necessary stochastic choice of the frames relies on probabilities independent from any coupling constants. In this way, electroweak effects (dominated by the V-A nature of W couplings to fermions), can be better separated from the ones of strong interactions. The separation is convenient for the measurements interpretation.

  6. A reference Pelton turbine - High speed visualization in the rotating frame

    NASA Astrophysics Data System (ADS)

    Solemslie, Bjørn W.; Dahlhaug, Ole G.

    2016-11-01

    To enable a detailed study the flow mechanisms effecting the flow within the reference Pelton runner designed at the Waterpower Laboratory (NTNLT) a flow visualization system has been developed. The system enables high speed filming of the hydraulic surface of a single bucket in the rotating frame of reference. It is built with an angular borescopes adapter entering the turbine along the rotational axis and a borescope embedded within a bucket. A stationary high speed camera located outside the turbine housing has been connected to the optical arrangement by a non-contact coupling. The view point of the system includes the whole hydraulic surface of one half of a bucket. The system has been designed to minimize the amount of vibrations and to ensure that the vibrations felt by the borescope are the same as those affecting the camera. The preliminary results captured with the system are promising and enable a detailed study of the flow within the turbine.

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

    SciTech Connect

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

    2011-11-15

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

  8. An anti-disturbance high-precision alignment for distributed POS based on inertial reference frame

    NASA Astrophysics Data System (ADS)

    Bai, Lijian; Wang, Yue

    2017-03-01

    The distributed POS is playing an important role in the ultra-high resolution aerial survey and remote sensing system, and can accurately provide time-spatial reference information for various imaging sensors. However, the distributed POS faces a special problem that the flexible arms used to connect the inertial measurement units (IMUs) would deteriorate the phenomenon that external disturbance leads to serious alignment errors. In order to improve the alignment precision of distributed POS in external disturbance, an anti-disturbance coarse alignment based on inertial reference frame is proposed. This method is developed mainly based on the structure of non-collinear vectors, which are constructed by a velocity vector determined by gravity vector integration. The disturbed acceleration and rotation is decreased a lot by the integral operation in the proposed method. Finally, the experiments were carried out and verified the validity of the proposed method.

  9. Effects of battlefield display frames of reference on navigation tasks, spatial judgements, and change detection.

    PubMed

    Thomas, Lisa C; Wickens, Christopher D

    This paper describes an experiment which illustrates the cause of 'cognitive tunnelling' as it affects information gathering and perception-based task performance in computer-generated terrain displays of varying frames of reference. Cognitive tunnelling refers to the effect where observers focus attention on information from specific areas of a display to the exclusion of information presented outside these areas. Previous research suggests that cognitive tunnelling is induced by more immersive or egocentric visual displays. Results from our preceding study suggested that an immersed split-screen display induces cognitive tunnelling and results in poorer information extraction and situation awareness than an exocentric display of the same information. The current study determined that failure of the observers to integrate information across the two views of the immersed display led to the cognitive tunnelling effect. Cognitive tunnelling was also affected by primacy of information initially presented within the larger egocentric view in the immersed display.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  11. Astrometry of International Celestial Reference Frame Sources Using the Second US Naval Observatory CCD Astrograph Catalog

    NASA Astrophysics Data System (ADS)

    Assafin, M.; Monken Gomes, P. T.; da Silva Neto, D. N.; Andrei, A. H.; Vieira Martins, R.; Camargo, J. I. B.; Teixeira, R.; Benevides-Soares, P.

    2005-06-01

    We present results of a pilot investigation on the astrometry of International Celestial Reference Frame (ICRF) sources using small- to medium-sized telescopes and the second US Naval Observatory CCD Astrograph Catalog (UCAC2). For this purpose, 31 ICRF sources were observed, mostly south of the equator, during 1997-2000. We used the automated 0.6 and 1.6 m Cassegrain telescopes equipped with CCD detectors located at Laboratório Nacional de Astrofísica, Brazil. The source positions were referred to UCAC2, with fainter 0.6 m telescope stars serving as a reference frame to the reductions of the 1.6 m telescope CCD fields. Observations were made in the V band in a compromise between the 579-643 nm bandpass (between V and R) of UCAC2 and the bluer ICRF sources. To ensure that UCAC2, with its magnitude bandpass system, is a reliable reference catalog for our V-band CCD frame reductions, we have also compared it against an independent set of star positions with similar characteristics obtained in the V band with the Valinhos CCD Meridian Circle, Brazil. Average values and errors for the optical-radio position offsets using the 0.6 m telescope were +4+/-8 mas (41 mas) and +1+/-8 mas (42 mas) for right ascension and declination, respectively. (Parenthetical values refer to standard deviation, i.e., to the typical error of a single measurement given the quantity of sources.) For the 1.6 m telescope, offsets were -12+/-9 mas (45 mas) and +8+/-9 mas (46 mas). An expected random error that increases with magnitude and affects the positions of the fainter 0.6 m telescope secondary stars is verified. No systematic errors were found within the attained position precision, including differential color refraction. External comparisons with independent telescope/catalog sets of precise source positions were also made, showing consistent results within the respective errors. Based on observations obtained at Laboratorio Nacional de Astrofísica (LNA), Rua Estados Unidos, 154 Bairro

  12. Long term dose monitoring onboard the European Columbus module of the International Space Station (ISS) in the frame of the DOSIS and DOSIS 3D project

    NASA Astrophysics Data System (ADS)

    Berger, Thomas

    The radiation environment encountered in space differs in nature from that on earth, consisting mostly of high energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on earth for occupational radiation workers. Accurate knowledge of the physical characteristics of the space radiation field in dependence on the solar activity, the orbital parameters and the different shielding configurations of the International Space Station (ISS) is therefore needed. For the investigation of the spatial and temporal distribution of the radiation field inside the European Columbus module the experiment “Dose Distribution Inside the ISS” (DOSIS), under the project and science lead of the German Aerospace Center (DLR), was launched on July 15th 2009 with STS-127 to the ISS. The DOSIS experiment consists of a combination of “Passive Detector Packages” (PDP) distributed at eleven locations inside Columbus for the measurement of the spatial variation of the radiation field and two active Dosimetry Telescopes (DOSTELs) with a Data and Power Unit (DDPU) in a dedicated nomex pouch mounted at a fixed location beneath the European Physiology Module rack (EPM) for the measurement of the temporal variation of the radiation field parameters. The DOSIS experiment suite measured during the lowest solar minimum conditions in the space age from July 2009 to June 2011. In July 2011 the active hardware was transferred to ground for refurbishment and preparation for the follow up DOSIS 3D experiment. The hardware for DOSIS 3D was launched with Soyuz 30S to the ISS on May 15th 2012. The PDPs are replaced with each even number Soyuz flight starting with Soyuz 30S. Data from the active detectors is transferred to ground via the EPM rack which is activated once a month for this action. The presentation will give an overview of the DOSIS and DOSIS 3D experiment and focus on the results from the passive radiation detectors from the DOSIS 3D experiment

  13. Device-dependent and device-independent quantum key distribution without a shared reference frame

    NASA Astrophysics Data System (ADS)

    Slater, Joshua A.; Branciard, Cyril; Brunner, Nicolas; Tittel, Wolfgang

    2014-04-01

    Standard quantum key distribution (QKD) protocols typically assume that the distant parties share a common reference frame. In practice, however, establishing and maintaining a good alignment between distant observers is rarely a trivial issue, which may significantly restrain the implementation of long-distance quantum communication protocols. Here we propose simple QKD protocols that do not require the parties to share any reference frame, and study their security and feasibility in both the usual device-dependent (DD) case—in which the two parties use well characterized measurement devices—as well as in the device-independent (DI) case—in which the measurement devices can be untrusted, and the security relies on the violation of a Bell inequality. To illustrate the practical relevance of these ideas, we present a proof-of-principle demonstration of our protocols using polarization entangled photons distributed over a coiled 10-km long optical fiber. We consider two situations, in which either the fiber spool's polarization transformation freely drifts, or randomly chosen polarization transformations are applied. The correlations obtained from measurements allow, with high probability, to generate positive asymptotic secret key rates in both the DD and DI scenarios (under the fair-sampling assumption for the latter case).

  14. Different Effects of Numerical Magnitude on Visual and Proprioceptive Reference Frames

    PubMed Central

    Blini, Elvio; Cattaneo, Zaira; Vallar, Giuseppe

    2013-01-01

    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 modulated the participants’ deviations in the visual straight ahead task, when the movement of the light was from left-to-right, with the small number bringing about a leftward deviation, the large number a rightward deviation. 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. PMID:23616777

  15. Modeling and simulation of inverter-fed induction motors using the natural ABC frame of reference

    NASA Astrophysics Data System (ADS)

    Hijazi, T. M.; Alhamadi, M. A.; Arkadan, A. A.; Demerdash, N. A.

    A time-domain equivalent network model is presented, in the natural ABC frame of reference, for computer-aided prediction of the performance of dc source-inverter fed induction motor systems and verified experimentally. The choice of this frame of reference for stator representation facilitates the integration of the machine and the electronic dc source-inverter models into one global equivalent network for the entire system. This model is most suited for the propulsion and actuation class of drives in which induction motors may substitute for brushless DC motors as prime movers. The model was used to simulate the performance of a 204-V, 1/3-hp, 60-Hz, 8-pole induction motor-inverter system, and the results were verified by test results obtained in the laboratory. The model was applied to a 440-V, 15-hp, 60-Hz, 8-pole induction motor-inverter system for purposes of evaluating the effects of 180 deg e and 120 deg e inverter conduction periods on the currents and torque profiles of the drive system.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    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.

  17. Insight into others' minds: spatio-temporal representations by intrinsic frame of reference.

    PubMed

    Sun, Yanlong; Wang, Hongbin

    2014-01-01

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

  18. Lost in space: multisensory conflict yields adaptation in spatial representations across frames of reference.

    PubMed

    Lohmann, Johannes; Butz, Martin V

    2017-03-27

    According to embodied cognition, bodily interactions with our environment shape the perception and representation of our body and the surrounding space, that is, peripersonal space. To investigate the adaptive nature of these spatial representations, we introduced a multisensory conflict between vision and proprioception in an immersive virtual reality. During individual bimanual interaction trials, we gradually shifted the visual hand representation. As a result, participants unknowingly shifted their actual hands to compensate for the visual shift. We then measured the adaptation to the invoked multisensory conflict by means of a self-localization and an external localization task. While effects of the conflict were observed in both tasks, the effects systematically interacted with the type of localization task and the available visual information while performing the localization task (i.e., the visibility of the virtual hands). The results imply that the localization of one's own hands is based on a multisensory integration process, which is modulated by the saliency of the currently most relevant sensory modality and the involved frame of reference. Moreover, the results suggest that our brain strives for consistency between its body and spatial estimates, thereby adapting multiple, related frames of reference, and the spatial estimates within, due to a sensory conflict in one of them.

  19. A radio optical reference frame. III - Additional radio and optical positions in the Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Jauncey, D. L.; Harvey, B. R.; White, G. L.; Reynolds, J. E.; Ma, C.; Johnston, K. J.; Nothnagel, A.; Nicolson, G.; Kingham, K.

    1992-01-01

    Radio and optical positions are presented for southern hemisphere extragalactic sources from the Parkes 2.7 GHz survey. Sixty-one sources were observed with Mark III VLBI at 8.4 GHz between Tidbinbilla, Australia, and Hartebeesthoek, South Africa. The results presented are part of the effort to establish a global reference frame of 400 extragalactic radio sources. Radio positions with about 10 milliarcsec errors have been estimated for 39 sources not previously in the present radio reference frame catalog, and provisional positions were obtained for two additional sources, bringing the total number of catalog sources to 276. The principal source of error is the uncalibrated ionosphere. Of the remaining sources five were completely undetected, six were either too faint or too resolved, and nine had previous catalog positions. Optical positions on the FK5 system have also been measured for four southern sources using prime focus plates from the Anglo-Australian 4 m telescope with an accuracy of 0.06 arcsec. This raises to 40 the number of radio sources with accurately measured positions for their optical counterparts.

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

    NASA Astrophysics Data System (ADS)

    Owen, S. E.; Webb, F.

    2005-12-01

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

  1. Computation of the 3D kinematics in a global frame over a 40m-long pathway using a rolling motion analysis system.

    PubMed

    Begon, Mickaël; Colloud, Floren; Fohanno, Vincent; Bahuaud, Pascal; Monnet, Tony

    2009-12-11

    A rolling motion analysis system has been purpose-built to acquire an accurate three-dimensional kinematics of human motion with large displacement. Using this device, the kinematics is collected in a local frame associated with the rolling motion analysis system. The purpose of this paper is to express the local kinematics of a subject walking on a 40 m-long pathway in a global system of co-ordinates. One participant performed five trials of walking while he was followed by a rolling eight camera optoelectronic motion analysis system. The kinematics of the trials were reconstructed in the global frame using two different algorithms and 82 markers placed on the floor organized in two parallel and horizontal lines. The maximal error ranged from 0.033 to 0.187 m (<0.5% of the volume diagonal). As a result, this device is accurate enough for acquiring the kinematics of cyclic activities with large displacements in ecological environment.

  2. Test of source selection for constructing a more stable and uniform celestial reference frame

    NASA Astrophysics Data System (ADS)

    Liu, N.; Liu, J.-C.; Zhu, Z.

    2017-04-01

    We aim to evaluate the possibility of improving the International Celestial Reference System realization starting from the ICRF2 catalogue by investigating the coordinate time series of radio sources observed by the very long baseline interferometry between 1979 and 2016. Sources with long observational history are selected as the candidates and the least-squares fits with special handling of the weights are performed to derive the linear drifts of the source coordinates. Then the sources are sorted, based on the normalized linear drift (i) over the whole sky, and (ii) in four homolographic areas divided by declinations. The axial stability of the reference system and sky distribution defined by the selected sources are evaluated, which are acted as the criterion for the final source lists. With our improved source selection scheme, two groups of sources are proposed and considered suitable for defining a more stable and homogeneous celestial reference system compared to the second version of the current International Celestial Reference Frame (ICRF2). The number of sources in the final lists are 323 and 294, respectively, and the global rotations of the axes derived from apparent motion of the sources are about two times better than the ICRF2.

  3. An investigation of Terrestrial Reference Frames for Sea-Level Studies: Experiences from the British Isles

    NASA Astrophysics Data System (ADS)

    Hansen, D. N.; Teferle, F. N.; Bingley, R. M.; Williams, S. D.; King, M.

    2010-12-01

    The use of Global Positioning System (GPS) measurements for geodetic fixing of tide gauges and the monitoring of their apparent vertical land motions was first recommended over two decades ago. Then, the idea was to bring tide gauge benchmarks into a common and global reference, i.e. a terrestrial reference frame (TRF), that would, with an adequate long-term stability, allow the computation of accurate geocentric sea level changes, decoupled from any vertical land motions affecting the individual sea level records. This principle seemed simple, but it was soon discovered that both the accuracies achieved with GPS and the then available TRFs were not sufficient for this purpose. Today, we know that accurate vertical land motion estimates may only be obtained from GPS vertical rates from global GPS networks which have been homogeneously processed over the complete data span and properly linked into to a TRF. Furthermore, it has for the first time been demonstrated that following these rules GPS vertical rates can be used to obtain estimates of geocentric sea level changes which are superior to those using vertical rates from global glacio-isostatic adjustment models. However, it has also been recognised that some remaining uncertainty in these GPS-based estimates stem from inaccuracies in today's TRFs, which can cause the obtained GPS vertical rates to be systematically offset to those from other techniques, such as absolute gravity, or other evidence for vertical land motion from geological information (in regions where these data are available) and/or regions of coherent sea level changes. In this presentation we will describe our experiences obtained from over a decade of monitoring the vertical land motions at tide gauges in the British Isles using GPS and absolute gravity measurements. We will present our latest homogeneously reprocessed GPS and absolute gravity vertical rates and discuss the impact on regional sea level when using various reference frame

  4. The International DORIS Service contribution to the 2014 realization of the International Terrestrial Reference Frame

    NASA Astrophysics Data System (ADS)

    Moreaux, Guilhem; Lemoine, Frank G.; Capdeville, Hugues; Kuzin, Sergey; Otten, Michiel; Štěpánek, Petr; Willis, Pascal; Ferrage, Pascale

    2016-12-01

    In preparation of the 2014 realization of the International Terrestrial Reference Frame (ITRF2014), the International DORIS Service delivered to the International Earth Rotation and Reference Systems Service a set of 1140 weekly solution files including station coordinates and Earth orientation parameters, covering the time period from 1993.0 to 2015.0. The data come from eleven DORIS satellites: TOPEX/Poseidon, SPOT2, SPOT3, SPOT4, SPOT5, Envisat, Jason-1, Jason-2, Cryosat-2, Saral and HY-2A. In their processing, the six analysis centers which contributed to the DORIS combined solution used the latest time variable gravity models and estimated DORIS ground beacon frequency variations. Furthermore, all the analysis centers but one excepted included in their processing phase center variations for ground antennas. The main objective of this study is to present the combination process and to analyze the impact of the new modeling on the performance of the new combined solution. Comparisons with the IDS contribution to ITRF2008 show that (i) the application of the DORIS ground phase center variations in the data processing shifts the combined scale upward by nearly 7-11 mm and (ii) thanks to estimation of DORIS ground beacon frequency variations, the new combined solution no longer shows any scale discontinuity in early 2002 and does not present unexplained vertical discontinuities in any station position time series. However, analysis of the new series with respect to ITRF2008 exhibits a scale increase late 2011 which is not yet explained. A new DORIS Terrestrial Reference Frame was computed to evaluate the intrinsic quality of the new combined solution. That evaluation shows that the addition of data from the new missions equipped with the latest generation of DORIS receiver (Jason-2, Cryosat-2, HY-2A, Saral), results in an internal position consistency of 10 mm or better after mid-2008.

  5. Stability of Precise Point Positioning with Different Techniques for Applying the IGb08 and IGS14 Reference Frames

    NASA Astrophysics Data System (ADS)

    Ries, P. A.; Heflin, M. B.; Amiri, N.; Sakumura, C.; Sibois, A. E.; David, M. W.

    2016-12-01

    In order to evaluate the accuracy of the station locations within both the IGb08 and IGS14 reference frames, we apply two different methods for constraining their positions within the reference frames. We produce time series data from 50 different stations between March 2011 and March 2012 including sites near large seismic events. For the first technique, we point position the stations against JPL's fiducial-free orbit and clock products and use a 7-parameter Helmert transformation on the network positions and covariance from the free solution to transform the position into each reference frame. For the second test, we perform precise orbit determination (POD) on the GPS constellation using a network of ground stations and apply a no-net-rotation (NNR) constraint from each frame on the network during POD. We then compare the stability of time series of stations point positioned against the NNR products generated in each frame and transformed into the reference frame with a 4-parameter Helmert transform. We also compare the stability between the positions obtained from the NNR products and a 4-parameter transformation against positions obtained from fiducial-free products and a 7-parameter transformation in each frame.

  6. Factors influencing superimposition error of 3D cephalometric landmarks by plane orientation method using 4 reference points: 4 point superimposition error regression model.

    PubMed

    Hwang, Jae Joon; Kim, Kee-Deog; Park, Hyok; Park, Chang Seo; Jeong, Ho-Gul

    2014-01-01

    Superimposition has been used as a method to evaluate the changes of orthodontic or orthopedic treatment in the dental field. With the introduction of cone beam CT (CBCT), evaluating 3 dimensional changes after treatment became possible by superimposition. 4 point plane orientation is one of the simplest ways to achieve superimposition of 3 dimensional images. To find factors influencing superimposition error of cephalometric landmarks by 4 point plane orientation method and to evaluate the reproducibility of cephalometric landmarks for analyzing superimposition error, 20 patients were analyzed who had normal skeletal and occlusal relationship and took CBCT for diagnosis of temporomandibular disorder. The nasion, sella turcica, basion and midpoint between the left and the right most posterior point of the lesser wing of sphenoidal bone were used to define a three-dimensional (3D) anatomical reference co-ordinate system. Another 15 reference cephalometric points were also determined three times in the same image. Reorientation error of each landmark could be explained substantially (23%) by linear regression model, which consists of 3 factors describing position of each landmark towards reference axes and locating error. 4 point plane orientation system may produce an amount of reorientation error that may vary according to the perpendicular distance between the landmark and the x-axis; the reorientation error also increases as the locating error and shift of reference axes viewed from each landmark increases. Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important. Construction of the regression model using reference points of greater precision is required for the clinical application of this model.

  7. Factors Influencing Superimposition Error of 3D Cephalometric Landmarks by Plane Orientation Method Using 4 Reference Points: 4 Point Superimposition Error Regression Model

    PubMed Central

    Hwang, Jae Joon; Kim, Kee-Deog; Park, Hyok; Park, Chang Seo; Jeong, Ho-Gul

    2014-01-01

    Superimposition has been used as a method to evaluate the changes of orthodontic or orthopedic treatment in the dental field. With the introduction of cone beam CT (CBCT), evaluating 3 dimensional changes after treatment became possible by superimposition. 4 point plane orientation is one of the simplest ways to achieve superimposition of 3 dimensional images. To find factors influencing superimposition error of cephalometric landmarks by 4 point plane orientation method and to evaluate the reproducibility of cephalometric landmarks for analyzing superimposition error, 20 patients were analyzed who had normal skeletal and occlusal relationship and took CBCT for diagnosis of temporomandibular disorder. The nasion, sella turcica, basion and midpoint between the left and the right most posterior point of the lesser wing of sphenoidal bone were used to define a three-dimensional (3D) anatomical reference co-ordinate system. Another 15 reference cephalometric points were also determined three times in the same image. Reorientation error of each landmark could be explained substantially (23%) by linear regression model, which consists of 3 factors describing position of each landmark towards reference axes and locating error. 4 point plane orientation system may produce an amount of reorientation error that may vary according to the perpendicular distance between the landmark and the x-axis; the reorientation error also increases as the locating error and shift of reference axes viewed from each landmark increases. Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important. Construction of the regression model using reference points of greater precision is required for the clinical application of this model. PMID:25372707

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  9. Absolute plate motion changes around 50 Ma in a Global Moving Hotspot Reference Frame

    NASA Astrophysics Data System (ADS)

    Steinberger, B. M.; Doubrovine, P. V.; Torsvik, T. H.

    2011-12-01

    To understand causes of plate motion changes around 50 Ma, it is important to know which plates also have changed their motion relative to the underlying mantle. Towards that end, we have developed a global reference frame that is based on fitting the age progression along five hotspot tracks: Hawaii, Louisville, Tristan, Reunion and New England. We use all available information on relative plate motions and two alternative plate chains - one through East and West Antarctica and one through Australia and Lord Howe Rise - to compute the motion of the Pacific relative to Africa. Our model also considers the predicted motion of these hotspots due to large-scale mantle flow: This flow is computed from mantle density anomalies inferred from seismic tomography. Hereby it is assumed that both seismic velocity and density anomalies in the mantle are due to temperature variations, except in parts of the uppermost mantle (tectosphere) and possibly parts of the lowermost mantle (Large Low Shear Velocity Provinces). We use a radial mantle viscosity structure that is consistent with mineral physics and the Haskell average inferred from postglacial rebound, and that also gives predictions for geoid and global mantle heat flux that agree well with observations. We compute the motion of mantle plume conduits, assuming they are initially vertical, and subsequently get advected with flow, but also rise buoyantly. Our resulting best-fit model yields acceptable fits to all hotspot tracks. It confirms that Pacific plate motion has changed at the time of the bend, but the Hawaiian hotspot has also moved southward by several hundred km. We also consider alternatively a paleomagnetic reference frame, which has been corrected for true polar wander (TPW) by interpreting the coherent rotation component of all continents around their common center of mass as TPW. Due to the TPW correction, both reference frames are rather similar. Bends in apparent polar wander (APW) paths are often

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  11. Completing the K-band Celestial Reference Frame in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    de Witt, A.; Bertarini, A.; Horiuchi, S.; Jacobs, C. S.; Jung, T.; Lovell, J. E. J.; McCallum, J. N.; Quick, J. F. H.; Sohn, B. W.; Phillips, C.; Ojha, R.

    2014-12-01

    K-band (22 GHz) radio observations have the potential to form the basis for the most accurate Celestial Reference Frame (CRF) ever constructed. Relative to the standard S/X (2.3/8.4 GHz) observing bands, K-band is expected to exhibit a reduction in extended source morphology and core-shift. This reduction in astrophysical systematics should allow for a more stable CRF at K-band and should also be advantageous in tying the VLBI radio frame to the Gaia optical frame. K-band CRF observations currently exist only from the all-northern Very Long Baseline Array (VLBA) and therefore must be complemented by observations from southern arrays in order to realize this potential. A collaboration was formed with the goal of completing sky coverage at K-band with specific emphasis on the Southern hemisphere where K-band CRF coverage is weak. Southern hemisphere observations to densify the CRF at K-band are under way and preliminary astrometric observations were carried out on 23 August 2013 between telescopes in Australia (Hobart 26 m), Korea (Tamna 21 m), and South Africa (HartRAO 26 m). More extensive astrometric observations were carried out on 21/22 December 2013 that also included the Tidbinbilla 70-m DSN antenna in Australia. A proposal for imaging source structure at K-band has been submitted to the Australian Telescope-Long Baseline Array (AT-LBA). We discuss some of our results as well as the implications for K-band CRF work.

  12. 3D Printing and 3D Bioprinting in Pediatrics

    PubMed Central

    Vijayavenkataraman, Sanjairaj; Fuh, Jerry Y H; Lu, Wen Feng

    2017-01-01

    Additive manufacturing, commonly referred to as 3D printing, is a technology that builds three-dimensional structures and components layer by layer. Bioprinting is the use of 3D printing technology to fabricate tissue constructs for regenerative medicine from cell-laden bio-inks. 3D printing and bioprinting have huge potential in revolutionizing the field of tissue engineering and regenerative medicine. This paper reviews the application of 3D printing and bioprinting in the field of pediatrics. PMID:28952542

  13. 3D Printing and 3D Bioprinting in Pediatrics.

    PubMed

    Vijayavenkataraman, Sanjairaj; Fuh, Jerry Y H; Lu, Wen Feng

    2017-07-13

    Additive manufacturing, commonly referred to as 3D printing, is a technology that builds three-dimensional structures and components layer by layer. Bioprinting is the use of 3D printing technology to fabricate tissue constructs for regenerative medicine from cell-laden bio-inks. 3D printing and bioprinting have huge potential in revolutionizing the field of tissue engineering and regenerative medicine. This paper reviews the application of 3D printing and bioprinting in the field of pediatrics.

  14. Improved Modeling of Vertical Crustal Motion in Canada for a New North American Reference Frame

    NASA Astrophysics Data System (ADS)

    Robin, C. M. I.; Craymer, M.; Ferland, R.; Lapelle, E.; Piraszewski, M.; Zhao, Y.; James, T. S.

    2016-12-01

    A national-scale crustal velocity model has been developed for Canada as part of the current realization of NAD83(CSRS). It is used to propagate coordinates to different reference epochs, and to support scientific studies such as natural hazards related to earthquakes and sea level rise. The current velocity model is based solely on continuous and campaign GPS data between 1994 and 2011.3. To improve on this, a new hybrid model has been created which incorporates a new GPS velocity field with GIA and elastic rebound models for improved accuracy, particularly in northern areas with sparse GPS coverage. Several GIA models and interpolation techniques were tested. Improvements to the GPS velocity field include the addition of new stations in key areas, 5 more years of data, and the reprocessing of all data with the latest software, orbits and antenna calibrations. We include all continuous GPS sites in Canada, the northern portions of the US, all of Greenland, repeated high accuracy campaign surveys of the Canadian Base Network, and a set of global sites used to define the reference frame. Initial uncertainty estimates for the hybrid model are also provided. It is envisaged that such a hybrid model can be used to provide an improved vertical crustal velocity model for a new North American reference system.

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

    PubMed

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

    2012-01-01

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

  16. Purkinje cells in posterior cerebellar vermis encode motion in an inertial reference frame.

    PubMed

    Yakusheva, Tatyana A; Shaikh, Aasef G; Green, Andrea M; Blazquez, Pablo M; Dickman, J David; Angelaki, Dora E

    2007-06-21

    The ability to orient and navigate through the terrestrial environment represents a computational challenge common to all vertebrates. It arises because motion sensors in the inner ear, the otolith organs, and the semicircular canals transduce self-motion in an egocentric reference frame. As a result, vestibular afferent information reaching the brain is inappropriate for coding our own motion and orientation relative to the outside world. Here we show that cerebellar cortical neuron activity in vermal lobules 9 and 10 reflects the critical computations of transforming head-centered vestibular afferent information into earth-referenced self-motion and spatial orientation signals. Unlike vestibular and deep cerebellar nuclei neurons, where a mixture of responses was observed, Purkinje cells represent a homogeneous population that encodes inertial motion. They carry the earth-horizontal component of a spatially transformed and temporally integrated rotation signal from the semicircular canals, which is critical for computing head attitude, thus isolating inertial linear accelerations during navigation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2014-01-01

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

  19. Superfluid vortex front at T→0: decoupling from the reference frame.

    PubMed

    Hosio, J J; Eltsov, V B; de Graaf, R; Heikkinen, P J; Hänninen, R; Krusius, M; L'vov, V S; Volovik, G E

    2011-09-23

    Steady-state turbulent motion is created in superfluid (3)He-B at low temperatures in the form of a turbulent vortex front, which moves axially along a rotating cylindrical container of (3)He-B and replaces vortex-free flow with vortex lines at constant density. We present the first measurements on the thermal signal from dissipation as a function of time, recorded at 0.2T(c) during the front motion, which is monitored using NMR techniques. Both the measurements and the numerical calculations of the vortex dynamics show that at low temperatures the density of the propagating vortices falls well below the equilibrium value, i.e., the superfluid rotates at a smaller angular velocity than the container. This is the first evidence for the decoupling of the superfluid from the container reference frame in the zero-temperature limit.

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

    NASA Astrophysics Data System (ADS)

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

    1989-08-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2014-01-01

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

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

    USGS Publications Warehouse

    Jobson, Harvey E.

    1980-01-01

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

  4. Evaluation of the Quantitative Accuracy of 3D Reconstruction of Edentulous Jaw Models with Jaw Relation Based on Reference Point System Alignment

    PubMed Central

    Li, Weiwei; Yuan, Fusong; Lv, Peijun; Wang, Yong; Sun, Yuchun

    2015-01-01

    Objectives To apply contact measurement and reference point system (RPS) alignment techniques to establish a method for 3D reconstruction of the edentulous jaw models with centric relation and to quantitatively evaluate its accuracy. Methods Upper and lower edentulous jaw models were clinically prepared, 10 pairs of resin cylinders with same size were adhered to axial surfaces of upper and lower models. The occlusal bases and the upper and lower jaw models were installed in the centric relation position. Faro Edge 1.8m was used to directly obtain center points of the base surface of the cylinders (contact method). Activity 880 dental scanner was used to obtain 3D data of the cylinders and the center points were fitted (fitting method). 3 pairs of center points were used to align the virtual model to centric relation. An observation coordinate system was interactively established. The straight-line distances in the X (horizontal left/right), Y (horizontal anterior/posterior), and Z (vertical) between the remaining 7 pairs of center points derived from contact method and fitting method were measured respectively and analyzed using a paired t-test. Results The differences of the straight-line distances of the remaining 7 pairs of center points between the two methods were X: 0.074 ± 0.107 mm, Y: 0.168 ± 0.176 mm, and Z: −0.003± 0.155 mm. The results of paired t-test were X and Z: p >0.05, Y: p <0.05. Conclusion By using contact measurement and the reference point system alignment technique, highly accurate reconstruction of the vertical distance and centric relation of a digital edentulous jaw model can be achieved, which meets the design and manufacturing requirements of the complete dentures. The error of horizontal anterior/posterior jaw relation was relatively large. PMID:25659133

  5. Determining sex by bone volume from 3D images: discriminating analysis of the tali and radii in a contemporary Spanish reference collection.

    PubMed

    Ruiz Mediavilla, Elena; Perea Pérez, Bernardo; Labajo González, Elena; Sánchez Sánchez, José Antonio; Santiago Sáez, Andrés; Dorado Fernández, Enrique

    2012-07-01

    The discriminant power of bone volume for determining sex has not been possible to determine due to the difficulty in its calculation. At present, new advancements based on 3D technology make it possible to reproduce the bone digitally and calculate its volume using computerized tools, which opens up a new window to ascertaining the discriminant power of this variable. With this objective in mind, the tali and radii of 101 individuals (48 males and 53 females) of a contemporary Spanish reference collection (twentieth century) (EML 1) were scanned using the Picza 3D Laser Scanner. Calculated for the tali were total volume, the volume of the posterior region, which includes the posterior calcaneal facet and other three volumes of the anterior region. Calculated for the radius were total volume, volume of the radius head, volume of the diaphysis, and volume of the distal end. The data are presented for all of the variables, distinguishing between the right and left side. The data were processed using the statistical program PASW Statistics 18, thereby obtaining classification functions for sex which accurately classify 90.9 % of tali and 93.9 % of radii on the basis of their total left and right volume, respectively. Studying the volume in different regions of the bone shows that the diaphysis of the right radius possesses a high level of discriminant power, offering classification functions which accurately classify 96.9 % of the sample. The validation test performed on a sample of 20 individuals from another contemporary Spanish reference collection (EML 2) confirms the high discriminant power of the volume obtaining an accurate classification rate of 80-95 % depending on the variable studied.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. The cascading effects of absolute reference frames and geomagnetic polarity timescales on global plate motions

    NASA Astrophysics Data System (ADS)

    Zahirovic, S.; Seton, M.; Müller, R. D.; Torsvik, T. H.

    2011-12-01

    Global plate motion models use Africa and the Pacific as the base of plate rotation hierarchies, with many other plates moving relative to them. Relative plate motions in the Mesozoic are generally well resolved where seafloor spreading histories are preserved to the present-day. However, the choice of absolute reference frames, whether they are fixed-hotspot, moving-hotspot, true-polar wander-corrected or pure paleomagnetic, can have significant consequences for the absolute plate velocities of smaller plates that are at the mercy of the cascading effects of movement within a complex plate motion hierarchy. We use GPlates to sample plate velocities through time at equally spaced mesh nodes that are contained within continuously closing plate polygons. We calculate root-mean square plate velocities to isolate the effects of different absolute reference frames on absolute plate velocity trends. Apart from being a quality-control tool for the creation of global plate motion models, this approach allows us to track the source of plate velocity spikes, some of which may be indicative of plate reorganisation events. We use a similar approach to test whether alternative geomagnetic polarity time-scales introduce or help reduce anomalous plate velocity fluctuations in global plate motion models. The choice of timescales can affect the seafloor spreading rates partitioned across stage rotations and models of sea level change. Such a workflow may help test alternative timescales, in order to study the model-dependence and controversies that have recently surfaced regarding proposed plate reorganisation events and the mid-Cretaceous seafloor spreading pulse.

  8. Impact of Glacial Isostatic Adjustment on North America Plate Specific Terrestrial Reference Frame

    NASA Astrophysics Data System (ADS)

    Herring, Thomas; Melbourne, Tim; Murray, Mark; Floyd, Mike; Szeliga, Walter; King, Robert; Phillips, David; Puskas, Christine

    2017-04-01

    We examine the impact of incorporating glacial isostatic adjustment (GIA) models in determining the Euler poles for plate specific terrestrial reference frames. We will specifically examine the impact of GIA models on the realization of a North America Reference frame. We use a combination of the velocity fields determined by the Geodesy Advancing Geosciences and EarthScope (GAGE) Facility which analyzes GPS data from the Plate Boundary Observatory (PBO) and other geodetic quality GPS sites in North America, and from the ITRF2014 re-analysis. Initial analysis of the GAGE velocity field shows reduced root-mean-square (RMS) scatter of velocity estimate residuals when the North America Euler pole is estimated including the ICE-6G GIA mode. The reduction in the north-south direction is from 0.69 mm/yr to 0.52 mm/yr, in the east-west direction from 0.34 mm/yr to 0.30 mm/yr and in height from 0.93 mm/yr to 0.72 mm/yr. The reduction in the height RMS is not surprising since the contemporary geodetic height velocity estimates are used in the developing the ICE-6G model. Contemporary horizontal motions are not used the GIA model development, and the reduction in horizontal RMS provides a partial validation of the model. There is no reduction in the horizontal velocity residual when the ICE-5G model is used. Although removing the ICE-6G model before fitting an Euler pole for the North American plate reduces the RMS of the residuals, the pattern of residuals is still systematic suggesting possibly that a spherically symmetric viscosity model might not be adequate for accurate modeling of the horizontal motions associated with GIA in North America. This presentation in focus on the prospects and impacts of incorporating GIA models in plate-specific Euler poles with emphasis on North America.

  9. ITRF2014: A new release of the International Terrestrial Reference Frame modeling nonlinear station motions

    NASA Astrophysics Data System (ADS)

    Altamimi, Zuheir; Rebischung, Paul; Métivier, Laurent; Collilieux, Xavier

    2016-08-01

    For the first time in the International Terrestrial Reference Frame (ITRF) history, the ITRF2014 is generated with an enhanced modeling of nonlinear station motions, including seasonal (annual and semiannual) signals of station positions and postseismic deformation for sites that were subject to major earthquakes. Using the full observation history of the four space geodetic techniques (very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite (DORIS)), the corresponding international services provided reprocessed time series (weekly from SLR and DORIS, daily from GNSS, and 24 h session-wise from VLBI) of station positions and daily Earth Orientation Parameters. ITRF2014 is demonstrated to be superior to past ITRF releases, as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities. The ITRF2014 long-term origin coincides with the Earth system center of mass as sensed by SLR observations collected on the two LAGEOS satellites over the time span between 1993.0 and 2015.0. The estimated accuracy of the ITRF2014 origin, as reflected by the level of agreement with the ITRF2008 (both origins are defined by SLR), is at the level of less than 3 mm at epoch 2010.0 and less than 0.2 mm/yr in time evolution. The ITRF2014 scale is defined by the arithmetic average of the implicit scales of SLR and VLBI solutions as obtained by the stacking of their respective time series. The resulting scale and scale rate differences between the two solutions are 1.37 (±0.10) ppb at epoch 2010.0 and 0.02 (±0.02) ppb/yr. While the postseismic deformation models were estimated using GNSS/GPS data, the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques, showing a very high level of consistency which enforces more the link

  10. A Stable Geodetic Reference Frame within the COCONET Footprint to Enable High-Accuracy Ground Deformation Study

    NASA Astrophysics Data System (ADS)

    Liu, H.; Wang, G.; Yu, J.

    2014-12-01

    COCONET(Continuously Operating Caribbean GPS Observational Network) is a multidisciplinary research infrastructure focused on improving the ability to understand, predict, and prepare for multiple natural hazards in the Caribbean, Central America, and Northern Andes. GPS data alone cannot provide accurate ground deformation information over time and space. A precise regional reference frame is needed in interpolating GPS observations to address regional and local ground deformations. Failure to use a precise reference frame would cause unintended negative consequences. The mainly purpose of this study is to establish a stable geodetic reference frame within the COCONet footprint (abbreviated as "COCONet-RF") and to provide positional time series and velocities (relative to COCONet-RF) of all permanent GPS stations within the COCONet footprint to the public. The GIPSY software package was used to calculate position within IGS08. The local reference frame was realized by a 14-parameter Helmert transformation technique. It will be periodically updated in order to synchronize with the update of the IGS reference frame. This stable COCONer-RF would provide a higher accuracy geodetic infrastructure for delineating the magnitude and spatial and temporal variations of ground deformations associated with landslides, faulting, subsidence, and volcanoes. Researchers who are not familiar with GPS data processing and reference transformation will be able to directly integrate COCONET products into their specific research.

  11. Comparison of HMD ownship status symbology and frame of reference orientation during two aircraft control tasks

    NASA Astrophysics Data System (ADS)

    Havig, Paul R.; Jenkins, J. Chris; Geiselman, Eric E.

    2002-08-01

    Recent technological advances allow symbology to be displayed on the pilot's visor. A major benefit of this is that the pilot will be able to take this information with them when they look off-boresight. However, when looking off-boresight the question arises as to what is the best orientation, or frame of reference, for attitude symbology against the horizon (i.e., forward or line-of-sight) in order to maximize interpretation and performance. This study tested five different symbologies (standard HUD, visually coupled acquisition and targeting symbology, arc segmented attitude reference, theta ball, and non-distributed flight reference) of which three have both forward and line-of-sight orientations. The experiment consisted of two different tasks, with the pilots performing either facing the monitor or rotated 90 degree(s) and looking over their shoulder (off-boresight). In the first task, pilots maintained straight and level flight with simulated turbulence. The second task had pilots interpret a static representation of their attitude and respond via a key press, and then the display went live and they had to fly to a new commanded attitude. This second task was similar to a recovery from unusual attitude methodology, except the end state was never straight and level. Instead, a second unknown end state attitude was commanded by the experiment. Results indicate that performance is better when the symbology is forward as opposed to line-of-sight referenced. Further, performance was best in both tasks for the non-distributed flight reference. We discuss these results in terms of implications for helmet-mounted display symbology design.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  13. Positional priming of visual pop-out search is supported by multiple spatial reference frames.

    PubMed

    Gokce, Ahu; Müller, Hermann J; Geyer, Thomas

    2015-01-01

    The present study investigates the representations(s) underlying positional priming of visual 'pop-out' search (Maljkovic and Nakayama, 1996). Three search items (one target and two 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.

  14. Positional priming of visual pop-out search is supported by multiple spatial reference frames

    PubMed Central

    Gokce, Ahu; Müller, Hermann J.; Geyer, Thomas

    2015-01-01

    The present study investigates the representations(s) underlying positional priming of visual ‘pop-out’ search (Maljkovic and Nakayama, 1996). Three search items (one target and two 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. PMID:26136718

  15. Developmental vision determines the reference frame for the multisensory control of action.

    PubMed

    Röder, Brigitte; Kusmierek, Anna; Spence, Charles; Schicke, Tobias

    2007-03-13

    Both animal and human studies suggest that action goals are defined in external coordinates regardless of their sensory modality. The present study used an auditory-manual task to test whether the default use of such an external reference frame is innately determined or instead acquired during development because of the increasing dominance of vision over manual control. In Experiment I, congenitally blind, late blind, and age-matched sighted adults had to press a left or right response key depending on the bandwidth of pink noise bursts presented from either the left or right loudspeaker. Although the spatial location of the sounds was entirely task-irrelevant, all groups responded more efficiently with uncrossed hands when the sound was presented from the same side as the responding hand ("Simon effect"). This effect reversed with crossed hands only in the congenitally blind: They responded faster with the hand that was located contralateral to the sound source. In Experiment II, the instruction to the participants was changed: They now had to respond with the hand located next to the sound source. In contrast to Experiment I ("Simon-task"), this task required an explicit matching of the sound's location with the position of the responding hand. In Experiment II, the congenitally blind participants showed a significantly larger crossing deficit than both the sighted and late blind adults. This pattern of results implies that developmental vision induces the default use of an external coordinate frame for multisensory action control; this facilitates not only visual but also auditory-manual control.

  16. A subduction zone reference frame based on slab geometry and subduction partitioning of plate motion and trench migration

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.

    2011-08-01

    The geometry of subducted slabs that interact with the transition zone depends critically on the partitioning of the subduction velocity (vS$\\perp$) at the surface into its subducting plate motion component (vSP$\\perp$) and trench migration component (vT$\\perp$). Geodynamic models of progressive subduction demonstrate such dependence with five distinct slab geometries and corresponding partitioning ratios (vSP$\\perp$/vS$\\perp$): slab draping (vSP$\\perp$/vS$\\perp$ ≤ 0.5), slab draping with recumbent folds (0.5 < vSP$\\perp$/vS$\\perp$ < ˜0.8), slab piling (˜0.8 ≤ vSP$\\perp$/vS$\\perp$ ≤ ˜1.2), slab roll-over with recumbent folds (˜1.2 < vSP$\\perp$/vS$\\perp$ < ˜1.5) and slab roll-over (vSP$\\perp$/vS$\\perp$ ≥ ˜1.5). The model findings have been applied to subduction zones in nature with well-resolved slab geometries, for which subduction partitioning ratios have been calculated during the last 20 million years in two global reference frames: the Indo-Atlantic and Pacific hotspot reference frames. The model-nature comparison determines in which reference frame subduction partitioning ratios are most in agreement with observed slab geometries. In the Indo-Atlantic frame, five (out of five) selected subduction zone segments with well-resolved slab geometries, plate velocities and trench velocities (Japan, Izu-Bonin, Mariana, Tonga, Kermadec) agree with the geodynamic model predictions, as calculated subduction partitioning ratios match the observed slab geometries. In the Pacific frame the partitioning ratio of only one subduction zone segment (Izu-Bonin) matches observations. It is thus concluded that the Indo-Atlantic hotspot reference frame is preferred over the Pacific one as a subduction zone reference frame in which to describe plate motions, subduction kinematics and mantle flow.

  17. The Two-Wrongs model explains perception-action dissociations for illusions driven by distortions of the egocentric reference frame

    PubMed Central

    Dassonville, Paul; Reed, Scott A.

    2015-01-01

    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 processing streams

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

    SciTech Connect

    Chen, J.E.

    1995-12-31

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

  19. Unassisted 3D camera calibration

    NASA Astrophysics Data System (ADS)

    Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.

    2012-03-01

    With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.

  20. Impact of uncertain reference-frame motions in plate kinematic reconstructions: A theoretical appraisal

    NASA Astrophysics Data System (ADS)

    Iaffaldano, Giampiero; Stein, Seth

    2017-01-01

    Geoscientists infer past plate motions, which serve as fundamental constraints for a range of studies, from observations of magnetic isochrons as well as hotspots tracks on the ocean floor and, for stages older than the Cretaceous, from paleomagnetic data. These observations effectively represent time-integrals of past plate motions but, because they are made at present, yield plate kinematics naturally tied to a present-day reference-frame, which may be another plate or a hotspots system. These kinematics are therefore different than those occurred at the time when the rocks acquired their magnetisation or when hotspot-related marine volcanism took place, and are normally corrected for the reference-frame absolute motion (RFAM) that occurred since then. The impact of true-polar-wander events on paleomagnetic data and the challenge of inferring hotspot drifts result in RFAMs being less resolved - in a temporal sense - and prone to noise. This limitation is commonly perceived to hamper the correction of plate kinematic reconstructions for RFAMs, but the extent to which this may be the case has not been explored. Here we assess the impact of uncertain RFAMs on kinematic reconstructions using synthetic models of plate motions over 100 million years. We use randomly-drawn models for the kinematics of two plates separated by a spreading ridge to generate a synthetic magnetisation pattern of the ocean floor. The kinematics we infer from such a pattern are outputs that we correct for synthetic RFAMs using two equivalent methods (a classical one as well as another that we propose and test here) and then compare to the 'true' motions input. We assess the misfits between true and inferred kinematics by exploring a statistically-significant number of models where we systematically downgrade the temporal resolution of RFAM synthetic data and add noise to them. We show that even poorly-resolved, noisy RFAMs are sufficient to retrieve reliable plate kinematic reconstructions

  1. Gaia Data Release 1. Reference frame and optical properties of ICRF sources

    NASA Astrophysics Data System (ADS)

    Mignard, F.; Klioner, S.; Lindegren, L.; Bastian, U.; Bombrun, A.; Hernández, J.; Hobbs, D.; Lammers, U.; Michalik, D.; Ramos-Lerate, M.; Biermann, M.; Butkevich, A.; Comoretto, G.; Joliet, E.; Holl, B.; Hutton, A.; Parsons, P.; Steidelmüller, H.; Andrei, A.; Bourda, G.; Charlot, P.

    2016-11-01

    Context. As part of the data processing for Gaia Data Release 1 (Gaia DR1) a special astrometric solution was computed, the so-called auxiliary quasar solution. This gives positions for selected extragalactic objects, including radio sources in the second realisation of the International Celestial Reference Frame (ICRF2) that have optical counterparts bright enough to be observed with Gaia. A subset of these positions was used to align the positional reference frame of Gaia DR1 with the ICRF2. Although the auxiliary quasar solution was important for internal validation and calibration purposes, the resulting positions are in general not published in Gaia DR1. Aims: We describe the properties of the Gaia auxiliary quasar solution for a subset of sources matched to ICRF2, and compare their optical and radio positions at the sub-mas level. Methods: Descriptive statistics are used to characterise the optical data for the ICRF sources and the optical-radio differences. The most discrepant cases are examined using online resources to find possible alternative explanations than a physical optical-radio offset of the quasars. Results: In the auxiliary quasar solution 2191 sources have good optical positions matched to ICRF2 sources with high probability. Their formal standard errors are better than 0.76 milliarcsec (mas) for 50% of the sources and better than 3.35 mas for 90%. Optical magnitudes are obtained in Gaia's unfiltered photometric G band. The Gaia results for these sources are given as a separate table in Gaia DR1. The comparison with the radio positions of the defining sources shows no systematic differences larger than a few tenths of a mas. The fraction of questionable solutions, not readily accounted for by the statistics, is less than 6%. Normalised differences have extended tails requiring case-by-case investigations for around 100 sources, but we have not seen any difference indisputably linked to an optical-radio offset in the sources. Conclusions: With

  2. Reference frame preferences in haptics differ for the blind and sighted in the horizontal but not in the vertical plane.

    PubMed

    Struiksma, Marijn E; Noordzij, Matthijs L; Postma, Albert

    2011-01-01

    We investigated which reference frames are preferred when matching spatial language to the haptic domain. Sighted, low-vision, and blind participants were tested on a haptic-sentence-verification task where participants had to haptically explore different configurations of a ball and a shoe and judge the relation between them. Results from the spatial relation "above", in the vertical plane, showed that various reference frames are available after haptic inspection of a configuration. Moreover, the pattern of results was similar for all three groups and resembled patterns found for the sighted on visual sentence-verification tasks. In contrast, when judging the spatial relation "in front", in the horizontal plane, the blind showed a markedly different response pattern. The sighted and low-vision participants did not show a clear preference for either the absolute/relative or the intrinsic reference frame when these frames were dissociated. The blind, on the other hand, showed a clear preference for the intrinsic reference frame. In the absence of a dominant cue, such as gravity in the vertical plane, the blind might emphasise the functional relationship between the objects owing to enhanced experience with haptic exploration of objects.

  3. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  4. The right frame of reference makes it simple: an example of introductory mechanics supported by video analysis of motion

    NASA Astrophysics Data System (ADS)

    Klein, P.; Gröber, S.; Kuhn, J.; Fleischhauer, A.; Müller, A.

    2015-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  7. Quantum back-action-evading measurement of motion in a negative mass reference frame

    NASA Astrophysics Data System (ADS)

    Møller, Christoffer B.; Thomas, Rodrigo A.; Vasilakis, Georgios; Zeuthen, Emil; Tsaturyan, Yeghishe; Balabas, Mikhail; Jensen, Kasper; Schliesser, Albert; Hammerer, Klemens; Polzik, Eugene S.

    2017-07-01

    Quantum mechanics dictates that a continuous measurement of the position of an object imposes a random quantum back-action (QBA) perturbation on its momentum. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion. As a consequence of this randomness, and in accordance with the Heisenberg uncertainty principle, the QBA puts a limitation—the so-called standard quantum limit—on the precision of sensing of position, velocity and acceleration. Here we show that QBA on a macroscopic mechanical oscillator can be evaded if the measurement of motion is conducted in the reference frame of an atomic spin oscillator. The collective quantum measurement on this hybrid system of two distant and disparate oscillators is performed with light. The mechanical oscillator is a vibrational ‘drum’ mode of a millimetre-sized dielectric membrane, and the spin oscillator is an atomic ensemble in a magnetic field. The spin oriented along the field corresponds to an energetically inverted spin population and realizes a negative-effective-mass oscillator, while the opposite orientation corresponds to an oscillator with positive effective mass. The QBA is suppressed by -1.8 decibels in the negative-mass setting and enhanced by 2.4 decibels in the positive-mass case. This hybrid quantum system paves the way to entanglement generation and distant quantum communication between mechanical and spin systems and to sensing of force, motion and gravity beyond the standard quantum limit.

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

    PubMed Central

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

    2014-01-01

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

  9. A Global Terrestrial Reference Frame from simulated VLBI and SLR data in view of GGOS

    NASA Astrophysics Data System (ADS)

    Glaser, Susanne; König, Rolf; Ampatzidis, Dimitrios; Nilsson, Tobias; Heinkelmann, Robert; Flechtner, Frank; Schuh, Harald

    2017-07-01

    In this study, we assess the impact of two combination strategies, namely local ties (LT) and global ties (GT), on the datum realization of Global Terrestrial Reference Frames in view of the Global Geodetic Observing System requiring 1 mm-accuracy. Simulated Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data over a 7 year time span was used. The LT results show that the geodetic datum can be best transferred if the precision of the LT is at least 1 mm. Investigating different numbers of LT, the lack of co-located sites on the southern hemisphere is evidenced by differences of 9 mm in translation and rotation compared to the solution using all available LT. For the GT, the combination applying all Earth rotation parameters (ERP), such as pole coordinates and UT1-UTC, indicates that the rotation around the Z axis cannot be adequately transferred from VLBI to SLR within the combination. Applying exclusively the pole coordinates as GT, we show that the datum can be transferred with mm-accuracy within the combination. Furthermore, adding artificial stations in Tahiti and Nigeria to the current VLBI network results in an improvement in station positions by 13 and 12%, respectively, and in ERP by 17 and 11%, respectively. Extending to every day VLBI observations leads to 65% better ERP estimates compared to usual twice-weekly VLBI observations.

  10. Quantum back-action-evading measurement of motion in a negative mass reference frame.

    PubMed

    Møller, Christoffer B; Thomas, Rodrigo A; Vasilakis, Georgios; Zeuthen, Emil; Tsaturyan, Yeghishe; Balabas, Mikhail; Jensen, Kasper; Schliesser, Albert; Hammerer, Klemens; Polzik, Eugene S

    2017-07-12

    Quantum mechanics dictates that a continuous measurement of the position of an object imposes a random quantum back-action (QBA) perturbation on its momentum. This randomness translates with time into position uncertainty, thus leading to the well known uncertainty on the measurement of motion. As a consequence of this randomness, and in accordance with the Heisenberg uncertainty principle, the QBA puts a limitation-the so-called standard quantum limit-on the precision of sensing of position, velocity and acceleration. Here we show that QBA on a macroscopic mechanical oscillator can be evaded if the measurement of motion is conducted in the reference frame of an atomic spin oscillator. The collective quantum measurement on this hybrid system of two distant and disparate oscillators is performed with light. The mechanical oscillator is a vibrational 'drum' mode of a millimetre-sized dielectric membrane, and the spin oscillator is an atomic ensemble in a magnetic field. The spin oriented along the field corresponds to an energetically inverted spin population and realizes a negative-effective-mass oscillator, while the opposite orientation corresponds to an oscillator with positive effective mass. The QBA is suppressed by -1.8 decibels in the negative-mass setting and enhanced by 2.4 decibels in the positive-mass case. This hybrid quantum system paves the way to entanglement generation and distant quantum communication between mechanical and spin systems and to sensing of force, motion and gravity beyond the standard quantum limit.

  11. Question of reference frames: visual direction-selective neurons in the accessory optic system of goldfish.

    PubMed

    Masseck, Olivia Andrea; Hoffmann, Klaus-Peter

    2009-11-01

    We investigated if visual direction-selective neurons in the pretectal area (APT) of goldfish (Carassius auratus auratus) preferred visual stimuli resulting from rotations around axes corresponding to the best responsive axes of the semicircular canals [optic flow that is consistent to a maximal activation of the horizontal canal pair (yaw), to a maximal activation of the right anterior/left posterior semicircular canal pair (RALP), and to a maximal activation of the left anterior/right posterior semicircular canal pair (LARP)]. Our sample of neurons recorded in the left pretectum had two preferred axes of rotation: first, rotation around the yaw axis and second, rotation around the RALP axis. Both axes of rotation correspond to best responsive axes of the semicircular canals. For this reason, coding in a reference frame defined by the vestibular system or the pulling direction of the eye muscles is suggested. In our population of recorded APT neurons, we did not find segregation of different preferred axes of rotation into different anatomical structures. Furthermore in all axes no bias for clockwise or counterclockwise rotations was obvious. This is particularly noteworthy for the yaw axis because preference for temporo-nasal and naso-temporal rotations was found at the same recording side. Hence we conclude that in fish the accessory optic system may consist of one nucleus on each side of the midbrain only, the APT. Segregation into different nuclei coding for different axes and different senses of rotation probably first developed in amphibians.

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

    PubMed

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

    2014-08-01

    This paper assesses the applicability of the Frame of Reference (FoR) approach for the environmental monitoring of large-scale offshore Marine Renewable Energy (MRE) projects. The focus is on projects harvesting energy from winds, waves and currents. Environmental concerns induced by MRE projects are reported based on a classification scheme identifying stressors, receptors, effects and impacts. Although the potential effects of stressors on most receptors are identified, there are large knowledge gaps regarding the corresponding (positive and negative) impacts. In that context, the development of offshore MRE requires the implementation of fit-for-purpose monitoring activities aimed at environmental protection and knowledge development. Taking European legislation as an example, it is suggested to adopt standardized monitoring protocols for the enhanced usage and utility of environmental indicators. Towards this objective, the use of the FoR approach is advocated since it provides guidance for the definition and use of coherent set of environmental state indicators. After a description of this framework, various examples of applications are provided considering a virtual MRE project located in European waters. Finally, some conclusions and recommendations are provided for the successful implementation of the FoR approach and for future studies. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. A cold pool reference frame for analyzing polar stratospheric clouds and tropospheric forcing

    NASA Astrophysics Data System (ADS)

    Fromm, M. D.

    2011-12-01

    The dominance of synoptic scale tropospheric forcing as a driver for Arctic PSC existence has been established for a single season [Teitelbaum et al., 2001, J. Geophys. Res.] and over the entire SAM II, POAM II, POAM III era [Fromm et al. 2003, J. Geophys. Res.]. These results suggest that a meteorological context for PSC occurrence and composition, based on synoptic-scale dynamics, is appropriate and useful for unified PSC studies. Here we analyze satellite PSC observations in a new geospatial context: the cold pool reference frame (CPRF). We present a CPRF using the canonical nitric acid trihydrate (NAT) saturation isotherm as the boundary, with isotherms for liquid ternary aerosol condensation and the water-ice frost point for inner PSC-composition "latitudes." The temperature minimum and the longitude of the temperature minimum mark the pole and axis of the CPRF, respectively. The CPRF also incorporates the air flow through the cold pool with the Montgomery stream function. With such information, we relate SAGE and POAM occurrence of PSCs with respect to the cold pool axis and the upwind/downwind PSC-composition latitude belts. The CPRF model, and a justification based on monthly average December 2002 meteorological analyses, is presented. To illustrate, we show the case of 19 December 2002 as well as monthly PSC results. We also apply the CPRF to PSC observations from the Arctic winter of 2010/2011.

  14. Frame-of-reference training for simulation-based intraoperative communication assessment.

    PubMed

    Gardner, Aimee K; Russo, Michael A; Jabbour, Ibrahim I; Kosemund, Matthew; Scott, Daniel J

    2016-09-01

    The purpose of this study was to examine the impact of frame-of-reference (FOR) training on assessments of intraoperative communication skills and identify areas of need to inform curricular efforts. Simulation instructors (M.D., Ph.D., Research Fellow, Simulation Technician) underwent a 2-hour FOR training session with the operating room communication instrument. They then independently rated communication skills of 19 PGY1s who participated in a team-based simulation. Residents completed self-assessments via video review of the scenario. Intraclass correlation coefficients were used to examine inter-rater reliability. Relationships between trained raters and resident scores were assessed with Pearson correlation coefficients and paired sample t tests. Inter-reliability after FOR training was .91. The correlation between trained rater scores and resident evaluations was nonsignificant. Residents significantly underestimated their intraoperative communication skills (P < .05). Use of names, closed loop communication, and sharing information with team members demonstrated consistently low ratings among all residents. These findings reveal that a number of individuals can be trained to reliably rate resident intraoperative communication performance and that residents tend to under-rate their communication skills. Copyright © 2016 Elsevier Inc. All rights reserved.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    PubMed

    Zill, Sasha N; Schmitz, Josef; Chaudhry, Sumaiya; Büschges, Ansgar

    2012-09-01

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

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

    PubMed Central

    Schmitz, Josef; Chaudhry, Sumaiya; Büschges, Ansgar

    2012-01-01

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

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

    PubMed Central

    Zhang, Jing; Ma, Ke; Hommel, Bernhard

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  20. Efficient quantum key distribution with trines of reference-frame-free qubits

    NASA Astrophysics Data System (ADS)

    Tabia, Gelo; Englert, Berthold-Georg

    2011-01-01

    We propose a rotationally-invariant quantum key distribution scheme that uses a pair of orthogonal qubit trines, realized as mixed states of three physical qubits. The measurement outcomes do not depend on how Alice and Bob choose their individual reference frames. The efficient key generation by two-way communication produces two independent raw keys, a bit key and a trit key. For a noiseless channel, Alice and Bob get a total of 0.573 key bits per trine state sent (98% of the Shannon limit). This exceeds by a considerable amount the yield of standard trine schemes, which ideally attain half a key bit per trine state. Eavesdropping introduces an ɛ-fraction of unbiased noise, ensured by twirling if necessary. The security analysis reveals an asymmetry in Eve's conditioned ancillas for Alice and Bob resulting from their inequivalent roles in the key generation. Upon simplifying the analysis by a plausible symmetry assumption, we find that a secret key can be generated if the noise is below the threshold set by ɛ=0.197.

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

    SciTech Connect

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

    2010-05-15

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

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

    PubMed

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

    2014-06-17

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

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

    NASA Astrophysics Data System (ADS)

    Standish, E. M.

    2003-08-01

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

  4. Geometric accuracy of 3D coordinates of the Leksell stereotactic skull frame in 1.5 Tesla- and 3.0 Tesla-magnetic resonance imaging: a comparison of three different fixation screw materials

    PubMed Central

    Nakazawa, Hisato; Mori, Yoshimasa; Yamamuro, Osamu; Komori, Masataka; Shibamoto, Yuta; Uchiyama, Yukio; Tsugawa, Takahiko; Hagiwara, Masahiro

    2014-01-01

    We assessed the geometric distortion of 1.5-Tesla (T) and 3.0-T magnetic resonance (MR) images with the Leksell skull frame system using three types of cranial quick fixation screws (QFSs) of different materials—aluminum, aluminum with tungsten tip, and titanium—for skull frame fixation. Two kinds of acrylic phantoms were placed on a Leksell skull frame using the three types of screws, and were scanned with computed tomography (CT), 1.5-T MR imaging and 3.0-T MR imaging. The 3D coordinates for both strengths of MR imaging were compared with those for CT. The deviations of the measured coordinates at selected points (x = 50, 100 and 150; y = 50, 100 and 150) were indicated on different axial planes (z = 50, 75, 100, 125 and 150). The errors of coordinates with QFSs of aluminum, tungsten-tipped aluminum, and titanium were <1.0, 1.0 and 2.0 mm in the entire treatable area, respectively, with 1.5 T. In the 3.0-T field, the errors with aluminum QFSs were <1.0 mm only around the center, while the errors with tungsten-tipped aluminum and titanium were >2.0 mm in most positions. The geometric accuracy of the Leksell skull frame system with 1.5-T MR imaging was high and valid for clinical use. However, the geometric errors with 3.0-T MR imaging were larger than those of 1.5-T MR imaging and were acceptable only with aluminum QFSs, and then only around the central region. PMID:25034732

  5. Combination of terrestrial reference frames based on space geodetic techniques in SHAO: methodology and main issues

    NASA Astrophysics Data System (ADS)

    He, Bing; Wang, Xiao-Ya; Hu, Xiao-Gong; Zhao, Qun-He

    2017-09-01

    Based on years of input from the four geodetic techniques (SLR, GPS, VLBI and DORIS), the strategies of the combination were studied in SHAO to generate a new global terrestrial reference frame as the material realization of the ITRS defined in IERS Conventions. The main input includes the time series of weekly solutions (or fortnightly for SLR 1983–1993) of observational data for satellite techniques and session-wise normal equations for VLBI. The set of estimated unknowns includes 3-dimensional Cartesian coordinates at the reference epoch 2005.0 of the stations distributed globally and their rates as well as the time series of consistent Earth Orientation Parameters (EOPs) at the same epochs as the input. Besides the final solution, namely SOL-2, generated by using all the inputs before 2015.0 obtained from short-term observation processing, another reference solution, namely SOL-1, was also computed by using the input before 2009.0 based on the same combination of procedures for the purpose of comparison with ITRF2008 and DTRF2008 and for evaluating the effect of the latest six more years of data on the combined results. The estimated accuracy of the x-component and y-component of the SOL-1 TRF-origin was better than 0.1 mm at epoch 2005.0 and better than 0.3 mm yr‑1 in time evolution, either compared with ITRF2008 or DTRF2008. However, the z-component of the translation parameters from SOL-1 to ITRF2008 and DTRF2008 were 3.4 mm and ‑1.0 mm, respectively. It seems that the z-component of the SOL-1 TRF-origin was much closer to the one in DTRF2008 than the one in ITRF2008. The translation parameters from SOL-2 to ITRF2014 were 2.2, ‑1.8 and 0.9 mm in the x-, y- and z-components respectively with rates smaller than 0.4 mm yr‑1. Similarly, the scale factor transformed from SOL-1 to DTRF2008 was much smaller than that to ITRF2008. The scale parameter from SOL-2 to ITRF2014 was ‑0.31 ppb with a rate lower than 0.01 ppb yr‑1. The external precision (WRMS

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

    ERIC Educational Resources Information Center

    Auer-Rizzi, Werner; Berry Michael

    2000-01-01

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

  7. Incremental validity of the frame-of-reference effect in personality scale scores: a replication and extension.

    PubMed

    Bing, Mark N; Whanger, James C; Davison, H Kristl; VanHook, Jayson B

    2004-02-01

    Context-specific personality items provide respondents with a common frame of reference unlike more traditional, noncontextual personality items. The common frame of reference standardizes item interpretation and has been shown to reduce measurement error while increasing validity in comparison to noncontextual items (M. J. Schmit, A. M. Ryan. S. L. Stierwalt. & S. L. Powell, 1995). Although the frame-of-reference effect on personality scales scores has been well investigated (e.g., M. J. Schmit et al., 1995), the ability of this innovation to obtain incremental validity above and beyond the well-established, noncontextual personality scale scores has yet to be examined. The current study replicates and extends work by M. J. Schmit et al. (1995) to determine the incremental validity of the frame-of-reference effect. The results indicate that context-specific personality items do indeed obtain incremental validity above and beyond both noncontextual items and cognitive ability, and in spite of socially desirable responding induced by applicant instructions. The implications of these findings for personnel selection are discussed.

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

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Craven, Rhonda G.

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

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

    ERIC Educational Resources Information Center

    Shen, Ji; Confrey, Jere

    2010-01-01

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

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

    ERIC Educational Resources Information Center

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

    2009-01-01

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

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    Nunez, Rafael E.; Cornejo, Carlos

    2012-01-01

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

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    Camilleri, Patrick

    2012-01-01

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

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

    ERIC Educational Resources Information Center

    Auer-Rizzi, Werner; Berry Michael

    2000-01-01

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

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

    ERIC Educational Resources Information Center

    Shen, Ji; Confrey, Jere

    2010-01-01

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

  17. The Internal/External Frame of Reference in the Self-Concept Development of Higher Education Students.

    ERIC Educational Resources Information Center

    Yeung, Alexander Seeshing; Lau, Ivy Cheuk-yin

    This study examined the internal/external (I/E) frame of reference model of self-concept (Marsh, 1986) with higher education students in Hong Kong (n=274). Structural equation models relating English and math achievement (both requirements for university entrance) to English and math self-concepts replicated the I/E model in that paths leading…

  18. An Extension to the Internal/External Frame of Reference Model to Two Verbal and Numerical Domains

    ERIC Educational Resources Information Center

    Moller, Jens; Streblow, Lilian; Pohlmann, Britta; Koller, Olaf

    2006-01-01

    Beside interindividual social comparisons, intraindividual dimensional comparisons in which students compare their achievements in one subject with their achievements in other subjects have an impact on their academic self-concepts. The internal/external frame of reference (I/E) model by Marsh (1986) assumes that dimensional comparisons lead to…

  19. The Internal/External Frame of Reference Model Revisited: Incorporating General Cognitive Ability and General Academic Self-Concept

    ERIC Educational Resources Information Center

    Brunner, Martin; Ludtke, Oliver; Trautwein, Ulrich

    2008-01-01

    The internal/external frame of reference model (I/E model; Marsh, 1986) is a highly influential model of self-concept formation, which predicts that domain-specific abilities have positive effects on academic self-concepts in the corresponding domain and negative effects across domains. Investigations of the I/E model do not typically incorporate…

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

    PubMed

    Expert, Fabien; Ruffier, Franck

    2015-02-26

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

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

    ERIC Educational Resources Information Center

    Nunez, Rafael E.; Cornejo, Carlos

    2012-01-01

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

  2. The Contribution of Starlette/Stella SLR to Terrestrial Reference Frame Definition

    NASA Astrophysics Data System (ADS)

    Govind, R.; Lemoine, F.; Altamimi, Z.; Le Bail, K.; Chinn, D.

    2007-12-01

    The Lageos-1 (L1) and Lageos-2 (L2) satellites have formed the basis of the ILRS contribution to the ITRF2005. These geodetic cannonball satellites, launched in 1976, and 1992 respectively are well suited for this purpose, by virtue of their high altitude, and lack of sensitivity to either high degree gravity terms or the deleterious effects of atmospheric drag. However, some SLR tracking stations have only limited tracking of the L1 and L2 satellites, with the result that these stations are not well determined in ITRF2005. In addition, we note that the results of analysis of the DORIS contribution to ITRF2005 indicated that the quality of the station positioning was directly proportional to the number of satellites in each weekly solution [Altamimi et al., JoG, 2006]. Therefore, in this paper we test the contribution of additional satellites to SLR-only weekly reference frame solutions. We analyze the SLR data to the Stella (STL) and Starlette (STA) satellites for the period from 1993 to 2006, and first perform a detailed analysis to assess the optimum arc parameterization in order to minimize orbit error, taking advantage of the new high-resolution gravity and ocean tide models that have been developed as a result of the GRACE, TOPEX/Poseidon and Jason missions. We then compare and contrast three series of SINEX solutions: L1+L2 only, STL+STA only, and a four-satellite combination based on L1+L2+STL+STA. We compare the quality of the weekly station position, the geocenter and scale estimates and assess whether there is any improvement or degradation in the estimated EOP.

  3. Mapping spatial frames of reference onto time: a review of theoretical accounts and empirical findings.

    PubMed

    Bender, Andrea; Beller, Sieghard

    2014-09-01

    When speaking and reasoning about time, people around the world tend to do so with vocabulary and concepts borrowed from the domain of space. This raises the question of whether the cross-linguistic variability found for spatial representations, and the principles on which these are based, may also carry over to the domain of time. Real progress in addressing this question presupposes a taxonomy for the possible conceptualizations in one domain and its consistent and comprehensive mapping onto the other-a challenge that has been taken up only recently and is far from reaching consensus. This article aims at systematizing the theoretical and empirical advances in this field, with a focus on accounts that deal with frames of reference (FoRs). It reviews eight such accounts by identifying their conceptual ingredients and principles for space-time mapping, and it explores the potential for their integration. To evaluate their feasibility, data from some thirty empirical studies, conducted with speakers of sixteen different languages, are then scrutinized. This includes a critical assessment of the methods employed, a summary of the findings for each language group, and a (re-)analysis of the data in view of the theoretical questions. The discussion relates these findings to research on the mental time line, and explores the psychological reality of temporal FoRs, the degree of cross-domain consistency in FoR adoption, the role of deixis, and the sources and extent of space-time mapping more generally. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. The Human Retrosplenial Cortex and Thalamus Code Head Direction in a Global Reference Frame

    PubMed Central

    Shine, Jonathan P.; Valdés-Herrera, José P.; Hegarty, Mary; Wolbers, Thomas

    2017-01-01

    Spatial navigation is a multisensory process involving integration of visual and body-based cues. In rodents, head direction (HD) cells, which are most abundant in the thalamus, integrate these cues to code facing direction. Human fMRI studies examining HD coding in virtual environments (VE) have reported effects in retrosplenial complex and (pre-)subiculum, but not the thalamus. Furthermore, HD coding appeared insensitive to global landmarks. These tasks, however, provided only visual cues for orientation, and attending to global landmarks did not benefit task performance. In the present study, participants explored a VE comprising four separate locales, surrounded by four global landmarks. To provide body-based cues, participants wore a head-mounted display so that physical rotations changed facing direction in the VE. During subsequent MRI scanning, subjects saw stationary views of the environment and judged whether their orientation was the same as in the preceding trial. Parameter estimates extracted from retrosplenial cortex and the thalamus revealed significantly reduced BOLD responses when HD was repeated. Moreover, consistent with rodent findings, the signal did not continue to adapt over repetitions of the same HD. These results were supported by a whole-brain analysis showing additional repetition suppression in the precuneus. Together, our findings suggest that (i) consistent with the rodent literature, the human thalamus may integrate visual, and body-based, orientation cues, (ii) global reference frame cues can be used to integrate HD across separate individual locales, and (iii) immersive training procedures providing full body-based cues may help to elucidate the neural mechanisms supporting spatial navigation. PMID:27307227

  5. Coursework selection: a frame of reference approach using structural equation modelling.

    PubMed

    Dickhäuser, Oliver; Reuter, Martin; Hilling, Christine

    2005-12-01

    Choice behaviour has far-reaching consequences on students' educational careers. Previous models on course selection for example, the model of achievement-related choices (Wigfield & Eccles, 2000) and of self-efficacy theory (Bandura, 1997), stress the importance of ability perceptions (self-concept of ability) as major determinants of choice. This article suggests a model of course selection, which assumes that comparisons within an internal frame of reference (as proposed by Marsh, 1986, for the association between achievement and self-concepts) can also be applied to the association between self-concepts and course selection. It is therefore hypothesized that course selection is not only positively influenced by the self-concept with respect to the corresponding subject, but also negatively with respect to alternative subjects. Moreover, it should be tested whether the effects of previous achievement on course selection are completely mediated by the self-concepts. These assumptions were empirically tested using a sample of 296 students from secondary school classes, who were specializing in, for example, chemistry or biology in the following school term. Self-concepts and course selection were assessed via questionnaire. The postulated models were tested using a structural equation modelling approach for ordinal variables. The core assumption, that course selection is determined by dimensional comparisons, was supported by significant negative paths from self-concepts on the selection of non-corresponding subjects. Furthermore, the effects of previous achievement on selection were completely mediated by self-concepts. Previous models of choice behaviour should be extended, by considering not only the selected alternatives, but also the unselected ones. The finding that the influence of achievement on choice is completely mediated by self-concepts, demonstrates that subjective interpretations of previous achievement determine subsequent behaviour.

  6. Effector-independent motor sequence representations exist in extrinsic and intrinsic reference frames.

    PubMed

    Wiestler, Tobias; Waters-Metenier, Sheena; Diedrichsen, Jörn

    2014-04-02

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

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

    PubMed Central

    Wiestler, Tobias; Waters-Metenier, Sheena

    2014-01-01

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

  8. The reciprocal internal/external frame of reference model using grades and test scores.

    PubMed

    Möller, Jens; Zimmermann, Friederike; Köller, Olaf

    2014-12-01

    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 on subsequent mathematics and VACH and academic self-concept within domains but have negative effects across domains. The main purpose is to validate the RI/EM and extend it using objective achievement indicators and grades. Two waves of data collection from grade 5 to grade 9 with N = 1,045 secondary school students were used. Test scores, grades, and self-concept data were obtained. The main analyses were conducted using hierarchical linear modelling. The positive longitudinal effects of grades and test scores on subsequent grades, test scores and academic self-concept within domains and the negative effects of grades and test scores on subsequent academic self-concept across domains supported the RI/EM. The effects of academic self-concept on subsequent grades and test scores across domains were near zero when prior achievement indicators were controlled for. Overall, the results using school grades as achievement measures were replicated using standardized achievement test scores. The results serve to highlight the importance of the combination of common theories, which are mostly investigated individually, to enhance our understanding of the complexity of within- and across-domain relations between academic self-concepts and achievement using grades as well as test scores. © 2014 The British Psychological Society.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Yu, J.; Wang, G.

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Yu, Jiangbo; Wang, Guoquan

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Yang, L.; Yu, J.; Wang, G.

    2016-12-01

    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.

  14. Derivation of acoustoelastic Lamb wave dispersion curves in anisotropic plates at the initial and natural frames of reference.

    PubMed

    C Kubrusly, Alan; M B Braga, Arthur; von der Weid, Jean Pierre

    2016-10-01

    The propagation speed of ultrasonic waves in pre-stressed media can be evaluated either at the natural or initial frames of reference. In this paper general equations that can be applied to the partial wave technique are presented in order to obtain the dispersion spectra of acoustoelastic Lamb waves in anisotropic plates in either frame of reference. Employing these equations, dispersion curves for the fundamental modes in a pre-stressed transversely isotropic aluminum plate were numerically obtained in both reference frames under longitudinal and transverse loading with the material transverse axis along each of the Cartesian directions, as well as the propagation along a non-principal direction. Results confirm that due to the material natural anisotropy, the speed variation depends not only on the pre-stress direction but also on the material orientation as well as on the polarization of the propagating mode. Similar to bulk waves, the relationship between the speed at the natural and initial frames is a function of the load direction.

  15. Electronic maps for terminal area navigation: effects of frame of reference and dimensionality.

    PubMed

    Wickens, C D; Liang, C C; Prevett, T; Olmos, O

    1996-01-01

    Two experiments are reported that contrast rotating versus fixed electronic map displays, which pilots used for a simulated approach to a landing. In Experiment 1, a rotating versus fixed-map display was experimentally crossed with a two-dimensional (2D) versus three-dimensional (3D) view (perspective map) as pilots' ability to maintain the flight path and demonstrate awareness of the location of surrounding terrain features were assessed. Rotating displays supported better flight path guidance and did not substantially harm performance on terrain awareness tasks. 3D displays led to a substantial cost for vertical control but did not differ from 2D displays in lateral control. In Experiment 2, pilots flew with the rotating 2D display and with an improved version of the rotating 3D display, designed to reduce the ambiguity of representing altitude information. Vertical control improved as a result of the 3D display design improvement, but lateral control did not. The results are discussed in terms of the costs and benefits of presenting information in 3D, ego-referenced format for both flight path control and terrain awareness.

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

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  19. Extending the ILRS Terrestrial Reference Frame Development Contribution to ITRF2014

    NASA Astrophysics Data System (ADS)

    Luceri, Vincenza; Pavlis, Erricos C.; Pace, Brigida; Kuzmicz-Cieslak, Magdalena; König, Daniel; Bianco, Giuseppe; Evans, Keith

    2015-04-01

    The announcement of a possible extension of the next International Terrestrial Reference Frame (ITRF) model to include all of 2014 required the extension of all techniques' contributions by an additional year within a tight delivery schedule (end of February 2015). The ILRS Analysis Working Group (AWG) agreed to support this activity and laid out a plan to ensure that we can meet this strict deadline. Although Satellite Laser Ranging (SLR) data have contributed to the definition of the ITRF over the past three decades, delivering products under such a tight schedule (only a few weeks after the last data are taken) was never before required. Careful planning to ensure the timely availability of the ancillary information required for the reduction of the SLR data and the fact that the analysis procedures of each contributing AC were already validated with the ITRF2013 submissions helped us meet the deadline and demonstrated that it is possible to do so even routinely. The ILRS contribution is only an extension to what was submitted for ITRF2013, with no other changes in modeling or standards of analysis. The main focus of our re-analysis is monitoring systematic errors at individual stations, accounting for undocumented discontinuities, and improving the target signature models. The latter has been addressed with the adoption of mm-accurate models for all of our targets. As far as the station systematics, the AWG had already embarked on a major effort to improve the handling of such errors prior to the development of ITRF2008. The re-analysis for ITRF2014 extends from 1983 to the end of 2014. As in the case of ITRF2008, station engineers and analysts have worked together to determine the magnitude and cause of systematic errors that were noticed during the analysis, rationalize them based on events at the stations, and develop appropriate corrections whenever possible. With the completion of ITRF2014 the ILRS will next turn its attention to the development of new

  20. Fixing the Extragalactic Reference Frame For the Proper Motion of the Carina Dwarf Spheroidal

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Majewski, Steven R.; Munoz, Ricardo R.

    2010-08-01

    The orbital shapes of Milky Way dwarf spheroidal (dSph) galaxies provide specific constraints on CDM models of hierarchical structure formation on small scales and for late infalling subhalos. Furthermore, many physical properties of these dSph systems are shaped by tidal impulses, the magnitude of which depends on the orbit of the dSph. Unfortunately, the tangential (i.e., proper) motions of distant Milky Way dSphs are extremely difficult to measure, and thus remain poorly constrained (or in most cases unknown). We propose to remedy this for the Carina dSph, for which we have used a large, unique set of photographic plates spanning a 14 year baseline and covering large enough area to allow for a precise proper motion measurement. We have digitized these plates and derived precise (1-2 mas/yr per star) relative proper motions for 565 confirmed Carina members, and >1000 more likely members; these lead to a bulk relative proper motion for the system defined to 0.04 mas/yr. Despite this extreme precision, the absolute (relative to the ``fixed'' extragalactic background) proper motion of Carina is still poorly constrained, due to the paucity of identified QSOs (only 7) in the field of view to fix the reference frame. With our proposed search for QSOs among the ~2000 objects in our proper-motion catalog, we expect to discover ~50 QSOs, which will improve the accuracy of our proper motion zero point by a factor of 3 in each dimension, and likely more. This will allow for a precise determination of the orbit of the Carina dwarf galaxy, with an expected accuracy 2× better than the recent proper motion for this object, which disagrees with the proper motion expected from the direction of Carina's tidal tails. This is a resubmission of a proposal that was granted time in 2010A; the observing run in Feb. 2010 was beset by poor weather conditions and instrument trouble, yielding very little usable data.

  1. Suspected time errors along the satellite laser ranging network and impact on the reference frame

    NASA Astrophysics Data System (ADS)

    Belli, Alexandre; Exertier, Pierre; Lemoine, Frank; Zelensky, Nikita

    2017-04-01

    Systematic errors in the laser ranging technologies must be considered when considering the GGOS objective to maintain a network with an accuracy of 1 mm and a stability of 0.1 mm per year for the station ground coordinates in the ITRF. Range and Time biases are identified to be part of these systematic errors, for a major part, and are difficult to detect. Concerning the range bias, analysts and working groups estimate their values from LAGEOS-1 & 2 observations (c.f. Appleby et al. 2016). On the other hand, time errors are often neglected (they are presumed to be < 100 ns) and remain difficult to estimate (at this level), from using the observations of geodetic satellites passes and precise orbit determination (i.e. LAGEOS). The Time Transfer by Laser Link (T2L2) experiment on-board Jason-2 is a unique opportunity to determine, globally and independently, the synchronization of all laser stations. Because of the low altitude of Jason-2, we computed the time transfer in non-common view from the Grasse primary station to all other SLR stations. We used a method to synchronize the whole network which consists of the integration of an Ultra Stable Oscillator (USO) frequency model, in order to take care of the frequency instabilities caused by the space environment. The integration provides a model which becomes an "on-orbit" time realization which can be connected to each of the SLR stations by the ground to space laser link. We estimated time biases per station, with a repeatability of 3 - 4 ns, for 25 stations which observe T2L2 regularly. We investigated the effect on LAGEOS and Starlette orbits and we discuss the impact of time errors on the station coordinates. We show that the effects on the global POD are negligible (< 1 mm) but are at the level of 4 - 6 mm for the coordinates. We conclude and propose to introduce time errors in the future analyses (IDS and ILRS) that would lead to the computation of improved reference frame solutions.

  2. Face-infringement space: the frame of reference of the ventral intraparietal area.

    PubMed

    McCollum, Gin; Klam, François; Graf, Werner

    2012-07-01

    Experimental studies have shown that responses of ventral intraparietal area (VIP) neurons specialize in head movements and the environment near the head. VIP neurons respond to visual, auditory, and tactile stimuli, smooth pursuit eye movements, and passive and active movements of the head. This study demonstrates mathematical structure on a higher organizational level created within VIP by the integration of a complete set of variables covering face-infringement. Rather than positing dynamics in an a priori defined coordinate system such as those of physical space, we assemble neuronal receptive fields to find out what space of variables VIP neurons together cover. Section 1 presents a view of neurons as multidimensional mathematical objects. Each VIP neuron occupies or is responsive to a region in a sensorimotor phase space, thus unifying variables relevant to the disparate sensory modalities and movements. Convergence on one neuron joins variables functionally, as space and time are joined in relativistic physics to form a unified spacetime. The space of position and motion together forms a neuronal phase space, bridging neurophysiology and the physics of face-infringement. After a brief review of the experimental literature, the neuronal phase space natural to VIP is sequentially characterized, based on experimental data. Responses of neurons indicate variables that may serve as axes of neural reference frames, and neuronal responses have been so used in this study. The space of sensory and movement variables covered by VIP receptive fields joins visual and auditory space to body-bound sensory modalities: somatosensation and the inertial senses. This joining of allocentric and egocentric modalities is in keeping with the known relationship of the parietal lobe to the sense of self in space and to hemineglect, in both humans and monkeys. Following this inductive step, variables are formalized in terms of the mathematics of graph theory to deduce which

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    ICRF-3 seeks to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverage relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames that are ready for comparison with the Gaia optical frame. Several specific actions are underway. A collaboration has started to improve at S/X-band precision of the VLBA Calibrator Survey's ~2200 sources which are typically 5 times less precise than the rest of the ICRF-2. S/X-band southern precision improvements are underway with observations using southern antennas such as the AuScope and HartRAO, S. Africa. We also seek to improve radio frequency coverage with X/Ka and K-band work. An X/Ka frame of 654 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which should strengthen the southern hemisphere in general. A K-band collaboration has formed with similar coverage and southern precision goals. On the analysis front, special attention is being given to combination techniques both of VLBI frames and of multiple data types. Consistency of the CRF with the TRF and EOP is another area of concern. Comparison of celestial frame solutions from various groups is underway in order to identify and correct systematic errors. Finally, work is underway to identify and pinpoint sources bright enough in both radio and optical to allow for a robust frame tie between VLBI and Gaia optical frames.

  4. Autonomous surgical robotics using 3-D ultrasound guidance: feasibility study.

    PubMed

    Whitman, John; Fronheiser, Matthew P; Ivancevich, Nikolas M; Smith, Stephen W

    2007-10-01

    The goal of this study was to test the feasibility of using a real-time 3D (RT3D) ultrasound scanner with a transthoracic matrix array transducer probe to guide an autonomous surgical robot. Employing a fiducial alignment mark on the transducer to orient the robot's frame of reference and using simple thresholding algorithms to segment the 3D images, we tested the accuracy of using the scanner to automatically direct a robot arm that touched two needle tips together within a water tank. RMS measurement error was 3.8% or 1.58 mm for an average path length of 41 mm. Using these same techniques, the autonomous robot also performed simulated needle biopsies of a cyst-like lesion in a tissue phantom. This feasibility study shows the potential for 3D ultrasound guidance of an autonomous surgical robot for simple interventional tasks, including lesion biopsy and foreign body removal.

  5. Superfast 3D absolute shape measurement using five binary patterns

    NASA Astrophysics Data System (ADS)

    Hyun, Jae-Sang; Zhang, Song

    2017-03-01

    This paper presents a method that recovers high-quality 3D absolute coordinates point by point with only five binary patterns. Specifically, three dense binary dithered patterns are used to compute the wrapped phase; and the average intensity is combined with two additional binary patterns to determine fringe order pixel by pixel in phase domain. The wrapped phase is temporarily unwrapped point by point by referring to the fringe order. We further developed a computational framework to reduce random noise impact due to dithering, defocusing and random noise. Since only five binary fringe patterns are required to recover one 3D frame, extremely high speed 3D shape measurement can be achieved. For example, we developed a system that captures 2D images at 3333 Hz, and thus performs 3D shape measurement at 667 Hz.

  6. Non-linear VLBI station motions and their impact on the celestial reference frame and Earth orientation parameters.

    PubMed

    Krásná, Hana; Malkin, Zinovy; Böhm, Johannes

    The increasing accuracy and growing time span of Very Long Baseline Interferometry (VLBI) observations allow the determination of seasonal signals in station positions which still remain unmodelled in conventional analysis approaches. In this study we focus on the impact of the neglected seasonal signals in the station displacement on the celestial reference frame and Earth orientation parameters. We estimate empirical harmonic models for selected stations within a global solution of all suitable VLBI sessions and create mean annual models by stacking yearly time series of station positions which are then entered a priori in the analysis of VLBI observations. Our results reveal that there is no systematic propagation of the seasonal signal into the orientation of celestial reference frame but position changes occur for radio sources observed non-evenly over the year. On the other hand, the omitted seasonal harmonic signal in horizontal station coordinates propagates directly into the Earth rotation parameters causing differences of several tens of microarcseconds.

  7. Nursing home staff members' subjective frames of reference on residents' achievement of ego integrity: A Q-methodology study.

    PubMed

    Lim, Sun-Young; Chang, Sung-Ok

    2017-02-28

    To discover the structure of the frames of reference for nursing home staff members' subjective judgment of residents' achievement of ego integrity. Q-methodology was applied. Twenty-eight staff members who were working in a nursing home sorted 34 Q-statements into the shape of a normal distribution. A centroid factor analysis and varimax rotation, using the PQ-method program, revealed four factors: identifying clues to residents' positive acceptance of their whole life span, identifying residents' ways of enjoying their current life, referencing residents' attitudes and competencies toward harmonious relationships, and identifying residents' integrated efforts to establish self-esteem. These subjective frames of reference need to be investigated in order to improve the relationships with nursing home residents and their quality of life. Consequently, the fundamental monitoring tools to help staff members make subjective judgments can be formed. © 2017 Japan Academy of Nursing Science.

  8. Functional correlates of the lateral and medial entorhinal cortex: objects, path integration and local-global reference frames.

    PubMed

    Knierim, James J; Neunuebel, Joshua P; Deshmukh, Sachin S

    2014-02-05

    The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between 'where' versus 'what' needs revision. We propose a refinement of this model, which is more complex than the simple spatial-non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience.

  9. Compared to what: What can we say about nonapeptide function and social behavior without a frame of reference?

    PubMed

    Kelly, Aubrey M; Ophir, Alexander G

    2015-12-01

    Our understanding of behavior and mechanism is undermined by the absence of a frame of reference because relationships between individuals and species are without context. We highlight a need to be more comparative, using nonapeptide (vasopressin and oxytocin) modulation of social behavior as an example. We reconsider the use of model organisms and the term 'social' in this context, contrasting two popular models for nonapeptide regulation of social behavior. We then propose that a frame of reference should be established by studying mechanisms of behavior across taxa along the same continua. If we are to ever establish a unifying theory of behavior, we must transcend individual examples and determine the relative relationships of behavior and mechanism among and between species.

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  15. Analysis of Slow (Theta) Oscillations as a Potential Temporal Reference Frame for Information Coding in Sensory Cortices

    PubMed Central

    Kayser, Christoph; Ince, Robin A. A.; Panzeri, Stefano

    2012-01-01

    While sensory neurons carry behaviorally relevant information in responses that often extend over hundreds of milliseconds, the key units of neural information likely consist of much shorter and temporally precise spike patterns. The mechanisms and temporal reference frames by which sensory networks partition responses into these shorter units of information remain unknown. One hypothesis holds that slow oscillations provide a network-intrinsic reference to temporally partitioned spike trains without exploiting the millisecond-precise alignment of spikes to sensory stimuli. We tested this hypothesis on neural responses recorded in visual and auditory cortices of macaque monkeys in response to natural stimuli. Comparing different schemes for response partitioning revealed that theta band oscillations provide a temporal reference that permits extracting significantly more information than can be obtained from spike counts, and sometimes almost as much information as obtained by partitioning spike trains using precisely stimulus-locked time bins. We further tested the robustness of these partitioning schemes to temporal uncertainty in the decoding process and to noise in the sensory input. This revealed that partitioning using an oscillatory reference provides greater robustness than partitioning using precisely stimulus-locked time bins. Overall, these results provide a computational proof of concept for the hypothesis that slow rhythmic network activity may serve as internal reference frame for information coding in sensory cortices and they foster the notion that slow oscillations serve as key elements for the computations underlying perception. PMID:23071429

  16. Egocentric and allocentric spatial reference frames in aging: A systematic review.

    PubMed

    Colombo, Desirée; Serino, Silvia; Tuena, Cosimo; Pedroli, Elisa; Dakanalis, Antonios; Cipresso, Pietro; Riva, Giuseppe

    2017-07-29

    Aging affects many aspects of everyday living, such as autonomy, security and quality of life. Among all, spatial memory and spatial navigation show a gradual but noticeable decline, as a result of both neurobiological changes and the general slowing down of cognitive functioning. We conducted a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines to identify studies that specifically investigated the role of allocentric and egocentric frames in healthy aging. Concerning spatial navigation, our results showed a preservation of egocentric strategies, along with specific impairments in the use of allocentric and switching abilities. Regarding spatial memory, instead, outcomes were more divergent and not frame-specific. With this perspective, spatial impairments were discussed considering the cognitive profile of mild cognitive impairment (MCI) and Alzheimer's Disease (AD). Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  18. User’s guide and reference to Ash3d: a three-dimensional model for Eulerian atmospheric tephra transport and deposition

    USGS Publications Warehouse

    Mastin, Larry G.; Randall, Michael J.; Schwaiger, Hans F.; Denlinger, Roger P.

    2013-01-01

    Ash3d is a three-dimensional Eulerian atmospheric model for tephra transport, dispersal, and deposition, written by the authors to study and forecast hazards of volcanic ash clouds and tephra fall. In this report, we explain how to set up simulations using both a web interface and an ASCII input file, and how to view and interpret model output. We also summarize the architecture of the model and some of its properties.

  19. PLOT3D user's manual

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Buning, Pieter G.; Pierce, Larry; Elson, Patricia A.

    1990-01-01

    PLOT3D is a computer graphics program designed to visualize the grids and solutions of computational fluid dynamics. Seventy-four functions are available. Versions are available for many systems. PLOT3D can handle multiple grids with a million or more grid points, and can produce varieties of model renderings, such as wireframe or flat shaded. Output from PLOT3D can be used in animation programs. The first part of this manual is a tutorial that takes the reader, keystroke by keystroke, through a PLOT3D session. The second part of the manual contains reference chapters, including the helpfile, data file formats, advice on changing PLOT3D, and sample command files.

  20. Modeling moving systems with RELAP5-3D

    DOE PAGES

    Mesina, G. L.; Aumiller, David L.; Buschman, Francis X.; ...

    2015-12-04

    RELAP5-3D is typically used to model stationary, land-based reactors. However, it can also model reactors in other inertial and accelerating frames of reference. By changing the magnitude of the gravitational vector through user input, RELAP5-3D can model reactors on a space station or the moon. The field equations have also been modified to model reactors in a non-inertial frame, such as occur in land-based reactors during earthquakes or onboard spacecraft. Transient body forces affect fluid flow in thermal-fluid machinery aboard accelerating crafts during rotational and translational accelerations. It is useful to express the equations of fluid motion in the acceleratingmore » frame of reference attached to the moving craft. However, careful treatment of the rotational and translational kinematics is required to accurately capture the physics of the fluid motion. Correlations for flow at angles between horizontal and vertical are generated via interpolation where no experimental studies or data exist. The equations for three-dimensional fluid motion in a non-inertial frame of reference are developed. As a result, two different systems for describing rotational motion are presented, user input is discussed, and an example is given.« less

  1. Modeling moving systems with RELAP5-3D

    SciTech Connect

    Mesina, G. L.; Aumiller, David L.; Buschman, Francis X.; Kyle, Matt R.

    2015-12-04

    RELAP5-3D is typically used to model stationary, land-based reactors. However, it can also model reactors in other inertial and accelerating frames of reference. By changing the magnitude of the gravitational vector through user input, RELAP5-3D can model reactors on a space station or the moon. The field equations have also been modified to model reactors in a non-inertial frame, such as occur in land-based reactors during earthquakes or onboard spacecraft. Transient body forces affect fluid flow in thermal-fluid machinery aboard accelerating crafts during rotational and translational accelerations. It is useful to express the equations of fluid motion in the accelerating frame of reference attached to the moving craft. However, careful treatment of the rotational and translational kinematics is required to accurately capture the physics of the fluid motion. Correlations for flow at angles between horizontal and vertical are generated via interpolation where no experimental studies or data exist. The equations for three-dimensional fluid motion in a non-inertial frame of reference are developed. As a result, two different systems for describing rotational motion are presented, user input is discussed, and an example is given.

  2. Evaluation of VLBI terrestrial reference frame solutions in the style of ITRF2014, JTRF2014, and DTRF2014

    NASA Astrophysics Data System (ADS)

    Soja, B.; Nilsson, T.; Glaser, S.; Balidakis, K.; Karbon, M.; Heinkelmann, R.; Gross, R. S.; Schuh, H.

    2016-12-01

    Global terrestrial reference frames (TRF) are primary products of geodesy, the importance of which is increasingly recognized by major political bodies such as the United Nations. Therefore, aiming for best practices in the determination of such frames is imperative, in particular because several promising concepts are available. As of 2016, three official International Terrestrial Reference Frame (ITRF) solutions have been released based on multi-technique data until the end of 2014 - ITRF2014, JTRF2014, and DTRF2014 - each following different approaches in terms of parameter estimation. Since also the data editing and the selection of local ties and datum stations, among other aspects, fundamentally differ between these ITRF solutions, it is all but impossible to single out the effect of different parameter estimation approaches by direct comparison. Therefore, we instead computed three TRF solutions utilizing the same input data set, stemming from more than 4000 very long baseline interferometry (VLBI) sessions from the time period 1980-2013. The first VLBI TRF solution mimics ITRF2014 in that it utilizes the data from the individual sessions at the parameter level, including the full covariances, and has its frame parameters estimated in a least squares adjustment. The same type of data is fed into a Kalman filter and smoother to create the second TRF solution, similar to JTRF2014. Finally, the normal equations from the individual sessions are stacked and then globally inverted to produce the DTRF2014-type solution. These three TRF solutions have been assessed in terms of how well the coordinate positions match the observational data, both in periods during which data have been used for their computation, i.e. up to 2013, as well as during later years. In particular, we have investigated whether the predictions from the Kalman filter solution are at a similar level of quality when compared to those from the two rather traditional solutions.

  3. Endostyle cell recruitment as a frame of reference for development and growth in the Urochordate Oikopleura dioica.

    PubMed

    Troedsson, Christofer; Ganot, Philippe; Bouquet, Jean-Marie; Aksnes, Dag L; Thompson, Eric M

    2007-12-01

    In models of growth and life history, and in molecular and cell biology, there is a need for more accurate frames of reference to characterize developmental progression. In Caenorhabditis elegans, complete fate maps of cell lineage provide such a standard of reference. To be more widely applicable, reference frames should be easier to measure while still providing strong predictive capacity. Towards this aim, we have analyzed growth of the endostyle in the appendicularian Oikopleura dioica at the cellular level, and measured its response to temperature and food availability. Specifically, we test the hypothesis that age of a specific developmental stage in O. dioica can be predicted from the number of endostyle cells and temperature. We show that the endostyle grows by recruiting cells from the posterior tip into the lateral arms of the organ in an anterior-posterior orientation and that the rate of increase in lateral arm endostyle cells is temperature-dependent but unresponsive to nutritional intake. Endostyle cells therefore serve as an accurate and easily measured marker to describe developmental progression. Conceptually, such a method of characterizing developmental progression should help bridge life-history events and molecular mechanisms throughout organismal aging, facilitating cross-disciplinary understanding by providing a common experimental framework.

  4. A Terrestrial Reference Frame (TRF), coordinates and velocities for South American stations: contributions to Central Andes geodynamics

    NASA Astrophysics Data System (ADS)

    Mackern, M. V.; Mateo, M. L.; Robin, A. M.; Calori, A. V.

    2009-12-01

    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.

  5. Non-linearity of geocentre motion and its impact on the origin of the terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Dong, Danan; Qu, Weijing; Fang, Peng; Peng, Dongju

    2014-08-01

    The terrestrial reference frame is a cornerstone for modern geodesy and its applications for a wide range of Earth sciences. The underlying assumption for establishing a terrestrial reference frame is that the motion of the solid Earth's figure centre relative to the mass centre of the Earth system on a multidecadal timescale is linear. However, past international terrestrial reference frames (ITRFs) showed unexpected accelerated motion in their translation parameters. Based on this underlying assumption, the inconsistency of relative origin motions of the ITRFs has been attributed to data reduction imperfection. We investigated the impact of surface mass loading from atmosphere, ocean, snow, soil moisture, ice sheet, glacier and sea level from 1983 to 2008 on the geocentre variations. The resultant geocentre time-series display notable trend acceleration from 1998 onward, in particular in the z-component. This effect is primarily driven by the hydrological mass redistribution in the continents (soil moisture, snow, ice sheet and glacier). The acceleration is statistically significant at the 99 per cent confidence level as determined using the Mann-Kendall test, and it is highly correlated with the satellite laser ranging determined translation series. Our study, based on independent geophysical and hydrological models, demonstrates that, in addition to systematic errors from analysis procedures, the observed non-linearity of the Earth-system behaviour at interannual timescales is physically driven and is able to explain 42 per cent of the disparity between the origins of ITRF2000 and ITRF2005, as well as the high level of consistency between the ITRF2005 and ITRF2008 origins.

  6. The assessment of the transformation of global tectonic plate models and the global terrestrial reference frames using the Velocity Decomposition Analysis

    NASA Astrophysics Data System (ADS)

    Ampatzidis, Dimitrios; König, Rolf; Glaser, Susanne; Heinkelmann, Robert; Schuh, Harald; Flechtner, Frank; Nilsson, Tobias

    2016-04-01

    The aim of our study is to assess the classical Helmert similarity transformation using the Velocity Decomposition Analysis (VEDA). The VEDA is a new methodology, developed by GFZ for the assessment of the reference frames' temporal variation and it is based on the separation of the velocities into two specified parts: The first is related to the reference system choice (the so called datum effect) and the latter one which refers to the real deformation of the terrestrial points. The advantage of the VEDA is its ability to detect the relative biases and reference system effects between two different frames or two different realizations of the same frame, respectively. We apply the VEDA for the assessment between several modern tectonic plate models and the recent global terrestrial reference frames.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    PubMed

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

    2014-04-04

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

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

    NASA Technical Reports Server (NTRS)

    Moyer, T. D.

    1976-01-01

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

  11. Radio-optical reference frame link using the U.S. Naval observatory astrograph and deep CCD imaging

    SciTech Connect

    Zacharias, N.; Zacharias, M. I.

    2014-05-01

    Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same bandpass. They provide accurate positions on the Hipparcos/Tycho-2 system for stars in the 10-16 mag range used as reference stars for the deep CCD imaging data. Here we present final optical position results of 413 sources based on reference stars obtained by dedicated astrograph observations that were reduced following two different procedures. These optical positions are compared to radio very long baseline interferometry positions. The current optical system is not perfectly aligned to the ICRF radio system with rigid body rotation angles of 3-5 mas (= 3σ level) found between them for all three axes. Furthermore, statistically, the optical-radio position differences are found to exceed the total, combined, known errors in the observations. Systematic errors in the optical reference star positions and physical offsets between the centers of optical and radio emissions are both identified as likely causes. A detrimental, astrophysical, random noise component is postulated to be on about the 10 mas level. If confirmed by future observations, this could severely limit the Gaia to ICRF reference frame alignment accuracy to an error of about 0.5 mas per coordinate axis with the current number of sources envisioned to provide the link. A list of 36 ICRF sources without the detection of an optical counterpart to a limiting magnitude of about R = 22 is provided as well.

  12. Auger electron angular distribution of double core-hole states in the molecular reference frame.

    PubMed

    Cryan, James P; Glownia, J M; Andreasson, J; Belkacem, A; Berrah, N; Blaga, C I; Bostedt, C; Bozek, J; Buth, C; DiMauro, L F; Fang, L; Gessner, O; Guehr, M; Hajdu, J; Hertlein, M P; Hoener, M; Kornilov, O; Marangos, J P; March, A M; McFarland, B K; Merdji, H; Petrović, V S; Raman, C; Ray, D; Reis, D; Tarantelli, F; Trigo, M; White, J L; White, W; Young, L; Bucksbaum, P H; Coffee, R N

    2010-08-20

    The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×10(11) photons in a ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

  13. Auger Electron Angular Distribution of Double Core-Hole States in the Molecular Reference Frame

    NASA Astrophysics Data System (ADS)

    Cryan, James P.; Glownia, J. M.; Andreasson, J.; Belkacem, A.; Berrah, N.; Blaga, C. I.; Bostedt, C.; Bozek, J.; Buth, C.; Dimauro, L. F.; Fang, L.; Gessner, O.; Guehr, M.; Hajdu, J.; Hertlein, M. P.; Hoener, M.; Kornilov, O.; Marangos, J. P.; March, A. M.; McFarland, B. K.; Merdji, H.; Petrović, V. S.; Raman, C.; Ray, D.; Reis, D.; Tarantelli, F.; Trigo, M.; White, J. L.; White, W.; Young, L.; Bucksbaum, P. H.; Coffee, R. N.

    2010-08-01

    The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×1011 photons in a ˜5fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

  14. Europeana and 3D

    NASA Astrophysics Data System (ADS)

    Pletinckx, D.

    2011-09-01

    The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

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

    ERIC Educational Resources Information Center

    Robinette, Laurie E.

    2010-01-01

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

  16. The non-relativistic cow experiment in the uniformly accelerated reference frame

    NASA Astrophysics Data System (ADS)

    Beyer, Horst; Nitsch, Jürgen

    1986-12-01

    In consideration of the more realistic experimental circumstances in the theoretical treatment of the COW experiment, the non-relativistic phase shift of the COW experiment performed in a uniformly accelerated reference system is derived. Thereby a new contribution of the phase shift is obtained, second order in the acceleration constant, which might be measurable in the near future by using ultra cold neutrons.

  17. Power quality improvement by unified power quality conditioner based on CSC topology using synchronous reference frame theory.

    PubMed

    Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

    2014-01-01

    This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems.

  18. Power Quality Improvement by Unified Power Quality Conditioner Based on CSC Topology Using Synchronous Reference Frame Theory

    PubMed Central

    Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

    2014-01-01

    This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems. PMID:25013854

  19. Quantum nonlocality and preferred frames of reference: A return to a Lorentzian interpretation of the special theory of relativity

    NASA Astrophysics Data System (ADS)

    Mujica-Parodi, Lilianne Rivka

    I argue in the dissertation that there exists a fundamental contradiction between quantum theory and the special theory of relativity and that most of the well- known arguments to the contrary suffer from internal inconsistencies that render them ineffective in resolving the conflict. After an examination of these proposed solutions, I conclude that only four of them actually succeed without degenerating into logical inconsistency. These are: (a) the acceptance of an inherent nonseparability within nonfactorizable systems; (b) the requirement that all physical description exist only with respect to a particular spacetime hyperplane; (c) the allowance of a symmetric understanding of causality in which effects may sometimes temporally precede their causes; or (d) the negation of a realist interpretation of relativity in which all statements in one frame of reference may be Lorentz transformable into equivalent statements in all other frames of reference. In conclusion, I argue that the first three of these options, but not the fourth, succomb to a global inconsistency with respect to their relationship within science, leaving only the ``Lorentzian interpretation'' as a viable option at this time.

  20. The statistical mapping of magnetosheath plasma properties based on THEMIS measurements in the magnetosheath interplanetary medium reference frame

    NASA Astrophysics Data System (ADS)

    Dimmock, A. P.; Nykyri, K.

    2013-08-01

    The magnetosheath operates as a natural filter between the solar wind and the magnetospheric plasma. As a result of this, the magnetosheath plays a crucial role in the plasma momentum and energy transport from the interplanetary medium into the magnetosphere. Statistical studies of the magnetosheath are difficult due to the dynamic nature of the terrestrial bow shock and the magnetopause. As a result of this, the spatial and temporal dependence of magnetosheath plasma properties under varying solar wind conditions is still not completely understood. We present a study of magnetosheath plasma properties using 5 years of THEMIS and OMNI data to produce statistical maps of fundamental magnetosheath plasma properties. The magnetosheath interplanetary medium reference frame is applied to present data in a normalized reference frame which accounts for both boundary and orbital motion. The statistical maps are compared with the MHD runs from the CCMC-BATS-R-US model which agree favorably. The results are also used to investigate the presence of any magnetosheath plasma parameter asymmetries and their possible causes.

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

    PubMed Central

    WU, JUN; ZHOU, LIU; SHI, PAN; HE, ZIJIANG J; OOI, TENG LENG

    2014-01-01

    The natural ground surface carries texture information that extends continuously from one’s feet to the horizon, providing a rich depth resource for accurately locating an object resting on it. Here, we showed that the ground surface’s role as a reference frame also aids in locating a target suspended in midair based on relative binocular disparity. Using real world setup in our experiments, we first found that a suspended target is more accurately localized when the ground surface is visible and the observer views the scene binocularly. In addition, the increased accuracy occurs only when the scene is viewed for 5 sec rather than 0.15 sec, suggesting that the binocular depth process takes time. Second, we found that manipulation of the configurations of the texture-gradient and/or linear-perspective cues on the visible ground surface affects the perceived distance of the suspended target in midair. Third, we found that a suspended target is more accurately localized against a ground texture surface than a ceiling texture surface. This suggests that our visual system usesthe ground surface as the preferred reference frame to scale the distance of a suspended target according to its relative binocular disparity. PMID:25384237

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

    NASA Technical Reports Server (NTRS)

    Le Bail, Karine; Gordon, David

    2010-01-01

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

  3. Directed Energy Beam Jitter Mitigation Using the Line-of-Sight Reference Frame

    DTIC Science & Technology

    2011-05-10

    technology readiness level of this beam control system. Outside of the laboratory environment, off-platform orientation references are unavailable...be ready once the power level is appropriate for operational use. 13 2 E x p e r i m e n t a l S e t u p a n d P r o c e d u r e 2.1...instrument for measuring platform rotational motion. 3 Applied Technology Associates, “ARS-14 MHD

  4. Speaking Volumes About 3-D

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1999, Genex submitted a proposal to Stennis Space Center for a volumetric 3-D display technique that would provide multiple users with a 360-degree perspective to simultaneously view and analyze 3-D data. The futuristic capabilities of the VolumeViewer(R) have offered tremendous benefits to commercial users in the fields of medicine and surgery, air traffic control, pilot training and education, computer-aided design/computer-aided manufacturing, and military/battlefield management. The technology has also helped NASA to better analyze and assess the various data collected by its satellite and spacecraft sensors. Genex capitalized on its success with Stennis by introducing two separate products to the commercial market that incorporate key elements of the 3-D display technology designed under an SBIR contract. The company Rainbow 3D(R) imaging camera is a novel, three-dimensional surface profile measurement system that can obtain a full-frame 3-D image in less than 1 second. The third product is the 360-degree OmniEye(R) video system. Ideal for intrusion detection, surveillance, and situation management, this unique camera system offers a continuous, panoramic view of a scene in real time.

  5. A 3d-3d appetizer

    NASA Astrophysics Data System (ADS)

    Pei, Du; Ye, Ke

    2016-11-01

    We test the 3d-3d correspondence for theories that are labeled by Lens spaces. We find a full agreement between the index of the 3d N=2 "Lens space theory" T [ L( p, 1)] and the partition function of complex Chern-Simons theory on L( p, 1). In particular, for p = 1, we show how the familiar S 3 partition function of Chern-Simons theory arises from the index of a free theory. For large p, we find that the index of T[ L( p, 1)] becomes a constant independent of p. In addition, we study T[ L( p, 1)] on the squashed three-sphere S b 3 . This enables us to see clearly, at the level of partition function, to what extent G ℂ complex Chern-Simons theory can be thought of as two copies of Chern-Simons theory with compact gauge group G.

  6. Visual Semantic Based 3D Video Retrieval System Using HDFS

    PubMed Central

    Kumar, C.Ranjith; Suguna, S.

    2016-01-01

    This paper brings out a neoteric frame of reference for visual semantic based 3d video search and retrieval applications. Newfangled 3D retrieval application spotlight on shape analysis like object matching, classification and retrieval not only sticking up entirely with video retrieval. In this ambit, we delve into 3D-CBVR (Content Based Video Retrieval) concept for the first time. For this purpose, we intent to hitch on BOVW and Mapreduce in 3D framework. Instead of conventional shape based local descriptors, we tried to coalesce shape, color and texture for feature extraction. For this purpose, we have used combination of geometric & topological features for shape and 3D co-occurrence matrix for color and texture. After thriving extraction of local descriptors, TB-PCT (Threshold Based- Predictive Clustering Tree) algorithm is used to generate visual codebook and histogram is produced. Further, matching is performed using soft weighting scheme with L2 distance function. As a final step, retrieved results are ranked according to the Index value and acknowledged to the user as a feedback .In order to handle prodigious amount of data and Efficacious retrieval, we have incorporated HDFS in our Intellection. Using 3D video dataset, we future the performance of our proposed system which can pan out that the proposed work gives meticulous result and also reduce the time intricacy. PMID:28003793

  7. Visual Semantic Based 3D Video Retrieval System Using HDFS.

    PubMed

    Kumar, C Ranjith; Suguna, S

    2016-08-01

    This paper brings out a neoteric frame of reference for visual semantic based 3d video search and retrieval applications. Newfangled 3D retrieval application spotlight on shape analysis like object matching, classification and retrieval not only sticking up entirely with video retrieval. In this ambit, we delve into 3D-CBVR (Content Based Video Retrieval) concept for the first time. For this purpose, we intent to hitch on BOVW and Mapreduce in 3D framework. Instead of conventional shape based local descriptors, we tried to coalesce shape, color and texture for feature extraction. For this purpose, we have used combination of geometric & topological features for shape and 3D co-occurrence matrix for color and texture. After thriving extraction of local descriptors, TB-PCT (Threshold Based- Predictive Clustering Tree) algorithm is used to generate visual codebook and histogram is produced. Further, matching is performed using soft weighting scheme with L2 distance function. As a final step, retrieved results are ranked according to the Index value and acknowledged to the user as a feedback .In order to handle prodigious amount of data and Efficacious retrieval, we have incorporated HDFS in our Intellection. Using 3D video dataset, we future the performance of our proposed system which can pan out that the proposed work gives meticulous result and also reduce the time intricacy.

  8. 3d-3d correspondence revisited

    DOE PAGES

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; ...

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  9. 3d-3d correspondence revisited

    SciTech Connect

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  10. Validation of reference materials for uranium radiochronometry in the frame of nuclear forensic investigations

    DOE PAGES

    Varga, Z.; Mayer, K.; Bonamici, C. E.; ...

    2015-05-11

    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 ²²⁰Th/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 proceduresmore » 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.« less

  11. Validation of reference materials for uranium radiochronometry in the frame of nuclear forensic investigations.

    PubMed

    Varga, Z; Mayer, K; Bonamici, C E; Hubert, A; Hutcheon, I; Kinman, W; Kristo, M; Pointurier, F; Spencer, K; Stanley, F; Steiner, R; Tandon, L; Williams, R

    2015-08-01

    The results of a joint effort by expert nuclear forensic laboratories in the area of age dating of uranium, i.e. the elapsed time since the last chemical purification of the material are presented and discussed. Completely separated uranium materials of known production date were distributed among the laboratories, and the samples were dated according to routine laboratory procedures by the measurement of the (230)Th/(234)U ratio. The measurement results were in good agreement with the known production date showing that the concept for preparing uranium age dating reference material based on complete separation is valid. Detailed knowledge of the laboratory procedures used for uranium age dating allows the identification of possible improvements in the current protocols and the development of improved practice in the future. The availability of age dating reference materials as well as the evolvement of the age dating best-practice protocol will increase the relevance and applicability of age dating as part of the tool-kit available for nuclear forensic investigations. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Investigations on the hierarchy of reference frames in geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Grafarend, E. W.; Mueller, I. I.; Papo, H. B.; Richter, B.

    1979-01-01

    Problems related to reference directions were investigated. Space and time variant angular parameters are illustrated in hierarchic structures or towers. Using least squares techniques, model towers of triads are presented which allow the formation of linear observation equations. Translational and rotational degrees of freedom (origin and orientation) are discussed along with and the notion of length and scale degrees of freedom. According to the notion of scale parallelism, scale factors with respect to a unit length are given. Three-dimensional geodesy was constructed from the set of three base vectors (gravity, earth-rotation and the ecliptic normal vector). Space and time variations are given with respect to a polar and singular value decomposition or in terms of changes in translation, rotation, deformation (shear, dilatation or angular and scale distortions).

  13. The first privately produced map in Norway with a geodetic reference frame

    NASA Astrophysics Data System (ADS)

    Pettersen, B. R.

    2009-04-01

    A map of the district surrounding lake Mjøsa in Norway was published in 1796 by the Topographical Society of Norway. Their members contributed private funds for this unique map and for the publication of the Topographical Journal, containing multidisciplinary descriptions, including environmental, of many regions of the country. The map was produced by Niels S. Darre, an army surveyor and cartographer, as a private undertaking in his own home district. The geodetic reference point of the map is the church at Vang, the position of which had been determined by repeated astronomical observations by its vicar, Abraham Pihl. He had been trained as an astronomical observer by professor Thomas Bugge at the Round Tower Observatory in Copenhagen. A supporting latitude determination near Lillehammer is also noted on the map, obtained by Maximillian Hell in 1769 on his return from Vardø in North-Norway to Vienna after a successful observation of the transit of Venus. The observed magnetic deviation from astronomically determined north is given. The map also identifies a marker of the great flood of the river Glomma in 1789, causing environmental and social devastation.

  14. Moving Forward in Space and Time: How Strong is the Conceptual Link between Spatial and Temporal Frames of Reference?

    PubMed Central

    Bender, Andrea; Rothe-Wulf, Annelie; Hüther, Lisa; Beller, Sieghard

    2012-01-01

    People often use spatial vocabulary to describe temporal relations, and this increasingly has motivated attempts to map spatial frames of reference (FoRs) onto time. Recent research suggested that speech communities, which differ in how they conceptualize space, may also differ in how they conceptualize time and, more specifically, that the preferences for spatial FoRs should carry over to the domain of time. Here, we scrutinize this assumption (a) by reviewing data from recent studies on temporal references, (b) by comparing data we had collected in previous studies on preferences for spatial and temporal FoRs in four languages, (c) by analyzing new data from dynamic spatial tasks that resemble the temporal tasks more closely, and (d) by assessing the co-variation of individual preferences of English speakers across space and time. While the first set of data paints a mixed picture, the latter three do not support the assumption of a close link between referencing preferences across domains. We explore possible reasons for this lack of consistency and discuss implications for research on temporal references. PMID:23162519

  15. 3D and Education

    NASA Astrophysics Data System (ADS)

    Meulien Ohlmann, Odile

    2013-02-01

    Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method o