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1

Dispersion correction through movement of the closed orbit  

SciTech Connect

The closed orbit correction system can be used to correct the vertical dispersion by displacing the orbit at the quadrupoles and sextupoles. The accuracy of the results have been verified by comparison with exact calculations. Results for correcting the horizontal dispersion are also given.

Parzen, G

1980-01-01

2

Closed orbit correction in the SSC  

Microsoft Academic Search

A global correction scheme proposed for use in the SSC (Superconducting Super Collider) is described. Various features of the SSC lattice that impact the ability to correct the orbit are discussed. Typical results for the residual RMS closed orbit in the arc are calculated to be 0.65 mm with peak values of 3 mm

G. Bourianoff; B. Cole; H. Ferede; F. Pilat

1991-01-01

3

Orbits Close to Asteroid 4769 Castalia  

Microsoft Academic Search

We use a radar-derived physical model of 4769 Castalia (1989 PB) to investigate close orbit dynamics around that kilometer-sized, uniformly rotating asteroid. Our methods of analysis provide a basis for systematic studies of particle dynamics close to any uniformly rotating asteroid.We establish that a Jacobi integral exists for particles orbiting this asteroid, examine the attendant zero-velocity surfaces, find families of

D. J. Scheeres; S. J. Ostro; R. S. Hudson; R. A. Werner

1996-01-01

4

Closed Orbit Distortion and the Beam-Beam Interaction  

SciTech Connect

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

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

2007-02-23

5

Closed orbit response to quadrupole strength variation  

SciTech Connect

We derive two formulae relating the variation in closed orbit in a storage ring to variations in quadrupole strength, neglecting nonlinear and dispersive effects. These formulae correct results previously reported [1,2,3]. We compare the results of the formulae applied to the ATF with simulations using MAD, and consider their application to beam-based alignment.

Wolski, Andrzej; Zimmermann, Frank

2004-01-20

6

Closed Orbit Distortion and the Beam-Beam Interaction. Final Report.  

National Technical Information Service (NTIS)

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nomina...

M. Furman Y. H. Chin J. Eden W. Kozanecki J. Tennyson

1992-01-01

7

Dispersion function and closed orbit distortion in accelerator rings  

SciTech Connect

Dispersion Function Distortion (DFD) affects accelerator operation and thus deserves attention, somehow as Closed Orbit Distortion (COD) does. Consequently, DFD correction schemes under computer control have been successfully developed and adopted in many rings such as PEP. It was realized during the author's study on the problem, however, that the existing DFD correction schemes ignore those terms that arise from bending magnets and their edges. Being of first order of correcting strength, the terms are significant in small rings, though really not important in big machines. This reminds of what has been noticed in the chromaticity calculation. A comparison between this note and the existing schemes shows a difference in DFD sensitivity matrix that is significant for sub-GeV machines and appears not negligible even for SPEAR. Many storage rings at energy around 0.7 to 3 GeV are being proposed, constructed or operated everywhere as synchrotron radiation generators. Vertical DFD correction should be an important part of their operation, because vertical DFD enlarges beam height and hence reduces light source brightness. This is the purpose the author had in mind when beginning to study the problem. In addition, a correct DFD analysis along with COD analysis can hopefully help spot magnet misalignments and remove them.

Liu, R.Z.

1984-02-01

8

Dynamics of Orbits Close to Asteroid 4179 Toutatis  

Microsoft Academic Search

We use a radar-derived physical model of 4179 Toutatis (975870) to investigate close-orbit dynamics around that irregularly shaped, non-principal-axis rotator. The orbital dynamics about this body are markedly different than the dynamics about uniformly rotating asteroids. The results of this paper are generally applicable to orbit dynamics about bodies in a non-principal-axis rotation state. The radar results support the hypothesis

D. J. Scheeres; S. J. Ostro; R. S. Hudson; E. M. DeJong; S. Suzuki

1998-01-01

9

Role of core-scattered closed orbits in nonhydrogenic atoms  

Microsoft Academic Search

While both diamagnetic and Stark spectra of hydrogen can be analyzed accurately in terms of classical orbits, in nonhydrogenic atoms the multielectron core induces additional spectral modulations that cannot be analyzed reliably in terms of standard periodic orbit-type theories. However, by extending closed-orbit theory to include core-scattered waves consistently, both diamagnetic and Stark photoabsorption spectra of nonhy- drogenic Rydberg atoms

P. A. Dando; T. S. Monteiro; D. Delande; K. T. Taylor

1996-01-01

10

On closed but non-geometrically similar orbits  

NASA Astrophysics Data System (ADS)

As is well known, the existence of geometrically similar orbits for a particle moving under a central conservative force is a consequence of the fact that the corresponding potential energy is a homogeneous function of the co-ordinates. In this paper, we consider a particular non-homogeneous potential of the form V = U + W, where U and W are homogenous functions of degrees -1 and -2, respectively, because, for this potential, the search of closed orbits, for discrete values of the angular momentum, is straightforward. We focus our attention on these daisy-like charming orbits and graphically show the consequences of the impossibility of geometrical similarity.

Brun, J. L.; Pacheco, A. F.

2006-11-01

11

Closed orbit change induced by nonzero dispersion rf cavities  

NASA Astrophysics Data System (ADS)

The particle motion in storage rings is coupled between the longitudinal and the transverse planes in the presence of nonzero dispersion rf cavities. We found that the particle motion can be modeled separately with a redefined closed orbit. The closed orbit can be described by a Green’s function, which was confirmed in the simulation and in the experiment. The pathlength is calculated from the redefined closed orbit, and we found that the longitudinal phase slip is related not only to the momentum, but also to the rf phase of the particle. The effect on the longitudinal motion becomes significant if the phase slip caused by the rf cavities is large or if the momentum compaction factor is small, such as in the lower alpha- c lattice which is intended to produce shorter bunches.

Guo, Weiming; Harkay, Katherine; Borland, Michael

2005-11-01

12

ACCELERATORS: Studies of closed orbit correction and slow orbit feedback for the SSRF storage ring  

NASA Astrophysics Data System (ADS)

Details of the active ways to suppress Closed Orbit Distortion (COD), including bending magnet sorting and survey and alignment of the magnets, are discussed based on the studies of affections to the COD by the bending magnet field error and the misalignment of quadrupoles. The closed orbit correction and the Slow Orbit Feed Back (SOFB) system for the SSRF storage ring are presented in this paper. With these available methods, better results were obtained during the commissioning period with 3 GeV beam energy.

Hou, Jie; Tian, Shun-Qiang; Zhang, Man-Zhou; Xu, Yi; Liu, Gui-Min

2009-02-01

13

Vertical profiles of atmospheric electric parameters close to ground  

Microsoft Academic Search

The ion-aerosol balance equations have been solved for different mixing strengths and two types of ionization profile to get vertical profiles of atmospheric electric parameters close to the Earth's surface. The inclusion of surface radioactivity in the model causes the decrease in electric field to be more intense at lower levels than at higher levels, an increase in the asymptotic

Madhuri Kulkarni; A. K. Kamra

2001-01-01

14

7. Close view of the lower portion of vertical sign ...  

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

7. Close view of the lower portion of vertical sign with the letters "A-G-O" after removal from theatre (Note: the steel I-beam was inserted and sheet metal side panels taken off to facilitate removal from theatre - Chicago Theater, 175 North State Street, Chicago, Cook County, IL

15

Magnetic field, closed orbit, and energy measurement in the Bevatron  

SciTech Connect

This report provides the information necessary for a better evaluation of particle energy in the Bevatron. Previously, the nominal magnetic field value and radius were used to calculate the value for the kinetic energy of the particle. This value was good to a few percent. Today, more and more experimenters would like to know the energy to a more precise value. To this end, corrections to the measured magnetic field values and the radial closed orbit are provided.

Crebbin, K.C.

1981-11-01

16

Orbital period modulation and magnetic cycles in close binaries  

NASA Astrophysics Data System (ADS)

We discuss the observed orbital period modulations in close binaries, and focus on the mechanism proposed by Applegate relating the changes of the stellar internal rotation associated with a magnetic activity cycle with the variation of the gravitational quadrupole moment of the active component; the variation of this quadrupole moment in turn forces the orbital motion of the binary stars to follow the activity level of the active star. We generalize this approach by considering the details of this interaction, and develop some illustrative examples in which the problem can be easily solved in analytical form. Starting from such results, we consider the interplay between rotation and magnetic field generation in the framework of different types of dynamo models, which have been proposed to explain solar and stellar activity. We show how the observed orbital period modulation in active binaries may provide new constraints for discriminating between such models. In particular, we study the case of the prototype active binary RS Canum Venaticorum, and suggest that torsional oscillations - driven by a stellar magnetic dynamo - may account for the observed behaviour of this star. Further possible applications of the relationship between magnetic activity and orbital period modulation, related to the recent discovery of binary systems containing a radio pulsar and a convecting upper main-sequence or a late-type low-mass companion, are discussed.

Lanza, A. F.; Rodono, M.; Rosner, R.

1998-06-01

17

Close collisions between light nuclei: Orbiting and fusion  

SciTech Connect

Our data have demonstrated that in close collisions the two nuclei first form a rotating dinuclear complex (DNC) which can break up into two complex fragments (Orbiting) or evolve into a compound nucleus. The binary fragment yield was found to be significant in contradiction with earlier views which held that whenever nucleus-nucleus capture occurs fusion is a certainty. The time duration of the dinuclear stage and the nature of its evolution into a compound nucleus were studied and a model which describes these processes will be presented. 25 refs., 14 figs.

Shapira, D.; Shivakumar, B.; Harmon, B.A.; Ayik, S.

1987-01-01

18

Closed orbits and their bifurcations in the crossed-field hydrogen atom  

SciTech Connect

A systematic study of closed classical orbits of the hydrogen atom in crossed electric and magnetic fields is presented. We develop a local bifurcation theory for closed orbits, which is analogous to the well-known bifurcation theory for periodic orbits and allows identifying the generic closed-orbit bifurcations of codimension 1. Several bifurcation scenarios are described in detail. They are shown to have as their constituents the generic codimension-1 bifurcations, which combine into a rich variety of complicated scenarios. We propose heuristic criteria for a classification of closed orbits that can serve to systematize the complex set of orbits.

Bartsch, Thomas; Main, Joerg; Wunner, Guenter [Institut fuer Theoretische Physik 1, Universitaet Stuttgart, D-70550 Stuttgart, (Germany)

2003-06-01

19

Weighted SVD algorithm for close-orbit correction and 10 Hz feedback in RHIC  

SciTech Connect

Measurements of the beam position along an accelerator are typically treated equally using standard SVD-based orbit correction algorithms so distributing the residual errors, modulo the local beta function, equally at the measurement locations. However, sometimes a more stable orbit at select locations is desirable. In this paper, we introduce an algorithm for weighting the beam position measurements to achieve a more stable local orbit. The results of its application to close-orbit correction and 10 Hz orbit feedback are presented.

Liu C.; Hulsart, R.; Marusic, A.; Michnoff, R.; Minty, M.; Ptitsyn, V.

2012-05-20

20

Multiport well design for sampling of ground water at closely spaced vertical intervals  

Microsoft Academic Search

Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely

Geoffrey N. Delin; Matthew K. Landon

1996-01-01

21

Study of closed orbit response to magnet vibrations at the SSRF storage ring  

NASA Astrophysics Data System (ADS)

This paper presents the analytical and simulation responses of the closed orbit distortion in the SSRF storage ring to random and plane wave like magnet vibrations respectively. It is shown that the use of girder is very beneficial in the view of suppressing this response function. Effect of the independently supported gradient bending magnets to the closed orbit response is given. An analytic formula is written to give a rough estimate of the closed orbit distortion due to ground motion, taking into account the closed orbit response function and girder transfer function. As an example, the result of SSRF case is given. Supported by SSRF Project

Chen, Jian-Hui; Zhao, Zhen-Tang; Dai, Zhi-Min; Liu, Gui-Min

2008-07-01

22

Solar Orbiter. The need to go close to the Sun  

NASA Astrophysics Data System (ADS)

The key objective of the Solar Orbiter, a mission of the European Space Agency 'Cosmic Vision' Program, is to fully understand how the Sun creates and controls the heliosphere. The issues addressed by the Solar Orbiter concern the solar dynamo, the origin of the solar wind, of the coronal mass ejections which drive the heliospheric variability, of the energetic particle radiation which fills the heliosphere. In order to pursue these investigations a unique mission profile is proposed. The spacecraft will approach the Sun to within 0.28 AU and reach an orbit inclination relative to the solar equator exceeding 25 degrees. The proximity to the Sun will also have the advantage that the spacecraft will fly in near synchronization with the Sun's rotation. The Solar Orbiter launch is foreseen in January 2017.

Antonucci, E.

23

Vertical Eye Position Control in Darkness: Orbital Position and Body Orientation Interact to Modulate Drift Velocity  

Microsoft Academic Search

How stable is vertical eye-in-head position control in darkness when no visual targets are present? We evaluated this while varying both body-in-space orientation and eye-in-orbit position in six subjects who were free from oculomotor\\/vestibular disease. Vertical eye movements were monitored using a CCD-video tracking system, and results were confirmed on one subject with the magnetic search coil. Three body orientations

H. C GOLTZ; E. L IRVING; M. J STEINBACH; M EIZENMAN

1997-01-01

24

Vertical structure of the atmosphere of Venus from Pioneer Venus orbiter radio occultations  

Microsoft Academic Search

Between December 1978 and February 1979 the Pioneer Venus orbiter spacecraft returned some 140 S band and X band radio occultation measurements of the Venus atmosphere. Results from 13 measurements, covering diverse latitudes from near equatorial to polar, are presented in this paper in the form of vertical profiles of temperature. The temperature profiles show a pronounced inversion at the

A. J. Kliore; I. R. Patel

1980-01-01

25

Orbit determination of close binary systems using lucky imaging  

NASA Astrophysics Data System (ADS)

We present relative positions of visual binaries observed in 2009 with the FastCam 'lucky-imaging' camera mounted on the 1.5-m Carlos Sánchez Telescope at the Observatorio del Teide. We obtained 424 CCD observations (averaged in 198 mean relative positions) of 157 binaries with angular separations in the range 0.14-15.40 arcsec, with a median separation of 0.51 arcsec. For a given system, each CCD image represents the sum of the best 10-25 per cent images from 1000-5000 short-exposure frames. Derived internal errors were 7 mas in ? and 1?2 (9 mas) in ?. When comparing to systems with very well known orbits, we find that the rms deviation in ? residuals is 23 mas, while the rms deviation in ? residuals is 0?73/?. We confirmed 18 Hipparcos binaries and we report new companions to BVD 36 A and J 621 B. For binaries with preliminary orbital parameters, the relative radial velocity was estimated as well. We also present four new revised orbits computed for LDS 873, BU 627 A-BC, BU 628 and HO 197 AB. This work discusses the first results on visual binaries using the FastCam lucky-imaging camera.

Rica, F. M.; Barrena, R.; Vázquez, G.; Henríquez, J. A.; Hernández, F.

2012-01-01

26

Closed Orbit Distortions Due to Survey and Alignment Errors in PEP I.  

National Technical Information Service (NTIS)

This note presents the results of computer simulations of the closed orbit distortions in PEP I. A computer program ALIGN was written to simulate the expected survey and alignment errors and to calculate the resulting orbit distortions. The goal of the su...

R. Sah

1976-01-01

27

ORBITAL DISTRIBUTIONS OF CLOSE-IN PLANETS AND DISTANT PLANETS FORMED BY SCATTERING AND DYNAMICAL TIDES  

SciTech Connect

We investigated the formation of close-in planets (hot Jupiters) by a combination of mutual scattering, Kozai effect, and tidal circularization, through N-body simulations of three gas giant planets, and compared the results with discovered close-in planets. We found that in about 350 cases out of 1200 runs ({approx}30%), the eccentricity of one of the planets is excited highly enough for tidal circularization by mutual close scatterings followed by secular effects due to outer planets, such as the Kozai mechanism, and the planet becomes a close-in planet through the damping of eccentricity and semimajor axis. The formation probability of close-in planets by such scattering is not affected significantly by the effect of the general relativity and inclusion of inertial modes in addition to fundamental modes in the tides. Detailed orbital distributions of the formed close-in planets and their counterpart distant planets in our simulations were compared with observational data. We focused on the possibility for close-in planets to retain non-negligible eccentricities ({approx}> 0.1) on timescales of {approx}10{sup 9} yr and have high inclinations, because close-in planets in eccentric or highly inclined orbits have recently been discovered. In our simulations we found that as many as 29% of the close-in planets have retrograde orbits, and the retrograde planets tend to have small eccentricities. On the other hand, eccentric close-in planets tend to have orbits of small inclinations.

Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2011-12-01

28

Gasdynamical study of close binary stars with elliptic orbits  

NASA Astrophysics Data System (ADS)

This paper describes approaches to numerical simulation of various classes of close binary stars using Eulerian gas dynamics and cartesian grids. Possible obstacles, advantages and drawbacks of different methods are discussed with respect to a brought-up classification of binary systems from point of view of a numerical method. Results of a 3D numerical simulation of envelopes of T Tauri stars are presented.

Sytov, A. Yu.

2013-09-01

29

Optimal low-thrust transfers between close near-circular coplanar orbits  

NASA Astrophysics Data System (ADS)

Four types of optimal solutions are demonstrated to exist for transfers (time of flight is not fixed) between close near-circular coplanar orbits. One solution is realized with the help of fixed orientation of the propulsion system (PS) along a transversal in the orbital coordinate system. Another is reached at fixed orientation of the PS in the inertial coordinate system. The third and fourth types of solutions change the PS orientation in the process of executing the maneuver. Regions of existence are established for all types of solutions, and algorithms for determination of parameters of these maneuvers are suggested. The algorithms were used to calculate parameters of the maneuvers of transfer from a launching orbit to a working Sun-synchronous orbit, and to calculate the maneuvers of supporting the parameters of such an orbit in a specified range.

Baranov, A. A.; de Prado, A. F. B.; Razumny, V. Yu.; Baranov, Anatoly A.

2011-06-01

30

Fermi-surface nesting, closed orbits, and the ''threshold field'' in an organic superconductor  

SciTech Connect

The Fermi surface of the organic superconductor (TMTSF)/sub 2/PF/sub 6/ (bis-tetramethyltetraselena- fulvalenium hexafluorophosphate) should be open in a one-electron picture. Magnetotransport results, on the other hand, indicate the presence in the metallic state of small closed and compensated orbits. Such orbits can arise if there is an instability of commensurate wave vectors nesting the Fermi surface. The areas calculated here for these orbits are shown to strongly favor nonoptimal nesting over optimal nesting (i.e., the optimal areas are far too small). A model of instability commensuration change at the observed threshold associated with the Shubnikov--de Haas effect, driven by the magnetic field dependence of the Landau-level energies for the optimal orbits, is seen to be consistent with the present results and with many of the novel properties of this material.

Kwak, J.F.

1983-09-15

31

Differential algebraic determination of high-order off-energy closed orbits, chromaticities, and momentum compactions  

Microsoft Academic Search

For some modern particle accelerators, including the planned muon collider, the accurate analysis of non-linear time-of-flight effects in the form of momentum compactions is critical for the preservation of bunch structure. A Differential Algebra-based (DA) method is presented that allows the determination of off-energy closed orbits and chromaticities to any order. By performing a coordinate transformation to the off-energy closed

Martin Berz; Béla Erdélyi; Weishi Wan; King-Yuen Ng

1999-01-01

32

Digital closed orbit feedback system for the advanced photon source storage ring  

Microsoft Academic Search

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of

Y. Chung; D. Barr; G. Decker

1995-01-01

33

Behavior of nonclassical recurrence amplitudes near closed-orbit bifurcations in atoms  

Microsoft Academic Search

We report an experimental and computational study of the energy dependence of nonclassical paths in atoms near bifurcations. The experiment employs scaled energy spectroscopy to measure the amplitudes of nonclassical orbits in helium singlet and triplet Stark Rydberg states (20close to bifurcations. We have also calculated this behavior for hydrogen. In both cases, the amplitude dependence on energy, just

M. L. Keeler; Heric Flores-Rueda; T. J. Morgan; J. Shaw

2004-01-01

34

Automatic correction of orbital elements using continuous thrust controlled in closed loop  

NASA Astrophysics Data System (ADS)

This work aims to study and simulate the control of a spacecraft trajectory in order to correct automatically and simultaneously the orbital elements that define the orbit: semi-major axis, eccentricity, periapse argument, inclination and right ascension of the ascending node. Thus, to perform the control of the trajectory was used a propulsion system able to apply thrust with adjustable magnitude and direction of application. In this study it was considered that the propulsion system is controlled in closed loop, so the adjustments of the magnitude and direction of thrust depends on the error generated by comparing a reference state (position and velocity) and a current state. The reference state is determined according to the final orbital parameters. The current state is estimated at each step of the simulation, therefore, the reference and current states must be determined and compared at each step in order to generate the error signal that is inserted into the trajectory control system. However, the control of the orbital parameters simultaneously can be characterized as a multi-objective problem with conflicting goals. The correction of the semi-major axis causes an eccentricity modification and vice-versa. One possibility to deal with this problem is to define when and where to make adjustments for each of the parameters. Thus, the automatic control seeks the best way to correct each parameter, adjusting each one sequentially. At the end of the process all orbital parameters are automatically adjusted and maintained due to the use of the closed loop control system.

Rocco, E. M.

2013-10-01

35

Multiport Well Design for Sampling of Ground Water at Closely Spaced Vertical Intervals  

USGS Publications Warehouse

Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples from the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Tracer experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorcarbon concentrations.

Delin, G. N.; Landon, M. K.

1996-01-01

36

Comparison of vertical-takeoff and horizontal-takeoff single-stage-to-orbit ascent performance  

NASA Astrophysics Data System (ADS)

A study was conducted to examine the ascent performance capability of the vertical-takeoff and horizontal-takeoff single-stage-to-orbit launchers. Both launchers, powered by Space Shuttle Main Engine rockets, were assumed to have a gross liftoff weight of 1,000,000 lb. The horizontal-takeoff launcher was assumed to be capable to take off from a conventional runway on its own power. The optimal ascent profile was designed to honor the dynamic pressure (900 psf), the axial load (3 g), and the normal load (1.25 g) constraints. Results of the study indicate that the vertical-takeoff performance with a burnout weight of 137,568 lb is not a strong function of the vehicle lift or wing area. The wing is required only for the reentry performance such as heating control, crossrange, and landing maneuvers. The horizontal-takeoff launcher has a burnout weight of 138,309 lb, but it will not have any payload capability if the ascent load is supported entirely by the vehicle landing gear at launch. Therefore, in order to make the horizontal-takeoff mode feasible, an undercarriage such as a trolley or a simple truss structure with wheels is required to alleviate the ascent load and, as a result, to reduce the landing gear weight. The horizontal-takeoff launcher, however, offers advantages over the winged vertical-takeoff launcher such as simpler launch preparedness and operation and a better launch abort capability.

Nguyen, Hai N.

1991-10-01

37

Importance of closely spaced vertical sampling in delineating chemical and microbiological gradients in groundwater studies  

USGS Publications Warehouse

Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, U.S.A. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in groundwater studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, USA. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in ground-water studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.

Smith, R. L.; Harvey, R. W.; LeBlanc, D. R.

1991-01-01

38

Differential algebraic determination of high-order off-energy closed orbits, chromaticities, and momentum compactions  

NASA Astrophysics Data System (ADS)

For some modern particle accelerators, including the planned muon collider, the accurate analysis of non-linear time-of-flight effects in the form of momentum compactions is critical for the preservation of bunch structure. A Differential Algebra-based (DA) method is presented that allows the determination of off-energy closed orbits and chromaticities to any order. By performing a coordinate transformation to the off-energy closed orbit, it is possible to compute momentum compactions analytically. This method has been implemented in the code COSY INFINITY and is tested for two cases where analytical solutions can be obtained by hand; agreement to machine precision is found. By contrast, comparisons are made with several codes that use conventional numerical methods for the determination of momentum compaction, and it is found that these approaches sometimes yield rather inaccurate results, especially for higher orders.

Berz, M.; Erdélyi, B.; Wan, W.; Ng, K.-Y.

1999-05-01

39

Digital closed orbit feedback system for the Advanced Photon Source storage ring  

Microsoft Academic Search

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed-orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the

Y. Chung; D. Barr; G. Decker; J. Galayda; F. Lenkszus; A. Lumpkin; A. J. Votaw

1996-01-01

40

Determination of the operation range of a vertical two-phase closed thermosyphon  

NASA Astrophysics Data System (ADS)

A comprehensive model, proposed for a vertical two-phase closed thermosyphon (TPCT) by the present authors, is further developed by utilizing the criteria for dryout, flooding and boiling limits to investigate the effects of filling ratio on them together, while the available models can just consider one or two limits of them. A new concept named dryout ratio is proposed, which can be used for predicting dryout limit. The empirical correlation and the empirical value, provided by other researchers, are used for predicting flooding and boiling limit, respectively. The experiments with nitrogen as working fluid are performed, and compared with the calculations. The maximum filling ratio is introduced, beyond which the liquid could be carried to condenser and the heat transfer performance can be deteriorated. And then the closed operation range of a vertical TPCT is finally determined, which has not been reported before. The effects of operating pressure and geometries on the range are also analyzed.

Jiao, B.; Qiu, L. M.; Gan, Z. H.; Zhang, X. B.

2012-06-01

41

Compensation for the effect of vacuum chamber eddy current by digital signal processing for closed orbit feedback  

SciTech Connect

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams. The relatively thick (1/2 inch) aluminum storage ring vacuum chamber at corrector magnet locations for the local feedback systems will induce significant eddy current. This will reduce the correction bandwidth and could potentially destabilize the feedback systems. This paper describes measurement of the effect of the eddy current induced in the APS storage ring vacuum chamber by a horizontal/vertical corrector magnet and its compensation using digital signal processing at 4 kHz sampling frequency with proportional, integral, and derivative (PID) control algorithm for closed orbit feedback. A theory of digital feedback to obtain the linear system responses and the conditions for optimal control will also be presented. The magnet field in the vacuum chamber shows strong quadrupole and sextupole components varying with frequency, in addition to significant attenuation and phase shift with bandwidth ({minus}3 dB) of 20 Hz for horizontal and 4 Hz for vertical fields relative to the magnet current. Large changes in the magnet resistance and inductance were also observed, as the result of reduced total magnetic energy and increased Ohmic heat loss.

Chung, Y.; Emery, L.; Kirchman, J.

1993-07-01

42

Automatic steering of x-ray beams from NSLS insertion devices using closed orbit feedback  

SciTech Connect

By the middle of this year (1989); there will be five insertion devices installed in the NSLS x-ray electron storage ring. X-ray beams from these devices will be stabilized by local automatic steering systems to reduce beam motion at the end of the beamline. Both the position of the source and the direction of the radiation will be controlled using beam position feedback to the closed orbit. Another system will be installed to stabilize the electron orbit for the LEGS Compton backscattering experiment. Each feedback system will employ at least one x-ray beam position detector; some will also utilize rf electron beam positron monitors. Analog hardware with a digital interface has been designed and will be installed in the near future. A totally digital realization of the feedback controller is under consideration. 6 refs., 6 figs.

Nawrocky, R.J.; Galayda, J.; Klein, J.D.; Singh, O.; Yu, L.H.

1989-01-01

43

Effect of the electron lenses on the RHIC proton beam closed orbit  

SciTech Connect

We are designing two electron lenses (E-lens) to compensate for the large beam-beam tune spread from proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). They will be installed at RHIC IR10. The transverse fields of the E-lenses bending solenoids and the fringe field of the main solenoids will shift the proton beam. We calculate the transverse kicks that the proton beam receives in the electron lens via Opera. Then, after incorporating the simplified E-lens lattice in the RHIC lattice, we obtain the closed orbit effect with the Simtrack Code.

Gu, X.; Luo, Y.; Pikin, A.; Okamura, M.; Fischer, W.; Montag, C.; Gupta, R.; Hock, J.; Jain, A.; Raparia, D.

2011-02-01

44

Tidal evolution of close binary stars. II - Orbital circularization of late-type binaries  

NASA Astrophysics Data System (ADS)

The premain-sequence evolution of close binary systems with masses ranging from 0.5 to 1.25 solar masses is described. It is demonstrated that most of the orbital circularization occurs during the Hayashi phase, and that the subsequent decrease in eccentricity on the main-sequence is negligible. The theoretical cutoff period, which separates the circular from the eccentric systems, lies between 7.2 and 8.5 days, depending on the masses and on the assumptions made about the initial conditions; it agrees well with the observed period of about 8 days. This cutoff period is a function of the initial radius of the stars on the Hayashi track. In these calculations, the values predicted by the star formation theory of Stahler et al. (1980) are used; hence the good agreement mentioned above provides a new validation of that theory. It is also shown that systems around that cutoff period reach the zero-age main-sequence with their components rotating faster than the orbital rate.

Zahn, J.-P.; Bouchet, L.

1989-10-01

45

Digital closed orbit feedback system for the advanced photon source storage ring  

SciTech Connect

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described in this paper. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm, application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware including the DSPs is distributed in 20 VME crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories.

Chung, Y.; Barr, D.; Decker, G. [and others

1995-12-31

46

Digital closed orbit feedback system for the Advanced Photon Source storage ring  

SciTech Connect

Closed orbit feedback for the Advanced Photon Source (APS) storage ring employs unified global an local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm. application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware, including the DSPS, is distributed in 20 VNE crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories.

Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

1995-10-20

47

Stability Orbits Close to 433 Eros Using a Shaped Polyhedral Source  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): A general characteristic of celestial minor planets as asteroids, objects of several recent studies, is the fact of having highly irregular shape. The recent observations and space probes that pass close to the asteroids with orbits near the Earth (NEOs) have shown the existence of binary and triple asteroid systems. The existence of these moons can be explained due to their irregular shape. One of the techniques used in the past decade to determine the shape with a good accuracy and estimate certain physical features (volume, mass, moments of inertia) of asteroids is the polyhedral model method. The aim of this study is to rebuild the shape and determine the physical characteristics of the asteroid 433 Eros using data from December 1998 observations of the probe NEAR-Shoemaker (Near Earth Asteroid Rendezvous). In our computations we use a code that avoids singularities from the line integrals of a homogeneous arbitrary shaped polyhedral source and is accurate. This code evaluates the gravitational potential function and its first and second order derivatives. Then, we find the location of the equilibrium points through the pseudo-potential energy and zero velocity curves. We also show the differences in the potential between our model and a point mass. Finally, taking the rotation of asteroid 433 Eros into consideration, we analyze the environment orbit dynamics compared with the analytical model.

Chanut, Thierry G.; Winter, O.

2013-05-01

48

Near-infrared spectroscopic search for the close orbiting planet HD 75289b  

NASA Astrophysics Data System (ADS)

We present a search for the near-infrared spectroscopic signature of the close orbiting extrasolar giant planet HD 75289b. We obtained ~230 spectra in the wavelength range 2.18-2.19 ?m using the Phoenix spectrograph at Gemini South. By considering the direct spectrum, derived from irradiated model atmospheres, we search for the absorption profile signature present in the combined star and planet light. Since the planetary spectrum is separated from the stellar spectrum at most phases, we apply a phase-dependent orbital model and tomographic techniques to search for absorption signatures. Because the absorption signature lies buried in the noise of a single exposure we apply a multiline deconvolution to the spectral lines available in order to boost the effective signal-to-noise ratio (S/N) of the data. The wavelength coverage of 80 Å is expected to contain ~100 planetary lines, enabling a mean line with S/N of 800 to be achieved after deconvolution. We are nevertheless unable to detect the presence of the planet in the data and carry out further simulations to show that broader wavelength coverage should enable a planet like HD 75289b to be detected with 99.9 per cent confidence. We investigate the sensitivity of our method and estimate detection tolerances for mismatches between observed and model planetary atmospheres.

Barnes, J. R.; Leigh, C. J.; Jones, H. R. A.; Barman, Travis S.; Pinfield, D. J.; Collier Cameron, A.; Jenkins, J. S.

2007-08-01

49

Boiling characteristics in small vertical tubes with closed bottom for nanofluids and nanoparticle-suspensions  

NASA Astrophysics Data System (ADS)

An experimental study was carried out to understand the nucleate boiling characteristics and the critical heat flux (CHF) of water, the water based nanofluids and the water based nanoparticle-suspensions in vertical small heated tubes with a closed bottom. Here, the nanofluids consisted of the base liquid, the CuO nanoparticles and the surfactant. The nanoparticle-suspensions consisted of the base liquid and CuO nanoparticles. The surfactant was sodium dodecyl benzene sulfate. The study focused on the influence of the nanoparticles and surfactant on the nucleate boiling characteristics and the CHF. The experimental results indicated that the nanoparticle concentrations of the nanofluids and nanoparticle-suspensions in the tubes do not change during the boiling processes; the nanoparticles in the evaporated liquid are totally carried away by the steam. The boiling heat transfer rates of nanofluids are poorer than that of the base liquid. However, the boiling heat transfer rates of nanoparticle-suspensions are better than that of the base liquid. Comparing with the base liquid, the CHF of the nanofluids and the nanoparticle-suspensions is higher. The CHF is only related to nanoparticle mass concentration when the tube length and the tube diameter are fixed. The experiment confirm that there is a thin nanoparticle coating layer on the heated surface after the nanofluids boiling test but there is no coating layer on the heated surface after the nanoparticle-suspensions boiling test. This coating layer is the main reason that deteriorates the boiling heat transfer rates of nanofluids. An empirical correlation was proposed for predicting the CHF of nanofluids boiling in the vertical tubes with closed bottom.

Lun-Chun, Lv; Zhen-Hua, Liu

2008-11-01

50

Strategic optimization of large-scale vertical closed-loop shallow geothermal systems  

NASA Astrophysics Data System (ADS)

Vertical closed-loop geothermal systems or ground source heat pump (GSHP) systems with multiple vertical borehole heat exchangers (BHEs) are attractive technologies that provide heating and cooling to large facilities such as hotels, schools, big office buildings or district heating systems. Currently, the worldwide number of installed systems shows a recurrent increase. By running arrays of multiple BHEs, the energy demand of a given facility is fulfilled by exchanging heat with the ground. Due to practical and technical reasons, square arrays of the BHEs are commonly used and the total energy extraction from the subsurface is accomplished by an equal operation of each BHE. Moreover, standard designing practices disregard the presence of groundwater flow. We present a simulation-optimization approach that is able to regulate the individual operation of multiple BHEs, depending on the given hydro-geothermal conditions. The developed approach optimizes the overall performance of the geothermal system while mitigating the environmental impact. As an example, a synthetic case with a geothermal system using 25 BHEs for supplying a seasonal heating energy demand is defined. The optimization approach is evaluated for finding optimal energy extractions for 15 scenarios with different specific constant groundwater flow velocities. Ground temperature development is simulated using the optimal energy extractions and contrasted against standard application. It is demonstrated that optimized systems always level the ground temperature distribution and generate smaller subsurface temperature changes than non-optimized ones. Mean underground temperature changes within the studied BHE field are between 13% and 24% smaller when the optimized system is used. By applying the optimized energy extraction patterns, the temperature of the heat carrier fluid in the BHE, which controls the overall performance of the system, can also be raised by more than 1 °C.

Hecht-Méndez, J.; de Paly, M.; Beck, M.; Blum, P.; Bayer, P.

2012-04-01

51

An analogue of the prime number theorem for closed orbits of shifts of finite type and their suspensions  

Microsoft Academic Search

Following the classical procedure developed by Wiener and Ikehara for the proof of the prime number theorem we find an asymptotic\\u000a formula for the number of closed orbits of a suspension of a shift of finite type when the suspended flow is topologically\\u000a weak-mixing and when the suspending function is locally constant.

William Parry

1983-01-01

52

Tidal evolution of close-in exoplanets in co-orbital configurations  

NASA Astrophysics Data System (ADS)

In this paper, we study the behavior of a pair of co-orbital planets, both orbiting a central star on the same plane and undergoing tidal interactions. Our goal is to investigate final orbital configurations of the planets, initially involved in the 1/1 mean-motion resonance (MMR), after long-lasting tidal evolution. The study is done in the form of purely numerical simulations of the exact equations of motions accounting for gravitational and tidal forces. The results obtained show that, at least for equal mass planets, the combined effects of the resonant and tidal interactions provoke the orbital instability of the system, often resulting in collision between the planets. We first discuss the case of two hot-super-Earth planets, whose orbital dynamics can be easily understood in the frame of our semi-analytical model of the 1/1 MMR. Systems consisting of two hot-Saturn planets are also briefly discussed.

Rodríguez, Adrián; Giuppone, Cristian A.; Michtchenko, Tatiana A.

2013-09-01

53

Orbital  

NASA Astrophysics Data System (ADS)

ORBITAL requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime Plug-in, version compatible with your OS and browser (available from MDL).

Hanson, Robert M.

2003-06-01

54

Orbital Disturbance Analysis due to the Lunar Gravitational Potential and Deviation Minimization through the Trajectory Control in Closed Loop  

NASA Astrophysics Data System (ADS)

A study evaluating the influence due to the lunar gravitational potential, modeled by spherical harmonics, on the gravity acceleration is accomplished according to the model presented in Konopliv (2001). This model provides the components x, y and z for the gravity acceleration at each moment of time along the artificial satellite orbit and it enables to consider the spherical harmonic degree and order up to100. Through a comparison between the gravity acceleration from a central field and the gravity acceleration provided by Konopliv's model, it is obtained the disturbing velocity increment applied to the vehicle. Then, through the inverse problem, the Keplerian elements of perturbed orbit of the satellite are calculated allowing the orbital motion analysis. Transfer maneuvers and orbital correction of lunar satellites are simulated considering the disturbance due to non-uniform gravitational potential of the Moon, utilizing continuous thrust and trajectory control in closed loop. The simulations are performed using the Spacecraft Trajectory Simulator-STRS, Rocco (2008), which evaluate the behavior of the orbital elements, fuel consumption and thrust applied to the satellite over the time.

Gonçalves, L. D.; Rocco, E. M.; de Moraes, R. V.

2013-10-01

55

Spin-orbit coupling induced spin-transfer torque and current polarization in topological-insulator/ferromagnet vertical heterostructures.  

PubMed

We predict an unconventional spin-transfer torque (STT) acting on the magnetization of a free ferromagnetic (F) layer within N/TI/F vertical heterostructures, which originates from strong spin-orbit coupling on the surface of a three-dimensional topological insulator (TI), as well as from charge current becoming spin polarized in the direction of transport as it flows perpendicularly from the normal metal (N) across the bulk of the TI layer. The STT vector has both in-plane and perpendicular components that are comparable in magnitude to conventional torque in F'/I/F (where I stands for insulator) magnetic tunnel junctions, while not requiring additional spin-polarizing F' layer with fixed magnetization, which makes it advantageous for spintronics applications. Our principal formal result is a derivation of the nonequilibrium Green function-based formula and the corresponding gauge-invariant nonequilibrium density matrix, which makes it possible to analyze the components of the STT vector in the presence of arbitrary strong spin-orbit coupling either in the bulk or at the interface of the free F layer. PMID:23215105

Mahfouzi, Farzad; Nagaosa, Naoto; Nikoli?, Branislav K

2012-10-17

56

Low Earth orbit satellite navigation errors and vertical total electron content in single-frequency GPS tracking  

NASA Astrophysics Data System (ADS)

In the context of space applications, the GPS system is presently a well-established and accepted tracking system. To meet the basic navigation requirements, most satellites in a low Earth orbit are equipped with single-frequency GPS receivers that measure the coarse acquisition code as well as the L1 phase. However, the resulting kinematic navigation solutions exhibit systematic position errors caused by elevation-dependent ionospheric path delays. In this study a simple analytical model is established, which quantitatively relates the position error to the vertical electron content and the mapping function. This model substantiates the empirical evidence of a mean radial offset that increases in proportion to the total electron content above the satellite. It is furthermore shown that the ratio between this offset and the vertical ionospheric path delay depends on the applied elevation mask angle. Representative ratios of 3-5 are obtained for the mapping function of the Lear ionosphere model and elevation cutoff angles of 10°, 5°, and 0°. This analytical result has further been confirmed by signal simulator tests as well as flight data of the CHAMP satellite.

Garcia-Fernã Ndez, Miquel; Montenbruck, Oliver

2006-10-01

57

Dynamical tides excited in rotating stars of different masses and ages and the formation of close in orbits  

NASA Astrophysics Data System (ADS)

We study the tidal response of rotating solar-mass stars, as well as more massive rotating stars, of different ages in the context of tidal captures leading to either giant exoplanets on close in orbits, or the formation of binary systems in star clusters. To do this, we adopt approaches based on normal mode and associated overlap integral evaluation, developed in a companion paper by Ivanov et al., and direct numerical simulation, to evaluate energy and angular momentum exchanges between the orbit and normal modes. The two approaches are found to be in essential agreement apart from when encounters occur near to pseudo-synchronization, where the stellar angular velocity and the orbital angular velocity at periastron are approximately matched. We find that the strength of tidal interaction being expressed in dimensionless natural units is significantly weaker for the more massive stars, as compared to the solar-mass stars, because of the lack of significant convective envelopes in the former case. On the other hand, the interaction is found to be stronger for retrograde as opposed to prograde orbits in all cases. In addition, for a given pericentre distance, tidal interactions also strengthen for more evolved stars on account of their radial expansion. In agreement with previous work based on simplified polytropic models, we find that energy transferred to their central stars could play a significant role in the early stages of the circularization of potential `Hot Jupiters'.

Chernov, S. V.; Papaloizou, J. C. B.; Ivanov, P. B.

2013-09-01

58

CYCLIC VARIATIONS OF ORBITAL PERIOD AND LONG-TERM LUMINOSITY IN CLOSE BINARY RT ANDROMEDAE  

SciTech Connect

Solutions of standard VR light curves for the eclipsing binary RT And were obtained using the PHOEBE program (ver. 0.3a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass-luminosity diagram. Times of minima data ({sup O} - C curve) were analyzed using the method of Kalimeris et al. A cyclic variation in the orbital period and brightness, with timescales of about 11.89 and 12.50 yr were found, respectively. This is associated with a magnetic activity cycle modulating the orbital period of RT And via the Applegate mechanism. To check the consistency of the Applegate model, we have estimated some related parameters of the RT And system. The calculated parameters were in accordance with those estimated by Applegate for other similar systems, except B, the subsurface magnetic field of which shows a rather high value for RT And.

Manzoori, Davood [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)], E-mail: d.manzoori@uma.ac.ir

2009-12-15

59

[Response properties of the jaw--closing muscle spindle during decreased occlusal vertical dimension in rats].  

PubMed

The masseter-muscle spindle is regarded as being highly adaptable to increases in the occlusal vertical dimension (iOVD), it is hypothesized that spindle function would adapt to a decrease in occlusal vertical dimension (dOVD) as well. Seventy-five 5-week-old female Wistar rats were divided into Control (n = 25) and Experimental (n = 50) groups; those in the Experimental group received a 2.0-mm composite resin build-up to the maxillary molars. The Experimental group was divided into the resin-removal group (n = 25, build-up resin was removed) and the non resin-removal group (n = 25) 8 weeks later; i. e., when the animals were 13 weeks old. Electrophysiological recordings were obtained from masseter-muscle spindle afferents in 13, 14, 15, 19, 21-week-old rats (n = 5 rats each) under general anesthesia Masseter-muscle spindle sensitivity was significantly lower in the resin-removal group 1 week after resin-removal and for the rest of the observation period. The present results indicate that masseter-muscle spindles may not completely adapt to dOVD and may affect jaw function. PMID:18421946

Fujita, Koichi

2008-03-01

60

Frozen orbits for satellites close to an earth-like planet  

NASA Astrophysics Data System (ADS)

We say that a planet is Earth-like if the coefficient of the second order zonal harmonic dominates all other coefficients in the gravity field. This paper concerns the zonal problem for satellites around an Earth-like planet, all other perturbations excluded. The potential contains all zonal coefficients J2 through J9. The model problem is averaged over the mean anomaly by a Lie transformation to the second order; we produce the resulting Hamiltonian as a Fourier series in the argument of perigee whose coefficients are algebraic functions of the eccentricity - not truncated power series. We then proceed to a global exploration of the equilibria in the averaged problem. These singularities which aerospace engineers know by the name of frozen orbits are located by solving the equilibria equations in two ways, (1) analytically in the neighborhood of either the zero eccentricity or the critical inclination, and (2) numerically by a Newton-Raphson iteration applied to an approximate position read from the color map of the phase flow. The analytical solutions we supply in full to assist space engineers in designing survey missions. We pay special attention to the manner in which additional zonal coefficients affect the evolution of bifurcations we had traced earlier in the main problem (J2 only). In particular, we examine the manner in which the odd zonal J3 breaks the discrete symmetry inherent to the even zonal problem. In the even case, we find that Vinti's problem (J4 + J22 = 0) p resents a degeneracy in the form of non-isolated equilibria; we surmise that the degeneracy is a reflection of the fact that Vinti's problem is separable. By numerical continuation we have discovered three families of frozen orbits in the full zonal problem under consideration; (1) a family of stable equilibria starting from the equatorial plane and tending to the critical inclination; (2) an unstable family arising from the bifurcation at the critical inclination; (3) a stable family also arising from that bifurcation and terminating with a polar orbit. Except in the neighborhood of the critical inclination, orbits in the stable families have very small eccentricities, and are thus well suited for survey missions.

Coffey, Shannon L.; Deprit, Andre; Deprit, Etienne

1994-05-01

61

Triple close approach in the three-body problem - A limit for the bounded orbits  

NASA Astrophysics Data System (ADS)

The results of Sundman (1912) and Birkhoff (1927) are used together with studies on the generalized Hill's curves to develop a moment of inertia lower bound for bounded orbits in the general three-body problem. The values obtained by these means are higher than those classically derived; when the energy integral goes to zero, for instance, this lower bound goes to the minimum moment of inertia of the corresponding parabolic Euler motion having the same angular momentum. It then constitutes the greatest lower bound.

Laskar, J.; Marchal, C.

1984-01-01

62

Asteroseismology in action: a test of spin-orbit synchronism in the close binary system Feige 48  

NASA Astrophysics Data System (ADS)

Aims: In this paper, we provide a test of spin-orbit synchronism in the close binary system Feige 48. This system is made of a rapidly pulsating subdwarf B (sdB) star with an unseen companion, most likely a white dwarf. The presence of nonradial oscillations offers the opportunity to infer the inner profile and period of rotation of the primary star through asteroseismology. This constitutes the key element for testing spin-orbit synchronism in depth, since stellar internal layers are inaccessible to traditional techniques. Methods: We carried out a new asteroseismic analysis of Feige 48 following the so-called “forward modeling” approach. This is done with our latest optimization algorithms, which have been updated to incorporate the effect of stellar rotation on pulsations, assuming various internal rotation laws. In this analysis, the simultaneous match of all the frequencies observed in Feige 48 leads objectively to the full identification of the pulsation modes through the determination of the indices k, ?, m. It also leads to determining the structural and rotational parameters of Feige 48. Results: Our optimal model, obtained with a solid-body rotation law, is characterized by a spin period of 9.028 ± 0.480 h. This value is remarkably similar to the system's orbital period of 9.024 ± 0.072 h, measured independently from radial velocity variations. We further demonstrate that the hypothesis of differential rotation of the core - including a fast rotating core - must be eliminated for Feige 48. Conclusions: These results strongly imply that Feige 48 rotates as a solid body in a tidally locked system. This constitutes the first explicit demonstration of spin-orbit synchronism in a binary star by asteroseismic means.

Van Grootel, V.; Charpinet, S.; Fontaine, G.; Brassard, P.

2008-06-01

63

Stellar Wind Disruption by an Orbiting Neutron Star: Neutron Star Close-up  

NSDL National Science Digital Library

A tiny neutron star orbits incessantly around a massive star with a diameter a million times larger than its own. The high luminosity of the massive star drives a strong wind from its surface. The neutron star crashes through this wind at over 300 kilometers per second. The gravity and X-ray luminosity of the neutron star act to disrupt the wind, producing an extended wake of dense gas trailing behind the neutron star. The large scale structure seen in the accretion wake is powered by the release of gravitational potential energy near the surface of the neutron star. The numerical simulations depicted here were computed using the Cray X-MP 48 at the National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign.

Mcconnell, Alan; Blondin, John; Stevens, Ian; Kallman, Tim; Fryxell, Bruce; Taam, Ron

1990-07-10

64

[Morphological, microscopic changes in the thyroid gland in the cases of hanging in vertical position with open and closed noose].  

PubMed

The aim of the morphological study was to search for traumatic changes in the thyroid in the cases of hanging in a vertical position with an open and closed noose. These changes would constitute an additional proof of intravital hanging and they would be useful in postmortem diagnosis of the hangings in which other commonly acknowledged features of intravitality are not discovered. In 33% of all cases, petechiae were observed in the thyroid gland. They appeared in 20% of the hangings with the closed noose, and in 13% of the hangings with the use of the open noose. The study showed that there was no difference between the open or closed, hard noose in terms of changes in the thyroid gland. There was also no correlation between the body position and the injury of the thyroid gland. In all the cases, hyperemia of the thyroid was observed and segmental expansion of blood vessels. The histopathological analysis showed that in one third of all the cases with negative macroscopic examination, it was discovered that microscopic changes indicated hanging alive. PMID:22715676

Ok?ota, Magdalena; Niemcunowicz-Janica, Anna; Dziecio?, Janusz; Ptaszy?ska-Sarosiek, Iwona; Klim, Beata; Sackiewicz, Adam; Za?uski, Janusz; Szeremeta, Micha?

65

A comparison of several lattice tools for computation of orbit functions of an accelerator  

Microsoft Academic Search

The values of orbit functions for accelerator lattices as computed with accelerator design programs may differ between different programs. For a simple lattice, consisting of identical constant-gradient bending magnets, the functions (horizontal and vertical betatron tunes, dispersions, closed orbit offsets, orbit lengths, chromaticities etc.) can be evaluated analytically. This lattice was studied with the accelerator physics tools SYNCH (1), COSY

Ernest D. Courant; J. Scott Berg; Dejan Trbojevic; Richard Talman; A. A. Garren

2003-01-01

66

A COMPARISON OF SEVERAL LATTICE TOOLS FOR COMPUTATION OF ORBIT FUNCTIONS OF AN ACCELERATOR  

Microsoft Academic Search

The values of orbit functions for accelerator lattices as computed with accelerator design programs may differ between different programs. For a simple lattice, consisting of identical constant-gradient bending magnets, the functions (horizontal and vertical betatron tunes, dispersions, closed orbit offsets, orbit lengths, chromaticities etc.) can be evaluated analytically. This lattice was studied with the accelerator physics tools SYNCH [1], COSY

E. DTRBOJEVIC; D. BERG; S. J. GARREN; A. A. TALMAN

2003-01-01

67

WASP-24 b: A NEW TRANSITING CLOSE-IN HOT JUPITER ORBITING A LATE F-STAR  

SciTech Connect

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer an effective temperature T{sub eff} = 6075 {+-} 100 K and a surface gravity of log g = 4.15 {+-} 0.10. A comparison of these parameters with theoretical isochrones and evolutionary mass tracks places only weak constraints on the age of the host star, which we estimate to be 3.8{sup +1.3}{sub -1.2} Gyr. The planetary nature of the companion was confirmed by radial velocity measurements and additional photometric observations. These data were fit simultaneously in order to determine the most probable parameter set for the system, from which we infer a planetary mass of 1.071{sup +0.036}{sub -0.038} M {sub Jup} and radius 1.3{sup +0.039}{sub -0.037} R{sub Jup}.

Street, R. A.; Lister, T. A.; Depagne, E. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Simpson, E.; Barros, S. C. C.; Pollacco, D.; Joshi, Y.; Todd, I. [Astrophysics Research Centre, Physics Building, Queen's University, Belfast, County Antrim, BT7 1NN (United Kingdom); Collier Cameron, A.; Enoch, B.; Parley, N. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Stempels, E. [Department of Physics and Astronomy, P.O. Box 516, SE-751 20 Uppsala (Sweden); Hebb, L. [Physics and Astronomy Department, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Triaud, A. H. M. J.; Queloz, D.; Segransan, D.; Pepe, F.; Udry, S. [Observatoire Astronomique de l'Universite de Geneve, 51 Chemin des Maillettes, 1290 Sauverny (Switzerland); West, R. G. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Norton, A. J. [Department of Physics and Astronomy, The Open University, N2041, Venables Building, Milton Keynes, MK7 6AA (United Kingdom)

2010-09-01

68

Close Approaches of the trans--Neptunian Objects to Pluto Left Observable Signatures on Their Orbital Distribution  

Microsoft Academic Search

It is shown that in addition to four outer planets (Jupiter to Neptune) also Pluto should be taken into account in studies of the orbital dynamics in the trans--Neptunian region. Pluto effect is particularly large on the orbits in the 2:3 Neptune mean motion resonance. The trajectories found stable over the age of the solar system when only the gravitational

F. Roig; D. Nesvorny; S. Ferraz-Mello

1999-01-01

69

Close Approaches of Trans-Neptunian Objects to Pluto Have Left Observable Signatures on Their Orbital Distribution  

Microsoft Academic Search

It is shown that in addition to four outer planets (Jupiter to Neptune) Pluto should be also taken into account in studies of the orbital dynamics in the trans-Neptunian region. Pluto's effect is particularly large on the orbits in the 2:3 Neptune mean motion resonance. The trajectories found stable over the age of the solar system when only the gravitational

D. Nesvorný; F. Roig; S. Ferraz-Mello

2000-01-01

70

Atomic-orbital close-coupling calculations of charge exchange and ionisation in collisions of H(1s) and highly charged neon and argon ions  

NASA Astrophysics Data System (ADS)

Atomic-orbital close-coupling calculations of neon and argon ions colliding with H(1s) will be presented. The high principal quantum numbers n that need to be included in the expansion of the wavefunction of the active electron in the ion center make very large basis sets necessary. The resulting state resolved charge exchange and ionisation cross sections are of special interest for nuclear fusion research.

Igenbergs, Katharina; Wallerberger, Markus; Schweinzer, Josef; Aumayr, Friedrich

2012-11-01

71

Counter-Orbitals: Another Class of Co-Orbitals  

NASA Astrophysics Data System (ADS)

Co-orbital companions share the same orbital period and semi-major axis about a primary (star or planet). Heretofore there have been three recognized classes of co-orbitals: (1) Trojans librate in tadpole-shaped orbits about the equilateral Lagrange points L4 and L5, 60 degrees ahead of or behind the secondary (planet or satellite). (2) Horse-shoe companions librate about both L4 and L5, as well as the L3 Lagrange point diametrically opposite the secondary. (3) ``Quasi-satellites'' appear to be in distant retrograde orbits about the secondary, but actually are in prograde orbits about the primary with the same period as the secondary. Quasi-satellite orbits lie outside the secondary's Hill sphere, and enclose both L1 and L2, and sometimes L4 and L5 as well. In addition, some asteroids and comets are found in hybrid orbits which alternate among the above three classes, or combine some of their features. New research now reveals a fourth class of co-orbitals, which does not appear to be known before, and may be called ``counter-orbitals''. Imagine reversing the inertial velocity of a distant quasi-satellite. Then it remains in orbit about the primary, with the same period, semi-major axis, eccentricity, and orbital plane, although retrograde. But instead of remaining relatively close to the secondary, now it passes the secondary twice per orbit, near periapsis and apoapsis. The attractive impulses at these conjunctions tend to stabilize this arrangement. Numerical simulations of the general three-body problem verify that counter-orbitals can persist for over 10,000 orbits, with small vertical excursions, but a wide range of eccentricities and mass ratios. For example, Charon can maintain counter-orbital companions at least up to 3 percent of its own mass, in eccentric orbits extending from about 7050 km out to 41700 km from the center of Pluto. This may present a collision hazard to the New Horizons spacecraft.

Dobrovolskis, Anthony R.

2012-10-01

72

Atomic-orbital close-coupling calculations for collisions involving fusion relevant highly charged impurity ions using very large basis sets  

SciTech Connect

The atomic-orbital close-coupling formalism is a well-known method for the semiclassical treatment of ion-atom collisions. Cross sections for these kinds of collisions are mainly needed in the analysis of certain spectroscopic data from nuclear fusion experiments as well as astrophysical data. We shall outline how the computational implementation can be improved in such a way that collisions involving heavy, highly charged impurity ions, such as Ar{sup 18+} can be treated. Furthermore we show and discuss exemplary results.

Igenbergs, Katharina; Wallerberger, Markus; Schweinzer, Josef; Aumayr, Friedrich [Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstr.8-10/134, A-1040 Vienna (Austria); Max-Planck-Institute of Plasma Physics, Boltzmannstr.2, D-85748 Garching (Germany); Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstr.8-10/134, A-1040 Vienna (Austria)

2012-05-25

73

Vertical stratification of ° 13 C values in closed natural and plantation forests in the Luquillo mountains, Puerto Rico  

Microsoft Academic Search

The variability of d13C values was measured in leaf, stem and root tissues of several tree species growing in closed natural and plantation forests in the Luquillo mountains of Puerto Rico. Results confirm a significant decrease of d13C values from the tree canopy to the forest floor. The values measured in understory plants growing in gaps were not significantly different

Ernesto Medina; Leonel Sternberg; Elvira Cuevas

1991-01-01

74

Technical Note: One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India - Seasonal characteristics of the aerosol vertical structure  

NASA Astrophysics Data System (ADS)

One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analysed. The data was split into four seasons: spring (March-May), summer (June-August), autumn (September-November) and winter (December-February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1-3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm-1 sr-1 and 142 Mm-1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared to other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.

Komppula, M.; Mielonen, T.; Arola, A.; Korhonen, K.; Lihavainen, H.; Hyvärinen, A.-P.; Baars, H.; Engelmann, R.; Althausen, D.; Ansmann, A.; Müller, D.; Panwar, T. S.; Hooda, R. K.; Sharma, V. P.; Kerminen, V.-M.; Lehtinen, K. E. J.; Viisanen, Y.

2012-05-01

75

Global and local horizontal-vertical decoupling  

SciTech Connect

In this paper the author investigated systematically the global and local effects of horizontal-vertical couplings on the beam and the measurement and control of these couplings. Piecemeal studies have been made on these subjects by different authors. For completeness, their results are integrated here wherever appropriate. This brings the understanding and execution of the coupling correction to the same degree of completeness as that of the closed orbit correction.

Teng, L.C. [Argonne National Lab., IL (United States). Advanced Photon Source

1997-06-01

76

Natural convection mass transfer at a vertical array of closely-spaced horizontal cylinders with special reference to electrochemical reactor design  

SciTech Connect

Many industrial electrochemical processes such as electrowinning of metals, electrochemical pollution control, and electroorganic and electroinorganic syntheses are diffusion-controlled processes whose rates depend on the geometry of the working electrode as well as the prevailing hydrodynamic conditions. Recently much work has been done to develop new electrochemical reactors which are more efficient than the traditional parallel plate electrochemical reactor used in conducting such processes. In line with this, the object of the present work was to study the natural convection mass transfer behavior of a new electrode geometry, namely an array of closely-spaced horizontal tubes. Natural convection mass transfer at a vertical array of closely-spaced horizontal cylinders was studied by an electrochemical technique involving the measurement of the limiting current of the cathodic deposition of copper from acidified copper sulfate solution. Various combinations of solution concentration, cylinder diameter, and number of cylinders per array were used including experiments on single cylinders. The mass transfer coefficient at the array was found to decrease with increasing number of cylinders, pass through a minimum, and then increase with further increase in the number of cylinders per array; the mass transfer coefficient increased with increasing cylinder diameter in the array. Mass transfer data for different arrays were correlated for the range 6.3 {times} 10{sup 9} < ScGr < 3.63 {times} 10{sup 10} by the equation Sh = 0.455(ScGr){sup 0.25} and for the range 6.3 {times} 10{sup 10} < ScGr < 3.63 {times} 10{sup 12} by the equation Sh = 0.0064(ScGr){sup 0.42}. The characteristic length used in the above correlations was obtained by dividing the array area by the perimeter projected onto a horizontal plane. Practical implications of the present results in designing electrochemical reactors with heat transfer facilities are highlighted.

Sedahmed, G.H.; Nirdosh, I. [Lakehead Univ., Thunder Bay, Ontario (Canada)

1995-06-01

77

Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties  

NASA Astrophysics Data System (ADS)

Context. To date, more than 30 planets have been discovered around giant stars, but only one of them has been found to be orbiting within 0.6 AU from the host star, in direct contrast to what is observed for FGK dwarfs. This result suggests that evolved stars destroy/engulf close-in planets during the red giant phase. Aims: We are conducting a radial velocity survey of 164 bright G and K giant stars in the southern hemisphere with the aim of studying the effect of the host star evolution on the inner structure of planetary systems. In this paper we present the spectroscopic atmospheric parameters (Teff, log g, ?, [Fe/H]) and the physical properties (mass, radius, evolutionary status) of the program stars. In addition, rotational velocities for all of our targets were derived. Methods: We used high resolution and high S/N spectra to measure the equivalent widths of many Fe i and Fe ii lines, which were used to derive the atmospheric parameters by imposing local thermodynamic and ionization equilibrium. The effective temperatures and metallicities were used, along with stellar evolutionary tracks to determine the physical properties and evolutionary status of each star. Results: We found that our targets are on average metal rich and they have masses between ~1.0 M? and 3.5 M?. In addition, we found that 122 of our targets are ascending the RGB, while 42 of them are on the HB phase. Based on observations collected at La Silla - Paranal Observatory under programs ID's 085.C-0557 and 087.C.0476.Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/536/A71

Jones, M. I.; Jenkins, J. S.; Rojo, P.; Melo, C. H. F.

2011-12-01

78

The TIROS-N Operational Vertical Sounder.  

National Technical Information Service (NTIS)

TIROS-N is the first of a new series of operational polar-orbiting meteorological satellites. Aboard each spacecraft is a third-generation complement of vertical sounding instruments capable of providing complete global coverage of vertical temperature da...

W. L. Smith H. M. Woolf C. M. Hayden D. W. Wark L. M. McMillin

1979-01-01

79

The Roche Limit for Close-orbiting Planets: Minimum Density, Composition Constraints, and Application to the 4.2 hr Planet KOI 1843.03  

NASA Astrophysics Data System (ADS)

The requirement that a planet must orbit outside of its Roche limit gives a lower limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly identified class of small planets with periods shorter than half a day. When the planet's radius is accurately known, this lower limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, a 0.6 R ? planet with the shortest known orbital period of 4.245 hr, the planet's mean density must be >~ 7 g cm-3. By modeling the planetary interior subject to this constraint, we find that the composition of the planet must be mostly iron, with at most a modest fraction of silicates (lsim 30% by mass).

Rappaport, Saul; Sanchis-Ojeda, Roberto; Rogers, Leslie A.; Levine, Alan; Winn, Joshua N.

2013-08-01

80

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

81

Interaction of Close-in Planets with the Magnetosphere of Their Host Stars. II. Super-Earths as Unipolar Inductors and Their Orbital Evolution  

NASA Astrophysics Data System (ADS)

Planets with several Earth masses and orbital periods of a few days have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, an important evolution issue is the efficiency of their retention in the proximity of their host stars. If these "super-Earths" attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction of these planets would have encountered an intense stellar magnetic field. These rocky planets have a higher conductivity than the atmosphere of their host stars and, therefore, the magnetic flux tube connecting them would slip though the envelope of the host stars faster than across the planets. The induced electromotive force across the planet's diameter leads to a potential drop which propagates along a flux tube away from the planet with an Alfvén speed. The foot of the flux tube would sweep across the stellar surface and the potential drop across the field lines drives a DC current analogous to that proposed for the electrodynamics of the Io-Jupiter system. The ohmic dissipation of this current produces potentially observable hot spots in the star envelope. It also heats the planet and leads to a torque which drives the planet's orbit to evolve toward both circularization and a state of synchronization with the spin of the star. The net effect is the damping of the planet's orbital eccentricity. Around slowly (or rapidly) spinning stars, this process also causes rocky planets with periods less than a few days to undergo orbital decay (or expansion/stagnation) within a few Myr. In principle, this effect can determine the retention efficiency of short-period hot Earths. We also estimate the ohmic dissipation interior to these planets and show that it can lead to severe structure evolution and potential loss of volatile material in them. However, these effects may be significantly weakened by the reconnection of the induced field.

Laine, Randy O.; Lin, Douglas N. C.

2012-01-01

82

Observable properties of orbits in exact bumpy spacetimes  

SciTech Connect

We explore the properties of test-particle orbits in bumpy spacetimes--stationary, reflection-symmetric, asymptotically flat solutions of Einstein equations that have a non-Kerr (anomalous) higher-order multipole-moment structure but can be tuned arbitrarily close to the Kerr metric. Future detectors should observe gravitational waves generated during inspirals of compact objects into supermassive central bodies. If the central body deviates from the Kerr metric, this will manifest itself in the emitted waves. Here, we explore some of the features of orbits in non-Kerr spacetimes that might lead to observable signatures. As a basis for this analysis, we use a family of exact solutions proposed by Manko and Novikov which deviate from the Kerr metric in the quadrupole and higher moments, but we also compare our results to other work in the literature. We examine isolating integrals of the orbits and find that the majority of geodesic orbits have an approximate fourth constant of the motion (in addition to the energy, angular momentum, and rest mass) and the resulting orbits are triperiodic to high precision. We also find that this fourth integral can be lost for certain orbits in some oblately deformed Manko-Novikov spacetimes, leading to ergodic motion. However, compact objects will probably not end up on these chaotic orbits in nature. We compute the location of the innermost stable circular orbit (ISCO) and find that the behavior of an orbit in the approach to the ISCO can be qualitatively different depending on whether the location of the ISCO is determined by the onset of an instability in the radial or vertical direction. Finally, we compute periapsis and orbital-plane precessions for nearly circular and nearly equatorial orbits in both the strong and weak field, and discuss weak-field precessions for eccentric equatorial orbits.

Gair, Jonathan R.; Li Chao; Mandel, Ilya [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 (United States)

2008-01-15

83

A COMPARISON OF SEVERAL LATTICE TOOLS FOR COMPUTATION OF ORBIT FUNCTIONS OF AN ACCELERATOR  

SciTech Connect

The values of orbit functions for accelerator lattices as computed with accelerator design programs may differ between different programs. For a simple lattice, consisting of identical constant-gradient bending magnets, the functions (horizontal and vertical betatron tunes, dispersions, closed orbit offsets, orbit lengths, chromaticities etc.) can be evaluated analytically. This lattice was studied with the accelerator physics tools SYNCH [1], COSY INFINITY [2], MAD [3], and TEAPOT [4]. It was found that while all the programs give identical results at the central design momentum, the results differ substantially among the various lattice tools for non-zero momentum deviations. Detailed results and comparisons are presented.

COURANT, E.DTRBOJEVIC,D.BERG,S.J.GARREN,A.A.TALMAN, R.

2003-05-12

84

Commissioning and Performance of the APS Real-Time Orbit Feedback System  

Microsoft Academic Search

The Advanced Photon Source (APS) is implementing a unified global and local closed orbit feedback system to stabilize both particle and photon beams. Beam stability requirements in the band up to 50Hz are 17mum in the horizontal plane and 4.5mum in the vertical plane. The global system is designed for a closed loop bandwidth of 100Hz. Feedback algorithms are implemented

J. Carwardine; G. Decker; K. Evans Jr.; A. Hillman; F. Lenkzsus; R. Merl; A. Pietryla

1997-01-01

85

Vertical mammaplasty.  

PubMed

Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques. PMID:15793463

Hidalgo, David A

2005-04-01

86

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals website is a distribution point for the orbital image generating program "Orbital Viewer" as well as the home of a collection of images generated with the program. Atomic and molecular orbitals are constructed. For atoms, the hydrogenic solution, up to n=30, is generated and for molecules the linear combination of atomic orbitals method is used.

Manthey, David

2009-03-24

87

Motion of dust in a planetary magnetosphere - Orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn's E ring  

Microsoft Academic Search

The orbital dynamics of micrometer-sized dust grains is explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force. The appropriate orbit-average equations are derived and applied to the E ring. Arguments are made for the existence of azimuthal and vertical asymmetries in the E ring. New understanding

D. P. Hamilton

1993-01-01

88

Orbits Around Black Holes in Triaxial Nuclei  

Microsoft Academic Search

We discuss the properties of orbits within the influence sphere of a supermassive black hole (BH), in the case that the surrounding star cluster is non-axisymmetric. There are four major orbit families; one of these, the pyramid orbits, have the interesting property that they can approach arbitrarily closely to the BH. We derive the orbit-averaged equations of motion and show

David Merritt; Eugene Vasiliev

2011-01-01

89

Examination of trajectories between low planetary orbits and circulation orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft (CASTLE) in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows an optimal three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by. Examining the parameters of the situation produces a Delta V profile for each planetary fly-by of the circulating orbit.

Knoedler, Andrew J.

90

An orbit fit program for localizing errors in RHIC  

SciTech Connect

Many errors in an accelerator are evidenced as transverse kicks to the beam which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this note, we introduce an algorithm for fitting the orbit based on an on-line optics model. By comparing the measured and fitted orbits, we first present results validating the algorithm. We then apply the algorithm and localize the location of the elusive source of vertical diurnal variations observed in RHIC. The difference of two trajectories (linear accelerator) or closed orbits (storage ring) should match exactly a betatron oscillation, which is predictable by the optics model, in an ideal machine. However, in the presence of errors, the measured trajectory deviates from prediction since the model is imperfect. Comparison of measurement to model can be used to detect such errors. To do so the initial conditions (phase space parameters at any point) must be determined which can be done by comparing the difference orbit to prediction using only a few beam position monitors (BPMs). The fitted orbit can be propagated along the beam line based on the optics model. Measurement and model will agree up to the point of an error. The error source can be better localized by additionally fitting the difference orbit using downstream BPMs and back-propagating the solution. If one dominating error source exist in the machine, the fitted orbit will deviate from the difference orbit at the same point.

Liu, C.; Minty, M.; Ptitsyn, V.

2011-11-01

91

Vertical Separation  

Microsoft Academic Search

A simple duopoly model is used to show the advantage to a manufacturer of se lling his product through an independent retailer (vertical separatio n) rather than directly to consumers (vertical integration). Vertical separation is profitable insofar as it induces more friendly behavio r from the rival manufacturer. The authors consider the case where fr anchise fees can be used

Giacomo Bonanno; John Vickers

1988-01-01

92

Circulant Orbitals for Atoms and Molecules  

Microsoft Academic Search

Circulant orbitals phi n for a closed-shell system are the orbitals obtained when the N canonical orthonormal Hartree-Fock orbitals lambda ell are subjected to a unitary transformation which is the discrete Fourier transformation. phi n=1\\/sqrt{N}sumelllambda ellomega (n-1)(ell -1), where omega =exp (2pi i\\/N). Electron densities associated with the orbitals phi n are each close to the average total electron density.

Robert G. Parr; Min-Bo Chen

1981-01-01

93

Optimal periodic relative orbit and rectilinear relative orbits with eccentric reference orbits  

NASA Astrophysics Data System (ADS)

The problem of two-body linearized periodic relative orbits with eccentric reference orbits is studied in this paper. The periodic relative orbit in the target-orbital coordinate system can be used in fly-around and formation-flying orbit design. Based on the closed-form solutions to the Tschauner-Hempel equations, the initial condition for periodic relative orbits is obtained. Then the minimum-fuel periodic-orbit condition with a single impulse is analytically derived for given initial position and velocity vectors. When considering the initial coasting time, the impulse position of the global minimum-fuel periodic orbit is proved to be near to the perigee of the target and can be obtained by numerical optimization algorithms. Moreover, the condition for a special periodic orbit, i.e., the rectilinear relative orbit in the target-orbital frame, is obtained. Numerical simulations are used to demonstrate the efficacy of the method, and show the geometry of the periodic relative orbit and the rectilinear relative orbit.

Zhang, Gang; Zhou, Di; Sun, Zhaowei; Cao, Xibin

2013-10-01

94

Model Calibration and Optics Correction Using Orbit Response Matrix in the Fermilab Booster  

SciTech Connect

We have calibrated the lattice model and measured the beta and dispersion functions in Fermilab's fast-ramping Booster synchrotron using the Linear Optics from Closed Orbit (LOCO) method. We used the calibrated model to implement ramped coupling, dispersion, and beta-beating corrections throughout the acceleration cycle, reducing horizontal beta beating from its initial magnitude of {approx}30% to {approx}10%, and essentially eliminating vertical beta-beating and transverse coupling.

Lebedev, V.A.; Prebys, E.; /Fermilab; Petrenko, A.V.; /Novosibirsk, IYF; Kopp, S.E.; McAteer, M.J.; /Texas U.

2012-05-01

95

On triangulated orbit categories  

Microsoft Academic Search

We show that the category of orbits of the bounded derived category of a hereditary category under a well-behaved autoequivalence is canonically triangulated. This answers a question by A. Buan, R. Marsh and I. Reiten which appeared in their study with M. Reineke and G. Todorov of the link between tilting theory and cluster algebras (closely related to work by

Bernhard Keller

2005-01-01

96

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

2007-06-05

97

Closed head injury.  

PubMed

Closed head injuries vary from the very minor to the catastrophic. It is often difficult to differentiate the severity at initial presentation. Serial assessment is very valuable. Awareness of facial injuries is aided by familiarity with facial bone anatomy and the clinical presentation of orbital, zygomatic, maxillary, and mandibular fracture. Functional injury such as concussion may coexist with other injuries. This article will discuss closed head trauma and outline specific injuries to the face, brain, skull, and its surroundings. PMID:23522509

Kerr, Hamish A

2013-02-08

98

Orbital Dynamics  

NSDL National Science Digital Library

This video from SpaceTEC National Aerospace Technical Education Center explains the mechanics of orbital dynamics and Newton's first law of motion. This three minute video is one of the aerospace certification readiness courses.

2011-07-27

99

Close triple star systems  

Microsoft Academic Search

Triple-star systems, especially those in which one star has very small mass, are examined. Observations that provide information about the physical nature of close systems, in particular, changes of the period of orbital revolution, are discussed. It is shown that the detection and study of these changes is best obtained by observations of the precise times of light minima in

F. B. Wood

1985-01-01

100

Arenstorf Orbit JS Model  

NSDL National Science Digital Library

Arenstorf orbits are closed trajectories of the restricted three-body problem. That is, two bodies of masses µ and 1-µ moving in a circular rotation, and a third body of negligible mass moving in the same plane. The computation of these orbits is very sensible to small errors and are a good test for the accuracy of numerical methods for solving Ordinary Differential Equations. This simulation compares the solution of two of these orbits using both a 4th-order fixed step and a 5(4) variable step Runge-Kutta algorithm. The adaptive solver uses an event to find the period of the orbit and stop there. Both the computations of the adaptive solver and the event are done with the step size and the tolerance indicated. The Arenstorf Orbit JS Model was developed using the Easy Java Simulations (Ejs) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

Franciscouembre

2013-08-28

101

Orbital YORP and asteroid orbit evolution, with application to Apophis  

NASA Astrophysics Data System (ADS)

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north-south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky-O'Keefe-Radzievskii-Paddack), operates even in the absence of thermal inertia, which the Yarkovsky effects require. However, unlike the Yarkovsky effects, which produce secular orbital changes over millions or billions of years, the change in an asteroid's orbital elements from orbital YORP operates only over the precession timescale of the orbit or of the asteroid's spin axis; this is generally only thousands or tens of thousands of years. Thus while the orbital YORP timescale is too short for an asteroid to secularly journey very far, it is long enough to warrant investigation with respect to 99942 Apophis, which might conceivably impact the Earth in 2036. A near-maximal orbital YORP effect is found by assuming Apophis is without thermal inertia and is shaped like a hemisphere, with its spin axis lying in the orbital plane. With these assumptions orbital YORP can change its along-track position by up to ±245 km, which is comparable to Yarkovsky effects. Though Apophis' shape, thermal properties, and spin axis orientation are currently unknown, the practical upper and lower limits are liable to be much less than the ±245 km extremes. Even so, the uncertainty in position is still likely to be much larger than the ˜0.5 km "keyhole" Apophis must pass through during its close approach in 2029 in order to strike the Earth in 2036.

Rubincam, David Parry

2007-12-01

102

Determining satellite close approaches  

NASA Astrophysics Data System (ADS)

This paper presents a numerical method to evaluate close approaches of two satellites. The algorithm is based on a space curve modeling technique originally developed by Overhauser, presented here as an independent derivation. The method to determine minimum spacing between two space objects is based on creating a relative distance waveform, delta(t), versus time. The waveform is produced from either uniform or arbitrarily spaced data points, from which intervals of close approach are obtained by extracting the real roots of a localized cubic polynomial. This method is free of both transcendental equations and the computation of acceleration terms of the two objects of interest. For this study, a close approach truth table is constructed using a 0.1 second sequential step along the orbits, then differencing the two position vectors. The close approach entrance and exit times for an ellipsoidal quadric surface are then located using a piecewise linear interpolator, and serve as a benchmark for comparison. The simulation results show this algorithm produces encounter times almost identical to those in the truth table, with a 99.84 percent reduction in computer runtime. The results, created from real orbital data, include solution sets for three operational uses of close-approach logic. For this study, satellite orbital motion is modeled using first-order secular perturbations caused by mass anomalies.

Alfano, Salvatore; Negron, David, Jr.

1993-06-01

103

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

104

Orbital pseudotumor.  

PubMed

Orbital pseudotumor is a benign condition that accounts for approximately 10% of all orbital mass lesions. Any part of the orbit may be involved. The etiology is unknown. The presentation may be either acute or subacute. Patients may present with a palpable mass, a swollen eyelid, congestion, pain, diminished ocular motility, and/or decreased visual acuity. Approximately, 25% of patients present with bilateral disease. A modest proportion of patients experience resolution of their symptoms without treatment. Biopsy is indicated for those who do not respond to, or relapse after, first-line therapy. Oral corticosteroids are the initial treatment and approximately 80% of patients respond. Roughly half of those who respond to corticosteroids relapse. Second-line therapy consists of either low-dose radiotherapy (20-30 Gy at 2 Gy per fraction), cytotoxic chemotherapy, or immunosuppressive agents. Radiotherapy results in long-term local control rates of 50% or higher. Limited lesions may be successfully resected. A small subset of patients may experience inexorable progression to a fixed, painful, sightless eye and require orbital exenteration. PMID:19738455

Mendenhall, William M; Lessner, Alan M

2010-06-01

105

Nuclear orbiting  

SciTech Connect

Nuclear orbiting following collisions between sd and p shell nuclei is discussed. The dependence of this process on the real and imaginary parts of the nucleus-nucleus potential is discussed, as well as the evolution of the dinucleus toward a fully equilibrated fused system. 26 refs., 15 figs.

Shapira, D.

1988-01-01

106

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

107

Dependence of the electronic effects of substituents in. pi. systems on the character of the. pi. -molecular orbitals. XII. Description of the vertical ionization potentials of substituted ethylenes and acetylenes  

SciTech Connect

It is shown that the vertical ionization potentials of ethylene and acetylene derivatives with substituents of the +M and -M type can be described in terms of the LCFO-MO method and by means of the parameters obtained form the ionization potentials of monosubstituted benzenes.

Koptyug, V.A.; Salakhutdinov, N.F.

1987-12-10

108

Orbital Dzyaloshinskii-Moriya exchange interaction  

NASA Astrophysics Data System (ADS)

A superexchange calculation is performed for multiorbital band models with broken inversion symmetry. Orbital-changing hopping terms allowed by the symmetry-breaking electric field lead to a new kind of orbital exchange interaction closely resembling the Dzyaloshinskii-Moriya spin exchange. Inversion symmetry breaking as present in surfaces and interfaces and a strong on-site repulsion, but not the spin-orbit interaction, are the requirements to observe the proposed effect. The mean-field phase diagram exhibits a rich structure including anti-ferro-orbital, ferro-orbital, and both single and multiple spiral-orbital phases, in close analogy with the Skyrmion spin crystal phase recently discovered in thin-film chiral magnets.

Kim, Panjin; Han, Jung Hoon

2013-05-01

109

Study of Abnormal Vertical Emittance Growth in ATF Extraction Line  

SciTech Connect

Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This longstanding problem has motivated studies of possible sources of this anomalous emittance growth. One possible contribution is non-linear magnetic fields in the extraction region experimented by the beam while passing off-axis through magnets of the DR during the extraction process. In this paper, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.

Alabau, M.; Faus-Golfe, A.; /Valencia U., IFIC; Alabau, M.; Bambade, P.; Brossard, J.; Le Meur, G.; Rimbault, C.; Touze, F.; /Orsay, LAL; Angal-Kalinin, D.; Jones, J.K.; /Daresbury; Appleby, R.; Scarfe, A.; /Manchester U.; Kuroda, S.; /KEK, Tsukuba; White, G.R.; Woodley, M.; /SLAC; Zimmermann, F.; /CERN

2011-11-04

110

Orbit analysis  

SciTech Connect

The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.

Michelotti, L.

1995-01-01

111

Europa Planetary Protection for Juno Jupiter Orbiter  

Microsoft Academic Search

NASA's Juno mission will launch in 2011 and explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the gravitational fields, magnetic fields, and auroral regions and its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close

Douglas Bernard; Robert Abelson; Jennie Johannesen; Try Lam; William McAlpine; Laura Newlin

2010-01-01

112

The higher excited electronic states and spin–orbit splitting of the valence band in three-dimensional assemblies of close-packed ZnSe and CdSe quantum dots in thin film form  

Microsoft Academic Search

Optical properties of as-deposited and annealed thin films composed of three-dimensional arrays of sphalerite-type ZnSe and CdSe quantum dots (QDs), synthesized by chemical deposition, were investigated. Neglecting the S–D mixing of hole states, the lowest “band to band” transitions in very small nanoclusters and in bulk-like clusters may be assigned as 1S?1S and 1S??1S, and are split by spin–orbit (SO)

Biljana Pejova; Biljana

2008-01-01

113

Vertical structure of debris discs  

NASA Astrophysics Data System (ADS)

Context: The vertical thickness of debris discs is often used as a measure of these systems' dynamical excitation, and as clues to the presence of hidden massive perturbers such as planetary embryos. However, this argument might be flawed because the observed dust should be naturally placed on inclined orbits by the combined effect of radiation pressure and mutual collisions. Aims: We critically reinvestigate this issue and numerically estimate the “natural” vertical thickness of a collisionally evolving disc, in the absence of any additional perturbing body. Methods: We use a deterministic collisional code, to follow the dynamical evolution of a population of indestructible test grains suffering mutual inelastic impacts. Grain differential sizes as well as the effect of radiation pressure are taken into account. Results: We find that, under the coupled effect of radiation pressure and collisions, grains naturally acquire inclinations of a few degrees. The disc is stratified with respect to grain sizes, the smallest grains having the largest vertical dispersion and the largest being clustered closer to the midplane. Conclusions: Debris discs should have a minimum “natural” observed aspect ratio hmin ~ 0.04±0.02 from visible to mid-IR wavelengths, where the flux is dominated by the smallest bound grains. These values are comparable to the estimated thicknesses of several vertically resolved debris discs, as illustrated by the specific example of AU Mic. For all systems with h ~ hmin, the presence (or absence) of embedded perturbing bodies cannot be inferred from the vertical dispersion of the disc.

Thébault, P.

2009-10-01

114

Advances in orbit drift correction in the advanced photon source storage ring  

SciTech Connect

The Advanced Photon Source storage ring is required to provide X-ray beams of high positional stability, specified as 17 {mu}m rms in the horizontal plane and 4.4 {mu}m rms in the vertical plane. The author reports on the difficult task of stabilizing the slow drift component of the orbit motion down to a few microns rms using workstation-based orbit correction. There are two aspects to consider separately the correction algorithm and the configuration of the beam position monitors (BPMs) and correctors. Three notable features of the correction algorithm are: low-pass digital filtering of BPM readbacks; {open_quotes}despiking{close_quotes} of the filtered orbit to desensitize the orbit correction to spurious BPM readbacks without having to change the correction matrix; and BPM intensity-dependent offset compensation. The BPM/corrector configuration includes all of the working BPMs but only a small set of correctors distributed around the ring. Thus only those orbit modes that are most likely to be representative of real beam drift are handled by the correction algorithm.

Emery, L.; Borland, M.

1997-06-01

115

Comparing gaseous and stellar orbits in a spiral potential  

NASA Astrophysics Data System (ADS)

It is generally assumed that gas in a galactic disc follows non-self-intersecting periodic stellar orbits closely. In order to test this common assumption, we have performed magnetohydrodynamics (MHD) simulations of a galactic-like disc under the influence of a spiral galactic potential. We have also calculated the actual orbit of a gas parcel and compared it to stable periodic stellar orbits in the same galactic potential and position. We found that the gaseous orbits approach periodic stellar orbits far from the major orbital resonances only. Gas orbits initialized at a given galactocentric distance but at different azimuths can be different, and scattering is conspicuous at certain galactocentric radii. Also, in contrast to the stellar behaviour, near the 4:1 (or higher order) resonance the gas follows nearly circular orbits, with much shorter radial excursions than the stars. Also, since the gas does not settle into a steady state, the gaseous orbits do not necessarily close on themselves.

Gómez, Gilberto C.; Pichardo, Bárbara; Martos, Marco A.

2013-04-01

116

Orbital and epicyclic frequencies of Maclaurin spheroids  

NASA Astrophysics Data System (ADS)

We present analytical formulae for the orbital and epicyclic frequencies in orbits around Maclaurin spheroids in Newtonian gravity. The Laplace equation for the gravitational potential implies that the orbital frequency squared is the arithmetic mean of the squares of the epicyclic frequencies, ? _r^2 + ? _z^2 = 2? _o^2. The radial epicyclic frequency has a maximum at radius r=?{2}ae for spheroid ellipticities e>1/?{2}, while for e = 0.834 583 18 it vanishes at the stellar equator (at r = a). For still larger ellipticities the innermost stable circular orbit (ISCO) is separated from the surface of the spheroid by a gap and has radius rms = 1.198 203 ae. The vertical epicyclic frequency is always larger than the orbital one, and always by a factor of ?{2} in the marginally stable orbit. The presence of periastron motion, nodal precession (whose sense is the same as in retrograde orbits in the Kerr metric) and of the ISCO makes the properties of orbital motion around Maclaurin spheroids analogous to those in the Kerr metric. We find that the condition for the existence of circular orbits in test-particle motion is ? _r^2 + ? _z^2 >0, equally for the Maclaurin spheroid and for the Kerr metric.

Klu?niak, W.; Rosi?ska, D.

2013-10-01

117

A Monte Carlo method for calculating orbits of comets  

Microsoft Academic Search

The present work is divided into two stages: 1. By using large numbers (several millions) of accurate orbit integrations with the K-S regularization, probability distributions for changes in the orbital elements of comets during encounters with planets are evaluated. 2. These distributions are used in a Monte Carlo simulation scheme which follows the evolution of orbits under repeated close encounters.

J. Q. Zheng; M. J. Valtonen; S. Mikkola; J. J. Matese; P. G. Whitman; H. Rickman

1994-01-01

118

ERS Orbit Control.  

National Technical Information Service (NTIS)

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; ove...

M. Rosengren

1991-01-01

119

RHIC BPM system average orbit calculations  

SciTech Connect

RHIC beam position monitor (BPM) system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation was developed just prior to the 2009 RHIC run and was made operational in March 2009. This paper discusses the new algorithm and performance with beam.

Michnoff,R.; Cerniglia, P.; Degen, C.; Hulsart, R.; et al.

2009-05-04

120

Geoscience Laser Altimeter System (GLAS) on the ICESat Mission: On-orbit measurement performance  

Microsoft Academic Search

The GLAS instrument on NASA's ICESat satellite has made over 904 million measurements of the Earth surface and atmosphere through June 2005. During its first seven operational campaigns it has vertically sampled the Earth's global surface and atmosphere on more than 3600 orbits with vertical resolutions approaching 3 cm. This paper summarizes the on-orbit measurement performance of GLAS to date.

James B. Abshire; Xiaoli Sun; Haris Riris; J. Marcos Sirota; Jan F. McGarry; Steve Palm; Donghui Yi; Peter Liiva

2005-01-01

121

Closing in on Close Reading  

ERIC Educational Resources Information Center

"A significant body of research links the close reading of complex text--whether the student is a struggling reader or advanced--to significant gains in reading proficiency and finds close reading to be a key component of college and career readiness" (Partnership for Assessment of Readiness for College and Careers, 2011, p. 7). When the author…

Boyles, Nancy

2013-01-01

122

Atmosphere and orbital stability of exosolar planets orbiting gamma Cephei  

Microsoft Academic Search

The recently discovered Jupiter-like planet (m sin i= 1.76 M_jup) in the binary system gamma Cephei moves in a so-called S-type orbit around its host-star with a distance of about 2.15 AU. It is the first planet that have been found in a close binary and is from the dynamical point of view a very stable configuration. Numerical computations in

H. Lammer; R. Dvorak; E. Pilat-Lohinger; B. Funk; F. Freistetter; I. Ribas; F. Selsis; E. F. Guinan; W. W. Weiss; S. J. Bauer

2003-01-01

123

Orbit Evolution in Common Envelopes  

NASA Astrophysics Data System (ADS)

We study how the inclination angle and eccentricity evolve during a common envelope phase. During a common envelope phase, a compact star is swallowed by its giant companion and spirals into a tighter orbit. A close binary results if the compact star releases enough energy to expel the envelope. We investigate possible fossil evidence of the common envelope phase on the inclination angle and the eccentricity. A convective common envelope leads to force component perpendicular to the orbital plane, and thus change the orbital inclination. This makes it harder to uniquely identify the signature of neutron star natal kicks. A common envelope is usually assumed to circularize orbits, but some eccentricity in fact arises both from the spiral-in process itself, and from random forces in the orbital plane. When the envelope is expelled, it might seem that the binary system would preserve whatever eccentricity had been established at the final stage of the inspiral. But tidal dissipation by the residual envelope can reduce the eccentricity. The final eccentricity depends on which of these effects wins or how they balance each other. We discuss applications and observational tests of these predictions.

Luan, Jing; Phinney, E. S.

2011-09-01

124

[Capabilities of physiotherapy for orbital trauma].  

PubMed

The article describes the results of conservative treatment of 78 patients with injuries of ocular adnexa (isolated fractures of orbital walls as well as cicatrical deformities of orbits and eyelids). Ophthalmological assessment was made both in the early and the late periods following blunt trauma. All patients underwent a standard assessment of functional ability of the eye and, additionally, an orbital computed tomography scan to characterize the fractures. In all cases physiotherapy (endonasal electrophoresis with proteolytic enzymes) was carried out to resolve the orbital hemorrhage. Binocular vision evaluation was done to control the effectiveness of the treatment. For that, the extent of diplopia in the central field and the total area of peripheral double vision were measured and the vertical edges of the diplopia zone were defined. PMID:24137981

125

Viking satellite orbit determination  

Microsoft Academic Search

During the summer of 1976, the two Viking spacecraft, each consisting of an orbiter-lander combination, were inserted into orbit about Mars. The paper describes the experiences of the Viking Satellite Orbit Determination Team in determining Mars centered ephemerides of the orbiters and positions of the landers from the two-way Doppler and range data, and synthesizes the different phases of the

C. E. Hildebrand; E. J. Christensen; D. H. Boggs; G. H. Born; H. Hokikian; J. F. Jordan; W. B. Howard

1977-01-01

126

Concepts of orbital mechanics  

Microsoft Academic Search

Parameters determining an orbit, perturbations acting on a satellite and orbital deviations resulting from them, and a study of the particular types of orbits relevant to the use of artificial earth satellites for finding and developing natural resources are presented. The discussion shows the constraints imposed on teledetective search by certain characteristics of the orbits.

A. Alouges

1974-01-01

127

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Hamilton, Douglas

128

The higher excited electronic states and spin orbit splitting of the valence band in three-dimensional assemblies of close-packed ZnSe and CdSe quantum dots in thin film form  

NASA Astrophysics Data System (ADS)

Optical properties of as-deposited and annealed thin films composed of three-dimensional arrays of sphalerite-type ZnSe and CdSe quantum dots (QDs), synthesized by chemical deposition, were investigated. Neglecting the S D mixing of hole states, the lowest “band to band” transitions in very small nanoclusters and in bulk-like clusters may be assigned as 1S?1S and 1S??1S, and are split by spin orbit (SO) splitting energy of the bulk material—?. The splitting energy between these transitions was found to be insensitive to QD size variations, which could be explained assuming that 1S hole states arising from valence band ?7 and ?8 components do not mix with higher angular momentum states and shift together to higher energies coupled via the isotropic hole mass. This implies significant difference between the SO splitting energies in the two semiconductors. Accounting for S D mixing of hole states, the observed transitions may be attributed to the fundamental ground state—(1S3/2, 1Se) and the ground state—(1S1/2, 1Se) ones. The observed “splittings” thus do not correspond exactly to SO splitting energy in both semiconductors, but are complex functions of it, as exact position of each hole energy level depends, besides on ?, also on other material-characteristic parameters.

Pejova, Biljana

2008-08-01

129

Spontaneous subperiosteal orbital hemorrhage.  

PubMed

Abstract Subperiosteal orbital hemorrhage typically results from trauma. Spontaneous subperiosteal orbital hemorrhage (SSOH) is rare and has been reported with sudden elevation of cranial venous pressure, bleeding diathesis, and sinusitis. This article presents a series of 9 patients (11 orbits) with SSOH and review the associated systemic conditions. 10 out of 11 orbits (91%) underwent surgical intervention due to advanced orbital signs or poor vision. PMID:23895577

Elia, Maxwell D; Shield, David; Kazim, Michael; Shinder, Roman; Yoon, Michael; McCulley, Timothy J; Shore, John W; Greene, Daniel; Servat, Juan J; Levin, Flora

2013-07-29

130

Orbital fractures: a review  

PubMed Central

This review of orbital fractures has three goals: 1) to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2) to explain how to assess and examine a patient after periorbital trauma, and 3) to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.

Joseph, Jeffrey M; Glavas, Ioannis P

2011-01-01

131

ERS orbit control  

Microsoft Academic Search

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; overhead Venice tower (12.508206 deg east, 45.314222 deg north). The launch, maneuvers for the initial acquisition of the operational orbit, orbit maintenance maneuvers,

Mats Rosengren

1991-01-01

132

Opening a closed Hamiltonian map  

NASA Astrophysics Data System (ADS)

A closed Hamiltonian map is opened by introducing an interaction with the outside of the system. The resulting open Hamiltonian system possesses an exit with escaping orbits through it. For such a system equipped with two or three exits, the exit basin structure of the escaping orbits is observed to have a fractal boundary and a boundary shared by the three basins, i.e., a Wada basin boundary. In the small size limit of the exits, a complete fractalization of the phase space, where the predictability of the future state is almost lost, is also observed.

Sanjuán, Miguel A. F.; Horita, Takehiko; Aihara, Kazuyuki

2003-03-01

133

Orbit-Orbit Interactions in Atomic Spectra  

Microsoft Academic Search

Empirical spectroscopic evidence suggests the existence of an orbit-orbit interaction between electrons, of the form alphal1.l2, and of a magnitude comparable to the spin-orbit interaction. The direct magnetic interaction is of this form, but previous calculations have yielded too small a magnitude. We suggest that the magnetic interaction is uniquely sensitive to the correlation of the interacting electrons, and that

C. W. Ufford; H. B. Callen

1958-01-01

134

Periodic orbits around areostationary points in the Martian gravity field  

NASA Astrophysics Data System (ADS)

This study investigates the problem of areostationary orbits around Mars in three-dimensional space. Areostationary orbits are expected to be used to establish a future telecommunication network for the exploration of Mars. However, no artificial satellites have been placed in these orbits thus far. The characteristics of the Martian gravity field are presented, and areostationary points and their linear stability are calculated. By taking linearized solutions in the planar case as the initial guesses and utilizing the Levenberg-Marquardt method, families of periodic orbits around areostationary points are shown to exist. Short-period orbits and long-period orbits are found around linearly stable areostationary points, but only short-period orbits are found around unstable areostationary points. Vertical periodic orbits around both linearly stable and unstable areostationary points are also examined. Satellites in these periodic orbits could depart from areostationary points by a few degrees in longitude, which would facilitate observation of the Martian topography. Based on the eigenvalues of the monodromy matrix, the evolution of the stability index of periodic orbits is determined. Finally, heteroclinic orbits connecting the two unstable areostationary points are found, providing the possibility for orbital transfer with minimal energy consumption.

Liu, Xiao-Dong; Baoyin, Hexi; Ma, Xing-Rui

2012-05-01

135

Transfer orbit determination accuracy for orbit maneuvers  

NASA Astrophysics Data System (ADS)

This work intends to show the accuracy of the orbital elements determined during transfer orbit as a function of data span, as well as the feasibility of performance maneuvers. The orbit estimator used is a weighted least squares algorithm. The observation vector is composed of angle data (azimuth and elevation) and range data and are from the Astra IC mission. The state vector is either propagated by Brower model or numerical integration (for small eccentricities and inclination). The complete software to determine the orbit has been developed by Hughes Aircraft and been used for all Hughes satellite mission.

Pinheiro, Mery Passos

136

Asymptotic orbital stability conditions for flows by estimates of singular values of the linearization  

Microsoft Academic Search

. We investigate vector elds on Riemannian manifolds. Using propertiesof associated variational systems and systems of normal variations we obtain conditionsfor positive asymptotic orbital stability of arbitrary orbits whose positivesemi-orbits are bounded and for the instability of closed orbits. A number of theseconditions leads to upper (or lower) estimates of the singular values of the tangentmap, in particular for the

Gennady Alekseevich Leonov; Antje Noack; Volker Reitmann

2001-01-01

137

Impact on Spin Tune From Horizontal Orbital Angle Between Snakes and Orbital Angle Between Spin Rotators  

SciTech Connect

To keep the spin tune in the spin depolarizing resonance free region is required for accelerating polarized protons to high energy. In RHIC, two snakes are located at the opposite side of each accelerator. They are configured to yield a spin tune of 1/2. Two pairs of spin rotators are located at either side of two detectors in each ring in RHIC to provide longitudinal polarization for the experiments. Since the spin rotation from vertical to longitudinal is localized between the two rotators, the spin rotators do not change the spin tune. However, due to the imperfection of the orbits around the snakes and rotators, the spin tune can be shifted. This note presents the impact of the horizontal orbital angle between the two snakes on the spin tune, as well as the effect of the vertical orbital angle between two rotators at either side of the collision point on the spin tune.

Bai,M.; Ptitsyn, V.; Roser, T.

2008-10-01

138

The higher excited electronic states and spin-orbit splitting of the valence band in three-dimensional assemblies of close-packed ZnSe and CdSe quantum dots in thin film form  

SciTech Connect

Optical properties of as-deposited and annealed thin films composed of three-dimensional arrays of sphalerite-type ZnSe and CdSe quantum dots (QDs), synthesized by chemical deposition, were investigated. Neglecting the S-D mixing of hole states, the lowest 'band to band' transitions in very small nanoclusters and in bulk-like clusters may be assigned as 1S{yields}1S and 1S{sub {delta}}{yields}1S, and are split by spin-orbit (SO) splitting energy of the bulk material-{delta}. The splitting energy between these transitions was found to be insensitive to QD size variations, which could be explained assuming that 1S hole states arising from valence band {gamma}{sub 7} and {gamma}{sub 8} components do not mix with higher angular momentum states and shift together to higher energies coupled via the isotropic hole mass. This implies significant difference between the SO splitting energies in the two semiconductors. Accounting for S-D mixing of hole states, the observed transitions may be attributed to the fundamental ground state-(1S{sub 3/2}, 1S{sub e}) and the ground state-(1S{sub 1/2}, 1S{sub e}) ones. The observed 'splittings' thus do not correspond exactly to SO splitting energy in both semiconductors, but are complex functions of it, as exact position of each hole energy level depends, besides on {delta}, also on other material-characteristic parameters. - Graphical abstract: Accounting for S-D mixing of hole states, the observed optical transitions in very small sphalerite-type ZnSe and CdSe nanoclusters are attributed to the ground state-(1S{sub 3/2}, 1S{sub e}) and the ground state-(1S{sub 1/2}, 1S{sub e}). The 'splittings' do not correspond to SO splitting energy, but are complex functions of it.

Pejova, Biljana [Faculty of Natural Sciences and Mathematics, Institute of Chemistry, Saints Cyril and Methodius University, PO Box 162, 1001 Skopje (Macedonia, The Former Yugoslav Republic of)], E-mail: biljana@iunona.pmf.ukim.edu.mk

2008-08-15

139

Modeling and simulation of a cubesat using nonlinear control in an elliptic orbit  

Microsoft Academic Search

In this paper we present dynamics and control of a spacecraft in an elliptic orbit. Our contribution is modeling and determination of the angular velocity of the satellite orbit reference frame using a Local Vertical\\/Local Horizontal (LVLH) orbit reference frame and an orbit propagator without the constraint of no out of plane motion. A non-linear passivity-based sliding surface controller is

Rune Schlanbusch; Espen Oland; Per Johan Nicklasson

2009-01-01

140

In Orbit Infrastructure.  

National Technical Information Service (NTIS)

A systematic approach to space activity by using a standardized automated multipurpose system of transportation and accomodation to, in, and from orbit, called In-Orbit Infrastructure (IOI) is discussed. The IOI needs of commercial space platforms for Ear...

J. Lacaze

1983-01-01

141

Variational definitions of orbital energies  

NASA Astrophysics Data System (ADS)

A formulation of Koopmans' theorem is derived for high-spin half-filled open shells in the restricted openshell Hartree-Fock (ROHF) method based on a variational treatment of both the initial (non-ionized) open-shell system X with spin S and the corresponding ions having a hole or an extra electron in the closed, open and virtual shells respectively. The six processes for forming ions with spin S+/-1/2 require two different definitions for canonical orbitals within each shell. These processes may be treated equivalently within a restricted CI using arbitrary non-canonical linear transforms of the ROHF orbitals optimal for the initial system. Canonical UHF orbitals also obey a variational principle for the ion energies, but they provide less appropriate estimates for actual states of the ion. Canonical spin-unrestricted Kohn-Sham orbitals with common exchange-correlation functionals suffer from all of the UHF problems and from selfinteraction error. They generally are not useful estimates for ion energies.

Davidson, Ernest R.

2012-12-01

142

An Orbit And Dispersion Correction Scheme for the PEP II  

SciTech Connect

To achieve optimum luminosity in a storage ring it is vital to control the residual vertical dispersion. In the original PEP storage ring, a scheme to control the residual dispersion function was implemented using the ring orbit as the controlling element. The 'best' orbit not necessarily giving the lowest vertical dispersion. A similar scheme has been implemented in both the on-line control code and in the simulation code LEGO. The method involves finding the response matrices (sensitivity of orbit/dispersion at each Beam-Position-Monitor (BPM) to each orbit corrector) and solving in a least squares sense for minimum orbit, dispersion function or both. The optimum solution is usually a subset of the full least squares solution. A scheme of simultaneously correcting the orbits and dispersion has been implemented in the simulation code and on-line control system for PEP-II. The scheme is based on the eigenvector decomposition method. An important ingredient of the scheme is to choose the optimum eigenvectors that minimize the orbit, dispersion and corrector strength. Simulations indicate this to be a very effective way to control the vertical residual dispersion.

Cai, Y.; Donald, M.; Shoaee, H.; White, G.; Yasukawa, L.A.; /SLAC

2011-09-01

143

OMPS Nadir early on-orbit performance evaluation and calibration  

NASA Astrophysics Data System (ADS)

OMPS is the latest advanced hyperspectral sensor suite flying onboard the Suomi National Polar-Orbiting Partnership (Suomi NPP) spacecraft. It measures ozone depletion in total column and vertical profile ozone abundances. OMPS on-orbit calibration is conducted through dark, lamp and solar measurements. Launched on October 28, 2011, OMPS Nadir has successfully undergone a thorough early orbit check (EOC) and is currently in the intensive calibration and validation (ICV) phase. The calibration data gathered during the on-orbit calibration and validation activities allows us to evaluate the sensor's early orbit performance and establish on-orbit calibration baseline. In this paper, we provide details of the sensor major on-orbit calibrations activities and present sensor level performance and calibration results from OMPS early orbit image data. These results have demonstrated that the OMPS has made a smooth transition from ground to orbit, and its early on-orbit performance meets or exceeds sensor level requirements and agrees with the predicted values determined during the prelaunch calibration and characterization. Examples of Nadir CCD orbital performance monitoring are provided.

Pan, C.; Weng, F.; Wu, X.; Kowalewski, M.; Jaross, G.; Flynn, L.

2012-11-01

144

Constraints on Triton's Orbital Evolution  

NASA Astrophysics Data System (ADS)

Three models have been proposed for the capture origin of Triton: Collision with a preexisting satellite (Goldreich 1989), Gas drag (McKinnon 1990), and three-body exchange (Agnor and Hamilton 2004). All three scenarios put Triton onto a highly elongated orbit which is subsequently circularized by satellite tides. Our goal here is to use the current state of the Neptunian system to constrain these capture scenarios. Triton strongly affects inner satellites (or an inner disk) directly via close pericenter passages before its orbit circularizes. Since satellite tides nearly conserve angular momentum, a simple tidal model puts Triton's minimum pericenter distance at aT/2 ˜ 7RN, where aT is its current semimajor axis. Our initial simulations show that some satellites orbiting outside Proteus (the outermost of the inner satellites at a=4.67RN) can survive these Triton passages. So why are there no known moonlets beyond 4.67RN? Seeking answers, we have integrated Triton's orbit backwards in time with a more sophisticated model that includes J2, solar perturbations, and satellite tides. We find that Triton's pericenter smoothly descends toward 7RN, as in the simple tidal model, but with superimposed oscillations at i) 1/2 Neptune's orbital period and ii) the nodal and apsidal precession periods. At a ˜ 94RN Triton encounters a Kozai-like resonance between these precession periods which causes its pericenter to dip to ˜ 4.2RN - well within the current orbit of Proteus. If Triton's orbit were ever this large, then the early inner satellite system must have been much smaller than it is today. Additional apsidal and nodal resonances between an early Triton on a highly elliptical orbit and the small inner satellites (with resonant arguments like 2nT - 2? sat) are strong enough to drive moonlet inclinations up to several degrees. We are using the stengths and locations of these resonances to further limit possible capture and evolution scenarios and will report on the status of these investigations.

Hamilton, D. P.; Zhang, K.; Agnor, C.

2005-05-01

145

Advanced Vertical Array Beamformer.  

National Technical Information Service (NTIS)

The advanced vertical array beamformer signal processor accomplishes acoustic beamforming of an underwater vertical array used in shallow water utilizing matched beam processing to suppress generated noise and/or ship radiated noise thereby increasing the...

T. C. Yang J. A. Mobbs

1998-01-01

146

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Laboratory, Jet P.; Administration, National A.

147

Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation  

SciTech Connect

Using multilayer linear polarizers, we have characterized the polarization state of radiation from bend-magnet beamline 9.3.2 at the Advanced Light Source as a function of vertical opening angle at photon energies of 367 and 722 eV. Both a fine slit and a coarse semi-aperture were stepped across the beam to accept different portions of the vertical radiation fan. Polarimetry yields the degree of linear polarization directly and the degree of circular polarization indirectly assuming an immeasurably small amount of unpolarized radiation based on the close agreement of the theoretical and experimental results for linear polarization. The results are in good agreement with theoretical calculations, with departures from theory resulting from uncertainty in the effective aperture of the measured beam. The narrow 0.037-mrad aperture on the orbit plane transmits a beam whose degree of linear polarization exceeds 0.99 at these energies. The wide semi-aperture blocking the beam from above and below transmits a beam with a maximum figure of merit, given by the square root of flux times the degree of circular polarization, when the aperture edge is on the orbit plane thus blocking only half of the total available flux. {copyright} {ital 1996 American Institute of Physics.}

Kortright, J.; Rice, M.; Hussain, Z.; Padmore, H.; Adamson, A.; Huff, W.; Young, A.; Moler, E.; Kellar, S.; Ynzunza, R.; Palomares, F.; Daimon, H.; Tober, E.; Fadley, C. [Center for X-Ray Optics, Advanced Light Source, Chemical Sciences Division, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)]|[Physics Department, University of California-Davis, Davis, CA 95616 (United States)]|[Department of Material Physics, Osaka University, Osaka (Japan)

1996-09-01

148

Vertical Map Storage.  

ERIC Educational Resources Information Center

Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

Perry, Joanne M.

1982-01-01

149

Orbital migration models under test  

NASA Astrophysics Data System (ADS)

Planet-disk interaction predicts a change in the orbital elements of an embedded planet. Through linear and fully hydrodynamical studies it has been found that migration is typically directed inwards. Hence, this migration process gives natural explanation for the presence of the 'hot' planets orbiting close to the parent star, and it plays a mayor role in explaining the formation of resonant planetary systems. However, standard migration models for locally isothermal disks indicate a too rapid inward migration for small mass planets, and a large number of massive planets are found very far away from the star. Recent studies, including more complete disk physics, have opened up new paths to slow down or even reverse migration. The new findings on migration are discussed and connected to the observational properties of planetary systems.

Kley, Wilhelm

2011-11-01

150

Painless orbital myositis  

PubMed Central

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis.

Chakor, Rahul T.; Santhosh, N. S.

2012-01-01

151

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

152

Painless orbital myositis.  

PubMed

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis. PMID:22919201

Chakor, Rahul T; Santhosh, N S

2012-07-01

153

Vertical bounce of two vertically aligned balls  

NASA Astrophysics Data System (ADS)

When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

Cross, Rod

2007-11-01

154

Problem of ``Vertical'' Correlation in Pi-Electron Systems  

Microsoft Academic Search

The problem of ``vertical'' correlation is re-examined. Defined in terms of the two-electron probability distribution function, ``vertical'' correlation is separated from the related ``in—out'' correlation effect. A study is made of the planar methyl anion and its isoelectronic analog, the planar ammonia molecule, to assess the importance of sigma antibonding orbitals for the correlation of the 2pz2 pair. These contribute

Millard H. Alexander

1967-01-01

155

INTERACTING BINARIES WITH ECCENTRIC ORBITS. III. ORBITAL EVOLUTION DUE TO DIRECT IMPACT AND SELF-ACCRETION  

SciTech Connect

The rapid circularization and synchronization of the stellar components in an eccentric binary system at the onset of Roche lobe overflow is a fundamental assumption common to all binary stellar evolution and population synthesis codes, even though the validity of this assumption is questionable both theoretically and observationally. Here we calculate the evolution of the orbital elements of an eccentric binary through the direct three-body integration of a massive particle ejected through the inner Lagrangian point of the donor star at periastron. The trajectory of this particle leads to three possible outcomes: direct accretion onto the companion star within a single orbit, self-accretion back onto the donor star within a single orbit, or a quasi-periodic orbit around the companion star, possibly leading to the formation of a disk. We calculate the secular evolution of the binary orbit in the first two cases and conclude that direct impact accretion can increase as well as decrease the orbital semimajor axis and eccentricity, while self-accretion always decreases the orbital semimajor axis and eccentricity. In cases where mass overflow contributes to circularizing the orbit, circularization can set in on timescales as short as a few percent of the mass-transfer timescale. In cases where mass overflow increases the eccentricity, the orbital evolution is governed by competition between mass overflow and tidal torques. In the absence of tidal torques, mass overflow results in direct impact can lead to substantially subsynchronously rotating donor stars. Contrary to assumptions common in the literature, direct impact accretion furthermore does not always provide a strong sink of orbital angular momentum in close mass-transferring binaries; in fact, we instead find that a significant part can be returned to the orbit during the particle orbit. The formulation presented in this paper together with our previous work can be combined with stellar and binary evolution codes to generate a better picture of the evolution of eccentric, Roche lobe overflowing binary star systems.

Sepinsky, J. F. [Department of Physics and Electrical Engineering, University of Scranton, Scranton, PA 18510 (United States); Willems, B.; Kalogera, V.; Rasio, F. A., E-mail: jeremy.sepinsky@scranton.ed, E-mail: b-willems@northwestern.ed, E-mail: vicky@northwestern.ed, E-mail: rasio@northwestern.ed [Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

2010-11-20

156

Polar Cloud Structure as Derived From the Pioneer Venus Orbiter  

Microsoft Academic Search

Pioneer Venus orbiter radio occultation data taken on orbits 9, 18, and 19 at S band (13.06 cm) are used to obtain vertical absorption coefficient profiles of the Venus clouds in the north polar regions. Resulting profiles show dense cloud decks at the 1.5- to 4.7-bar level in the Venus atmosphere. The cloud decks are lower in altitude and more

J. B. Cimino; C. Elachi; A. J. Kliore; D. J. McCleese; I. R. Patel

1980-01-01

157

Circular orbits in Einstein-Gauss-Bonnet gravity  

SciTech Connect

The stability under radial and vertical perturbations of circular orbits associated to particles orbiting a spherically symmetric center of attraction is studied in the context of the n-dimensional: the Newtonian theory of gravitation, Einstein's general relativity, and the Einstein-Gauss-Bonnet theory of gravitation. The presence of a cosmological constant is also considered. We find that this constant as well as the Gauss-Bonnet coupling constant are crucial to have stability for n>4.

Rosa, Valeria M.; Letelier, Patricio S. [Departamento de Matematica, Universidade Federal de Vicosa, 36570-000 Vicosa, M.G. (Brazil); Departamento de Matematica Aplicada-IMECC, Universidade Estadual de Campinas, 13083-970 Campinas, S.P. (Brazil)

2008-10-15

158

Examination of a constrained three-impulse trajectory between low planetary orbits and circulating orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows a three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by resulting in a Delta V profile for each encounter. When the location of the first impulse of the trajectory is constrained to an arbitrary value then launch windows for each orbit of the spaceport can be determined. The length of the windows depend primarily upon the Delta V capability of the Taxi.

Knoedler, Andrew J.

159

The atomic orbitals of the topological atom.  

PubMed

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure. PMID:23758358

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

160

The atomic orbitals of the topological atom  

NASA Astrophysics Data System (ADS)

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure.

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

161

Orbits and Interiors of Planets  

NASA Astrophysics Data System (ADS)

The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies. The first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. Chapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the "Nice" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. The last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical "fixed points," characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin( i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems,

Batygin, Konstantin

2012-05-01

162

On the vertical wind shear of Saturn's Equatorial Jet at cloud level  

NASA Astrophysics Data System (ADS)

In this work we analyze and compare the vertical cloud structure of Saturn's Equatorial Zone in two different epochs: the first one close to the Voyagers flybys (1979-1981) and the second one in 2004, when the Cassini spacecraft entered its orbit around the planet. Our goal is to retrieve the altitude of cloud features used as zonal wind tracers in both epochs. We reanalyze three different sets of photometrically calibrated published data: ground-based in 1979, Voyager 2 PPS and ISS observations in 1981, and we analyze a new set of Hubble Space Telescope images for 2004. For all situations we reproduced the observed reflectivity by means of a similar vertical model with three layers. The results indicate the presence of a changing tropospheric haze in 1979-1981 ( P˜100 mbar, ?˜10) and in 2004 ( P˜50 mbar, ?˜15) where the tracers are embedded. According to this model the Voyager 2 ISS images locate cloud tracers moving with zonal velocities of 455 to 465 (±2) m/s at a pressure level of 360 ± 140 mbar. For HST observations, our previous works had showed cloud tracers moving with zonal wind speeds of 280±10 m/s at a pressure level of about 50±10 mbar. All these values are calculated in the same region ( 3°±2° N). This speed difference, if interpreted as a vertical wind shear, requires a change of 90-20+50 ms per scale height, two times greater than that estimated from temperature observations. We also perform an initial guess on Cassini ISS vertical sounding levels, retrieving values compatible with HST ones and Cassini CIRS derived vertical wind shear, but not with Voyager wind measurements. We conclude that the wind speed velocity differences measured between 1979-1981 and 2004 cannot be explained as a wind shear effect alone and demand dynamical processes.

Pérez-Hoyos, S.; Sánchez-Lavega, A.

2006-01-01

163

Heat transfer during condensation in vertical closed thermosiphons  

NASA Astrophysics Data System (ADS)

The results are presented of an experimental investigation of the hydrodynamic characteristics of a two-phase layer and of the heat-transfer behavior under characteristic operating conditions of the condensing section of a thermosiphon.

Bezrodnyi, M. K.; Moklyak, V. F.

1986-07-01

164

Finite Orbit Analysis of Energetic Particles In Tokamak Plasmas  

Microsoft Academic Search

Energetic particles are commonly generated in tokamak plasmas, whether by NBI or RF, and in reactors, Alpha-particles are intrinsically present. For these particles, the orbit widths may not be small compared with the minor radius; in fact, for regions sufficiently close to the axis, one can argue that finite orbit effects are important for nearly all particles. In this work,

S. C. Chiu; V. S. Chan

2000-01-01

165

Global Orbit Patterns for Dynamical Systems On Finite Sets  

Microsoft Academic Search

In this paper, the study of the global orbit pattern (gop) formed by all the periodic orbits of discrete dynamical systems on a finite set X allows us to describe precisely the behaviour of such systems. We can predict by means of closed formulas, the number of gop of the set of all the function from X to itself. We

René Lozi; Clarisse Fiol

2009-01-01

166

Global Orbit Patterns for One Dimensional Dynamical Systems  

Microsoft Academic Search

In this article, we study the behaviour of discrete one-dimensional dynamical systems associated to functions on finite sets. We formalise the global orbit pattern formed by all the periodic orbits (gop) as the ordered set of periods when the initial value thumbs the finite set in the increasing order. We are able to predict, using closed formulas, the number of

Rene Lozi; Clarisse Fiol

2009-01-01

167

Lorenz Attractor Periodic Orbits  

NSDL National Science Digital Library

The butterfly-like Lorenz attractor is a simplified model of two-dimensional convective fluid flow and is one of the best known images of chaos. Embedded in this attractor are unstable periodic orbits described by Viswanath and this model computes a number of these orbits. Each periodic orbit is classified by the number of times the trajectory orbits the A and B fixed points before it repeats. Note that because the attractor is chaotic and because of numerical errors and the finite precision of the initial conditions, errors accumulate and the trajectory leaves the vicinity of a periodic orbit after a half dozen cycles. The Lorenz Attractor Periodic Orbits Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_chaos_LorenzAttractor.jar file will run the program if Java is installed.

Christian, Wolfgang

2009-05-20

168

Earth orbiting stations  

Microsoft Academic Search

The earth-orbiting station has evolved through Salyut, Skylab, and the Apollo-Soyuz project. The Shuttle combined with Spacelab will permit low-earth-orbit flights of up to 30 days. Later manned and automated free-flying Spacelabs will extend stay-times to 60 days. Bigger space stations housing 6-12 crewmen for up to six months could be built up from modules carried into orbit. Future space

D. W. Patterson; J. W. Gurr; G. V. Butler

1975-01-01

169

GPS-LEO orbiter occultation orbital analyses and event determination  

NASA Astrophysics Data System (ADS)

A good knowledge of the vertical profiles of temperature and humidity throughout the atmosphere are crucial to understand the present state of the Earth's atmosphere and it's modeling. The application of radio occultation technique has a heritage of over 2 decades in NASA's planetary exploration program to study the atmosphere of most of the major bodies in the solar system. Results from NASA's planetary program experiment have proven to be very effective at characterizing the atmosphere of a planet. However, the use of radio occultation technique to remote sensing the Earth's atmosphere is only practical to be implemented recently with the advent of the matured Global Positioning System (GPS). The GPS occultation technique is well suited to observe the Earth's atmosphere, due to it excellent geographical coverage, all weather capability, long-term stability, self-calibration and high vertical resolution. The GPS/MET (GPS Meteorology) experiment launched in April 1995 is the proof-of-concept of this technique. The results from this experiment is appealing and shown that the GPS occultation technique is a promising candidate to monitor the Earth's atmosphere. With the advancement of receiver technologies and lower system cost, the GPS occultation technique is a promising tool to predict the long-term climatic changes and numerical weather modeling of the Earth's atmosphere at a higher precision. This paper briefly describes the radio occultation concept and the GPS satellite systems, which form the basis understanding of this subject matter. This is followed by a detail description of the occultation geometries between the GPS satellites and a LEO orbiter. A method to determine the occultation event is discussed and thoroughly analyzed in terms of orbit inclinations, altitudes, receiver sampling rates, antenna positioning (aft and fore pointing), and antenna mask angles. A simulator is developed using MATLAB for the orbital analyses and occultation determination in 2-D and 3-D display and in GISO (Gall Isographic) map to give the overall picture on the total occultation events per day. Finally, results are presented and discussed.

Abdul Rashid, Z. A.; Cheng, P. P.

2003-04-01

170

Idiopathic orbital pseudotumour.  

PubMed

Idiopathic orbital pseudotumour (IOP) is a benign inflammatory condition usually confined to the orbit. This may involve single or multiple intraorbital structures. Extraorbital extension can also occur. The imaging appearances often mimic other orbital diseases. Both computed tomography (CT) and magnetic resonance imaging (MRI) are frequently used to investigate orbital diseases, and it is important for radiologists to be aware of the variety of imaging appearances that occur in IOP. We present the imaging appearances in histopathologically confirmed cases of IOP and discuss the clinical features, natural history, and differential diagnosis of this condition. PMID:21546008

Ding, Z X; Lip, G; Chong, V

2011-05-04

171

Orbital Evolution of Jupiter-family Comets  

NASA Astrophysics Data System (ADS)

The orbital evolution of more than 25,000 Jupiter-family comets (JFCs) under the gravitational influence of planets was studied. After 40 Myr one considered object (with initial orbit close to that of Comet 88P) got aphelion distance Q<3.5 AU, and it moved in orbits with semi-major axis a=2.60-2.61 AU, perihelion distance 1.7orbit close to that of Comet 94P) moved in orbits with a=1.95-2.1 AU, q>1.4 AU, Q<2.6 AU, e=0.2-0.3, and i=9-33 deg for 8 Myr (and it had Q<3 AU for 100 Myr). So JFCs can rarely get typical asteroid orbits and move in them for Myrs. In our opinion, it can be possible that Comet 133P (Elst--Pizarro) moving in a typical asteroidal orbit was earlier a JFC and it circulated its orbit also due to non-gravitational forces. JFCs got near-Earth object (NEO) orbits more often than typical asteroidal orbits. A few JFCs got Earth-crossing orbits with a<2 AU and Q<4.2 AU and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Three considered former JFCs even got inner-Earth orbits (with Q<0.983 AU) or Aten orbits for Myrs. The probability of a collision of one of such objects, which move for millions of years inside Jupiter's orbit, with a terrestrial planet can be greater than analogous total probability for thousands other objects. Results obtained by the Bulirsch-Stoer method and by a symplectic method were mainly similar (except for probabilities of close encounters with the Sun when they were high). Our results show that the trans-Neptunian belt can provide a significant portion of NEOs, or the number of trans-Neptunian objects migrating inside solar system could be smaller than it was earlier considered, or most of 1-km former trans-Neptunian objects that had got NEO orbits disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes if these lifetimes are not small. The obtained results show that during the accumulation of the giant planets the total mass of icy bodies delivered to the Earth could be about the mass of water in Earth's oceans. Several our papers on this problem were put in http://arXiv.org/format/astro-ph/ (e.g., 0305519, 0308448). This work was supported by NASA (NAG5-10776) and INTAS (00-240).

Ipatov, S. I.; Mather, J. C.

2004-05-01

172

Strategies Analysis for GPS Vertical Velocity Estimation, a Preparing Study for Investigating Vertical Motions of Tibetan Plateau  

NASA Astrophysics Data System (ADS)

As the largest area of high topography, the Tibetan Plateau is always the focus of Geosciences. As a key clue to many important scientific questions, the vertical motions of the plateau and its borderlands are still not quite clear. Is the plateau rising taller because of the ongoing contraction as India plate is colliding with Eurasia plate? Or is it collapsing due to the extension driven by its excess gravitational potential energy? Or is it undergoing a balance status, or experiencing more complicated dynamic models? GPS measurements from the Tibetan Plateau and its surroundings currently are dense enough and precise enough to make meaningful measurements of vertical motions in Tibet and its surrounding areas, which may be helpful to answer the above questions. We try to estimate the vertical velocity of hundreds of GPS sites around Tibetan Plateau, study the pattern of their vertical deformations, and investigate better models to explain the vertical movements. In order to achieve better GPS vertical accuracy which should be enough to reflect the vertical motions in Tibetan Plateau, GPS data set need to be reprocessed and reanalyzed using the next generation of models and orbits, which include absolute phase center models, improved tropospheric, ocean loading models, and re-analyzed orbits. We systematically evaluate and compare different analysis strategies using long-running GPS stations from Tibet and somewhere else around the world, and assess how different analysis strategies can affect the vertical velocity estimation. Based on the comparison among solutions with absolute phase center models and reprocessed orbits and other possible factors, we try to find the best strategy for vertical velocity evaluation of Tibetan Plateau.

Fu, Y.; Freymueller, J. T.; Wang, Q.; Xu, C.

2009-12-01

173

The Zero Gradient Synchrotron Closed Orbit Position Monitoring System  

Microsoft Academic Search

Four segment induction electrodes are being installed in each of the eight Zero Gradient Synchrotron (ZGS) straight sections. Due to the presence of other equipment, these electrodes can only be 10-in long in the direction of beam travel. The small length-to-width ratio of these electrodes creates special problems. Five pieces of information are transmitted from each electrode to give detailed

C. W. Potts

1971-01-01

174

Linear Optics From Closed Orbits (LOCO): An Introduction  

SciTech Connect

The LOCO code is used to find and correct errors in the linear optics of storage rings. The original FORTRAN code was written to correct the optics of the NSLS X-Ray ring, and was applied soon thereafter to debug problems with the ALS optics. The ideas used in the code were developed from previous work at SLAC. Several years ago, LOCO was rewritten in MATLAB. As described in this newsletter, the MATLAB version includes a user-friendly interface, with many useful fitting and analysis options. LOCO has been used at many accelerators. Presently, a search for LOCO in the text of papers on the Joint Accelerator Conferences Website yields 107 papers. A comprehensive survey of applications will not be included here. Details of recent results at a few light sources are included in this newsletter. In the past, the quality of LOCO fitting results varied significantly, depending on the storage ring. In particular, the results were mixed for colliding beam facilities, where there tend to be fewer BPMs that in light sources. Fitting rings with less BPM data to constrain the fit optics parameters often led to unreasonably large fit quadrupole gradient variations. Recently, modifications have been made to the LOCO fitting algorithm which leads to much better results when the BPM data does not tightly constrain the fit parameters. The modifications are described in this newsletter, and an example of results with this new algorithm is included.

Safranek, James; /SLAC

2009-06-18

175

Natural Convection between Concentric Vertical Cylinders  

Microsoft Academic Search

The motion of a fluid in the closed annular cavity formed by two concentric vertical cylinders and two horizontal planes has been analyzed by a numerical solution of the equations of motion and energy using a high-speed digital computer. The motion is generated by a radial density gradient caused by the thermal boundary conditions which are, typically: inner cylinder at

G. de Vahl Davis; R. W. Thomas

1969-01-01

176

Comet Odyssey: Comet Nucleus Orbiter  

NASA Astrophysics Data System (ADS)

Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use a solar-electric powered spacecraft to effect a rendezvous with periodic comet 46P/Wirtanen in October 2013. Arrival is 96 days after perihelion at a heliocentric distance of 1.61 AU. Comet Odyssey's science payload includes narrow- and wide-angle CCD cameras, an infrared thermal imager, a gas chromatograph/mass spectrometer, an XRD/XRF dust compositional analyzer, and a dust counter and accumulation sensors. The Comet Odyssey spacecraft implementation uses a high heritage approach of flight proven and redundant hardware. The 3-engine ion propulsion subsystem is derived from that on Dawn but includes the capability for multi-engine thrusting. Comet Odyssey will approach the Wirtanen nucleus and make repeated slow flybys through the active cometary coma for a period of three months. It will then be placed in a ˜100-km radius orbit around the nucleus, with a plan to eventually orbit at 40-km altitude or less. From that altitude the narrow-angle camera will map the entire nucleus surface at 1 meter/pixel and the thermal imager will map at 19 meter/pixel. The orbital portion of the nominal mission will last 4.5 months, following the comet outward from the Sun to 3.3 AU as the comet evolves from an active to a quiescent state. En route to P/Wirtanen, the Comet Odyssey spacecraft will perform a close flyby of the 200-km diameter, G-type, main belt asteroid 19 Fortuna in January 2012 and make appropriate remote sensing observations.

Weissman, P. R.; Smythe, W. D.; Spitz, S. J.; Bernard, D. E.; Bailey, R. W.

2004-11-01

177

Asymmetries in vertical vorticity and vertical velocity arising during nonlinear homogeneous spindown  

NASA Astrophysics Data System (ADS)

During the spindown of a unidirectional, geostrophic current in a homogeneous fluid, asymmetry arises in the vertical velocity and vertical relative vorticity fields. A closed-form, time-dependent solution valid to order Rossby number is derived to explore these asymmetries. Momentum advection in the interior and the Ekman layer leads to competing tendencies in the vertical vorticity's evolution. In the interior, momentum advection hastens spindown in cyclonic regions. In the Ekman layer, momentum advection weakens Ekman pumping over Ekman suction and thus tends to slow the spindown of cyclonic vorticity. It is shown that the former effect dominates, and hence cyclonic vorticity decays faster than anticyclonic vorticity.

Benthuysen, J. A.; Thomas, L. N.

2012-07-01

178

Orbital characteristics of exoplanets in triple systems  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): More than 20% of the 'Hot-Jupiters' (extrasolar planets with Jovian mass and orbits very close to the central star) are in retrograde orbit with respect to the total angular momentum of the system. The Kozai-Lidov Mechanism, based on secular theory, has been proposed as a mechanism that plays an important role in producing such orbits by several authors. In the present work we study the secular dynamics of a triple system composed by a Sun-like central star and a Jupiter-like planet, which are under the gravitational influence of a further perturbing star (brown dwarf), using the Eccentric Kozai-Lidov Mechanism. The main goal is to study the orbital evolution of the planet. In special, we investigate the orientation (inclination) and the shape (eccentricity) of its orbit. One key feature explored is the time needed for the first flip in its orientation (prograde to retrograde). The gravitational potential is developed in closed form up to the fourth order. In order to develop the long-period disturbing potential the double-averaged method is applied. We have compared the secular evolution of systems with and without the fourth order part of the disturbing potential.

Carvalho, Jean Paulo; Vilhena de Moraes, R.; Almeida Prado, A. B.; Winter, O.

2013-05-01

179

Saturn Orbiter Mission Study.  

National Technical Information Service (NTIS)

A preliminary analysis of the important aspects of missions orbiting the planet Saturn is provided. Orbital missions to Saturn is given serious consideration for the 1980's, or after flybys by Pioneer 10/G and Mariner Jupiter-Saturn 1977. An attempt is ma...

W. C. Wells R. J. Sullivan

1973-01-01

180

Devising geodetic satellite orbits  

Microsoft Academic Search

In the present paper, an intermediate theory of satellite motion, developed within the framework of the problem of six fixed centers with allowance for the influence of eight zonal harmonics of the geopotential, is applied to the analysis of quasi-geosynchronous and heliosynchronous orbits of geodetic satellites. Expressions for selecting nominal parameters for such orbits are proposed.

E. L. Lukashevich

1979-01-01

181

Tethered Orbital Refueling Study.  

National Technical Information Service (NTIS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazi...

D. A. Fester L. K. Rudolph E. R. Kiefel P. W. Abbott P. Grossrode

1986-01-01

182

Stability of halo orbits.  

PubMed

We predict new populations of trapped nonequatorial ("halo") orbits of charged dust grains about an arbitrary axisymmetric planet. Simple equilibrium and stability conditions are derived, revealing dramatic differences between positively and negatively charged grains in prograde or retrograde orbits. Implications for the Cassini mission to Saturn are discussed. PMID:11019061

Howard, J E; Dullin, H R; Horányi, M

2000-04-10

183

From surface to orbit  

Microsoft Academic Search

Space travel is highly expensive and has significant limitations. Among all space activities the process of travelling from the surface to orbit requires the greatest amount of energy, materials and cost. Basically even today, more than 61 years after the first artificial satellite was set to orbit, these difficulties have been the greatest barriers of the dawn of the real

Andras Bela Olah

2011-01-01

184

Spontaneous orbital haemorrhage.  

PubMed Central

A 57-year-old housewife, with controlled hypertension, presented with acute right proptosis and visual loss with external ophthalmoplegia due to spontaneous orbital haemorrhage. Vision and ocular motility were returned to normal by the rapid surgical evacuation of the blood. Acute orbital haemorrhage is an ocular emergency requiring urgent treatment to prevent the usual previously reported outcome of permanent visual loss. Images

Brooks, A. M.; Finkelstein, E.

1984-01-01

185

Space Shuttle orbiter avionics  

Microsoft Academic Search

The paper concerns the Orbiter's integrated avionic system, which consists of multiple computers with attendant software, multifunction man-machine interfaces, digital communications, and multipurpose instrumentation and data handling capability. The design and verification tasks discussed include hardware and software simulation leading to the flight test phases. Some of the major attributes of the orbiter avionic system include redundancy to support time-critical

L. M. Carrier; R. G. Minor

1977-01-01

186

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management.

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

187

Lunar orbiting and landing missions  

Microsoft Academic Search

Orbits for a lunar orbiting spacecraft and unmanned lunar surface rovers are identified. The orbit to the moon is divided into two phases: one is the lunar transfer phase and the other is the landing phase. For each phase standard orbits are designed, and mission profiles are presented. The minimum weight of the lunar orbiting spacecraft is estimated to be

Tsutomu Iwata; Kazumi Okuda; Yutaka Kaneko

1989-01-01

188

Hunger enhances vertical vection.  

PubMed

Hunger was found to facilitate visually induced illusory upward and downward self-motions (vertical vection), but not illusory self-motion in depth (vection in depth). We propose that the origin of this hunger effect lies in the possibility that vertical self-motions (both real and illusory) are more likely to induce changes in visceral state. PMID:23362680

Seno, Takeharu; Ito, Hiroyuki; Sunaga, Shoji; Palmisano, Stephen

2012-01-01

189

Aiding vertical guidance understanding  

Microsoft Academic Search

A study was conducted to evaluate training and displays for the vertical guidance system of a modern glass cockpit airliner. The experiment consisted of a complete flight performed in a fixed-base simulator with airline pilots. Three groups were used to evaluate a new flight mode annunciator display and vertical navigation training. Results showed improved pilot performance with training and significant

Everett Palmer; Martin Alkin; Peter Polson; Daniel McCrobie; Lance Sherry

1999-01-01

190

Massive congenital orbital teratoma.  

PubMed

Orbital teratomas are rare embryonic tumors composed of a wide diversity of tissues derived from the three germinal layers. The presenting features include, a healthy newborn with extreme unilateral proptosis; marked stretching of the eyelids over a tense, fluctuating mass, with elongation of the palpebral fissure; enlargement of the bony orbit (two to three times normal size) with subsequent nasal and malar deformities; and transillumination of all or part of the orbital mass. Commonly the eye is normally developed but often vision is not preserved either due to exposure or secondary optic atrophy. The objective in the management of orbital teratoma is to save the eye to encourage orbitofacial development, maintain cosmesis and retain some vision. We report a case of massive congenital orbital teratoma successfully removed by an eyelid-sparing exenteration technique. PMID:16304523

Gnanaraj, Lawrence; Skibell, Bentley C; Coret-Simon, Judith; Halliday, William; Forrest, Christopher; DeAngelis, Dan D

2005-11-01

191

Orbital endoscopic surgery  

PubMed Central

Minimally invasive ?keyhole? surgery performed using endoscopic visualization is increasing in popularity and is being used by almost all surgical subspecialties. Within ophthalmology, however, endoscopic surgery is not commonly performed and there is little literature on the use of the endoscope in orbital surgery. Transorbital use of the endoscope can greatly aid in visualizing orbital roof lesions and minimizing the need for bone removal. The endoscope is also useful during decompression procedures and as a teaching aid to train orbital surgeons. In this article, we review the history of endoscopic orbital surgery and provide an overview of the technique and describe situations where the endoscope can act as a useful adjunct to orbital surgery.

Selva, Dinesh

2008-01-01

192

Stability of Frozen Orbits Around Europa  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): A planetary satellite of interest at the present moment for the scientific community is Europa, one of the four largest moons of Jupiter. There are some missions planned to visit Europa in the next years, for example, Jupiter Europa Orbiter (JEO, NASA) and Jupiter IcyMoon Explorer (JUICE, ESA). In this work we are formulating theories and constructing computer programs to be used in the design of aerospace tasks as regards the stability of artificial satellite orbits around planetary satellites. The studies are related to translational motion of orbits around planetary satellites considering polygenic perturbations due to forces, such as the nonspherical shape of the central body and the perturbation of the third body. The equations of motion will be developed in closed form to avoid expansions in eccentricity and inclination. For a description of canonical formalism are used the Delaunay canonical variables. The canonical set of equations, which are nonlinear differential equations, will be used to study the stability of orbits around Europa. We will use a simplified dynamic model, which considers the effects caused by non-uniform distribution of mass of Europa (J2, J3 and C22) and the gravitational attraction of Jupiter. Emphasis will be given to the case of frozen orbits, defined as having almost constant values of eccentricity, inclination, and argument of pericentre. An approach will be used to search for frozen orbits around planetary satellites and study their stability by applying a process of normalization of Hamiltonian. Acknowledges: FAPESP

Cardoso Dos Santos, Josué; Vilhena de Moraes, R.; Carvalho, J. S.

2013-05-01

193

Orbital Evolution of Planetesimals due to the Galactic Tide: Formation of the Comet Cloud  

Microsoft Academic Search

We have investigated the orbital evolution of planetesimals perturbed by the Galactic tide using analytical expressions. We consider the vertical component of the tidal force from the Galactic disk. The Galactic tide increases or decreases the perihelia and randomizes the inclination of planetesimals with large aphelion distances. We applied the analytical solutions to the orbital evolution of planetesimals that form

A. Higuchi; E. Kokubo; H. Kinoshita; T. Mukai

2007-01-01

194

Planet-C: Venus Climate Orbiter mission of Japan  

Microsoft Academic Search

The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science

Masato Nakamura; Takeshi Imamura; Munetaka Ueno; Naomoto Iwagami; Takehiko Satoh; Shigeto Watanabe; Makoto Taguchi; Yukihiro Takahashi; Makoto Suzuki; Takumi Abe; George L. Hashimoto; Takeshi Sakanoi; Shoichi Okano; Yasumasa Kasaba; Jun Yoshida; Manabu Yamada; Nobuaki Ishii; Takahiro Yamada; Kazunori Uemizu; Tetsuya Fukuhara; Koh-Ichiro Oyama

2007-01-01

195

Halo orbit station keeping for International Sun-Earth Explorer-C \\/ISEE-C  

Microsoft Academic Search

The ISEE-C spacecraft must be kept close to an unstable 'halo' orbit with a series of discrete orbital maneuvers set at intervals at least one month apart. A numerical algorithm has been developed to compute a velocity correction at any point on the trajectory which will minimize the distance between the satellite orbit and the nominal halo path. This algorithm

H. Heuberger

1977-01-01

196

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

197

Lunar Prospector Orbit Determination Results.  

National Technical Information Service (NTIS)

The orbit support for Lunar Prospector (LP) consists of three main areas: (1) cislunar orbit determination, (2) rapid maneuver assessment using Doppler residuals, and (3) routine mapping orbit determination. The cislunar phase consisted of two trajectory ...

M. Beckman M. Concha

1998-01-01

198

Harmonically excited orbital variations  

SciTech Connect

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

Morgan, T.

1985-08-06

199

Mars Reconnaissance Orbiter Accelerometer Experiment Results  

NASA Astrophysics Data System (ADS)

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis precessed from the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis was brought dramatically from 40,000km at MOI to 460 km at aerobraking completion (ABX) August 30, 2006. After ABX, a few small propulsive maneuvers established the Primary Science Orbit (PSO), which without aerobraking would have required an additional 400 kg of fuel. Each of the 400 plus aerobraking orbits provided a vertical structure and distribution of density, scale heights, and temperatures, along the orbital path, providing key in situ insight into various upper atmosphere (greater than 100 km) processes. One of the major questions for scientists studying Mars is: "Where did the water go?" Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extended vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both near the surface and in the upper atmosphere. Thus the water balance throughout the entire atmosphere from subsurface to exosphere may both be critical. Comparisons of data from Mars Global Surveyor (MGS), MO and MRO help characterize key temporal and spatial cycles including: winter polar warming, planetary scale gravity waves, latitudinal, seasonal, and diurnal variations, and variations from perihelion to aphelion. This will validate and constrain both upper atmospheric circulation models used to understand the nature of high-altitude variability and transport processes, and engineering models used to plan future missions.

Keating, G. M.; Bougher, S. W.; Theriot, M. E.; Zurek, R. W.; Blanchard, R. C.; Tolson, R. H.; Murphy, J. R.

2007-05-01

200

Flight Mechanics of Manned SubOrbital Reusable Launch Vehicles with Recommendations for Launch and Recovery  

Microsoft Academic Search

An overview of every significant method of launch and recovery for manned sub-orbital Reusable Launch Vehicles (RLV) is presented here. We have categorized launch methods as vertical takeoff, horizontal takeoff, and air launch. Recovery methods are categorized as wings, aerodynamic decelerators, rockets, and rotors. We conclude that both vertical takeoff and some air launch methods are viable means of attaining

Marti Sarigul-Klijn; Nesrin Sarigul-Klijn

201

Approach to key technologies identification for rocket powered single stage to orbit vehicles  

Microsoft Academic Search

A reusable vertical take off, vertical landing rocket powered single stage to orbit vehicle has been studied as a part of the Ae´rospatiale future launchers systematic study policy. The main goal of this study is to investigate the key points of this kind of configurations, especially identify, classify and quantify the specific problems, key technologies, tools and test facilities needed

F. Deneu; P. Terrenoire

1996-01-01

202

Vertical Line Test  

NSDL National Science Digital Library

In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

203

Removal of orbital debris  

NASA Astrophysics Data System (ADS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

204

Orbital blood cyst.  

PubMed Central

A blood cyst of the orbit is an unusual cause of proptosis and most likely arises in a pre-existing haemangioma. If the cyst occurs at the apex of the orbit the blood should be aspirated. This is followed by excision of the cyst wall, the dissection being done with the aid of an operating microscope. If there is evidence of intracranial connection of the blood cyst, namely, splayed superior orbital fissure or cerebrospinal fluid leak, then the patient should be treated with an antibiotic to prevent intracranial infection. Images

Sevel, D.; Rosales, A.

1978-01-01

205

Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.  

PubMed

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system. PMID:22722249

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-06-21

206

FAST DIGITAL ORBIT FEEDBACK SYSTEMS AT NSLS.  

SciTech Connect

We are implementing digital orbit feedback systems to replace the analog ones in both the VUV and the X-ray rings. We developed an original VME-based design which is run by a powerful Motorola 2305 CPU and consists entirely of off-the-shelf VME boards. This makes the system inexpensive and easy to configure, and allows for high digitizing rates. The new 5 kHz digital global feedback system is currently operational in the VUV ring, and the X-ray system is in the commissioning phase. Some of the parameters achieved include vertical correction bandwidth of 200 Hz (at DC gain of 100) and typical orbit drift over a fill of <3% of the rms beam size. In this paper we discuss the system architecture, implementation and performance.

PODOBEDOV,B.; KUSHNER,B.; RAMAMOORTHY,S.; TANG,Y.; ZITVOGEL,E.

2001-06-18

207

Spatial Distribution of Vertical Shear.  

National Technical Information Service (NTIS)

Spatial variations in small scale vertical shear in the upper ocean are described, relationships between small scale vertical shear and density stratification are investigated, and the potential for predicting mean vertical shear from measurements of the ...

S. L. Patterson F. C. Newman D. M. Rubenstein R. B. Lambert

1981-01-01

208

Vertical Multijunction Solar Cells.  

National Technical Information Service (NTIS)

A theoretical analysis of the vertical multijunction (VMJ) solar cell was performed which indicated that using silicon certain configurations could be fabricated to satisfy the program objectives. Results indicate that initial AMO efficiencies of 15% can ...

P. M. Stella

1973-01-01

209

Unstable periodic orbits in human epileptic activity  

NASA Astrophysics Data System (ADS)

We examine in detail subdural recordings from a patient with an epileptic focal seizure, highly unusual in the ongoing nature of the discharges and in the lack of cognitive impairment. We applied a recent method for detecting unstable periodic orbits to the series of time intervals between successive spike discharges, and report that a few unstable fixed points exist within their apparent random fluctuations. The statistical significance of this underlying deterministic dynamics is assessed using surrogate data. In particular, the approaches of trajectories toward the unstable periodic patterns are observed in the sequences immediately following the perceptual tasks. This suggests that the act of perception contributes in a highly specific manner to pulling the epileptic activities towards particular unstable periodic orbits, which closely resemble the technique called chaos control for stabilization of unstable periodic orbits.

Le van Quyen, Michel; Martinerie, Jacques; Adam, Claude; Baulac, Michel; Varela, Francisco J.

1997-09-01

210

Europa Planetary Protection for Juno Jupiter Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Juno mission will launch in 2011 and explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the gravitational fields, magnetic fields, and auroral regions and its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close to Europa or the other Galilean satellites, planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design. The science mission is concluded with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction due to impact into an icy body.

Bernard, Douglas; Abelson, Robert; Johannesen, Jennie; Lam, Try; McAlpine, William; Newlin, Laura

211

Energy level diagrams for black hole orbits  

NASA Astrophysics Data System (ADS)

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed-form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Levin, Janna

2009-12-01

212

Optical lattices: Orbital dance  

NASA Astrophysics Data System (ADS)

Emulating condensed-matter physics with ground-state atoms trapped in optical lattices has come a long way. But excite the atoms into higher orbital states, and a whole new world of exotic states appears.

Lewenstein, Maciej; Liu, W. Vincent

2011-02-01

213

Exploratory Orbit Analysis.  

National Technical Information Service (NTIS)

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four ...

L. Michelotti

1989-01-01

214

Electric Propulsion Orbital Platform.  

National Technical Information Service (NTIS)

This paper describes the Electric Propulsion Orbital Platform (EPOP), of which the primary objective is to provide an instrumented platform for testing electric propulsion devices in space. It is anticipated that the first flight, EPOP-1, will take place ...

1993-01-01

215

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies.

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

216

Molecular orbitals of solids  

SciTech Connect

The molecular orbital contains, in general, a linear combination of orbitals of all equivalent atoms in the molecule, and for its construction one can use the method projection operators or induced representation. In this paper, for the expansion of space group representations obtained on induction of representation of local symmetry groups into a space group, the authors use the Mackey linkage theory and the generalized Frobenius reciprocity theorem. On the basis of the Mackey theory a classification of the chemical interactions in crystals composed of one orbital was obtained. Molecular orbitals for the O/sub h//sup 7/ groups of diamond were obtained, and a symmetric analysis of the zone structure of diamond, silicon, and germanium was performed.

Yarzhemskii, V.G.; Murav'ev, E.N.

1987-11-01

217

Orbit Physlet Problems  

NSDL National Science Digital Library

A Danish Website for Interactive Science Education. Html pages in this directory contain scripts that were written by Morten Brydensholt and coworkers for the Orbit website. This commercial website is in Danish. This site provides English translations of this material.

Christian, Wolfgang; Belloni, Mario

2008-02-19

218

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

219

Theory of Orbits  

NASA Astrophysics Data System (ADS)

Theory of Orbits treats celestial mechanics as well as stellar dynamics from the common point of view of orbit theory, making use of concepts and techniques from modern geometric mechanics. It starts with elementary Newtonian mechanics and ends with the dynamics of chaotic motion. The two volumes are meant for students in astronomy and physics alike. Prerequisite is a physicist's knowledge of calculus and differential geometry.

Boccaletti, Dino; Pucacco, Giuseppe

220

The Exoplanet Orbit Database  

NASA Astrophysics Data System (ADS)

We present a database of well-determined orbital parameters of exoplanets, and their host stars' properties. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The database is available in a searchable, filterable, and sortable form online through the Exoplanets Data Explorer table, and the data can be plotted and explored through the Exoplanet Data Explorer plotter. We use the Data Explorer to generate publication-ready plots, giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the different selection biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semimajor-axis distribution from apparently singleton systems.

Wright, J. T.; Fakhouri, O.; Marcy, G. W.; Han, E.; Feng, Y.; Johnson, John Asher; Howard, A. W.; Fischer, D. A.; Valenti, J. A.; Anderson, J.; Piskunov, N.

2011-04-01

221

Two Body Orbits Model  

NSDL National Science Digital Library

The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation. It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.   An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters. Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog. Selecting the âstudentâ checkbox creates a ready-to-run package with the new configuration without the Customization dialog. The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run Java archive. Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Christian, Wolfgang

2012-07-18

222

Secular Orbital Evolution of Compact Planet Systems  

NASA Astrophysics Data System (ADS)

Recent observations have shown that at least some close-in exoplanets maintain eccentric orbits despite tidal circularization timescales that are typically much shorter than stellar ages. We explore gravitational interactions with a more distant planetary companion as a possible cause of these unexpected non-zero eccentricities. For simplicity, we focus on the evolution of a planar two-planet system subject to slow eccentricity damping and provide an intuitive interpretation of the resulting long-term orbital evolution. We show that dissipation shifts the two normal eigenmode frequencies and eccentricity ratios of the standard secular theory slightly, and we confirm that each mode decays at its own rate. Tidal damping of the eccentricities drives orbits to transition relatively quickly between periods of pericenter circulation and libration, and the planetary system settles into a locked state in which the pericenters are nearly aligned or nearly anti-aligned. Once in the locked state, the eccentricities of the two orbits decrease very slowly because of tides rather than at the much more rapid single-planet rate, and thus eccentric orbits, even for close-in planets, can often survive much longer than the age of the system. Assuming that an observed close-in planet on an elliptical orbit is apsidally locked to a more distant, and perhaps unseen companion, we provide a constraint on the mass, semi-major axis, and eccentricity of the companion. We find that the observed two-planet system HAT-P-13 might be in just such an apsidally locked state, with parameters that obey our constraint reasonably well. We also survey close-in single planets, some with and some without an indication of an outer companion. None of the dozen systems that we investigate provides compelling evidence for unseen companions. Instead, we suspect that (1) orbits are in fact circular, (2) tidal damping rates are much slower than we have assumed, or (3) a recent event has excited these eccentricities. Our method should prove useful for interpreting the results of both current and future planet searches.

Zhang, Ke; Hamilton, Douglas P.; Matsumura, Soko

2013-11-01

223

Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas  

NASA Astrophysics Data System (ADS)

A model for the non-inductive initiation of a closed flux surface observed in electron cyclotron (EC) heated toroidal plasmas is presented. First, a pressure-driven equilibrium toroidal current develops under a weak external vertical field so as to counter balance the pressure-ballooning and current-hoop forces. When the self-field from the current almost cancels out the external vertical field, a forward energetic part of electrons in the velocity space begins to make cross-field passing (CFP) orbits. The CFP electrons are generated by the EC heating of bulk electrons and subsequent pitch-angle scattering, which is analyzed using the Fokker-Planck equation. They provide an additional current that closes the field lines. The model is examined for experiments in the small low aspect ratio device of LATE and in the large conventional device of JT-60U with a search for appropriate modes of EC heating. Simultaneous coincidence of the model with these two experiments is obtained in terms of microwave power and driven current. The results predict that initiation of a closed flux surface requires more and more EC power as the plasma major radius increases. In particular, careful injection of high N? EC waves is needed for large devices, both for initiation of a closed flux surface and for subsequent enlargement of the flux surface by the usual EC current drive onto the closed flux area.

Maekawa, T.; Yoshinaga, T.; Uchida, M.; Watanabe, F.; Tanaka, H.

2012-08-01

224

Secondary star magnetic fields in close binaries  

NASA Astrophysics Data System (ADS)

In this paper an attempt is made to use magnetic braking to constrain the surface polar field strengths of the secondary stars in close binaries with orbital periods between Porb ~ 3 and 7 h. By using a standard Mestel & Spruit model, assuming field saturation, a linear relation was obtained between the mass transfer and orbital period, for the period range under consideration, which allows constraining the surface polar field between B?,2 ~ 2900 and 3300 G. It has been shown that the predicted mass-transfer rates correlate with the Verbunt & Zwaan empirical mass transfer versus orbital period relation. Furthermore, it has been shown that the closed field lines, that is, the so-called dead zone, of the secondary star envelopes a substantial fraction of the binary, including the white dwarf, for all orbital periods under consideration. It has been shown that the interaction of the white dwarf field with the surrounding envelope can result in the intermediate polars entering the period gap being magnetically synchronized over time-scales ?syn <= 107yr. This mechanism may then play a significant role in the orbital evolution of the intermediate polars into the polars. Furthermore, surface magnetic field structures in the L1 region may play a significant role in the fragmentation of the mass flow near the L1 region, which may explain the inferred fragmented mass transfer, that is, the blobby mass flow, in magnetic cataclysmic variables.

Meintjes, P. J.; Jurua, E.

2006-11-01

225

Orbit Determination in the Pluto System  

NASA Astrophysics Data System (ADS)

The once simple binary system of Pluto and Charon has, until now, eluded a precise description of its orbital motion. The most important component that makes this system so difficult is a consequence of its fully relaxed spin-orbit state. The surface of Pluto has a highly variable albedo that also changes with time. These albedo variations lead to a shift of the photocenter relative to the center of the body. The synchronicity of the rotation of Pluto and the orbit of Charon couples the albedo pattern to the astrometry and lead, if uncorrected, to erroneous values for the orbital elements. In this presentation we will show results based on astrometry with the Hubble Space Telescope that now span nearly 20 years. We use two-body Keplerian orbit fits to describe the motions of all satellites as a tool to understand and remove the astrometric effects of the albedo pattern. The most immediate result of this work is a demonstration that the orbit of Charon is very close to circular (1-sigma limit is 3 km out of round). We also present an analysis of the degree to which albedo effects (spatial and temporal) impact the astrometry the resulting orbit determinations. These considerations show the value and necessity of combining photometric and astrometric data to further improve the dynamical description of this system. This work is a necessary precursor to upcoming New Horizons encounter with Pluto as well as our on-going work to determine the masses of the outer satellites. This work was supported by grants from NASA Planetary Astronomy and from the Space Telescope Science Institute.

Buie, Marc W.; Grundy, W. M.; Tholen, D. J.

2012-05-01

226

Comparison of orbit phasing maneuvers  

Microsoft Academic Search

Prussing and Chiu developed a general analysis method for optimizing multiple-impulse, time-fixed rendezvous between circular orbits. Orbit phasing maneuvers, where the maneuvering spacecraft simply changes position within the same orbit, are a subset of these general maneuvers. The present analysis compares the use of simple orbit phasing maneuvers with the optimal maneuvers derived by Prussing and Chiu to determine the

John M. Hanson

1990-01-01

227

Simple Closing Midwater Trawl for Small Boats  

Microsoft Academic Search

A closing midwater-trawl system for a small boat (7 m) was developed to apportion hydroacoustic population estimates among fish species by collecting vertically stratified limnetic fish samples. These stratified samples could also be used for providing biological data on the fish or for feeding and behavior studies. The 3 × 7-m rectangular trawl used a double-line, hydraulically operated cable system

Hermann J. Enzenhofer; Jeremy M. B. Hume

1989-01-01

228

Mean value coordinates for closed triangular meshes  

Microsoft Academic Search

Constructing a function that interpolates a set of values defined at vertices of a mesh is a fundamental operation in computer graphics. Such an interpolant has many uses in applications such as shading, parameterization and deformation. For closed polygons, mean value coordinates have been proven to be an excellent method for constructing such an interpolant. In this paper, we generalize

Tao Ju; Scott Schaefer; Joe D. Warren

2005-01-01

229

Probing Evolutionary Trends in Close Binaries from Observed Period Changes  

NASA Astrophysics Data System (ADS)

O-C diagrams analysis offers an opportunity to view the very late orbital evolution history (about 100 yrs) of nearly synchronized close binaries. The orbital period function P(E) becomes known in this way and hence it can be related with the most important physical mechanisms that modulate the orbital period of such binary systems through J - P (angular momentum - orbital period relations). Given the P(E) function and a variety of the implemented parameters, analytic parametric solutions can be sought in order to have estimations of the action of the most important of the physical mechanisms driving the observed orbital period variation trends. Preliminary analytic parametric solutions of such a generalized (non-conservative) J - P equation involving mass loss, magnetic braking and tidal evolution are presented here for some detached synchronized pairs (mainly members of the RS CVn group) whose orbital period variations are known by O-C diagram analysis.

Nanouris, N.; Kalimeris, A.; Antonopoulou, E.; Livaniou-Rovithis, H.

2010-12-01

230

Closed-loop nominal and abort atmospheric ascent guidance for rocket-powered launch vehicles  

NASA Astrophysics Data System (ADS)

An advanced ascent guidance algorithm for rocket-powered launch vehicles is developed. The ascent guidance function is responsible for commanding attitude, throttle and setting during the powered ascent phase of flight so that the vehicle attains target cutoff conditions in a near optimal manner while satisfying path constraints such as maximum allowed bending moment and maximum allowed axial acceleration. This algorithm cyclically solves the calculus-of-variations two-point boundary-value problem starting at vertical rise completion through orbit insertion. This is different from traditional ascent guidance algorithms which operate in an open-loop mode until the high dynamic pressure portion of the trajectory is over, at which time there is a switch to a closed loop guidance mode that operates under the assumption of negligible aerodynamic forces. The main contribution of this research is an algorithm of the predictor-corrector type wherein the state/costate system is propagated with known (navigated) initial state and guessed initial costate to predict the state/costate at engine cutoff. The initial costate guess is corrected, using a multi-dimensional Newton's method, based on errors in the terminal state constraints and the transversality conditions. Path constraints are enforced within the propagation process. A modified multiple shooting method is shown to be a very effective numerical technique for this application. Results for a single stage to orbit launch vehicle are given. In addition, the formulation for the free final time multi-arc trajectory optimization problem is given. Results for a two-stage launch vehicle burn-coast-burn ascent to orbit in a closed-loop guidance mode are shown. An abort to landing site formulation of the algorithm and numerical results are presented. A technique for numerically treating the transversality conditions is discussed that eliminates part of the analytical and coding burden associated with optimal control theory.

Dukeman, Greg A.

231

ARTEMIS Maneuvers into Lunar Orbit  

NASA Video Gallery

This animation visualizes the maneuvers required to move the ARTEMIS spacecraft from their kidney-shaped paths on each side of the moon to orbiting the moon. It took one and a half years, over 90 orbit maneuvers, many gravitational boosts and surprisingly little fuel to move the two spacecraft. The spacecraft have been through orbits never before attempted and made lovely curlicue leaps from one orbit to the next to reach their destination orbit.

Holly Zell

2011-06-23

232

THE FATE OF MOONS OF CLOSE-IN GIANT EXOPLANETS  

SciTech Connect

We show that the fate of moons of a close-in giant planet is mainly determined by the migration history of the planet in the protoplanetary disk. As the planet migrates in the disk from beyond the snow line toward a multi-day period orbit, the formed and forming moons become unstable as the planet's sphere of influence shrinks. Disk-driven migration is faster than the moons' tidal orbital evolution. Moons are eventually ejected from around close-in exoplanets or forced into collision with them before tides from the planet affect their orbits. If moons are detected around close-in exoplanets, they are unlikely to have been formed in situ, instead they were captured from the protoplanetary disk on retrograde orbits around the planets.

Namouni, Fathi, E-mail: namouni@obs-nice.f [Universite de Nice, CNRS, Observatoire de la Cote d'Azur, BP 4229, 06304 Nice (France)

2010-08-20

233

Close vs. Closed Reading: Interpreting the Clues.  

ERIC Educational Resources Information Center

|Discusses how "close" reading led to "closed" reading (a work's one true meaning is available only to a select few). Advocates "open" reading, returning authority over the text to students. Espouses the detective story as an open text which has been "closed" by the author but which resists closure. (SR)|

Beehler, Sharon A.

1988-01-01

234

GOCE Precise Science Orbits  

NASA Astrophysics Data System (ADS)

GOCE (Gravity field and steady-state Ocean Circulation Explorer), as the first ESA (European Space Agency) Earth Explorer Core Mission, is dedicated for gravity field recovery of unprece-dented accuracy using data from the gradiometer, its primary science instrument. Data from the secondary instrument, the 12-channel dual-frequency GPS (Global Positioning System) receiver, is used for precise orbit determination of the satellite. These orbits are used to accu-rately geolocate the gradiometer observations and to provide complementary information for the long-wavelength part of the gravity field. A precise science orbit (PSO) product is provided by the GOCE High-Level Processing Facility (HPF) with a precision of about 2 cm and a 1-week latency. The reduced-dynamic and kinematic orbit determination strategies for the PSO product are presented together with results of about one year of data. The focus is on the improvement achieved by the use of empirically derived azimuth-and elevation-dependent variations of the phase center of the GOCE GPS antenna. The orbits are validated with satellite laser ranging (SLR) measurements.

Bock, Heike; Jäggi, Adrian; Meyer, Ulrich; Beutler, Gerhard; Heinze, Markus; Hugentobler, Urs

235

Exomoon habitability constrained by energy flux and orbital stability  

NASA Astrophysics Data System (ADS)

Context. Detecting massive satellites that orbit extrasolar planets has now become feasible, which led naturally to questions about the habitability of exomoons. In a previous study we presented constraints on the habitability of moons from stellar and planetary illumination as well as from tidal heating. Aims: Here I refine our model by including the effect of eclipses on the orbit-averaged illumination. I then apply an analytic approximation for the Hill stability of a satellite to identify the range of stellar and planetary masses in which moons can be habitable. Moons in low-mass stellar systems must orbit their planet very closely to remain bounded, which puts them at risk of strong tidal heating. Methods: I first describe the effect of eclipses on the stellar illumination of satellites. Then I calculate the orbit-averaged energy flux, which includes illumination from the planet and tidal heating to parametrize exomoon habitability as a function of stellar mass, planetary mass, and planet-moon orbital eccentricity. The habitability limit is defined by a scaling relation at which a moon loses its water by the runaway greenhouse process. As a working hypothesis, orbital stability is assumed if the moon's orbital period is less than 1/9 of the planet's orbital period. Results: Due to eclipses, a satellite in a close orbit can experience a reduction in orbit-averaged stellar flux by up to about 6%. The smaller the semi-major axis and the lower the inclination of the moon's orbit, the stronger the reduction. I find a lower mass limit of ? 0.2 M? for exomoon host stars that allows a moon to receive an orbit-averaged stellar flux comparable to the Earth's, with which it can also avoid the runaway greenhouse effect. Precise estimates depend on the satellite's orbital eccentricity. Deleterious effects on exomoon habitability may occur up to ? 0.5 M? if the satellite's eccentricity is ? 0.05. Conclusions: Although the traditional habitable zone lies close to low-mass stars, which allows for many transits of planet-moon binaries within a given observation cycle, resources should not be spent to trace habitable satellites around them. Gravitational perturbations by the close star, another planet, or another satellite induce eccentricities that likely make any moon uninhabitable. Estimates for individual systems require dynamical simulations that include perturbations among all bodies and tidal heating in the satellite.

Heller, R.

2012-09-01

236

Ballistics and Orbits Model  

NSDL National Science Digital Library

The EJS Ballistics and Orbits model displays ballistic trajectories near the Earth. The model shows the trajectory with respect to the inertial coordinate system and the trajectory as seen from a point of view that is co-rotating with the Earth. You can examine and modify this simulation if you have EJS installed by right-clicking within the plot and selecting âOpen EJS Modelâ from the pop-up menu item. The Ballistics and Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_nl_teunissen_ballistics_and_orbits.jar file will run the program if Java is installed. Additional information about this model can be found by visiting the authorâs web site: http://www.cleonis.nl/index.htm.

Teunissen, Cleon

2009-11-03

237

Orbit utilization - Current regulations  

NASA Astrophysics Data System (ADS)

It is pointed out that an increasingly efficient use of the geostationary satellite orbit and spectrum is necessary to accommodate the growing number of planned U.S. domestic satellites, as well as those of other countries. Technical efficiency can be maximized by designing satellites in a homogeneous manner which minimizes transmission differences between satellites. However, flexibility is also needed to design domestic satellite facilities to respond to the diverse demands in a competitive market. The Federal Communication Commission (FCC) seeks to achieve a balance between these goals in their domestic satellite policies and regulations. In December 1980, the FCC authorized the construction of some 22 new domestic satellites and the launch of 18 satellites. Attention is given to orbit use policies and reduced orbital spacings.

Lepkowski, R. J.

238

Orbital varix thrombosis.  

PubMed Central

Three patients have been described with a thrombosed orbital varix. The clinical, imaging, surgical, and pathologic features of this disorder are described. A pathophysiologic mechanism has been proposed and this entity has been placed in the spectrum of orbital vascular lesions. Recommendations for the diagnostic evaluation and management of patients with thrombosed orbital varices have been offered. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 FIGURE 18 FIGURE 19 FIGURE 20 FIGURE 21 FIGURE 22 FIGURE 23 FIGURE 24 FIGURE 25 FIGURE 26 FIGURE 27 FIGURE 28 FIGURE 29 FIGURE 30

Bullock, J D; Goldbert, S H; Connelly, P J

1989-01-01

239

Orbital Superstructures in Spinels  

NASA Astrophysics Data System (ADS)

Orbital degrees of freedom often lead to specific types of orbital and spin ordering. Complicated and interesting superstructures are observed in B-sublattice of spinels. This is connected with the geometric frustration of this lattice and with the interconnection of edge-sharing MO6 octahedra, which is especially important for transition metals with partially-filled t2g levels. In some such systems (MgTi2O4, CuIr2S4, AlV2O4) there appears strange superstructures with the formation of spin gap states. In other cases (ZnV2O4) structural transitions, apparently connected with orbital ordering, are followed by long-range magnetic ordering. Last but not least, the famous Verwey transition in magnetite Fe3O4 leads to a very complicated structural pattern, accompanied by the appearance of ferroelectricity. In this talk I will discuss all these examples, paying main attention to an interplay of charge, spin and orbital degrees of freedom. In particular, for MgTi2O4, and CuIr2S4 we proposed the picture of orbitally-driven Peierls state [1]. Similar phenomenon can also explain situation in ZnV2O4 [2], although the corresponding superstructure has not yet been observed experimentally. Finally, I propose the model of charge and orbital ordering in magnetite [3], which uses the idea of an interplay of site- and bond-centered ordering [4] and which seems to explain both the structural data and the presence of ferroelectricity in Fe3O4 below Verwey transition. [1] D.I.Khomskii and T.Mizokawa, Phys.Rev.Lett. 94, 156402 (2005); [2] Hua Wu, T.Mizokawa and D.I.Khomskii, unpublished; [3] D.I.Khomskii, unpublished; [4] D.V.Efremov, J.van den Brink and D.I.Khomskii, Nature Mater. 3, 853 (2004)

Khomskii, Daniel

2006-03-01

240

Searching sequences of resonant orbits between a spacecraft and Jupiter  

NASA Astrophysics Data System (ADS)

This research shows a study of the dynamical behavior of a spacecraft that performs a series of close approaches with the planet Jupiter. The main idea is to find a sequence of resonant orbits that allows the spacecraft to stay in the region of the space near the orbit of Jupiter around the Sun gaining energy from each passage by the planet. The dynamical model considers the existence of only two massive bodies in the systems, which are the Sun and Jupiter. They are assumed to be in circular orbits around their center of mass. Analytical equations are used to obtain the values of the parameters required to get this sequence of close approaches. Those equations are useful, because they show which orbits are physically possible when taking into account that the periapsis distances have to be above the surface of the Sun and that the closest approach distances during the passage by Jupiter have to be above its surface.

Formiga, J. K. S.; Prado, A. F. B. A.

2013-10-01

241

Orbital dermoids in children.  

PubMed

Orbital dermoid cysts are benign congenital choristomas. They are common in pediatric population, developing adjacent to suture lines, most commonly located in antero-lateral fronto-zygomatic suture, and are slowly progressive. Complete surgical excision without rupture of cyst is the standard of care. Deep orbital cysts cause proptosis, require imaging, and may present a surgical challenge with a difficult approach. Rupture of the cyst leads to severe inflammatory reaction in surrounding tissues. Overall prognosis remains good with isolated reports of malignancy masquerading as dermoid cysts. PMID:16912019

Ahuja, Rakesh; Azar, Nathalie F

242

[A Roman orbital implant?].  

PubMed

During an excavation in Regensburg/Germany the skeleton of an approximately 20-year-old Roman man was found who was buried in the 3rd/4th century after Christ. A "stone" was found which fitted into the left orbit precisely. After a thorough investigation of the "stone" and with the ophthalmohistorical literature in mind an orbital "implant" as well as a petrified medical paste ("Kollyrium") could be ruled out almost with certainty. Possibly the "stone" served another medical purpose or was used for protection of the eye. PMID:23011607

Rohrbach, J M; Harbeck, M; Holzhauser, P; Tekeva-Rohrbach, C I; Mach, M; Codreanu-Windauer, S

2012-09-25

243

THE ORBITAL PERIOD OF SWIFT J1626.6-5156  

SciTech Connect

We present the discovery of the orbital period of Swift J1626.6-5156. Since its discovery in 2005, the source has been monitored with Rossi X-Ray Timing Explorer, especially during the early stage of the outburst and into the X-ray modulating episode. Using a data span of {approx}700 days, we obtain the orbital period of the system as 132.9 days. We find that the orbit is close to a circular shape with an eccentricity 0.08, that is one of the smallest among Be/X-ray binary systems. Moreover, we find that the timescale of the X-ray modulations varied, which led to earlier suggestions of orbital periods at about a third and half of the orbital period of Swift J1626.6-5156.

Baykal, Altan [METU, Physics Department, Ankara 06531 (Turkey); Goegues, Ersin [Sabanci University, Faculty of Engineering and Natural Sciences, Orhanli-Tuzla, Istanbul 34956 (Turkey); Inam, Sitki Cagdas [Department of Electrical and Electronics Engineering, Baskent University, Ankara 06530 (Turkey); Belloni, Tomaso, E-mail: altan@astroa.physics.metu.edu.t [INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy)

2010-03-10

244

Local orbitals by minimizing powers of the orbital variance.  

PubMed

It is demonstrated that a set of local orthonormal Hartree-Fock (HF) molecular orbitals can be obtained for both the occupied and virtual orbital spaces by minimizing powers of the orbital variance using the trust-region algorithm. For a power exponent equal to one, the Boys localization function is obtained. For increasing power exponents, the penalty for delocalized orbitals is increased and smaller maximum orbital spreads are encountered. Calculations on superbenzene, C(60), and a fragment of the titin protein show that for a power exponent equal to one, delocalized outlier orbitals may be encountered. These disappear when the exponent is larger than one. For a small penalty, the occupied orbitals are more local than the virtual ones. When the penalty is increased, the locality of the occupied and virtual orbitals becomes similar. In fact, when increasing the cardinal number for Dunning's correlation consistent basis sets, it is seen that for larger penalties, the virtual orbitals become more local than the occupied ones. We also show that the local virtual HF orbitals are significantly more local than the redundant projected atomic orbitals, which often have been used to span the virtual orbital space in local correlated wave function calculations. Our local molecular orbitals thus appear to be a good candidate for local correlation methods. PMID:21599041

Jansík, Branislav; Høst, Stinne; Kristensen, Kasper; Jørgensen, Poul

2011-05-21

245

Local orbitals by minimizing powers of the orbital variance  

NASA Astrophysics Data System (ADS)

It is demonstrated that a set of local orthonormal Hartree-Fock (HF) molecular orbitals can be obtained for both the occupied and virtual orbital spaces by minimizing powers of the orbital variance using the trust-region algorithm. For a power exponent equal to one, the Boys localization function is obtained. For increasing power exponents, the penalty for delocalized orbitals is increased and smaller maximum orbital spreads are encountered. Calculations on superbenzene, C60, and a fragment of the titin protein show that for a power exponent equal to one, delocalized outlier orbitals may be encountered. These disappear when the exponent is larger than one. For a small penalty, the occupied orbitals are more local than the virtual ones. When the penalty is increased, the locality of the occupied and virtual orbitals becomes similar. In fact, when increasing the cardinal number for Dunning's correlation consistent basis sets, it is seen that for larger penalties, the virtual orbitals become more localthan the occupied ones. We also show that the local virtual HF orbitals are significantly more local than the redundant projected atomic orbitals, which often have been used to span the virtual orbital space in local correlated wave function calculations. Our local molecular orbitals thus appear to be a good candidate for local correlation methods.

Jansík, Branislav; Høst, Stinne; Kristensen, Kasper; Jørgensen, Poul

2011-05-01

246

Some Remarks Concerning the Accelerated Orbital Motion of Celestial Bodies  

NASA Astrophysics Data System (ADS)

A general explanation of the accelerated orbital motion of celestial bodies is proposed. That explanation is based on nonstatic solutions, conformally equivalent to basic static ones, within the framework of Rosen's bimetric gravitation theory (a criticized theory). As the Birkhoff's theorem for spherically symmetric gravitational fields, is not valid in that theory, there is a possibility to explain different phenomena of the orbital motion related to close binaries, but also to the secularly accelerated planets of the Solar system.

Lukacevic, I.

2009-09-01

247

Vertical Bargraph Display.  

National Technical Information Service (NTIS)

The program involves the generation of an advance approach to electronic aircraft instrumentation. The display media is a twisted nematic liquid crystal display (TN LCD). The instrument was designed as a one-for-one replacement for the existing vertical b...

S. Aftergut G. M. Gozeba C. R. Stein R. L. Skovholt W. W. Thurlow

1975-01-01

248

Vertical Differentiation among Occupations.  

ERIC Educational Resources Information Center

|It is reported that research on the socioeconomic achievement process has begun to generate anomalous findings, many of which involve occupational status as conventionally measured. The author proposes a theory of vertical occupational differentiation based on the role activities of occupational incumbents. (Author/RLV)|

Spaeth, Joe L.

1979-01-01

249

The flexural behavior of PACSAT (passive communication satellite) in orbit  

NASA Astrophysics Data System (ADS)

This report presents an analysis of the libration and vibration of a passive communications satellite known as PACSAT. It addresses the effects of various disturbing mechanical forces on verticality and straightness. Phenomena considered include orbital ellipticity, earth oblateness, solar and lunar gravity, radiation pressure, micrometeorial impacts, and thermal bending effects. The last two are the most important. It is concluded that the flexural misbehavior of PACSAT in orbit is such that it is most improbable that the present design (unsupported linear array) can perform its communications functions.

Sollfrey, W.

1983-02-01

250

Anticipation, Orbital Stability, and Energy Conservation in Discrete Harmonic Oscillators  

SciTech Connect

We make a systematic analysis of the dual incursive model of the discrete harmonic oscillator. We derive its closed form solution, and identify its natural frequency of oscillation. We study its orbital stability, and the conservation of its total energy. We finally propose a superposed model that conserves energy with absolute precision, and exhibits a high degree of orbital stability. Within the conjecture that spacetime is discrete, the above results lead to the conclusion that discretization must be accompanied by anticipation, in order to guarantee orbital stability and energy conservation.

Antippa, Adel F. [Departement de Physique, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, G9A 5H7 (Canada); Dubois, Daniel M. [Centre for Hyperincursion and Anticipation in Ordered Systems, CHAOS asbl, Institute of Mathematics, B37, University of Liege, Grande Traverse 12, B-4000 LIEGE 1 (Belgium)

2004-08-19

251

Energetic particle orbits in the National Spherical Tokamak Experiment  

SciTech Connect

The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The large poloidal magnetic field in the outboard region of spherical tokamaks causes neutral beam injected ions to be born on trapped orbits even with cotangential injection. Numerical solutions to the equations for particle motion and for guiding center drifts are compared in several magnetic equilibria for a range of particle initial conditions. Even when r{sub L}/a{approximately}1/4 the guiding center orbits closely resemble the path of the instantaneous center of gyration of the particle motion; exceptions occur primarily for orbits near the trapped/passing boundary. Finite Larmor radius effects are included in guiding center simulations of prompt orbit loss in the National Spherical Tokamak Experiment (NSTX) [J. Spitzer {ital et al.}, Fusion Technol. {bold 30}, 1337 (1996)]. Orbit loss in the NSTX is caused primarily by collisions with the close fitting conducting shell, and severe losses would be expected with counter directed injection. While most orbits are similar to those found in conventional tokamaks, additional orbit types are possible in spherical tokamaks. {copyright} {ital 1997 American Institute of Physics.}

Mikkelsen, D.R.; White, R.B.; Akers, R.J.; Kaye, S.M.; McCune, D.C.; Menard, J.E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

1997-10-01

252

Accessibility, stabilizability, and feedback control of continuous orbital transfer.  

PubMed

This paper investigates the problem of low-thrust orbital transfer using orbital element feedback from a control-theoretic standpoint, concepts of controllability, feedback stabilizability, and their interaction. The Gauss variational equations (GVEs) are used to model the state-space dynamics. First, the notion of accessibility, a weaker form of controllability, is presented. It is then shown that the GVEs are globally accessible. Based on the accessibility result, a nonlinear feedback controller is derived that asymptotically steers a vehicle from an initial elliptic Keplerian orbit to any given elliptic Keplerian orbit. The performance of the new controller is illustrated by simulating an orbital transfer between two geosynchronous Earth orbits. It is shown that the low-thrust controller requires less fuel than an impulsive maneuver for the same transfer time. Closed-form, analytic expressions for the new orbital transfer controller are given. Finally, it is proved, based on a topological nonlinear stabilizability test, that there does not exist a continuous closed-loop controller that can transfer a spacecraft to a parabolic escape trajectory. PMID:15220148

Gurfil, Pini

2004-05-01

253

Venus orbiter: Ishtar  

Microsoft Academic Search

ISHTAR or VENUS ORBITER is a mission to Venus similar to the mission Mars Express to Mars, with the use, possibly, of the same spacecraft and subsystems. This mission has been proposed to ESA for a feasibility study as a small mission (F2, F3). We shall describe here briefly the scientific objectives of the mission, and how could be implemented.

V. Formisano

2002-01-01

254

Orbital physics in RIXS  

NASA Astrophysics Data System (ADS)

In contrast to magnetism, phenomena associated with the orbital degrees of freedom in transition metal oxides had always been considered to be very difficult to observe. However, recently resonant inelastic x-ray scattering (RIXS) has established itself as a perfect probe of the orbital excitations [1] and orbital order [2] in transition metal oxides. Here we give a brief overview of these recent theoretical and experimental advances which have inter alia led to the observation of the separation of the spin and orbital degree of freedom of an electron [1, 3].[4pt] [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, J. van den Brink, T. Schmitt, Nature 485, 82 (2012).[0pt] [2] P. Marra, K. Wohlfeld, J. van den Brink, Phys. Rev. Lett. 109, 117401 (2012).[0pt] [3] K. Wohlfeld, M. Daghofer, S. Nishimoto, G. Khaliullin, J. van den Brink, Phys. Rev. Lett. 107, 147201 (2011).

Wohlfeld, Krzysztof; Marra, Pasquale; Grueninger, Markus; Schmitt, Thorsten; van den Brink, Jeroen

2013-03-01

255

Orbital debris issues  

Microsoft Academic Search

Orbital debris issues fall into three major topics: Environment Definition, Spacecraft Hazard, and Space Object Management. The major issue under Environment Definition is defining the debris flux for sizes smaller (10 cm in diameter) than those tracked by the North American Aerospace Defense Command (NORAD). Sources for this size debris are fragmentation of larger objects, either by explosion or collision,

D. J. Kessler

1985-01-01

256

Lunar Exploration Orbiter  

Microsoft Academic Search

Phase 0 investigations for the German Lunar Exploration Orbiter (LEO) mission were carried out during 2007 leading to a sophisticated mission concept currently in phase A to be further detailed. Following an announcement of opportunity, also in 2007, the German Space Agency (DLR) received several proposals for the instrumentation of the LEO mission from the national science community. A board

Carsten Henselowsky; Ralf Jaumann; Uwe Kummer; Friedhelm Claasen

2008-01-01

257

Orbital Forces: Student Page  

NSDL National Science Digital Library

This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

258

Lunar orbiter gravity analysis  

Microsoft Academic Search

This paper presents the results to date of the Jet Propulsion Laboratory (JPL) effort at analyzing the tracking data from the five Lunar Orbiter spacecraft. Emphasis is placed on the long-arc evaluation, to which most of the work was directed, rather than on the mascon analysis, which will be reported separately.

J. Lorell

1970-01-01

259

ARTEMIS Orbits Magnetic Moon  

NASA Video Gallery

NASA's THEMIS spacecraft have completed their mission and are still working perfectly, so NASA is re-directing the outermost two spacecraft to special orbits around the Moon. Now called ARTEMIS, they will study the solar wind and the tail of Earth's magnetosphere as well as their combined effect on the moon and its weak magnetic field.

gsfcvideo

2010-10-22

260

Smartphone Photos From Orbit  

NASA Website

These images of Earth were reconstructed from photos taken by three smartphones in orbit, or "PhoneSats." The trio of PhoneSats launched on April 21, 2013, aboard the Antares rocket from NASA's Wallops Flight Facility and ended a ...

261

Baton Orbit Model  

NSDL National Science Digital Library

Baton Orbit Model shows the trajectory of a baton-like object orbiting under the influence of a 1/r^2 force. This model was motivated by the tumbling motion of one of Saturnâs moons, Hyperion. Hyperion is the only celestial body in our solar system which exhibits chaotic tumbling. The chaotic motion is attributed to the uneven mass distribution and highly elliptical orbit of the moon. In order to model the behavior of Hyperion, we approximate its shape using a baton-like object composed of two point masses connected by a mass-less rod. This uneven mass distribution causes a net force and a net torque on its center of mass. The Baton Orbit Model was developed as a final project in a sophomore-level Computational Physics course (Phy 200) using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Barrick, Jessie

2012-06-16

262

Pediatric orbital tumors.  

PubMed

The proper management of orbital tumors in children requires a knowledge of the lesions commonly seen in this area, in addition to the appropriate methods of investigation and treatment. A multidisciplinary approach is most beneficial in obtaining the desired results. PMID:2829096

Stefanyszyn, M A; Handler, S D; Wright, J E

1988-02-01

263

Orbital dermoid cyst  

Microsoft Academic Search

Over a thirteen year period forty patients underwent surgery to remove an orbital dermoid cyst. Cysts which became manifest after the age of three years were deeper and larger than most that were noted before that age. Three out of four epidermoid cysts appeared after the age of 17 years and had an intracranial component. The majority of cysts showed

W W Ehrlich; J E Wright

1987-01-01

264

Precipitation Sensing in GEO Orbit with High Resolution  

NASA Astrophysics Data System (ADS)

Now casting of precipitation in geostationary orbit is a strongly requirements , two of difficults are antenna and radiometer receiver,it should satisfies high spatial and time resolution, this paper present two satellites with large scale feed array cofiguration get over 600 spot beams cove 3.5% China area, work in 118GHz for atmospheric temperature vertical profille and 183GHz for humidity vertical profille, two satellites consists of interferometric synthetic aperture it can satisfies weather nowcasting both spatial and time resolution in suspect zone for now casting requirements.

You, Rui

2012-07-01

265

Minimum-time orbital rendezvous between neighboring elliptic orbits  

Microsoft Academic Search

Time-optimal rendezvous maneuvers are studied. The system considered consists of a target vehicle (nonmaneuvering vehicle) in a known elliptic orbit and an interceptor vehicle (maneuvering vehicle) in a neighboring elliptic orbit such that the ratio of the distance between the two vehicles to the radius of the target-vehicle orbit is small. The interceptor vehicle has propulsive jet systems which can

K. T. Alfriend; Y. Kashiwagi

1969-01-01

266

Close encounters of three black holes  

SciTech Connect

We present the first fully relativistic long-term numerical evolutions of three equal-mass black holes in a system consisting of a third black hole in a close orbit about a black-hole binary. These close-three-black-hole systems have very different merger dynamics from black-hole binaries; displaying complex trajectories, a redistribution of energy that can impart substantial kicks to one of the holes, distinctive waveforms, and suppression of the emitted gravitational radiation. In one configuration the binary is quickly disrupted and the individual holes follow complicated trajectories and merge with the third hole in rapid succession, while in another, the binary completes a half-orbit before the initial merger of one of the members with the third black hole, and the resulting two-black-hole system forms a highly elliptical, well separated binary that shows no significant inspiral for (at least) the first t{approx}1000M of evolution.

Campanelli, Manuela; Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2008-05-15

267

Autonomous Aerobraking for Mars Orbiters  

NASA Astrophysics Data System (ADS)

Autonomous Aerobraking is a developing technology that will reduce cost and increase flexibility of an aerobraking orbiter around Mars. Currently in its second phase of development, autonomous aerobraking could be implemented for a 2018 Mars orbiter.

Prince, J. L.

2012-06-01

268

THEMIS Orbits and Data at SPDF  

NASA Astrophysics Data System (ADS)

The Space Physics Data Facility (SPDF) within Goddard's Heliospheric Physics Laboratory has worked closely with the THEMIS team to adapt SPDF's orbit and data tools/services to the special needs of the THEMIS mission. We will explain and demonstrate these systems that now include Level-2 data from the THEMIS ground and space instruments and the latest orbits and orbit predictions. CDAWeb now serves current FluxGate Magnetometer (FGM), ElectroStatic Analyzer (ESA), Solid-State Telescope (SST), Electric Field Instrument (EFI) and Search Coil Magnetometer (SCM) data from all 5 THEMIS spacecraft and magnetometer data from 20+ THEMIS ground stations. CDAWeb displays include line plots and spectrograms and outputs are now also available in PDF and Postscript. The latest version of the 3-D interactive orbit viewer now includes the capability to follow the magnetic ground tracks of the THEMIS satellites and their relation to the THEMIS ground stations making it an excellent tool for the coordinated analysis of THEMIS space and ground data. The SSCWeb system allows complex queries involving magnetic conjunctions between satellites and between satellites and ground stations, and region occupancy. Several THEMIS-specific queries were set up and saved and are now available for easy (one click) usage. THEMIS is utilizing the Common Data Format (CDF) for its data products, a format developed and maintained by SPDF and the backbone of the CDAWeb system. A number of CDF routines were customized for most efficient use by the THEMIS team.

Bilitza, D.; McGuire, R. E.; Candey, R. M.; Chimiak, R. A.; Harris, B. T.; Han, D. B.; Kovalick, T. J.; Johnson, R. C.; Leckner, H. A.; Angelopoulos, V.

2007-12-01

269

Measurement of Orbital Volume after Enucleation and Orbital Implantation  

PubMed Central

Introduction This article reports experience relating to the measurement of orbital volume by means of cone beam computed tomography (CBCT) and Cranioviewer program software in patients who have undergone enucleation and orbital implantation. Patients and Methods CBCT scans were made in 30 cases, 10 of which were later excluded because of various technical problems. The study group therefore consisted of 20 patients (8 men and 12 women). The longest follow-up time was 7 years, and the shortest was 1 year. In all 20 cases, the orbital volume was measured with Cranioviewer orbital program software. Slices were made in the ventrodorsal direction at 4.8 mm intervals in the frontal plane, in both bony orbits (both that containing the orbital implant and the healthy one). Similar measurements were made in 20 patients with various dental problems. CBCT scans were recorded for the facial region of the skull, containing the orbital region. The Cranioviewer program can colour the area of the slices red, and it automatically measures the area in mm. Results In 5 of the 20 cases, the first 4 or all 5 slices revealed that the volume of the operated orbit was significantly smaller than that of the healthy orbit, in 12 cases only from 1 to 3 of the slices indicated such a significant difference, and in 3 cases no differences were observed between the orbits. In the control group of patients with various dental problems, there was no significant difference between the two healthy orbits. The accuracy of the volume measurements was assessed statistically by means of the paired samples t-test. Summary To date, no appropriate method is avaliable for exact measurement of the bony orbital volume, which would be of particular importance in orbital injury reconstruction. However, the use of CBCT scans and Cranioviewer orbital program software appears to offer a reliable method for the measurement of changes in orbital volume.

Lukats, Olga; Vizkelety, Tamas; Markella, Zsolt; Maka, Erika; Kiss, Maria; Dobai, Adrienn; Bujtar, Peter; Szucs, Attila; Barabas, Jozsef

2012-01-01

270

Close binary neutron star systems  

NASA Astrophysics Data System (ADS)

We present a method to calculate solutions to the initial value problem in (3 + 1) general relativity corresponding to binary neutron-star systems (BNS) in irrotational quasi-equilibrium orbits. The initial value equations are solved using a conformally flat spatial metric tensor. The stellar fluid dynamics corresponds to that of systems with zero vorticity in the inertial reference frame. Irrotational systems like the ones analyzed in the present work are likely to resemble the final stages of the evolution of neutron-star binaries, thus providing insights on the inspiral process. The fluid velocity is derived from the gradient of a scalar potential. A numerical program was developed to solve the elliptic equations for the metric fields and the fluid velocity potential. We discuss the different numerical techniques employed to achieve high resolution across the stellar volume, as well as the methods used to find solutions to the Poisson-like equations with their corresponding boundary conditions. We present sequences of quasi-stable circular orbits which conserve baryonic mass. These sequences mimic the time evolution of the inspiral and are obtained without solving the complex evolution equations. They also provide sets of initial value data for future time evolution codes, which should be valid very close to the final merger. We evaluate the emission of gravitational radiation during the evolution through multipole expansions methods.

Marronetti, Pedro

1999-12-01

271

Transient co-orbital asteroids  

Microsoft Academic Search

We analyze the orbital behavior of four new co-orbital NEOs and the Earth horseshoe object 2002 AA29. The new objects are 2001 CK32, a 3753 Cruithne-like co-orbital of Venus, 2001 GO2 and 2003 YN107, two objects with motion similar to 2002 AA29. 2001 CK32 is on a compound orbit. The asteroid reverses its path when the mean longitude difference is

R. Brasser; K. A. Innanen; M. Connors; C. Veillet; P. Wiegert; Seppo Mikkola; P. W. Chodas

2004-01-01

272

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. Grain heights are less than their diameter so the grains resemble antacid tablets, coins, or poker chips. These grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by grain and channel sizes. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; Steel, Fiona

2011-03-01

273

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We experimentally study jamming of cylindrical grains in a vertical channel. The grains have a low aspect-ratio (height/diameter < 1) so their shape is like antacid tablets or poker chips. They are allowed to fall through a vertical channel with a square cross section. The channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. It is observed that grains sometimes jam in this apparatus. In a jam, grains form a stable structure from one side of the channel to the other with nothing beneath them. Jams may be strong enough to support additional grains above. The probability of a jam occurring is a function of the grain height and diameter. We will present experimental measurements of the jamming probability in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; McCausland, Jeffrey; Steel, Fiona

2010-03-01

274

Vertical axis wind turbine  

Microsoft Academic Search

A vertical axis wind turbine is provided based on the co-pending application ser. No. 890,998, filed Mar. 28, 1978, now U.S. Pat. No. 4,204,805. In this improved system the centrifugal forces of rotation produce no bending moments in the air foil spars. Also, the center of mass, the center of useful aerodynamic pressure and the center of main bearing supported

Bolie

1981-01-01

275

Prospective Ukrainian lunar orbiter mission  

Microsoft Academic Search

Ukraine has launch vehicles that are able to deliver about 300 kg to the lunar orbit. Future Ukrainian lunar program may propose a polar orbiter. This orbiter should fill principal information gaps in our knowledge about the Moon after Clementine and Lunar Prospector missions and the future missions, like Smart-1, Lunar-A, and Selene. We consider that this can be provided

Y. Shkuratov; L. Litvinenko; V. Shulga; Y. Yatskiv; V. Kislyuk

2002-01-01

276

Semiclassical quantization using diffractive orbits  

Microsoft Academic Search

Diffraction, in the context of semiclassical mechanics, describes the manner in which quantum mechanics smooths over discontinuities in classical mechanics. Semiclassical quantization then requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this Letter we construct the corresponding diffractive zeta function and apply it to a scattering problem which has only diffractive periodic orbits. We

Niall D. Whelan

1996-01-01

277

Integrable approximation of J 2-perturbed relative orbits  

NASA Astrophysics Data System (ADS)

Most existing satellite relative motion theories utilize mean elements, and therefore cannot be used for calculating long-term bounded perturbed relative orbits. The goal of the current paper is to find an integrable approximation for the relative motion problem under the J 2 perturbation, which is adequate for long-term prediction of bounded relative orbits with arbitrary inclinations. To that end, a radial intermediary Hamiltonian is utilized. The intermediary Hamiltonian retains the original structure of the full J 2 Hamiltonian, excluding the latitude dependence. This formalism provides integrability via separation, a fact that is utilized for finding periodic relative orbits in a local-vertical local-horizontal frame and determine an initialization scheme that yields long-term boundedness of the relative distance. Numerical experiments show that the intermediary-based computation of orbits provides long-term bounded orbits in the full J 2 problem for various inclinations. In addition, a test case is shown in which the radial intermediary-based initial conditions of the chief and deputy satellites yield bounded relative distance in a high-precision orbit propagator.

Lara, M.; Gurfil, P.

2012-11-01

278

Blepharoplasty revealing orbital lymphoma.  

PubMed

Blepharoplasty is a frequent request in consultations of plastic surgery. Patients are often presenting with a progressive swelling of the eyelids. For functional or aesthetic reasons, we commonly perform a superior and/or inferior blepharoplasty to correct this problem. We present the case of a 72-year-old woman who consulted us with a prominent unattractive swelling of both lower eyelids. Because of the atypical and suspicious presentation, supplementary examinations were conducted, and the fat was also sent for analysis. A diagnosis of unilateral orbital lymphoma was obtained. The patient was treated as a primarily localized lymphoma with a positive outcome. When correctly diagnosed and treated, orbital lymphomas can have a very good prognosis. PMID:22214799

Marival, Talia; Carpentier, Séverine; Vandaele, Shiran; de Fontaine, Serge

2013-03-01

279

Orbital changes and climate  

Microsoft Academic Search

At the 41,000-period of orbital tilt, summer insolation forces a lagged response in northern ice sheets. This delayed ice signal is rapidly transferred to nearby northern oceans and landmasses by atmospheric dynamics. These ice-driven responses lead to late-phased changes in atmospheric CO2 that provide positive feedback to the ice sheets and also project ‘late’ 41-K forcing across the tropics and

William F. Ruddiman

2006-01-01

280

The Solar Orbiter mission  

NASA Astrophysics Data System (ADS)

The ESA/NASA Solar Orbiter mission will address the central question of heliophysics: How does the Sun create and control the heliosphere? The heliosphere represents a uniquely accessible domain of space, where fundamental physical processes common to solar, astrophysical and laboratory plasmas can be studied under conditions impossible to reproduce on Earth and unfeasible to observe from astronomical distances. In this paper, we present a brief overview of the mission.

Müller, Daniel; St. Cyr, O. Chris

2013-09-01

281

Orbital cystic neurinoma  

Microsoft Academic Search

Summary ¶A 64-year-old woman presented with a 6-month history of exophthalmus of her right eye. She had no neurological deficit except for the exophthalmus and numbness in the right side of her forehead (frontal nerve territory). Neuro-imaging demonstrated a cystic mass in the right orbit. The tumour was totally removed by microsurgical transcranial surgery. The histological diagnosis was neurinoma. The

J. Tokugawa; Y. Nakao; K. Mori; M. Maeda

2003-01-01

282

Behavior of Jupiter Non-Trojan Co-Orbitals  

NASA Astrophysics Data System (ADS)

Searching for the non-Trojan Jupiter co-orbitals we have numerically integrated orbits of 3160 asteroids and 24 comets discovered by October 2010 and situated within and close to the planet co-orbital region. Using this sample we have been able to select eight asteroids and three comets and analyze their orbital behavior in a great detail. Among them we have identified five new Jupiter co-orbitals: (241944) 2002 CU147, 2006 SA387, 2006 QL39, 2007 GH6, and 200P/Larsen, as well as we have analyzed six previously identified co-orbitals: (118624) 2000 HR24, 2006 UG185, 2001 QQ199, 2004 AE9, P/2003 WC7 LINEAR-CATALINA and P/2002 AR2 LINEAR. (241944) 2002 CU147 is currently on a quasi-satellite orbit with repeatable transitions into the tadpole state. Similar behavior shows 2007 GH6 which additionally librates in a compound tadpole-quasi-satellite orbit. 2006 QL39 and 2000P/Larsen are the co-orbitals of Jupiter which are temporarily moving in a horseshoe orbit occasionally interrupted by a quasi-satellite behavior. 2006 SA387 is moving in a pure horseshoe orbit. Orbits of the latter three objects are unstable and according to our calculations, these objects will leave the horseshoe state in a few hundred years. Two asteroids, 2001 QQ199 and 2004 AE9, are long-lived quasi-satellites of Jupiter. They will remain in this state for a few thousand years at least. The comets P/2002 AR2 LINEAR and P/2003 WC7 LINEAR-CATALINA are also quasi-satellites of Jupiter. However, the non-gravitational effects may be significant in the motion of these comets. We have shown that P/2003 WC7 is moving in a quasi-satellite orbit and will stay in this regime to at least 2500 year. Asteroid (118624) 2000 HR24 will be temporarily captured in a quasi-satellite orbit near 2050 and we have identified another one object which shows similar behavior - the asteroid 2006 UG185, although, its guiding center encloses the origin, it is not a quasi-satellite. The orbits of these two objects can be accurately calculated for a few hundred years forward and backward.

Wajer, P.; Królikowska, M.

2012-03-01

283

Ionospheric Imaging from Geostationary Orbit  

NASA Astrophysics Data System (ADS)

An ultraviolet imager is under development to image the ionosphere and thermosphere from geostationary orbit. The instrument will consist of two telescopes, one with a filter wheel to measure the atomic oxygen airglow emission at 130.4 nm and 135.6 nm and molecular nitrogen Lyman-Birge-Hopfield bands near 142.5 nm. The second telescope will image the atomic oxygen ion resonance multiplet at 83.4 nm. Both telescopes will have a field of regard of 1.5 degrees with resolutions of 0.01 degrees providing spatial coverage of 1500 km x 1500 km with a resolution of 10 km x 10 km. The telescopes will be mounted to a two-axis gimbal to image various regions of the disk and limb of the Earth. This instrument is tentatively planned to fly aboard an Air Force Space Test Program satellite in 2005. The primary science goals of the experiment are to image the nightside ionosphere using measurements of the OI 135.6 nm nightglow produced from radiative recombination of electrons with oxygen ions. These observations will be used to study the variability and dynamics of ionospheric irregularities. Secondary objectives include measurement of vertical profiles of electron density at night on the limb of the Earth and measurement of dayside oxygen ion profiles using the 83.4 nm resonant line. Additional objectives include: measurement of the dayside limb profiles of neutral density; studies of thermospheric heating and geomagnetic storms using observations of disk ratios of oxygen to nitrogen; studies of the morphology of the equator-ward edges of the aurora. It is anticipated that nightside ionospheric images can be obtained within 100 to 1000 seconds to allow high time resolution studies of the space weather effects in the ionosphere.

McCoy, R. P.; Wood, K. S.; Dymond, K. F.; Thonnard, S. E.

2001-05-01

284

Mars Advanced Studies: Next Generation Orbiters  

NASA Astrophysics Data System (ADS)

With the discovery of potentially large amounts of water near the Martian poles in form of permafrost close to the surface, the interests of the scientific community drive the advanced studies for mars exploration. The Mars Advanced Studies Office is seeking to build an integrated plan for mars exploration into the next decade. A series of advanced studies of potential candidate missions are being investigated. The studies cover mars orbiters, Landers, rovers, drills, sample return, and robotic outposts. The Next Generation Mars Orbiters are driven by the science community priorities. This has led to a series of concept missions to study the subsurface, the stratigraphy, the composition of the surface elements on mars, climatic changes, magnetic remnants over ancient terrain, and gravity experiments.

Deutsch, M.-J.

285

Europa planetary protection for Juno Jupiter Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Juno mission launched in 2011 and will explore Jupiter and its near environment starting in 2016. Planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design. In particular Juno's polar orbit, which enables scientific investigations of parts of Jupiter's environment never before visited, also greatly assist avoiding close flybys of Europa and the other Galilean satellites. The science mission is designed to conclude with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction in the event of impact with an icy body.

Bernard, Douglas E.; Abelson, Robert D.; Johannesen, Jennie R.; Lam, Try; McAlpine, William J.; Newlin, Laura E.

2013-08-01

286

Myeloma-associated orbital amyloidosis.  

PubMed

Orbital amyloidosis is extremely rare and may be localized finding or secondary to a systematic process. The majority of the patients with orbital amyloidosis have primary localized disease. We report a 55 year old male with multiple myeloma and secondary amyloidosis who presented with incidental bilateral orbital masses on MRI. Biopsy revealed amyloid deposition. We review the previously published cases of the orbital amyloidosis secondary to systematic light chain (AL) amyloidosis, including one patient with multiple myeloma. The clinical signs and symptoms, histopathologic findings, and radiographic features of orbital amyloidosis are discussed. PMID:20572755

Goshe, Jeff M; Schoenfield, Lynn; Emch, Todd; Singh, Arun D

2010-06-23

287

Late correction of orbital deformities.  

PubMed

Orbital fractures are some of the most challenging injuries the oral surgeon deals with on a daily basis. Delay of the treatment of orbital fractures impacts the final result. Late orbital reconstruction is sometimes necessary for inadequate primary reconstruction or for severe injuries with adequate primary reconstruction. Healing and wound contraction make secondary reconstruction more difficult to restore the orbital contents back to normal. There are different materials available for orbital reconstruction, and there is no consensus about which is best. Early surgical intervention may improve the ultimate outcome, but identifying patients at risk of late complications is difficult. PMID:23017201

Palmieri, Celso F; Ghali, G E

2012-09-24

288

Commissioning and Performance of the APS Real-Time Orbit Feedback System  

NASA Astrophysics Data System (ADS)

The Advanced Photon Source (APS) is implementing a unified global and local closed orbit feedback system to stabilize both particle and photon beams. Beam stability requirements in the band up to 50Hz are 17?m in the horizontal plane and 4.5?m in the vertical plane. The global system is designed for a closed loop bandwidth of 100Hz. Feedback algorithms are implemented digitally using multiple digital signal processors with an update rate presently at 1kHz. Computing power is distributed in 20 VME crates around the storage ring, and each crate communicates with all others via a fast reflective memory network. The system has access to as many as 320 rf beam position monitors and has two x-ray beam position monitors per x-ray beamline. Up to 283 corrector magnets are available in each plane. Both global and local systems have been tested with beam, and the global system will shortly be online for user studies. The paper describes commissioning experience and measured sy! stem performance.

Carwardine, J.; Decker, G.; Evans, K., Jr.; Hillman, A.; Lenkzsus, F.; Merl, R.; Pietryla, A.

1997-05-01

289

Orbital exenteration: a 13 year Manchester experience  

PubMed Central

Background/aims: Orbital exenteration is a psychologically and anatomically disfiguring procedure reserved for the treatment of potentially life threatening malignancies or relentlessly progressive conditions unresponsive to other treatments. In this study the authors aimed to review their experience with exenteration, including indications, outcomes, and reasons for the increased rate of exenterations over the past 15 months. Method: This retrospective study reviewed operating department records via a computerised database to identify all patients who had undergone exenteration of the orbit from 1 January 1991 to 1 April 2004 inclusive, at the Manchester Royal Eye Hospital. Where case records were unavailable, attempts were made to obtain patient data from general practitioners, local health authorities, and referring hospitals. Results: 69 orbits of 68 patients were identified. The mean age of the cohort was 68.2 years, with 33 males and 35 females having undergone exenterations. In total, 31 patients had previously undergone treatments undertaken by the referring specialty with a mean time from the primary procedure to exenteration of 115 months. 14 different tumours were encountered, of which basal cell carcinoma (28), melanoma (10), sebaceous cell carcinoma (nine), and squamous cell carcinoma (six) were the most common. An increasing incidence was observed in cases of BCCs requiring exenteration. 30 patients received orbital prosthesis within an 11 month period post-exenteration. Conclusion: Exenteration is a procedure performed with increasing frequency in this unit over the past 15 months, the majority the result of BCCs. A large proportion of these exenterations had undergone previous treatments under a variety of non-ophthalmic specialties in other units. Exenterations are disfiguring procedures that may, therefore, be reduced in incidence by aggressive removal at the time of primary removal. Once performed, the cosmetic rehabilitation is long, with multiple postoperative visits, independent of the method used to close the orbital defect.

Rahman, I; Cook, A E; Leatherbarrow, B

2005-01-01

290

Quasi-satellite Orbits in the Context of Coorbital Dynamics  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): The investigations on long-term evolution of asteroid’s orbits are crucial to understanding the route through which the present configuration of the Solar system came to be. The so-called coorbiting asteroids (which share their orbits with major planets) attract the special attention in this connection: are they the primordial remnants of the building blocks of the corresponding major planet or are they the "migrants" from the other parts of the Solar system? The most well known examples of co-orbits in natural objects are provided by Trojan groups of asteroids and by asteroids moving in horseshoe orbits. These asteroids are precluded from having relatively close encounters with their host planets. However, there exists another class of coorbiting objects in which the opposite is true: they remain very near to the host planet eternally or, at least, for long enough time. Since typically they never enter the planet’s Hill sphere, they cannot be considered as satellites in the usual sense of the word. In order to emphasize this specific they are called quasi-satellites (QS). We explore the properties of QS-orbits under the scope of the restricted spatial circular three-body problem. Via double numerical averaging, we construct evolutionary equations which describe the long-term behaviour of the orbital elements of an asteroid. Special attention is paid at possible transitions between the motion in a QS-orbit and that in another type of orbit available in the 1:1 mean motion resonance. To illustrate the typical rates of the orbital elements's secular evolution, the dynamics of the near-Earth asteroid 2004GU9 was studied. This asteroid will keep describing a QS-orbit for the next several hundreds of years. This work was supported by the grant of the Russian Academy of Sciences Presidium Program 22: "Fundamental problems of research and exploration of the Solar system".

Sidorenko, Vladislav; Artemyev, A.; Neishtadt, A.; Zelenyi, L.

2013-05-01

291

Vertically moored platform anchoring  

SciTech Connect

An improved system is disclosed for anchoring a floating vessel which is anchored only by parallel and essentially vertical conduits. The anchoring load is carried by units of concentric pipes including an outer riser pipe and inner strings of casing. Drilling wells and/or production of oil and gas or like operations are conducted through these casings. The tension of the inner casing string is transmitted to the floating vessel through the upper end of the outer riser pipe. The system prevents excessive buildup of stresses in the upper end of the inner casing due to the bending caused by excursions caused by the waves, the wind and the current.

Blenkarn, K.A.; Beynet, P.A.

1984-02-14

292

Subsonic aerodynamic characteristics of a circular body earth-to-orbit transport  

Microsoft Academic Search

To reduce the weight and improve the performance of future earth-to-orbit transports, the use of circular cross sections in the fuselage bodies of these vehicles is being considered at the Langley Research Center. Structurally, circular cross sections are stronger and lighter than other shapes. A study has been made applying the circular body concept to a vertical-takeoff, delta-winged, single-stage-to-orbit transport.

R. A. Lepsch Jr.; I. O. MacConochie

1986-01-01

293

A Concept of Two-Stage-To-Orbit Reusable Launch Vehicle  

NASA Astrophysics Data System (ADS)

Reusable Launch Vehicle (RLV) has a capability of delivering a wide rang of payload to earth orbit with greater reliability, lower cost, more flexibility and operability than any of today's launch vehicles. It is the goal of future space transportation systems. Past experience on single stage to orbit (SSTO) RLVs, such as NASA's NASP project, which aims at developing an rocket-based combined-cycle (RBCC) airplane and X-33, which aims at developing a rocket RLV, indicates that SSTO RLV can not be realized in the next few years based on the state-of-the-art technologies. This paper presents a concept of all rocket two-stage-to-orbit (TSTO) reusable launch vehicle. The TSTO RLV comprises an orbiter and a booster stage. The orbiter is mounted on the top of the booster stage. The TSTO RLV takes off vertically. At the altitude about 50km the booster stage is separated from the orbiter, returns and lands by parachutes and airbags, or lands horizontally by means of its own propulsion system. The orbiter continues its ascent flight and delivers the payload into LEO orbit. After completing orbit mission, the orbiter will reenter into the atmosphere, automatically fly to the ground base and finally horizontally land on the runway. TSTO RLV has less technology difficulties and risk than SSTO, and maybe the practical approach to the RLV in the near future.

Yang, Yong; Wang, Xiaojun; Tang, Yihua

2002-01-01

294

Torsional nystagmus during vertical pursuit.  

PubMed

We examined three patients with cavernous angioma within the middle cerebellar peduncle. Each patient had an unusual ocular motor finding: the appearance of a strong torsional nystagmus during vertical pursuit. The uncalled-for torsion changed direction when vertical pursuit changed direction. In one patient, we recorded eye movements with the magnetic field technique using a combined direction and torsion eye coil. The slow-phase velocity of the inappropriate torsional nystagmus was linearly related to the slow-phase velocity of vertical smooth pursuit, and changed direction when vertical pursuit changed direction. This torsional nystagmus also appeared during fixation suppression of the vertical vestibulo-ocular reflex (VOR), but was minimal during vertical head rotation when fixing a stationary target in the light. We suggest that inappropriately directed eye movements during pursuit might be another ocular motor sign of cerebellar dysfunction. Furthermore, we speculate that the signals used for vertical smooth pursuit are, at some stage, encoded in a semicircular canal VOR coordinate framework. To illustrate, for the vertical semicircular canals, vertical and torsional motion are combined on the same cells, with the anterior semicircular canals mediating upward movements and the posterior semicircular canals mediating downward movements. For the right labyrinth, however, both vertical semicircular canals produce clockwise slow phases (ipsilateral eye intorts, contralateral eye extorts). The opposite is true for the vertical semicircular canals in the left labyrinth; counterclockwise slow phases are produced. Hence, to generate a pure vertical VOR, the anterior or posterior semicircular canals on both sides of the head must be excited so that opposite-directed torsional components cancel. Thus, if pursuit were organized in a way similar to the VOR, pure vertical pursuit would require that oppositely-directed torsional components cancel in normals. If this did not happen, a residual torsional nystagmus could appear during attempted vertical pursuit. PMID:8797162

FitzGibbon, E J; Calvert, P C; Dieterich, M; Brandt, T; Zee, D S

1996-06-01

295

Role of long quantum orbits in high-order harmonic generation  

SciTech Connect

Single-atom high-order harmonic generation is considered in the strong-field approximation, as formulated in the Lewenstein model, and analyzed in terms of quantum orbits. Orbits are classified according to the solutions of the saddle-point equations. The results of a numerical integration are compared with the saddle-point approximation and the uniform approximation. Approximate analytical solutions for long orbits are presented. The formalism developed is used to analyze the enhancement of high-order harmonic generation near channel closings. The enhancements exactly at the channel closings are extremely narrow and built up by the constructive interference of a very large number of quantum orbits. Additional broader enhancements occur slightly below channel closings. They are generated by the interplay of a medium number of orbits.

Milosevic, D.B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany); Becker, W. [Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany)

2002-12-01

296

The Dynamics of Objects in Orbits Resembling That of P\\/Encke  

Microsoft Academic Search

The overall orbital evolution of bodies resembling that of P\\/Encke is studied by numerical integration. Dynamical paths are found that connect orbits of this type to their possible sources, i.e., the asteroidal main belt and the Jupiter family of comets. Possible end-states for these orbits include ejection from the region of the inner planets, due to close encounters with Jupiter,

G. B. Valsecchi; A. Morbidelli; R. Gonczi; P. Farinella; Ch. Froeschle; Cl. Froeschle

1995-01-01

297

Solar Orbiter: a high-resolution mission to the sun and inner heliosphere  

Microsoft Academic Search

The key mission objective of the Solar Orbiter is to study the Sun from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar rotation in order to examine the solar surface and the space above from a co-rotating vantage point at high spatial resolution. Solar Orbiter will also provide images of the Sun's polar regions from

Bernhard Fleck; E. Marsch; Ester Antonucci; Peter A. Bochsler; J. L. Bougeret; R. Harrison; R. P. Marsden; M. Coradini; Oscar Pace; Rainer Schwenn; Jean-Claude Vial

2001-01-01

298

Orbital tuberculosis in childhood with intracranial extension: a case report  

PubMed Central

The common causes of orbital masses in pediatric age group include pseudotumour, lymphomas, hemangioma and dermoid cyst. Orbital tuberculosis is rare especially in children. We report a case of 5 year old child who presented with proptosis and gross diminution of vision due to orbital tuberculoma. Ocular examination of the left eye revealed proptosis with the eyeball displaced downwards and forwards. Vision was counting finger close to face. CT Scan showed an extraconal soft tissue mass along posteromedial side of left orbit with lateral displacement of medial rectus muscle. On antitubercular treatment, proptosis regressed and visual recovery was observed over a period of six month vision, in the left eye at the last followup was 20/30.

2010-01-01

299

Orbital tuberculosis in childhood with intracranial extension: a case report.  

PubMed

The common causes of orbital masses in pediatric age group include pseudotumour, lymphomas, hemangioma and dermoid cyst. Orbital tuberculosis is rare especially in children. We report a case of 5 year old child who presented with proptosis and gross diminution of vision due to orbital tuberculoma. Ocular examination of the left eye revealed proptosis with the eyeball displaced downwards and forwards. Vision was counting finger close to face. CT Scan showed an extraconal soft tissue mass along posteromedial side of left orbit with lateral displacement of medial rectus muscle. On antitubercular treatment, proptosis regressed and visual recovery was observed over a period of six month vision, in the left eye at the last followup was 20/30. PMID:20205883

Tuli, Navneet

2010-01-28

300

Massive Satellites of Close-In Gas Giant Exoplanets  

NASA Astrophysics Data System (ADS)

We study the orbits, tidal heating and mass loss from satellites around close-in gas giant exoplanets. The focus is on large satellites which are potentially observable by their transit signature. We argue that even Earth-size satellites around hot Jupiters can be immune to destruction by orbital decay; detection of such a massive satellite would strongly constrain theories of tidal dissipation in gas giants, in a manner complementary to orbital circularization. The star's gravity induces significant periodic eccentricity in the satellite's orbit. The resulting tidal heating rates, per unit mass, are far in excess of Io's and dominate radioactive heating out to planet orbital periods of months for reasonable satellite tidal Q. Inside planet orbital periods of about a week, tidal heating can completely melt the satellite. Lastly, we compute an upper limit to the satellite mass loss rate due to thermal evaporation from the surface, valid if the satellite's atmosphere is thin and vapor pressure is negligible. Using this upper limit, we find that although rocky satellites around hot Jupiters with orbital periods less than a few days can be significantly evaporated in their lifetimes, detectable satellites suffer negligible mass loss at longer orbital periods.

Cassidy, Timothy A.; Mendez, Rolando; Arras, Phil; Johnson, Robert E.; Skrutskie, Michael F.

2009-10-01

301

MASSIVE SATELLITES OF CLOSE-IN GAS GIANT EXOPLANETS  

SciTech Connect

We study the orbits, tidal heating and mass loss from satellites around close-in gas giant exoplanets. The focus is on large satellites which are potentially observable by their transit signature. We argue that even Earth-size satellites around hot Jupiters can be immune to destruction by orbital decay; detection of such a massive satellite would strongly constrain theories of tidal dissipation in gas giants, in a manner complementary to orbital circularization. The star's gravity induces significant periodic eccentricity in the satellite's orbit. The resulting tidal heating rates, per unit mass, are far in excess of Io's and dominate radioactive heating out to planet orbital periods of months for reasonable satellite tidal Q. Inside planet orbital periods of about a week, tidal heating can completely melt the satellite. Lastly, we compute an upper limit to the satellite mass loss rate due to thermal evaporation from the surface, valid if the satellite's atmosphere is thin and vapor pressure is negligible. Using this upper limit, we find that although rocky satellites around hot Jupiters with orbital periods less than a few days can be significantly evaporated in their lifetimes, detectable satellites suffer negligible mass loss at longer orbital periods.

Cassidy, Timothy A.; Johnson, Robert E. [Engineering Physics Program, University of Virginia, Charlottesville, VA 22904-4325 (United States); Mendez, Rolando; Arras, Phil; Skrutskie, Michael F., E-mail: tac2z@virginia.ed, E-mail: rem5d@cms.mail.virginia.ed, E-mail: arras@virginia.ed, E-mail: rej@virginia.ed, E-mail: mfs4n@virginia.ed [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)

2009-10-20

302

Neptune Orbiter Mission Scenario Based on Nuclear Electric Propulsion and Aerocapture Orbital Insertion  

NASA Astrophysics Data System (ADS)

insertion of spacecraft into elliptical orbit around target planet is proposed for Neptune orbiter mission. The primary goal of combining nuclear electric propulsion (NEP) and aerocapture orbital insertion is a reduction of a trip time comparing to that of similar mission, which would use nuclear electric propulsion only. One of the limitations of the all NEP orbiter is that at the planetary approach it must match its arrival velocity with Neptune's orbital speed in order to initiate slow capture into the desired orbit using low thrust electric propulsion. Use of aerocapture for insertion into closed elliptical orbit around Neptune through a single aerodynamically controlled atmospheric pass gives advantage of having higher entry velocities than it would be possible in case of all NEP scenario, thus reducing trip time required for interplanetary transfer. propulsion and thermal protection systems. Moreover, because faster interplanetary trip times for combined NEP/Aerocapture orbiter result in a higher entry velocities into the Neptune's atmosphere, they will also drive the increase in aerobrake mass fraction. In addition, aerocapture at Neptune also presents a challenge for aerobrake's guidance system which must target vehicle to the desired atmospheric exit conditions in the presence of significant uncertainties in Neptune's atmospheric density. Hence, there is a need to design a robust nominal aerocapture trajectory capable of accommodating density dispersions and also optimized for minimum thermal protection mass, thus contributing to overall reduction of aerobrake mass fraction. determine the optimal combination between reduction of the trip time and increase in aerobrake mass fraction was undertaken. The initial assumptions on aerobrake thermal protection materials and NEP system characteristics were based on near term state of the art technology, corresponding to 2007-2010 time frame, when such a mission to Neptune could be launched. interplanetary trajectory simulation including capture into orbit around Neptune. In these low thrust trajectory simulations the trust level and the specific impulse of a single electric rocket engine were fixed, thus allowing to optimize number of engines and their thrust time history for a rapid transfer to Neptune. Therefore, for combined NEP/Aerocapture mission use of this approach made possible to determine the change in NEP mass fraction, comparing to that one of all NEP mission scenario where spacecraft velocity at its arrival would have to be matched with Neptune's orbital speed. atmosphere, where vehicle was captured into a highly elliptical orbit, which insures periodical close fly-by of the biggest Neptune's moon Triton, thus allowing its scientific observation. Nominal trajectories found in the process of aerocapture simulations were optimized for minimum mass of aerobrake's thermal protection system and were also shown to withstand significant density variations which are likely to be encountered in Neptune's atmosphere. These nominal trajectories were used to determine sensitivity of aerobrake's thermal protection system mass fraction to the variation of atmospheric entry velocity resulted from shorter trip times to Neptune. that for the same initial mass at the low earth orbit, all NEP mission flight time is 11-12 years, when as for the mission scenario which combines NEP and aerocapture flight time can be reduced to 5-6 years. Such a reduction in mission flight time represents much faster scientific return and it also translates into a higher chance of mission success and significant operational cost savings due to much shorter mission time.

Jits, R.

2002-01-01

303

Electric Propulsion Orbital Platform  

NASA Astrophysics Data System (ADS)

This paper describes the Electric Propulsion Orbital Platform (EPOP), of which the primary objective is to provide an instrumented platform for testing electric propulsion devices in space. It is anticipated that the first flight, EPOP-1, will take place on the Shuttle-deployed Wake Shield Facility in 1996, and will be designed around a commercial 1.8 kW arcjet system which will be operated on gaseous hydrogen propellant. Specific subsystems are described, including the arcjet system, the propellant and power systems, and the diagnostics systems.

Friedly, V. J.; Ruyten, Wilhelmus M.; Litchford, R. J.; Garrison, G. W.

1993-01-01

304

Lunar Exploration Orbiter (LEO)  

NASA Astrophysics Data System (ADS)

The Moon is an integral part of the Earth-Moon system, it is a witness to more than 4.5 b. y. of solar system history, and it is the only planetary body except Earth for which we have samples from known locations. The Moon is our closest companion and can easily be reached from Earth at any time, even with a relatively modest financial budget. Consequently, the Moon was the first logical step in the exploration of our solar system before we pursued more distant targets such as Mars and beyond. The vast amount of knowledge gained from the Apollo and other lunar missions of the late 1960's and early 1970's demonstrates how valuable the Moon is for the understanding of our planetary system. Even today, the Moon remains an extremely interesting target scientifically and technologically, as ever since, new data have helped to address some of our questions about the Earth-Moon system, many questions remained. Therefore, returning to the Moon is the critical stepping-stone to further exploring our immediate planetary neighborhood. In this concept study, we present scientific and technological arguments for a national German lunar mission, the Lunar Explorations Orbiter (LEO). Numerous space-faring nations have realized and identified the unique opportunities related to lunar exploration and have planned missions to the Moon within the next few years. Among these missions, LEO will be unique, because it will globally explore the Moon in unprecedented spatial and spectral resolution. LEO will significantly improve our understanding of the lunar surface composition, surface ages, mineralogy, physical properties, interior, thermal history, gravity field, regolith structure, and magnetic field. The Lunar Explorations Orbiter will carry an entire suite of innovative, complementary technologies, including high-resolution camera systems, several spectrometers that cover previously unexplored parts of the electromagnetic spectrum over a broad range of wavelengths, microwave and radar experiments, a very sensitive magnetometer and gradiometer, a subsatellite, and a state-of-the-art optical communication system. The Lunar Explorations Orbiter concept is technologically challenging but feasible, and will gather unique, integrated, interdisciplinary data sets that are of high scientific interest and will provide an unprecedented new context for all other international lunar missions. In fact, the Lunar Explorations Orbiter will further establish Germany as a leader among space-faring nations and will demonstrate expertise and technological know-how, which is "Made in Germany". With its high visibility, LEO will foster the growing acceptance of space exploration in Germany and will capture the imagination of the general public.

Jaumann, R.; Spohn, T.; Hiesinger, H.; Jessberger, E. K.; Neukum, G.; Oberst, J.; Helbert, J.; Christensen, U.; Keller, H. U.; Mall, U.; Böhnhardt, H.; Hartogh, P.; Glassmeier, K.-H.; Auster, H.-U.; Moreira, A.; Werner, M.; Pätzold, M.; Palme, H.; Wimmer-Schweingruber, R.; Mandea, M.; Lesur, V.; Häusler, B.; Hördt, A.; Eichentopf, K.; Hauber, E.; Hoffmann, H.; Köhler, U.; Kührt, E.; Michaelis, H.; Pauer, M.; Sohl, F.; Denk, T.; van Gasselt, S.

2007-08-01

305

Orbital physics (Communication arising): Experimental quest for orbital waves  

Microsoft Academic Search

One challenge in condensed-matter physics is the experimental confirmation of a new kind of elementary excitation - orbital waves, or orbitons, which are predicted to exist in an orbitally ordered state. Saitoh et al. have observed three peaks at 160, 144 and 126 meV in the Raman scattering of orbitally ordered lanthanum manganate (LaMnO3), and interpret these as evidence of

M. Grüninger; R. Rückamp; M. Windt; P. Reutler; C. Zobel; T. Lorenz; A. Freimuth; A. Revcolevschi

2002-01-01

306

Boundary-value problem formulations for computing invariant manifolds and connecting orbits in the circular restricted three body problem  

NASA Astrophysics Data System (ADS)

We demonstrate the remarkable effectiveness of boundary value formulations coupled to numerical continuation for the computation of stable and unstable manifolds in systems of ordinary differential equations. Specifically, we consider the circular restricted three-body problem (CR3BP), which models the motion of a satellite in an Earth-Moon-like system. The CR3BP has many well-known families of periodic orbits, such as the planar Lyapunov orbits and the non-planar vertical and halo orbits. We compute the unstable manifolds of selected vertical and halo orbits, which in several cases leads to the detection of heteroclinic connections from such a periodic orbit to invariant tori. Subsequent continuation of these connecting orbits with a suitable end point condition and allowing the energy level to vary leads to the further detection of apparent homoclinic connections from the base periodic orbit to itself, or the detection of heteroclinic connections from the base periodic orbit to other periodic orbits. Some of these connecting orbits are of potential interest in space mission design.

Calleja, R. C.; Doedel, E. J.; Humphries, A. R.; Lemus-Rodríguez, A.; Oldeman, E. B.

2012-10-01

307

Orbitally Induced Peierls State in Spinels  

NASA Astrophysics Data System (ADS)

We consider the superstructures, which can be formed in spinels containing on B sites the transition-metal ions with partially filled t2g levels. We show that, when such systems are close to the itinerant state (e.g., have an insulator-metal transition), there may appear in them an orbitally driven Peierls state. We explain by this mechanism the very unusual superstructures observed in CuIr2S4 (octamers) and MgTi2O4 (chiral superstructures) and suggest that a similar phenomenon should be observed in NaTiO2 and possibly in some other systems.

Khomskii, D. I.; Mizokawa, T.

2005-04-01

308

Orbitally induced Peierls state in spinels.  

PubMed

We consider the superstructures, which can be formed in spinels containing on B sites the transition-metal ions with partially filled t(2g) levels. We show that, when such systems are close to the itinerant state (e.g., have an insulator-metal transition), there may appear in them an orbitally driven Peierls state. We explain by this mechanism the very unusual superstructures observed in CuIr2S4 (octamers) and MgTi2O4 (chiral superstructures) and suggest that a similar phenomenon should be observed in NaTiO2 and possibly in some other systems. PMID:15904164

Khomskii, D I; Mizokawa, T

2005-04-19

309

Centropages behaviour: Swimming and vertical migration  

NASA Astrophysics Data System (ADS)

The evolutionary success of any species living in a variable environment depends on its capacity to enhance the probability of finding food and mates, and escaping predators. In the case of copepods of the genus Centropages, as in all planktonic copepods, their swimming behaviour is closely tied to these vital aspects, and shows a high degree of plasticity and adaptive capacity. Swimming mechanisms of Centropages change radically during development, mainly in the transition between naupliar stages to the 1st copepodite; nauplii do not produce feeding currents, whereas copepodites do. Adults and late developmental stages of C. typicus, C. hamatus and C. velificatus spend most of the time in slow swimming and resting breaks, with occasional and brief fast swimming (escape reactions) and grooming events. Slow swimming is closely related to the creation of feeding currents, and results from the beating of the cephalic appendages in a “fling and clap” manner. The proportion of time allocated to the different swimming activities depends on sensory cues like type and concentration of food, presence of potential mates, light intensity, hydrodynamic flow, etc. The responses of Centropages to changes in flow velocity fluctuations (small-scale turbulence) are similar to the escape responses (fast swimming) triggered by the presence of potential predators. Centropages generally have standard nocturnal vertical migration patterns involving considerable vertical displacements. This behaviour is closely related to the narrow spectral sensitivity and the low intensity threshold of the genus, and has important consequences for the active vertical transport of matter and energy. The variety of responses of Centropages to environmental changes, and in general all the aspects related to its swimming behaviour seem to be controlled by the trade-off between energetic gains (food intake), losses (swimming energy expenditure), and predation risk. Behavioural plasticity and adaptation appear to be the most relevant characteristics for the success of the genus in a wide range of marine environments.

Alcaraz, Miguel; Saiz, Enric; Calbet, Albert

2007-02-01

310

Neuronal activity related to vertical eye movement in the region of the interstitial nucleus of Cajal in alert cats  

Microsoft Academic Search

(1) Discharge characteristics of neurons in the region of the interstitial nucleus of Cajal (INC) were studied in alert cats during spontaneous or visually induced eye movement and sinusoidal vertical (pitch) rotation. Activity of a majority of cells (n = 68) was closely related to vertical eye position with or without bursting activity during on-direction saccades. They were called vertical

K. Fukushima; J. Fukushima; C. Harada; T. Ohashi; M. Kase

1990-01-01

311

Observation of picometer vertical emittance with a vertical undulator.  

PubMed

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic. PMID:23215388

Wootton, K P; Boland, M J; Dowd, R; Tan, Y-R E; Cowie, B C C; Papaphilippou, Y; Taylor, G N; Rassool, R P

2012-11-08

312

Observation of Picometer Vertical Emittance with a Vertical Undulator  

NASA Astrophysics Data System (ADS)

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

Wootton, K. P.; Boland, M. J.; Dowd, R.; Tan, Y.-R. E.; Cowie, B. C. C.; Papaphilippou, Y.; Taylor, G. N.; Rassool, R. P.

2012-11-01

313

The orbital surgeon.  

PubMed Central

While the number of orbital surgeons is limited, it is hoped these can be recognized and patients referred to them by ophthalmologists not interested or trained in that specialty. Let the orbital surgeon determine whether he can handle the problem in 1 to 2 days, or whether a neurosurgeon should do the procedure or make it a joint effort. It may well involve other specialty team effort approaches. It is essential to have an understanding of x-rays, CT, angiography, and MRI techniques and films. Sit with these specialists to learn more and help to avoid negative, misdiagnosis reports in the interest of the patient. Use judgement in helping the patient decide on ophthalmic or the more extensive neurosurgical approach after careful study and what is in their best interest. The team approach is used in well established medical centers with the ophthalmologist and neurosurgeon (or other specialist) working together in the best interest of the patient. This is more interesting and keeps the ophthalmologist in the mainstream of medicine. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 2 FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 3 D FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 A FIGURE 6 B FIGURE 7 A FIGURE 7 B FIGURE 7 C FIGURE 8 A FIGURE 8 B FIGURE 9

Kennedy, R E

1988-01-01

314

Coupled Spin, Mass, Magnetic field, and Orbital Evolution of Accreting Neutron stars  

Microsoft Academic Search

The present study is mainly addressed to the coupled spin, mass, magnetic field, orbital separation, and orbital period evolution of a neutron star entering a close binary system with a low mass main sequence companion, which loses mass in form of homogenous stellar wind. We apply flux expulsion of the magnetic field from the superfluid superconductive core of a neutron

M. Mirtorabi; A. Javadi Khasraghi; S. Abdolrahimi

2006-01-01

315

Impact risk analysis for a spacecraft in Cosmo-Skymed orbit  

Microsoft Academic Search

This paper presents a case study of Micrometeoroids and Orbital Debris risk assessment for a spacecraft flying in an orbit close to that of the Italian Cosmo-Skymed constellation. The aim of the analysis was to calculate the failure flux impinging on the satellite external shell, taking into account both geometry and materials of satellite surfaces. Furthermore the analysis included the

Cinzia Giacomuzzo; Alessandro Francesconi; Luciano Anselmo

2010-01-01

316

Hypothesis of a spin-orbit resonance between the Earth and Venus's core  

Microsoft Academic Search

The observation that the spin period of Venus is extremely close, although not equal, to the p = ?5 spin-orbit resonance with the Earth makes it very improbable that such a situation is fortuitous. This leads one to explore hypotheses in which the Earth spin-orbit resonance plays some role in Venus's observed spin rate. This paper proposes one such hypothesis.

Gérard V. Caudal

2010-01-01

317

Secular love and tidal numbers of synchronously orbiting satellites  

Microsoft Academic Search

The secular Love and the secular tidal numbers have been computed for eight synchronously orbiting satellites in the solar system for which the triaxiality parameters and satellite-centric gravitational constant are available. Excepting Deimos the total mass of which should be first refined, the secular Love and tidal numbers are rather close to unity, as a rule. That is why, the

M. Bursa

1988-01-01

318

Relative Navigation In Elliptical Orbits Using An Iterative Nonlinear Filter  

Microsoft Academic Search

The two step filter is applied to process intersate llite radar measurements to determine the motion of one satelli te relative to another in close elliptical orbits. Thi s filter breaks a nonlinear estimation problem into two stat e vectors. The \\

James L. Garrison

1997-01-01

319

Geostationary versus non geostationary orbits  

NASA Astrophysics Data System (ADS)

The issue of which satellite orbit, such as low earth orbit, medium earth orbit, highly elliptical orbit, geosynchronous orbit, etc., is best for a particular telecommunications role is not always straightforward. The technical, operational, financial, service, and reliability considerations must all be carefully assessed and detailed trade-off analysis undertaken. This article provides in some detail the type of methodology that can be utilized to conclude which particular set of orbital parameters would seem to be optimum for various missions. Ironically, many of the trade-off considerations today are similar to those some 30 years ago when the field of satellite communications was getting started. One major difference today is that satellite launch and operation is much more reliable. The general methodology presented here should be adaptable to addressing almost any proposed satellite system design and its optimum deployment.

Pritchard, Wilbur

320

Geostationary Earth Orbit Satellite Model  

NSDL National Science Digital Library

The Geostationary Earth Orbit Satellite Model is a simple angular velocity model that uses Java3D for a realistic visualization of satellites in geostationary orbits. Students can view and explore the behavior of geostationary orbits, non-geostationary orbits, and non-physical orbits. This model tests the Java 3D implementation of the EJS 3D library. A warning message will appear if the Java 3D library is not available. The Geostationary Earth Orbit Satellite Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Wee, Loo K.

2012-04-08

321

Orbital myositis: Diagnosis and management  

Microsoft Academic Search

Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young\\u000a adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital\\u000a and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most\\u000a common presentation is acute and unilateral, which initially responds to

Roberta M. S. Costa; Oana M. Dumitrascu; Lynn K. Gordon

2009-01-01

322

CBERS-2 LEOP Orbit Analysis  

Microsoft Academic Search

This work presents an analysis of CBERS-2 orbit during LEOP (Launching and Early Orbit Phase), including the main aspects related to the INPE´s pass to pass improvement of the initial orbit determination process application. This is the second of four sun-synchronous earth observation satellites foreseen to be developed and manufactured within a cooperation program between Brazil and China. A short

V. Orlando; H. K. Kuga; J. Tominaga

2004-01-01

323

Intrinsic stability of periodic orbits  

Microsoft Academic Search

Families of orbits of a conservative, two degree-of-freedom system are represented by an unsteady velocity field with components u(x,y,t) and v(x,y,t). It is shown that a necessary condition for stable periodic orbits is satisfied when the orbit-averaged divergence is zero, which results in bounded normal variations. A sufficient condition for stability is derived from the requirement that tangential variations do

Michael E. Hough

1987-01-01

324

Ancient schwannoma of the orbit.  

PubMed

Schwannoma, also referred to as neurilemmoma or peripheral neurinoma, is an unusual orbital benign tumour that may pose diagnostic challenges. Awareness of the clinical features that may be associated with the tumour and prompt surgical excision with histopathologic examination enable correct diagnosis. The authors describe a progressively increasing inferolateral orbital mass in a 32-year-old patient that was demonstrated to be an orbital ancient schwannoma. PMID:23316621

Pecorella, I; Toth, J; Lukats, O

2012-08-01

325

Orbiter Servicer Rendezvous Simulation (ORSIM)  

NASA Astrophysics Data System (ADS)

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration/quantities of logistics platforms and OMVs which conform to the dynamics of differential nodal precession, given user-prescribed values of the scheduled maintenance cycle and required servicing times. ORSIM is coded in FORTRAN-77 and is resident on an IBM PC/AT.

Amato, Amiel; Hoffman, Mickie D.

326

Halo Orbits in Cosmological Disk Galaxies: Tracers of Formation History  

NASA Astrophysics Data System (ADS)

We analyze the orbits of stars and dark matter particles in the halo of a disk galaxy formed in a cosmological hydrodynamical simulation. The halo is oblate within the inner ~20 kpc and triaxial beyond this radius. About 43% of orbits are short axis tubes—the rest belong to orbit families that characterize triaxial potentials (boxes, long-axis tubes and chaotic orbits), but their shapes are close to axisymmetric. We find no evidence that the self-consistent distribution function of the nearly oblate inner halo is comprised primarily of axisymmetric short-axis tube orbits. Orbits of all families and both types of particles are highly eccentric, with mean eccentricity >~ 0.6. We find that randomly selected samples of halo stars show no substructure in "integrals of motion" space. However, individual accretion events can clearly be identified in plots of metallicity versus formation time. Dynamically young tidal debris is found primarily on a single type of orbit. However, stars associated with older satellites become chaotically mixed during the formation process (possibly due to scattering by the central bulge and disk, and baryonic processes), and appear on all four types of orbits. We find that the tidal debris in cosmological hydrodynamical simulations experiences significantly more chaotic evolution than in collisionless simulations, making it much harder to identify individual progenitors using phase space coordinates alone. However, by combining information on stellar ages and chemical abundances with the orbital properties of halo stars in the underlying self-consistent potential, the identification of progenitors is likely to be possible.

Valluri, Monica; Debattista, Victor P.; Stinson, Gregory S.; Bailin, Jeremy; Quinn, Thomas R.; Couchman, H. M. P.; Wadsley, James

2013-04-01

327

Dynamics of geckos running vertically  

Microsoft Academic Search

Geckos with adhesive toe pads rapidly climb even smooth vertical surfaces. We challenged geckos (Hemidactylus garnotii) to climb up a smooth vertical track that contained a force platform. Geckos climbed vertically at up to 77·cm·s -1 with a stride frequency of 15·Hz using a trotting gait. During each step, whole body fore-aft, lateral and normal forces all decreased to zero

K. Autumn; S. T. Hsieh; D. M. Dudek; J. Chen; C. Chitaphan; R. J. Full

2006-01-01

328

Coupled resonator vertical cavity laser  

SciTech Connect

The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

1998-01-01

329

30.VERTIGO AND VERTICALITY IN  

Microsoft Academic Search

The vertical dimension is crucial to Super Monkey Ball on all levels1, and invites us to meditate on vertigo and verticality, falling and failing in the construc- tion of space and game-play in this game and in comput- er-games as such. In Super Monkey Ball, the vertical dimension should be mastered (landing on tiny islands with the ball glider), avoided

Troels Degn Johansson

330

On the centrality of vertices of molecular graphs.  

PubMed

For acyclic systems the center of a graph has been known to be either a single vertex of two adjacent vertices, that is, an edge. It has not been quite clear how to extend the concept of graph center to polycyclic systems. Several approaches to the graph center of molecular graphs of polycyclic graphs have been proposed in the literature. In most cases alternative approaches, however, while being apparently equally plausible, gave the same results for many molecules, but occasionally they differ in their characterization of molecular center. In order to reduce the number of vertices that would qualify as forming the center of the graph, a hierarchy of rules have been considered in the search for graph centers. We reconsidered the problem of "the center of a graph" by using a novel concept of graph theory, the vertex "weights," defined by counting the number of pairs of vertices at the same distance from the vertex considered. This approach gives often the same results for graph centers of acyclic graphs as the standard definition of graph center based on vertex eccentricities. However, in some cases when two nonequivalent vertices have been found as graph center, the novel approach can discriminate between the two. The same approach applies to cyclic graphs without additional rules to locate the vertex or vertices forming the center of polycyclic graphs, vertices referred to as central vertices of a graph. In addition, the novel vertex "weights," in the case of acyclic, cyclic, and polycyclic graphs can be interpreted as vertex centralities, a measure for how close or distant vertices are from the center or central vertices of the graph. Besides illustrating the centralities of a number of smaller polycyclic graphs, we also report on several acyclic graphs showing the same centrality values of their vertices. © 2013 Wiley Periodicals, Inc. PMID:23955387

Randi?, Milan; Novi?, Marjana; Vra?ko, Marjan; Plavši?, Dejan

2013-08-19

331

Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Lunar Reconnaissance Orbiter (LRO) plans to launch in October 2008 with a companion secondary impactor mission, LCROSS, as the inaugural missions for the Exploration System Mission Directorate. LRO is a pathfinder whose objective is to obtain the needed information to prepare for eventual human return to the Moon. LRO will undertake at least one baseline year of operation with additional extended mission phase sponsored by NASA's Science Mission Directorate. LRO will employ six individual instruments to produce accurate maps and high-resolution images of future landing sites, to assess potential lunar resources, and to characterize the radiation environment. LRO will also test the feasibility of one advanced technology demonstration package. The LRO payload includes: Lunar Orbiter Laser Altimeter (LOLA) which will determine the global topography of the lunar surface at high resolution, measure landing site slopes, surface roughness, and search for possible polar surface ice in shadowed regions; Lunar Reconnaissance Orbiter Camera (LROC) which will acquire targeted narrow angle images of the lunar surface capable of resolving meter-scale features to support landing site selection, as well as wide-angle images to characterize polar illumination conditions and to identify potential resources; Lunar Exploration Neutron Detector (LEND) which will map the flux of neutrons from the lunar surface to search for evidence of water ice, and will provide space radiation environment measurements that may be useful for future human exploration; Diviner Lunar Radiometer Experiment (DLRE) which will chart the temperature of the entire lunar surface at approximately 300 meter horizontal resolution to identify cold-traps and potential ice deposits; Lyman-Alpha Mapping Project (LAMP) which will map the entire lunar surface in the far ultraviolet. LAMP will search for surface ice and frost in the polar regions and provide images of permanently shadowed regions illuminated only by starlight; Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which will investigate the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background space radiation. The technology demonstration is an advanced radar (mini-RF) that will demonstrate X- and S-band radar imaging and interferometry using a light-weight synthetic aperture radar.

Morgan, T.; Chin, G.

2007-08-01

332

Axial rotation, orbital revolution and solar spin-orbit coupling  

Microsoft Academic Search

The orbital motion of the Sun has been linked with solar variability, but the underlying physics remains unknown. A coupling of the solar axial rotation and the barycentric orbital revolution might account for the relationships found. Some recent published studies addressing the physics of this problem have made use of equations from rotational physics in order to model particle motions.

James H. Shirley

2006-01-01

333

Orbital Fluctuations and Orbital Flipping in RVO3 Perovskites  

SciTech Connect

The effect of the average A-site ionic radius hIRi and variance on the orbital and magnetic order in R3+-doped YVO3 was studied in Y1-xLaxVO3 and Y1-x(La0.2337Lu0.7663)xVO3 with fixed . The orbital flipping temperature T_CG increases nonlinearly with increasing R-site variance, indicating that the V-O-V bond angle is not the primary driving force stabilizing the C-type orbitally ordered phase. The suppressed thermal conductivity in the G-type orbitally ordered phase signals some remaining orbital randomness that is enhanced by t2 and et hybridization in 3T_1g site symmetry.

Yan, J.-Q. [Ames Laboratory; Zhou, J.-S. [University of Texas, Austin; Goodenough, J. B. [University of Texas, Austin; Ren, Y. [Argonne National Laboratory (ANL); Cheng, J. G. [Harbin Institute of Technology; Zarestky, Jerel L [ORNL; Garlea, Vasile O [ORNL; Liobet, A. [Los Alamos National Laboratory (LANL); Zhou, H. D. [University of Texas, Austin; Sui, Y. [Harbin Institute of Technology; Su, W. H. [Harbin Institute of Technology; McQueeney, R. J. [Ames Laboratory

2007-01-01

334

PyORBIT: A Python Shell For ORBIT  

SciTech Connect

ORBIT is code developed at SNS to simulate beam dynamics in accumulation rings and synchrotrons. The code is structured as a collection of external C++ modules for SuperCode, a high level interpreter shell developed at LLNL in the early 1990s. SuperCode is no longer actively supported and there has for some time been interest in replacing it by a modern scripting language, while preserving the feel of the original ORBIT program. In this paper, we describe a new version of ORBIT where the role of SuperCode is assumed by Python, a free, well-documented and widely supported object-oriented scripting language. We also compare PyORBIT to ORBIT from the standpoint of features, performance and future expandability.

Jean-Francois Ostiguy; Jeffrey Holmes

2003-07-01

335

Orbital Fluctuations and Orbital Flipping in RVO3 Perovskites  

NASA Astrophysics Data System (ADS)

The effect of the average R-site ionic radius ?IR? and variance on the orbital and magnetic order in R3+-doped YVO3 was studied in Y1-xLaxVO3 and Y1-x(La0.2337Lu0.7663)xVO3 with fixed ?IR?. The orbital flipping temperature TCG increases nonlinearly with increasing R-site variance, indicating that the V-O-V bond angle is not the primary driving force stabilizing the C-type orbitally ordered phase. The suppressed thermal conductivity in the G-type orbitally ordered phase signals some remaining orbital randomness that is enhanced by t2 and et hybridization in T1g3 site symmetry.

Yan, J.-Q.; Zhou, J.-S.; Goodenough, J. B.; Ren, Y.; Cheng, J. G.; Chang, S.; Zarestky, J.; Garlea, O.; Liobet, A.; Zhou, H. D.; Sui, Y.; Su, W. H.; McQueeney, R. J.

2007-11-01

336

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe ...  

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

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe (VTL). Machining the fixture for GE Turboshroud. G.S. O'Brien, operator. - Juniata Shops, Machine Shop No. 1, East of Fourth Avenue at Third Street, Altoona, Blair County, PA

337

Orbital xanthogranuloma in adults.  

PubMed Central

The onset of periorbital xanthogranuloma in adults is rare and may be accompanied by haematological abnormalities and malignancy. The appearance of the eyelid lesions is virtually diagnostic, producing readily recognisable diffuse, yellow plaques, and affected patients should be investigated and reviewed regularly for systemic disease. Three cases are described, in which periorbital cutaneous plaques were associated with abnormal tissues in the superior part of the orbit; these abnormal tissues caused displacement or restricted movement of the globe or upper eyelid. The possibility that two cases represent a necrobiotic type of xanthogranuloma is presented. Nine years after the onset of xanthogranuloma one patient developed non-Hodgkin's lymphoma. A multiple-drug regimen of systemic chemotherapy, given for lymphoma, caused a marked clinical reduction in the periorbital xanthogranuloma. Images

Rose, G. E.; Patel, B. C.; Garner, A.; Wright, J. E.

1991-01-01

338

Exploratory orbit analysis  

SciTech Connect

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four or six dimensional nonlinear dynamical system is at least as difficult as analyzing events in high-energy collisions; the consequences of doing it badly, or slowly, would be at least as devastating; and yet the level of effort and expenditure invested in the latter, the very attention paid to it by physicists at large, must be two orders of magnitude greater than that given to the former. It is difficult to choose the model which best explains the behavior of a physical device if one does not first understand the behavior of the available models. The time is ripe for the development of a functioning EOA environment, which I will try to describe in this paper to help us achieve this goal.

Michelotti, L.

1989-03-01

339

TOPEX orbital radiation study  

SciTech Connect

The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

Stassinopoulos, E.G.; Barth, J.M.

1984-04-01

340

Orbital exenteration--simplified.  

PubMed Central

In summary, a simplified technique of orbital exenteration has been presented. Results, with complications, in eleven cases have been described. The advantages of the operative method described are: (1) full thickness skin provides better cushion for self-retaining prosthesis, (2) skin with intact blood supply is much less likely to be rejected, (3) no donor site with added discomfort and care, (4) local recurrence of neoplasm is easily detected, (5) operating time shortened and (6) favorable patient acceptance. Images FIGURE 8 A FIGURE 8 B FIGURE 9 FIGURE 10 FIGURE 11 A FIGURE 11 B FIGURE 11 C FIGURE 11 D FIGURE 12 FIGURE 13 A FIGURE 13 B FIGURE 14 A FIGURE 14 B FIGURE 15 FIGURE 16 FIGURE 17

Coston, T O; Small, R G

1981-01-01

341

Orbital science's 'Bermuda Triangle'  

NASA Astrophysics Data System (ADS)

The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.

Sherrill, Thomas J.

1991-02-01

342

[Rhabdomyosarcoma of the orbit].  

PubMed

The authors evaluated 9 years' experience with the diagnosis and treatment of embryonic rhabdomyosarcoma of the orbit in children. They evaluated in detail a group of 5 children treated and followed up for 1-9 years. Due to comprehensive surgical, radiation and chemotherapeutic treatment all patients survive and in 80% the visual function is preserved. For differential diagnostic problems, with regard to the variable manifestation of rhabdomyosarcoma which may imitate orbitocellulitis, chalaseon, epibulbar lipodermoid or papilloma, the authors emphasize the importance of rapid primary diagnosis by NMR and biopsy. In the treatment they appreciate greatly a combination of radiotherapy and chemotherapy which is a modern trend and can eradicate the tumour without radical surgery. PMID:9213517

Gerinec, A; Chynoranský, M; Galbavý, S

1997-02-01

343

BENEFITS OF VERTICAL INTEGRATION OF LIGNITE MINES AND POWER PLANTS  

Microsoft Academic Search

(1) Overview Benefits of vertical integration of mine-mouth power plants and nearby coal mines or at least from very close their relationships through long-term contracts has been already described from the point of view of transaction costs economics by Wiliamson (1985), Joskow (1987) and Kerkvliet (1991). Although mentioned authors described situation on electric energy market over 20 years their observed

Leszek JURDZIAK

344

Pool boiling heat transfer in vertical annular crevices  

Microsoft Academic Search

Effects of vertical annuli on nucleate pool boiling heat transfer of water at atmospheric pressure have been obtained experimentally. Experiments were performed for annuli with a height of 570 mm and gap sizes of 3.9 and 15 mm. Through the tests, tube bottom confinement (open or closed) has been investigated, too, and the whole results are compared with a single

Myeong-Gie Kang

2002-01-01

345

The vertical, laminar, isothermal free jet with buoyancy and diffusion  

Microsoft Academic Search

The flow of a vertical, laminar, isothermal jet with strong buoyancy and diffusion is treated numerically. Computational results are compared with Laser-Doppler and interferometric measurements performed in an axisymmetric jet of hydrogen. The close agreement indicates that the numerical procedure is also appropriate for investigating laminar diffusion flames.

D. Stirnberg; E. Ronkholz; W. Merzkirch

1983-01-01

346

Is it necessary to go beyond the ponctual mass approximation for tidal perturber in close systems?  

Microsoft Academic Search

With the discoveries of very close star-planet systems with planet orbiting sometimes at several star radius but also with well-known situations in our solar system where natural satellites are very close to their parent planet the validity of the ponctual mass approximation for the tidal perturber (respectively the parent star or planet when we study the close planet or natural

Stephane Mathis; C. Le Poncin-Lafitte

2008-01-01

347

Lévy Flights of Binary Orbits due to Impulsive Encounters  

NASA Astrophysics Data System (ADS)

We examine the evolution of an almost-circular Keplerian orbit interacting with unbound perturbers. We calculate the change in eccentricity and angular momentum that results from a single encounter, assuming that the timescale for the interaction is shorter than the orbital period. The orbital perturbations are incorporated into a Boltzmann equation that allows for eccentricity dissipation. We present an analytic solution to the Boltzmann equation that describes the distribution of orbital eccentricity and relative inclination as a function of time. The eccentricity and inclination of the binary do not evolve according to a normal random walk but perform a Lévy flight. The slope of the mass spectrum of perturbers dictates whether close gravitational scatterings are more important than distant tidal ones. When close scatterings are important, the mass spectrum sets the slope of the eccentricity and inclination distribution functions. We use this general framework to understand the eccentricities of several Kuiper belt systems: Pluto, 2003 EL61, and Eris. We use the model of Tholen et al. to separate the non-Keplerian components of the orbits of Pluto's outer moons Nix and Hydra from the motion excited by interactions with other Kuiper belt objects. Our distribution is consistent with the observations of Nix, Hydra, and the satellites of 2003 EL61 and Eris. We address applications of this work to objects outside of the solar system, such as extra-solar planets around their stars and millisecond pulsars.

Collins, Benjamin F.; Sari, Re'em

2008-12-01

348

The Orbit of Halley's Comet  

Microsoft Academic Search

RECENT investigations by Brady1 have yielded the suggestion that the historical observations of Halley's Comet can be interpreted as indicating the existence of a large planet beyond Pluto having an orbital period of 464 yr. One of us2 has carried out a detailed study of the past orbit of Halley's Comet using an extension of Cowell and Crommelin's method of

T. Kiang; P. A. Wayman

1973-01-01

349

Orbital evolution around irregular bodies  

Microsoft Academic Search

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids

A. Rossi; F. Marzari; P. Farinella

1999-01-01

350

Giant Orbitals Currents in Nanostructures  

NASA Astrophysics Data System (ADS)

The possibility and origin of giant orbital currents [1] in nanostructures is investigated by model calculations. We compare two models: (i) a model where electrons are confined to a ``racetrack'' around the dot and (ii) a tight-binding model where atomic spin-orbit coupling creates macroscopic currents at the periphery of the dots. The first model yields expressions very similar to Ref. 1, but the corresponding spin-orbit coupling [2] is negligibly small, because it strongly decreases with increasing orbital radius. Furthermore, the orbital moment rapidly collapses due to a redistribution of electron with wave vectors of opposite sense of rotation. In the second model, the relatively strong intra-atomic spin-orbit interaction yields orbital currents that add [3] between neighboring atoms and create a macroscopic current at the periphery of the dot. This current corresponds to a magnetic Berry phase and cannot dissipate, because the underlying atomic orbital moments are quantized. References: [1] A. Hernando, P. Crespo, and M. A. Garc'ia, Phys. Rev. Lett. 96, 057206 (2006). [2] R. Skomski, IEEE Trans. Magn. 32, 4794 (1996). [3] J. Zhang, R. Skomski, Y. F. Lu, and D. J. Sellmyer, Phys. Rev. B 75, 214417 (2007).

Skomski, Ralph; Sellmyer, D. J.

2010-03-01

351

Multimodality imaging of the orbit  

PubMed Central

The role of imaging is well established in the evaluation of orbital diseases. Ultrasonography, Computed tomography and Magnetic resonance imaging are complementary modalities, which allow direct visualization of regional anatomy, accurate localization and help to characterize lesions to make a reliable radiological diagnosis. The purpose of this pictorial essay is to highlight the imaging features of commonly encountered pathologies which involve the orbit.

Hande, Pradipta C; Talwar, Inder

2012-01-01

352

Removing Orbital Debris with Lasers  

Microsoft Academic Search

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collisional cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1 cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma

Claude R. Phipps; Kevin L. Baker; Brian Bradford; E. Victor George; Stephen B. Libby; Duane A. Liedahl; Bogdan Marcovici; Scot S. Olivier; Lyn D. Pleasance; James P. Reilly; Alexander Rubenchik; David N. Strafford; Michael T. Valley

2011-01-01

353

Environmental dynamics at orbital altitudes  

Microsoft Academic Search

The influence of real satellite aerodynamics on the determination of upper atmospheric density was investigated. A method of analysis of satellite drag data is presented which includes the effect of satellite lift and the variation in aerodynamic properties around the orbit. The studies indicate that satellite lift may be responsible for the observed orbit precession rather than a super rotation

G. R. Karr

1976-01-01

354

The Mars Reconnaissance Orbiter Mission  

Microsoft Academic Search

The Mars Reconnaissance Orbiter (MRO) will be launched in August 2005 by an Atlas V 401 expendable launch vehicle from Cape Canaveral Air Force Station, USA. It will deliver to Mars orbit a payload to conduct remote sensing science observations, identify and characterize sites for future landers, and provide critical telecom\\/navigation relay capability for follow-on missions. The mission is designed

James E. Graf; Richard W. Zurek; Howard J. Eisen; Benhan Jai; M. D. Johnston; Ramon DePaula

2005-01-01

355

Semiclassical Quantisation Using Diffractive Orbits  

Microsoft Academic Search

Diffraction, in the context of semiclassical mechanics, describes the man- ner in which quantum mechanics smooths over discontinuities in the classical mechanics. An important example is a billiard with sharp corners; its semi- classical quantisation requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this paper we construct the corre- sponding zeta function and apply

N. D. Whelan

356

Pseudosymmetry analysis of molecular orbitals.  

PubMed

We introduce a pseudosymmetry analysis of molecular orbitals by means of the newly proposed irreducible representation measures. To do that we define first what we consider as molecular pseudosymmetry and the relationships of this concept with those of approximate symmetry and quasisymmetry. We develop a general algorithm to quantify the pseudosymmetry content of a given object within the framework of the finite group algebra. The obtained mathematical expressions are able to decompose molecular orbitals by means of the irreducible representations of any reference symmetry point group. The implementation and usefulness of the pseudosymmetry analysis of molecular orbitals is demonstrated in the study of ? and ? orbitals in planar and nonplanar polycyclic aromatic hydrocarbons and the t2 g and eg character of the d-orbitals in the [FeH6](3-) anion in its high spin state along the Bailar twist pathway. PMID:23436743

Casanova, David; Alemany, Pere; Falceto, Andrés; Carreras, Abel; Alvarez, Santiago

2013-02-22

357

Functions and Vertical Line Test  

NSDL National Science Digital Library

This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

2010-01-01

358

The anterior vertical SMAS lift  

Microsoft Academic Search

With minimal skin and SMAS undermining, as well as a rotation point that is closest to the nasolabial folds and jowls, the “anterior vertical SMAS lift” reduces the risk of hematoma while optimizing direct pull on those surface features that require improvement. The vertical rotation enhances the malar region and decreases preauricular skin excision. Further, the author has found this

Robert W. Bernard

2003-01-01

359

Fast vertical mining using diffsets  

Microsoft Academic Search

A number of vertical mining algorithms have been proposed recently for association mining, which have shown to be very effective and usually outperform horizontal approaches. The main advantage of the vertical format is support for fast frequency counting via intersection operations on transaction ids (tids) and automatic pruning of irrelevant data. The main problem with these approaches is when intermediate

Mohammed Javeed Zaki; Karam Gouda

2003-01-01

360

Emotional sounds influence vertical vection.  

PubMed

While viewing a large vertically moving sinusoidal luminance grating, the perception of upward self-motion (vection) was modulated by positive sounds (e.g., a baby's laughter). This may be because positive emotion and the spatial metaphor of vertical directions were unified in the mind. PMID:23155739

Sasaki, Kyoshiro; Seno, Takeharu; Yamada, Yuki; Miura, Kayo

2012-01-01

361

Polar Air Quality and Climate from a Molniya Orbit  

NASA Astrophysics Data System (ADS)

The Arctic is a region of rapid climate change with warming temperatures and depleting summer ice which may be exacerbated by transport of soot and other anthropogenic material from mid-latitudes. It is also the source of winter storms delivering cold air to lower latitudes. Currently data is available for these areas from polar orbiting satellites, but only intermittently at a given location as the satellites pass overhead. Data from geostationary satellites, useful at lower latitudes, is not available for the Arctic because viewing angles to high latitude locations from geostationary orbit are poor. We are proposing the use of a satellite in a Molniya orbit for the acquisition of data for high latitudes which is a quasi-stationary orbit close to apogee. This talk will describe a proposal to the Canadian Space Agency for a mission aimed at the acquisition of air quality and climate data in boreal polar regions and mid-latitudes. Molniya orbits (named after the Russian communications satellite series that first used them) are highly elliptical orbits with an inclination of approximately 63°. At this inclination, the Earth oblateness perturbation does not cause any change to the orbit's argument of perigee. Further, if the orbit semi-major axis is chosen appropriately, the orbit can be timed to have a period of half a day (typical Molniya orbits have an apogee altitude of about 39750 km and a perigee altitude of about 600 km). The result of these two constraints is that the satellite is at apogee over the same high latitude location on the Earth every two orbits. At the alternate apogees, it is over a location at the same latitude but 180° away in longitude. Either location provides viewing coverage of the entire Earth above 60°N, and reasonable viewing down to 50°N. Further, because the satellite is travelling slowly at apogee, the viewing geometry is maintained for approximately 2/3 of the orbit (8 hr out of every 12). The suite of instruments we are baselining all have heritage in previous Canadian flight programs such as SciSat and include a high spectral resolution infrared sounder, a multiwavelength camera, an imaging spectrometer and an auroral imager. The first three instruments will provide information on a wide range of air quality indicator species including aerosols as well as clouds, and will provide temperature, pressure and wind estimates useful for weather predictions and climate studies. The auroral imager will allow examination of an interesting question related to solar-climate interactions in the middle atmosphere through the medium of the aurora.

O'Neill, N.; McConnell, J. C.; Mullins, M.; Chesser, H.; Solheim, B.; Kaminski, J.; Strong, K.; Jones, D.; Drummond, J.; Martin, R.; McElroy, C. T.; Evans, W. F.; Giroux, J. G.; Soucy, M. A.; Buijs, H. L.; Moreau, L. M.; Buttner, G.; Rahnama, P.; Rowlands, N.; Hackett, J.; Bell, A.

2008-05-01

362

Closed Loop Control System Applied to Earth-Moon Transfer Maneuver Using Continuous Thrust  

Microsoft Academic Search

This work considers the problem of controlling the trajectory during orbital transfer maneuvers, using a propulsive system capable of applying continuous thrust for a long period of time. Some non-ideality of the thrusters and their effects on the control system during the transfer orbit were analyzed. It was considered a control system in closed loop and low-thrust propulsion with high

Evandro Marconi Rocco; Helio Koiti Kuga; Antonio Prado; Eliel Wellington Marcelino

2010-01-01

363

Open and closed loop guidance for an airbreathing winged launch vehicle  

Microsoft Academic Search

A complete optimal trajectory (airbreathing ascent and return flights, and rocket flight) allowing 17 tons to be put into a transfer orbit of the Hermes type, has been computed for a TSTO (two-stages-to-orbit) airbreathing launcher thanks to the optimization software from ONERA, based on the “generalized projected gradient” method. Then a closed loop guidance law was synthesized and tested but

Fl. Richard; B. Christophe

1995-01-01

364

The Closed Booth.  

ERIC Educational Resources Information Center

|Seven reasons excerpted from "Language Laboratory Learning" (1960) by Fernand Marty are cited for a preference for individual rooms or closed booths to language laboratories with open booths. The author specifies additional psychological and acoustical advantages of the closed booth system. Weaknesses inherent in the open booth laboratory are…

Hanson, Edwin M.

1968-01-01

365

Response of vibration-isolated object to ground motions with intense vertical accelerations  

Microsoft Academic Search

This paper reports the results of shaking table tests performed to assess the response of an object placed on a vibration isolator to intense ground motions whose peak accelerations are close to or over the gravity acceleration in both vertical and horizontal directions. The passive vertical and horizontal vibration isolator, developed by the authors, has rolling load-bearing elements and constant-force

Yoshikazu Araki; Shinya Kawabata; Takehiko Asai; Takeshi Masui

2011-01-01

366

LETTER TO THE EDITOR: Holonomy invariance, orbital resonances and kilohertz QPOs  

NASA Astrophysics Data System (ADS)

Quantized orbital structures are typical for many aspects of classical gravity (Newton's as well as Einstein's). The astronomical phenomenon of orbital resonances is a well-known example. Recently, Rothman et al (2001 Class. Quantum Grav. 18 1217-33) discussed quantized orbital structures in the novel context of a holonomy invariance of parallel transport in Schwarzschild geometry. We present here yet another example of quantization of orbits, one that is closely related to orbital resonances and closely analogous to holonomy invariance. This strong-gravity effect may have been already directly observed as the puzzling kilohertz quasi-periodic oscillations (QPOs) in the x-ray emission from a few accreting galactic black holes and several neutron stars.

Abramowicz, M. A.; Almergren, G. J. E.; Kluzniak, W.; Thampan, A. V.; Wallinder, F.

2002-04-01

367

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future exploration. Precision Orbit Determination is used to achieve the accuracy requirements, and to precisely geolocate the high-resolution datasets obtained by the LRO instruments. In addition to the tracking data most commonly used to determine spacecraft orbits in planetary missions (radiometric Range and Doppler), LRO benefits from two other types of orbital constraints, both enabled by the Lunar Orbiter Laser Altimeter (LOLA) instrument. The altimetric data collected as the instrument's primary purpose can be used to derive constraints on the orbit geometry at the times of laser groundtrack intersections (crossovers). The multi-beam configuration and high firing-rate of LOLA further improves the strength of these crossovers, compared to what was possible with the MOLA instrument onboard Mars Global Surveyor (MGS). Furthermore, one-way laser ranges (LR) between Earth International Laser Ranging Service (ILRS) stations and the spacecraft are made possible by the addition of a small telescope mounted on the spacecraft high-gain antenna. The photons received from Earth are transmitted to one LOLA detector by a fiber optics bundle. Thanks to the accuracy of the LOLA timing system, the precision of 5-s LR normal points is below 10cm. We present the first results of the Precision Orbit Determination (POD) of LRO through the commissioning and nominal phases of the mission. Orbit quality is discussed, and various gravity fields are evaluated with the new (independent) LRO radio tracking data. The altimetric crossovers are used as an independent data type to evaluate the quality of the orbits. The contribution of the LR data is assessed. Multi-arc solutions over entire months are presented, which allow to strengthen the LR data because fewer clock-related parameters need to be adjusted. Finally, a preliminary 1-month solution with altimetric crossover constraints is evaluated and discussed

Lemoine, F. G.; Mazarico, E.; Rowlands, D. D.; Torrence, M. H.; McGarry, J. F.; Neumann, G. A.; Mao, D.; Smith, D. E.; Zuber, M. T.

2010-05-01

368

GPS orbit processing in support of low earth orbiter precise orbit determination  

Microsoft Academic Search

There are currently an increasing number of LEO missions incorporating dual frequency GPS receivers for Satellite to Satellite Tracking. The majority of LEO precise orbit determination (POD) strategies rely on high quality GPS orbits and clocks such as those supplied by the IGS Final product. The availability of these products may not satisfy operational requirements due to their ten day

I. Romero; H. Boomkamp; J. Dow; C. Garcia

2003-01-01

369

On-Orbit-Servicing Spacecraft Flyaround Orbit Design and LQR Keep Control in Eccentric Orbits  

Microsoft Academic Search

The paper presents the initialization condition for chaser flying around target and optimal keeping control algorithm to satisfy the requirement of on-orbit-servicing in eccentric orbits. The necessary condition for chaser fly around is presented by detailed analyzing with the time variant linear relative motion formula and resolution. Then, the condition for target to locate at the center of fly around

Wang Feng; Cao Xibin; Chen Xueqin

2007-01-01

370

Closed-cycle gas dynamic laser design investigation. Final report  

Microsoft Academic Search

A conceptual design study was made of a closed cycle gas-dynamic laser to provide definition of the major components in the laser loop. The system potential application is for long range power transmission by way of high power laser beams to provide satellite propulsion energy for orbit changing or station keeping. A parametric cycle optimization was conducted to establish the

G. W. Ketch; W. E. Young

1977-01-01

371

Close encounters and collisions of comets with the earth  

Microsoft Academic Search

A computer search for earth-approaching comets among those listed in Marsden's (1983) updated orbit catalog has identified 36 cases at which minimum separation distance was less than 2500 earth radii. A strong representation of short period comets in the sample is noted, and the constant rate of the close approaching comets in the last 300 years is interpreted to suggest

Z. Sekanina; D. K. Yeomans

1984-01-01

372

Study of a Close-Grid Geodynamic Measurement System.  

National Technical Information Service (NTIS)

The Clogeos (Close-Grid Geodynamic Measurement System) concept, a complete range or range-rate measurement terminal installed in a satellite in a near-polar orbit with a network of relatively simple transponders or retro-reflectors on the ground at interv...

1977-01-01

373

First ARTEMIS Spacecraft Successfully Enters Lunar Orbit  

NASA Website

The first of the two ARTEMIS spacecraft entered lunar orbit this morning. ARTEMIS was the first mission to orbit the moon's Lagrangian points and this is the first ever attempt to move from the Lagrangian into lunar orbit.

374

Semi-Active Orbital Debris Sweeper.  

National Technical Information Service (NTIS)

An orbital debris sweeper is provided for removing particles from orbit which otherwise may impact and damage an orbiting spacecraft. The debris sweeper includes a central sweeper core which carries a debris monitoring unit, and a plurality of large area ...

A. J. Petro

1990-01-01

375

Radiation therapy for orbital lymphoma  

SciTech Connect

Purpose: To describe radiation techniques and evaluate outcomes for orbital lymphoma. Methods and Materials: Forty-six patients (and 62 eyes) with orbital lymphoma treated with radiotherapy between 1987 and 2003 were included. The majority had mucosa-associated lymphoid tissue (48%) or follicular (30%) lymphoma. Seventeen patients had prior lymphoma at other sites, and 29 had primary orbital lymphoma. Median follow-up was 46 months. Results: The median dose was 30.6 Gy; one-third received <30 Gy. Electrons were used in 9 eyes with disease confined to the conjunctiva or eyelid, and photons in 53 eyes with involvement of intraorbital tissues to cover entire orbit. Local control rate was 98% for all patients and 100% for those with indolent lymphoma. Three of the 26 patients with localized primary lymphoma failed distantly, resulting in a 5-year freedom-from-distant-relapse rate of 89%. The 5-year disease-specific and overall survival rates were 95% and 88%, respectively. Late toxicity was mainly cataract formation in patients who received radiation without lens block. Conclusions A dose of 30 Gy is sufficient for indolent orbital lymphoma. Distant relapse rate in patients with localized orbital lymphoma was lower than that reported for low-grade lymphoma presenting in other sites. Orbital radiotherapy can be used for salvage of recurrent indolent lymphoma.

Zhou Ping [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)]. E-mail: pzhou@partners.org; Ng, Andrea K. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Silver, Barbara [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Li Sigui [Department of Biostatistical Sciences, Dana-Farber Cancer Institute, Boston, MA (United States); Hua Ling [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Mauch, Peter M. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2005-11-01

376

Computed tomography of the orbit  

SciTech Connect

In less than a decade computed tomography (CT scanning) had a profound impact on diagnostic radiology. Radiology of the orbit is no exception. As early as 1973, reports published in the radiological literature indicated that this new noninvasive imaging method was a highly effective way of demonstrating intraorbital mass lesions. As CT scanners became widely available, computed tomography became a significant adjunct to ophthalmological diagnosis. Today the main indications for CT scanning of the orbit are: (1) suspected mass lesions, most frequently presenting as exophthalmos, (2) orbital trauma, including foreign bodies, (3) some congenital anomalies, and (4) suspicion of extension into the orbit of extraorbital disease processes. Along with ultrasonography, another new noninvasive imaging technique, CT has replaced a number of more invasive and often less effective diagnostic methods, such as orbital pneumography, venography, and arteriography as major imaging techniques in orbital pathology. The paper discusses current practices in the technique of CT scanning of the orbit including the important aspect of radiation dosimetry and the clinical applications, using a number of cases to illustrate its use.

Alker, G.J.; Leslie, E.V.; Banna, M.; Pallie, W.; Rudin, S.; Bednarek, D.R.; Oh, Y.S.

1981-01-01

377

The calculation of orbit length change of the recycler due to main injector ramp  

SciTech Connect

Orbit length of beam in the Recycler changes during the Main Injector ramps. The unknown kicks from the effects generated by stray field are distributed around the ring. To estimate the changes, simulated virtual kicks are created around each lambertson, C-magnet and their bus of the Main Injector. An orbit measurement consists of the readout of all of the Recycler beam position monitors (BPMs). The orbit lengths difference is calculated by comparing the horizontal closed orbit of the beam with a reference orbit. The calculation methods are described first. The analysis presented here includes the calculation of the orbit length changes and the strength of the simulated kicks before and after LAM52 and V701 magnet bus work done.

Xiao, Meiqin; /Fermilab

2005-05-01

378

Orbit compensation for the time-varying elliptically polarized wiggler with switching frequency at 100 hz  

SciTech Connect

In October 1996, the elliptically polarized wiggler, installed in the X13 straight section of the NSLS X-ray ring, was commissioned at an operating frequency of 100 hz. This wiggler generates circularly polarized photons in the energy range of 0.1 to 10 keV with AC modulation of polarization helicity. The vertical magnetic field is produced by a hybrid permanent magnet structure, and the horizontal magnetic field is generated by an electromagnet capable of switching at frequencies up to 100 hz. Here, the authors discuss the compensation of the residual vertical and horizontal orbit motion utilizing a time-domain algorithm employing a function generator to drive trim coils at the wiggler ends, and the wideband high precision orbit measurement system of the X-ray ring. The residual orbit motion has been reduced to a level below 1 micron, and the device has been run in regular operations with no negative effect on other users.

Singh, O.; Krinsky, S.

1997-07-01

379

Options for human {open_quote}{open_quote}return to the moon{close_quote}{close_quote} using tomorrow{close_quote}s SSTO, ISRU, and LOX-augmented NTR technologies  

Microsoft Academic Search

The feasibility of conducting human missions to the Moon is examined assuming the use of three {open_quote}{open_quote}high leverage{close_quote}{close_quote} technologies: (1) a single-stage-to-orbit (SSTO) launch vehicle, (2) {open_quote}{open_quote}{ital in}-{ital situ}{close_quote}{close_quote} {ital resource} {ital utilization} (ISRU)specifically {open_quote}{open_quote}lunar-derived{close_quote}{close_quote} liquid oxygen (LUNOX), and (3) LOX-augmented nuclear thermal rocket (LANTR) propulsion. Lunar transportation system elements consisting of a LANTR-powered lunar transfer vehicle (LTV) and a

Borowski

1996-01-01

380

Geostationary orbit determination using SATRE  

NASA Astrophysics Data System (ADS)

A new strategy of precise orbit determination (POD) for GEO (Geostationary Earth Orbit) satellite using SATRE (SAtellite Time and Ranging Equipment) is presented. Two observation modes are proposed and different channels of the same instruments are used to construct different observation modes, one mode receiving time signals from their own station and the other mode receiving time signals from each other for two stations called pairs of combined observations. Using data from such a tracking network in China, the results for both modes are compared. The precise orbit determination for the Sino-1 satellite using the data from 6 June 2005 to 13 June 2005 has been carried out in this work. The RMS (Root-Mean-Square) of observing residuals for 3-day solutions with the former mode is better than 9.1 cm. The RMS of observing residuals for 3-day solutions with the latter mode is better than 4.8 cm, much better than the former mode. Orbital overlapping (3-day orbit solution with 1-day orbit overlap) tests show that the RMS of the orbit difference for the former mode is 0.16 m in the radial direction, 0.53 m in the along-track direction, 0.97 m in the cross-track direction and 1.12 m in the 3-dimension position and the RMS of the orbit difference for the latter mode is 0.36 m in the radial direction, 0.89 m in the along-track direction, 1.18 m in the cross-track direction and 1.52 m in the 3-dimension position, almost the same as the former mode. All the experiments indicate that a meter-level accuracy of orbit determination for geostationary satellite is achievable.

Lei, Hui; Li, Zhigang; Yang, Xuhai; Wu, Wenjun; Cheng, Xuan; Yang, Ying; Feng, Chugang

2011-09-01

381

Atmospheric structure from Mars Reconnaissance Orbiter accelerometer measurements  

NASA Astrophysics Data System (ADS)

Designed for aerobraking, Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that will safely use the atmosphere of Mars to aerobrake over 500 orbits. MRO periapsis precesses from the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis is brought dramatically from ˜40,000km at MOI to 460 km at aerobraking completion (ABX) mid September 2006. After ABX, a few small propulsive maneuvers will establish the Primary Science Orbit (PSO), which without aerobraking would have required an additional 400 kg of fuel. Each of the 500 plus aerobraking orbits provides a vertical structure and distribution of density, scale heights, and temperatures, along the orbital path, providing key in situ insight into various upper atmosphere (> 100 km) processes. One of the major questions for scientists studying Mars is: "Where did the water go?" Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extends vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both the lower atmosphere and the upper atmosphere, thus the water balance throughout the entire atmosphere from subsurface to exosphere may be equally critical. Comparisons of data from Mars Global Surveyor (MGS), MO and MRO will help characterize key temporal and spatial cycles including: polar vortices, winter polar warming, dust storms, planetary scale gravity waves, and gravitational tides associated with topography; this will validate and constrain both upper atmospheric circulation models used to understand the nature of high-altitude variability and transport processes, and engineering models used to plan future missions.

Keating, G.; Bougher, S.; Theriot, M.; Zurek, R.; Blanchard, R.; Tolson, R.; Murphy, J.

382

Dehumidification -- Closed loop systems  

SciTech Connect

Dehumidification is the removal of water from the air. Dehumidification equipment treats the ambient air before it is introduced to the enclosure. A closed loop system is one that theoretically routes all the air exiting an enclosure through the appropriate filter media and treatment equipment and then returns it to the enclosure. By establishing a closed loop system, the ``treated`` air is continuously processed, which improves the efficiency of this operation. The generic types of dehumidification equipment and their application in a closed loop system will be presented. This article will deal solely with the use of dehumidification and other related equipment used to control the environment within the work enclosure.

Wyatt, C.H. [Enviro-Air Control Corp., Houston, TX (United States); Crowe, A.R. [C.H. Heist Ltd., Oakville, Ontario (Canada)

1996-05-01

383

Enceladus' Influence on the Vertical Structure of Saturn's E Ring  

NASA Astrophysics Data System (ADS)

Within ~+/- 20,000 km of Enceladus' orbit, Saturn's tenuous E ring has a double-banded appearance, with the number of particles depleted by a few percent within +/- 1000 km of the planet’s equatorial plane (Hedman et al. 2012). We wish to understand this vertical structure, to learn if it might indicate launch speeds or a sweeping effect of Enceladus. We have combined order-of-magnitude analytical estimates and numerical simulations that include Enceladus and Saturn's gravity up to J6 in short-term (1-2 days) and longer-term 200-yr) integrations. Because most particles emanating from the surface geysers will fall back on the moon, the E ring must be dominated by particles that barely escaped. Hence we follow the orbits of many hundreds of particles launched near Enceladus' southern pole with speeds between ~ 0.8 to 2 times the nominal escape speed (i.e., that from an isolated sphere). We illustrate some contorted trajectories within the three-body problem for such launch conditions. Typically, gravitational deceleration after launch followed by a few gravitational kicks from the moon induce many particles to attain orbital inclinations corresponding to a maximum height of ~4rE (rE = radius of Enceladus = 250 km), or about one Hill radius for Enceladus. The vertical epicyclic motions of such inclined orbits account the observed two-banded structure. Simultaneous gravitational interactions will scatter particles to produce a two-banded, radially extended (+/-10,000km) Gaussian core on either side of Enceladus, as observed. In our simple model, particles are lost by collisions into Enceladus in ~ 100 yrs; mutual impacts are ignored. Since gravity alone can generate in short order the most prominent features in the observed structures, non-gravitational forces (cf. Kempf et al. 2010) mostly affect other aspects of the E ring structure and evolution.

Burns, Joseph A.; Agarwal, M.; Hedman, M. M.; Tiscareno, M. S.

2013-10-01

384

Imaging of metastatic orbital leiomyosarcoma.  

PubMed

A 74-year-old man with a previous history of lower leg soft tissues leiomyosarcoma and multiple metastasis presented with a progressive painless proptosis of the left eye. Orbital ultrasound, CT, and MRI revealed a large mass in the left medial orbit. The mass was surgically removed and pathologic examination confirmed the diagnosis of a metastatic orbital leiomyosarcoma. The imaging characteristics of this rare tumor are comprehensively detailed, using complementary ultrasound, CT, and MRI, the combination of which allowed planning of total excision of the lesion. PMID:16304527

Voros, Gerasimos M; Birchall, Daniel; Ressiniotis, Thomas; Neoh, Christopher; Owen, Rona I; Strong, Nicholas P

2005-11-01

385

Orbital overlap and chemical bonding.  

PubMed

The chemical bonds in the diatomic molecules Li(2)-F(2) and Na(2)-Cl(2) at different bond lengths have been analyzed by the energy decomposition analysis (EDA) method using DFT calculations at the BP86/TZ2P level. The interatomic interactions are discussed in terms of quasiclassical electrostatic interactions DeltaE(elstat), Pauli repulsion DeltaE(Pauli) and attractive orbital interactions DeltaE(orb). The energy terms are compared with the orbital overlaps at different interatomic distances. The quasiclassical electrostatic interactions between two electrons occupying 1s, 2s, 2p(sigma), and 2p(pi) orbitals have been calculated and the results are analyzed and discussed. It is shown that the equilibrium distances of the covalent bonds are not determined by the maximum overlap of the sigma valence orbitals, which nearly always has its largest value at clearly shorter distances than the equilibrium bond length. The crucial interaction that prevents shorter bonds is not the loss of attractive interactions, but a sharp increase in the Pauli repulsion between electrons in valence orbitals. The attractive interactions of DeltaE(orb) and the repulsive interactions of DeltaE(Pauli) are both determined by the orbital overlap. The net effect of the two terms depends on the occupation of the valence orbitals, but the onset of attractive orbital interactions occurs at longer distances than Pauli repulsion, because overlap of occupied orbitals with vacant orbitals starts earlier than overlap between occupied orbitals. The contribution of DeltaE(elstat) in most nonpolar covalent bonds is strongly attractive. This comes from the deviation of quasiclassical electron-electron repulsion and nuclear-electron attraction from Coulomb's law for point charges. The actual strength of DeltaE(elstat) depends on the size and shape of the occupied valence orbitals. The attractive electrostatic contributions in the diatomic molecules Li(2)-F(2) come from the s and p(sigma) electrons, while the p(pi) electrons do not compensate for nuclear-nuclear repulsion. It is the interplay of the three terms DeltaE(orb), DeltaE(Pauli), and DeltaE(elstat) that determines the bond energies and equilibrium distances of covalently bonded molecules. Molecules like N(2) and O(2), which are usually considered as covalently bonded, would not be bonded without the quasiclassical attraction DeltaE(elstat). PMID:17024702

Krapp, Andreas; Bickelhaupt, F Matthias; Frenking, Gernot

2006-12-13

386

Orbit determination study results for the Venus Radar Mapper orbiter  

Microsoft Academic Search

The Venus Radar Mapper (VRM), to be launched by the U.S. in July 1988 is described and Doppler-only and Doppler plus N-Delta-VLBI data analyses are contrasted in order to evaluate the importance of VLBI data to VRM orbit determination (OD). VRM OD study results are summarized by showing the accuracy of various orbital parameters for ten cases selected over a

P. B. Esposito; S. Demcak

1986-01-01

387

Orbit determination and control for the European Student Moon Orbiter  

NASA Astrophysics Data System (ADS)

This paper presents the preliminary navigation and orbit determination analyses for the European Student Moon Orbiter. The severe constraint on the total mission ?v and the all-day piggy-back launch requirement imposed by the limited available budget, led to the choice of using a low-energy transfer, more specifically a Weak Stability Boundary one, with a capture into an elliptic orbit around the Moon. A particular navigation strategy was devised to ensure capture and fulfil the requirement for the uncontrolled orbit stability at the Moon. This paper presents a simulation of the orbit determination process, based on an extended Kalman filter, and the navigation strategy applied to the baseline transfer of the 2011-2012 window. The navigation strategy optimally allocates multiple Trajectory Correction Manoeuvres to target a so-called capture corridor. The capture corridor is defined, at each point along the transfer, by back-propagating the set of perturbed states at the Moon that provides an acceptable lifetime of the lunar orbit.

Zuiani, Federico; Gibbings, Alison; Vetrisano, Massimo; Rizzi, Francesco; Martinez, Cesar; Vasile, Massimiliano

2012-10-01

388

Close It Up  

NSDL National Science Digital Library

As learners play this challenging strategy game, they build understanding of area and perimeter. On each turn, a player draws a line between two dots next to each other on the grid. When you close a shape, mark it as yours. You can make any shapes, as long as theyâre closed. Keep taking turns until there is no more room. The player with the most area wins. Includes easier and harder variations. Available as a downloadable pdf and in Spanish.

Terc

2010-01-01

389

Closed-Loop Systems  

NSDL National Science Digital Library

Teachers' Domain presents this interactive lesson on closed-loop systems, which includes an animation that describes the typical components of a closed-loop system (error detector, controller, actuator, and measurement device), and describes the input and output signals for each component. The interactive lesson includes three sections: introduction, system overview, and adjustment scenarios. The activity includes 18 screens with reading materials as well as a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

2010-10-11

390

Saturated Activity: Very Close, Detached Binary Stars  

NASA Astrophysics Data System (ADS)

It is proposed to obtain EUVE spectra of 4 close, synchronized, late-type binary stars with orbital/rotational periods shorter than 1.2 day, to study stellar coronal activity at very high, saturated levels. Among stars of spectral types between late-F to mid-K, only components of very close binary systems (and very rare young stars) can have such short rotational periods. Together with the EGO-1 and EGO-2 results for DH Leo and TZ CrB obtained by others, the spectra will be utilized in a comprehensive discussion of the saturated stellar activity, in relation to and in contrast with, the previously obtained by us spectra of the single, rapidly-rotating young star, AB Dor (P=0.51 day, EGO-1) and of two contact binary systems, 44i Boo (P=0.27 day) and VW Cep (P=0.28 day, EGO-2).

Rucinski, Slavek M.

391

Capture of Centaurs into Trojan-like Orbits  

NASA Astrophysics Data System (ADS)

Large scale simulations of Centaurs have yielded vast amounts of data, the analysis of which allows both the bulk behaviour of the objects and interesting rare scenarios to be studied. One such rare behaviour is the temporary capture of Centaurs onto Trojan-like orbits. Such captures are generally short (10kyr - 100kyr), but occur with sufficient frequency that there is the possibility that photometric studies of the Trojan asteroids may reveal outliers with Centaur-like as opposed to Asteroidal characteristics. Uranus and Neptune seem to have great difficulty capturing objects into the 1:1 resonance, while Jupiter captures some, and Saturn the most. It is possible that the fact that the orbits of Jupiter and Saturn lie close to the 5:2 MMR helps ease objects into these temporary Trojan orbits.

Horner, J.; Evans, N. W.

2005-08-01

392

Asteroid searching and orbit determination  

NASA Astrophysics Data System (ADS)

This lecture reviews some basic information on asteroids relating to the ASTROD project, as well as the current progress on asteroid searching. The online resources on asteroid orbit determination are also introduced.

Zhu, Jin; Gao, Jian; Guan, Min; Yang, Bin

393

Reduced domestic satellite orbit spacing  

NASA Astrophysics Data System (ADS)

The demand for services provided by communications satellites in geostationary orbit is growing, and problems arise with respect to the required increase in capacity. One approach for providing such an increase involves the employment of more satellites operating at smaller orbital spacings. The present investigation is concerned with the results of technical studies conducted by the Federal Communications Commission (FCC) to determine the feasibility of reducing orbital spacings between U.S. 'domestic fixed satellites' (domsats). Attention is given to details regarding the usable orbital arc, an adjacent satellite interference model, antenna sidelobe patterns, a single entry analysis, a 4/6 GHz aggregate analysis, results for the 4/6 GHz bands, results for the 12/14 GHz bands, data services, voice services, video reception, and high power spot beams.

Sharp, G. L.

394

Transfer to Librations Point Orbits.  

National Technical Information Service (NTIS)

To help develop a mission analysis tool for the selection of optimum transfer orbits and launch window calculations, an analytical study of approximate admissible transfer trajectories was done to identify the domains of existence of solutions, and provid...

1986-01-01

395

Orbit IMU Alignment: Error Analysis.  

National Technical Information Service (NTIS)

A comprehensive accuracy analysis of orbit inertial measurement unit (IMU) alignments using the shuttle star trackers was completed and the results are presented. Monte Carlo techniques were used in a computer simulation of the IMU alignment hardware and ...

R. W. Corson

1980-01-01

396

Visualization of Molecular Orbitals: Formaldehyde  

ERIC Educational Resources Information Center

|Describes a computer program that plots a solid" representation of molecular orbital charge density which can be used to analyze wave functions of molecules. Illustrated with diagrams for formaldehyde. (AL)|

Olcott, Richard J.

1972-01-01

397

Real and Hybrid Atomic Orbitals.  

ERIC Educational Resources Information Center

|Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)|

Cook, D. B.; Fowler, P. W.

1981-01-01

398

Vertical axis wind turbine airfoil  

SciTech Connect

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

399

Mated Vertical Ground Vibration Test.  

National Technical Information Service (NTIS)

The Mated Vertical Ground Vibration Test (MVGVT) was considered to provide an experimental base in the form of structural dynamic characteristics for the shuttle vehicle. This data base was used in developing high confidence analytical models for the pred...

E. W. Ivey

1980-01-01

400

General orbital invariant MP2-F12 theory  

NASA Astrophysics Data System (ADS)

A general form of orbital invariant explicitly correlated second-order closed-shell Møller-Plesset perturbation theory (MP2-F12) is derived, and compact working equations are presented. Many-electron integrals are avoided by resolution of the identity (RI) approximations using the complementary auxiliary basis set approach. A hierarchy of well defined levels of approximation is introduced, differing from the exact theory by the neglect of terms involving matrix elements over the Fock operator. The most accurate method is denoted as MP2-F12/3B. This assumes only that Fock matrix elements between occupied orbitals and orbitals outside the auxiliary basis set are negligible. For the chosen ansatz for the first-order wave function this is exact if the auxiliary basis is complete. In the next lower approximation it is assumed that the occupied orbital space is closed under action of the Fock operator [generalized Brillouin condition (GBC)] this is equivalent to approximation 2B of Klopper and Samson [J. Chem. Phys. 116, 6397 (2002)]. Further approximations can be introduced by assuming the extended Brillouin condition (EBC) or by neglecting certain terms involving the exchange operator. A new approximation MP2-F12/3C, which is closely related to the MP2-R12/C method recently proposed by Kedžuch et al. [Int. J. Quantum Chem. 105, 929 (2005)] is described. In the limit of a complete RI basis this method is equivalent to MP2-F12/3B. The effect of the various approximations (GBC, EBC, and exchange) is tested by studying the convergence of the correlation energies with respect to the atomic orbital and auxiliary basis sets for 21 molecules. The accuracy of relative energies is demonstrated for 16 chemical reactions. Approximation 3C is found to perform equally well as the computationally more demanding approximation 3B. The reaction energies obtained with smaller basis sets are found to be most accurate if the orbital-variant diagonal Ansatz combined with localized orbitals is used for the first-order wave function. This unexpected result is attributed to geminal basis set superposition errors present in the formally more rigorous orbital invariant methods.

Werner, Hans-Joachim; Adler, Thomas B.; Manby, Frederick R.

2007-04-01

401

[Orbital epidermoid cyst. Case report].  

PubMed

Epidermoid tumors represent 1% of all primary intracranial tumors. Most of them occur intradurally in cerebellopontine angle and parasellar citerns. The intra-orbital location accounts for 4 to 5% of all primary intra-orbital tumors. We report the case of a 23-year-old girl with progressive right proptosis who had developed 6 months earlier. The tumor was removed via an external orbitotomy approach. Histology confirmed the diagnosis. PMID:17916370

Bertal, A; Hilmani, S; Chrifi Alaoui, S; Sami, A; Achouri, A; Ouboukhlik, A; El Kamar, A; El Azhari, A

2007-10-03

402

Low-orbit navigation concepts  

NASA Astrophysics Data System (ADS)

Low-orbit, inexpensive navigation satellite concepts applicable to civil aviation are developed as an alternative to GPS. Details are provided on orbits, signal structure, positioning software, power budget, and estimated costs and risks. Comprehensive error analysis indicates that a 2 dRMS accuracy of approxiamtely 85 m is achievable, and that the system is fault-tolerant. Rough estimates indicate that the satellite configuration will cost about $300 million.

Rome, H. James

403

Horizontal Inequity and Vertical Redistribution  

Microsoft Academic Search

Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by

Peter J. Lambert; Xavier Ramos

1997-01-01

404

Analysis of RSO's close approaches with the ISS during two years flight  

NASA Astrophysics Data System (ADS)

On Nov 20, 1998 the first module of the ISS - Zarya, was successfully launched from Baykonur cosmodrome. On Dec 6 1998 another module - Unity, was docked to Zarya and since that almost two years, till Jul 2000, the ISS had been orbiting the Earth in such configuration, sometimes changing it with rare Shuttle visits. It is interesting to analyze the orbital "vicinity" of the ISS during this period of relatively stable flight with minimal amount of dynamical operations. A posteriori analysis of whole orbital archive revealed some close approaches with the ISS. Technique of close approaches calculations and archive maintenance will be discussed in this presentation.

Agapov, V. M.; Khutorovsky, Z. N.

2001-10-01

405

Exoplanet Orbit Database (Wright+, 2011)  

NASA Astrophysics Data System (ADS)

We present a database of well determined orbital parameters of exoplanets, and their host stars' properties. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The Database is available in a searcheable, filterable, and sortable form on the Web at http://exoplanets.org through the Exoplanets Data Explorer Table, and the data can be plotted and explored through the Exoplanet Data Explorer Plotter. We use the Data Explorer to generate publication-ready plots giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the different selection biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semi-major axis distribution from apparently singleton systems. (2 data files).

Wright, J. T.; Kakhouri, O.; Marcy, G. W.; Han, E.; Feng, Y.; Johnson, J. A.; Howard, A. W.; Fischer, D. A.; Valenti, J. A.; Anderson, J.; Piskunov, N.

2013-01-01

406

Low Earth orbit communications satellite  

NASA Astrophysics Data System (ADS)

A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.

Moroney, D.; Lashbrook, D.; McKibben, B.; Gardener, N.; Rivers, T.; Nottingham, G.; Golden, B.; Barfield, B.; Bruening, J.; Wood, D.

407

Satellite Orbital Interpolation Comparison Methods  

NASA Astrophysics Data System (ADS)

A satellite or artificial probe orbit is made of time series of orbital elements such as state vectors (position and velocities, keplerian orbital elements) given at regular or irregular time intervals. These time series are fitted to observations, so that differences between observations (distance, radial velocity) and the theoretical quantity be minimal, according to a statistical criterion, mostly based on the least-squared algorithm. These computations are carried out using dedicated software, such as the GINS used by GRGS, mainly at CNES Toulouse and Paris Observatory. From an operational point of view, time series of orbital elements are 7-day long. Depending on the dynamical configurations, more generally, they can typically vary from a couple of days to some weeks. One of the fundamental parameters to be adjusted is the initial state vector. This can lead to time gaps, at the level of a few dozen of centimeters between the last point of a time series to the first one of the following data set. The objective of this presentation consists in the improvement of an interpolation method freed itself of such possible "discontinuities" resulting between satellite's orbit arcs when a new initial bulletin is adjusted. We show the principles of interpolation for these time series and compare solutions coming from different interpolation methods such as Lagrange polynomial, spline cubic, Chebyshev orthogonal polynomial and cubic Hermite polynomial. These polynomial coefficients are used to reconstruct and interpolate the satellite orbits without time gaps and discontinuities and requiring a weak memory size.

Richard, J.-Y.; Deleflie, F.; Gambis, D.

2012-04-01

408

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The U.S. Lunar Reconnaissance Orbiter (LRO) mission will be launched in October 2008, and will carry out a detailed mapping of the Moon using a science payload of multiple instruments, including the Lunar Orbiter Laser Altimeter (LOLA), and the Lunar Reconnaissance Orbiter Camera (LROC) (Chin, 2007). One of the primary goals of the LRO mission is develop a geodetic grid for the planet. A subsidiary goal is the improvement of the lunar gravity field. The environment for POD on LRO is especially challenging. The spacecraft will orbit the Moon at a mean altitude of 50 km, and the expected error from the Lunar Prospector series of gravity models (to degree 100 or to degree 150) can be expected to be hundreds of meters. LRO will be tracked by S Band Doppler from White Sands, New Mexico, and Dongara, Australia, as well as by one-way laser ranging from Satellite Laser Ranging (SLR) tracking stations on the Earth. However, unlike the Japanese lunar mission SELENE (Kaguya), no direct tracking will be available while the spacecraft is over the lunar farside. We review the status of orbit modelling for LRO, for both the geopotential modelling and the nonconservative force models, as well as anticipated improvements. We discuss the modelling for the one-way laser ranging observable, and how the data from the one-way laser ranging (LR) system will be acquired from selected stations of the global stations of the SLR network. We discuss the orbit determination strategies which we expect to implement on this mission, including the use of altimeter crossovers from the LOLA instrument to supplement the Earth-based tracking and we review the projected orbit determination accuracies that will be attainable.

Lemoine, Frank; Rowlands, David; McGarry, Jan; Neumann, Gregory; Chinn, Douglas; Mazarico, Erwan; Torrence, Mark

409

Project Freebird: An orbital transfer vehicle  

NASA Astrophysics Data System (ADS)

Freebird is a space-based orbital transfer vehicle designed to repair and deorbit orbital assets. Freebird is based at International Space Station Alpha (ISSA) at an inclination of 51.6 deg and is capable of three types of missions: crewed and teleoperated LEO missions, and extended robotic missions. In a crewed local configuration, the vehicle can visit inclinations between 30.8 deg and 72.4 deg at altitudes close to 390 km. Adding extra fuel tanks extends this range of inclination up to 84.9 deg and down to 18.3 deg. Furthermore, removing the crew module, using the vehicle in a teleoperated manner, and operating with extra fuel tanks allows missions to polar and geosynchronous orbits. To allow for mission flexibility, the vehicle was designed in a semimodular configuration. The major system components include a crew module, a 'smart box' (which contains command, communications, guidance, and navigation equipment), a propulsion pack, extra fuel tanks, and a vehicle storage facility (VSF) for storage purposes. To minimize risk as well as development time and cost, the vehicle was designed using only proven technology or technology which is expected to be flight-qualified in time for the intended launch date of 2002. And, because Freebird carries crew and operates near the space station, it must meet or exceed the NASA reliability standard of 0.994, as well as other standard requirements for such vehicles. The Freebird program was conceived and designed as a way to provide important and currently unavailable satellite repair and replacement services of a value equal to or exceeding operational costs.

Aneses, Carlos A.; Blanchette, Ryan L.; Brann, David M.; Campos, Mario J.; Cohen, Lisa E.; Corcoran, Daniel J., III; Cox, James F.; Curtis, Trevor J.; Douglass, Deborah A.; Downard, Catherine L.

1994-08-01

410

Counterfactual closeness and predicted affect  

Microsoft Academic Search

Empirical research on counterfactual thinking has found a closeness effect: people report higher negative affect if an actual outcome is close to a better counterfactual outcome. However, it remains unclear what actually is a “close” miss. In three experiments that manipulate close counterfactuals, closeness effects were found only when closeness was unambiguously defined either with respect to a contrasted alternative,

Anton Kühberger; Christa Großbichler; Angelika Wimmer

2011-01-01

411

Origin and detectability of co-orbital planets from radial velocity data  

NASA Astrophysics Data System (ADS)

We analyse the possibilities of detection of hypothetical exoplanets in co-orbital motion from synthetic radial velocity (RV) signals, taking into account different types of stable planar configurations, orbital eccentricities and mass ratios. For each nominal solution corresponding to small-amplitude oscillations around the periodic solution, we generate a series of synthetic RV curves mimicking the stellar motion around the barycentre of the system. We then fit the data sets obtained assuming three possible different orbital architectures: (a) two planets in co-orbital motion, (b) two planets in a 2/1 mean-motion resonance (MMR) and (c) a single planet. We compare the resulting residuals and the estimated orbital parameters. For synthetic data sets covering only a few orbital periods, we find that the discrete RV signal generated by a co-orbital configuration could be easily confused with other configurations/systems, and in many cases the best orbital fit corresponds to either a single planet or two bodies in a 2/1 resonance. However, most of the incorrect identifications are associated with dynamically unstable solutions. We also compare the orbital parameters obtained with two different fitting strategies: a simultaneous fit of two planets and a nested multi-Keplerian model. We find that, even for data sets covering over 10 orbital periods, the nested models can yield incorrect orbital configurations (sometimes close to fictitious MMRs) that are nevertheless dynamically stable and with orbital eccentricities lower than the correct nominal solutions. Finally, we discuss plausible mechanisms for the formation of co-orbital configurations, by the interaction between two giant planets and an inner cavity in the gas disc. For equal-mass planets, both Lagrangian and anti-Lagrangian configurations can be obtained from same initial condition depending on final time of integration.

Giuppone, C. A.; Benítez-Llambay, P.; Beaugé, C.

2012-03-01

412

Capture of comets from the Oort cloud into Halley-type and Jupiter-family orbits  

NASA Astrophysics Data System (ADS)

This paper analyzes the capture of comets into Halley-type and Jupiter-family orbits from the nearparabolic flux of the Oort cloud. Two types of capture into Halley-type orbits are found. The first type is the evolution of near-parabolic orbits into short-period orbits (with heliocentric orbital periods P < 200 years) as a result of close encounters with giant planets. This process is followed by a very slow drift of cometary orbits into the inner part of the Solar System. Only those comets may pass from short-period orbits into Halley-type and Jupiter-family orbits, which move in orbits with perihelion distances q < 13 au. In the second type of capture, the perihelion distances of cometary orbits become rather small (< 1.5 au) during the first stage of dynamic evolution under the action of perturbations from the Galaxy, and then their semimajor axes decrease as a result of diffusion. The capture takes place, on average, in 500 revolutions of the comet about the Sun, whereas in the first case, the comet is captured, on average, after 12500 revolutions. The region of initial orbital perihelion distances q > 4 au is found to be at least as important a source of Halley-type comets as the region of perihelion distances q < 4 au. More than half of the Halley-type comets are captured from the nearly parabolic flux with q > 4 au. The analysis of the dynamic evolution of objects moving in short-period orbits shows that the distribution of Centaurs orbits agrees well with the observed distribution corrected for observational selection effects. Hence, the hypothesis associating the origin of Centaurs with the Edgeworth-Kuiper belt and the trans-Neptunian region exclusively should be rejected.

Biryukov, E. E.

2007-06-01

413

Space Tourism: Orbital Debris Considerations  

NASA Astrophysics Data System (ADS)

Space activities after a phase of research and development, political competition and national prestige have entered an era of real commercialization. Remote sensing, earth observation, and communication are among the areas in which this growing industry is facing competition and declining government money. A project like International Space Station, which draws from public money, has not only opened a window of real multinational cooperation, but also changed space travel from a mere fantasy into a real world activity. Besides research activities for sending man to moon and Mars and other outer planets, space travel has attracted a considerable attention in recent years in the form of space tourism. Four countries from space fairing nations are actively involved in the development of space tourism. Even, nations which are either in early stages of space technology development or just beginning their space activities, have high ambitions in this area. This is worth noting considering their limited resources. At present, trips to space are available, but limited and expensive. To move beyond this point to generally available trips to orbit and week long stays in LEO, in orbital hotels, some of the required basic transportations, living requirements, and technological developments required for long stay in orbit are already underway. For tourism to develop to a real everyday business, not only the price has to come down to meaningful levels, but also safety considerations should be fully developed to attract travelers' trust. A serious hazard to space activities in general and space tourism in particular is space debris in earth orbit. Orbiting debris are man-made objects left over by space operations, hazardous to space missions. Since the higher density of debris population occurs in low earth orbit, which is also the same orbit of interest to space tourism, a careful attention should be paid to the effect of debris on tourism activities. In this study, after a review of the current work on space tourism and debris situation in low earth orbit suitable orbits for space tourism activities with regard to the presence of orbital debris are discussed.

Mahmoudian, N.; Shajiee, S.; Moghani, T.; Bahrami, M.

2002-01-01

414

Orbital eccentricity of WASP-12 and WASP-14 from new radial velocity monitoring with SOPHIE  

NASA Astrophysics Data System (ADS)

As part of the long-term radial velocity monitoring of known transiting planets, we have acquired new radial velocity data for the two transiting systems WASP-12 and WASP-14, each harbouring a gas giant on a close orbit (orbital period of 1.09 and 2.24 d, respectively). In both cases, the initial orbital solution suggested a significant orbital eccentricity, 0.049 ± 0.015 for WASP-12b and 0.091 ± 0.003 for WASP-14b. Since then, measurements of the occultation of WASP-12 in the infrared have indicated that one projection of the eccentricity (e cos ?) was close to zero, casting doubt on the eccentricity from the initial radial velocity orbit. Our measurements show that the radial velocity data are compatible with a circular orbit. A MCMC analysis taking into account the presence of correlated systematic noise in both the radial velocity and photometric data gives e= 0.017+0.015-0.010. In contrast, we confirm the orbital eccentricity of WASP-14b, and refine its value to e= 0.0877 ± 0.0030, a 10? detection. WASP-14b is thus the closest presently known planet with a confirmed eccentric orbit. Based on observations made at the 1.93-m telescopes at Observatoire de Haute-Provence (CNRS), France with the SOPHIE spectrograph.

Husnoo, Nawal; Pont, Frédéric; Hébrard, Guillaume; Simpson, Elaine; Mazeh, Tsevi; Bouchy, François; Moutou, Claire; Arnold, Luc; Boisse, Isabelle; Díaz, Rodrigo F.; Eggenberger, Anne; Shporer, Avi

2011-06-01

415

Reproduction on orbit by plants in the Brassicaceae family  

NASA Astrophysics Data System (ADS)

Previous studies on growth and development during spaceflight had indicated that the transition from vegetative to reproductive growth was particularly difficult for plants. Our objective has been to study how the spaceflight environment impacts the different steps in plant reproduction. This goal has been pursued in two general ways: by using plants that had been pre-grown to the flowering stage on earth, and by using plants that developed completely on orbit. Our objectives have been met by a combination of experiments that required essentially no crew time on orbit, and those that required an extensive commitment of crew time. The plants chosen for the studies were closely related members of the family Brassicaceae: Arabidopsis thaliana and Brassica rapa. In a series of short-duration experiments with Arabidopsis on the space shuttle we found that depletion of carbon dioxide in closed chambers resulted in aborted development of both the male and female reproductive apparatus in microgravity. Normal development was restored by addition of carbon dioxide or by providing air flow. A subsequent shuttle experiment with Brassica utilizing hardware that provides a vigorous air flow confirmed embryo development following pollination on orbit. Brassica plants grown from seed on the Mir space station produced seed that germinated and grew when replanted on orbit. Future experiments will determine effects of multiple generations in space.

Musgrave, Mary E.; Kuang, Anxiu; Xiao, Ying; Matthews, Sharon W.

1999-01-01

416

Periodic-Orbit Approach to Universality in Quantum Chaos  

NASA Astrophysics Data System (ADS)

We show that in the semiclassical limit, classically chaotic systems have universal spectral statistics. Concentrating on short-time statistics, we identify the pairs of classical periodic orbits determining the small-? behavior of the spectral form factor K(?) of fully chaotic systems. The two orbits within each pair differ only by their connections inside close self-encounters in phase space. The frequency of occurrence of these self-encounters is determined by ergodicity. Permutation theory is used to systematically sum over all topologically different families of such orbit pairs. The resulting expansions of the form factor in powers of ? coincide with the predictions of random-matrix theory, both for systems with and without time-reversal invariance, and to all orders in ?. Our results are closely related to the zero-dimensional nonlinear sigma model of quantum field theory. The relevant families of orbit pairs are in one-to-one correspondence to Feynman diagrams appearing in the perturbative treatment of the sigma model.

Müller, Sebastian

2005-12-01

417

A census of orbital properties of the M31 satellites  

NASA Astrophysics Data System (ADS)

We present an analysis of the dynamics of the M31 satellite system. Proper motion data exist for only two of the M31 satellites. We account for this incompleteness in velocity data by a statistical analysis using a combination of the timing argument and phase-space distribution functions. These models provide a good fit to the bulk of the M31 satellites and we offer a table of orbital properties, including period, eccentricity and semimajor axis. This enables us to search for evidence of group infall based on orbital similarity rather than propinquity on the sky. Our results favour an association between Cass II and NGC 185, as the orbital parameters are in close agreement, but not for NGC 185 and NGC 147, which have often been associated in the past. Other possible satellite groupings include the pair And I and And XVII; the pair And IX and And X; and the triple And V, And XXV and NGC 147. And XXII has been claimed as a satellite of M33; we find that they are not moving independently along the same orbit, but cannot determine whether they are orbiting each other or are unrelated. Two satellites, And XII and And XIV, have high line-of-sight velocities, consistent with very recent infall from the edge of the Local Group. They are not well described by our underlying smooth phase-space distribution function, and are reanalysed without priors on their orbital parameters. For And XIV, multiple pericentric passages are possible and improved distance information is needed to draw further conclusions. For And XII, orbits which assume at least one pericentric passage can be ruled out and it must be on its first infall into the M31 system.

Watkins, Laura L.; Evans, N. Wyn; van de Ven, Glenn

2013-04-01

418

Point Vortices: Finding Periodic Orbits and their Topological Classification  

NASA Astrophysics Data System (ADS)

The motion of point vortices constitutes an especially simple class of solutions to Euler's equation for two dimensional, inviscid, incompressible, and irrotational fluids. In addition to their intrinsic mathematical importance, these solutions are also physically relevant. Rotating superfluid helium can support rectilinear quantized line vortices, which in certain regimes are accurately modeled by point vortices. Depending on the number of vortices, it is possible to have either regular integrable motion or chaotic motion. Thus, the point vortex model is one of the simplest and most tractable fluid models which exhibits some of the attributes of weak turbulence. The primary aim of this work is to find and classify periodic orbits, a special class of solutions to the point vortex problem. To achieve this goal, we introduce a number of algorithms: Lie transforms which ensure that the equations of motion are accurately solved; constrained optimization which reduces close return orbits to true periodic orbits; object-oriented representations of the braid group which allow for the topological comparison of periodic orbits. By applying these ideas, we accumulate a large data set of periodic orbits and their associated attributes. To render this set tractable, we introduce a topological classification scheme based on a natural decomposition of mapping classes. Finally, we consider some of the intriguing patterns which emerge in the distribution of periodic orbits in phase space. Perhaps the most enduring theme which arises from this investigation is the interplay between topology and geometry. The topological properties of a periodic orbit will often force it to have certain geometric properties.

Smith, Spencer Ambrose

419

Fine-needle aspiration cytology of orbital and eyelid lesions.  

PubMed

Fine-needle aspiration cytology (FNAC) of orbital lesions is now increasingly popular. Because of its unique location and the occurrence of varieties of lesions, diagnosis of orbital lesion is a challenge to the cytopathologists. FNAC of orbital and eyelid tumors is a suitable diagnostic technique that necessitates close co-operation between the ophthalmologist and pathologist. No radical procedure should be planned on the basis of FNAC, but it allows the diagnosis of a new primary lesion or the recurrence or metastasis of a tumor and can be done to identify lesions that require either specific medical therapy, as in nonresectable, inflammatory, and lymphoid tumors, or limited surgery for benign resectable neoplasms. With the help of various ancillary techniques a definitive diagnosis is possible on orbital and adnexal lesions. It is essential to have a detailed knowledge on the FNAC of these lesions and their potential pitfalls. In this present review, we have discussed various orbital lesions, their clinical presentations, cytomorphology, and ancillary techniques to confirm the diagnosis. Diagn. Cytopathol. 2013;41:1000-1011. © 2013 Wiley Periodicals, Inc. PMID:23457033

Agrawal, Pallavi; Dey, Pranab; Lal, Anupam

2013-03-01

420

Anisotropic distribution of orbit poles of binary asteroids  

NASA Astrophysics Data System (ADS)

Our photometric observations of 18 mainbelt binary systems in more than one apparition revealed a strikingly high number of 15 having positively re-observed mutual events in the return apparitions. Our simulations of the survey showed that the data strongly suggest that poles of mutual orbits between components of binary asteroids are not distributed randomly: The null hypothesis of the isotropic distribution of orbit poles is rejected at a confidence level greater than 99.99%. Binary orbit poles concentrate at high ecliptic latitudes, within 30° of the poles of the ecliptic. We propose that the binary orbit poles oriented preferentially up/down-right are due to formation of small binary systems by rotational fission of critically spinning parent bodies with poles near the YORP asymptotic states with obliquities near 0 and 180°. An alternative process of elimination of binaries with poles closer to the ecliptic by the Kozai dynamics of gravitational perturbations from the sun does not explain the observed orbit pole concentration as in the close asteroid binary systems the J2 perturbation due to the primary dominates the solar-tide effect.

Pravec, P.; Scheirich, P.; Vokrouhlický, D.; Harris, A. W.; Kusnirak, P.; Hornoch, K.; Pray, D. P.; Higgins, D.; Galád, A.; Világi, J.; Gajdos, S.; Kornos, L.; Oey, J.; Husárik, M.; Cooney, W. R.; Gross, J.; Terrell, D.; Durkee, R.; Pollock, J.; Reichart, D.; Ivarsen, K.; Haislip, J.; Lacluyze, A.; Krugly, Y. N.; Gaftonyuk, N.; Dyvig, R.; Reddy, V.; Stephens, R. D.; Chiorny, V.; Vaduvescu, O.; Longa, P.; Tudorica, A.; Warner, B. D.; Masi, G.; Brinsfield, J.; Gonçalves, R.; Brown, P.; Krzeminski, Z.; Gerashchenko, O.; Marchis, F.

2011-10-01

421

Orbits and masses in the multiple system LHS 1070  

NASA Astrophysics Data System (ADS)

Aims: We present a study of the orbits of the triple system LHS 1070, with the aim to determine individual masses of its components. Methods: Sixteen new relative astrometric positions of the three components in the K band were obtained with NACO at the VLT, Omega CASS at the 3.5 m telescope on Calar Alto, and other high-spatial-resolution instruments. We combined them with data from the literature and fit orbit models to the dataset. We derived an improved fit for the orbit of LHS 1070 B and C around each other, and an estimate for the orbit of B and C around A. Results: The orbits are nearly coplanar, with a misalignment angle of less than 10°. The masses of the three components are MA = 0.13...0.16 M?, MB = 0.077 ± 0.005 M?, and MC = 0.071 ± 0.004 M?. Therefore, LHS 1070 C is certainly, and LHS 1070 B probably a brown dwarf. Comparison with theoretical isochrones shows that LHS 1070 A is either fainter or more massive than expected. One possible explanation would be that it is a binary. However, the close companion reported previously could not be confirmed. Based on observations collected at the European Southern Observatory, Chile, proposals number 60.A-9026, 66.C-0219, 67.C-0354, 68.C-0539, 70.C-0476, 072.C-0022, 074.C-0637, 078.C-0386, 380.C-0179, 382.C-0324, and 382.C-0329.

Köhler, R.; Ratzka, T.; Leinert, Ch.

2012-05-01

422

FOUR FIRST AND TWO RECALCULATED ORBITS FOR BINARIES  

SciTech Connect

In this paper, we analyze new orbital elements, and quantities that can be derived from them, for six binaries. For four of them, WDS 00251+4803 = HDS 56, WDS 01071-0036 = HDS 144 AB, WDS 06426+3955 = HDS 930, and WDS 21014+4037 = HDS 2995, the orbital elements are calculated for the first time. For the other two, WDS 04195+3800 = HDS 552 and WDS 23209+1643 = HEI 88, the orbital elements are recalculated. Five binaries, denoted as HDS, were discovered during the Hipparcos mission while the remaining binary was discovered somewhat earlier. HEI 88 was measured for the first time in 1978. All studied pairs are close, with almost all measured separations less than 0.3 arcsec. For these binaries the observations were usually performed using the speckle-interferometric technique with the exception of HEI 88, which was observed visually on eight occasions. The resulting orbital periods fall within 13 and 69 years. In addition to the orbital elements, we also give (O-C) residuals in {theta} and {rho}, masses, dynamical parallaxes, absolute magnitudes, spectral types, and ephemerides for the next five years.

Cvetkovic, Z., E-mail: zcvetkovic@aob.bg.ac.rs [Astronomical Observatory, Volgina 7, 11060 Belgrade 38 (Serbia)

2011-04-15

423

Kondo Effect in the Presence of Spin--Orbit Coupling  

NASA Astrophysics Data System (ADS)

Recently, a series of noncentrosymmetric superconductors has been a subject of considerable interest since the discovery of superconductivity in CePt3Si. In noncentrosymmetric materials, the degeneracy of bands is lifted in the presence of spin--orbit coupling. This will bring about new effects in the Kondo effect since the band degeneracy plays an important role in the scattering of electrons by localized spins. We investigate the single-impurity Kondo problem in the presence of spin--orbit coupling. We examine the effect of spin--orbit coupling on the scattering of conduction electrons, by using the Green's function method, for the s--d Hamiltonian, with employing a decoupling procedure. As a result, we obtain a closed system of equations of Green's functions, from which we can calculate physical quantities. The Kondo temperature TK is estimated from a singularity of Green's functions. We show that TK is reduced as the spin--orbit coupling constant ? is increased. When 2? kF is comparable to or greater than kBTK(?=0), TK shows an abrupt decrease as a result of the band splitting. This suggests a Kondo collapse accompanied with a sharp decrease of TK. The log T-dependence of the resistivity will be concealed by the spin--orbit interaction.

Yanagisawa, Takashi

2012-09-01

424

Understanding and improving the Fermilab booster high field orbit  

SciTech Connect

This note is an account of the authors' effort in both understanding the Booster high field orbit and controlling it through displacements of the main combined function magnets. We were able to achieve the second goal with considerable accuracy while having limited success with the first, due to insufficient knowledge of the Booster dynamics. This work was initiated in Spring 1987 with the orbit control via magnet moves the chief purpose. A series of magnet moves in 1987 and 1988 resulting from this study testified to its reliability. The understanding of the Booster orbit in general remains an ongoing process in which we keep modifying our model with the hope of eventually having a quantitative grasp of the closed orbit and being able to manipulate it with more flexibility and accuracy. In this paper we give a brief description of the Booster environment in which the magnet moves are carried out, together with background information concerning the magnet moves. The method we use is discussed. The result of the moves is documented, and our effort to understand the Booster high field orbit is given a detailed account. 12 figs., 5 tabs.

Chao, Y.; Ketcham, L.; Moore, C.D.

1989-03-01

425

The orbital theory of Pleistocene climate : support from a revised chronology of the marine delta18 O record  

Microsoft Academic Search

Observations of delta18O in five deep-sea cores provide a basis for developing a geological time scale for the past 780000 years and for evaluating the orbital theory of Pleistocene ice ages. The statistical evidence of a close relationship between the time-varying amplitudes of orbital forcing and the time-varying amplitudes of the isotopic response implies that orbital variations are the main

J. Imbrie; J. D. Hays; D. G. Martinson; A. McIntyre; A. C. Mix; J. J. Morley; N. G. Pisias; W. L. Prell; N. J. Shackleton

1984-01-01

426

THE ORBITS OF THE OUTER URANIAN SATELLITES  

SciTech Connect

We report on the numerically integrated orbits for the nine outer Uranian satellites. The orbits are calculated based on fits to the astrometric observations for the period from 1984 to 2006. The results include the state vectors, post-fit residuals, and mean orbital elements. We also assess the accuracy of the orbital fits and discuss the need for future measurements.

Brozovic, M.; Jacobson, R. A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)], E-mail: marina.brozovic@jpl.nasa.gov

2009-04-15

427

Optimal parking orbits for manned Mars missions  

Microsoft Academic Search

This paper summarizes a Mars parking orbit optimization effort. This parking orbit study includes the selection of optimal elliptic Mars parking orbits that meet mission constraints and that include pertinent apsidal misalignment losses. Mars missions examined are for the opportunity years of 2014, 2016, and 2018. For these mission opportunities, it is shown that the optimal parking orbits depend on

Michael L. Cupples; Jill A. Nordwall

1993-01-01

428

Elements of a Chemical Orbital Theory  

NASA Astrophysics Data System (ADS)

Interaction is important in chemistry. Interactions of atoms form chemical bonds. Bonds interact with each other in molecules to determine the molecular properties. Interactions of molecules give rise to chemical reactions. Electrons control atoms, bonds, and molecules. The behavior of electrons is simply and effectively represented by orbitals, which contain wave properties, i.e., phase and amplitude. In our chemical orbital theory we consider the interactions of the orbitals of atoms, bonds and molecules. The elements of the chemical orbital theory are separated into three groups: (1) interactions of two orbitals, (2) interactions of three orbitals, and (3) cyclic interactions of more than two orbitals. Here, general aspects of the interactions of two orbitals are summarized to show the background of this volume and assist nonspecialists to read the following chapters. Among the keywords are: phase and amplitude of orbitals, strength of orbital interactions, electron delocalization, electron localization, exchange repulsion, ionization energy, electronic spectrum, frontier orbitals, reactivity, selectivity, orbital symmetry, and so on. The remaining elements of the chemical orbital theory, i.e., an orbital mixing rule for the three-orbital interactions and an orbital phase theory for the cyclic interactions, are introduced briefly.

Inagaki, Satoshi

429

Atomic Electron Populations by Molecular Orbital Theory.  

National Technical Information Service (NTIS)

The detailed distribution of electrons in molecules can be broken down into atomic orbital populations if an atomic orbital basis is used for a molecular orbital wave function (LCAO). A total assignment of all electrons in a molecule to atomic orbitals (a...

W. J. Hehre R. F. Stewart J. A. Pople

1968-01-01

430

Mars Reconnaissance Orbiter Accelerometer Experiment Results  

Microsoft Academic Search

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis

G. M. Keating; S. W. Bougher; M. E. Theriot; R. W. Zurek; R. C. Blanchard; R. H. Tolson; J. R. Murphy

2007-01-01

431

Poynting-Robertson drag and orbital resonance  

Microsoft Academic Search

Both the Poynting-Robertson drag and resonant orbits appear to be very important for the motion of small grains in the early solar system. While orbital resonances are very often stable and tend to force bodies into noncircular orbits, the Poynting-Robertson drag produces secular variations in the semimajor axis and tends to circularize the orbits. This paper presents a numerical study

R. Gonczi; Ch. Froeschle; C. Froeschle

1982-01-01

432

The superior orbital fissure and its contents  

Microsoft Academic Search

Topographic landmarks for the superior orbital fissure are useful for general orientation and approach to the middle fossa, cavernous sinus and orbit. In this study, the microsurgical anatomy and morphometry of the superior orbital fissure and its related structures were examined in 57 disarticulated sphenoid bones, 102 skull bases and 58 adult cadaveric heads. The superior orbital fissure was observed

F. Govsa; G. Kayalioglu; M. Erturk; T. Ozgur

1999-01-01

433

Osseous Anatomy of the Orbital Apex  

Microsoft Academic Search

The osseous anatomy of the orbital apex may be difficult to conceptualize because of the dif- ferent shapes and orientations of the optic ca- nal, superior and inferior orbital fissures, and foramen rotundum. However, knowing this anatomy is crucial to evaluate complex frac- tures, tumors, and inflammatory processes in- volving the orbital apex. Evaluating osseous anatomy of the orbital apex

David L. Daniels; Leighton P. Mark; Mahmood F. Mafee; Bruce Massaro; Lloyd E. Hendrix; Katherine A. Shaffer; David Morrissey; Charles W. Horner

434

The superior orbital fissure and its contents  

Microsoft Academic Search

Summary Topographic landmarks for the superior orbital fissure are useful for general orientation and approach to the middle fossa, cavernous sinus and orbit. In this study, the microsurgical anatomy and morphometry of the superior orbital fissure and its related structures were examined in 57 disarticulated sphenoid bones, 102 skull bases and 58 adult cadaveric heads. The superior orbital fissure was

F. Govsa; G. Kayalioglu; M. Erturk; T. Ozgur

1999-01-01

435

Closing the Health Gap  

NSDL National Science Digital Library

The US Department of Health and Human Services (HHS) and ABC Radio Networks are working together to help African-Americans gain access to the best possible information regarding health issues. HHS reports that life expectancies for African-Americans lag five years behind expectancies for White Americans. The new Website Closing the Health Gap has links to information on health conditions such as diabetes and cancer as well as consumer health resources that relate to African-Americans' particular needs. Each page offers links, publications, and any news related to the subject, all in an effort to close "the health gap."

2001-01-01

436

Closed liver injury.  

PubMed

The purpose of this article is to familiarize sports medicine physicians with evaluation, initial management, and treatment of athletes with closed liver trauma. Ten percent of abdominal injuries are caused during sports-related activities. The liver is the most commonly injured organ in blunt abdominal trauma. Physical examination findings may be subtle or absent in patients with underlying liver injury. A paradigm shift toward nonoperative management in hemodynamically stable patients has led to a decrease in mortality. Return-to-play guidelines do not exist for closed liver injuries. These decisions are usually made on a case-by-case basis using basic return to play principles. PMID:23522504

Casiero, Deena C

2013-02-01

437

Secular motion around synchronously orbiting planetary satellites.  

PubMed

We investigate the secular motion of a spacecraft around the natural satellite of a planet. The satellite rotates synchronously with its mean motion around the planet. Our model takes into account the gravitational potential of the satellite up to the second order, and the third-body perturbation in Hill's approximation. Close to the satellite, the ratio of rotation rate of the satellite to mean motion of the orbiter is small. When considering this ratio as a small parameter, the Coriolis effect is a first-order perturbation, while the third-body tidal attraction, the ellipticity effect, and the oblateness perturbation remain at higher orders. Then, we apply perturbation theory and find that a third-order approach is enough to show the influence of the satellite's ellipticity in the pericenter dynamics. Finally, we discuss the averaged system in the three-dimensional parametric space, and provide a global description of the flow. PMID:16396586

Lara, Martin; San-Juan, Juan F; Ferrer, Sebastián

2005-12-01

438

THE ORBITAL EVOLUTION OF GAS GIANT PLANETS AROUND GIANT STARS  

SciTech Connect

Recent surveys have revealed a lack of close-in planets around evolved stars more massive than 1.2 M{sub sun}. Such planets are common around solar-mass stars. We have calculated the orbital evolution of planets around stars with a range of initial masses, and have shown how planetary orbits are affected by the evolution of the stars all the way to the tip of the red giant branch. We find that tidal interaction can lead to the engulfment of close-in planets by evolved stars. The engulfment is more efficient for more-massive planets and less-massive stars. These results may explain the observed semimajor axis distribution of planets around evolved stars with masses larger than 1.5 M{sub sun}. Our results also suggest that massive planets may form more efficiently around intermediate-mass stars.

Villaver, Eva [Universidad Autonoma de Madrid, Departamento de fisica Teorica C-XI, 28049 Madrid (Spain); Livio, Mario, E-mail: eva.villaver@uam.e, E-mail: mlivio@stsci.ed [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2009-11-01

439

Orbital manifestations of Noonan syndrome.  

PubMed

Noonan syndrome describes a rare multisystem condition that manifests with Turner syndrome phenotype combined with numerous systemic and facial characteristics. The most common systemic findings include cardiac defects, short stature, chest deformity, hearing loss, and bleeding diatheses. Patients with Noonan syndrome are also at a greater risk of developing various types of malignancies. Facial characteristics of Noonan syndrome consist of broad forehead, low-set ears, short and webbed neck, and low hairline. External ocular findings include hypertelorism, ptosis, epicanthal folds, antimongoloid slant, downward-sloping palpebral fissures, and malar flattening. In this case series and review of the literature, the authors present 2 cases of Noonan syndrome that embody the diverse spectrum of orbital manifestations associated with this rare disorder. The first case demonstrates more profound orbital pathology, including bilateral orbital giant cell reparative granulomas, proptosis, hypertelorism, shallow orbits, upper eyelid ptosis, and lower eyelid retraction. The second case displays classic Turner-syndrome-like facial characteristics including a broad forehead with low hairline, low-set ears, and short and webbed neck. Orbital findings were subtle and consisted of bilateral lower eyelid retraction and shallow orbits. In conclusion, Noonan syndrome is a rare congenital disorder with a wide spectrum of clinical findings. Various intraorbital and extraorbital tumors may occur in patients with Noonan syndrome, with giant cell reparative granuloma being the most commonly encountered. In patients with orbital tumors and eyelid retraction, the authors describe successful treatment through decompression, tumor extraction, and lower eyelid retractor release. Patients who present with ocular irritation and exposure due to less severe lower eyelid malposition may be successfully treated with lower eyelid retraction repair combined with lateral internal tarsoconjunctival tarsorrhaphy. PMID:21464791

Randolph, John C; Sokol, Jason A; Lee, Hui Bae H; Nunery, William R

440

Effect of Vertical Vibrations on the Onset of Binary Convection  

NASA Astrophysics Data System (ADS)

In the present work the linear stability analysis of double diffusive convection in a binary fluid layer is performed. The major intention of this study is to investigate the influence of time-periodic vertical vibrations on the onset threshold. A regular perturbation method is used to compute the critical Rayleigh number and wave number. A closed form expression for the shift in the critical Rayleigh number is calculated as a function of frequency of modulation, the solute Rayleigh number, Lewis number, and Prandtl number. These parameters are found to have a significant influence on the onset criterion; therefore the effective control of convection is achieved by proper tuning of these parameters. Vertical vibrations are found to enhance the stability of a binary fluid layer heated and salted from below. The results of this study are useful in the areas of crystal growth in micro-gravity conditions and also in material processing industries where vertical vibrations are involved

Swamy, M. S.

2013-08-01

441

Bonding in Transition Metal Silyl Dimers. Molecular Orbital Theory.  

National Technical Information Service (NTIS)

Molecular orbital studies of Mn2(CO)8 (Si(C6H5)2)2 and Pt2(H3P)4(SiC6H5C1)2 have been made by interacting disilene fragments with transition metal dimers. In the former complex, it is found that the Mn-Mn distance is close to the sum of the atomic radii b...

A. B. Anderson C. A. Tessier-Youngs E. A. Zarate P. Shiller W. J. Youngs

1989-01-01

442

Research of the orbital evolution of asteroid 2012 DA14  

NASA Astrophysics Data System (ADS)

Research of the orbital evolution of asteroid 2012 DA14 on the time interval from 1800 to 2206 is made, an object close approaches with Earth and the Moon are detected, the probability of impact with Earth is calculated. The used mathematical model is consistent with the DE405, the integration was performed using a modified Everhart's method of 27th order, the probability of collision is calculated using the Monte Carlo method.

Zausaev, A. F.; Denisov, S. S.; Derevyanka, A. E.

443

Continuation of Periodic Orbits in Symmetric Hamiltonian Systems  

Microsoft Academic Search

The idea of everything returning eventually to its point of departure has a strong hold on humanity, with many historical,\\u000a philosophical and religious implications. Classical examples are the need to construct a calendar and the subsequent search\\u000a for orbits in the solar system in which the planets follow a closed track and repeat their history over and over again.\\u000a \\u000a Nature,

Jorge Galán-Vioque; André Vanderbauwhede

444

Enhancement of Rashba coupling in vertical In0.05Ga0.95As/GaAs quantum dots  

NASA Astrophysics Data System (ADS)

We study the spin-splitting energies in low-potential-barrier quantum dots, finding splitting energies that are orbital state dependent. The theoretical analysis is done with a generalization of the Fock-Darwin states in the presence of spin-orbit interactions. We discuss experimental evidence indicating that the Rashba interaction strength in vertical InxGa1-xAs/GaAs quantum dots is in the range 80 meV Å ??R? 120 meV Å. This enhanced spin-orbit interaction can be understood from the high penetration of the electron wave function into the quantum well with low-potential barrier.

Huang, S. M.; Badrutdinov, A. O.; Serra, L.; Kodera, T.; Nakaoka, T.; Kumagai, N.; Arakawa, Y.; Tayurskii, D. A.; Kono, K.; Ono, K.

2011-08-01

445

Closing the Loop Sampler.  

ERIC Educational Resources Information Center

Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

California Integrated Waste Management Board, Sacramento.

446

Commission 42: Close Binaries  

Microsoft Academic Search

The triennial report from Commission 42 covers various topics like massive binaries, contact systems, cataclysmic variables and low-mass binary stars. We try in a number of sections to provide an update on the current status of the main research areas in the field of close binaries. It is not a formal review, even complete or comprehensive, but an attempt to

Alvaro Giménez; Slavek Rucinski; P. Szkody; D. Gies; Y.-W. Kang; J. Linsky; M. Livio; N. Morrell; R. Hilditch; B. Nordström; I. Ribas; E. Sion; S. Vrielman

2007-01-01

447

Closing the Loop Sampler.  

ERIC Educational Resources Information Center

|Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

California Integrated Waste Management Board, Sacramento.

448

The long-term interaction of the Italian satellites abandoned in GEO with the orbital debris environment  

Microsoft Academic Search

Four Italian satellites have been launched, so far, in geostationary orbit: SIRIO, Italsat 1, Italsat 2, and SICRAL. The latter is the only one still operational: in fact, Sirio was abandoned close to the geopotential equilibrium point at 75?E in 1985, Italsat 1 was re-orbited above the geosynchronous altitude at the beginning of 2001 and Italsat 2 was moved, in

Luciano Anselmo; Carmen Pardini

2005-01-01

449

Orbital Metastasis of Breast Carcinoma  

PubMed Central

We report a case of orbital metastasis in a previously diagnosed metastatic breast cancer in a 46-year old woman presenting with diplopia and proptosis of her left eye bulb. An orbital computed-tomography (CT) and a magnetic resonance imaging (MRI) both revealed an intra-orbital extra-bulbar mass of 1.5 × 3 cm in size, in the left orbit. The patient had been diagnosed with stage IV breast cancer 4 years before. She had received chemotherapy with docetaxel and was on hormone therapy at the time of presentation of her eye symptoms. Current treatment included systemic combination therapy with docetaxel and capecitabine as well as local irradiation with stereotactic radiosurgery (cyberknife). There was a gradual improvement of local symptoms and signs. The metastatic involvement of the orbit in malignant tumors is a rarely diagnosed condition. Breast cancer accounts for the majority of these cases. The appearance of eye symptoms in patients with a history of cancer should always be investigated with a consideration of ocular metastatic disease.

Vlachostergios, Panagiotis J.; Voutsadakis, Ioannis A.; Papandreou, Christos N.

2009-01-01

450

Anterior Orbit and Adnexal Amyloidosis  

PubMed Central

Purpose: To describe six cases of anterior orbital and adnexal amyloidosis and to report on proteomic analysis to characterize the nature of amyloid in archived biopsies in two cases. Materials and Methods: The clinical features, radiological findings, pathology, and outcome of six patients with anterior orbit and adnexal amyloidosis were retrieved from the medical records. The biochemical nature of the amyloid was determined using liquid chromatography/mass spectroscopy archived paraffin-embedded tissue in two cases. Results: Of the six cases, three had unilateral localized anterior orbit and lacrimal gland involvement. Four of the six patients were female with an average duration of 12.8 years from the time of onset to presentation eyelid infiltration by amyloid caused ptosis in five cases. CT scan in patients with lacrimal gland involvement (n = 3) demonstrated calcified deformable anterior orbital masses and on pathological exmaintionamyloid and calcific deposits replaced the lacrimal gland acini. Ptosis repair was performed in three patients with good outcomes. One patient required repeated debulking of the mass and one patient had recurrenct disease. Proteomic analysis revealed polyclonal IgG-associated amyloid deposition in one patient and AL kappa amyloid in the second patient. Conclusion: Amyloidosis of the anterior orbit and lacrimal gland can present with a wide spectrum of findings with good outcomes after surgical excision. The nature of amyloid material can be precisely determined in archival pathology blocks using diagnostic proteomic analysis.

Al Hussain, Hailah; Edward, Deepak P.

2013-01-01

451

RHIC VERTICAL AC DIPOLE COMMISSIONING.  

SciTech Connect

The RHIC vertical ac dipole was installed in the summer of 2001. The magnet is located in the interaction region between sector 3 and sector 4 common to both beams. The resonant frequency of the ac dipole was first configured to be around half of the beam revolution frequency to act as a spin flipper. At the end of the RHIC 2002 run, the ac dipole frequency was reconfigured for linear optics studies. A 0.35 mm driven betatron oscillation was excited with the vertical ac dipole and the vertical betatron functions and phase advances at each beam position monitor (BPM) around the RHIC yellow ring were measured using the excited coherence. We also recorded horizontal turn-by-turn beam positions at each BPM location to investigate coupling effects. Analysis algorithms and measurement results are presented.

BAI,M.; DELONG,J.; HOFF,L.; PAI,C.; PEGGS,S.; PIACENTINO,J.; OERTER,B.; ODDO,P.; ROSER,T.; SATOGATA,T.; TRBOJEVIC,D.; ZALTSMAN,A.

2002-06-02

452

FORMING CLOSE-IN EARTH-LIKE PLANETS VIA A COLLISION-MERGER MECHANISM IN LATE-STAGE PLANET FORMATION  

SciTech Connect

The large number of exoplanets found to orbit their host stars in very close orbits have significantly advanced our understanding of the planetary formation process. It is now widely accepted that such short-period planets cannot have formed in situ, but rather must have migrated to their current orbits from a formation location much farther from their host star. In the late stages of planetary formation, once the gas in the protoplanetary disk has dissipated and migration has halted, gas giants orbiting in the inner disk regions will excite planetesimals and planetary embryos, resulting in an increased rate of orbital crossings and large impacts. We present the results of dynamical simulations for planetesimal evolution in this later stage of planet formation. We find that a mechanism is revealed by which the collision-merger of planetary embryos can kick terrestrial planets directly into orbits extremely close to their parent stars.

Ji Jianghui; Jin Sheng [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Tinney, C. G., E-mail: jijh@pmo.ac.cn, E-mail: qingxiaojin@gmail.com [Department of Astrophysics, School of Physics, University of New South Wales, NSW 2052 (Australia)

2011-01-20