Generic Techniques for the Calibration of Robots with Application of the 3-D Fixtures and Statistical Technique on the PUMA 500 and ARID Robots

A relatively simple, inexpensive, and generic technique that could be used in both laboratories and some operation site environments is introduced at the Robotics Applications and Development Laboratory (RADL) at Kennedy Space Center (KSC). In addition, this report gives a detailed explanation of the set up procedure, data collection, and analysis using this new technique that was developed at the State University of New York at Farmingdale. The technique was used to evaluate the repeatability, accuracy, and overshoot of the Unimate Industrial Robot, PUMA 500. The data were statistically analyzed to provide an insight into the performance of the systems and components of the robot. Also, the same technique was used to check the forward kinematics against the inverse kinematics of RADL's PUMA robot. Recommendations were made for RADL to use this technique for laboratory calibration of the currently existing robots such as the ASEA, high speed controller, Automated Radiator Inspection Device (ARID) etc. Also, recommendations were made to develop and establish other calibration techniques that will be more suitable for site calibration environment and robot certification

Measuring nonadiabaticity of molecular quantum dynamics with quantum fidelity and with its efficient semiclassical approximation

We propose to measure nonadiabaticity of molecular quantum dynamics rigorously with the quantum fidelity between the Born-Oppenheimer and fully nonadiabatic dynamics. It is shown that this measure of nonadiabaticity applies in situations where other criteria, such as the energy gap criterion or the extent of population transfer, fail. We further propose to estimate this quantum fidelity efficiently with a generalization of the dephasing representation to multiple surfaces. Two variants of the multiple-surface dephasing representation (MSDR) are introduced, in which the nuclei are propagated either with the fewest-switches surface hopping (FSSH) or with the locally mean field dynamics (LMFD). The LMFD can be interpreted as the Ehrenfest dynamics of an ensemble of nuclear trajectories, and has been used previously in the nonadiabatic semiclassical initial value representation. In addition to propagating an ensemble of classical trajectories, the MSDR requires evaluating nonadiabatic couplings and solving the Schr\"{o}dinger (or more generally, the quantum Liouville-von Neumann) equation for a single discrete degree of freedom. The MSDR can be also used to measure the importance of other terms present in the molecular Hamiltonian, such as diabatic couplings, spin-orbit couplings, or couplings to external fields, and to evaluate the accuracy of quantum dynamics with an approximate nonadiabatic Hamiltonian. The method is tested on three model problems introduced by Tully, on a two-surface model of dissociation of NaI, and a three-surface model including spin-orbit interactions. An example is presented that demonstrates the importance of often-neglected second-order nonadiabatic couplings.Comment: 14 pages, 4 figures, submitted to J. Chem. Phy

Spectroscopy of clusters in the ESO Distant Cluster Survey (EDisCS)

We present spectroscopic observations of galaxies in 4 clusters at z = 0.7-0.8 and in one cluster at z~0.5 obtained with the FORS2 spectrograph on the VLT as part of the ESO Distant Cluster Survey (EDisCS), a photometric and spectroscopic survey of 20 intermediate to high redshift clusters. We describe our target selection, mask design, observation and data reduction procedures, using these first 5 clusters to demonstrate how our strategies maximise the number of cluster members for which we obtain spectroscopy. We present catalogues containing positions, I-band magnitudes and spectroscopic redshifts for galaxies in the fields of our 5 clusters. These contain 236 cluster members, with the number of members per cluster ranging from 30 to 67. Our spectroscopic success rate, i.e. the fraction of spectroscopic targets which are cluster members, averages 50% and ranges from 30% to 75%. We use a robust biweight estimator to measure cluster velocity dispersions from our spectroscopic redshift samples. We also make a first assessment of substructure within our clusters. The velocity dispersions range from 400 to 1100 km s-1. Some of the redshift distributions are significantly non-Gaussian and we find evidence for significant substructure in two clusters, one at z~0.79 and the other at z~0.54. Both have velocity dispersions exceeding 1000 km s-1 but are clearly not fully virialised; their velocity dispersions may thus be a poor indicator of their masses. The properties of these first 5 EDisCS clusters span a wide range in redshift, velocity dispersion, richness and substructure, but are representative of the sample as a whole. Spectroscopy for the full dataset will allow a comprehensive study of galaxy evolution as a function of cluster environment and redshift.Comment: 18 pages, 27 figures, accepted for publication in A&A, Table 4 is available ahead of journal publication by downloading the source files for this astro-ph submission or from first author on request ([email protected]

Why Use a Hamilton Approach in QCD?

We discuss $QCD$ in the Hamiltonian frame work. We treat finite density $QCD$ in the strong coupling regime. We present a parton-model inspired regularisation scheme to treat the spectrum ($\theta$-angles) and distribution functions in $QED_{1+1}$. We suggest a Monte Carlo method to construct low-dimensionasl effective Hamiltonians. Finally, we discuss improvement in Hamiltonian $QCD$.Comment: Proceedings of Hadrons and Strings, invited talk given by H. Kr\"{o}ger; Text (LaTeX file), 3 Figures (ps file

Astrometric planet search around southern ultracool dwarfs II: Astrometric reduction methods and a deep astrometric catalogue

We describe the astrometric reduction of images obtained with the FORS2/VLT camera in the framework of an astrometric planet search around 20 M/L-transition dwarfs. We present the correction of systematic errors, the achieved astrometric performance, and a new astrometric catalogue containing the faint reference stars in 20 fields located close to the Galactic plane. We detected three types of systematic errors in the FORS2 astrometry: the relative motion of the camera's two CCD chips, errors that are correlated in space, and an error contribution of yet unexplained origin. The relative CCD motion has probably a thermal origin and usually is 0.001-0.010 px (~0.1-1 mas), but sometimes amounts to 0.02-0.05 px (3-6 mas). This instability and space-correlated errors are detected and mitigated using reference stars. The third component of unknown origin has an amplitude of 0.03-0.14 mas and is independent of the observing conditions. We find that a consecutive sequence of 32 images of a well-exposed star over 40 min at 0.6" seeing results in a median r.m.s. of the epoch residuals of 0.126 mas. Overall, the epoch residuals are distributed according to a normal law with a chi2~1. We compiled a catalogue of 12000 stars with I-band magnitudes of 16-22 located in 20 fields, each covering ~2x2'. It contains I-band magnitudes, ICRF positions with 40-70 mas precision, and relative proper motions and absolute trigonometric parallaxes with a precision of 0.1 mas/yr and 0.1 mas at the bright end, respectively.Comment: 17 pages, 19 figures, 4 tables, accepted for publication in A&A on March 14, 201

The Proper Motion of PSR J0205+6449 in 3C 58

We report on sensitive phase-referenced and gated 1.4-GHz VLBI radio observations of the pulsar PSR J0205+6449 in the young pulsar-wind nebula 3C 58, made in 2007 and 2010. We employed a novel technique where the ~105-m Green Bank telescope is used simultaneously to obtain single-dish data used to determine the pulsar's period as well as to obtain the VLBI data, allowing the VLBI correlation to be gated synchronously with the pulse to increase the signal-to-noise. The high timing noise of this young pulsar precludes the determination of the proper motion from the pulsar timing. We derive the position of the pulsar accurate at the milliarcsecond level, which is consistent with a re-determined position from the Chandra X-ray observations. We reject the original tentative optical identification of the pulsar by Shearer and Neustroev (2008), but rather identify a different optical counterpart on their images, with R-band magnitude ~24. We also determine an accurate proper motion for PSR J0205+6449 of (2.3 +- 0.3) mas/yr, corresponding to a projected velocity of only (35 +- 6) km/s for a distance of 3.2 kpc, at p.a. -38 deg. This projected velocity is quite low compared to the velocity dispersion of known pulsars of ~200 km/s. Our measured proper motion does not suggest any particular kinematic age for the pulsar.Comment: 10 pages, 7 figures; accepted for publication in MNRA

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

Gaia's very accurate astrometric measurements will allow the International Celestial Reference Frame (ICRF) to be improved by a few orders of magnitude in the optical. Several sets of quasars are used to define a kinematically stable non-rotating reference frame with the barycentre of the Solar System as its origin. Gaia will also observe a large number of galaxies which could obtain accurate positions and proper motions although they are not point-like. The optical stability of the quasars is critical and we investigate how accurately the reference frame can be recovered. Various proper motion patterns are also present in the data, the best known is caused by the acceleration of the Solar System Barycentre, presumably, towards the Galactic centre. We review some other less-well-known effects that are not part of standard astrometric models. We model quasars and galaxies using realistic sky distributions, magnitudes and redshifts. Position variability is introduced using a Markov chain model. The reference frame is determined using the algorithm developed for the Gaia mission which also determines the acceleration of the Solar System. We also test a method to measure the velocity of the Solar System barycentre in a cosmological frame. We simulate the recovery of the reference frame and the acceleration of the Solar System and conclude that they are not significantly disturbed in the presence of quasar variability which is statistically averaged. However, the effect of a non-uniform sky distribution of the quasars can result in a correlation between the reference frame and acceleration which degrades the solution. Our results suggest that an attempt should be made to astrometrically determine the redshift dependent apparent drift of galaxies due to our velocity relative to the CMB, which in principle could allow the determination of the Hubble parameter.Comment: published in A&A, revised version (v2) (Abstract is same as v1 as the character limit is 1920, see the pdf for v2