Autonomous 3D geometry reconstruction through robot-manipulated optical sensors

Many industrial sectors face increasing production demands and the need to reduce costs, without compromising the quality. The use of robotics and automation has grown significantly in recent years, but versatile robotic manipulators are still not commonly used in small factories. Beside of the investments required to enable efficient and profitable use of robot technology, the efforts needed to program robots are only economically viable in case of large lot sizes. Generating robot programs for specific manufacturing tasks still relies on programming trajectory waypoints by hand. The use of virtual simulation software and the availability of the specimen digital models can facilitate robot programming. Nevertheless, in many cases, the virtual models are not available or there are excessive differences between virtual and real setups, leading to inaccurate robot programs and time-consuming manual corrections. Previous works have demonstrated the use of robot-manipulated optical sensors to map the geometry of samples. However, the use of simple user-defined robot paths, which are not optimized for a specific part geometry, typically causes some areas of the samples to not be mapped with the required level of accuracy or to not be sampled at all by the optical sensor. This work presents an autonomous framework to enable adaptive surface mapping, without any previous knowledge of the part geometry being transferred to the system. The novelty of this work lies in enabling the capability of mapping a part surface at the required level of sampling density, whilst minimizing the number of necessary view poses. Its development has also led to an efficient method of point cloud down-sampling and merging. The article gives an overview of the related work in the field, a detailed description of the proposed framework and a proof of its functionality through both simulated and experimental evidences

Chandra and RXTE studies of the X-ray/gamma-ray millisecond pulsar PSR J0218+4232

We report on high-resolution spatial and timing observations of the millisecond pulsar PSR J0218+4232 performed with the Chandra X-ray Observatory (CXO) and the Rossi X-ray Timing Explorer (RXTE). With these observations we were able to study a) the possible spatial extent at X-ray energies of the DC source coincident with PSR J0218+4232 in detail (CXO), b) the relative phasing between the X-ray, radio and gamma-ray profiles (CXO and RXTE) and c) the spectral properties at energies beyond 10 keV (RXTE). We found no indications for extended emission at X-ray energies down to ~ 1 arcsec scales and confirmed the presence of a point-like DC-component. The 2 non-thermal pulses in the X-ray profile are found to be aligned with 2 of the 3 pulses visible at radio-frequencies and more importantly with the two gamma-ray pulses seen in the EGRET 100-1000 MeV pulse profile. The latter reduces now the random occurrence probability for the detected gamma-ray signal to ~ 1.E-6, which corresponds to a 4.9 sigma detection significance.Comment: 8 pages,7 figures, accepted for publication in Adv Sp Res: Proceedings of the 34th COSPAR Scientific Assembly held in Housto

A comprehensive X-ray and multiwavelength study of the Colliding Galaxy Pair NGC2207/IC2163

We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC2207/IC2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultra-luminous X-ray sources (ULXs), 7 of which were not detected previously due to X-ray variability. Twelve sources show significant long-term variability, with no correlated spectral changes. Seven sources are transient candidates. One ULX coincides with an extremely blue star cluster (B-V = -0.7). We confirm that the global relation between the number and luminosity of ULXs and the integrated star formation rate (SFR) of the host galaxy also holds on local scales. We investigate the effects of dust extinction and/or age on the X-ray binary (XRB) population on sub-galactic scales. The distributions of Nx and Lx are peaked at L(IR)/L(NUV)~1, which may be associated with an age of ~10 Myr for the underlying stellar population. We find that ~1/3 of the XRBs are located in close proximity to young star complexes. The luminosity function of the X-ray binaries is consistent with that typical for high-mass X-ray binaries, and appears unaffected by variability. We disentangle and compare the X-ray diffuse spectrum with that of the bright XRBs. The hot interstellar medium dominates the diffuse X-ray emission at E<1 keV, has a temperature kT=0.28 (+0.05/-0.04) keV and intrinsic 0.5-2 keV luminosity of 7.9e+40 erg/s, a factor of ~2.3 higher than the average thermal luminosity produced per unit SFR in local star-forming galaxies. The total X-ray output of NGC2207/IC2163 is 1.5e+41 erg/s, and the corresponding total integrated SFR is 23.7 Msol/yr.Comment: 24 pages, 11 figures, 11 tables. Accepted for publication in The Astrophysical Journa

Liquid-gas phase transition in nuclear matter including strangeness

We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction $f_s$ between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a non-trivial function of the strangeness fraction.Comment: 15 pages, 7 figure

The formation of helium lines in the spectrum of COM J1740-5340

The He I 5876A absorption line recently discovered in the spectrum of the companion to the millisecond pulsar PSR J1740-5340 is tentatively attributed to electron impact excitations due to the irradiation of its atmosphere by gamma-rays emitted by the pulsar's magnetosphere. Numerical calculations, similar to those carried out previously for Type Ib SNe, indicate that a pulsar beam with photon energies ~ 1 MeV gives rise to a 5876A line of the observed strength if the beam's spin-down conversion efficiency approaches 1%. However, a significant difficulty for the proposed mechanism is the strength of the singlet line at 6678A. Compared to the corresponding triplets, singlet lines are weak because of the loss of excitation when photons emitted in decays to the ground state ionize hydrogen atoms, an effect absent in the hydrogen-free atmospheres of Type Ib SNe.Comment: Accepted for publication in A&