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This work presents an algorithm for scene change detection from point clouds to enable autonomous robotic caretaking in future space habitats. Autonomous robotic systems will help maintain future deep-space habitats, such as the Gateway space station, which will be uncrewed for extended periods. Existing scene analysis software used on the International Space Station (ISS) relies on manually-labeled images for detecting changes. In contrast, the algorithm presented in this work uses raw, unlabeled point clouds as inputs. The algorithm first applies modified Expectation-Maximization Gaussian Mixture Model (GMM) clustering to two input point clouds. It then performs change detection by comparing the GMMs using the Earth Mover's Distance. The algorithm is validated quantitatively and qualitatively using a test dataset collected by an Astrobee robot in the NASA Ames Granite Lab comprising single frame depth images taken directly by Astrobee and full-scene reconstructed maps built with RGB-D and pose data from Astrobee. The runtimes of the approach are also analyzed in depth. The source code is publicly released to promote further development., Comment: 15 pages, 7 figures, Manuscript was presented at the AIAA SciTech Forum in Orlando, FL, USA, 8 - 12 January 2024. Video presentation: [https://www.youtube.com/watch?v=7WHp0dQYG4Y]. Code: [https://github.com/nasa/isaac/tree/master/anomaly/gmm-change-detection]

We conduct a long-timescale ($5000\,$d) 3-D simulation of a common-envelope event with a $2\,M_{\odot}$ red giant and a $1\,M_{\odot}$ main sequence companion, using the moving-mesh hydrodynamic solver MANGA. Starting with an orbital radius of $52\,R_{\odot}$, our binary shrinks to an orbital radius of $5\,R_{\odot}$ in $200\,$d. We show that over a timescale of about $1500\,$d, the envelope is completely ejected while $80$ per cent is ejected in about $400\,$d. The complete ejection of the envelope is solely powered by the orbital energy of the binary, without the need for late-time reheating from recombination or jets. Motivated by recent theoretical and observational results, we also find that the envelope enters a phase of homologous expansion about $550\,\rm d$ after the start of our simulation. We also run a simplified 1-D model to show that heating from the central binary in the envelope at late times does not influence the ejection. This homologous expansion of the envelope would likely simplify calculations of the observational implications such as light curves.

Univariate normal regression models are statistical tools widely applied in many areas of economics. Nevertheless, income data have asymmetric behavior and are best modeled by non-normal distributions. The modeling of income plays an important role in determining workers' earnings, as well as being an important research topic in labor economics. Thus, the objective of this work is to propose parametric quantile regression models based on two important asymmetric income distributions, namely, Dagum and Singh-Maddala distributions. The proposed quantile models are based on reparameterizations of the original distributions by inserting a quantile parameter. We present the reparameterizations, some properties of the distributions, and the quantile regression models with their inferential aspects. We proceed with Monte Carlo simulation studies, considering the maximum likelihood estimation performance evaluation and an analysis of the empirical distribution of two residuals. The Monte Carlo results show that both models meet the expected outcomes. We apply the proposed quantile regression models to a household income data set provided by the National Institute of Statistics of Chile. We showed that both proposed models had a good performance both in terms of model fitting. Thus, we conclude that results were favorable to the use of Singh-Maddala and Dagum quantile regression models for positive asymmetric data, such as income data., Comment: 22 pages, 11 figures

The quiescent emission of the anomalous X-ray pulsar (AXP) 4U 0142+61 extends over a broad range of energy, from radio up to hard X-rays. In particular, this object is unique among soft gamma-ray repeaters (SGRs) and AXPs in presenting simultaneously mid-infrared emission and pulsed optical emission. In spite of the many propositions to explain this wide range of emission, it still lacks one that reproduces all the observations. Filling this gap, we present a model to reproduce the quiescent spectral energy distribution of 4U 0142+61 from mid-infrared up to hard X-rays using plausible physical components and parameters. We propose that the persistent emission comes from a magnetic accreting white dwarf (WD) surrounded by a debris disk. This model assumes that: (i) the hard X-rays are due to the bremsstrahlung emission from the post-shock region of the accretion column; (ii) the soft X-rays are originated by hot spots on the WD surface; and (iii) the optical and infrared emissions are caused by an optically thick dusty disk, the WD photosphere, and the tail of the postshock region emission. In this scenario, the fitted model parameters indicate that 4U 0142+61 harbors a fast-rotator magnetic near-Chandrasekhar WD, which is very hot and hence young. Such a WD can be the recent outcome of a merger of two less massive WDs. In this case, 4U 0142+61 can evolve to an SN Ia and hence can give hints of the origin of these important astrophysical events. Additionally, we also present a new estimate of 4U 0142+61 distance, 3.78 (errors: +0.12 / -0.18 kpc), based on the measured Hydrogen column density and new interstellar extinction 3D maps., Comment: ApJ accepted

Place recognition is a challenging problem in mobile robotics, especially in unstructured environments or under viewpoint and illumination changes. Most LiDAR-based methods rely on geometrical features to overcome such challenges, as generally scene geometry is invariant to these changes, but tend to affect camera-based solutions significantly. Compared to cameras, however, LiDARs lack the strong and descriptive appearance information that imaging can provide. To combine the benefits of geometry and appearance, we propose coupling the conventional geometric information from the LiDAR with its calibrated intensity return. This strategy extracts extremely useful information in the form of a new descriptor design, coined ISHOT, outperforming popular state-of-art geometric-only descriptors by significant margin in our local descriptor evaluation. To complete the framework, we furthermore develop a probabilistic keypoint voting place recognition algorithm, leveraging the new descriptor and yielding sublinear place recognition performance. The efficacy of our approach is validated in challenging global localization experiments in large-scale built-up and unstructured environments., Comment: ICRA 2019 Submission with RA-L option, version 2

A nanostructured trigonal SnSe2 was produced by mechanical alloying, and the effect of high-pressures up to 25.8 GPa on it was investigated. The literature reports refined structural data for SnS2 for pressures up to 20 GPa. These data were used as input data in a crystallographic software to calculate the shell structures around the Sn, Se, and S atoms placed at the origin. The shell structures were used to simulate the partial and total structure factors Sij(K) and S(K), and by Fourier transformation the partial and total pairs distribution functions Gij(R) and G(R) were obtained. The effect of high-pressure on the SnSe2 and SnS2 structures were followed by observing the changes in the Gij(R) functions. Also, the effect of high-pressure on the smallest angle Sn-X (X=Se,S)-Sn, intralayer distance Sn-X (X=Se,S), and interlayers distance X-X (X=Se,S) was studied. The interlayers distance X-X (X=Se,S) changes faster than the intralayer distance Sn-X (X=Se,S). An enhancement of the average power factor at 20 GPa and 800 K for SnS2 was reported. Using the interlayers distance S-S and intralayer distance Sn-S, it was evidenced that the enhancement of average power factor may be associated with the changes of the interlayers distance S-S that is faster than that of the intralayer distance Sn-S., Comment: No comments. arXiv admin note: text overlap with arXiv:1803.02479

An approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high pressure or temperature was early proposed by us, and in this study, it was applied to investigate de effect of high pressure on the rhombohedral Bi2Te3 phase. The refined structural parameters obtained from the Rietveld refinement of the XRD patterns measured for pressures up to 9.1 GPa were used as input data to simulate the partial and total structure factors SBiBi, SBiTe, STeTe, and SBi2Te3. Fourier transformation of the Sij factors permitted to obtain the partial and total pairs distribution functions GBiBi, GBiTe, GTeTe, and GBi2Te3. The first coordination shells of these Gij functions are formed by subshells and, with increasing pressure in the 1.1 to 6.3 GPa range, occur a partial separation of subshells. Also, the increase of pressure in this range promotes a drastic reduction in the values of the intralayer angles TeBiTe, and consequently, in the intralayer distance TeTe. A drastic reduction in the interlayers distance Te-Te was also observed. Several studies are reported in the literature, including one carried out by us, show the presence of an ETT in this pressure range. The obtained results suggest that the ETT is related with the decrease of the intralayer angles TeBiTe, and intra- and interlayer distance TeTe. Experimental results describing the pressure dependence the thermoelectric power, electrical resistivity, and power fator for rhombohedral Bi2Te3 are reported, and an enhancement of the power factor in the 1.1 to 6.3 GPa range is observed. The results obtained in this study give evidence that this enhancement in the power factor is related with the decrease of the intralayer angles TeBiTe, and with the decrease of intralayer- and interlayers homopolar TeTe bonds.

An approach combining the Rietveld method and pairs distribution function analysis was developed and can help to understand the effect of temperature and/or high-pressure on crystalline materials. It was applied to orthorhombic Ta2O5 compound, and the obtained results were compared with the experimental pairs distribution function reported in the literature, and an excellent agreement was reached. The approach permitted to simulate average pairs distribution functions GTa-Ta(R), GTa-O(R), and GO-O(R) and the average radial distribution functions RDFTa-Ta(R), RDFTa-O(R), and RDFO-O(R). The coordination numbers for the first neighbors were obtained, and used in the expression to calculate the Cowley-Warren chemical short-range order parameter {\alpha}CW . The calculated value suggests a preference for forming homopolar pairs in the first coordination shell. Previous study on the effect of high-pressure on orthorhombic Ta2O5 showed a pressure-induced amorphization process. This amorphization can be associated with the preference for forming homopolar pairs in the first coordination shell.