Learning a Bias Correction for Lidar-only Motion Estimation

This paper presents a novel technique to correct for bias in a classical estimator using a learning approach. We apply a learned bias correction to a lidar-only motion estimation pipeline. Our technique trains a Gaussian process (GP) regression model using data with ground truth. The inputs to the model are high-level features derived from the geometry of the point-clouds, and the outputs are the predicted biases between poses computed by the estimator and the ground truth. The predicted biases are applied as a correction to the poses computed by the estimator. Our technique is evaluated on over 50km of lidar data, which includes the KITTI odometry benchmark and lidar datasets collected around the University of Toronto campus. After applying the learned bias correction, we obtained significant improvements to lidar odometry in all datasets tested. We achieved around 10% reduction in errors on all datasets from an already accurate lidar odometry algorithm, at the expense of only less than 1% increase in computational cost at run-time.Comment: 15th Conference on Computer and Robot Vision (CRV 2018

The lambda-dimension of commutative arithmetic rings

It is shown that every commutative arithmetic ring $R$ has $lambda$-dimension $leq 3$. An example of a commutative Kaplansky ring with $lambda$-dimension 3 is given. If $R$ satisfies an additional condition then $lambda$-dim($R$

Cognition animale et humaine

Cognition animale et humaineL'analyse comparée de la cognition ou de l'intelligence comptait parmi les préoccupations de Darwin et de ses premiers successeurs, mais elle a été négligée pendant un demi-siècle. Au cours des dernières décennies, trois grandes approches ont été développées: les recherches sur la communication animale, les théories du traitement de l'information et l'approche piagétienne du développement cognrtif des animaux. Même si beaucoup de travail reste à accomplir pour comprendre l'évolution des structures et des processus cognitifs, ces trois approches révèlent, notamment chez les anthropoides, une capacité insoupçonnée à manipuler des symboles et permettent déjà d'identifier quelques étapes cruciales de la phylogenèse de la cognition humaine.Animal and Human CognitionThe comparative analysis of cognition or intelligence was a central issue in the early Darwinian era but was abandoned during half a century. In the last decades, three important paradigms have been developed in order to address this issue: animal communication studies; information processing as applied to animals; and comparative Piagetian studies. Although they are far from having solved the problem of the evolution of cognition, these paradigms have revealed, particularly in the great apes, an unsuspected capacity to use symbols and have identified crucial stages in the phytogeny of human cognition

Chemical Evolution of the Juvenile Universe

Only massive stars contribute to the chemical evolution of the juvenile universe corresponding to [Fe/H]<-1.5. If Type II supernovae (SNe II) are the only relevant sources, then the abundances in the interstellar medium of the juvenile epoch are simply the sum of different SN II contributions. Both low-mass (~8-11M_sun) and normal (~12-25M_sun) SNe II produce neutron stars, which have intense neutrino-driven winds in their nascent stages. These winds produce elements such as Sr, Y, and Zr through charged-particle reactions (CPR). Such elements are often called the light r-process elements, but are considered here as products of CPR and not the r-process. The observed absence of production of the low-A elements (Na through Zn including Fe) when the true r-process elements (Ba and above) are produced requires that only low-mass SNe II be the site if the r-process occurs in SNe II. Normal SNe II produce the CPR elements in addition to the low-A elements. This results in a two-component model that is quantitatively successful in explaining the abundances of all elements relative to hydrogen for -3<[Fe/H]<-1.5. This model explicitly predicts that [Sr/Fe]>-0.32. Recent observations show that there are stars with [Sr/Fe]<-2 and [Fe/H]<-3. This proves that the two-component model is not correct and that a third component is necessary to explain the observations. This leads to a simple three-component model including low-mass and normal SNe II and hypernovae (HNe), which gives a good description of essentially all the data for stars with [Fe/H]<-1.5. We conclude that HNe are more important than normal SNe II in the chemical evolution of the low-A elements, in sharp distinction to earlier models. (Abridged)Comment: 10 pages, 9 figures, to appear in Pub. Astron. Soc. Australi

Homeworking, telecommuting and journey to workplaces - Are differences among genders and professions varying over space?

The aim of this paper is to assess differences on homeworking and teleworking behaviour among genders considering age groups, professional statuses, household structures and car access. The analysis is based on a sample of more than 30,000 workers responding to the 2001 origin-destination (O-D) survey data in Quebec City (Canada). Moreover, this paper puts specific emphasis on linking those differences in behaviour to the location of workplaces related to living places of the respondents. During the O-D survey, every worker was asked to disclose the frequency of homeworking and teleworking he/she was experiencing during the preceding weeks. Answers were later aggregated into six categories: never working at home (88.4% of respondents), working at home 1 day per two weeks or less (4.8%), 1 day per week (1.7%), 2 or 3 days per week (1.2%), 4 days or more per week (0.7%), always working at home (3.2% – homeworkers). However, those patterns show significant differences among genders (higher proportion of females are working entirely at home; higher proportion of males are occasionally working at home), age groups (younger workers seldom work at home and the proportion of teleworker increases with age – about 16% among the 55-64 years old and 27% among the elderly) and professional status (proportion of teleworkers is strongly related to qualifications and decisional status of the person, yielding higher levels of teleworking for managers, self-employed persons, professors and lawyers than for office clerks, technicians and non-qualified workers). This last relationship is very strong suggesting that job empowerment (especially ability to control time schedule) is of paramount importance for the development of teleworking. However, having higher family constraints, lone parents are seeking more flexibility on their work agenda: 12% are experiencing some level of teleworking on top of 3% of them which are homeworkers. Again, the difference appears more significant among male than among female workers, suggesting again a better control of the first group on their work schedule. Moreover, owning a driver license or holding a bus pass does not have the expected effect on teleworking: car drivers are working at home more frequently than other people; conversely 92% of bus users are going to their work place every weekday, leaving a mere 8% to teleworking and homeworking. Significant differences appear when considering workplaces and home locations within the city. People working near the city centre are more willing than others to consider teleworking, people living in the suburban areas show higher levels of homeworking. Finally, significant differences of travel time from home to work were found among various categories of teleworkers and homeworkers. Preliminary results suggest that the development of teleworking could be highly rooted to labour market and household structures as well as to the urban form. Urban sprawl is probably impeding development of teleworking, at least for Quebec City.

Fano Resonances in Mid-Infrared Spectra of Single-Walled Carbon Nanotubes

This work revisits the physics giving rise to the carbon nanotubes phonon bands in the mid- infrared. Our measurements of doped and undoped samples of single-walled carbon nanotubes in Fourier transform infrared spectroscopy show that the phonon bands exhibit an asymmetric lineshape and that their effective cross-section is enhanced upon doping. We relate these observations to electron-phonon coupling or, more specifically, to a Fano resonance phenomenon. We note that only the dopant-induced intraband continuum couples to the phonon modes and that defects induced in the sidewall increase the resonance probabilities.Comment: 5 pages, 4 figures and 1 Supplementary Information File (in pdf

Growth response and water relations of three-year-old planted black spruce and jack pine seedlings in site prepared lichen woodlands

Black spruce-lichen woodlands are low tree density stands within the closed crown, North American boreal forest that represent a diverging post-fire type of black spruce forest. As natural densification of lichen woodlands has never been observed, afforestation remains the only way of shifting these stands to closed canopy stands. The objective of the study was to evaluate site preparation effects on growth and water relations of black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) seedlings in black spruce-lichen woodlands (LW), compared to managed black spruce-feathermoss stands (BSFM). Site preparation treatments in LW were no preparation (LWno), patch scarification (LWps), and disk scarification (LWds). The operationally managed BSFM stands stood for the control. Results from the third growing season indicate that soil water availability in intact or lightly prepared patch scarified LW is a limiting variable for seedling growth for both black spruce and jack pine seedlings. However, once LW are prepared with disk scarification, this planting check factor is significantly reduced, to the point of being equal to BSFM in terms of water availability and seedling water relations. The significant seedling growth difference, in favor of BSFM, might be a consequence of the lower level of pre-plantation disturbance in LW, compared to BSFM. Our results also suggest that jack pine, through higher water stress tolerance, could constitute a wise silvicultural choice over black spruce, especially with LW established on coarse drought-prone material