A probabilistic data-driven model for planar pushing

This paper presents a data-driven approach to model planar pushing interaction to predict both the most likely outcome of a push and its expected variability. The learned models rely on a variation of Gaussian processes with input-dependent noise called Variational Heteroscedastic Gaussian processes (VHGP) that capture the mean and variance of a stochastic function. We show that we can learn accurate models that outperform analytical models after less than 100 samples and saturate in performance with less than 1000 samples. We validate the results against a collected dataset of repeated trajectories, and use the learned models to study questions such as the nature of the variability in pushing, and the validity of the quasi-static assumption.Comment: 8 pages, 11 figures, ICRA 201

Tactile Mapping and Localization from High-Resolution Tactile Imprints

This work studies the problem of shape reconstruction and object localization using a vision-based tactile sensor, GelSlim. The main contributions are the recovery of local shapes from contact, an approach to reconstruct the tactile shape of objects from tactile imprints, and an accurate method for object localization of previously reconstructed objects. The algorithms can be applied to a large variety of 3D objects and provide accurate tactile feedback for in-hand manipulation. Results show that by exploiting the dense tactile information we can reconstruct the shape of objects with high accuracy and do on-line object identification and localization, opening the door to reactive manipulation guided by tactile sensing. We provide videos and supplemental information in the project's website http://web.mit.edu/mcube/research/tactile_localization.html.Comment: ICRA 2019, 7 pages, 7 figures. Website: http://web.mit.edu/mcube/research/tactile_localization.html Video: https://youtu.be/uMkspjmDbq

A double-slit proposal for quantum annealing

We formulate and analyze a double-slit proposal for quantum annealing, which involves observing the probability of finding a two-level system (TLS) undergoing evolution from a transverse to a longitudinal field in the ground state at the final time $t_f$. We demonstrate that for annealing schedules involving two consecutive diabatic transitions, an interference effect is generated akin to a double-slit experiment. The observation of oscillations in the ground state probability as a function of $t_f$ (before the adiabatic limit sets in) then constitutes a sensitive test of coherence between energy eigenstates. This is further illustrated by analyzing the effect of coupling the TLS to a thermal bath: increasing either the bath temperature or the coupling strength results in a damping of these oscillations. The theoretical tools we introduce significantly simplify the analysis of the generalized Landau-Zener problem. Furthermore, our analysis connects quantum annealing algorithms exhibiting speedups via the mechanism of coherent diabatic transitions to near-term experiments with quantum annealing hardware.Comment: 19 pages, 3 figure

More than a Million Ways to Be Pushed: A High-Fidelity Experimental Dataset of Planar Pushing

Pushing is a motion primitive useful to handle objects that are too large, too heavy, or too cluttered to be grasped. It is at the core of much of robotic manipulation, in particular when physical interaction is involved. It seems reasonable then to wish for robots to understand how pushed objects move. In reality, however, robots often rely on approximations which yield models that are computable, but also restricted and inaccurate. Just how close are those models? How reasonable are the assumptions they are based on? To help answer these questions, and to get a better experimental understanding of pushing, we present a comprehensive and high-fidelity dataset of planar pushing experiments. The dataset contains timestamped poses of a circular pusher and a pushed object, as well as forces at the interaction.We vary the push interaction in 6 dimensions: surface material, shape of the pushed object, contact position, pushing direction, pushing speed, and pushing acceleration. An industrial robot automates the data capturing along precisely controlled position-velocity-acceleration trajectories of the pusher, which give dense samples of positions and forces of uniform quality. We finish the paper by characterizing the variability of friction, and evaluating the most common assumptions and simplifications made by models of frictional pushing in robotics.Comment: 8 pages, 10 figure

Rumba Abierta

This music clip is from the CD entitled Come Fly With Us. The band was directed by Dr. Robert Washut.https://scholarworks.uni.edu/jazzband/1101/thumbnail.jp

Exploring the biological function of carboxypeptidase O: analysis of expression and association with chylomicrons and lipid droplets

Carboxypeptidase O (CPO) is a membrane-bound peptidase that cleaves acidic and polar C-terminal amino acids of peptides; however, its biological function remains unknown. CPO is strongly expressed in the small intestine, where it has been proposed to participate in digestion events at the brush border by extracellular cleavage of dietary peptides. At the subcellular level, CPO is anchored to the inner leaflet of the endoplasmic reticulum (ER) membrane, where it has been shown to associate with lipid droplets (LDs). The ER membrane also represents the site of iv chylomicron formation, a process that shares many similarities with that of LDs biogenesis. We sought to investigate a potential role of CPO in LD and chylomicron formation. Using a stablyexpressing human colon carcinoma (Caco-2) cell model, we evaluated CPO association with LDs and apoB, a chylomicron biomarker, by immunofluorescence microscopy. The association of CPO with LDs was dependent on the time elapsed post-feeding (ANOVA, p \u3c 0.05), and was lowest at 6 h (17.9%), reaching a maximum at 12 h (29.8%) and later slightly decreasing at 24 h (26.3%). Our results indicate that CPO associated with apoB, further showing a similar association pattern as that of LDs at the three time points. However, we express a limited level of confidence in these results since the immunocytochemistry images presumably suggest lower association levels than those reported in the quantification data. Overall, our findings strengthen the hypothesis that CPO plays an intracellular role in the formation of lipid droplets in enterocytes. To better understand the potential biological role of CPO, we performed an in-depth analysis of data from several gene expression databases and platforms. RNA-Seq and microarray expression data showed high expression in the ileum epithelium and mucosa. Modulation of CPO expression, which was mainly characterized by downregulation in the ileum, was found in ulcerative colitis and Crohn’s disease, with the latter showing stronger modulation. RNA-Seq data also showed prominent expression in Peyer’s patches and basophils, which suggested a promising role of CPO in immunity

Improved catalyst regeneration process to increase poison removal and improve performance recovery

2021 Spring.Includes bibliographical references.Internal combustion engines are partly responsible for increasing amounts of carbon dioxide, nitrogen, carbon monoxide, hydrocarbons, aldehydes, and particulate matter in the atmosphere. These emissions have detrimental health effects on humans and negatively impact the environment by contributing to the formation of acid rain and photochemical smog. Large bore two-stroke natural gas engines are used commonly for power generation, and in order to meet the National Emissions Standards for Hazardous Air Pollutants set by the Environmental Protection Agency, engine manufacturers commonly select oxidation catalysts as the exhaust aftertreatment of choice. These catalysts degrade over time due to thermal, chemical, and mechanical reasons. Lubrication oil makes its way through the combustion chamber and onto the catalyst, degrading the unit. To estimate the degradation rate of the units and to find the best restoration method, two identical alumina-platinum oxidation catalysts were used in a dual setting, combining a field degradation engine and a laboratory testing engine. The lubrication oil from the cylinder makes its way to the catalyst and creates a layer of volatile hydrocarbons at the very surface that reduces the surface area and catalytic activity of the unit. Moreover, the additives from the oil, such as sulfur, phosphorus, and zinc actively poison the crystallites and minimize the reduction efficiency of the units. The wash-coat is turned into a powder and analyzed, showing sulfur is the most prevalent poison, constituting approximately 8.97% of the wash-coat when the units are degraded. Phosphorus constitutes roughly 2.55%, and zinc makes up less than 0.50% of the wash-coat and is the most superficial poison. Sulfur is not only the most prevalent but also penetrates deeper into the wash-coat than the rest of the poisons, but phosphorus is seen to interact chemically with the platinum crystallites, suggesting a stronger de-activation by phosphorus. Platinum is more active in its metallic form, and the catalyst of interest improves in performance after being chemically reduced in a 5% hydrogen purge at 450°C, indicating the platinum crystallites were oxidized in the aging process. The units were aged, then restored with the industry standard washing procedure, then aged again until reaching non-compliance with the emissions standards set by the Environmental Protection Agency, and then restored a second time with a modified version of the industry standard washing process. In order to find the best restoring process, variations of the industry standard chemical wash are tested, and the result proves unsuccessful to modify the washing procedure. Moreover, the industry standard washing process is enhanced by adding two new steps, carbon baking and crystallite restoration. The combination of both baking and washing is tested with elemental and performance analysis. The laboratory elemental analysis suggests the baking restoration steps should be added before washing, which is in agreement with the performance bench testing results. The levels of sulfur and phosphorus are respectively brought down to 0.692% and 0.689% after applying the modified restoration process to the units, and zinc is reduced to 0.048% of the wash-coat. However, the slipstream performance results with real exhaust from a Cummins QSK19G do not fully agree with the addition of the baking steps to the industry washing standard restoration, likely because the combined restoration was tested on a catalyst that had been previously washed and re-aged, which is known in the industry to produce less successful restoring results. The catalysts can be aged and restored two to three times before the reduction efficiency increase from the restoration is not great enough to financially motivate catalyst users to restore the units instead of replacing them

iTETRIS Platform Architecture for the Integration of Cooperative Traffic and Wireless Simulations

The use of cooperative wireless communications can support driving through dynamic exchange of Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) messages. Traffic applications based on such systems will be able to generate a safer, faster, cheaper and cleaner way for people and goods to move. In this context, the iTERIS project aims at providing the framework to combine traffic mobility and wireless communication simulations for large scale testing of traffic management solutions based on cooperative systems. This paper addresses the description and explanation of the implementation choices taken to build a modular and interoperable architecture integrating heterogeneous traffic and wireless simulators, and application algorithms supporting traffic management strategies. The functions of an “in-between” control system for managing correct simulation executions over the platform are presented. The inter-block interaction procedures identified to ensure optimum data transfer for simulation efficiency are also introduced