Real-Time odor classification through sequential bayesian filtering

The classification of volatiles substances with an e-nose is still a challenging problem, particularly when working under real-time, out-of-the-lab environmental conditions where the chaotic and highly dynamic characteristics of the gas transportation induce an almost permanent transient state in the e-nose readings. In this work, a sequential Bayesian filtering approach is proposed to efficiently integrate information from previous e-nose observations while updating the belief about the gas class on a real-time basis. We validate our proposal with two real olfaction datasets composed of dynamic time-series experiments (gas transitions are Considered, but no mixture of gases), showing an improvement in the classification rate when compared to a stand-alone probabilistic classifier.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Online Estimation of 2D Wind Maps for Olfactory Robots

This work introduces a novel solution to approximate in real time the 2D wind flow present in a geometrically known environment. It is grounded on the probabilistic framework provided by a Markov random field and enables the estimation of the most probable wind field from a set of noisy observations, for the case of incompressible and steady wind flow. Our method delivers reasonably precise results without falling into common unrealistic assumptions like homogeneous wind flow, absence of obstacles, etc., and performs very efficiently (less than 0.5 seconds for an environment represented with a 100x100 cell grid). This approach is then quite suitable for applications that require real-time estimation of the wind flow, as for example, the localization of gas sources, prediction of the gas dispersion, or the mapping of the gas distribution of different chemicals released in a given scenario.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Robotic Experiment Toward Understanding Human Gas-Source Localization Strategies

This paper describes an experiment for gas-source localization with a human-teleoperated mobile robot devised to gather data on how humans search for odor-sources. To that end, more than 150 repetitions of the search process are recorded for 69 test subjects, under 4 sensor configurations (including electronic nose, anemometer and video camera) and 4 scenarios (i.e. with different wind-flow conditions and gas-source position). The experiment has been carried out with a ROS-based simulator that allows driving the robot while recording data of interest (e.g. driving commands, robot localization, sensor measurements, groundtruth, etc.) for further analyzing the human process of gas-source searching, and computational fluid dynamics (CFD) to generate realistic and repeatable test conditions. The manuscript describes the different environmental parameters and sensor combinations of the experiment, and explains the methodology under which it was executed. The obtained dataset is publicly available at http://mapir.isa.uma.es/mapirwebsite/index.php/253-gsl-dataset.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Configurable Smart E-Nose for Spatio-Temporal Olfactory Analysis

This paper describes a novel electronic nose (enose) aimed at applications that require knowing not only the gas composition and concentration, but also its temporal and spatial evolution. This is done by capturing additional information related to the chemical substance such as the timestamp and geo-location of the measurements, as well as other physical magnitudes of the environment like temperature and humidity for correcting and interpreting the data. The device has been conceived following a modular architecture as a set of independent smart modules, which are interconnected and controlled through an I2C interface by a central processing unit. Each smart module can identify itself, store settings for autoconfiguration and perform signal pre-processing of the measured variables. Smart module types include: chemical sensors, communication interfaces, batteries, data storage, GPS, temperature and humidity.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Creating maps of VOC odors in urban areas by cycling with a portable e-nose

This work describes an application for monitoring volatile organic compounds (VOCs) in urban areas, likely coming from residential waste or the public sewage system. The objective is to obtain a spatial and temporal representation of such odors by means of a gas distribution map, from which valuable information such as the location, or the time-intervals of maximum strength of the nuisance odors can be inferred. The necessary data: chemical, temporal and spatial; is provided by a GPS and a specific e-nose accommodating eight metal oxide (MOX) gas sensors, both mounted on a bicycle. The results of a monitoring campaign carried out in a town in southern Spain are presented. The campaign comprises nine measurement runs distributed along three consecutive days, with a total path of more than 90Km. Fig.1 shows an illustrative example of the data collected during this process, and the generated geo-referenced gas distribution maps. As can be appreciated, the chemical, temporal and spatial data are successfully merged to obtain representative information about the presence of VOCs in the urban area. A deeper analysis comprising the study of the areas showing the higher VOCs concentration, as well as the temporal variability among the different days and hours within the day are also provided.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.Proyectos de Excelencia de la Junta de Andalucía: TEP08-4016 y TEP2012-53

Surface Chemistry of Ternary Nanocrystals: Engineering the Deposition of Conductive NaBiS2 Films

The ability to engineer the surface chemistry of complex ternary nanocrystals is critical to their successful application in photovoltaic, thermoelectric, and other energy conversion devices. For many years, several studies have shed light into the surface chemistry of unary and binary semiconductor nanocrystals, as well as their surface modification with monodentate and multidentate ligands in a variety of applications. In contrast, our understanding of the surface chemistry and ligand modification of ternary and other complex multinary nanocrystals remains relatively limited. Recently, our group reported the synthesis of colloidal NaBiS2 semiconductor nanocrystals with sizes tunable between 2–60 nm, and a light absorption edge of ca. 1.4 eV. Here, we use a combination of infrared and nuclear magnetic resonance spectroscopies to show that the as-made NaBiS2 nanocrystals are capped by oleylamine and neodecanoate ligands. We investigate biphasic liquid-liquid exchange as a means to replace these native ligands with either carboxylate-terminated lipoic acid or with small iodide ligands, leading in both cases to solubility in polar solvents—such as methanol, water, and dimethylformamide. We also investigate a layer-by-layer, biphasic solid-liquid exchange approach to prepare films of NaBiS2 nanocrystals capped with halide ligands—iodide, bromide, chloride. Upon exchange and removal of the native ligands, we show that the resistance of NaBiS2 nanocrystal films greatly decreases, with their measured conductivity being comparable to that of films made of isostructural PbS nanocrystals, which have been used in solar cells. Lastly, we report the first solar cell device made of NaBiS2 nanocrystal films with a limited power conversion efficiency (PCE) of 0.07. Further nanostructuring and ligand optimization may enable the preparation of much more efficient energy conversion devices based on NaBiS2 as well as other non-toxic and Earth-abundant, biocompatible multinary semiconductors

Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk

Accepted for publication in a forthcoming issue of Astronomy & Astrophysics. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHK s near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.Peer reviewe