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This work discusses a novel method for estimating the location of a gas source based on spatially distributed concentration measurements taken, e.g., by a mobile robot or flying platform that follows a predefined trajectory to collect samples. The proposed approach uses a Physics-Guided Neural Network to approximate the gas dispersion with the source location as an additional network input. After an initial offline training phase, the neural network can be used to efficiently solve the inverse problem of localizing the gas source based on measurements. The proposed approach allows avoiding rather costly numerical simulations of gas physics needed for solving inverse problems. Our experiments show that the method localizes the source well, even when dealing with measurements affected by noise., Comment: Submission to the International Symposium of Electronic Nose (ISOEN)

An analysis of the relationship between the bandwidth of acoustic signals and the required resolution of steered-response power phase transform (SRP-PHAT) maps used for sound source localization is presented. This relationship does not rely on the far-field assumption, nor does it depend on any specific array topology. The proposed analysis considers the computation of a SRP map as a process of sampling a set of generalized cross-correlation (GCC) functions, each one corresponding to a different microphone pair. From this approach, we derive a rule that relates GCC bandwidth with inter-microphone distance, resolution of the SRP map, and the potential position of the sound source relative to the array position. This rule is a sufficient condition for an aliasing-free calculation of the specified SRP-PHAT map. Simulation results show that limiting the bandwidth of the GCC according to such rule leads to significant reductions in sound source localization errors when sources are not in the immediate vicinity of the microphone array. These error reductions are more relevant for coarser resolutions of the SRP map, and they happen in both anechoic and reverberant environments., Comment: Any paper that cite this one has to thank IEEE for easing the open access of the article

Acoustic reverberation is one of the most relevant factors that hampers the localization of a sound source inside a room. To date, several approaches have been proposed to deal with it, but have not always been evaluated under realistic conditions. This paper proposes exploiting spatial diversity as an alternative approach to achieve robustness against reverberation. The theoretical arguments supporting this approach are first presented and later confirmed by means of simulation results and real measurements. Simulations are run for reverberation times up to 2 s, thus providing results with a wider range of validity than in other previous research works. It is concluded that the use of systems consisting of several, sufficiently separated, small arrays leads to the best results in reverberant environments. Some recommendations are given regarding the choice of the array sizes, the separation among them, and the way to combine SRP-PHAT maps obtained from diverse arrays.

A transversal study of the pitch variability of parkinsonian voices in read speech is presented. 30 patients suffering from Parkinson's disease (PD) and 32 healthy speakers were recorded while reading a text without voiceless phonemes. The fundamental frequency contours were calculated from the recordings, and the following measures were used for describing them: mean, minimum, maximum, and standard deviation of the estimated fundamental frequencies. Results based on these measures indicate that the influence of PD on some aspects of intonation can be masked by the effects of aging, especially for male voices. However, some parameters such as the relative fundamental frequency range exhibit lower correlations with age than with PD stage, as evaluated using the Hoehn and Yahr scale. These correlations between relative fundamental frequency range and PD stage reach moderate-to-high values in the case of women. Additionally, three parameters describing the form of the fundamental frequency modulation spectrum were investigated for correlation with age and PD stage. The study of this modulation spectrum provides some insight into the ability of the speakers to plan the intonation of full phrases. For both male and female populations, significant correlations were found between parameters obtained from the modulation spectrum of fundamental frequency and the PD stage. Nevertheless, the quantitative assessment of the performance of regression models built from these modulation parameters and fundamental frequency range suggests that such measures are likely to be of limited value in the early diagnosis of PD due to inter-speaker variability.

PODIUM is a compact spacecraft navigation unit, currently being designed to provide interplanetary missions with autonomous position and velocity estimations. The unit will make use of Pulsar X-ray observations to measure the distance and distance rate from the host spacecraft to the Solar System Barycenter. Such measurements will then be used by the onboard orbit determination function to estimate the complete orbital elements of the spacecraft. The design aims at 6 kg of mass and 20 W of power, in a volume of 150 mm by 240 mm by 600 mm. PODIUM is designed to minimize the impact on the mission operational and accommodation constraints. The architecture is based on a grazing incidence X-ray telescope with focal distance limited to 50 cm. The effective area shall be in the range 25 to 50 cm2 for photon energies in the range 0.2-10 keV, requiring nesting of several mirrors in the Wolter-1 geometry. Grazing incidence angles will be very small, below 2 deg. The current target FOV is 0.25 deg. The pulsars photon arrivals are detected with a single pixel Silicon Drift Detector (SDD) sensor with timing accuracy below 1usec. The unit has no gimbaling to meet the applicable power, size and mass requirements. Instead, the host spacecraft shall slew and point to allow pulsar observation. The avionics architecture is based on a radiation hardened LEON4 processor, to allow a synchronous propagation task and measurement generation and orbit determination step in an asynchronous task. PODIUM will enable higher autonomy and lower cost for interplanetary missions. L2 space observatories and planetary flybys are the current reference use cases. Onboard autonomous state estimation can reduce the ground support effort required for navigation and orbit correction/maintenance computation, and reduce the turnaround time, thus enabling more accurate maneuvers, reducing the orbit maintenance mass budget.

The performance of gold nanoparticles (NPs) in applications depends critically on the structure of the NP-solvent interface, at which the electrostatic surface polarization is one of the key characteristics that affects hydration, ionic adsorption, and electrochemical reactions. Here, we demonstrate significant effects of explicit metal polarizability on the solvation and electrostatic properties of bare gold NPs in aqueous electrolyte solutions of sodium salts of various anions (Cl$^-$, BF$_4$$^-$, PF$_6$$^-$, Nip$^-$(nitrophenolate), and 3- and 4-valent hexacyanoferrate (HCF)), using classical molecular dynamics simulations with a polarizable core-shell model of the gold atoms. We find considerable spatial heterogeneity of the polarization and electrostatic potentials on the NP surface, mediated by a highly facet-dependent structuring of the interfacial water molecules. Moreover, ion-specific, facet-dependent ion adsorption leads to large alterations of the interfacial polarization. Compared to non-polarizable NPs, polarizability modifies water local dipole densities only slightly, but has substantial effects on the electrostatic surface potentials, and leads to significant lateral redistributions of ions on the NP surface. Besides, interfacial polarization effects on the individual monovalent ions cancel out in the far field, and effective Debye-H\"uckel surface potentials remain essentially unaffected, as anticipated from continuum `image-charge' concepts. Hence, the explicit charge response of metal NPs is crucial for the accurate description and interpretation of interfacial electrostatics (as, e.g., for charge transfer and interface polarization in catalysis and electrochemistry).

We study the solvation and electrostatic properties of bare gold (Au) nanoparticles (NPs) of $1$-$2$ nm in size in aqueous electrolyte solutions of sodium salts of various anions with large physicochemical diversity (Cl$^-$, BF$_4$$^-$, PF$_6$$^-$, Nip$^-$(nitrophenolate), 3- and 4-valent hexacyanoferrate (HCF)) using nonpolarizable, classical molecular dynamics computer simulations. We find a substantial facet selectivity in the adsorption structure and spatial distribution of the ions at the Au-NPs: while sodium and some of the anions (e.g., Cl$^-$, HCF$^{3-}$) adsorb more at the `edgy' (100) and (110) facets of the NPs, where the water hydration structure is more disordered, other ions (e.g., BF$_4$$^-$, PF$_6$$^-$, Nip$^-$) prefer to adsorb strongly on the extended and rather flat (111) facets. In particular, Nip$^-$, which features an aromatic ring in its chemical structure, adsorbs strongly and perturbs the first water monolayer structure on the NP (111) facets substantially. Moreover, we calculate adsorptions, radially-resolved electrostatic potentials, as well as the far-field effective electrostatic surface charges and potentials by mapping the long-range decay of the calculated electrostatic potential distribution onto the standard Debye-H\"uckel form. We show how the extrapolation of these values to other ionic strengths can be performed by an analytical Adsorption-Grahame relation between effective surface charge and potential. We find for all salts negative effective surface potentials in the range from $-10$ mV for NaCl down to about $-80$ mV for NaNip, consistent with typical experimental ranges for the zeta-potential. We discuss how these values depend on the surface definition and compare them to the explicitly calculated electrostatic potentials near the NP surface, which are highly oscillatory in the $\pm 0.5$ V range.

Polar crystals composed of charged ionic planes cannot exist in nature without acquiring surface changes to balance an ever-growing dipole. The necessary changes can manifest structurally or electronically. An electronic asymetry has long been observed in the LaAlO3/SrTiO3 system. Electron accumulation is observed near the LaAlO3/TiO2-SrTiO3 interface, while the LaAlO3/SrO-SrTiO3 stack is insulating. Here, we observe evidence for an asymmetry in the surface chemical termination for nominally stoichiometric LaAlO3 films in contact with the two different surface layers of SrTiO3 crystals, TiO2 and SrO. Using several element specific probes, we find that the surface termination of LaAlO3 remains AlO2 irrespective of the starting termination of SrTiO3 substrate surface. We use a combination of cross-plane tunneling measurements and first principles calcula- tions to understand the effects of this unexpected termination on band alignments and polarity compensation of LaAlO3/SrTiO3 heterostructures. An asymmetry in LaAlO3 polarity compensation and resulting electronic properties will fundamentally limit atomic level control of oxide heterostructures.

This abstract describes the segmentation system used to participate in the challenge ISIC 2017: Skin Lesion Analysis Towards Melanoma Detection. Several preprocessing techniques have been tested for three color representations (RGB, YCbCr and HSV) of 392 images. Results have been used to choose the better preprocessing for each channel. In each case a neural network is trained to predict the Jaccard Index based on object characteristics. The system includes black frames and reference circle detection algorithms but no special treatment is done for hair removal. Segmentation is performed in two steps first the best channel to be segmented is chosen by selecting the best neural network output. If this output does not predict a Jaccard Index over 0.5 a more aggressive preprocessing is performed using open and close morphological operations and the segmentation of the channel that obtains the best output from the neural networks is selected as the lesion., Comment: 4 pages, 4 figures, abstract submitted to participate in the challenge ISIC 2017