Neural NILM: Deep Neural Networks Applied to Energy Disaggregation

Energy disaggregation estimates appliance-by-appliance electricity consumption from a single meter that measures the whole home's electricity demand. Recently, deep neural networks have driven remarkable improvements in classification performance in neighbouring machine learning fields such as image classification and automatic speech recognition. In this paper, we adapt three deep neural network architectures to energy disaggregation: 1) a form of recurrent neural network called `long short-term memory' (LSTM); 2) denoising autoencoders; and 3) a network which regresses the start time, end time and average power demand of each appliance activation. We use seven metrics to test the performance of these algorithms on real aggregate power data from five appliances. Tests are performed against a house not seen during training and against houses seen during training. We find that all three neural nets achieve better F1 scores (averaged over all five appliances) than either combinatorial optimisation or factorial hidden Markov models and that our neural net algorithms generalise well to an unseen house.Comment: To appear in ACM BuildSys'15, November 4--5, 2015, Seou

Kinks Dynamics in One-Dimensional Coupled Map Lattices

We examine the problem of the dynamics of interfaces in a one-dimensional space-time discrete dynamical system. Two different regimes are studied : the non-propagating and the propagating one. In the first case, after proving the existence of such solutions, we show how they can be described using Taylor expansions. The second situation deals with the assumption of a travelling wave to follow the kink propagation. Then a comparison with the corresponding continuous model is proposed. We find that these methods are useful in simple dynamical situations but their application to complex dynamical behaviour is not yet understood.Comment: 17pages, LaTex,3 fig available on cpt.univ-mrs.fr directory pub/preprints/94/dynamical-systems/94-P.307

Envelope Structure of Starless Core L694-2 Derived from a Near-Infrared Extinction Map

We present a near-infrared extinction study of the dark globule L694-2, a starless core that shows strong evidence for inward motions in molecular line profiles. The J,H, and K band data were taken using the European Southern Observatory New Technology Telescope. The best fit simple spherical power law model has index p=2.6 +/- 0.2, over the 0.036--0.1 pc range in radius sampled in extinction. This power law slope is steeper than the value of p=2 for a singular isothermal sphere, the initial condition of the inside-out model for protostellar collapse. Including an additional extinction component along the line of sight further steepens the inferred profile. Fitting a Bonnor-Ebert sphere results in a super-critical value of the dimensionless radius xi_max=25 +/- 3. The unstable configuration of material may be related to the observed inward motions. The Bonnor-Ebert model matches the shape of the observed profile, but significantly underestimates the amount of extinction (by a factor of ~4). This discrepancy in normalization has also been found for the nearby protostellar core B335 (Harvey et al. 2001). A cylindrical density model with scale height H=0.0164+/- 0.002 pc viewed at a small inclination to the cylinder axis provides an equally good radial profile as a power law model, and reproduces the asymmetry of the core remarkably well. In addition, this model provides a basis for understanding the discrepancy in the normalization of the Bonnor-Ebert model, namely that L694-2 has prolate structure, with the full extent (mass) of the core being missed by assuming symmetry between the profiles in the plane of the sky and along the line-of-sight. If the core is sufficiently magnetized then fragmentation may be avoided, and later evolution might produce a protostar similar to B335.Comment: 38 pages, 7 figures, accepted to Astrophysical Journa

Some properties of the k-dimensional Lyness' map

This paper is devoted to study some properties of the k-dimensional Lyness' map. Our main result presentes a rational vector field that gives a Lie symmetry for F. This vector field is used, for k less or equal to 5 to give information about the nature of the invariant sets under F. When k is odd, we also present a new (as far as we know) first integral for F^2 which allows to deduce in a very simple way several properties of the dynamical system generated by F. In particular for this case we prove that, except on a given codimension one algebraic set, none of the positive initial conditions can be a periodic point of odd period.Comment: 22 pages; 3 figure

Weekly variability of hydrography and transport of northwestern inflows into the northern North Sea

Quantifying the variability of North Sea inflows and understanding the temporal variability of their physical properties are essential for understanding, modelling and managing the ecosystems of the North Sea. The Joint North Sea Information System (JONSIS) line hydrographic section crosses the path of the main inflows of Atlantic water into the northwestern North Sea. We use observations from an autonomous underwater glider to observe the inflows at high spatial and temporal resolutions. The glider completed 10 partial sections of the JONSIS line in October and November of 2013. Key water masses of the inflow are identified; their spatial distribution varies greatly from section to section. This is not apparent from long-running ship surveys of the JONSIS line, which are generally several months apart. In particular, the distribution of water of most recent Atlantic origin varies as summer stratification decays throughout autumn: at the start of the deployment it is present as a thin layer beneath the thermocline; at the end of the deployment, it occupies the full depth of the water column. Thermohaline flow, i.e. that which is driven by horizontal density gradients, is focused into three or four jets (approximately 10 km wide). Jets as narrow as these have not previously been observed in the region. We also observe baroclinic eddies. The thermohaline transport of the inflows is compared with the absolute transport that is derived by referencing geostrophic shear to the glider's dive-average current. Thermohaline transport (approximately 0.2 Sv) is consistently smaller than absolute transport (approximately 0.5 Sv). The week-to-week variability in hydrography and flow structure identified in this study is relevant to on-going efforts to define a background state against which the nature of anthropogenic changes can be assessed, and future modelling efforts should represent the spatial and temporal variability that we have identified

Comparison of Magnetic Field Structures on Different Scales in and around the Filamentary Dark Cloud GF 9

New visible polarization data combined with existing IR and FIR polarization data are used to study how the magnetic field threading the filamentary molecular cloud GF 9 connects to larger structures in its general environment. We find that when both visible and NIR polarization data are plotted as a function of extinction, there is no evidence for a plateau or a saturation effect in the polarization at Av ~ 1.3 as seen in dark clouds in Taurus. This lack of saturation effect suggests that even in the denser parts of GF 9 we are still probing the magnetic field. The visible polarization is smooth and has a well-defined orientation. The IR data are also well defined but with a different direction, and the FIR data in the core region are well defined and with yet another direction, but are randomly distributed in the filament region. On the scale of a few times the mean radial dimension of the molecular cloud, it is as if the magnetic field were `blind' to the spatial distribution of the filaments while on smaller scales within the cloud, in the core region near the IRAS point source PSC 20503+6006, polarimetry shows a rotation of the magnetic field lines in these denser phases. Hence, in spite of the fact that the spatial resolution is not the same in the visible/NIR and in the FIR data, all the data put together indicate that the field direction changes with the spatial scale. Finally, the Chandrasekhar and Fermi method is used to evaluate the magnetic field strength, indicating that the core region is approximately magnetically critical. A global interpretation of the results is that in the core region an original poloidal field could have been twisted by a rotating elongated (core+envelope) structure. There is no evidence for turbulence and ambipolar diffusion does not seem to be effective at the present time.Comment: 33 pages, 6 tables, 8 figures, Accepted by Ap

Near Infrared polarimetry of a sample of YSOs

Our goal is to study the physical properties of the circumstellar environment of young stellar objetcs (YSOs). In particular, the determination of the scattering mechanism can help to constrain the optical depth of the disk and/or envelope in the near infrared. We used the IAGPOL imaging polarimeter along with the CamIV infrared camera at the LNA observatory to obtain near infrared polarimetry measurements at the H band of a sample of optically visible YSOs, namely, eleven T Tauri stars and eight Herbig Ae/Be stars. An independent determination of the disk (or jet) orientation was obtained for twelve objects from the literature. The circumstellar optical depth could be then estimated comparing the integrated polarization position angle (PA) with the direction of the major axis of the disk projected in the plane of the sky. In general, optically thin disks have polarization PA perpendicular to the disk plane. In contrast, optically thick disks produce polarization PA parallel to the disks. Among the T Tauri stars, three are consistent with optically thin disks (AS 353A, RY Tau and UY Aur) and five with optically thick disks (V536 Aql, DG Tau, DO Tau, HL Tau and LkHalpha 358). Among the Herbig Ae/Be stars, two stars show evidence of optically thin disk (Hen 3-1191 and VV Ser) and two of optically thick disks (PDS 453 and MWC 297). Our results seem consistent with the fact that optically thick disks at near infrared bands are associated more likely with younger YSOs. Marginal evidence of polarization reversal is found in RY Tau, RY Ori, WW Vul, and UY Aur. On the first three cases this feature can be associated to the UXOR phenomenon. Correlations with the IRAS colours and the spectral index yielded evidence of an evolutionary segregation with the disks tend to be optically thin when they are older.Comment: 15 pages, 15 figures, accepted in Astronomy and Astrophysic

Study of Interplanetary Magnetic Field with Ground State Alignment

We demonstrate a new way of studying interplanetary magnetic field -- Ground State Alignment (GSA). Instead of sending thousands of space probes, GSA allows magnetic mapping with any ground telescope facilities equipped with spectropolarimeter. The polarization of spectral lines that are pumped by the anisotropic radiation from the Sun is influenced by the magnetic realignment, which happens for magnetic field (<1G). As a result, the linear polarization becomes an excellent tracer of the embedded magnetic field. The method is illustrated by our synthetic observations of the Jupiter's Io and comet Halley. Polarization at each point was constructed according to the local magnetic field detected by spacecrafts. Both spatial and temporal variations of turbulent magnetic field can be traced with this technique as well. The influence of magnetic field on the polarization of scattered light is discussed in detail. For remote regions like the IBEX ribbons discovered at the boundary of interstellar medium, GSA provides a unique diagnostics of magnetic field.Comment: 11 pages, 19 figures, published in Astrophysics and Space Scienc