Measuring Electric Fields From Surface Contaminants with Neutral Atoms

In this paper we demonstrate a technique of utilizing magnetically trapped neutral Rb-87 atoms to measure the magnitude and direction of stray electric fields emanating from surface contaminants. We apply an alternating external electric field that adds to (or subtracts from) the stray field in such a way as to resonantly drive the trapped atoms into a mechanical dipole oscillation. The growth rate of the oscillation's amplitude provides information about the magnitude and sign of the stray field gradient. Using this measurement technique, we are able to reconstruct the vector electric field produced by surface contaminants. In addition, we can accurately measure the electric fields generated from adsorbed atoms purposely placed onto the surface and account for their systematic effects, which can plague a precision surface-force measurement. We show that baking the substrate can reduce the electric fields emanating from adsorbate, and that the mechanism for reduction is likely surface diffusion, not desorption.Comment: 7 pages, 6 figures, published in Physical Review

Einfluss von Betonzusatzmitteln auf die Energieund CO2-Bilanz von Beton

The energy consumption and the C02 emissions during the production of two different concrete mixes with identical concrete properties were compared. The two concrete samples were prepared with and without the addition of a superplasticizer. Less energy was consumed and less C02 was emitted for the case of concrete production including a superplasticizer as compared to the case of concrete production without a superplasticizer. This is due to the fact, that when a superplasticizer is used, less cement is needed to produce concrete with the same properties as those of concrete without superplasticizers. However, the relatively small dijferences in the energy consumption and in the C02 emissions become insignificant, if the entire life cycle of a building is considered. Effects like durability and the need for maintenance are expected to have a much higher influence on the life cycle assessment of concrete building

Measurement of the Temperature Dependence of the Casimir-Polder Force

We report on the first measurement of a temperature dependence of the Casimir-Polder force. This measurement was obtained by positioning a nearly pure 87-Rb Bose-Einstein condensate a few microns from a dielectric substrate and exciting its dipole oscillation. Changes in the collective oscillation frequency of the magnetically trapped atoms result from spatial variations in the surface-atom force. In our experiment, the dielectric substrate is heated up to 605 K, while the surrounding environment is kept near room temperature (310 K). The effect of the Casimir-Polder force is measured to be nearly 3 times larger for a 605 K substrate than for a room-temperature substrate, showing a clear temperature dependence in agreement with theory.Comment: 4 pages, 4 figures, published in Physical Review Letter

Real-time lattice boltzmann shallow waters method for breaking wave simulations

We present a new approach for the simulation of surfacebased fluids based in a hybrid formulation of Lattice Boltzmann Method for Shallow Waters and particle systems. The modified LBM can handle arbitrary underlying terrain conditions and arbitrary fluid depth. It also introduces a novel method for tracking dry-wet regions and moving boundaries. Dynamic rigid bodies are also included in our simulations using a two-way coupling. Certain features of the simulation that the LBM can not handle because of its heightfield nature, as breaking waves, are detected and automatically turned into splash particles. Here we use a ballistic particle system, but our hybrid method can handle more complex systems as SPH. Both the LBM and particle systems are implemented in CUDA, although dynamic rigid bodies are simulated in CPU. We show the effectiveness of our method with various examples which achieve real-time on consumer-level hardware.Peer ReviewedPostprint (author's final draft

Stagnate summers : climate induced changes in physical mixing parameters in Missouri reservoirs

Lakes and reservoirs are important environmental sentinels for climate change. As air temperatures rise so do the temperatures of these water bodies affecting their physical, chemical, and biological properties. Being used for drinking water supplies, fisheries, and human recreation, these long term potential changes can be an important factor for their use. Climate change has been associated with altering physical reservoir parameters, such as mixing depth, water temperatures, and water chemistry. Using a historical dataset to find both break points and monotonic trends that may indicate climate having influenced our reservoirs we found little in terms of monotonic trends. However, we did witness changes in all systems in regards to break points for almost every parameter. Our systems cannot directly correlate to having had climate change based effects, as we can neither support or refute its evidence in our reservoirs as changes relating to climate do not only impact physical parameters but also animal and plant communities, and social factors such as use (influenced by cyanobacteria blooms). It is even plausible that increased in reservoir production and turbidity could lead to shifts in physical trends that would otherwise be different in non-affected reservoirs. Over all more information is needed to create a better picture of exactly how climate change is impacting the physical mixing parameters in Missouri reservoirs as they are complex and varied systems.Cody Kimbell, John R. Jones, Daniel Obrecht, and Rebecca North (University of Missouri, Columbia

UNSUPERVISED SIGNAL SEGMENTATION BASED ON TEMPORAL SPECTRAL CLUSTERING

ABSTRACT This paper presents an approach for applying spectral clustering to time series data. We define a novel similarity measure based on euclidean distance and temporal proximity between vectors. This metric is useful for conditioning matrices needed to perform spectral clustering, and its application leads to the detection of abrupt changes in a sequence of vectors. It defines a temporal segmentation of the signal. When the input to the algorithm is a speech signal, we further process the segments and achieve their labeling in one of three phonetic classes: silence, consonant or vowel. When the input signal is a video stream, the algorithm detects scene changes in the sequence of images. Our results are compared against classic unsupervised and supervised techniques, and evaluated with the phonetically labeled multi-language corpus OGI-MLTS and the video database of the french video indexing campaign ARGOS

Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror

We present experimental results showing the diffuse reflection of a Bose-Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure

Automatic extraction of prosodic features for automatic language identification

The aim of this study is to propose a new approach to Automatic Language Identification: it is based on rhythmic modelling and fundamental frequency modelling and does not require any hand labelled data. First we need to investigate how prosodic or rhythmic information can be taken into account for Automatic Language Identification. A new automatically extracted unit, the pseudo syllable, is introduced. Rhythmic and intonative features are then automatically extracted from this unit. Elementary decision modules are defined with gaussian mixture models. These prosodic modellings are combined with a more classical approach, a vocalic system acoustic modelling. Experiments are conducted on the five European languages of the MULTEXT corpus: English, French, German, Italian and Spanish. The relevance of the rhythmic parameters and the efficiency of each system (rhythmic model, fundamental frequency model and vowel system model) are evaluated. The influence of these approaches on the performances of automatic language identification system is addressed. We obtain 91 % of correct identification with 21 s. utterances using all the information sources.Le but de cette étude est de proposer une nouvelle approche pour l’identification automatique des langues, basée sur une modélisation du rythme, ne nécessitant pas de données étiquetées manuellement. Il faut tout d’abord savoir comment apporter des informations sur la prosodie, le rythme pour l’identification automatique des langues. Pour répondre à cette question nous avons introduit une nouvelle unité, la pseudo-syllabe, qui est automatiquement extraite. Des paramètres rythmiques et intonatifs sont alors calculés à partir de cette unité. Des modèles élémentaires pour chaque type de paramètres sont définis en utilisant des mélanges de lois gaussiennes. Ces modélisations de la prosodie sont couplées à une approche plus classique utilisant une modélisation acoustique des systèmes vocaliques. Les expériences sont menées sur les cinq langues européennes du corpus MULTEXT. L’intérêt des paramètres rythmiques, et l’efficacité de chaque système (modèle rythmique, modèle de la fréquence fondamentale et modèle vocalique) sont évalués. L’impact de ces approches sur les performances d’identification est analysé. Nous obtenons des résultats de 91% d’identification correcte avec des fichiers de 21 secondes

Buildings LCA and digitalization: Designers\u27 toolbox based on a survey

In a context of digitalization and increasing quality requirements, the building sector is facing an increasing level of complexity regarding its design process. This results in a growing number of involved actors from different domains, a multitude of tasks to be completed and a higher degree of needed expertise. New buildings are also required to reach higher performances in terms of environmental quality. To that regard, the exploitation of the full potential of digital tools can facilitate the integration of environmental aspects in the planning process, limit productivity shortcomings and reduce environmental impacts, which can result from an unaware decision making. Building environmental assessment can be performed through several Life Cycle Assessment (LCA)-based tools. “Pure calculation” tools quantify final buildings\u27 environmental potential, while “complex tools” additionally support decision making during the planning process. It is often difficult to choose the best suitable tool, which strongly depends on the user\u27s needs. Within the IEA EBC Annex 72, a survey was realized with the main objective of creating a comprehensive overview of the existing tools dedicated to buildings LCA. The questionnaire included the usability, functionality, compliance, data reliability and interoperability of the analysed tools. Lastly, based on the survey outcomes and their critical assessment, a procedure for the identification and selection of a tool has been proposed based on user\u27s needs. As a result, this work outlines main features of currently available building LCA tools, for which there is a harmonized status in terms of usability and overall applied LCA methodology. Despite the need for more automatized workflows, tools\u27 embedding is mostly not yet applicable in system chains or limited to a restricted number of tools

Hierarchical Hidden Markov Model in Detecting Activities of Daily Living in Wearable Videos for Studies of Dementia

International audienceThis paper presents a method for indexing activities of daily living in videos obtained from wearable cameras. In the context of dementia diagnosis by doctors, the videos are recorded at patients' houses and later visualized by the medical practitioners. The videos may last up to two hours, therefore a tool for an efficient navigation in terms of activities of interest is crucial for the doctors. The specific recording mode provides video data which are really difficult, being a single sequence shot where strong motion and sharp lighting changes often appear. Our work introduces an automatic motion based segmentation of the video and a video structuring approach in terms of activities by a hierarchical two-level Hidden Markov Model. We define our description space over motion and visual characteristics of video and audio channels. Experiments on real data obtained from the recording at home of several patients show the difficulty of the task and the promising results of our approach