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Jia D.,University of British Columbia | Cathary O.,Ecole Nationale Superieure de Techniques Avancees | Peng J.,University of British Columbia | Bi X.,University of British Columbia | And 6 more authors.
Fuel Processing Technology | Year: 2015

Fluidization of biomass particles in the absence of inert bed materials has been tested in a pulsed fluidized bed with vibration, with the pulsation frequency ranging from 0.33 to 6.67 Hz. Intermittent fluidization at 0.33 Hz and apparently ‘normal' fluidization at 6.67 Hz with regular bubble patterns were observed. Pulsation has proven to be effective in overcoming the bridging of irregular biomass particles induced by strong inter-particle forces. The vibration is only effective when the pulsation is inadequate, either at too low a frequency or too low in amplitude. Drying of biomass has been carried out to quantify the effectiveness of gas pulsation for fluidized bed dryers and torrefiers in terms of gas-solid contact efficiency and heat and mass transfer rates. The effects of gas flow rate, bed temperature, pulsation frequency and vibration intensity on drying performance have been systematically investigated. While higher temperature and gas flow rate are favored in drying, there exists an optimal range of pulsation frequency between 0.75 Hz and 1.5 Hz where gas-solid contact is enhanced in both the constant rate drying and falling rate drying periods. © 2015 Elsevier B.V. Source

Boukhers Z.,University of Siegen | Shirahama K.,University of Siegen | Li F.,Ecole Nationale Superieure de Techniques Avancees | Grzegorzek M.,University of Siegen
Proceedings - International Workshop on Content-Based Multimedia Indexing | Year: 2015

To detect an event which is defined by the interaction of objects in a video, it is necessary to capture their spatio-temporal relation. However, the video only displays the original 3D space which is projected onto a 2D image plane. This paper introduces a method which extracts 3D trajectories of objects from 2D videos. Each trajectory represents the transition of an object's positions in the 3D space. We extract such trajectories by combining object detection with depth estimation that estimates the depth information in 2D videos. The major problem for this is the inconsistency between object detection and depth estimation results. For example, significantly different depths may be estimated for the region of the same object, and an object region that is appropriately shaped by estimated depths may be missed. To overcome this, we first initialise the 3D position of an object by selecting the frame with the highest consistency between the object detection and depth estimation results. Then, we track the object in the 3D space using particle filter, where the 3D position of this object is modelled as a hidden state to generate its 2D visual appearance. Experimental results demonstrate the effectiveness of our method. © 2015 IEEE. Source

Gepperth A.,Ecole Nationale Superieure de Techniques Avancees
Neural Networks | Year: 2013

This is a simulation-based contribution exploring a novel approach to the open-ended formation of multimodal representations in autonomous agents. In particular, we address the issue of transferring ("bootstrapping") feature selectivities between two modalities, from a previously learned or innate reference representation to a new induced representation. We demonstrate the potential of this algorithm by several experiments with synthetic inputs modeled after a robotics scenario where multimodal object representations are "bootstrapped" from a (reference) representation of object affordances. We focus on typical challenges in autonomous agents: absence of human supervision, changing environment statistics and limited computing power. We propose an autonomous and local neural learning algorithm termed PROPRE (projection-prediction) that updates induced representations based on predictability: competitive advantages are given to those feature-sensitive elements that are inferable from activities in the reference representation. PROPRE implements a bi-directional interaction of clustering ("projection") and inference ("prediction"), the key ingredient being an efficient online measure of predictability controlling learning in the projection step. We show that the proposed method is computationally efficient and stable, and that the multimodal transfer of feature selectivity is successful and robust under resource constraints. Furthermore, we successfully demonstrate robustness to noisy reference representations, non-stationary input statistics and uninformative inputs. © 2012 Elsevier Ltd. Source

Ecole Polytechnique - Palaiseau, Ecole Nationale Superieure De Techniques Avancees and French National Center for Scientific Research | Date: 2013-04-11

A method for producing electromagnetic radiation comprising: firing a first laser pulse and generating a plasma region, the first laser pulse penetrating at least partially into the plasma region to create a plasma density wake in the plasma region; providing a group of charged particles in the plasma region arranged so as to be accelerated in the plasma density wake of the first laser pulse; reflecting the first laser pulse after the first laser pulse has penetrated into the plasma region, to give a reflected laser pulse; and arranging the reflected laser pulse to interact with the group of charged particles to generate an electromagnetic radiation.

A device for generating a secondary source from a primary optical source emitting a first optical beam focused onto a surface in movement, with which said first beam interacts so as to generate a secondary beam, includes an optical device for controlling the orientation and position of said surface to determine the orientation and position of the emission point of said secondary source on said surface. The device comprises: a control laser beam split into two branches, a fixed reference beam and a mobile analysis beam reflected by the surface in movement; means for making said reference and analysis beams interfere to generate interference fringes; means for imaging the interference fringes carrying information about the orientation and position of said surface; means for analyzing said interference images; and means for generating a feedback loop for controlling the orientation and position of said surface in movement based on the analysis.

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