554 research outputs found
Learning to Extract Motion from Videos in Convolutional Neural Networks
This paper shows how to extract dense optical flow from videos with a
convolutional neural network (CNN). The proposed model constitutes a potential
building block for deeper architectures to allow using motion without resorting
to an external algorithm, \eg for recognition in videos. We derive our network
architecture from signal processing principles to provide desired invariances
to image contrast, phase and texture. We constrain weights within the network
to enforce strict rotation invariance and substantially reduce the number of
parameters to learn. We demonstrate end-to-end training on only 8 sequences of
the Middlebury dataset, orders of magnitude less than competing CNN-based
motion estimation methods, and obtain comparable performance to classical
methods on the Middlebury benchmark. Importantly, our method outputs a
distributed representation of motion that allows representing multiple,
transparent motions, and dynamic textures. Our contributions on network design
and rotation invariance offer insights nonspecific to motion estimation
Dense Motion Estimation for Smoke
Motion estimation for highly dynamic phenomena such as smoke is an open
challenge for Computer Vision. Traditional dense motion estimation algorithms
have difficulties with non-rigid and large motions, both of which are
frequently observed in smoke motion. We propose an algorithm for dense motion
estimation of smoke. Our algorithm is robust, fast, and has better performance
over different types of smoke compared to other dense motion estimation
algorithms, including state of the art and neural network approaches. The key
to our contribution is to use skeletal flow, without explicit point matching,
to provide a sparse flow. This sparse flow is upgraded to a dense flow. In this
paper we describe our algorithm in greater detail, and provide experimental
evidence to support our claims.Comment: ACCV201
ADQPCI: Data Acquisition Board for Educational purposes
En este trabajo se presenta una de las placas de adquisición de datos que se ha desarrollado con fines docentes para su utilización en prácticas relacionadas con sistemas en tiempo real e
informática industrial y se plantean algunas de las ventajas e inconvenientes frente a la utilización
de placas comerciales. A lo largo del trabajo se detalla el diseño del hardware, en el que se ha
priorizado la facilidad de programación, siendo ésta una de las ventajas frente a las placas
comerciales. En estas prácticas es fundamental que el alumno tome conciencia de la importancia
de la interfaz hardware-software, si se quiere conseguir un sistema fiable y que explote al máximo
las características del hardware. Con el desarrollo de una placa de adquisición de datos se
consigue un sistema que el alumno puede utilizar en varias asignaturas de su titulación que están
relacionadas con el desarrollo y programación de sistemas empotrados.In this work a data acquisition board developed for educational use in subjects related to real-time
systems and industrial computing, is presented. The main advantages and disadvantages of using
these boards versus the use of commercial boards are discussed. The hardware design described
along this work emphasizes the facility of programming the board, which is one of the main
advantages versus the commercial boards. In these practices it is essential that student
comprehend the importance of the hardware-software interface in order to obtain a reliable system
which exploits in a maximum way the characteristics of the hardware. The development of a data
acquisition board allows to obtain a system that the students can use in several course during his
university career which are related to the development and programming of embedded system
CAN2PCI: Board with Interface to CAN and PCI Bus for educational purposes
En este trabajo se presenta una placa con interfaz al bus CAN y PCI desarrollada para la
utilización en prácticas de las asignaturas relacionadas con redes de control. Se trata de una
placa de altas prestaciones pensada para su utilización docente gracias a su facilidad de
programación. La placa dispone de dos canales CAN independientes y permite acceso directo a
los registros del controlador CAN. Las prácticas tienen como objetivo conocer la red de control en
los niveles físico y de enlace y desarrollar un software de conectividad (middleware) que realice la
interfaz entre estas capas y la de aplicación de usuario. Se exponen también brevemente las
prácticas realizadas en una de las asignaturas donde se imparte redes de control, en la que es
fundamental la utilización de un hardware conocido que permita programar las funciones básicas
que operan directamente con el controlador de bus CANIn this work the development of a board with interface to the CAN and PCI bus for its use in lab
courses related to control networks, is presented. This board has high benefits and advantages
and has been implemented for educational purposes due to its programming facility. The board
has two independent CAN channels and it allows direct access to the registers of the CAN
controller. The objective of the lab experiments is to study the control networks in the physical and
link levels and to develop a middleware that performs the interface between these layers and the
user application. The experiments done in one of the courses, which includes control networks, are
briefly described. In these practical labs it is very important the use of a known hardware that
allows programming the basic functions which directly operate with the CAN bus controlle
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High-brightness broad-area diode lasers with enhanced self-aligned lateral structure
Broad-area diode lasers with increased brightness and efficiency are presented, which are fabricated using an enhanced self-aligned lateral structure by means of a two-step epitaxial growth process with an intermediate etching step. In this structure, current-blocking layers in the device edges ensure current confinement under the central stripe, which can limit the detrimental effects of current spreading and lateral carrier accumulation on beam quality. It also minimizes losses at stripe edges, thus lowering the lasing threshold and increasing conversion efficiency, while maintaining high polarization purity. In the first realization of this structure, the current block is integrated within an extreme-triple-asymmetric epitaxial design with a thin p-doped side, meaning that the distance between the current block and the active zone can be minimized without added process complexity. Using this configuration, enhanced self-aligned structure devices with 90 µm stripe width and 4 mm resonator length show up to 20% lower threshold current, 21% narrower beam waist, and slightly higher (1.03 ) peak efficiency in comparison to reference devices with the same dimensions, while slope, divergence angle and polarization purity remain almost unchanged. These results correspond to an increase in brightness by up to 25%, and measurement results of devices with varying stripe widths follow the same trend. © 2020 The Author(s). Published by IOP Publishing Ltd
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Measurements of the velocity distribution for granular flow in a Couette cell
© 2018 American Physical Society. In this paper, magnetic resonance velocimetry is used to measure the spatially resolved velocity and velocity fluctuations for granular flow in a Couette cell for four different particle sizes. The largest particles studied (dp=1.7mm) showed significant slip at the inner wall. The remaining particles showed no slip and all exhibit the same behavior in the profiles of the mean velocity and variance of velocity. The measurements demonstrate that the velocity and variance in velocity scale with the inner wall velocity U; the variance does not scale with U2. The experimental data were compared with a kinetic theory based model of granular flow and a hydrodynamic model. It was found that the shear rate scales with an exponent of 1.5-2.0 with respect to the velocity fluctuations (uy2), compared with the value of 1.0 expected from kinetic theory. The difference in the exponent is consistent with the effect of collective dynamics as described by the hydrodynamic model
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High-power diode lasers with in-situ-structured lateral current blocking for improved threshold, efficiency and brightness
We present high-power GaAs-based broad-area diode lasers with a novel variant of the enhanced self-aligned lateral structure ‘eSAS’, having a strongly reduced lasing threshold and improved peak conversion efficiency and beam quality in comparison to their standard gain-guided counterparts. To realize this new variant (eSAS-V2), a two-step epitaxial growth process involving in situ etching is used to integrate current-blocking layers, optimized for tunnel current suppression, within the p-Al0.8GaAs cladding layer of an extreme-triple-asymmetric epitaxial structure with a thin p-side waveguide. The blocking layers are thus in close proximity to the active zone, resulting in strong suppression of current spreading and lateral carrier accumulation. eSAS-V2 devices with 4 mm resonator length and varying stripe widths are characterized and compared to previous eSAS variant (eSAS-V1) as well as gain-guided reference devices, all having the same dimensions and epitaxial structure. Measurement results show that the new eSAS-V2 variant eliminates an estimated 89% of lateral current spreading, resulting in a strong threshold current reduction of 29% at 90 μm stripe width, while slope and series resistance are broadly unchanged. The novel eSAS-V2 devices also maintain high conversion efficiency up to high continuous-wave optical power, with an exemplary 90 μm device having 51.5% at 20 W. Near-field width is significantly narrowed in both eSAS variants, but eSAS-V2 exhibits a wider far-field angle, consistent with the presence of index guiding. Nonetheless, eSAS-V2 achieves higher beam quality and lateral brightness than gain-guided reference devices, but the index guiding in this realization prevents it from surpassing eSAS-V1. Overall, the different performance benefits of the eSAS approach are clearly demonstrated
Occlusion and Motion Reasoning for Long-Term Tracking
International audienceObject tracking is a reoccurring problem in computer vision. Tracking-by-detection approaches, in particular Struck (Hare et al., 2011), have shown to be competitive in recent evaluations. However, such approaches fail in the presence of long-term occlusions as well as severe viewpoint changes of the object. In this paper we propose a principled way to combine occlusion and motion reasoning with a tracking-by-detection approach. Occlusion and motion reasoning is based on state-of-the-art long-term trajectories which are labeled as object or background tracks with an energy-based formulation. The overlap between labeled tracks and detected regions allows to identify occlusions. The motion changes of the object between consecutive frames can be estimated robustly from the geometric relation between object trajectories. If this geometric change is significant, an additional detector is trained. Experimental results show that our tracker obtains state-of-the-art results and handles occlusion and viewpoints changes better than competing tracking methods
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