Search results for " time"
showing 10 items of 3005 documents
Fast Green’s Function Method for Ultrafast Electron-Boson Dynamics
2020
The interaction of electrons with quantized phonons and photons underlies the ultrafast dynamics of systems ranging from molecules to solids, and it gives rise to a plethora of physical phenomena experimentally accessible using time-resolved techniques. Green's function methods offer an invaluable interpretation tool since scattering mechanisms of growing complexity can be selectively incorporated in the theory. Currently, however, real-time Green's function simulations are either prohibitively expensive due to the cubic scaling with the propagation time or do neglect the feedback of electrons on the bosons, thus violating energy conservation. We put forward a computationally efficient Gree…
A branch-and-cut algorithm for the Team Orienteering Problem
2017
The Team Orienteering Problem aims at maximizing the total amount of profit collected by a fleet of vehicles while not exceeding a predefined travel time limit on each vehicle. In the last years, several exact methods based on different mathematical formulations were proposed. In this paper, we present a new two-index formulation with a polynomial number of variables and constraints. This compact formulation, reinforced by connectivity constraints, was solved by means of a branch-and-cut algorithm. The total number of instances solved to optimality is 327 of 387 benchmark instances, 26 more than any previous method. Moreover, 24 not previously solved instances were closed to optimality.
Use of H.264 real-time video encoding to reduce display wall system bandwidth consumption
2015
This paper compares the DXT and JPEG image compression techniques used in display wall solutions SAGE and DisplayCluster with hardware accelerated H.264 video encoding that is used in the display wall system developed by the authors of this paper. The obtained processing power usage and generated bandwidth measurements presented in this paper demonstrate that hardware accelerated H.264 encoding offers multiple benefits over software implemented H.264, DXT and JPEG.
Embedded Real-Time Surveillance Using Multimodal Mean Background Modeling
2008
Automated video surveillance applications require accurate separation of foreground and background image content. Cost-sensitive embedded platforms place real-time performance and efficiency demands on techniques to accomplish this task. In this chapter, we evaluate pixel-level foreground extraction techniques for a low-cost integrated surveillance system. We introduce a new adaptive background modeling technique, multimodal mean (MM), which balances accuracy, performance, and efficiency to meet embedded system requirements. Our evaluation compares several pixel-level foreground extraction techniques in terms of their computation and storage requirements, and functional accuracy for three r…
Application Layer FEC for Mobile TV Delivery in IP Datacast Over DVB-H Systems
2009
In this paper we investigate the potential gain that can be obtained in DVB-H using application layer forward error correction (AL-FEC) to perform a multi-burst protection of the transmission for improving the reception of streaming services for mobile terminals. Compared to the conventional approach with link layer multi protocol encapsulation FEC (MPE-FEC), this technique allows to increase the robustness of the DVB-H transmission not only as a function of the capacity devoted for error repair (FEC overhead), but also as a function of the number of bursts jointly encoded. The main drawback of this approach is an increase of the network latency, that can be translated into a larger service…
Improving Chord Lookup Protocol for P2PSIP-Based Communication Systems
2009
Chord has been suggested as mandatory overlay technology in the future P2PSIP-based communication systems. Chord allows for the available peer/resource lookup in no more than hops, where N is the total number of the peers in the overlay network. However, as a protocol originally designed for background downloading applications, Chord has a few drawbacks when supporting P2PSIP real-time communication systems. These drawbacks are related to ID assignment, the relation between ID and physical location, the routing styles and lack of cache, etc. In this paper, we investigate several approaches that can improve the efficiency of the peer/resource lookup algorithm. After that, we simulate two sys…
LifeRescue: A web based application for emergency responders during fire emergency response
2016
In order to respond to any kind of building fire emergencies, first-responders have to use lot of time to get access to the emergency data such as location of the victims who are still inside the building, location of the hazardous material, location of the resources and location of the exits in order to perform search and rescue. However, search is possibly one of the most dangerous activities on the fire ground. Sometimes the visibility is zero and the environment is really hot. Because of the limited operating time in the building, the key to successful search is how quickly emergency responders can get access to the emergency related information in order to save victims and the property…
Temporal Fairness Provisioning in Multi-Rate Contention-Based 802.11e WLANs
2005
The IEEE 802.11e extensions for QoS support in WLAN define the transmission opportunity (TXOP) concept, in order to limit the channel holding times of the contending stations in the presence of delay-sensitive traffic. We evaluate the use of TXOP for a different purpose: "temporal fairness" provisioning among stations employing different data rates. We show that the equalization of the channel access times allows each station to obtain its throughput basically (1) proportional to its transmission rate, and (2) independent of the transmitted frame length. This also improves the aggregate throughput of the overall WLAN. For a given TXOP limit, i.e., a granted channel access time, a station is…
Is the Erich arch bar the best intermaxillary fixation method in maxillofacial fractures? : a systematic review
2015
Background Intermaxillary fixation is used to achieve proper occlusion during and after oral and maxillofacial fracture surgery. The aim of this systematic review was to compare Erich arch bar fixation with other intermaxillary fixation methods in terms of the operating time, safety during installation, oral health maintenance and occlusal stability. Material and Methods An electronic online search was conducted of the Scirus, PubMed, Ovid, Cochrane Library and VHL databases. A clinical trial dating from the inception of the data bases until August 2013 was selected. Studies that compared Erich arch bars with other intermaxillary fixation methods in patients older than 18 years-old were inc…
Alta definición ecográfica en tiempo real (HDLive US) en Obstetricia y Ginecología / High real time ultrasound definition (HDLive US) in Obstetrics a…
2013
Los ultrasonidos de alta definición en tiempo real (HDLive US) incorporan un software que calcula la propagación de la luz a través de superficies y en relación con la dirección de la misma. Esta fuente de luz puede ser posicionada libremente con el fin de iluminar las áreas de interés deseadas, permitiendo así imágenes de mejor calidad, una mayor sensación de profundidad y una visión más sencilla de superficies fetales. Mostramos casos de embriones y fetos normales, así como algunas malformaciones para señalar las posibilidades de esta nueva tecnología. El auténtico potencial de esta nueva tecnología esta aún por revelar. La HDLive representa, en nuestra opinión, una verdadera innovación y…