1,721,507 research outputs found
Cooperation Strategies for Enhanced Connectivity at Home
Full text linkWHILE AT HOME , USERS MAY EXPERIENCE A POOR I NTERNET SERVICE while being connected to their 802.11 Access Points (APs). The AP is just one component of the Internet Gateway (GW) that generally includes a backhaul connection (ADSL, fiber,etc..) and a router providing a LAN. The root cause of performance degradation may be poor/congested wireless channel between the user and the GW or congested/bandwidth limited backhaul connection. The latter is a serious issue for DSL users that are located far from the central office because the greater the distance the lesser the achievable physical datarate. Furthermore, the GW is one of the few devices in the home that is left always on, resulting in energy waste and electromagnetic pollution increase. This thesis proposes two strategies to enhance Internet connectivity at home by (i) creating a wireless resource sharing scheme through the federation and the coordination of neighboring GWs in order to achieve energy efficiency while avoiding congestion, (ii) exploiting different king of connectivities, i.e., the wired plus the cellular (3G/4G) connections, through the aggregation of the available bandwidth across multiple access technologies. In order to achieve the aforementioned strategies we study and develop: • A viable interference estimation technique for 802.11 BSSes that can be implemented on commodity hardware at the MAC layer, without requiring active measurements, changes in the 802.11 standard, cooperation from the wireless stations (WSs). We extend previous theoretical results on the saturation throughput in order to quantify the impact in term of throughput loss of any kind of interferer. We im- plement and extensively evaluate our estimation technique with a real testbed and with different kind of interferer, achieving always good accuracy. • Two available bandwidth estimation algorithms for 802.11 BSSes that rely only on passive measurements and that account for different kind of interferers on the ISM band. This algorithms can be implemented on commodity hardware, as they require only software modifications. The first algorithm applies to intra-GW while the second one applies to inter-GW available bandwidth estimation. Indeed, we use the first algorithm to compute the metric for assessing the Wi-Fi load of a GW and the second one to compute the metric to decide whether accept incoming WSs from neighboring GWs or not. Note that in the latter case it is assumed that one or more WSs with known traffic profile are requested to relocate from one GW to another one. We evaluate both algorithms with simulation as well as with a real test-bed for different traffic patterns, achieving high precision. • A fully distributed and decentralized inter-access point protocol for federated GWs that allows to dynamically manage the associations of the wireless stations (WSs) in the federated network in order to achieve energy efficiency and offloading con- gested GWs, i.e, we keep a minimum number of GWs ON while avoiding to create congestion and real-time throughput loss. We evaluate this protocol in a federated scenario, using both simulation and a real test-bed, achieving up to 65% of energy saving in the simulated setting. We compare the energy saving achieved by our protocol against a centralized optimal scheme, obtaining close to optimal results. • An application level solution that accelerates slow ADSL connections with the parallel use of cellular (3G/4G) connections. We study the feasibility and the potential performance of this scheme at scale using both extensive throughput measurement of the cellular network and trace driven analysis. We validate our solution by implementing a real test bed and evaluating it "in the wild, at several residential locations of a major European city. We test two applications: Video-on-Demand (VoD) and picture upload, obtaining remarkable throughput increase for both applications at all locations. Our implementation features a multipath scheduler which we compare to other scheduling policies as well as to transport level solution like MTCP, obtaining always better result
Determination of Heteronuclear Dipolar Contributions To Proton Spin-lattice Relaxation Induced By Low Abundant Nuclei
No full textProton Detection of Heteronuclear Dipolar Couplings
No full textA method is proposed for the calculation of heteronuclear dipolar coupling between two 1/2 nuclei, X and Y, by measuring the spin-lattice relaxation rates of the abundant Y nucleus and of the satellite peaks (1H, 31P, 19F) due to the scalar coupling of Y with the less abundant X nucleus. The 1H-13C dipolar interaction has been evaluated from the proton spin-lattice relaxation rates of tyrosine in water solution and the effective correlation times of the aromatic moiety have been calculated
Re-Representar lo re-presentado: una exploración de paisajes digitales a través del juego y el dibujo arquitectónico
Full text linkDipartimento di Architettura e Design, Politecnico di TorinoÁrea de Composición Arquitectónica, Departamento de Construcciones Arquitectónicas, Universidad de GranadaHUM 813: Architecture and Contemporary Cultur
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Interaction Study of Bioactive Molecules with Fibrinogen and Human Platelets Determined by 1H-NMR Relaxation Experiments
No full textIn order to investigate the interaction processes between bioactive molecules and macromolecular receptors
NMR methodology based on the analysis of selective and non-selective spin–lattice relaxation rate
enhancements of ligand protons was used.
The contribution from the bound ligand fraction to the observed relaxation rate in relation to macromolecular
target concentration allowed the calculation of the normalized affinity index
in which the
effects of motional anisotropies and different proton densities have been removed.
In this paper, we applied this methodology to investigate the affinity of epinephrine and isoproterenol
towards two different systems: fibrinogen and platelets
Double-Inverter Drive System for Electric Ship Propulsion
No full textIn this paper a new electric ship propulsion system is proposed as combination of a double generator set with a double inverter feeding a wound-rotor synchronous machine.
Each generator set is composed by a diesel engine directly coupled to a compact, permanent magnet, synchronous generator. A diode rectifier connects the output of the generator to a variable voltage dc bus. The dc bus feeds one of the input sides of the double inverter. The double inverter acts as a multilevel converter and it is able to drive the 3-phase, 6-wire motor coupled to the propeller. The two generator sets can operate either jointly or one at a time,
depending on the power demand from the drive system. The working point of each diesel engine is determined in order to supply power to the propeller with maximum efficiency
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