Search results for "ion channel"
showing 10 items of 567 documents
WLC24-1: Dynamic MAC Parameters Configuration for Performance Optimization in 802.11e Networks
2006
Quality of service support in wireless LAN is a theme of current interest. Several solutions have been proposed in literature in order to protect time-sensitive traffic from best-effort traffic. According to the EDCA proposal, which is a completely distributed solution, the service differentiation is provided by giving probabilistically higher number of channel accesses to stations involved in real-time applications. To this purpose, the MAC parameter settings of each contending stations can be tuned dynamically. In this paper, we face the problem of tuning the EDCA MAC parameters in common scenarios in which a given number of low-rate delay-sensitive traffic flows share the channel with so…
Dynamic Channel Aggregation Strategies in Cognitive Radio Networks with Spectrum Adaptation
2011
In cognitive radio networks, channel aggregation techniques which combine several channels together as one channel have been proposed in many MAC protocols. In this paper, spectrum adaptation is proposed in channel aggregation and two strategies which dynamically adjust channel occupancy of ongoing traffic flows are further developed. The performance of these strategies is evaluated using continuous time Markov chain models. Moreover, models in the quasi-stationary regime are analyzed and the closed-form capacity expression is derived in this regime. Numerical results demonstrate that the capacity of the secondary network can be improved by using channel aggregation with spectrum adaptation.
Dynamic Flow-Adaptive Spectrum Leasing with Channel Aggregation in Cognitive Radio Networks.
2020
Cognitive radio networks (CRNs), which allow secondary users (SUs) to dynamically access a network without affecting the primary users (PUs), have been widely regarded as an effective approach to mitigate the shortage of spectrum resources and the inefficiency of spectrum utilization. However, the SUs suffer from frequent spectrum handoffs and transmission limitations. In this paper, considering the quality of service (QoS) requirements of PUs and SUs, we propose a novel dynamic flow-adaptive spectrum leasing with channel aggregation. Specifically, we design an adaptive leasing algorithm, which adaptively adjusts the portion of leased channels based on the number of ongoing and buffered PU …
Turbulent Superfluid Profiles in a Counterflow Channel
2010
We have developed a two-dimensional model of quantised vortices in helium II moving under the influence of applied normal fluid and superfluid in a counterflow channel. We predict superfluid and vortex-line density profiles which could be experimentally tested using recently developed visualization techniques.
Exact and Approximate Algorithms for Two–Criteria Topological Design Problem of WAN with Budget and Delay Constraints
2004
This paper studies the problem of designing wide area networks (WAN). In the paper the two-criteria topology assignment problem with two constraints is considered. The goal is select flow routes, channel capacities and network topology in order to minimize the total average delay per packet and the leasing cost of channels subject to the budget constraint and delay constraint. The problem is NP-complete. Then, the branch and bound method is used to construct the exact algorithm. Also the approximate algorithm is presented. Some computational results are reported. Based on computational experiments, several properties of the considered problem are formulated.
The Two-Criteria Topological Design Problem in WAN with Delay Constraint: An Algorithm and Computational Results
2003
The problem is concerned with designing of wide area networks (WAN). The problem consists in selection of flow routes, channel capacities and wide area network topology in order to minimize the total average delay per packet and the leasing cost of channels subject to delay constraint. The problem is NP complete. Then, the branch and bound method is used to construct the exact algorithm. Lower bound of the criterion function is proposed. Computational results are reported. Based on computational experiments, several properties of the considered problem are formulated.
Optical nonlinear correlation based on nonuniform subband decomposition
1999
We present a nonlinear correlation to improve the selectivity for optical pattern recognition. The approach is based on morphological correlation which involves a threshold decomposition concept. Hereby, we propose a subband decomposition in the Fourier domain to perform the threshold decomposition operation. We consider two frequency bands that give rise to two separate channels. We apply the morphological correlation to each channel using a localized threshold decomposition. Then, we define a two-channel morphological correlation. The final detection decision is made as a combination of both correlation outputs. The two-channel morphological correlation yields improved discrimination capa…
Effective-field-theory predictions of the muon-deuteron capture rate
2018
We quantify the theoretical uncertainties of chiral effective-field-theory predictions of the muon-deuteron capture rate. Theoretical error estimates of this low-energy process is important for a reliable interpretation of forthcoming experimental results by the MuSun collaboration. Specifically, we estimate the three dominant sources of uncertainties that impact theoretical calculations of this rate: those resulting from uncertainties in the pool of fit data used to constrain the coupling constants in the nuclear interaction, those due to the truncation of the effective field theory, and those due to uncertainties in the axial radius of the nucleon. For the capture rate into the ${}^1S_0$ …
Muon capture revisited
1990
Abstract The problem of inclusive muon capture in nuclei is studied by calculating the capture rate in asymmetric infinite nuclear matter and using the local density approximation to evaluate the capture rates in nuclei. It is shown that the method is rather reliable and allows one to improve on approximations used in the past. The need for a strong nuclear renormalization is shown, reducing the capture rates by about a factor two in medium and heavy nuclei. By using standard effective interactions in the spin-isospin channel one can account for this renormalization and one finds a remarkable overall agreement with the measured capture rates for a large list of nuclei through the periodic t…
Brokerage from within: A conceptual framework
2021
Situated between various social worlds, brokers are highly mobile figures, in a physical and an ideational sense; they channel scarce information and resources, translate different languages and jargons, and mediate and facilitate between individuals and/or organisations, the local and the global, in a wide range of settings. Taking an in-depth ethnographic look at the actual work of brokers and their particular life stories, contributions to this special issue examine brokers’ successes and failures, their vulnerabilities and limitations, (changing) interests and motivations within the cultural contexts that these brokers are part of. By adopting a comparative perspective in a thematic an…