Search results for " Lower"
showing 10 items of 378 documents
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.
Parameter optimization for amplify-and-forward relaying systems with pilot symbol assisted modulation scheme
2009
Article published in the journal:Wireless Sensor Network Also available from publisher: http://dx.doi.org/10.4236/wsn.2009.11003 Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol assisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. …
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.
COVID-19, an opportunity for developing countries?
2020
The COVID-19 outbreak was declared by the World Health Organization (WHO) as global pandemic in March 2020. Considering the necessity to implement rapid response to control the pandemic and the fragility and the state of need of low income countries, it will be mandatory to develop a global approach in order to reduce the spread of infection and the creation of community viral reservoirs. So far, we could hypothesize a worst case scenario in which when the COVID-19 outbreak hits a peak in Africa and in low-income countries, the majority of such countries will be unprepared, with low resources allocated for affording the viral emergency and the consequences will be catastrophic with no lesso…
Coupled cluster calculations of the vertical excitation energies of tetracyanoethylene
2003
The vertical spectrum of tetracyanoethylene was studied using coupled cluster theory. It was found that the lowest singlet-singlet transition, which corresponds to the excitation from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) excitation, occurs at 5.16 eV in the gas phase and is lowered approximately 0.1 eV due to solvent effects in acetonitrile. A parallel study on the ethene spectrum showed the quality of the basis sets and methods used, by placing the V state 7.92 eV above the ground state and giving an energy for the 0-0 transition of 5.42 eV to be compared with the experimental value of 5.50 eV.
New results for finding common neighborhoods in massive graphs in the data stream model
2008
AbstractWe consider the problem of finding pairs of vertices that share large common neighborhoods in massive graphs. We give lower bounds for randomized, two-sided error algorithms that solve this problem in the data-stream model of computation. Our results correct and improve those of Buchsbaum, Giancarlo, and Westbrook [On finding common neighborhoods in massive graphs, Theoretical Computer Science, 299 (1–3) 707–718 (2004)]
Debt Sustainability and Fiscal Space in a Heterogeneous Monetary Union: Normal Times Vs the Zero Lower Bound
2020
In this paper we study fiscal policy effects and fiscal space for countries in a monetary union with different levels of public debt. We develop a dynamic stochastic general equilibrium (DSGE) model of a two-country monetary union, calibrated to match the characteristics of Spain and Germany, in which debt sustainability is endogenously determined a la Bi (2012) to shape the responses of the risk premium on public debt. Policy shocks change the market’s expectation about future primary surplus, producing a direct effect on the sovereign risk premium and macroeconomic responses of the economy. In normal times the costs of a government spending driven fiscal consolidation in the high-debt cou…
GLOBAL DELAY TIME FOR GENERAL DISTRIBUTED NETWORKS WITH APPLICATIONS TO TIMING ANALYSIS OF DIGITAL MOS INTEGRATED CIRCUITS
1989
We consider here a general nerwork composed by n‐distributed parameters lines (with telegraph‐equations models) and m‐capacitors, all connected by a resistive multiport. An asymptotic stability property drives us to define and evaluate a global parameter (“λ‐delay time”) which describes the speed of signals propagation through the network. Because of its simplicity of calculation and its tightness, the given upper bound of the λ‐delay time is useful in timing analysis of MOS integrated chips.
Personalized management of dyslipidemias in patients with diabetes-it is time for a new approach (2022)
2022
AbstractDyslipidemia in patients with type 2 diabetes (DMT2) is one of the worst controlled worldwide, with only about 1/4 of patients being on the low-density lipoprotein cholesterol (LDL-C) target. There are many reasons of this, including physicians’ inertia, including diabetologists and cardiologists, therapy nonadherence, but also underusage and underdosing of lipid lowering drugs due to unsuitable cardiovascular (CV) risk stratification. In the last several years there is a big debate on the risk stratification of DMT2 patients, with the strong indications that all patients with diabetes should be at least at high cardiovascular disease (CVD) risk. Moreover, we have finally lipid lowe…
Nutraceuticals in Lipid-Lowering Treatment
2014
Lipid-lowering drugs may cause adverse effects and, although lipid targets may be achieved, a substantial residual cardiovascular (CV) risk remains. Treatment with agents mimicking proteins present in the body, such as incretin-based therapies, provided promising results. However, in order to improve lipids and CV risk, lifestyle measures remain important. Some researchers focused on nutraceuticals that may beneficially affect metabolic parameters and minimize CV risk. Chitosan, a dietary fiber, can regulate lipids with benefit on anthropometric parameters. The beneficial properties of dietary supplements (such as green tea extract, prebiotics, plant sterols, and stanols) on plasma lipids,…