1,708 research outputs found

    Robust Power and Subcarrier Allocation for OFDM-based Cognitive Radio Networks Considering Spectrum Sensing Uncertainties

    Get PDF
    ‎In this paper‎, ‎we address power and subcarrier allocation for cooperative cognitive radio (CR) networks in the presence of spectrum sensing errors‎. ‎First‎, ‎we derive the mutual interference of primary and secondary networks affecting each other by taking into account spectrum sensing errors‎. ‎Then‎, ‎taking into account the interference constraint imposed by the cognitive network to the primary user and the power budget constraint of cognitive network‎, ‎we maximize the achievable data rates of secondary users‎. ‎Besides‎, ‎in a multi secondary user scenario‎, ‎we propose a suboptimal but low complexity power and subcarrier allocation algorithm to solve the formulated optimization problem‎. ‎Our numerical results indicate that the proposed power loading scheme increases the cognitive achievable data rates compared to classical power loading algorithms that do not consider spectrum sensing errors‎

    On invariant sets in Lagrangian graphs

    Get PDF
    In this exposition, we show that a Hamiltonian is always constant on a compact invariant connected subset which lies in a Lagrangian graph provided that the Hamiltonian and the graph are smooth enough. We also provide some counterexamples for the case that the Hamiltonians are not smooth enough.Comment: 4 page

    Critical Exponents of Quantum Phase Transition Between U(5) and O(6) Limits of Interacting Boson Model

    Get PDF
    In this paper, Landau theory for phase transitions is shown to be a useful approach for quantal system such as atomic nucleus. A detailed analysis of critical exponents of ground state quantum phase transition between U(5) and O(6) limits of interacting boson model is presented. Our results suggest a similarity between these two frameworks and a second order phase transition between these limits based on a discontinuity in the heat capacity

    Small and medium scale aquaculture value chain development in Egypt: Situation analysis and trends

    Get PDF

    Fractional Dehn twists in knot theory and contact topology

    Full text link
    Fractional Dehn twists give a measure of the difference between the relative isotopy class of a homeomorphism of a bordered surface and the Thurston representative of its free isotopy class. We show how to estimate and compute these invariants. We discuss the the relationship of our work to stabilization problems in classical knot theory, general open book decompositions, and contact topology. We include an elementary characterization of overtwistedness for contact structures described by open book decompositions.Comment: We have removed an incorrect assumption about properties of meridional disks of Heegaard decompositions of S^3 and have added a conjecture about stabilizations of knots in S^

    A new kind of Lax-Oleinik type operator with parameters for time-periodic positive definite Lagrangian systems

    Full text link
    In this paper we introduce a new kind of Lax-Oleinik type operator with parameters associated with positive definite Lagrangian systems for both the time-periodic case and the time-independent case. On one hand, the new family of Lax-Oleinik type operators with an arbitrary uC(M,R1)u\in C(M,\mathbb{R}^1) as initial condition converges to a backward weak KAM solution in the time-periodic case, while it was shown by Fathi and Mather that there is no such convergence of the Lax-Oleinik semigroup. On the other hand, the new family of Lax-Oleinik type operators with an arbitrary uC(M,R1)u\in C(M,\mathbb{R}^1) as initial condition converges to a backward weak KAM solution faster than the Lax-Oleinik semigroup in the time-independent case.Comment: We give a new definition of Lax-Oleinik type operator; add some reference

    Incidence and predisposing factors of cognitive disorders following off-pump coronary artery bypasses graft surgery

    Get PDF
    Patients and Methods: A total of 171 patients who had undergone off-pump CABG without any history of psychiatric disorders were enrolled. Samples were selected according to a purposive sampling method. The Mini-Mental State Examination (MMSE) questionnaire was given to each patients to assess the incidence of cognitive disorder during the first 24 hours of surgery in ICU. To compare creatinine, erythrocytes sedimentation rate, extubation time, and patients’ age between those with and those without postoperative cognitive disorder, independent-samplest test was employed. To compare two groups in terms of any history of diseases such as diabetes, hypertension, and hyperlipidemia, and qualitative C-reactive protein (CRP), Chi square test was used. Results: Results showed that 75% of patients had postoperative cognitive disorder. There was a significant association between the history of hypertension, CRP, and preoperative creatinine levels in both cognitive disorder and control groups. Background: Cognitive disorder, which is a common problem for the hospitalized patients, is a fluctuating cognitive destruction that leads to the loss of consciousness. It is usually accompanied by increased mortality, prolonged hospital stay, and decreased rehabilitation. Objectives: The purpose of this study was to determine the risk factors associated with cognitive disorder after coronary artery bypasses graft surgery (CABG). Conclusions: Given the significant prevalence of postoperative cognitive disorder and significant association between the history of hypertension, CRP, and preoperative creatinine and cognitive disorder, the detection of patient’s clinical symptoms may improve diagnosis, treatment, and even prevention of cognitive disorder. © 2014, Iranian Society of Regional Anesthesia and Pain Medicine (ISRAPM); Published by Kowsar

    Settlement of a Building Founded on Difficult Soil

    Get PDF
    Many coastal areas in Benghazi have been reclaimed from lagoons. Quite often such areas are covered by debris, rubbish and other artificial fills over many years. The proximity of these deposits to the Mediterranean Sea coupled with the seasonal moisture variations has resulted in the formation of the so-called Sabkha soils having a high proportion of chemical content. Settlement records of a four storey building founded on sabkha soil are prescuted for seven years. The building underwent large settlement resulting in a tilt from the vertical. It is found that, for Sabkha soils, the measured settlement is larger than that predicted according to conventional theories. Based on this case study and constructions experience of many contractors in such areas, a number of useful suggestions are given for practicing engineers
    corecore