Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
In this work, we develop an anchor-less relative localisation algorithm aimed to be used in multi-robot teams. The localisation is performed based on the Received Signal Strength Indicator (RSSI) readings collected from the messages exchanged between nodes. We use the RSSI as a rough estimate of the inverse of distance between any pair of communicating nodes, and we claim that such estimates provide a coarse information of the nodes relative localisation
Read moreIn this paper, we propose a new two-way time synchronization (TS) method for OFDM-based wireless systems. It relies on the time-reversal (TR) technique in order to remove the effect of the channel phase after the signal round-trip. For this reason, the method is named TR-TS. TR technique yields a linear phase rotation across subcarriers, regardless whether the channel is minimum, maximum, or mixed phase. This phase is proportional to the difference
Read moreIn this paper we address the problem of blind recovery of multiple OFDM data streams in a Multiple-Input Multiple-Output (MIMO) system. We propose an equalization algorithm which is based on a combined criterion designed to cancel both intersymbol interference (ISI) and co-channel interference (CCI). ISI is minimized by using a modified Vector Constant Modulus criterion while CCI is minimized by a decorrelation criterion. We establish conditions
Read moreIn this paper we introduce a Riemannian algorithm for minimizing (or maximizing) a real-valued function {mathcal J} of complex-valued matrix argument {mathbf W} under the constraint that {mathbf W} is an n×n unitary matrix. This type of constrained optimization problem arises in many array and multi-channel signal processing applications. We propose a conjugate gradient (CG) algorithm on the Lie group of unitary matrices $U(n)$. The algorithm fully
Read moreIn many engineering applications we deal with constrained optimization problems with respect to complex-valued matrices. This paper proposes a Riemannian geometry approach for optimization of a real-valued cost function {mathcal J} of complex-valued matrix argument {mathbf W}, under the constraint that {mathbf W} is an $n times n$ unitary matrix. We derive steepest descent (SD) algorithms on the Lie group of unitary matrices $U(n)$. The proposed
Read moreOver the last half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its main stem, a grand experiment was inadvertently run in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain. We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the
Read moreTo evaluate whether serum GH and IGF1 levels achieved after 3 months treatment with somatostatin analogues (SSA) are concordant with the efficacy of SSA after longer treatment with the same dose. Patients and methods: From 71 patients with acromegaly treated with SSA in our clinic, in 38 of them (28 women, 10 men, aged 22–62 years) data on serum GH and IGF1 were available at baseline, after 3 months and at the last evaluation on the same SSA dose.
Read moreA long term follow – up of thyrotoxic patients treated surgically is required not only for early detection of hypothyroid patients with poor compliance with treatment, but also for revealing late postoperative hyperthyroidism. Regarding the prevalence of postoperative hyperthyroidism, two previous studies found that 16% relapsed after 20 years (Kalk WJ, 1978) and 19% of post – thyroidectomy thyrotoxicosis occurred 20 -50 years after surgical
Read moreTreatment with hormone analogues can challenge the precise measurement by interference with the routinely used immunoassays systems, related to the presence of autoantibodies in the serum, interference with associated therapy or the presence of altered forms of the hormone, with modified biological activity and/or immunoreactivity. In patients with acromegaly treated with the hGH antagonist Pegvisomant (PEG) (Somavert®), most of the assays are deeply
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