2,329,134 research outputs found
Optimal Bandwidth and Power Allocation for Sum Ergodic Capacity under Fading Channels in Cognitive Radio Networks
This paper studies optimal bandwidth and power allocation in a cognitive
radio network where multiple secondary users (SUs) share the licensed spectrum
of a primary user (PU) under fading channels using the frequency division
multiple access scheme. The sum ergodic capacity of all the SUs is taken as the
performance metric of the network. Besides all combinations of the peak/average
transmit power constraints at the SUs and the peak/average interference power
constraint imposed by the PU, total bandwidth constraint of the licensed
spectrum is also taken into account. Optimal bandwidth allocation is derived in
closed-form for any given power allocation. The structures of optimal power
allocations are also derived under all possible combinations of the
aforementioned power constraints. These structures indicate the possible
numbers of users that transmit at nonzero power but below their corresponding
peak powers, and show that other users do not transmit or transmit at their
corresponding peak power. Based on these structures, efficient algorithms are
developed for finding the optimal power allocations.Comment: 28 pages, 6 figures, submitted to the IEEE Trans. Signal Processing
in June 201
Optimization models of the supply of power structures’ organizational units with centralized procurement
Management of the state power structures’ organizational units for materiel and technical support requires the use of effective tools for supporting decisions, due to the complexity, interdependence, and dynamism of supply in the market economy. The corporate nature of power structures is of particular interest to centralized procurement management, as it provides significant advantages through coordination, eliminating duplication, and economy of scale. This article presents optimization models of the supply of state power structures’ organizational units with centralized procurement, for different levels of simulated materiel and technical support processes. The models allow us to find the most profitable options for state power structures’ organizational supply units in a centre-oriented logistics system in conditions of the changing needs, volume of allocated funds, and logistics costs that accompany the process of supply, by maximizing the provision level of organizational units with necessary material and technical resources for the entire planning period of supply by minimizing the total logistical costs, taking into account the diverse nature and the different priorities of organizational units and material and technical resources
Acoustic energy transmission in cast iron pipelines
In this paper we propose acoustic power transfer as a method for the remote powering of pipeline sensor nodes. A theoretical framework of acoustic power propagation in the ceramic transducers and the metal structures is drawn, based on the Mason equivalent circuit. The effect of mounting on the electrical response of piezoelectric transducers is studied experimentally. Using two identical transducer structures, power transmission of 0.33 mW through a 1 m long, 118 mm diameter cast iron pipe, with 8 mm wall thickness is demonstrated, at 1 V received voltage amplitude. A near-linear relationship between input and output voltage is observed. These results show that it is possible to deliver significant power to sensor nodes through acoustic waves in solid structures. The proposed method may enable the implementation of acoustic - powered wireless sensor nodes for structural and operation monitoring of pipeline infrastructure
Signatures of Emerging Subsurface Structures in Acoustic Power Maps
We show that under certain conditions, subsurface structures in the solar
interior can alter the average acoustic power observed at the photosphere above
them. By using numerical simulations of wave propagation, we show that this
effect is large enough for it to be potentially used for detecting emerging
active regions before they appear on the surface. In our simulations,
simplified subsurface structures are modeled as regions with enhanced or
reduced acoustic wave speed. We investigate the dependence of the acoustic
power above a subsurface region on the sign, depth, and strength of the wave
speed perturbation. Observations from the Solar and Heliospheric
Observatory/Michelson Doppler Imager (SOHO/MDI) prior and during the emergence
of NOAA active region 10488 are used to test the use of acoustic power as a
potential precursor of magnetic flux emergence.Comment: 7 pages, 5 figures, accepted for publication in Solar Physics on 21
March 201
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