1,286 research outputs found
An induction theorem and nonlinear regularity models
A general nonlinear regularity model for a set-valued mapping , where and are metric spaces, is considered
using special iteration procedures, going back to Banach, Schauder, Lusternik
and Graves. Namely, we revise the induction theorem from Khanh, J. Math. Anal.
Appl., 118 (1986) and employ it to obtain basic estimates for studying
regularity/openness properties. We also show that it can serve as a
substitution of the Ekeland variational principle when establishing other
regularity criteria. Then, we apply the induction theorem and the mentioned
estimates to establish criteria for both global and local versions of
regularity/openness properties for our model and demonstrate how the
definitions and criteria translate into the conventional setting of a
set-valued mapping .Comment: 28 page
A secure network coding based modify-and-forward scheme for cooperative wireless relay networks
This paper investigates the security at the physical layer of cooperative relay communications. Inspired by the principle of physical-layer network coding (PNC), we propose a new secure relaying scheme, namely secure PNC-based modify-and-forward (SPMF). In the proposed scheme, the relay node linearly combines the decoded data from the source node with an encrypted key before conveying the mixed data to the destination node. As both the linear PNC operation and encrypted key at the relay are unknown to the eavesdropper, the SPMF scheme provides a double security level in the system. Particularly, taking into account the practical scenario of the imperfect knowledge shared between the relay and destination, the secrecy outage probability (SOP) of the proposed SPMF scheme is analysed and evaluated in comparison with modify-and-forward, cooperative jamming, decode-and-forward and direct transmission schemes. The proposed scheme is shown to achieve a performance improvement of up to 3 dB when compared to the conventional schemes under imperfect knowledge of shared information between the nodes
A power-splitting relaying protocol for wireless energy harvesting and information processing in NOMA systems
Non-orthogonal multiple access (NOMA) along with cooperative communications have been recognized as promising candidates for the fifth generation (5G) wireless networks and have attracted many researchers. Every networked device however has its own limited power supply. To this extent, this paper investigates a power-splitting relaying (PSR) protocol for wireless energy harvesting and information processing in the NOMA systems to prolong the lifetime of the energy-constrained relay nodes in wireless networks so as to avail the ambient radio-frequency (RF) signal as well as to simultaneously harvest the energy and process the information. Decode-and-forward relaying is employed at the relay node where the energy from the received RF signal is harvested and exploited to forward the information to the destination. Specifically, the outage probability and ergodic rate of the PSR protocol are derived to realize the impacts of energy harvesting time, energy harvesting efficiency, power splitting ratio, source data rate, and the distance between nodes. It is also shown that an increased energy harvesting efficiency results in an enhanced performance and an outperformance in terms of the energy efficiency is achieved with the employment of the NOMA when compared to the conventional orthogonal multiple access. Numerical results are provided to verify the findings
On the performance of NOMA in SWIPT systems with power-splitting relaying
This paper presents a decode-and-forward (DF) relaying protocol, namely power-splitting relaying (PSR), employed at relay nodes in NOMA technique. The PSR is considered for simultaneous wireless information and power transfer (SWIPT) systems. The relaying node is both energy harvesting from the received radio frequency (RF) signal and information forwarding to the destination. The outage performance and ergodic rate of the PSR are analyzed to realize the impacts of energy harvesting time, energy harvesting efficiency, power splitting ratio, source data rate, and the distance between the source and relay nodes. The simulation results show that NOMA schemes have the lower outage probability compared to the that of the conventional orthogonal multiple access (OMA) schemes at the destination node. Numerical results are provided to verify the findings
Policy Uncertainty and Firm Cash Holdings
This research examines the relation between government economic policy uncertainty and firm cash holdings. We find evidence that policy uncertainty is positively related to firm cash holdings due to firms’ precautionary motives and, to a lesser extent, investment delays. The relation between policy uncertainty and cash holdings is more pronounced for firms dependent on government spending and extends beyond business cyclicality. Further analysis indicates that the effects of policy uncertainty on corporate cash holdings are distinct from those of political, market, or other macroeconomic uncertainty
Edge of Infinity: The Clash between Edge Effect and Infinity Assumption for the Distribution of Charge on a Conducting Plate
We re-examine a familiar problem given in introductory physics courses, about
determining the induced charge distribution on an uncharged
``infinitely-large'' conducting plate when placing parallel to it a uniform
charged dielectric plate of the same size. We show that, no matter how large
the plates are, the edge effect will always be strong enough to influence the
charge distribution deep in the central region, which totally destroyed the
infinity assumption (that the surface charge densities on the two sides are
uniform and of opposite magnitudes). For a more detailed analysis, we solve
Poisson's equation for a similar setting in two-dimensional space and obtain
the exact charge distribution, helping us to understand what happens how charge
distributes at the central, the asymptotic, and the edge regions
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