On the accuracy of perturbative solutions to wave scattering from rough closed surfaces

The method of small perturbations is applied to the problem of plane-wave scattering from a soft circular surface with sinusoidal roughness. Rayleigh-theory and extinction-theorem perturbative solutions of arbitrary order are developed, and they are compared to each other as well as to an exact solution. A numerical study yields quantitative information about effects associated with the use of the Rayleigh hypothesis, about the merit of higher-order solutions, and about the reliability of the error criteria that measure a posteriori the conformity of perturbative solutions to the boundary condition. It is shown that the accuracy of perturbative solutions depends not only on the height, but also on the slope, of surface corrugations. Moreover, it is shown that the Rayleigh hypothesis does not affect the accuracy of far-field perturbative calculations. The mean extinction error is proposed as a measure for the error of the extinction-theorem perturbative solution.     

Two-dimensional optical lattice solitons

We study various families of two-dimensional discrete or lattice solitons, and show that they are possible only when their power level exceeds a critical threshold. In addition, we show that gap-lattice solitons exist only when the lattice possesses a complete 2D band gap. Our results suggest that these conditions are universally valid, irrespective of the nature of the nonlinearity or the specific structure of the index lattice. The analysis explains fundamental aspects of behavior of two-dimensional discrete solitons that have been very recently observed in photosensitive optical crystals.     

Strongly nonlinear second order differential inclusions with generalized boundary conditions

In this paper, we study second order differential inclusions in with a maximal monotone term and generalized boundary conditions. The nonlinear differential operator need not be necessary homogeneous and incorporates as a special case the one-dimensional p-Laplacian. The generalized boundary conditions incorporate as special cases well-known problems such as the Dirichlet (Picard), Neumann and periodic problems. As application to the proven results we obtain existence theorems for both “convex” and “nonconvex” problems when the maximal monotone term A is defined everywhere and when not (case of variational inequalities).     

Synthese von ringsubstituierten Titanocen-Sulfidotetraselenid-Chelaten

Summary Reaction of the titanocene complexes (RC₅H₄)₂Ti(SH)₂, [R = CH₃, Si(CH₃)₃] with elemental selenium in refluxing carbon disulfide leads to H₂S evolution and to selective formation of the titanocene sulfidotetraselenides (RC₅H₄)₂TiSSe₄. In these compounds the SSe₄ chain acts as a bidentate chelating ligand.

     

A nontrivial solution of mountain-pass type for a hemivariational inequality

We consider a class of noncoercive hemivariational inequalities involving the p-Laplacian. Our goal is to obtain the existence of a nontrivial solution. Using the mountain-pass theorem for locally Lipschitz functionals we obtain the desired result.     

A weak nonsmooth palais-smale condition and coercivity

In this paper we show that a generally nonsmooth locally Lipschitz function which satisfies the nonsmooth C-condition (nonsmooth Cerami condition) and is bounded from below, is coercive. The Cerami condition is a weak form of the well-known Palais-Smale condition, which suffices to prove minimax principles.     

Zero-Forcing Successive Decoding Under Nakagami-<Emphasis Type="Italic">m</Emphasis> Fading Channels

In this paper, the performance of a multiuser distributed spatial multiplexing system is analytically investigated. The system operates under a Nakagami-m fading environment. All the users, equipped with single antennas, are simultaneously transmitting their streams to a multi-antenna receiver. Zero-forcing is applied along with successive interference cancellation as a means for efficient detection of the received streams. New exact closed-form expressions with regards to some important performance metrics, namely, outage probability and ergodic capacity of each stream are presented. Both the analytical expressions and the simulation results show the impact of channel severity and scale of antenna array to the overall system performance. A particular emphasis on the scenario of the emerging massive multiple input-multiple output systems is provided.     

An adaptive end‐to‐end RTO calculation framework for DTNs with scheduled connectivity

In this work, we propose an end‐to‐end retransmission framework for dynamically calculating efficient retransmission time‐out intervals in delay‐tolerant networks (DTNs) with scheduled connectivity. The proposed framework combines deterministic and statistical information about the network state to calculate worst‐case estimates about the expected round trip times. Such information includes connectivity schedules, convergence layer protocols specifics, communication link characteristics, and network statistics about the maximum expected packet error rates and storage congestion. We detail the implementation of the proposed framework within the end‐to‐end application data conditioning layer proposed for the DTN architecture, realized by the Delay‐Tolerant Payload Conditioning protocol, as part of the Interplanetary Overlay Network–DTN reference implementation, and evaluate its performance in a complex deep‐space emulation scenario in our DTN testbed. Our results show that our approach achieves great accuracy in round‐trip time estimations and, therefore, faster retransmissions of lost data, in comparison to the statically configured retransmission mechanism of the original Delay‐Tolerant Payload Conditioning protocol. As a result, in‐order data reception rate and storage requirements on the receiver side are significantly improved, at minimum or even zero extra cost in transmission overhead due to duplicate transmissions.