Analysis of the joint use of the proactive and reactive methods of the topology information dissemination in ad-hoc wireless networks

A number of routing protocols for wireless ad-hoc (self-organizing) networks selects routes according to the topology information obtained by the station. Hence, the method of these protocols used to disseminate topology information strongly affects the network performance. An unsuccessful choice of the method can lead to a large amount of traffic and the information obsolescence. These factors diminish the network performance and make it impossible to meet quality of service requirements in transmitting realtime multimedia data, which is a topical problem. The routing protocol combining the proactive and reactive methods of the topology information dissemination has been proposed. It is demonstrated that this protocol is efficient in a wide range of scenarios applied to the exchange of real-time multimedia data.     

Harnessing the Melting Peculiarities of Ultra‐High Molecular Weight Polyethylene Fibers for the Processing of Compacted Fiber Composites

Summary: Compacted fiber composites offer unique properties due to their lack of an extraneous matrix. The conditions of processing ultra‐high molecular weight polyethylene (UHMWPE) fibers were simulated in a heated pressure cell. In situ X‐ray diffraction measurements were used to follow the relevant transitions and the changes in the degree of crystallinity during melting and crystallization. The results strongly support the suggestion that the hexagonal crystal phase, in which the chain conformation is extremely mobile on the segmental level, constitutes the physical basis of compaction technologies for processing UHMWPE fibers into a single‐polymer composite. This report suggests that using a pseudo‐phase diagram outlining the occurrence of different phases during slow heating and the degree of crystallinity can provide valuable insight into the technological parameters relevant for optimal processing conditions.

Degree of crystallinity as a function of pressure and temperature in a region relevant to compaction processes.     

On the shape of the boundary of a feasibility set for heat-to-work converters

It has been shown that the feasibility set for thermodynamic systems using heat energy in the target flux rate–heat flux rate plane has been bounded above. The thermal efficiency coefficient of a system decreases with increasing productivity. The target flux rate also decreases beginning from a certain heat flux rate. It turns out that the efficiency coefficient that corresponds to its maximum does not depend on irreversible factors and is a function of the reversible efficiency coefficient alone in many cases. This feature of systems and the possibility of its application have been considered.     

Design of Chemical Engineering Systems with Chance Constraints

In the design of chemical process under uncertainty in initial information, an important problem is to determine a structure in which the control system will guarantee that all constraints are satisfied despite variations in internal and external factors at the operation stage. A method has been proposed for solving onestage optimization problems with chance constraints in the design of optimal flexible chemical processes. The developed approach makes it possible to avoid multidimensional integration in each of the iterations of problem solving, thus reducing the computational effort. The efficiency of the proposed approach is illustrated by model examples.     

Using compositions of Markov models to determine functional gene fragments

Algorithmic compositions in the form of expert mixtures with exclusive competence zones are considered in order to increase the quality of classification of gene fragments with the help of models based on Markov chains.     

Randomness versus Fault-Tolerance

We investigate the relations between two major properties of multiparty protocols: fault tolerance (or resilience ) and randomness . Fault-tolerance is measured in terms of the maximum number of colluding faulty parties, t , that a protocol can withstand and still maintain the privacy of the inputs and the correctness of the outputs (of the honest parties). Randomness is measured in terms of the total number of random bits needed by the parties in order to execute the protocol. Previously, the upper bound on the amount of randomness required by general constructions for securely computing any nontrivial function f was polynomial both in n , the total number of parties, and the circuit-size C(f) . This was the state of knowledge even for the special case t=1 (i.e., when there is at most one faulty party). In this paper we show that for any linear-size circuit, and for any number t < n/3 of faulty Received 30 April 1998 and revised 3 January 1999 and 1 July 1999     

Very high frequency radiowave scattering by a disturbed sea surface Part I: Scattering from a slightly disturbed boundary

This paper considers the scattering of very high frequency (VHF) electromagnetic waves from a random weakly corrugated surface by the perturbation method. The calculations show that the scattering has a resonant nature, i.e., only certain Fourier components of the surface shape are responsible for scattering in every given direction. Experiments carried out in a water basin confirmed the results of the calculations. The backscattered intensity is proportional to the spectral density of those Fourier components of the surface oscillation that have a resonant space period. In these experiments, resonant maxima of the reflected signal corresponding to the second-order approximation of the perturbation method were also observed. The frequency spectrum of the scattered electromagnetic field is also investigated. It is shown that the spectrum of the scattered radiation is shifted from the incident frequency by a certain value related to the phase velocity of the resonantly scattering Fourier component of the surface shape. The experimentally observed dependence of the scattered intensity on frequency and the theoretically predicted one are very much alike.