Gossip-based aggregation of trust in decentralized reputation systems

Decentralized Reputation Systems have recently emerged as a prominent method of establishing trust among self-interested agents in online environments. A key issue is the efficient aggregation of data in the system; several approaches have been proposed, but they are plagued by major shortcomings. We put forward a novel, decentralized data management scheme grounded in gossip-based algorithms. Rumor mongering is known to possess algorithmic advantages, and indeed, our framework inherits many of their salient features: scalability, robustness, a global perspective, and simplicity. We demonstrate that our scheme motivates agents to maintain a very high reputation, by showing that the higher an agent’s reputation is above the threshold set by its peers, the more transactions it would be able to complete within a certain time unit. We analyze the relation between the amount by which an agent’s average reputation exceeds the threshold and the time required to close a deal. This analysis is carried out both theoretically, and empirically through a simulation system called GossipTrustSim. Finally, we show that our approach is inherently impervious to certain kinds of attacks. A preliminary version of this article appeared in the proceedings of IJCAI 2007.     

Treatment of intestinal paresis in children

In the paper, a clinical experience with treatment of intestinal paresis in 545 children, aged from 1 day to 13 years, including 225 children operated upon for peritonitis is summarized. The authors differentiate 3 stages in the development of intestinal paresis depending on the degree of intensity of systemic and local disturbances. The employed methods of treatment in intestinal paresis were classified by the principle of their effect as 3 groups. Application of some or other method of the paresis therapy is determined by the stage of its development. In treatment of postoperative intestinal paresis a continuous peridural blockade is considered to be the method of choice. Utilization of the latter enabled the authors to reveal a number of postoperative complications: mechanic intestinal obstruction, incompetent anastomosis, etc.     

A cure for benign positional vertigo

Benign positional vertigo is a common clinical entity encountered in any dizzy clinic. It is easily diagnosed on the basis of historical information and a positive Dix-Hallpike position test. The available evidence suggests that this condition is due to involvement of the posterior semicircular canal. The pathophysiology of this condition can be explained theoretically on the basis of free-floating particles within the endolymph of the posterior semicircular canal that move under the influence of gravity with certain provocative positional changes. Based on this theoretical model, a variety of particle-repositioning manoeuvres have been developed that attempt to relocate the loose particles from the posterior semicircular canal to the utricular sac. If the particles are kept in the utricular sac for a period of 48 h by maintaining the patient in an upright position, the clinical symptoms are relieved in a high proportion of patients. If the manoeuvre is unsuccessful on a first attempt, or if the benign positional vertigo recurs at a later date, the condition can usually be relieved by a second manoeuvre. Bilateral benign positional vertigo can be treated by performing a manoeuvre on one side followed by a manoeuvre on the other side at a later date. On occasion, posterior canal benign positional vertigo is converted to horizontal canal benign positional vertigo, but this subsides readily within the 48-h post-manoeuvre period.     

Resonance radiation from imperfections. Part II: dislocation arrays and asymptotic solutions

Elastic radiation due to various dislocation patterns in a circular cylinder is considered in order to investigate the effect of size and location of imperfections on acoustic emission signals. The results show the marked influence of these parameters on the vibrations of the outer surface and confirm the existence of impotent dislocations. For certain arrays the frequency response may be qualitatively different from that due to a discrete imperfection.     

Evaluation of training in creative problem solving.

"The experiment was designed to evaluate the effects of a creative problem-solving course on creative abilities and selected personality variables." There were 3 matched groups of 54 Ss each. 1 group was enrolled in courses in creative problem solving; the other 2 were enrolled in other courses. 11 prepost test measures were used. "Results are interpreted to indicate that the creative problem-solving course produces a significant increment on certain ability measures associated with practical creativity and on the personality variable dominance." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of the parameters of HEMT GaN/AlN/AlGaN heterostructures for microwave transistors using numerical simulation

The numerical simulation, and theoretical and experimental optimization of field-effect microwave high-electron-mobility transistors (HEMTs) based on GaN/AlN/AlGaN heterostructures are performed. The results of the study showed that the optimal thicknesses and compositions of the heterostructure layers, allowing high microwave power implementation, are in relatively narrow ranges. It is shown that numerical simulation can be efficiently applied to the development of microwave HEMTs, taking into account basic physical phenomena and features of actual device structures.     

Specific features of proton interaction with transistor structures having a 2D AlGaN/GaN channel

It has been shown that the interaction of 1 MeV protons at doses of (0.5–2) × 10¹⁴ cm^–2 with transistor structures having a 2D AlGaN/GaN channel (AlGaN/GaN HEMTs) is accompanied not only by the generation of point defects, but also by the formation of local regions with a disordered nanomaterial. The degree of disorder of the nanomaterial was evaluated by multifractal analysis methods. An increase in the degree of disorder of the nanomaterial, manifested the most clearly at a proton dose of 2 × 10¹⁴ cm^–2, leads to several-fold changes in the mobility and electron density in the 2D channel of HEMT structures. In this case, the transistors show a decrease in the source–drain current and an order-of-magnitude increase in the gate leakage current. In HEMT structures having an enhanced disorder of the nanomaterial prior to exposure to protons, proton irradiation results in suppression of the 2D conductivity in the channel and failure of the transistors, even at a dose of 1 × 10¹⁴ cm^–2.     

Microwave power amplifiers based on AlGaN/GaN transistors with a two-dimensional electron gas

A technique for synthesis of microwave power amplifiers based on transistors with a AlGaN/GaN heterojunction is discussed. Special focus is on the development of a technique for synthesis of transformation circuits of the power amplifier to increase efficiency with a retained high output power. The use of independent matching at the harmonic frequencies and fundamental frequency makes it possible to control the attainable efficiency in a wide frequency band along with the total suppression of harmonics beyond the operational band. Microwave power amplifiers for operation at 4 and 9 GHz have been developed and experimentally investigated.