A stability criterion for asynchronous multirate linear systems

A stability criterion is developed for linear, asynchronous multirate sampled-data systems. Such systems typically include a linear, time variant, continuous-time plant and several unsynchronized digital controllers. The analysis method uses a time-domain approach based on the closed-loop state transition matrix. The result is sufficient stability criterion which gives an objective measure of long-term and short-term stability. A simple example illustrates the method     

Effect of puffer volume and operating force on dielectric recovery performance in thermal puffer-type gas circuit breaker

In order to investigate the influence of puffer volume V/sub P/ and operating force to dielectric performance of GCB at current interruption, we calculated the prospective dielectric withstand voltage V/sub W/ between arcing contacts. The withstand voltage was calculated by the electric field strength appeared on arcing contacts and the allowable electric field strength E/sub W//sup */ of hot gas due to thermal puffer action. We could clarify that large initial puffer volume V/sub P/ can increase withstand voltage V/sub W/ at current breaking point and also that an optimum point exists in operating force F. For example, it was found that in case of the operating force of 1000 kgf, the puffer volume V/sub P/ of 1.2 liter would be best choice in the interrupting condition of i=50 kA and arcing time of 1.35 cycle.     

Generalized concentration dependence of makromolecule selfdiffusion coefficients in polyethyleneoxide solutions

Summary The polyethyleneoxide (PEO) macroraolecule translational mobility in dioxane and benzene solutions was studied by pulsed field gradient nmr. The generalized dependence describing the macromolecule translational mobility in solutions — invariant with respect to the polymer molecular mass, solvent,as well as to temperature — was obtained.     

On Pontryagin’s example with many evadors

The problem of pursuit of a single evador or several evadors by a group of pursuers with equal capabilities of all players is considered in Pontryagin’s example under the condition that the characterstic equation has at least one positive root. Some sufficient conditions of the solvability of the pursuit problems are obtained.     

Internet user behavior: compared study of the access traces and application to the discovery of communities

With an ever-increasing emphasis on human activity (idea exchange, shopping, gaming, etc.) being mediated through the data network, the understanding of Internet users' behavior has become a rising challenge. Research dealing with the analysis and modeling of Internet user behavior can be roughly split in to two main approaches. The first is based on sociocognitive observation of users' practices in a standardized context. The second approach focuses on the analysis of productions and the traces of users' activity. This paper relates to the latter approach and presents a comparative analysis of Internet navigation traces (URLs versus keywords) to characterize individual or group-of-users' behavior when accessing the Web. The proposed models are based on the study of accesses redundancy seen as global static parameters and from the angle of time evolution. We also study the use of these models, in particular, to categorize a population of users in communities of interests. This study enables us to draw some conclusions on the compared performances of the two kinds of trace exploitation, as raw information, as well as the self-similar properties of the models.     

Photoelectrochemically Studying the Formation of Oxide Films on Titanium Alloys with Cobalt, Chromium, and Copper

The regularities of oxide film formation on Ti50Co, Ti45Cr, and Ti50Cu alloys are voltammetrically studied in boric-borate-buffer and sodium sulfate solutions at temperatures of 25 and 50°C with concurrently measuring the photocurrents. The band gaps of the films are determined.     

VIAM and Materials Science

Metal Science and Heat Treatment -