A Device for Measurements of Dielectric Characteristics of Liquid Crystalline Materials, Solid Substances, and Their Melts

The device developed allows one to measure the dielectric characteristics of solid substances and their melts at frequencies of 20–20000 Hz and in a wide temperature range of 20–250°C. The measured temperature dependencies of the dielectric permittivities of several molecular and liquid crystals (stilbene, diphenyl, naphthalene, cholesterylpelargonate, and 8OCB) are presented.     

A rheological study of laminar–turbulent transition in drag reducing polymeric solutions

Presented herein are the studies of laminar–turbulent transition in micropolar and power law fluids flowing in a circular pipe. For some parametric values of micropolar and power law fluids, both depict the drag reducing properties. The parametric values of these representations have been obtained from the experimental results of Mc-Comb. It has been observed that, in both the cases, as the drag-reducing property in the solution increases, the first transition point moves towards the walls of the pipe. It is also observed that the onset of early turbulence phenomenon occurs for the drag-reducing polymeric solutions.     

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.     

Use of tension springs in the drive of the displacement system of a cryogenic cooler

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 5, p. 17, May, 1989.     

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 -     

Radiation safety of a population inhabiting the area where a nuclear facility is situated

Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 81–83, August, 1989.