Temperature dependence of the dielectric characteristics of a 5CB liquid crystal within the relaxation region

The temperature dependence of the real part of the permittivity of a 4-n-pentyl-4-cyanobiphenyl liquid crystal was studied within a broad frequency range of 30–5000 MHz and in the temperature interval 20–60°C in the vicinity of the nematic-isotropic-liquid phase transition. It was established that the dispersion of the longitudinal component of the permittivity can be fitted well by a sum of two Debye terms with strongly differing relaxation times. The temperature and frequency dependence of the shorter relaxation time was determined for which the best fit between calculations and experiment was achieved.     

Physical principles of the design of electrically controllable microstrip devices

Electrically controllable microstrip microwave devices are investigated in which liquid crystals, high-temperature superconducting films, or varactors are used as active media. It is demonstrated that comparatively large controllable phase shifts can be obtained using resonant liquid crystal or varactor phase shifters; however, in this case, the working frequency band of the devices become significantly narrower. The possibilities of obtaining maximum frequency tuning of filters whose bandwidth in the tuning frequency range remains unchanged or changes by a preset law are demonstrated. Varactor designs of two-channel power dividers with a smoothly varying division coefficient between the channels are considered. An original device protecting from a radio pulse based on a superconducting film in which total pulse reflection is observed when the pulse power exceeds a preset threshold is investigated. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 36–45, September, 2008.     

On the Maximal Cut in a Random Hypergraph

Doklady Mathematics - This paper deals with the problem of finding the max-cut for random hypergraphs. We consider the classical binomial model $$H(n,k,p)$$ of a random k-uniform hypergraph on n...     

Wien effect in molten magnesium chloride

Results of studying the dependence of conductivity of molten magnesium chloride on the electric field intensity are presented. Limiting conductivities of the MgCl₂ melt are obtained that exceed the ordinary values by 265 and 253% at 1000 and 1040 K.