Precision Experiment on the Study of Helium Isotopes Cryosorption in Terrestrial Conditions and at Lower Gravity

Characteristic features of gaseous helium adsorption near the -point at low pressure were discussed at the international seminar on low temperature physics in microgravity CWS-97. It has been shown in that paper that at ⁴He cryosorption on the argon cryolayer near the ⁴He -point, a jump-like pressure change above the cryolayer took place. At ³He cryosorption on the argon layer formed in identical conditions an abrupt pressure change above the cryolayer in the ⁴He -point area has not been observed. The present study deals with the isothermal behavior of the cryopanel in terrestrial conditions. Experiments were conducted to study the character of the temperature change with respect to the column height of liquid helium inside the helium cryostat in the case of vapor pumping and in the case of warming up of liquid helium and cryopanel due to heat coming.Temperature stratification of liquid helium due to natural convection has been calculated. Calculation program for integral characteristics of the liquid heating and cooling process has been compiled accounting for the stratification effect. These characteristics include the cold nucleus volume, nucleus temperature, height of the stratification layer, temperature profile in this layer, time of these stages depending on the given rate of the pressure growth in the system.Problems of the precision experiment to study helium isotopes cryosorption (⁴He and ³He) in terrestrial conditions and at lower gravity have been discussed.     

Radiation-chemical synthesis of poly(vinyl alcohol) hydrogel containing dicyclohexano-18-crown-6

Radiation-chemical synthesis of poly(vinyl alcohol) hydrogels containing physically immobilized dicyclohexano-18-crown-6 was carried out. Remarkable gel fraction of 40-70% was observed at absorbed dose of about 5 kGy. Increasing degree of poly(vinyl alcohol) crosslinking led to growth of the efficiency of crown ether immobilization. Post-irradiation thermal annealing of the hydrogel samples at 120 °C for 0.5-5 h resulted in an increase of crown ether retention as compared with non-annealed samples by approximately 20% at the same absorbed dose. Preliminary results on a sorption behavior of the crown-containing hydrogels with respect to Sr²⁺ cations in 2.4 M HNO₃ solution are presented.     

On the possibility of decreasing spherical and chromatic aberrations in flat combined axisymmetric magnetoelectrostatic lenses

It is shown that the coefficients of both spherical and chromatic aberrations in flat combined axisymmetric magnetoelectrostatic lenses can be decreased by a factor of six as compared to the analogous coefficients for pure magnetic lenses, provided appropriate values are selected for the ratio of dimensions of the electrodes and pole tips of the combined lens, electric potentials on the electrodes, and ampere-turns of the field-exciting coil.     

The effect of vacuum rarefaction during foundry by gasified models

The cooling of liquid metal in the process of filling the mold during foundry by gasified models is investigated based on an analysis of the equation of thermal conductivity during thermal destruction of the model material. It is shown that crystallization of metal is expanded top-down, and the intensity of cooling increases as the pouring rate increases and rarefaction in a casting box increases. An equation for calculating the temperature of the metal surface that takes into account the energy of thermal destruction of the model material, pouring rate, initial temperature of metal, rarefaction in the casting box, and the cross-section area of the casting during foundry by gasified models is suggested.     

Universal application of heat-resistant ferrite steels in various sectors of industry

The experience and prospects of using economically alloyed chromium steels in various fields of machine building are discussed. The main trends in improving the service resistance of products owing to new metallurgical, design, or technological solutions are identified.     

Double-channel parametric transducers with linear conversion functions

The design methods and technology are considered of precision instrumental transducers for an extensive class of automatic devices and systems operating in conditions of strong external interference. The paper is based on a report presented at the Transducers-98 Conference. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 39–45, May, 1999.