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The computation methods of the thermodynamic properties are used for theoretical studies of multicomponent refrigerant blends (MRBs) for low-temperature throttling refrigeration units, providing cryostatting modes for cooled objects in the temperature range of –90 – –160 °С. The article presents the comparative analysis of the state equations for calculating thermodynamic properties of multicomponent refrigerant mixtures. Quantitative and qualitative differences in the results of calculations in the lowtemperature region are determined.

Theoretical studies of refrigerant blends in closed-loop throttling low-temperature refrigeration machines, which provide the specified cryostatting mode for cooled objects in the temperature range of – 90 to – 160°С, require computation of thermodynamic properties and phase equilibria. A method of computation of the phase equilibria and thermodynamic properties of multi-component refrigerant blends is presented based on the use of the two-parameter Redlich–Kwong equation of state in the Soave modification.

A comprehensive investigation of the properties of poly(paraphenylene-1,3,4-oxadiazole) fibers showed that items based on them were dimensionally stable during operation up to 400°C and retained high strength indicators after prolonged action of soil microorganisms. The fiber tensile strength remained at 78-80% after exposure to light for 2,000 h; at 93-95%, if a stabilizer was added. The investigation results predict high retention of mechanical properties of cloth based on Arselon® fiber during operation of items made from them under Russian Northwest and similar conditions.

A method for strengthening a nonwoven fabric for the manufacture of filter bags with Arselon fiber by introducing a reinforcing mesh is proposed. The technological scheme of the device for feeding the mesh into the nonwoven fabric is developed. The optimal calendering parameters of the reinforced fabric are determined, providing the required characteristics of the filtering nonwoven fabric.

The article presents a description of a new method of calculation by means of which the distribution of the temperature of a mixture of coolants along the working circuit of a low-temperature refrigerating machine may be calculated to a first approximation and the quantitative composition of a charge mixture of coolants determined for a given composition of the circulating mixture of coolants.

The duration of crystallization process of an eutectic solution of an infinite plate may be presented as a sum of three components: duration of the cooling process of the eutectic solution of liquid phase τ1 from initial temperature tI to the crystallization beginning; duration of crystallization process τ2 and duration of the precooling process of solid phase τ3 to certain final temperature t f in the plate center.

The annual cycle and long-term trend of the methane total column in the atmosphere over the Petergof station (St. Petersburg State University) are analyzed on the basis of data obtained from Fourier-transform infrared spectrometry and EMAC-model calculations. The amplitude of the annual cycle of the total column of CH4 amounts to 2.1 and 1.5% according to experimental and model data, respectively. For the atmospheric column-averaged mole fraction of CH4, the amplitude of its annual cycle is smaller than that for its total column and amounts to 1.1 and 0.6% according to experimental and model data, respectively. The results of local continuous measurements of surface CH4 concentrations showed that, in 2013, the atmospheric column-averaged mole fractions of CH4 and the amplitudes of diurnal variations in its local concentration were characterized by the same dynamics of seasonal variations. An analysis made on the basis of simulation results showed that atmospheric conditions (under which Fourier-transform IR measurements were performed) could increase the amplitude of the annual cycle of the total column of CH4 2.5 times when compared to the true one. The results of Fourier-transform IR measurements and EMAC-model calculations showed that, during 2009–2012, the atmospheric concentration of CH4 increased at a rate of ~0.2% per year. If measurement data obtained in 2013 are added, this rate decreases to ~0.13% per year.

We present a joint analysis of data obtained by Fourier transform infrared measurements of CH4 and EMAC model calculations for Petergof station (St. Petersburg State University) in 2009–2012. The systematic differences between observed and calculated data are 1.3% and 0.3% for the values of total column and atmospheric column-averaged mole fraction of methane, respectively. The high correlation for experimental and model data of the total column (r = 0.8) indicates that EMAC reproduces the total variability of the methane total column in the atmosphere due to meteorological processes. Using model data, we have analyzed the effect of meteorological conditions typical for Fourier transform IR observations on the resulting estimates of the mean values of total column and column-averaged mole fraction of CH4. We have shown that there can be systematic shifts (up to ~0.4%) in the experimental estimates for the mean value relative to the “true” value. This fact should be taken into account in comparing the climatological or model data with the results of Fourier transform IR measurements, especially for stations with a relatively small number of observation days.

The work is related to the problem by P. Erdős about the estimation of the numbers $$A_N = _{\left| z \right| = 1}^{\max } \left| {\left( {z - z_1 } \right)\left( {z - z_2 } \right) \cdots \left( {z - z_N } \right)} \right|,{\text{ where }}\left| {z_j } \right| \equiv 1,$$ as N→∞.We shall deal with the case where the z j are all possible roots of the unity ordered in such a way that all the roots of degree n follow the roots of degree n-1. Within the group of roots of degree n, the enumeration can vary. We prove that ln A N grows like √N, and we get estimates of possible values of the lower limit of the ratio (ln A N /√N as well as exact bounds of the upper limit of this ratio.

Results of experimental research of low-temperature multicomponent mixed-refrigerant throttling refrigerator are given. Appliance of refrigerator in new domestic-made ultralow-temperature freezer for cryoconservation and long-term storage of medical and biological objects at temperature minus 150°C is described. Within experimental research, test bench with development prototype of ultralow-temperature medical freezer is made. Experimental and theoretical studies are compared. Availability and amount of local composition shift is defined. Ways to improve simulation model and increase energy efficiency of cryostatting systems are determined.

The experimental results on preliminary compression of short laser pulses with initial natural frequency modulation in cholesteric liquid crystals are presented for the first time. The theory of these phenomena is developed in a nonstationary dynamic diffraction approach of the light pulses on a spatially periodic structure under condition of Bragg resonance. Such a type of autonomous compact compressor without any additional optical element is large-aperture (the whole laser beam is transformed), universal (operates at any weak power) and has at the same time a high breaking-down intensity (not less than 2 GW/cm2). They are very useful as universal optical laser technique elements.

1. The numerical experiment showed that a cable conveyor of the given design satisfies medical requirements with respect to the accuracy of forming the therapeutic dose, since the error of setting the source in position does not exceed the permissible limit.

This chapter is mainly devoted to studying those properties of Banach lattices and operators on them whose description requires the vector lattice structure as well as the pure Banach space structure. In particular, we study the properties of the operators acting between vector lattices and remaining to be order bounded under multiplication by arbitrary Banach endomorphisms in these lattices. In spite of being natural, such classes of operators have attracted very little attention of mathematicians. At present, the theory of p-absolutely summing operators plays a key role in solving the arising problems; in Sections 3.1–3.3 and 3.5, we briefly expose those results of the theory which are most important for us. The reader interested in a more complete presentation of the theory will refer to the monographs [42, 32, 45] and the articles [20, 22, 39].

The character of the relationship between the coefficient of plasticity of a ferrite powder and its specific surface is determined by the particle shape and size of the powder. Because of this, such curves can be employed for undirectly assessing the morphological characteristics of ferrite powders. The addition of polyvinyl alcohol has been found to have a marked deleterious effect on the plasticity of ferrite powders. The character of the relationship between the coefficient of plasticity of a ferrite powder and its water content has been established. Stability of water content is shown to be an important factor, ensuring high quality of compacts, minimizing waste due to cracking, and decreasing the rate of wear of die sets.

It is shown that a Banach space X with the Orlicz property is isomorphic to a Hilbert space if and only if in the class C2(X) of twice continuously Frechet differentiable functions one can find a nonzero function with a bounded support.

The effect of an external heavy atom on the EPR spectra of radicals in homogeneous liquid solutions was investigated. Broadening of the lines in the EPR spectrum of the fluorescein semiquinone radical in water-ethanol solution was found under the effect of the external heavy atom. It was hypothesized that this broadening is due to an increase in the anisotropy of the g-factor due to potentiation of the spinorbital interaction on contact with the external heavy atom.

The thermoelastic residual stresses in anisotropic rings and cylinders with characteristics that vary over the thickness are determined. The calculation of the stresses in wound glass-reinforced plastic parts is illustrated by examples.

The elastic constants and thermal expansion coefficients of a composite consisting of a matrix with low elastic properties and exceptionally stiff fibers have been experimentally determined. The curvature of the reinforcement in the specimens has been investigated. The results of the experiments are compared with the corresponding theoretical characteristics. The calculations are based on a model with an ideal arrangement of the fibers [4] and a model that takes the curvature of the reinforcement into account [5, 6].

A thermocouple with welded electrodes possesses a considerable thermal inertia. Thermocouples without junctions are virtually inertialess and are capable of measuring rapidly changing temperatures on the surfaces of solid conducting bodies.