The influence of geometric (length, diameter and wall thickness of a unit equivalent channel of the nozzle), thermophysical (density and heat capacity of the nozzle material) and operating parameters (air flow through the regenerator and the time of one stage of accumulation / regeneration of thermal energy) on the thermal efficiency of stationary switching regenerative heat exchangers was studied . It was revealed that by varying the length and diameter of the channel and air flow, it is possible to increase thermal efficiency up to 10%. It was found that the wall thickness of a single channel, the density and heat capacity of the material of the nozzle, as well as the time of one stage, slightly aff ect the thermal efficiency of the regenerative heat exchanger.

The paper describes the problem of the reliability analysis for individual reinforced concrete (RC) beams by the rebar strength criterion in cross section with a normal crack. It is proposed to evaluate the stress in the rebar by measurements of the crack width at the level of the rebar using the functional dependence of the crack width and the strain (deformation) in the reinforcement. It is also proposed to replace the modulus of elasticity of steel reinforcement on the secant modulus of elasticity, taking into account the increased reinforcement strain in cross section with crack. The work considers two options of the crack width in beam: less and greater than the ultimate crack width. The reliability analysis of RC beams by the rebar strength is based on the possibility theory and fuzzy set theory by the reason of small statistical data from measurements on existing individual RC beams. The use of offered reliability analysis methods will allow preventing the failures of reinforced concrete beams and in some cases to obtain economic benefit from the possibility of further operation of RC beams with cracks, even with a crack width more than ultimate value.

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The problem of reconstruction of a vibration field in an unmeasured region of a thin cylindrical shell is considered. The forced vibrating shell of finite dimension is divided into two parts: the first part (the measurement region) is accessible for measuring any vibration characteristics while the second part (the reconstruction region) is considered as ‘‘inaccessible.’’ The problem is solved using the general approach–see the presentation by Yu. I. Bobrovnitskii at this Special Session. The vibration field of the shell was modeled by a finite sum of normal waves, amplitudes of which were determined by equating the modeling values to the data. The SVD technique was used in the inverse procedure for parameter identification. Most attention was paid to finding an appropriate method for choosing the best model of the shell which minimized the reconstruction error. For the measurement error 0.08 of the experiment conducted, the reconstruction error varied from 0.2 to 0.7 as the measurement region diminished from 0.7 to 0.3.