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The present paper is devoted to the development of the method for searching an approximate solution of non-stationary problems on a variable interval. This method was first proposed by L.I. Slepyan. Here, the field of its applicability has been expanded to systems of equations, including equations of both hyperbolic and parabolic type. We describe the procedure of such approach in detail on a number of classical partial differential equations and compare the obtained results with exact analytical solution. Also, we consider a dynamic non-coupled thermoelastic problem. The method of expansion on a variable interval allows us to estimate the material response to a thermal disturbance at a large distance from the source.

The problem of a heating source acting on a certain part of a beam surface and moving along it with given speed is solved. It is shown that the most significant role in formation of the beam deflection under loading by a compression force is played by concentrated moments occurring at the moving boundary of the heating source. It is noted that for a source speed less than some critical value, the beam deflection is essentially nonmonotonic. In this case, the largest beam bending deflection occurs when the source speed reaches a value corresponding to the Euler critical force.

Within the framework of the one-temperature model of thermoelasticity, the analysis of the effect of electon localization processes on the thermoelastic response of conductors under pulsed laser irradiation is performed. It is shown that the localization of electrons can lead to a significant tightening of the deformation processes in conductors compared with the processes that develop according to the usual thermoelastic mechanism.

Study of various wound healing methods is a relevant issue of modern veterinary medicine. One of the investigated methods of wound healing is moist wound healing in a hydrated environment using hydrogel patches. In described clinical case, an eight-year-old female American Pit Bull Terrier was subjected to mast cell tumor surgical removal on the left hindlimb. During the patient postoperative treatment, Sorbalgon®, Hydrocoll® and HydroClean® dressings were used to protect the surgical site and maintain high moist environment in the wound. The dressings absorbed wound exudate and stimulated both the surgical site cleansing and the granulation tissue formation, made it possible to heal large wound on the limb without the keloid scar development.

Antimicrobial resistance formation in various bacteria is a serious biosafety threat. In this regard, the important issue in medical and veterinary fields is not only the rational use of antibacterial drugs, but also the search for ways to significantly reduce the need for antibiotics. Three studies designed to research into these challenges are described. The results indicated that (1) the bacteriuria presences in 62.4 +/-4.1% of urine samples obtained from companion animals (the microflora count in urine samples is estimated from ’++’ to ’Entire Field-of-View’); (2) 16.3 +/-4.0% of samples from companion animals showed bacteria with low antibiotics sensitivity, and 8.1 +/-3.0% of samples contained bacteria resistant to 30 antibiotics included in the susceptibility test; (3) the Bovhyaluronidaze azoximer reduce antimicrobial therapy duration statistically significant (p=0.0089). The studies were conducted at the facilities of St. Petersburg State University of Veterinary Medicine and Bars veterinary clinic chain in St. Petersburg, Russia. A randomized clinical trial of Bovhyaluronidaze azoximer effect on course of disease and treatment duration of acute and chronic prostatitis and urocystitis, including complicated by urolithiasis, was conducted in 54 dogs. Animals were randomly assigned to intervention (n=34) and control (n=20) groups. Animals of both groups received the antimicrobial therapy. Interventional group patients additionally received Bovhyaluronidaze azoximer in the form of rectal suppositories. The antimicrobial therapy mean duration in intervention group animals took 14.88 +/-4.98 days, in control group animals — 18.65 +/-5.40 days. The study findings imply that bacteriuria is widely prevalent in companion animals and antimicrobial resistance is increasing issue in veterinary medicine. Bovhyaluronidaze azoximer contributes to microcirculation restore and increases the bioavailability of antibacterial drugs at the site of infection. This makes its relevant for use in the complex treatment for septic and inflammatory processes. This allows to reduce the antimicrobial course duration (and completely decline antibiotic therapy in some cases) and prevent the formation of chronic inflammation and infection sites.

Metal–matrix composites based on an aluminum matrix reinforced with ceramic particles are widely used as structural materials in the aerospace and automotive industries. The main problems in the manufacture are the uniformity of the distribution of particles over the volume, poor adhesion of ceramic particles to the matrix metal, and the formation of aluminum carbide at the interfaces, leading to undesirable embrittlement. We propose a new technique for the manufacture of metal–matrix composites, which consists in creating a composite material, when carbide nanostructures form a framework in the volume of an aluminum matrix, and which allows solving the above problems. A finite element model of deformation of a metal–matrix composite reinforced with carbide structures is constructed.

Loss of stability under uniaxial tension in an infinite plate with a circular inclusion made of another material is analyzed. The influence exerted by the elastic modulus of the inclusion on the critical load is examined. The minimum eigenvalue corresponding to the first critical load is found by applying the variational principle. The computations are performed in Maple and are compared with results obtained with the finite element method in ANSYS 13.1. The computations show that the instability modes are different when the inclusion is softer than the plate and when the inclusion is stiffer than the plate. As the Young’s modulus of the inclusion approaches that of the plate, the critical load increases substantially. When these moduli coincide, stability loss is not possible.

Increasing the number of dogs and cats kept in urban households makes relevant research of new effective methods of treatment of companion animals. We conducted studies of the effect of Bovhyaluronidaze azoximer on the treatment duration of suppurative wounds. The study was carried out on 42 animals (24 cats and 18 dogs) with septic processes in two groups. The animals of the both groups were given conventional therapy; in animals of the experimental group the Bovhyaluronidaze azoximer preparation was additionally included as a part of a complex therapy. The effect of the use Bovhyaluronidaze azoximer preparation was evaluated by three indicators: the wound cleansing from purulonecrotic masses duration, the duration of existence of edema, the number of managements of wound. The median wound cleansing time in the experimental group improve on 2.29 days. The median duration of existence of edema in the experimental group was in less time on 1.57 days in comparison with the control group. The median number of required managements of wound is reduced by 5.00 manipulations in the experimental group in comparison with the control group. The results of our study show that Bovhyaluronidaze azoximer can be recommended for use in the therapy of suppurative wounds.

Agriculture modernization is a topical issue for both the global and domestic economy. Intensification of livestock farming results in an increased production of manure. Recycling of manure into bedding is one of the modern utilization technologies. National regulations do not specify requirements for currently applied bedding types, including manure-based bedding. The foreign experience, however, demonstrates several economic, zootechnical and hygienic advantages of this material. The field veterinary study revealed the positive health effect of bedding. The cows housed without bedding featured threefold higher risk of surgical diseases of limbs. Technical and economic assessment of a dairy farm with 1000 dairy cows showed the following annual operating costs when the major part of manure was passively composted and a part of manure was recycled into the bedding by (1) aerobic solid-state fermentation in a chamber fermenter and finish drying in a dryer drum – 24.2 million roubles; (2) aerobic solid-state fermentation in a drum fermenter – 21.7 million roubles; and (3) thermal drying in a dryer drum – 27.5 million roubles. At the same time, if all manure produced was composted and the bedding was purchased from external sources, the costs would be 27.9 to 35.2 million roubles depending on the bedding material.

An improved method to measure the dynamic viscoelastic properties of elastomers is proposed. The method is based on the analysis of forced oscillation of a cylindrical sample loaded with an inertial mass. No special equipment or instrumentation other than the ordinary vibration measurement apparatus is required. Upper and lower surfaces of the viscoelastic material sample were bonded to a load disc and a rigid base plate, respectively. The rigid base plate was subject to forced oscillations driven by a vibration exciter. Two accelerometers were attached to monitor the displacement of the base plate and the load disc. The recorded magnitude ratio and the phase difference between the load disc and the base plate vibrations represent the axial, dynamic deformation of the sample. The data are sufficient to obtain the dynamic properties of the sample, oscillation properties of vibration exciter, whereas the sensitivity of gauges having no effect on the calculation results. For accurate calculation of the properties, a two-dimensional numerical model of cylindrical sample deformation was used. Therefore, a form factor, which takes into account the sample sizes in one-dimensional models, is not required in this method. Typical measurement of the viscoelastic properties of a silicone rubber Silastic® S2 were measured over the frequency range from 10 Hz to 3 kHz under deformations (ratio of vibration magnitude to sample thickness) from 10−4% to 5%. It was shown that the modulus of elasticity and the loss tangent fall on a single curve when the ratio of load mass to sample mass changed from 1 to 20. When the sample diameter was varied from 8 to 40 mm, the modulus of elasticity fall on the same curve, but the loss tangent curves showed some degree of scatter. Studied temperature dependence and nonlinear behavior of viscoelastic properties is found not to be associated with this effect.

Hydrogen embrittlement of materials is one of the important factors for an estimation of serviceability of designs. In spite of the fact that many works are devoted to research of hydrogen influence on properties of metals and alloys, there are enough “white” spots in this problem, in particular, the influence of kinetic processes inside a material, giving rise to hydrogen redistribution, on the basic strength characteristics at static and dynamic loading. The absence of an authentic mechanical model, whose description is based on the basic fundamental principles of rational mechanics, makes the problem rather actual, since, inherently, the presence of such a model would allow to describe the influence of internal kinetics on the macroparameters of a material, which is today extremely important in view of the huge amount of hypotheses which are ready to confirm only special experiments and do not allow to use them in other cases. The present work offers a model based on experimental data on the decrease in break energy of internuclear bonds at landing particles of hydrogen, i.e., the decrease in a level of the free energy. The offered model allows to explain the localization of hydrogen in the field of the increased concentration of stresses and change of material properties.

Over the past forty years intensive investigations into the use of compliant surfaces have been undertaken, both theoretically and experimentally, in order to obtain turbulent drag reduction in boundary–layer flows. Although positive results were found in some of the studies, none of these had been successfully validated by independent researchers. In this paper the results are reported of a recent investigation carried out by the authors to verify the experimental results of Semenov in 1991 and Kulik and co–workers in 1991, who successfully demonstrated the ability of compliant surfaces to reduce the skin–friction drag and surface–flow noise in a turbulent boundary layer. A strain–gauge force balance was used in the present study to directly measure the turbulent skin–friction drag of a slender body of revolution in a water tunnel. Changes in the structure of turbulent boundary layer over a compliant surface in comparison with that over a rigid surface were also examined. The results clearly demonstrate that the turbulent skin friction is reduced for one of the two compliant coatings tested, indicating a drag reduction of up to 7 per cent within the entire speed range of the tests. The intensities of skin–friction and wall–pressure fluctuations measured immediately downstream from the compliant coating show reductions in the intensities of up to 7 and 19 per cent, respectively. The results also indicate reductions in turbulence intensity by up to 5 per cent across almost the entire boundary layer. Furthermore, an upwards shift of the logarithmic velocity profile is also evident indicating that the thickness of the viscous sublayer is increased as a result of turbulent drag reduction due to the compliant coating. It is considered that the results of the present experimental investigation convincingly demonstrate for the first time since the earlier work in Russia (by Semenov and Kulik) that a compliant surface can indeed produce turbulent drag reduction in boundary–layer flows.

In modern constructions, thin-layer coats are often used as protecting or strengthening elements. Deformations of such constructions may cause significant stresses on the interface between the base and the coat because of the difference in their physical mechanical properties, which leads to the destruction or detachment of the cover. The impact of static or shock loads on the emergence and development of delamination in multilayer constructions has been studied fairly well, but much less is known about destructions of this type under nonstationary (vibrational) loads. The interest in the latter is caused by the fact that even small variable actions may cause the localization of oscillations in a neighborhood of inhomogeneities (such as inclusions, defects, construction elements, etc.) [1] (and lead to the emergence and growth of defects, which strongly affects the reliability and functionality of the whole construction. The possibility of the localization of oscillations near initial delamination and the impact of localization on the growth of the delamination are studied and a model for analyzing conditions under which a detachment zone grows or ceases to grow is suggested. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Information is given on the change in turbulent friction and pressure pulsations on a wall with the application of single-layer monolithic coatings. The viscoelastic properties of the materials used are characterized.

The boundary region of a turbulent boundary layer contributes greatly to the drag. Intense turbulence is generated in this region. Below we investigate the interaction of an elastic boundary with a viscous sublayer for a decrease in the Reynolds stresses, and for a corresponding decrease in the drag. It does not seem possible to investigate the general case. Therefore, the problem is solved within the framework of the limitations made by Sternberg [1] for the theory of a viscous sublayer in a turbulent flow near a solid smooth wall.

An experimental study of the hydrodynamic drag of the dolphin is reported. The results are compared with calculations for the steady-state motion of a similar rigid model, and previously reported data on the hydrodynamic drag of the dolphin are refined. The drag turns out to be much less than the calculated drag, even when the initial laminar region is taken into account. Several conclusions can be drawn from the results: 1) The experimental results show quite reliably that hydrodynamically the dolphin is in fact a unique phenomenon. 2) The phenomenon is explained in terms of Gray's paradox for the dolphin. 3) The mechanism by which the dolphin's drag is reduced is apparently controllable. 4) Flow around the dolphin can be assumed to be laminar undetached flow.