Application of R-Functions Theory to Study Parametric Vibrations and Dynamical Stability of Laminated Plates

The problem of nonlinear parametric vibrations and stability analysis of the symmetric laminated plates is considered. The proposed method is based on multimode approximation of displacements and solving series auxiliary linear tasks. The main feature of the work is the application of the R-functions theory, which allows investigating parametric vibrations of plates with complex shape and different boundary conditions

Stability investigation of nonlinear vibrations of plates by R-functions method

The parametric vibrations of plates with cutouts subjected to in-plane periodic and compressive loads, are studied. The proposed approach is based on R-functions method and the classical variational approach. The influence of cutouts parameters, as well as static factors of load on stability regions and nonlinear vibrations are investigated

Investigation of the parametric vibration of the orthotropic plates subjected to periodic in plane forces by multi-modal approximation and R-functions method

The original method of studying parametric vibrations of orthotropic plate with complex shape is proposed. Suggested approach is based on combined application of variational methods and the R-functions theory. Using the proposed method and developed software the regular and chaotic regimes of T-shaped plate are analyzed

Investigation of the Parametric Vibrations of Laminated Plates by RFM

The R-functions theory is applied to study free vibration and dynamic instability of the symmetrically laminated plates subjected to combined static and periodic axial forces. It is assumed that subcritical state of the plate may be inhomogeneous. Theoretical formulation is made on the classical plate theory (CTP). The developed approach is based on combined application of Ritz’s method, Galerkin procedure, R-functions theory and Bolotin’s method. The buckling, instability zones and response curves for laminated plate with different external cutouts are presented and discussed. Effects of plate geometrical parameters, parking of layers, mechanical characteristics of the material on buckling, natural frequencies and parametric resonance are also studied

Dynamical instability of laminated plates with external cutout

A method to study dynamical instability and non-linear parametric vibrations of symmetrically laminated plates of complex shapes and having different cutouts is proposed. The first-order shear deformation theory (FSDT) and the classical plate theory (CPT) are used to formulate a mathematical statement of the given problem. The presence of cutoutses sentially complicates the solution of buckling problem, since the stress field is non-uniform. At first, a plane stress analysis is carried out using the variational Ritz method and the R-functions theory. The obtained results are applied to investigate buckling and parametric vibrations of laminated plates. The developed method uses the R-functions theory, and it may be directly employed to study laminated plates of arbitrary forms and different boundary conditions. Besides, the proposed method is numerical-analytical, what greatly facilitates a solution of similar-like non-linear problems. In order to show the advantage of the developed approach, instability zones and response curves for the layered cross- and angle-ply plates with external cutouts are constructed and discussed

Stochastic theory of ferroelectric domain structure formation dominated by quenched disorder

A self-consistent stochastic model of domain structure formation in a uniaxial ferroelectric, quenched from a high-temperature paraelectric phase to a low-temperature ferroelectric phase, is developed with an account of the applied electric field and the feedback effect via local depolarization fields. Both polarization and field components are considered as Gauss random variables. A system of integro-differential equations for correlation functions of all involved variables is derived and solved analytically and numerically. Phase diagram in terms of the average value and dispersion of polarization reveals different possible equilibrium states and available final single-domain and multi-domain states. The time-dependent evolution of the average polarization and dispersion discloses a bifurcation behavior and the temperature-dependent value of the electric field, deciding between the single-domain and multi-domain final states, which can be interpreted as the coercive field. Analytical and numerical results for the time-dependent correlation length and correlation functions exhibit plausible agreement with available experimental data.Comment: 33 pages, 10 figure

A study on the thermodynamic changes in the mixture of polypropylene (PP) with varying contents of technological and post-user recyclates for sustainable nanocomposites

The use of recycled materials can address some of the issues associated with the cost and environmental implications of non-renewable materials. So the prime aim of this work was to determine the thermodynamic changes in the polypropylene (PP) mixtures depending on the percentage amount of different origin recyclates for sustainable nanocomposites. In this study, different polypropylene mixtures with the addition of PP recyclates from a selective waste collection system and in-plant recycling system have been subjected to detailed analysis. It was obvious that recyclates from technological waste were of higher quality than post-user recyclates obtained from a selective waste collection system. The influence of the source of the recyclates on the different properties of the processed materials has been studied in detail. The content of the repeatedly processed material in the technological recyclates was found to explain the unexpected influence of the recyclates content on the properties of the final product. A mathematical model was also formulated to calculate the content of the material with certain amount of recirculations in the in-plant recycling system since no analyses concerning the content of the repeatedly processed material in the technological recyclates added to the original material were found in the literature

METABOLITHOTROPIC ASPECTS OF CARDIOPROTECTIVE ACTION OF NEW COMBINED MEDICINE BASED ON L-ARGININE AND THIOTRIAZOLIN AT MODELING OF MYOCARDIAL INFARCTION

  Objectives: The actual problem of modern medicine is the development of medications in treatment of cardiovascular system diseases. Different combinations of L-arginine with thiotriazolin in acute myocardial ischemia were examined as part of study and the optimal combination has been established - 4:1, named Argitryl.†The aim is to study the antioxidant, energotropic, and nitric oxide (NO)-modulating mechanisms of the cardioprotective effects of L-arginine with thiotriazolin (4:1) (Argitryl) drug candidate compared to 4.2% solution for injections Tivortin†(TOV Yuriya-Farm,†Ukraine) on the model of pituitrin-isadrin infarction of myocardium in laboratory rats.Methods: The study was conducted in accordance with Guidelines of State Expert Center of the Ministry of Health of Ukraine. All manipulations were carried out in accordance with the European Convention for the protection of vertebrate animals used for experimental and other scientific purposes.†The experiments were performed on 40 white outbred rats weighing 170–180 g. The antioxidant activity of the drugs was assessed by reduction of biochemical marker oxidative stress and an increase in the activity of the antioxidant system of the myocardium.Results: The study of energy metabolism has shown that the modeling of myocardial infarction leads to typical ischemic injuries - decrease in ATP, discoordination of the Krebs cycle, activation of anaerobic glycolysis in the cytosolic fraction of the heart of rats from the control group. Administration of Tivortin to animals does not lead to a significant decrease in ischemic injuries in the energy metabolism of the myocardium. The brightest anti-ischemic effect was observed with the appointment of Argitryl.â€Conclusion: The ascertained braking reaction of oxidative stress compared to the control group was found as a result of administration of Argitryl and Tivortin to animals with pituitrin-isadrin myocardial infarction. It was also found that the administration of Argitryl and Tivortin has a positive effect on the indices of the energy metabolism of the ischemic myocardium and leads to the normalization in conjugated NO system/renewed thiols. Argitryl significantly exceeds Tivortin on the influence of antioxidant, energy-tropic, and NO-modulating mechanisms of cardioprotective and anti-ischemic action on the studied indicatorsÂ