Analysis of spatial vibrations of piezoceramic eccentric cylindrical shells interacting with an annular fluid layer

The work is devoted to a numerical study of the behavior of vertically oriented eccentric (non-coaxial) electroelastic shells, containing a fluid in the gap between them. The solution of the problem is found in the framework of a three-dimensional formulation using the finite element method. The shells are made of the piezoelectric material polarized in the radial direction. Thin-walled structures are considered in the framework of the classical theory based on the Kirchhoff – Love hypotheses, as well as the equations of linear electroelasticity. The distribution of the electric potential through the thickness is assumed linear. The fluid is considered within the framework of a potential theory. The study of the low natural frequencies and vibration modes is carried out for different variants of the boundary conditions at the edges of the shells, the level of fluid in the gap and the eccentricity of the inner shell. The influence of the electric boundary conditions specified on the parts of the shells surfaces covered with electrodes is estimated

My contemporaries in 20^<th> century.

Original PCR screens for CD74-ROS1 translocation and BCR-ABL1 reversion (only results for 96 clones are shown for each rearrangement). (A) PCR screen on gDNA for clones harbouring CD74-ROS1 and ROS1-CD74 rearrangements. Asterisk indicates positive clone. (B) PCR screen on gDNA for clones harbouring repaired BCR and ABL1 genes. (PPTX 1609 kb

The breast cancer tumor suppressor BRCA2 promotes the specific targeting of RAD51 to single-stranded DNA

Individuals with BRCA2 mutations are predisposed to breast cancers owing to genome instability. To determine the functions of BRCA 2, the human protein was purified. It was found to bind selectively to single-stranded DNA (ssDNA), and to ssDNA in tailed duplexes and replication fork structures. Monomeric and dimeric forms of BRCA 2 were observed by EM. BRCA 2 directed the binding of RA D51 recombinase to ssDNA, reduced the binding of RA D51 to duplex DNA and stimulated RA D51-mediated DNA strand exchange. These observations provide a molecular basis for the role of BRCA 2 in the maintenance of genome stability

An aeroelastic stability of the circular cylindrical shells containing a flowing fluid

The paper is concerned with the analysis of the panel flutter of circular cylindrical shells containing an ideal compressible liquid and subjected to the external supersonic gas flow. The aerodynamic pressure is calculated based on the quasi-static aerodynamic theory. The behavior of the liquid is described in the framework of the potential theory. Using the Bubnov–Galerkin method, the corresponding wave equation together with the impermeability condition and specified boundary conditions are transformed into the system of equations. The classical shell theory based on the Kirchhoff–Love hypotheses and the principle of virtual displacements are used as the mathematical framework for the elastic structure dynamic problem. A solution to the problem is searched for by a semi-analytical version of the finite element method and involves the calculation of the complex eigenvalues of the coupled system of equations using the Muller-based iterative algorithm. The reliability of the obtained numerical solution of the aeroelastic and hydroelastic stability problem has been estimated by comparing it with the available theoretical data. For shells with different dimensions and variants of boundary conditions the numerical experiments have been performed to estimate the influence of velocity of the internal liquid flow on the value of static pressure in the unperturbed gas flow, which is taken as a variable parameter. It has been found that a growth of liquid velocity causes a change in the flutter type of stability loss. It has been shown that with increase of linear dimensions of the shell the stabilizing effect of the internal liquid flow extending the boundaries of aeroelastic stability changes to the destabilizing effect. Specific values of geometrical dimensions determining the variation in the character of dynamic behavior of the system depend on the prescribed combination of boundary conditions

Aeroelastic stability of plate interacting with a flowing fluid

The paper presents the results of a numerical study of the dynamic behavior of the deformable plate interacting both with the external supersonic gas flow and the internal fluid flow. The constitutive relations describing the behavior of ideal compressible fluid in the case of small perturbations are written in terms of the perturbation velocity potential and transformed using the Bubnov–Galerkin method. The aero- and dynamic pressures are calculated based on the quasi-static aerodynamic theory. The strains in the plate evaluated following the Timoshenko hypotheses. A mathematical formulation of the dynamic problem of elastic structure is developed using the variational principle of virtual displacements, which takes into account the work done by the inertia forces, aerodynamic and hydrodynamic pressures. Calculation of complex eigenvalues of the coupled system of two equations is performed using an algorithm based on implicitly restarted Arnoldi method. The stability criterion is based on an analysis of the complex eigenvalues of system of two equations obtained for increasing flow or gas velocity. The reliability of the obtained numerical solution has been estimated by comparing it with the available theoretical data. A few numerical examples were considered to demonstrate the existence of different types of instability depending on the velocities of fluid or gas flow, combinations of kinematic boundary conditions prescribed at the edges of the plate, and the fluid layer height. It has been found that a violation of the smoothness of the obtained relationships and diagrams of stability is caused by a change in the flutter mode, or change of the type of loss of stability

Experimental and numerical investigation of eigenfrequencies of rectangular plates, interacting with a fluid

The method of laser vibrometry was applied to investigate the vibrations of elastic plates interacting with a liquid for different variants of plate clamping. The obtained results are used to verify the developed finite-element algorithm designed to solve the problem of spatial vibrations of one or two parallel rectangular plates interacting with a quiescent viscous fluid. The results of calculations of the natural frequencies and damping decrement obtained under different boundary conditions and the height of the fluid layer are discussed. It has been demonstrated that for the configurations considered, viscosity of the liquid has a significant effect on the damping decrement, in contrast to frequencies of vibrations

Experimental and numerical investigation of eigenfrequencies of rectangular plates, interacting with a fluid

The method of laser vibrometry was applied to investigate the vibrations of elastic plates interacting with a liquid for different variants of plate clamping. The obtained results are used to verify the developed finite-element algorithm designed to solve the problem of spatial vibrations of one or two parallel rectangular plates interacting with a quiescent viscous fluid. The results of calculations of the natural frequencies and damping decrement obtained under different boundary conditions and the height of the fluid layer are discussed. It has been demonstrated that for the configurations considered, viscosity of the liquid has a significant effect on the damping decrement, in contrast to frequencies of vibrations