The ultrastructural characteristics of the changes in the rat liver in the dynamics of experimental endotoxemia

Electron microscopic study was performed in the experiments on the rat liver while intravenously administering E. coli endotoxin. The dynamics of ultrastructural disorders during endotoxemia has been established and the role of "Kupffer cell-hepatocyte" microsystem in the liver detoxification function is shown.     

On quantitative a priori measures of identifiability of coefficients of linear dynamic systems

A number of quantitative a priori measures of identifiability of coefficients of linear dynamic control systems are proposed. The criteria are based on numerical characteristics of the lower bound of the asymptotic variance of estimates of the coefficients, which is approximately calculated using the mean value of the inverse information matrix. Information matrices are calculated in the limit case of small noise amplitude. Additive observation noise is considered. In this case, the optimal estimates of coefficients correspond to the smallest distance between observations of trajectories and the solution set of the system. Numerical examples are given.     

Estimation of trends and identification of time series dynamics in short observation sections

Formulas for estimating the trend of a time series by measurements of readings of the summarized “series plus trend” process with additive random disturbances in measurements have been proposed. The series and trend dynamics is described by linear difference equations of a given order. The estimation is based on ensemble measurements of short sections of the summarized process (not longer than transient characteristics). Methods for identifying the parameters of equations and series and trend processes on measurements of the summarized process have been proposed. Applications to the analysis of control systems have been considered.     

Compression resistance and hysteresis of carbon fibre tows with grown carbon nanotubes/nanofibres

Growth of carbon nanotubes (CNT) or carbon nano-fibres (CNF) on fibrous substrates is a way to increase the fracture toughness of fibre reinforced composites (FRC), with encouraging results reported in the recent years. The issues for these materials related to manufacturing of these composites are, however, less investigated. Following the study of compressibility of woven carbon fibre preforms with CNT/CNFs grown on the fibres using the CVD method [Compos Sci Technol 2011; 71(3): 315-325], this paper describes compression tests on the carbon tows used in these fabrics. The results of the measurements include pressure vs. thickness diagrams in consecutive compression cycles and hysteresis of the compression. The results confirm a drastic change of compressibility of fibrous assemblies in the presence of CNT/CNF grafting.     

Electrically and magnetically induced transfer of solvated ions in an isolated solution of salt in a polar dielectric

Solutions of metal salts in liquid polar dielectrics were considered in the approximation of a single ion placed in a system of liquid polar dielectric molecules and a system of interacting charged particles, such as cations, anions, and polarized liquid polar dielectric molecules, arranged around them. The sizes of the solvated ion clusters were estimated in the approximation of a single ion and in the approximation of the existence of a self-consistent field in the solution volume. The characteristic frequencies of the external electric field were determined so that, being imposed on an aqueous salt solution, it produces the effect of the induced transfer of solvated ions. The behavior of the solutions under the action of external asymmetric electrical and alternating magnetic fields was analyzed.     

Compressibility of carbon woven fabrics with carbon nanotubes/nanofibres grown on the fibres

Growth of carbon nanotubes (CNT) or carbon nano-fibres (CNF) on carbon fibrous substrates is a way to increase the fracture toughness of fibre reinforced composites (FRC), with encouraging results reported in the recent years. If these nano-engineered FRC (nFRC) are destined to leave laboratories and enter industrial-scale production, a question of adapting the existing composite manufacturing methods will arise. The paper studies compressibility of woven carbon fibre performs (two types of fabrics) with CNT/CNF grown on the fibres using the CVD method. The results include pressure vs thickness and pressure vs fibre volume fraction diagrams for one and four layers of the fabric. Morphology of the nFRC is studied with SEM. It is shown that the pressure needed to achieve the target fibre volume fraction of the preform increases drastically (for example, from 0.05 MPa to more than 0.5 MPa for a fibre volume fraction of 52%) when CNT/CNF are grown on it. No change in nesting of the fabric plies is noticed. The poor compressibility can lower the achievable fibre volume fraction in composite for economical vacuum assisted light-RTM techniques and increase the pressure requirements in autoclave processing.     

A model for the compression of a random assembly of carbon nanotubes

A model for calculation of the compression resistance of a random assembly of carbon nanotubes (CNTs) is proposed. The model is based on the theory of geometry and compression of fibrous materials with randomly oriented fibres. It accounts for the orientation distribution and volume fraction of CNTs in the assembly, the bending rigidity of a CNT and its decrease after onset of buckling and for friction and slippage between CNTs. The model also allows for calculation the number of contacts between CNTs in the assembly and of the percolation threshold. The predicted compression resistance is compared with experimental data on compression of “buckydisks” made of CNTs.     

Permeability prediction for the meso–macro coupling in the simulation of the impregnation stage of Resin Transfer Moulding

The impregnation stage of the Resin Transfer Moulding process can be simulated by solving the Darcy equations on a mould model, with a ‘macro-scale’ finite element method. For every element, a local ‘meso-scale’ permeability must be determined, taking into account the local deformation of the textile reinforcement. This paper demonstrates that the meso-scale permeability can be computed efficiently and accurately by using meso-scale simulation tools. We discuss the speed and accuracy requirements dictated by the macro-scale simulations. We show that these requirements can be achieved for two meso-scale simulators, coupled with a geometrical textile reinforcement modeller. The first solver is based on a finite difference discretisation of the Stokes equations, the second uses an approximate model, based on a 2D simulation of the flow.     

Stress distribution in outer and inner plies of textile laminates and novel boundary conditions for unit cell analysis

The local stress–strain distribution in a unit cell of a textile laminate depends on the distance of the ply to the surface, the number of plies in the laminate, and the stacking sequence. A conventional meso FE analysis employs boundary conditions for a unit cell of the textile composite based on the assumption of periodicity in the thickness direction. In that case, the stress concentration can be drastically underestimated, especially in outer plies. This paper describes the interaction of plies, local stresses and displacements. To avoid the analysis of the whole laminate and to reduce it to the boundary value problem on one unit cell only, novel boundary conditions are introduced. These conditions are based on the analysis of a single unit cell: they account for the number of the plies in the laminate, distinguish between the outer and inner plies, and reproduce the meso stress–strain state with good precision.