Modeling of radiative - conductive heat transfer in compositing materials

A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity

Peculiarities of phonon spectra and lattice heat capacity in Ir and Rh

A simple pseudopotential model is proposed, which allows the phonon spectra and temperature dependence of the lattice heat capacity of Ir and Rh be described with a high enough accuracy. A careful comparison of the calculated and experimental values of the lattice heat capacity is carried out, with the procedure of the identification of the phonon contribution to the heat capacity and determination of the characteristics (momenta) of the phonon density of states from the experimental values of the total heat capacity of metal at a constant pressure being described in detail. The results of the theoretical calculations explain, in particular, such peculiar feature of Ir and Rh, unusual for cubic metals, as a sharp (more than by a factor of 1.5) decrease in the effective Debye temperature with increasing termperature. The temperature dependence of the mean square amplitude of atomic displacements in Ir and Rh has been calculated. Basing on the band calculations the manifestation of the Kohn singularities in the phonon spectra of Ir are discussed.Comment: 15 pages, LaTeX2e, 12 figures in postscrip

Peculiarities of anharmonic lattice dynamics and thermodynamics of alkaline-earth metals

The calculations are performed for a broad range of the properties of Ca and Sr in the fcc and bcc phases. A detailed information on the magnitude and character of temperature dependence of anharmonic effects in the lattice dynamics over the entire Brillouin zone (frequency shifts and phonon damping, Gruneisen parameters) is given. A detailed comparison of the computational results for the heat capacity and thermal expansion with the experimental data is carried out; the theoretical results are in good agreement with the experiment.Comment: 16 pages, 19 Postscript figures, Revte

Close Packing of Atoms, Geometric Frustration and the Formation of Heterogeneous States in Crystals

To describe structural peculiarities in inhomogeneous media caused by the tendency to the close packing of atoms a formalism based on the using of the Riemann geometry methods (which were successfully applied lately to the description of structures of quasicrystals and glasses) is developed. Basing on this formalism we find in particular the criterion of stability of precipitates of the Frank-Kasper phases in metallic systems. The nature of the ''rhenium effect'' in W-Re alloys is discussed.Comment: 14 pages, RevTex, 2 PostScript figure

The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten

Several transition metals were examined to evaluate their potential for improving the ductility of tungsten. The dislocation core structure and Peierls stress and barrier of $1/2$ screw dislocations in binary tungsten-transition metal alloys (W$_{1-x}$TM$_{x}$) were investigated using first principles electronic structure calculations. The periodic quadrupole approach was applied to model the structure of $1/2$ dislocation. Alloying with transition metals was modeled using the virtual crystal approximation and the applicability of this approach was assessed by calculating the equilibrium lattice parameter and elastic constants of the tungsten alloys. Reasonable agreement was obtained with experimental data and with results obtained from the conventional supercell approach. Increasing the concentration of a transition metal from the VIIIA group, i.e. the elements in columns headed by Fe, Co and Ni, leads to reduction of the $C^\prime$ elastic constant and increase of elastic anisotropy A=$C_{44}/C^\prime$. Alloying W with a group VIIIA transition metal changes the structure of the dislocation core from symmetric to asymmetric, similar to results obtained for W$_{1-x}$Re$_{x}$ alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503 (2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry, the values of the Peierls stress and barrier are reduced. The latter effect could lead to increased ductility in a tungsten-based alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any of the transition metals from the VIIIA group should have similar effect as alloying with Re.Comment: 12 pages, 8 figures, 3 table

Modeling of radiative - conductive heat transfer in compositing materials

A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity

Fermi liquid theory of electronic topological transitions and screening anomalies in metals

General expressions for the contributions of the Van Hove singularity (VHS)in the electron density of states to the thermodynamic potential $\Omega are obtained in the framework of microscopic Fermi liquid theory. The renormalization of the singularities in$\Omega connected with the Lifshitz electronic topological transition (ETT) is found. Screening anomalies due to virtual transitions between VHS and the Fermi level are considered. It is shown that, in contrast with the one-particle picture of ETT, the singularities in $\Omega turns out to be two-sided for interacting electrons.Comment: 8 pages RevTeX, with minor corrections (Introduction and Conclusions are rewritten, new references are added), to appear in Physical review

Use of the technique of physiotherapy exercises after operative measures on the backbone including with use of metalwork

According to WHO data the degenerative dystrophic diseases of a backbone(DDDB) occur in 80% of the population and make up to 90% of all cases of chronic diseases [2,6,9,12,13,27]. Disks and meniskoida, bodies of vertebras, own mioligamentamy device of a backbone and its joints are exposed to degenerative dystrophic process. Owing to irritation of nervous structures of a backbone there are difficult neuroreflex not radicular syndromes wilh tonic, neirodystrophic, vegetovascular frustration [19,22,23]. Now in treatment of this pathology a certain progress due to introduction in clinical practice of new technologies and performance of minimum invasive operative measures is noted. However expeditious treatment of hernias, even at good short-term results, does not exclude preservation of neurodystrophic changes and also a disease recurrence as eliminates only a mechanical compression factor [5,8,10,27].The research objective consisted in development of a complex medical physical culture for patients with degenerative dystrophic diseases of lumbosacral department of a backbone after operative measures on a backbone including with use of metalwork.По данным ВОЗ дегенеративно-дистрофические заболевания позвоночника (ДДЗП) встречаются у 80 % населения и составляют до 90 % всех случаев хронических заболеваний [2,6,9,12,13,27]. Дегенеративно-дистрофическому процессу подвергаются диски и менискоиды, тела позвонков, собственный миолигамектарный аппарат позвоночника и его суставы. Вследствие раздражения нервных структур позвоночника возникают сложные нейрорефлекторные не корешковые синдромы с тоническими, нейродистрофическими, вегетативно-сосудистыми расстройствами [19,22,23]. В настоящее время в лечении данной патологии отмечается определенный прогресс за счет внедрения в клиническую практику новых технологий и выполнения минимально инвазивных оперативных вмешательств. Однако оперативное лечение грыж, даже при хороших непосредственных результатах, не исключает сохранения нейродистрофических изменений, а также рецидивов заболевания, так как устраняет только механический компрессионный фактор [5,8,10,27]. Цель исследования состояла в разработке комплекса лечебной физкультура для пациентов с дегенеративно-дистрофическим заболеваниями пояснично-крестцового отдела позвоночника после оперативных вмешательств на позвоночнике в том числе с применением металлоконструкций