Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil...     

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Convective heat transfer in laser-irradiated graphite

The gas dynamic and thermal processes developing near the surface of graphite after exposure to a 20-nsec laser pulse with an energy E- 0.1–1 J and a wavelength of 0.6943 m are investigated experimentally and by mathematical modeling. The times required for the shock wave to degenerate into an acoustic wave are also considered. Typical density profiles over the axial section of the inhomogeneity are presented for various moments of time. It is noted that the rate of ascent of the thermal inhomogeneity is much higher than the free convection velocity. The convective heat-transfer processes are studied in detail through numerical solution of the system of two-dimensional Navier-Stokes equations. The results of the calculations are in satisfactory agreement with the experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 180–182, May–June, 1989.     

Modeling of the low-temperature production of gas-sensitive tin oxide films

The deposition of tin oxide films by reactive sputtering of a stoichiometric target is investigated. Conditions are determined for the formation of a crystal layer structure and the acquisition of gas sensitivity without subsequent high-temperature annealing. Zh. Tekh. Fiz. 69, 112–113 (April 1999)     

Domain wall dynamics in a double-layer uniaxial magnetic film with different magnetic anisotropy in the layers

Motion of an isolated domain wall in a double-layered magnetic film is investigated through solving the Slonczewski equations by a numerical method for the same gyromagnetic ratio and different anisotropy constants in the layers. Dependences of the threshold field and the limiting velocity of disruption of the steady state motion of the film on the magnetic anisotropy constant in one of the layers are obtained. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 3–7, August, 2007.     

A New Approach to Increasing the Resolution of a Mass Spectrometer with Wedge-Shaped Reflectors

The paper describes the investigation of the ion-optical properties of a laser TOF mass spectrometer including two successively positioned wedge-shaped ion mirrors. Some specific properties of the configuration of ion trajectories near their reflection in the second ion reflector are found. The dependence of aberrations on ion energy acquired toothed shape for the resolution of the analyzer higher than 3000–5000. The approximation of the dependence gave a 15^th degree polynomial. The calculation of polynomial coefficients showed a great contribution to the duration of ion packets for aberrations of higher order. The discovered features allowed us to suggest a way of the local correction of nearby trajectories in the total ion flux. By correcting the local motion of individual groups of ions, we could reduce temporary aberration to 1–1.6 ns, depending on ion energy. For the time of ion flight ~35 μs, such duration limits the resolution of the analyzer by a value not less than 10000. The real length of ion drift path was about 30 cm. The total overall sizes of the ionoptical system were ~24 × 19 × 5 cm.     

Mass-spectrometric elemental analysis of solid substances in Russia

The review surveys the achievements of Russian scientists in mass-spectrometric analysis made in the past decade. Attention is focused on direct and indirect methods for the elemental analysis of solid and powdered materials. Among them are mass-spectrometric elemental analysis techniques with spark, laser, glow discharge, and inductively coupled plasma ionization. The applications of the above techniques to various areas of science, technology, and industry are described, in particular, the elemental analysis of nuclear technology materials, the determination of trace impurities in high-purity substances, some applications in medicine, biology, ecology, and basic research. Some achievements in the mass-spectrometric technique for the determination of the elemental composition of solid and powdered materials are considered. Some characteristics of methods are given: the range of the analyzed elements, errors in the determination of concentrations, and the limit of detection.