A novel application of atomic force microscope to identify the Ag and I planes of β-AgI single crystals

 Atomic Force Microscopy is used to determine the crystallographic polarity of the surfaces of β-AgI single crystals. The studies reveal that the hexagonal packed Ag⁺ plane is the (001) and the I^– plane is the (001–). This observation is also consistent with the earlier x-ray diffraction measurements and chemical etching techniques as well as the polarizability and electronegativity of the ions. Received: 27 October 1997/Accepted: 28 October 1997     

New applications of photostrictive ferroics

 Photostriction in ferroelectrics arises from a superposition of photovoltaic and inverse piezoelectric effects. (Pb,La)(Zr,Ti)O₃ ceramics doped with WO₃ exhibit large photostriction under irradiation of near-ultraviolet light, and are applicable to remote control actuators and photoacoustic devices. Using a bimorph configuration, a photo-driven relay and a micro walking device have been developed, which are designed to start moving as a result from the irradiation, having neither electric lead wires nor electric circuits. The mechanical resonance of the bimorph was also induced by an intermittent illumination of purple-color light; this verified the feasibility of applying photostriction for ”photophone” applications. Received: 10 September 1997/Accepted: 9 October 1997     

Concept of low-entropy compression as applied to the development of chemically clean hypersonic wind tunnels

An analysis of the thermodynamic constraints on the possible development of chemically clean hypersonic wind tunnels (in which the air temperature remains below the oxidation temperature of nitrogen) yields the conclusion that the acceleration of the gas stream before entering the supersonic nozzle in these wind tunnels should be nonsteady-state. Thermodynamically ideal parameters are determined for this system and technical solutions are proposed. Pis’ma Zh. Tekh. Fiz. 23, 21–25 (October 12, 1997)     

An Efficient Algebraic Algorithm for the Geometric Completion to Involution

 We describe an adaption of a differential algebraic completion algorithm for linear systems of partial differential equations that allows us to deduce intrinsic differential geometric information like the number of prolongations and projections needed for the completion. This new hybrid algorithm represents a much more efficient realisation of the classical Cartan–Kuranishi completion than previous purely geometric ones. A classical problem in geometric completion theory is the existence of δ-singular coordinate systems in which the algorithms do not terminate. We develop a new and a very simple criterion for δ-singularity based on a comparison of the Janet and the Pommaret division. This criterion can also be used for the direct construction of δ-regular coordinates. Received: July 28, 2000; revised version: October 16, 2001     

Sculptured thin films – I. Concepts

 A report on the conceptualization of sculptured thin films (STFs), as well as on recent theoretical advances thereon, is presented. The morphology of a STF is described in terms of a spatially varying unit vector called the director, whose piecewise specification assists in setting up frequency-dependent constitutive relations of the STF. These relations lead in turn to a 4×4 matrix differential equation for the propagation of electromagnetic waves in the STF. Optical, suboptical, infrared and even millimeter-wave applications are possible, as well as acoustic and piezoelectric ones. Received: 12 September 1997 / Accepted: 15 October 1997     

Fabrication of BaTiO3/Cu composite by reducing Cu2O under nitrogen atmosphere

BaTiO₃–Cu ferroelectric/metal composite was successfully fabricated by sintering Cu₂O-added BaTiO₃ pellet under nitrogen gas flow. In the results of XRD analysis of the sintered body, it was found that cuprous oxide was reduced to copper in the atmosphere of 100 ml/min nitrogen gas flow, but was not reduced and remained as itself in air. Lattice parameter changes of the specimens sintered at 1280 °C in 100 ml/min nitrogen gas flow indicated that solubility limit of cuprous oxide (Cu₂O) into BaTiO₃ is thought to be less than 1 wt%. The melt from cuprous oxide is thought as a good sintering aid to densify BaTiO₃. In this experiment, we determined the optimum sintering condition to get BaTiO₃–Cu ferroelectric/metal composite with more than 95% of relative density. From the results of DTA and TG analysis, cuprous oxide is considered to dissociate into copper and oxygen gas and form the eutectic melt of BaTiO₃–Cu at around 900 °C in more than 50 ml/min nitrogen flow rate atmosphere. Received: 29 October 2001 / Reviewed/Accepted: 3 November 2001     

Breakup of a highly charged bubble in a dielectric liquid into parts of comparable size

An analysis is made of the conditions for instability of a charged gas bubble in a dielectric liquid. It is shown that unlike a charged droplet, the criterion for instability of a bubble is determined by two dimensionless parameters: the Rayleigh parameter and the ratio of the gas pressure in the parent bubble to the Laplace pressure. Pis’ma Zh. Tekh. Fiz. 23, 60–65 (October 12, 1997)     

A Multiscale/stabilized Formulation of the Incompressible Navier–Stokes Equations for Moving Boundary Flows and Fluid–structure Interaction

This paper presents a multiscale/stabilized finite element formulation for the incompressible Navier–Stokes equations written in an Arbitrary Lagrangian–Eulerian (ALE) frame to model flow problems that involve moving and deforming meshes. The new formulation is derived based on the variational multiscale method proposed by Hughes (Comput Methods Appl Mech Eng 127:387–401, 1995) and employed in Masud and Khurram in (Comput Methods Appl Mech Eng 193:1997–2018, 2006); Masud and Khurram in (Comput Methods Appl Mech Eng 195:1750–1777, 2006) to study advection dominated transport phenomena. A significant feature of the formulation is that the structure of the stabilization terms and the definition of the stabilization tensor appear naturally via the solution of the sub-grid scale problem. A mesh moving technique is integrated in this formulation to accommodate the motion and deformation of the computational grid, and to map the moving boundaries in a rational way. Some benchmark problems are shown, and simulations of an elastic beam undergoing large amplitude periodic oscillations in a viscous fluid domain are presented.     

Damages to conic specimens of titanium and aluminum alloys under impact loading

We present the results of experimental determination of the character of damage to specimens having the shape of truncated cones made of titanium VT14 and aluminum AMg6 alloys under impact loading and perform a numerical analysis of longitudinal stresses at the sites of formation of rear cleavage cracks. Translated from Problemy Prochnosti, No. 5, pp. 110–112, September–October, 1997.     

Fiber-optic detector using a mid-infrared diode laser and an acoustooptic modulator

Data are given for an infrared detector based on a semiconductor injection laser, which operates at a wavelength of 3.3 μm and is coupled by a chalcogenide optical fiber to an acoustooptic modulator made from an amorphous Si-Te alloy. The beam modulation coefficient reaches 70% for a pulse duration ≳0.3 μs, making the detector well suited to gas-analysis applications. Pis’ma Zh. Tekh. Fiz. 23, 14–18 (October 26, 1997)     

On the Number of Special Permutation-Invariant Orbits and Terms

 This note presents a lower and an upper bound for the cardinality of the set of special permutation-invariant orbits and a formula for the number of special terms. Received: August 24, 1994; revised version: October 17, 1996/March 21, 1997     

Characteristics of a submicrosecond transverse discharge in mixtures of helium with N2 and CO molecules and xenon atoms

An investigation is made of the electrical and optical characteristics of a moderate-pressure transverse discharge in typical active media of infrared CO lasers. The discharge was ignited in a system of unprofiled “ grid-plane” electrodes with automatic ultraviolet preionization by a corona discharge and had a 2×3 cm aperture. The pulse repetition frequency was 1–10 Hz, the current pulse length was ≤0.5 μs, and the pressure of the working mixtures was 10–100 kPa. Studies were made of the transverse discharge current voltage pulses, and also the spectral and temporal characteristics of the plasma radiation in N₂:CO, He:N₂:CO, and He: N₂:CO:Xe mixtures in the ultraviolet and visible ranges. Pis’ma Zh. Tekh. Fiz. 23, 71–76 (October 12, 1997)     

Production of a functionally graded artificial tooth root by unique sequence of processes

 A unique sequence of processes is used to produce a prototype of a functionally graded artificial tooth root: (1) Dry-jet spraying of the mixture of Ti and Al₂O₃ ultrafine particles (UFPs) produced by radio-frequency plasma onto the surface of a cylindrical Ti rod, where the composition of the UFPs is changed gradually in the outward radial direction from Ti to Al₂O₃; (2) Temperature-gradient sintering of the deposited composite, where the Ti – and the Al₂O₃– rich sides are heated simultaneously at about 1400 K and 1800 K, respectively; (3) Plasma spray coating of hydroxyapatite (HAP) onto the outermost Al₂O₃ surface of the sintered composite. The final product has compressive strength of more than 200 MPa and is durable against fatigue test of 10⁷ stress cycles at 1000 N. The adhesion strength between the Ti substrate and the Ti-Al₂O₃ functionally graded layer exceeds 65 MPa. No contamination with heavy metals is detected throughout the processes and biological cell growth is confirmed to occur on the HAP surface. With these mechanical and biochemical properties the composite produced here is considered to be highly suitable for an artificial tooth root. A series of processes developed here are expected to be applied to the production of various kinds of fine-grained functionally graded materials with complicated forms. Received: 13 October 1997 / Accepted: 27 October 1997     

General case of the dissipation of energy in elastic materials in the process of transverse oscillations

We formulate and solve a general problem of the dissipation of energy in materials in the process of oscillations of structural members of mechanical systems. Translated from Problemy Prochnosti, No. 5, pp. 35–45, September–October, 1997.     

Thermal and mechanical properties of porous Y-PSZ/zircon composites

 The thermal and mechanical properties of sintered porous composites of yttria-partially-stabilized-zirconia (Y-PSZ) and zircon (ZrSiO₄) were investigated for a broad range of compositions. Fracture strengths of these composites were significantly improved with the zircon addition (0 to 50wt%). The addition of zircon also improved the thermal shock resistance. Specimens sintered at 1500^oC for 6 h with 15–20% porosity were shown to have superior strength and thermal shock resistance. These findings have been used in the manufacturing of ceramic permanent molds for brass casting. Received: 5 December 1997 / Accepted: 13 December 1997     

Nonresonant optical nonlinearity of ZnO composite nanoparticles with different interfacial chemical environments

 ZnO nanoparticles coated by surfactant molecules were synthesized by microemulsion method. Under proper thermal treatment, a new ZnO/surfactant composite nanoparticles were formed and exhibited an unique optical property. The third-order optical nonlinearity χ⁽³⁾ of ZnO composite nanoparticles with different interfacial chemical environment were measured by single-beam Z-scan technique, the sign and magnitude of both the real and imaginary parts of χ⁽³⁾ at 790 nm were measured to be: –5.2×10^–16 m²/W and 11.6 cm/Gw for ZnO/DBS composite nanoparticles (DBS, dodecyl benzene sulfonate, anionic surfactant); and –2.2x10^–17 m²/W, 0.45 cm/Gw for ZnO/CTAB composite nanoparticles (CTAB, cetyltrimethyl ammonium bromide, cationic surfactant). The ultrafast nonlinear response time (∼250 fs) measured by time-resolved pump-probe technique at excitation wavelength of 647 nm suggests that the optical nonlinearity below band-gap originate mainly from a rapid electronic polarization process or virtual process such as the optical Stark effect. Received: 19 December 1997 / Accepted: 22 December 1997     

Energy relations in the thermomechanical fracture of materials

This work is devoted to the theoretical substantiation of the thermodynamic equation of the limiting state deduced earlier. The analysis of the energy state of the ideal crystal lattice in the process of its deformation and fracture demonstrates the existence of the ultimate value of the ratio of mechanical energy to thermal energy under thermomechanical loading. This observation specifies the relationship between the eleasticity modulus, heat capacity, the coefficient of linear thermal expansion, and the work of fracture of the material. This relationship is consistent with the well-known energy, deformation, and power equations of the limiting state. We also analyze the characteristics of interatomic bonds in the process of fracture and present the results of numerical calculation of the ratio of mechanical energy to thermal energy for different potentials of interaction. Translated from Problemy Prochnosti, No. 5, pp. 14–22, September–October, 1997.     

Compatibility of poly(α-methyl styrene-co-acrylonitrile) with PMMA: A neutron and cloud point study

Cloud point (CP) experiments were perform-ed using blends of deuterated polymethylmethacrylate (PMMA(D)) and a statistical copolymer P(αMS – co- AN) which consists of α-methylstyrene (αMS) and acrylonitrile (AN). A lower critical solution temperature (LCST) behavior is found. The corresponding interaction parameter χ is calculated accounting for temperature and concentration dependence. In order to improve the accuracy, temperature dependent small-angle neutron scattering experiments are performed for a 50/50 blend which reveal spinodal and binodal temperatures. Additionally, bilayers of P(αMS – co- AN) and PMMA(D) are prepared and annealed. The compositions of coexisting phases and the interface widths are determined by neutron reflectometry (NR). Interaction parameters calculated from the compositions of coexisting phases are in agreement with SANS and CP results. Effects of molar mass distribution are discussed. Received: 17 October 2000 / Reviewed and accepted: 18 October 2000     

An Elementary Proof to the Weight Distribution Formula of the First Order Shortened Reed-Muller Coset Code

 Let RM(m, r) be the shortened Reed-Muller code of order r and of length 2 ^m −1. A simple proof to the Kasami’s weight distribution formula (see [2] and [3, p. 441]) of the cosets of RM(m, 1) in RM(m, 2) is given. The derivation of this distribution formula (21) is based only on elementary properties of the trace map and the Dickson theory of quadratic forms (see [1, pp. 197–199] and [3, pp. 434–442]) is no longer needed. Received: September 25, 1996; revised version: March 11, 1997     

On the design of microelectronic water and gas flowmeters—Sensors of a new generation

We consider the sources of reduced accuracy in pressure microsensors and ways to eliminate them. We present theoretical calculations that make it possible to increase accuracy with our method. We also consider the technology for producing and designing microsensors. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 15–18, October, 1997.