Evanescent and propagating fields of a strongly focused beam

Evanescent- and propagating-field distributions from a strongly-focused-wave beam with subwavelength waist w(a) < lambda as a function of polar angle and distance are investigated. Exact amplitudes and intensities of evanescent E(ev) and propagating E(p) fields, including interference terms, are presented both in near- and far-field regions. It is shown that the amplitude of E(ev) decays as exp(-r/w(a)) in the near-field region and that evanescent waves do not contribute to the far field in the forward direction as they do in the transverse directions theta = pi/2, even though the oscillating evanescent field of the same strength but opposite in sign to the propagating field exists in the transverse plane.     

Classical photometry of prefractal surfaces

Using the scale invariance of classical photometry, we develop an approach to finding the photometric function of prefractal structures that form a random topography. The photometric function of the prefractal surfaces is found as the general solution of the resulting differential equation in partial derivatives. The function depends on two parameters: the number of hierarchical levels of the prefractal structures and the roughness parameter of the single-level generation. As a limiting case, the approach includes our previous theory that considered fractoids.     

Thermal Radiative Properties of Ceramic of Cubic ZrO2Stabilized with Y2O3at High Temperatures

The results are given of the investigation of the normally hemispherical reflectivity of ceramic of cubic zirconia stabilized with 8 mol % yttria for the wavelengths of 0.488, 0.6328, 1.15, and 1.39 m both in the process of its rapid heating in air by CO₂-laser radiation from room temperature to 3200 K and in the process of subsequent cooling after the heating radiation is discontinued. It is demonstrated that, in the entire investigated spectral range under conditions of a layer of melt 250–500 m thick on the surface, an optically infinite layer is realized in the melt, and the reflection is largely defined by the refractive index. This latter layer remains optically infinite even immediately after solidification; however, by the end of the solidification process, its reflectivity somewhat increases due to cracks and pores. Measurements of the reflection under conditions of continuous stepwise heating by fluxes of relatively low intensity and in the course of subsequent cooling have produced data on the reflectivity of the layer under close-to-isothermal conditions. Some estimates are made of the values of the absorption coefficient of the melt.     

Dynamic Tag Reduction for Low-Power Caches in Embedded Systems with Virtual Memory

This paper presents a low-power tag organization for physically tagged caches in embedded processors with virtual memory support. An exceedingly small subset of tag bits is identified for each application hot-spot so that only these tag bits are used for cache access with no performance sacrifice as they provide complete address resolution. The minimal subset of physical tag bits is dynamically updated following the changes in the physical address space of the application. Operating system support is introduced in order to maintain the reduced tags during program execution. Efficient algorithms are incorporated within the memory allocator and the dynamic linker in order to achieve dynamic update of the reduced tags. The only hardware support needed within the I/D-caches is the support for disabling bitlines of the tag arrays. An extensive set of experimental results demonstrates the efficacy of the proposed approach.     

Phase diagram of the UO2-FeO1+x system

Phase-relation studies of the UO₂-FeO_1+x system in an inert atmosphere are presented. The eutectic point has been determined, which corresponds to a temperature of (1335 ± 5) °C and a UO₂ concentration of (4.0 ± 0.1) mol.%. The maximum solubility of FeO in UO₂ at the eutectic temperature has been estimated as (17.0 ± 1.0) mol.%. Liquidus temperatures for a wide concentration range have been determined and a phase diagram of the system has been constructed.     

A new approach to designing electrical machines on the basis of numerical simulation

An approach that enables one to calculate the electromagnetic field in an electric machine in conjunction with the calculation of currents in windings and the rotation of a rotor under the effect of electromagnetic forces and loads is considered. The capacities of the considered methods for designing electrical machines are demonstrated for a number of examples. The calculated results are compared with the experimental data obtained for an induction electric motor with two short-circuited windings on the rotor.     

Application of incubation time approach to simulate dynamic crack propagation

The incubation time criterion for dynamic fracture is applied to simulate dynamic crack propagation. Being incorporated into ANSYS finite element package, this criterion is used to simulate the classical dynamic fracture experiments of Ravi-Chandar and Knauss on dynamic crack propagation in Homalite-100. In these experiments a plate with a cut simulating the crack was loaded by an intense pressure pulse applied on the faces of the cut. The load consisted of two consequent trapezoidal pulses. This, in the experimental conditions used by Ravi-Chandar and Knauss, resulted in a crack initiation, propagation, arrest and reinitiation. Dependence of the crack length on time was measured in those experiments. The results for crack propagation obtained by FEM modelling are in agreement with experimental measurements of crack length histories. This result shows the applicability of the incubation time approach to describe the initiation, propagation and arrest of dynamically loaded cracks.     

Specific features of kinetics of molecular beam epitaxy of compounds in the GaN-AlN system

The effect of growth conditions (V/III ratio, substrate temperature) on the properties of materials in AlN-GaN systems is discussed. A concept of the growth of the AlN/AlGaN/GaN multilayer heterostructure, which provides the improvement of crystal quality and surface morphology of the layers, is suggested and realized. The improvement of the properties of GaN in the AlN/AlGaN/GaN/AlGaN multilayer heterostructure is confirmed by a considerable increase in electron mobility in the two-dimensional electron gas formed at the upper heterointerface GaN/Al_0.3Ga_0.7N.     

Phase transformation in the binary section of the UO2-FeO-Fe system

Phase transformations in the oxide binary section of the UO₂-FeO-Fe ternary system were studied. The melting onset point of the UO₂-FeO heterogeneous system (1335±5°C) was determined and the fusion curve of this system was constructed. The limiting solubility of FeO in the UO₂ solid solution was measured. The changes in crystal parameters in formation of the solid solution were determined. Uranium dioxide was found to be insoluble in the wüstite phase (FeO).     

Preparation of sols from water-alcohol solutions of tetraethyl orthosilicate and SnCl<Subscript>4</Subscript> and the effect of sol composition on the surface morphology of sol-gel films

We describe a process for the preparation of sols from water-alcohol solutions of tetraethyl orthosilicate and SnCl₄. The kinetics of this process have been studied by measuring the electrical conductivity of the sols, and the optical absorption spectra of the sols have been measured. The surface morphology of films prepared from the sols has been examined by scanning electron microscopy. The results are used to assess the influence of preparation conditions, sol composition, and processes underlying sol formation on the surface morphology of the gas-sensing films prepared from the sols.