Bandpass filters using periodically loaded combline resonators

A novel combline filter is proposed for cellular‐radio base stations. The Q‐factor is significantly improved. The eigenvalue equation is expressed with the single‐team approximation in the gap region of the combline resonator. A two‐pole combline filter is designed. The calculation, simulation, and experiment results are presented and are in good agreement. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Modern Teaching and Training in Metallurgical Engineering

This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated.     

Analyzing clusters of class characteristics in OO applications

The transition from Java 1.4 to Java 1.5 has provided the programmer with more flexibility due to the inclusion of several new language constructs, such as parameterized types. This transition is expected to increase the number of class clusters exhibiting different combinations of class characteristics. In this paper we investigate how the number and distribution of clusters are expected to change during this transition. We present the results of an empirical study were we analyzed applications written in both Java 1.4 and 1.5. In addition, we show how the variability of the combinations of class characteristics may affect the testing of class members.     

Calculations of the Probability of Positron Trapping by a Vacancy in a Metal and the Estimation of the Vacancy Contribution to the Work Function of Electrons and Positrons

The probabilities of the localization of positrons in monovacancies of Al and Cu have been calculated as functions of the energy and temperature. The vacancy was simulated by a void with a radius equal to the radius of the Wigner—Seitz cell in the model of stable jellium. Using the Fermi—Dirac golden rule for transitions, the formula for the rate of positron trapping by a vacancy has been derived as the function of the positron energy. For the thermalized positrons, the rate of localization near the triple point proved to be, on the order of magnitude, close to the rate of annihilation. Within the framework of our previously proposed models, the contribution of vacancies to the work function of electrons and positrons has been demonstrated based on the example of Al. The physical situations where the vacancy effect can manifest have been considered.     

On calculating the energy characteristics of a metal film with a dielectric coating

A method for calculating the characteristics of a metal film in a dielectric surroundings is suggested. The most interesting case of asymmetric metal-dielectric sandwiches, in which the dielectrics on both sides of the film are different, is considered in the context of the Kohn-Sham modified method. The spectrum, the electron work function, and the surface energy of polycrystalline and single-crystal films placed into passive insulators are calculated for the first time. In general, the dielectric surroundings leads to a negative change in the electron work function and the surface energy. In addition to size-effect-related changes, the shift of the work function is determined by the arithmetic mean of the dielectric constants of the surrounding media. Calculations have been performed for Na, Al, and Pb.     

On the influence of the effective mass of electrons on the Fermi energy of metal–insulator nanosandwiches

The size dependences of the Fermi energy of metallic films of Al and Pb bordering with the dielectrics SiO₂, Al₂O₃, HfO₂, ZrO₂, and TiO₂ have been calculated. The model of free electrons and an asymmetric potential well has been modified by the introduction of the effective masses of electrons in the metal and in the insulator. The evolution of the size oscillations of the Fermi energy of metallic films in different dielectric surroundings upon the variation of the effective masses of electrons both in the metal and in the insulator has been analyzed. It has been shown that the allowance for the effective mass of electrons in the metal leads to a more substantial change in the position of the Fermi level in comparison with the allowance for the effective mass of the dielectric.     

Peculiar electric properties of polarized layer in alkaline silicate glasses

Broadband dielectric spectroscopy (BDS) was applied to study polarization phenomena in alkaline silicate glasses, in particular, properties and structure of subsurface (anodic) polarized layers forming in poling with deposited film electrodes of different structures. A model of poled glasses which does not contradict experimental data is proposed. In accordance with the model, a poled glass is presented as two resistor-capacitor circuits in a series connection, one of which is the polarized layer and another is the rest of the sample. It is found that the electric properties of the layers essentially depend on the structure of the anodic electrode used in glass poling. It is also shown that the dielectric response of poled glass samples is mainly determined by the electric properties of the submicron polarized layers and this gives an opportunity to reveal specific properties of the layers rather than ones of the glass sample bulk. Revealed temperature dependence of DC conductivity of the polarized layers obeys Arrhenius's law, and determining activation energy does not depend on the electrode. Finally, it is noted that today above-mentioned information about polarized layers can be obtained only by BDS.