Analysis of a two-dimensional symmetric problem on extension of an Al-polyimide-Cu layered structure with a model crack

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

     

Effects of metal-support interactions on the synthesis of methanol over palladium

The synthesis of methanol and other products from CO and H₂ was studied over Pd catalysts prepared by adsorption of Pd(π-C₃H₃)₂ on MgO, ZnO, La₂O₃, γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ as well as over a SiO₂-supported Pd catalyst prepared from PdCl₂ and Pd black. Both the activity and selectivity of Pd were affected strongly by the nature of the support and the composition of the Pd precursor. The specific activity for methanol synthesis decreased in the order $\text{Pd}\text{La}{}_2\text{O}{}_3$ ? $\text{Pd}\text{SiO}{}_2$ [derived from PdCl₂] > $\text{Pd}\text{ZrO}{}_2$ > $\text{Pd}\text{ZnO}\text{≈}\text{Pd}\text{MgO}$ > PdTiO₂ > $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{≈}\text{Pd}\text{SiO}{}_2$ [derived from Pd(π-C₃H₅)₂] ? Pd black, while the specific activity for hydrocarbon synthesis decreased in the order $\text{Pd}\text{TiO}{}_2\text{?}\text{Pd}\text{ZrO}{}_2$ > $\text{Pd}\text{La}{}_2\text{O}{}_3$ > $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{≈}\text{Pd}\text{SiO}{}_2$ [derived from PdCl₂] ? $\text{Pd}\text{SiO}{}_2$ [derived from Pd(π-C₃3H₅)₂] ≈ Pd black ? $\text{Pd}\text{MgO}\text{?}\text{Pd}\text{ZnO}$. Dimethyl ether production was observed over four of the catalysts and the activity for formation of this product decreased in the order $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{?}\text{Pd}\text{TiO}{}_2\text{?}\text{Pd}\text{MgO}\text{≈}\text{Pd}\text{ZrO}{}_2$. The effects of support composition on the catalytic properties of Pd are discussed in the light of current ideas concerning metal-support interactions and the acid-base properties of the support.     

Studies on Charge Carrier Transport in an Injection Laser with Frequency Modulation of the Optical Radiation

Russian Microelectronics - One of the promising approaches to solve the problem of increasing the efficiency for interelement connections consists in the use of integrated optical switching...     

Circuit model for functionally integrated injection laser modulators

This paper proposes a circuit model for injection lasers with functionally integrated optical-radiation modulators. This model takes into account the design and structural features of the functionally-integrated injection laser modulators (FIILMs), as well as the effect exerted by the spatial distributions of electrons, holes, and photons in the FIILMs’ active region on the behavior of the physical processes there.     

On estimating the efficiency of a neural optimizer for the parameters of a PID controller for heating objects control

In this work, we consider the problems of estimating the energy efficiency of applying a neural optimizer to tune a PID controller in controlling a laboratory heating furnace for cast bars. We estimate the electric power savings achieved when running the technological process with the optimizer as compared to a regular PID controller.     

Diffusion-drift model of the transport of charge carriers and photons in injection lasers

A mathematical model is proposed that can be used for numerical analysis of the dynamics of processes in injection lasers with allowance for their structural features; nonuniform spatial distributions of electrons, holes, and photons; and various mechanisms of radiative recombination. Results of numerical modeling of double-heterostructure injection lasers performed using the proposed model are compared to the results obtained using the equations of laser kinetics. Boundaries of applicability of these models are considered.

     

The Possibility of Using Rail-Gun Arcs for Cleaning Metal Surfaces

Results are given of theoretical and experimental investigations of the physical characteristics of a free electric arc moving in a self-magnetic field along metal surfaces of different shapes contaminated by dielectric deposits. Similarly to welding, a direct-action arc is used, when the material being cleaned is one of the electrodes stabilizing the electric arc. Compared to plasmotrons, a facility using rail-gun arcs may exhibit a higher specific heat flux. This enables one to attain higher efficiency and capacity by reducing the loss of heat for heating the plate to be cleaned. Experiments are performed with steel samples contaminated by paraffin films. Data are obtained on the rate of arc propagation and its geometric characteristics, on the heat flux to the electrode being cleaned, on the cleaning capacity at different amplitudes of current, and on the thickness of paraffin coating. The basic possibility of removing dielectric deposits from metal surfaces with the aid of electric-arc treatment is demonstrated.     

Study of transient processes in a <Emphasis Type="Italic">p-i-n</Emphasis> photodetector using the nonstationary physical-topological model

We developed a nonstationary diffusion-drift physico-topological model of a GaAs p-i-n photodetector for operation as an element of an optical switch integrated circuit, together with a high-speed injection laser based on a double heterostructure with a functionally integrated radiation modulator.     

A functionally integrated injection laser-modulator with the radiation frequency modulation

The construction technique and structure of injection lasers with functionally integrated optical-radiation frequency modulators, characterized by the maximal terahertz modulation frequencies, are proposed. The proposed structure of injection laser-modulators ensures the possibility of their fabrication in a single technological cycle using traditional technological operations.