Hardware implementation of radial-basis neural networks with Gaussian activation functions on FPGA

Neural Computing and Applications - This article introduces a method for realizing the Gaussian activation function of radial-basis (RBF) neural networks with their hardware implementation on...     

Preceramic paper-derived Ti3Al(Si)C2-based composites obtained by spark plasma sintering

The paper describes the structure and properties of preceramic paper-derived Ti₃Al(Si)C₂-based composites fabricated by spark plasma sintering. The effect of sintering temperature and pressure on microstructure and mechanical properties of the composites was studied. The microstructure and phase composition were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. It was found that at 1150 °C the sintering of materials with the MAX-phase content above 84 vol% leads to nearly dense composites. The partial decomposition of the Ti₃Al(Si)C₂ phase becomes stronger with the temperature increase from 1150 to 1350 °C. In this case, composite materials with more than 20 vol% of TiC were obtained. The paper-derived Ti₃Al(Si)C₂-based composites with the flexural strength > 900 MPa and fracture toughness of >5 MPa m^1/2 were sintered at 1150 °C. The high values of flexural strength were attributed to fine microstructure and strengthening effect by secondary TiC and Al₂O₃ phases. The flexural strength and fracture toughness decrease with increase of the sintering temperature that is caused by phase composition and porosity of the composites. The hardness of composites increases from ~9.7 GPa (at 1150 °C) to ~11.2 GPa (at 1350 °C) due to higher content of TiC and Al₂O₃ phases.     

Single-electron transfer living radical copolymerization of SWCNT-g-PMMA via graft from approach

The sidewall functionalization of single-walled carbon nanotubes (SWCNTs) was established by poly (methyl methacrylate) (PMMA) using controlled radical polymerization (CRP) method. A bromide functionalized SWCNT (SWCNT-Br) has been used as an initiator for the synthesis of SWCNT-graft-PMMA (SWCNT-g-PMMA). The efficiency of the sacrificial initiator (S) was monitored during the polymerization process. The obtained polymers possess a uniform distribution of molecular weight with a lower polydispersity index of 1.36. The SWCNTs-based initiator acts as an efficient medium for the controlled growth of polymer on the SWCNTs surfaces. The presence of bimodal gel permeation chromatographic (GPC) curve for the SWCNT-g-PMMA(S) obtained through sacrificial initiator (S) confirms uncontrolled behavior. However, the clear sharp peak for SWCNT-g-PMMA obtained without sacrificial initiator shows its well-controlled process of polymerization, which acts as a mimic to bone cement. The efficiency of the functionalization of SWCNT and the controlled formation of SWCNT-g-PMMA composites were characterized by TGA, Raman, TEM, NMR, XPS and dispersion measurements.     

Effect of cadmium-selenide quantum dots on the conductivity and photoconductivity of nanocrystalline indium oxide

The effect of cadmium-selenide quantum dots addition on the electrical and photoelectric properties of nanocrystalline indium oxide with nanocrystal dimensions in the range from 7 to 40 nm is studied. By impedance spectroscopy, it is shown that the addition of quantum dots substantially influences the resistance of interfaces between In₂O₃ crystals. A change in the character of the photoconductivity spectrum of In₂O₃ upon the addition of CdSe quantum dots is detected, and it is established that this change depends on the In₂O₃-nanocrystal dimensions. An energy band diagram is proposed to explain the observed change in the photoconductivity spectrum of In₂O₃ upon the addition of CdSe quantum dots.     

Initiation of PETN detonation by an impactor and a high-enthalpy gas flow

This paper compares two methods of near-threshold initiation of a loose-packed PETN charge: by impact of a plate and by injection of an intense flow of hot gases into the powder. Synchrotron diagnostics of material density was used. Both methods lead to the development of detonation in about 10 μs, but the nature of initiation differs sharply. Initiation by an impermeable piston involves the formation of a dense plug of compressed material. After some delay, a wave is formed at the front of this plug which initiates chemical reaction and accelerates to normal detonation. For high-enthalpy initiation by a hot gas flow, the compression of the powder is low and the process develops in the gas-permeable material, starting from the stage of rapid convective combustion followed by transition to detonation.     

Study of spin centers in nanocrystalline titanium dioxide with a high degree of photocatalytic activity

Electron spin resonance spectroscopy is used to study the effects of illumination and changes in temperature on spin centers in nanocrystalline anatase powders synthesized by sol-gel methods with various complexing agents. A correlation between the concentration of oxygen radicals at the surface and the rate of photocatalytic decomposition of organic compounds in the presence of TiO₂ is observed. It is shown that the concentration of centers active in the electron spin resonance spectra can be used for monitoring the photocatalytic activity of TiO₂.     

Specific features of the sol-gel formation and optical properties of 3d metal/porous silicon composites

The composition and optical properties of composite materials based on porous silicon with iron, cobalt, and nickel deposited by the sol-gel technique are studied. It is shown that the deposition of metal-oxide films onto the surface of porous silicon enables stabilization of the photoluminescence and an increase in its intensity, as well as the storage of hydrogen in the porous layer.     

Modification of the structure and hydrogen content of amorphous hydrogenated silicon films under conditions of femtosecond laser-induced crystallization

We have studied the Raman spectra of initially amorphous hydrogenated silicon (a-Si:H) films upon their exposure to femtosecond laser-radiation pulses with the fluence varied within 30–155 mJ/cm². The distribution of the volume fraction of a crystalline phase over the surface of processed films is determined for the first time and a correlation is established between changes in this value and the hydrogen content in a-Si:H films upon the crystallization induced by femtosecond laser radiation.     

Spectroscopic analysis of the arc plasma of underwater wet flux-cored arc welding

Experiments in air and under water (0.4 m depth) were conducted and the spectrum signals collected. The width of the weld under water was about two-thirds of the width in air, suggesting that the arc plasma was compressed by the water environment. The two sets of spectrum signals were largely similar except for the ultraviolet spectrum, from where the environmental effects were inferred. The analysis identified a unique peak at 656.2793 nm in the underwater spectrum, consistent with H atomic transitions, suggesting that H atoms become involved, although without affecting the overall spectral similarity of the two environments. In either environment the arc plasma was mainly composed of self-shielding gas and evaporated metals, with only minor effects stemming from the interaction with water.