Laser stimulated low-temperature crystallization of amorphous silicon

Laser annealing of amorphous silicon (a-Si) at different initial temperatures (77 and 300 K) has been studied. It is established that the laser-stimulated crystallization of silicon is possible at relatively low temperatures. A theoretical model is proposed, which explains this phenomenon by melting via the electron mechanism followed by recrystallization.     

Heat losses in a tunnel kiln for brick firing

The results of experimental studies of heat losses via the enclosing structures of an operating brick-firing kiln using a thermal imager are described. __________ Translated from Steklo i Keramika, No. 4, pp. 24–25, April, 2006.     

Application of the blind source separation method to feature extraction of machine sound signals

As the result of vibration emission in air, a machine sound signal carries important information about the working condition of machinery. But in practice, the sound signal is typically received with a very low signal-to-noise ratio. To obtain features of the original sound signal, uncorrelated sound signals must be removed and the wavelet coefficients related to fault condition must be retrieved. In this paper, the blind source separation technique is used to recover the wavelet coefficients of a monitored source from complex observed signals. Since in the proposed blind source separation (BSS) algorithms it is generally assumed that the number of sources is known, the Gerschgorin disk estimator method is introduced to determine the number of sound sources before applying the BSS method. This method can estimate the number of sound sources under non-Gaussian and non-white noise conditions. Then, the partial singular value analysis method is used to select these significant observations for BSS analysis. This method ensures that signals are separated with the smallest distortion. Afterwards, the time-frequency separation algorithm, converted to a suitable BSS algorithm for the separation of a non-stationary signal, is introduced. The transfer channel between observations and sources and the wavelet coefficients of the source signals can be blindly identified via this algorithm. The reconstructed wavelet coefficients can be used for diagnosis. Finally, the separation results obtained from the observed signals recorded in a semi-anechoic chamber demonstrate the effectiveness of the presented methods .     

A double-layer current conduction model for high-κ gate dielectric materials with interfacial oxide or silicate layer

The current-voltage (I-V) characteristics of metal-oxide-semiconductor (MOS) structures with hafnium oxide as the gate dielectric film were studied. Sharp shifts from a low-voltage ohmic regime to a tunneling conduction were observed in the high-voltage range. The paper demonstrates that this behavior can be described very well with a double-layer dielectric model. Excellent fittings of the experimental curves were obtained and the related key structural and physical parameters were obtained. The model fitting further suggests the optimal annealing conditions for preparing the hafnium oxide films.     

Functional characteristics of Bi2Sr2Ca2Cu3O10 + δ/ZrN composites

We present the results of investigation of the magnetic, transport, structural, and mechanical properties of composites obtained by introducing finely dispersed zirconium nitride into a matrix of a Bi₂Sr₂Ca₂Cu₃O_{10 + δ} (Bi2223) high-temperature superconductor. It is established that the introduction of ZrN particles in the range of very small concentrations (0.1–0.3 wt %) leads to a significant (more than threefold) increase in the critical current density of Bi2223 and increases the density of the composite, while the microhardness of the superconducting phase remains unchanged.     

Specular reflection of thermal neutrons from Gd-containing layers and optimization of antireflective underlayers for polarizing coatings

A detailed analysis of specular neutron reflection from an absorbing medium is given. The experimental studies revealed that oxidation and roughness of the surface are the main factors that determine the neutron reflectivity of Gd-containing layers. It is concluded that the empirical approach used at present does not guarantee optimization of underlayer parameters (composition and thickness) and technological regimes. An algorithm of optimization is proposed, in which account is taken of the substrate potential, the dependence of the underlayer potential on the thermal neutron wavelength, the polarizing coating imperfections that enhance reflection of neutrons with the undesired spin. The antireflective TiZrGd underlayer for CoFe/TiZr supermirrors produced at the magnetron facility DIOGEN (PNPI, Gatchina) is optimized.     

Hydrogen-driven denitrification of wastewater in an anaerobic submerged membrane bioreactor: potential for water reuse.

An anaerobic submerged membrane bioreactor was coupled with a novel hydrogen delivery system for hydrogenotrophic denitrification of municipal final effluent containing nitrate. The biological treatment unit and hydrogen delivery unit were proven successful in removing nitrate and delivering hydrogen, respectively. Complete hydrogen transfer resulted in reducing nitrate below detectable levels at a loading of 0.14 kg Nm(-3) d(-1). The produced water met all drinking water guidelines except for color and organic carbon. However, the organic carbon was removed by 72% mostly by membrane rejection. To reduce the organic carbon and color of the effluent, post treatment of the produced water is required.     

Synthesis of ductile titanium-titanium boride (Ti-TiB) composites with a beta-titanium matrix: The nature of TiB formation and composite properties

The study focused on the in-situ synthesis of titanium (Ti)-titanium boride (TiB) composites with β phase in the matrix by reaction sintering of TiB₂ with Ti and alloying element powders. The goal was to examine the nature of TiB whisker formation in three different kinds of powder mixtures: (1) β-Ti alloy powders and TiB₂; (2) α-Ti powder, a master alloy (Fe-Mo) powder containing the β-stabilizing elements, and TiB₂; and (3) α-Ti powder, a β-stabilizing elemental powder (Mo or Nb), and TiB₂. The effects of powder packing and the relative locations of powder particles on the morphological changes in TiB whisker formation and their growth were studied at processing temperatures ranging from 1100°C to 1300°C. The morphology, size, and distribution of whiskers were found to be influenced by the powder-packing conditions. A large particle-size ratio in bimodally packed mixtures led to the formation of a TiB monolithic layer around β grains. With a relatively finer starting powder, smaller size ratio, and trimodal packing arrangement, the TiB whiskers were found to be distributed more homogeneously in the matrix. The study also used the X-ray direct comparison method and the structure factor for the β phase to determine the volume fraction of TiB phase from X-ray data. Tensile tests and fractographic investigations were carried out on selected composites. The evolution of the composite microstructure, the influence of powder-packing variables, and the morphology and growth of TiB whiskers and their effect on mechanical properties are discussed.