Effects of Doping Trivalent Ions in Bismuth Borate Glasses

Bismuth borate glasses from the system: 40Bi₂O₃–59B₂O₃–1Tv₂O₃ (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi₂O₃–60B₂O₃, 37.5Bi₂O₃–62.5B₂O₃ and 38Bi₂O₃–60B₂O₃–2Al₂O₃ were prepared by melt quenching and characterized by density, UV-visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X-ray diffraction (XRD). Bi₃B₅O₁₂ was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare-earth ions promote the formation of metastable BiBO₃–I and BiBO₃–II phases during glass crystallization.     

Characterization of aluminides formed on superalloy 690 substrate

Ni-Cr-Fe based superalloy 690 substrate, pack aluminized at 1273 K, revealed formation of multilayer comprising (NiCr)Al + Cr₅Al₈, Ni₂Al₃ + Cr₅Al₈, NiAl and γ phases. Knoop hardness number varied from 225 to 1142 along the cross-section. Wear and friction tests on aluminized specimen were performed in dry medium using reciprocating sliding wear and friction machine with tungsten carbide ball at 15 N load with frequencies at 10, 15 and 20 Hz. The coefficient of friction, the static ones were obtained in the vicinity of 0.2, 0.3 and 0.5, while dynamic ones were 0.3, 0.4 and 0.4 respectively. For the ball, the wear rate was 1.9 × 10^?6, 1.2 × 10^?5 and 1.5 × 10^?5 mm³/Nm, whereas the wear rate was 5.8 × 10^?5, 3.8 × 10^?4 and 4.6 × 10^?4 mm³/Nm respectively for the aluminized specimen indicating good adherent surface coating.     

Intelligent Biohybrid Materials for Therapeutic and Imaging Agent Delivery

Many molecular imaging techniques rely on tracer methods to visualize specific physiological processes in cells, animals, and humans. A new family of "smart" delivery systems for biomolecules has opened new opportunities for the molecular imaging field. One class of polymeric carriers reversibly become membrane destabilizing in response to sharp pH changes and were designed for delivering proteins and nucleic acids to intracellular compartments. These carriers could enable the use of imaging agents and intracellular reporters whose site of action made them previously inaccessible. A second class of stimuli-responsive polymer-biomolecule conjugates can be reversibly formed into particles of closely defined sizes. The ability to control when and where the protein or DNA species is in the free versus particle form may allow imaging applications that exploit their differential size and diffusion properties.     

Steady-state creep of orthotropic rotating disks of variable thickness

Creep analysis of orthotropic rotating disks with variable thickness has been carried out for secondary stage of creep. Norton's power law of creep is employed to derive general expressions for stresses and strain rates in the disks. These expressions have been utilized to find stress and strain rate distributions for disks with the following types of thicknesses - (i) constant thickness, (ii) linearly varying thickness, and (iii) hyperbolically varying thickness. The numerical computations to study the effects of anisotropy and the profile of the disks on stresses and strains have been carried out employing the method of successive approximations. Five different cases of anisotropy have been considered. Selecting a certain type of material anisotropy and an optimum profile for the disk may result in a better design for the turbine disks.     

Source codes as random number generators

A random number generator generates fair coin flips by processing deterministically an arbitrary source of nonideal randomness. An optimal random number generator generates asymptotically fair coin flips from a stationary ergodic source at a rate of bits per source symbol equal to the entropy rate of the source. Since optimal noiseless data compression codes produce incompressible outputs, it is natural to investigate their capabilities as optimal random number generators. We show under general conditions that optimal variable-length source codes asymptotically achieve optimal variable-length random bit generation in a rather strong sense. In particular, we show in what sense the Lempel-Ziv (1978) algorithm can be considered an optimal universal random bit generator from arbitrary stationary ergodic random sources with unknown distributions     

Prediction of solidification time during solidification of aluminum base alloy castings cast in CO2-sand mold

Solidification of molten metals during various casting methods poses many practical problems associated with phase transformation and heat transfer processes. Evaluation of solidification time is one of the very important parameters used for assessing the properties of the material. In the present study, experimental investigation was carried out to measure the solidification time in a cylindrical hollow casting cast in CO₂-Sand molds and the same has been compared with the results obtained through computed by using an implicit alternating direction (IAD) method, including the treatment of interfacial nodes between metal and mold, and boundary nodes at the mold surface. Aluminum-4.5% copper alloy has been used. Computed cooling curves at various locations and temperature distributions in core-metal-mold were presented. The results shows that the solidification time obtained by experimental study compares well with the one predicted by the analysis made through IAD modeling. A successful comparison with reported experimental results shows that the technique is appropriate for simulation of solidification process of aluminum castings.     

X-ray diffraction study of epitaxial zinc and cadmium films prepared by hot-wall technique

Hot-wall technique greatly improves the quality of zinc and cadmium films deposited on glass substrate. At substrate temperature the growth of such films is well ordered, showing highly preferred orientation along c-axis. However, if the substrate temperature is increased beyond certain limit, we get polycrystalline growth of the films. This shows that the growth of zinc and cadmium films on glass substrate strongly depends on the substrate temperature.     

Learning pattern classification-a survey

Classical and recent results in statistical pattern recognition and learning theory are reviewed in a two-class pattern classification setting. This basic model best illustrates intuition and analysis techniques while still containing the essential features and serving as a prototype for many applications. Topics discussed include nearest neighbor, kernel, and histogram methods, Vapnik-Chervonenkis theory, and neural networks. The presentation and the large (though nonexhaustive) list of references is geared to provide a useful overview of this field for both specialists and nonspecialists