Growth of nano-α-Fe2O3 in a titania matrix by the sol–gel route

Nano--Fe2O3 in a titania matrix was prepared by the sol–gel route. The nanocomposites containing various sizes of -Fe2O3 were precipitated by the heat treatment of the dried gel in a temperature range 100–1200 °C. Differential thermal analysis of the TiO2–Fe2O3 system showed peaks at 325, 390 and 730 °C. The formation of anatase as well as the rutile phase of TiO2 and the growth of -Fe2O3 were predicted from the above peak analysis. These results were in agreement with the X-ray diffraction studies. The sizes of the nanoparticles were analysed by transmission electron microscopic studies. The Mossbauer spectra of TiO2–Fe2O3 nanocomposites showed paramagnetic and superparamagnetic doublets for all the specimens containing nanoparticles of -Fe2O3. The electron paramagnetic resonance study indicated the presence of a paramagnetic phase in the nanocomposite samples. © 1998 Chapman & Hall     

A frequentist approach to mapping under uncertainty

An asynchronous stochastic approximation based (frequentist) approach is proposed for mapping using noisy mobile sensors under two different scenarios: (1) perfectly known sensor locations and (2) uncertain sensor locations. The frequentist methodology has linear complexity in the map components, is immune to the data association problem and is provably consistent. The frequentist methodology, in conjunction with a Bayesian estimator, is applied to the Simultaneous Localization and Mapping (SLAM) problem of Robotics. Several large maps are estimated using the hybrid Bayesian/Frequentist scheme and results show that the technique is robust to the computational and performance issues inherent in the purely Bayesian approaches to the problem.     

The Ni3Al-Ni3Cr-Ni3Mo section of the Ni-Cr-Al-Mo system

An investigation is reported of the constitution of the 75 at % nickel section of the Ni-Cr-Al-Mo system in the temperature range 1523 to 1073 K. Alloys in the region 10 to 20 at % Al were annealed at 1523, 1273, and 1073 K, respectively, and subjected to electron microprobe analysis, X-ray diffraction, and microscopical and hardness examination. Constitutional data are presented as partial isothermal sections and as vertical sections. At 1523 K the section consists only of fields containing ,+ and , the last mentioned phase being predominant. With decreasing temperature the and + fields increase in extent. Also, the NiMo and Ni₃Mo phases were encountered in the ternary Ni-Al-Mo alloy studied. The quaternary + alloys showed small lattice mismatch values, i.e. up to 0.25%. Raft like morphologies of were found in the quaternary alloys, resulting from directional coarsening. Observations of as-cast structures are also reported.     

Microstructure and optical absorption of silver granules in oxide glasses produced by ion-exchange and reduction treatments

An electron micrographic investigation has been carried out on two oxide glasses containing alkali ions and subjected to a sodiumsilver ion-exchange followed by reduction treatments at various temperatures. The presence of metallic silver in the silver-rich droplet phases has been confirmed by selected-area electron diffraction. The silver-rich phases are found to have diameters ranging from 3 to 50 nm. The nucleus density of these particles is found to have a maximum value at temperatures in the range 250 to 300° C. The optical absorption spectra of the reduced glasses show a maximum around a wavelength of 400 nm. Maxwell-Garnett theory has been used to calculate the optical absorption and the predicted wavelength for maximum absorption is in reasonable agreement with the experimental value.     

ParFUM: a parallel framework for unstructured meshes for scalable dynamic physics applications

Unstructured meshes are used in many engineering applications with irregular domains, from elastic deformation problems to crack propagation to fluid flow. Because of their complexity and dynamic behavior, the development of scalable parallel software for these applications is challenging. The Charm++ Parallel Framework for Unstructured Meshes allows one to write parallel programs that operate on unstructured meshes with only minimal knowledge of parallel computing, while making it possible to achieve excellent scalability even for complex applications. Charm++’s message-driven model enables computation/communication overlap, while its run-time load balancing capabilities make it possible to react to the changes in computational load that occur in dynamic physics applications. The framework is highly flexible and has been enhanced with numerous capabilities for the manipulation of unstructured meshes, such as parallel mesh adaptivity and collision detection.     

Effect of Cold Deformation on the Machinability of a Free Cutting Steel

The effect of cold deformation on the machinability of a free cutting steel has been investigated through characterization of the variation in size and morphology of the sulfide inclusions. The machinability has been indexed in terms of cutting force, surface roughness, and chip characteristics. The possible interrelations between inclusion characterizing parameters and machinability indices have been examined. Increased cold deformation was found to increase interinclusion spacing as well as aspect ratio of the inclusions. These variations in inclusion characteristics, in turn, were found to reduce the cutting forces and the chip length up to a critical amount of deformation. The results highlight the influence of inclusion characterizing parameters on machinability characteristics of free cutting steels.     

BION-2: Predicting Positions of Non-Specifically Bound Ions on Protein Surface by a Gaussian-Based Treatment of Electrostatics

Ions play significant roles in biological processes—they may specifically bind to a protein site or bind non-specifically on its surface. Although the role of specifically bound ions ranges from actively providing structural compactness via coordination of charge–charge interactions to numerous enzymatic activities, non-specifically surface-bound ions are also crucial to maintaining a protein’s stability, responding to pH and ion concentration changes, and contributing to other biological processes. However, the experimental determination of the positions of non-specifically bound ions is not trivial, since they may have a low residential time and experience significant thermal fluctuation of their positions. Here, we report a new release of a computational method, the BION-2 method, that predicts the positions of non-specifically surface-bound ions. The BION-2 utilizes the Gaussian-based treatment of ions within the framework of the modified Poisson–Boltzmann equation, which does not require a sharp boundary between the protein and water phase. Thus, the predictions are done by the balance of the energy of interaction between the protein charges and the corresponding ions and the de-solvation penalty of the ions as they approach the protein. The BION-2 is tested against experimentally determined ion’s positions and it is demonstrated that it outperforms the old BION and other available tools.     

First Ply Failure Loads of Composite Conoidal Shell Roofs with Varying Lamination

A number of industrial structures need large column free open spaces. Though the conoidal shells are doubly curved they are singly ruled too and are easy to fabricate and thus preferred in the industry. The laminated composites are well established today and there is a relevant question regarding the performance of different stacking options when the laminates are used to fabricate structural units. First ply failure analysis of conoidal shells are missing in the literature. This article uses the finite element method to evaluate relative performances of conoidal shells with varying laminations in terms of their first ply failure loads.     

Multiferroic behavior in glass-crystal nanocomposites containing Te2NiMnO6

Nanocomposites containing nanocrystals of Te₂NiMnO₆ were synthesized by suitable heat treatment of a glass with composition 2 TeO₂·NiO·MnO (molar ratio). The crystallites had dimensions in the range 17-41 nm. X-ray diffraction data of the specimens were analyzed by using a TREOR computer programme. Lattice parameters extracted by this method indicated that the crystal symmetry was monoclinic. The nanocomposites exhibited weak ferromagnetism in the temperature range 2-300 K. They also showed ferroelectric hysteresis at room temperature with a remanent polarization of 0.015 μC/cm². The specimens showed a magnetodielectric (MD) behavior with dielectric constant increasing as a function of applied magnetic field. The MD parameter obtained in the present system was 0.55%.     

Intermediate Si-Al spinel phase formation in phase transformation of diphasic mullite gel

Al₂O₃-SiO₂ diphasic mullite gel (Si/Al=1/3) has been synthesized by using Al(NO₃)₃·9H₂O and Ludox in basic conditions. Its phase transformation behaviour has been studied by qualitative and quantitative X-ray diffraction techniques. The results indicate that a noncrystalline alumino-silicate phase forms together with the slow crystallization of Si-Al spinel phase of a mullite-like composition up to 1250 °C. Thereafter, it transforms suddenly to orthorhombic mullite around 1325 °C. Earlier studies, e.g. alkali leaching, and measurement of co-ordination number of aluminium in 1000 °C heated diphasic gel, confirm Si-Al spinel formation as an intermediary phase.