Sol-Gel Processing and Pyroelectric Properties of Highly Oriented Pb(Mg,Zn)1/3Nb2/3O3 Thin Films

Thin films of Pb(Mg,Zn)_1/3Nb_2/3O₃ (PMZN) were fabricated by spin casting the partially hydrolyzed Pb-Mg-Zn-Nb-O complex alkoxide sols on (111)Pt-coated MgO (100) planes. A strong preferential orientation of (100) perovskite was observed in the thin film derived from the sol exhibiting pseudoplastic behavior. A small-angle X-ray scattering experiment in the Porod region was performed to correlate the observed preferential orientation with the network structure of precursor in the PMZN sol. It was shown that weakly branched precursor systems led to highly oriented perovskite grains after thin-film formation. The highly (100) oriented PMZN film exhibited a larger pyroelectric coefficient (>2 μC/(cm²-K)) and pyroelectric figure-of-merit ( F _D > 4 × 10^1–4 Pa^−1/2) than the PMZN thin film having randomly oriented grains.     

Structure of sol-gel prepared ferroelectric Bi3.4La0.6Ti3O12

The Bi_3.4La_0.6Ti₃O₁₂ (BLT) thin film and powder have been prepared by a sol-gel method with annealing at 700^°C. Randomly oriented BLT thin film exhibits a large remanent polarization, 2P _r = 72 μC/cm², with a dc applied field strength of 320 kV/cm. Structure of sol-gel derived BLT powder has been investigated by neutron scatterings, and refined by a Rietveld method resulting a reasonable goodness of fit (wR _p = 6.7%, and R _p = 5.7%) using an orthorhombic (B2cb, a = 5.4221 Å, b = 5.4032 Å, and c = 32.8361 Å). Two different TiO₆ octahedra exhibit different polarization directions; (100) from Ti(1)O₆, and (011) from Ti(2)O₆, which explains the observed large 2P _r of the randomly oriented BLT thin film.     

Normal vector compression of 3D mesh model based on clustering and relative indexing

As the transmission of 3D shape models through Internet becomes more important, the compression issue of shape models gets more critical. While the compressions of topology and geometry have been explored significantly, the same issue for normal vectors has not yet been studied as much as it deserves.

Presented in this paper is an approach to compress the normal vectors of a 3D mesh model using the concept of clustering and relative indexing. The model is assumed to be manifold triangular mesh model with normal vectors associated with vertices. The proposed scheme clusters the normal vectors of given model and the representative normal vector of each cluster is referred to via a mixed use of relative as well as absolute indexing concepts. It turns out that the proposed approach achieves a significant compression ratio (less than 10% of the original VRML model files) without a serious sacrifice of the visual quality.     

Structural and Magnetic Properties of the New La2SrCo2FeO9 Triple Perovskite

In this work, we report synthesis and characterization of the new La₂SrCo₂FeO₉ triple perovskite material. The samples were produced by the solid-state reaction method. The analyses of the XRD patterns were made by Rietveld refinement through the GSAS code. The results reveal that the material crystallizes in an orthorhombic complex perovskite, space group Immm (#71) with lattice parameters a=5.4314(3) ?, b=5.4583(3) ? and c=7.7018(2) ?. SEM micrographs evidence a strongly diffused granular morphology with mean grain size of 2 μm and the EDX spectra show that the chemical composition of samples are in good agreement with the nominal values of the stoichiometric formula. ⁵⁷Fe Mössbauer spectroscopy recorded at 300 K reveals two sites in concordance with the X-ray diffraction measurements, and its valence state is +3, as determined from the isomer shift found. At 4.2 K magnetic ordering with canting of the Fe moments is found. Measurements of the magnetization as a function of temperature permitted us to determine the ferromagnetic characteristic of material with an effective magnetic moment of 9.7μ _B.     

Modified harmony search optimization for constrained design problems

Constrained optimization is a major real-world problem. Constrained optimization problems consist of an objective function subjected to both linear and nonlinear constraints. Here a constraint handling procedure based on the fitness priority-based ranking method (FPBRM) is proposed. It is embedded into a harmony search (HS) algorithm that allows it to satisfy constraints. The HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. Here, the original heuristic HS was improved by combining both improved and global-best methods along with the FPBRM. The resulting modified harmony search (MHS) was then compared with the original HS technique and other optimization methods for several test problems.     

Retardation of High-Temperature Fuel Ash Corrosion of Fireside Boiler Tubes via Nanoparticles

The high-temperature corrosion rate of boiler tubes was studied as a function of inhibitor concentration, time, and temperature in the absence and presence of fuel ash. Samples of steel tubes were taken from boilers that operate in Northern Baghdad Station for Electric Power Generation. Fuel ash was collected from the boiler combustion chamber, as well. Normal and nano-MgO were used as a corrosion inhibitor in different mixing ratios. A weight loss technique was used to evaluate the corrosion rates, while scanning electron microscopy was used to study the surface morphology. It was seen that corrosion rates increased with both time and temperature, and decreased with the addition of inhibitors. The maximum inhibitor efficiency was 81 %, obtained via using nano-MgO at mixing weight ratio 2:1, 600 °C, and 10 h. The Presence of fuel ash had harmful effects on the steel surface.     

Chemical Properties and Oxidative Stability of Perilla Oils Obtained From Roasted Perilla Seeds As Affected by Extraction Methods

Abstract: The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC‐CO₂], mechanical press, and solvent extraction) were studied. The SC‐CO₂ extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC‐CO₂‐extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press‐extracted and hexane‐extracted oils (P < 0.05). The SC‐CO₂‐extracted oil showed the greatly lower oxidative stability than press‐extracted and hexane‐extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods.     

Mesh-offset-based method to generate a delta volume to support the maintenance of partially damaged parts through 3D printing

Journal of Mechanical Science and Technology - Three-dimensional (3D) printing technology is an excellent tool for implementing multi item, small scale production or for manufacturing objects of...