Decomposition of Two Aluminum Sulfates and Characterization of the Resultant Aluminas

Two special types of anhydrous aluminum sulfate with extreme grain shapes were prepared; one, obtained by precipitation from concentrated sulfuric acid solution, is rhombohedral near cubic single-crystal grains and the other, from acetic acid solution, consists of very thin flaky particles. The morphology of sulfate and calcined alumina, the sulfate decomposition, the η-α alumina transformation, and the crystallite growth of α alumina were studied and compared with those processes for reagent-grade sulfate. The morphology of anhydrous sulfate was shown to greatly affect the heat-treatment characteristics of alumina and the sulfate decomposition behavior.     

11B and 27Al Nuclear Quadrupole Interactions in SiO2-B2O3-Al2O3-R2O Glass Systems

Quadrupole interactions of ¹¹B and ²⁷Al in SiO₂-B₂O₃-Al₂O₃-R₂O glass systems were investigated to determine the structure of these glasses, which should be amenable to chemical strengthening. The ratio of BO₄ units to BO₃ units approached unity as the R₂O/Al₂O₃ ratio for compounds having fixed B₂O₃ contents approached unity. Nuclear quadrupole coupling constants ( e²Qq/h =2.73 to 2.93 MHz) were measured for the NMR spectra of ¹¹B triangles. The line shapes of ²⁷Al spectra varied with chemical composition, but a few glasses exhibited ²⁷Al line shapes similar to those of the AlO₄ triclusters in SiO₂-Al₂O₃-Na₂O glasses. Compositional trends in the formation of BO₄ and AlO₄ were deduced from the NMR spectra.     

Optical and EPR Studies of Redox Interactions of Polyvalent Ions (Cr, Cu) in Glass

Chromium centers in isolated Cr ions and Cr(III)-Cu(II) redox interactions were investigated by optical and EPR spectra. Line shapes and intensities of high-field Cr(III)-Cu(II) superimposed EPR absorption lines were sensitive to alkali content of host glasses. High-field chromium g values (1.94 to 1.99) and intensities (190 to 3600) were calculated. The increase in g values from 1.96 to 1.98 is related to an increase in Cr(V) and to a conversion from Cu(I) to Cu(II) with increased alkali content. Two components of Cr powder spectra near g = 2.0 and g = 5.0 correspond to isolated octahedral Cr centers described by Landry et al. Cr-Cr pair structure was not observed for low Cr₂O₃ concentrations. Three components of optical absorption bands near 340 nm, 430 to 460 nm, and 600 nm were measured in Cr(III)-Cu(II) redox systems. Electronic interactions of Cr(III)-Cu(II) redox systems and the structure of Cr centers are discussed.     

A successive projection method for binary pattern recognition with multilayer feedforward neural networks

Error back-propagation (BP) is one of the most popular ideas used in learning algorithms for multilayer neural networks. In BP algorithms, there are two types of learning schemes, online learning and batch learning. The online BP has been applied to various problems in practice, because of its simplicity of implementation. However, efficient implementation of the online BP usually requires an ad hoc rule for determining the learning rate of the algorithm. In this paper, we propose a new learning algorithm called SPM, which is derived from the successive projection method for solving a system of nonlinear inequalities. Although SPM can be regarded as a modification of online BP, the former algorithm determines the learning rate (step-size) adoptively based on the output for each input pattern. SPM may also be considered a modification of the globally guided back-propagation (GGBP) proposed by Tang and Koehler. Although no theoretical proof of the convergence for SPM is given, some simulation results on pattern classification problems indicate that SPM is more effective and robust than the standard online BP and GGBP     

NUCLEATION AND GROWTH OF OXIDE NANOPARTICLES PREPARED BY INDUCTION THERMAL PLASMAS

The reactive evaporation method of injected metal powders was investigated for preparing oxide nanoparticles. The method has advantages such as evaporation is enhancement of the injected powder owing to exothermic reaction heat of the metal powder oxidation in induction thermal plasmas. Tangential gas flow injection to the plasma tail flame controls the diameter and the yield of the oxide nanoparticles. The purpose of this research is to investigate the effect of the injection gas flow on the preparation mechanism of oxide nanoparticles in thermal plasmas by experimental work and numerical analysis. An increase in the flow rate of the injection gas leads to an increase in the diameter as well as the yield of the prepared nanoparticles. Numerical analysis for nucleation and growth provides the preparation mechanism of the oxide nanoparticles; however, a more sophisticated model should be developed.     

Finite spectrum assignment of linear systems with a class of non-commensurate delays

This paper is concerned with finite spectrum assignment of linear systems with non-commensurate delays. It is proved that if a feedforward pass between states variables does not have multi non-commensurate delays in parallel but only one or no delay in series, then the system is finite spectrum assignable even though the feedback pass has multi non-commensurate delays in parallel.     

Heat-induced Gelation of Chicken Gizzard Myosin

Chicken gizzard myosin solution formed a gel when heated above 40°C. The rigidity of the gel was constant above 65°C. Maximum pH for gel formation was 5.9 at 0.6M and 5.7 at 0.15M KCl. Higher rigidity of the myosin gel was observed at low ionic strength than at high ionic strength. Rigidities of myosin at 0.6M KCl increased by (mg/mL)^2.5 and at 0.15M (mg/mL)^{1, 4} myosin concentration. The strength of gizzard myosin gels was comparable to that of myosin gels from chicken breast muscle under similar conditions.     

Mn和V对TiAl合金热腐蚀的影响

Mn和V对TiAl金属间化合物在900℃(Na，K)2SO4熔盐中热腐蚀行为的影响有所不同．TiAl合金中加入Mn后，最外层的腐蚀产物为以Al2O3为主、另有少量TiO2的混合物；内层是Al，Ti和Mn的混合氧化物以及Ti的硫化物．加Mn在一定程度上减弱了TiAl合金的耐蚀性TiAl和TiAl-Mn合金中加入V后耐蚀性明显变差，最外层腐蚀产物以TiO2为主，并含有少量Al2O3和微量的V2O5，腐蚀层中的V2O5引起Al2O3的酸性溶解，因而不能形成保护性的Al2O3层，形成的TiO2和Al2O3混合膜的黏附性差，较易剥落。     

Microinfrared reflection spectroscopic mapping: application to the detection of hydrogen-related species in natural quartz

A new method of microinfrared reflection spectroscopy and mapping analysis is briefly introduced. It was used to detect distributions and structures of hydrogen‐related species (e.g. H₂O, SiOH and SiH) in plastically deformed natural quartz. We used a Fourier transform‐infrared spectrometer with a microscopic imaging system fully automated for all microscope functions (e.g. focusing, aperture, stage motion and measurements). Mapping can be made in thin sections with a thickness of 50 µm at room temperature and low temperatures (77 K) using a liquid N₂ cooling system. Infrared reflection spectra were obtained by five scans for each point with a range from 4000 to 400 cm^?1. The spectra were measured five times within about 2.5 s at each position. The scanning interval was 100–150 µm using a 100 × 100 µm² aperture. All obtained spectral data were stored in computer memory to construct two‐dimensional mappings of infrared absorption. From the comparisons between infrared mapping images and deformation microstructures, in addition to the molecular H₂O around 3600–3400 cm^?1, the hydrogen‐related point defects (i.e. SiOH and SiH) around 970–900 cm^?1 within quartz grains and between grain boundaries increased with decreasing grain sizes (increasing plastic strain). The method can detect the SiOH and SiH along grain boundaries that enhance the hydrolytic weakening of natural quartz.     

Time‐lapse lab‐based x‐ray nano‐CT study of corrosion damage

An experimental protocol (workflow) has been developed for time‐lapse x‐ray nanotomography (nano‐CT) imaging of environmentally driven morphological changes to materials. Two case studies are presented. First, the leaching of nanoparticle corrosion inhibitor pigment from a polymer coating was followed over 14 days, while in the second case the corrosion damage to an AA2099 aluminium alloy was imaged over 12 hours. The protocol includes several novel aspects relevant to nano‐CT with the use of a combination of x‐ray absorption and phase contrast data to provide enhanced morphological and composition information, and hence reveal the best information to provide new insights into the changes of different phases over time. For the pigmented polymer coating containing nominally strontium aluminium polyphosphate, the strontium‐rich components within the materials are observed to leach extensively whereas the aluminium‐rich components are more resistant to dissolution. In the case of AA2099 it is found that the initial grain boundary corrosion is driven by the presence of copper‐rich phases and is then followed by the corrosion of grains of specific orientation.