Characterization of a New TiO<Subscript>2</Subscript> Nanoflower Prepared by the Sol–Gel Process in a Reverse Microemulsion

TiO₂ nanoflowers were synthesized for the first time via the sol–gel method inside a reverse microemulsion. The characterization of the products by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) show that this material is constituted of belt-shaped particles that change into a nanoflower morphology after heat treatment at 600 °C. A proposed model could explain the growth process from nanobelt to nanoflower.     

Robust diagnosis to measurement uncertainties using bond graph approach: Application to intelligent autonomous vehicle

This paper deals with robust bond graph model-based fault detection and isolation to improve the robustness of the diagnosis system in presence of measurements and parameters uncertainties. We develop a procedure of measurement uncertainties modeling directly on the graph. By using the structural and causal properties of the bond graph, the robust diagnosis is performed. The interest of the developed methodology consists in using the graphical tool not only for measurement uncertainties modeling, but also for designing robust fault detection and isolation algorithms. Moreover, this method can be easily automated. The developed approach is validated by an application to an electromechanical traction system of intelligent autonomous vehicle.     

Development of size-selective sampling of Bacillus anthracis surrogate spores from simulated building air intake mixtures for analysis via laser-induced breakdown spectroscopy

Size-selective sampling of Bacillus anthracis surrogate spores from realistic, common aerosol mixtures was developed for analysis by laser-induced breakdown spectroscopy (LIBS). A two-stage impactor was found to be the preferential sampling technique for LIBS analysis because it was able to concentrate the spores in the mixtures while decreasing the collection of potentially interfering aerosols. Three common spore/aerosol scenarios were evaluated, diesel truck exhaust (to simulate a truck running outside of a building air intake), urban outdoor aerosol (to simulate common building air), and finally a protein aerosol (to simulate either an agent mixture (ricin/anthrax) or a contaminated anthrax sample). Two statistical methods, linear correlation and principal component analysis, were assessed for differentiation of surrogate spore spectra from other common aerosols. Criteria for determining percentages of false positives and false negatives via correlation analysis were evaluated. A single laser shot analysis of approximately 4 percent of the spores in a mixture of 0.75 m(3) urban outdoor air doped with approximately 1.1 x 10(5) spores resulted in a 0.04 proportion of false negatives. For that same sample volume of urban air without spores, the proportion of false positives was 0.08.     

Thermal stability evaluation of polypropylene protected with grafted amine

Summary Polypropylene containing a grafted amine as oxidation protector was subjected to γ-irradiation for the evaluation of thermal stability. Several formulations were prepared containing hindered amine, Sanduvor PR 31 (0.1, 0.2 and 0.3% w/w) and CaCO₃ (0.6% w/w). The stability assessment was carried out in air by oxygen uptake procedure under isothermal and isobaric conditions (165 °C and normal pressure, respectively). The exposure doses were placed in the range from 0 to 70 kGy. The changes appeared in the main kinetic parameters (oxidation induction time and oxidation rate) evaluated for thermal degradation of irradiated PP specimens are presented and the stability analysis is explained starting from the behaviour differences of various formulations of radiation processed polypropylene. On the low dose range, the drop in thermal stability of modified polypropylene films occurs more abrupt than it was observed for the samples irradiated at higher doses.     

Simulation of complex liquids in micropump

Complex liquids can be encountered in many applications of microdevices. In the present study, the performance of microscrew pump using complex liquid is investigated numerically. The microscrew pump operation depends on the surface sweep forces. It consists of a screw placed inside a microchannel. When the screw rotates, a net force is transferred to the fluid due to differential pressure on the depth of the thread and pressure gradient along the screw axis, thus causing the fluid to displace. Three-dimensional complex liquid simulations of micropump were performed.The effect of screw pitch, thread, Reynolds number and pump load on the micropump performance has been studied. The simulations of complex liquids indicate that the highest bulk velocity is achieved with high thread depth at low Reynolds number. However, effective pumping is accomplished at low Reynolds number, high pressure load and high thread depths.     

Effect of maternal dietary vitamin C intake on the level of vitamin C in breastmilk among nursing mothers in Baghdad,Iraq

The vitamin C content of breastmilk was investigated in a group of nursing mothers attending maternal and child health centers in Baghdad during 1998-2000. Two hundred healthy, nonsmoking, 28- to 38-year-old lactating women were studied. Individual samples of breastmilk were obtained for estimation of vitamin C. Dietary data were collected by using 24-hour food recalls. The mean intake of vitamin C was far below the Food and Agriculture Organization/World Health Organization requirement of 26 +/- 2.13 (SD) mg/day). The vitamin C content of breastmilk was significantly correlated with the maternal intake of vitamin C (r = 0.61, p < .01). The vitamin C content of breastmilk varied with the season. The level was much higher in summer (3.9 +/- 1.05 mg/100 ml) than in winter (3.02 +/- 2.01 mg/100 ml; p < .05). This fluctuation indicates the dependence of breastmilk vitamin C on dietary intake. The results show the need to increase the consumption of vegetables and fruits and to monitor maternal ascorbic acid intake.     

Low Earth-orbit satellite attitude stabilization with fractional regulators

Fractional Order Control methods were applied to a three-axis reaction wheels satellite attitude control system. To show the advantages of this method, a comparative study between a Linear Quadratic Regulator and a Fractional Order Control was established through two principal fractional control laws. The aim is to establish an efficient control law which satisfies a given specification and maintains sufficient stability and accuracy even under the strong effects of intrinsic parameters uncertainties, and also external perturbations.     

Stress Relaxation of Nonlinear Thermoviscoelastic Materials Predicted from Known Creep

A method to predict the stress relaxation response of nonlinear thermoviscoelastic materials from known creep data is presented. For given nonlinear creep properties, and creep compliance represented by the Prony series, it is shown that the Schapery creep model can be transformed into a set of first order nonlinear differential equations. By solving these equations the nonlinear stress relaxation curves for different strain and temperature levels are established. The strain/temperature-dependent constitutive equation can then be constructed for any nonlinear thermoviscoelastic model, as needed for engineering applications. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural,optical and electrical properties of Ag doped PbS thin films: role of Ag concentration

The present work reports on the chemical synthesizes of (0–8 at.%) silver (Ag)-doped PbS thin films with tunable opto-electrical properties. From the X-ray diffraction analyses, it was understood that the preferred growth orientation of Ag:PbS films was dependent on the Ag doping concentration. The variation in the Ag:PbS films orientation was reflected in the film morphology as observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM studies revealed that the variation in Ag concentration lead to different grain shapes for different grain orientations. The AFM study showed that the RMS roughness of the undoped PbS film has been reduced considerably due to silver doping. From the optical studies, a widening in the optical band gap was revealed after Ag-doping due to the quantum confinement effect. It was obtained that 4 at.% Ag-doped PbS thin films display an optimum band gap value of 1.45 eV. As for electrical characterization result, the resistivity reduces and the carrier density improved with 4 at.% Ag concentration. Based on all the data, it was concluded that the 4 at.% Ag-doped PbS thin film showed the best morphological, optical and electrical behavior, which recommend it as an active layer for solar cell devices.