Microstructure and mechanical properties of Al-Si-Mg alloys fabricated by twin roll casting and subsequent symmetric and asymmetric rolling

Al-Si-Mg aluminum alloys were asymmetrically cold-rolled using differential speed rolling mills. The textural and microstructural evolution with the consecutive working sequence was investigated using an electron backscatter diffraction. There were texture and microstructure variations with the speed ratio and a reduction in the area. Strongly-developed recrystallized cube orientations, {100}?001?, remained during symmetric rolling. The weakened cube orientation mainly changed into random orientations during subsequent annealing, and a small amount of cube orientations remained. However, during asymmetric rolling with a speed ratio of 2, the shear deformation penetrated through the entire thickness direction, and a strong shear texture of rotated cube, {100}?011?, developed. The distinct shear texture was recrystallized into {356}?0 17 14? components. The mechanical properties of the symmetrically- and asymmetrically-fabricated sheets were compared with each other. More balanced planar isotropic values of strength and elongation were obtained from the symmetrically-fabricated sheets, which are mainly due to the weakened random texture.     

A photo-induced dissolution of UO2 sintered pellets in a simulated solution

The objective of this study is to improve the established dissolution technique of UO₂ target by using a photochemical reaction. Photo-dissolution tests of UO₂ sintered powder and pellets were carried out in a simulated nitric acid solution at about 50 °C under UV irradiation. The simulated solution consists of 2 M nitric acid containing elements such as Cs, Sr, Zr, Ru, Mo and Nd. The light source is a Hg-lamp emitting 254 nm wavelength. As results, in the dark reaction, UO₂ sintered pellets were hardly dissolved, whereas UO₂ was rapidly dissolved after 7 hours of dissolution time in the UV irradiation. The very low dissolution rate in the dark reaction was due to surface characteristics of sintered pellets: UO₂ sintered pellet is very dense and has extremely low specific surface area. However, the dissolution rate of UO₂ sintered pellet was considerably increased in the simulated solution under UV irradiation. This was attributed to the fact that ruthenium and molybdenum ions in the simulated solution could accelerate the dissolution of UO₂ under UV irradiation. Additionally, when the pulverized sintered UO₂ powder was used, the dissolution rate of UO₂ increased more rapidly than that of UO₂ sintered pellet.     

Study for the Gas Flow through a Critical Nozzle

In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.     

In vivo assessment of odour retention in an antimicrobial silver chloride-treated polyester textile

An investigation is described in which the effects of bleaching on the reflectance value and yellowness or colour difference of jute were studied. Different concentrations and pH values of solutions of bleaching powder, sodium hypochlorite, and a combination of bleaching powder and hydrogen peroxide were treated under different conditions. The bleached samples were also reduced with potassium borohydride and sodium hydrosulphite. Bleaching with bleaching powder at a fixed available-chlorine concentration (0.25%) at pH 10.5 for 20 min and then exhausting the bath is shown to work better than four successive treatments of 7.5 min each, followed by antichlor treatments. Even better, however, were samples that had been bleached with a combination of bleaching powder and hydrogen peroxide and subsequently reduced with potassium borohydride. Infra-red spectra showed that carbonyl groups resulting from the peroxide treatment disappeared after reduction with borohydride.     

Development of oscillation method for reducing foodborne pathogens on lettuce and spinach

In this study, the efficacy of an oscillator for reducing the numbers of foodborne pathogens on lettuce and spinach was tested. A cocktail of three strains each of Salmonella typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes cells and of Bacillus cereus spores was inoculated onto lettuce and spinach leaves and followed by oscillation at 10 Hz and 20 Hz for up to 30 s. After treatment of inoculated lettuce leaf with an oscillator at 20 Hz for 30 s, 2.58, 2.82, 2.21 and 2.22 Log₁₀ CFU/g reductions were obtained with the cells of S. typhimurium, E. coli O157:H7 and L. monocytogenes and the spores of B. cereus, respectively. In the case of the oscillation treatment of spinach leaf, 2.89, 3.73, 2.46 and 2.25 Log₁₀ CFU/g reductions of those pathogens were achieved under the same condition. Statistically significant reductions were observed after oscillation treatment at 20 Hz for 5-10 s. The oscillation treatment at 10 Hz led to slightly less reductions of the pathogens tested as compared to the treatment at 20 Hz. In conclusion, the oscillation method developed shows to be highly efficacious in reducing foodborne pathogens on lettuce and spinach leaves.     

Atrazine degradation and enzyme activities in an agricultural soil under two tillage systems

The content of atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) as well as the activities of two soil enzymes (urease and beta-glucosidase) were evaluated in an acid agricultural soil, located in a temperate humid zone (Galicia, NW Spain), with an annual ryegrass-maize rotation under conventional tillage (CT) and no tillage (NT). Samples were collected during two consecutive years from the arable layer at two depths (0-5 cm and 5-20 cm) and different times after atrazine application. Hydroxyatrazine and deisopropylatrazine were the main metabolites resulting from atrazine degradation in the acid soil studied, the highest levels being detected in the surface layer of the NT treatment. A residual effect of atrazine was observed since hydroxyatrazine was detected in the arable layer (0-5 cm, 5-20 cm) even one year after the herbicide application. Soil enzyme activities in the upper 5 cm layer under NT were consistently higher than those in the same layer under CT. Urease and beta-glucosidase activities decreased with depth in the profile under NT but they did not show any differences between the two depths for the plots under CT. For both tillage systems enzyme activities also reflected temporal changes during the maize cultivation; however, no consistent effect of the herbicide application was observed.     

用连续振动阻抗法进行预应力钢筋混凝土梁桥的混合健康监测

提出连续振动阻抗法,对预应力钢筋混凝土桥梁的两种破坏形式(即预应力筋破坏或梁破坏)进行混合健康监测。监测包括3个步骤:第一步,通过监测加速信号的变化,对整体破坏进行预警。第二步,通过振动和阻抗识别模式,将破坏类型分为预应力筋破坏或梁破坏。第三,基于形状模式和频率方法,通过测量试验室中几个预应力筋和梁的加速响应和电子-机械阻抗,对所提系统的可行性进行评估。     

Effect of diffuser angle on the discharge coefficient of miniature critical nozzles

Many studies on critical nozzles have been made to accurately measure the mass flow rate of gas and standardize its performance as a flow meter. Recently, much interest has been given to measuring very small mass flow rates in industrial fields, such as MEMS applications. However, the design and performance data of the critical nozzles obtained thus far have been applied mainly to critical nozzles with comparatively large diameters, and available studies on miniature critical nozzles are lacking. In this study, computational fluid dynamics (CFD) method was applied to investigate the influence of the diffuser angle on the discharge coefficient of miniature critical nozzles. In computations, the throat diameter of a critical nozzle varied from 0.2 to 5.0 mm, and the diffuser angle changed from 2° to 8°. The computational results were validated with some available experimental data. The present computational results accurately predicted the discharge coefficient of gas flows through miniature critical nozzles. The discharge coefficient is considerably influenced by the diffuser angle as the throat diameter of the nozzle becomes smaller below a certain value. This implies that miniature critical nozzles should be designed with careful consideration of its effects.     

Gas absorption in vertical slug flow

An investigation has been made of gas absorption characteristics in unstable vertical slug flow. The process studied was the absorption of hexane from an inert carrier gas into paraffin oil. Gas-phase properties were varied by use of nitrogen, helium and Freon-14 as carriers, while variation of liquid-phase properties was achieved by using light and heavy paraffin oils and their mixtures. Absorption efficiencies were high, ranging from 0.75 to 0.99 The values depended not only on operating and system variables, but also on absorber geometry with a distinct discontinuity being observed when the overall mass transfer efficiency was plotted against absorber length H. This discontinuity was particularly marked for the heavy paraffin oil and was found to be related to the variation of slug surface area with H. Flow rates and system properties were found to affect the mass transfer coefficients and a comparison of experimental values with those predicted by the penetration theory suggested that not all the slug surface area was effective in mass transfer.     

An implicit enumeration scheme for the flowshop problem with no intermediate storage

The scheduling of batch processing of materials may be modeled as a flowshop scheduling problem with no intermediate storage, for which the objective is to minimize the makespan. This paper presents a branch and bound procedure which makes use of lower bounds based on estimates of the mean and the variance of makespans derived from the completion of fixed partial sequences of job assignments. Methods of obtaining these estimates are given and a heuristic rule is used to obtain an initial solution which serves as an upper bound to the optimum.