Post-failure behaviour of impulsively loaded circular plates

The dynamic plastic response of a simply supported circular plate is analysed. Emphasis is given to the plate behaviour after it has broken free from the supports due to a local material failure. The theoretical rigid plastic analysis predicts various features of the response such as the time to failure, residual kinetic energy and the critical velocity at failure. The residual kinetic energy of the plate could be significant enough to cause secondary impact damage. It is shown that the shape of the plate changes after breaking free from the supports, which is important for forensic investigations. The solution for various cases were proven to be exact in the context of the upper and lower bounds theorems of the theory of plasticity. (C) 2009 Elsevier Ltd. All rights reserved.

Scaling of structures subject to impact loads when using a power law constitutive equation

It is well known that structures subjected to dynamic loads do not follow the usual similarity laws when the material is strain rate sensitive. As a consequence, it is not possible to use a scaled model to predict the prototype behaviour. In the present study, this problem is overcome by changing the impact velocity so that the model behaves exactly as the prototype. This exact solution is generated thanks to the use of an exponential constitutive law to infer the dynamic flow stress. Furthermore, it is shown that the adopted procedure does not rely on any previous knowledge of the structure response. Three analytical models are used to analyze the performance of the technique. It is shown that perfect similarity is achieved, regardless of the magnitude of the scaling factor. For the class of material used, the solution outlined has long been sought, inasmuch as it allows perfect similarity for strain rate sensitive structures subject to impact loads. (C) 2009 Elsevier Ltd. All rights reserved.

Improvement of the cavitation erosion resistance of UNS S31803 stainless steel by duplex treatment

A duplex surface treatment consisting of High Temperature Gas Nitriding (HTGN) followed by Low Temperature Plasma Nitriding (LTPN) was carried out in an UNS S31803 duplex stainless steel. The HTGN treatment was intended to produce a relatively thick and hard fully austenitic layer giving mechanical support to the thinner and much harder expanded austenite layer. HTGN was performed at 1200 degrees C for 3 h, in a 0.1 MPa N(2) atmosphere while LTPN, was carried out in a 75% N(2) + 25% H(2) atmosphere, at 400 degrees C for 12 h, under a 250 Pa pressure, and 450 V. An expanded austenite gamma(N) layer, 2.3 mu m thick, 1500 HVO.025 hard, was formed on top of a 100 mu m thick, 330 HV 0.1 hard, fully austenitic layer, containing 0.9 wt% N. For comparison purposes LTPN was carried out with UNS S30403 stainless steel specimens obtaining a 4.0 mu m thick, 1500 HV 0.025 hard, expanded austenite layer formed on top of a fully austenitic matrix having 190 HV 0.1. The nitrided specimens were tested in a 20 kHz vibratory cavitation-erosion testing equipment. Comparison between the duplex treated UNS S31803 steel and the low temperature plasma nitrided UNS S30403 steel, resulted in incubation times almost 9 times greater. The maximum cavitation wear rate of the LTPN UNS S30403 was 5.5 g/m(2)h, 180 times greater than the one measured for the duplex treated UNS S31803 steel. The greater cavitation wear resistance of the duplex treated UNS S31803 steel, compared to the LTPN treated UNS S30403 steel was explained by the greater mechanical support the fully austenitic, 330 HV 0.1 hard, 100 mu m layer gives to the expanded austenite layer formed on top of the specimen after LTPN. A strong crystallographic textured surface, inherited from the fully austenitic layer formed during HTGN, with the expanded austenite layer showing {101} crystallographic planes//surface contributed also to improve the cavitation resistance of the duplex treated steel. (C) 2010 Elsevier B.V. All rights reserved.

Spent NiMH batteries-The role of selective precipitation in the recovery of valuable metals

The production of electronic equipment, such as computers and cell phones, and, consequently, batteries, has increased dramatically. One of the types of batteries whose production and consumption has increased in recent times is the nickel metal hydride (NiMH) battery. This study evaluated a hydrometallurgical method of recovery of rare earths and a simple method to obtain a solution rich in Ni-Co from spent NiMH batteries. The active materials from both electrodes were manually removed from the accumulators and leached. Several acid and basic solutions for the recovery of rare earths were evaluated. Results showed that more than 98 wt.% of the rare earths were recovered as sulfate salts by dissolution with sulfuric acid, followed by selective precipitation at pH 1.2 using sodium hydroxide. The complete process. precipitation at pH 1.2 followed by precipitation at pH 7, removed about 100 wt.% of iron and 70 wt.% of zinc from the leaching solution. Results were similar to those found in studies that used solvent extraction. This method is easy, economic, and does not pose environmental threats of solvent extraction. (C) 2009 Elsevier B.V. All rights reserved.

Photo-Fenton removal of water-soluble polymers

This paper presents the results of experiments carried out in a laboratory-scale photochemical reactor on the photodegradation of different polymers in aqueous solutions by the photo-Fenton process. Solutions of three polymers, polyethyleneglicol (PEG), polyacrylamide (PAM), and polyvinylpyrrolidone(PVP), were tested under different. conditions. The reaction progress was evaluated by sampling and analyzing the total organic carbon concentration in solution (TOC) along the reaction time. The behavior of the different polymers is discussed, based oil the evolution of the TOC-time curves. Under specific reaction conditions, the formation and coalescence of solid particles was Visually observed. Solids formation occurred simultaneously to a sharp decrease in the TOC of the liquid phase. This may be favorable for the treatment of industrial wastewater containing polymers, since the photodegradation process can be Coupled with solid separation systems. which may reduce the treatment cost. (C) 2008 Elsevier B.V. All rights reserved.

Micropatterning of single-walled carbon nanotube forest

In this work, high-aligned single-walled carbon nanotube (SWCNT) forest have been grown using a high-density plasma chemical vapor deposition technique (at room temperature) and patterned into micro-structures by photolithographic techniques, that are commonly used for silicon integrated circuit fabrication. The SWCNTs were obtained using pure methane plasma and iron as precursor material (seed). For the growth carbon SWCNT forest the process pressure was 15 mTorr, the RF power was 250W and the total time of the deposition process was 3 h. The micropatterning processes of the SWCNT forest included conventional photolithography and magnetron sputtering for growing an iron layer (precursor material). In this situation, the iron layer is patterned and high-aligned SWCNTs are grown in the where iron is present, and DLC is formed in the regions where the iron precursor is not present. The results can be proven by Scanning Electronic Microscopy and Raman Spectroscopy. Thus, it is possible to fabricate SWCNT forest-based electronic and optoelectronic devices. (C) 2010 Elsevier B.V. All rights reserved.

Miniaturized structures for removal or selection of particles from liquid flow

The aim of this work was the development of miniaturized structures useful for retention and/or selection of particles and viscous substances from a liquid flow. The proposed low costs structures are similar to macroscopic wastewater treatment systems, named baffles, and allow disassemble. They were simulated using FEMLAB 3.2b package and manufactured in acrylic with conventional tools. Tests for retention or selection of particles in water or air and viscous fluids in water were carried out. Either in air or water particles with 50 mu m diameter will be retained but not with 13 mu m diameter. In aqueous flow, it is also possible the retention of viscous samples, such as silicone 350 cSt. The simulated results showed good agreement with experimental measurements. These miniaturized structures can be useful in sample pretreatment for chemical analysis and microorganism manipulation. (C) 2007 Elsevier B.V. All rights reserved.

Fixed-point DSP implementation of nonlinear H(infinity) controller for large gap electromagnetic suspension system

Electromagnetic suspension systems are inherently nonlinear and often face hardware limitation when digitally controlled. The main contributions of this paper are: the design of a nonlinear H(infinity) controller. including dynamic weighting functions, applied to a large gap electromagnetic suspension system and the presentation of a procedure to implement this controller on a fixed-point DSP, through a methodology able to translate a floating-point algorithm into a fixed-point algorithm by using l(infinity) norm minimization due to conversion error. Experimental results are also presented, in which the performance of the nonlinear controller is evaluated specifically in the initial suspension phase. (C) 2009 Elsevier Ltd. All rights reserved.

On the basic reproduction number and the topological properties of the contact network: An epidemiological study in mainly locally connected cellular automata

We study the spreading of contagious diseases in a population of constant size using susceptible-infective-recovered (SIR) models described in terms of ordinary differential equations (ODEs) and probabilistic cellular automata (PCA). In the PCA model, each individual (represented by a cell in the lattice) is mainly locally connected to others. We investigate how the topological properties of the random network representing contacts among individuals influence the transient behavior and the permanent regime of the epidemiological system described by ODE and PCA. Our main conclusions are: (1) the basic reproduction number (commonly called R(0)) related to a disease propagation in a population cannot be uniquely determined from some features of transient behavior of the infective group; (2) R(0) cannot be associated to a unique combination of clustering coefficient and average shortest path length characterizing the contact network. We discuss how these results can embarrass the specification of control strategies for combating disease propagations. (C) 2009 Elsevier B.V. All rights reserved.

Direct drinking water treatment by spiral-wound ultrafiltration membranes

This paper presents the results of a research on direct drinking water treatment through an ultrafiltration pilot plant unit using spiral-wound membranes (3500 MWCO). The source of water is the Guarapiranga Reservoir, an eutrophicated water body located in the metropolitan region of Sao Paulo, Brazil. The data were collected during a period of almost 3400 h, from August 2005 to January 2006. The main objective of the study was to evaluate the membrane production capacity and contaminant removal efficiency. It was verified that the system was able to produce a high quality permeate with a flow close to the specified by the membrane manufacturer. The average permeate flow was 19.7 L.h(-1).m(-2), at 467 kPa and 25 degrees C, with a global water recovery of almost 85%. The removal efficiencies for TOC, UV light absorption, and turbidity were 85%, 56%, and 95%, respectively. The results provide substantial evidence of the technical feasibility of spiral-wound UF membranes for direct drinking water treatment from euthrophicated sources, as an alternative for conventional drinking water treatment systems.

A generalized multi-period mean-variance portfolio optimization with Markov switching parameters

In this paper, we deal with a generalized multi-period mean-variance portfolio selection problem with market parameters Subject to Markov random regime switchings. Problems of this kind have been recently considered in the literature for control over bankruptcy, for cases in which there are no jumps in market parameters (see [Zhu, S. S., Li, D., & Wang, S. Y. (2004). Risk control over bankruptcy in dynamic portfolio selection: A generalized mean variance formulation. IEEE Transactions on Automatic Control, 49, 447-457]). We present necessary and Sufficient conditions for obtaining an optimal control policy for this Markovian generalized multi-period meal-variance problem, based on a set of interconnected Riccati difference equations, and oil a set of other recursive equations. Some closed formulas are also derived for two special cases, extending some previous results in the literature. We apply the results to a numerical example with real data for Fisk control over bankruptcy Ill a dynamic portfolio selection problem with Markov jumps selection problem. (C) 2008 Elsevier Ltd. All rights reserved.

Effects of the herbicides acetochlor and metolachlor on antioxidant enzymes in soil bacteria

The aim of this study was to investigate the antioxidant responses of three bacteria (SD1. KD and K9) isolated from soil previously treated with the herbicides metolachlor and acetochlor. By 165 rRNA gene sequencing, we determined that SD1 is phylogenetically related to Enterobacter asburiae, while KD and K9 have divergent genomes that more closely resemble that of Enterobacter amnigenus. Decreased levels of lipid peroxidation were observed in SD1 and KD following treatment with 34 mM metolachlor or 62 mM acetochlor, respectively, indicating that both bacteria were able to adapt to an increase in ROS production. In the presence of 34 mM metolachlor or 62 mM acetochlor, all bacterial isolates exhibited increases in total catalase (CAT) activity (81% for SDI, 53% for KD and 59% for K9), whereas total SOD activity (assessed based on the profile and intensity of the bands) was slightly reduced when the bacteria were exposed to high concentrations of the herbicides (340 mM metolachlor or 620 mM acetochlor). This effect was due to a specific reduction in SOD IV (K9 and KD isolates) by 45% and 90%, respectively, and SOD V (SD1 isolate) isoenzymes by 60%. The most striking result was obtained in the SD1 isolate, where two novel isoenzymes of glutathione reductase (GR) that responded specifically to metolachlor were identified. In addition, acetochlor was shown to induce the expression of a new 57 kDa protein band in the K9 and KD isolates. The bacteria isolated from the herbicide-contaminated soil exhibited an efficient antioxidant system response at herbicide concentrations of up to 34 mM metolachlor or 62 mM acetochlor. These data suggest a mechanism for tolerance that may include the control of an imbalance in ROS production versus scavenging. The data suggest that specific isoenzymes of CAT and GR could be involved in this herbicide tolerance mechanism. (C) 2011 Elsevier Ltd. All rights reserved.

Body weight as an indicator of fat-free mass in active elderly women

Objective: Fat-free mass (FFM) reduction and the tendency for a reduction in surrounding fatty issue and increase in the middle are a natural consequence of growing old and should be studied in order to gain a better understanding of the aging process. This study set out to find the FFM differences between active elderly women in two age groups (60-69 and 70-80 years) and to determine which of the anthropometric measurements, body weight (BW), abdominal circumference (AC), or body mass index (BMI) are the best predictors of FFM variation within the group. Methods: Eighty-one (n = 81) active elderly women of the Third Age willingly signed up to participate in the research during the activities at the University of the Third Age (UTA) in Brazil. The research was approved by the Research Ethics Committee of the Faculty of Medical Sciences of the State University of Campinas (UNICAMP). Body weight (BW), height (H) and the BMI were measured according to the international standards. The AC was measured in centimetres at the H of the navel and body composition was ascertained using bioimpedance analysis. The SAS program was used to perform the statistical analysis of independent samples and parametric data. Results: The results showed FFM values with significant differences between the two groups, with the lowest values occurring among the women who were over 70 years of age. In the analysis, the Pearson`s Correlation Coefficient for each measured independent variable was ascertained, with the BW measurement showing the highest ratio (0.900). Conclusions: The BW measurement was regarded as reliable, low-cost and easy to use for monitoring FFM in elderly women who engage in physical activities. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Bacterial communities and biogeochemical transformations of iron and sulfur in a high saltmarsh soil profile

Microbial community structure in saltmarsh soils is stratified by depth and availability of electron acceptors for respiration. However, the majority of the microbial species that are involved in the biogeochemical transformations of iron (Fe) and sulfur (S) in such environments are not known. Here we examined the structure of bacterial communities in a high saltmarsh soil profile and discuss their potential relationship with the geochemistry of Fe and S. Our data showed that the soil horizons Ag (oxic-suboxic), Bg (suboxic), Cri (anoxic with low concentration of pyrite Fe) and Cr-2 (anoxic with high concentrations of pyrite Fe) have distinct geochemical and microbiological characteristics. In general, total S concentration increased with depth and was correlated with the presence of pyrite Fe. Soluble + exchangable-Fe, pyrite Fe and acid volatile sulfide Fe concentrations also increased with depth, whereas ascorbate extractable-Fe concentrations decreased. The occurrence of reduced forms of Fe in the horizon Ag and oxidized Fe in horizon Cr-2 suggests that the typical redox zonation, common to several marine sediments, does not occur in the saltmarsh soil profile studied. Overall, the bacterial community structure in the horizon Ag and Cr-2 shared low levels of similarity, as compared to their adjacent horizons, Bg and Cr-1, respectively. The phylogenetic analyses of bacterial 16S rRNA gene sequences from clone libraries showed that the predominant phylotypes in horizon Ag were related to Alphaproteobacteria and Bacteroidetes. In contrast, the most abundant phylotypes in horizon Cr-2 were related to Deltaproteo-bacteria, Chloroflexi, Deferribacteres and Nitrospira. The high frequency of sequences with low levels of similarity to known bacterial species in horizons Ag and Cr-2 indicates that the bacterial communities in both horizons are dominated by novel bacterial species. (c) 2008 Elsevier Ltd. All rights reserved.

Sensory evaluation and physicochemical optimisation of soy-based desserts using response surface methodology

The objective of this study was to develop a dessert that contains soy protein (SP) (1%, 2%, 3%) and guava juice (GJ) (22%, 27%, 32%) using Response Surface Methodology (RSM) as the optimisation technique. Water activity, physical stability, colour, acidity, pH, iron, and carotenoid contents were analysed. Affective tests were performed to determine the degree of liking of colour, creaminess, and acceptability. The results showed that GJ increased the values of redness, hue angle, chromaticity, acidity, and carotenoid content, while SP reduced water activity. Optimisation suggested a dessert containing 32% GJ and 1.17% SP as the best proportion of these components. This sample was considered a source of fibres, ascorbic acid, copper, and iron and garnered scores above the level of `slightly liked` for sensory attributes. Moreover, RSM was shown to be an adequate approach for modelling the physicochemical parameters and the degree of liking of creaminess of desserts. (C) 2010 Elsevier Ltd. All rights reserved.