Uniform Polarization Scattering With Fiber-Coil-Based Polarization Controllers

A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions     

Diagram of phase transformations in the austenite of hardened alloy Fe-28% Mn-8.5% Al-1% C-1.25% Si as a result of aging due to isothermal heating

The phase composition and the morphology of structures formed as a result of isothermal holds in the range of aging temperatures of hardened alloy Fe-28% Mn, 8.5% Al-1% C-1.25% S are studied. A diagram of the decomposition of initial austenite is plotted starting with the early stages and ending with the moment when the system attains the equilibrium state.     

A new family of continuous/discontinuous three-dimensional boundary elements with application to acoustic wave propagation

This paper presents a new family of continuous/discontinuous three-dimensional boundary elements which has been implemented in a computer system for acoustic wave propagation in the frequency domain. The system includes elements of different geometrical shapes, 'order of interpolation and degree of continuity. Results of several tests are included to show the efficiency of the family of elements.     

Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil

Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml^-1 or µg F g^-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg^-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible.     

Tuning of 802.11e network parameters

This paper introduces a mechanism which dynamically tunes the parameters of the 802.11e contention-based access method. The proposed mechanism aims at providing QoS as well as ameliorating the problem of delay asymmetry.     

Specific consumption of liquid biofuels in gasoline fuelled engines

Oxygenated fuels increase fuel consumption due to their low enthalpy of combustion; however, their high antiknock index renders them suitable for use in engines with a high compression rate, increasing their thermal yield. This study evaluated the performance of biorenewable oxygenated fuels (ethanol and isoamyl alcohol) and partially renewable fuels (ETBE: ethyl tert-butyl ether, TAEE: tert-amyl ethyl ether and di-TAE: di-tert-amyl ether) with high degree of purity and in mixtures with automotive gasoline, based on tests with Otto cycle engines. Among the oxygenated fuels evaluated here, di-TAE was found to present the best characteristics of performance, both individually and in mixtures with gasoline.     

Development of correlation between potassium hydroxide number and conductivity of concentrated natural rubber latex

Increase in the ion concentration in the medium was found to increase conductivity and potassium hydroxide number (KOH No) in natural rubber latex (NRL). Addition of long chain fatty acids can increase the ion concentration in the medium and stability of NRL. A series of concentrated natural rubber latex samples from three different areas with different soils and climatic conditions were tested for the parameters such as KOH No and conductivity. They have been measured over a period of 62 days, upon addition of soap to natural rubber latex concentrate. The result showed that there was a strong positive linear correlation between conductivity and KOH No. The regression equation to express the relationship between the variables has also been found. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Mycological survey for potential aflatoxin and ochratoxin producers and their toxicological properties in harvested Brazilian black pepper.

A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis.     

Superconductivity in a new quaternary phase with HgSm0.5In0.5Pb2 composition

This work reports a systematic study on the structural and superconducting properties in the Hg-Sm-In-Pb system. It is investigated how In and Sm dopings influence the superconducting properties of the HgPb₂ phase which was recently reported. Results for the HgSm_1 − xPb₂ system show that Sm atoms substitute Hg vacancies in the tetragonal phase which do not affect the onset critical temperature of the HgPb₂ compound. Simultaneous Sm and In doping effects on the properties of the HgPb₂ phase are also studied. Experimental and simulations of X-ray powder diffractograms suggest that the HgSm_1 − xIn_xPb₂ system (0.2 ≤ x ≤ 0.7) has a pseudo-cubic structure with lattice parameters near 4.88 Å. Superconducting properties measurements show that this system has an optimum doping at x ∼ 0.5 with the onset critical temperature close to 6.9 K. This is the highest superconducting critical temperature for the AuCu prototype so far reported.     

Steady-State Control Reference and Token Conservation Laws in Continuous Petri Net Systems

This paper addresses several questions related to the control of timed continuous Petri nets under infinite server semantics. First, some results regarding equilibrium states and control actions are given. In particular, it is shown that the considered systems are piecewise linear, and for every linear subsystem the possible steady states are characterized. Second, optimal steady-state control is studied, a problem that surprisingly can be computed in polynomial time, when all transitions are controllable and the objective function is linear. Third, an interpretation of some controllability aspects in the framework of linear dynamic systems is presented. An interesting finding is that noncontrollable poles are zero valued.