Metallized photoresist grating as a polarizing beam splitter

We propose and demonstrate the use of a simple holographic relief photoresist grating covered with an aluminum film as a reflecting polarizing beam splitter. The polarizing effects were achieved as a result of the nonsinusoidal profile of the grating. The best parameters of the gratings for optimizing the polarizing-beam-splitting properties were found by the introduction of the experimental profiles in diffraction calculation software. Theoretical and experimental results are presented, confirming the feasibility of the element.     

Oil spills debris clean up by thermal desorption

Oil spills represent a significant environmental issue in Brazil. This paper presents the latest results of a comprehensive experimental programme aimed at understanding how the presence of spilled oil affects the properties of sands and at studying alternatives to remediate the affected shores. Results indicate that oil causes a slight increase in grain size and uniformity, and oiled debris presents a smaller void ratio but a larger unit weight. It was also observed that effective strength parameters for both the natural and oiled debris were the same although the undrained strength of a natural sand is much higher than that of the contaminated sand. At ambient temperature, oiled debris emits methane and ammonia, and these emissions tend to increase with rising temperatures. On the other hand, the oil and grease content from oiled debris decreases with rising temperature and prolonged exposure. Finally, in situ thermal desorption seems to be a promising method for cleaning debris from oil spills. It is simple, fast and avoids all the difficulties associated with digging up the soil for disposal or cleanup.     

Evaluation of the salt accumulation process during inundation in water resource of Contas river basin (Bahia-Brazil) applying principal component analysis

The high salinization in some reservoirs of the Contas river basin (Bahia-Brazil) has been erroneously attributed only to concentration by evaporation. However, recent studies of this basin have shown that in period of intense rainfalls, occur an increase of the saline concentration in the flowing rivers of the reservoirs. The application of statistical methods (cluster and principal components analysis) have shown that this fact can be attributed to the discharge of saline waters from the small reservoirs of every drained area, provoked by inundation, is also an important factor in the salinization process. Thus the study of the geochemical variables: Na(+), K(+), Ca(2+), Mg(2+), Cl(-), SO(4)(2-) and CO(3)(2-), showed one group formed by Na(+) and Cl(-), attributed to the discharge of saline water provoked by inundation from a small reservoir, and a second group constituted by Ca(2+), Mg(2+), K(+) and SO(4)(2-), due to an increase provoked by the evaporation in the salinization process.     

RRS + LS-SVM: a new strategy for “a priori” sample selection

We present in this work a new Sparse Hybrid Classifier, by using reduced remaining subset (RRS) with least squares support vector machine (LS-SVM). RRS is a sample selection technique based on a modified nearest neighbor rule. It is used in order to choose the best samples to represent each class of a given database. After that, LS-SVM uses the samples selected by RRS as support vectors to find the decision surface between the classes, by solving a system of linear equations. This hybrid classifier is considered as a sparse one because it is able to detect support vectors, what is not possible when using LS-SVM separately. Some experiments are presented to compare the proposed approach with two existent methods that also aim to impose sparseness in LS-SVMs, called LS ²-SVM and Ada-Pinv.     

Scintillating properties of pure and doped BGO ceramics

The ceramic processing and characterization of Bi₄Ge₃O₁₂ pure and doped with Eu³⁺ and Nd³⁺ was performed in order to investigate its potential use in radiation detector devices. Single phase Bi₄Ge₃O₁₂ in pure state and containing 1% of the dopands Nd³⁺ and Eu³⁺ were produced via a solid state route and their photoluminescent and radioluminescent properties were investigated. When excited at 200–230 nm, pure BGO ceramics presented a wide photoluminescent band emission centered at 450 nm, assigned to the Bi³⁺ internal transitions. For the doped samples under the same excitation, this wide band was superposed by the emission peaks of the rare earth dopands, at around 600 nm for BGO:Eu³⁺ and at 350 nm, 430 and 600 nm for BGO:Nd³⁺. Radioluminescence measurements presented similar results and allowed the determination of the light output efficiency of the three scintillators. The values determined were 4 × 10³ photons/MeV for BGO:Nd and 5.9 × 10³ photons/MeV for BGO:Eu, which are higher than the value 3.9 × 10³ photons/MeV determined previously for the pure ceramic. A selective sensibility of the BGO:Eu ceramics to the nature and energy of the radiation, which is not observed in pure samples, was also presented and discussed.     

Processing of submicrometric CaTi0.8Fe0.2O3-δ ceramics by mechanical activation

Effects of mechanical activation of precursors in order to obtain CaTi_0.8Fe_0.2O_3-δ are reported. Mixtures of CaCO₃, TiO₂ and Fe₂O₃ were dry-grinded in Teflon or zirconia containers using planetary ball-mills at different rotations (200, 300 and 500 rpm) and for various periods of time. The perovskite is not formed just by milling and a subsequent heat treatment at 800–1,000 °C was necessary. This still represents a significant advantage over the classical ceramic route as a result of the improved reaction kinetics due to the smaller grain size (<100 nm) of the activated powders and a modification of the thermodynamic initial state. Dense ceramic samples showing a bimodal submicrometric grain-size distribution (100–200 and 250–500 nm) were obtained after sintering the activated powders at 1,150 °C TEM revealed homogeneous samples, free from inhomogeneities such as core-shell grains typically observed in ceramics obtained from non-activated precursors sintered at 1,320–1,350 °C.     

Optimal design in vibration control of adaptive structures using a simulated annealing algorithm

Advanced reinforced composite structures incorporating piezoelectric sensors and actuators are increasingly becoming important due to the development of smart structures. These structures offer potential benefits in a wide range of engineering applications such as vibration and noise suppression, shape control and precision positioning. This paper presents a finite element formulation based on the classical laminated plate theory for laminated structures with integrated piezoelectric layers or patches, acting as sensors and actuators. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of freedom for the generalized displacements, and one additional electrical potential degree of freedom for each surface bonded piezoelectric element layer or patch. The control is initialized through a previous optimization of the core of the laminated structure, in order to minimize the vibration amplitude and maximize the first natural frequency. Also the optimization of the patches position is performed to maximize the piezoelectric actuators efficiency. The simulated annealing algorithm is used for these purposes. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers or patches, and to calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the optimization of an illustrative adaptive laminated plate case. The influence of the position and number of piezoelectric patches, as well as the control gain, are investigated and the results are presented and discussed.     

Precordial mapping in acute myocardial infarction

Serial precordial mapping was done in 30 patients with acute anterior myocardial infarction, 27 transmural and 3 subendorcardial. The sum of ST elevations in the 48 lead map was designated as sigma ST. Normal sigma ST was calculated as 27.1+/-3.1 in males and 14.3+/-2.8 in females. In infarction it was 100.4+/-58.2 in males and 84.8+/-50.9 in females on the 1st day of admission. Sigma ST was elevated on day 1 and tended to fall gradually. In 6 patients it was normal by day 7 and in 7 it was still abnormal by day 21. This fall roughly correlated with fall in SGOT and CPK levels. Significant elevation of sigma ST occurred in 14 of 27 cases after day 1. In 10 of 27 cases significant re-elevation occurred on day 4 or after i.e. when the patient was outside the ICCU. In 10 of the 14 re-elevations there was pain or worsening of clinical picture and in 12 there was re-elevation of SGOT. This elevation presumably implied infarct extension. There was a tendency to more arrhythmias in the patients with higher sigma ST and of the 4 deaths in the series 3 had very high sigma ST and high levels of SGOT. The patient with the highest sigma ST 295 died in cardiogenic shock. The number of risk factors was found to be higher in the high sigma ST group.     

Effect of thermal treatments on tensile strength of commercially cast pure titanium and Ti-6Al-4V alloys

Heating titanium structures is assumed to relieve tensions induced by the casting process as well as possibly optimizing some mechanical properties. The aim of this investigation was to evaluate the effect of thermal treatments on tensile strength of commercially pure titanium (CP Ti) and Ti-6Al-4V alloy. Thirty dumbbell rods, with diameters of 3.0 mm at the central segment and lengths of 42 mm, were cast for each metal using the Rematitan System. CP Ti and Ti-6Al-4V specimens were randomly divided into three groups of ten: a control group that received no thermal treatment and two test groups. One (T1) was heated at 750 ^∘C for 2 h and the other (T2) was annealed at 955 ^∘C for 1 h and aged at 620 ^∘C for 2 h. Tensile strength was measured with a universal testing machine (MTS model 810). Tensile strength means and standard deviations were statistically compared using a Kruskal-Wallis test at a α = 0.05 significance level. No statistically significant differences in tensile strength were observed among CP Ti groups. For the Ti-6Al-4V alloy, the control and T1 groups revealed statistically higher tensile strengths when compared to the T2 group, with no significant difference between the control and T1 groups.