Evaluation of the thixoformability of the A332 Alloy (Al–9.5?wt%Si–2.5?wt%Cu)

The main purpose of this article is to develop and/or use a commercial conventional low-cost raw material as thixoforming material in order to diminish the costs of the thixoforming process. Semi-solid technology usually uses aluminium low-silicon alloys such A356 (Al–7.0 wt%Si) as raw materials. High silicon content alloys with a quasi-eutectic composition diminish the semi-solid range, making it difficult to control the thixoforming temperature, although present excellent mechanical properties. This article reports on the semi-solid behaviour of Al–9.5 wt%Si–2.5 wt%Cu (A332). Thermo-Calc simulations and experimental DSC techniques were used to map the temperature transition from solid to liquid in order to achieve the best semi-solid behaviour and hence the best thixoforming temperature. Samples were reheated at three temperatures to 30, 45 and 60% of the solid fraction applying holding times of 0, 30, 90 and 210 s. The morphological evolution and semi-solid behaviour of the samples at these temperatures were determined via the fixed platen compression test. The structure showed the best semi-solid behaviour at 572 °C, with an apparent viscosity of up to 1.5 × 10⁵ Pa s. The results indicated that the semi-solid behaviour of the commertial Al–9.5 wt%Si–2.5 wt%Cu alloy is similar to that of the alloy A356. Despite its large dendritic structure it is possible, with the correct combination of temperature and time, to use this alloy as raw material for the thixoforming process. Furthermore, semi-solid parts can be produced by thixoforging using this low-cost material without any special preparation.     

The Role of Si and Cu Alloying Elements on the Dendritic Growth and Microhardness in Horizontally Solidified Binary and Multicomponent Aluminum-Based Alloys

Horizontal directional solidification (HDS) experiments were carried out with Al-3wtpctCu, Al-3wtpctSi, and Al- 3wtpctCu-5.5wtpctSi alloys in order to analyze the interrelation between the secondary dendrite arm spacing (λ ₂) and microhardness (HV). A water-cooled horizontal directional solidification device was applied. Microstructural characterization has been carried out using traditional techniques of metallography, optical, and SEM microscopy. The ThermoCalc software was used to generate the phase equilibrium diagrams as a function of Cu and Si for the analyzed alloys. The effects of Si and Cu elements on the λ ₂ and HV evolution of the hypoeutectic binary Al-Cu and Al-Si alloys have been analyzed as well as the addition of Si in the formation of ternary Al-Cu-Si alloy. The secondary dendrite arm spacing was correlated with local solidification thermal parameters such as growth rate (V _L), cooling rate (T _R), and local solidification time (t _SL). This has allowed to observe that power experimental functions given by λ ₂ = Constant (V _L)^−2/3, λ ₂ = Constant (T _R)^−1/3 and λ ₂ = Constant (t _SL)^1/3 may represent growth laws of λ ₂ with corresponding thermal parameters for investigated alloys. Hall–Petch equations have also been used to characterize the dependence of HV with λ ₂. A comparative analysis is performed between λ ₂ experimental values obtained in this study for Al-3wtpctCu-5.5wtpctSi alloy and the only theoretical model from the literature that has been proposed to predict the λ ₂ growth in multicomponent alloys. Comparisons with literature results for upward directional solidification were also performed.

     

A middleware solution for integrating and exploring IoT and HPC capabilities

Even with the considerable advances in the development of middleware solutions, there is still a substantial gap in Internet of Things (IoT) and high-performance computing (HPC) integration. It is not possible to expose services such as processing, storage, sensing, security, context awareness, and actuating in a unified manner with the existing middleware solutions. The consequence is the utilization of several solutions with their particularities, thus requiring different skills. Besides that, the users have to solve the integration and all heterogeneity issues. To reduce the gap between IoT and HPC technologies, we present the JavaCá&Lá (JCL), a middleware used to help the implementation of distributed user-applications classified as IoT-HPC. This ubiquity is possible because JCL incorporates (1) a single application programming interface to program different device categories; (2) the support for different programming models; (3) the interoperability of sensing, processing, storage, and actuating services; (4) the integration with MQTT technology; and (5) security, context awareness, and actions services introduced through JCL application programming interface. Experimental evaluations demonstrated that JCL scales when doing the IoT-HPC services. Additionally, we identify that customized JCL deployments become an alternative when Java-Android and vice-versa code conversion is necessary. The MQTT brokers usually are faster than JCL HashMap sensing storage, but they do not perform distributed, so they cannot handle a huge amount of sensing data. Finally, a short example for monitoring moving objects exemplifies JCL facilities for IoT-HPC development.     

Swarm optimisation algorithms applied to large balanced communication networks

In the last years, several combinatorial optimisation problems have arisen in the computer communications networking field. In many cases, for solving these problems it is necessary the use of meta-heuristics. An important problem in communication networks is the Terminal Assignment Problem (TAP). Our goal is to minimise the link cost of large balanced communication networks. TAP is a NP-Hard problem. The intractability of this problem is the motivation for the pursuits of Swarm Intelligence (SI) algorithms that produce approximate, rather than exact, solutions. This paper makes a comparison among the effectiveness of three SI algorithms: Ant Colony Optimisation, Discrete Particle Swarm Optimisation and Artificial Bee Colony. We also compare the SI algorithms with several algorithms from literature. Simulation results verify the effectiveness of the proposed algorithms. The results show that SI algorithms provide good solutions in a better running time.     

Fuzzy-based algorithm for Fongbe continuous speech segmentation

Text-independent speech segmentation is a challenging topic in computer-based speech recognition systems. This paper proposes a novel time-domain algorithm based on fuzzy knowledge for continuous speech segmentation task via a nonlinear speech analysis. Short-term energy, zero-crossing rate and the singularity exponents are the time-domain features that we have calculated in each point of speech signal in order to exploit relevant information for generating the significant segments. This is down for the phoneme or syllable identification and the transition fronts. Fuzzy logic technique helped us to fuzzify the calculated features into three complementary sets namely: low, medium, high and to perform a matching phase using a set of fuzzy rules. The outputs of our proposed algorithm are silence, phonemes, or syllables. Once evaluated, our algorithm produced the best performances with efficient results on Fongbe language (an African tonal language spoken especially in Benin, Togo and Nigeria).     

Introduction of sulfur groups onto the surface of carbon blacks

Three methods were employed to introduce sulfur groups (thiol and thio ester groups) onto the surface of a carbon black. Positive results were obtained and controled by functional group analysis and radiochemistry.     

Point-source effects on N and P uptake in a forested and an agricultural Mediterranean streams

We examined the effect of point-source inputs from wastewater treatment plants (WWTP) on in-stream uptake of ammonium, nitrate and phosphate and compared it between two streams draining catchments with contrasting land use. The selected streams were La Tordera and Gurri (NE Spain), draining a forest- and an agriculture-dominated catchment, respectively. In each stream, we compared nutrient uptake metrics, estimated from nutrient additions, between two reaches located upstream and downstream of a WWTP input. Measurements were done on 8-9 dates during 2002-2003.In La Tordera, the point-source increased concentrations of all studied nutrients; whereas in Gurri, this effect was less evident. Point-source effects on nutrient uptake differed between the two streams, and among solutes. In La Tordera, uptake lengths (S_w) of ammonium and phosphate averaged hundreds of meters above the point-source, and increased (i.e., decreased uptake efficiency) 4 and 5 times, respectively, below the point-source. S_w of nitrate was ≥ 2 km regardless of reach location. In Gurri, S_w of all studied nutrients was within the km range in the two reaches. In this stream, diffuse nutrient inputs from adjacent fields may overwhelm the local effect of the point-source input.Uptake velocities (v_f) of the studied nutrients ranged between 10EXP^− 6 and 10EXP^− 4 m/s in the two streams, and were similar between the two reaches in each stream. However, phosphate v_f decreased under increasing concentrations following a power function. This trend remained significant when combining our results with those compiled from literature, suggesting the efficiency loss response may be a general trend for phosphate across streams.The relative increases in uptake rates (U) below the point-source were proportional to the relative point-source contribution to downstream nutrient loads, especially for ammonium and nitrate. However, the increases in U were not enough to compensate for the increases in nutrient loads downstream of the WWTP input.     

Role of cellulose ether polymers on ibuprofen release from matrix tablets

Cellulose derivatives are the most frequently used polymers in formulations of pharmaceutical products for controlled drug delivery. The main aim of the present work was to evaluate the effect of different cellulose substitutions on the release rate of ibuprofen (IBP) from hydrophilic matrix tablets. Thus, the release mechanism of IBP with methylcellulose (MC25), hydroxypropylcellulose (HPC), and hydroxypropylmethylcellulose (HPMC K15M or K100M) was studied. In addition, the influence of the diluents lactose monohydrate (LAC) and β-cyclodextrin (β-CD) was evaluated. Distinct test formulations were prepared containing: 57.14% of IBP, 20.00% of polymer, 20.29% of diluent, 1.71% of talc lubricants, and 0.86% of magnesium stearate as lubricants. Although non-negligible drug-excipient interactions were detected from DSC studies, these were found not to constitute an incompatibility effect. Tablets were examined for their drug content, weight uniformity, hardness, thickness, tensile strength, friability, porosity, swelling, and dissolution performance. Polymers MC25 and HPC were found to be unsuitable for the preparation of this kind of solid dosage form, while HPMC K15M and K100M showed to be advantageous. Dissolution parameters such as the area under the dissolution curve (AUC), the dissolution efficiency (DE_{20 h}), dissolution time (t 50%), and mean dissolution time (MDT) were calculated for all the formulations, and the highest MDT values were obtained with HPMC indicating that a higher value of MDT signifies a higher drug retarding ability of the polymer and vice-versa. The analysis of the drug release data was performed in the light of distinct kinetic mathematical models—Kosmeyer-Peppas, Higuchi, zero-, and first-order. The release process was also found to be slightly influenced by the kind of diluent used.