Very high-order accurate finite volume scheme for the convection-diffusion equation with general boundary conditions on arbitrary curved boundaries

Obtaining very high-order accurate solutions in curved domains is a challenging task as the accuracy of discretization methods may dramatically reduce without an appropriate treatment of boundary conditions. The classical techniques to preserve the nominal convergence order of accuracy, proposed in the context of finite element and finite volume methods, rely on curved mesh elements, which fit curved boundaries. Such techniques often demand sophisticated meshing algorithms, cumbersome quadrature rules for integration, and complex nonlinear transformations to map the curved mesh elements onto the reference polygonal ones. In this regard, the reconstruction for off-site data method, proposed in the work of Costa et al, provides very high-order accurate polynomial reconstructions on arbitrary smooth curved boundaries, enabling integration of the governing equations on polygonal mesh elements, and therefore, avoiding the use of complex integration quadrature rules or nonlinear transformations. The method was introduced for Dirichlet boundary conditions and the present article proposes an extension for general boundary conditions, which represents an important advance for real context applications. A generic framework to compute polynomial reconstructions is also developed based on the least-squares method, which handles general constraints and further improves the algorithm. The proposed methods are applied to solve the convection-diffusion equation with a finite volume discretization in unstructured meshes. A comprehensive numerical benchmark test suite is provided to verify and assess the accuracy, convergence orders, robustness, and efficiency, which proves that boundary conditions on arbitrary smooth curved boundaries are properly fulfilled and the nominal very high-order convergence orders are effectively achieved.     

Effect of the cerium (III) chloride heptahydrate on the corrosion inhibition of aluminum alloy

In the present work, the corrosion protection of aluminum alloy AA2024-T3 has been studied in NaCl solution, with and without the addition of cerium (III) chloride heptahydrate. The corrosion inhibitor efficiency after immersion into 10 mM NaCl, with or without 3 mM of CeCl₃·7H₂O at 20°C, 40°C, and 60°C was investigated. The performed quantitative tests include electrochemical techniques, such as the method of quasipotentiostatic polarization (Tafel extrapolation), cyclic polarization, and electrochemical impedance s pectroscopy to determine corrosion rate (v_corr), inhibition efficiency (η %), protective ability (γ), degree of coverage (ϑ), and pitting nucleation resistance. The samples were analyzed with scanning electron microscopy and energy dispersive X-ray analysis to evaluate and characterize the precipitates formed on the surface of aluminum samples and to determine dominant type of corrosion. The formation of Ce³⁺ precipitates occurred on cathodic intermetallic sites and the surface, in general, resulting in improved corrosion resistance. Tested cerium (III) chloride heptahydrate proved to be an effective inorganic corrosion inhibitor for AA2024-T3 in chloride solution, which, by the action of cerium ions, reduced corrosion on the surface of the studied aluminum alloy.     

A modified nanoelectronic spiking neuron model

Spiking neural networks (SNNs) first came to the attention of scientists due to the search for a structure capable of emulating more closely the behavior of the human brain. The biological nervous system has some characteristics that allow it to process a large amount of data very quickly. It is also a fault-tolerant system, with a high level of parallelism. Low power consumption is another feature of the human brain that is desirable for electronic circuits. In this context, several models of artificial spiking neurons were developed, aiming to construct networks able to combine the best characteristics of the human brain. Most of these models, however, lack validation in larger networks. This paper proposes the implementation of an SNN based on a nanoelectronic spiking neuron model developed in previous works. To validate the behavior of an isolated neuron in a network, logic gates (NOT, OR, AND, and XOR) are used as a benchmark. The goal of this paper is to present a feasibility study on the possibility of implementing such nanoelectronic spiking neuron networks based on this spiking neuron model. Nanoelectronics represents an appealing implementation due to the gains regarding occupied area and power consumption, which are inherent characteristics of this technology. The neuron model was modified for simulation at room temperature. An information code based on the amplitude of the pulses presented at the output of the neuron was developed. During deployment of this approach, some limitations regarding the neuron model were detected; some possible solutions are proposed as future work.     

Development of an asymptotic modeling methodology for tibio-femoral contact in multibody dynamic simulations of the human knee joint

A new methodology for modeling articular tibio-femoral contact based on the recently developed asymptotic model of frictionless elliptical contact interaction between thin biphasic cartilage layers is presented. The developed mathematical model of articular contact is extended to the case of contact between arbitrary viscoelastic incompressible coating layers. The approach requires use of the smooth contact surface geometry and efficient contact points detection methods. A generalization of the influence surface theory based method for representing articular surfaces from the unstructured noisy surface data is proposed. The normal contact forces are determined analytically based on the exact solution for elliptical contact between thin cartilage layers modeled as viscoelastic incompressible layers. The effective geometrical characteristics of articular surfaces are introduced for use in the developed asymptotic models of elliptical contact between articular surfaces.     

The Use of Static and Humidity Cell Tests to Assess the Effectiveness of Coal Waste Desulfurization on Acid Rock Drainage Risk

The environmental benefits of waste desulfurization were evaluated in the Santa Catarina coal field, Brazil. Coal waste from a beneficiation plant was separated into three density fractions, using a two stage process. Characterization of these fractions indicated that the low (D?<?2.2 g/cm³) and high (D?>?2.7 g/cm³) density fractions were potentially suitable for energy and sulfuric acid production, respectively. The waste fraction of intermediate density (2.2?<?D?<?2.7 g/cm³) represented 69% of the total mass studied and had a relatively low sulfide content, and it was postulated that it may be suitable for land disposal with minimum risk to the surrounding environment. This hypothesis was tested using laboratory-scale static and kinetic tests, which indicated that although the fraction remained net acid generating, the rate and net amount of metals, salts, and acidity that leached was considerably less than that of the discards before separation. It was concluded that this approach could reduce the amount of waste generated, as well as the associated pollution risk.     

Measures for diffusion of solar PV in selected African countries

This paper investigates how African governments are considering supporting and promoting the diffusion of solar PV. This issue is explored by examining so-called ‘technology action plans (TAPs)’, which were main outputs of the Technology Needs Assessment project implemented in 10 African countries from 2010 to 2013. The paper provides a review of three distinct but characteristic trajectories for PV market development in Kenya (private-led market for solar home systems), Morocco (utility-led fee-for service model) and Rwanda (donor-led market for institutional systems). The paper finds that governments’ strategies to promoting solar PV are moving from isolated projects towards frameworks for market development and that there are high expectations to upgrading in the PV value chain through local assembly of panels and local production of other system elements. Commonly identified measures include support to: local production; financing schemes; tax exemptions; establishment and reinforcement of standards; technical training; and research and development.     

Synthesis and comparison of low-power high-throughput architectures for SAD calculation

Video applications are increasingly present in consumer electronic devices which require low-power and low-energy consumption. Sum of Absolute Differences (SAD) is the most used distortion metric in video coding implementation and consumes a relative large area in the motion estimation hardware. This paper presents the standard-cells synthesis and a comprehensive analysis of various parallel hardware architectures alternatives for SAD calculation, focusing on different design constraints such as high-performance (maximum throughput) and the tradeoff between high-performance and low-power dissipation (namely an isoperformance target). Low-power techniques supported by commercial standard-cells tools are exercised in this design, such as clock gating, multi-threshold (VT) and a combination of slow and fast standard-cells. We achieved significant power reduction for the architectures with lower frequencies and higher parallelism, slow cells and mainly with only one pipeline stage.