Evaluating Different Solutions to Design Fault Tolerant Systems with SRAM-based FPGAs

The latest SRAM-based FPGA devices are making the development of low-cost, high-performance, re-configurable systems feasible, paving the way for innovative architectures suitable for mission- or safety-critical applications, such as those dominating the space or avionic fields. Unfortunately, SRAM-based FPGAs are extremely sensitive to Single Event Upsets (SEUs) induced by radiation. SEUs may alter the logic value stored in the memory elements the FPGAs embed. A large part of the FPGA memory elements is dedicated to the configuration memory, whose content dictates how the resources inside the FPGA have to be used to implement any given user circuit, SEUs affecting configuration memory cells can be extremely critics. Facing the effects of SEUs through radiation-hardened FPGAs is not cost-effective. Therefore, various fault-tolerant design techniques have been devised for developing dependable solutions, starting from Commercial-Off-The-Shelf (COTS) SRAM-based FPGAs. These techniques present advantages and disadvantages that must be evaluated carefully to exploit them successfully. In this paper we mainly adopted an empirical analysis approach. We evaluated the reliability of a multiplier, a digital FIR filter, and an 8051 microprocessor implemented in SRAM-based FPGA’s, by means of extensive fault-injection experiments, assessing the capability provided by different design techniques of tolerating SEUs within the FPGA configuration memory. Experimental results demonstrate that by combining architecture-level solutions (based on redundancy) with layout-level solutions (based on reliability-oriented place and route) designers may implement reliable re-configurable systems choosing the best solution that minimizes the penalty in terms of area and speed degradation.     

Coupling phenomena and vortex transitions in superconducting Ni/Nb multilayers

We have studied some structural and superconducting properties of Ni/Nb multilayered films prepared by magnetron sputtering. Magnetization measurements allowed us to establish a rich H × T diagram that indicates a 3D-2D dimensional crossover of the vortex system, as revealed by the parallel upper critical field behavior. Consistently, it was identified a possible decoupling line associated with the transition of Abrikosov vortex lines into vortex pancakes, starting around the same crossover region. An irreversibility line was also determined and it suggests different regimes of the vortex matter, where the role played by the Ni ferromagnetic layers might be relevant.     

Cumulative impact assessment on air quality from multiple open pit mines

Both open pit mine and smelter projects can have significant impacts on a variety of environmental resources. Among these, air quality of the surroundings is a key issue. Additionally, the environmental assessment of projects demands integrated approach taking in account all pollution sources. Therefore, specific focus has been put on the methodology for assessing impacts on air quality. This paper proposes an integrated index of environmental impact aiming to quantify the air quality impact of industrial operations around an urban area, in case of scarcity of in situ acquired data. This proposed pollution index is demonstrated by a case study conducted in the municipality of Congonhas, Brazil, in which contributions of five open pit mines and two smelters were studied. To achieve the pollution index, the wind rose and distances from the centroids of effective areas to the urban nucleus itself were considered, taking into account the wind projection areas from windward impacting sources on the leeward impacted urban site. The proposed index also includes the squared wind speed (proportional to the kinetic energy transferred in uplifting dust from ground surface). The method proposed is considered suitable for impact assignment for each one of the air pollution sources in the neighborhood of studied area. Some fluid dynamic aspects of airborne particulate matter are also studied by proposing a new equation for threshold saltation speed.     

The use of remote-sensing techniques to monitor dense reservoir networks in the Brazilian semiarid region

Reservoirs are the main water source in the Brazilian semiarid region, especially in the crystalline-geology watersheds, forming high-density reservoir networks (HdRN). However, in most cases, the construction of these reservoirs has been done without technical supervision. The objective of this work was to map and evaluate the spatial distribution of the 25,000 km² Orós Reservoir Basin (ORB) HdRN, in semiarid Brazil, with the help of remote-sensing tools associated with geographic information systems (GIS). Using LANDSAT 5 images of the end of the 2011 rainy season of the ORB, the remote-sensing technique allowed the identification of 6002 polygons, which corresponded to only 4717 reservoirs (implying a misidentification of 21%). Between 2002 and 2011, a 17.5% increase (and 1.81% annual increase) in the number of reservoirs in the basin was observed, still lower than the annual increment from 1970 to 2002, when an average increase of 2.64% per year was observed, in other studies. The perimeter of the reservoirs ranged from 0.250 to 560 km and the individual water surface area ranged from 0.004 to 195.0 km², resulting in a total surface of 465.0 km². Analysing the surface area of the strategic reservoirs, results showed that the estimation of the surface area (from remote sensing with manual polygon adjustment) yielded values very close to those of the on-site monitored areas, with R² = 0.99 and normalized difference index ranging from ?0.02 to +0.09. The reservoir density in the ORB in 2011 was 0.19 reservoirs km^–2, higher than the recommended optimum density of 0.15 reservoirs km^–2 basin. Analysis of reservoir density by municipality recorded values ranging from 0.02 to 0.40 reservoirs km^–2. The sedimentary-geology municipalities presented a reservoir density on average 80% lower than the that of the crystalline-geology municipalities, indicating a strong relationship between geology and reservoir density. Neither population density nor rainfall explained the spatial distribution of reservoirs within the basin, both yielding R² lower than 0.1. This remote-sensing survey of reservoirs demonstrated two major flaws: the misidentification of shadows as reservoirs and the inability to identify the presence of macrophytes, which negatively affected the number and surface area of the target reservoirs. Despite these problems, remote sensing has been shown to be a technique of great potential in the planning and management of water resources in regions with dense reservoir networks.     

Cloud reflectivity profile classification using MSG/SEVIRI infrared multichannel and TRMM data

This work analyses the capability of utilizing cloud-top multispectral radiation to extract information about the vertical reflectivity profile of clouds. Reflectivity profiles and cloud type classification were collected using the Tropical Rainfall Measuring Mission (TRMM) 2A25 algorithm and brightness temperature multispectral channels (3.9, 6.2, 8.7, 10.8, and 12 μm) from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) aboard the Meteosat Second Generation (MSG) satellite. The analysis was performed on four cloud types: convective, warm, and stratiform with and without bright band, using a four-channel combination (10.8–3.9, 6.2–10.8, 8.7–10.8, and 10.8–12.0 μm). The study was applied over Tropical Africa at the MSG subsatellite point, in August 2006. Sixteen individual profile types were detected: three warm, four convective, three stratiform without bright band, and six stratiform with bright band. These cloud profile types were examined using cloud-top multichannel brightness temperature differences. The channel combination results demonstrated that the information obtained from cloud-top radiation enables us to detect specific individual characteristics within the cloud reflectivity profile. The channel combinations employed in this study were effective in identifying warm and cold cloud types. In the 10.8–3.9 and 8.7–10.8 μm channels, brightness temperature differences were indicated in the detection of warm clouds, while the 6.2–10.8 μm channel was noted to be very efficient in classifying cold clouds. Cold clouds types were much more difficult to classify because they possess a similar multichannel signature, which caused ambiguity in the classification. In order to reduce this uncertainty, it was necessary to use texture information (space variability) to acquire a clearer distinction between different cloud types. The survey analysis showed good performance in classifying cloud types, with an accuracy of about 77.4% and 73.5% for night and day, respectively.     

Use of Ponkan mandarin peels as biosorbent for toxic metals uptake from aqueous solutions

Waste Ponkan mandarin (Citrus reticulata) peel was used as biosorbent to extract Ni(II), Co(II) and Cu(II) from aqueous solutions at room temperature. To achieve the best adsorption conditions the influence of pH and contact time were investigated. The isotherms of adsorption were fitted to the Langmuir equation. Based on the capacity of adsorption of the natural biosorbent to interact with the metallic ions, the following results were obtained 1.92, 1.37 and 1.31 mmol g(-1) for Ni(II), Co(II) and Cu(II), respectively, reflecting a maximum adsorption order of Ni(II)>Co(II)>Cu(II). The quick adsorption process reached the equilibrium before 5, 10 and 15 min for Ni(II), Co(II) and Cu(II), respectively, with maximum adsorptions at pH 4.8. In order to evaluate the Ponkan mandarin peel a biosorbent in dynamic system, a glass column was fulfilled with 1.00 g of this natural adsorbent, and it was fed with 5.00 x 10(-4)mol l(-1) of Ni(II) or Co(II) or Cu(II) at pH 4.8 and 3.5 ml min(-1). The lower breakpoints (BP(1)) were attained at concentrations of effluent of the column attained the maximum limit allowed of these elements in waters (>0.1 mg l(-1)) which were: 110, 100 and 130 bed volumes (V(effluent)/V(adsorbent)), for Ni(II), Co(II) and Cu(II), respectively. The higher breakpoints (BP(2)) were attained when the complete saturation of the natural adsorbent occurred, and the values obtained were: 740, 540 and 520 bed volumes for Ni(II), Co(II) and Cu(II), respectively.     

Chromium(VI) adsorption from aqueous solution by Hevea Brasilinesis sawdust activated carbon

Adsorption capacity of Cr(VI) onto Hevea Brasilinesis (Rubber wood) sawdust activated carbon was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ) and standard entropy (DeltaS degrees ) were evaluated. Adsorption kinetics of Cr(VI) ions onto rubber wood sawdust activated carbon were analyzed by pseudo first-order and pseudo second-order models. Pseudo second-order model was found to explain the kinetics of Cr(VI) adsorption most effectively. Intraparticle diffusion studies at different temperatures show that the mechanism of adsorption is mainly dependent on diffusion. The rate of intraparticle diffusion, film diffusion coefficient and pore diffusion coefficient at various temperatures were evaluated. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of rubber wood sawdust activated carbon at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherm in the temperature range studied. The result shows that the rubber wood sawdust activated carbon can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.     

Hydrogen production in an upflow anaerobic packed bed reactor used to treat cheese whey

In this work, an upflow anaerobic packed bed reactor configuration to produce hydrogen using cheese whey as the substrate was tested. The microbiological composition was linked to the reactor operation.