Switching model predictive attitude control for a quadrotor helicopter subject to atmospheric disturbances

In this article a switching model predictive attitude controller for an unmanned quadrotor helicopter subject to atmospheric disturbances is presented. The proposed control scheme is computed based on a piecewise affine (PWA) model of the quadrotor's attitude dynamics, where the effects of the atmospheric turbulence are taken into consideration as additive disturbances. The switchings among the PWA models are ruled by the rate of the rotation angles and for each PWA system a corresponding model predictive controller is computed. The suggested algorithm is verified in experimental studies in the execution of sudden maneuvers subject to forcible wind disturbances. The quadrotor rejects the induced wind disturbances while performing accurate attitude tracking.     

Development of [60] fullerene supported on silica catalysts for the photo-oxidation of alkenes

Simple or successive incipient wetness impregnation followed by heating at 180 °C is proved an efficient preparation method for dispersing effectively onto the silica surface various amounts of C₆₀ in the range 1–4% (w/w). BET, XRD, DRS, TGA, microelectrophoresis and photoluminescence have been used to characterize the photocatalysts prepared. A high dispersion was obtained for the quite stable supported C₆₀ phase, comprised mainly from relatively small or medium size C₆₀ clusters/aggregates. The photocatalytic activity was assessed in the singlet oxygen oxidation of alkenes by examining the photo-oxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0–5 °C in CH₃CN, under oxygen atmosphere and using a 300 W xenon lamp as the light source. The heterogeneous catalysts obtained were proved to be active in the photocatalytic oxidation of olefins via a ¹O₂ ene reaction. The catalysts exhibited significant conversion, turnover number and turnover frequency values, substantially higher than those achieved over the unsupported C₆₀. The conversion increases with the amount of the supported C₆₀ up to a value equal to 3% (w/w) and then it decreases whereas turnover number and turnover frequency decreases monotonically as the amount of the supported C₆₀ increases. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis of fine chemicals.     

Read-out of soft X-ray contact microscopy microradiographs by focused ion beam/scanning electron microscope

A novel focused ion beam-based technique is presented for the read-out of microradiographs of Caenorhabditis elegans nematodes generated by soft x-ray contact microscopy (SXCM). In previous studies, the read-out was performed by atomic force microscopy (AFM), but in our work SXCM microradiographs were imaged by scanning ion microscopy (SIM) in a focused ion beam/scanning electron microscope (FIB/SEM). It allows an ad libitum selection of a sample region for gross morphologic to nanometric investigations, with a sequence of imaging and cutting. The FIB/SEM is less sensitive to height variation of the relief, and sectioning makes it possible to analyse the sample further. The SXCM can be coupled to SIM in a more efficient and faster way than to AFM. Scanning ion microscopy is the method of choice for the read-out of microradiographs of small multicellular organisms.     

Mechanical and barrier properties of MOCVD processed alumina coatings on Ti6Al4V titanium alloy

This study focuses on the implementation of different aluminum oxide coatings processed by metal-organic chemical vapor deposition from aluminum tri-isopropoxide on commercial Ti6Al4V titanium alloy to improve its high temperature corrosion resistance. Films grown at 350 °C and at 480 °C are amorphous and correspond to formulas AlOOH, and Al₂O₃, respectively. Those deposited at 700 °C are composed of γ-Al₂O₃ nanocrystals dispersed in a matrix of amorphous alumina. Their mechanical properties and adhesion to the substrates were investigated by indentation, scratch and micro tensile tests. Hardness and rigidity of the films increase with increasing deposition temperature. The hardness of the coatings prepared at 350 °C and 480 °C is 5.8 ± 0.7 GPa and 10.8 ± 0.8 GPa respectively. Their Young's modulus is 92 ± 8 GPa (350 °C) and 155 ± 6 GPa (480 °C). Scratch tests cause adhesive failures of the films grown at 350 °C and 480 °C whereas cohesive failure is observed for the nanocrystalline one, grown at 700 °C. Micro tensile tests show a more progressive cracking of the latter films than on the amorphous ones. The films allow maintaining good mechanical properties after corrosion with NaCl deposit during 100 h at 450 °C. After corrosion test only the film deposited at 700 °C yields an elongation at break comparable to that of the as processed samples without corrosion. The as established processing–structure–properties relation paves the way to engineer MOCVD aluminum oxide complex coatings which meet the specifications of the high temperature corrosion protection of titanium alloys with regard to the targeted applications.     

Application of adaptive comfort behaviors in Chilean social housing standards under the influence of climate change

Currently, energy performance indicators for buildings are associated with the primary energy source consumption, CO₂ emissions or net energy distribution, which together set the building’s energy efficiency. The evaluation is frequently based on setpoint temperatures and hours of operation. However, these fixed parameters are not suitable for social housing simulation as their performance tends to be in free running, excluding extremely cold or warm conditions. Therefore, a more successful assessment for the efficiency of these buildings is the users’ capability to live within adaptive comfort ranges without air conditioning systems. The aim of this research is to analyze new Chilean standards for sustainable social housing in the context of climate change using the adaptive comfort approach addressed in EN 15251:2007. Using EnergyPlus simulation software, 16 parametric series are analyzed for current conditions and validated against on-site measurements. Meanwhile, a prediction for the climate in 2050 has also been taken into account. The case study is the most widespread low cost dwelling model. The study demonstrates that the period of time within thermal comfort conditions varies substantially if analysis is done using the adaptive comfort standard or the Sustainable Construction Code (CCS) for Chilean housing. Considering climate change, the percentage of time fluctuates from ?19.00% to 24.30%. Concluding that the adaptive comfort model has a greater capacity to positively assess indoor temperatures for social housing in Central-Southern Chile. This research also establishes that it is possible to provide homes where standards are improved within comfort conditions without using artificial means, 99.67% of the time currently and 88.89% in the future.     

El Sur Global: Future Resilient City

Shifting the focus from futuristic visions, Alfredo Brillembourg and Hubert Klumpner with Alexis Kalagas of interdisciplinary design practice Urban-Think Tank urge us to ‘forget about utopia’, for in the most part the urban environment of 2050 is already built. Architects’ sights need to be set on the sometimes grim and unfolding reality of favelas and the world's informal cities.     

Soil degradation in the tropical forests of the Dominican Republic's Pedernales province in relation to heavy metal contents

Two of the National Parks of the only Biosphere Reserve in the Caribbean Islands, the Jaragua-Bahoruco-Enriquillo reserve, occur mostly within the Pedernales province (Dominican Republic). In these National Parks, Jaragua and Bahoruco, almost every tropical forest ecosystem is represented, as are the land uses most common to the Dominican Republic. Despite soil being a key natural resource that needs to be considered in any sustainable development programme, the literature contains very little information on the soils of this region. In this study, we analysed 41 topsoil samples representing the main forest types and land uses of the province. The factors examined were fertility (OM, N, P, K) and heavy metal contents (Cu, Cr, Pb, Cd, Ni, Zn). Mean OM, N and total and available metal levels were almost invariably higher in the natural forest soils compared to those given over to human activities, especially cultivated soils. This difference suggests the uptake of metals by the crops and, to a lesser extent, by animals feeding on crop remains and grassland plants. This hypothesis is supported by high total and available metal contents, especially of Zn, Cu, Pb and, in smaller measure, of Cr recorded in the solid waste landfill of the city of Pedernales. It appears that the cutting down and burning practices of a nomad type of cultivation, as well as the pressures of intensive agriculture and livestock rearing have resulted in heavy metals bound to the soil's OM. We propose this is an important point to consider for the management of these lands.     

Spatial heterogeneity of personal exposure to airborne metals in French urban areas

The spatial distribution of urban population exposures to ambient air particles was investigated as part of the Genotox'ER study conducted in four metropolitan areas (Grenoble, Paris, Rouen and Strasbourg) in France. In each city, 60 to 90 non-smoking adult and children volunteers were selected. Subjects lived in three different urban sectors: one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment. The Harvard Chempass multi-pollutant personal sampler was used to sample PM10 and PM2.5 particles during 48 h during two different seasons ('hot' and 'cold'). The elemental composition of the filters was analysed by Particle-Induced X-ray Emission (PIXE). Sixteen elements were found to be over the method detection limits: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb. The relative concentrations of elements of crustal origin (Si, Al, Ca) were higher in the coarse fraction of PM10 filters, while elements associated with combustion processes (traffic emissions or industrial combustion) presented higher relative concentrations in the PM2.5 fraction (S, Ni, V, Pb). Spatial heterogeneity of elemental exposures by urban sector is substantial for some metals of health concern, with 20% to 90% greater exposure values, on average, in the traffic proximity or industrial sectors, compared to the background sector, for Fe, Zn, Cu, V and Cr. This spatial heterogeneity should not be overlooked in epidemiological or risk assessment studies.     

Rethinking shared environment as a source of variance underlying attention-deficit/hyperactivity disorder symptoms: Comment on Burt (2009).

Burt (2009) recently published a meta-analysis of twin studies on behaviors associated with childhood psychopathologies, concluding that the finding that traits associated with attention-deficit/hyperactivity disorder (ADHD) were the only behaviors that did not show a significant influence of shared environment (C) was surprising. We agree, highlighting four methodological issues that may account for this finding: (a) the use of nonlinear transformations to normalize skewed data; (b) low power to detect C and the subsequent presentation of reduced models; (c) the negative confounding of dominant genetic (D) and C influences in twin models with data exclusively from monozygotic and dizygotic twin pairs reared together; and (d) the correction used for contrast effects (a form of rater bias), which may lead to an overestimate of additive genetic (A) or D parameters at the expense of C. We offer suggestions for future research to address these issues, and we emphasize the need for additional research to examine possible shared environmental factors related to ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization and Modeling of Precipitation Kinetics in a Fe-Si-Ti Alloy

In this article, we present a systematic study of precipitation kinetics in a Fe-Si-Ti alloy in the temperature range 723?K to 853?K (450?°C to 580?°C), combining complementary tools (transmission electron microscopy (TEM), atom probe tomography (APT), and small-angle neutron scattering (SANS)). We show that the Heusler phase Fe₂SiTi dominates the precipitation process in the investigated time and temperature range, regardless of the details of the initial temperature history. A numerical model based on the evolution of precipitate size classes gives very good agreement with the experimental results, and its application to different alloy compositions provides directions for future alloy optimization.