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NiO nanofoams show improved results for hydrogen storage applications.

The reuse of industrial waste plays a crucial role in avoiding environmental impacts caused by incorrect disposal. Industrial production commonly generates huge volumes of wastes, and also increased costs associated with waste management and landfills maintenance. This study investigates the reuse of grit waste, from the cellulose kraft industry, as filler in gypsum plaster. Samples were prepared in proportions of 100/0, 85/15, 75/25 and 50/50 gypsum/grits and tested at 7, 14, 21 and 28 days. The mechanical resistance with incorporation of up to 25 wt% grit as filler is greater than that recommended in the regulatory standards. Flexural and compression strength tests for 15 wt% of gypsum replaced achieved values of 4.5 and 8.3 MPa, respectively. The manufacture of gypsum/grit is a viable solution for waste management and has great potential for enabling fabrication of gypsum plaster board, a low-cost and more sustainable new material.

In the present work, LaNi0.5Ti0.5O3, LaNi0.5Ti0.45Co0.05O3, and LaNi0.45Co0.05Ti0.5O3 perovskites were synthesized using the modified Pechini method. After reduction, the studied perovskites changed crystal structure from the perovskite crystal structure to a cubic symmetry, with space group $Pm\bar{3}m$. The reduction partially decomposed the samples to Ni0 (Co free perovskite), Ni0–Co0, La2O3, La2TiO5, and non-stoichiometric La2NiO4, depending on H2 content of the reductive gases. The degree of reduction of nickel from LaNi0.5Ti0.5O3 reduced with 1.8% H2/Ar and 10% H2/Ar was equal to 36.5% and 95.3%, respectively, while that from LaNi0.5Ti0.45Co0.05O3 or LaNi0.45Co0.05Ti0.5O3, including cobalt, reduced with 10% H2/Ar, was equal to 71.9% and 93.9%, respectively. LaNi0.5Ti0.45Co0.05O3 showed Ni3+ and Co3+ amounts higher than the other perovskites. By increasing H2 content in the reductive mixture from 1.8% to 10%, sintering of metallic nickel was not observed. Moreover, Ni0 displayed weaker metal–support interaction than that observed for Co0, where the support was composed of La containing oxides. LaNi0.5Ti0.5O3 perovskite was used as a catalyst for steam reforming of methane. Syngas production was attributed to the number of Ni sites determined using Rietveld Refinement of X-ray diffraction pattern of this catalyst after the reaction.

In the present work, LaNi

Energy coupling between the solar wind and the Earth's magnetosphere can affect the electron population in the outer radiation belt. However, the precise role of different internal and external mechanisms that leads to changes of the relativistic electron population is not entirely known. This paper describes how ultralow frequency (ULF) wave activity during the passage of Alfvenic solar wind streams contributes to the global recovery of the relativistic electron population in the outer radiation belt. To investigate the contribution of the ULF waves, we searched the Van Allen Probes data for a period in which we can clearly distinguish the enhancement of electron fluxes from the background. We found that the global recovery that started on 22 September 2014, which coincides with the corotating interaction region preceding a high‐speed stream and the occurrence of persistent substorm activity, provides an excellent scenario to explore the contribution of ULF waves. To support our analyses, we employed ground‐ and space‐based observational data and global magnetohydrodynamic simulations and calculated the ULF wave radial diffusion coefficients employing an empirical model. Observations show a gradual increase of electron fluxes in the outer radiation belt and a concomitant enhancement of ULF activity that spreads from higher to lower L‐shells. Magnetohydrodynamic simulation results agree with observed ULF wave activity in the magnetotail, which leads to both fast and Alfven modes in the magnetospheric nightside sector. The observations agree with the empirical model and are confirmed by phase space density calculations for this global recovery period.

Made available in DSpace on 2021-06-25T10:24:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 The near-Earth interplanetary environment conditions affect the dynamics of the relativistic electron population quasitrapped in the radiation belts. A complex chain of processes observed in the magnetosphere can contribute to the variability of these populations when interplanetary structures, such as the interplanetary counterpart of a solar coronal mass ejection (ICME), and high-speed solar wind streams interact with the magnetosphere. However, as these processes can coexist, it is hard to untangle the relative contribution of each process to the loss of particles and the eventual repopulation. Here we show evidence that it is possible to distinguish the relative contribution of mechanisms related to the loss of the outer radiation belt electrons for an event observed on July 19 and 20, 2016. The interaction of an ICME's turbulent sheath with the Earth's magnetosphere resulted in a decrease in the outer radiation belt relativistic electron population. The ultralow frequency (ULF) and chorus wave activities are detected in the outer radiation belt during the time when the Earth's magnetosphere is under the influence of the ICME's sheath region, as well as the ICME's magnetic cloud region, while the electromagnetic ion cyclotron (EMIC) waves in the outer belt are observed only during the sheath region. Dynamic mechanisms such as magnetopause shadowing, outward radial diffusion driven by ULF waves, pitch-angle scattering driven by both EMIC and chorus waves are quantitatively analyzed. Our results suggest that the structures of the ICMEs can trigger the drivers to generate the different dynamic mechanisms responsible for the radiation belt population variability. National Space Science Center State Key Laboratory of Space Weather Chinese Academy of Sciences National Institute for Space Research—INPE NASA Goddard Space Flight Center Space Science Laboratory University of California Universidade Estadual Paulista-UNESP Instituto de Ciência e Tecnologia Laboratory for Atmosphere and Space Physics—LASP National Space Science Center Chinese Academy of Sciences Universidade Estadual Paulista-UNESP Instituto de Ciência e Tecnologia

Fluoride can cause some diseases to humans when ingested in large quantities and for a long time. Due to this, it is necessary to remove or reduce the amount of fluoride in effluents before release into the water bodies. This work aimed to evaluate the ability of hydrocalumites synthesized by two different methodologies and calcined hydrocalumite in reducing the content of fluoride in aqueous solutions. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N

Magnetic field reconnection has shown to be the dominant process in the solar wind-Earth’s magnetosphere interaction. It enables mass, momentum, and energy exchange between different plasma regimes, and it is regarded as an efficient plasma acceleration and heating mechanism. Reconnection has been observed to occur in laboratory plasmas, at planetary magnetospheres in our Solar System, and the Sun. In this work, we focus on analyzing the characteristics of magnetic reconnection at the Earth’s magnetosphere according to spaceborne observations in the vicinity of our planet. Firstly, the locations where magnetic field reconnection are expected to occur within the vast magnetospheric region are addressed, and is shown how they are influenced by changes in the interplanetary magnetic field direction. The main magnetic field and plasma signatures of magnetic reconnection are discussed from both theoretical and observational points of view. Spacecraft observations of ion inertial length scale reconnection are also presented.

Image analysis and understanding are challenging tasks, usually having segmentation as a major step. Boundary detection is a type of segmentation which aims to highlight the boundaries of the objects in a scene. Models based on Convolutional Neural Networks (CNN) have presented promising results for boundary detection, where the input usually is the entire image or some patches, often described in the RGB color model. In this paper, we provide a qualitative analysis of boundary detection algorithms based on CNN but considering images in different color models. We have used the color models RGB, Lab, Luv, dRdGdB, YO1O2 and HSV for this analysis. The Holistically-Nested Edge Detection (HED) and Convolutional Encoder Decoder Network (CEDN) are the CNN's chosen due to their high performance. The benchmark BSDS is the boundary detection evaluator. Experiments show that the results of the edge detection process tend to be similar when training the CNN with weights randomly initialized, regardless of the color model used. For the HED architecture, the use of Lab and Luv color models has resulted in a significant improvement to the case of transfer learning and fine-tuning of weights.

The effects of high-energy particle precipitation on mesospheric and stratospheric ozone have been investigated during the last decades. However, while these effects have been widely discussed for the auroral region, little is known about the role of the high-energy particle precipitation on the stratospheric composition and thermal structure in the tropical/subtropical region. Here we show that the spatial distribution of both the stratospheric ozone and temperature in the southern hemisphere matches the pattern of the Southern Hemisphere Magnetic Anomaly. We found that during the austral winter and spring, in the subtropical region (below 30°S), the reduction of the stratospheric ozone and temperature occurs systematically in the magnetic anomaly area. The differences between the temperatures inside the magnetic anomaly (60°W) and outside the anomaly (150°E) for 42.5°S from June to November are higher than 2 K. The maximum difference at this latitude is approximately 5.9 K and occurs in October during the austral spring.

Analysis of particle pitch angle distributions (PADs) has been used as a means to comprehend a multitude of different physical mechanisms that lead to flux variations in the Van Allen belts and also to particle precipitation into the upper atmosphere. In this work we developed a neural network-based data clustering methodology that automatically identifies distinct PAD types in an unsupervised way using particle flux data. One can promptly identify and locate three well-known PAD types in both time and radial distance, namely, 90deg peaked, butterfly, and flattop distributions. In order to illustrate the applicability of our methodology, we used relativistic electron flux data from the whole month of November 2014, acquired from the Relativistic Electron-Proton Telescope instrument on board the Van Allen Probes, but it is emphasized that our approach can also be used with multiplatform spacecraft data. Our PAD classification results are in reasonably good agreement with those obtained by standard statistical fitting algorithms. The proposed methodology has a potential use for Van Allen belt's monitoring.

Magnetopause shadowing and wave-particle interactions are recognized as the two primary mechanisms for losses of electrons from the outer radiation belt. We investigate these mechanisms, sing satellite observations both in interplanetary space and within the magnetosphere and particle drift modeling. Two interplanetary shocks sheaths impinged upon the magnetopause causing a relativistic electron flux dropout. The magnetic cloud (C) and interplanetary structure sunward of the MC had primarily northward magnetic field, perhaps leading to a concomitant lack of substorm activity and a 10 day long quiescent period. The arrival of two shocks caused an unusual electron flux dropout. Test-particle simulations have shown 2 to 5 MeV energy, equatorially mirroring electrons with initial values of L 5.5can be lost to the magnetosheath via magnetopause shadowing alone. For electron losses at lower L-shells, coherent chorus wave-driven pitch angle scattering and ULF wave-driven radial transport have been shownto be viable mechanisms.

In this chapter we introduce a special kind of neural network known as a self-organizing map (SOM) and use it to cluster/classify pitch angle-resolved particle flux data obtained by instruments onboard satellites orbiting the Earth. As an example of the technique, we employ electron flux data at both relativistic and subrelativistic energies provided by two instruments onboard one of the twin NASA’s Van Allen Probes. For these data sets the SOM can identify the shapes of three well-known types of pitch angle distributions, and from that knowledge one can infer the associated physical mechanisms in the near-Earth space environment, particularly in the Van Allen radiation belts region. The SOM-based methodology can be used with multiplatform spacecraft data, thus enabling a prompt characterization of the physical processes throughout the Earth’s magnetosphere. The steps required to apply our neural network-based approach to pitch angle-resolved particle flux data from any spacecraft mission are laid out.

The plasma of the solar wind incident upon the Earth’s magnetosphere can produce several types of geoeffective events. Among them, an important phenomenon consists of the interrelation of the magnetospheric–ionospheric current systems and the charged-particle population of the Earth’s Van Allen radiation belts. Ultra-low-frequency (ULF) waves resonantly interacting with such particles have been claimed to play a major role in the energetic particle flux changes, particularly at the outer radiation belt, which is mainly composed of electrons at relativistic energies. In this article, we use global magnetohydrodynamic simulations along with in situ and ground-based observations to evaluate the ability of two different solar wind transient (SWT) events to generate ULF (few to tens of mHz) waves in the equatorial region of the inner magnetosphere. Magnetic field and plasma data from the Advanced Composition Explorer (ACE) satellite were used to characterize these two SWT events as being a sector boundary crossing (SBC) on 24 September 2013, and an interplanetary coronal mass ejection (ICME) in conjunction with a shock on 2 October 2013. Associated with these events, the twin Van Allen Probes measured a depletion of the outer belt relativistic electron flux concurrent with magnetic and electric field power spectra consistent with ULF waves. Two ground-based observatories apart in 90∘ longitude also showed evidence of ULF-wave activity for the two SWT events. Magnetohydrodynamic (MHD) simulation results show that the ULF-like oscillations in the modeled electric and magnetic fields observed during both events are a result from the SWT coupling to the magnetosphere. The analysis of the MHD simulation results together with the observations leads to the conclusion that the two SWT structures analyzed in this article can be geoeffective on different levels, with each one leading to distinct ring current intensities, but both SWTs are related to the same disturbance in the outer radiation belt, i.e. a dropout in the relativistic electron fluxes. Therefore, minor disturbances in the solar wind parameters, such as those related to an SBC, may initiate physical processes that are able to be geoeffective for the outer radiation belt.

We study the effect of Earth's dipole tilt angle and interplanetary magnetic field (IMF) Bx and By components on the location of reconnection and the energy conversion at the magnetopause. We simulate southward IMF satisfying both inward- and outward-type Parker spiral conditions during three different dipole tilt angles using a global magnetohydrodynamic model GUMICS-4. We find that positive (negative) Bx contributes to the magnetopause reconnection line location by moving northward (southward) and positive (negative) dipole tilt angle by moving it southward (northward). The tilt shifts the dayside load region toward the winter hemisphere and the summer cusp toward the equatorial plane. Magnetic flux hence piles effectively in the summer hemisphere leading to increased magnetopause currents that enhance the Poynting flux through the magnetopause. We find that the intensity of the energy conversion in the generators is strongly affected by the dipole tilt angle, whereas intensity in the load region is mainly affected by IMF Bx.

Using global magnetohydrodynamic (MHD) simulations, we investigate the role played by a complex solar structure composed of a corotating interaction region (CIR) followed by solar wind Alfvénic fluctuations on the magnetosphere’s nightside, equatorial electric field oscillations in the ultra-low-frequency range. A series of numerical experiments are performed employing synthetic solar wind inputs resembling those of a real CIR+Alfvénic fluctuation event that reached Earth’s magnetosphere on 2003 April 20. The following is found: (i) Radial electric field component fluctuations are excited via magnetopause boundary motions driven either by solar wind density variations characteristic of CIRs or by solar wind Alfvénic fluctuations with a given oscillation period. (ii) Azimuthal electric field component fluctuations nearer to Earth, that is, at radial distances R less than about 5R E ( Earth radius), are apparently not related to either of the two types of sinusoidal solar wind Alfvénic fluctuations used in this study featuring monochromatic frequencies of 0.833 mHz (20-minute period) and 1.666 mHz (10-minute period). Instead, these innermost azimuthal component fluctuations show enhanced activity when inner magnetosphere convection increases as a result of a southward turning of the interplanetary magnetic field component B z . (iii) Lastly, outermost (R ≳ 7 R E) azimuthal electric field oscillations weakly respond to monochromatic solar wind Alfvénic fluctuations by showing power spectral density peaks at both driving frequencies, but only near the flanks of the magnetopause, thus suggesting that such oscillations are being excited also owing to magnetopause boundary motions driven by solar wind Alfvénic fluctuations.

We present near-simultaneous measurements from two THEMIS spacecraft at the dayside magnetopause with a 1.5 h separation in local time. One spacecraft observes a high-density plasmaspheric plume while the other does not. Both spacecraft observe signatures of magnetic reconnection, providing a test for the changes to reconnection in local time along the magnetopause as well as the impact of high densities on the reconnection process. When the plume is present and the magnetospheric density exceeds that in the magnetosheath, the reconnection jet velocity decreases, the density within the jet increases, and the location of the faster jet is primarily on field lines with magnetosheath orientation. Slower jet velocities indicate that reconnection is occurring less efficiently. In the localized region where the plume contacts the magnetopause, the high-density plume may impede the solar wind-magnetosphere coupling by mass loading the reconnection site.

Neste trabalho, o conceito e a origem histórica do processo físico conhecido como reconexão magnética são apresentados, bem como um dos primeiros modelos analíticos que serviu como base teórica para futuras investigações do fenômeno. A reconexão pode ocorrer entre dois ou mais regimes de plasmas magnetizados próximos o suficiente para que efeitos magneto-hidrodinâmicos não ideais permitam a reestruturação topológica dos seus respectivos campos magnéticos. Como consequência, o plasma pode ser acelerado num curto espaço de tempo, tal como observado em fenômenos físicos explosivos como, por exemplo, as explosões (flares) solares. Focam-se nos primeiros esforços analíticos propostos para explicar o processo segundo a perspectiva da magneto-hidrodinâmica. A reconexão magnética tem o potencial de tornar-se um mecanismo universal o qual pode ser utilizado no auxílio ao entendimento de uma miríade de processos físicos ocorrendo tanto em plasmas de laboratório, como em plasmas astrofísicos. In this work both the concept and historical origins of the physical process known as magnetic reconnection are presented, as well as one of the first analytical models which was used as theoretical basis for future investigations on the phenomenon. Magnetic reconnection can occur between two or more magnetized plasma regimes which are close enough to allow non-ideal magnetohydrodynamic effects to take place and consequently change the topological structure of the interacting magnetic fields. As a result, the plasma can be accelerated in a short amount of time, as has been observed in explosive physical phenomena like solar flares. In this work, it is emphasized the first mathematical efforts employed in order to understand and describe reconnection according to the point of view of magnetohydrodynamics. Magnetic reconnection has the potential of becoming a universal mechanism which can be used to help to understand a myriad of physical processes occurring in both laboratory and astrophysical plasmas.

Manganita de lantânio dopada com estrôncio (LSM) e cromita (LSC) em pó, bem como as correspondentes amostras não dopadas, foram sintetizadas pelo método de combustão, usando dois diferentes combustíveis (ureia e glicina). A ignição da mistura reacional com ureia leva mais tempo e a temperatura máxima é maior do que usando glicina, para as amostras dopadas. Os cálculos teóricos de calor de reação e temperatura de chama adiabática indicam condições favoráveis à combustão. No entanto, a calcinação é uma etapa essencial para uma boa cristalização da fase perovskita. Os padrões de difração de raios X mostraram a formação apenas da fase perovskita para as amostras sintetizadas com uréia. Os tamanhos de cristalitos estão na faixa de 19-25 nm, com valores menores quando a ureia é usada como combustível. Análises de microscopia eletrônica de varredura mostraram a presença de aglomerados, formados por partículas finas de diferentes formas. A análise termogravimétrica revelou que a perda de peso é muito maior para as manganitas, com queima completa dos orgânicos em 850-900 ºC.Lanthanum strontium manganite (LSM) and chromite (LSC) powders, as well as the corresponding non-doped samples, were synthesized by the combustion method, using two different fuels (urea and glycine). The ignition of the reagent mixture with urea takes a longer time and the maximum temperature is higher than using glycine, for doped samples. The theoretical calculations of exothermic heat and adiabatic flame temperatures indicate favorable conditions for combustion to occur. However, calcination is an essential step for a good crystallization of perovskite phase. X-ray diffraction patterns showed formation of only perovskite phase for the samples synthesized with urea. The crystallite sizes are in the range of 19-25 nm, with smaller values when urea was used as fuel. Scanning electron microscopy showed the presence of agglomerates, formed by fine particles of different shapes. Thermogravimetric analysis revealed that the weight loss is much higher for manganites, with complete burn out of organics at 850-900 ºC.

This work presents the development of a UAV cooperative strategy based on consensus navigation to solve the rendezvous problem. The Laplacian matrix is weighted by the distance among the vehicles, i.e., as closer a UAV is from another as higher the communication link is. Therefore, the communication graph, which characterizes the consensus navigation, is a dynamic one. Following, some simulation results are shown in order to illustrate the theoretical aspects, and also to validate the proposal. Finally, the analysis of the Laplacian matrix and the UAV communication during flight is also presented to determine the consensus meeting point.

Field-dependent conductivity at low electric fields was observed from low to room temperature in pressed pellets of doped poly(3-methylthiophene). The room temperature data showed good agreement with Bardeen's theory of charge-density wave depinning and the values of the parameters obtained are consistent with a strong electron–phonon interaction as expected for quasi-one dimensional systems.

We show room temperature charge-density wave (CDW) characteristics in d.c. and a.c. electric data in pressed pellets of lightly doped poly(3-methylthiophene). The possibility of a Peierls glass is discussed and metastables states are observed. D.C. and A.C. data also show a state with negative differencial resistance.