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• A robust self-adaptive fault identification scheme is presented for an active distribution system. • The proposed scheme introduces a novel method to discriminate internal and external faults. • The proposed scheme is investigated against noise and heavy PV switching. • The scheme has high-speed performance and high accuracy level. Recently, the issue of protection in active distribution networks has been greater than before due to mushrooming use of photovoltaic (PV) generation units. PV systems coupled to power electronics devices and their control strategies causes significant changes to fault current characteristics leading to maloperation of fault identification schemes. Therefore, this paper proposes a robust self-adaptive fault identification scheme that incorporates the presence of PV systems and considers the effect of uncertainty arising due to their high penetration levels. The real-time voltage and current measurements are captured locally by advanced one-end measuring facilities, considering the uncertain temperature and irradiation conditions, of solar generation units. First, the proposed scheme employs wavelet transform, statistical alienation concept, and fuzzy logic to identify the fault criteria. Then, it uses fuzzy concept-based the system features to obtain the optimal protection scheme setting. For simulation analysis, a 10 MW solar farm-connected to a real-world active distribution system is emulated in PSCAD-EMTDC simulator to create intensive study cases, and the proposed scheme is implemented in MATLAB software. Several fault parameters are examined in the scheme comprising different fault types, fault locations, and transition resistances. Also, the uncertainty arising from PV plants and different loading conditions are taken full consideration in the developed scheme. Simulation results have verified the validity of fault identification scheme; nonetheless, the computational burden is kept reasonable. The proposed scheme is investigated under white gaussian and impulsive noise. Furthermore, sensitivity analysis and comparative study are conducted in terms of accuracy, high decision speed, and sampling frequency variation. The proposed scheme succeeds to detect and classify internal faults for both on/off-grid operation modes and differentiate them from external ones in the case of on-grid mode. The proposed scheme has dominance performance including high speed fault detection within, a half cycle, and provides accuracy more than 98 %. [ABSTRACT FROM AUTHOR]

• A new scheme is developed to identify the fault using reactive power measurements. • The reactive-power superiority compared with active measurements is investigated. • The optimal mother wavelet is selected based fault identification scheme. • The proposed scheme is immune to different fault parameters. • Testing the fault identification scheme at different operating conditions. The process of fault-identification in teed transmission lines (TTLs) has considerable attention in recent years. In this line, this paper proposes a novel scheme for fault detection, classification and faulted-phase/s identification on the basis of reactive-power components of TTLs. The current and voltage measurements are collected from a single-end measuring system of teed circuits. Based on the filtering of measured currents and voltages signals using improved recursive wavelet transform, the reactive-power measurements are computed. Thereafter, the Wavelet Multi-Resolution Analysis Technique (WMRAT) is employed for decomposition of reactive-power measurements. An improved recursive wavelet (IRW) transform that has good time-frequency characteristics is proceed to remove dc offsets and harmonics from the measured signals. The ATP/EMTP package and MATLAB program are used to simulate the faulted cases and verify of operating the proposed fault-identification scheme. Simulation outcomes show that the proposed scheme has the capability to detect and classify different fault types in TTLs. The presented scheme is designated to be insensitive to different fault resistances, different fault locations, and inception angles. In addition, the proposed scheme is also tested under different technical aspects such as different sampling rates, different locations of the single-end measuring system, loading change and source parameters variation. The superiority of reactive-power compared with active power measurements during faults occurrence is also investigated to show the notability of the proposed scheme. The obtained results corroborate that the proposed scheme can be correctly identified different fault types and locations along the line. [ABSTRACT FROM AUTHOR]

The thermal decomposition course of europium acetate tetrahydrate (Eu(CH3COO)3·4H2O) was probed on heating up to 1000 °C in a dynamic atmosphere of air by thermogravimetry and differential thermal analysis. The solid- and gas-phase decomposition products were identified by X-ray diffractometry, ex- and in situ infrared spectroscopy and mass spectrometry. Results obtained showed the acetate to dehydrate stepwise at 145–283 °C, and then decompose stepwise to yield eventually cubic-Eu2O3 at ≥663 °C encompassing the formation of intermediate oxycarbonate (Eu2O(CO3)2/Eu2O2(CO3) solid products (at 347–466 °C)) and H2O, (CH3)2CO and CO2 as primary gaseous products. A considerable enhancement of the production of the primary gas phase products at 400–450 °C and the emergence of (CH3)2C=CH2, CH4 and CO molecules in the gas phase are ascribed to reactions occurring at the gas/solid interface at the expense of some of the primary products. These interfacial activities impart application-worthy adsorptive and catalytic functions for the associated solid products. [ABSTRACT FROM AUTHOR]

Abstract: The issue of size-sensitivity of the surface properties of anatase TiO2 is addressed by examining three samples synthesized by aqueous sol–gel method having different particle sizes on the nanoscale (8–19nm). A number of characterization methods, namely, X-ray powder diffractometry, infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, sorptiometry and electron microscopy are employed. The data obtained reveal interrelated dependencies of the surface area, porosity, nitrogen and pyridine adsorption capacity and strength, and catalytic methylbutynol decomposition activity on the size of titania nanoparticles. Pertinent size-dependent bulk properties are also revealed and used to account for the changes conceded by the surface properties. Accordingly, going from 19 to 8-nm sized titania particles has been found to stabilize the anatase structure, weaken the surface acidity, and blueshift the UV absorption edge of titania. [Copyright &y& Elsevier]

Abstract: The surface properties of sol–gel synthesized anatase titania (TiO2) nanoparticles are probed by sorptiometry, infrared absorption spectroscopy, UV–vis diffuse reflectance spectroscopy and high resolution transmission electron microscopy. The results reveal strong correlations of the surface area, porosity, pyridine adsorption capacity and strength, and catalytic methylbutynol decomposition activity. [ABSTRACT FROM AUTHOR]

Various todorokite-type Mn(IV)-oxides, namely, Mg-, Ni- and Cu-todorokite, were synthesized via hydrothermal treatment of corresponding buserites. The bulk chemical and phase compositions, crystalline structure, particle morphology and thermal stability, were determined by means of atomic absorption spectroscopy, X-ray powder diffractometry, infrared spectroscopy, and thermogravimetry. The surface chemical composition, texture and structure were assessed using X-ray photoelectron spectroscopy, nitrogen sorptiometry, and scanning and high-resolution transmission electron microscopy. The results revealed that (i) the bulk is crystalline and thermally stable up to 200 °C, (ii) nature of the decomposition residues is dependent on type of the divalent metal ion contained, (iii) the crystallites are nano-sized fibrils and expose low-index (0 0 2) crystal facet, (iv) the surface chemical composition reflects that of the bulk, and (v) the surface texture constitutes moderate specific areas, slit-shaped mesopores associated with particle interstices, and micropores assuming surface accessibility for the bulk structural tunnels of the test todorokites. Thus, application of such test oxides as shape-selective oxidation catalysts has been rendered worth attempting. [Copyright &y& Elsevier]

Bi/Fe-citrate xerogel, prepared by sol-gel processing, was first carbonized and, then, calcined at 300–700 °C for 1 h. The gel and its calcination products were characterized by thermal analyses (TG/DTA), X-ray powder diffractometry (XRD), Fourier-transform infrared spectrophotometry (FTIR), BET-specific surface area measurement (S BET), and Ultraviolet–Visible diffuse reflectance spectrometry (UV–Vis DRS). It was found that the carbonization step helps to subside the effects of a glowing thermal decomposition event, thus suppressing the formation of parasitic phases (such as Fe 2 O 3 and Bi 2 Fe 4 O 9). Rhombohedral-BiFeO 3 yielded at 500 °C was found to assume qualifying properties for photo-assisted applications. Image 1 • Bi/Fe-citrate xerogel is obtained via sol-gel processing and drying at 80 °C. • Thermal decomposition (in air) of the gel encompasses a glowing event near 300 °C. • Impacts of the heat released are subsided via 400 °C pre-carbonization of the gel. • Consequently, 500 °C calcination of the carbonized gel yields pure BiFeO 3. • The BiFeO 3 assumes qualifying properties for photo-assisted applications. [ABSTRACT FROM AUTHOR]

Abstract: Chemical interactions in mixed, aqueous solutions of NH4HCO3 and M(NO3)3·9H2O, where M stands for Ho, Sm, or La, were facilitated under various hydrothermal treatment conditions (pH 8–12 and temperature=75–135°C). The solution chemistry established did not make available necessary concentrations of soluble HCO3 − and MO(OH)2 − species for the formation of dawsonite-type ammonium hydroxymetalocarbonates, NH4M(CO3)(OH)2, but, alternatively, high concentrations of soluble CO3 2−, and M(H2O) n 3+ or M(H2O) n−1(OH)2+ facilitating, respectively, precipitation of corresponding hydrated carbonate, M2(CO3)2·2H2O, or carbonate hydroxide, MCO3(OH). X-ray powder diffractometry, infrared spectroscopy, and thermal analyses proved alternative formation of Ho2(CO3)3·2H2O or LaCO3(OH) under the whole set of hydrothermal treatment conditions probed, and Sm2(CO3)3·2H2O at pH<10 or SmCO3(OH) at pH≥10, thus implying dependence of the composition of the product carbonate compound on the hydrolysability of the initial M(H2O) n 3+ species and, hence, the metal ionic size (La>Sm>Ho). Calcination of the various hydrothermal treatment products at ≥600°C resulted in the thermal genesis of the corresponding sesqui-oxides (M2O3). Bulk and surface characterization studies of the product oxides, employing N2 sorptiometry and scanning electron microscopy, in addition to the above analytical techniques, revealed overall strong crystallinity, large average crystallite size, and well-defined particle morphology. They revealed, moreover, surfaces, though of limited accessibilities (≤13m2/g), exposing OH groups of various coordination symmetries and, hence, acid–base properties, thus furnishing promising surface catalytic attributes. [Copyright &y& Elsevier]

Abstract: 5 and 10wt%-TiO2-containing aramid–titania hybrid films were prepared using sol–gel processing improved by the inclusion of 3-isocyanato-propyltriethoxysilane (ICTOS) to strengthen bonding of the titania species to the polymer backbone and, hence, lessen its agglomeration. The films were thermally degraded by heating at 450°C in a dynamic atmosphere of air. The solid residues were found by thermogravimetry, X-ray diffractometry and electron microscopy to consist dominantly of uniformly agglomerated rod-like anatase-TiO2 nanoparticles, irrespective of the titania content of the film. The recovered titania particle morphology and surface microstructure were examined by field emission scanning and high-resolution transmission electron microscopy, respectively. Whereas, the particle surface chemistry and texture were assessed, respectively, by means of X-ray photoelectron spectroscopy and N2 sorptiometry. The recovered titanias were found, irrespective of the film content of titania, to enjoy not only a high temperature (up to 800°C) stable nanoscopic anatase bulk structure, but also a high-temperature stable surface chemical composition (lattice Ti4+ and O2−, and adsorbed OH/CH x species), (101)-faceted microstructure and highly accessible (145–112m2/g), uniform mesoporous texture with average pore diameter in the narrow range of 3.9–6.3nm. Increasing the calcination temperature up to 1100°C enhances an anatase → rutile transition, the extent of which is larger the higher the titania content of the film. [Copyright &y& Elsevier]

Abstract: Spherical-particle MCM-41 was synthesized at room temperature, and, then, impregnated with aqueous solutions of NH4VO3 to produce variously loaded VO x /MCM-41 composite materials. Bulk and surface properties of the materials thus produced were characterized by means of X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), N2 sorptiometry and X-ray photoelectron spectroscopy (XPS). Results obtained indicated that subsequent calcination at 550°C (for 2h) of the blank and impregnated MCM-41 particles, results in materials assuming the same bulk structure of MCM-41, and exposing uniformly mesporous, high area surfaces (P w =2.0–2.3nm; 974–829m2/g), except for the material obtained at 20wt%-V2O5 that was shown to suffer a considerable loss on surface area (down to 503m2/g). XPS results implied that the immobilization of the VO x species occurs via interaction with surface OH/H2O groups of MCM-41, leading to the formation of vanadate (VO3 −) surface species, as well as minor V–O–Si and V2O5-like species. However, in all cases, the vanadium sites remained pentavalent and exposed on the surface. [Copyright &y& Elsevier]

The need for highly concentrated hydrogen peroxide solutions to fuel spacecraft propulsion systems necessitates the development of new catalytic formulations mainly based on supported manganese oxides. In order to improve the preparation of such catalysts, the thermal decomposition and the hydrothermal reduction of different permanganate precursors were studied, as well as the effect of washing on the products. The test samples were characterized by X-ray power diffraction (XRD) and surface area determination, and compared for their catalytic activity towards H2O2 decomposition using a constant pressure reactor (for 1.71% H2O2) and a constant volume reactor (for 50% H2O2). The catalysts prepared by thermal decomposition of KMnO4 or NaMnO4·H2O have shown the intermediate formation of potassium (or sodium) manganate, and its partial dissolution during washing with water; higher catalytic activity and larger surface area were observed for the decomposition products of KMnO4. The hydrothermal reduction yielded products exhibiting larger surface area and higher specific catalytic activity when carried out under stoichiometric conditions. Comparable kinetic parameters were determined using both catalytic reactors. Unsupported and alumina supported catalysts displayed comparable activity per gram of manganese. [Copyright &y& Elsevier]