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21.
The high-temperature corrosion behaviour of the Cr containing ferritic alloys Crofer 22 APU and Crofer 22 H were investigated for their potential application as interconnects in planar-type solid oxide electrolysis cells (SOECs) operating at 800 °C for syngas production in steam/CO2 co-electrolysis mode. To simulate the operating conditions for this application, oxidation tests in relevant atmospheres with and without electric current were conducted. The corrosion behaviour was influenced by the electric current resulting in accelerated oxidation on the negative side and suppressed oxidation on the positive side. The scale structure was influenced by a combination of atmosphere and electric current effects. The modified oxidation of the interconnect steels due to the electric current effect could have detrimental impact for the O2 side and beneficial effect for the CO2/H2O side in an SOEC stack operating in co-electrolysis mode. 相似文献
22.
Josu Daniel García‐Espinoza Mehdi Zolfaghari Petia Mijaylova Nacheva 《Water and Environment Journal》2020,34(2):232-246
The fate of pharmaceuticals in the aquatic environment is significantly affected by the presence of humic acids (HA). In this work, the synergistic effect of electrochemical oxidation (EO) and ultraviolet irradiation (UVI) was evaluated for HA removal and for the simultaneous degradation of three pharmaceuticals (carbamazepine, propranolol and sulfamethoxazole) in presence of HA. The effectiveness of EO, UVI and their combination for HA removal was assessed using different operating parameters, such as type of anode (Nb/BDD and Ti/IrO2), supporting electrolyte (NaCl, NaBr and Na2SO4), current density (8.1, 16.1, 28.2, 40.3, and 48.4 mA/cm2), pH (3, 7 and 9) and NaCl electrolyte concentration (7, 14 and 21 mM). The use of non‐active anode Nb/BDD, NaCl electrolyte and combination EO‐UVI was the most efficacious option for HA removal, due to the production of hydroxyl radicals as well as active chlorine species (HClO, Cl● and ClO?) generated by anodic oxidation and by UVI. The effectiveness of the EO process was enhanced coupling EO with UVI, however the energetic consumption increased. The composition of the electrolyte was the pivotal parameter since a complete degradation of the pharmaceuticals was achieved by both processes EO and EO‐UVI using NaCl as electrolyte; this is attributed to the indirect oxidation by electrogenerated active chlorine which dominates the pharmaceuticals degradation. 相似文献
23.
Seabra JC Ciompi F Pujol O Mauri J Radeva P Sanches J 《IEEE transactions on bio-medical engineering》2011,58(5):1314-1324
Vulnerable plaques are the major cause of carotid and coronary vascular problems, such as heart attack or stroke. A correct modeling of plaque echomorphology and composition can help the identification of such lesions. The Rayleigh distribution is widely used to describe (nearly) homogeneous areas in ultrasound images. Since plaques may contain tissues with heterogeneous regions, more complex distributions depending on multiple parameters are usually needed, such as Rice, K or Nakagami distributions. In such cases, the problem formulation becomes more complex, and the optimization procedure to estimate the plaque echomorphology is more difficult. Here, we propose to model the tissue echomorphology by means of a mixture of Rayleigh distributions, known as the Rayleigh mixture model (RMM). The problem formulation is still simple, but its ability to describe complex textural patterns is very powerful. In this paper, we present a method for the automatic estimation of the RMM mixture parameters by means of the expectation maximization algorithm, which aims at characterizing tissue echomorphology in ultrasound (US). The performance of the proposed model is evaluated with a database of in vitro intravascular US cases. We show that the mixture coefficients and Rayleigh parameters explicitly derived from the mixture model are able to accurately describe different plaque types and to significantly improve the characterization performance of an already existing methodology. 相似文献
24.
25.
Contamination and Ecological Risk Assessment of Long-Term Polluted Sediments with Heavy Metals in Small Hydropower Cascade 总被引:2,自引:0,他引:2
Yovana Todorova Stilyana Lincheva Ivaylo Yotinov Yana Topalova 《Water Resources Management》2016,30(12):4171-4184
The identification of contamination level and ecological risks, associated with heavy metal pollution of sediments in small hydropower cascade was done on the base of index analyses approach. The concentration of As, Cd, Cu, Hg, Pb, Zn, total organic carbon and percentage of fines were determined in sediments of two habitats in cascade sequence – river and dam. Correlation and multivariate analyses suggest that As, Cu, Pb and Zn are associated with similar anthropogenic source. Cadmium and mercury originate from different source and have specific moving. Based on the contamination and background indices the sediments in Middle Iskar cascade are moderate contaminated at least and are subject of intensive hydrological and technological mixing. The potential ecological risk index (PERI) classifies the sediments in dam site with the higher risk level. Suitable indicators for express assessment of metal pollution in “river” sediments are contamination/enrichment indices which are more sensitive for local concentration increase of less toxic metals. In “dam” sites the process of sedimentation affects strongly the degree of metals accumulation and differences in toxicity are clearly presented – PER/PERI in combination with content of fine sediment fractions and TOC have a potential for rapid identification of sediment-associated risks. 相似文献
26.
In this article, a novel technique for user’s authentication and verification using gait as a biometric unobtrusive pattern is proposed. The method is based on a two stages pipeline. First, a general activity recognition classifier is personalized for an specific user using a small sample of her/his walking pattern. As a result, the system is much more selective with respect to the new walking pattern. A second stage verifies whether the user is an authorized one or not. This stage is defined as a one-class classification problem. In order to solve this problem, a four-layer architecture is built around the geometric concept of convex hull. This architecture allows to improve robustness to outliers, modeling non-convex shapes, and to take into account temporal coherence information. Two different scenarios are proposed as validation with two different wearable systems. First, a custom high-performance wearable system is built and used in a free environment. A second dataset is acquired from an Android-based commercial device in a ‘wild’ scenario with rough terrains, adversarial conditions, crowded places and obstacles. Results on both systems and datasets are very promising, reducing the verification error rates by an order of magnitude with respect to the state-of-the-art technologies. 相似文献
27.
Christian Franke Olaf Stenzel Steffen Wilbrandt Mark Schürmann Josephine Wolf Vera Todorova Brenda Doherty Prof. Dr. Norbert Kaiser 《真空研究与实践》2016,28(1):28-32
Determination of the Optical Constants of Common Substrate Materials in the NIR/MIR‐Spectral Regions An approach is reported for determining the optical constants of substrates and single layer coatings in the near and mid‐infrared spectral regions. A combination of the algorithm from Nichelatti and a multi‐oscillator model has been used to determine the optical constants of the substrates. Thus, the approach even works when the sample transmittance is vanishing. We demonstrate the application of the approach to the evaluation of transmission and reflection spectra of common substrates (CaF2, Q1, Sapphire) measured by a Fourier‐Transform‐Infrared spectrophotometer. The comparison of the calculated optical constants with values reported in literature confirms the validity of the used approach. We also demonstrate the IR characterisation of a tantalum oxide single layer deposited onto a Q1 substrate by means of the multi‐oscillator‐model. The results are again in good agreement with literature data. 相似文献
28.
Silviya Todorova Georgi Kadinov Krasimir Tenchev Yuri Kalvachev Vladislav Kostov-Kytin 《Journal of Materials Science》2007,42(10):3315-3320
Monometallic cobalt and bimetallic Co–Pt samples of various particle sizes have been prepared using SiO2 and synthetic kenyaite (layered silicate) as a support. They are characterized by elemental analysis, XRD, TPR, and XPS.
Cobalt is introduced by two methods—classical impregnation and ammonia method. The ammonia method of preparation leads to
the formation of finely dispersed Co3O4 on both supports. Besides, hardly reducible cobalt silicate phases appear predominantly on the SiO2 support. The Co3O4 particle size varies between 5 and 20 nm, depending on the support. The monometallic Co samples prepared by ammonia method
on both supports are more active in benzene combustion than the impregnated ones due to the finer dispersion of the easily
reducible Co3O4. Addition of Pt improves the activity and the promoting effect is more evident for the impregnated sample. This is explained
with the synergy effect of cobalt oxide species and Pt. The less promoting effect of Pt on the catalytic activity of the bimetallic
kenyaite-supported samples is attributed to the stronger interaction between the Co oxide phase and Pt during the preparation
process. 相似文献
29.
N. D. Bakhteeva E. V. Todorova N. N. Kolobylina A. L. Vasil’ev V. P. Sirotinkin 《Russian Metallurgy (Metally)》2013,2013(3):206-216
The structure and phase composition of aluminum-based polycrystalline alloys (85 at % Al) containing transition (Fe, Ni) and rare-earth (La) metals are studied by metallography, differential scanning calorimetry, X-ray diffraction, and electron-microscopic analysis after melt quenching and subsequent severe plastic deformation (SPD) by shear under pressure. The melt-quenched alloys are shown to have a four-phase structure consisting of an aluminum-based solid solution, intermetallics Al3Ni and Al11La3, and iron intermetallics. SPD results in the fragmentation and spheroidization of all phase constituents of the alloys and in the dissolution of the iron intermetallics. A multiphase nanostructured state forms in the alloys. The nanocrystallite sizes after SPD at various deformation parameters are determined. The microhardness is maximal after deformation corresponding to six anvil revolutions at a pressure of 8 or 10 GPa. The structural parameters and the microhardnesses are compared after SPD by shear under pressure of the alloys having the same compositions and different structural states (namely, amorphous and polycrystalline) before deformation. An amorphous-nanocrystalline structure with the minimum nanograin sizes and the maximum microhardnesses forms in the alloys having an initial amorphous structure and subjected to SPD. 相似文献
30.
The infra-red (IR) transmission spectra of SiOx (x ≤ 2) layers containing crystalline or amorphous Si nanoparticles deposited on p-Si substrates is simulated in the range 300-1500 cm− 1. To that purpose the average dielectric function of the nanocomposites is calculated by means of the Bruggeman effective medium approximation. The IR spectra of the system (film and substrate) are computed. The results are compared with experimental IR spectra measured on Si-SiOx nanocomposite layers with identical composition, fabricated by thermal evaporation of SiO in vacuum followed by thermal annealing at 700 °C or 1030 °C. A good correspondence between theory and experiment is found from where valuable information about important characteristics of the investigated nanocomposites is obtained, such as matrix density, homogeneity and composition of the layers. 相似文献