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81.
Tiago Santos Celso S. F. Gomes Luc Hennetier Vítor A. F. Costa Luís C. Costa 《International Journal of Applied Ceramic Technology》2021,18(5):1801-1813
Industrial competition and environmental concerns lead to the exploration of alternative and energy-efficient technologies for ceramic materials processing. The main objective of this work was to present microwave heating as a viable option for stoneware processing. Stoneware functional properties are presented and discussed, with emphasis on impact strength, water absorption, porosity, and color. Microstructure analyses show that microwave- and gas-fired samples have higher densifications than electrically fired samples. A relevant finding for processing conditions is that microwave firing requires temperatures approximately 100°C lower than those required by conventional firing. Microwave-fired samples’ rupture energies are approximately twice (0.57 ± 0.06 (J)) those of the reference samples (0.26 ± 0.03 (J)), and their water absorptions are approximately one-half (1.5% at 1170°C and 0.8% at 1190°C) of those of the reference samples (2.0%), whereas the water absorption of electrically fired samples at 1180°C has been estimated to be 7.5%. Color analysis also evidences a shift to lower microwave firing temperatures, what is attributed to the enhanced transformations promoted by microwave heating when comparing with the transformations promoted by conventional (gas or electric) heating. 相似文献
82.
采用CO2激光器在316L不锈钢表面获得了超薄的铜熔覆层,文中分析和讨论了激光熔覆工艺参数加激光功率,熔覆速度,离焦量以及送粉率等对熔覆层质量的影响,提出了熔覆工艺的优化方法,使铜层的熔覆厚度可控制在100μm之内,稀释率小于10%以及很小的热变形。 相似文献
83.
A. Santos P. Yustos A. Quintanilla G. Ruiz F. Garcia-Ochoa 《Applied catalysis. B, Environmental》2005,61(3-4):323-333
Catalytic wet oxidation of phenol as a model pollutant has been performed in a three phase fixed-bed reactor (FBR) by using a commercial catalyst based on copper oxide in order to analyze the variables affecting significantly the copper leaching. It has been found that temperature has an almost negligible influence in the range studied (70–160 °C). On the contrary, an important effect of the pH value was noticed. The copper leaching reduces when the pH of the solution fed to the reactor increases, being almost negligible at pH ≥ 5. Moreover, the composition of the reaction media also influences the leaching. Higher copper concentrations than those expected by the effect of the acid aqueous media have been measured in the reactor effluent when phenol, catechol, hydroquinone, p-benzoquinone and maleic acid are present in the reaction media. On the contrary, oxalic acid has a negative influence on the leaching, since it captures the copper in solution to form copper oxalate which precipitates on the catalyst surface. For a previously acidified medium, the acetic and formic acids do not have any other effect on the copper leaching. It has been also demonstrated that as copper in solution decreases, so does phenol conversion, because the homogeneous catalysis contributes significantly to the oxidation reactions even in fixed-bed reactors. 相似文献
84.
E. M Andrade J. R Araújo Neto M. J. S Guerreiro J. C. N Santos H. A. Q Palácio 《Water Resources Management》2017,31(13):4103-4116
Dry tropical forests account for over 1,000,000 km2, and there is still lack of knowledge on their hydrologic processes. The curve number (CN) hydrologic model developed by the Natural Resources Conservation Service (NRCS) is widely applied for runoff determination in various parts of the world, but not so in tropical semiarid regions. This study analyzes the impact of land use changes on the CN model in a tropical semiarid environment, in two catchments of native dry tropical forest and thinned dry tropical forest land use from 2009 to 2012. The CN model was calibrated and validated for the NRCS recommended initial abstraction ratio λ = 0.2, and for λ evaluated from rainfall and runoff data. A reliability analysis was performed using Monte Carlo simulation. Model goodness-of-fit was assessed with statistical criteria. A total of 42 and 40 rainfall-runoff events were analyzed for the native and thinned dry tropical forest, respectively. Characteristic λ values of 0.15 and 0.11 were determined for the two respective catchments. Although CN values were similar for both land uses, CNλ=0.20 = 80 and CNmedian λ = 77, the thinned catchment showed a higher CN model parameters variability. The CN model was more sensitive to variations of CN values than to those of λ. This study showed that no matter the vegetation management in a dry tropical forest environment, modeled runoff is not affected by λ, but rather affected by CN, which represents soil, landuse and management. 相似文献
85.
A.C.S.F. Santos S. Damyanova G.N.R. Teixeira L.V. Mattos F.B. Noronha F.B. Passos J.M.C. Bueno 《Applied Catalysis A: General》2005,290(1-2):123-132
The effect of CeO2 loading (1–20 wt.%) on the properties and catalytic behaviors of CeO2–Al2O3-supported Pt catalysts on the partial oxidation of methane was studied. The catalysts were characterized by SBET, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC). XRD and TPR results showed that the pretreatment temperature of the support influences on the amount of CeO2 with fluorite structure. The pretreatment temperature of the support and CeO2 loading influenced the morphology of Pt. OSC analysis showed a significant increase in the oxygen storage capacity per weight of CeO2 for samples with high CeO2 loading (12 and 20 wt.%). TPR analyses showed that the addition of Pt promotes the reduction of CeO2. This effect was more significant for the catalysts with high CeO2 loading (≥12 wt.%). The dispersion of Pt, measured by the rate of cyclohexane dehydrogenation, increases with increasing of the pretreatment temperature of the support. It was shown that the kind of the support is very important for obtaining of catalysts resistant to carbon formation. The catalysts with high CeO2 loading (≥12 wt.%) showed the highest catalytic activity and stability in the reaction of partial oxidation of methane due to a higher Pt–CeO2 interface. 相似文献
86.
87.
Three groups of diesters have been isolated and identified in the lipids of steer meibomian glands. The first group, designated
as α Type I, with the abbreviated formula FA-αOHFA-FA1c, consisted of α-hydroxy fatty acids esterified to fatty acids and
fatty alcohols in the approximate molar ratio 1∶1∶1. The second group, designated as ω Type I-St, with the abbreviated formula
FA-ωOHF A-St, consisted of ω-hydroxy fatty acids esterified to fatty acids and sterols in the approximate molar ratio 1∶1∶1.
The third group, designated as α,ω Type II, with the abbreviated formula FA-α,ωdiol-FA, consisted of α,ω-diols esterified
to 2 moles of fatty acids. The sum of the different diesters comprised about 9% of total steer meibomian lipids.
Capillary GLC of the fatty acids of αType I diesters showed the fatty acids to be a family with a two-cluster profile, one
at C12 to C20 and the other at C21 to C31, with anteiso chains predominating. Fatty acids from ωType I-St and α,ωType II diesters gave mainly a one-cluster profile
in the short long chain, C23 to C30, with anteiso chains predominating, while the α-hydroxy fatty acids were short chain C13 to C18 acids with C16 predominating. The sterols in diesters ωType I-St were cholesterol (∼60%), Δ7 cholestenol (∼35%) and an unidentified compound
(∼5%) with a GLC retention time slightly longer than Δ7 cholestenol on SE-30 phase. The ω-hydroxy fatty acids and α,ω-diols
both were of exceedingly long chain lengths, C29−C38, and showed similar GLC profiles. Two types of triesters comprising approximately 1% of total steer meibomian lipids have
been isolated but incompletely characterized. In terms of molar ratios, one group of triesters gave fatty acids:ω-hydroxy
fatty acids:α-hydroxy fatty acids:sterols + fatty alcohols as approximately 1∶1∶1∶1. The other contained fatty acids, α-hydroxy
fatty acids and α,ω-diols in what appears to be a complex mixture of several triesters. Diesters ωType I and α,ωType II also
were found in human meibum. Hitherto these two diesters have not been found in any animal tissue. 相似文献
88.
Helen L. Ngo Alberto Nuñez Wenbin Lin Thomas A. Foglia 《European Journal of Lipid Science and Technology》2007,109(3):214-224
Branched‐chain (bc) saturated fatty acids (SFA) have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids (UFA) and have better low‐temperature properties than linear SFA. Previous studies in converting UFA to bc‐FA using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting UFA to bc‐FA in higher yields and conversions. In this work, we examined the scope and potential of the zeolite‐catalyzed synthesis of bc‐FA starting from readily available monounsaturated linear FA. Our results show that common UFA such as oleic acid can be converted to bc‐isomers using modified Ferrierite zeolite catalysts with high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the FA chain were determined from the GC‐MS spectra of the picolinyl esters of the bc‐FA. 相似文献
89.
The adsorption of cobalt phthalocyanine dye onto activated carbon in a continuous stirred tank adsorber was studied. The variables investigated were: adsorbent mass, adsorbent particle size and fluid flowrate. Several models based on film, pore and surface diffusion were constructed and fitted to the experimental data. Experimental results showed: (i) the increasing importance of the film mass transfer resistance for increasing adsorbent loads; (ii) the increasing importance of the surface diffusion mechanism for increasing adsorbent loads; and (iii) the better discrimination among different models for higher adsorbent loads and lower flowrate. 相似文献
90.
The alignment of information systems with the business goals of an organisation, although a topic of great importance, is not always properly valued or taken into consideration. In general, managers have different opinions to chief information officers (CIOs) in relation to IS, especially with regard to their importance and value to the business and also in terms of investment needs. Here, we discuss and study new approaches to methods and tools for assessing the relative importance of each information system to business, focusing on the financial sector including banks and insurance companies. We suggest the introduction of new key indicators for better decision support and to identify investment priorities, and present results regarding the relative importance of each process to support the business strategy. The primary goal for the inherent research project is to analyse the main problems and difficulties encountered by IS and IT managers, featuring different players and how they relate. The main contributions of this work are the CRUDi framework as a tool to improve alignment between business and IS strategies and the CRUDi survey and its results qualifying the financial sector's opinion regarding the relative importance of processes and investments. 相似文献