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991.
Aleksándros El Áurens Meira de Souza Leonardo José Lins Maciel Nelson Medeiros de Lima Filho Cesar Augusto Moraes de Abreu 《Catalysis Today》2010,149(3-4):413-417
A nickel catalyst (5.75 wt.%) supported on gamma-alumina was evaluated through autothermal reforming of methane (ATR). The reforming process was pointed to hydrogen production, following thermodynamic and stoichiometric predictions. The catalyst was characterised by several methods including atomic absorption spectroscopy (AAS), B.E.T.-N2, X-ray diffraction (XRD), scanning electron microscope (SEM) and thermal analyses (thermogravimetry, TG; derivate thermogravimetry, DTG; and differential thermal analysis, DTA). Experimental evaluations in a fixed-bed reactor (1023–1123 K, 1.00 bar, 150–400 cm3/min feed) presented methane conversions in the range of 40–65%. The effluent mixtures provided hydrogen yields in the range of 78–84%, carbon monoxide 3–14%, and carbon dioxide 5–18%. High molar H2/CO ratios, ranging from 8 to 90, were obtained. Operating autothermal conditions (excess of steam, 1023–1123 K, 1.00 bar) provided low coke formation and high hydrogen selectivity (81%) for methane reforming. 相似文献
992.
César Marconi María José Castillo Mabel Ramini Hernán Svoboda 《Welding International》2013,27(9):618-628
ABSTRACTFillet joints are one of the most commonly used joints in various industries, in particular for agricultural machinery. However, the complexity of the pieces that require welding often makes accessibility difficult for the welder for this kind of joint, and working and displacement angles are important aspects to be evaluated. In addition, in the GMAW process, the use of the Ar-20%CO2 mixture as the shield gas has increased at the expense of 100% CO2, generally requiring an adjustment of the electrical parameters. On the other hand, the incorporation of new materials with higher strength also involves optimizing the welding procedure. The aim of this study was to evaluate the effect of two shield gases (Ar-20% CO2 and 100% CO2), three working angles (30, 45 and 60°) and two displacement angles (45° using the push technique and 60° using the pull technique) on the dimensional characteristics of the seam and the mechanical strength of the fillet joint from a microalloyed steel with high strength welded using GMAW. The highest levels of penetration corresponded to the test specimens welded using the pull technique and with CO2. The over thickness was smaller for conditions with the push technique and the gas mixture. The microhardness of the weld metal, for a similar working angle, was higher for the gas mixture in all cases. Indices of acceptability were developed, which graded geometric aspects and these were compared with the mechanical properties obtained on the welds, showing a good correlation. 相似文献
993.
Bruno F. Machado Helder T. Gomes Philippe Serp Philippe Kalck José L. Figueiredo Joaquim L. Faria 《Catalysis Today》2010,149(3-4):358-364
Carbon xerogels are mesoporous materials obtained upon pyrolysis of the dried gels resulting from polycondensation of resorcinol and formaldehyde. Treatment with nitric acid under severe conditions introduces high amounts of oxygen containing functional groups onto the surface of the material, leading however to the collapse of its porous structure. The resulting material is then used to support 1 wt.% Pt, Ir and Ru monometallic catalysts by wet impregnation using organometallic precursors. The catalysts are characterized by N2 adsorption–desorption isotherms at 77 K, temperature programmed desorption coupled with mass spectrometry, scanning and transmission electron microscopy, and H2 chemisorption. The liquid-phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol is used in order to assess the catalytic performance of the prepared materials. Pt and Ru catalysts are initially very selective towards the hydrogenation of the olefinic double bond, while Ir is mostly selective towards the carbonyl group. After a thermal post-reduction treatment at 973 K, selectivity towards cinnamyl alcohol is significantly improved regardless of the metal nature. The Pt catalyst exhibits the best behavior, a complete shift in C=C to C=O hydrogenation being detected. The improvement in selectivity is rationalized in terms of both an increase in metal particle size and a modification in the surface chemistry of the catalyst after the post-reduction treatment. 相似文献
994.
José A. Larrauri Pilar Rupérez F. Saura-Calixto 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,205(1):39-42
Antioxidant compounds associated with some types of dietary fibres may be responsible in part for the beneficial effects
on health of high-dietary-fibre diets. The antioxidant activity of a high-dietary-fibre mango peel product and of some commercial
samples was determined by the ferric thiocyanate colorimetric method. At a concentration of 0.05%, the antioxidant activity
of mango peel dietary fibre was 0.75 times as effective as that of 2-tert-butyl-4-hydroxyanisol (BHA) and 1.4 and 3.4 times higher, respectively, than that of French PARAD’OX (a commercial polyphenols
concentrate) and of DL-α-tocopherol. All Bran, Quaker Oats, lemon and apple fibre did not exhibit any antioxidant capacity. The obtention of high-dietary-fibre
products with bioactive compounds could be useful for the food industry and the antioxidant activity may be a new property
to consider in the quality evaluation of these ingredients.
Received: 25 January 1996 / Revised version: 10 June 1996 相似文献
995.
Maria José Ocio Pablo Salvador Fernandez Miguel Rodrigo Paula Periago A. Martinez 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,205(4):325-328
A time temperature integrator (TTI) was developed by immobilizing Bacillus stearothermophilus spores in a cylindrical particle consisting of an alginate-starch-mushroom purée. The particle showed homogeneous spore distribution,
and when heated over a temperature range of 121 – 130° C negligible spore leakage was observed after the thermal process.
The experimental data on spore survivor levels obtained for each temperature-time combination were compared with theoretical
predictions using a mathematical model. The results showed a good correlation between the experimental and theoretical data.
All these results provide evidence that this artificial particle could be a very reliable TTI for monitoring the thermal impact
on micro-organisms during validating sterilization processes in continuous aseptic systems.
Received: 25 February 1997 相似文献
996.
Isothermal mechanical spectrometry experiments were carried out between 10−4 and 100 Hz on strain hardening aluminum samples, after annealings at various temperatures ranging between 300 and 700 K.
For lower annealing temperatures (<480 K), internal friction spectra exhibit only a low frequency background. After annealings
above 480 K, a relaxation peak superimposed to the background stands out. The peak height is, first, increasing for annealing
temperatures below 580 K and then decreasing. The apparent relaxation parameters are found to be strongly dependent on the
annealing temperature. The evolution of the internal friction spectra cannot be correlated with a grain boundary relaxation
but with a reversible motion of dislocation segments inside dislocation networks developed during recovery annealings. 相似文献
997.
Virtual adjustable sources are introduced in equivalent network representation of boundary conditions. For this purpose, integral equations are to be solved simple application of analog Kirchoff’s and Ohm’s laws. These adjustable sources represent generalized trial quantities. In order to illustrate this proposed approach, equivalent network representation of lossy planar transmission lines with arbitrary metallization thickness is presented. 相似文献
998.
Miguel Ángel Rincón‐Cervera María Dolores Suárez‐Medina José Luis Guil‐Guerrero 《European Journal of Lipid Science and Technology》2009,111(9):920-925
Fifteen roes from different marine fish species available in Spain were analyzed in order to determine their fatty acid (FA) composition, especially the eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA) contents. Roes from Atlantic bonito (Sarda sarda), European squid (Loligo vulgaris), cuttlefish (Sepia spp.), lumpfish (Cyclopterus lumpus), European hake (Merluccius merluccius), Atlantic salmon (Salmo salar) and gonads of male Atlantic mackerel (Scomber scombrus) reached EPA + DHA amounts higher than 30% of the total FA, and among them, roes from lumpfish, European hake and salmon provide different FA type ratios that could make them adequate as dietary sources of EPA and DHA. 相似文献
999.
BACKGROUND: Skin diseases have only recently been considered as a possible public health problem in developing countries. Data supporting this matter are scarce. The aim of this study is to report the experience of a specialized dermatologic center in Bamako (Mali) in order to complete two previous studies conducted in the Bamako area: a prevalence study in the general population and a study in nonspecialized health centers of Bamako. It is our intention to provide a comprehensive picture of the problem of skin diseases in an African developing country. METHODS: We retrospectively collected all cases of skin diseases diagnosed during consultations provided at the Institut Marchoux in Bamako, the only center specializing in dermatology in Mali, during the year 1993. RESULTS: A total of 10,575 new outpatients were seen with 10,889 skin diseases. The main skin diseases registered were as follows: infectious dermatoses (41% of all diagnoses, including scabies (16.6%), superficial mycoses (13.6%), and primary pyoderma (5.6%)), dermatitis (20.4%), papular urticaria (4.4%), acne (4.2%), pityriasis alba (3.6%), keratoderma (3.6%), and urticaria (3%). Typical tropical infectious diseases accounted for only 1% of all diagnoses. CONCLUSIONS: It appears that certain skin diseases (mainly scabies and pyoderma) are an important health problem for the population of the Bamako area. Public health policies should be implemented in order to manage this problem rationally. 相似文献
1000.
José R. Sendra Javier del Pino Antonio Hernández Benito González Javier García Andrés García-Alonso Antonio Nunez 《Analog Integrated Circuits and Signal Processing》2003,35(2-3):121-132
In this work we propose a modification to the conventional lumped equivalent circuit model for integrated inductors. Also the widely used parametric model is modified. The proposed models expand the frequency range where the integrated inductor behavior is accurately predicted. They are useful in developing automatic tools to assist the designers in selecting and automatically laying-out integrated inductors [1]. This work is based on measurements from integrated inductors fabricated in a standard silicon process. 相似文献