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61.
Luis Henrique Guilherme Carlos Alberto Della Rovere Sebastião Elias Kuri Marcelo Falção de Oliveira 《Welding International》2016,30(4):268-276
The AISI 444 stainless steel (SS) has become an option to substitute the AISI 316L SS because of its low cost and satisfactory corrosion resistance. However, the use of AISI 444 alloy tubes in heat exchangers causes the welding of a dissimilar joint. The aim of this study was evaluate the corrosion resistance of the tube-to-tubesheet welded by a TIG process composed of AISI 316L and AISI 444. Preparation of samples was executed through replication of tube-to-tubesheet joints. In order to test the corrosion resistance of the welded joint, the following tests were applied: sensitisation, mass loss from room temperature up to 90 °C and electrochemical corrosion tests in 0.5 mol/L HCl and 0.5 mol/L H2SO4 electrolytes. The results have shown that the dissimilar joint suffers galvanic corrosion with increased degradation of the heat-affected zone of the AISI 444 tube. Nevertheless, the mechanisms of localised corrosion (pit and intergranular) were more active in the AISI 316L alloy. It is concluded that the dissimilar joint showed better corrosion resistance than the welded joint composed solely of AISI 316L at temperatures up to 70 °C, as the conditions observed in this work. 相似文献
62.
Moritz von Stosch Rui Oliveira Joana Peres Sebastião Feyo de Azevedo 《Journal of Process Control》2012,22(7):1171-1181
A general hybrid semi-parametric process control framework is proposed in this study. The motivation was the integration of different levels of knowledge systems into a general hybrid semi-parametric control structure, of which the general linear controller or the PID controller are, for instance, particular cases.Several hybrid semi-parametric control structure variants and tuning methods are benchmarked in relation to a simulated bioprocess control problem, namely closed-loop control of the biomass concentration through manipulation of the substrate feeding rate, coupled with the closed-loop control of the dissolved oxygen concentration through the stirring velocity. The results demonstrate that (i) due to the hybrid approach the control loop can be closed without any additional identification experiments; (ii) the incorporation of different types of knowledge can enhance the controller performance, when compared to structures without a priori knowledge; (iii) knowledge incorporation seems to facilitate the tuning of the controller; and (iv) the control action can be analyzed in relation to structural information incorporated into the hybrid controller. 相似文献
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64.
Jian Liu Mariavittoria Craighero Vandna K. Gupta Dorothea Scheunemann Sri Harish Kumar Paleti Emmy Järsvall Youngseok Kim Kai Xu Juan Sebastián Reparaz L. Jan Anton Koster Mariano Campoy-Quiles Martijn Kemerink Anna Martinelli Christian Müller 《Advanced functional materials》2024,34(18):2312549
Functionally graded materials (FGMs) are widely explored in the context of inorganic thermoelectrics, but not yet in organic thermoelectrics. Here, the impact of doping gradients on the thermoelectric properties of a chemically doped conjugated polymer is studied. The in-plane drift of counterions in moderate electric fields is used to create lateral doping gradients in films composed of a polythiophene with oligoether side chains, doped with 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4TCNQ). Raman microscopy reveals that a bias voltage of as little as 5 V across a 50 µm wide channel is sufficient to trigger counterion drift, resulting in doping gradients. The effective electrical conductivity of the graded channel decreases with bias voltage, while an overall increase in Seebeck coefficient is observed, yielding an up to eight-fold enhancement in power factor. Kinetic Monte Carlo simulations of graded films explain the increase in power factor in terms of a roll-off of the Seebeck coefficient at high electrical conductivities in combination with a mobility decay due to increased Coulomb scattering at high dopant concentrations. Therefore, the FGM concept is found to be a way to improve the thermoelectric performance of not yet optimally doped organic semiconductors, which may ease the screening of new materials as well as the fabrication of devices. 相似文献
65.
66.
Maria Etelvina Pinto Fernanda De Mattos Egydio Sebastião Roberto Taboga S.M.L. Chamindrani Mendis‐Handagama Rejane Maira Góes 《Microscopy research and technique》2010,73(2):119-127
Information on postnatal Leydig cell (LC) differentiation in the Mongolian gerbil has been unavailable. Therefore, current investigation was designed to examine LC lineage differentiationin this rodent, from birth to adulthood. Gerbil testes at 1 day, 1–7 weeks (w), 2 and 3 months of age were conventionally processed by light and transmission electron microscopy. Immunocytochemistry for specific markers of steroidogenic enzymes, namely 3β‐hydroxysteroid dehydrogenase (3β‐HSD) and 11β‐hydroxysteroid steroid dehydrogenase 1 (11β‐HSD1) and also for androgen receptor (AR) was performed. The establishment of adult Leydig cell populations (ALC) during testis maturation in the gerbil follows the pattern previously described in other mammalian species, with the four progressive stages of differentiation. The LC progenitors were identified at second w by 3β‐HSD expression; the first newly formed ALC were recognized at fourth w whereas immature ALC appeared at fifth w. The latter were recognized by abundance of cytoplasmic lipid, in addition to expression of 11β‐HSD1 and intense nuclear AR immunoreaction. Mature ALC in gerbil exhibited irregular eccentric nuclei and a cytoplasmic canaliculus in the perinuclear area. Only one third of mature ALC in adult gerbils showed a high expression of 11β‐HSD1 and AR expression was highly variable among them. In conclusion, the process of differentiation of ALC population in gerbil follows the pattern previously established for other rodents. However, the resulting mature ALC are strikingly different due their singular asymmetric morphology and presence of a cytoplasmic canaliculus and as well as their functional heterogeneity. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc. 相似文献
67.
Manuel Cuevas Sebastián Sánchez Vicente Bravo Nicolás Cruz Juan F. García 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(3):461-467
BACKGROUND: Olive stones were pretreated with liquid hot water (LHW or autohydrolysis) at maximum temperatures between 175 and 225 °C (severity factors, logR0, between 2.73 and 4.39) to be subjected (both liquid and solid components) afterwards to enzymatic hydrolysis with cellulases from Trichoderma viride. Ethanol fermentation of hydrolysates was performed with the non‐traditional yeast Pachysolen tannophilus ATCC 32691. RESULTS: After the enzymatic step, yields of hemicellulose solubilization reached 100%, while the cellulose was only partially hydrolysed (23%, logR0 = 4.39). The maximum yields in total reducing sugars and acetic acid, at the upper end of the severity range, was close to 0.25 and 0.04 g g?1 dry stone, respectively. During the fermentation stage, the increase in R0 reduced the maximum specific growth rate, biomass productivity, and overall biomass yield. The overall yields of ethanol and xylitol ranged, respectively, from 0.18 to 0.25 g g?1 and from 0.01 to 0.13 g g?1. CONCLUSIONS: The results demonstrate the possibility of producing ethanol from olive stones, making use of the cellulose and hemicellulose fraction of the waste. It was confirmed that the overall yield in xylitol strongly depended on severity factor, while the overall yield in ethanol remained practically constant for all the pretreatment conditions tested. Copyright © 2008 Society of Chemical Industry 相似文献
68.
A set of segmented poly(ester‐urethane)s were prepared from diisocyanates HDI or MDI and using 1,4‐butanediol and D ‐glucose‐derived cyclic diols (1,4 : 3,6‐dianhydro‐D ‐glucitol (isosorbide) or 2,4;3,5‐di‐O‐methylidene‐D ‐glucitol (gludioxol) or mixtures of them) as extenders. Hydroxyl end‐capped polycaprolactone with a molecular weight of 3000 g·mol?1 was used as soft segment. Two polymerization methods, in solution and in bulk, were applied for the synthesis of these poly(ester‐urethane)s. The influence of the preparation procedure and composition in cyclic extender on synthesis results, structure, and properties of the novel poly(ester‐urethane)s was comparatively evaluated and discussed. The effect of replacement of 1,4‐butanediol by isosorbide or gludioxol on hydrodegradability was also assessed; the hydrolysis rate increased noticeably with the presence of glucitol derived units, although degradation of the polymers took place essentially by hydrolysis of the polyester soft segment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
69.
70.
Sebastián Suárez Flavio Soldera Carlos González Oliver Diego Acevedo Frank Mücklich 《Advanced Engineering Materials》2012,14(7):499-502
The thermal expansion behavior of Ni matrix composites reinforced with multiwalled carbon nanotubes (MWNT) fabricated by pressureless sintering and hot uniaxial pressing was studied in the range between 50 and 1050 °C and compared to that of pure Ni. The results show an active interaction between the MWNT and the Ni matrix by reducing the coefficient of thermal expansion (CTE) of pure Ni up to 76% between 50 and 400 °C. This reduction is due to the strong interfacial interaction between the matrix and the reinforcement and the low intrinsic CTE of the nanotubes. This outstanding behavior may be very useful in applications were low CTE is required as for example structural materials. 相似文献