José A. Reglero Ruiz  Saúl Vallejos  Ana M. Sanjuán  Félix C. García  Mikel Múgica  Miguel Ángel Rodríguez‐Pérez  José M. García 《应用聚合物科学杂志》2018,135(7)

Microcellular polymers have been produced by ScCO₂ foaming, based on 1‐vinyl‐2‐pyrrolidone (VP) and butyl‐acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 µm). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity values. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45872.  相似文献   

    

Fabricio Alcalde Bessia  Martin Pérez  José Lipovetzky  Natalia Alejandra Piunno  Horacio Mateos  Iván Sidelnik  Juan Jerónimo Blostein  Miguel Sofo Haro  Mariano Gómez Berisso 《International Journal of Circuit Theory and Applications》2018,46(10):1848-1857

This paper presents the use of commercial off the shelf CMOS image sensors for the acquisition of X‐ray images with high spatial resolution. The X‐ray images, with application in biology, electronic components inspection, and paleontology research, are obtained with 8‐keV photons from a Cu tube. The quantum efficiency of the detector is estimated using attenuation lengths of photons in the sensor and compared to traditional scintillator conversion layers. The spatial resolution observed with the sensor is limited by the charge redistribution produced after photon interaction with Si.  相似文献   

    

Ricardo MONTEIRO  Miguel ARA&#  JO  Raimundo DELGADO  M&#  rio MARQUES 《Frontiers of Structural and Civil Engineering》2018,12(1):109

The increasing awareness of the general society toward the seismic safety of structures has led to more restrictive performance requirements hence, many times, to the need of using new and more accurate methods of analysis of structures. Among these, nonlinear static procedures are becoming, evermore, the preferred choice of the majority of design codes, as an alternative to complete nonlinear time-history analysis for seismic design and assessment of structures. The many available software tools should therefore be evaluated and well understood, in order to be easily and soundly employed by the practitioners. The study presented herein intends to contribute to this need by providing further insight with respect to the use of commonly employed structural analysis software tools in nonlinear analysis of bridge structures. A comparison between different nonlinear modeling assumptions is presented, together with the comparison with real experimental results. Furthermore, alternative adaptive pushover procedures are proposed and applied to a case study bridge, based on a generic plastic hinge model. The adopted structural analysis program proved to be accurate, yielding reliable estimates, both in terms of local plastic hinge behavior and global structural behavior.  相似文献   

    

Neftal&#  SARMIENTO-SOLANO  Miguel P. ROMO 《Frontiers of Structural and Civil Engineering》2018,12(1):81

To evaluate the effects of dam height, valley narrowness and width of concrete slabs on the first-dam reservoir filling in-plane transversal normal stresses in the concrete face of CFRD´s, 3D finite difference analyses were carried out. Behavior of rockfill dams considered in this study was defined from the monitoring of a number of 3D sets of pressure cells and extensometers installed in three large dams in Mexico. The 3D analyses results show that high in-plane transversal compressive stresses develop within the concrete panels located in the central concrete face zone upon dam reservoir filling loading. Likewise, in-plane induced tensile transversal stresses in the zones near the abutments increase the potential of slabs cracking and damaging the waterstops in-between the vertical and perimetral joints. From the results of the 3D finite difference analyses, a simple method to estimate in-plane normal stresses in the concrete face is advanced and through comparisons with the results of a 3D case numerical study, its accuracy assessed.  相似文献   

    

Miguel Ángel Rincón‐Cervera  Raúl Galleguillos‐Fernández  Valeria González‐Barriga  Rodrigo Valenzuela  Alfonso Valenzuela 《European Journal of Lipid Science and Technology》2018,120(10)

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Franco Paolo Rivas  María Elisa Cayré  Carmen A. Campos  Marcela P. Castro 《Journal of Food Safety》2018,38(1)

The aim of the study was to determine if natural and artificial casings (ovine, porcine, bovine, collagen, and cellulose casings), serve as carriers for the application of the bacteriocin sakacin G produced by Lactobacillus curvatus ACU‐1. Mode of action of the cell‐free supernatant (CFS) containing the bacteriocin was also studied to determine whether Listeria monocytogenes inhibition could be tantamount to Listeria innocua one. Cylindrical vessels were filled with sterile meat emulsion and were wrapped with the different casings. Half the systems were treated with the CFS containing sakacin G, while the other half was taken as control systems. All systems were inoculated with L. innocua ATCC 33090. L. innocua was able to grow on all the studied casings. Collagen casing treated with CFS inhibited Listeria growth. A bacteriostatic effect was observed in the systems with porcine, ovine, bovine and cellulosic casings treated with CFS. The bacteriocin maintained its activity until the end of the trial. All casings were widely promising as antimicrobial application supports, being effective carriers to be used in a wide range of meat products.

Practical applications

Based on its advantageous characteristics, bacteriocins attracted considerable interest as natural food preservatives to extend shelf life and safety of meat and meat products. The application of sakacin G produced by Lactobacillus curvatus ACU‐1 on different natural and artificial casings would allow the preservation of a wide range of meat products that are stuffed into them, such as several types of sausages, wiener, salami, and mortadella, among others. The major advantage relies on its application, since it is not necessary to modify the production process or add extra wrappings to support the antimicrobial substance.  相似文献   

    

Gerd Sparovek  Laura Barcellos Antoniazzi  Alberto Barretto  Ana Cristina Barros  Maria Benevides  Gran Berndes  Estevo do Prado Braga  Miguel Calmon  Paulo Henrique Groke  Fbio Nogueira de Avelar Marques  Mauricio Palma Nogueira  Luis Fernando Guedes Pinto  Vinicius Precioso 《Biofuels, Bioproducts and Biorefining》2016,10(3):204-221

A key question for food, biofuels, and bioproducts production is how agriculture affects the environment, and social and economic development. In Brazil, a large agricultural producer and among the biologically wealthiest of nations, this question is challenging and opinions often clash. The Brazilian parliament and several stakeholders have recently debated the revision of the Forest Act, the most important legal framework for conservation of natural vegetation on Brazilian private agricultural lands. Past decades have shown improvements in the agricultural sector with respect to productivity and efficiency, along with great reductions in deforestation and growth of environmentally certified production. However, the opposing sides in the debate have ignored this progress and instead continue to entrench their respective combative positions. A structured exchange involving nine experts associated with major producer interests (livestock, crops, planted forest, and charcoal) and environmental NGOs was moderated based on a framework that sorted viewpoints into four categories: (i) common ground – compatible interests considered to be high priority for Brazilian sustainable agricultural development; (ii) serving exclusive nature conservation interest; (iii) serving exclusive agricultural production interest; and (iv) mainly serving the purpose of sustaining dispute. We conclude that the majority of actions and expected future trends reflect achievements and ambitions to balance production and conservation, but much public opinion – and in turn decisions in the parliament and government for agriculture and conservation – is shaped by a perceived conflict between these objectives and a debate that has become, at least to some extent, an end in itself. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

Javier Marcos  Íigo de la Parra  Miguel García  Luis Marroyo 《Progress in Photovoltaics: Research and Applications》2016,24(5):680-691

A model to simulate the fluctuations generated by a fleet of dispersed photovoltaic (PV) plants solely based on irradiance data measured at one single location is proposed. This simple model has been satisfactorily tested to quantify the power variability of a generic PV fleet, simply by defining two parameters: mean PV plant size and the number of plants in the PV fleet. Specifically, the model provides series of simulated power outputs that may be used in the grid operator simulation programmes, reproducing critical parameters, such as daily maximum fluctuation or the reserves required to offset these fluctuations. The model is created and validated against experimental 1‐s data collected throughout 2013 at six PV plants in Spain dispersed over 1100 km², totaling 17 MWp. Likewise, the model has been succesfully tested against another irradiance dataset, four sites across the state of Colorado, USA, and spread over 2400 km². Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

    

Enrique Castillo  Aida Calvio  Zacarías Grande  Santos Snchez‐Cambronero  Inmaculada Gallego  Ana Rivas  Jos María Menndez 《Computer-Aided Civil and Infrastructure Engineering》2016,31(3):193-218

The article provides a new Markovian–Bayesian network model to evaluate the probability of accident associated with the circulation of trains along a given high speed or conventional railway line with special consideration to human error. This probability increases as trains pass throughout the different elements encountered along the line. A Bayesian network, made up of a sequence of several connected Bayesian subnetworks, is used. A subnetwork is associated with each element in the line that implies a concentrated risk of accident or produces a change in the driver's attention, such as signals, tunnel, or viaduct entries or exits, etc. Bayesian subnetworks are also used to reproduce segments without signals where some elements add continuous risks, such as rolling stock failures, falling materials, slope slides in cuttings and embankments, etc. All subnetworks are connected with the previous one and some of them are multi‐connected because some consequences are dependent on previous errors. Because driver's attention plays a crucial role, its degradation with driving time and the changes due to seeing light signals or receiving acoustic signals is taken into consideration. The model updates the driver's attention level and accumulates the probability of accident associated with the different elements encountered along the line. This permits us to generate a continuously increasing risk graph that includes continuous and sudden changes indicating where the main risks appear and whether or not an action must be taken by the infrastructure manager. Sensitivity analysis allows the relevant and irrelevant parameters to be identified avoiding wastes of time and money by concentrating safety improvement actions only on the relevant ones. Finally, some examples are used to illustrate the model. In particular, the case of the Orense–Santiago de Compostela line, where a terrible accident took place in 2013.  相似文献   

    

Antoni Cladera  Antonio Marí  Jesús Miguel Bairn  Carlos Ribas  Eva Oller  Noemí Duarte 《Structural Concrete》2016,17(6):1017-1032

A simplified mechanical model is presented for the shear strength prediction of reinforced and prestressed concrete members with and without transverse reinforcement, with I, T or rectangular cross‐section. The model, derived with further simplifications from a previous one developed by the authors, incorporates the contributions of the concrete compression chord, the cracked web, the dowel action and the shear reinforcement in a compact formulation. The mechanical character of the model provides valuable information about the physics of the problem and incorporates the most relevant parameters governing the shear strength of structural concrete members. The predictions of the model fit very well the experimental results collected in the ACI‐DAfStb databases of shear tests on slender reinforced and prestressed concrete beams with and without stirrups. Due to this fact and the simplicity of the derived equations it may become a very useful tool for structural design and assessment in engineering practice.  相似文献