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排序方式: 共有103条查询结果,搜索用时 15 毫秒
21.
Lídia Eloy Moura Carolina Oliveira de Souza Eleidiana Andréia Seixas de Oliveira Paulo Vitor França Lemos Janice Izabel Druzian 《应用聚合物科学杂志》2018,135(34)
Active packaging can be defined as packaging that includes additives that help to extend the shelf life of food; among the advantages of its use is the possibility to reduce the amount of additives added to the food during processing. The aim of this study was to develop, characterize, and apply active films of low‐density polyethylene, incorporating carotenoid and yerba mate extracts as active additives. Active films were obtained by extrusion and were characterized for water vapor permeability, thickness, color, and mechanical and thermal properties. The effectiveness of the films was evaluated using butter packed in the formulated films. There was a significant reduction in thickness, and mechanical, thermal, and water vapor barrier parameters of the films compared to the control. The concentration of additives directly influenced coloration and antioxidant and antimicrobial action of the films. The formulated films provided protection against oxidative action and inhibition of microbial growth. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46461. 相似文献
22.
Voltage‐Induced Coercivity Reduction in Nanoporous Alloy Films: A Boost toward Energy‐Efficient Magnetic Actuation 下载免费PDF全文
Alberto Quintana Jin Zhang Eloy Isarain‐Chávez Enric Menéndez Ramón Cuadrado Roberto Robles Maria Dolors Baró Miguel Guerrero Salvador Pané Bradley J. Nelson Carlos Maria Müller Pablo Ordejón Josep Nogués Eva Pellicer Jordi Sort 《Advanced functional materials》2017,27(32)
Magnetic data storage and magnetically actuated devices are conventionally controlled by magnetic fields generated using electric currents. This involves significant power dissipation by Joule heating effect. To optimize energy efficiency, manipulation of magnetic information with lower magnetic fields (i.e., lower electric currents) is desirable. This can be accomplished by reducing the coercivity of the actuated material. Here, a drastic reduction of coercivity is observed at room temperature in thick (≈600 nm), nanoporous, electrodeposited Cu–Ni films by simply subjecting them to the action of an electric field. The effect is due to voltage‐induced changes in the magnetic anisotropy. The large surface‐area‐to‐volume ratio and the ultranarrow pore walls of the system allow the whole film, and not only the topmost surface, to effectively contribute to the observed magnetoelectric effect. This waives the stringent “ultrathin‐film requirement” from previous studies, where small voltage‐driven coercivity variations were reported. This observation expands the already wide range of applications of nanoporous materials (hitherto in areas like energy storage or catalysis) and it opens new paradigms in the fields of spintronics, computation, and magnetic actuation in general. 相似文献
23.
The consensus problem with general linear dynamics and undirected graphs is studied in this paper by means of event-triggered control strategies. A novel consensus protocol is proposed, where each agent implements a model of the decoupled dynamics of its neighbors. Under this control strategy, transmission of information does not occur continuously but only at discrete points in time. The approach presented in this paper provides both a decentralized control law and a decentralized communication policy. We are able to design thresholds that only depend on local information and guarantee asymptotic consensus. Positive inter-event times are guaranteed for particular cases of the linear dynamics. In an extension, a positive constant is added to the thresholds in order to exclude Zeno behavior for general linear dynamics. The difference between agents trajectories can be bounded in this case and bounds on the state disagreement are derived. 相似文献
24.
Eloy Roura Arnau Oliver Mariano Cabezas Joan C. Vilanova Àlex Rovira Lluís Ramió-Torrentà Xavier Lladó 《Computer methods and programs in biomedicine》2014
Brain extraction, also known as skull stripping, is one of the most important preprocessing steps for many automatic brain image analysis. In this paper we present a new approach called Multispectral Adaptive Region Growing Algorithm (MARGA) to perform the skull stripping process. MARGA is based on a region growing (RG) algorithm which uses the complementary information provided by conventional magnetic resonance images (MRI) such as T1-weighted and T2-weighted to perform the brain segmentation. MARGA can be seen as an extension of the skull stripping method proposed by Park and Lee (2009) [1], enabling their use in both axial views and low quality images. Following the same idea, we first obtain seed regions that are then spread using a 2D RG algorithm which behaves differently in specific zones of the brain. This adaptation allows to deal with the fact that middle MRI slices have better image contrast between the brain and non-brain regions than superior and inferior brain slices where the contrast is smaller. MARGA is validated using three different databases: 10 simulated brains from the BrainWeb database; 2 data sets from the National Alliance for Medical Image Computing (NAMIC) database, the first one consisting in 10 normal brains and 10 brains of schizophrenic patients acquired with a 3 T GE scanner, and the second one consisting in 5 brains from lupus patients acquired with a 3 T Siemens scanner; and 10 brains of multiple sclerosis patients acquired with a 1.5 T scanner. We have qualitatively and quantitatively compared MARGA with the well-known Brain Extraction Tool (BET), Brain Surface Extractor (BSE) and Statistical Parametric Mapping (SPM) approaches. The obtained results demonstrate the validity of MARGA, outperforming the results of those standard techniques. 相似文献
25.
F. Bertinchamps M. Treinen P. Eloy A.-M. Dos Santos M.M. Mestdagh E.M. Gaigneaux 《Applied catalysis. B, Environmental》2007,70(1-4):360-369
A previous investigation of the chlorobenzene combustion activity of VOx/TiO2, VOx–WOx/TiO2 and VOx–MoOx/TiO2 catalysts in the presence of NO pointed out the activation effect of NO. The suggested three-step mechanism based on catalytic performances data only was: (1) chlorobenzene is oxidized on the surface of the VOx phase (as described by Mars–van Krevelen), (2) NO gets oxidized to NO2, mainly on WOx and MoOx, and (3) the in situ produced NO2 assists O2 in the reoxidation of the VOx phase thus speeding up the oxidation step of the Mars–van Krevelen mechanism. The latter effect macroscopically corresponds to the observed increase of chlorobenzene conversion. This contribution aims at validating this hypothetical mechanism by pointing out the favourable occurrence of an oxidation of NO to NO2 on the WOx and MoOx phases and by pointing out the higher efficiency of NO2 than O2 to reoxidize the reduced VOx sites. In addition, the present contribution clearly demonstrates that, in the absence of NO, the chlorobenzene total oxidation occurred following the Mars–van Krevelen mechanism. Moreover, a thorough characterization of the oxidation state of the vanadium proving that the improvement of the catalyst activity brought by the simultaneous presence of NO and O2 is linked to the stronger reoxidation of the VOx active phase. Furthermore, plotting all the catalytic activity data versus the mean vanadium oxidation level clearly depicts, for the first time, the strong dependence between them. Under a mean vanadium oxidation level of 4.82 the catalyst is inactive while above 4.87 the activity is stabilized at a high level of conversion independent of the vanadium oxidation level. 相似文献
26.
Eloy Asensio César Medina Moisés Frías María Isabel Sánchez de Rojas 《Materials and Structures》2018,51(4):101
In light of the large amounts of cement used in plain concrete and given the exothermal reactions involved in its hydration, the control and assessment of heat of hydration are instrumental to prevent future shortcomings in structural durability. This article describes the design of new eco-efficient cements containing different percentages of fired clay-based construction and demolition waste (CC&DW). The new cements (CCDWC) were characterised for pozzolanicity and their heat of hydration was assessed based on a semi-adiabatic method described in European standards. The inclusion of CC&DW retarded the heating of mortar and lowered its maximum temperatures, more significantly with the increase of replacement ratios. The design of such CC&DW-bearing low and very low heat of hydration cements may well prompt the introduction of new applications of bulk cement or cement-high mixes, in which heat may have adverse effects on durability. 相似文献
27.
Characterization of Ceramic‐Based Construction and Demolition Waste: Use as Pozzolan in Cements 下载免费PDF全文
Eloy Asensio César Medina Moisés Frías María Isabel Sánchez de Rojas 《Journal of the American Ceramic Society》2016,99(12):4121-4127
Depending on its composition and properties, construction and demolition waste (C&DW) may be used today as recycled aggregate to manufacture more eco‐efficient concrete, for drainage or as a sub‐base in roads and on occasion as a decorative or esthetic element in pedestrian pathways in parks and landscaped grounds. In Spain, 54% of C&DW is ceramic‐based (CB‐C&DW). Since the use of such waste as recycled aggregate is not envisaged in Spanish legislation, it is presently stockpiled in landfills, an environmentally, technically, and economically detrimental procedure. The CB‐C&DW recycled at 12 Spanish waste management plants was assessed to determine the feasibility of its use as an alternative to pozzolans such as silica fume and fly ash presently added to cement during manufacture. The proportion of ceramic‐based material contained in this recycled waste varied from plant to plant. The effect of the ceramic‐based material content on the chemical and mineralogical composition, morphology, and pozzolanic activity of CB‐C&DW was explored in a more exhaustive study of two types of waste, one with 20 and the other with 100% ceramic‐based material content. In light of its chemical and mineralogical composition, morphology and lime fixation capacity, this type of C&DW was found to be apt for use as a pozzolan, and hence as a valid alternative for manufacturing more eco‐efficient cements. 相似文献
28.
A nonhomogeneous Markov process is applied for analysing a cohort of women with breast cancer that were submitted to surgery.
The follow-up was scheduled every month. Three states are considered: no relapse, relapse and death. As relapse times change
over time, we have extended previous approaches for a time-homogeneous model to a nonhomogeneous multistate process. The transition
intensity functions among states are the hazard rate functions of different lognormal distributions; we therefore build the
likelihood function for this model, estimate the parameters and compare the empirical and nonhomogeneous models in terms of
the survival probability functions. The parameter estimation is done following the maximum likelihood method. The effect of
treatments is incorporated as covariates by means of the lognormal hazard rate functions, following the proportional hazard
model. Thus, we have a multistate model with multidimensional covariates. Survival functions for the different cohorts submitted
to treatments are obtained and goodness-of-fit tests are performed.
The first author gratefully acknowledges the financial support by DGES, Proyecto PB97-0827, Ministerio de Educación y Cultura,
Spain. 相似文献
29.
Tunable Magnetism in Nanoporous CuNi Alloys by Reversible Voltage‐Driven Element‐Selective Redox Processes 下载免费PDF全文
Alberto Quintana Enric Menéndez Eloy Isarain‐Chávez Jordina Fornell Pau Solsona François Fauth Maria Dolors Baró Josep Nogués Eva Pellicer Jordi Sort 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(21)
Voltage‐driven manipulation of magnetism in electrodeposited 200 nm thick nanoporous single‐phase solid solution Cu20Ni80 (at%) alloy films (with sub 10 nm pore size) is accomplished by controlled reduction‐oxidation (i.e., redox) processes in a protic solvent, namely 1 m NaOH aqueous solution. Owing to the selectivity of the electrochemical processes, the oxidation of the CuNi film mainly occurs on the Cu counterpart of the solid solution, resulting in a Ni‐enriched alloy. As a consequence, the magnetic moment at saturation significantly increases (up to 33% enhancement with respect to the as‐prepared sample), while only slight changes in coercivity are observed. Conversely, the reduction process brings Cu back to its metallic state and, remarkably, it becomes alloyed to Ni again. The reported phenomenon is fully reversible, thus allowing for the precise adjustment of the magnetic properties of this system through the sign and amplitude of the applied voltage. 相似文献
30.