排序方式: 共有28条查询结果,搜索用时 15 毫秒
1.
Imane Mayouf Melia Guessoum Mónica Fuensanta José Miguel Martín Martìnez 《Polymer Engineering and Science》2020,60(5):944-955
The potential of ε-caprolactam (CAP) and trimellitic anhydride (TMA) compounds as novel chain extenders for poly(lactic acid) (PLA) has been assessed; the amounts of 0.01, 0.025, and 0.05 wt% each additive have been added. The chain extension was evidenced by the increase in PLA/CAP and PLA/TMA viscosities in mixing torque measurements and by infrared spectroscopy. PLA reaction with CAP and TMA has also been confirmed from contact angle and surface free energy studies, which have shown that the increase in TMA amount decreased the hydrophilicity of PLA due to the decreased concentration of terminal surface hydroxyl groups. However, the addition of CAP accentuated the PLA hydrophilicity as indicated by the increase in the polar component of the surface energy. On the other hand, the glass transition temperature of PLA/TMA and PLA/CAP decreased as a result of a local plasticizing effect, which favored the chain mobility and the crystallization of PLA due to the concomitant nucleating effect of the chain extenders moieties too. Furthermore, the higher molecular weight of PLA/CAP and PLA/TMA was responsible for their increased thermal stability and higher impact strength with respect to PLA. POLYM. ENG. SCI., 60:944–955, 2020. © 2020 Society of Plastics Engineers 相似文献
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Pedro J. Martínez de la Cuesta Eloísa Rus Martínez Fuensanta I. Palomino Prez Francisca Romero Sarria 《加拿大化工杂志》1999,77(6):1169-1175
The esterification process of ethenyl benzene and its derivative compounds (p-methyl, p-methoxy, p-chloro, m-methyl, m-nitro and m-chloro, respectively) was carried out with acetic acid and using perchloric acid as a catalyst. From the effects of the variables studied it could be concluded that: the temperature and the catalyst concentration influence positively over the olefin conversion, whereas the initial olefin concentration exert no effect over the same; and that the presence of perchloric salts exerts a different influence, depending on the temperature and on the catalyst concentration. It has been proven that the substituted radicals in the m- or p- positions exert an important influence over the conversion of the studied olefins, presenting growing reactivity in the following order: m-nitro ethenyl benzene, m-chloro ethenyl benzene, p-chloro ethenyl benzene, m-methyl ethenyl benzene, ethenyl benzene, p-methyl ethenyl benzene and p-methoxy ethenyl benzene. Finally, a kinetic and thermodynamic study has been done and the corresponding parameters have been calculated, with an adequate fitting. 相似文献
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Fullerton M Woods RL Vera-Diaz FA Peli E 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(12):B174-B187
We used a new method to measure the perceived quality of contrast-enhanced motion video. Patients with impaired vision (n=24) and normally sighted subjects (n=6) adjusted the level of MPEG-based enhancement of 8 videos (4 min each) drawn from 4 categories. They selected the level of enhancement that provided the preferred view of the videos, using a decreasing-step-size staircase procedure. Most patients made consistent selections of the preferred level of enhancement, indicating an appreciation of and a perceived benefit from the MPEG-based enhancement. The selections varied between patients and were correlated with letter contrast sensitivity, but the selections were not affected by training, experience, or video category. We measured just noticeable differences directly for videos and mapped the image manipulation (enhancement in our case) onto an approximately linear perceptual space. These tools and approaches will be of value in other evaluations of the image quality of motion video manipulations. 相似文献
4.
Josefa Madrid M Dolores Megías Fuensanta Hernndez 《Journal of the science of food and agriculture》1999,79(4):580-584
A simple, rapid and sensitive capillary gas chromatographic method was investigated to determine volatile fatty acids (VFA) in juice from silage made from artichoke and orange byproducts. The procedure uses a capillary column fused‐silica, 30 m×0.25 mm×0.25 mm ID and coated with FFAP‐TR. Centrifuged samples can be injected directly after lowering the pH to 1 and using a simple deproteinisation method. No adsorption, tailing or ghost phenomena occured. Separate analyses of VFA are quick and reliable. The average duration of an analyses is 7 min. The concentration, not only of the major acids, such as acetic acid, but also of the minor fermentation products such as butyric acid can be determined. The retention times of the products of fermentation and the extraction reagents were sufficiently different to avoid interference problems. © 1999 Society of Chemical Industry 相似文献
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Antonio Bdalo Jos L Gmez Elisa Gmez M Fuensanta Mximo M Claudia Montiel 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(5):552-558
The kinetics of the asymmetric hydrolysis of N‐acetyl‐DL ‐butyrine catalyzed by L ‐aminoacylase to obtain optically pure L ‐butyrine is described. Some of the constants are determined from the initial reaction rates and others from long‐term experiments in batch reactors by the numerical integration of the reactor design equation and minimization of the kinetic parameters. The methodology described can be applied to the kinetic study of other complex biocatalytic systems. Studies on enzyme activation by adding different divalent metal ions and enzymatic deactivation are also included. © 2002 Society of Chemical Industry 相似文献
6.
Ionela‐Daniela Carja Diana Serbezeanu Tachita Vlad‐Bubulac Corneliu Hamciuc Vicente Forrat Prez Maria Dolores Romero Snchez Celia Guillem Lpez Mnica Fuensanta Soriano 《应用聚合物科学杂志》2015,132(16)
In this study, a commercial epoxy resin was mixed with a phosphorus‐containing oligomer and thermally cross‐linked using a mixture of two aliphatic amines as curing agents. The miscibility and the influence of the phosphorus‐containing oligomer on the characteristics of epoxy thermosets were investigated by scanning electron microscopy (SEM), thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. SEM revealed that phosphorus‐containing oligomer was well dispersed into the epoxy matrix. Dynamic mechanical analysis indicated an increase in storage modulus as the phosphorus‐containing oligomer content loaded into epoxy matrix increased. Thermogravimetric analysis showed that the onset temperature of phosphorus‐containing epoxy thermosets and the peak corresponding to the temperature of decomposition decreased compared with the ones corresponding to the neat epoxy system, whereas the char yield increased with the increase in phosphorus content added into the epoxy networks. To better understand the mechanism of action of phosphorus‐containing epoxy thermosets, the char residue was investigated by SEM and energy‐dispersive X‐ray spectroscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41822. 相似文献
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Evaluation of soil quality using multiple lineal regression based on physical, chemical and biochemical properties 总被引:2,自引:0,他引:2
Zornoza R Mataix-Solera J Guerrero C Arcenegui V García-Orenes F Mataix-Beneyto J Morugán A 《The Science of the total environment》2007,378(1-2):233-237
The aim of this work is to obtain an expression using multiple lineal regressions (MLR) to evaluate environmental soil quality. We used four forest soils from Alicante province (SE Spain), comprising three Mollisols and one Entisol, developed under natural vegetation with minimum human disturbance, considered as reference soils of high quality. We carried out MLR integrating different soil physical, chemical and biochemical properties, and we searched those regressions with Kjeldahl nitrogen (N(k)), soil organic carbon (SOC) or microbial biomass carbon (MBC) as predicted parameter. We observed that Mollisols and Entisols presented different relationships among their properties. Thus, we searched different equations for both groups of soils. The selected equation for Mollisols was N=0.448 (P) + 0.017 (water holding capacity) + 0.410(phosphatase) - 0.567 (urease) + 0.001 (MBC) + 0.410 (beta - glucosidase) - 0.980, and for the Entisol SOC = 4.247 (P) + 8.183 (beta-glucosidase) -7.949 (urease) + 17.333. Equations were applied to samples from two forest soils in advanced degree of degradation, one for Mollisols and the other one for the Entisol. We observed a clear deviation in the predicted parameters values related to the real properties. The obtained results show that MLR is a good tool for soil quality evaluation, because it seems to be capable of reflecting the balance among its properties, as well as deviations from it. 相似文献
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Maria-Isabel Sanchez-Segura Fuensanta Medina-Dominguez Arturo Mora-Soto 《Information Sciences》2010,180(14):2721-2742
Low efficiency of use of software engineering best practices and poor quality of the products developed are two of the main reasons for the failure of software projects. This paper describes an architectural model, based on the re-use of process and project assets supported by collaborative mechanisms, which improves the efficiency of use of software processes; and a set of quality parameters under validation. This model was implemented in real software projects. 相似文献
10.
José Ramón Soler Fuensanta Francisco Javier López-Brea Espiau Frode Weierud 《Cryptologia》2013,37(4):301-328
Abstract The presentation of a brief study of the use of Enigma Machines in Spain, during the Spanish Civil War (1936–1939) and later, until their final replacement. 相似文献