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941.
Denis Mihaela Panaitescu Cristian Andi Nicolae Adriana Nicoleta Frone Ioana Chiulan Paul Octavian Stanescu Constantin Draghici Michaela Iorga Mona Mihailescu 《应用聚合物科学杂志》2017,134(19)
The widespread application of poly(3‐hydroxybutyrate) (PHB) in the food packaging and biomedical fields has been hindered by its high brittleness, slow crystallization, poor thermal stability, and narrow processing window. To overcome these limitations, a mixture of biodegradable and biocompatible plasticizers was used to modify PHB. Epoxidized soybean oil (ESO), acetyl tributyl citrate, poly(ethylene glycol) 4000 (PEG4000), and poly(ethylene glycol) 6000 (PEG6000) were tested to improve PHB melt processing and to achieve balanced thermal and mechanical properties. These plasticizers increased the flexibility and decreased the melt viscosity, improving the processability. The tensile strength was maintained within the limit of experimental error for ESO and decreased slightly (6–7%) for the other plasticizers. PEG6000 and ESO delayed the decomposition process of PHB. The plasticizers did not hinder the crystallization, and poly(ethylene glycol)s increased the crystallinity. The change in the interplanar distance and crystallite size, correlated with lamellar stack dimensions, gave more information on the plasticizers' effects in PHB. The blend with 5 wt % ESO was considered suitable for the fabrication of marketable PHB films. This study showed that it is possible to tailor the rheological, thermal, and mechanical behavior of a commercial PHB through the addition of a second plasticizer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44810. 相似文献
942.
The synthesis and optimization of novel bioactive components is key to the development of antifouling marine coatings. It was recently demonstrated that medetomidine (MM) has perfect antibarnacle behavior along with good ecological properties. To investigate the applicability of MM in self‐polishing marine paints, a large set of mixtures of MM with two commercial alkyd resins (ARs) was prepared. The nature and strength of the intermolecular interaction as a function of composition in both the liquid and solid states were studied using NMR and FTIR techniques, respectively. It was found that at low concentrations MM molecules were coordinated to alkyd resin chains by hydrogen bonding. This interaction had a multidentate character (i.e., one molecule of MM interacted with several ? COOH species of ARs) that resulted in stronger bonding between the two compounds. However, at higher MM concentrations an ionic association between the two compounds began, which at a large MM content resulted in microphase separation. It was noted that the strong interaction between medetomidine and the alkyd resins investigated was a positive factor for the application of these compounds in self‐polishing marine paints. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006 相似文献
943.
Summary A 1,4-dihydropyridine structure bearing a derivative of chiral 2-aminobutanol was used as NADH models. The so obtained reagents were grafted on a Merrifield resin. One of them allowed the obtention of an enantiomeric excess as good as that obtained with the corresponding unbound reagent. 相似文献
944.
Avoidance of occupied ovisposition sites supposes that females perceive information related to their own progency. Fatty acids identified from egg extracts have been reevaluated using a different extraction method, and we have investigated the dose-dependent oviposition response of European grape vine moths (Lobesia botrana) to myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, methyl palmitate, methyl oleate, and ethyl palmitate; all except ethyl palmitate have been identified from eggs ofL. botrana. A methylene dichloride extract of eggs fromL. botrana revealed the presence of saturated free fatty acids (myristic, palmitic, and stearic) and unsaturated acids (palmitoleic, oleic, linoleic, and linolenic) in amounts ranging from 3.9 ng/egg equivalent for myristic acid to 30 ng/egg equivalent for palmitic and oleic acids. The extract also contained traces of methyl palmitate and methyl stearate. The greatest avoidance indexes were observed in response to palmitic, palmitoleic, and oleic acids. All the other compounds tested caused weaker responses. A reduction in the number of eggs laid was observed when moths were exposed to each of the esters applied at 0.3 µg per application spot. Reduction in eggs laid was also observed at a 10-fold higher dose of oleic acid. The present results confirm that general and simple molecules can be involved in the regulation of oviposition site selection and that they may participate in chemical marking of the eggs. 相似文献
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947.
A preliminary study of cushion properties of a 3D printed thermoplastic polyurethane Kelvin foam
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Changfeng Ge Lakshmi Priyadarshini Denis Cormier Liao Pan Jonathan Tuber 《Packaging Technology and Science》2018,31(5):361-368
The cells in conventional packaging foams have random size and orientation, and the energy‐absorbing behaviour of these foams is determined by the collective contribution of different sizes of cells. In contrast to the random nature of stochastic foams, 3D printing technologies allow engineers to design and produce foams having engineered cellular structures. In this study, engineered cellular structures based on the classic Kelvin 1887 model were 3D printed in 30 × 30 × 30 mm thermoplastic polyurethane cubes with a repeating size of 216 unit cells. One hundred consecutive cyclic compression tests were performed to assess the 3D printed foam's resilience and energy absorption characteristics. The stress‐strain curve of the 3D printed thermoplastic polyurethane foam indicated viscoelastic behaviour and a Mullins effect indicative of resilient rubber. A long wave buckling mode was observed during cyclic compression cycles due to the Kelvin structure. The cushion factor computed from the stress‐strain curve was close to that of a metal spring with linear elasticity. The combination of the 3D printed foam's resilience, its much lower density than rubber, and the complete geometric freedom of the engineered cellular structures offer designers the potential to create high‐performance cushion materials tailored for packaging applications. 相似文献
948.
Gonzalo Nelis Michel Gamache Denis Marcotte Xiaoyu Bai 《Optimization and Engineering》2016,17(4):813-832
A new algorithm for the optimal stope design problem is proposed. It is based on a previous methodology developed by Bai et al. (Comput Geosci 52:361–371, 2013a) where a cylindrical coordinate system is used to define geomechanical restrictions and to find the optimal stope around an initial raise. The new algorithm extends this work using an integer programming formulation and a new set of constraints, aimed to solve geomechanical issues present on the original methodology. The new formulation is tested on two synthetic and one real deposits. An economic, geomechanical and feasibility analysis is performed, comparing the new results with Bai’s methodology. This methodology achieves better stope designs in terms of geomechanical stability and wall regularity, generating feasible stopes for real use. It also allows further extensions to incorporate other geometrical constraints in order to obtain more regular stope designs. 相似文献
949.
Robust sliding mode‐based extremum‐seeking controller for reaction systems via uncertainty estimation approach
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This paper deals with the design of a robust sliding mode‐based extremum‐seeking controller aimed at the online optimization of a class of uncertain reaction systems. The design methodology is based on an input–output linearizing method with variable‐structure feedback, such that the closed‐loop system converges to a neighborhood of the optimal set point with sliding mode motion. In contrast with previous extremum‐seeking control algorithms, the control scheme includes a dynamic modelling‐error estimator to compensate for unknown terms related with model uncertainties and unmeasured disturbances. The proposed online optimization scheme does not make use of a dither signal or a gradient‐based optimization algorithm. Practical stabilizability for the closed‐loop system around to the unknown optimal set point is analyzed. Numerical experiments for two nonlinear processes illustrate the effectiveness of the proposed robust control scheme. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
950.
Peter Brusilovsky Jung Sun Oh Claudia López Denis Parra Wei Jeng 《New Review of Hypermedia and Multimedia》2017,23(2):81-111
This paper investigates the feasibility of maintaining a social information system to support attendees at an academic conference. The main challenge of this work was to create an infrastructure where users’ social activities, such as bookmarking, tagging, and social linking could be used to enhance user navigation and maximize the users’ ability to locate two important types of information in conference settings: presentations to attend and attendees to meet. We developed Conference Navigator 3, a social conference support system that integrates a conference schedule planner with a social linking service. We examined its potential and functions in the context of a medium-scale academic conference. In this paper, we present the design of the system’s socially enabled features and report the results of a conference-based study. Our study demonstrates the feasibility of social information systems for supporting academic conferences. Despite the low number of potential users and the short timeframe in which conferences took place, the usage of the system was high enough to provide sufficient data for social mechanisms. The study shows that most critical social features were highly appreciated and used, and provides direction for further research. 相似文献