共查询到20条相似文献,搜索用时 139 毫秒
1.
Abstract Effect of the inorganic salts on the conversion of halo‐ester (ethyl‐2‐bromoisobutyrate, EtOBuBr) hydrolyzing in an alkaline aqueous solution/organic solvent two‐phase medium was investigated. The rate of hydrolyzing EtOBuBr and the conversion are obviously affected by the inorganic salts. The experimental data verify the proposed mechanism of hydrolysis. The reaction steps which hydrolyze these bromo‐alkyl bonds (Br‐C bond) and ester functional groups (–COOR) are developed and discussed. A kinetic model of the main reaction steps was established in which the rate expressions were derived. The intrinsic rate constants of the reactions were determined from the experimental data of EtOBuBr hydrolysis via parameter estimation. The results indicated that the conversion of hydrolyzing EtOBuBr is highly dependent on the concentration of alkaline compound in the aqueous solution. It is also found that sodium carbonate, sodium chloride, sodium nitrate and sodium sulfate inhibit the reaction, while calcium carbonate enhances it. The corresponding rate constants of hydrolyzing EtOBuBr in a variety of inorganic salt concentrations were searched. 相似文献
2.
3.
4.
Migration of di‐(2‐ethylhexyl)adipate (DEHA) and acetyl tributyl citrate (ATBC) plasticizers from PVC film into the food stimulant of isooctane 下载免费PDF全文
V. Lajqi‐Makolli M. Kerolli‐Mustafa I. Malollari J. Lajqi 《Materialwissenschaft und Werkstofftechnik》2015,46(1):16-23
Chemical migration from food packing is influenced by several factors such as nature of chemicals, complexity of food, temperature, packing material used and properties of the migrating substances. Chemical compounds that are incorporated within polymeric packaging materials may interact with food components during processing or storage and migrate into the food by jeopardizing the food safety. This migration is higher if food remains in contact with packing material for extended time. Polyvinyl chloride (PVC) film such as di‐(2‐ethylhexyl) adipate (DEHA) and acetyl tributyl citrate (ATBC) are still widely used as a food packing material due to its flexibility, transparency and low water permeability. The present study covers the main migration phenomena of both plasticizers (di‐(2‐ethylhexyl) adipate (DEHA) and acetyl tributyl citrate (ATBC)) from PVC‐film into isooctane food stimulant using a direct gas chromatographic method. An exposure period of 48 h at 30 °C and 4 °C was used. The obtained results showed DEHA levels ranging of 7.2 mg/dm2 while, no ATBC migration from PVC‐film was observed. Results are discussed in relation to EU legislation proposed upper limit for DEHA specific migration (18 mg/L or 3 mg/dm2) and overall migration limit (OM) of 10 mg/dm2. 相似文献
5.
Helge Klippstein Hany Hassanin Alejandro Diaz De Cerio Sanchez Yahya Zweiri Lakmal Seneviratne 《Advanced Engineering Materials》2018,20(9)
6.
7.
8.
Bioinspired Surfaces with Superwettability for Anti‐Icing and Ice‐Phobic Application: Concept,Mechanism, and Design 下载免费PDF全文
Songnan Zhang Jianying Huang Yan Cheng Hui Yang Zhong Chen Yuekun Lai 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(48)
Ice accumulation poses a series of severe issues in daily life. Inspired by the nature, superwettability surfaces have attracted great interests from fundamental research to anti‐icing and ice‐phobic applications. Here, recently published literature about the mechanism of ice prevention is reviewed, with a focus on the anti‐icing and ice‐phobic mechanisms, encompassing the behavior of condensate microdrops on the surface, wetting, ice nucleation, and freezing. Then, a detailed account of the innovative fabrication and fundamental research of anti‐icing materials with special wettability is summarized with a focus on recent progresses including low‐surface energy coatings and liquid‐infused layered coatings. Finally, special attention is paid to a discussion about advantages and disadvantages of the technologies, as well as factors that affect the anti‐icing and ice‐phobic efficiency. Outlooks and the challenges for future development of the anti‐icing and ice‐phobic technology are presented and discussed. 相似文献
9.
Determination of dynamic rotation factor for DWTT specimens by strain analysis and hardness measurement 下载免费PDF全文
J. Fang J.W. Zhang Y.D. Zhou 《Fatigue & Fracture of Engineering Materials & Structures》2016,39(7):830-838
As to accurately ascertain the value of dynamic rotation factor r*, strain analysis‐based measurement was performed on the bent low‐blow specimens by means of two approaches. (i) Surface strain analysis on the ligament indicates a critical transition zone from the necking to swelling, where the total strain reaches the minimum as undeformed material. (ii) Hardness measurement on the thickness‐reduction specimen also reflects a typical V‐shape distribution of interior plasticity along the ligament as observed from the surface, suggesting the location of true rotation centre relative to the neutral strain axis where the hardness is nearly invariable without any work hardening. As a result, the obtained value of r* maintains nearly 0.45 for (B × 4B) size drop‐weight tear test‐type specimens after their crack initiation and propagation, well consistent with the values calculated from the slip‐line field theory. 相似文献
10.
11.
Flexible Ionic‐Electronic Hybrid Oxide Synaptic TFTs with Programmable Dynamic Plasticity for Brain‐Inspired Neuromorphic Computing 下载免费PDF全文
Rohit Abraham John Jieun Ko Mohit R. Kulkarni Naveen Tiwari Nguyen Anh Chien Ng Geok Ing Wei Lin Leong Nripan Mathews 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(32)
Emulation of biological synapses is necessary for future brain‐inspired neuromorphic computational systems that could look beyond the standard von Neuman architecture. Here, artificial synapses based on ionic‐electronic hybrid oxide‐based transistors on rigid and flexible substrates are demonstrated. The flexible transistors reported here depict a high field‐effect mobility of ≈9 cm2 V?1 s?1 with good mechanical performance. Comprehensive learning abilities/synaptic rules like paired‐pulse facilitation, excitatory and inhibitory postsynaptic currents, spike‐time‐dependent plasticity, consolidation, superlinear amplification, and dynamic logic are successfully established depicting concurrent processing and memory functionalities with spatiotemporal correlation. The results present a fully solution processable approach to fabricate artificial synapses for next‐generation transparent neural circuits. 相似文献
12.
Irina Lokteva Michael Koof Michael Walther Gerhard Grübel Felix Lehmkühler 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(20)
Self‐assembled nanocrystal superlattices have attracted large scientific attention due to their potential technological applications. However, the nucleation and growth mechanisms of superlattice assemblies remain largely unresolved due to experimental difficulties to monitor intermediate states. Here, the self‐assembly of colloidal PbS nanocrystals is studied in real time by a combination of controlled solvent evaporation from the bulk solution and in situ small‐angle X‐ray scattering (SAXS) in transmission geometry. For the first time for the investigated system a hexagonal closed‐packed (hcp) superlattice formed in a solvent vapor saturated atmosphere is observed during slow solvent evaporation from a colloidal suspension. The highly ordered hcp superlattice is followed by a transition into the final body‐centered cubic superlattice upon complete drying. Additionally, X‐ray cross‐correlation analysis of Bragg reflections is applied to access information on precursor structures in the assembly process, which is not evident from conventional SAXS analysis. The detailed evolution of the crystal structure with time provides key results for understanding the assembly mechanism and the role of ligand–solvent interactions, which is important both for fundamental research and for fabrication of superlattices with desired properties. 相似文献
13.
14.
Flexible and Tough Poly(lactic acid) Films for Packaging Applications: Property and Processability Improvement by Effective Reactive Blending 下载免费PDF全文
Wannee Chinsirikul Jareenuch Rojsatean Bongkot Hararak Noppadon Kerddonfag Ajcharaporn Aontee Kanisorn Jaieau Pramote Kumsang Chao Sripethdee 《Packaging Technology and Science》2015,28(8):741-759
This study demonstrates a practical means to overcome inherent brittleness problem of poly(lactic acid) (PLA) and make PLA feasible as packaging material. PLA with suitable processability is utterly required for package manufacturers, where flexible, tough PLA film is essential for packers and end users. Highly flexible PLA films with 60‐fold increase in elongation at break (Eb) over that of the neat PLA were successfully produced by integrating effective reactive blending and economical film blowing process. The ‘two‐step’ blending was used to prepare PLA compound; poly(butylene adipate‐co‐terephthalate) (PBAT – another biodegradable polymer) was first blended with 0.5–1% chain extender (epoxy‐functionalized styrene acrylic copolymer) (ESA), followed by subsequent blending with PLA in twin‐screw extruder. Blown films of reactive blend of PLA/PBAT/ESA (80/20/1) showed impressively high Eb of 250% versus a very low Eb of 4% for the neat PLA. Resulting blown films still possessed high modulus of 2 GPa, yield stress of 50–60 MPa and good toughness of ~100 MPa. Significant enhancement in the film's ductility was attributed to homogeneous blend with developed fine strand‐like structure as a result of effective in situ compatibilization and good interfacial adhesion between the PLA and PBAT. PLA/PBAT/ESA blend also offered improved processability. Resulting films had acceptable haze of ~10% for common packaging, and clearer film close to PLA (≤2%) could be obtained by designing PLA skin layers in multilayer structure. Films of PLA/PBAT/1%ESA exhibit potential as packaging material; their mechanical and optical properties are comparable with or even exceed some existing films used in the market. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
Jong‐Shyong Wu Der‐Wei Chen Hsi‐Ming Chou 《International journal for numerical methods in engineering》1999,45(9):1277-1295
The eigenvalues of a uniform cantilever beam carrying any number of spring–damper–mass systems with arbitrary magnitudes and locations were determined by means of the analytical‐and‐numerical‐combined method (ANCM). First of all, each spring–damper–mass system was replaced by a massless effective spring with spring constant keff, which is the main point that the ANCM is available for the present problem. Next, the equation of motion for the ‘constrained’ beam (with spring–damper–mass systems attached) was derived by using the natural frequencies and normal mode shapes of the ‘unconstrained’ beam (without carrying any attachments) incorporated with the expansion theorem. Finally, the equation of motion for the ‘constrained’ beam in ‘complex form’ is separated into the real and the imaginary parts. From either part, a set of simultaneous equations were obtained. Since the simultaneous equations are in ‘real form’, the eigenvalues of the ‘constrained’ beam were determined with the conventional numerical methods. To confirm the reliability of the presented theory, all the numerical results obtained from the ANCM were compared with the corresponding ones obtained from the conventional finite element method (FEM) and good agreement was achieved. Because the order of the property matrices for the equation of motion derived by using the ANCM is much lower than that by using the conventional FEM, the storing memory and the CPU time required by the ANCM are much less than those required by the FEM. Besides, the solution of the equation of motion derived from the ANCM can always be obtained with the general personal computers, but that from the FEM can sometimes be obtained only with the computers of workstations or main frames when the total degrees of freedom exceeding a certain limit. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
16.
17.
Chan Lee Hobeom Kim Seyoung Im 《International journal for numerical methods in engineering》2017,110(11):1069-1100
The node‐based or edge‐based smoothed finite element method is extended to develop polyhedral elements that are allowed to have an arbitrary number of nodes or faces, and so retain a good geometric adaptability. The strain smoothing technique and implicit shape functions based on the linear point interpolation make the element formulation simple and straightforward. The resulting polyhedral elements are free from the excessive zero‐energy modes and yield a robust solution very much insensitive to mesh distortion. Several numerical examples within the framework of linear elasticity demonstrate the accuracy and convergence behavior. The smoothed finite element method‐based polyhedral elements in general yield solutions of better accuracy and faster convergence rate than those of the conventional finite element methods. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
19.