关键词： Beet-pulp   Starch   Brick   Drying kinetics   SEM   Mechanical properties  

摘要： Buildings account for a large share of the primary energy and materials use in Europe. Therefore, the EU has set several energy and materials targets for the built environment and other sectors. Novel low-carbon materials can play a major role in the transition towards meeting those targets. Moreover, agriculture produces by- or waste products that could be used as constituent of innovative agro-materials for construction. Recently, beet pulp based-material is being investigated on the material scale and promising results are pointed out regarding its interesting mechanical, hygrothermal and acoustical properties for building insulation use. In this context, the paper aims to study experimentally two types of beet-pulp starch composites: whole bricks and hollowed bricks. The manufacturing of the two types of bricks is detailed. A comparative study is then achieved regarding the drying kinetics, mechanical properties as well as internal structure composition. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Calcium silicate hydrate (CSH)   Calcium hydroxide (CH)   Tensile mechanical properties   Fracture properties   Reactive molecular dynamics simulations  

摘要： This paper firstly investigated the mechanical and fracture properties of calcium silicate hydrate and calcium hydroxide composite by reactive molecular dynamics simulations. The results show that the calcium hydroxide has the highest tensile strength and Young's modulus, just followed by calcium silicate hydrate and CSH-CH composite. The obtained fracture toughness of CSH, CH and CSH-CH composite are consistent with experimental results, showing the fracture toughness is independent of size. The failure mechanisms of CSH-CH composite under tensile loading are revealed in terms of bond-breakage. The results can provide necessary parameter inputs for multi-scale mechanical and fracture study of cement paste.

关键词： Thigmomorphism   Bedding plants   Mechanical stress   Growth dynamics  

摘要： Ornamental plants are bred and purchased for their aesthetical features such as colorful flowers and leaves, as well as compact and elegant stature. Petunia is one of the most popular bedding plants for urban areas and gardens, therefore, control of its growth and branching is essential. In commercial horticulture, the most common method to control growth dynamics is via growth regulators. Mechanical stimulation is proposed as an environmentally friendly alternative to chemical regulators. In this study, the efficiency of MS was tested on two cultivars of Petunia x atkinsiana. A brushing apparatus was set to stroke apical parts of young plants 40, 60 or 80 times per day between 14 March and 25 April. Several parameters, such as stem length, the number of branches, mature leaf area, the number of open flowers, were measured four times during the whole experiment: three times during the stimulation period, on 20 March, 4 and 25 April, and the last time on 18 May, three weeks after the stimulation stopped. For biochemical analyses, 1 cm apical stem fragments were collected on 20 March, 25 April and 18 May. The results show that MS affects the growth dynamics in petunia, but the response appears to be cultivar specific. In both cultivars, brushing with 80 strokes per day produced the most spectacular effects in growth reduction. On the last day of brushing the POD and IAA oxidase activities in the strongly reacting cultivar were the highest in plants rubbed 80 x per day. The results indicate that MS can be very effective in controlling stem growth in at least some cultivars of petunia, replacing hormonal treatments.

关键词： beta-Amino carbonyl compounds   Ionic liquids   Hammett acidity   DFT   Dual catalyst/solvent  

摘要： Catalysis is important in various applications of organic chemistry and its output product control for stereoselective compounds is outrageous. Establishment of experimental facts of stereoselective compounds from catalysis and their validation using theoretical evidences is the key to understand various mechanisms of optically active compounds. A family of new ionic liquids (ILs) with various imidazolium cations and camphorsulfonate anion as environmentally benign liquid salts have been synthesized and deployed for catalysis of beta-amino carbonyl compounds. The products were formed using Its as a homogeneous catalyst with excellent product yield and diastereoselectivity. The effect of counter ions. Hammett acidity and viscosity of ILs along with solvent and temperature are explored in terms of reaction kinetics and product yields. Density functional theory (DFT) was used to investigate thermodynamical study of mechanistic pathway of the reaction. The DFT calculations predicted that the catalysis mechanism involved both counterions of the IL Moreover, it is evidenced that the syn-pathway required lower activation energy while anti-pathway led to thermodynamically stable *** study explores new avenues for using Its as potential homogeneous catalysts for the production of stereoselective species. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Molecular dynamics   polycrystal   interatomic potential   Voigt Reuss Hill   elastic modulus  

摘要： The choice of a proper interatomic potential is critical to obtaining accurate and realistic molecular dynamics results. However, previous studies that have tested the suitability of a potential to predict mechanical properties often do so using elastic constants from a triaxial stress state that ignores Poisson's effect. While this method is suitable it is not consistent with macroscale experimental methods and cannot provide the complete loading behaviour. Further, there is a lack of knowledge as to whether accuracy in predicting elastic constants from a fixed volume condition indicates accuracy for elastic moduli from uniaxial tensile simulations. Moreover, those studies that did account for Poisson's effect studied only one crystal orientation and thus assumed potential accuracy is independent of crystal orientation. Results from the current study demonstrated that accuracy of a potential is dependent on the crystal direction. Further, the most accurate potentials for elastic constants calculated using a fixed volume condition were not necessarily the most accurate at predicting elastic moduli from a physically realisable tension test. Finally, the Voigt Reuss Hill (VRH) method was shown to accurately predict polycrystalline mechanical properties from single crystal data as a function of temperature.

关键词： Nanocomposites  

摘要： In this research, copper chromite (CuCr2O4) nanoparticles (NPs) were synthesized by the sol-gel auto-combustion method. The effects of CuCr2O4 NPs and polyurethane (PU) on the tensile strength of the epoxy (EP) resin were studied by considering different weight percentages (wt%). The response surface methodology (RSM) coupled with central composite design (CCD) (RSM/CCD) methods were also used to optimize the Young's modulus, yield strength, and ultimate tensile strength of the EP/PU/CuCr2O4 nanocomposites. The composition structure and morphology of the EP/PU/CuCr2O4 nanocomposites were determined using the Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction, UV-vis diffuse reflection, Scanning Electron Microscopy, X-ray energy dispersive spectroscopy, and thermogravimetric analysis. It was also shown that the RSM/CCD methods could be utilized effectively to find the optimum process variables in the tensile test of the EP/PU/CuCr2O4 nanocomposites. Moreover, the tensile test revealed that the presence of the CuCr2O4 NPs in the EP/PU matrix improved the mechanical properties. Best results were obtained with the 0.76 wt% of the CuCr2O4 NPs and the 2.6 wt% PU in the epoxy resin. The molecular dynamic simulation was used to illustrate the effect of the NPs on the interaction energy and mechanical properties of this nanocomposite. The calculated interaction energy for the EP/PU/CuCr2O4 nanocomposites was -437.96 Kcal/mol. The results showed that Young's modulus had relative agreement with the experimental results.

关键词： Multiple mechanical systems   event-triggered control   switched dynamics   leader-following consensus  

摘要： This paper investigates the event-triggered leader-following consensus problem for a class of multiple mechanical systems with switched dynamics. Based on the graph theory, Lyapunov stability theory, backstepping technique and event-triggered control theory, an event-triggered protocol is proposed for the considered multiple mechanical systems. It is proved that the practical leader-following consensus can be achieved by the proposed protocol. Meanwhile, to exclude the Zeno behaviour, a positive lower bound of inter-event intervals is given. Finally, we provide a numerical simulation to illustrate the effectiveness of the given protocol.

关键词： mechanoradical   kinetics   kaolinite  

摘要： Kaolinite is a versatile material with many applications in various fields such as in cosmetics or wastewater treatment. Here, we report the first evaluation of mechanoradicals formation on activated kaolinite powders, and its kinetics, via wet-grinding in ethanol using a free-radical scavenger (2,2-diphenyl-1-picrylhydrazyl;DPPH). Increasing the duration of ball milling of two reference kaolinite samples resulted in increased DPPH consumption due to an increase in the surface area of the processed powders. The correlation between the increasing rates of the surface areas and DPPH consumption yielded information on the density of radical species that may react with ethanol to form H radicals on the newly created surfaces of the kaolinite powders. The radical density was much lower than that reported previously for quartz, possibly due to the anisotropic nature of the kaolinite crystal structure. The actual surfaces that take part in the radical formation reaction were mainly newly created edge surfaces rather than basal surfaces. The kaolinite sample with fewer defects was more resistant to delamination, and thus its edge-to-basal surface-area ratio was also higher, which may have resulted in higher reactivity during mechanical processing. This knowledge is key for industrial applications of processed kaolinite powders.

关键词： crosslinking   differential scanning calorimetry   resins   theory and modeling   thermosets  

摘要： This work reports on nonisothermal degradation kinetics of polyurethane (PU)-based powder coatings containing 1, 3, and 5%wt% vinyltrimethoxysilane functionalized Al2O3 (V-Al2O3) nanoparticles. Thermogravimetric analysis of PU/V-Al2O3 powder coatings with different V-Al2O3 contents has been performed at different heating rates. Variation of activation energy (E-a) of PU/V-Al2O3 powder coatings was modeled as a function of partial mass loss by using Kissinger-Akahira-Sunose, Ozawa-Wall-Flynn and modified Coats-Redfern isoconversional approaches. The results revealed hindered decomposition process of PU/V-Al2O3 nanocomposite powder coatings, featured by an increase in activation energy of degradation from similar to 158 for blank PU to 225, 183, and 229 kJ/mol for nanocomposites filled with 1, 3, and 5 wt% of V-Al2O3, respectively. Likewise, pre-exponential factor values increased for samples containing V-Al2O3 nanoparticles compared to that of blank sample. Sestak-Berggren kinetic model appropriately captured thermal degradation behavior of PU/V-Al2O3 nanocomposites than that of nth order decomposition kinetic reaction models.

关键词： 纯电动汽车   锂离子动力电池   标准   安全要求  

摘要： 随着锂离子动力电池在电动汽车上的广泛应用,其安全性得到越来越多的关注。分析了国内外锂离子动力电池在机械安全方面的测试标准,对机械冲击试验、跌落试验、翻转试验、针刺试验、振动试验、海水浸泡试验方法中的试验条件和参数进行了比较分析。指出了相关标准存在的不足,并指出了不同标准之间因试验条件不同而不具有可比性。