标准号: LY/T 1202-2020

摘要： 本文件规定了以汽油机为动力的步进式草坪修剪机(以下简称“草坪机”)的术语和定义、型号编制方法、技术要求及试验方法、标志、使用说明书、包装、运输和贮存。本文件适用于以汽油机为动力的旋刀步进式草坪机和滚刀步进式草坪机，包括配备载有坐姿操作者乘人附件的步进式草坪机，并配备有:—金属切割装置，和/或;—非金属切割装置由一个或多个切割部件铰接安装在一个近似圆形的驱动装置上，切割部件依靠离心力来实现切割，且每个切割部件的切割能量(动能)不小于10)。

关键词： hydrogen sensor   palladium   nanograting   nanotransducer   self-powered sensor  

摘要： This study proposes a reliable and self-powered hydrogen (H-2) gas sensor composed of a chemo-mechanically operating nanostructured film and photovoltaic cell. Specifically, the nanostructured film has a configuration in which an asymmetrically coated palladium (Pd) film is coated on a periodic polyurethane acrylate (PUA) nanograting. The asymmetric Pd nanostructures, optimized by a finite element method simulation, swell upon reacting with H-2 and thereby bend the PUA nanograting, changing the amount of transmitted light and the current output of the photovoltaic cell. Since the degree of warping is determined by the concentration of H-2 gas, a wide concentration range of H-2 (0.1-4.0%) can be detected by measuring the self-generated electrical current of the photovoltaic cell without external power. The normalized output current changes are similar to 1.5%, similar to 2.8%, similar to 3.5%, similar to 21.5%, and 25.3% when the concentrations of H-2 gas are 0.1%, 0.5%, 1.0%, 1.6%, 2%, and 4%, respectively. Moreover, because Pd is highly chemically reactive to H-2 and also because there is no electrical current applied through Pd, the proposed sensor can avoid device failure due to the breakage of the Pd sensing material, resulting in high reliability, and can show high selectivity against various gases such as carbon monoxide, hydrogen sulfide, nitrogen dioxide, and water vapor. Finally, using only ambient visible light, the sensor was modularized to produce an alarm in the presence of H-2 gas, verifying a potential always-on H-2 gas monitoring application.

关键词： Microfluidics  

摘要： Cell mechanical properties are powerful biomarkers for label-free phenotyping. To date, microfluidic approaches assay mechanical properties by measuring changes in cellular shape, applying extensional or shear flows or forcing cells to pass through constrictions. In general, such approaches use high-speed imaging or transit time measurements to evaluate cell deformation, while cell dynamics in-flow after stress imposition have not yet been considered. Here, we present a microfluidic approach to apply, over a wide range, tuneable compressive forces on suspended cells, which result in well distinct signatures of deformation-dependent dynamic motions. By properly conceiving microfluidic chip geometry and rheological fluid properties, we modulate applied single-cell forces, which result in different motion regimes (rolling, tumbling or tank-treating) depending on the investigated cell line. We decided to prove our approach by testing breast cell lines, with well-known mechanical properties. We measured a set of in-flow parameters (orientation angle, aspect ratio, cell deformation and cell diameter) as a backward analysis of cell mechanical response. By such an approach, we report that the highly invasive tumour cells (MDA-MB-231) are much more deformable (6-times higher) than healthy (MCF-10A) and low invasive ones (MCF-7). Thus, we demonstrate that a microfluidic design with tuneable rheological fluid properties and direct analysis of bright-field images can be suitable for the label-free mechanical phenotyping of various cell lines.

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.