标准号: LY/T 3169-2019

摘要： 本标准规定了以锂离子电池为动力源的手持式修枝链锯的（以下简称“锂电修枝锯”）的术语和定义、型号编制方法、基本参数、技术要求及试验方法、标志、使用说明书、包装、运输、贮存与处理。本标准适用于在一般环境条件下，以标称电压不大于直流75V可充电锂离子电池包（电池组）供电的用于修整树冠、造材等作业的锂电修枝锯。

关键词： Genetics   Fluorescence   Pest control   Cations   Nucleic acid structure  

摘要： The non-targeted action of fungicides leads to DNA damage of organisms, which causes several serious diseases such as cancer, behavioral change, and nausea. The mechanistic aspects of DNA damage by fungicides are not much known, irrespective of its importance. Spectroscopic and molecular dynamics simulation techniques have been employed to bring out the key aspects of the mechanism of DNA damage by an important fungicide, namely, n-dodecylguanidine acetate (dodine). The hydrocarbon and guanidinium groups of dodine interact in the adenine (A)-thymine (T) region of the minor groove of DNA via electrostatic and hydrophobic interactions. The accommodation of dodine in the minor groove of DNA interrupts the cone of hydration of DNA by removing water from its surface. The interaction of dodine in the minor groove of DNA perturbs inclination, twist, roll, and slide of base pairs in the A-T region, which broadens the minor groove as well as elongates the first strand of DNA, causing the loss of its helicity and base stacking. The detailed understanding of dodine-induced DNA damage may guide the development of fungicide with minimal non-targeted genotoxic effect.

关键词： Stress-strain curves  

摘要： Coarse-grained (CG) molecular dynamics simulations have been employed to study the thermo-mechanical response of a physically cross-linked network composed of zwitterionic moieties and fully flexible elastomeric polymer chains. In this work, we used the effective Lennard-Jones interactions for our bead-spring model of zwitterionic cross-linkers (ZCLs). The effects of ZCL functionality, its chain length and the attractive interaction strength (epsilon) of end-groups on the thermo-mechanical properties are explored. We developed one particular system with versatile functionality of ZCLs at constant molecular weight with variable functional sites, observing that the stress-strain curve is increased with the functionality, evidenced by the bond orientation through the second-order Legendre polynomials. In the case of the length of the tri-functional ZCL, we found that a shorter length leads to a higher modulus and a relatively greater value of glass-transition temperature (T-g). In addition, we found that with the increase of the attractive interaction strength (epsilon) on the tri-functional ZCL, the stress-strain behaviour and the chain orientation are reinforced, accompanied by an enhancement of T-g. Lastly, we examined the effect of the cross-linker functionality on the tension-recovery process, as well as the fracture behaviour, by performing the typical tri-axial deformation. The results of tension-recovery and tri-axial deformation correspondingly proved the presence of physical linkages of end-groups, and strong attractive forces between end-linking groups were revealed through visual molecular dynamics (VMD) analysis. Generally, we anticipate that our work could provide some guidelines for the rational design and preparation of high performance zwitterionic cross-linked elastomeric materials.

关键词： Nanowires  

摘要： The systematic understanding of an overall deformation mechanism of metallic iron (Fe) nanowires (NWs) with the pre-existing oxide shell layer (Fe/FexOy) under various mechanical loading conditions is of critical importance for their various applications. Herein, we perform molecular dynamics simulations using ReaxFF reactive interatomic potential to systematically investigate the effect of the pre-existing oxide shell layer on the underlying intrinsic mechanical deformation mechanism and related mechanical properties of metallic [001]-oriented Fe NWs under both uniaxial tension and compressive loading. Three different diameters of the NWs are investigated to elucidate the size effect. The Fe NWs with the preoxide shell layer possess unique and intriguing mechanical properties and deformation mechanisms. In particular, the oxide shell layer with the combined effect of the diameter and the applied uniaxial loading mode dictates the strength and the overall stress-strain behaviors of the NWs. Interestingly, the oxide-coated NWs clearly exhibit the diameter-dependent elastic deformation intrinsic mechanism and related properties as compared to the pristine counterparts. Specifically, the pre-existing oxide shell layer expedites the onset of tensile plasticity by drastically reducing the tensile yield stress and significantly decreasing the tensile elastic limit. Contrary to the tensile loading, the presence of the oxide shell layer reduces or increases the compressive yield stress of the pristine Fe NW with respect to its diameter. However, the pre-existing oxide shell layer leads to a significantly delayed onset of compressive plasticity, that is, a significant increase in the compressive elastic limit. Published under license by AIP Publishing.

关键词： activation energy   curing kinetics   DSC   fast curing   mechanical properties  

摘要： Fast curing epoxy resins were prepared by the reactions of diglycidyl ether of bisphenol A with isophorone diamine (IPD) and N-(3-aminopropyl)-imidazole (API), and their curing kinetics and mechanical properties influenced by IPD content were also investigated. The analysis of curing kinetics was based on the nonisothermal differential scanning calorimetry (DSC) data with the typical Kissinger, Ozawa, and Flynn-Wall-Ozawa models, respectively. The glass-transition temperature was also measured by the same technique. Additionally, the mechanical properties including flexural, impact, and tensile performances were tested, and the curing time was estimated by isothermal DSC. The degree of cure (alpha) dependency of activation energy (E-a) revealed the complexity of curing reaction. Detailed analysis of the curing kinetics at the molecular level indicated that the dependence of E-a on the alpha was a combined effect of addition reaction, autocatalytic reaction, viscosity, and steric hindrance. From the nonisothermal curves, the curing reaction mechanism could be proposed according to the increasingly obvious low temperature peaks generated by the addition reaction of epoxy group with the primary amines in API and IPD molecules. Using the preferred resin formulation, the resin system could be cured within 10 min at 120 degrees C with a relatively good mechanical performance. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47950.

关键词： Coupling   mechanical shock   molecular dynamics   thermomechanical responses  

摘要： A series of dynamic shock compressions of metal films are simulated using molecular dynamics method. Characteristics of mechanical shock load are analyzed theoretically. Thermomechanical responses induced by mechanical shock, including pressure, temperature, volumetric strain, and shear strain, are presented graphically and analyzed from viewpoint of thermomechanical coupling. The results show that the temperature rise caused by volumetric strain (elastic) is reversible, while that caused by shear strain is irreversible. Under the same mechanical shock load, several metal films exhibit significant differences in thermomechanical responses and the potential reasons are analyzed from the differences of thermophysical parameters.

关键词： 发展   对策   思考  

摘要： 本文论述了灵山县农业机械化事业在设施空白、水平低下的状态下起步,从无到有、由少至多、由低级到高级不断向前发展。指出了农业机械化是转变农业发展方式,没有农业机械化,就没有农业农村现代化。对农业机械化的发展前景进行了分析,提出了做好农业机械化工作的措施对策。

关键词： 动力专业工程   压力管道   压力容器   管理与控制  

摘要： 机械工业项目一般是为生产机械工业产品建造工业厂房及配套设施,通常包含动力专业工程,如氧气、压缩空气、各种切割或焊接用气体系统。这些系统大都包含压力容器和压力管道,储存并输送高压、易燃易爆的流体,属于特种设备,危险性较大。为了预防特种设备事故的发生,动力专业工程质量极为重要。文章以某机械工业园项目动力工程为例,阐述了EPC总承包商对于其承包范围内动力专业工程的管理与控制要点。

关键词： 机械式变速器   耦合性能   动力模型   测试  

摘要： 汽车的动力性与变速器关系密切,为保证汽车的动力性与舒适性,需对变速器的耦合动力性能进行分析.根据机械式汽车变速器的结构与传动运行原理,构建变速器换档过程的动力模型;计算轴承各方向的刚度值,结合弹簧阻尼单元模拟变速器的运行过程,并对轴系齿轮啮合过程进行耦合受力分析,得到齿轮副基元间的啮合刚度矩阵;根据变速器动力模型与耦合刚度矩阵,进行相关数据计算,构建传动轴与变速器耦合动力学模型.通过仿真实验测试变速器耦合动力性能,根据变速器各档位运行效率曲线与换档时间变化分析变速器的耦合动力性能.

关键词： 振动   筛分机械   动力学分析  

摘要： 建立了振动筛分机械的物理模型和数学模型,进行了动力学分析,求出了解析解。对偏心配重质量进行了优化,对振动轴承的寿命进行了校核,对连接螺栓强度进行了校核,对振动电动机启动条件进行了核验。可用于解决生产实际问题。