关键词： MOLECULAR dynamics -- Simulation methods   POLYMERS   FINITE element method   DATA analysis   COMPUTER simulation   CONTINUUM mechanics   CONTACT mechanics  

摘要： This paper studies the rheology of weakly entangled polymer melts and films in the glassy domain and near the rubbery domain using two different methods: molecular dynamics (MD) and finite element (FE) simulations. In a first step, the uniaxial mechanical behavior of a bulk polymer sample is studied by means of particle-based MD simulations. The results are in good agreement with experimental data, and mechanical properties may be computed from the simulations. This uniaxial mechanical behavior is then implemented in FE simulations using an elasto-viscoelasto-viscoplastic constitutive law in a continuum mechanics (CM) approach. In a second step, the mechanical response of a polymer film during an indentation test is modeled with the MD method and with the FE simulations using the same constitutive law. Good agreement is found between the MD and CM results. This work provides evidence in favor of using MD simulations to investigate the local physics of contact mechanics, since the volume elements studied are representative and thus contain enough information about the microstructure of the polymer model, while surface phenomena (adhesion and surface tension) are naturally included in the MD approach.

关键词： 园林机械   汽油机   草坪修边机   术语   定义  

标准号: LY/T 2080-2012

摘要： 本标准规定了以汽油机为动力的手持式草坪修边机（以下简称为修边机）的术语和定义、技术要求、试验方法、检验规则、标志、使用说明书、包装、运输和贮存。 本标准适用于以汽油机为动力的手持式修边机。以其它内燃机为动力的修边机亦可参照使用。

关键词： Morphology   Crystallization   Crystal structure   Nanocomposites   Kinetics  

摘要： Biodegradable poly(epsilon-caprolactone) (PCL) and octavinyl-polyhedral oligomeric silsesquioxanes (ovi-POSS) nanocomposites were prepared at low ovi-POSS loadings via a solution casting method in this work. Scanning electron microscopy observation reveals not only the fine dispersion but also the crystallization of ovi-POSS in the PCL matrix. The overall isothermal melt crystallization kinetics, spherulitic morphology, crystal structure, and dynamic mechanical properties of neat PCL and its nanocomposites were studied with various techniques. The presence of ovi-POSS has enhanced the overall isothermal melt crystallization rates of PCL in the nanocomposites;however, the crystallization mechanism and crystal structure of PCL remain unchanged despite the ovi-POSS loading. In addition, the storage modulus of the nanocomposites has been enhanced significantly relative to neat PCL, while the glass transition temperature varies slightly irrespective of the presence of ovi-POSS.

标准号: JIS B9126-3-2012

标准号: JIS B9126-5-2012

标准号: JIS B9100-2012

标准号: JIS B9126-2-2012

标准号: JIS B9126-1-2012

摘要： The mechanical failure of mature amyloid fibers produces fragments that act as seeds for the growth of new fibrils. Fragmentation may also be correlated with cytotoxicity. We have used steered atomistic molecular dynamics simulations to study the mechanical failure of fibrils formed by the amyloidogenic fragment of human amylin hIAPP20-29 subjected to force applied in a variety of directions. By introducing systematic variations to this peptide sequence in silico, we have also investigated the role of the amino-acid sequence in determining the mechanical stability of amyloid fibrils. Our calculations show that the force required to induce mechanical failure depends on the direction of the applied stress and upon the degree of structural order present in the beta-sheet assemblies, which in turn depends on the peptide sequence. The results have implications for the importance of sequence-dependent mechanical properties on seeding the growth of new fibrils and the role of breakage events in cytotoxicity.

关键词： 内燃机车   混合动力   交流传动   运输机械   俄罗斯   控股   制造   批量生产  

摘要： 俄罗斯运输机械控股公司研制的TЭM35型内燃机车是俄罗斯首台采用交流传动的混合动力内燃机车。与批量生产的内燃机车相比，在功率相同的情况下，新型机车的燃油消耗和技术维护费用显著降低。此外，由于采用了功率较小的柴油机，在很大程度上减少了有害物质的排放。在经常制动、停车、起动、加速的工况下，混合动力内燃机车的优势更加明显。