关键词： elasticity   gels   soft matter   suspensions   vitrification  

摘要： The microscopic nonlinear Langevin equation theory of activated glassy dynamics is applied to dense fluids of spherical particles that interact via a finite range Hertzian contact soft repulsion. The activation barrier and mean alpha relaxation time are predicted to be rich functions of volume fraction and particle stiffness, exhibiting a non-monotonic variation with concentration at high volume fractions. The latter is due to a structural "soft jamming" crossover where the real space local cage order weakens when soft particles significantly overlap. The highly variable dependences of the relaxation time on temperature and volume fraction are reasonably well collapsed onto two distinct master curves that are qualitatively consistent with a recent scaling ansatz and computer simulation study. A kinetic vitrification diagram is constructed and compared to its dynamic crossover analog. Intersection of the dynamic crossover and soft jamming threshold boundaries occurs for particles that are sufficiently soft, implying the nonexistence of a clear activated dynamics regime or kinetic arrest transition for such particles. The isothermal dynamic fragility is predicted to vary over a wide range as a function of particle stiffness, and soft particles behave as strong glasses. Qualitative comparisons with simulations and microgel experiments reveal good agreement. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592563]

关键词： muscle   work loop   motor control   neuromechanics   posture   running  

摘要： Muscles are multi-functional structures that interface neural and mechanical systems. Muscle work depends on a large multi-dimensional space of stimulus (neural) and strain (mechanical) parameters. In our companion paper, we rewrote activation to individual muscles in intact, behaving cockroaches (Blaberus discoidalis L.), revealing a specific muscle's potential to control body dynamics in different behaviours. Here, we use those results to provide the biologically relevant parameters for in situ work measurements. We test four hypotheses about how muscle function changes to provide mechanisms for the observed control responses. Under isometric conditions, a graded increase in muscle stress underlies its linear actuation during standing behaviours. Despite typically absorbing energy, this muscle can recruit two separate periods of positive work when controlling running. This functional change arises from mechanical feedback filtering a linear increase in neural activation into nonlinear work output. Changing activation phase again led to positive work recruitment, but at different times, consistent with the muscle's ability to also produce a turn. Changes in muscle work required considering the natural sequence of strides and separating swing and stance contributions of work. Both in vivo control potentials and in situ work loops were necessary to discover the neuromechanical coupling enabling control.

关键词： ab initio calculations   configuration interactions   hydrogen compounds   potential energy surfaces   reaction rate constants   triplet state   vibrational states  

摘要： A new global potential energy surface for the lowest triplet electronic state (a(3)A '') of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13 000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the augmented correlation-consistent polarized valence quintuple zeta basis set. Two minima and five saddle points were found on the potential energy surface. Low-lying vibrational states were obtained in this new potential using the Lanczos method and assigned. In addition, thermal rate constants for the N + OH -> H + NO reactions were obtained using an exact wave packet method. Reasonably good agreement with experimental data was obtained. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592375]

关键词： activation energy   crosslinking   curing of polymers   dielectric properties   elastomers  

摘要： Peroxide crosslinkable ethylene-propylenediene monomer (EPDM) compounds are formulated systems in which the base polymer generally comprises only a small fraction of the total composition. Knowledge of the intercomponent dependency is therefore crucial for successful product development. In this study, we have investigated the effect of formulation components on key material properties of cured, filled, and oil extended EPDM. In studying the impact of individual components, the clay filler was found to have a significant and negative effect on cure performance and to a lesser extent on the dielectric strength as well. On the other hand, the oil plasticizer was found to have a positive effect on recovery of the cure efficiency in filled compounds. It was also found that the interaction of the filler, the plasticizer oil, and the peroxide impacted both the mechanical properties as well as the dielectric strength. Given the complexity of the system, a statistical experimental design method was adopted to study the interactions of the components and their impact of final properties. For selected compositions, the cure behavior and the evolution of properties with extent of cure were studied. The cure was also modeled and compared to previously proposed models available in the literature. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2191-2200, 2011

关键词： 草坪   割草机   试验   安全措施   园林机械   柴油机   内燃机  

标准号: GB 26509-2011

摘要： 本标准规定了以汽(柴)油机为动力的步进式草坪割草机的术语和定义、安全技术要求和试验方法、使用说明书和标识。 本标准涉及的应消除或降低危害程度的一些重大危险列于附录A 中。 本标准也适用于以其他内燃机为动力的步进式草坪机的对应部件,也适用于除乘人附件外的拖乘式草坪机。 本标准不适用于坐骑式草坪机,也不适用于切割部件为非金属柔线或自由定心式非金属切割器、每个切割部件的切割能量(动能)不大于10J的草坪机。

关键词： 工程机械   业绩   每股收益   净利润   年报  

摘要： 潍柴动力（000338）2011年3月31日发布年报。年报称，2010年公司营业总收入为632．80亿元，利润总额92．45亿元。归属于母公司股东的净利润67．82亿元。基本每股收益4．07元。

关键词： 中国航天科技集团公司   机械厂   西安   专业技术人员   航天企业   固定资产   机械加工   旋压加工  

摘要： 中国航天科技集团公司第四研究院西安航天动力机械厂（7414厂）是一个军民结合、寓军于民的航天企业，始建于1969年，拥有固定资产3．2亿元，员工1600人；其中研究员16人，国家特级技师4人，各类专业技术人员312人；设有机械加工、钣焊、热处理、工模具等专业车间；拥有旋压加工、精密加工、数控加工等多个专业加工中心；还有化工容器、换热器、蒸压釜、