关键词： 农用设备   动力传动系统   动力传动工程   安全装置  

标准号: GB/T 24667.1-2009

摘要： GB/T 24667的本部分规定了自走式、悬挂式、半悬挂式和牵引式农业机械中不使用工具打开的动力传动运动件防护装置设计和制造安全要求和判定方法。本部分还规定了制造厂应提供的安全操作信息(包括遗留风险)的类型。 本部分不适用于拖拉机、航空器、气垫车辆、草坪和园艺设备的动力传动运动件防护装置。

关键词： 农用设备   动力传动系统   传动轴系   农用拖拉机   万向接头   机械连接  

标准号: GB/T 17126.2-2009

摘要： GB/T 17126的本部分给出了农业拖拉机和自走式机械用动力输出万向节传动轴的类型和使用规范，规定了各类联接装置用动力输接装置的尺寸及间隙范围。本部分目的是保证具有匹配动力水平的机具和拖拉机上的动力输出传动系与相邻联接装置间有适当的间隙。 本部分不适用于高杆作物或甘蔗作业用高地隙拖拉机与机具机组，也不适用于从事草坪割草或地面护理作业所需重心较低的地隙农业拖拉机，还不适用于因必需功能设计为非对称型的机具。

关键词： 农用挂车   动力传动系统   传动轴系   万向接头   农用拖拉机   防护罩   农用设备   强度试验  

标准号: GB/T 5263-2009

摘要： 本标准规定了确定农林拖拉机和机械动力输出万向节传动轴防护罩的强度和耐磨性的实验室试验方法及验收规范。本标准应与GB/T 17126配合使用。 本标准适用于动力输出万向节传动轴防护罩及其止动装置的试验。本标准不适用于作为阶梯使用的动力输出万向节传动轴防护罩的试验。

关键词： 农用设备   动力传动系统   传动轴系   农用拖拉机   万向接头   机械连接  

标准号: GB/T 17126.1-2009

摘要： GB/T 17126的本部分规定了农业拖拉机或自走式机械的动力输出万向节传动轴和机具的动力输入连接装置。 本部分确立了在给定制造和安全要求下，动力输出万向节传动轴静态和动态扭转强度的测定方法。 本部分适用于动力输出万向节传动轴和至少通过两个轴承与传动轴机械连接的防护罩。 本部分不适用于通过设置位置进行防护的动力输出万向节传动轴，也不适用于逆传限制的装置和转矩限制器机械性的评价。 本部分未考虑环境方面的因素。

关键词： 农用设备   动力传动系统   动力传动工程   安全装置  

标准号: GB/T 24667.2-2009

摘要： GB/T 24667的本部分规定了自走式、悬挂式、半悬挂式和牵引式农业机械中使用工具才能打开的动力传动运动件防护装置设计和制造安全要求和判定方法。本部分还规定了制造厂应提供的安全操作信息(包括遗留风险)的类型。 本部分不适用于拖拉机、航空器、气垫车辆、草坪和园艺设备的动力传动运动件防护装置。

关键词： REACTION mechanisms (Chemistry)   SUBSTITUTION reactions   MACROMOLECULES   PHENOL   NUCLEOPHILIC reactions   QUANTUM theory   MOLECULAR dynamics   SIMULATION methods & models  

摘要： A combination of molecular dynamics simulations and quantum chemistry calculations affords a good understanding of the reaction between [NPCl2](n), and the bifunctional nucleophile aminophenol HO-C6H4-NH2 in THF solution and in the presence of alkali carbonates. This reaction is regiospecific at room temperature favoring the attack by the NH2 group, and only at higher temperatures the attack by the OH is activated. It is also explained why the reaction of HO-C6H4-NH2 with {[NP(O2C12H8)](1-x)[NPCl2](x)}(n) and Cs2CO3 at reflux proceeds exclusively by the OH giving aryloxyphosphazenes with terminal NH2 substituents. Molecular dynamics simulations have been performed on model systems consisting on [NPCl2](n) chains surrounded by aminophenol molecules or ions obtained by deprotonation of either the OH or NH2 groups. Quantum mechanics calculations consisted in density functional theory (DFT) computation of the reaction mechanism of aminophenol with the phosphoranimine (NH2)Cl2P(= NH) as a simple model for the NPCl2 phosphazene units, using B3LYP approximation with 6-31G(d). Our results provide evidence to support that the macromolecular substitution reactions of poly(dichlorophosphazene) with aryloxide ions are diffusion controlled and governed by the atomic charges, while the reaction with amino-arenes are directed by hydrogen interactions between the NH, hydrogens and the phosphazene nitrogen atoms that initiate a lower activation energy stepwise mechanism competing with a concerted mechanism. The combined methodology employed in this work seems to be useful to address the regiochemistry of the macromolecular substitution on polyphosphazenes with heterobifunctional nucleophiles which is a central issue in the design of polymers with predetermined chemical composition and structure.

关键词： OXIDATION   THIOCYANATES   HYDROGEN-ion concentration   CHEMICAL kinetics   CHEMICAL reactors   TEMPERATURE effect   SULFATES   AMMONIUM  

摘要： The wet oxidation of thiocyanate has been investigated in a I-L semibatch reactor at temperatures in the range of 438.15-468.15 K and total pressures between 2.0 x 10(3) kPa and 8.1 x 10(3) kPa. The initial pH value of the reaction media was varied between pH 2 and pH 12 and was found to be a key parameter in the rate of thiocyanate degradation. The evolution of concentration of substrate and products (sulfate and ammonium) were analyzed. Based on the experimental data and bibliography information, a kinetic model was obtained and, here, possible pathways, depending on the initial pH of the media, are suggested for thiocyanate oxidation.

关键词： Foams  

摘要： Heterogeneous materials usually break through a process of microcracking that eventually leads to final rupture after accumulation and coalescence of many microcracks. The statistical properties of microcracking rupture have been known to resemble critical point statistics, with many of the physical quantities obeying power law distributions. However, there is no clear understanding of the origin of these distributions and of the specific values observed for the power law exponents. In this paper, we review the special case of polymeric foams that have the advantage of containing a single material component, the polymer, as opposed to usual heterogeneous materials such as composites. First, we briefly review the typical features of the polymeric foam mechanical response up to rupture that have been widely studied previously. Then, we focus on a less well-known aspect: the rupture dynamics of polymeric foams. We not only show that polymeric foams behave like other heterogeneous materials, i.e. they display power law statistics, but we are also able to test the effect on the power laws of the following properties: the foam heterogeneity by changing its density, the foam mechanical response by changing its temperature and the mechanical history by comparing creep tests and tensile tests.

关键词： 农业劳动力   膳食能量   农业机械化   协整分析   江苏省  

摘要： 本文采用江苏省1983～2007年的数据,运用协整和误差修正模型,对农业劳动力人均膳食能量节省与人均农机动力水平之间的关系进行实证研究。结果表明:农业劳动力人均膳食能量节省与人均农机动力之间存在长期均衡关系,无论是长期还是短期,提高人均农机动力水平对增加人均膳食能量节省都有明显的正效应;短期内人均农机动力变化是人均膳食能量节省的Granger原因;农业机械化水平的提高可能还导致了农民膳食能量结构的变化。

关键词： 高速并联机械手   弹性构件   弹性动力学   动应力   固有频率  

摘要： 采用有限元方法建立了一种新型两自由度平动并联机械手的弹性动力学模型.在该模型的基础上,分析了机械手在工作空间的前四阶固有频率的分布情况,研究了在外力和刚体惯性力激励下机械手动平台的位置误差,给出了构件在各个时刻的最大动应力及其出现的位置.结果表明:系统的固有频率与其位形有关,机械手动平台的位置误差主要由高速运动时的刚体惯性力引起,机械手各个柔性构件的动应力谱是变幅应力谱.