关键词： mechanical alloy   hydrogen-sorption properties   thermal stability   thermodesorption spectroscopy   reactive mechanical alloying  

摘要： We report on studies of the process of cyclic hydriding-dehydriding (eight cycles) of a mechanical alloy synthesized in a ball mill by grinding powder mixture Mg + 10 wt.% TiH2 + 10 wt.% Fe in argon medium. Hydrogen-sorption properties and thermal stability of the mechanical alloy are studied employing thermodesorption spectroscopy at hydrogen pressure of 0.1 MPa. Hydrogen capacity of the mechanical alloy is determined to be 4.9 wt.%, and onset temperature of hydrogen desorption from the alloy under this study equals 220A degrees C. Kinetics of the process of hydrogen desorption from the hydride phases of the mechanical alloy is examined. The present studies have revealed that mechanical treatment of the magnesium powder in Ar medium with both Fe and Ti additives causes a greater effect on improving the kinetics of hydrogen desorption from hydride phase MgH2 of the alloy and decreasing its thermal stability in comparison with that caused by mechanical treatment of the same powder with either Fe or Ti additives in hydrogen medium.

关键词： Nano composites   Thermomechanical properties   Mechanical properties   Thermal analysis  

摘要： In this investigation, Polyetherimide (PEI) reinforced with multi-walled carbon nanotube (MWCNT) using novel melt blending technique. Surface of MWCNTs are modified by acid treatment as well as by plasma treatment. PEI nano composites with 2 wt% treated MWCNT shows about 15% improvement in mechanical properties when compared to unfilled PEI. The thermal decomposition kinetics of PEI/MWCNT nano composites has been critically analyzed by using Coats - Redfern model. The increase in activation energy for thermal degradation by 699 kJ/mol for 2 wt% MWCNT implies improvement in the thermal properties of PEI. Studies under Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM) depict significant interfacial adhesion with uniform dispersion of MWCNT in polymer matrix due to surface functionalization. 0.5 wt% chemically modified MWCNT shows typical alignment of MWCNT. There is a significant improvement in mechanical properties and thermal properties for surface functionalized MWCNT reinforced. (C) 2016 Elsevier Ltd. All rights reserved.

标准号: GB/T 33003-2016

摘要： 本标准规定了永久附在便携式农林机械、草坪和园艺动力机械上的单带式产品安全标志的设计原则和要求。这些标志设置在产品的可用空间十分有限，不使用多带式安全标志传达必要安全信息。

标准号: GB/T 4269.2-2016

摘要： 本部分规定了农业拖拉机和机械的操作者操纵机构和其他显示装置用符号。 本部分适用于农业拖拉机和机械，如联合收获机、棉花采摘机和饲料收获机等的操纵机构和显示装置用符号。

关键词： CRYSTALLIZATION kinetics   POLYCONDENSATION   SUCCINATES   POLYETHYLENE   CRYSTAL morphology   MECHANICAL properties of polymers   POLYESTERS  

摘要： Through a two-step melt polycondensation method, three poly(ethylene succinate-co-ethylene suberate) (PESSub) copolymers containing different contents of ethylene suberate (ESub) from 4.8 to 15.3 mol % and with similar molecular weights were successfully synthesized in this research. To demonstrate the effect of the ESub composition, the crystallization kinetics, morphology, and mechanical properties of PESSub were systematically studied. The crystal structure of PESSub was the same as that of PES;however, with increasing ESub composition, the degree of crystallinity values slightly decreased. The increase of the ESub content led to a depression in the glass transition temperature, cold crystallization temperature, cold crystallization enthalpy, melting point, heat of fusion, and equilibrium melting point of PESSub. Increasing the ESub composition retained the crystallization mechanism but decreased the crystallization rates and spherulitic growth rates. The copolymers with higher ESub component showed greater elongation at break but smaller tensile strength and Young's modulus. The crystallization behavior and mechanical properties of the synthesized novel copolyesters were well-regulated by adjusting the content of the ESub units.

关键词： 机械通气模式   呼吸窘迫   早产儿   血流动力学  

摘要： 目的探讨不同机械通气模式对早产儿呼吸窘迫综合征（融）S）血流动力学的影响及护理效果。方法选择2013年1月-2015年12月我科收治的早产儿RDS 60例，随机分为常频通气（CMV）模式组和高频振荡通气（HFOV）模式组，每组30例。两组均给予保温、营养支持、保证内环境的平稳以及预防感染等。在此基础上，分别采取CMV模式机械通气治疗和HFOV模式机械通气治疗。比较两组通气8～12h后心率、血气分析结果、机械通气时间、住院时间以及并发症情况。结果两组通气8-12h后心率、TCS02、PH值、PCP2以及PO2比较无显著性差异（P〉0．05）；HFOV模式组机械通气时间、住院时间较CMV模式组明显缩短（P〈0．05）；两组并发症发生率比较无显著性差异（P〉0．05）。结论HFOV与CMV治疗早产儿RDS均具有较好的临床效果，而且安全性高，可以有效改善早产儿的血流动力学，但HFOV治疗可更快速改善早产儿呼吸窘迫症状，明显缩短机械通气时间和住院时间，值得临床进一步研究。

关键词： 农业动力机械   清洗   保养   生产工具   机械零部件   技术含量   知识素质   使用技术  

摘要： 近年来,以拖拉机为主的各类农业动力机械迅速增长.农业动力机械是一种技术含量高、结构相对复杂的专门化生产工具,一般作业的条件比较恶劣,操作人员的使用技术水平和专业知识素质差别较大.同时,作为一种生产工具,随着使用期限的延长,机械零部件因磨损而引起性能下降,影响使用.因此农业动力机械应当注重保养和清洗.

关键词： 机械动力学   课堂教学   实验教学   科研教学   研究生教育  

摘要： 随着机械结构向轻量化方向的发展,机械动力学分析方法广为采用。传统的课题教学过程中以抽象的公式推导为主,学生很难理解其实际含义。通过设计动力学分析的相关实验,将理论分析与实验操作相结合,学生感触了具有真实物理意义的模态参数;另一方面,将实验分析过程导入学生的科研活动,让学生自主开发相关分析实验,扩展达到学生应用理论和实验方法解决实际问题的能力。教学实践表明,理论、实验和科研相融合的分析方法,对提高教学质量、提升学生动手能力、发展科研探索有很好的价值,尤其在工程学的专业硕士培养有很好的推广价值。

关键词： Molecular dynamics   Amorphous alumina   Units AlOx   Crystalline   Mechanical properties  

摘要： Molecular dynamics (MD) simulations of amorphous alumina have been carried out to investigate the pressure induced structural transformation and mechanical properties. We found that not only the fraction of units AlOx (x = 4, 5, 6) but also the density of each AlOx type change upon compression. The density of sample can be expressed through the fraction and partial density of units AlOx. With increasing pressure, O atoms are more ordered than Al atoms and form fcc and hcp clusters. The same units AlOx link togetheito form atomic clusters (AC) of type AC(4), AC(5) and AC(6) (AC(4), AC(5) and AC(6) consist of units AlO4, AlO5 and AlO6, respectively). The Young's modulus can also be expressed-through the fraction and partial Young's modulus of units AlOx. (C) 2016 Elsevier B.V. All rights reserved.

关键词： 垂悬转子   变换矩阵   轴向加载   动力学机械行为  

摘要： 通过矩阵变换的方式对轴向加载状态下的连带轮盘弹性轴的动力学机械行为进行了研究。将传统的变换矩阵进行了修正,考虑了轴向力的作用,然后进行计算编程,进一步实现轴向载荷对悬臂转子系统稳定性和固定频率方面影响的研究。本文研究对象分为两种,一种为悬臂的自由转子系统;另一种则包含了中间支撑的影响。研究发现转子的回转效应会明显影响杆轴-轮盘系统的动力学行为,不仅会使稳态临界载荷增加,还会使失稳形态从发散转变为振颤。