关键词： 动力总成生产线项目   工程项目全面风险管理   机械安全   风险评估   风险控制  

摘要： 随着整车企业越来越多的新车项目开展,在技术难度较高的动力总成(发动机和变速箱)这一块,生产线本身就是一个高度集成化的技术产品。在动力总成生产线制造工程项目中,机械安全设计管理是工程管理中的重要环节之一,它关系到今后工厂运行的整体安全。本文通过对工程项目风险管理的原则和流程、风险评估方法、风险控制策略进行比较分析,并结合动力总成生产线项目的特点,确定机械安全设计管理的本土化策略,并结合实例进行说明。在安全设计原则方面,通过对机器的全生命周期以及项目特点的研究,提出关注基于动力总成生产线项目的业务目标、基于成本和影响的风险评估、基于技术与经验的风险控制三大原则进行。在安全设计流程方面,结合动力总成生产线项目的开发流程,提出节点控制的流程。在安全设计风险评估、评价方面,结合风险管理中风险评估理论和过程、常用的工具和技术以及动力总成生产线项目机械安全设计的特点,总结出适合项目的本土化风险识别策略。在安全设计风险控制方面,引入“两阶段”的风险控制理论,根据动力总成特点细化出每一阶段可以采用的措施,并结合实例进行说明。

关键词： 机械设计制造及其自动化   机械工程专业   材料成型及控制工程   三峡大学   国家特色专业   学院   在读研究生   本科学生  

摘要： 2014年1月原机械与材料学院更名为机械与动力学院,学院现设有机械设计制造及其自动化、机械电子工程、材料成型及控制工程、工业工程、能源与动力工程、核工程与核技术六个本科专业,其中机械设计制造及其自动化为国家特色专业、第二批卓越工程师教育培养计划专业和省本科品牌专业,材料成型及控制工程为第三批卓越工程师教育培养计划专业。拥有机械工程一级硕士点、机械工程专业学位点、机械工程领域工程硕士点工业工程专业学位点,机械制造及其自动化为湖北省重点学科。目前,在校全日制本科学生近2000人,在读研究生160余

ISBN: (纸本)9787562949749

关键词： Thermodynamics   Kinetics   Catalysis   Mechanism   Carbene   Organometallic  

摘要： As we try to find ways to oxidize atmospheric nitrogen, it becomes important to us to understand oxygen atom transfer (OAT) reactions. We began with understanding OAT to different types of tri substituted phosphines (PR3, R=alkyl, aryl). We used mesityl nitrile oxide (MesCNO) as OAT reagent. We explored thermodynamic, kinetic, mechanistic pathways of OAT and figured out the differences in P=O bond strength as well as the effect of different substitutions (R groups in PR3) on the rate of OAT. With the help of computational analyses, we found that the is initial interaction between phosphorous and carbon of MesCNO. We wanted to explore the C=O bond strengths in NHC carbenes as they are electronically similar to phosphines by performing OAT from MesCNO. Instead of OAT, we made NHC-MesCNO adducts where the carbine carbon and the carbon of CNO in MesCNO were connected. This further solidified our theory of previously proposed phosphine-MesCNO intermediate through R3P˙˙˙˙C(Mes)NO interaction. These adducts showed higher rate of OAT compared to MesCNO itself. That encouraged us to explored the chemistry of these adducts. Not only by MesCNO, we also explored adducts formed between MesCNO and several isocyanates (RNCO, R=Ph, adamentyl, 2,6-di (trifluoro methyl) phenyl). Isocyanate adducts showed higher dipolemoment compared to MesCNO adducts. We, then moved on from OAT to non-metal such as phosphines to early transition metal complex such as vanadium tris anilide. In this instance we used several OAT reagents containing N-O bonds with different bond strengths. They showed significant differences in mechanism in OAT. Unfortunately, VO bond strength too great to transfer the oxygen from vanadium. We used another vanadium complex, V[(Me3SiNCH 2CH2)3N] with axial amine ligand and observed that VO bond strength decreases due to the presence of the axial amine ligand. Adducts formed between Ad-NC (Ad=adamantyl) and two vanadium complexes mentioned previously showed the same type o

关键词： 机械智能化   人力资源就业   技术性失业  

摘要： 当前,我国正在进行新一轮产业结构的调整,新技术、新模式、新方法的应用,极大地推动了各行业的发展。一方面推动了我国经济的快速发展,另一方面则造成大批一线员工技术性失业,带来了新的社会问题。能否正确解决大批一线员工的失业问题,是我国社会稳定、经济持续发展的重要保证。针对这一问题,提出并探讨轻工业机械智能化程度与劳动力需求关系,研究机械智能化生产带来劳动者失业的社会问题:探索应对这一问题的措施,力求解决我国经济发展中的技术性失业问题。

关键词： Glass transition  

摘要： Graphene oxide (GO) was synthesized and nanocomposites were prepared using different contents of the GO and vinyl ester resin (VE). The suspension was sonicated in order to prevent agglomeration. The non-isothermal differential scanning calorimetry (DSC) technique was used to study the cure kinetics of neat VE and 0.3 wt% GO/VE nanocomposite. Kissinger and Ozawa equations were used to determine the activation energy (E-a). The E-a values of the cured GO/VE nanocomposite showed a decrease with respect to the neat VE. It is concluded that GO has a catalytic effect in the cure reaction. The dynamic curing process was modeled to predict the degree of curing and curing rate of resin. The modeling results showed a good agreement between the experimental data and model for different heating rates (5, 10, 15 and 20 degrees C min(-1)). The glass transition temperature (T-g) was obtained from the maximum peak temperature of the loss factor curve. The T-g was increased by nearly 10 degrees C by the addition of 0.4 wt% GO to VE. Tensile mechanical tests were studied and the nanocomposite of 0.3 wt% GO/VE showed higher elongation and tensile strength. This percent (0.3 wt% GO/VE) was selected for non-isothermal differential scanning calorimetry (DSC) to study the cure kinetics. Scanning electron microscopy (SEM) was studied to discern the surface features and dispersion of GO. The thermal stability of the cured VE and its nanocomposite was investigated with thermogravimetric analysis (TGA). The char yields increased with the addition of 0.3, 1.5, and 3 wt% of GO to the vinyl ester resin. The addition of GO improved the polymer flame retardancy and thermal resistance.

关键词： 轨迹规划   动力学模型   时间最优   能量最优  

摘要： 机械臂轨迹规划是机器人运动规划领域中至关重要的经典研究方向之一。随着机器人时代的到来,机械臂在工业制造中得到了广泛的应用,如何更好的利用机械臂的运动性能,获得运行时间较短或者消耗能量更少的运动轨迹成为人们关注的重点。本文在总结归纳机械臂运动学轨迹规划、动力学轨迹规划和动力学模型参数辨识等方向上研究成果的基础上,开展了以下几部分工作：1.本文介绍了一种离线动力学参数辨识框架,并且重点改进了参数估计方法,采用带权重的最小二乘法进行参数估计,使得在参数估计的过程中可以对精确的测量数据和不精确的测量数据区别对待。最后在弹性机械腿上验证此辨识流程的有效性。2.本文将基于动力学模型的时间最优轨迹规划问题变换为凸问题进行求解,通过改进此凸问题的目标函数,即添加额外的表示能量和力矩变化率的代价函数,使得规划轨迹在兼顾时间较优的情况下更加便于机械臂执行。3.本文基于时间最优轨迹规划的结果,给出一种给定运动时间的能量最优轨迹规划方法,通过采用动态规划算法,在时间轴上进行搜索得到给定运动时间的能量最优轨迹。

关键词： 三峡大学   学院   卓越工程师教育培养计划  

摘要： 2014年1月原机械与材料学院更名为机械与动力学院,学院现设有机械设计制造及其自动化、机械电子工程、材料成型及控制工程、工业工程、能源与动力工程、核工程与核技术六个本科专业,其中机械设计制造及其自动化为国家特色专业、第二批卓越工程师教育培养计划专业和省本科品牌专业,材料成型及控制工程为第三批卓越工程师教育培养计划专业。拥有机械工程一级硕士点、机械工程专业学位点、机械工程

关键词： 二尖瓣置换术   机械瓣   血流动力学  

摘要： 目的探讨不同类型机械瓣对二尖瓣置换术患者术后血流动力学的影响.方法选择我院收治的52例行二尖瓣置换术患者作为研究对象，根据术中使用机械瓣类型的不同将患者分为双叶瓣组和倾斜碟瓣两组，每组26例，术后对患者进行1年的随访，观察两组患者手术后的血流动力学超声参数.结果双叶瓣组和倾斜碟瓣组患者术后左房内径(LA)及E波峰值速度之间的差异有统计学意义(<0.05).两组患者的左室内径(LV)/右室内径(RV)/平均跨瓣压差(MPG)以及肺动脉收缩压(PASP)组间差异未见统计学意义(＞0.05).结论在二尖瓣置换手术中使用双叶瓣对患者血流动力学的影响优于倾斜碟瓣.

关键词： Rate constants  

摘要： The mechanism, thermochemistry and kinetics of hydrogen abstraction pathways in the atmospheric reaction of glycolaldehyde with a hydroxyl radical, in the absence and presence of a single-water molecule under tropospheric conditions, are investigated. The pathways are explored through high-level quantum mechanical computations employing a global reaction route mapping method at the levels of coupled-cluster and density-functional theories employing BHandHLYP and M06-2X exchange-correlation functionals. The reaction is found to be dominated by the hydrogen abstraction pathways involving the aldehydic site in glycolaldehyde, both in the presence and absence of water. The spin-density from the natural orbital analysis and molecular orbitals predict that a few of the pathways, water-free as well as with water, proceed through a proton-coupled electron-transfer mechanism rather than the conventional free radical mechanism. The overall rate constant for the water-free reaction at room temperature, calculated using the transition state theory, at the CCSD(T)//BHandHLYP level, is found to be in good agreement with the experimental results, though the rate constants corresponding to the water-assisted reaction are found to be smaller by several orders of magnitude, but M06-2X was observed to overestimate the rate constants. However, contrary to the negative temperature-dependence exhibited by the rate constants observed in the case of the water-free reaction, the water-assisted rate constants exhibit a correct Arrhenius behavior with significant tunneling at low temperatures. Notably, cis-trans interconversion in glycolaldehyde is observed to be feasible along the water-assisted pathways contrary to that along the water-free pathways. Besides this, the present work also explored an addition reaction pathway for the addition of a hydroxy radical to the carbonyl group of glycolaldehyde which can result in species like hydroxyl-formaldehyde, hydroxyl-methyl and a dihydroxy radi