双螺旋弹簧质量系统动态响应分析

许多工程结构应用了双螺旋弹簧质量系统(如炮闩的复进簧),这种系统的非线性动态响应分析的解法国内外尚属罕见;本文分析计算了在纵向冲击载荷作用下,双螺旋弹簧质量系统中的动态应力变化规律及其最大值;理论计算结果与实验符合良好.这种方法可用来进行双螺旋弹簧质量系统的动态强度设计计算.     

螺旋理论与旋光方向

利用螺旋理论的规律可以推断分子的旋光方向,反之,从旋光方向也可以推断分子的构型和构象。     

并列式双扭簧的最大动应力分析

对并列式双扭簧的动应力进行了研究，计算了弹簧在主工作方向有预荷载情况下受冲击激励时的最大应力及发生位置。为检验计算结果的正确性，对弹簧螺旋梁危险点应变做了实验测量，其结果与计算结果相符。     

Chemical Biology for Understanding Matrix Metalloproteinase Function

The matrix metalloproteinase (MMP) family has long been associated with normal physiological processes such as embryonic implantation, tissue remodeling, organ development, and wound healing, as well as multiple aspects of cancer initiation and progression, osteoarthritis, inflammatory and vascular diseases, and neurodegenerative diseases. The development of chemically designed MMP probes has advanced our understanding of the roles of MMPs in disease in addition to shedding considerable light on the mechanisms of MMP action. The first generation of protease‐activated agents has demonstrated proof of principle as well as providing impetus for in vivo applications. One common problem has been a lack of agent stability at nontargeted tissues and organs due to activation by multiple proteases. The present review considers how chemical biology has impacted the progress made in understanding the roles of MMPs in disease and the basic mechanisms of MMP action.     

混炼方式对螺旋纳米碳纤维增强天然橡胶复合材料力学性能的影响

采用干法和湿法两种混炼工艺制备了螺旋纳米碳纤维(HCNFs)/炭黑(CB)/天然橡胶(NR)复合材料,通过扫描电镜、拉伸试验机和应变扫描仪分别对所制备复合材料的界面形貌、力学性能和Payne效应进行了测试分析,考察了混炼方式对复合材料宏观力学性能及Payne效应的影响。结果表明,与纯CB填料相比,在干湿两种混炼方式下,添加适量的HCNFs(1～6份)能提高HCNFs/CB/NR复合材料的300%定伸应力、扯断伸长率、拉伸强度和硬度。与干法混炼相比,湿法混炼能明显增强HCNFs/CB/NR复合材料的Payne效应,并提升在HCNFs高添加量(2～6份)条件下的拉伸强度和扯断伸长率,这主要源于湿法混炼能够有效改善HCNFs在橡胶基质中的分散性。     

卧式螺旋管内紊流传热

在宽广的参数范围内对卧式螺旋管内紊流换热特性进行了详细的试验研究, 试验结果表明,螺旋管内强化换热是紊流流动与二次流动共同作用的结果,Reynolds数越大,二次流对强化换热的贡献越小,平均换热系数也越接近于等条件下的直管换热;换热系数在圆截面上的分布很不均匀,最外侧换热系数可达最内侧的3～4倍,最内侧是平均换热系数的0.5倍,并得到了截面上局部换热系数的计算式;换热系数在流动方向的分布具有周期性。     

管壳式换热器强化传热研究进展

管壳式换热器作为工程中应用广泛的换热器,具有结构坚固、适应性强、能够利用和回收热能等优点。在追求高能源利用效率的背景下,换热器的强化传热得到广泛关注。本文重点阐述了管壳式换热器的强化传热相关研究进展,包括换热器本身几何结构的优化、换热流体的热物性改善以及多种强化传热技术结合的复合强化传热方法。其中几何结构优化主要包括改变换热管管型、增加管内插入物以及壳程中的隔板优化研究等。换热流体热物性改善包括纳米流体提高热导率、潜热型热流体提高比热容等。复合强化传热是将多种强化方法结合,可弥补单一方法的不足,以获得更高强化传热效果。最后指出管壳式换热器强化传热未来的研究方向在于持续开发强化传热管、制备稳定的纳米流体及潜热型流体以及多种强化方式复合提高强化效果。     

横置螺旋簧隔振器非线性弹性参数的计算

针对横置螺旋簧隔振器的大位移小形变问题,在Mottershead线性螺旋杆单元和牛顿-拉斐逊带动坐标迭代法的基础上,计算拟合了隔振器位移与载荷的关系式.结果表明,隔振器主工作方向上刚度是受压时变软受拉时变硬明确了二次非线性的存在.并与直杆单元的计算结果和实验结果进行了比较     

Numerical prediction of a nusselt number equation for stirred tanks with helical coils

A methodology to obtain a Nusselt correlation for stirred tank reactors is presented. The novelty of the approach is the use of a validated computational model to obtain the heat‐transfer coefficients. The advantages of this new approach are many, including the possibility of testing different heat‐transfer configurations to obtain their Nusselt correlation without performing experimental runs. Physical phenomena involved was represented both qualitatively and quantitatively. The classical experimental work of (Oldshue and Gretton, Chem Eng Prog. 1954;50(12):615–621) illustrates the procedure. A sufficient number of virtual points in the whole range of the Reynolds number should be obtained. Results strongly depend on mesh refinement in the boundary layer, so a procedure is suggested to guarantee heat‐transfer coefficients are accurately estimated. The final Nusselt correlation was compared against all the 107 experimental points of the work by (Oldshue and Gretton, Chem Eng Prog. 1954;50(12):615–621), and an average deviation on the results of 10.7%. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3912–3924, 2017