基于格子玻尔兹曼方法的横向交变质量力对核沸腾影响的数值分析

采用格子玻尔兹曼方法的单组份伪势模型与有限差分耦合的混合热格子玻尔兹曼模型,对在横向交变质量力作用下的单汽泡核态沸腾过程进行了研究,探讨了在不同接触角和过热度下,横向交变质量力的振幅和交变频率对汽泡脱离底壁的脱离特性的影响。结果表明,施加横向交变质量力会造成汽泡脱离直径减小,同时加速汽泡脱离底壁。其次,壁面越疏水,汽泡的脱离行为受到横向交变质量力的影响越大;壁面过热度越大,汽泡的脱离行为受到横向质量力的影响也越大。另外,在模拟工况下,当横向交变质量力的振幅大于0.01时,添加横向交变质量力会使汽泡的脱离直径与脱离周期均减小;而横向交变质量力的交变频率仅在某一频段时,使得汽泡的脱离周期减小。     

工作靴内底特性检测

该文研究内底革的实用性,尤其是用于工作靴的内底。因为该类鞋用于条件恶劣的环境,要求穿着舒适,利于健康。重要的两方面是:环境卫生性能和关于明确的肌肉运动体系的物理性能。人们的脚每天频繁运动,容易失水且使表面硬化,如果鞋内底能解决此问题则是既耗费低又简单的方法。对各种材料的内底进行检测发现能承受最大撞击力的材料是硅内底和胶原填充内底。     

岩石切削过程中破坏机制的离散元分析

利用离散单元方法(DEM)对两种不同属性的花岗石样本模型进行了切割模拟,通过调整不同的切削参数计算并分析了岩石切削过程中的切削力、切削深度、切削比能及切削力倾角的变化规律,从细观上探讨了临界切深对岩石脆性破坏模式和塑性破坏模式及其转变的影响,指出了当切削深度逐渐增大时,破坏模式依次从塑性破坏模式到过渡破坏模式最后转变为脆性破坏模式,同时切削力倾角并不随切削深度变化。将离散单元法分析的结果与实际实验进行了比较,表明该方法是合理的。     

江苏油田三种典型钻具组合复合井导向力计算分析

结合江苏油田导向钻井技术现场试验中采用的三种典型的滑动导向钻具组合,在计算复合钻井导向力的基础上,探讨了两个主要因素对复合钻井导向力的影响规律,理论计算结果与现场试验结果基本吻合,通过设计钻具组合的结构和施工参数,可以提高井眼轨迹控制精度。     

基于力反馈的脊柱外科机器人系统的设计与实现

本文针对脊柱椎管狭窄症减压手术中椎管壁磨削不安全这一问题,介绍一种基于力反馈控制策略的脊柱外科机器人系统,包括监控磨削过程的检测子系统、完成磨削手术操作的运动驱动子系统和再现磨削信息状况的控制显示子系统。利用脊柱磨削手术过程中磨削力的变化特点,提出基于力反馈的脊柱外科机器人控制策略,辅助医生实现安全的脊柱手术操作。最后通过仿真实验和模拟骨实验,验证了此基于力反馈控制策略的脊柱外科机器人系统的可行性。     

原子力显微镜在高分子物理实验教学中的应用

原子力显微镜主要用来表征样品的表面结构与形貌,操作容易、简便,分辨能力可达到纳米级别,是目前对材料分析与纳米科技研究的重要工具之一.以聚合物的支化结构、聚氨酯的微相分离结构、聚合物的结晶熔融行为和流延法单向拉伸制备高密度聚乙烯微孔膜4个实验为例,将原子力显微镜运用于高分子物理实验教学中,以更好地阐明聚合物结构与性能之间的关系,使学生可以更好地理解相关高分子物理的基本概念和理论,同时使他们分析和解决问题的能力得到提升.     

高层斜交网格结构体系的性能研究

为研究钢管混凝土柱的轴向恢复力模型,设计制作了8个钢管混凝土柱试件并对其进行轴向往复加载,分析其受力机理和恢复力特性。基于试验结果,选用退化三线型模型,建立了钢管混凝土柱无量纲骨架曲线模型,并提出其轴拉与轴压方向的峰值承载力和位移的计算方法。鉴于钢管混凝土试件在轴拉与轴压方向受力机理的差异,对滞回曲线的正负向选用不同的滞回规则,建立了相应的卸载刚度函数。据此提出了钢管混凝土柱的轴向恢复力模型,并与试验滞回曲线进行对比,验证了恢复力模型的合理性,所建立的恢复力模型可为斜交网格结构体系的弹塑性分析提供依据。     

设置垫板的形件螺栓连接滞回性能试验研究

该文综述了对称和非对称型摩擦耗能连接40多年以来的发展历史和研究现状。摩擦耗能连接可用于结构的减震耗能,通过合理设计可实现地震作用下带摩擦耗能连接结构的低损伤,提高结构的韧性。研发滞回性能稳定、重复性好的摩擦耗能连接是相关研究的主要目标之一。该文从微观和宏观两个方面介绍了金属滑移面之间的摩擦磨损机理,从摩擦磨损的角度讨论了不同摩擦片材料对摩擦连接减震性能的影响。描述了螺栓预紧力大小对摩擦连接减震性能的影响,也总结了摩擦连接的抗腐蚀和抗火性能。阐述了摩擦耗能连接在钢结构支撑、梁柱节点和柱脚节点的应用,并介绍了相关节点的设计方法。对此类连接的关键技术进行了总结,并对该技术的后续研究进行了展望。     

Isocyanate-rich cellulose nanocrystals and their selective insertion in elastomeric polyurethane

Cellulose nanocrystals (CNC) were successfully obtained and modified with 1,6-hexamethylene diisocyanate (HDI) by means of in situ polymerization varying the CNC/HDI molar ratio to evaluate the number of anchored chains to the CNC. The modification was examined by elemental analysis, nuclear magnetic resonance (¹³C NMR) and attenuated total reflection Fourier transform infrared spectroscopy (IR-ATR). Nanocomposites containing 1.5 wt% CNC, modified and unmodified, were prepared by solvent casting. Thermal and mechanical properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the polyurethane matrix and depending on surface chemistry, the nanoreinforcement interacts selectively with matrix nanodomains. This interpretation is supported by differences in thermal and mechanical properties of the nanocomposites and also confirmed by AFM images. Isocyanate rich cellulose nanocrystals interacted with matrix hard phase, promoting physical association with hard segments, enhancing stiffness and dimensional stability versus temperature of the nanocomposite.     

Back to the future: Brake reaction times for manual and automated vehicles

Rear-end collisions are often quoted as being a major cause of road traffic accidents. In response to this, a great deal of ergonomics research effort has been directed towards the analysis of brake reaction times. However, the engineering solution has been to develop advanced systems for longitudinal control, which, it is argued, will mitigate the problem of rear-end collisions. So far, though, there have been few empirical studies to determine how brake reaction times will be affected by such vehicle automation. This paper presents a literature review summarizing the current state of knowledge about driver responses in non-automated vehicles. The review covers driver factors, vehicle factors and situational factors. Following the review, some empirical data are presented from a driving simulator experiment assessing brake reaction times of skilled and unskilled drivers under two different levels of automation. When compared to previous data gathered during manual driving, there seems to be a striking increase in reaction times for these automated conditions. Implications for the design and safety of automated vehicle systems are discussed.