Modelling and dynamic analysis of spline-connected multi-span rotor system

Meccanica - Self-excited oscillation induced by the internal frictions of spline joints is a major cause of rotor system instability. In this study, the dynamic equations of spline-connected...     

复杂势场量子弹球中疤痕态的量子化条件

量子疤痕是波函数在经典不稳定周期轨道周围反常凝聚的一种量子或波动现象.人们对疤痕态的量子化条件进行了大量研究,对深入理解半经典量子化起到了一定的促进作用.之前大部分研究工作主要集中在硬墙量子弹球上,即给定边界形状的无穷深量子势阱系统.本文研究具有光滑复杂势场的二维量子弹球系统,考察疤痕态的量子化条件及其重复出现的规律,得到了与硬墙弹球不一样的结果,对理解这类现象是一个有益的补充.这些结果将有助于理解具有无规长程杂质分布的二维电子系统的态密度谱和输运行为.     

真空条件下LiCl溶液蒸发量随浓度变化规律研究

除湿溶液再生是除湿空调系统的核心过程,为了提高除湿溶液再生效率,以蒸发量作为评价标准,在不同的真空度下对不同浓度LiCl溶液进行再生。对不同再生条件下,溶液的再生情况进行数学模拟及实验研究,并将模拟结果与实验结果进行对比分析,结果表明,实验结果同模拟结果具有相同的变化趋势。在6 kPa和8 kPa的压强下,LiCl溶液的蒸发量随浓度的增大先上升后下降,而在1 kPa的压强下,LiCl溶液的蒸发量随浓度的增大呈现出先下降再升高接着又下降的趋势。     

Nonlinear vibration effects on the fatigue life of fluid-conveying pipes composed of axially functionally graded materials

Nonlinear Dynamics - Fatigue is inevitable in pipes conveying fluid due to unwanted vibration. Internal resonance occurs in such pipes due to pre-pressure. For the first time, the effects of...     

Fully distributed spherical formation tracking control for nonlinear vehicles with spatiotemporal uncertainties and digraphs

Nonlinear Dynamics - This paper addresses the spherical formation tracking control problem of nonlinear vehicles under digraphs, where the dynamics of vehicle contains spatiotemporal uncertainties...     

Experimental validation of internal model approach for tracking control of a MEMS micromirror without angular velocity measurement

Nonlinear Dynamics - This paper addresses the angular tracking control for an electromagnetic MEMS micromirror. The problem is formulated in the output regulation framework for output feedback...     

双曲冷却塔塔筒水平地震响应分析

为明确冷却塔在水平地震下的内力环向分布特征及内在原因,同时探究不同地震波时程与规范反应谱所得内力差异的原因,以某大型双曲冷却塔为例,在动力特性分析的基础上,通过反应谱方法和时程方法的水平地震响应计算及对比分析,对上述两个问题进行了研究。研究表明:由于仅侧弯振型对水平地震有贡献,而塔筒的侧弯振型和实际响应均表现为整体侧倾并伴随微弱的截面“流动”变形,这也使塔筒各内力的环向分布分别呈现正弦、余弦分布特征;其整体侧倾可类比于悬臂杆结构,塔筒子午向轴力FY、子午向弯矩MY、剪力FXY和扭矩MXY的环向分布可借助悬臂杆侧倾时截面正应力和剪应力分布来解释;而截面“流动”变形则决定了环向轴力FX和环向弯矩MX的环向分布;整体侧移显著而截面变形极小也使FY和FXY的幅值在塔筒中下部明显大于FX;由于冷却塔第1阶侧弯振型在水平地震响应中往往起绝对主导作用,因此可先对所选地震波计算得到其反应谱,对比第1阶侧弯振型周期对应的水平地震影响系数α值,即可初步推断不同时程及规范反应谱方法所得结果的大小关系。     

复合材料失效判据有效性验证方法研究

为系统地验证复合材料失效判据计算精度和有效性范围,给出了4种材料体系、6种铺层形式的层合板在单轴、双轴载荷下的失效试验数据,用以评估复合材料失效判据在单向层合板失效包线、多向层合板初始失效包线、多向层合板最终失效包线、层合板变形及层合板的破坏特性等五个方面的预测能力。并根据验证方法和有效性评估策略对失效判据计算精度进行量化考核,给出了失效判据在五个层面上的计算精度。     

Theoretical study on the catalytic properties of single-atom catalyst stabilised on silicon-doped graphene sheets

ABSTRACT

The stable configurations, electronic structures and catalytic activities of single-atom metal catalyst anchored silicon-doped graphene sheets (3Si-graphene-M, M?=?Ni and Pd) are investigated by using density functional theory calculations. Firstly, the adsorption stability and electronic property of different gas reactants (O₂, CO, 2CO, CO/O₂) on 3Si-graphene-M substrates are comparably analysed. It is found that the coadsorption of O₂/CO or 2CO molecules is more stable than that of the isolated O₂ or CO molecule. Meanwhile, the adsorbed species on 3Si-graphene-Ni sheet are more stable than those on the 3Si-graphene-Pd sheet. Secondly, the possible CO oxidation reactions on the 3Si-graphene-M are investigated through Eley–Rideal (ER), Langmuir–Hinshelwood (LH) and new termolecular Eley–Rideal (TER) mechanisms. Compared with the LH and TER mechanisms, the interaction between 2CO and O₂ molecules (O₂?+?CO → CO₃, CO₃?+?CO → 2CO₂) through ER reactions (< 0.2?eV) are an energetically more favourable. These results provide important reference for understanding the catalytic mechanism for CO oxidation on graphene-based catalyst.