摘要：经典克拉尼图形(Chladni patterns,CP)是特征向量的视觉表示,在振动分析、乐器设计、粒子操纵和分离等领域中具有广泛的应用.均质结构通常会表现出高度规则化的CP,这限制它们的应用场景.因此,实现面向应用来逆向设计结构的CP是非常重要的,而这可以通过使用拓扑优化来实现CP的逆向设计.本研究提出了一种使用基于密度的拓扑优化算法来设计结构CP的方法.优化列式中,给出了描述图形的指标函数,并以最小化特征向量和目标CP之间的误差构建了优化目标.数值结果表明,所提出的方法可以为指定的单阶或多阶CP生成新颖的材料分布.这表明了本文所提出的方法能够实现CP的精确定制设计,进一步为面向应用的需求提供了更多选择.

摘要：非晶合金是非晶材料家族中的新成员,由于缺乏原子排列长程有序特征,具有独特的性能和广泛应用前景.然而,非晶合金的形成、成分设计和形变问题在该领域长期未得到解决,制约着新型非晶合金的高效开发.传统上,多组元非晶合金的成分设计主要遵循相图研究范式,以温度调控为出发点,确定低液相线的成分为落脚点,尤其强调深共晶成分.然而,对于缺乏相图的多组元体系则力所不及,亟需新的理论突破.本文综述了非晶转变中的热力学与动力学基本规律,重点探讨了热力学与动力学性质之间的关联性,尤其是梳理了材料熔化熵与熔点粘度、熔点等多个非晶形成经典参量之间的内在关联,提出并论证了熔化熵和振动熵为非晶形成的关键热力学参量,可有效指导高性能非晶合金的设计和表征.结合实际应用中对非晶材料的工程要求,讨论了化学成分调控对非晶合金剪切带的萌生密度和扩展稳定性的影响,并总结了在单调加载和疲劳加载条件下剪切带行为对非晶合金断裂过程的作用.最后展望了振动熵和构型熵之间争议问题,提出未来工作中需要发展具有物理意义玻璃形成能力指标和可靠数据库的需求,混合加载模式下的韧性以及疲劳和韧性之间的权衡等问题.本文为进一步建立高性能非晶材料成分设计路径提供了参考与指导.

摘要：区别于常规稳定注液方式,不稳定注入水力压裂在施工过程中通过改变注入流量、利用流量变化产生的动态效应来提高压裂改造效果。其中压裂液沿管柱的流动规律对于压裂施工过程至关重要。本文建立了管柱内流体瞬态流动的动力学模型,该模型考虑了储层渗流与非恒定摩阻的影响。分别采用特征线法与有限差分法对上述模型进行求解。进一步分析了地质参数与注入方案对井底波动压力的影响。结果表明,不稳定注入可以使管柱内流体压力产生明显波动。此外,波动压力在传播过程中会发生衰减,注入流量变化频率与井深参数对井底的压力波动幅值影响显著。本研究有助于理解不稳定注入水力压裂的施工原理,并为压裂施工中的注液方案设计提供指导。

摘要：Three-dimensional(3D)bioprinting has been used widely for the construction of hard tissues such as bone and ***,constructing soft tissues with complex structures remains a *** this study,complex structures characterized by both tunable elastic modulus and porosity were printed using freeform reversible embedding of suspended hydrogels(FRESHs)printing methods.A mixture of alginate and gelatin was used as the main functional component of the *** analysis showed that this bioink possesses shear thinning and shear recovery properties,supporting both cryogenic and FRESH printing *** printing capabilities and limitations of cryogenic and FRESH printing were then analyzed by printability tests.A series of complex structures were printed by FRESH printing methods which could not be realized using conventional *** tests and scanning electron microscopy analysis showed that the printed structure is of excellent flexibility and could be applied in various conditions by adjusting its mechanical modulus and porosity.L929 fibroblast cells maintained cell viability in cell-laden-printed structures,and the addition of collagen further improved the hydrogels’***,all results provided useful insight into the building of human soft tissue organ blocks.

摘要：一些鸟类的脖颈具有出色的柔性弯曲能力,模仿其特性可以设计仿生机器人.该类仿生设计的主要挑战是如何处理鸟类脖颈固有的灵活性和冗余的自由度.本文以鸡的脖颈结构为例,提出了一种模仿其脖颈结构特征的仿生超冗余机器人的设计方法.在我们的设计中,首先研究鸡脖颈的多骨节连接与运动特性,并定义了一个具有弹簧和万向节组合的仿生椎骨单元(BVU)来模拟鸡脖颈结构.然后,由三根钢丝平行驱动的三个仿生椎骨单元形成单个颈椎节段.最后,连接四个相同的颈椎节段构成了所提出的仿生超冗余机器人.结合几何分析法和Denavit-Hartemberg(D-H)参数法,研究了仿生超冗余机器人的驱动空间、关节空间和任务空间的运动学关系.通过蒙特卡洛方法进一步计算了可达工作空间.此外,原型样机的单平面运动实验的最大位置偏差约为四个颈椎节段总长度的5.8%.同时,一系列空间形状的展示,包括S形仿生弯曲配置和对兴趣目标体的成功缠绕和提升,证明了所提出的设计方法的有效性、机器人具有优异的灵活性和应用潜力.

摘要：For a series plug-in hybrid electric vehicle,higher working efficiency can be achieved by the drive system with two small motors in parallel than that with one big motor ***,the overly complex structure will inevitably lead to a substantial increase in the development *** improve the system price-performance ratio,a new kind of series-parallel hybrid system evolved from the series plug-in hybrid system is *** to the technical parameters of the selected components,the system model is established,and the vehicle dynamic property and pure electric drive economy are *** on the dynamic programming,the energy management strategy for the drive system under the city driving cycle is developed,and the superiority validation of the system is *** the studied vehicle driven by the designed series-parallel plug-in hybrid system,compared with the one driven by the described series plug-in hybrid system,the dynamic property is significantly improved because of the multi-power coupling,and the fuel consumption is reduced by 11.4%with 10 city driving *** a word,with the flexible configuration of the designed hybrid system and the optimized control strategy of the energy management,the vehicle performance can be obviously improved.

摘要：The availability equivalence of different designs for a repairable multi-state series-parallel system(RMSPS) is discussed in this *** system components are assumed to be independent,and their failure and repair rates to be *** system availability is defined as the ability of the system to satisfy consumer *** improvement method and standby redundancy method are used to improve the system *** evaluate availability of the both original and improved systems,a fast technique,based on universal generating function,is *** availability equivalence factor is introduced to compare different system *** types of availability equivalence factors of the system are derived.A numerical example is provided to illustrate how to utilize the obtained results.

摘要：By using a plane wave expansion method, some important cobweb cladding structure are analysed. Taking a dielectric parameters of designing the hollow-core fibre with material PMMA, for example, the tolerance of the parameters is discussed. The results show that the parameters of the structure possess oneself of a regularity and limit, and have a larger tolerance for the structural parameters in fabrication.

摘要：The experimental die apparatus of the solid granules medium forming on sheet metal was designed and *** parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully trial-produced as *** to the analysis of the changing trends of the cross-section shape and the wall thickness during the process,it can be found that the shape of the free deformation zone of the sheet metal,which is the most critical thinning area,can be described as an approximately spherical *** to this forming feature,back pressure deep drawing technology with solid granules medium on sheet metal was proposed to restrain drastic thinning at the bottom of the part through the joint friction effect of solid granules medium,the back pressure tringle and the sheet ***,the deep drawing limit of the sheet metal is significantly *** order to fabricate thin-walled rotary parts with great drawing ratio and complex cross-sections,a finite element model based on the material property test of the solid granules medium was established to optimize the scheme of the back pressure deep *** effects on the forming performance of sheet metal from back pressure load and the approach of blank holding control were analyzed through this model.

摘要：由于双足机器人有着强非线性和非光滑性的响应特性,为双足机器人设计高性能的步态控制器依旧是一个开放的研究领域.为了克服这些挑战,本文首先提出了一个包含躯干,并考虑碰撞与摩擦的三连杆双足机器人模型.随后,采用双延迟深度确定性策略梯度算法为该机器人设计了强化学习控制器.为了同时在下坡和上坡中实现节能周期步态,本文基于庞家莱截面法和幂函数构建了能为控制器提供学习指引的奖励函数.因此,所提出的控制器能够在不依赖于预先设计的参考轨迹或嵌入的不稳定周期步态的情况下,学会自适应输出精确的余弦力矩来实现控制目标.通过和神经网络比例微分控制器的对比研究表明,在不同的斜坡上,所提出的强化学习控制器均能实现精确、高效的周期步态,并具有较强的适应性和鲁棒性.