椭圆声学超材料模型构建与带隙分析

通过在一个元胞内引入多个椭圆散射体可以构成多振子椭圆声学超材料,本文研究了椭圆散射体不同排列方式下振子间的耦合作用,以及这种耦合作用对能带结构的影响,并通过对振动模态的研究阐明了带隙产生的物理机制。研究表明,当散射体为椭圆时,相同散射体不同的排列方式对应不同的能带结构,带隙结构与椭圆散射体的数量以及散射体之间的耦合相关,随着散射体数量增加带隙结构将趋于一致

新型压电导电材料阻尼特性研究

采用共混法以环氧树脂为基体,PMN为压电相,分别添加不同质量分数的铜粉、铝粉、碳纳米管、石墨以及两相混合物作为导电相,制备压电导电复合材料,探究不同导电相对压电导电材料阻尼特性的影响。实验结果表明:当Al含量为20%时,Al/PMN/Epoxy复合材料损耗因子峰值达到0.78,明显优于添加其他相的压电导电阻尼材料

用DDES方法对凹腔火焰稳定的研究

本文采用数值模拟的方法对超燃冲压发动机凹腔的稳焰进行研究。采用DDES(DelayedDetached –Eddy Simulation)湍流模型和有限速率化学反应来模拟来流Ma 数为2.5 的超燃冲压发动机凹腔内的稳焰过程。数值结果展示了凹腔内燃烧的过程，本文基于此将探讨凹腔内的稳焰机制以及凹腔内燃烧状态下激波和剪切层的相互作用

用RANS 方法对凹腔支板组合的三维模拟

本文用RANS 方法在本实验室设计超燃冲压发动机模型上对一种新型凹腔支板组合进行模拟。讨论了该凹腔支板组合下冷流和燃烧对湍流流场的影响，并比较了不同喷孔和支板的相对位置得对燃烧的影响。结果表明，无燃烧流场三维效应明显，有燃烧流场燃料效率较高，但未实现凹腔支板组合的匹配，若燃料的注入与支板凹腔稳焰组合达到较好的匹配，有利于控制燃烧室内释热分布

H-S管对超声速欠膨胀自由射流的激励

将激励装置Hartmann-Sprenger(H-S)管集成到传统物超声速射流装置中,来激励射流剪切层中的大尺度结构,并利用纹影成像对其进行实验研究.通过对瞬态纹影图和时均纹影图的分析表明有激励射流可以有效增大射流的扩散宽度,并且在2.2kHz以上激励频率的情况下均有明显的激励效果,扩散宽度相对于无激励情况,增大了近70%

Industrial Ｒobot Components Assembly Based on Machine Vision Technology

为了实现机器人生产线上零部件的自动化装配,对机器视觉在工业机器人底座与一轴减速器装配中的应用进行了研究。针对底座位姿识别,提出了基于Hough变换的底座表面圆形特征识别算法。针对减速器在相机视场中因为镜头曲率原因无法通过圆识别检测其外侧安装孔的问题,提出了基于链码的姿态识别算法。分析了视觉算法库Open CV中的摄像机模型。最后通过实验对视觉算法进行了验证,实验结果表明视觉算法稳定、可靠,配合高精度大负载工业机器人的应用,实现了底座与减速器的智能装配

USING AUTOMATIC DIFFERENTIATION IN THE OPTIMIZATION of XIAMEN SofTWARE

比起有限差分方法来,运用自动微分方法计算函数的梯度在计算时间和计算精度方面都具有明显的优势.使用伴随模式计算函数的梯度,在XIAMEn软件优化中得到了明显的加速效果.使用Adg系统自动生成伴随模式,大大降低了伴随模式的开发时间和难度.重点讨论了伴随模式实现的几个关键难题,并给出了几个典型应用的数值结果.Compared to the Finite Differecing method,the Automatic Differentiation method has significant advantage in terms of the running time and the computational precision.By using the adjoint model to claculate gradinents,the XIAMEN software is optimized with apperent speedup.The ADG sofware is used to automatically generate the adjoint model,which dramatically reducing the labors and the difficulty of the implementation process.Severel related techniques are discussed and several testing results are presented.国家自然科学基金项目“自动微分方法研究及其实现”(60503031;10871014);国家973项目(2004CB418304);中国科学院重要方向项目(KZCX3-SW-230)的资助

Menger Fractal Acoustic Metamaterials with Double-Negative Property

We construct new three-dimensional fractal acoustic metamaterials by adopting Menger structure, which have the double-negative property with a single structure. By adopting the finite element method and S-parameter retrieval method, the effective parameters of the acoustic metamaterials with different fractal orders are researched separately. The results show that with the increase of the fractal orders, the frequency ranges of negative effective parameters become wider. Furthermore, with the increase of the fractal order, the structure become lighter, which shows a promising application in engineering

Directional Metastable Wetting Evolution of Droplets on Artificial Patterned Microcavity Surfaces

Controllable wetting transition on artificial microtextured surfaces has significant applications in many industrial fields. In this work, the droplet spreading and the directional wetting transition are investigated on the substrate surface with the patterned microcavities. The results show that the macroscopic inward wetting transition from the periphery to the center of the droplet strongly depends on the mesoscopic sequential transition from Cassie to Wenzel state in the microcavities on the substrate surfaces. The semiquantitative relationship between sagging depth of meniscus in the microcavities and the droplet spreading velocity is set up by utilizing scaling-law analysis in terms of mechanical equilibrium of the meniscus. This finding is expected to help to clarify the issues on the mechanism and main affecting factors of the wetting transition on the patterned surface