基于特征值分析的多尺度结构优化设计方法

基于特征值分析，提出了多尺度结构优化设计方法.该方法被用于分析宏观结构上作用有最不利荷载时，使宏观结构刚度最大的宏观拓扑结构和微观材料分布.引入约束条件为最不利荷载的Euclid范数等于1，根据Rayleigh-Ritz定理，可以将结构的柔顺度转换为一个与局部荷载向量维数相同的对称矩阵，这样就将作用有最不利荷载的柔顺度最小问题转换为求解对称矩阵的最大特征值最小问题，同时最不利荷载可以通过最大特征值矩阵的特征向量求得.最后通过算例验证所提多尺度结构优化设计方法的有效性，并说明宏观拓扑结构和微观材料分布的合理性.所提出的多尺度优化方法具有迭代稳定、收敛迅速等特点.该文拓扑优化中密度函数的更新是基于灵敏度分析和移动渐近线方法（method of moving asymptotes，MMA）.     

科学家首次研制出五模式超常材料

超常材料(Metamaterials)是指一类拥有天然材料所不具备物理性质的新型人工材料。研究证明,以恰当方式修改材料的宏观结构可以在一定程度上突破表观物理规律的限制,实现负折射率、超吸收、各向异性等超凡特性。科学家于1995年提出五模式[1](Pentamode,penta在古希腊语中有"5"之意)超常材料的设想,他们将弹性材料刚度矩阵     

云模式的航空应用探讨

以中尺度数值模式为动力框架与显式方案的云模式耦合，对云场的宏观分布和云中水含量，云粒子谱分布进行模拟，进而探讨其在航空方面的应用。     

Characterization of various structures in gas-solid fluidized beds by recurrence quantification analysis

Gas-solid fluidized beds are widely considered as nonlinear and chaotic dynamic systems. Pressure fluc- tuations were measured in a fluidized bed of 0.15 m in diameter and were analyzed using multiple approaches： discrete Fourier transform （DFT）, discrete wavelet transform （DWT）, and nonlinear recur- rence quantification analysis （RQA）. Three different methods proposed that the complex dynamics of a fluidized bed system can be presented as macro, meso and micro structures. It was found from DFT and DWT that a minimum in wide band energy with an increase in the velocity corresponds to the transition between macro structures and finer structures of the fluidization system. Corresponding transition veloc- ity occurs at gas velocities of 0.3, 0.5 and 0.6 m]s for sands with mean diameters of 150, 280 and 490/~m, respectively. DFT, DWT, and RQA could determine frequency range of0-3.125 Hz for macro, 3. ! 25-50 Hz for meso, and 50-200 Hz for micro structures. The RQA showed that the micro structures have the least periodicity and consequently their determinism and laminarity are the lowest. The results show that a combination of DFT, DWT, and RQA can be used as an effective approach to characterize multi-scale flow behavior in gas-solid fluidized beds.     

Preparing three-dimensional graphene architectures： Review of recent developments

The recent development of synthesis processes to assemble graphene sheets into porous three-dimensional （3D）macroscopic structures are reviewed, including our efforts on 3D graphene structures. Mechanisms for building 3D graphene architectures and their composite materials are also summarized. The functional systems based on 3D graphene architectures provide a significant enhancement in the efficacy due to their unique structures and properties.     

光纤扰动入侵检测技术

光纤中通过一定幅值恒定的光，当有外界扰动如振动、弯曲、挤压时，光纤中光的强度将随外界扰动而变化。外界扰动对光纤中光通量的影响主要是微扰损耗，即由光纤的几何不均匀性引起损耗，如宏观结构上折射率和直径的不均匀性、微弯损耗等。由光纤传输理论，这种不均匀性引起的耗损或以散射形式出现或以模式耦合的形式出现。     

化学化工中结构的多层次和多尺度研究方法

多尺度的术语现在被广泛地使用 ,例如Ｖｉｌｌｅｍａｕｘ[1] 提出计算化学工程的多尺度应用 ,Ｌｅｒｏｕ[2 ] 和Ｎｇ的文章“化学反应工程 ,研究多目标任务的多尺度方法”等 ,但不同学者所认同的“尺度”的含义可能并不相同。对于从事化学和化工的人来说 ,传统上最重视的是结构、性能和制备的关系。因此 ,我们最关注的应是结构的尺度 ,或具有一定有序结构的单元的尺度。有序结构具有多层次 ,可按尺度大致区分为以下几种。　　 ( 1 )微观结构 (前纳米 ) :例如分子结构、晶胞结构。图 1是维生素Ｃ的分子结构 ,图中所标尺度是 0 .1ｎｍ ,维生素…     

Manufacturing tolerant topology optimization

In this paper we present an extension of the topology optimization method to include uncertainties during the fabrication of macro, micro and nano structures. More specifically, we consider devices that are manufactured using processes which may result in （uniformly） too thin （eroded） or too thick （dilated） structures compared to the intended topology. Examples are MEMS devices manufactured using etching processes, nano-devices manufactured using e-beam lithography or laser micro-machining and macro structures manufactured using milling processes. In the suggested robust topology optimization approach, under- and over-etching is modelled by image processing-based ＂erode＂ and ＂dilate＂ operators and the optimization problem is formulated as a worst case design problem. Applications of the method to the design of macro structures for minimum compliance and micro compliant mechanisms show that the method provides manufacturing tolerant designs with little decrease in performance. As a positive side effect the robust design formulation also eliminates the longstanding problem of one-node connected hinges in compliant mechanism design using topology optimization.     

强场非次序三重电离亚光周期动力学的研究

电子关联是自然界中的一种普遍现象,它决定了物质的宏观结构,影响着化学反应,它也是物质超导性的本质原因。因此电子关联的研究是目前的一个热点。在强场激光脉冲作用下发生双电离的原子产生的电子对体现了强烈的相关性,它为我们研究电子相关性提供了一个新的途径,近二十年来,已经被广泛的研究。作为一种更为复杂的电子关联作用,强场非次序三重电离,目前人们对它的认识还比较浅。     

控制原子非顺序双电离的新方法——双色场方法

电子关联是自然界中的一种普遍现象，它决定了物质的宏观结构，影响着化学反应，它也是物质超导性的本质原因。因此电子关联的研究是目前的一个热点。在强场激光脉冲作用下发生双电离的原子产生的电子对体现了强烈的相关性，它为我们研究电子相关性提供了一个新的途径。