A level set method for structural topology optimization with multi-constraints and multi-materials

Combining the vector level set model, the shape sensitivity analysis theory with the gradient projection technique, a level set method for topology optimization with multi-constraints and multi-materials is presented in this paper. The method implicitly describes structural material interfaces by the vector level set and achieves the optimal shape and topology through the continuous evolution of the material interfaces in the structure. In order to increase computational efficiency for a fast convergence, an appropriate nonlinear speed mapping is established in the tangential space of the active constraints. Meanwhile, in order to overcome the numerical instability of general topology optimization problems, the regularization with the mean curvature flow is utilized to maintain the interface smoothness during the optimization process. The numerical examples demonstrate that the approach possesses a good flexibility in handling topological changes and gives an interface representation in a high fidelity, compared with other methods based on explicit boundary variations in the literature. The project supported by the National Natural Science Foundation of China (59805001, 10332010) and Key Science and Technology Research Project of Ministry of Education of China (No.104060)     

无穷大周期加筋微穿孔板结构振动响应及吸声特性

研究在平面声波斜入射情况下,无穷大双周期加筋的微穿孔薄板结构的振动响应及吸声性能.首先在马大猷和Takahashi微穿孔板声学理论基础上,建立了微穿孔加筋薄板结构振动的半解析模型;然后应用傅里叶变换及空间波数分析方法,将周期加筋微穿孔薄板的振动位移及辐射声压表示为频域内波数的分量迭加形式;最后通过对波数分量进行求解,并利用傅里叶逆变换得到双周期加筋的微穿孔薄板的振动响应及吸声系数表达式.计算结果表明,薄板的弯曲振动在水中对吸声的影响较大,空气中仅对轻质穿孔板的低频吸声效果有一定影响;同时微穿孔率对周期加筋薄板吸声系数的影响明显,通过改变穿孔率和加筋周期等可有效地提高水中微穿孔薄板结构的吸声性能.     

扩张的圈Schr?dinger-Virasoro代数的二上同调群

本文研究了扩张的圈Schr?dinger-Virasoro代数,给出了这类李代数的所有二上同调群,同时得到了这类李代数的所有泛中心扩张.     

多维不可微平稳正态过程的极值

讨论了强相关多维不可微平稳正态过程的渐进性质 ,给出了其最大值的极限分布     

与函数周期性有关的两类问题

函数的图象与性质是高中数学的重点内容,也是函数知识与解析几何知识的交汇点,2001年全国高考数学压卷题就是涉及函数奇偶性、对称性、周期性、数列、数列极限等的综合题,本文就与函数周期性有关的两类问题作一些探讨.     

磁控溅射制备本征ZnO/Ag/ZnO透明导电薄膜的性质研究

室温下采用射频磁控溅射氧化锌（ZnO）粉末靶、银（Ag）靶,在玻璃衬底上制备ZnO/Ag/ZnO透明导电薄膜。首先,ZnO厚度为30 nm时,改变Ag厚度制备3层透明导电薄膜,研究Ag层厚度及膜层间配比对光电性能的影响;其次,按ZnO∶Ag厚度比为30∶11比例制备不同厚度的3层透明导电薄膜,研究多层厚度对薄膜光电性能的影响。结果表明：Ag厚度为8 nm及11 nm的ZnO/Ag/ZnO表面相对平整,结晶程度较好,在可见光范围内最高透过率达到90%及86%,并且方块电阻为6 Ω/□及3.20 Ω/□,具有优良的光电性;当按配比制备ZnO/Ag/ZnO 3层膜时,增加ZnO厚度对Ag层的增透作用反而减弱,同时增加Ag层厚度也会降低3层薄膜的整体光学性。     

Complete Gluonic Phase in Two-Flavour Colour Superconductivity

We study a typical complete gluonic phase （LGP） in two-flavour colour superconductivity （2SC） by calculating the essential cubic and quartic interfering term between the gluonic condensates （Az^（8）） and/Az^（6）） with a gauged NJL model. It is proven that the coefficients of the cubic interfering term and the vacuum contributions of the cubic and quartic interfering term are all equal to zeroes. The coefficients of the quartic interfering term and the /Az^（6）） ＇s quartic self-interaction term at stationary points of Larkin-Ovchinnikov-Fulde-Ferrell （LOFF） phase are calculated. Comparisons among the effective potentials of LOP, g2SC and LOFF phase indicate that LOP could be the genuine ground state of 2SC for some reasonable paxameters.     

高效半解析方法分析周期正交加筋板的振动-声辐射特性

为了对水下无穷大双周期正交加筋板结构模型在简谐面力激励下的振动响应及声辐射特性进行更为合理的理论预测与分析,建立了加筋板结构的数学模型。结合傅里叶变换、泊松迭加公式及空间波数法,将周期加筋板的振动响应及辐射声压表达为关于结构位移谐波分量的函数方程,对加筋板模型提出了高效分析求解方法并进行了谐波分量截断求解。验证了方法的正确性,并分析了结构的振动特性以及加强筋周期间距和扭矩对辐射声压的影响。结果表明,加强筋的扭转作用影响加筋板结构的振动模态频率,对于较高精度要求的工程应用,加强筋的扭转作用不能忽略。通过调节加强筋周期间距及横截面尺寸,可以降低薄板在较低频域区间的远场辐射声压。     

97MeV 16O+51V反应中α粒子与类弹产物的关联测量

测量了α粒子与类弹产物的关联,得到的α粒子符合能谱呈现出类弹、类靶相继发射的特征;α粒子与类弹产物¹²C的关联表明了弹核破裂(break-up)机制的存在.在类弹产物探测方向附近,观察到核的阴影效应.