STUDY ON PARAMETERS FOR TOPOLOGICAL VARIABLES FIELD INTERPOLATED BY MOVING LEAST SQUARE APPROXIMATION

This paper presents a new approach to the structural topology optimization of continuum structures. Material-point independent variables are presented to illustrate the existence condition,or inexistence of the material points and their vicinity instead of elements or nodes in popular topology optimization methods. Topological variables field is constructed by moving least square approximation which is used as a shape function in the meshless method. Combined with finite element analyses,not only checkerboard patterns and mesh-dependence phenomena are overcome by this continuous and smooth topological variables field,but also the locations and numbers of topological variables can be arbitrary. Parameters including the number of quadrature points,scaling parameter,weight function and so on upon optimum topological configurations are discussed. Two classic topology optimization problems are solved successfully by the proposed method. The method is found robust and no numerical instabilities are found with proper parameters.     

宁波服装博物馆设计方案探析

分析了小型专题博物馆在国内外的发展特点和趋势;针对宁波服装博物馆项目的设计实践,从地域文化、空间形态、展陈互动结合、传统现代结合等几个方面提出了小型专题博物馆的创新设计理念和设计方法.     

Three-dimensional interfacial wave theory of dendritic growth： （Ⅰ）. multiple variables expansion solutions

Dendritic pattern formation at the interface between liquid and solid is a commonly observed phenomenon in crystal growth and solidification process. The theoretical investigation of dendritic growth is one of the most profound and highly challenging subjects in the broad areas of interfacial pattern formation, condensed matter physics and materials science, preoccupying many researchers from various areas. Some longstanding key issues on this subject finally gained a breakthrough in the late of last century, via the `{Interfacial Wave} (IFW) Theory' on the ground of systematical global stability analysis of the basic state of dendritic growth. The original form of the IFW theory mainly focus on the investigation of various axi-symmetric unsteady perturbed modes solutions around the axi-symmetric basic state of system of dendritic growth. In reality, the system may allow various non-axi-symmetric, unsteady perturbed states. Whether or not the system of dendritic growth allows some growing non-axi-symmetric modes? Will the stationary dendritic pattern be destroyed by some of such non-axi-symmetric modes? Or, in one word, what is the stability property of the system, once the non-axi-symmetric modes can be evoked? The answers for these questions are important for the solid foundation of IFW theory. The present work attempts to settle down these issues and develop a three-dimensional (3D) interfacial wave theory of dendritic growth. Our investigations verify that dendritic growth indeed allows a discrete set of non-axi-symmetric unstable global wave modes, which gives rise to a set of multiple arms spiral waves propagating along the Ivantsov's paraboloid.     

Sexually transmitted infections and the marriage problem

We study an SIS epidemiological model for a sexually transmitted infection in a monogamous population where the formation and breaking of couples is governed by individual preferences. The mechanism of couple recombination is based on the so-called bar dynamics for the marriage problem. We compare the results with those of random recombination – where no individual preferences exist – for which we calculate analytically the infection incidence and the endemic threshold. We find that individual preferences give rise to a large dispersion in the average duration of different couples, causing substantial changes in the incidence of the infection and in the endemic threshold. Our analysis yields also new results on the bar dynamics, that may be of interest beyond the field of epidemiological models.     

电磁驱动大尺寸MEMS扫描镜的研究

基于微机电系统工艺,设计并制作了一种电磁驱动大尺寸的二维扫描振镜.分析了两种不同的电磁驱动方式产生的力的大小,选择驱动力较大的双极子方式作为驱动.运用有限元法模拟了器件的谐振频率静态及动态响应,仿真结果与实际测得的结果一致.描述了振镜的工艺流程及封装方式,并制备了振镜.实验测得振镜在120mA静态电流驱动下,慢轴和快轴分别能达到的最大转角为±4.5°及±5°,慢轴及快轴的谐振频率分别为348Hz及660Hz,并得到在此谐振频率下的李萨如图形.将器件用于激光成像系统之中,使得散斑对比度下降到4.2%,激光成像质量得到很大提升.     

高分辨率CMOS相机沿轨长条带钟摆式搜索成像设计

为实现面阵相机对沿轨方向长条带区域一定重叠率的推凝视成像,设计了高分辨CMOS传感器的钟摆式搜索成像模型.通过长条带逐层区域划分和成像重叠率渐近变化构建,计算了钟摆式搜索成像参量和卫星实时推凝指向姿态,并利用多次小幅逼近的PD控制器分析了搜索成像姿态控制精度与成像像移失配量.利用高分CMOS原理样机和小卫星姿控仿真平台对P5型曲面LED靶标系统进行地面等比缩放的长条带钟摆式搜索成像仿真试验.结果表明:帧间重叠率大于85%的钟摆式搜索成像比全凝视成像区域扩大了4倍;控制周期为10 Hz时,其姿态控制精度优于0.05°,姿态稳定度优于0.003°/s,搜索成像对应的图像传递函数能够达到0.141 1.     

快速城市化背景下宁波北仑绿地系统演化及生态服务响应

城市绿地是城市自然生态系统的重要组成部分, 我国东南沿海地区是城市化速度最快的区域之一, 快速城市化导致建设用地的大量增加, 并引起区域绿地景观格局及生态价值的显著变化. 本文选取东南沿海中部的宁波市北仑区为研究区域, 以其1990、1995、2000、2005、2010和2015年6期土地利用变化数据为基础提取绿地, 借助ArcGIS和Fragstats软件, 应用景观生态学方法和基于专家知识的生态系统服务价值化方法对快速城市化背景下北仑区绿地景观动态演化及其生态价值变化进行了研究. 结果表明: (1)绿地是北仑区的主要景观类型, 1990~2015年间快速城市化导致北仑区1406hm2绿地转化为建设用地; (2)北仑区绿地景观异质性减弱, 趋于集中式发展, 整体破碎度降低; (3)截止2015年, 绿地的生态服务价值总量比1990年减少了6%, 生态环境出现恶化, 主要是建设用地占用绿地导致生态总价值下降; (4)北仑区绿地系统生态价值等级由中心向外围降低呈不规则环状, 且高价值区逐渐向东南方向减少并转变为较低价值区.     

Background and amplitude encoded fringe patterns for 3D surface-shape measurement

This paper presents a new fringe projection method for surface-shape measurement that uses background and amplitude encoded high-frequency fringe patterns. The background and amplitude, combined as a codeword, identify the wrapped phase fringe order to partially unwrap the phase to a low frequency. The low-frequency wrapped phase map is then directly used to reconstruct the surface based on geometry constraints without requiring additional images as in other temporal phase-unwrapping methods. Measurements performed on a double-hemisphere, mask, and manikin head, using projected fringe patterns with 48 periods, demonstrated the ability of the method to perform 3D shape measurement with only four projected patterns and captured images, using a single camera and projector.     

基于Quickbird影像的中小城市绿地景观格局分析——以乐清市为例

摘要：基于2009年Quickbird影像数据解译获得的乐清市城区绿地分布图,在GIS的支持下,运用景观生态学的原理和方法,对城区绿地景观格局进行了较系统的分析.结果表明：绿地景观结构不尽合理,以公园绿地为优势类型,道路绿地与居住绿地明显偏少;全区绿地多样性指数偏低,绿地类型不够丰富;绿地景观整体破碎度较高,其中新区的破碎度高于老区;绿地斑块分维数偏低,斑块形状较规则,缺乏自然形状,人工痕迹较重.论文对分析结果进行了讨论,并针对上述问题提出了相应的对策和建议,以期能为其他中小城市绿地格局分析与绿地建设提供参考.     

A theory on constructing blocked two-level designs with general minimum lower order confounding

Completely random allocation of the treatment combinations to the experimental units is appropriate only if the experimental units are homogeneous. Such homogeneity may not always be guaranteed when the size of the experiment is relatively large. Suitably partitioning inhomogeneous units into homogeneous groups, known as blocks, is a practical design strategy. How to partition the experimental units for a given design is an important issue. The blocked general minimum lower order confounding is a new criterion for selecting blocked designs. With the help of doubling theory and second order saturated design, we present a theory on constructing optimal blocked designs under the blocked general minimum lower order confounding criterion.