A cooperative approach for topology control in Wireless Sensor Networks

The choice of the transmission power levels adopted in Wireless Sensor Networks (WSNs) is critical to determine the performance of the network itself in terms of energy efficiency, connectivity and spatial reuse, since it has direct impact on the physical network topology.In this paper, a cooperative, lightweight and fully distributed approach is introduced to adaptively tune the transmission power of sensors in order to match local connectivity constraints. To accurately evaluate the topology control solution, a small-scale testbed based on MicaZ sensor nodes is deployed in indoor and outdoor scenarios. Practical measures on local and multi-hop connectivity, convergence time and emitted power are used to compare the proposed approach against previous solutions. Moreover, mathematical programming formulations of the topology (power) control problem are introduced to assess the optimality of the distributed algorithm. Finally, simulation analysis complements the experimental evaluation in large-scale static and mobile WSN scenarios, where a testbed implementation becomes unfeasible.     

Imposing maximum length scale in topology optimization

This paper presents a technique for imposing maximum length scale on features in continuum topology optimization. The design domain is searched and local constraints prevent the formation of features that are larger than the prescribed maximum length scale. The technique is demonstrated in the context of structural and fluid topology optimization. Specifically, maximum length scale criterion is applied to (a) the solid phase in minimum compliance design to restrict the size of structural (load-carrying) members, and (b) the fluid (void) phase in minimum dissipated power problems to limit the size of flow channels. Solutions are shown to be near 0/1 (void/solid) topologies that satisfy the maximum length scale criterion. When combined with an existing minimum length scale methodology, the designer gains complete control over member sizes that can influence cost and manufacturability. Further, results suggest restricting maximum length scale may provide a means for influencing performance characteristics, such as redundancy in structural design.     

Keypoint Detection and Local Feature Matching for Textured 3D Face Recognition

In this study we concentrate on qualitative topological analysis of the local behavior of the space of natural images. To this end, we use a space of 3 by 3 high-contrast patches ℳ. We develop a theoretical model for the high-density 2-dimensional submanifold of ℳ showing that it has the topology of the Klein bottle. Using our topological software package PLEX we experimentally verify our theoretical conclusions. We use polynomial representation to give coordinatization to various subspaces of ℳ. We find the best-fitting embedding of the Klein bottle into the ambient space of ℳ. Our results are currently being used in developing a compression algorithm based on a Klein bottle dictionary.     

Investigation on topology of platelet-like effect-pigments in automotive surface-coatings

To investigate the interrelation between the orientation of platelet-like effect pigments in surface coatings and their coloristic properties, two metallic basecoat systems (Al, Al–blue mixture) have been deliberately blended with a colorless organic extender (nearly spherical), that allows for a systematic disturbance of the alignment of the pigment particles. As methods of investigation, goniospectrophotometry, confocal Laser-scanning microscopy, and microscopic image analysis of basecoat cross-cuts have been employed. From the reflection-indicatrix, the variation of colorimetrical quantities with deorientation agent content have been derived in a direct way. Moreover, the phase-function of the Al-pigments has been determined from fitting the equation of radiative transfer to the experimental reflection surfaces. The phase-function provides information about the distribution function of polar angles of the pigment particles in 3-dimensional space. The distribution function of the orientation angle of Al-pigments in cross-cuts of basecoats as obtained from microscopic image analysis can be satisfactorily explained within a simulation model, that allows for a calculation of the distribution function for when assuming the individual distribution functions for polar- and azimuthal-angle of the surface normal of the pigment particles, taking fully into account induced axes of anisotropy.     

Constructal tree-shaped two-phase flow for cooling a surface

This paper documents the strong relation that exists between the changing architecture of a complex flow system and the maximization of global performance under constraints. The system is a surface with uniform heating per unit area, which is cooled by a network with evaporating two-phase flow. Illustrations are based on the design of the cooling network for a skating rink. The flow structure is optimized as a sequence of building blocks, which starts with the smallest (elemental volume of fixed size), and continues with assemblies of stepwise larger sizes (first construct, second construct, etc.). The optimized flow network is tree shaped. Three features of the elemental volume are optimized: the cross-sectional shape, the elemental tube diameter, and the shape of the elemental area viewed from above. The tree that emerges at larger scales is optimized for minimal amount of header material and fixed pressure drop. The optimal number of constituents in each new (larger) construct decreases as the size and complexity of the construct increase. Constructs of various levels of complexity compete: the paper shows how to select the optimal flow structure subject to fixed size (cooled surface), pressure drop and amount of header material.     

周期性圆环结构的拓扑优化设计

基于拓扑优化方法开展了周期性圆环结构的构型优化设计,分析了不同载荷工况下不同子结构数、内外半径比和内外蒙皮厚度对优化结果的影响规律。结果表明:周期性圆环结构具有明显的尺寸效应;相同体分比下,子结构数较少时优化结构刚度较高,但优化构型变动大;随着子结构数增多,结构刚度减弱并趋于极限值,优化构型稳定不变且受内外半径比和蒙皮厚度变化影响很小;而不同工况下,可忽略尺寸效应的临界子结构数存在差异,蒙皮厚度变化对结构效率的影响不同。     

某发射塔起重机悬臂梁结构拓扑优化设计

基于有限元理论和拓扑优化方法,以某航天发射塔起重机悬臂梁为研究对象,以刚度值的质量控制为目标,通过理论建模、静力学计算和拓扑计算对悬臂梁进行质量优化,经对比分析确定最优结构形式。结果表明：优化后的结构性能和经济性能满足工程要求。目前该设计已经在工程实践中成功应用。     

机械系统拓扑结构的通用表达模型设计

提出了一种适用于机械系统的通用拓扑模型——环基树拓扑结构模型 ,研究了环基树的性质及自动生成算法 ,介绍了运动和力的拓扑表等概念 ,给出了两个基于环基树结构的通用自由度计算公式。研究结果为机械系统的计算机表达、管理、维护和加工提供了统一机制 ,构成了机械系统计算机辅助装配和性能分析统一建模的重要基础