Issues in the scaling of multi-robot systems for general problem solving

Problem solving using multi-agent robotic systems has received significant attention in recent research. Complex strategies are required to organize and control these systems. Biological-inspired methodologies are often employed to bypass this complexity, e.g. self-organization. However, another line of research is to understand the relationship between low-level behaviors and complex high-level strategies. In this paper, we focus on understanding the interference caused in multi-robotic systems for the problem of search and tagging. Given a set of targets that must be found and tagged by a set of robots, what are the effects of scaling the number of robots and sensor ranges? Intuitively, increasing robot numbers, or sensor strength would seem beneficial. However, experience suggests that path and sensor interference caused by increased robots, increased targets, and sensor range will be harmful. The following investigation uses several abstract models to elucidate the issues of robot scaling and sensor noise.     

Spectral Network (SpecNet)—What is it and why do we need it?

Effective integration of optical remote sensing with flux measurements across multiple scales is essential for understanding global patterns of surface-atmosphere fluxes of carbon and water vapor. SpecNet (Spectral Network) is an international network of cooperating investigators and sites linking optical measurements with flux sampling for the purpose of improving our understanding of the controls on these fluxes. An additional goal is to characterize disturbance impacts on surface-atmosphere fluxes. To reach these goals, key SpecNet objectives include the exploration of scaling issues, development of novel sampling tools, standardization and intercomparison of sampling methods, development of models and statistical methods that relate optical sampling to fluxes, exploration of component fluxes, validation of satellite products, and development of an informatics approach that integrates disparate data sources across scales. Examples of these themes are summarized in this review.     

基于软实时多处理器系统的动态低功耗算法

结合DVS技术和(m,k)-firm模型，提出一个保证完成率、适用于软实时多电压多处理器系统中有依赖关系任务集的动态低功耗算法VAP_DY。该算法权衡应用的性能需求、执行时间的不确定性和系统对合理执行失败的容忍来动态调整每个处理器运行时的供电电压,以降低多处理器系统的总功耗。分析和实验结果表明，VAP_DY能够在保证时间和完成率约束的条件下有效降低系统功耗。     

Scaling of cylindrical shells under axial impact

A technique of correcting scaled strain rate sensitive structures subject to dynamic loads is described and applied to a shell under axial impact. The prototype and models responses were simulated using finite element method. Final deformed shape, collapse mode, displacement at the top of the shell and maximum force of scaled models are compared to the respective prototype. It is shown that the models response are quite different from the prototype if no correction is performed. By correcting the initial impact velocity, the models scale quite well and it is even possible to obtain the transition phenomenon between global and progressive buckling of shells subject to the axial impact of a mass.     

Scaling law for penetration depth in laser welding

A simple scaling law for penetration depth in laser welding is proposed considering heat flow characteristics and multiple reflections. First, a process parameter is identified that is proportional to the surface temperature during laser processing, and the parameter is modified by accounting for the effect of multiple reflections. As a result, the normalized penetration depth is expressed as a function of a single parameter that is a combination of laser intensity, interaction time and an indicator of the strength of multiple reflections. The obtained scaling law is applicable not only to conduction mode welding but also to keyhole mode welding, and provides insight into why and how penetration depth changes in a particular way. Systematic and extensive welding experiments were conducted using a 2 kW multi-mode fiber laser and two types of steels. The experimental results were in good agreement with the proposed scaling law.     

Nanoscale periodic and faceted structures formation on Si(1 0 0) by oblique angle oxygen ion sputtering

The dynamics of ripple topography on silicon surfaces generated by oxygen ion bombardment with increasing fluences have been investigated by atomic force microscopy (AFM). At the early stages of sputtering, periodic ripples with the wave vector parallel to ion beam direction are developed. At the late stages of sputtering, the ripple structure tends to break down and the surface becomes faceted. The growth rate of the ripples and the scaling exponents of the faceted surface have been determined. The results are discussed with reference to the Bradley–Harper theory and its nonlinear extension. Finally, the ripple wavelength is found to be a linear function of the bombarding energy.     

含引发机制的A_(f-)A_g型缩聚反应的标度研究

讨论了含引发机制的Af-Ag型缩聚反应体系,根据该反应体系的数量分布函数,导出凝胶点附近分布函数和高分子矩的渐进表示式,进一步应用标度变换,得到了描述溶胶-凝胶相变的广义标度律,揭示出含引发机制的Af-Ag型缩聚反应体系的固化过程是一个相变过程。     

Simulation support for performance assessment of building components

The determination of performance metrics for novel building components requires that the tests are conducted in the outdoor environment. It is usually difficult to do this when the components are located in a full-scale building because of the difficulty in controlling the experiments. Test cells allow the components to be tested in realistic, but controlled, conditions. High-quality outdoor experiments and identification analysis methods can be used to determine key parameters that quantify performance. This is important for achieving standardised metrics that characterise the building component of interest, whether it is a passive solar component such as a ventilated window, or an active component such as a hybrid photovoltaic module.     

Feed water pretreatment for desalination plants

Effective membrane pretreatment is a crucial requirement for trouble free and cost effective RO desalination. Pretreatment construction costs are significant and may reach as much as 10%-20% of the total desalination plant capital costs. This paper presents a general review of the central factors involved in assessing raw water quality. The main foulant categories are described and the various unit operations commonly applied are reviewed. Pretreatment aspects of desalination offer fertile grounds for advancing desalination technologies. Promising research directions are highlighted.