A Grid as Smart as the Internet

A new era of electricity is dawning that combines the decarbonization of the grid with the extensive electrification of all sectors of society. A grid as smart as the internet is needed to harness the full potential of renewables, accommodate technology disruptions, embrace the rise of prosumers, and seamlessly integrate nano-, mini-, and micro-grids. The internet is built upon a layered architecture that facilitates technology innovations, and its intelligence is distributed throughout a hierarchy of networks. Fundamental differences between data flows and power flows are examined. The current operating paradigm of the grid is based on the conviction that a centralized grid operator is necessary to maintain instantaneous power balance on the grid. A new distributed paradigm can be realized by distributing this responsibility to sub-grids and requiring each sub-grid to maintain its net power balance. A grid as smart as the internet based on this new paradigm, as well as a hierarchical network structure and a layered architecture of operating principles, is presented.     

A 'green' chitosan-silver nanoparticle composite as a heterogeneous as well as micro-heterogeneous catalyst

In this paper, we report on the catalytic activity of a new metal nanoparticle-polymer composite consisting of Ag nanoparticles (NPs) and environmentally friendly ('green') chitosan. The polymer (chitosan) not only acted as the reducing agent for the metal ions, but also stabilized the product NPs by anchoring them. The majority of the particles produced in this way had sizes less than 5?nm. The catalytic activity of the composite was investigated photometrically by monitoring the reduction of 4-nitrophenol (4NP) in the presence of excess NaBH(4) in water, under both heterogeneous and micro-heterogeneous conditions. The reaction was first order with respect to the concentration of 4NP. We also observed that the apparent rate constant, k(app), for the reaction was linearly dependent on the amount of Ag NPs present in the composite. Moreover, the turn-over frequency (TOF) of the catalyst was found to be (1.5 ± 0.3) × 10(-3)?s(-1), when the reaction was carried out under heterogeneous conditions. The Ag NPs in the composite retained their catalytic activities even after using them for ten cycles. Our observations also suggest that the catalytic efficiency under micro-heterogeneous conditions is much higher than under heterogeneous conditions. Thus the composite we have represents an ideal case of an environmentally friendly and stable catalyst, which works under heterogeneous as well as micro-heterogeneous conditions with the advantage of nanoscopic particles as the catalyst.     

Mission success with components not as good as new

It is shown how the probability of mission success can be determined for cases of components which are not as good as new at the beginning of a mission and are not repaired during the mission. After a short definition of the appropriate conditional distribution functions of components lives, a few typical examples of plausible missions for redundant systems are discussed. Among these are such that are time-critical or—concerning flights—space-critical. Since only (advanced) probabilistic reasoning is used, there are no limitations as to the types of life distributions.     

凝胶成型法制备多孔羟基磷灰石生物陶瓷及其性能研究

介绍了一种新型的凝胶成型法来制备多孔羟基磷灰石支架材料.利用体视显微镜等对制备的多孔羟基磷灰石孔洞结构进行观察.结果表明这种方法可以很好地控制多孔支架材料的孔洞结构与大小.孔分布均匀且内部连通,孔径在300μm～500μm之间.体外模拟试验表明羟基磷灰石具有良好的生物相容性,这种孔洞结构的特点更有利于骨细胞的生长.对压缩性能和孔隙率的测定结果表明,压缩强度和孔隙率随不同工艺参数的变化而变化.     

Designer as chameleon

The roles adopted by a design engineer during a design project are examined. The case for ‘role switching’ is presented, and the different roles are described where some relate to particular phases of the design process and others are more general. Situations likely to cause ‘role overload’ are explored for single and multiple projects, and the paper demonstrates that the complexity of the design process is wholly misrepresented by the common ‘drawing office image’.     

Materials as Machines

Machines are systems that harness input power to extend or advance function. Fundamentally, machines are based on the integration of materials with mechanisms to accomplish tasks—such as generating motion or lifting an object. An emerging research paradigm is the design, synthesis, and integration of responsive materials within or as machines. Herein, a particular focus is the integration of responsive materials to enable robotic (machine) functions such as gripping, lifting, or motility (walking, crawling, swimming, and flying). Key functional considerations of responsive materials in machine implementations are response time, cyclability (frequency and ruggedness), sizing, payload capacity, amenability to mechanical programming, performance in extreme environments, and autonomy. This review summarizes the material transformation mechanisms, mechanical design, and robotic integration of responsive materials including shape memory alloys (SMAs), piezoelectrics, dielectric elastomer actuators (DEAs), ionic electroactive polymers (IEAPs), pneumatics and hydraulics systems, shape memory polymers (SMPs), hydrogels, and liquid crystalline elastomers (LCEs) and networks (LCNs). Structural and geometrical fabrication of these materials as wires, coils, films, tubes, cones, unimorphs, bimorphs, and printed elements enables differentiated mechanical responses and consistently enables and extends functional use.     

Injury as disease

Consideration of injury as disease is an arbitrary distinction that nonetheless may have some utility. The disease concept includes the understanding that the agents and mechanisms of human/environmental interaction for injury causation are similar to those for many of the chronic diseases, with differences in the timing rather than the agent or mechanism of the transmission. As with other aspects of medical practice, injury control requires careful and knowledgeable epidemiologic, technological, psychological and social planning, and equally careful and knowledgeable attention to proper evaluation of intervention programs. Such evaluation has rarely been attempted with behavioral interventions but has been carried out somewhat more often with environmental countermeasures. Evaluation of both costs and benefits must include attention to factors that often cannot be measured in economic terms and that may differ not only in degree but in kind. Therefore, no methods for comparability may exist at this time for some of these costs and effects.