The importance of orientation in proton transport of a polymer film based on an oriented self-organized columnar liquid-crystalline polyether

We prepared membranes based on a liquid-crystalline side-chain polyether obtained by chemical modification of commercial poly(epichlorohydrin) (PECH) with dendrons. This polymer exhibited a columnar structure, which could form an ion channel in the inner part. The columns were successfully oriented by taking advantage of surface interactions between the polymer and hydrophilic substrates, as confirmed by X-ray diffraction analysis (XRD), environmental scanning electron microscopy (ESEM) and optical microscopy between crossed polars (POM). Column orientation was found to be crucial for effective transport: the oriented membranes exhibited proton transport comparable to that of Nafion® N117 and no water uptake. An increase in sodium ion concentration in the feed phase suggested a proton/cation antiport. On the contrary, no proton transport was detected on unoriented membranes based on the same liquid-crystalline side-chain polyether or on unmodified PECH.     

A structure oriented compact thermal model for multiple heat source ASICs

This paper proposes a methodology for the extraction of a compact thermal model for multiple heat source devices, which can be used for estimation of the overall temperature field. This extraction is based on the physical parameters as well as on the layout and the packaging of the device. The model directly represents the regions surrounding a source by a resistance network containing the specific parameters of source and chip in analytical form, so that it is easy to vary parameters like power dissipation and thermal conductivity within a wide range. In order to obtain a good and fast approximation of the continuous case, the shape of the volume elements represented by a node in the network is chosen regarding the direction of the heat flow within these elements. Therefore these volume elements are not rectangular but pyramid- or parallelogram-like structures. The temperature fields of multiple sources add up for the total temperature distribution, by the use of a matrix field representation.     

Decentralising a service-oriented architecture

Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a self-organising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.     

Evolving strategy for a probabilistic game of imperfect information using genetic programming

We provide the complete record of methodology that let us evolve BrilliAnt, the winner of the Ant Wars contest. Ant Wars contestants are virtual ants collecting food on a grid board in the presence of a competing ant. BrilliAnt has been evolved through a competitive one-population coevolution using genetic programming and fitnessless selection. In this paper, we detail the evolutionary setup that lead to BrilliAnt’s emergence, assess its direct and indirect human-competitiveness, and describe the behavioral patterns observed in its strategy.

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Self-assembly of polymeric microspheres of complex internal structures.

Self-assembly can easily produce intricate structures that would be difficult to make by conventional fabrication means. Here, self-assembly is used to prepare multicomponent polymeric microspheres of arbitrary internal symmetries. Droplets of liquid prepolymers are printed onto a water-soluble hydrogel, and are allowed to spread and coalesce into composite patches. These patches are then immersed in an isodense liquid, which both compensates the force of gravity and dissolves the gel beneath the polymers. Subsequently, the patches fold into spheres whose internal structures are dictated by the arrangement of the droplets printed onto the surface. The spheres can be solidified either thermally or by ultraviolet radiation. We present a theoretical analysis of droplet spreading, coalescence and folding. Conditions for the stability of the folded microspheres are derived from linear stability analysis. The composite microbeads that we describe are likely to find uses in optics, colloidal self-assembly and controlled-delivery applications.     

Dynamics of the arch-type reconfigurable machine tool

Reconfigurable manufacturing systems (RMS) address challenges in modern manufacturing systems arising from product variety and from rapid changes in product demand. This paper considers an arch-type reconfigurable machine tool (RMT) that has been built to demonstrate the basic concepts of RMT design. The arch-type RMT was designed to achieve customized flexibility and includes a passive degree-of-freedom, which allows it to be reconfigured to machine a family of parts. The kinematic and dynamic capabilities of the machine are presented, including the experimental frequency response functions (FRFs) and computed stability lobes of the machine in different configurations. A comparison of FRFs and stability lobes of the arch-type RMT reveals almost similar dynamic characteristics at different reconfiguration positions. These similar characteristics arise because the dominant mode where chatter occurs is due to the spindle–tool–tool holder assembly. Consequently, to ensure consistent dynamic behavior regardless of reconfiguration, a desirable dynamic design feature for RMTs is that the machine's structural frequencies are less dominant than the structural frequencies of the spindle, tool and tool holder.     

An event routing service for distributed applications: computer telephony—a case study

This paper presents an event routing service (ERS) that represents a pattern for the establishment and processing of lightweight sessions between a source and a destination of events. It is based on the CORBA notification service. To illustrate the features of the proposed service, its application in computer telephony is discussed in detail. Most of the positive features of the ERS are inherited from the CORBA notification service, but its implementation requires a novel protocol describing the lightweight session establishment mechanism. The implementation of ERS is described and its application to routing events in a computer telephony system is presented. The paper concludes with a performance measurement study. Copyright © 2002 John Wiley & Sons, Ltd.     

Electrostatic self-assembly of macroscopic crystals using contact electrification

Self-assembly of components larger than molecules into ordered arrays is an efficient way of preparing microstructured materials with interesting mechanical and optical properties. Although crystallization of identical particles or particles of different sizes or shapes can be readily achieved, the repertoire of methods to assemble binary lattices of particles of the same sizes but with different properties is very limited. This paper describes electrostatic self-assembly of two types of macroscopic components of identical dimensions using interactions that are generated by contact electrification. The systems we have examined comprise two kinds of objects (usually spheres) made of different polymeric materials that charge with opposite electrical polarities when agitated on flat, metallic surfaces. The interplay of repulsive interactions between like-charged objects and attractive interactions between unlike-charged ones results in the self-assembly of these objects into highly ordered, closed arrays. Remarkably, some of the assemblies that form are not electroneutral-that is, they possess a net charge. We suggest that the stability of these unusual structures can be explained by accounting for the interactions between electric dipoles that the particles in the aggregates induce in their neighbours.