Determination of scattering parameters of junctions associated with electromagnetic topology

This paper is dedicated to the determination of topological S parameters in the transmission line networks. We are especially interested in ideal junctions which consist of short circuit connections. For this type of junctions, it is impossible to deduce the S parameters from the usual impedance or admittance matrices which are not defined in this case. We suggest a method allowing a direct calculation of S. This procedure is described and then carried out for a two wire fork. At last, an experimental application is given for this model.     

Toward a narra-topography: A pilot study applied to Marguerite Duras' novelModerato Cantabile

Although lexical frequencies are familiar measures of stylistic and thematic analysis, only recently have some stylostatisticians been tempted to investigate the relationship between the frequency and topography of repeated lexical items. In the present paper the authors have turned to the study of the four focal types of discursive narratology, using Marguerite Duras'Moderato Cantabile. Their intent is to uncover aspects of narratological performance which further elucidate the communicative strategies in the story. Part 1 summarizes the problematic between frequency and topography. It describes how a topographical index can be computed for any repeated item and how a Global Topography Index (GTI) can summarize the major topographical characteristics of any text sequence. Part 2 presents a four-cell typology of narrational mode: a segmentation of the verbal chain into narrating and narrated speech acts, with each text sequence tagged according to its discursive function: overt sender intervention for story coherence or comment on the focal level of a narrating present; representation of discrete or unlocalized events on the focal level of a mimeticized past. In Part 3 the focal encodings are displayed in numerical and graphic form, first according to the eight surface chapter divisions and then according to twenty-six subsets of approximately equal length. The fluctuations of the topography indices are reviewed, with particular attention being paid to the manifestation of cluster effects. Although sender interventions predominate, the relativized behavior of each focal type contributes to a climactic unraveling of the intrigue in the final chapters. In conclusion, the authors stress the dichotomy between the calm surface of the chapters and the agitated tensions of the twenty-six subsets.     

An account of the systematic error in judging what is reachable.

An account of the postural determinants of perceived reachability is proposed to explain systematic overestimations of the distance at which an object is perceived to be reachable. In this account, these errors are due to a mapping of the limits of prehensile space onto a person's perceived region of maximum stretchability, in the context of a whole-body engagement. In support of this account, 6 experiments on the judged reachability of both static and dynamic objects are reported. We tentatively conclude that the mental imagery of action is grounded and calibrated in reference to multiple skeletal degrees of behavioral freedom. Accordingly, this calibration is a source of systematic error in reachability judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental Study of Alumina Particle Removal From a Plane surface

Micron and submicron alumina particles are often used for the mechanical polishing of the GaAs wafers processed in the microelectronic industry. A better understanding of the adhesion mechanisms is the key factor for the particle removal and for the optimisation of the industrial chemical cleaning. However, the nature and the strength of the complex interactions occurring between asymmetrical alumina particles and the surface remain unclear. Thus, an experimental study of the detachment of asymmetrical alumina particles in adhesive contact with a glass plate was done using a specially designed shear stress flow chamber. A series of experiments was performed to measure the shear stress necessary to remove individual alumina particles (of 3 and 0.3 µm nominal size) under various chemical solutions (diluted ammonia, surfactant and glycerol). Then the effects of the particle size, the resting time, the pH and the nature of the chemical solutions used for the removal of the alumina particles was characterised in terms of percentage of alumina particles detached. Results have shown that the longer the resting time, the more adherent the particles are. Moreover, it was found that the ammonia solution gives the best particle removal rate (80%) because of the strong repulsive electrostatic interactions between the alumina particles and the glass surface, both being charged negatively in a basic solution.     

Increasing Reliability in Cable-Free Radio LANs Low Level Forwarding in HIPERLAN

Radio LANs are emerging in the computing world. They are supported by distinct configurations: on the one hand radio LANs with base stations and a wired backbone, on the other hand radio LANs implementing Intra-forwarding. Adding a new node in a radio LAN with Intra-forwarding, increases the reliability, while this reliability decreases with ad hoc or hub configurations. This advantage of Intra-forwarding is quantified. Intra-forwarding, as defined in the HIPERLAN standard, is based on a hop-by-hop policy and link check procedures. It is shown how point-to-point packets and broadcast packets are forwarded. The three basic components of Intra-forwarding needed to build and update the Intra-forwarding database are described. The originality of this approach is the use of multipoint relays which enable better scalability. The correctness of the Intra-forwarding protocol is proved and its cost is evaluated.     

Films and fibers of oriented single wall nanotubes

As-produced nanotubes form a light, fragile and isotropic soot. Different efforts are made to process nanotubes into macroscopic forms of more practical use and more controlled properties. We briefly review in this paper two methods recently proposed to make films of magnetically aligned nanotubes and fibers by using an electrophoretic method. Preferential orientation of the nanotubes in the plane of the films or along the fiber axis is an important feature of the obtained materials. Then we describe in details a different, spinning like, process for making fibers out of single wall carbon nanotubes. This process consists of dispersing the nanotubes in a surfactant solution, re-condensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. The behaviors of the surfactant-stabilized dispersions, which are also presented, are critical for this process. The degree of nanotubes alignment in dried fibers has been characterized by X-ray scattering. It is found to be smaller than the alignment obtained in the previous materials. However, the processing is simpler and faster and potentially scalable for large-scale production.     

An approach to the synthesis of qualitative ecological information from aquatic coleoptera communities

A list of 196 Coleoptera taxa, larvae and adults, covering 113 species, was obtained from several surveys of a flood plain of the Rhô river. From published reports and personal experience, each taxon is linked with the modalities of nine environmental and three biological variables. The resulting 12 ecological profiles for 196 taxa are analysed by correspondence analysis. The simultaneous ordination of the taxa and variables allows presentation of the more synthetic correspondence between the Coleoptera and their ecological and biological characteristics. The niche dimensions of the 12 variables tested here are organized along a current-substrate gradient, from stones in rapid flow to mud in still water, which is associated with the other ecological conditions. This ordination reflects environmental conditions in a transverse direction, particularly from the central channel to the furthest annexes of the river. The Coleoptera are shown to be describers of the connectivity with the main channel. The 196 studied taxa are positioned along the gradient. They are subdivided into seven faunal groups based on their habitat range or niche width. The larger species are confined to the stagnant side of the gradient. Other variables, such as feeding and vertical distribution, clearly separate carnivores from herbivores and also larvae from adults. The next step of this study will be to extend these investigations to other functional variables and to all the species of Coleoptera in France. The information given by the Coleoptera will then be compared with actual field measurements.     

Onr-partition designs in hamming spaces

The concept of the combinatorial matrix of an unrestricted code and the notion of anr-partition design admitted by a code are introduced and discussed in detail. The theory includes a characterization of completely regular codes, and a combinatorial interpretation of the fact that the distinct rows of the distance distribution matrix of a code are linearly independent. In general, it is possible to compute the distance distribution matrix of any code admitting a given partition design by solving a well-defined system of linear equations; this is an efficient technique provided the number of classes in the partition is relatively small.     

Prebiotic synthesis of sequential peptides on the Hadean beach by a molecular engine working with nitrogen oxides as energy sources

Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry.