Stress-strain relationships in uniaxial extension of high cis-1,4-polyisoprene networks with different molecular weight precursors

Equilibrium stress-strain relationships in uniaxial extension for high cis-1,4-polyisoprene (Shell IR 307) networks were obtained by extrapolation of relaxation measurements to infinite time through a BKZ constitutive equation. Three series of networks were investigated, each series being characterized by its polymer precursor molecular weight. Influence of crosslinking density was studied through varying amounts of dicumyl peroxide as crosslinking agent. These results were used to test Flory and Erman's recent molecular elasticity theory of imperfect networks with constraints on junctions. It was shown that this later theory treating entanglements as restrictions on junction fluctuations could be reasonably used to characterize network topology. A universal value of 0.50 for the interpenetration parameter I is confirmed and an interpretation of parameter ζ in terms of network inhomogeneity is tentatively given.     

Monoepoxy polymerization initiated by BF3-amine complexes in bulk. III. Influence of γ-butyrolactone on polymer formation

The influence of γ-butyrolactone (γ-BL), used as solvent of BF₃-amine complexes, on the polymerization of monoepoxides was studied. Different intermediate reaction products of PGE initiated by BF₃-4-methoxyaniline (BF₃-4MA) previously solubilized in γ-BL (55% by weight), were separated and analyzed by ¹H-NMR. It is shown that there is the opening of both epoxy and γ-BL. The latter does not homopolymerize, but copolymerizes well with epoxy groups. The use of a large quantity of γ-BL leads to a decreasing molar mass of the formed polymer. The kinetic study allowed to propose the mechanism of the cationic polymerization of epoxy initiated by BF₃-amine complex in the presence of γ-BL. © 1994 John Wiley & Sons, Inc.     

Hardness and fracture toughness of thermoelectric La<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>4</Subscript>

Lanthanum telluride (La_3?x Te₄) is a state-of-the-art n-type high temperature thermoelectric material that behaves as a weak and brittle ceramic. Vickers microindentation hardness testing was explored as a rapid analysis technique to characterize the mechanical properties of this material. An indentation size effect was observed with hardness values ranging from 439 ± 31 kgf/mm² (0.01 kgf/10 s contact time) to 335 ± 6 kgf/mm² (0.5 kgf/10 s contact time). The Vickers indentation fracture toughness, K _VIF, based on measurements of crack lengths emanating from the corners of the Vickers indents was 0.70 ± 0.06 MPa m^1/2.     

Comparison of contact resistance between accumulation-mode and inversion-mode multigate FETs

The performances of accumulation-mode and inversion-mode multigate FETs are compared. The influence of gate underlap on the electrical properties is analyzed. Both simulation results and experimental data show that in a device with gate underlap, accumulation-mode devices have a higher current drive, lower source and drain resistance and less process variability than inversion-mode FETs.     

A difference-set cyclic code (1057,813,34)

This paper presents an overview of the implementation of a difference-set cyclic code (1057,813,34). It is easy to achieve coding and decoding circuits. The decoding lays on the analysis of the composite remainder R_c (x) and the use of a decoding matrix of 33 Boolean equations. The error-correcting algorithm has been improved, so the difference-set cyclic code (1057,813,34) can correct up to 26 random errors instead of the 16 previous random errors found by the theory. Moreover, 3 decoding algorithms have been simulated and allow the comparison of their respective efficiency. The hardware achievement is quite easy because the necessary logical elements such as shift delay registers, positive-and gates, positive-or gates, positive-exclusive-or gates exist as a set of libraries.     

Adaptive mesh generation for progressive radiosity: A ray-tracing based algorithm.

The radiosity method is one of the most popular rendering algorithms. It allows to simulate interreflections of light accurately between surfaces as energy transfers are well designed. However, this algorithm and its derivatives need to break scenes into a relatively large number of small elements to approximate the illumination function. Even with a very large number of elements, not all the illumination effects can be simulated. In fact, there are always artefacts when modelling sharp shadows, besides shadows falling between mesh vertices can be missed entirely. To reduce the computational cost of such methods and to increase the accuracy of the radiosity solution, adaptive mesh generation is well suited. In this paper, we present a ray-tracing based algorithm for adaptive mesh generation which resolves all the illumination problems without lengthening computation time too much. This method allows a small number of initial elements and increases element density in critical locations while solving the illumination problem.     

Arbitrarily shaped multiple spatial cluster detection for case event data

An original method is proposed for spatial cluster detection of case event data. A selection order and the distance from the nearest neighbour are attributed to each point, once pre-selected points have been taken into account. This distance is weighted by the expected distance under the uniform distribution hypothesis. Potential clusters are located by modelling the multiple structural change of the distances on the selection order and the best model (containing one or several potential clusters) is selected using the double maximum test. Finally a p-value is obtained for each potential cluster. With this method multiple clusters of any shape can be detected.     

Hemispheric Specialization in the Primary Auditory Area of Awake and Anesthetized Starlings (Sturnus vulgaris).

Although evidence exists for a lateralization of song production, few studies have focused on the perceptual aspect of lateralization in songbirds. In the present study, the authors recorded neuronal responses to a variety of species-specific and artificial, nonspecific stimuli in both hemispheres of awake and anesthetized male starlings (Sturnus vulgaris). Recordings were made in the primary auditory area of the songbird brain, the Field L complex. The right hemisphere exhibited significantly more responsive units than the left hemisphere in awake birds, and this difference was significantly reduced in anesthetized birds. Furthermore, clear hemispheric specialization toward categories of behaviorally relevant stimuli and precise parameters of these stimuli were found. The main auditory area of the starling's brain thus appears to show some degree of lateralization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimisation de ľefficacité de couplage entre un guide ďonde confiné et une fibre optique monomode par ľintermédiaire ďune lentille boule

Theoretical coupling efficiency between a channel waveguide and a single-mode optical fibre using a ball lens is optimized by varying the parameters of the optical system such as the relative position of the components, the refractive index and the size of the lens. A specific software has been used for the optimization. Numerical calculations have been done under the Gaussian approximation of the fields distributions. The losses due to waveguides misalignments with respect to their ideal position have been evaluated. All these theoretical results are compared with those obtained from buttcoupling.