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An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A study has been made of the fracture toughness and resistance-curve behavior of a laminate consisting of alternating layers of brittle Nb3Al intermetallic and ductile Nb metal, using layer thicknesses of ∼500 and 125 μm, respectively. Effective resistance-curve toughening of Nb3Al was achieved in such a coarse-scale layered structure with only 20 vol.% of the Nb reinforcement phase. Specifically, the toughness of Nb3Al was increased from ∼1 MPa✔m to well over 20 MPa✔m (and as high as 70 MPa✔m in certain samples) after several millimeters at stable crack growth. These values are significantly greater than other Nb/Nb3Al composites containing Nb as ∼ 20 μm sized particulates or 1–2 μm thick Nb layers (in the form of a microlaminate), both containing at least 40 vol.% of the ductile phase. The source of such ductile-phase toughening was attributed to crack blunting at, and renucleation across, the ductile Nb layers, which in turn led to extensive bridging and plastic deformation within the Nb layers in the crack wake. Since the extent of crack trapping by the ductile layer and plastic deformation are limited by layer thickness, the present coarser-scale laminates tend to display better fracture resistance compared to composites with finer-scale ductile reinforcements.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The authors present a rigorous analysis and a detailed experimental study of a chaotic attractor observed from a widely-used practical circuit: namely, a second-order phase-locked loop as an FM demodulation. The existence of chaos in this system proven rigorously by using Melnikov's method, and explicit expressions are derived which specify the possible region of chaos, or, more accurately, the region of existence of the homoclinic orbits. Chaos has been demonstrated in actual experiments in which an IC is used as an FM demodulator. It has also been confirmed by computer simulation. Thus, it has been verified that horseshoe chaos occurs for a wide range of parameter values in practical phase-locked loop FM demodulator systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Studies on the palladium-catalyzed formation of aryl amines, aryl ethers and a-aryl carbonyl compounds from aryl halides are reported.These studies range from synthetic methodology, to detailed mechanistic analysis, to new methods one can use to screen for catalytic covalent bond formation.Improved methods for formation of aryl ethers and room temperature amination chemistry have resulted from a mechanistic understanding of the reaction.Over the past 20 years, palladium-catalyzed methods for aromatic substitution have provided useful routes to biaryl, alkynyl-aryl and vinyl-aryl compounds [1,2], The palladium-catalyzed formation of aromatic carbon-heteroatom bonds has become a useful synthetic tool in the past few years [3].The new direct formation of a-aryl carbonyl compounds provides a method to form sp 3 -aromatic carbon-carbon bonds [4±7], The purpose of this presentation is to provide examples of C±N, C±O and C±C bond formation that have been developed recently in the author's laboratory and to provide mechanistic information that allows one to understand why one type of catalyst is more effective than another for a particular class of transformation (Scheme 1).
We prove analytically that 2-element memristive circuits consisting of a passive linear inductor in parallel with a passive memristor, or an active memristive device, can be described explicitly by a Hamiltonian equation, whose solutions can be periodic or damped, and can be represented analytically by the constants of the motion along the circuit Hamiltonian. Generalizations to 3-element and 2N-element memristive Hamiltonian circuits are also presented where complex bifurcation phenomena including chaos, abound.