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91.
This short review describes a breakthrough provided by the synthesis of d6 metal complexes containing the intact molecules P4 and P4S3. The coordinated cage molecules acquire unexpected reactivity and undergo dismutation reactions in mild conditions in the presence of water. The outcomings are obtained either in form of free or coordinated molecules; the former are hypophosphorous and phosphorous acids, the latter comprise, besides phosphine, PH3, such species as thiophosphinous acid, PH2SH, diphosphane, P2H4, 1-hydroxytriphosphane, PH(OH)PHPH2 and 1,1,4-tris-hydroxytetraphosphane, P(OH)2PHPHPH(OH), which are either unknown or extremely reactive as free molecules. The formation of the above molecules provides a clue to the hydrolytic activation of the P4 and P4S3 cage molecules. 相似文献
92.
Florian Meirer Jordi Cabana Yijin Liu Apurva Mehta Joy C. Andrews Piero Pianetta 《Journal of synchrotron radiation》2011,18(5):773-781
The ability to probe morphology and phase distribution in complex systems at multiple length scales unravels the interplay of nano‐ and micrometer‐scale factors at the origin of macroscopic behavior. While different electron‐ and X‐ray‐based imaging techniques can be combined with spectroscopy at high resolutions, owing to experimental time limitations the resulting fields of view are too small to be representative of a composite sample. Here a new X‐ray imaging set‐up is proposed, combining full‐field transmission X‐ray microscopy (TXM) with X‐ray absorption near‐edge structure (XANES) spectroscopy to follow two‐dimensional and three‐dimensional morphological and chemical changes in large volumes at high resolution (tens of nanometers). TXM XANES imaging offers chemical speciation at the nanoscale in thick samples (>20 µm) with minimal preparation requirements. Further, its high throughput allows the analysis of large areas (up to millimeters) in minutes to a few hours. Proof of concept is provided using battery electrodes, although its versatility will lead to impact in a number of diverse research fields. 相似文献
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95.
A general framework for models describing adhesive contact between rigid bodies is proposed. The intensity of adhesion is supposed to decrease under the action of prescribed tangential and normal relative displacements. The reduction is attributed to progressive damage, and comes with energy dissipation. Additional dissipation due to viscosity and friction is also taken into account. The response of the interface is described by a single state variable. It is determined by general laws expressing a mechanical version of the first two laws of thermodynamics, combined with a set of phenomenological assumptions. 相似文献
96.
97.
Piero Bassanini Daniela Mansutti 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1986,37(6):849-858
Summary The effects of transverse gravity on steady flow past a split plate are investigated, by adopting the wake model proposed in the preceding paper (I). The existence and uniqueness of the solution as well as the convergence of an iteration process involving the free streamlines are proved for large Froude numbers by means of the Banach contraction mapping principle using Lipschitz norms.
Sunto Si studiano gli effetti dovuti ad un campo di gravità uniforme trasversale sul flusso con scia attorno ad un profilo sottile con spoiler usando un modello proposto nel precedente lavoro (I). Si dimostra l'esistenza, unicità, e la convergenza di un procedimento iterativo sulle linee di corrente libere, per grandi numeri di Froude, mediante il principio di contrazione in spazi di Banach.相似文献
98.
Probabilistically induced domain decomposition methods for elliptic boundary-value problems 总被引:1,自引:0,他引:1
Juan A. Acebrn Maria Pia Busico Piero Lanucara Renato Spigler 《Journal of computational physics》2005,210(2):421-438
Monte Carlo as well as quasi-Monte Carlo methods are used to generate only few interfacial values in two-dimensional domains where boundary-value elliptic problems are formulated. This allows for a domain decomposition of the domain. A continuous approximation of the solution is obtained interpolating on such interfaces, and then used as boundary data to split the original problem into fully decoupled subproblems. The numerical treatment can then be continued, implementing any deterministic algorithm on each subdomain. Both, Monte Carlo (or quasi-Monte Carlo) simulations and the domain decomposition strategy allow for exploiting parallel architectures. Scalability and natural fault tolerance are peculiarities of the present algorithm. Examples concern Helmholtz and Poisson equations, whose probabilistic treatment presents additional complications with respect to the case of homogeneous elliptic problems without any potential term and source. 相似文献
99.
Piero Villaggio 《Continuum Mechanics and Thermodynamics》1996,8(2):115-120
Let an infinitely long cylinder move perpendicular to its length in an infinite mass of liquid which is at rest at infinity. If the cylinder is rigid, the whole effect of the presence of the liquid may be represented by adding to the inertia per unit length of the solid cylinder the mass per unit length of the displaced fluid. If, however, the cylinder is elastically deformable, the mass of the moving fluid depends on the change in shape of the, initially circular, cross-sections of the cylinder. Thus the added mass is no longer a constant, but a function of the pressure exerted by the fluid on the solid cylinder. 相似文献
100.
Gianpietro Del Piero 《Meccanica》1972,7(4):248-254
Summary The possibility of enlarging the definition of collapse of elastic-plastic structures to include dynamic problems is first examined. It is concluded that the most satisfactory definition is the one given in terms of plastic dissipation. The simple case of a single-degree of freedom oscillator is then studied in detail. After giving some upper bounds for the dissipation with the aid of suitable a priori inequalities, a typical property of stability of the solution is employed to obtain a fairly severe bracketing of velocities throughout the motion. A numerical example, taken from a problem of seismic design, shows that the latter result leads to further improvements in majorizing the plastic dissipation.
This research was supported in part by the C.N.R., Gruppo Nazionale per la Fisica Matematica e per le Applicazioni della Matematica alla Fisica e all'Ingegneria. 相似文献
Sommario Si studia aapprima l'estensione della definizione di collasso di una struttura elastoplastica ai problemi di tipo dinamico, concludendo che la miglior caratterizzazione é quella in termini di dissipazione plastica. Si passa poi a considerare il caso di un oscillatore a un grado di libertà, per cui si calcolano limitazioni superiori della dissipazione ricorrendo a opportune diseguaglianze a priori. Utilizzando inoltre una proprietà di stabilità della soluzione, tipica dei problemi di Plasticità, si riescono a dare strette limitazioni per la velocità. Come mostrato da un esempio numerico tratto da un problema sismico, esse conducono anche ad una più accurata delimitazione della dissipazione plastica.
This research was supported in part by the C.N.R., Gruppo Nazionale per la Fisica Matematica e per le Applicazioni della Matematica alla Fisica e all'Ingegneria. 相似文献