10,000 publications from this institution
Abstract The collapse of the Bretton Woods System in 1971–3 led to ambitious efforts to reform the international monetary system, mainly through the deliberations of the Committee of Twenty (C-20). Many of the issues considered by the C-20 will be familiar to aficionados of twenty-first century discussions of international monetary reform. Ultimately, attempts to reach a consensus in the C-20 were unsuccessful. This paper seeks to identify explanations for that failure in an effort to limit the likelihood that it will be repeated.
The task of visual object recognition benefits from feature selection as it reduces the amount of computation in recognizing a new instance of an object, and the selected features give insights into the classification process. We focus on a class of current feature selection methods known as embedded methods: due to the nature of multi-way classification in object recognition, we derive an extension of the Relevance Vector Machine technique to multi-class. In experiments, we apply Relevance Vector Machine on the problem of digit classification and study its effects. Experimental results show that our classifier enhances accuracy, yields good interpretation for the selected subset of features and costs only a constant factor of the baseline classifier
Different cluster models of isolated MoVI molybdate species anchored on silica surface were investigated using density functional theory (DFT). Isolated molybdate centers were modeled as either a penta-coordinated mono-oxo species or a tetra-coordinated di-oxo species. Standard free energy changes for interconversion between mono-oxo and di-oxo species indicate that these two species can coexist in equilibrium on the surface of amorphous silica with di-oxo species being the favored species at high temperature and low partial pressures of water. Comparison of Raman-spectra from experiment and DFT suggests that di-oxo species might be the prominent species responsible for the peak at 988 cm-1. This conclusion is strongly supported by the similarity in the EXAFS spectra obtained from experiment and theory. The thermodynamics for H2 reduction of isolated molybdate species were determined and found to be in reasonable agreement with experimental observation. DFT calculations of the structure and properties of the reduced MoIV centers and comparison of these with experimental results suggest that the reduced centers are present as mono-oxo species.
Temperature-programmed desorption (TPD) of physisorbed mesitylene molecules has been used as a nondestructive surface probe to distinguish the surface adsorption sites of model Ziegler−Natta polymerization catalysts. A MgCl2-supported titanium chloride film (TiClx/MgCl2) was fabricated on an inert gold substrate by codeposition of Mg metal and TiCl4 from the gas phase. The mesitylene TPD probe revealed two types of surface adsorption sites. The dominant site was attributed to the basal plane of these halide crystallites. The minor site could be tentatively attributed to a defective structure at the basal plane boundaries or other crystal planes. Due to the chlorine termination nature of the catalyst surface, the metal ions under the chlorine layer could not be differentiated directly with the physisorbed mesitylene molecules. However, the mesitylene TPD profile was able to monitor compositional changes in the outermost chlorine layer accompanying the reaction of the catalyst film with the triethylaluminum cocatalyst, electron beam irradiation of the film surface, and diffusion of bulk chlorine to minimize the number of defect sites.
[reaction: see text] N-Alkyl- and N-arylanilines were synthesized from arenes by a two-step sequence of iridium-catalyzed borylation and copper-catalyzed coupling with amines. Diaryl ethers were obtained by a related sequence of arene borylation, followed by coupling with phenols. In particular, 3,5-disubstituted arylamines and aryl ethers were prepared by initiating this sequence with meta-substituted arenes.
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.
In this letter, we show how algebraic graph theory can be used to derive sufficient conditions for an array of resistively coupled nonlinear oscillators to synchronize. These conditions are derived from the connectivity graph, which describes how the oscillators are connected. In particular, we show how such a sufficient condition is dependent on the algebraic connectivity of the connectivity graph. Intuition tells us that if the oscillators are more "closely connected" to each other, then they are more likely to synchronize. We discuss how to quantify connectedness in graph-theoretical terms and its relation to algebraic connectivity and show that our results are in accordance with this intuition. We also give an upper bound on the coupling conductance required for synchronization for arbitrary graphs, which is in the order of n/sup 2/, where n is the number of oscillators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
We present the bifurcation analysis of Chua’s circuit equations with a smooth nonlinearity, described by a cubic polynomial. Our study focuses on phenomena that can be observed directly in the numerical simulation of the model, and on phenomena which are revealed by a more elaborate analysis based on continuation techniques and bifurcation theory. We emphasize how a combination of these approaches actually works in practice. We compare the dynamics of Chua’s circuit equations with piecewise-linear and with smooth nonlinearity. The dynamics of these two variants are similar, but we also present some differences. We conjecture that this similarity is due to the central role of homoclinicity in this model. We describe different ways in which the type of a homoclinic bifurcation influences the behavior of branches of periodic orbits. We present an overview of codimension 1 bifurcation diagrams for principal periodic orbits near homoclinicity for three-dimensional systems, both in the generic case and in the case of odd symmetry. Most of these diagrams actually occurs in the model. We found several homoclinic bifurcations of codimension 2, related to the so called resonant conditions. We study one of these bifurcations, a double neutral saddle loop.
We propose and analyze a new proportional share allocation algorithm for time shared resources. We assume that the resource is allocated in time quanta of size q. To each client, we associate a weight which determines the relative share from the resource that the client should receive. We define the notion of fairness in the context of an idealized system in which the resource is assumed to be granted in arbitrarily small intervals of time. Mainly, we show that in steady conditions our algorithm guarantees that the difference between the service time that a client should receive in the idealized system and the service time it actually receives in the real system is bounded by the size q of a time quantum. The algorithm provides support for dynamic operations, such as a client joining or leaving the competition (for the resource), and changing a client&apos;s weight. By using an efficient augmented binary search tree data structure we implement these operations in O(log n), where n represe...
A model is tested to rapidly evaluate the vibrational properties of alloys with site disorder. It is shown that length-dependent transferable force constants exist and can be used to accurately predict the vibrational entropy of substitutionally ordered and disordered structures in Au-Cu, Au-Pd, and Cu-Pd. For each relevant force constant, a length-dependent function is determined and fitted to force constants obtained from first-principles pseudopotential calculations. We show that these transferable force constants can accurately predict vibrational entropies of L12-ordered and disordered phases in Cu3Au, Au3Pd, Pd3Au, Cu3Pd, and Pd3Au. In addition, we calculate the vibrational entropy difference between L12-ordered and disordered phases of Au3Cu and Cu3Pt.
