Data envelopment analysis models of investment funds

This paper develops theory missing in the sizable literature that uses data envelopment analysis to construct return-risk ratios for investment funds. It explores the production possibility set of the investment funds to identify an appropriate form of returns to scale. It discusses what risk and return measures can justifiably be combined and how to deal with negative risks, and identifies suitable sets of measures. It identifies the problems of failing to deal with diversification and develops an iterative approximation procedure to deal with it. It identifies relationships between diversification, coherent measures of risk and stochastic dominance. It shows how the iterative procedure makes a practical difference using monthly returns of 30 hedge funds over the same time period. It discusses possible shortcomings of the procedure and offers directions for future research.     

Rhenium(VII) polyhydrides supported by chelating bis -phosphine ligands: DPEphos,xantphos and biphep

Three new rhenium polyhydride complexes, [ReH₇(L₂)], incorporating bidentate organophosphorus ligands (L₂ = DPEphos, xantphos and biphep), were successfully synthesized using the corresponding [ReOCl₃(L₂)] complexes as precursors. The polyhydride complexes were characterized by IR, ¹H and ³¹P NMR, and elemental analysis.     

Dispersion and deposition mechanisms of particles suspended in a turbulent plane Couette flow

Inertial particle transfer in a turbulent plane Couette flow (C flow) was studied using Direct Numerical Simulation (DNS) of the flow combined with a Lagrangian particle tracking approach for particles with Stokes numbers (St) 5, 25 and 125. The particle concentration was assumed low enough, so that the simulations were done under one-way coupling condition.     

One-dimensional ventsel-freidlin theory and its analogue for singular perturbations of degenerate diffusions

We make some remarks about deriving the large deviations estimates for the Ventsel-Freidlin perturbed system and adapt these methods to derive similar results for singular perturbations of degenerate one-dimensional diffusions where β and ω are independent Brownian motions. This corresponds to a singular perturbation of the degenerate second-order operator     

Radial sample load distribution under overload conditions: Analytical scale columns

The homogeneity of the sample load across the radial cross section of analytical scale columns was determined when operating under overload conditions. The study was performed using active flow technology columns operating in parallel segmentation mode. The outlet segmentation ratio was varied to enable different volume fractions of mobile phase, and thus sample, to elute from the peripheral and central flow regions of the column. The amount of solute exiting the peripheral and radial central exit ports was determined as a function of the flow segmentation ratio. The experimental data using an analytical scale column with dimensions, 100?×?4.6?mm, indicated that the sample load distribution was essentially uniform as a function of the column radial cross section.     

Homogenization of parabolic problem with nonlinear transmission condition

In this paper, we investigate the periodic homogenization of nonlinear parabolic equation arising from heat exchange in composite material problems. This problem, defined in periodical domain, is nonlinear at the interface. This nonlinearity models the heat radiation on the interface, which constitutes the transmission boundary conditions, between the two components of the material. The main challenge is, first, to show the well-posedness of the microscopic problem using the topological degree of Leray–Schauder tools. Then, we apply the two scale convergence to identify the equivalent macroscopic model using homogenization techniques. Finally, in order to confirm the efficiency of the homogenization process, we present some numerical results obtained via finite element approximation.     

Phase field approach with anisotropic interface energy and interface stresses: Large strain formulation

A thermodynamically consistent, large-strain, multi-phase field approach (with consequent interface stresses) is generalized for the case with anisotropic interface (gradient) energy (e.g. an energy density that depends both on the magnitude and direction of the gradients in the phase fields). Such a generalization, if done in the “usual” manner, yields a theory that can be shown to be manifestly unphysical. These theories consider the gradient energy as anisotropic in the deformed configuration, and, due to this supposition, several fundamental contradictions arise. First, the Cauchy stress tensor is non-symmetric and, consequently, violates the moment of momentum principle, in essence the Herring (thermodynamic) torque is imparting an unphysical angular momentum to the system. In addition, this non-symmetric stress implies a violation of the principle of material objectivity. These problems in the formulation can be resolved by insisting that the gradient energy is an isotropic function of the gradient of the order parameters in the deformed configuration, but depends on the direction of the gradient of the order parameters (is anisotropic) in the undeformed configuration. We find that for a propagating nonequilibrium interface, the structural part of the interfacial Cauchy stress is symmetric and reduces to a biaxial tension with the magnitude equal to the temperature- and orientation-dependent interface energy. Ginzburg–Landau equations for the evolution of the order parameters and temperature evolution equation, as well as the boundary conditions for the order parameters are derived. Small strain simplifications are presented. Remarkably, this anisotropy yields a first order correction in the Ginzburg–Landau equation for small strains, which has been neglected in prior works. The next strain-related term is third order. For concreteness, specific orientation dependencies of the gradient energy coefficients are examined, using published molecular dynamics studies of cubic crystals. In order to consider a fully specified system, a typical sixth order polynomial phase field model is considered. Analytical solutions for the propagating interface and critical nucleus are found, accounting for the influence of the anisotropic gradient energy and elucidating the distribution of components of interface stresses. The orientation-dependence of the nonequilibrium interface energy is first suitably defined and explicitly determined analytically, and the associated width is also found. The developed formalism is applicable to melting/solidification and crystal-amorphous transformation and can be generalized for martensitic and diffusive phase transformations, twinning, fracture, and grain growth, for which interface energy depends on interface orientation of crystals from either side.     

Gauss–Seidel Estimation of Generalized Linear Mixed Models With Application to Poisson Modeling of Spatially Varying Disease Rates

Generalized linear mixed models (GLMMs) are often fit by computational procedures such as penalized quasi-likelihood (PQL). Special cases of GLMMs are generalized linear models (GLMs), which are often fit using algorithms like iterative weighted least squares (IWLS). High computational costs and memory space constraints make it difficult to apply these iterative procedures to datasets having a very large number of records.

We propose a computationally efficient strategy based on the Gauss–Seidel algorithm that iteratively fits submodels of the GLMM to collapsed versions of the data. The strategy is applied to investigate the relationship between ischemic heart disease, socioeconomic status, and age/gender category in New South Wales, Australia, based on outcome data consisting of approximately 33 million records. For Poisson and binomial regression models, the Gauss–Seidel approach is found to substantially outperform existing methods in terms of maximum analyzable sample size. Remarkably, for both models, the average time per iteration and the total time until convergence of the Gauss–Seidel procedure are less than 0.3% of the corresponding times for the IWLS algorithm. Platform-independent pseudo-code for fitting GLMS, as well as the source code used to generate and analyze the datasets in the simulation studies, are available online as supplemental materials.     

Solvatochromic Solvent Polarity Measurements In Analytical Chemistry: Synthesiss And Applications Of Et-30

Abstract

The E_T(30) scale of solvent polarity has been shown to be useful in examining many diverse analytical processes. It is based on the charge transfer absorption of 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridinio)phenolate (referred to as ET-30 in this paper). Unfortunately, use of the E_T(30) scale has been hindered by (a) the lack of a commercial source of the ET-30 dye and (b) the lack of an English language synthetic procedure. Here we discuss recent applications of the E_T(30) scale to analytical techniques, as well as a simplified procedure for the synthesis of ET-30.     

Solid structures in a highly agitated bed of granular materials

A series of experiments are described in which bubbles and solid structures are produced in a highly agitated bed of vertically shaken granular materials. To identify the physical mechanisms behind bubbling, three-dimensional simulations of the aforementioned systems are performed on a graphics processing unit (GPU). The gas dynamics above and within shaken granular materials is solved using large-eddy simulations (LES) while the dynamics of grains is described through molecular dynamics. Here, the interaction between the grain surfaces is modeled using the generalized form of contact theory developed by Hertz. In addition, the coefficient of kinetic friction is assumed to depend on the relative velocity of slipping. The results show both a qualitative and a quantitative agreement between simulations and experiments. They imply that the instantaneous formation and failure of granular aggregates could play an important role in the nucleation, growth, departure and collapse of bubbles in shaken granular materials. This promising effort in GPU computing may position the GPU as a compelling future alternative to traditional simulation techniques.