Simulation of continuous sample paths of random fields using trigonometric series

The problem of simulating random fields on a digital computer using random trigonometric series is considered. Convergence in distribution of the sample paths as continuous functions is demonstrated when the structure function is bounded by . Methods for simulating homogeneous and homogeneous increment random fields are presented. As an example, random index of refraction fluctuations are simulated using both a fractal model and a homogeneous random field model.     

High-dimensional visual analytics: interactive exploration guided by pairwise views of point distributions

We introduce a method for organizing multivariate displays and for guiding interactive exploration through high-dimensional data. The method is based on nine characterizations of the 2D distributions of orthogonal pairwise projections on a set of points in multidimensional Euclidean space. These characterizations include such measures as density, skewness, shape, outliers, and texture. Statistical analysis of these measures leads to ways for 1) organizing 2D scatterplots of points for coherent viewing, 2) locating unusual (outlying) marginal 2D distributions of points for anomaly detection and 3) sorting multivariate displays based on high-dimensional data, such as trees, parallel coordinates, and glyphs     

The evaluation of computer hardware/software plans for municipalities

This paper presents a methodology employing systems analysis techniques which may be used to evaluate alternative data processing plans for municipalities. The basic information which must be formulated for the analysis includes the following three areas: general hardware specifications, implementation schedules for database applications, and cost profiles which include capital and operating expense estimates. Specific factors are developed which may be used to assign numeric ratings to the relative advantages of each plan, and as a basis for making recommendations in the areas of hardware, software, staffing and costs. The methodology is illustrated by the analysis and evaluation of five plans developed to meet the data processing needs of a large metropolitan area.     

Sterol metabolism: XXXIII. On derivation of cholesterol 7-alkoxyl ethers

The facile acid-catalyzed conversion of cholest-5-ene-3β,7α-diol (but not of cholest-5-ene-3β, 7β-diol) in methanol or ethanol solution to the corresponding 7α-methyl or 7α-ethyl ethers and epimerization of the 7α-alkyl ethers to the corresponding 7β-alkyl ethers were established. The epimeric cholest-5-ene-3β, 7-diols, their 7-methyl ethers, and their 7-ethyl ethers are readily interconverted in acidified solvents, the quasiequatorial 7β-epimer predominating in each case. Both 7α- and 7β-alkyl ethers may be encountered as artifacts in analyses of sterol mixtures from mammalian tissues.     

Exact and approximate area-proportional circular Venn and Euler diagrams

Scientists conducting microarray and other experiments use circular Venn and Euler diagrams to analyze and illustrate their results. As one solution to this problem, this paper introduces a statistical model for fitting area-proportional Venn and Euler diagrams to observed data. The statistical model outlined in this paper includes a statistical loss function and a minimization procedure that enables formal estimation of the Venn/Euler area-proportional model for the first time. A significance test of the null hypothesis is computed for the solution. Residuals from the model are available for inspection. As a result, this algorithm can be used for both exploration and inference on real data sets. A Java program implementing this algorithm is available under the Mozilla Public License. An R function venneuler() is available as a package in CRAN and a plugin is available in Cytoscape.     

Review: membrane materials for the removal of water from industrial solvents by pervaporation and vapor permeation

Organic solvents are widely used in a variety of industrial sectors. Reclaiming and reusing the solvents may be the most economically and environmentally beneficial option for managing spent solvents. Purifying the solvents to meet reuse specifications can be challenging. For hydrophilic solvents, water must be removed prior to reuse, yet many hydrophilic solvents form hard-to-separate azeotropic mixtures with water. Such mixtures make separation processes energy-intensive and cause economic challenges. The membrane processes pervaporation (PV) and vapor permeation (VP) can be less energy-intensive than distillation-based processes and have proven to be very effective in removing water from azeotropic mixtures. In PV/VP, separation is based on the solution–diffusion interaction between the dense permselective layer of the membrane and the solvent/water mixture. This review provides a state-of-the-science analysis of materials used as the selective layer(s) of PV/VP membranes in removing water from organic solvents. A variety of membrane materials, such as polymeric, inorganic, mixed matrix, and hybrid, have been reported in the literature. A small subset of these is commercially available and highlighted here: poly (vinyl alcohol), polyimides, amorphous perfluoro polymers, NaA zeolites, chabazite zeolites, T-type zeolites, and hybrid silicas. The typical performance characteristics and operating limits of these membranes are discussed. Solvents targeted by the United States Environmental Protection Agency for reclamation are emphasized and ten common solvents are chosen for analysis: acetonitrile, 1-butanol, N,N-dimethyl formamide, ethanol, methanol, methyl isobutyl ketone, methyl tert-butyl ether, tetrahydrofuran, acetone, and 2-propanol. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.     

High Temperature Alkaline Degradation of Phenyl β-D-Glucopyranoside

Reaction rates and product distributions have been determined for the degradation of phenyl β-D-glucopyranoside in aq. alkali under various conditions. The effects of a stronger nucleophile, variations in hydroxide ion concentration at constant ionic strength, changes in temperature, and the level of ¹⁸O incorporation from the solvent into the product phenol were investigated. The degradation rate decreased greatly for the 2-O-methyl analog. The results indicate that, at both 100 and 170°C, phenyl β-D-glucopyranoside degradation proceeded by an SNicB(2) reaction. At both temperatures the expected SNicB(2) product, levoglucosan, formed in less than quantitative yields because of competing reactions which occurred after the rate-determining step.     

Alkaline Degradation of 1,5-Anhydro-4-0-β-D-Glucopyranosyl-2,3,4-Tri-O-Methyl-D-Glucitol

The title compound (2) was degraded at 150-180°C in oxygen-free 0.5-2.5M aqueous NaOH. Degradation occurred by cleavage of both the glycosyl-oxygen bond (80-95%) and the oxygen-aglycon bond (5-20%). Cleavage of the glycosyl-oxygen bond yielded 1, 5-anhydro-2, 3, 6-tri-O-methyl-D-glucitol (5) from the aglycon. The reactive intermediate, 1, 6-anhydro-β-D-glucopyranose, was formed from the glycosyl moiety in amounts (50-88%) dependent upon the reaction conditions. Cleavage of the oxygen-aglycon bond resulted in unidentified products, probably acidic and fragmentary in nature and quantified as a mass deficit. Data for cleavage of the glycosyl-oxygen bond is consistent with an S_NicB(2¹) mechanism while that for oxygen-aglycon bond cleavage is consistent with an S_N1 mechanism.     

Membrane‐assisted vapor stripping: energy efficient hybrid distillation–vapor permeation process for alcohol–water separation

BACKGROUND: Energy efficient alternatives to distillation for alcohol recovery from dilute solution are needed to improve biofuel sustainability. A process integrating steam stripping with a vapor compression step and a vapor permeation membrane separation step is proposed. The objective of this work is to estimate the energy and process costs required to make a fuel grade ethanol (0.5 wt% water) from 1 and 5 wt% ethanol aqueous streams using the proposed process. RESULTS: Using process simulation and spreadsheeting software, the proposed membrane‐assisted vapor stripping process was estimated to require as little as 8.9 MJ of fuel‐equivalent energy per kg of fuel grade ethanol recovered from a 1 wt% ethanol feed stream, 2.5 MJ kg^?1 for a 5 wt% ethanol solution. This represents an energy saving of at least 43% relative to standard distillation producing azeotropic ethanol (6 wt% water). Process costs were also found to be lower than for distillation at the 3.0 × 10⁶ kg‐ethanol year^?1 scale modeled. CONCLUSION: In this hybrid system, the stripping column provides high ethanol recoveries and low effluent concentrations while the vapor compression‐membrane component enables the efficient recovery of latent and sensible heat from both the retentate and permeate streams from the membrane system. Published in 2008 by John Wiley & Sons, Ltd.