Permutation graphs, fast forward permutations, and sampling the cycle structure of a permutation

A permutation P on {1,..,N} is a_fast_forward_permutation_ if for each m the computational complexity of evaluating P^m(x)$ is small independently of m and x. Naor and Reingold constructed fast forward pseudorandom cycluses and involutions. By studying the evolution of permutation graphs, we prove that the number of queries needed to distinguish a random cyclus from a random permutation on {1,..,N} is Theta(N) if one does not use queries of the form P^m(x), but is only Theta(1) if one is allowed to make such queries. We construct fast forward permutations which are indistinguishable from random permutations even when queries of the form P^m(x) are allowed. This is done by introducing an efficient method to sample the cycle structure of a random permutation, which in turn solves an open problem of Naor and Reingold.Comment: Corrected a small erro

An Ensemble-Proper Orthogonal Decomposition Method for the Nonstationary Navier-Stokes Equations

The definition of partial differential equation (PDE) models usually involves a set of parameters whose values may vary over a wide range. The solution of even a single set of parameter values may be quite expensive. In many cases, e.g., optimization, control, uncertainty quantification, and other settings, solutions are needed for many sets of parameter values. We consider the case of the time-dependent Navier-Stokes equations for which a recently developed ensemble-based method allows for the efficient determination of the multiple solutions corresponding to many parameter sets. The method uses the average of the multiple solutions at any time step to define a linear set of equations that determines the solutions at the next time step. To significantly further reduce the costs of determining multiple solutions of the Navier-Stokes equations, we incorporate a proper orthogonal decomposition (POD) reduced-order model into the ensemble-based method. The stability and convergence results for the ensemble-based method are extended to the ensemble-POD approach. Numerical experiments are provided that illustrate the accuracy and efficiency of computations determined using the new approach

Secrets and lies: digital security in a networked world

Bestselling author Bruce Schneier offers his expert guidance on achieving security on a networkInternationally recognized computer security expert Bruce Schneier offers a practical, straightforward guide to achieving security throughout computer networks. Schneier uses his extensive field experience with his own clients to dispel the myths that often mislead IT managers as they try to build secure systems. This practical guide provides readers with a better understanding of why protecting information is harder in the digital world, what they need to know to protect digital information, how t

To mesh or not to mesh: flexible wireless indoor communication among mobile robots in industrial environments

Mobile robots such as automated guided vehicles become increasingly important in industry as they can greatly increase efficiency. For their operation such robots must rely on wireless communication, typically realized by connecting them to an existing enterprise network. In this paper we motivate that such an approach is not always economically viable or might result in performance issues. Therefore we propose a flexible and configurable mixed architecture that leverages on mesh capabilities whenever appropriate. Through experiments on a wireless testbed for a variety of scenarios, we analyse the impact of roaming, mobility and traffic separation and demonstrate the potential of our approach

Occupational mobility among blacks in South Africa

Bibliography: leaf 200-205.This study seeks to examine the extent, pattern, implications and determinants of occupational mobility among Blacks in South Africa and the economic context in response to which such mobility is occurring. Analysis is concentrated on the period 1960 to 1981 with particular emphasis on the 1970's. It is indicated that during this period notable changes occurred in the division of labour which was characterised by the rapid entry of blacks into 'petty bourgeois' and skilled manual occupations. This process took place in the context of rapid economic growth and particularly of rapid industrialisation. Emphasis is placed on an analysis of the determinants of occupational mobility among blacks in two cities in South Africa. The influence of socio-economic background and education are identified as being of primary importance as determinants of mobility. Particular attention is paid to an investigation of the effects that the legal status of black workers in urban areas has on the variables identified as notable determinants of occupational mobility, and directly on mobility itself. The emergent pattern of mobility and the determinants thereof are compared to the findings of studies in several other countries which provide the yardstick against which the domestic results can be measured. Finally, projections are made of the demand for and supply of labour till 1990. The implications of these projections, particularly for the educational system and skilled labour shortages are analysed

Jewish Muslim Dialogue: The Interreligious Challenge of the 21st Century

The 2009 Adolph and Ruth Schnurmacher Lecture in Judaic Studies… Rabbi Marc Schneier, Chairman, World Jewish Congress United States, President, The Foundation for Ethnic Understanding.https://digitalcommons.fairfield.edu/bennettcenter-posters/1272/thumbnail.jp

Feasibility demonstration for electroplating ultra-thin polyimide film

The effect of electrodeposition variables on film thickness was investigated using a dilute polyimide solution as a bath into which aluminum (as foil or as a vapor deposited coating) was immersed. The electrodeposited film was dried for 2 hours at 93 C (primarily to remove solvent) and cured for 18 hours at 186 C. Infrared studies indicate that imide formation (curing) occurs at 149 C under vacuum. From a conceptual viewpoint, satisfactory film metallized on one side can be obtained by this method. The cured ultra thin polyimide film exhibits properties equivalent to those of commercial film, and the surface appearance of the strippable polyimide film compares favorably with that of a sample of commercial film of thicker gauge. The feasibility of manufacturing approximately one million sq m of ultra thin film capable of being joined to fabricate an 800 m by 9 800 m square from starting material 0.5 to 1 m wide for space erectable structures was demonstrated