Investigation of the ionospheric Faraday rotation for use in orbit corrections

The possibility of mapping the Faraday factors on a worldwide basis was examined as a simple method of representing the conversion factors for any possible user. However, this does not seem feasible. The complex relationship between the true magnetic coordinates and the geographic latitude, longitude, and azimuth angles eliminates the possibility of setting up some simple tables that would yield worldwide results of sufficient accuracy. Tabular results for specific stations can easily be produced or could be represented in graphic form

Ionospheric range-rate effects in satellite-to-satellite tracking

Investigation of ionospheric range and range-rate corrections in satellite-to-satellite tracking were investigated. Major problems were cited and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information, as a simple median model cannot possibly account for the complex interaction of the many variables. The findings provide a basis from which the residual errors can be estimated after ionospheric modeling is incorporated in the reduction. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits

Explanation of the computer listings of Faraday factors for INTASAT users

Using a simplified form of the Appleton-Hartree formula for the phase refractive index, a relationship was obtained between the Faraday rotation angle along the angular path and the total electron content along the vertical path, intersecting the angular at the height of maximum electron density. Using the second mean value theorem of integration, the function B cosine theta second chi was removed from under the integral sign and replaced by a 'mean' value. The mean value factors were printed on the computer listing for 39 stations receiving signals from the INTASAT satellite during the specified time period. The data is presented by station and date. Graphs are included to demonstrate the variation of the Faraday factor with local time and season, with magnetic latitude, elevation and azimuth angles. Other topics discussed include a description of the bent ionospheric model, the earth's magnetic field model, and the sample computer listing

On the Job Search and the Wage Distribution

Estimates of the structural parameters of a job separation model derived from the theory of on-the-job search are reported in this paper. Given that each employer pays the same wage to observably equivalent workers but wages are dispersed across employers, the theory implies that an employer's separation flow is the sum of an exogenous outflow unrelated to the wage paid and a job-to-job flow that decreases with the employer's wage. The specification estimated allows worker search effort to depend on the wage currently earned. The empirical results imply that search effort declines with the wage paid, as the theory predicts, using Danish IDA data for the years 1994-1995. Furthermore, the estimates for the full sample and four occupational sub-samples explain the employment effect, defined as the horizontal difference between the distribution of wages earned and the distribution of wages offered.

A Multistage Stochastic Programming Approach to the Dynamic and Stochastic VRPTW - Extended version

We consider a dynamic vehicle routing problem with time windows and stochastic customers (DS-VRPTW), such that customers may request for services as vehicles have already started their tours. To solve this problem, the goal is to provide a decision rule for choosing, at each time step, the next action to perform in light of known requests and probabilistic knowledge on requests likelihood. We introduce a new decision rule, called Global Stochastic Assessment (GSA) rule for the DS-VRPTW, and we compare it with existing decision rules, such as MSA. In particular, we show that GSA fully integrates nonanticipativity constraints so that it leads to better decisions in our stochastic context. We describe a new heuristic approach for efficiently approximating our GSA rule. We introduce a new waiting strategy. Experiments on dynamic and stochastic benchmarks, which include instances of different degrees of dynamism, show that not only our approach is competitive with state-of-the-art methods, but also enables to compute meaningful offline solutions to fully dynamic problems where absolutely no a priori customer request is provided.Comment: Extended version of the same-name study submitted for publication in conference CPAIOR201

Mode Combinations and International Operations: Theoretical Issues and an Empirical Investigation

An enduring characteristic of extant literature on foreign operation modes is its discrete choice approach, where companies are assumed to choose one among a small number of distinctive alternatives. • In this paper, detailed information about the operations of six Norwegian companies in three key markets (China, UK and USA) is used as the basis for an exploration of the extent to which, and how and why, companies combine clearly different foreign operation modes. We examine their use of foreign operation mode combinations within given value activities as well as within given countries. • The study reveals that companies tend to combine modes of operation; thereby producing unique foreign operation mode “packages” for given activities and/or countries, and that the packages are liable to be modified over time – providing a potentially important optional path for international expansion. • The data show considerable variation across cases; ranging from extensive use of mode combinations to a singular focus on a specific mode of operation. The study contributes to a refinement of our understanding of the path of internationalisation, and throws up a number of awkward theoretical questions about the process