The importance of the electronic contribution to linear magnetoelectricity

We demonstrate that the electronic contribution to the linear magnetoelectric response, usually omitted in first-principles studies, can be comparable in magnitude to that mediated by lattice distortions, even for materials in which responses are strong. Using a self-consistent Zeeman response to an applied magnetic field for noncollinear electron spins, we show how electric polarization emerges in linear magnetoelectrics through both electronic- and lattice-mediated components -- in analogy with the high- and low-frequency dielectric response to an electric field. The approach we use is conceptually and computationally simple, and can be applied to study both linear and non-linear responses to magnetic fields.Comment: 5 pages, 3 figure

The Influence of Resource Quality on Technological Persistence: Charcoal Iron in Quebec

Technological advances in the steel industry during the nineteenth century led to the dis-placement of charcoal, a vegetable fuel, by coke, a mineral fuel. Aspects of the technology developed to utilize coke, however, were also applicable to charcoal blast furnaces. The province of Quebec was the centre of the Canadian iron-making industry during the nineteenth century, but the technological advances introduced into processes for smelting iron with charcoal were not accepted in that province as they were elsewhere. The author looks to characteristics of the ore used in Quebec and the type of charcoal available locally to explain the persistence of old charcoal technology in Quebec iron smelters. The retention of old technology by Quebec iron-makers was a sensible response to local conditions. Moreover the small Canadian domestic market provided little incentive to adopt large-scale technologies during most of the nineteenth century. The Quebec experience with charcoal iron manufacture illustrates the subtle blend of factors that are involved in the assessment of technological change by potential beneficiaries. Résumé Les progrès techniques survenus dans l'indus-trie de l'acier au cours du XIXe siècle ont mené au remplacement du charbon de bois, com-bustible végétal, par le coke, combustible minéral. Les aspects de la technologie mise au point pour utiliser le coke, cependant, étaient aussi applicables aux fourneaux à charbon de bois. Le Québec était le centre de l'industrie canadienne de la sidérurgie au XIXe siècle mais les progrès techniques introduits dans le processus de fonte du fer par le charbon de bois n'y étaient pas acceptés comme ils l'étaient ailleurs. L'auteur voit dans les caractéristiques du minerai utilisé au Québec et dans le type de charbon de bois disponible localement l'explication de la persistance de la vieille technique au charbon de bois dans les fonderies du Québec. Cette conservation de la vieille technique constituait une réponse raisonnable des maîtres des forges aux conditions locales. En outre, au Canada, pendant la plus grande partie du XIXe siècle, l'étroitesse du marché national n 'incitait guère à adopter des technologies à grande échelle. L'expérience québécoise touchant l'utilisation du charbon de bois pour produire de la fonte illustre la subtile combinaison de facteurs qui intervient dans l'évaluation des changements techniques par leurs éventuels bénéficiaires

High-resolution, slant-angle scene generation and validation of concealed targets in DIRSIG

Traditionally, synthetic imagery has been constructed to simulate images captured with low resolution, nadir-viewing sensors. Advances in sensor design have driven a need to simulate scenes not only at higher resolutions but also from oblique view angles. The primary efforts of this research include: real image capture, scene construction and modeling, and validation of the synthetic imagery in the reflective portion of the spectrum. High resolution imagery was collected of an area named MicroScene at the Rochester Institute of Technology using the Chester F. Carlson Center for Imaging Science\u27s MISI and WASP sensors using an oblique view angle. Three Humvees, the primary targets, were placed in the scene under three different levels of concealment. Following the collection, a synthetic replica of the scene was constructed and then rendered with the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model configured to recreate the scene both spatially and spectrally based on actual sensor characteristics. Finally, a validation of the synthetic imagery against the real images of MicroScene was accomplished using a combination of qualitative analysis, Gaussian maximum likelihood classification, grey-level co-occurrence matrix derived texture metrics, and the RX algorithm. The model was updated following each validation using a cyclical development approach. The purpose of this research is to provide a level of confidence in the synthetic imagery produced by DIRSIG so that it can be used to train and develop algorithms for real world concealed target detection