Cartographic distortions make dielectric spacetime analog models imperfect mimickers

It is commonly assumed that if the optical metric of a dielectric medium is identical to the metric of a vacuum space-time then light propagation through the dielectric mimics light propagation in the vacuum. However, just as the curved surface of the Earth cannot be mapped into a flat plane without distortion of some surface features, so too is it impossible to project the behavior of light from the vacuum into a dielectric analog residing in Minkowski space-time without introducing distortions. We study the covariance properties of dielectric analog space-times and the kinematics of a congruence of light in the analog, and show how certain features can be faithfully emulated in the analog depending on the choice of projection, but that not all features can be simultaneously emulated without distortion. These findings indicate conceptual weaknesses in the idea of using analog space-times as a basis for transformation optics, and we show that a certain formulation of transformation optics closely related to analog space-times resolves these issues.Comment: 15 pages, 4 figure

Covariant kinematics of light in media and a generalized Raychaudhuri equation

There is ongoing interest in adopting various tools and ideas from general relativity for optical applications and the study of light propagation through natural or engineered media. Here, the covariant kinematics of light propagating through arbitrary dielectric media in curved space-times are derived, allowing for analysis and tracing of congruences of light through media that may smoothly vary in character between vacuum, positively refracting, and negatively refracting; or null, timelike, and spacelike with respect to the background metric. The kinematics are then used to generalize the Raychaudhuri equation -- an important tool in general relativity that describes the focus of a congruence. These results will be useful for the analysis of optical devices, particularly those designed using transformation optics, and serve as theoretical tools to study generalized concepts in general relativity.Comment: 22 pages, 1 figure. This version has changes to conform with version published in Phys Rev

Enhancing Inter functional coordination and marketing performance: utilization of the motivation/ability/opportunity framework

This paper integrates a large literature on intra-organisational relationships with the aim to understand how to enhance coordination between different functional units inside an organisation and to empirically examine the impact of inter functional coordination on marketing performance. By drawing on the Motivation/Ability/Opportunity (MAO) theoretical framework, this research attempts to examine factors to enhance employees? motivation/ability/opportunity to coordinate on improving inter functional coordination. The research also empirically examined the impact of inter functional coordination on marketing performance in terms of adaptiveness, effectiveness, efficiency and creativity of marketing programmes. The research conceptual model was tested with data collected from 274 structured surveys in medium to large Egyptian firms. Regression analysis was employed as a tool for testing the research hypotheses. The research findings suggest that the use of cross functional teams, resource dependency, joint reward systems, management support, positively affect the level of inter functional coordination. The research also showed that some factors, for example employees? interpersonal skills, might hinder coordination between functional units and these issues should be resolved in order to establish an effective inter functional coordination. The research provides empirical evidence of the direct positive impact of inter functional coordination on marketing performance

An experimental approach to determine the heat transfer coefficient in directional solidification furnaces

The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was experimentally determined using in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the theoretical value estimated by standard heat transfer calculations

A novel approach to determine the heat transfer coefficient in directional solidification furnaces

The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was determined using an approach utilizing in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the value estimated by standard heat transfer calculations

Push clocks: a new approach to charge-coupled devices clocking

A new approach to charge-coupled device clocking has been developed—dynamic push clocks. With dynamic push clocks, the charge is transferred by pushing it from one storage site to another. The push clock approach results in a larger signal dynamic range, larger signal-to-noise ratio, and better performance at both high and low frequencies