Implementation of a digital optical phase conjugation system and its application to study the robustness of turbidity suppression by phase conjugation

In this work, we report a novel high capacity (number of degrees of freedom) open loop adaptive optics method, termed digital optical phase conjugation (DOPC), which provides a robust optoelectronic optical phase conjugation (OPC) solution. We showed that our prototype can phase conjugate light fields with ~3.9 x 10^(−3) degree accuracy over a range of ~3 degrees and can phase conjugate an input field through a relatively thick turbid medium (μ_sl ~13). Furthermore, we employed this system to show that the reversing of random scattering in turbid media by phase conjugation is surprisingly robust and accommodating of phase errors. An OPC wavefront with significant spatial phase errors (error uniformly distributed from – π/2 to π/2) can nevertheless allow OPC reconstruction through a scattering medium with ~40% of the efficiency achieved with phase error free OPC

Global Coal Risk Assessment: Data Analysis and Market Research

Coal-fired power plants are the largest contributor to the greenhouse gas emissions that cause climate change. In 2010, 61 countries produced coal and 104 countries consumed it. Global coal production reached 7,228.712 million tonnes that year and coal consumption reached 7,238.028 million tonnes. More than 60 percent of the coal consumed was used to generate power.This working paper assesses current global coal risks to the climate. It identifies the countries and companies involved in global coal production and consumption, and sheds light on global trends by mapping the proposed new coal power plants and related infrastructure. The paper is organized into five parts. Part 1 lists the proposed new coal-fired plants around the world, based on available data. Part 2 lists existing coal-fired plants. Part 3 offers an overview of the global coal trade, including analyses of country trends. Part 4 summarizes available studies of coal financing. Part 5 notes data gaps that can be filled by future research