Search

A total of 1,625 tornadoes occurred in the United States in 2011, resulting in economic losses that exceeded $25 billion. Two tornado outbreaks stand out because they caused more than half of those losses. The tornadoes that cut through Tuscaloosa, Alabama, on April 27 and Joplin, Missouri, on May 22 were responsible for a combined 223 fatalities and more than 13,000 damaged buildings in the two cities. Although the economic losses associated with tornado damage are well documented, the writers argue that the overall impact should encompass longer term, broader considerations such as the social disruption and psychological effects that impact communities. This paper examines observations by tornado damage assessment teams led by the first author in these two medium-sized cities and suggests that the evolution of building codes and past approaches to construction have led to conditions that made this extent of damage possible. The authors outline a multidisciplinary path forward that incorporates engineering research and social and economic studies into a new design paradigm leading to building code changes and social practices that will improve resistance and mitigate future losses at a community level from tornadoes.

Simulation of semiconductor diode laser performance involves interaction between multiple physics domains. This report presents the governing equations and finite-element (FE) implementation of such a simulation, including coupled calculation of electronic band structure, determined by solving Schrodinger's equation; carrier distribution and potential in the active region, solved using a drift-diffusion model; electrostatic potential in the ohmic regions, governed by Laplace's equation; temperature distribution, governed by Fourier's law and the heat equation; and light propagation, described by Maxwell's equations. Preliminary simulation results are provided for stripe lasers based on the GaAs/AlGaAs material system, including asymmetrically waveguided devices. Important implementation issues are discussed, particularly computation across multiple length scales and formulation of appropriate boundary conditions. Simulation results are compared to previous calculations reported in the literature. Advancement of the technical component is paralleled by development of a graphical user interface for ease of use by non-experts in FE methods., The original document contains color images.