A review of nonlinear constitutive models for metals

Over the past two decades a number of thermomechanical constitutive theories have been proposed for viscoplastic metals. These models are in most cases similar in that they utilize a set of internal state variables which provide locally averaged representations of microphysical phenomena such as dislocation rearrangement and grain boundary sliding. The state of development of several of these models is now at the point where accurate theoretical solutions can be obtained for a wide variety of structural problems at elevated temperatures. The fundamentals of viscoplasticity are briefly reviewed and a general framework is outlined. Several of the more prominent models are reviewed, and predictions from models are compared to experimental results

Progressive failure methodologies for predicting residual strength and life of laminated composites

Two progressive failure methodologies currently under development by the Mechanics of Materials Branch at NASA Langley Research Center are discussed. The damage tolerance/fail safety methodology developed by O'Brien is an engineering approach to ensuring adequate durability and damage tolerance by treating only delamination onset and the subsequent delamination accumulation through the laminate thickness. The continuum damage model developed by Allen and Harris employs continuum damage laws to predict laminate strength and life. The philosophy, mechanics framework, and current implementation status of each methodology are presented

Symmetric photon-photon coupling by atoms with Zeeman-split sublevels

We propose a simple scheme for highly efficient nonlinear interaction between two weak optical fields. The scheme is based on the attainment of electromagnetically induced transparency simultaneously for both fields via transitions between magnetically split F=1 atomic sublevels, in the presence of two driving fields. Thereby, equal slow group velocities and symmetric cross-coupling of the weak fields over long distances are achieved. By simply tuning the fields, this scheme can either yield giant cross-phase modulation or ultrasensitive two-photon switching.Comment: Modified scheme, 4 pages, 1 figur

Electronic Cigarettes in Maine: Health Effects, Marketing, Use, and Regulation

Electronic cigarettes (e-cigarettes) are electronic nicotine-delivery systems (ENDS) that deliver a vapor of nicotine and other potentially dangerous chemicals to the user; nonusers are also exposed. Driven by a well-funded advertising campaign, use of e-cigarettes has increased in Maine until it now exceeds the use of combustible cigarettes among youth. In 2015, 14.5 percent of female high school students and 18.8 percent of male high school students in Maine reported current use of e-cigarettes. Maine laws and city ordinances restrict e-cigarette use in some places where combustible cigarettes are banned, but legislative gaps remain. Most Maine schools, colleges, and hospitals also ban e-cigarettes, but again gaps remain. This article explores the marketing and use of e-cigarettes nationwide and in Maine and proposes policies to restrict access and use, particularly by youth

Outdoor Smoke-Free Policies in Maine

Incontrovertible evidence of the deadly impacts from both direct tobacco use and environmental exposure to tobacco smoke has led to the institution of smoking bans, first in indoor venues and, more recently, in some outdoor area. This article reviews the science behind smoking bans as well as the history and policy implications of smoking bans with an emphasis on the experience in Maine. As examples we focus on recent outdoor smoking bans in South Portland (parks and beaches) and smoke-free campus rules at a Maine hospital (Franklin Memorial Hospital) and a part of the University of Maine system (University of Southern Maine). Our conclusions highlight the interconnections among federal, state, municipal, and public institutional efforts to limit smoking and suggest pathways by which smoke-free areas can be expanded in Maine and elsewhere

Blue Swimmer Crab ( Portunus armatus ) and Mud Crab Scylla serrata and Scylla olivacea ) Resources in the North Coast and Gascoyne Coast Bioregions, Western Australia

Blue swimmer crab (Portunus armatus) are found along the entire Western Australia (WA) coast, in a range of estuarine, inshore and continental shelf areas (\u3c50 m). In the North Coast Bioregion (NCB), commercial fishing primarily occurs as part of the Pilbara Crab Managed Fishery (PCMF) which spans the inshore waters from Onslow through to Port Hedland, with most fishing activity taking place around Nickol Bay