Chaotic motion of space charge wavefronts in semiconductors under time-independent voltage bias

A standard drift-diffusion model of space charge wave propagation in semiconductors has been studied numerically and analytically under dc voltage bias. For sufficiently long samples, appropriate contact resistivity and applied voltage - such that the sample is biased in a regime of negative differential resistance - we find chaos in the propagation of nonlinear fronts (charge monopoles of alternating sign) of electric field. The chaos is always low-dimensional, but has a complex spatial structure; this behavior can be interpreted using a finite dimensional asymptotic model in which the front (charge monopole) positions and the electrical current are the only dynamical variables.Comment: 12 pages, 8 figure

Predictor Aided Tracking in a System with Time Delay - Performance Involving Flat Surface, Roll, and Pitch Conditions

Predictor aided human tracking performance with time delay control under flat surface, roll, pitch, and roll and pitch condition

Gender, Source Country Characteristics and Labor Market Assimilation among Immigrants: 1980-2000

We use 1980, 1990 and 2000 Census data to study the impact of source country characteristics on the labor supply assimilation profiles of married adult immigrant women and men. Women migrating from countries where women have high relative labor force participation rates work substantially more than women coming from countries with lower relative female labor supply rates, and this gap is roughly constant with time in the United States. These differences are substantial and hold up even when we control for wage offers and family formation decisions, as well as when we control for the emigration rate from the United States to the source country. Men's labor supply assimilation profiles are unaffected by source country female labor supply, a result that suggests that the female findings reflect notions of gender roles rather than overall work orientation. Findings for another indicator of traditional gender roles, source country fertility rates, are broadly similar, with substantial and persistent negative effects of source country fertility on the labor supply of female immigrants except when we control for presence of children, in which case the negative effects only become evident after ten years in the United States.fertility, labor supply, immigration, assimilation, gender

Introduction to a Special Issue on the Impact of Immigrant Legalization Initiatives: International Perspectives on Immigration and the World of Work

This article is the third in a series to celebrate the 70th anniversary of the ILR Review. The series features articles that analyze the state of research and future directions for important themes the journal has featured over its many years of publication. In this issue, we also feature a special cluster of articles and book reviews on one of the most critical labor market issues across the globe—the legalization and integration of immigrants into national labor markets. Despite the urgent need for immigration reform in the United States, there is a paucity of US research that looks at the impact of a shift from unauthorized to legal immigrant status in the workplace. The US immigration literature has also paid little attention to immigrant legalization policies outside of the United States, despite the fact that other countries have implemented such policies with far more regularity. The articles in this special issue draw on studies of legalization initiatives in major immigrant destinations: Canada, Italy, and the United Kingdom. Together they underscore the importance of cross-national perspectives for understanding the range of legalization programs and their impact on immigrant workers, the workplace, and the labor market. These findings contribute to key questions in migration scholarship and inform the global policy debate surrounding the integration and well-being of immigrant

Anisotropy effects in a mixed quantum-classical Heisenberg model in two dimensions

We analyse a specific two dimensional mixed spin Heisenberg model with exchange anisotropy, by means of high temperature expansions and Monte Carlo simulations. The goal is to describe the magnetic properties of the compound (NBu_{4})_{2}Mn_{2}[Cu(opba)]_{3}\cdot 6DMSO\cdot H_{2}O which exhibits a ferromagnetic transition at $T_{c}=15K$. Extrapolating our analysis on the basis of renormalisation group arguments, we find that this transition may result from a very weak anisotropy effect.Comment: 8 pages, 10 Postscript figure

Universality of the Gunn effect: self-sustained oscillations mediated by solitary waves

The Gunn effect consists of time-periodic oscillations of the current flowing through an external purely resistive circuit mediated by solitary wave dynamics of the electric field on an attached appropriate semiconductor. By means of a new asymptotic analysis, it is argued that Gunn-like behavior occurs in specific classes of model equations. As an illustration, an example related to the constrained Cahn-Allen equation is analyzed.Comment: 4 pages,3 Post-Script figure