Decomposition Based Search - A theoretical and experimental evaluation

In this paper we present and evaluate a search strategy called Decomposition Based Search (DBS) which is based on two steps: subproblem generation and subproblem solution. The generation of subproblems is done through value ranking and domain splitting. Subdomains are explored so as to generate, according to the heuristic chosen, promising subproblems first. We show that two well known search strategies, Limited Discrepancy Search (LDS) and Iterative Broadening (IB), can be seen as special cases of DBS. First we present a tuning of DBS that visits the same search nodes as IB, but avoids restarts. Then we compare both theoretically and computationally DBS and LDS using the same heuristic. We prove that DBS has a higher probability of being successful than LDS on a comparable number of nodes, under realistic assumptions. Experiments on a constraint satisfaction problem and an optimization problem show that DBS is indeed very effective if compared to LDS.Comment: 16 pages, 8 figures. LIA Technical Report LIA00203, University of Bologna, 200

Opportunity Road: The Promise and Challenge of America's Forgotten Youth

There are millions of youth ages 16 to 24 who are out of school and out of work. They cost the nation billions of dollars every year and over their lifetimes in lost productivity and increased social services. They also represent an opportunity for the nation to tap the talents of millions of potential leaders and productive workers at a time when America's skills gap is significant. The central message of this report is that while these youth face significant life challenges, most start out with big dreams and remain confident or hopeful that they can achieve their goals; most accept responsibility for their futures; and most are looking to reconnect to school, work and service. They point the way to how they can effectively reconnect to education, productive work and civic life. On behalf of Civic Enterprises and the America's Promise Alliance, Peter D. Hart Research Associates undertook a national cross-section of opportunity youth in 23 diverse locations across the United States in August 2011 to learn about common elements in their personal histories and their lives today, and to explore opportunities to reconnect them to work and school. At the time of the survey, respondents were ages 16 to 24, neither enrolled in school nor planning to enroll in the coming year, were not working, and had not completed a college degree. In addition, they were not disabled such as to prevent long-term employment, were not incarcerated, and were not a stay-at-home parent with a working spouse. What the authors found was both heartbreaking and uplifting, frustrating and hopeful. Despite many growing up in trying circumstances of little economic means and weak family and social supports, the youth they surveyed were optimistic about their futures. More than half believed they would graduate college when they were growing up and their hopes remain high that they will achieve the American Dream with a strong family life of their own and a good job one day. For this reason, the authors believe they are truly "opportunity youth"--both for their belief in themselves that must be nurtured and for the opportunity they hold for America

A cellular automaton for the factor of safety field in landslides modeling

Landslide inventories show that the statistical distribution of the area of recorded events is well described by a power law over a range of decades. To understand these distributions, we consider a cellular automaton to model a time and position dependent factor of safety. The model is able to reproduce the complex structure of landslide distribution, as experimentally reported. In particular, we investigate the role of the rate of change of the system dynamical variables, induced by an external drive, on landslide modeling and its implications on hazard assessment. As the rate is increased, the model has a crossover from a critical regime with power-laws to non power-law behaviors. We suggest that the detection of patterns of correlated domains in monitored regions can be crucial to identify the response of the system to perturbations, i.e., for hazard assessment.Comment: 4 pages, 3 figure

Anisotropy-based mechanism for zigzag striped patterns in magnetic thin films

In this work we studied a two dimensional ferromagnetic system using Monte Carlo simulations. Our model includes exchange and dipolar interactions, a cubic anisotropy term, and uniaxial out-of-plane and in-plane ones. According to the set of parameters chosen, the model including uniaxial out-of-plane anisotropy has a ground-state which consists of a canted state with stripes of opposite out-of-plane magnetization. When the cubic anisotropy is introduced zigzag patterns appear in the stripes at fields close to the remanence. An analysis of the anisotropy terms of the model shows that this configuration is related to specific values of the ratio between the cubic and the effective uniaxial anisotropy. The mechanism behind this effect is related to particular features of the anisotropy's energy landscape, since a global minima transition as a function of the applied field is required in the anisotropy terms. This new mechanism for zigzags formation could be present in monocrystal ferromagnetic thin films in a given range of thicknesses.Comment: 910 pages, 10 figure

Adaptation to Hypoxia: A Chimera?

"The Chimera was, according to Greek mythology, a monstrous fire-breathing hybrid creature of Lycia in Asia Minor, composed of the parts of more than one animal [...]