Welfare Reform and Immigrant Participation in the Supplemental Security Income Program

We examine the effect of the 1996 welfare reform legislation on participation in the Supplemental Security Income (SSI) program by immigrants. Although none of the immigrants on the SSI rolls before welfare reform lost eligibility, the potential exists for future impacts on the SSI caseload and the well-being of recent immigrants. We use microdata files from the Social Security Administration’s Continuous Work History Sample matched to administrative data on SSI participation for the period 1993 to 1999. We estimate simple models of SSI participation and compare our results to the existing literature. We then estimate a series of difference-in-differences models of SSI participation. These models compare SSI participation by immigrants relative to nativeborn individuals, and among affected immigrants relative to unaffected immigrants and native-born individuals, before and after welfare reform. Descriptive results indicate that the percentage of immigrants and natives receiving SSI decreased after welfare reform, but by a larger percentage for natives than for immigrants. The probability of SSI participation decreased after welfare reform for immigrants who were affected by the legislation relative to immigrants who were unaffected. The difference-in-differences estimate is positive for immigrants relative to otherwise similar natives, but the estimated effect among affected immigrants is about half as large as the effect for unaffected immigrants. When the sample is limited to low earners as a proxy for the SSI means test, the results are qualitatively unchanged but quantitatively much stronger. Authors’ Acknowledgements We are grateful to Ulyses Balderas for assisting with the collection of some data used here. A previous version of this paper was presented at the 2004 Western Regional Science Association Annual Meeting, February 25-28, 2004, Maui, HI.

Free energy functionals for efficient phase field crystal modeling of structural phase transformations

The phase field crystal (PFC) method has emerged as a promising technique for modeling materials with atomistic resolution on mesoscopic time scales. The approach is numerically much more efficient than classical density functional theory (CDFT), but its single mode free energy functional only leads to lattices with triangular (2D) or BCC (3D) symmetries. By returning to a closer approximation of the CDFT free energy functional, we develop a systematic construction of two-particle direct correlation functions that allow the study of a broad class of crystalline structures. This construction examines planar spacings, lattice symmetries, planar atomic densities and the atomic vibrational amplitude in the unit cell of the lattice and also provides control parameters for temperature and anisotropic surface energies. The power of this new approach is demonstrated by two examples of structural phase transformations.Comment: 4 pages, 4 figure

Legal U.S. Immigration: Influences on Gender, Age, and Skill Composition

The authors develop empirical models that enable them to examine the influence of two important determinants - source country characteristics and U.S. immigration policy - on the gender, age, and skills of immigrants coming to America.https://research.upjohn.org/up_press/1064/thumbnail.jp

Skill-biased technological change and the business cycle

Over the past two decades, technological progress in the United States has been biased towards skilled labor. What does this imply for business cycles? We construct a quarterly skill premium from the CPS and use it to identify skill-biased technology shocks in a VAR with long-run zero and sign restrictions. Hours fall in response to skill-biased technology shocks, indicating that part of the technology-induced fall in hours is due to a compositional shift in labor demand. Investment-specific technology shocks reduce the skill premium, indicating that capital and skill are not complementary in aggregate production

Problem-Based Learning: A Tale of Three Courses

Courses in engineering and science are typically taught deductively, through transmission of information from instructor to student, followed by practice problems to reinforce what was covered in readings and lectures. Yet in our personal and professional lives, we learn experientially – by facing a real situation and attempting to address it, and from our related successes and failures. Experiential education emphasizes a mixture of content and experiences, connection of learning to meaning and to the world outside of the classroom, and reflection on this for higher order learning and development of new skills and capabilities. Problem-based Learning (PBL) is an inductive, active learning approach that connects learning to real world problems, and provides a context in which students can tether their knowledge and internalize course concepts. Students are thus motivated to seek out a deeper understanding of the concepts they need to address the problems presented in a course. This research focuses on going beyond the technical lecture to enhance the student experience through PBL and experiential education techniques, based on implementation in the Rochester Institute of Technology’s (RIT) College of Engineering Technology, in courses in telecommunications engineering and environmental sustainability. PBL content was developed and implemented with a goal of motivating and exciting students, and enabling them to internalize the knowledge for deeper understanding. This included enhancing students’ ability to think critically about real-world challenges in engineering and sustainability, as well as their ability to address these challenges through an inductive, experiential approach that mirrors the way they will need to approach problem solving in professional practice. Assessments suggest initial challenges for students in self-directed research and working outside of their comfort zone, but ultimately there is evidence of tangible value for student learning, skill development, and ability to succeed and thrive in the field

Crossover Scaling of Wavelength Selection in Directional Solidification of Binary Alloys

We simulate dendritic growth in directional solidification in dilute binary alloys using a phase-field model solved with an adaptive-mesh refinement. The spacing of primary branches is examined for a range of thermal gradients and alloy compositions and is found to undergo a maximum as a function of pulling velocity, in agreement with experimental observations. We demonstrate that wavelength selection is unambiguously described by a non-trivial crossover scaling function from the emergence of cellular growth to the onset of dendritic fingers, a result validated using published experimental data.Comment: 4 pages, four figures, submitted to Physical Review Letter

Importance of the Doppler Effect to the Determination of the Deuteron Binding Energy

The deuteron binding energy extracted from the reaction ${}^1H(n,\gamma){}^2H$ is reviewed with the exact relativistic formula, where the initial kinetic energy and the Doppler effect are taken into account. We find that the negligible initial kinetic energy of the neutron could cause a significant uncertainty which is beyond the errors available up to now. Therefore, we suggest an experiment which should include the detailed informations about the initial kinetic energy and the detection angle. It could reduce discrepancies among the recently reported values about the deuteron binding energy and pin down the uncertainty due to the Doppler broadening of $\gamma$ ray.Comment: 5 page