On the period of the coherent structure in boundary layers at large Reynolds numbers

The period of the large coherent structure in a subsonic, compressible, turbulent boundary layer was determined using the autocorrelation of the velocity and pressure fluctuations for Reynolds numbers between 5,000 and 35,000. In low Reynolds number flows the overall correlation period scaled with the outer variables - namely, the free stream velocity and the boundary layer thickness

The re-emission spectrum of digital hardware subjected to EMI

The emission spectrum of digital hardware under the influence of external electromagnetic interference is shown to contain information about the interaction of the incident energy with the digital circuits in the system. The generation mechanism of the re-emission spectrum is reviewed, describing how nonlinear effects may be a precursor to the failure of the equipment under test. Measurements on a simple circuit are used to demonstrate how the characteristics of the re-emission spectrum may be correlated with changes to the digital waveform within the circuit. The technique is also applied to a piece of complex digital hardware where Similar, though more subtle, effects can be measured. It is shown that the re-emission spectrum can be used to detect the interaction of the interference with the digital devices at a level well below that which is able to cause static failures in the circuits. The utility of the technique as a diagnostic tool for immunity testing of digital hardware, by identifying which subsystems are being affected by external interference, is also demonstrated

Baryons in the Field Correlator Method

The ground and $P$-wave excited states of $nnn$, $nns$ and $ssn$ baryons are studied in the framework of the field correlator method using the running strong coupling constant in the Coulomb-like part of the three-quark potential. The string correction for the confinement potential of the orbitally excited baryons, which is the leading contribution of the proper inertia of the rotating strings, is estimated.Comment: 6 pages, 2 figures. Talk given at APS April Meeting, Denver, Colorado, May 2-5, 2009 and at the Tenth Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2009), San Diego, California, May 26-31, 200

Exploring Contractor Renormalization: Tests on the 2-D Heisenberg Antiferromagnet and Some New Perspectives

Contractor Renormalization (CORE) is a numerical renormalization method for Hamiltonian systems that has found applications in particle and condensed matter physics. There have been few studies, however, on further understanding of what exactly it does and its convergence properties. The current work has two main objectives. First, we wish to investigate the convergence of the cluster expansion for a two-dimensional Heisenberg Antiferromagnet(HAF). This is important because the linked cluster expansion used to evaluate this formula non-perturbatively is not controlled by a small parameter. Here we present a study of three different blocking schemes which reveals some surprises and in particular, leads us to suggest a scheme for defining successive terms in the cluster expansion. Our second goal is to present some new perspectives on CORE in light of recent developments to make it accessible to more researchers, including those in Quantum Information Science. We make some comparison to entanglement-based approaches and discuss how it may be possible to improve or generalize the method.Comment: Completely revised version accepted by Phy Rev B; 13 pages with added material on entropy in COR

Dynamic wetting with two competing adsorbates

We study the dynamic properties of a model for wetting with two competing adsorbates on a planar substrate. The two species of particles have identical properties and repel each other. Starting with a flat interface one observes the formation of homogeneous droplets of the respective type separated by nonwet regions where the interface remains pinned. The wet phase is characterized by slow coarsening of competing droplets. Moreover, in 2+1 dimensions an additional line of continuous phase transition emerges in the bound phase, which separates an unordered phase from an ordered one. The symmetry under interchange of the particle types is spontaneously broken in this region and finite systems exhibit two metastable states, each dominated by one of the species. The critical properties of this transition are analyzed by numeric simulations.Comment: 11 pages, 12 figures, final version published in PR

Using personal statements in college admissions::An investigation of gender bias and the effects of increased structure

Personal statements are among the most commonly used instruments in college admissions procedures. Yet, little research on their reliability, validity, and fairness exists. The first aim of this paper was to investigate hypotheses about adverse impact and underprediction for female applicants, which could result from lower tendencies to use agentic language compared to male applicants. Second, we examined if rating personal statements in a more structured manner would increase reliability and validity. Using personal statements (250 words) from a large cohort of applicants to an undergraduate psychology program at a Dutch University, we found no evidence for adverse impact for female applicants or more agentic language use by male applicants, and no relationship between agentic language use and personal statement ratings. In contrast, we found that personal statements of female applicants were rated slightly more positively than those of males. Exploratory analyses suggest that female applicants’ better writing skills might explain this difference. A more structured approach to rating personal statements yielded higher, but still only ‘moderate’ inter-rater reliability, and virtually identical, negligible predictive validity for first year GPA and dropout

Urban robotic experimentation: San Francisco, Tokyo and Dubai

Advances in robotics, artificial intelligence and automation have the potential to transform cities and urban social life. However, robotic restructuring of the city is complicated and contested. Technology is still evolving, robotic infrastructure is expensive and there are technical, trust and safety challenges in bringing robots into dynamic urban environments alongside humans. This article examines the nascent field of ‘urban robotics’ in three emblematic yet diverse national-urban contexts that are leading centres for urban robotic experimentation. Focusing on the experimental application of autonomous social robots, the article explores: (i) the rationale for urban robotic experiments and the interests involved, and (ii) the challenges and outcomes of creating meaningful urban spaces for robotic experimentation. The article makes a distinctive contribution to urban research by illuminating a potentially far-reaching but under-researched area of urban policy. It provides a conceptual framework for mapping and understanding the highly contingent, spatially uneven and socially selective processes of robotic urban experimentation

A Top-down and Bottom-up look at Emissions Abatement in Germany in response to the EU ETS

This paper uses top-down trend analysis and a bottom-up power sector model to define upper and lower boundaries on abatement in Germany in the first phase of the EU Emissions Trading Scheme (2005-2007). Long-term trend analysis reveals the decoupling of economic activity and carbon emissions in Germany that has occurred since 1996 and has accelerated since 2005, in response to rising commodities prices, the introduction of a carbon trading, and other measures undertaken in Germany. Differing emission intensity trends and emissions counterfactuals are constructed using emissions, power generation, and macroeconomic data. Resulting top-down estimates set the upper bound of abatement in Phase I at 121.9 mn tons for all EU-ETS sectors and 56.7 mn tons for the power sector only. Using the tuned version of the model “E-simulate” a lower boundary of Phase I abatement is established at 13.2 million tons, based only on fuel switching in the power sector, which constitutes 61% of German ETS sector emissions. The paper characterizes abatement, critically discusses the underlying assumptions of the outcomes, and examines the impact of two main factors on power sector abatement, namely price and load.Massachusetts Institute of Technology. Center for Energy and Environmental Policy Research