Social Learning and Course Choice

We use a broad sample of students to examine the course selection process and find evidence of social learning from peers. We also find that as the number of times students solve the course selection problem increases, they rely less on social learning and more on their own experience, limiting the potential for herd behaviour. Our results give insight to instructors about the reasons why students may be in their classes and suggest that information about courses and help in evaluating this information is especially important for students early in their college careers.

Paper Session II-C - Operational Space Support to Tactical Forces

The driving reasons for developing space systems in DOD at the dawn of the space age were strategic in nature. Arms control and intettigence constituted space imperatives at the height of the Cold War. Tactical applications came later and with much less priority. Although much of this division of priorities continues today, Space Support to the Warflghters has become an increasingly common theme. Acquisition driven by combat related requirements is the new imperative by which development organizations must abide. We\u27ve become so quickly attuned to this activity that we have identified a separate mission area and given it a name: Force Enhancement. We talk about it as though we knew what it was, and refer to it as though others understand what we mean. In fact, very few understand the term. Many engaged in the area are even working counter to our warfighters\u27 true needs. To understand such an argumentative statement, consider the following observations. Ground mobile forces (which also include air units) must have small, rugged1 radio receivers in order to operate in a battle zone. They need to take their comm with them when they move, and they need to move in a hostile environment. These forces also need assured access to communications networks so they get the support they need when they need it. Their lives depend on responsiveness and they cannot tolerate delays in critical combat situations. Their comm requirements are simple: keep it small, rugged, and! guarantee access

Paper Session III-C - Prudent Planning for Space Operations

This- paper has been developed, in four separate but interrelated parts. Each part could stand alone. Together, the four sections cover broad subject areas rather than focusing on narrow issues. These subject areas mutually affect, each other, however.. Taken together, they make a strong statement about certain directions \u27for the USAF in space.

Paper Session IV-A - Optimum Military Space Force Structure Characteristics

This paper describes the characteristics of operational military space systems in the conceptual (year 2015) future. Many studies have been completed in recent years, and more are currently underway. All seem to have arrived at similar conclusions, however. Therefore, this paper summarizes what appears to have become a shared vision of the future. Air Force Space Policy tells us that there are four mission areas for activity: Space Support, Force Enhancement, Space Control, and Force Application. The shared vision described here covers only the first two. Desired characteristics of launch vehicles, satellite control systems, and those spacecraft designed to assist terrestrial forces are presente

Search for Supersymmetry Using Boosted Higgs Bosons and Missing Transverse Momentum in Proton-Proton Collisions at 13 TeV

A search for physics beyond the Standard Model in events with one or more high-momentum Higgs bosons decaying to pairs of b quarks in association with missing transverse momentum is presented. The data, corresponding to an integrated luminosity of 35.9 fb-1, were collected with the CMS detector at the Large Hadron Collider in proton-proton collisions at the center-of-mass energy &radic;s = 13TeV. The analysis utilizes a new b quark tagging technique based on jet substructure to identify jets from Higgs ⟶ bb̅&nbsp;decays. Events are categorized by the number of bb̅-tagged jets, the mass of the jets, and the missing transverse momentum. No significant deviations from Standard Model expectations are observed. In the context of supersymmetry, limits on the cross sections of pair-produced gluinos are set, assuming that gluinos decay to quark pairs and a Higgs or Z boson, and the lightest supersymmetric particle. The decay chain proceeds through an intermediate particle assumed to be the second lightest in the theory. Assuming a large mass splitting between these two neutral particles, and 100% NLSP branching fraction to Higgs bosons, the lower limit on the gluino mass is found to be 2010 GeV.</p

R-modes in Neutron Stars with Crusts: Turbulent Saturation, Spin-down, and Crust Melting

Rossby waves (r-modes) have been suggested as a means to regulate the spin periods of young or accreting neutron stars, and also to produce observable gravitational wave radiation. R-modes involve primarily transverse, incompressive motions of the star's fluid core. However, neutron stars gain crusts early in their lives: therefore, r-modes also imply shear in the fluid beneath the crust. We examine the criterion for this shear layer to become turbulent, and derive the rate of dissipation in the turbulent regime. Unlike dissipation from a viscous boundary layer, turbulent energy loss is nonlinear in mode energy and can therefore cause the mode to saturate at amplitudes typically much less than unity. This energy loss also reappears as heat below the crust. We study the possibility of crust melting as well as its implications for the spin evolution of low-mass X-ray binaries. Lastly, we identify some universal features of the spin evolution that may have observational consequences.Comment: 12 pages, 4 figures, submitted to Ap

Source illusion devices for flexural Lamb waves using elastic metasurfaces

Metamaterials with the transformation method has greatly promoted the development in achieving invisibility and illusion for various classical waves. However, the requirement of tailor-made bulk materials and extreme constitutive parameters associated to illusion designs hampers its further progress. Inspired by recent demonstrations of metasurfaces in achieving reduced versions of electromagnetic cloaks, we propose and experimentally demonstrate source illusion devices to manipulate flexural waves using metasurfaces. The approach is particularly useful for elastic waves due to the lack of form-invariance in usual transformation methods. We demonstrate metasurfaces for shifting, transforming and splitting a point source with "space-coiling" structures. The effects are found to be broadband and robust against a change of source position, with agreement from numerical simulations and Huygens-Fresnel theory. The proposed approach provides an avenue to generically manipulate guided elastic waves in solids, and is potentially useful for applications such as non-destructive testing, enhanced sensing and imaging

Uncertainty quantification in medical image segmentation with normalizing flows

Medical image segmentation is inherently an ambiguous task due to factors such as partial volumes and variations in anatomical definitions. While in most cases the segmentation uncertainty is around the border of structures of interest, there can also be considerable inter-rater differences. The class of conditional variational autoencoders (cVAE) offers a principled approach to inferring distributions over plausible segmentations that are conditioned on input images. Segmentation uncertainty estimated from samples of such distributions can be more informative than using pixel level probability scores. In this work, we propose a novel conditional generative model that is based on conditional Normalizing Flow (cFlow). The basic idea is to increase the expressivity of the cVAE by introducing a cFlow transformation step after the encoder. This yields improved approximations of the latent posterior distribution, allowing the model to capture richer segmentation variations. With this we show that the quality and diversity of samples obtained from our conditional generative model is enhanced. Performance of our model, which we call cFlow Net, is evaluated on two medical imaging datasets demonstrating substantial improvements in both qualitative and quantitative measures when compared to a recent cVAE based model.Comment: 12 pages. Accepted to be presented at 11th International Workshop on Machine Learning in Medical Imaging. Source code will be updated at https://github.com/raghavian/cFlo