635 research outputs found
user's guide to viscosity solutions of second order partial differential equations
The notion of viscosity solutions of scalar fully nonlinear partial
differential equations of second order provides a framework in which startling
comparison and uniqueness theorems, existence theorems, and theorems about
continuous dependence may now be proved by very efficient and striking
arguments. The range of important applications of these results is enormous.
This article is a self-contained exposition of the basic theory of viscosity
solutions.Comment: 67 page
Effect of Intermetallic Growth on Durability of High Temperature Solders (SnAg, SAC305, SAC+Mn, SnAg+Cu Nano) in Thermal and Vibration Environments
The RoHS ban of lead from electronics has pushed the industry to find lead free alternatives. In high temperature environments, high lead solders have typically been used. A suitable lead free replacement alloy is required. In this study quad flat packages (QFP) and 2512 chip resistors soldered with commercially available Sn3.5Ag and SAC305, and experimental SAC+Mn and SnAg+Cu Nano alloys on ENIG finished copper were subjected to three tests. Isothermal aging at 185°C for up to 1000 hours and at 200°C for up to 500 hours were performed to measure the interfacial intermetallic thickness, assess intermetallic compounds, and view the microstructure. A durability assessment was performed featuring thermal cycling ranges of -40 to 185°C and -40 to 200°C intermixed with 50G vibration cycling to determine the most durable solder alloy. Failure analysis was performed to understand the durability results. Finally, shear testing was performed to determine a correlation between shear strength and durability. The results show SAC305 is the most reliable solder under these conditions
Convexity criteria and uniqueness of absolutely minimizing functions
We show that absolutely minimizing functions relative to a convex Hamiltonian
are uniquely determined by their boundary
values under minimal assumptions on Along the way, we extend the known
equivalences between comparison with cones, convexity criteria, and absolutely
minimizing properties, to this generality. These results perfect a long
development in the uniqueness/existence theory of the archetypal problem of the
calculus of variations in Comment: 34 page
Opportunity for All: How the American Public Benefits From Internet Access at U.S. Libraries
Examines the use of free computer and Internet access in public libraries, by income level, age, race/ethnicity, and online activity. Explores libraries' role as a community resource for social media, education, employment, e-government, and other areas
Identifying First-person Camera Wearers in Third-person Videos
We consider scenarios in which we wish to perform joint scene understanding,
object tracking, activity recognition, and other tasks in environments in which
multiple people are wearing body-worn cameras while a third-person static
camera also captures the scene. To do this, we need to establish person-level
correspondences across first- and third-person videos, which is challenging
because the camera wearer is not visible from his/her own egocentric video,
preventing the use of direct feature matching. In this paper, we propose a new
semi-Siamese Convolutional Neural Network architecture to address this novel
challenge. We formulate the problem as learning a joint embedding space for
first- and third-person videos that considers both spatial- and motion-domain
cues. A new triplet loss function is designed to minimize the distance between
correct first- and third-person matches while maximizing the distance between
incorrect ones. This end-to-end approach performs significantly better than
several baselines, in part by learning the first- and third-person features
optimized for matching jointly with the distance measure itself
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