Garvin’s generalized problem revisited

One of the great classical problems in theoretical seismology is Garvin’s problem, which deals with the response of an elastic half-space subjected to a blast line source applied in its interior. However, Garvin (Exact transient solution of the buried line source problem. Proceedings of the Royal Society of London, Series A 1956;528–541[4]) himself provided only the solution for points on the free surface of the half-space. Although a rigorous extension to points in the interior of the half-space was given nearly decade-and-a-half later by Alterman and Loewenthal (Algebraic expressions for the impulsive motion of an elastic half-space. Israel Journal of Technology 1969; 7 (6):495–504[1]), these scientists published their paper in a technical journal of rather restricted circulation, as a result of which their complete solution remained largely unnoticed by the geophysical and soil dynamics communities. This article revisits Garvin’s generalized problem, presents a concise rendition and summary together with a very effective and accurate simplification, and examines the response characteristics for a pair of buried source-receiver location. It also includes a compact and very effective Matlab program for its evaluation.Universidad Nacional Autonoma de Mexico (Project IN104712)Universidad Nacional Autonoma de Mexico (Project IC100511

A Complex Network Approach to Analyzing the Structure and Dynamics of Power Grids

Electrical energy generation and distribution systems are good examples of complex systems. They include continuous, discrete, and social dynamics. They are operated by millions of human and non-human (or electro-mechanical) agents, and they show statistical properties found in other complex systems, such as power-law distributions in failure sizes. A number of recent large blackouts in Europe and North America have emphasized the societal importance of understanding these dynamics. Classical electromagnetic analysis alone frequently does not provide the insight required to characterize and mitigate risks in the electricity infrastructure. The objective of this thesis is to obtain insights into the dynamics of power grids using tools from the science of complex systems. In particular, this thesis will compare the topology, electrical structure, and attack/failure tolerance of power grids with those of theoretical graph structures such as regular, random, small-world, and scale-free networks. Simulation results in this thesis will describe the cost of the disturbances as a function of failure or attack sizes. The cost associated with network perturbations is often measured by changes on the diameter or average path length, whereas in the electricity industry, the loss of power demand (or blackout size) is the best indicator of the cost or impact of disturbances to electricity infrastructure

FPGA Implementation for Real-Time Background Subtraction Based on Horprasert Model

Background subtraction is considered the first processing stage in video surveillance systems, and consists of determining objects in movement in a scene captured by a static camera. It is an intensive task with a high computational cost. This work proposes an embedded novel architecture on FPGA which is able to extract the background on resource-limited environments and offers low degradation (produced because of the hardware-friendly model modification). In addition, the original model is extended in order to detect shadows and improve the quality of the segmentation of the moving objects. We have analyzed the resource consumption and performance in Spartan3 Xilinx FPGAs and compared to others works available on the literature, showing that the current architecture is a good trade-off in terms of accuracy, performance and resources utilization. With less than a 65% of the resources utilization of a XC3SD3400 Spartan-3A low-cost family FPGA, the system achieves a frequency of 66.5 MHz reaching 32.8 fps with resolution 1,024 × 1,024 pixels, and an estimated power consumption of 5.76 W

Systematic generation of finite-range atomic basis sets for linear-scaling calculations

Basis sets of atomic orbitals are very efficient for density functional calculations but lack a systematic variational convergence. We present a variational method to optimize numerical atomic orbitals using a single parameter to control their range. The efficiency of the basis generation scheme is tested and compared with other schemes for multiple zeta basis sets. The scheme shows to be comparable in quality to other widely used schemes albeit offering better performance for linear-scaling computations

Imaging the Kirkendall effect in pyrite (FeS2) thin films: cross-sectional microstructure and chemical features

This investigation provides novel data on the structure and chemical composition of pyrite thin films and new hints concerning their formation mechanism. From TEM-HAADF data, it has been found that the films are composed of two different layers: one is very compact and the other one is quite porous with many voids separating a few groups of grains. This porous layer is always in direct contact with the substrate, and its thickness is quite similar to that of the original Fe film. The average size of pyrite grains is equal in both layers, what suggests that the same process is responsible for their formation. Concentration profiles of sulfur, iron and some impurities (mainly sodium and oxygen from the glass substrate) through both layers are given in this work, and thus chemical inhomogeneities of the films are proved by the obtained stoichiometric ratios (S/Fe). Moreover, Na from sodalime glass substrates mainly accumulates at the pyrite grain boundaries and barely dopes them. The obtained results support the hypothesis that the iron sulfuration process essentially induces the diffusion of iron atoms, what leads to the porous layer formation as a manifestation of the Kirkendall Effect. Therefore, it seems that the same mechanisms that operate in the synthesis of surface hollow structures at the nanoscale are also active in the formation of pyrite thin films ranging from several tens to hundreds of nanometersMembers of MIRE Group acknowledge the financial support of the Spanish MICINN under project RTI2018-099794-B-I00. E. Flores acknowledges the intramural CSIC project 2D-MeSes funding and the service from the MiNa Laboratory at IMN, and funding from CM (project SpaceTec, S2013/ICE2822), MINECO (project CSIC13-4E1794) and EU (FEDER,FSE). Financial support through the project UMA18-FEDERJA-041 is gratefully acknowledge

Interassociation Consensus Statement on Cardiovascular Care of College Student-Athletes

Cardiovascular evaluation and care of college student-athletes is gaining increasing attention from both the public and medical communities. Emerging strategies include screening of the general athlete population, recommendations of permissible levels of participation by athletes with identified cardiovascular conditions, and preparation for responding to unanticipated cardiac events in athletic venues. The primary focus has been sudden cardiac death and the utility of screening with or without advanced cardiac screening. The National Collegiate Athletic Association convened a multidisciplinary task force to address cardiovascular concerns in collegiate student-athletes and to develop consensus for an interassociation statement. This document summarizes the task force deliberations and follow-up discussions, and includes available evidence on cardiovascular risk, pre-participation evaluation, and the recognition of and response to cardiac arrest. Future recommendations for cardiac research initiatives, education, and collaboration are also provided