Cross-correlation imaging of ambient noise sources

We develop and apply a novel technique to image ambient seismic noise sources. It is based on measurements of cross-correlation asymmetry defined as the logarithmic energy ratio of the causal and anticausal branches of the cross-correlation function. A possible application of this technique is to account for the distribution of noise sources, a problem which currently poses obstacles to noise-based surface wave dispersion analysis and waveform inversion. The particular asymmetry measurement used is independent of absolute noise correlation amplitudes. It is shown how it can be forward-modelled and related to the noise source power-spectral density using adjoint methods. Simplified sensitivity kernels allow us to rapidly image variations in the power-spectral density of noise sources. This imaging method correctly accounts for viscoelastic attenuation and is to first order insensitive to unmodelled Earth structure. Furthermore, it operates directly on noise correlation data sets. No additional processing is required, which makes the method fast and computationally inexpensive.We apply the method to three vertical-component cross-correlation data sets of different spatial and temporal scales. Processing is deliberately minimal so as to keep observations consistent with the imaging concept. In accord with previous studies, we image seasonally changing sources of the Earth's hum in the Atlantic, Pacific and the Southern Ocean. The sources of noise in the microseismic band recorded at stations in Switzerland are predominantly located in the Atlantic and show a clear dependence on both season and frequency. Our developments are intended as a step towards full 3-D inversions for the sources of ambient noise in various frequency bands, which may ultimately lead to improvements of noise-based structural imaging.This research was supported by the Swiss National Supercomputing Center (CSCS) in the form of the GeoScale and CH1 projects, by the Swiss National Science Foundation (SNF) under grant 200021 149143 and by the Netherlands Organisation for Scientific Research (VIDI grant 864.11.008). Iber-Array data are a contribution of the Team Consolider-Ingenio 2010 TOPO-IBERIA (CSD2006-00041).Peer reviewe

The accelerating influence of humans on mammalian macroecological patterns over the late Quaternary

The transition of hominins to a largely meat-based diet ~1.8 million years ago led to the exploitation of other mammals for food and resources. As hominins, particularly archaic and modern humans, became increasingly abundant and dispersed across the globe, a temporally and spatially transgressive extinction of large-bodied mammals followed; the degree of selectivity was unprecedented in the Cenozoic fossil record. Today, most remaining large-bodied mammal species are confined to Africa, where they coevolved with hominins. Here, using a comprehensive global dataset of mammal distribution, life history and ecology, we examine the consequences of “body size downgrading” of mammals over the late Quaternary on fundamental macroecological patterns. Specifically, we examine changes in species diversity, global and continental body size distributions, allometric scaling of geographic range size with body mass, and the scaling of maximum body size with area. Moreover, we project these patterns toward a potential future scenario in which all mammals currently listed as vulnerable on the IUCN\u27s Red List are extirpated. Our analysis demonstrates that anthropogenic impact on earth systems predates the terminal Pleistocene and has grown as populations increased and humans have become more widespread. Moreover, owing to the disproportionate influence on ecosystem structure and function of megafauna, past and present body size downgrading has reshaped Earth\u27s biosphere. Thus, macroecological studies based only on modern species yield distorted results, which are not representative of the patterns present for most of mammal evolution. Our review supports the concept of benchmarking the “Anthropocene” with the earliest activities of Homo sapiens

A new absolute arrival time data set for Europe

The main aim of this study is to create a data set of accurate absolute arrival times for stations in Europe which do not report to the International Seismological Centre (ISC). Waveforms were obtained from data centres and temporary experiments and a semi-automatic picking method was applied to determine absolute arrival times for P and S phases. 85 000 arrival times were picked whose distribution of residuals shows generally low standard deviations on the order of 0.5-0.7 s. Furthermore, mean teleseismic station residuals reflect the properties of the underlying crust and uppermost mantle. Comparison to ISC data for matching event-station-phase combinations also confirms the good quality of the new absolute arrival time picks. Most importantly, this data set complements the ISC data as it fills regional data coverage gaps in Europ

Hamiltonian Dynamics of Linearly Polarized Gowdy Models Coupled to Massless Scalar Fields

The purpose of this paper is to analyze in detail the Hamiltonian formulation for the compact Gowdy models coupled to massless scalar fields as a necessary first step towards their quantization. We will pay special attention to the coupling of matter and those features that arise for the three-handle and three-sphere topologies that are not present in the well studied three torus case -in particular the polar constraints that come from the regularity conditions on the metric. As a byproduct of our analysis we will get an alternative understanding, within the Hamiltonian framework, of the appearance of initial and final singularities for these models.Comment: Final version to appear in Classical and Quantum Gravit

Valoración del apoyo de la Unidad Asesoría en Red, uso de herramientas digitales e intereses para continuar aprendiendo. Reporte del cuestionario a profesores de ITESO

Reporte de los hallazgos de un cuestionario en línea donde profesores del ITESO compartieron su valoración acerca de la labor de la Unidad Asesoría en Red, del Centro de Aprendizaje en Red. Indicaron usos de herramientas digitales, y sus intereses o necesidades para continuar aprendiendo a propósito de la práctica universitaria y el aprendizaje en red, en la red. La consulta se realizó de junio a agosto de 2014.ITESO, .A.C

Aprendizaje organizacional en una empresa de tecnología de la información

Este documento tiene como propósito exponer el trabajo y los resultados obtenidos durante el Proyecto (PAP) “Aprendizaje organizacional en una empresa de tecnología de la información” primavera 2023. El objetivo principal consistió en dar continuidad al proyecto realizado en otoño del 2022 “Formalización y restructuración de una empresa trasnacional”. El propósito general de este proyecto fue elaborar 2 descripciones de puesto para asistente administrativo y técnico en ensamble, documentar el proceso de contratación, actualizar organigrama y realizar auditoría de recursos humanos. La finalidad es contar con una mejor organización de documentos, para agilizar procesos, al igual que se tiene mejor control y seguimiento de las actividades relacionadas con la empresa, ayudando a detectar áreas de oportunidades y corregir posibles errores. A lo largo de nueve semanas de igual número de sesiones de trabajo, se completó con éxito el programa de trabajo establecido para desarrollar las descripciones de puesto de trabajo, el organigrama actualizado y el documento de proceso de contratación. Debido al tiempo empleado en la elaboración del documento de proceso de contratación, la auditoría de recursos humanos se realizará el próximo periodo, a través de la intervención del siguiente equipo PAP.ITESO, A.C

uDDS: A Middleware for Real-time Wireless Embedded Systems

[EN] A Real-Time Wireless Distributed Embedded System (RTWDES) is formed by a large quantity of small devices with certain computing power, wireless communication and sensing/actuators capabilities. These types of networks have become popular as they have been developed for applications which can carry out a vast quantity of tasks, including home and building monitoring, object tracking, precision agriculture, military applications, disaster recovery, industry applications, among others. For this type of applications a middleware is used in software systems to bridge the gap between the application and the underlying operating system and networks. As a result, a middleware system can facilitate the development of applications and is designed to provide common services to the applications. The development of a middleware for sensor networks presents several challenges due to the limited computational resources and energy of the different nodes. This work is related with the design, implementation and test of a micro middleware for RTWDES; the proposal incorporates characteristics of a message oriented middleware thus allowing the applications to communicate by employing the publish/subscribe model. Experimental evaluation shows that the proposed middleware provides a stable and timely service to support different Quality of Service (QoS) levels. © 2011 Springer Science+Business Media B.V.This work was developed as a part of the D2ARS Project supported by CYTED. UNESCO code 120325;330417;120314;120305.González, A.; Mata, W.; Villaseñor, L.; Aquino, R.; Simó Ten, JE.; Chávez, M.; Crespo Lorente, A. (2011). uDDS: A Middleware for Real-time Wireless Embedded Systems. Journal of Intelligent and Robotic Systems. 64(3-4):489-503. https://doi.org/10.1007/s10846-011-9550-zS489503643-4Akyildiz, I.F., Su, W., Sankarasubramaniam, Y., Cayirci, E.: A survey on sensor networks. IEEE Commun. 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