A Computational Channel Model for Magnetic Induction-Based Subsurface Applications

There are many underground applications based on magnetic fields generated by an oscillating magnetic source. For them, a magnetic dipole in a three-layered region with upper semi-infinite air layer can be a convenient idealization used for their planning, development, and operation. Solutions are in the form of the well-known Sommerfeld integral expressions that can be evaluated by numerical methods. A set of field expressions to be numerically evaluated by an efficient algorithm are not collected comprehensively yet, or at least in a directly usable form. In this paper, the explicit magnetic field solutions for the vertical magnetic dipole and the horizontal magnetic dipole for a general source-observer location are derived from the Hertz vector. They can be properly combined to model the problem of a tilted magnetic dipole source for horizontally or inclined stratified media. As a result, a complete set of integral equations of the Sommerfeld type valid from the near zone to the far zone are formulated. A method for numerical evaluation of the field expressions for high accurate computations is described. The numerical results are validated using the finite element method for all the possible source-receiver configurations and three well-spanned frequencies of typical subsurface applications. Both numerical solutions agree according to the normalized root-mean-square error-based fit metric. Numerical results for two cases of study are presented to see its usefulness for subsurface applications. A MATLAB implementation of the mathematical description outlined in this paper and the proposed evaluation method is freely available for download

IEEE Antennas Propag Mag

An efficient procedure for modeling medium frequency (MF) communications in coal mines is introduced. In particular, a hybrid approach is formulated and demonstrated utilizing ideal transmission line equations to model MF propagation in combination with full-wave sections used for accurate simulation of local antenna-line coupling and other near-field effects. This work confirms that the hybrid method accurately models signal propagation from a source to a load for various system geometries and material compositions, while significantly reducing computation time. With such dramatic improvement to solution times, it becomes feasible to perform large-scale optimizations with the primary motivation of improving communications in coal mines both for daily operations and emergency response. Furthermore, it is demonstrated that the hybrid approach is suitable for modeling and optimizing large communication networks in coal mines that may otherwise be intractable to simulate using traditional full-wave techniques such as moment methods or finite-element analysis.YLH8/Intramural CDC HHS/United States2015-10-14T00:00:00Z26478686PMC460587

Projeto de um amplificador de potência para aplicação em sistemas de comunicação Through The Earth de curtas distâncias

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade UnB Gama, Engenharia Eletrônica, 2020.Os sistemas de comunicação Through the Earth são reconhecidamente resistentes em situações extremas e por isso, têm se tornado o foco de diversos projetos e estudos sobre aplicações em cenários pós- desastres envolvendo mineração e barragens de rejeitos de minério. Esses sistemas empregam sinais de baixa frequência, geralmente abaixo de 30KHz, para atravessar o solo, rochas e outros obstáculos entre o transmissor e o receptor, apesar das grandes perdas de potência nesse tipo de canal. Nesse contexto, esse trabalho apresenta primeiramente o embasamento teórico para o projeto de um transmissor aplicado a sistemas de comunicação TTE de curtas distâncias. A partir disso, o projeto e simulação do circuito amplificador de potência do transmissor TTE. E finalmente, a implementação, em placa de circuito impresso, do PA aplicado à transceptores em sistemas de comunicação Through the Earth para curtas distâncias. Outros trabalhos de conclusão de curso apresentados na Universidade de Brasília discorrem sobre os módulos que compõem o projeto completo do transceptor.Through the Earth (TTE) communication systems are admittedly robust when it comes to extreme situations, that said many projects and studies are currently focusing attention on how to apply it to post-disaster environments involving mining and tailings dams. Those sorts of systems work based on the fact that low-frequency signals, below 30KHz, are more likely to traverse soil, rocks and some other kinds of hindrances between the transmitter and receiver, despite the amount of power loss along the way. In this sense, the present essay starts by developing a theoretical basis on how to design a power amplifiers and transmitters applicable to a TTE system. Followed by the design and simuliation of the amplifier circuit and testing to characterize the behavior of the power amplifier system. Finally, these results are used as the building blocks for the implementation of the shortdistances TTE communication PA’s printed circuit board. Other compositions presented at the University of Brasília, discuss the building blocks of the entire transceiver design

Bibliography of communication and research products 2012

This document presents a bibliography of NIOSH communication and research products for the year 2012. Product types include journal articles, book chapters, numbered publications, abstracts/proceedings, control technology reports, fatality assessment and control evaluation reports, fire fighter fatality investigation and prevention reports, an author index, a keyword Index, and the National Occupational Research Agenda (NORA) IndexI. Journal articles -- II. Books or book chapter -- III. NIOSH numbered publications -- IV. Proceedings -- V. Abstracts -- VI. Control technology reports -- VII. Fire fighter fatality investigation and prevention reports -- VIII. Health hazard evaluation reports -- IX. Author index-- X. Keyword index -- XI. National Occupational Research Agenda (NORA) index."April 2013."Also available via the World Wide Web as an Acrobat .pdf file (4.87 MB, 129 p.)