Critical infrastructure systems are essential for the continuous functionality of modern global societies. Some examples of these systems include electric energy, potable water, oil and gas, telecommunications, and the internet. Different topologies underline the structure of these networked systems. Each topology (i.e., physical layout) conditions the way in which networks transmit and distribute their flow. Also, their ability to absorb unforeseen natural or intentional disruptions depends on complex relations between network topology and optimal flow patterns. Most of the current research on large networks is focused on understanding their properties using statistical physics, or on developing advanced models to capture network dynamics. Despite these important research efforts, almost all studies concentrate on specific networks. This network-specific approach rules out a fundamental phenomenon that may jeopardize the performance predictions of current sophisticated models: network response is in general interdependent, and its performance is conditioned on the performance of additional interacting networks. Although there are recent conceptual advances in network interdependencies, current studies address the problem from a high-level point of view. For instance, they discuss the problem at the macro-level of interacting industries, or utilize economic input-output models to capture entire infrastructure interactions. This study approaches the problem of network interdependence from a more fundamental level. It focuses on network topology, flow patterns within the networks, and optimal interdependent system performance. This approach also allows for probabilistic response characterization of interdependent networked systems when subjected to disturbances of internal nature (e.g., aging, malfunctioning) or disruptions of external nature (e.g., coordinated attacks, seismic hazards). The methods proposed in this study can identify the role that each network element has in maintaining interdependent network connectivity and optimal flow. This information is used in the selection of effective pre-disaster mitigation and post-disaster recovery actions. Results of this research also provide guides for growth of interacting infrastructure networks and reveal new areas for research on interdependent dynamics. Finally, the algorithmic structure of the proposed methods suggests straightforward implementation of interdependent analysis in advanced computer software applications for multi-hazard loss estimation.

Made available in DSpace on 2016-04-04T18:31:25Z (GMT). No. of bitstreams: 1 Diego Cesar Valente e Silva.pdf: 2949032 bytes, checksum: 9f8f72c0ab49b16ab87dbd229e5acc93 (MD5) Previous issue date: 2009-02-09 / This work presents an experimental investigation on the implementation of wireless sensor networks (IEEE 802.15.4) over fiber optics. Such investigation was performed with the utilization of IEEE 802.15.4 transceivers, an optical fiber infrastructure inside a field-trial network, called KyaTera Network, and directly modulated lasers and photodiodes designed for usual lab applications. The analysis comprised optical and electrical signal-to-noise ratio meausermentes and packet error rate evaluation under different conditions of transmission (e.g., payload length and time between consecutive frames). Results indicate that the RF signals of the sensor network may be properly propagated through unamplified optical links of up to 100 km or for longer distances with the use of optical amplifiers. / Esse trabalho apresenta uma investiga??o experimental da implementa??o de redes de sensores (IEEE 802.15.4) sobre fibras ?pticas. Tal investiga??o foi realizada com a utiliza??o de transceptores IEEE 802.15.4, de uma infra-estrutura de fibras ?pticas localizada dentro uma rede experimental, chamada Rede KyaTera, e de lasers com modula??o direta e foto-diodos projetados para opera??es usuais em laborat?rios. A an?lise compreendeu medidas a raz?o sinal-ru?do ?ptica e el?trica e a avalia??o da taxa de erro de quadros sob diferentes condi??es de transmiss?o (p. ex., tamanho de payload e intervalo de tempo entre quadros sucessivos). Os resultados indicam que os sinais de RF da rede de sensores podem ser propagados adequadamente, sem amplifica??o ?pticapor, em enlaces de at? 100 km ou por dist?ncias ainda maiores, com a utiliza??o de amplificadores ?pticos.