Ineradicable Humanity: Literary Responses to Darwin in Zola, Hardy, and the Utopian Novel

No abstract

A hybrid MAC protocol for emergency response wireless sensor networks

We introduce ER-MAC, a novel hybrid MAC protocol for emergency response wireless sensor networks. It tackles the most important emergency response requirements, such as autonomous switching from energy-efficient normal monitoring to emergency monitoring to cope with heavy traffic, robust adaptation to changes in the topology, packet prioritisation and fairness support. ER-MAC is designed as a hybrid of the TDMA and CSMA approaches, giving it the flexibility to adapt to traffic and topology changes. It adopts a TDMA approach to schedule collision-free slots. Nodes wake up for their scheduled slots, but otherwise switch into power-saving sleep mode. When an emergency occurs, nodes that participate in the emergency monitoring change their MAC behaviour by allowing contention in TDMA slots to achieve high delivery ratio and low latency. In its operation, ER-MAC prioritises high priority packets and sacrifices the delivery ratio and latency of the low priority ones. ER-MAC also guarantees fairness over the packets' sources and offers a synchronised and loose slot structure to allow nodes to join or leave the network. Simulations in ns-2 show the superiority of ER-MAC over Z-MAC, a state-of-the art hybrid MAC protocol, with higher delivery ratio, lower latency, and lower energy consumption. When a cluster of nodes in the network detects fire, nodes with ER-MAC deliver twice as many high priority emergency packets and four times faster than Z-MAC. This is achieved by ER-MAC with only one fifth as much energy as Z-MAC

Multiple sink and relay placement in wireless networks

Wireless sensor networks are subject to failures. Deployment planning should ensure that when a sink or sensor node fails, the remaining network can still be connected, and so may require placing multiple sinks and relay nodes in addition to sensors. For network performance requirements, there may also be path-length constraints for each sensor node. We propose two local search algorithms, GRASP-MSP and GRASP-MSRP, to solve the problem of multiple sink placement and the problem of multiple sink and relay placement, respectively. GRASP-MSP minimises the deployment cost, while ensuring that each sensor node in the network is double-covered, i.e. it has two length-constrained paths to two sinks. GRASP-MSRP deploys sinks and relays to minimise the deployment cost and to guarantee that all sensor nodes in the network are double-covered and noncritical. A sensor node is noncritical if upon its removal, all remaining sensor nodes still have length-constrained paths to sinks. We evaluate the algorithms empirically and show that both GRASP-MSP and GRASP-MSRP outperform the closely-related algorithms from the literature for the lowest total deployment cost

Fault-tolerant relay deployment based on length-constrained connectivity and rerouting centrality in wireless sensor networks

Wireless Sensor Networks (WSNs) are prone to failures. To be robust to failures, the network topology should provide alternative routes to the sinks so when failures occur the routing protocol can still offer reliable delivery. We define l-CRC, a new centrality index which measures a node’s importance to connectivity and efficient delivery in the network. We then use this centrality index to concentrate on the most important nodes, providing alternative paths around the nodes with high centrality. Varying l-CRC allows us to trade off cost for robustness. We introduce GRASP-ABP, a local search algorithm for initial robust topology design. We evaluate the algorithm empirically in terms of the number of additional nodes it suggests and its runtime. We then evaluate the robustness of the designs against node failures in simulation, and we demonstrate that the centrality-based GRASP-ABP’s designs are able to offer reliable delivery, comparable to competitor algorithms, but with fewer additional relays and faster runtime

A fault-tolerant relay placement algorithm for ensuring k vertex-disjoint shortest paths in wireless sensor networks

Wireless sensor networks (WSNs) are prone to failures. To be robust to failures, the network topology should provide alternative routes to the sinks so when failures occur the routing protocol can still offer reliable delivery. Our contribution is a solution that enables fault-tolerant WSN deployment planning by judicious use of a minimum number of additional relays. A WSN is robust if at least one route with an acceptable length to a sink is available for each sensor node after the failure of any nodes. In this paper, we define the problem for increasing WSN reliability by deploying a number of additional relays to ensure that each sensor node in the initial design has k length-bounded vertex-disjoint shortest paths to the sinks. To identify the maximum k such that each node has k vertex-disjoint shortest paths, we propose Counting-Paths and its dynamic programming variant. Then, we introduce GRASP-ARP, a centralised offline algorithm that uses Counting-Paths to minimise the number of deployed relays. Empirically, it deploys 35% fewer relays with reasonable runtime compared to the closest approach. Using network simulation, we show that GRASP-ARP’s designs offer a substantial improvement over the original topologies, maintaining connectivity for twice as many surviving nodes after 10% of the original nodes have failed

Planning the deployment of multiple sinks and relays in wireless sensor networks

Wireless sensor networks are subject to failures. Deployment planning should ensure that when a data sink or sensor node fails, the remaining network can still be connected, and so may require placing multiple sinks and relay nodes in addition to sensor nodes. For network performance requirements, there may also be path-length constraints for each sensor node. We propose four algorithms, Greedy-MSP and GRASP-MSP to solve the problem of multiple sink placement, and Greedy-MSRP and GRASP-MSRP for the problem of multiple sink and relay placement. Greedy-MSP and GRASP-MSP minimise the deployment cost, while ensuring that each sensor node in the network is double-covered, i.e. it has two length-constrained paths to two sinks. Greedy-MSRP and GRASP-MSRP deploys sinks and relays to minimise the deployment cost and to guarantee that all sensor nodes in the network are double-covered and noncritical. A sensor node is noncritical if upon its removal, all remaining sensor nodes still have length-constrained paths to sinks. We evaluate the algorithms empirically and show that these algorithms outperform the closely-related algorithms from the literature for the lowest total deployment cost

Perspectives on Cultural Context: The Use of an Online Participatory Learning Environment as an Expansion of the Museum Visit

Technology offers opportunities for museums to expand the ways in which cultural perspectives relevant to objects on display can be exchanged and understood. Multimedia content offered online in an environment with user input capabilities can encourage dialogue and enrich visitor experiences of museums. This action research project using narrative analysis was an effort to develop the use of web technology in museum education practice, with an emphasis on constructivist learning. Concepts including the visitor-centered museum and multiple narratives led the researcher to collaborate with a pre-service art teacher education classroom and a local Hindu community to create content that might better develop understandings of one museum's Hindu sculpture collection that are personal, cultural, and complex

Fault-tolerant relay deployment for k node-disjoint paths in wireless sensor networks

Ensuring that wireless sensor networks (WSNs) are robust to failures requires that the physical network topology will offer alternative routes to the sinks. This requires sensor network deployments to be planned with an objective of ensuring some measure of robustness in the topology, so that when failures occur that routing protocols can continue to offer reliable delivery. Our contribution is a solution that enables fault-tolerant WSN deployment planning by judicious use of a minimum number of additional relay nodes. A WSN is robust if at least one route to a sink is available for each remaining sensor node after the failure of up to k-1 nodes. In this paper, we define the problem for increasing WSN reliability by deploying a number of additional relay nodes to ensure that each sensor node in the initial design has k node-disjoint paths to the sinks. We present GRASP-ARP, a centralised offline algorithm to be run during the initial topology design to solve this problem. We have implemented this algorithm and demonstrated in simulation that it improves the efficiency of relay node placement for k node-disjoint paths compared to the most closely related published algorithms

ER-MAC: A hybrid MAC protocol for emergency response wireless sensor networks

This paper introduces ER-MAC, a hybrid MAC protocol for emergency response wireless sensor networks. ERMAC is designed as a hybrid of the TDMA and CSMA approaches, giving it the flexibility to adapt to traffic and topology changes. It adopts a TDMA approach to schedule collision-free slots. Nodes wake up for their scheduled slots, but otherwise switch into power-saving sleep mode. When an emergency occurs, nodes that participate in the emergency monitoring change their MAC behaviour by allowing contention in TDMA slots to achieve high delivery ratio and low latency. ER-MAC offers a synchronised and loose slot structure to allow nodes to join or leave the network. Simulations in ns-2 show that ERMAC outperforms Z-MAC with higher delivery ratio, lower latency, and lower energy consumption

Autonomous discovery and repair of damage in Wireless Sensor Networks

Wireless Sensor Networks in volatile environments may suffer damage, and connectivity must be restored. The repairing agent must discover surviving nodes and damage to the physical and radio environment as it moves around the sensor field to execute the repair. We compare two approaches, one which re-generates a full plan whenever it discovers new knowledge, and a second which attempts to minimise the required number of new radio nodes. We apply each approach with two different heuristics, one which attempts to minimise the cost of new radio nodes, and one which aims to minimise the travel distance. We conduct extensive simulation-based experiments, varying key parameters, including the level of damage suffered, and comparing directly with the published state-of-the-art. We quantify the relative performance of the different algorithms in achieving their objectives, and also measure the execution times to assess the impact on being able to make autonomous decisions in reasonable time