Wetland Functions

This resource explains a number of critical functions performed by wetlands. Students will discover that wetlands moderate impacts from flooding, control erosion, purify water, and provide habitat for fish and wildlife. They also provide a unique natural environment for people to enjoy outdoor recreation activities. It is part of a module that aims to help students get to know the complexities of wetlands, discover wildlife, enjoy the experience of being outdoors, and learn how necessary wetlands are to the health of our environment. Although it is about wetlands in New England for educators and their middle school students, it suggests ways to study wetland characteristics, why wetlands are important, and how students and teachers can help protect a local wetland in any part of the country. An associated set of activities is also available. Educational levels: Middle school

Energy Efficient Location Aided Routing Protocol for Wireless MANETs

A Mobile Ad-Hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without using any centralized access point, infrastructure, or centralized administration. In this paper we introduce an Energy Efficient Location Aided Routing (EELAR) Protocol for MANETs that is based on the Location Aided Routing (LAR). EELAR makes significant reduction in the energy consumption of the mobile nodes batteries by limiting the area of discovering a new route to a smaller zone. Thus, control packets overhead is significantly reduced. In EELAR a reference wireless base station is used and the network's circular area centered at the base station is divided into six equal sub-areas. At route discovery instead of flooding control packets to the whole network area, they are flooded to only the sub-area of the destination mobile node. The base station stores locations of the mobile nodes in a position table. To show the efficiency of the proposed protocol we present simulations using NS-2. Simulation results show that EELAR protocol makes an improvement in control packet overhead and delivery ratio compared to AODV, LAR, and DSR protocols.Comment: 9 Pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS 2009, ISSN 1947 5500, Impact factor 0.423, http://sites.google.com/site/ijcsis

Flooding control in route discovery for reactive routing in mobile ad hoc networks

Routing is a very important function in the network layer of the OSI model for wired and wireless networks. Mobile Ad hoc Networks (MANETs) are a collection of wireless nodes forming a temporary network that is supposed to be constructed on the fly without infrastructure and prior setup. This fashion of setup demands that the nodes act as routers for other nodes. This necessitates the need of a robust dynamic routing scheme. Routing protocols are classified into three main categories: proactive, reactive, and hybrid. Reactive routing has been the focus of research in recent years due to its control traffic overhead reduction. Reactive routing operation involves three main steps: route discovery, packet delivery, and route maintenance. If a source node, initiating the message, knows the route to the destination, this route is used to transmit the message; otherwise, the source node will initiate a route discovery algorithm to build the route, which highlights the importance of this phase of the on-demand routing process. This thesis work will present a route discovery algorithm that will try to find the route between the sender and the intended receiver in relatively short periods of end-to-end delay, least amount of control traffic overhead, and a loop free path between the two communicating parties. Furthermore, performance comparison between the proposed algorithm and other standard algorithms, namely basic flooding and flooding with self-pruning, will be conducted. The proposed route discovery algorithm can be used in several approaches serving ad hoc network setup, where connectivity establishment and maintenance is important

Route duration improvement in wireless sensor and actuator networks based on mobility parameters and flooding control

Mobility of nodes is one of the main causes of broken links in wireless networks. Although several theoretical models for links and routes selection have been proposed in the literature, so far little effort has been made to apply them to the existing routing protocols. In this article, a decision tree has been incorporated in a reactive routing protocol in order to select the most long-lived routes. The decision tree is based on nodes ’ mobility parameters typically considered by the theoretical models, such as distance between nodes, relative speed, and nodes ’ directions. The flooding techniques used within the routing protocols for the routing discovery procedures cause a massive usage of control packets which in turn has negative impact on the performance of the networks. So, an improved flooding control is presented in this article that enhances the performance of the proposed route selection based on a decision tree, in turn reducing overheads and the power consumption caused by the control packets. These two proposed approaches have been implemented over a widely used reactive routing protocol such as Ad Hoc On-Demand Distance Vector (AODV) to obtain performance results using Network Simulator 2 simulation tool. The performances of the proposed approaches have been compared with that of the AODV implementation in terms of general performance and path duration. The simulation results show that the proposed route selection significantly improves the results of AOD

Protect, Adapt or Relocate? Responding to Climate Change in Coastal Indonesia

On the coast of Java, Semarang City faces a multitude of climate-related problems including sea-level rise, flash and tidal floods, subsidence and coastal erosion. Using four case-study villages, this working paper explores how households are coping with the impacts of climate change. How do they decide whether to protect, adapt or relocate their property to areas less affected, and what are the costs? Understanding household risk assessments and decision-making processes should effectively tailor government policies to reduce vulnerability and support local adaptation strategies. By bringing together all stakeholders, an urban climate governance approach should ensure a more resilient city

Consumption soothing and vulnerability in the Zone Lacustre, Mali

"This paper explores risk sharing in the Zone Lacustre, Mali, as viewed through the lens of consumption smoothing. We find that idiosyncratic shocks appear to have little impact on consumption, and that households respond to these shocks in a variety of ways. In general, nonpoor households are more likely to enter into new income-generating activities while poor households are more likely to engage in credit or gift exchange or to ration consumption. When we construct a stronger test for consumption smoothing, we find that changes in household income lead to modest changes in consumption. Covariant shocks, as measured by village/round dummies, always lead to changes in consumption. These results are robust to concerns regarding bias resulting from measurement error or endogeneity of changes in income. Lastly, we find that households with access to improved water control infrastructure are less vulnerable than those that rely on rainfall or the flooding of the Niger River." Authors' AbstractVulnerability ,Consumption shocks ,

Towards Opportunistic Data Dissemination in Mobile Phone Sensor Networks

Recently, there has been a growing interest within the research community in developing opportunistic routing protocols. Many schemes have been proposed; however, they differ greatly in assumptions and in type of network for which they are evaluated. As a result, researchers have an ambiguous understanding of how these schemes compare against each other in their specific applications. To investigate the performance of existing opportunistic routing algorithms in realistic scenarios, we propose a heterogeneous architecture including fixed infrastructure, mobile infrastructure, and mobile nodes. The proposed architecture focuses on how to utilize the available, low cost short-range radios of mobile phones for data gathering and dissemination. We also propose a new realistic mobility model and metrics. Existing opportunistic routing protocols are simulated and evaluated with the proposed heterogeneous architecture, mobility models, and transmission interfaces. Results show that some protocols suffer long time-to-live (TTL), while others suffer short TTL. We show that heterogeneous sensor network architectures need heterogeneous routing algorithms, such as a combination of Epidemic and Spray and Wait