An efficient scalable scheduling mac protocol for underwater sensor networks

Underwater Sensor Networks (UWSNs) utilise acoustic waves with comparatively lower loss and longer range than those of electromagnetic waves. However, energy remains a challenging issue in addition to long latency, high bit error rate, and limited bandwidth. Thus, collision and retransmission should be efficiently handled at Medium Access Control (MAC) layer in order to reduce the energy cost and also to improve the throughput and fairness across the network. In this paper, we propose a new reservation-based distributed MAC protocol called ED-MAC, which employs a duty cycle mechanism to address the spatial-temporal uncertainty and the hidden node problem to effectively avoid collisions and retransmissions. ED-MAC is a conflict-free protocol, where each sensor schedules itself independently using local information. Hence, ED-MAC can guarantee conflict-free transmissions and receptions of data packets. Compared with other conflict-free MAC protocols, ED-MAC is distributed and more reliable, i.e., it schedules according to the priority of sensor nodes which based on their depth in the network. We then evaluate design choices and protocol performance through extensive simulation to study the load effects and network scalability in each protocol. The results show that ED-MAC outperforms the contention-based MAC protocols and achieves a significant improvement in terms of successful delivery ratio, throughput, energy consumption, and fairness under varying offered traffic and number of nodes

Optimization Strategies Of Electrode Arrays Used In Numerical And Field 2D Resistivity Imaging Surveys.

Tesis ini membentangkan kaedah baru untuk memilih satu set susunatur yang akan memberi maklumat sub-permukaan yang maksimum menggunakan survei pengimejan elektrik 2D untuk pengukuran empat elektrod yang terhad. This thesis presents new techniques to select the set of array configurations that will give the maximum amount of information of the subsurface with 2D electrical imaging surveys for a limited number of four-electrode measurements

Environmental Geophysical Analysis of a Portion of the Muddy and Roaring Creek Watersheds, West Virginia

This thesis presents a new environmental geophysical analysis derived from airborne and ground measurements of electromagnetics and total magnetic field collected from the Muddy and Roaring Creek watersheds located in northeastern Preston County, West Virginia. This region is referred to as the T&T mine area. In the simplest representation, with respect to subsurface Acid Mine Drainage (AMD) impacted water systems, the subsurface regions can be thought of as containing three pools of AMD contaminated water. The objectives of this project were to determine the location of these subsurface pools, the lateral extent of a contaminated mine pool located at a depth of about 300 feet, and to determine areas of groundwater recharge to the mine pool. Geophysical data analyzed included frequency-domain electromagnetic (EM) conductivity (380, 1400, 6200, 25k and 102k Hz), VLF (VLF1I from Cutler station, VLF2I from Seattle station), and total field magnetics. In order to check the airborne data, ground measurements were collected using EM34 and EM47 instruments. These data were collected for the National Energy Technology Laboratory of the U.S. Department of Energy as part of their active and ongoing environmental geophysical program. Cultural noise was removed from some of the conductivity dataset using ER MAPPER software and applying a variety of spatial frequency filters. ER MAPPER, ERDAS Imagine, ERDAS Virtual GIS, ESIR Arc/Info, and ESRI ArcView software package were then used to display and interpret the data. The geometry of the high-conductivity pools were imaged using a variety of techniques including Hue Saturation and Intensity (HSI) algorithms and unsupervised classification using ER MAPPER and Arc/Info software. After the pool geometry was determined, a series of geophysical profiles were extracted from the edges of the three pools. I interpret these data as showing the geometry of the mine pools and regions of contrasting groundwater conductivity related to discharge

Analyzing the Factors that Lead to Housing and Construction Cost Escalation: A Case Study Focused on Riyadh, Saudi Arabia

Riyadh city suffers from high housing and construction costs, which have increased by more than 200% over the last 7 years. This problem led to a significant interest from the government and the citizens of the city in understanding the causes of housing and construction cost escalation and the best strategies to address this problem in the short and long-terms, in order to find solutions for affordable housing. In response to the absence of research regarding this problem, the researcher has decided to conduct a scientific survey about the factors that might have led to this problem in Riyadh. While conducting the literature review, the researcher identified 16 possible factors that were mentioned as possible causes for this problem. Thus, the main objective of this study is to identify the main factors that affect housing cost escalation. All of the survey samples were collected from construction industry professionals and experts working in Riyadh. The sample size required was calculated using the statistical equation mentioned in Chapter 4, and based on an estimated level of confidence of 90%, standard error of 10%, and a standard deviation calculated from 30 random samples collected initially. The required sample size was estimated to be at least 215 surveys, and the researcher was able to collect a total of 237 surveys. After collecting the data, the researcher analyzed the data through Microsoft Excel software by applying descriptive statistics, means, modes, and standard deviations. Tables and figures have been used to show the results of the survey. After analyzing the data, the researcher identified the main factors based on the mode and mean averages. The researcher has identified four major impacting factors that affected housing and construction costs. The most impacting factors on housing and construction cost are the corruption in selling land, speculative purchases of land, high demand for housing, and the high population growth rate in Riyadh. The main recommendations that should help the government to solve this problem are: to apply an annual tax on large plots, prevent speculative purchases in housing areas, monitor the prices of consruction materials, and revive small cities around Riyadh to reduce congestion and crowding