PhD, University of Cincinnati, 2008, Engineering : Computer Science and Engineering

Wireless Ad Hoc Networks have emerged as an advanced networking paradigm based on collaborative efforts among multiple self-organized wireless communication devices. Without the requirement of a fixed infrastructure support, wireless ad hoc networks can be quickly deployed anywhere at any time when needed. The decentralized nature, minimal configuration and quick deployment of wireless ad hoc networks make them suitable for various applications, from disaster rescue, target tracking to military conflicts. Wireless ad hoc networks can be further categorized into mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), and wireless mesh networks (WMNs) depending on their applications.Security is a big challenge in wireless ad hoc networks due to the lack of any infrastructure support, dynamic network topology, shared radio medium, and resource-constrained wireless users. Most existing security mechanisms applied for the Internet or traditional wireless networks are neither applicable nor suitable for wireless ad hoc network environments. In MANETs, routing security is an extremely important issue, as the majority of the standard routing protocols assume non-hostile environments. Once deployed in a hostile environment and working in an unattended mode, existing routing protocols are vulnerable to various attacks. To address these concerns, we propose an anonymous secure routing protocol for MANETs in this dissertation, which can be incorporated with existing routing protocols and achieve enhanced routing security with minimum additional overheads. In WSNs, key distribution and management is the core issue of any security approaches. Due to extremely resource-constrained sensor nodes and lack of any infrastructure support, traditional public-key based key distribution and management mechanisms are commonly considered as too expensive to be employed in WSNs. In this dissertation, we propose two efficient pairwise key pre-distribution and management mechanisms f (open full item for complete abstract)

Committee: Dharma Agrawal (Committee Chair); Jerome Paul (Committee Member); Wen-Ben Jone (Committee Member); Chia-Yung Han (Committee Member); Ernest Hall (Committee Member) Subjects: Communication; Computer Science

Doctor of Philosophy, The Ohio State University, 2005, Food, Agricultural, and Biological Engineering

Leaf surface wetness detection is important in plant production for pesticide application evaluation, disease management, and misting control. Efficient application of pesticides may be possible using the feedback from the leaf wetness detection system reducing both the overall input cost and environmental contamination. The goal of this study was to develop non-contact sensing techniques for leaf surface wetness detection. Several non-contacting techniques using spectral, thermal, and imaging sensors were evaluated for the development of an automated feedback controlled spraying system. The study was divided into several sub studies focusing on leaf level and canopy level experiments inside a laboratory under artificial illumination, and canopy level experiments in a greenhouse under natural solar illumination. Multispectral reflectance of the leaves and canopies was measured using a spectroradiometer and a custom built low cost multispectral imaging system. The changes of surface temperature and spectral reflectance in visible (400-700 nm), very-near-infrared (700-1300 nm) and near-infrared ranges (1300-2500 nm) caused by leaf surface moisture were investigated. The spectral information collected using the non-contact sensors was a mixture of reflectance of the objects of interest and also the background in the sensor's field of view. For accurate leaf surface water analysis, background compensation techniques were evaluated to obtain compensated reflectance spectra. Two approaches were investigated for background reflectance compensation, a spectral approach, which aimed at compensating the measured reflectance for background-contamination using a linear unmixing technique, and a spatial approach, which aimed at extracting only the vegetation pixels from the multispectral images using a vegetation index. Visible and near-infrared regions were found less affected by background whereas very-near-infrared regions had large background effects. Background-reflectance (open full item for complete abstract)

Committee: Peter Ling (Advisor) Subjects: Engineering, Agricultural