Reliable data delivery in low energy ad hoc sensor networks

Reliable delivery of data is a classical design goal for reliability-oriented collection routing protocols for ad hoc wireless sensor networks (WSNs). Guaranteed packet delivery performance can be ensured by careful selection of error free links, quick recovery from packet losses, and avoidance of overloaded relay sensor nodes. Due to limited resources of individual senor nodes, there is usually a trade-off between energy spending for packets transmissions and the appropriate level of reliability. Since link failures and packet losses are unavoidable, sensor networks may tolerate a certain level of reliability without significantly affecting packets delivery performance and data aggregation accuracy in favor of efficient energy consumption. However a certain degree of reliability is needed, especially when hop count increases between source sensor nodes and the base station as a single lost packet may result in loss of a large amount of aggregated data along longer hops. An effective solution is to jointly make a trade-off between energy, reliability, cost, and agility while improving packet delivery, maintaining low packet error ratio, minimizing unnecessary packets transmissions, and adaptively reducing control traffic in favor of high success reception ratios of representative data packets. Based on this approach, the proposed routing protocol can achieve moderate energy consumption and high packet delivery ratio even with high link failure rates. The proposed routing protocol was experimentally investigated on a testbed of Crossbow's TelosB motes and proven to be more robust and energy efficient than the current implementation of TinyOS2.x MultihopLQI

Mechanochemical models for generating biological pattern and form in development

The central issue in development is the formation of spatial patterns of cells in the early embryo. The mechanisms which generate these patterns are unknown. Here we describe the new Oster-Murray mechanochemical approach to the problem, the elements of which are experimentally well documented. By way of illustration we derive one of the basic models from first principles and apply it to a variety of problems of current interest and research. We specifically discuss the formation of skin organ patterns, such as feather and scale germs, cartilage condensations in the developing vertebrate limb and finally wound healing

The architecture of a video image processor for the space station

The architecture of a video image processor for space station applications is described. The architecture was derived from a study of the requirements of algorithms that are necessary to produce the desired functionality of many of these applications. Architectural options were selected based on a simulation of the execution of these algorithms on various architectural organizations. A great deal of emphasis was placed on the ability of the system to evolve and grow over the lifetime of the space station. The result is a hierarchical parallel architecture that is characterized by high level language programmability, modularity, extensibility and can meet the required performance goals

Spin wave dispersion softening in the ferromagnetic Kondo lattice model for manganites

Spin dynamics is calculated in the ferromagnetic (FM) state of the generalized Kondo lattice model taking into account strong on-site correlations between e_g electrons and antiferromagnetic (AFM) exchange among t_{2g} spins. Our study suggests that competing FM double-exchange and AFM super-exchange interaction lead to a rather nontrivial spin-wave spectrum. While spin excitations have a conventional Dq^2 spectrum in the long-wavelength limit, there is a strong deviation from the spin-wave spectrum of the isotropic Heisenberg model close to the zone boundary. The relevance of our results to the experimental data are discussed.Comment: 6 RevTex pages, 3 embedded PostScript figure

Large-Sample comparison of TCP congestion control mechanisms over wireless networks

As new congestion control mechanisms are developed, their performance relative to existing mechanisms needs to be understood; in particular over wireless networks. This study aimed to evaluate existing TCP congestion control mechanisms using a comprehensive and reproducible methodology designed to be representative of real world usage of wireless networks. The study sought to investigate whether any existing mechanism could provide significant performance benefits over CUBIC and be recommended for adoption. The findings of this study showed that YeAH demonstrated an increase in throughput of 3%–5% over CUBIC, with no penalty to latency. While this small improvement may assist applications requiring the highest available performance, it is unlikely that it will provide a significant improvement over existing congestion control mechanisms. As such, it is the conclusion of this study that use of alternate congestion control mechanisms would not provide noticeable improvements in performance in most applications

Radiation-effects Research Facilities

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Ion-Molecule Reactions in Unsaturated Hydrocarbons: Allene, Propyne, Diacetylene, and Vinylacetylene

Ion-molecule reactions in allene, propyne, diacetylene, and vinylacetylene (1-buten-3-yne) have been studied at near-thermal energies by the technique of ion cyclotron resonance mass spectrometry. Rate coefficients and branching ratios are reported for the reactions of C_3H^+_n (n = 1-4) with allene and propyne and for the reactions of C_4H^+_n (n = 0-5) with diacetylene and vinylacetylene. Branching ratios are also given for the reactions of C_4H^+_n, C_5H_n, and C_6H^+_n with propyne and for reactions of C_6H^+_n with diacetylene and vinylacetylene. More than 90% of the reactive channels lead to product ions having a larger carbon skeleton than the reactant ion. Evidence for ions with the same m/e ratio having differing reactivities was obtained for C_3H^+_3, C_6H^+_7, and C_7H^+_7. Ion reaction sequences in allene and propyne were followed at higher pressures (l0^(-4) torr) to investigate secondary, tertiary, and higher order processes

A hydrogen energy carrier. Volume 2: Systems analysis

A systems analysis of hydrogen as an energy carrier in the United States indicated that it is feasible to use hydrogen in all energy use areas, except some types of transportation. These use areas are industrial, residential and commercial, and electric power generation. Saturation concept and conservation concept forecasts of future total energy demands were made. Projected costs of producing hydrogen from coal or from nuclear heat combined with thermochemical decomposition of water are in the range $1.00 to$1.50 per million Btu of hydrogen produced. Other methods are estimated to be more costly. The use of hydrogen as a fuel will require the development of large-scale transmission and storage systems. A pipeline system similar to the existing natural gas pipeline system appears practical, if design factors are included to avoid hydrogen environment embrittlement of pipeline metals. Conclusions from the examination of the safety, legal, environmental, economic, political and societal aspects of hydrogen fuel are that a hydrogen energy carrier system would be compatible with American values and the existing energy system

A hydrogen energy carrier. Volume 1: Summary

The production, technology, transportation, and implementation of hydrogen into the energy system are discussed along with the fossil fuel cycle, hydrogen fuel cycle, and the demands for energy. The cost of hydrogen production by coal gasification; electrolysis by nuclear energy, and solar energy are presented. The legal aspects of a hydrogen economy are also discussed