This dissertation focuses on data communication over shallow, long-range underwater acoustic (UWA) channels, which are characterized by relatively long, time-varying impulse responses and acute sensitivity to Doppler effects. The latter is a result of the slow speed of sound in water, while the former is a consequence of the waveguide nature of shallow, long-range UWA channels. A succession of novel receiver algorithms are developed which recover digital information transmitted across such channels. The first considers the case of a single, fixed source transducer transmitting information to a single, fixed receive hydrophone. The second extends the first to allow nontrivial source motion, for instance, that of an autonomous undersea vehicle. The third extends the second to allow processing of data received on an array of hydrophones. The algorithms employ iterative detection. Iterative processing is creating a paradigm shift in digital communication, made possible by ever-increasing computational capabilities. There are two major components to the algorithms: an equalizer and a decoder. The main focus of this dissertation is the former which, because of the features of the UWA channel, and since the channel is not assumed known a priori at the receiver, entails adaptive resampling to correct for Doppler distortion, adaptive filtering to estimate the time-varying channel, and adaptive equalization to compensate for intersymbol interference produced by the long channel impulse responses. While decoding is performed using standard methods, its role is nonetheless crucial to the overall functioning of the algorithms. In fact, they rely on the iterative exchange of information between equalizer and decoder, and the improvement of that information with each iteration. Successful performance of the algorithms is demonstrated using data from at-sea experiments

Navaho Indians created the first native United States tapestries. Their rugs, originally called blankets, are a unique American art form in a land so often considered an extension of Western "old world" culture. Through three centuries, the Navaho weaving has progressed from a rudimentary and utilitarian blanket to a visual art form and a highly developed technical craft. In the early stages of development the Navahos' weaving resembled that of their teachers, the Pueblo Indians, but in later stages the weavers' skill improved and their designs became more original. Today, Navaho rugs are of a high technical and design quality and bring a fine price and prestige to the weaving artist. Traders played an important role in promoting the sales and development of the Navaho rug. During the period 1880 to 1920, the weavers (Navaho women) no longer sold directly to their buyers; instead, the rug was merchandised by the trader who helped the weaver by interpreting the type of rug the buyers wanted. Traders interjected their own ideas into that interpretation of the buyers' wants, and they also taught the buyers to understand and appreciate the Navaho aesthetic. An especially important trader was J. L. Hubbell, the most successful of the nine major traders on the Navaho reservation in the late 19th and early 20th century, the era known as the trader period of the Navaho rug business. According to George Wharton James, omitting the name of Hubbell when talking about the development of the Navaho weaving a rt would be similar to leaving out the name of Edison when talking about the phonograph. Hubbell greatly increased the visibility of the Navaho rug through both verbal and visual communication. His letters and spoken comments were augmented by paintings known as rug studies. Hubbell commissioned rug studies, or paintings of especially fine rugs and hung them in the trading post as ever present examples of good design.