Adaptive antenna system design for multi-element combining with transient interrupted channels

This paper presents an analysis and design procedure for a buoyant cable array antenna used for satellite communications. The towed multi-element array is susceptible to washovers and fluctuations due to the ocean wave interaction with the floating hose where the elements are housed. A model of system performance for coherent multi-element combining is presented based on the dropouts and fades of the individual elements. The array design, including the number and spacing of elements, is shown to be highly dependent on the individual element exposure characteristics and the degree of correlation of the fades between channels. The joint statistics of the array are analyzed using a binary conditional element exposure model and a first-order Markov interelement correlation model. Using this analysis, a family of array designs meeting the communications requirements is produced.     

Novel amplified fiber-optic recirculating delay line processor

The application of optical amplifiers (OAs) to fiber-optic delay line signal processing is demonstrated. Both erbium-doped fiber amplifiers (EDFAs) and semiconductor optical amplifiers (SOAs) are applicable. Analytical results are presented for both amplified and unamplified fiber-optic recirculating delay lines (AFORDLs and UFORDLs). In the AFORDL an OA is inserted in the fiber loop. It is shown that the active AFORDL structure is capable of realizing all-fiber filters not possible with the passive UFORDL. This result is significant because it shows that the OAs can function beyond just the trivial optical loss compensation to provide extra flexibility not available in passive designs. An AFORDL design is presented which has a pole near +1 and a zero at -1 in the Z-plane resulting in useful characteristics in the magnitude and phase responses. The results suggest that extension of the concept to higher-order filters has the potential to lead to the realization of more complex optical processors     

The design, synthesis, and characterization of a PAMAM-based triple helical collagen mimetic dendrimer

The synthesis and characterization of a collagen mimetic dendrimer composed of the Gly-Pro-Nleu sequence is described. The dendrimer is built on a ‘first generation’ poly(amidoamine) core and is synthesized in 38% yield. This dendrimer exhibits a melting temperature of 25 °C, which is in between previously studied analogous molecules of identical sequence and length.     

The special section on professional communication in Russia: anAmerican perspective

Enormous changes that have taken place in the last few years in Russia have revealed a need for Russian technical communicators to refocus their expertise and skills in order to enter the global marketplace successfully and competitively. Rather than dwell on the familiar differences between Americans and Russians, Cold War adversaries, a common ground exists and is growing. We share a mutual interest in the successful entry of Russian technical communicators in the global marketplace. We also share an understanding that technology is central to civilization as we know it, and that the masters of technology have a substantial influence on all activities that they touch; a belief that technology has had a major beneficial effect on the peoples of the world, but that with such power comes the potential for large, serious, and potentially devastating influences; the idea that the embrace of technology is a good cultural fit with cultures formed from revolutions, for technology in the later part of this century has come to be synonymous with rapid change, and cultures with revolutionary heritage welcome change; the notion that technological breakthroughs have profound influences on the nature of work, liberating the traditional intensive physical nature of labor to the emergence of a knowledge worker; and the belief that the global marketplace forces the need for clear and rapid communication across borders, as well as among cultures. If we can agree on these technical communications issues, then we have a firm foundation for building a gateway to communication in the global market     

Biotechnology for production of fuels,chemicals, and materials from biomass

Applied Biochemistry and Biotechnology - Biological systems can convert renewable resources, including lignocellulosic biomass, starch crops, and carbon dioxide, into fuels, chemicals, and...