Positioning of a wireless relay node for useful cooperative communication

Given the exorbitant amount of data transmitted and the increasing demand for data connectivity in the 21st century, it has become imperative to search for pro-active and sustainable solutions to the effectively alleviate the overwhelming burden imposed on wireless networks. In this study a Decode and Forward cooperative relay channel is analyzed, with the employment of Maximal Ratio Combining at the destination node as the method of offering diversity combining. The system framework used is based on a three-node relay channel with a source node, relay node and a destination node. A model for the wireless communications channel is formulated in order for simulation to be carried out to investigate the impact on performance of relaying on a node placed at the edge of cell. Firstly, an AWGN channel is used before the effect of Rayleigh fading is taken into consideration. Result shows that performance of cooperative relaying performance is always superior or similar to conventional relaying. Additionally, relaying is beneficial when the relay is placed closer to the receiver

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

High spatial and spectral quality diode-laser-based pump sources for solid-state lasers and optical parametric oscillators

In this thesis the use of high spatial- and spectral-quality diode-laser pump sources for solid-state lasers and continuous-wave optical parametric oscillators (cw OPOs) is investigated. While diode lasers are potentially attractive, compact, low-cost pump sources for solid-state lasers and cw OPOs, the difficulty in obtaining moderate output powers, while retaining high spatial beam quality and spectral purity, often limits the potential of such lasers in these applications. Techniques for obtaining high-power, high spatial- and spectral-quality output from diode lasers are reviewed and the design, development and characterisation of an injection-locked broad-area diode-laser system is described. This system produced output powers of &ap;400mW in a near-diffraction-limited beam (M2&ap;w1.3) and with a spectral width of <30MHz. The injection-locked system was used as the pump source for a quasi-three-level 946-nm Nd:YAG laser. End-pumped solid-state lasers of this type can offer potentially efficient, low-threshold operation if a near-diffraction limited pump source is used allowing optimal overlap with the laser mode. A model, including pump beam quality effects, is developed for such lasers and used to highlight the advantages of a near- diffraction-limited pump source, especially in the case of the 946-nm Nd:YAG transition which suffers from low gain and significant reabsorption losses. A 946-nm Nd: YAG laser pumped by the injection-locked system is described, yielding cw output powers up to 120mW with a 46% slope efficiency, performance comparable to Ti:sapphire- or dye-laser pumping, and 27ns Q-switched pulses having peak powers of 180W. 50W, 20ns pulses at 473nm were obtained by second-harmonic generation in KNbOs. The performance and relative merits of various cw OPO configurations, in the context of diode-laser pumping, are discussed and the development of a doubly- resonant OPO (DRO) based on periodically-poled lithium niobate is described. When pumped by the injection-locked system, this device showed a threshold of 25mW and .tuning of the outputs over 1.15- 1.25 mum at the signal and 2.3-2.65 mum at the idler was obtained by variation of crystal temperature, PPLN grating period and pump wavelength. When pumping with a 100mW single-mode diode laser, a 15mW OPO threshold was observed while retaining a similar tuning range. This represented the first demonstration of a cw DRO directly pumped by a single-mode diode laser. The achievement of such spectral coverage while pumping with this source points to the potential of such systems as compact, tunable sources in the near-to mid-infrared

Numerical Simulations

This book will interest researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modeling and computer simulation. Although it represents only a small sample of the research activity on numerical simulations, the book will certainly serve as a valuable tool for researchers interested in getting involved in this multidisciplinary field. It will be useful to encourage further experimental and theoretical researches in the above mentioned areas of numerical simulation

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 42)

A subject index is provided for over 4900 patents and patent applications for the period May 1969 through December 1992. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 36)

A subject index is provided for over 4600 patents and patent applications for the period May 1969 through December 1989. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

Development of biomedical devices for the extracorporeal real-time monitoring and perfusion of transplant organs

The goal of this Thesis is to develop a range of technologies that could enable a paradigm shift in organ preservation for renal transplantation, transitioning from static cold storage to warm normothermic blood perfusion. This transition could enable the development of novel pre-implantation therapies, and even serve as the foundation for a global donor pool. A low-hæmolysis pump was developed, based on a design first proposed by Nikola Tesla in 1913. Simulations demonstrated the theoretical superiority of this design over existing centrifugal pumps for blood recirculation, and provided insights for future avenues of research into this technology. A miniature, battery-powered, multimodal sensor suite for the in-line monitoring of a blood perfusion circuit was designed and implemented. This was named the ‘SmartPipe’, and proved capable of simultaneously monitoring temperature, pressure and blood oxygen saturations over the biologically-relevant ranges of each modality. Finally, the Thesis details the successful implementation and optimisation of a combined microfluidic and microdialysis system for the real-time quantitation of creatinine in blood or urine through amperometric sensing, to act as a live renal function monitor. The range of detection was 4.3μM – 500μM, with the possibility of extending this in both directions. This work also details and explores a novel methodology for functional monitoring in closed-loop systems which avoids the need for sensor calibration, and potentially overcomes the problems of sensor drift and desensitisation.Open Acces

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 37)

A subject index is provided for over 4600 patents and patent applications for the period May 1969 through June 1990. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 44)

A subject index is provided for over 5500 patents and patent applications for the period May 1969 through December 1993. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers