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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Shear Forces Developed in Link Beams of Eccentric Braced Frames

Evans, John Paul 01 May 2012 (has links)
Eccentric braced frames have been a topic of research in seismic design over the past twenty years. The idea of eccentric bracing is a relatively new method used in practice to satisfy seismic design requirements. They have been proven to give reliable results in tests using simulated earthquake events, as well as provide an economical advantage over other framing methods. Two one-story eccentric braced frame models were created using computer generated finite element analysis. The example chosen for this study are discussed further. The maximum shear stress distribution in the link beam of the frame, using finite element analysis, will be investigated herein. The results of the shear stress produced gives insight to shear forces developed in the link beam of eccentric braced frames. The results of shear forces produced are compared with those calculated by structural engineers using commonly used hand calculated equations.
2

Development of an antenna system for a relay-based wireless network : simulation and measurement of antenna systems for relay-based wireless network, covering the backhaul and access links and applying beam forming technology

Petropoulos, Ioannis January 2012 (has links)
The proliferation of modern wireless networks increases demand for high capacity and throughput in order to provide faster, more robust, efficient and broadband services to end users. Mobile WiMAX and LTE are examples of such networks in which for some cases they have exposed limited connectivity due to harsh environment. Relay stations are preferred to overcome problems of weak or no access for such network devices, that are placed in specific positions to maintain high quality of data transfer at low cost and provide the required connectivity anywhere anytime. These stations should be equipped with an antenna system capable of establishing communication between base station (backhaul link) and end users (access link). This thesis focuses on the design and development of a new antenna system that is suitable for a relay-based wireless network. Planar geometries of microstrip patch antennas are utilized. The antenna system comprises two antenna modules: a new design of a single antenna for access link and a new design of an antenna array for backhaul link realization. Both antenna specifications are compatible with the IEEE802.16j protocol standard. Hence, relay station should be capable of pointing its radiation pattern to the base station antenna, thus to achieve the desired radiation pattern of the relay station, a new beam-forming module is proposed, designed and developed to generate the proper radiation pattern. The beam-forming module incorporating digital phase shifters and attenuator chips is fabricated and tested. The optimization process using the Least Mean Square (LMS) algorithm is considered in this study to assign the proper phase and amplitude that is necessary to each radiation element excitation current, to produce the desired steered radiation pattern. A comprehensive study on the coupling effects for several relative positions between two new backhaul and access link antenna elements is performed. Two new antenna configurations for coupling reduction are tested and the simulated and measured results in terms of antenna radiation performances were compared and commented.

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