Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 49 for “"cross polarization"”.
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Biomedical solid state NMR : an ADRF cross polarization study of calcium phosphates and bone mineral
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1996.
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Synthesis of dual offset Gregorian reflector antennas with very low cross polarization under practical constraints for mass production
… starts with a complete survey of the depolarization characteristics of axisymmetric and offset reflector antennas. Single and dual reflector configurations are considered. Cross polarization (XPOL) and beam squint are examined in detail. Although many of the phenomena are known, they are …
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Variable permittivity dielectric material loaded stepped-horn antenna
… Input return loss, gain, aperture efficiency and cross-polarization characteristics are studied. Comparisons indicate that any kind of loading with dielectric material along the taper tend to improve the gain level for the entire bandwidth, aperture efficiency may increase and cross-polarization …
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In-situ 13C CM-MAS NMR study of dilute acid biomass pretreatment on 13C enriched poplar wood
… spinning) spectra were obtained in both the CP (cross polarization) and DP (direct polarization) modes, the contrasts in this combination yielding valuable qualitative information on the effect of pretreatment on local molecular mobilities. In addition, spin-lattice relaxation values for 13C and …
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Embedded microvascular networks for electronically reconfigurable materials
… wireless devices, a coplanar waveguide and a cross-polarization patch antenna. The coplanar waveguide achieves phase reconfiguration with a single serpentine channel design, while the cross-polarization antenna achieves polarization reconfiguration using dual 3D network architectures.
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Multiple reflector scanning antennas
… low aperture efficiency and poor side lobe and cross polarization performance. This dissertation introduces a new approach to the design of scanning spherical reflector systems, in which the performance weaknesses of high cross polarization and high side lobe levels are avoided. Moreover, the …
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Structural studies of amyloid fibrils using solid-state NMR
… method for highly accurate distance measurement across parallel [beta]-sheets in amyloid fibrils has been developed. This method combines the a double quantum filtered version of the dipolar recoupling sequence DRAWS with the simulation and data fitting program SPINEVOLUTION to provide a simple …
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Characterization of the wood/isocyanate bondline
… The present research describes the use of ¹⁵N cross-polarization, magic-angle spinning (CP/MAS) NMR as a technique for probing the cure chemistry and bondline morphology of pMDI-bonded wood composites. A 99% ¹⁵N-enriched pMDI resin with desirable adhesive properties was synthesized. A series of …
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Rain attenuation and depolarization along 10 to 30 GHz earth space links predicted from s-band dual-polarized radar measurements
… that is capable of predicting attenuation and cross polarization at 10-30 GHz from dual-polarization radar data with a high degree of accuracy. FORWP uses a rigorous backscattering computer model BSCAT to infer rain drop size distribution along the slant path from radar measured reflectivity …
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Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology
… nanoscale, but being too dispersed for forming a crosslinked network. With CP/MAS NMR, intermolecular cross-polarization experiments are found unsuitable to probe the angstrom scale morphology of the wood adhesive interphase. However, observing the influence of the PF resins on the spin lattice …
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Concept Demonstrator for MeerKAT Operation from 14.5 to 20 GHz
… was used for the front-end receiver. A single polarization wide-axially corrugated horn with low side-lobes and cross-polarization has been designed for the proof of concept with a predicted aperture efficiency of 60% including surface accuracy loss when illuminating the MeerKAT reflector. The …
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Rain depolarization scatter prediction
… extends an existing mathematical model of rain depolarization and attenuation to include the expected variances as well as the usually predicted mean values. It emphasizes depolarization and develops data for waves with frequencies ranging from 4 to 34.8 GHz propagating in rain cells which vary in …
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Development of Efficient Techniques for the Analysis and Design of Antennas in Dual-Reflectarray Configuration
… the accuracy for the prediction of co- and cross-polar patterns and antenna gain respect to the case of using ideal feed models. In the second part, as a preliminary validation, the proposed analysis method has been used to design a dual-reflectarray antenna that emulates previous …
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Improving port isolation in dual-polarized microstrip patch antenna arrays
… polarized ports must be maximized and radiation cross-polarization minimized. To prevent the port isolation degradation due to presence of the feed network lines surrounding the radiator the "folded" feed optimized to maximize the port isolation is introduced. The analysis of the port isolation …
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Inverse problems in electromagnetics
… split-ring resonators, which signifies that the cross polarization terms of the metamaterial are quantitatively investigated for the first time. Finally, an optimization approach is designed to achieve the retrieval of general bianisotropic media with 72 unknown parameters. The hybrid algorithm …
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Moxon based RFID tag reader and GPS antenna
… high forward gain, low backward radiation, high cross-polarization, small size and low manufacture cost. The Moxon antenna based on a two element Yagi-Uda antenna over the ground reflector is one of the most favorite antennas for HAM operators which can produce outstanding front to back ratio of …
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Structure and dynamics studies by solid-state nuclear magnetic resonance spectroscopy
… The 205T1 direct excitation and H-205T1 cross polarization experiments are demonstrated. The fourth chapter describes the application of 205T1 high resolution solid state NMR to the investigation of the behavior of a small ion channel in the liquid crystalline phase. Here, thallium …
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NMR Applications in Soft Materials Science: Correlation of Structure, Dynamics, and Transport
… array of SSNMR techniques, including: 1) ¹³C cross-polarization magic angle spinning (CPMAS) with varying cross-polarization (CP) contact time, 2) ¹³C single-pulse magic angle spinning (MAS) with varying delay time, 3) ²³Na single-pulse MAS, 4) two dimensional phaseadjusted spinning sideband …
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Design and implementation of the pillbox antenna for SASARII
… power gain, 3 dB beamwidth, return loss and cross-polarization measurements are discussed. The test results are analyzed and compared to the simulations and theoretical predictions to measure the performance of the antenna. This dissertation winds up by discussing the conclusions to the …
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Polarization behaviour of on-body communication channels at 2.45 GHz
… planar antennas. In addition, the effect of the polarization of the antenna on channel path gain is studied and channel cross polarization discrimination is quantified, using both simulation and measurement.
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