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The asymmetric radio frequency (RF) self‐interference cancellation (SIC) architecture is studied, and the closed‐loop control of RF SIC based on software radio is realized. This system uses a circulator to isolate the receiving and transmitting chains, and its RF reconstruction chain is composed of a 4‐tap filter with fixed delay and tunable attenuation for each tap. The optimization of tap filter and asymmetric power divider's power allocation ratio is discussed. In the experiment, sensing, calibration, optimization algorithms and hardware control programs were proposed. A closed‐loop gradient descent algorithm for tuning the variable attenuator is implemented on the GNU Radio. From 910 MHz to 930 MHz, the isolation between the receiving and transmitting ports increases 40 dB, achieving an isolation of more than 65 dB and the transmission energy efficiency increases by 60%. [ABSTRACT FROM AUTHOR]

Although the dynamic response of telecommunication guyed masts in turbulent winds may be analyzed using a number of numerical models, limited experimental verification of the dynamic analysis results has been performed. Full-scale measurements, where available, have proven to be difficult to correlate with analytical models due to the uncertainty inherent in field measurements. As a result, the need for systematic validation and calibration of existing analytical models remains. A wind tunnel study was therefore undertaken on a dynamically scaled aeroelastic model of a 300 m guyed mast in turbulent boundary layer flow conditions. Dynamic responses measured during the wind tunnel tests are presented, including dynamic displacements, bending moments and peak factors, as well as natural frequencies and mode shapes. Comparisons are also made with results from an existing frequency domain analysis model. It was found that good agreement was generally achieved between the frequency domain analytical model and the wind tunnel tests with respect to both the magnitude and distribution of the monitored responses. Observed differences between mean and dynamic mast bending moment distributions in both the measured and predicted results support the contention that the conventional 'gust factor' wind loading approach is not suitable for guyed masts. Key words: guyed masts, dynamic response, wind tunnel testing, wind loading, aeroelastic model, dynamic analysis, frequency domain methods. Pour les mats haubanes servant aux telecommunications, la reaction dynamique lors de vents turbulents peut etre analysee par plusieurs modeles numeriques; toutefois, peu de verifications experimentales des resultats de l'analyse dynamique ont ete realisees. Les mesures a pleine echelle, lorsque disponibles, se sont revelees difficiles a correler aux modeles analytiques en raison de l' incertitude inherente aux mesures prises sur le terrain. Il en decoule un besoin de validation et d' etalonnage systematiques des modeles analytiques existants. Une etude en soufflerie a donc ete entreprise sur un modele aeroelastique a echelle dynamique d' un mat haubane de 300 m dans des conditions de couche limite turbulente. Les reactions dynamiques mesurees durant les essais en soufflerie sont presentees, incluant les deplacements dynamiques, les moments de flexion et les facteurs de pointe, ainsi que les frequences naturelles et les modes de configuration. Des comparaisons sont egalement realisees avec les resultats d'un modele d'analyse du domaine des frequences existant. La correlation etait generalement reussie entre le modele analytique du domaine des frequences et les essais en soufflerie quant a l' amplitude et a la distribution des reactions verifiees. Les differences remarquees entre les distributions moyenne et dynamique du moment de flexion dans le mat dans les resultats mesures et predits soutiennent l'opinion que l'approche de charge due au ≪ facteur de rafales de vent ≫ n' est pas adequate pour les mats haubanes. Mots-cles : mats haubanes, reaction dynamique, essai en soufflerie, charge due au vent, modele aeroelastique, analyse dynamique, methodes de domaine des frequences. [Traduit par la Redaction], 1. Introduction Because of their height and overall flexibility, guyed telecommunication masts are inherently sensitive to dynamic excitation provided by wind turbulence. Their low self weight and equipment loads also [...]

An efficient electron field emitter based on a monolayer graphene coated well aligned Mo tip array has been designed, fabricated, and evaluated. The advantages of this hybrid nanostructure film morphology are explored and discussed. Efficient and stable field emissions with low turn-on fields have been observed with the new devices. It is further found that the combination of graphene and Mo tip array leads to significant improvements in efficiency for the nanoscale heterostructure emitters. [ABSTRACT FROM AUTHOR]