170,130 research outputs found
Sviluppo di un sistema LED per inibire la crescita di microflora: Contrasto del biodegrado in ambienti ipogei. Il caso dell'area archeologica di Palazzo Valentini (Roma)
No full textPiante, alghe e cianobatteri, in quanto organismi fotoautotrofi, utilzzano la luce solare per produrre l'energia biochimica necessaria al loro sostentamento; allo stesso scopo possono anche utilizzare fonti di illuminazione artificiale presenti in musei o siti ipogei, in cui vengono trasportati come spore o pollini dai visitatori esterni e trovano condizioni microclimatiche favorevoli alla loro crescita e riproduzione. Tali processi implicano una colonizzazione di superfici e manufatti di interesse storico-artistico e la costituzione di strati di ancoraggio per altri organismi biodeteriogeni più complessi. Le analisi di identificazione delle specie di microflora infestanti gli scavi delle domus Romane (II sec. d.C.) di Palazzo Valentini a Roma sono state affiancate dallo studio dello spettro di assorbimento molecolare delle clorofille estratte dalle suddette specie e da misure colorimetriche di riflettanza ed assorbanza condotte sulle stesse. Sono state in seguito studiate diverse sorgenti LED monocromatiche allo scopo di combinarle in un circuito sperimentale il cui spettro di emissione risultasse non ideoneo all'attività fotosintetica delle specie fotoautotrofe infestanti
Elección matrimonial en la ciudad de Córdoba a fines de la Colonia y comienzos del período Independiente
No full textFil: Colantonio, S. E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Antropología Biológica y Cultural; Argentina.Fil: Colantonio, S. E. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Estudios sobre Cultura Y sociedad; Argentina.Fil: Kuffer, C. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Estudios sobre Cultura Y sociedad; Argentina.La homogamia es muy frecuente en las poblaciones humanas y representa un factor decisivo en su subdivisión. Un elemento asociado con los comportamientos homogámicos es la ancestría, ya que la elección conyugal ocurre a veces entre personas emparentadas con una frecuencia mayor a la esperada por azar, y también que determinados linajes casen entre sí con mayor frecuencia que la esperada.Fil: Colantonio, S. E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Antropología Biológica y Cultural; Argentina.Fil: Colantonio, S. E. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Estudios sobre Cultura Y sociedad; Argentina.Fil: Kuffer, C. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Estudios sobre Cultura Y sociedad; Argentina.Ciencias Sociales Interdisciplinaria
An approach to harmonic load- and source-pull measurements for high-efficiency PA design
No full textHigh-efficiency power-amplifier design requires numerous efforts to investigate both input and output harmonic terminations effects. A simplified theoretical approach to clarify the relevance of such terminations is presented here, and design criteria to improve efficiency for high-frequency applications are briefly discussed. An advanced active load/source-pull test-bench has been used to validate theoretical harmonic tuning techniques, characterizing an active device. The adopted optimization strategy is presented, together with measured results obtained with a medium-power 1-mm MESFET at 1 GHz. Input second harmonic impedances effects are stressed, showing a drain efficiency spread between 37%-49% for a fixed input power level, corresponding to 1-dB compression. Finally, as predicted by the presented theory, after input second harmonic tuning, further improvements are obtained, increasing fundamental output load resistive part, demonstrating an additional drain efficiency enhancement, which reaches a level of 55% at 1-dB compression
Development of integrated innovative techniques for paintings examination: The case studies of The Resurrection of Christ attributed to Andrea Mantegna and the Crucifixion of Viterbo attributed to Michelangelo's workshop
No full textThis is the accepted manuscript (post-peer reviewed) of the following final paper: "Laureti, S., Colantonio, C., Burrascano, P., Melis, M., Calabrò, G., Malekmohammadi, H., Sfarra, S., Ricci, M., Pelosi, C. , Development of integrated innovative techniques for paintings examination: The case studies of The Resurrection of Christ attributed to Andrea Mantegna and the Crucifixion of Viterbo attributed to Michelangelo's workshop, (2019) Journal of Cultural Heritage, 40, pp. 1-16, https://doi.org/10.1016/j.culher.2019.05.005
S-Band Class-C-F Power Amplifier with 2nd Harmonic Control at the Input
No full textPower amplifiers (PAs) are the most power-consuming devices in a transmitter. Their performance in efficiency is crucial to the efficiency of the whole system. Therefore, the issue of high efficiency PA has remained hot over the years. This paper presents an approach to design an S-band single stage class-F PA biased in class-C condition. Through the manipulation of the 2nd harmonic at the input, shaping the voltage waveform at the gate node, a class-F PA with proper output matching network (OMN) is realized. The proposed class-C-F PA achieved 60% drain efficiency (DE) and 36.3 dBm of output power around the 3 dB compression point. The methodology of taking the input non-linearity into consideration is also presented. Its feasibility has been verified through both the design and measurements
A Ka-band 33 dBm Stacked Power Amplifier Cell in 100 nm GaN-on-Si Technology
No full textThis work presents a self-biased 2-stacked power amplifier cell that shows, in simulations, an output power in excess of 33 dBm and gain and power added efficiency (PAE) above 6 dB and 27 %, respectively, over a 33.5 GHz to 39.5 GHz bandwidth. The cell has been developed on a commercial 100 nm GaN-on-Si process, applying space derating rules at center frequency, where the output power is almost 33.8 dBm, the associated gain is higher than 7 dB and PAE is above 35 %
A Comprehensive Harmonic Analysis of Current-Mode Power Amplifiers
No full textThis work presents a comprehensive theoretical analysis of current-mode power amplifiers as a function of input power for different biasing classes under the common simplifying assumption of constant transconductance and hard current cut-off/saturation. Typically, the theoretical analysis of power amplifier performance and behavior are carried out only at maximum output power. However, to achieve high data-rates, modern telecommunication systems adopt signals characterized by a very high peak-to-average power ratio, thus it is useful to analyze the power amplifier behavior as a function of power back-off. Moreover, in many cases, to enhance the efficiency and/or to apply harmonic shaping techniques, a clipped drain-source current, which approaches a square wave, is required. The classical analysis can be extended to low power levels only under the assumption of power-independent conduction angle, which is true only for class-A and class-B amplifiers, and does not take into account possible waveform clipping at maximum current. This work presents a complete theoretical Fourier analysis of FET-based power amplifiers as a function of quiescent drain-source current at any input power level and accounting for the clipped current case, up to the square-wave limit, reorganizing and completing the material that can be found in classical textbooks in the field
Biodemografía y evolución: interfase biología-sociedad
No full textFil: Albeza, M.V. Universidad Nacional de Salta. Consejo de Investigación; Argentina.Fil: Colantonio, S.E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Acreche, N. Universidad Nacional de Salta. Consejo de Investigación; Argentina.Fil: Kuffer, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.La configuración del pool génico de una población está determinada por factores biológicos, sociales y culturales. Es en la conformación de parejas donde la interacción de estos factores se evidencia con más fuerza, ya que puede dar cuenta de tres de los cuatro factores de cambio en las poblaciones humanas.Fil: Albeza, M.V. Universidad Nacional de Salta. Consejo de Investigación; Argentina.Fil: Colantonio, S.E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Acreche, N. Universidad Nacional de Salta. Consejo de Investigación; Argentina.Fil: Kuffer, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Ciencias Sociales Interdisciplinaria
The AB-C Doherty power amplifier. Part II: validation
No full textIn part I, the complete theoretical (and nonlinear) analysis of a Doherty amplifier employing a Class AB bias condition for the Main Amplifier and a Class C one for the Auxiliary device has been presented. In this article, the experimental validation of the proposed theory is presented, describing the step-by-step procedure to be adopted when designing an AB-C Doherty. The amplifier was realized at 2.14 GHz in hybrid form using two (0.5 mu m, 1 mm gate periphery) GaN HEMTs. (c) 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE 19: 307-316, 2009
- …
