Design of a Broadband Amplifier for High Speed Applications

This paper provides comprehensive insight into the design approach followed for an amplifier dedicated to high speed base band signals. To demonstrate the methodology, an amplifier consisting of nine PHEMT cascode cells within a distributed amplifier topology was designed. The resulting frequency response is 40 GHz at the 3-dB point, and the output voltage for a 43 Gbps eye diagram is 7.3 Vpp at the chip terminal

Os discursos de licenciandos, professores universitários e secundários contribuindo para a reestruturação curricular de um curso de licenciatura em Física

Este estudo foca-se na reestruturação curricular de um curso de licenciatura em Física de uma universidade pública. No processo foram analisados, discursos de licenciandos, docentes universitários e professores em exercício procurando-se entender como as demandas desses grupos influenciaram na estrutura curricular resultante. Para interpretar os efeitos de sentidos presentes em documentos e discursos dos sujeitos envolvidos foram adotados referenciais teórico-metodológicos embasados em teorias críticas e na Análise de Discurso de linha francesa. A proposta final situou-se entre as exigências legais e a realidade acadêmica. A legislação consultada, os professores em exercício, os licenciandos e os formadores na Universidade, subsidiaram ou sinalizaram o que e como a estrutura curricular do Curso poderia ter ou ser alterada

Tropical cyclone activity affected by volcanically induced ITCZ shifts

Volcanic eruptions can inject a large amount of aerosol particles, which interact with solar radiation and consequently can affect the climate worldwide, hence the intensity and frequency of extreme events for a few years following the eruption. However, only a handful of studies have investigated the impacts of volcanic eruptions on tropical cyclone activity. Through a set of sensitivity modeling experiments, our study demonstrates that volcanic eruptions by shifting the Intertropical convergence zone can impact tropical cyclone activity up to 4 years following the eruption. These results will prove valuable to society, allowing us to better prepare for the consequences of changes in tropical cyclone activity following large volcanic eruptions

A 43-Gbps Lithium Niobate Modulator Driver Module

This paper describes the realization of a 43-Gbps Lithium Niobate modulator driver module. The NRZ driver module utilizes four stages of GaAs p-HEMT MMIC amplifiers integrated with an output level detector and feedback loop to provide thermal stability and external control of the output swing. The bias and loop control circuitry are contained in the housing on a PC board external to the sealed MIC section. The integrated module (50.8 x 73.4 x 9.5 mm 3) provides 6.0 Vp-p controllable single-ended output voltage while dissipating only 4 watt

Piezoelectric Microfiber Composite Actuators for Morphing Wings

Morphing wing technologies provide expanded functionality in piloted and robotic aircraft, extending particular vehicle mission parameters as well as increasing the role of aviation in both military and civilian applications. However, realizing control surfaces that do not void the benefits of morphing wings presents challenges that can be addressed with microfiber composite actuators (MFCs). We present two approaches for realizing control surfaces. In one approach, flap-like structures are formed by bonding MFCs to each side of a metal substrate. In the other approach, MFCs are bonded directly to the wing. Counter intuitively, the flap approach resulted in larger voltage actuation curvatures, with increased mass load. Actuation performance, defined as the ratio of curvature per applied voltage, was as large as 5.8 ± 0.2 × 10−4 (kV⋅mm)−1. The direct bonding approach reveals that at zero wing pressure, up to 63 ± 3  μm of displacement could be realized

THREE METHODS TO EVALUATE THE USE OF EVAPORATIVE COOLING FOR HUMAN THERMAL COMFORT

This paper presents three methods that can be used as reference for efficientuse of evaporative cooling systems, applying it, latter, to several Braziliancities, characterized by different climates. Initially it presents the basicprinciples of direct and indirect evaporative cooling and defines theeffectiveness of the systems. Afterwards, it presents three methods thatallows to determinate where the systems are more efficient. It concludesthat evaporative cooling systems have a very large potential to propitiatethermal comfort and can still be used as an alternative to conventionalsystems in regions where the design wet bulb temperature is under 24ºC

Creation of Rydberg Polarons in a Bose Gas

We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a $p$-wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral lineshape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, $n$. Spectral features are described with a functional determinant approach (FDA) that solves an extended Fr\"{o}hlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with FDA.Comment: 5 pages, 3 figure

Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC

The lifetimes and decay channels of ultralong-range Rydberg molecules created in a dense BEC are examined by monitoring the time evolution of the Rydberg population using field ionization. Studies of molecules with values of principal quantum number, $n$, in the range $n=49$ to $n=72$ that contain tens to hundreds of ground state atoms within the Rydberg electron orbit show that their presence leads to marked changes in the field ionization characteristics. The Rydberg molecules have lifetimes of $\sim1-5\,\mu$s, their destruction being attributed to two main processes: formation of Sr$^+_2$ ions through associative ionization, and dissociation induced through $L$-changing collisions. The observed loss rates are consistent with a reaction model that emphasizes the interaction between the Rydberg core ion and its nearest neighbor ground-state atom. The measured lifetimes place strict limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.Comment: 9 pages, 8 figure