Calibração de um lisímetro simplificado de pesagem.

O crescente uso da água e a redução de sua disponibilidade têm se tornado preocupação cada vez maior em todo o mundo. Em termos mundiais, a agricultura é responsável pela utilização de 70% da água doce consumida no planeta, por isso tem sido alvo de crítica pela sociedade demandando que sua utilização seja da forma mais racional possível. O presente trabalho tem como objetivo a construção e calibração de um lisímetro de pesagem em solo não vegetado de custo reduzido

A Simple Method to Identify Parametric Oscillations in Power Amplifiers Using Harmonic Balance Solvers

A qualitative method to verify the presence of parametric oscillations at f_0/2 in power amplifiers (PAs) is presented and validated. It relies on the simultaneous application of fundamental and subharmonic tones to trigger possible parametric oscillations and can be implemented in any commercial harmonic balance solver without requiring any external software that may be expensive or however not available to the designer. Wide applicability is guaranteed by the fact that this method does not require access to any internal node of the circuit. In fact, the amplifier is handled as a black-box where only the input and output ports are accessible. The stability check is first demonstrated on a simplified case study and then validated on a real K-band integrated PA, where it correctly reproduces with simulations the parametric oscillations observed by measurements. On the redesigned amplifier, the proposed test predicted the absence of oscillations, which has been confirmed by the experimental characterization

Optimisation of a Doherty power amplifier based on dual-input characterisation

The success of the Doherty architecture compared to other efficiency enhancement techniques derives mainly from its simple design and full-RF nature, not requiring complex digital signal processing to achieve high back-off efficiency. In this work we propose a design strategy for the optimisation of a Doherty power amplifier to mitigate the typical practical issues of this architecture related to inaccuracy of the non-linear model and of the manufacturing. The approach is based on the experimental characterisation of a dual-input Doherty prototype without input section. This test structure is obtained from a single-input Doherty amplifier, designed only through non-linear simulations, by removing the input section and allowing for separate control of the two RF inputs. From the collected data, approximated functions for the phase shift and power splitting versus frequency are identified to be realizable in hardware with RF networks. Compared to the reference single-input Doherty stage, a significantly improved behavior is registered in terms of output power (up to 2.7 dB), efficiency at saturation and back-off (30 % and 15 % respectively) and power gain (2 dB)

A 5-W GaN Doherty Amplifier for Ka-Band Satellite Downlink With 4-GHz Bandwidth and 17-dB NPR

This letter presents the design and experimental characterization of a GaN-Si monolithic Doherty power amplifier (PA) for the Ka-band satellite downlink. The fabricated amplifier favorably compares with the current state of the art, achieving from 16.3 to 20.3 GHz (4 GHz, 22% relative bandwidth), a record band to date, 36.6-37.7-dBm output power, 23%-31% power-added efficiency, 18-22-dB gain at saturation, and around 20% power-added efficiency at 6-dB output back-off. At 18.8 GHz, the amplifier shows a noise-to-power ratio higher than 17 dB at all power levels, making it suitable for satellite applications where additional linearization is usually unfeasible

Evaluation of a stacked-FET cell for high-frequency applications

This paper presents the design, electromagnetic simulation strategies and experimental characterisation of a two-stage stacked-FET cell in a 100 nm GaN on Si technology around 18.8 GHz, suited for Ka band satellite downlink applications. A good agreement is found between the electromagnetic simulations and the measured performance on the manufactured prototype, thus demonstrating that a successful voltage combining architecture can be obtained in the frequency range of interest with the selected topology, based on a symmetric fork-like connection between the transistors. This proves the effectiveness of an appropriate electromagnetic simulation set-up in correctly predicting the crosstalk, which typically affects this structure, leading to a correct stacking operation

3–20 GHz GaN MMIC Power Amplifier Design Through a COUT Compensation Strategy

This paper presents the design approach for a compact, single-stage, wideband MMIC power amplifier. A method is proposed to compensate the output capacitance of the active device over a frequency range as wide as possible, with minimum impact on the achievable output power, that leads to a 2- element compensating network. A 3- section transformer is then adopted for a real-to-real transformation. The CW characterization shows output power higher than 32dBm and drain efficiency between 35% and 45%, over a fractional bandwidth of 148%, from 3 GHz to 20 GHz

Food safety in collective catering: Knowledge, attitudes and correct application of GHP/GMP knowledge among foodservice workers

Food safety critically reliant on the behaviors adopted by foodservice personnel, involved in various stages of meal preparation, from the supply of raw food materials until its distribution to the consumer. The purpose of this work was to collect information on the level of knowledge on food safety, the correct application of the Good Hygiene Practices (GHP) and Good Manufacturing Practices (GMP) and the attitudes of the operators involved in collective catering. The survey was conducted among 15 social catering companies in Apulia (Italy) using a modified Sharif and Al-Malki (2010) anonymous questionnaire intended to assess the knowledge, attitudes and practices of the food handlers. The results highlight the need to improve both knowledge and practices regarding food hygiene and safety in order to minimize the risk of transmitting foodborne diseases. More careful planning, implementation, monitoring and evaluation of training programs for foodservice workers is required, taking into consideration the provisions of European food laws

Unusual presentation of fatal disseminated varicella zoster virus infection in a patient with lupus nephritis: A case report

Background: The risk of life-threatening complications, such as visceral disseminated varicella zoster virus (VZV) infection, is greater in immunosuppressed individuals, such as systemic lupus erythematosus (SLE) patients. Case presentation: Here, a case is reported of a Caucasian woman diagnosed with lupus nephritis and anti-phospholipid syndrome, who was subjected to mycophenolate mofetil and high-dose steroid remission-induction therapy. Two months later she developed abdominal pain followed by a fatal rapid multi-organ failure. As no typical skin rashes were evident, death was initially attributed to catastrophic anti-phospholipid syndrome. However, autopsy and virological examinations on archival material revealed a disseminated VZV infection. Conclusions: Overall, this case highlights the importance of having a high clinical suspicion of fatal VZV infections in heavily immunosuppressed SLE patients even when typical signs and symptoms are lacking