Application of a low-cost camera on a UAV to estimate maize nitrogen-related variables

The development of small unmanned aerial vehicles and advances in sensor technology have made consumer digital cameras suitable for the remote sensing of vegetation. In this context, monitoring the in-field variability of maize (Zea mays L.), characterized by high nitrogen fertilization rates, with a low-cost color-infrared airborne system could be the basis for a site-specific nitrogen (N) fertilization support system. An experimental field with different N treatments applied to silage maize was monitored during the years 2014 and 2015. Images of the field and reference destructive measurements of above ground biomass, its N concentration and N uptake were taken at V6 and V9 development stages. Classical normalized difference vegetation indices (NDVI) and the indices adjusted by crop ground cover were calculated and regressed against the measured variables. Finally, image colorgrams were used to explore the potential of band-related information in variable estimation. A colorgram is a linear signal that summarizes the color content of each digital image. It is composed of a sequence of the frequency distribution curves of the camera bands, of their related parameters and of results of the principal components analysis applied to each image. The best predictors were found to be the ground cover and the adjusted green-based NDVI: regression equation at V9 resulted in R2 of 0.7 and RRMSE < 25% in external validation. Colorgrams did not improve prediction performance due to the spectral limitations of the camera. Therefore, the feasibility of the method should be tested in future research. In spite of limitations of sensor setup, the modified camera was able to estimate maize biomass due to the very high spatial resolution. Since the above ground biomass is a robust proxy of N status, the modified camera could be a promising tool for a low-cost N fertilization support system

Olea europaea, una pianta mediterranea nei suoi numerosi aspetti

Olea europaea L. costituisce l'elemento fondamentale della vegetazione mediterranea. L'uso di questa pianta \ue8 antichissimo ed il presente lavoro \ue8 una raccolta di dati che vogliono illustrarne sinteticamente gli aspetti botanici, storici, commerciali, alimentari, cosmetici, medicinali, artistico-letterari, con particolare attenzione alla sua presenza nel territorio ligure

Lo scavo urbano pluristratificato di Piazza Castello n. 18 a Padova

Breve presentazione di una scelta di materiali cronologicamente significativi per l’inquadramento del sito patavino di Piazza Castello, dove la sequenza cronologica appare ininterrotta dall’VIII sec. a.C. all’età romana imperiale

Comparison of Feedback and Feedforward Strategies for Active Structural-Acoustic Control of Broadband Sound Transmission into a Cavity

This work presents an experimental comparison of four strategies for active structural- acoustic control (ASAC) aimed at minimizing the transmission of sound through a flat panel into a contiguous cavity. The implemented feedback and feedforward designs, while prevalent in the literature, had not been previously compared on a single panel-cavity system. The test-bed was designed to achieve a dynamic response similar to a single panel in a typical rotorcraft fuselage. This paper presents a performance comparison of four broad categories of ASAC systems such as: classic feedback control (direct velocity feedback DVF), predictive feedback control (generalized predictive control (GPC)), adaptive feed- forward control (filtered-X LMS control) and hybrid feedback-feedforward control (hybrid GPC). The control architectures implemented during this study are all multi-input/multi- output in order to allow the direct application of the resulting insight to more practical situations. Both the vibration and the acoustic performance are recorded for each case under equivalent conditions to allow a fair comparison and are here presented. It turns out that the classic feedback control does not allow to achieve high noise reduction as FXLMS or hybrid GPC that can reduce the averaged total sound power up to 14 dB. In particular the hybrid GPC gives significant improvement with respect to the basic GPC because uses information about the disturbance acting on the system

Active Solutions for Reduction of the Transmission of Structure-Borne Noise to the Cabin Structure on a A109 Mockup

The paper presents some preliminary results of active control strategies aimed at reducing the transmission of structure-borne noise to the cabin structure on a AgustaWestland A109 helicopter mockup. The experiments were performed on a full-scale mockup consisting of a gearbox housing connected to the fuselage via two front and two rear struts and an anti-torque plate. The mockup is provided with two electric motors that appropriately drive the gearbox at the nominal rotating speed. A suitable aerodynamic brake is attached to the rotor must in order to reproduce the load effect of the rotor blades. Peaks at the gear meshing frequencies reveal amplitudes very close to those acquired during in-flight measurements. Rear gearbox struts and the anti-torque plate were equipped with piezoelectric actuators and some control algorithms were designed and implemented to change the transfer function at the connection between the gearbox and the cabin. Vibration and acoustic results inside the cabin are presented and critical issues of the adopted solutions are discussed