Remote Sensing Evaluation Drone Herbicide Application Effectiveness for Controlling Echinochloa spp. in Rice Crop in Valencia (Spain).

Rice (Oryza sativa L.) is a staple cereal in the diet of more than half of the world's population. Within the European Union, Spain is a leader in rice production due to its climate and tradition, accounting for 26% of total EU production in 2020. The Valencian rice area covers around 15,000 hectares and is strongly influenced by biotic and abiotic factors. An important biotic factor affecting rice production is weeds, which compete with rice for sunlight, water and nutrients. The dominant weed in Spain is Echinochloa spp., although wild rice is becoming increasingly important. Rice cultivation in Valencia takes place in the area of L'Albufera de Valencia, which is a natural park, i.e., a special protection area. In this natural area, the use of phytosanitary products is limited, so it is necessary to use the minimum amount possible. Therefore, the objective of this work is to evaluate the possibility of using remote sensing effectively to determine the effectiveness of the application of the herbicide cyhalofop-butyl by drone for the control of Echinochloa spp. in rice crops in Valencia. The results will be compared with those obtained by using sterilisation machines (electric backpack sprayers) to apply the herbicide. To evaluate the effectiveness of the application, the reflectance obtained by the satellite sensors in the red and near infrared (NIR) wavelengths, as well as the normalised difference vegetation index (NDVI), were used. The remote sensing results were analysed and complemented by the number of rice plants and weeds per area, plant dry weight, leaf area, BBCH phenological state, SPAD index values, chlorophyll content and relative growth rate. Remote sensing is validated as an effective tool for determining the efficacy of an herbicide in controlling weeds applied by both the drone and the electric backpack sprayer. The weeds slowed down their development after the treatment. Depending on the phenological state of the crop and the active ingredient of the herbicide, these results are applicable to other areas with different climatic and environmental conditions.

Application of Phase-Reversal Fresnel Zone Plates for High-Resolution Robotic Ultrasonic Non-Destructive Evaluation.

Nowadays the development of automated inspection systems based on six degrees of freedom robotic manipulators is a highly relevant topic in ultrasonic non-destructive testing. One of the issues associated with such development is the problem of acquiring high-resolution results. In this article, the application Phase-Reversal Fresnel Zone Plates is considered for solving this problem. Such acoustic lenses can solve the task of high-resolution results acquisition by using a single unfocused transducer. Furthermore, Phase-Reversal Fresnel Zone Plates can provide the desired focusing depth with the fixed thickness of the coupling layer. It is important in the case of application of devices which provide localized coupling. In this paper a proper design of Phase-Reversal Fresnel Zone Plate was determined according to the conditions of planned experiments. Its efficiency was verified via the Finite Element Method modeling. In all performed experiments the relative error of flaws size estimation did not exceed 6% whereas the signal-to-noise ratio was not lower than 17.1 dB. Thus, experimental results demonstrate that the application of Phase-Reversal Fresnel Zone Plates allowed to obtain results with high lateral resolution and signal-to-noise ratio. These results demonstrate the reasonability of the development of devices that provide localized coupling and use Phase-Reversal Fresnel Zone Plates.

Cylindrical 3D printed configurable ultrasonic lens for subwavelength focusing enhancement.

In this study, we report the characteristics of acoustic jets obtained through a mesoscale (radius less than 5 wavelengths) ABS cylinder made with a 3D printer. We have analyzed the influence of cylinder size on the characteristic parameters of an acoustic jet, such as maximum acoustic intensity at focus, Full Width at Half Maximum and length of Acoustic Jet. FWHM below 0.5 wavelength in AJ was experimentally obtained. It has been observed that there are two operating regimes depending on the cylinder radius: the resonant and the non-resonant. In the resonant regime, the excitation of Whispering Gallery Modes results in optimal parameter values of the acoustic jet. However, as it is a resonant regime, any minimal variation in cylinder size, working frequency or refractive index would make resonance disappear. In non-resonant mode, a phononic crystal has been embedded inside the cylinder and the characteristic parameters of the acoustic jet have been studied. These have been observed to improve. Finally, we have shown that curved acoustic jets can be obtained with the ABS cylinder with a phononic crystal embedded inside.

Transient Analysis of Fresnel Zone Plates for Ultrasound Focusing Applications.

Fresnel Zone Plates are planar lenses that can be used to focus ultrasound beams. This kind of acoustic lenses can play a key role in the resolution of ultrasonic NDT systems. In this type of pulse-echo applications, the pulse duration is an important parameter that specifies the axial resolution, and thus, shorter ultrasound pulses provide higher resolutions. However, acoustic lenses exhibit a transient response that should be considered when setting the pulse duration, as pulses shorter than the transient state duration result in degradation in the response of acoustic lenses in terms of focal intensity, focal displacement, and lateral and axial resolutions. In this work, a thorough analysis of the transient response of Fresnel Zone Plates is discussed, demonstrating that the transient state should be considered in order to achieve optimal focusing performance. Theoretical and numerical results are presented, showing very good agreement.

Ultrasonic focusing with mesoscale polymer cuboid.

In this paper, we demonstrate that, contrary to what the Geometrical Optics laws dictate, a flat polymer mesoscale cuboid immersed in water with no need of negative refraction can focus sound. Two main polymers were considered and lens parameters compared: PMMA and Rexolite®. It was concluded that Rexolite® is preferable for acoustic jet formation. The nature of the formation of the foci along the longitudinal axis, that is to say along the wave propagation axis, is numerically and experimentally demonstrated. In addition, the conditions under which a cubic particles lens of this type forms a single localized region with a sub-diffraction transverse size (approximately 0.44 wavelength) are determined. The comparisons of the acoustic wave pressures and the focal distance between the Finite Element Method based numerical results and the experimental results show fair agreement.

Bifocal Ultrasound Focusing Using Bi-Fresnel Zone Plate Lenses.

In this work, we present a bifocal Fresnel zone plate (BiFZP) capable of generating focusing profiles with two different foci. The performance of the BiFZP is demonstrated in the ultrasound domain, with a very good agreement between the experimental measurements and the finite element method (FEM) simulations. This lens becomes an appealing alternative to other dual-focusing lenses, in which the foci location can only be set at a limited range of positions, such as M-bonacci zone plates. Moreover, the variation of the operating frequency has also been analyzed, providing an additional dynamic control parameter in this type of lenses.

Application of Phase-Reversal Fresnel Zone Plates for Improving The Elevation Resolution in Ultrasonic Testing with Phased Arrays.

Currently, phased arrays have found wide application in ultrasonic nondestructive testing. Volumetric results provided by the.

Acoustic Focusing Enhancement In Fresnel Zone Plate Lenses.

The development of flat acoustic lenses for different applications such as biomedical engineering is a topic of great interest. Flat lenses like Fresnel Zone Plates (FZPs) are capable of focusing energy beams without the need of concave or convex geometries, which are more difficult to manufacture. One of the possible applications of these type of lenses is tumor ablation through High Intensity Focused Ultrasound (HIFU) therapies with real time Magnetic Resonance Imaging (MRI) monitoring. In order to be MRI compatible, the FZP material cannot have electromagnetic interaction. In this work, a Phase-Reversal FZP (PR-FZP) made of Polylactic Acid (PLA) manufactured with a commercial 3D printer is proposed as a better, more efficient and MRI compatible alternative to conventional Soret FZPs. Phase-Reversal lenses, unlike traditional FZPs, take advantage of all the incident energy by adding phase compensation regions instead of pressure blocking regions. The manufactured PR-FZP achieves 21.9 dB of focal gain, which increases the gain compared to a Soret FZP of its same size by a factor of 4.0 dB. Both numerical and experimental results are presented, demonstrating the improved focusing capabilities of these types of lenses.

Design of Acoustical Bessel-Like Beam Formation by a Pupil Masked Soret Zone Plate Lens.

The image performance of acoustic and ultrasound sensors depends on several fundamental parameters such as depth of focus or lateral resolution. There are currently two different types of acoustic diffractive lenses: those that form a diffraction-limited spot with a shallow depth of focus (zone plates) and lenses that form an extended focus (quasi-Bessel beams). In this paper, we investigate a pupil-masked Soret zone plate, which allows the tunability of a normalized angular spectrum. It is shown that the depth of focus and the lateral resolution can be modified, without changing the lens structure, by choosing the size of the pupil mask. This effect is based on the transformation of spherically-converging waves into quasi-conical waves, due to the apodization of the central part of the zone plate. The theoretical analysis is verified with both numerical simulations and experimental measurements. A Soret zone plate immersed in water with D/2F = 2.5 and F = 4.5 λ changes its depth of focus from 2.84 λ to 5.9 λ and the lateral resolution increases from 0.81 λ to 0.64 λ at a frequency of 250 kHz, by modifying the pupil mask dimensions of the Soret zone plate.

Manipulation of focal patterns in acoustic Soret type zone plate lens by using reference radius/phase effect.

The manipulation of focal patterns of acoustic underwater Soret Zone Plate lens in far fields, such as manipulation (optimization) of Sidelobe Level and the design of long depth of focus by selecting the simple free parameter called reference radius (phase) has been demonstrated.Two effects have been studied by means of numerical simulations. Regarding the first effect, simulations demonstrate diffraction limited focal spot (0.47 wavelength) and 3 dB reduction of the first Side Lobe Level using Soret ZP with an optimal reference radius and without causing neither main lobe broadening or gain reduction. In the second effect, by using numerical simulations an increasing of depth of focus, more than 2 times, in comparison with classical Soret ZP with high numerical aperture (F/D = 2.5), was observed.