RESUMO

Through the methodology of optical surface design based on concentric rings, this paper proposes the design of freeform mirrors, initially by employing segmented rings, each of them with different spherical radii of curvature, and then by employing segmented conic rings with different conic constants in each of the segments. These surfaces will then produce the desired images. For the case of segmented spherical rings, mathematical expressions were deduced to obtain the image points as a function of the radii of curvature. Furthermore, it is shown that in the case where conic rings were used, there is a decrease in spherical aberration, which allows the manipulation of the generated image. Finally, several proposals are presented for the design of mirrors to generate both the desired size of the image and the desired distribution of energy, together with their analyses.

RESUMO

This paper presents the application of CORPS (coherently radiating periodic structures) for feeding CRA (concentric rings array) with a reduced number of phase shifters. The proposed design technique for the structure of concentric rings provides a better scanning capability with respect to other existing configurations. This design technique utilizes 2 × 3 or 4 × 7 CORPS networks depending on the configuration or the number of antenna elements in the phased array system. These CORPS networks are set strategically in the feeding network to provide several advantages with respect to others in the scanning capability and the reduction of the number of phase shifters of the array system. The contribution of this paper is the full antenna system design of phased CRA for analyzing scanning and the reduction of phase shifters. The proposed phased array reduces the number of phase shifter devices in CRA for a scanning range of ±25° in the elevation plane. Differential evolution (DE) was applied to optimize the amplitudes of the proposed system. Several design cases were analyzed using full-wave simulation results to verify the phased array model and to take mutual coupling into account. Full-wave simulation results provide radiation patterns with low SLL in all scanning directions. The proposed phased array was validated by experimental measurements of the full antenna system prototype.

Assuntos

RESUMO

Watermelon is an important vegetable crop in Mexico and produced on 358,105 ha, with nearly 1.5 x 106 tons. In September 2019, brown, irregular shape to round lesions with concentric rings were observed on the leaves and stems of watermelon plants in Sonora State. The surface of the lesions contained abundant cup-shaped sporodochia covered by masses of olive-green to black conidia. Edge sections of symptomatic tissues were cut from the leaves, disinfected in 70% ethanol for 1 min and subsequently washed twice with distilled water. Disinfected tissue samples were transferred to PDA medium and incubated at 27°C for 15 days. White colonies were observed with spordochia arranged in concentric rings with characteristic of greenish-black masses of conidia. Spore masses stained with lactophenol blue were examined microscopically. Conidia were nonseptate and rod-shaped with rounded ends that measured 6.65 ± 0.54 x 1.56 ± 0.25 µm (n = 100). The characteristics of the fungus were similar to those reported for Paramyrothecium foliicola (Rennberger and Keinath, 2020). Molecular identification was performed on a representative isolate. RNA polymerase II second largest subunit (RPB2), calmodulin (CmdA) and the ß-tubulin (B-tub) genes were amplified and sequenced with the primer sets RPB2-5F2-RPB2-7cR, CAL228F-CAL737R and Bt2a-Bt2b, respectively. These sequences were submitted to GenBank with the acc. nos. MW116070 for RPB2, MW116071 for CmdA and MW116072 for B-tub. BLASTn analysis of the sequences demonstrated 99.34 to 100% identity with Paramyrothecium foliicola (acc. nos. MN398043, MN593713 and MN398138). Koch's postulates were verified on 15-day-old watermelon seedlings and mature fruit. One point of each of ten watermelon seedlings and six points of each of five fruit were marked for inoculation. A plug of mycelium obtained from a monosporic pure culture (grown for 15 days in PDA) was applied to each point without wounds. PDA only medium was included as the controls. The pathogenicity tests were repeated twice. Treated seedlings and fruit were kept in plastic bags at 27°C for 15 days. The first symptoms appeared 4 days after inoculation on the seedlings and 3 days after inoculation on the fruit. At the end of the test, the symptoms were similar to those observed initially in the field. The pathogen was re-isolated from lesion edges, and the morphological characteristics of the pathogen were determined to correspond with those of the inoculated fungus. Control seedlings and fruits remained healthy. P. foliicola has been reported to cause leaf spot disease on wild rocket and basil (Matic et al., 2019) and, recently, on watermelon in South Carolina (Rennberger and Keinath, 2020). To the best of our knowledge, this report is the first to describe P. foliicola causing leaf spot and stem canker on watermelon in Mexico.

RESUMO

This paper presents the design of aperiodic concentric ring arrays for ultra-wide bandwidths (UW-ACRA). This design of ultra-wideband arrays considers the synthesis of concentric rings in two cases: 1) non-uniform spacing between rings with non-uniform spacing between antenna elements of the same ring (UW-ACRAelements); and 2) non-uniform spacing between rings assuming that spacing between antenna elements of the same ring to be equal (UW-ACRArings). This is in order to eliminate the occurrence of grating lobes and generating array structures with useful ultra-wideband properties. The synthesis process is carried out by the well-known method of differential evolution (DE). Wireless sensor networks can take advantage of these properties to achieve less data traffic, efficient delivery of information and better energy efficiency.