In this article, a design concept to take advantage of two coupled slots and their inductive coupling to provide the necessary 90° phase difference for CP realization is presented. Initially, two ...individual identical slots are arranged in coupling to each other in a perpendicular position, thus acquiring a pair of orthogonal linear polarization with equal amplitude. Simultaneously, an inherent 90° phase difference is naturally produced by the inductive coupling between two slot radiators. In order to clearly illustrate the evolution principle of this proposed CP realization method, the whole structure is in general modeled as an equivalent three-port network for efficient study. Based on these two achieved conditions, a CP slot antenna with one minimum AR point of 4.7% AR bandwidth (ARBW) is satisfactorily realized. After that, based on this proposed design concept, an additional slot is introduced to construct a new inductive coupling, thus facilitating two AR points under triple-mode resonance. With this arrangement, a wideband CP slot antenna with an improved ARBW of 14.1% is successfully implemented, which in turn validates the effectiveness and flexibility of this CP design approach. Finally, both the CP slot antenna element and wideband CP antenna are implemented, fabricated, and tested. The measured results of the antenna prototypes are found in good agreement with the simulated results, thereby confirming the design concept.
In this article, a low-profile third-order absorber with high selectivity is proposed. Compared with traditional absorbers that perform similar functions using a multilayer composite structure, the ...developed absorber utilizes the slot-line loading technique to obtain a third-order multimode resonance response with only one resonator. As well, the absorber has relatively better polarization insensitivity and large incidence angle stability. With the detailed analysis of surface current distribution in different modes, the action mechanisms of multimode resonance, rectangularity, and effective absorption are revealed. Finally, the absorbers are fabricated for demonstration. From 15.58 to 16.60 GHz, the absorber can attain an absorption bandwidth of 6.3% under an absorption ratio of >90%. Due to the increase in order, the rectangularity can be up to 67%. As expected, the proposed absorber has the attractive advantages of high-selectivity, low profile, and third-order performance, which is of great application potential in radar stealth and solving electromagnetic interference technology.
Summary
This paper proposes a high‐selective crossover with a third‐order filtering characteristic, high passband isolation, and multiple controllable transmission zeros based on a coupled topology ...using single‐ and dual‐mode resonators. By virtue of the odd‐ and even‐mode feature of the stub‐loaded dual‐mode ring resonator, not only can the two resonant modes for different passbands be relatively independently controlled, but also better isolation can be achieved. With a single‐mode resonator and stub‐loaded dual‐mode resonant coupling topology, the resultant crossover can perform third‐order filtering performance in two distinct passbands/channels and generate several transmission zeros outside the desired bands to improve the isolation between the passbands. Experimental results demonstrate that, compared with conventional works, the filtering order of the proposed crossover is promoted and its passband isolation can be significantly improved by about 8 dB. The proposed work may facilitate its widespread applications in high‐performance multichannel integrated microwave systems for avoiding interference between multiple intersecting signal paths.
This paper proposes a high‐selective crossover with a third‐order filtering characteristic, high passband isolation, and multiple controllable transmission zeros based on a coupled topology using single‐ and dual‐mode resonators. Compared with conventional works, the filtering order of the proposed crossover is promoted, and its passband isolation can be significantly improved. The proposed work may facilitate its widespread applications in high‐performance multichannel integrated microwave systems.
In this paper, a kind of coplanar waveguide (CPW)‐fed series stub structure is proposed and its application in wideband bandpass filters (BPFs) is developed based on the coplanar strip (CPS) dual ...stubs. Compared with its conventional CPS dual‐series‐stub counterparts, the proposed one excited by even‐mode CPW lines possesses enhanced immunity against unexpected resonance of the CPS‐based series stubs. By virtue of this attractive performance, desired resonance can be well realized with predicted in‐band characteristics. Subsequently, the application in its constituted wideband BPFs is investigated with synthesis design method. In final, one third‐order and one fifth‐order BPFs are designed, fabricated, and measured to verify the proposed structure. Measured results are found in reasonably good agreement with the synthesized and the simulated ones.
•Dual-band cross-polarization converter.•Only one multi-mode resonator is utilized rather than composite structure of multiple resonators.•Multiple resonant modes are achieved by separating intrinsic ...degenerated modes of resonator.
This paper proposes a dual-band linear polarization converter based on multi-mode metasurface. The converter consists of square-patch-resonator-based metasurface etched with cross-slot, which is beneficial to separate the degenerate modes of the patch resonator in the first band, as well as to generate additional resonant modes for the second conversion band. Different from the traditional method of using multiple resonators for dual-band polarization converters, the proposed one only utilizes one multi-mode resonator. Additionally, the two bands can be tuned relatively independently by appropriately changing the physical parameters of the resonator. To verify the design method, one sample is fabricated and measured. The proposed linear polarization converter works in the two frequency ranges of 3.16–3.52 GHz and 7.19–8.61 GHz with a polarization conversion rate (PCR) ≥ 90 %.
This paper proposes a class of balanced wideband phase shifters with wide phase shift range and good common-mode (CM) suppression. Both the balanced filtering units in the reference and main branches ...consist of horizontal half-wavelength branches and vertical quarter-wavelength loaded stubs but with dissimilar sizes. The differential-mode (DM) section of these two units can achieve (<inline-formula> <tex-math notation="LaTeX">2N + 1 </tex-math></inline-formula>)th-order Chebyshev amplitude response while with discrepant phase characteristics, which can be utilized in the design of balanced phase shifters with large phase shift. As another interesting feature, the proposed balanced filtering unit functions as the conventional branch-line bandstop response in CM, and its frequency selectivity can be further enhanced by using the so-called signal-interference method. The proposed balanced wideband phase shifters have the advantages of wide phase shift range, low phase deviation, high level and wide range for CM rejection in both two branches. The 30°, 60°, 90°, 120°, 150°, and 180° balanced phase shifters are then studied and designed. As the typical examples, 30°, 90°, and 180° phase shifters are designed, fabricated, and measured. The 30° and 90° phase shifters have a fifth-order Chebyshev response, while the 180° phase shifter is of fifth-order and third-order Chebyshev responses in the reference and main branches, respectively. The measured results show that the phase shift values are 30.14° ± 2.2°, 90.75° ± 4.05°, and 180.1° ± 5.5°, the phase shift bandwidths are 73%, 68.5%, and 66.8%, and the CM rejections are −23.3, −22, and −14.6 dB, respectively.
One of the biggest challenges for the practical application of forward osmosis (FO) is lack of high-performance FO membranes. In this study, a novel thin film nanocomposite (TFNC) FO membrane was ...fabricated based on a layered double hydroxide nanoparticles (LDH-NPs) blended ultrafiltration substrate. The influence of the LDH-NPs addition on the physicochemical properties of the ultrafiltration substrate and the resultant FO membrane was systematically investigated. The addition of LDH-NPs endowed the ultrafiltration substrate with increased porosity, surface hydrophilicity, surface pore diameter, mechanical strength and thermal stability. Consequently, all the resultant TFNC FO membranes obtained increased water permeability as compared with pristine FO membrane. Specifically, the TFNC membrane with a 2wt% LDH-NPs dosage exhibited a water flux of 18.1Lm−2h−1 (~42.5% higher than that of the pristine FO membrane) with little compromise in reverse salt flux. Moreover, this membrane reached a higher water flux of 26.9Lm−2h−1 when 2M NaCl was used as draw solution. The water-flux increase could be attributed to the decrease of the structural parameter (S value) of the LDH-NPs blended ultrafiltration substrate. The loaded LDH-NPs facilitated the development of a considerable amount of finger-liked macrovoids, which decreased the support layer tortuosity thus favoring the inhibition of internal concentration polarization. As a result, a moderate water flux was obtained. To the best of our knowledge, this is the first reported TFNC membrane using LDH-NPs blended substrates for FO applications.
A novel thin film nanocomposite forward osmosis membrane based on layered double hydroxide nanoparticles blended polysulfone substrate was fabricated and investigated.
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•Thin film FO membrane with LDH-NPs blended PSf substrate was fabricated.•The addition of LDH-NPs endowed the PSf substrate with increased properties.•The water flux was increased from 12.7 to 18.1Lm−2h−1 by the addition of LDH-NPs.•This contribution represents the first application of LDH-NPs in FO membranes.
Previous phylogenetic analyses of species within the genus Golovinomyces (Ascomycota, Erysiphales), based on ITS and 28S rDNA sequence data, revealed a co-evolutionary relationship between powdery ...mildew species and hosts of certain tribes of the plant family Asteraceae. Golovinomyces growing on host plants belonging to the Heliantheae formed a single lineage, comprised of a morphologically differentiated complex of species, which included G. ambrosiae, G. circumfusus, and G. spadiceus. However, the lineage also encompassed sequences retrieved from Golovinomyces specimens on other Asteraceae tribes as well as other plant families, suggesting the involvement of a plurivorous species. A multilocus phylogenetic examination of this complex, using ITS, 28S, IGS (intergenic spacer), TUB2 (beta-tubulin), and CHS1 (chitin synthase I) sequence data was carried out to clarify the discrepancies between ITS and 28S rDNA sequence data and morphological differences. Furthermore, the circumscription of species and their host ranges were emended.
The phylogenetic and morphological analyses conducted in this study revealed three distinct species named, viz., (1) G. ambrosiae emend. (including G. spadiceus), a plurivorous species that occurs on a multitude of hosts including, Ambrosia spp., multiple species of the Heliantheae and plant species of other tribes of Asteraceae including the Asian species of Eupatorium; (2) G. latisporus comb. nov. (≡ Oidium latisporum), the closely related, but morphologically distinct species confined to hosts of the Heliantheae genera Helianthus, Zinnia, and most likely Rudbeckia; and (3) G. circumfusus confined to Eupatorium cannabinum in Europe.
The present results provide strong evidence that the combination of multi-locus phylogeny and morphological analysis is an effective way to identify species in the genus Golovinomyces.
Coupled magmatic and tectonic activity plays an important role in high-temperature hydrothermal circulation at mid-ocean ridges. The circulation patterns for such systems have been elucidated by ...microearthquakes and geochemical data over a broad spectrum of spreading rates, but such data have not been generally available for ultra-slow spreading ridges. Here we report new geophysical and fluid geochemical data for high-temperature active hydrothermal venting at Dragon Horn area (49.7°E) on the Southwest Indian Ridge. Twin detachment faults penetrating to the depth of 13 ± 2 km below the seafloor were identified based on the microearthquakes. The geochemical composition of the hydrothermal fluids suggests a long reaction path involving both mafic and ultramafic lithologies. Combined with numerical simulations, our results demonstrate that these hydrothermal fluids could circulate ~ 6 km deeper than the Moho boundary and to much greater depths than those at Trans-Atlantic Geotraverse and Logachev-1 hydrothermal fields on the Mid-Atlantic Ridge.
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