Development of C-Shaped Parasitic MIMO Antennas for Mutual Coupling Reduction

In the 5G system, multiple-input multiple-output (MIMO) antennas for both transmitting and receiving ends are required. However, the design of MIMO antennas at the 5G upper band is challenging due to the mutual coupling issues. Many techniques have been proposed to improve antenna isolation; however, some of the designs have impacts on the antenna performance, especially on the gain and bandwidth reduction, or an increase in the overall size. Thus, a design with a detailed trade-off study must be implemented. This article proposes a new C-shaped parasitic structure around a main circular radiating patch of a MIMO antenna at 16 GHz with enhanced isolation features. The proposed antenna comprises two elements with a separation of 0.32λ edge to edge between radiation parts placed in a linear configuration with an overall dimension of 15 mm × 26 mm. The C-shaped parasitic element was introduced around the main radiating antenna for better isolation. Based on the measurement results, the proposed structure significantly improved the isolation from −23.86 dB to −32.32 dB and increased the bandwidth from 1150 MHz to 1400 MHz. For validation, the envelope correlation coefficient (ECC) and the diversity gain (DG) were also measuredas 0.148 dB and 9.89 dB, respectively. Other parameters, such as the radiation pattern, the total average reflection coefficient and the mean effective gain, were also calculated to ensure the validity of the proposed structure. Based on the design work and analysis, the proposed structure was proven to improve the antenna isolation and increase the bandwidth, while maintaining the small overall dimension.

Conceptual Configuration Synthesis of Line-Foldable Deployable Space Truss Structures Utilizing Graph Theory and Entropy

From the perspective of the truss as a whole, this research presents an approach to synthesizing conceptual configurations for deployable space truss structures that are line-foldable with the help of graph theory and entropy. First, according to graph theory, the bijection between a truss and its graph model is established by defining a bijective mapping between set elements. Therefore, operations can be performed based on graph models. Second, the principle of configuration evolution is interpreted by employing Maxwell’s rule, it also discusses the necessary and sufficient condition of configuration evolution. Configurations of evolution belong to three phases: space configuration, transformation configuration, and linear configuration. And it finds that the reasonable transformation configuration plays a key role. Further, maximum clique detection depending on backtracking is used to screen out unreasonable transformation configurations. Third, it introduces entropy, and the phenomenon of entropy change in configuration evolution is revealed and induction weights of rigid links are defined. It calculates the weight value of a transformation configuration by adding up induction weights of rigid links removed, also, weight values are used to classify transformation configurations. Finally, based on the previous analysis, a procedure to synthesize transformation configurations is formed and it is verified by a truss model with 7 nodes. This research lays the foundation for geometric dimension design and engineering applications.

Spectral-Luminescent and Electroluminescent Properties of Charge-Transfer Systems Based on Electron-Donating Diphenylamine Derivatives and Acceptors of Dibenzothiophene Sulfone and Phenanthridine

Spectral characteristics and luminescence under the photo- and electro-excitation of substituted dibenzthiophene sulfone and phenanthridine were studied in this paper. Diphenylamines are substituents introduced in the 2nd and 7th positions (linear configuration) or the 3rd and 6th positions (angular configuration) of dibenzthiophene sulfone or phenanthridine. All molecules show delayed fluorescence, both in solutions and films produced by thermal vacuum deposition. The value of the energy gap between the S1 and T1 states has been estimated and is shown to depend not only on the spatial arrangement of the fragments among themselves (linear or angular), but also on the nature of the substituent in diphenylamine. The highest electroluminescence brightness was found for the molecules, in which triplet levels are involved, both through the process of triplet-triplet annihilation and through thermally activated delayed fluorescence.

β-Amyloid peptides tailor switching behaviors of Donor-Acceptor Stenhouse Adducts

Molecular switching plays a critical role in biological and displaying systems. Here we demonstrate the first use of peptides to operate molecular switches of donor-acceptor Stenhouse adducts (DASAs), a series of negative photochromes that are highly promising for applications ranging from smart material to biological systems. Fluorescence imaging proved Aβ40 species could make SHA-2 more stable in the linear configuration than without peptide and decrease the rate of molecular switching. According to molecular dynamics simulation, SHA-2 bound to protein resulted in substantial changes in the tertiary structure of Aβ40 monomer with the region of Glu22-Ala30 partially unfolded and being more exposed to water. This structural change is likely to impede the aggregation of Aβ40, as evidenced by fluorescence and ProteoStat® aggresome detection experiments. SHA-2 is able to inhibit the aggregation of Aβ40 by producing the off-pathway structures. These results open ample opportunities for optically addressable potential widely apply DASAs in the biological system based on this peptides-tailor process.

Highly efficient binary copper−iron catalyst for photoelectrochemical carbon dioxide reduction toward methane

A rational design of an electrocatalyst presents a promising avenue for solar fuels synthesis from carbon dioxide (CO2) fixation but is extremely challenging. Herein, we use density functional theory calculations to study an inexpensive binary copper−iron catalyst for photoelectrochemical CO2 reduction toward methane. The calculations of reaction energetics suggest that Cu and Fe in the binary system can work in synergy to significantly deform the linear configuration of CO2 and reduce the high energy barrier by stabilizing the reaction intermediates, thus spontaneously favoring CO2 activation and conversion for methane synthesis. Experimentally, the designed CuFe catalyst exhibits a high current density of −38.3 mA⋅cm−2 using industry-ready silicon photoelectrodes with an impressive methane Faradaic efficiency of up to 51%, leading to a distinct turnover frequency of 2,176 h−1 under air mass 1.5 global (AM 1.5G) one-sun illumination.

O(3P) + CO2 scattering cross-sections at superthermal collision energies for planetary aeronomy

ABSTRACT We report new elastic and inelastic cross-sections for O(3P) + CO2 scattering at collision energies from 0.03 to 5 eV, of major importance to O escape from Mars, Venus, and CO2-rich atmospheres. The cross-sections were calculated from first principles using three newly constructed ab initio potential energy surfaces correlating to the lowest energy asymptote of the complex. The surfaces were restricted to a planar geometry with the CO2 molecule assumed to be in linear configuration fixed at equilibrium. Quantum-mechanical coupled-channel formalism with a large basis set was used to compute state-to-state integral and differential cross-sections for elastic and inelastic O(3P) + CO2 scattering between all pairs of rotational states of CO2 molecule. The elastic cross-sections are 35 per cent lower at 0.5 eV and more than 50 per cent lower at 4 + eV than values commonly used in studies of processes in upper and middle planetary atmospheres of Mars, Earth, Venus, and CO2-rich planets. Momentum transfer cross-sections, of interest for energy transport, were found to be proportionally lower than predicted by mass scaling.