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Organic semiconductors are attracting considerable attention as a new thermoelectric material because of their molecular diversity, non-toxicity and easy processing. The side chains which are introduced into two-dimensional (2D) transition metal dichalcogenides (TMDs) by covalent modification lead to a significant decrease in their thermal conductivity. Here, we describe a simple approach to preparing the side chains covalent modification TaS2 (SCCM-TaS2) organic/inorganic hybrid structures, which is a homogeneous and non-destructive technique that does not depend on defects and boundaries. Electrical conductivity of 3,401 S cm-1 and a power factor of 0.34 mW m-1 K-2 are obtained for a hybrid material of SCCM-TaS2, with an in-plane thermal conductivity of 4.0 W m-1 K-1, which is 7 times smaller than the thermal conductivity of the pristine TaS2 crystal. The power factor and low thermal conductivity contribute to a thermoelectric figure of merit (ZT) of ~0.04 at 443 K.

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A miniaturized, high‐selectivity, wideband A‐T‐A frequency selective rasorber (FSR) based on compact spiral resonators (CSR) is proposed here. The lossy layer of the FSR consists of the CSR and a Jerusalem cross, with four resistors soldered onto the surface. The underlying layer is a bandpass frequency selective surface (FSS) with an extremely narrow slit. The dimensions of the FSR unit are only 0.079 λL × 0.079 λL × 0.078 λL. The extremely narrow‐slitted FSS and CSR together provide a narrowband frequency response, enhancing the selectivity of the FSR. Additionally, a prototype of an FSR was fabricated and tested, achieving results highly consistent with simulations. [ABSTRACT FROM AUTHOR]

In this paper, we propose for the first time a novel feed approach to a tightly coupled dipole array (TCDA). Firstly, compact zigzagging microstrip feedlines are utilized as baluns to feed our array elements to obtain wideband impedance-matching characteristics. Secondly, this array is designed on ultrathin substrates aiming at obtaining ultra-tight coupling between the dipole arms of two neighboring elements. Some irreplaceable parasitic pads are developed and added to the radiating arms to improve both the impedance and radiation characteristics of the TCDA. With these technologies, a 12 × 12 TCDA prototype is designed, fabricated and measured for verification. The array achieves an impressive impedance bandwidth spanning of 4–18 GHz for S 11 < − 10   dB . Its radiation patterns and realized gain are measured to verify its stable electromagnetic characteristics. Its realized gain is from 15 dB to 25 dB within the operating frequency band. Its efficiency is around 91%. Its measured results show good agreement with simulations. [ABSTRACT FROM AUTHOR]

A planar ultra-wideband modular antenna array with an ultra-low profile based on a tight coupling effect is proposed. The antenna array is composed of multi-layer printed circuit boards. Since its frequency operation can extend up to the grading lobe frequency, the number of T/R components for the antenna aperture is reduced to the greatest extent. Specifically, a horizontal "fin" structure is added on the parallel feeding lines, which assists in improving the impedance matching of the array. In order to break the bandwidth limitation of the low-frequency loop mode, a capacitive short-circuit probe is introduced to push the common-mode resonance point into the low-frequency band. Finally, subject to Active VSWR < 3, the array can realize E-plane, H-plane, and D-plane ± 45° beam scan coverage across the 6:1 frequency band (3.48–20.97 GHz). A 128-element prototype was processed and tested to validate the design. This array not only has the advantages of low profile, modularity, easy assembly, and maintenance but also minimizes the number of T/R components and reduces the cost of phased array antennas. [ABSTRACT FROM AUTHOR]

An ultra‐wideband and wide‐scan tightly coupled dipoles array based on frequency selective surface (FSS) is proposed, and the traditional wide‐angle scan impedance matching dielectric layer is replaced by FSS with printed metal strips to achieve the tuning of the scanning impedance of the array. Additionally, the metal strip FSS, dipole radiating elements and feeding structure are all printed on the same printed circuit board, and the whole design is highly integrated. Finally, a low‐cost lightweight single‐polarization tightly coupled antenna array with ultra‐wide band and wide scan performance is presented. Subject to the criterion of active Voltage standing Wave ratio(VSWR) < 3, beam scanning coverage of ±45° along E plane, H plane and D plane can be accomplished within the frequency band range across 0.4–2 GHz. An array prototype was produced and tested, and the results showed that the effectiveness of the design was well validated. [ABSTRACT FROM AUTHOR]

Organic semiconductors are attracting considerable attention as a new thermoelectric material because of their molecular diversity, non-toxicity and easy processing. The side chains which are introduced into two-dimensional (2D) transition metal dichalcogenides (TMDs) by covalent modification lead to a significant decrease in their thermal conductivity. Here, we describe a simple approach to preparing the side chains covalent modification TaS2 (SCCM-TaS2) organic/inorganic hybrid structures, which is a homogeneous and non-destructive technique that does not depend on defects and boundaries. Electrical conductivity of 3,401 S cm−1 and a power factor of 0.34 mW m−1 K−2 are obtained for a hybrid material of SCCM-TaS2, with an in-plane thermal conductivity of 4.0 W m−1 K−1, which is 7 times smaller than the thermal conductivity of the pristine TaS2 crystal. The power factor and low thermal conductivity contribute to a thermoelectric figure of merit (ZT) of ~0.04 at 443 K. The improvement of thermoelectric performance of materials by reducing lattice thermal conductivity is challenging. Here, the authors find the side chains covalent modification of transition metal disulfides reducing the lattice thermal conductivity. [ABSTRACT FROM AUTHOR]

Thermal rectifiers and thermal transistors are expected to be widely used for efficient thermal management and energy cascade utilization due to their excellent directional thermal management. Two-dimensional micro/nano materials have huge potential in the applications of thermal transistors, thermal logic circuits, and thermal rectifiers owing to the phase transition and thermal rectification phenomenon. Herein, a lithium intercalation method was used to transform 2H-MoS 2 into the 1T phase with a purity of 76%, and a suspended microelectrode was applied to measure the thermal conductivity and thermal rectification coefficient of the same MoS 2 film with 1T and 2H phases in suit. The thermal conductivity and thermal rectification effect of two-phase MoS 2 couple with its phase state and structure were also obtained. The results demonstrate that the thermal conductivities of MoS 2 in both 1T and 2H phases decrease with increasing temperature. It is also found that the thermal rectification coefficient has no obvious dependence on the temperature and phase change but the asymmetric structure. Furthermore, a thermal rectifier and transistor with a high thermal rectification effect are designed. The direction and magnitude of heat flow through the samples can be effectively controlled and managed by adjusting the phase, size, and structural asymmetry of the different samples. The maximum thermal rectification coefficient of the thermal rectifiers is up to 0.8.

High-quality ultrasmooth surface is needed in modern optics, while the existing ultrasmooth surface processing methods are difficult to meet the requirement of the surface figure. In order to solve this problem, the active feed polishing (AFP) is taken as the research object, and the dual-rotor tool path is put forward for this technology. This tool path is generated based on the motion synthesis principle, which realizes smooth connection between different sections. At the same time, the eccentricity, the speed ratio, the velocity, and other parameters can be modified easily, avoiding using the complicated dual-rotor polishing mechanism. In order to further analyze the removal error, the removal amount calculation method for the dual-rotor path is researched and proposed. The simulation analysis results show that the greatest influence factor for the removal error is the sampling interval, the influence of the eccentricity and the speed ratio is less, and the velocity has little impact on it. In addition, the removal error can be controlled within acceptable range by reasonable selection of process parameters. Finally, through a processing experiment of a 100 mm plane lens, the feasibility and effectiveness of this path is verified. This experimental result shows that the AFP technology using the dual-rotor tool path can effectively correct the surface shape while reducing the surface roughness.