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An all-in-one self-sustained integrated system composed of a Si film solar cell, spray-printed a micro-supercapacitor and a gas sensor, exhibits excellent flexibility and durability. [Display omitted] Printable micro-supercapacitors (MSCs) with remarkable versatility, customizability, high power density and long cycling lifespan, are regarded as a promising class of miniaturized power source for wearable and portable microelectronics. Herein, we demonstrate a novel Fe-based zeolitic imidazolate framework (Fe-ZIF)/graphene (FZG) heterostructure with high specific surface area and outstanding electrical conductivity for planar MSCs (FZG-MSCs) worked in a high-voltage ionic liquid gel electrolyte via a spray-printed strategy. The fully printed FZG-MSCs deliver a high areal energy density of 9.5 μWh/cm2, extraordinary cyclability, and tailored voltage/capacitance output. Furthermore, using a fully printed FZG-MSC, we seamlessly integrate a monolithically planar all-flexible self-sustained sensor system with a mounted solar cell and a printable NH 3 gas sensor on the same side of single flexible substrate. The self-sustained sensor system exhibits high-sensitivity NH 3 detection with a good response of 18.3% at 20 ppm and linear sensibility exposed to 2–20 ppm. Such a fully integrated system can utilize the converted solar energy stored in the MSC, and offer efficient electricity to power microelectronics whenever needed. Therefore, this contribution of printable planar device and integrated system paves a new avenue for constructing flexible microelectronics. [ABSTRACT FROM AUTHOR]

A CMOS transimpedance amplifier (TIA) with broad band and high gain based on negative Miller capacitance and capacitive degeneration has been proposed and designed. The theoretical analysis shows that by introducing negative Miller capacitance into the feedforward common gate (FCG) amplifier circuit, the bandwidth limitation caused by the internal parasitic capacitance can be reduced, and by cascading the capacitive degeneration-based common source (CS) amplifier as the gain stage, the amplifier gain can be improved simultaneously. The proposed TIA is designed and simulated in TSMC 65 nm CMOS process, The simulation results show that the −3 dB bandwidth of the amplifier circuit is 23.7 GHz, the transimpedance gain is 60.1 dBΩ, the average equivalent input noise current spectral density is less than 40.7 pA/√Hz, the power consumption is 4.8 mW, and the circuit layout area is 0.0027 mm2. In Comparison to the published TIA circuits, the bandwidth of the designed CMOS TIA is increased by 12.7 GHz, the gain is increased by 18.1 dBΩ and the circuit layout area becomes smaller. All the results demonstrate that the designed TIA can be used in the photoelectric detection circuit with broader bandwidth and higher gain. • A CMOS transimpedance amplifier (TIA) with broadband and high gain is presented. • Based on FCG-TIA, negative Miller capacitance and capacitive degeneration are combined to improve the performances. • The bandwidth and transresistance gain of the proposed TIA are 23.7 GHz and 60.1 dBΩ, respectively. • The layout area is small because of the inductorless structure of the proposed TIA. [ABSTRACT FROM AUTHOR]

The postulation of hydrogen as an energy carrier for the future and the possibility of obtaining it from a renewable source such as various alcohols, has positioned the oxidative steam reforming of ethanol (OSRE) process as very promising to produce H 2 at low temperatures. Motivated by the absence of a study that in a rigorous, articulated and coherent manner establishes the maximum correlation of the results reported in the literature regarding the current knowledge of the OSRE and with the perspective of identifying or proposing the ideal catalyst and reaction conditions, this manuscript addresses, for the first time to our knowledge, several aspects concerning a fundamental level understanding of the OSRE process and focuses on the influence of both the main experimental parameters of the reaction (such as temperature, molar ratios of the feed stream and space velocity), as well as the most noted aspects of the catalyst (structural, basic/acid and Redox properties and metallic phases). Special emphasis is placed on the conditions that lead to obtaining high H 2 selectivity at relatively low temperatures and with high catalyst stability. Consequently, the ideal catalyst and conditions for the OSRE are proposed. • Aspects for the fundamental understanding of the OSRE. • Ideal catalyst and conditions for the OSRE for H 2 production. • Comparison of catalytic performance in the OSRE for H 2 production reported so far. [ABSTRACT FROM AUTHOR]

In this research, we developed a wideband electromagnetic wave absorber suitable for the X-band frequency by using a unique hybrid nanocomposite structure made of FeWO 4 embellished with Ag 3 PO 4 nanopowders. Simple chemical hydrothermal and microwave-aided hydrothermal procedures were used to successfully produce single-phase spherical-like FeWO4 and FeWO4@Ag3PO4 nanocomposite powders. Using XRD, FTIR, VSM, FESEM, and VNA methods, the phase constituents, morphological, magnetic, and electromagnetic properties of the produced nanocomposite materials were assessed. The resin-based nanocomposite absorber sample allows to obtain a maximum reflection loss of −21 dB with a matching thickness of 1.8 mm at the ferromagnetic resonance of 10.4 GHz with a 3.8 GHz effective absorption bandwidth, which is evaluated using the waveguide technique, when the filler loading percentage reaches 40 wt percent (S40). S40 had superior impedance matching capabilities, a wide effective absorption bandwidth, and a high absorption capacity when compared to other produced absorber samples. The best sample is prepared for free-space testing with the dimension of 200 × 200 mm and an optimum thickness of 1.8 mm, and the results demonstrate a good agreement between the waveguide and free-space technique results. This absorber sample's wideband absorption capacity was attained by adjusting the magneto-electric composition and enhancing the interfacial characteristics brought on by the core-shell construction. In this study, a design approach for efficient microwave absorbers based on a magneto-electric hybrid nanocomposite structure is presented, using waveguide and free-space experimental methods in two different ways. [ABSTRACT FROM AUTHOR]

A coplanar waveguide resonator (CPR) is presented for kinetic inductance (L k) and penetration depth (λ L) measurements of superconducting boron doped nanocrystalline diamond (B-NCD) at microwave frequencies of 0.4 to 1.2 GHz and at temperatures below 3 K. Using finite element modelling and experimental measurements, this work demonstrates that thin granular B-NCD films (thickness d ≈ 500 nm) on Si have a large penetration depth ( λ L ≈ 3.8 μm), and therefore an associated high kinetic inductance per square ( L k , □ ≈ 670 to 690 pH/ □). These values are much larger than those typically obtained for films on single crystal diamond, which is likely due to the high granularity of the nanocrystalline films. Based on the measured Q factors of the structure, the calculated surface resistance is found to be around ≈ 1 to 6 μΩ at T < 2 K in the 0.4 to 1.2 GHz range, demonstrating the potential for granular B-NCD for high quality factor superconducting microwave resonators and highly sensitive kinetic inductance detectors. [Display omitted] [ABSTRACT FROM AUTHOR]

Spring hinges, due to their lightweight and energy-saving characteristics, have emerged as an imperative power source for deploying spacecraft appendages. In this paper, a modified constant-torque spring hinge (MCTSH) is proposed for aerospace applications. The conventional constant-torque hinge (CCTSH) is enhanced to bridge the gap toward new applications, resulting in a more compact structure with less friction and wide-range output torques. A novel torque control method is elaborated on for deployable, MCTSH-driven and multi-link mechanisms, thereby simplifying the design procedure via reducing the design variables by half. Given the intricate coupling effects of multi-link mechanisms, a synchronous deployment technique integrating the Newton-Euler dynamics, the design of experiments (DOE) method and the optimization is introduced, and its performance is verified by both simulations and experiments on multi-link grippers. The results demonstrate the high potential of the proposed method for deployable mechanisms toward aerospace applications, e.g., solar array panels and antennas. [ABSTRACT FROM AUTHOR]

The rapid development of modern communication systems propels the demand of high performance and miniaturization of RF/microwave components. Power dividers and filters are indispensable circuit components in amplifiers and antenna feed-networks which occupy large footprint of circuit broads, particularly at low frequency. The purpose of this study is to initiate a new type of planar transmission line with unique dual signal-path characteristics and ultimately achieve circuit miniaturization. In this paper, a novel technique of consolidating microstrip lines (MLs) and coplanar waveguide (CPW) lines on a single dielectric substrate, designated as the composite microstrip/CPW line (CM/CPW line), is proposed. With reference to the average line length of ML and CPW, it warrants a physical length reduction of 48.3% and further achieves a reduction of 80.8% after zigzagging CM/CPW line. The proof-of-concept design example of a two-way Wilkinson power divider (WPD) has demonstrated the effectiveness of the miniaturization technique. The simulation, in combination with the experimental results, validates that a size reduction factor of 86.9% when compared to conventional one has been achieved while maintaining a fractional bandwidth of 57.7% for the WPD. [ABSTRACT FROM AUTHOR]

This study proposed, for the first time, a newly developed metal–insulator-insulator–metal (MIIM)-based log-spiral rectenna for energy harvesting applications. The designed resonant log-spiral antenna at 28.3 THz forwards the absorbed infrared (IR) electromagnetic (EM) radiations to the installed double insulator-based MIIM rectifying diode. The realized MIIM diode is formed by sandwiching the two insulators among the designed resonant antenna terminals (hot spot region). Antenna terminals are used as the electrodes of the rectifying diode. This novel approach ensures the maximum transfer of captured IR EM radiations by the antenna to the rectifying part with good impedance matching and thus increases the overall conversions efficiency. The study presents an in-depth analysis of the impact of the changing metal types (Au, Al, Ag, and Cu) and insulating materials (Al 2 O 3 , Cu 2 O, Ta 2 O 5 , TiO 2 , and ZnO with10 different formations) on the realized rectenna performance in terms of captured E-field enhancement, I/V , resistivity, and responsivity characteristics. It is found that the overall performance of the proposed double insulator-based rectenna system is better for the asymmetric configuration of Au- Al 2 O 3 - Cu 2 O –Cu and it exhibits 100% enhanced non-linearity as compared to MIM-based configuration. [ABSTRACT FROM AUTHOR]

In this research, a novel high permittivity ceramic silicone composite substrate (HPCSCS) based antenna design is proposed for RF energy harvesting (RFEH). The HPCSCS is prepared using high-permittivity barium titanate (BaTiO 3) ceramic powder mixed with RTV silicone sealant (RTVSS) which possesses a high permittivity value of 11.9. Five different antenna designs were simulated in CST software and one design has been finalized based on design geometry, bandwidth, gain, and reflection coefficient. Moreover, the proposed antenna design is optimized with the addition of a coplanar waveguide. The designed antenna has a thickness of 0.06 mm and provides a wide operating band range from 0.7 GHz to 3 GHz. It provides a reflection coefficient of –32 dB and a positive gain of 1.84 dB at the operating frequency of 2.66 GHz demonstrating the excellent wide bandwidth of 885 MHz. A prototype of the antenna is fabricated and mounted on an HPCSCS for measurement through a vector network analyzer with a good match between the simulated and measured results. The rectenna system (antenna + rectifier) for RFEH has been developed and tested, which achieved a maximum rectifier conversion efficiency of 57 % at 0 dBm and produced a maximum output voltage of 1.35 V at 0 dBm. [ABSTRACT FROM AUTHOR]

This paper examines a short-range Millimeter-wave antenna characterized by its compact design, coplanar waveguide feeding, and folded dipole shape, that operates across multiple frequency spectrums. The radiator is designed on a Rogers TMM4 material having the dimensions of 1.05 λ L × 1.05 λ L × 0.057 λ L (λ L : wavelength associated with the bottommost cut-off frequency). Adoption of a folded shape serves to augment the electrical dimension of the antenna by expanding the current-carrying path, thereby facilitating the attainment of the necessary frequency spectrums. The proposed antenna operates at 22.44–23.77 GHz (5.75 %), 26.68–30.35 GHz (12.87 %), 38.1–43.46 GHz (13.14 %), 49.13–54.48 GHz (10.33 %) and 57.63–67.85 GHz (16.29 %) spectrums with maximum gain and radiation efficiency of 8dBi and 94.5 % respectively. The work further delves into an in-depth analysis of antenna characteristics, encompassing aspects such as radiation pattern, surface current, group delay, and transfer function. All examined characteristics affirm that the proposed antenna exhibits versatility for diverse frequency bands, including but not limited to n257, n259, n260, n261, and various other 5G/beyond 5G wireless technologies. [ABSTRACT FROM AUTHOR]

Superconducting quantum circuits (SQC) are one of the most promising hardware platforms for quantum computing, yet their performance is currently limited by the presence of various structural defects inside the circuit's structure. Despite impressive progress in the past decade, a precise understanding of the origin of these defects from various fabrication processes and their impact on coherence is still lacking. In this study, we performed a comprehensive investigation on the microstructure, superconductivity, and resonator quality factor of Nb films deposited by high-power impulse magnetron sputtering (HiPIMS) and direct current (DC) magnetron sputtering. A suite of characterization techniques, including electron microscopy with spectroscopy, secondary ion mass spectrometry, magneto-optical microscopy, and pump-probe reflectivity spectroscopy is used. We reveal that niobium (Nb) resonators fabricated using HiPIMS exhibit a smaller average grain size, thicker surface oxide with larger thickness variations (rougher surface), and a thicker amorphous Nb/Si interface layer compared to samples deposited by DC sputtering. We identified that the amorphous Nb oxides (mainly located at the Nb surface and along the grain boundaries) and Nb-Si amorphous layers (at the Nb/Si interface) are major and potential sources of two-level system (TLS), while off-stochiometric oxides and suboxides of Nb close to the surface, crystalline defects (i.e., dislocations at grain boundary, point defects introduced during deposition) are main contributors of non-TLS sources. Our findings clarify the relationship between different defects and coherence loss mechanisms, highlighting the importance of material microstructure control on performance optimization in SQC. [Display omitted] [ABSTRACT FROM AUTHOR]

A new Graphene nano-antenna has been designed and proposed in this paper for optical frequency applications with optimized gain performance. The proposed design uses a Silicon Lens and subsequent layers to match the dielectric constant between the antenna and air. The different patch materials are taken and studied for better results. The proposed antenna has been simulated upon a Highly resistive silicon substrate having a high dielectric constant of 11.9. The base of the proposed antenna is designed on a square substrate of 6000 μ m length and 300 μ m height. The slotted "bow-tie" antenna is placed on it with an aperture area of 156. 8 μ m × 42 μ m. A silicon layer is placed over it for improved performance. Further, it has been optimized by placing 16 stacked aligning layers to match the dielectric constants. The gain and efficiency improvement are achieved after each layer or coating over the lens. The resonant frequencies obtained are 0.4THz, 1THz, and 2.2THz having triple bands. The maximum gain obtained is 36.89 dB and the maximum radiation efficiency is 97%. HFSS 21.0 software is the used environment for the simulation and optimization. [ABSTRACT FROM AUTHOR]

In this paper, a new topological acoustic interlayer is proposed, which is formed by combining multi-order resonators in the form of the triangular lattice in the normal direction of the acoustic interlayer. Through the strong resonance of the resonator, the distribution of modes in the acoustic interlayer is directly induced to form a combination of modes with different topological states to support the subwavelength multi-channel lossless directional acoustic transmission in barrier-free space. Since there are no scatterers, not only can the required frequency band be directly achieved through the resonance frequency of the resonator alone, but also the background medium space in which the acoustic wave transmitting is a uniform medium, so the transmission is secret and the structure is ventilated. More importantly, there is more space in the normal direction of the barrier-free interlayer for design sub-wavelength multi-channel transmission. Furthermore, the random obstacles in interlayer do not affect the transmission under the pseudo spin modes. Finally, experimental verification is carried out. This research paves the way for the engineering application of multi-band acoustic antennas, covert communication, ventilated devices and other multi-functional devices, and will bring new enlightenment to the fields of elastic wave, light wave and electromagnetic wave. [ABSTRACT FROM AUTHOR]

The microwave dielectric properties of Zn(1- x)Ti x Al 2 O 4 (ZTA) ceramic nanomaterials were investigated with a focus towards their use as wireless antennas. The ZTA nanoparticles were prepared using the sol-gel technique at 700 °C for one hour. The inclusion of titanium decreased the nanomaterials' crystallite size and surface shape, which influenced their dielectric permittivity (ε r). Based on the tested material and microwave antenna theory, ZTA was used to fabricate wireless patch antennas, which were then examined using a PNA series network analyzer. The measured results reveal that the return loss and impedance bandwidths of the antenna were −44.83 dB simulated and −34.88 dB measured, and 240 MHz for simulated and 220 MHz for measured, respectively. At 5.1 GHz operating frequency, the Zn 0.94 Ti 0.06 Al 2 O 4 -based patch antenna demonstrated an exceptional combination of return loss (-34.88 dB), compact size (9.3× 6.3 mm2), and broad bandwidth (220 MHz) as well as VSWR<2. Ultimately, the fabricated antenna showcases a gain of 4.24 decibels and a directivity of 5.97 decibels. [ABSTRACT FROM AUTHOR]

The structural, morphological, and wideband electromagnetic response of (1-x) MgFe 1.98 O 4 + x BaFe 12 O 19 composites with x = 20, 40, 60, and 80 wt percent (wt%) were investigated. The composites' sintering temperature was optimised to be 1250 °C for 2 h. The phase purity and independent existence of the end members in the composites were verified using XRD, Raman and FTIR spectroscopy. The microstructures of the sintered composites indicate the effect of grain growth on the density and grain packing efficiency. The relative permittivity of the composites is in the 9–11 range, while the relative permeability is between 1.4 and 2.8. The increase in BaFe 12 O 19 concentration from 20 to 80 wt% resulted in a dilution effect in permeability and enhanced saturation magnetization and coercive field strength. The composites with 20–80 wt% BaFe 12 O 19 possess a characteristic impedance ranging from 0.55 to 0.38 and a miniaturisation factor ranging from 5.16 to 3.82 at 900 MHz. The composites containing 20 and 40 wt% BaFe 12 O 19 exhibited appreciable miniaturisation factors of 5.16 and 5.24, respectively, with characteristic impedances of 0.55 and 0.47. Furthermore, these composites have low magnetic and dielectric losses of the order of 10−1 and 10−3, respectively, making them suitable candidates for resonator antenna applications. A magneto-dielectric resonator antenna using the composite comprising 40 wt% BaFe 12 O 19 , with a density greater than 95%, was designed, simulated and fabricated. The fabricated magneto-dielectric resonator antenna resonated at a frequency of 14.7 GHz, with a significantly low return loss of −44 dB and wide impedance bandwidth of 1.44 GHz, suggesting the application potential of the dual-ferrite composite in the Ku-band frequency range. [ABSTRACT FROM AUTHOR]

Flexible inkjet-printed antenna is presented. The proposed antenna is designed on a synthetic paper substrate with an area of 35 × 40 mm2 to provide frequency bands for many popular wireless applications. Simulation and measurement are used to study the performances, including the frequency bands, radiation patterns, peak gains and efficiency, of the antenna in two severely bending conditions with a curvature radius of 20 mm in the forward and backward directions. The antenna printed in photo papers material could not be fully flexible due to cracks introduced to the coating material on the surface of the photo paper. Hence, the resin coated material was only suitable for curved devices. The synthetic paper material used in this paper does not have a resin coating, therefore, the antenna does not lose its flexibility and can be bent in both the forward and backward directions without any cracks. Results show that bending in these two conditions has insignificant effects on the performances of the antenna. With a curvature radius of 20 mm in the forward direction, the measured peak gain and efficiency of the antenna are in the ranges from −3 to +2 dBi and 40% to 60%, respectively. The results together with the low cost make the antenna most suitable for many flexible 5G communications devices. [ABSTRACT FROM AUTHOR]

In this paper, a smart multi-user wireless link based on a graphene quantum well vertical hybrid plasmonic waveguide-fed nano-antenna is proposed. The theoretical method and finite element method (FEM) are used to verify that the vertical hybrid plasmonic waveguide (VHPW) supports both even and odd fundamental modes. Utilizing multi-mode graphene quantum well VHPW leads to the design of a selective mode nano-antenna with intermediate broadside and end-fire radiation patterns with high directivities of 9.38 dBi and 11.8 dBi at 193.5 THz, respectively, obtained by the finite-difference time-domain method. Also, to verify the accuracy of nano-antenna results, the FEM approach is used. The nano-antenna performance as a wireless inter/intra-chip link is investigated, which confirms the even mode plays a key role to create a multiple-access wireless system. Based on the amazing features of graphene as an epsilon-near-zero and absorptive/transparent material, the accessibility of receivers is easily controlled. The effect of a single row array structure and its application as beam steering is studied. Finally, to estimate the performance of quantum well nano-antenna as a real device, which is compatible with electron-beam lithography and lift-off fabrication techniques, the effect of metal layer roughness and 5% tolerance for geometrical parameters are investigated. [Display omitted] [ABSTRACT FROM AUTHOR]

The new radiator incorporated with nanocomposites improve radiation characteristics of nonagon shaped antenna. The design comprise two nanocomposite materials loaded in slots that separately enhance lower and upper band radiation. The CPW antenna consists of nonagon shaped ring with heptagon radiating element that consists of inverted U and rigid shaped slots. The longer slot has been deliberately chosen to accommodate mid-frequency of two resonance frequencies and shorter slot isolates surface current distributed along radiating patch, left and right side. The Poly (3, 4 ethyelene dioxythiophene): Polystyrene Sulfonate-Silver nanowire (PEDOT:PSS-AgNW) nanocomposite filled in shorter slot improves gain, bandwidth and return loss of upper band, magnetite - Polyaniline (Fe 3 O 4 -PANI) filled in longer slot enhance lower band. The measured result proved to improve bandwidth, gain, radiation efficiency and polarization of lower, upper band. The flexible attributes of radiator studied extensively by wearable application by placing them on wrist and jeans. The fabricated antenna produce a bandwidth of 2.12–3.29 GHz in lower band, 4.51–6.00 GHz in upper band for 2.40/5.20/5.80 GHz WLAN, 2.50/5.50 GHz WiMAX, 2.40/4.90/5.20/5.50/5.80 GHz WiFi, 5G SUB-6 GHz and ISM bands. [ABSTRACT FROM AUTHOR]

The fabrication of narrow-slot Lead-Selenide (PbSe) gratings is critical for advancing mid-infrared (MIR) device technologies, for applications in spectroscopy, thermal imaging, and environmental monitoring. The primary challenge to achieve this goal is the increased irregularity and reactive ion etching (RIE) lag in etched profiles as slot width decreases. This research highlights the charging effect, attributed to accumulated charge on non-conductive photoresist, as the main cause of these irregularities. Introducing a conductive copper layer neutralizes this charge, enabling successful etching of gratings with significantly improved profiles and slot widths down to 0.7 μm. This solution, offering improved MIR device sensitivity and resolution, and opening new avenues for scientific and practical applications in fields ranging from security to healthcare. [Display omitted] • Copper layer improves PbSe grating etching profiles. • Enables etching of slots down to 0.7 μm width. • Addresses charged shading and ion-focusing issues. • Opens new avenues for improving MIR devices. [ABSTRACT FROM AUTHOR]

This work adopts a composite strategy combining "large anisotropic structure" and "strong dielectric material", which is a pioneer work reported on urchins CuCo 2 S 4 /C absorber. An environmentally friendly (eco-friendly) CuCo 2 S 4 /C composites were prepared through a facile route including an ion exchange method and a simple physical grinding process. The resultant CuCo 2 S 4 /C composites exhibit an urchins-like morphology with carbon nanoparticles anchored randomly on the tentacles of the urchins. The urchins CuCo 2 S 4 /C composites display an optimal reflection loss value of −44.2 dB at the thickness of 2.2 mm, and the effective bandwidth with RL < −10 dB reaches 7.12 GHz at a thickness of 2.4 mm. The outstanding electromagnetic (EM) wave absorption performance is mainly benefited from the synergistic effects between the anisotropic structure of CuCo 2 S 4 and conductive carbon particles. By adjusting the component ratio during the grinding process, an optimized combination of conduction loss and polarization loss can be achieved, and the impedance matching level can be regularly controlled and improved while increasing the effective absorption bandwidth. These results indicate that the sea urchin CuCo 2 S 4 /C composite material designed in this work can serve as an ideal candidate for high-performance electromagnetic wave absorption and has certain reference significance for the development of more sulfide semiconductor based absorbing materials. • "Large anisotropic structure" and "strong dielectric material" combining strategy. • The first work reported on urchins CuCo 2 S 4 /C absorber. • The effective bandwidth with RL < −10 dB reaches 7.12 GHz at a thickness of 2.4 mm. • Simple preparation and low cost. [ABSTRACT FROM AUTHOR]

• This manuscript proposed a unique mirror symmetric µ-near-zero wide band-stop metamaterial shield for EMI shielding applications in the C- and X-band. • The proposed design intends to employ a shared metamaterial structure to serve two distinct microwave bands with extended shielding bandwidth. • The wide band-stop characteristics as well as frequency and bandwidth modulation flexibility make the structure unique for EMI shielding applications. • The simple shorting metallic strip in the proposed structure can control the shielding spectrum from C-band to X-band with an outstanding band-stop enhancement capability of 170.63%, which significantly outperforms the existing state-of-the-art metamaterials. • The proposed metamaterial prototypes are fabricated and experimentally verified their shielding performance and show promising results for wideband EMI shielding applications. In this paper, a µ-near-zero wide band-stop metamaterial (MM) shield is conducted for electromagnetic interference (EMI) shielding purposes in the C- and X-band. The proposed design intends to employ a shared MM structure to serve two distinct microwave bands with extended shielding bandwidth. The proposed structure consists of metal strip coupled four identical quartiles based unique mirror symmetric resonator and designed on a low-loss Rogers 5880 substrate within a compact physical dimension of 7.5 mm × 7.5 mm × 1.575 mm. The speciality of the proposed MM is its wide band-stop functionality with maximum shielding bandwidth and effectiveness of 4.33 GHz and 66.6 dB, respectively. Moreover, four shorting metal strips among adjacent quartiles can control the shielding spectrum from C-band to X-band with an outstanding band-stop enhancement capability of 170.63 %, which significantly outperforms the existing MMs. Therefore, the proposed MM structure can be utilized for two distinct wide frequency spectrums shielding by introducing simple shorting metallic strips. The electromagnetic radiation shielding phenomena are also explained using surface current and electric and magnetic field distribution. The proposed MM prototypes are fabricated and experimentally verified with numerical results. The promising shielding performance of the developed MM demonstrates the potentiality for shielding undesired electromagnetic radiation. [ABSTRACT FROM AUTHOR]

A series of Mn-substituted Z-type hexaferrite ceramics (Ba 1.5 Sr 1.5 Co 2 Fe (23 - x) Mn x O 41 ; 0.0 ≤ x ≤ 0.5 at a step of 0.1) were prepared via double sintering method. According to EDS data, Mn3+ ions were uniformly distributed throughout the lattice. The relative densities of all samples were higher than 90%, enriching the maxima at x = 0.1 and x = 0.2 (above 95%), which indicated compact grain growth. The greatest saturation magnetization (56.18 emu/g) was achieved at x = 0.1 and then dropped with a further doping of Mn3+ ion, the coercivity showed the opposite trend. Moreover, both permeability and permittivity of the samples drastically changed with the increase of x. Particularly, the samples with x = 0.1–0.2 possessed close permeability (μ′) and permittivity (ε′), and they have relatively high miniaturization factors (n x=0.1 = 12.74, n x=0.2 = 10.38) in the frequency range 10 MHz to 1 GHz. Ba 1.5 Sr 1.5 Co 2 Fe 22.9 Mn 0.1 O 41 ceramics exhibits best microwave properties, μ′ = 11.26, ε′ = 14.42, magnetic loss tangent tan δ μ = 0.048, dielectric loss tangent tan δ ε = 0.0024, and Snoek constant = 17.433 GHz. Consequently, these Mn-substituted hexaferrite ceramics with impedance matching have great application potential for ultra-high frequency miniaturized antenna substrates. • The high-frequency magnetic-dielectric properties of Mn-substituted Z-type hexaferrite ceramics were systematically investigated. • The relative densities of all samples were higher than 90%, enriching the maxima at x = 0.1 and x = 0.2 (above 95%). • The x=0.1 sample exhibits best microwave properties with μ′ = 11.26, ε′ = 14.42, tanδ μ = 0.048, tanδ ε = 0.0024, and Snoek constant ~ 17.433 GHz. • The miniaturization factors of x = 0.1 and 0.2 samples were greater than 10 (n x=0.1 = 12.72, n x=0.2 = 10.35) in the frequency range 10 MHz to 1 GHz. [ABSTRACT FROM AUTHOR]

A wide-angle scanning millimeter-wave (mm-wave) phased array with enhanced bandwidth and isolation using novel triple-function electric walls (TEWs) is presented in this work. First, a novel concept for element beamwidth broadening is proposed by using a suspended horizontal magnetic current (SHMC) with a conical pattern. Then, based on this concept, an antenna element is designed using the proposed TEWs. TEWs not only broaden the element beamwidth by forming a suspended horizontal magnetic current(SHMC), but also widen the element bandwidth by introducing a new mode. Meanwhile, the proposed TEWs can be used as a band-stop filter in the array to reduce the mutual coupling. Based on the three beneficial functions of the proposed TEWs, a wide-angle scanning mm wave phased array with enhanced bandwidth and isolation is designed. Measured results show that the phased array achieves an active impedance bandwidth of 19.3% (24.7-30 GHz) and a good isolation of more than 15 dB. Meanwhile, a wide 3 dB scanning angle larger than ± 74 ° is achieved by the proposed array with the maximum scanning angle of ± 80 ° at 27 GHz. [ABSTRACT FROM AUTHOR]

In the present study, scattering of surface gravity waves by multiple slotted vertical barriers arranged in a zig-zag manner is analyzed by employing Computational Fluid Dynamics (CFD) and validated with physical model tests. The porosity of the vertical slotted barrier is varied from 10% to 40%, and the number of slotted barriers varied from 1 to 6. The results from CFD correlate well with the laboratory measurements on the scattering coefficients for a wide range of input conditions giving a high level of confidence. For relatively short waves (h / λ > 0.3, h - water depth and λ - wave length), slotted barriers up to 3 numbers and porosity from 20% to 30% are required to achieve wave transmission coefficient in the range of 0.2 to 0.3. For relatively long waves (h / λ < 0.3), slotted barriers of 5 to 6 numbers and porosity in the range of 10% to 20% are needed to obtain wave transmission of 0.2 to 0.3. The results presented in this study can be used for a wide range of wave damping applications in the field of coastal engineering. [ABSTRACT FROM AUTHOR]

The activities presented under this paper were focused on designing, manufacturing, testing and evaluation of a metallic antenna reflector for space applications. The main challenge was to obtain a low mass, while maintaining the reflector capability to withstand the mechanical loads encountered during the launching phase, as well as the harsh space environment with significant temperature variations, without any detrimental effect over the dimensional stability of the reflective surface. The chosen material was titanium alloy for the reflector and stainless steel for fasteners and mounting supports. Manufacturing parameters have been investigated aiming for low internal stresses during processing and to obtain the best results in terms of dimensional accuracy and surface roughness. One of the five analysed reflector architectures (reflector breadboards) was selected and manufactured using two different finishing operations, milling and turning, the latter being the one presenting the best results. Dimensional accuracy of the reflector breadboard, before and after vibration and environmental tests, was found to be smaller than the imposed requirements, thus validating the reflector proposed design. After the breadboarding activity, an optimized version of the antenna reflector (demonstrator), also validated by structural analysis, was developed. Unfortunately, the measured profile deviation of the demonstrator was higher than the imposed requirements (by 50%), mainly due to internal stresses during mechanical processing of the new geometry. Before the experimental evaluation of the reflector demonstrator, a surface coating was developed and applied to the reflective surface of the demonstrator. Despite the profile deviation, the demonstrator meets the imposed mechanical requirements and offers important lessons to be applied in the future development activities. • Design for a spacecraft antenna reflector with low mass and high dimensional stability of the reflective surface. • Development and optimization process for a titanium antenna reflector. • Stiffening structure design for a thin wall titanium antenna reflector. [ABSTRACT FROM AUTHOR]

To improve the combustion stability at micro scale, the micro combustor with a central and bilateral slotted blunt body (MCSB) exhibiting significant combustion performance improvement is designed. The new one can not only effectively prevent the flame tip opening, but also exhibit higher combustion efficiency and blown-off limit. Its blown-off limit can reach 756 cm3/s at the flow rate ratio of 0.2 and the bluff body angle of 90°, which is 61.5% higher than that of the conventional one with the blown-off limit of 468 cm3/s. The combustion efficiency improves with the growth of the flow rate ratio, while the blown-off limit of MCSB increases first and then decreases. The blown-off limit of MCSB with the bluff body angle of 90° reaches to the peak value of 792 cm3/s at the flow rate ratio of 0.15. Moreover, the increase of the bluff body angle provides better combustion efficiency and stability. • Proposed a novel micro combustor with a central and bilateral slotted bluff body. • Studied the influence of flow rate ratio on combustion performance. • Investigated the effect of bluff body angle on combustion characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel ZnO-NiCo 2 O 4 -NiCo 2 O 4 core–shell Microstructure was designed with two different morphologies of NiCo 2 O 4. • The NCO-1 shell increased attenuation capability and NCO-2 shell improved impedance matching. • Both strong reflection loss of −59.93 dB and wide absorption bandwidth of 7.04 GHz. • RCS simulation also indicates that ZNN has outstanding MA performance and good practicability. Core-shell structural design is an attractive strategy to achieve high-performance microwave absorbers. Nevertheless, it still remains a problem to simultaneously obtain superior microwave dissipation and impedance matching for microwave absorption (MA) materials. In this work, ZnO-NiCo 2 O 4 -NiCo 2 O 4 (ZNN) core–shell microstructure is designed and fabricated by covering NiCo 2 O 4 nanosheets on the surface of ZnO nanorod and next growth of NiCo 2 O 4 nanoparticles. With the synergies from the NiCo 2 O 4 nanosheets improving the microwave attenuation capability and the NiCo 2 O 4 nanoparticles increasing the impedance matching, ZNN possesses efficient MA performance: the strongest reflection loss is −59.93 dB at the corresponding thickness of 2.6 mm, and the maximum absorption bandwidth is 7.04 GHz at 2.4 mm, which covers the entire Ku-band. RCS simulation also indicates that ZNN has outstanding MA performance. Moreover, this study proposes a point for the utilization of nickel–cobalt oxides in MA materials, and offers a reference for the design of core–shell structural absorbers. [ABSTRACT FROM AUTHOR]

This paper propose an inverted sequential load-modulated balanced amplifier (ISLMBA) for extending the dynamic power range of a power amplifier (PA) over a wide bandwidth. The proposed ISLMBA consists of a control amplifier (CA) and a balanced PA (BPA) pair. A composited impedance inverter is inserted between each BPA transistor and the output coupler. The composited impedance inverter is composed by the intrinsic elements and output matching network (OMN) of the BPA transistor. In this way, the intrinsic elements can be fully absorbed into the impedance inverter over a wide bandwidth. Meanwhile, the load modulation trajectories of the BPA transistors can be optimized over a wide bandwidth by tuning the characteristic impedance of the impedance inverter. The theoretical current, voltage and load-modulation profiles of the ISLMBA are comprehensively analyzed. It is illustrated that the proposed ISLMBA could maintain high efficiency at deep output back-off power level over a wide bandwidth. Moreover, this work designs and fabricates an ISLMBA operating over 1.3–2.55 GHz to verify the proposed PA architecture. The fabricated ISLMBA exhibits a saturation drain efficiency (DE) of 54.5%–73.8% and a saturation output power of 42.9–45.9 dBm. At the same time, the fabricated ISLMBA achieves a 10 dB back-off DE of 42.1%–63.9% over the frequency band of interest. When the fabricated ISLMBA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 10.2 dB at 2.0 GHz, the measured adjacent channel leakage ratios (after predistortion) are −47.7 and −48.8 dBc at the lower and upper bands, respectively. [ABSTRACT FROM AUTHOR]

A non-uniform aperture distribution slotted waveguide antenna is presented. The slotted waveguide antenna array is chosen for its ease for aperture distribution control and the flexibility of gain adjustment. Multiple aperture distribution functions, including uniform, binominal, Chebyshev, and Blackman, have been extensively investigated to achieve the best possible side lobe suppression. These distribution functions have been converted to slot displacement from the center line of the antenna. Number of slots in the proposed array is chosen to be eight to satisfy the required gain for mm-wave radar tracking application. The proposed antenna is simulated and optimized using the full wave simulator package (CSTMWS). Rounded edge slots are adapted instead of the sharp ones, as they are more applicable for the CNC fabrication process. An eight-slot waveguide antenna is fabricated and gold-plated, considering the Chebyshev distribution approach. The proposed design achieves very stable radiation characteristics and performance over the operating bandwidth, which extends from 33.6 GHz up to 35.9 GHz. At 35 GHz, the total realized gain of the overall antenna is found to be 13.4 dBi, with an overall radiation efficiency of 95.21 %. An obvious low SLL of −30 dB is obtained at the frequency of 35 GHz. The low side lobe level parameter is very crucial for radar applications as it enhances the overall target SNR and reduces false target observations. The pre-stated antenna characteristics make it a good candidate for mm-wave radar applications and point-to-point communications (P2P). [ABSTRACT FROM AUTHOR]

This paper presents a novel formulation for a generalized helical antenna that incorporates non-uniform helix diameters, non-uniform helix spacing, and non-uniform wire cross-section, providing additional degrees of freedom for optimization. By carefully defining the transition between the helix and the center feed point, a thicker wire was used at the base to enhance the antenna's operating bandwidth capability and mechanical strength, eliminating the need for additional support structures. The fabrication process utilized metal additive manufacturing (MAM) with Maraging steel. The results demonstrate that the helical antenna with a tapered cross-section wire (with a thicker base and a thinner tip) exhibits significantly better performance compared to the control models for operation in the X-band. This design amalgamates impedance matching from antennas with uniform thick wires and radiation characteristics from antennas with uniform thin wires. The major contribution of this work is the demonstration that employing tapered wire cross-sections can enhance helical antenna performance, thereby introducing a new design parameter in metal additive manufacturing. Specifically, we present an eight-turn helical antenna that achieved a measured reflection coefficient less than − 10 dB and axial ratio less than 1 dB over the X band, with a peak realized gain in RHCP of 10.8 dBic. • We propose and experimentally characterize a helical antenna with variable helix spacing, helix diameter, and wire cross-section diameter. • We demonstrate that metal additive manufacturing (MAM) is a suitable manufacturing platform for building this complex-shaped antenna in high-quality steel, making it possible to exploit degrees of freedom that previous manufacturing technologies did not allow. • The characterization of the antenna reveals that the proposed design outperforms previous proposals with a uniform cross-section in terms of operating bandwidth and axial rate. [ABSTRACT FROM AUTHOR]

Coplanar capacitance imaging technology (CCIT) is a non-destructive method with intuitive and accurate identification. This paper aims to realize defect identification in asphalt materials based on the CCIT using coplanar single-pair electrode capacitance sensor (CSCS). Firstly, the Linear Back Projection (LBP) algorithm, the Landweber algorithm, and the Kalman-Filter (KF) algorithm, are compared and evaluated. Then, the principal component analysis (PCA) method is utilized to fuse the reconstructed images. In addition, the OTSU method, the iterative threshold (IT) method, and the genetic algorithm (OA) method, is compared and utilized to quantify the defective region. Finally, this investigation analyzes the reconstructed and segmented images of defects in asphalt materials. It is concluded that the KL algorithm is the most suitable algorithm to reconstruct the defective images. The PCA method improve the quality of the reconstructed defective images. The defective region is determined by the OTSU method, which is the most approximate imaging segment method. It is found that the CCIT can detect the invisible defect depth in asphalt materials. The different defect mediums in various asphalt materials can be identified by the CCIT. The segmented defective region error in asphalt materials is less than 13%, demonstrating that the CCIT is effective for the identification of defect shape details in asphalt materials. The segmented imaging precision of square defects in asphalt materials is the highest; circular defects are the next lowest; and triangular defects are the lowest. The outcomes of this research can assist engineers in realizing intuitive and high-accuracy identification of various invisible defects in shallow asphalt layers in bridge deck asphalt pavement utilizing the CCIT. • The KL algorithm is chosen to reconstruct the images of invisible defects. • The quality of the reconstructed defective images is improved using the PCA method. • The OTSU method based on threshold segmentation is selected to quantify the defect region. • The reconstructed and segmented images of different shapes of air void and moisture defects in asphalt materials are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, new 3 dB/10 dB filtering couplers using branch line loading, multi-line hybrid coupling, and electromagnetic coupling, which are based on self-packaged suspended coplanar waveguide-microstrip (SCPW-MS) hybrid and broadside coupled suspended coplanar waveguide (BC SCPW) techniques, have been proposed. The filtering function is achieved by the branch line loaded resonator, multi-line hybrid coupling and electromagnetic coupling of the SCPW resonator. All of the proposed filtering couplers have been fabricated and measured, and the experimental results approach to the predictions. The advantages of the new designs with low insertion loss of no more than 0.82 dB, favorable isolation of more than 18 dB, phase imbalance of no more than ± 5°, and multiple transmission zeros in some works to introduce high frequency selectivity, and self-packaging have been demonstrated. The dual-layer routing of the core circuit not only retains the advantages of SCPW, but also improves the design flexibility. [ABSTRACT FROM AUTHOR]

Through analyzing different cross-sections of the complex ball grid array (CBGA) sandwiched by silicon interposers, various distributed capacitances of the CBGA and the significance of the CBGA's coplanar capacitances are revealed. From the analyses, the composition of the CBGA's capacitance is found to have similarity with that of the coplanar waveguide's capacitance. Based on the electric-field coupling mechanism of the coplanar waveguide, geometrical analysis of the CBGA, and analysis of multiconductor transmission lines, analytical equations are derived to allow accurate modeling the equivalent circuit of the CBGA for 3D silicon-interposer packaging. The modeled equivalent circuit of the CBGA is validated with the full wave electromagnetic simulation, and it is demonstrated to have a good accuracy up to 40 GHz. Moreover, the CBGA structure can be further optimized for impedance matching with the guidance of the derived analytical equations. [ABSTRACT FROM AUTHOR]

Neuromorphic computing has been a candidate to work like human brains to deal with big data energy-efficiently beyond the von Neumann architecture. As an important part, artificial synapses based on waveguides with phase-change materials (PCMs) play a critical role in neural networks. However, because of demanding conditions of triggering intermediate phase states to achieve multilevel weights it is relatively difficult to obtain accurate multilevel weights. In this work, we designed a photonic synapse based on slot-ridge waveguides with multi-block Ge 2 Sb 2 Te 5 (GST) to precisely and easily get multilevel weights by triggering the specific number of GST islands between crystalline and amorphous states. The properties of the GST material were analyzed by Raman spectroscopy and spectroscopic ellipsometry and the nonlinearity factor of photonic synaptic weights was optimized for the number of GST islands. The recognition tasks of MNIST and the optical recognition of NIST were performed by multilayer perceptron, and the optimal accuracy of the optical recognition of NIST was 92.7 % for 5 GST islands. The accuracy of MNIST was improved by 2 % for 5 GST islands compared with that of 2 GST islands. Besides, the electro-thermal phase transition conditions of crystallization and reamorphization were also obtained by simulation. This work will open the way to precisely and easily achieve photonic synapses with multilevel weights in the future. • This work achieves multilevel weights of photonic synapses with GST to avoid the demanding triggering condition. • Photonic synapses based on slot-ridge waveguides with GST achieve multilevel weights by dividing the block GST into islands. • The nonlinearity factor is optimized for the number of islands in the mapping between normalized transmission and weights. • The optimal accuracy of the optical recognition of NIST is 92.7% while that of MNIST is improved by 2%. • The electro-thermal phase transition conditions are obtained by using Joule heat model. [ABSTRACT FROM AUTHOR]

In this paper, we propose a topological acoustic waveguide which can transmit high-precision and multiband sound energy with backscattering suppression and no energy loss. It is a kind of acoustic waveguide with spatial lattice uniformity without destroying lattice position. This acoustic structure is obtained by integrating two kinds of multi-stage resonators arranged in a triangular lattice pattern in the air environment. On one hand, the introduction of internal modes greatly improves the transmission accuracy of topological acoustic waveguide compared with the Bragg scattering alone under the same overall structure size. On the other hand, it greatly improves the utilization rate of the internal space of the structure and makes full use of the multi-modal in structure to construct more sound transmission bands. After introducing the rotational scattering mechanism, the numerical and experimental results show that up to seven high-precision acoustic transmission channels with backscattering suppression and no energy loss below 14 kHz are obtained along the sonic crystal interface with different topological states in this topological acoustic waveguide. This research paves the way for engineering applications of high-precision acoustic transmission, multi-band acoustic antennas, acoustic logic control, covert sound transmission and other multifunctional acoustic devices. [ABSTRACT FROM AUTHOR]

Tunable metastructur (MS) is popular for research today, but it is complex and difficult to manipulate, so a novel solution has been proposed. In this paper, a MS based on gravitational field and graphene modulation is presented, which can achieve polarization conversion, amplitude modulation, and operating band shift in the range of the gigahertz (GHz) band. The proposed polarization converter (PC) consists of mercury-filled glass cavities, graphene resonators, a copper substrate, and a polyimide dielectric layer. The mercury flows to different parts through the specially designed glass cavities under the effect of the gravitational field, which results in different functions. When the proposed device is not flipped, within 2.53–4.38 GHz (the relative bandwidth is 54.28 %), the linear-polarized electromagnetic wave can be efficiently converted to the circular-polarized ones, whose axial ratio is less than 3 dB. Moreover, when it is flipped, the designed PC can realize the function of cross-polarization conversion and maintain a polarization conversion rate above 90 % in the band of 3.92–7.36 GHz (the relative bandwidth is 60.99 %). The joint tuning of graphene and gravitational field and related parameters are discussed. Moreover, the physics mechanism of the proposed device is explained according to the surface current diagrams. The proposed PC possesses the advantages of broadband, novel tuning, multifunctional modulation, etc. It can be used in the field of communication, electromagnetic countermeasures, and the electromagnetic wave modulation field. [Display omitted] • The Ms utilizes gravitational field and external voltage jointly. • The Ms can realize LCPC and amplitude modulation in different states. • The Ms supplements the traditional multifunctional MS. • The tailored methods are more flexible and convenient. • The Ms has the advantages of ultra-wide bandwidth. [ABSTRACT FROM AUTHOR]

• 3D printed composite materials were prepared using a two-step method of ball milling co mixing and melt extrusion, as well as FDM technology. • The GR-TiN/PLA/TPU composite material was prepared through FDM technology, achieving a synergistic effect of absorption and mechanical properties. • By analyzing electromagnetic parameters and microscopic morphology, the absorption mechanism of composite materials was elaborated in detail. • The reflection loss and absorption bandwidth of the composite material are -29.08dB and 6.80GHz, respectively, with a tensile strength of 20.2MPa. In this paper, GR-TiN/PLA/TPU composite wires were prepared by melt extrusion forming process and GR-TiN/PLA/TPU composites were obtained by fused deposition moulding (FDM) technique. The effects of graphene content on the wave absorption properties and mechanical properties of the composites were investigated. With the increase of graphene content, the wave absorption performance of the composite gradually enhanced, but the mechanical properties decreased. When the GR content is 4 wt%, its maximum reflection loss is −29.08 dB at 15.60 GHz, and the effective absorption bandwidth reaches 6.80 GHz when the thickness of the absorber layer is 3.0 mm, and the tensile strength reaches 20.2 MPa.The excellent wave absorption performance can be attributed to the fact that the composite of graphene and titanium nitride not only improves the impedance matching performance of the composite but also forms abundant folds and bumps inside the composite, forms a three-dimensional micro-conducting network and enhances the interfacial polarization loss and electrical conductivity. [ABSTRACT FROM AUTHOR]

From the beginning of crystal plasticity studies, the cause for the small percentage of expended work retained as stored work has been a quandary. From forensic analyses of plastic deformation studies, it was deduced that coplanar annihilation of dislocations occur since slip takes place in small slip-patch areas of mean slip distance squared. A simple model predicts that the athermal annihilation factor A between expended and stored energy is about 20 comparable to the observed 5% for stored work. The derived A ranged from 19 at 20 K to 25 at 300 K for copper. Using the functional constitutive relation which can replicate the stress-strain diagram, analyses invoking the imposed shear strain to assess the height between coplanar slip planes indicate that structure evolution due to monopole dislocations result in the principle of similitude. However, the break-down of this Stage II structure occurs when cross-slip and the accompanying double cross-slip is incurred resulting in increasing height between slip planes. The consequences of these bypass mechanisms are the change of the random array of dislocations to that of clustered patterns with the increase in mean slip distance leading to cell structure formation. This evolution can be examined using the shear flow stress versus the inverse mean slip distance plot. Hence the bases for decoding work-hardening of face-centred cubic metals using constitutive relations have become possible. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A three-dimensional plasmonic wavelength demultiplexer is investigated using slit- and stub-type filters consisting of metal–insulator–metal waveguides. To achieve a narrow bandwidth of the slit-type filter, a dielectric material is inserted into the slit section and the metal thickness is deliberately chosen to be 0. 2 μ m. Then, a demultiplexer is considered with the two filters being placed in parallel. Numerical results show that a separation of 18.9 dB between the two output ports is obtained at 1. 31 μ m , while it is only 9.8 dB at 1. 55 μ m. To improve the separation, stub sections forming an attenuation pole are introduced into the waveguides. It is found that the separation is successfully improved to more than 20 dB at both wavelengths. All calculations are performed using the finite-difference time-domain method based on the trapezoidal recursive convolution technique. [ABSTRACT FROM AUTHOR]

Mode properties of a confocal elliptical dielectric nanowire coated with double-layer graphene are analyzed by using the separation of variables method (SVM). The graphene surface plasmon modes could be tuned by changing the working wavelength, the distance between semi-major axes, the Fermi energy level of graphene and the geometry parameters. The results show that the semi-analytical results of SVM are completely consistent with the numerical simulation results of finite element method (FEM). Compared with the elliptical dielectric nanowire coated with single-layer graphene, the novel waveguide structure has stronger mode confinement, lower propagation loss, larger propagation length, wider adjustable working wavelength and wider adjustable Fermi energy level of graphene. The waveguide may be exploited for many applications such as plasmon resonances, detectors and microstrip antennas. [ABSTRACT FROM AUTHOR]

Dispersion problem has always constrained the development of see-through near-eye displays with diffractive waveguide. Here, we propose a design method and optical systems for one-layer achromatic surface microstructure composed with a triple-carved-sub-grating. The triple-carved-sub-grating with specified period is designed based on rigorous coupled wave theory, corresponding to Red (R), Green (G) and Blue (B) wavelengths, respectively. The surface microstructure with period of 18.9um is realized by synthesizing the three sub-gratings together, and it is verified numerically that the diffractive angle of R, G, and B wavelengths is 35°under the normal incidence of TE polarization, which imply that the surface microstructure diffracts the certain RGB wavelengths achromatically. A diffraction waveguide with achromatic surface microstructure is also modeled to analysis the stray light and color correction, and the results indicate that the diffraction waveguide transmits image with little stray light. Via proper duplication it could be utilized as the combining optics of diffractive-waveguide near-eye display and head-up display because of its light and compact features. [ABSTRACT FROM AUTHOR]

A silicon waveguide mode (de)multiplexer is theoretically proposed for compact on-chip mode (de)multiplexing (MDM). The (de)multiplexing of E 11 y , E 21 y , E 31 y , E 12 y , E 22 y and E 32 y modes is realized by cascading asymmetric Y-junctions and the E 21 y ∕ E 12 y mode rotators. Beam propagation method is adopted in the design and optimization. For a 124 μ m-long device, the mode crosstalk among all channels is less than -24 dB. The insertion loss can be lowered to 0.96 dB at optical wavelength of 1550 nm. This proposed design method can be extended to the construction of higher-order mode (de)MUX. • Cascaded asymmetric Y-junctions with mode rotator realize the six-mode (de)multiplexing. • The length of six-mode (de)MUX is optimized to be only 124 μ m by beam propagation method. • Low excess loss of 0.96 dB and mode crosstalk smaller than −24 dB are theoretically expected. [ABSTRACT FROM AUTHOR]

A compact silicon-based TM-pass/TE-divide polarization beam splitter based on contra-directional grating couplers (CDGCs) is proposed, where two identical corrugated strip waveguides are located at both sides of a central slot waveguide with corrugations on the bottom silicon layer. The waveguide widths are optimized so that only TE mode can satisfy the contra-directional coupling condition. The TE mode will be contra-directionally coupled to the corrugated strip waveguides by using CDGCs, and the final outputs from the two drop ports will be equal. The TM mode is hardly affected and direct passes through the central slot waveguide, the outputs at two drop ports are nearly negligible due to large phase mismatch. The coupling length of the designed device is 14 μ m. The simulation results at the central wavelength of 1550 nm indicate that, the extinction ratio is 38.4 dB (20.9 dB) and the insertion loss is − 3. 26 dB (− 0. 14 dB) for TE (TM) mode. Besides, the fabrication tolerances and the power distribution along the propagation direction are presented. [ABSTRACT FROM AUTHOR]

A silicon nitride waveguide crossing based on multimode-interference is designed and fabricated. By optimizing the structure parameters with finite difference time domain method, 0.3 dB insertion loss and −75 dB crosstalk at 1550 nm are obtained. Then the designed waveguide crossing is fabricated based on the double strip silicon nitride waveguide. The measured results show the insertion loss and crosstalk are about 0.6 dB and below −42 dB, respectively, in the wavelength range of 1520 nm ∼ 1640 nm with low polarization dependence. The waveguide crossing could be a key building block for the silicon nitride waveguide platform. [ABSTRACT FROM AUTHOR]

This paper presents a technique to enhance an overall performance of advanced recycling folded cascode operational transconductance amplifier (RFC OTA). It adopts an input stage comprising a cross coupled MOS differential pair biased by a constant DC current source in addition to an adjustable floating voltage source. The proposed modification shows a substantial improvement in transconductance leading to boost dc gain, gain-bandwidth and slew rate of conventional FC-OTA. The structure is designed and implemented in 0.18 μm CMOS technology. In addition to transconductance enhancement, a remarkable improvement in a phase margin is achieved using a Miller compensation technique to ensure the stability of OTA. The simulation results demonstrate the performance of the proposed OTA with 72 dB gain and unity gain bandwidth of 128 MHz for a capacitive load of 10 pF. The modified RFC OTA shows 550% improvement in gain bandwidth product (GBW) and 20 dB hike in the gain compared to the conventional FC-OTA, which has 19.85 MHz GBW and 51.9 dB respectively. The Miller compensated OTA shows 36% improvement in a phase margin compared to non-compensated OTA with a slight reduction of 6% in GBW. This paper proposes modifications in the IRFC-OTA which involve- • Enhancing the transconductance using unbalanced current flow into input stage by adopting adjustable floating voltage source. • Enhancing the phase margin of OTA by incorporating a Miller compensation scheme. • Proposed OTA shows 20 dB, 9 dB and 6 dB hike over conventional FC, RFC and IRFC-OTA structures. • Simulation results confirms that proposed OTA achieves 550% and 300% improvement in GBW and slew rate compared to FC OTA. • The Miller compensated OTA shows 33% improvement in phase margin with minor reduction in GBW compared to original structure. [ABSTRACT FROM AUTHOR]

Cold-formed steel studs and purlins with staggered slotted perforations in webs are used in building structures to produce a better thermal performance of the profiles and for the energy efficiency of structures. On the other hand, the slotted webs result in an unfavourable effect in terms of the structural performance of the element, prominently their shear, bending and combined bending and shear strengths. Relatively little research has been reported on this subject despite its importance. Many research studies have been undertaken to examine the behaviour of conventional cold-formed steel (CFS) channel sections subject to combined bending and shear. To date, however, no research has been carried out to investigate how CFS channels with staggered slotted perforations behave under combined bending and shear actions. An extensive study on this area is therefore essential. Finite element (FE) models of CFS channels with staggered slotted perforations were developed to investigate their combined bending and shear capacity. A parametric study was conducted in detail by developing FE models based on the validation process with available experimental data. This paper presents the FE analysis details of CFS channels with staggered slotted perforations subject to combined bending and shear actions and the FE results. New design equations were also proposed to predict the combined bending and shear capacity of steel channels with staggered slotted perforations. • Combined bending and shear behavior of channels with staggered slotted perforations have been investigated • Finite element models showed satisfactory agreement with available test data • All influencing parameters were considered in the parametric studies including aspect ratio • Staggered slotted perforations significantly reduced the combined bending and shear capacity • New design equations were proposed to predict the combined bending and shear capacity of slotted perforated steel channels [ABSTRACT FROM AUTHOR]

• The failure of asphalt materials is located by the capacitance distribution measurement. • The failure depth in asphalt materials can be predicted using the-maximum change capacitance. • The spatially resolved capacitance measurement determines the failure shape details of asphalt materials. Compared to traditional non-destructive testing (NDT) methods, coplanar capacitance technology has advantages in intuitive identification and accurate location for identifying and locating the various failures in asphalt materials. At present, research on coplanar capacitance technology for various failure detection and location in asphalt materials is missing. Therefore, this paper aims to develop a various failure detection and location method in asphalt materials using coplanar capacitance technology. Firstly, the capacitance distribution measurement on the single-pair electrode capacitance sensor with constant area (CSCS) is utilized to locate the various failures of asphalt materials. Then, the various failure depth inside asphalt materials can be predicted using a standard curve of the various failure depth-maximum change capacitance. Finally, based on the single-pair electrode capacitance sensor with variable area (VSCS), the spatially resolved capacitance measurement determines the various failure shape details of asphalt materials. It is found that the Ultrasonic Tomography Technology (UTT) method can only identify internal various failures in asphalt materials and is unable to determine the location of various failures. Nevertheless, the capacitance distribution measurement can identify air void and water intrusion various failures in asphalt materials. And the relative error of the measured location results inside asphalt materials is within 7. The predicted curves of various failure depths in asphalt materials have a coefficient of determination (R2) of greater than 0.984. The maximum change capacitance can be utilized to estimate the various failure depth in asphalt materials. The UTT method makes it difficult to determine the shapes and sizes of various failures in asphalt materials. But the spatially resolved capacitance measurement can determine the various failure shape details of asphalt materials. And the errors in the reconstructed results with failure shape details inside asphalt materials are less than 11%. The findings of this investigation can help engineers realize intuitive identification and precise location of invisible failures in shallow asphalt layers in bridge deck asphalt pavement using coplanar capacitance technology. [ABSTRACT FROM AUTHOR]