Search

Radio frequency (RF), microwave, and millimeter-wave (mmW) multiport interferometric receivers present a competitive solution for the front-end reception of low-power multistandard and multifunction wireless applications. The systematic generation of rectified waves in a conventional direct-conversion interferometric receiver is highly related to temporal and power changes and the number of subsignals in the frequency band of interest. It can cause the receiver to saturate and, thus, requires auxiliary power-hungry tunable amplifiers and a data converter for compensation. This work presents a heterodyne detection in an RF/microwave interferometric receiver, the first of its kind, which separates the desired frequency signals from the rectified wave components with two output ports through a frequency offset. This architecture also makes use of the field-effect transistor (FET)-based power detectors to combine the received and reference signals, which reduces a theoretical multiport junction loss of 6 dB to 3 dB. In this way, the proposed receiver is set to support the development of an ultralow-power concurrent dual-band wireless system using a single wave-correlator circuit. A mathematical model of the proposed system is derived and subsequently prototyped using off-the-shelf components to evaluate its carrier-to-noise power ratio (CNR) and error vector magnitude (EVM) performances, which can be extended for integrated circuits (ICs) implementation, such as CMOS and III–V ICs. The power detectors only require a bias voltage at gate terminals with zero direct current (dc) power consumption for optimum voltage responsivity and CNR performances. The demodulation of various modulated digital signals, including QPSK, QAM-16, QAM-32, and QAM-64, has been successfully demonstrated in the 24- and 28-GHz mmW frequency bands at 4 MSps of the symbol rate with a maximum EVM of 11.43% root-mean-square (rms) free from any postprocessing linearization and calibration.

Application of metal organic frameworks (MOFs) on sensors is of great interest for researchers. Film forming ability of the sensing material is very important for both the preparation process and sensing properties of the devices. Humidity sensors based on UIO-66 derived polyelectrolyte films were well prepared by in situ thiol-ene click cross-linking polymerization in this work. The hydrophilicity of the sensing film could be controlled by the feed ratios. The optimized humidity sensor shows a fast response to RHs change (Res/Rec time is 3.1 s/1.5 s, respectively) with ∼1.2% RH of humidity hysteresis. The water molecules adsorption behavior of the film and the sensing mechanism were also be investigated. The humidity sensor with good water and thermal stability and repeatability was applied in breath monitoring, which can well distinguish different breath states.

In this work, we propose, develop, and demonstrate a fundamental and comprehensive theoretical foundation for the first time to formulate and devise known and unknown reciprocal and/or nonreciprocal ferrite components with arbitrarily concurrent multimode features based on the substrate-integrated waveguide (SIW) technology. To achieve such a universal design, a nonreciprocal unit cell (NRUC) is first defined and characterized. Then, an approach is proposed and investigated to deploy a sufficient number of NRUCs next to each other as a kernel multimode SIW topology. The kernel configuration transforms the incident guided-wave into several separate segments, propagating in parallels independently and along each NRUC, which can be manipulated separately. This methodology grants a general solution to forge ferrite components in a multimode configuration, discussed in detail to corroborate the proposed generalized theory. Finally, two multimode components are studied and demonstrated for the first time as application examples for the proposed theory. Namely, a dual-mode circulator and a triple-mode gyrator are prototyped, fabricated, and measured, exhibiting an excellent agreement with simulation results that effectively validate the presented theoretical foundation in this work.

Symmetrical solid oxide fuel cells (SSOFCs) could be alternative energy conversion devices due to their simple fabrication process and low cost. Herein, perovskite La0.6Ce0.1Sr0.3Fe0.95Ru0.05O3–δ (LCSFR) was synthesized and evaluated as a high-performance electrode for SSOFCs based on the electrolyte of La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM). LCSFR retains their stable perovskite crystal structure in both reducing and oxidizing atmospheres, though a minor amount of LaSrFeO4 phase is present under reducing conditions. Morphology investigation shows that homogeneously dispersed Ru metallic nanoparticles are exsolved on the surface of LCSFR after being reduced. The polarization resistance (Rp) of LCSFR-CGO (Ce0.9Gd0.1O2–δ) is about 0.11 Ω⋅cm2 at 800 °C in air, while the value of Rp for LCSFR-CGO in wet H2 (3% H2O) increases up to 0.32 Ω⋅cm2. The symmetrical LCSFR-CGO|LSGM|LCSFR-CGO cell demonstrates a performance with an open circuit potential (OCV) of 1.07 V and a maximum peak power density of 904 mW/cm2 at 800 °C using wet H2 as the fuel. This high performance indicates that LCSFR is a candidate electrode for SSOFCs.

This work summarizes an outdoor dynamic measurement of ambient radiofrequency (RF) power density in the core areas of Montreal city, which can eventually be exploited for possible battery-free Internet of Things (IoT) sensor network planning. The measurement covers a frequency range of 400–2700 MHz. The power density along major streets, roads, and highways is captured and analyzed, which differs from previous stationary measurements. Results indicate that cellular communication bands (GSM/LTE850 and LTE700) are the best choice for RF energy recycling in downtown (populated) areas. The largest average power levels of GSM/LTE850 and LTE700 bands are −35.50 and −36.95 dBm, respectively. In contrast, in suburban areas where cellular communication signals are generally weak, the digital television band with a peak level of −47.68 dBm presents the largest among all frequency bands. Moreover, one separate measurement at a fixed location is conducted on a typical workday to study the effects of foot traffic on ambient RF power density. Results illustrate that no obvious fluctuations are detected during this daytime measurement. For example, both average power levels of GSM/LTE850 and LTE700 remain at a relatively stable level of −25 dBm throughout the measurement. With the advance of far-field wireless power transfer and backscattering techniques, ambient RF power-enabled battery-free IoT sensors are feasible and will contribute to the planning and implementation of a smarter and greener city.

This paper presents a novel fixed abrasive tool namely grain boundary cohesion fixed abrasive pellet (GBCFAP) which is able to provide higher finishing efficiency as well as better surface/subsurface quality of sapphire substrate during the chemo-mechanical grinding (CMG) process. The manufacturing procedures of GBCFAP are introduced in detail in this paper. It is found that the sintering temperature plays an important role to the strength of GBCFAP, and the strength of GBFCAP could be flexibly adjusted by sintering temperature. The experiment result suggests that the recommended sintering temperature ranges from 600 to 650 °C according to current CMG conditions. Meanwhile, comparing with conventional resin bound CMG wheel, 600 °C sintered GBCFAP CMG wheel performs better in terms of material removal rate and surface/subsurface quality since the chemical effect and mechanical effect during CMG process are well balanced. Meanwhile, the solid phase reaction between sapphire and Cr2O3 abrasive is demonstrated by TEM observation and XPS quantification.

A scalable planar 2-D active array antenna configuration that can realize amplified radiation through co-existing active devices is proposed, studied, and demonstrated in this work. The input and output of these amplifying active devices are directly integrated with the feed network and array elements, respectively, thereby eliminating the matching networks typically required in an amplifier circuit. A comprehensive analysis of the rectangular patch antenna (RPA) performance with different feeding techniques is initially analyzed and the choice of nonradiating edge feed RPA as array elements is justified for not only realizing the maximum radiation efficiency but also facilitating the direct active device integration. Subsequently, a physical arrangement of these array elements is devised to reduce cross-polarization. The design of $4\times {2}$ active array antenna unit cell operating at 5.8 GHz is then discussed through extensive analysis of active devices, optimization procedure, potential excitation signal control, and influence of faulty transistors. From simulations, this active array scheme has realized a higher matching bandwidth and exhibited an amplifier gain of around 13.6 dB, compared with its passive counterpart. Eventually, these unit cells are integrated through an equal power hybrid feed network for realizing an $8\times {8}$ active array antenna configuration that is fabricated and measured. The measured results of the experimental prototype match reasonably well with the simulation results, thereby confirming the proposed integration technique. The resulting paralleled configuration promises efficient handling of greater powers, making them suitable for high-power applications.

This article presents a novel class of dual-mode substrate-integrated waveguide (SIW) bandpass filters exploiting perturbed SIW rectangular cavities. By introducing metallized via-holes along the central line of an SIW rectangular cavity, the resonant frequency of TE101 mode can be shifted close to that of TE201 mode, thus creating a dual-mode resonator. This structure implements a doublet, which provides two poles and one or two transmission zeros (TZs). The pass bandwidth, spurious-free bandwidth, and positions of the TZs can be fully controlled by modifying the length of the perturbation, the side ratio of the rectangular cavity, and the offset of the input/output ports, respectively. Eight two-pole SIW filters are designed and investigated to demonstrate the high design flexibility. Moreover, a four-pole SIW filter with the asymmetric response and a five-pole SIW filter with quasi-elliptic response are designed, fabricated, and measured to describe the extension of the proposed approach to higher order filters.

In this communication, a dual-band on-chip meander-line monopole antenna is proposed and demonstrated for emerging fifth-generation (5G)-compatible Internet of Things (IoT)-served sensor nodes. The targeted 28/60 GHz compact antenna is a hybrid structure of meander-line monopole antenna and packaging substrate to both shield the antenna from its deployed environment and to enhance the antenna radiation efficiency as well as the gain over the two bands of interest. The antenna model and design analysis are presented in this work together with a fabricated and tested 65 nm bulk CMOS chip. The prototyped on-chip antenna exhibits a measured gain of −10 dBi at 28 GHz with a bandwidth of 5.3% and 0 dBi at 60 GHz with a bandwidth of 5.9%. A radiation efficiency of 45% and 30% is obtained at 28 and 60 GHz, respectively. The antenna occupies a space of $0.25\times0.3$ mm2 ( $\lambda /43\times \lambda /35.7$ at 28 GHz). The on-chip antenna solution proposed in this work addresses the highly desirable yet challenging overall design of future wireless systems (5G and beyond) which hit the mark on compactness, cost, and compatibility. In addition, this work provides a viable design platform for achieving frequency diversity and multifunctionality of future wireless involving power harvesting, data transfer, and sensing operation.

This letter introduces a simple technique to reduce cross polarization in multilayer antipodal linearly tapered slot antenna taking advantage of the slab air-filled substrate integrated waveguide (SAFSIW) topology. The operation mechanism is presented together with simulations and experimental validations. The measured results show a reflection coefficient lower than –17 dB over the Ka -band. A measured gain of 13 ± 1.35 dBi is observed in the overall Ka -band. The proposed broadband structure achieves a measured cross-polarization isolation of better than 16.07 dB at endfire direction over the Ka -band, which is a significant improvement compared to its multilayer AFSIW implementation counterpart.

This letter presents a novel class of compact dual-mode bandpass filters based on half-mode substrate-integrated waveguide (HMSIW) cavities. By using both TE102 and TE301 modes of the HMSIW rectangular cavity as resonant modes and TE101 mode as nonresonating mode, a novel HMSIW doublet with two poles and two transmission zeros (TZs) is implemented. The TZs can be located at one side or both sides of the passband. Therefore, flexible responses can be obtained. A two-pole HMSIW filter with asymmetric response and a four-pole HMSIW filter with quasi-elliptic response have been designed, fabricated, and measured, to demonstrate and verify the proposed structure. Compared with substrate-integrated waveguide (SIW) counterparts, the dual-mode HMSIW filters have the advantage of smaller size.

The dissemination of circulating tumor cells (CTCs) in peripheral blood is an important intermediate step for cancer metastasis. It has become one of the most promising targets of “liquid biopsy”, on account of providing complete information of cell biology. However, due to the extremely rarity, complex environment and strong heterogeneity of CTC in peripheral blood, the development of efficient enrichment and separation methods are the key in the accurate detection of CTC. Currently reported CTC enrichment and analysis techniques are mainly based on the physical or biological characteristics of CTC. They are commonly combined with the traditional techniques including density gradient centrifugation, superfine membrane filtration and immunomagnetic separation, the novel methods such as microfluidic chip separation and two-dimensional electrophoresis-field separation, and the analysis techniques such as reverse transcription-polymerase chain reaction, flow cytometry, immunocytochemistry, photoacoustic imaging, surface-enhancement Raman scattering and electrochemistry to realize accurate detection of CTC. In this review, we summarized the recent processes on enrichment and novel detection methods of CTC and discussed the challenges and their clinical application status, which could provide reference for the further improvement of the technology of enrichment, accurate counting and molecular phenotype analysis for CTC, as well as the application in scientific research and clinical practice.

Recently, there are significant progresses in the growth of organic-inorganic lead halide perovskite single crystals, however, due to their susceptible nucleation and growth mechanisms and solvent requirements, the efficient and generalized growth for these single crystals is still challenging. Here we report the work towards this target with a polymer-controlled nucleation process for the highly efficient growth of large-size high-quality simple ternary, mixed-cations and mixed-halide perovskite single crystals. Among them, the carrier lifetime of FAPbBr3 single crystals is largely improved to 10199 ns. Mixed MA/FAPbBr3 single crystals are synthesized. The crucial point in this process is suggested to be an appropriate coordinative interaction between polymer oxygen groups and Pb2+, greatly decreasing the nuclei concentrations by as much as 4 orders of magnitudes. This polymer-controlled route would help optimizing the solution-based OIHPs crystal growth and promoting applications of perovskite single crystals., Research into single crystal organic-inorganic halide perovskites have gained momentum due to the potential applications, yet the growth is still a challenge. Here, the authors demonstrate a universal method based on polymer controlled nucleation process to achieve large-size and high-quality perovskite single crystals.

Electromagnetic waves have been widely exploited as signal, carrier, and power for wireless and wireline systems over the electromagnetic spectrum. As the classical approach, parametric interactions among localized or discrete signal processing devices are usually accomplished by electromagnetic fields or waves guided in conductor and/or dielectric bounded structures. These structures feature specific circuit functions in an electronic or photonic manner. Such electromagnetic circuits now face a number of application issues, such as geometrical complexity, power handling capability, and flexible reconfigurability, when they are used in certain large-scale electromagnetic systems, like in a massive multiple-input and multiple-output (MIMO). In this work, we propose and present an unconventional approach to realize a desired interaction or operation among devices. Such an interaction relies on wave or field interferences induced by a set of coherent antenna array over their near-field region where signal processing can be accomplished spatially. Fundamental functions and operation mechanisms of the proposed spatial signal processing approach are discussed and demonstrated in this work. It is worth mentioning that the proposed approach is universally applicable to all physical wave devices and systems, such as acoustic and electromagnetic waves.

In this work, we present a comprehensive analysis of port impedance effects on a signal coupled across two-port networks, derive an equation to evaluate the impedances for a specified coupling, and demonstrate two beam-shaping active array antenna prototypes to validate the theory. In this context, the generalized S-parameters are theoretically studied and verified through an example. Subsequently, a closed-form equation is derived to accurately evaluate the port impedances that enable the achievement of a desired magnitude and phase of the signal coupling across the two-port network. The meaningfulness of all the potential results and the additional capabilities of derived equations are then discussed. With this understanding, a general modeling procedure is formulated to achieve the simultaneous amplification and phase shifting only through the active devices, without resorting to any additional passive circuitry. As a proof of concept, two $1 \times 5$ active array antenna prototypes are developed and fabricated at 5 GHz: one for broadside radiation with a sidelobe level of less than −20 dB requirement, and the other for flat-top radiation beam between −10° and 30°. They are integrated with a $1 \times 5$ Wilkinson power divider that is designed for radiation pattern measurements, and the corresponding results agree reasonably well with the simulated counterparts and theory, thereby proving the developed concept. Such solutions demonstrate the inherent advantages of being low-loss, compact, and efficient, which are essential for the next generation of wireless systems.

For sustainable environment development in the countryside and rural tourism destinations, we must pay greater attention to acoustic environment management and rural soundscape planning. Field surv...

In Part I of this two-part work, we have presented the theoretical foundation and physical mechanism of the mode-selective transmission line (MSTL). This part is devoted to its excitation scheme, practical transition design, and experimental verification. The MSTL excitation is first explained by comparison with a conductor-backed coplanar waveguide (CBCPW). To produce the specific mode excitation, an ultrabroadband transition between CBCPW and MSTL is proposed. It has a tapered structure operating as a tapered-mode coupler, which supports smooth evolution from the fixed CPW mode of CBCPW to the frequency-dependent dominant mode of MSTL. This modal evolution along the transition is analytically treated based on a local normal mode theory. Couplings between the local normal modes are negligible as a result of gradual tapering, thereby effectively suppressing higher order modes in MSTL and sustaining a mode purity over an ultrabroad frequency range. For experimental demonstration purposes, back-to-back CBCPW-to-MSTL transition circuits are physically realized. The measured results are in agreement with the prediction, showing a return loss of 15 dB from 3 to 109 GHz; the single transition introduces a relatively low insertion loss of 1.84 dB at 100 GHz. The propagation characteristics of MSTL are also extracted from the measured S-parameters, which provides an excellent validation of the proposed structure.

Fibrous perovskite oxide has been the most promising cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its efficient mass and charge transfer. Herein, a core–shell fiber...

We present a multifilament current method (MFCM) incorporated with generalized sheet transition condition (GSTC) to simulate 2-D cylindrical metasurfaces with arbitrary cross sections. The GSTC casts in the form of an impedance-type boundary condition to relate the tangential fields on two sides of a cylindrical metasurface. The MFCM is subsequently introduced and formulated by employing the GSTC. The doublet-current unit, including both electric and magnetic filamentary sources, is introduced in order to capture both co- and cross-polarized scattered and transmitted fields from the GSTC characterized cylindrical metasurfaces. Three illustrative examples are presented to validate the proposed simulation technique. The behaviors of filamentary sources in terms of scattered field singularities and the ill-conditioning issue of the constructed matrix are also discussed in detail. In comparison to existing numerical methods, the proposed technique has its merits on simplicity and conciseness.

This article presents the generation scheme of picosecond (ps) pulses based on both step recovery diode (SRD) topology and nonlinear transmission line (NLTL) scheme with a focus on simultaneous rise and fall time compression. First, the SRD topology is suggested and investigated for manifesting the capability of pulse compression. The SRD solution is then integrated with different NLTL schemes for alienating and achieving rise or fall time compression in the ps regime. It is observed that single NLTL integration only sharpens the rising or falling edge at the same time. To overcome this challenge, two NLTLs having different diode polarities are then integrated with SRD topology-based ps pulse generator to compress rise and fall time simultaneously. The theory of NLTL is developed in each case, and based on it, the shortest rise and fall time is selected for the final design. Several parameters that are responsible for waveform distortion are also investigated in detail as well. Finally, we have fabricated four different pulse generators in which the first three only compress the rise time whereas the fourth one is responsible for both rise and fall time compressions. The overall pulse duration for the first three generators falls within 80–95 ps having different ringing levels and they are based on rise time compression only. The pulse duration for the fourth pulse generator is almost 25 ps having a detailed ringing level of −14.24 dB and full-width at half-maximum (FWHM) of 10.1 ps based on both rise and fall time compressions. Finally, all these pulse generators are compared with the state of the arts in the literature where they utilize different techniques for sharpening and the superiority of our proposed designs is provided. These generators will find their key role and will be the best candidates for ultra-wide band (UWB) radars for electromagnetic imaging and sensing applications, ultrafast electronic techniques including edge sharpening, future oscilloscopes, comb, or pulse generators, and geophysical exploration.

In this article, three frequency independent optical paths are designed and analyzed. A two-parabolic-mirror system and a four-parabolic-mirror system are studied and developed over 140–220 GHz to achieve precision complex permittivity measurements of a dielectric substrate. To achieve a wide plane wave zone for the center of the four-parabolic-mirror system, two 80-mm-length corrugated horns are designed and fabricated for the measurement systems. The Gaussicity of the corrugated horn is larger than 97.4%. For the multiple reflection model and direct wave model, two closed-form expressions of loss tangent are derived from the transmission parameters (insertion losses) of the measurement systems. Meanwhile, the resolution and uncertainty of loss tangent can be calculated according to the working frequency, the thickness of the wafer, the real part of the relative permittivity, and the $| {{S_{21}}} |$ measurement uncertainty. The complex permittivity of the Rogers/Duroid series PCB substrates, which are commonly used at microwave frequencies, and silicon wafers are measured in G -band.

This article introduces two-way broadband air-filled substrate integrated waveguide (AFSIW) isolated power dividers/combiners based on surface mounted absorbing materials. The proposed structures take advantage of the AFSIW multilayer feature. The absorber implementation is found highly tolerant of variations in dimensions and positioning. Three different power dividers/combiners topologies are analyzed theoretically, simulatively, and experimentally. The measurement results validate the broadband responses of the fabricated Ka-band demonstrators. The proposed power dividers/combiners are intended to exploit high-power AFSIW system on substrate (up to few hundred watts).

A generalized mesh-network equivalent model for a microstrip rectangular patch antenna (RPA), which is simple yet efficient is proposed, studied, and demonstrated in this article. The mesh-network equivalent model is established through the segmentation of RPA width and radiation parameters into $M$ sections, as well as the segmentation of RPA length into $N$ sections. A general design procedure to realize the mesh-network equivalent model is addressed and described for any number of RPA segmentations, as desired by specific applications. Subsequently, the proposed mesh-network equivalent model is used to accurately evaluate the input impedance responses at various feed positions along the length of RPA. In addition, to include the effects of a slot etched inside the RPA geometry, a generalized microstrip coupled line equivalent model is proposed, analyzed, and discussed in detail. Eventually, the microstrip coupled line model in conjunction with the proposed mesh-network equivalent model can accurately estimate the input impedance response of a slotted RPA, and has been verified for RPA with center slot, edge slot, and multiple slots as examples in this work. Two cases with multiport excitation of RPA are also analyzed and presented as a part of this work. For demonstration purposes, all these prototypes are designed, fabricated, and measured at 28 GHz. The proposed equivalent model-based results are validated by measured and simulated counterparts. Furthermore, the extension of the proposed mesh-network model to accommodate slots of smaller size inside RPA, RPA loaded with via, inverted-F antenna, and multimode operation are demonstrated and discussed through a comparison between mesh-network modeling results and simulation results.

Emerging and disruptive information and communication technology (ICT) RaD is principally driven by the growing needs of signal generation, collection, transmission, processing, and storage as well as the applications of massive data sets in our fast-evolving information society. Such data set-related operations call for fundamental wireless- and wireline-empowered capabilities as well as many others. The next breed in ICT is closely related to, and enabled on a large scale by, the much-publicized 5G and future heterogeneous wireless systems [1]-[4], which in the future will connect everyone and everything at different speeds for various functions and services. This will propel us toward a much more connected, smarter world.

Coal gasification technology is a very important industrial technology, in which the Radiant Syngas Cooler (RSC) plays a pivotal role in the heat storage and heat recovering process. Ash deposit in RSC is a critical factor which may seriously affect the performance of RSC or even result in a shutdown. Therefore, conducting research on the deposit process of RSC is extremely worthwhile. In this study, we create an RSC model with the application of an optimized Critical Velocity Model (CVM) and perform simulations using the CFD method. With the simulating method, we conduct a series of analysis to obtain a more detailed description of the ash distribution and heat transfer in the RSC. Research shows that the CVM proposed in this paper can be precisely applied to the heat transfer process in a RSC, and not only can this method obtain the distribution of ash deposit similar to other methods but also determine the conversion of the ash deposit thickness to heat resistance, which makes the forecast of the overall heat exchange more accurate. According to the study, the ash thickness changes with the vertical height of RSC. For the division wall and panels, the ash thickness increased from the bottom, and then reached a maximum value at about 2/3 of total height. Under the influence of ash deposition, the total heat transfer rate of RSC decreased by 10.4%, and the outlet temperature of syngas increased by 5.7%. This result can provide a reference for the predictive analysis of RSC.

Mode-selective transmission line (MSTL) has been studied and realized in support of ultrabroadband and ultrafast electromagnetic signal guidance. Its operation is based on the fact that its dominant mode behaves as a quasi-TEM microstrip mode at low frequencies and is gradually converted into a quasi-TE10 waveguide mode at higher frequencies notwithstanding its longitudinal uniformity. In the first part of this work (Part I), the physical mechanism of the frequency-dependent modal behavior is presented. From the viewpoint of mode coupling, MSTL is heuristically considered as a coupled system consisting of one microstrip line and two half-mode substrate-integrated waveguides (HM-SIWs). Coupled-mode theory and normal-mode analysis are combined to sequentially analyze HM-MSTL, a relatively simple case, and MSTL. The coupled-mode theory provides an approximate representation for the normal modes of each coupled system, thus gaining in-depth physical insight into the MSTL mode-guidance behavior. A comparison between approximate fields derived from the theoretical analysis and exact fields extracted from the rigorous numerical simulation is made to support the modal analysis. A parametric study is then carried out to examine the effect of geometrical parameters on the MSTL characteristics and performance, thereby providing meaningful guidance in the MSTL design and optimization. A further discussion of mode selectivity is given at the end of this article.

In this work, directly perforated substrate integrated waveguides (SIWs) in the form of periodic air holes are studied with a focus on the electromagnetic shielding effect by examining its bandpass and stopband filtering characteristics. Two different configurations of the air-filled holes are considered for this electromagnetic bandgap structure, which are called shielded and unshielded cases. In both the scenarios, the relationship between the center frequency of the bandgap and the structural material and geometric parameters is established and used for the bandgap investigation. In addition, the impact that the shielding of the air-filled holes yields on the loss of the structure is systematically examined. Finally, equivalent circuits for both the cases are formulated and experimentally verified up to 30 GHz.

In this article, a densely integrated and unified paralleled amplifier and antenna architecture is proposed and demonstrated for next-generation millimeter-wave (mmW) and terahertz (THz) front-end modules. It makes use of topologically paralleled transistors cohabitated within a compact rectangular patch antenna (CRPA) as a unified cell. This design simultaneously amplifies and radiates power without resorting to any power divider, input and output matching networks, or power combiner whatsoever, therefore, greatly reducing front-end loss, size, and complexity. Then, the unified unit cell is self-consistently distributed to form a unified planar array with active elements between array elements as power feeders. In this demonstration, the input power is sequentially amplified, radiated through each array element, and spatially added up, resulting in low on-board circuit losses and efficient radiation. In this article, we investigate and present challenges and early results of implementing this unification concept of active circuitry and antenna at mmW frequencies. Using a standard 65-nm CMOS process, a set of chips were designed, fabricated, and tested under different amplifier biasing conditions at 146 GHz for experimental demonstration. The realized low-loss, matched, and compact unified prototypes have demonstrated an amplified radiation, with power enhancement of 3.4 dB through single element and 6 dB through $2 \times 2$ layout compared to their respective passive counterparts. Moreover, frequency tuning is observed varying drain bias and self-matching is improved with increasing gate bias. Therefore, the feasibility of a unique feature in the architectural implementation of low-loss, compact, and densely integrated and topologically cohabitated mmW and THz front-end modules is confirmed.

Hydrothermal treatment for dairy manure into value-added hydrochar and bio-oil is a potential technology for its resource utilization. During the process of treatment, extractant is applied to the separation of hydrochar and bio-oil. In this study, three polar extractants (ethyl acetate, dichloromethane, diethyl ether) and two nonpolar extractants (n-hexane and petroleum ether) were used, and the physico-chemical properties of hydrochar and the composition of bio-oil were investigated. Compared with nonpolar extractants, polar extractants could extract the bio-oil absorbed on the hydrochar exterior and interior surface, resulting in more mass loss of hydrochar and better extraction performance on the production of bio-oil. The decrease of H/C atomic ratio and the increase of O/C atomic ratio indicated the demethanation tendency to occur during the extraction process, and enhanced the hydrochar stability. The scanning electron microscope and specific surface area analysis revealed that polar extractant had a more positive effect than nonpolar extractant on the occurrence of disperse spherical microparticles and the augment of hydrochar specific surface area. The bio-oil from polar extractant mainly consisted of N-containing compounds, ketones, phenols and acids, while the bio-oil from nonpolar extractant mainly consisted of esters, alkanes and aromatics. These results reveal that the hydrochar extracted by polar solvent exerts a greater potential for the production of carbon-based material.

The TM shielding effectiveness (SE) analyses of slotted carbon fiber reinforced polymer (CFRP)-based shells are presented in this letter. The multifilament doublet current method (MFDCM) is deployed to simulate the scattered and penetrated fields in the considered situation. The inner and outer regions of a slotted shell are separated by a hybrid boundary, which contains the material and slot parts. The material part is constituted of multilayered CFRP materials, whereas the slot part is a virtual boundary. A tensorial boundary condition (TBC) is then constructed to stand for the slotted shell with a chain matrix. The MFDCM is subsequently formulated by employing the TBC to estimate the EM performances of interests. Different slot angles of the shell and conductivity of the CFRP material are considered in our numerical calculations. Only transverse magnetic (TM) case is considered herein, yet the transverse electric (TE) situation can be handled straightforwardly with a similar formulation.

A particle-resolved study of a collision system composed of heavy particles and light particles in a homogeneous isotropic turbulence has been performed. Direct numerical simulations (DNS) of this system were conducted using lattice Boltzmann method (LBM). The effects of hydrodynamics on the collision particles were accounted by directly resolving the flow around finite-size particles with an interpolated bounce-back scheme. A large-scale stochastic forcing scheme was implemented within the mesoscopic multiple-relaxation-time LBM approach to maintain turbulence intensity at targeted levels. Both kinematic and dynamic collision kernels were evaluated to study the correlation of total collision events and turbulent kinetic energy (TKE) dissipation rate. The results show that collisions between particles increase with the increase of TKE dissipation rate as radial relative velocities between particles increase with it. It is found that the dynamic collision kernels do not match with the kinematic collision kernels which is derived from point-particle method. Quantitatively, they were approximately 4 to 10 times smaller than the corresponding dynamic collision kernels. Therefore, it is not reasonable to estimate the kinematic collision kernel in particle-resolved simulations as its rationales are not valid. However, the collision behavior can still be accounted for by means of the dynamic collision kernel since it is obtained from the direct statistical analysis of the collision events.

This study presents a 3D Discrete Element Method (DEM) model for the progressive failure analysis of Carbon Fiber Reinforced Polymer (CFRP) composite materials subjected to uniaxial tensile loading. Particles in the model are packed and bonded in regular patterns (hexagonal or square). The relationship between the bond stiffness and material properties is established based on the average strain energy method. The random distribution of bond strengths calibrated from experiments with a variation of 30% and 10% following a normal distribution law is assigned to the bonds in 0∘ and 90∘ plies to capture random cracks, respectively. Tsai-Hill failure criterion is utilized for the calibration of bond strength of [Formula: see text] plies to predict their failures in composite laminates. Quantitative and qualitative analyses were conducted for predicting the damage initiation and propagation of the cross-ply and Quasi-Isotropic (QI) composite laminates under tensile loading, respectively. Two interface stiffnesses were utilized in the failure prediction of cross-ply composite laminates, and it was found that the numerical results with the interface stiffness calculated from fracture energy are in good, quantitative agreements with the experiments. All the four stages of the failure process of QI composite laminates are well captured by the 3D DEM model, including isolated cracks, inner delamination cracks, outer delamination cracks and final failure.

Ambient power rectifiers are pivotal for batteryless or self-powered internet of things architectures and self-sustained communication/sensor platforms. The core of rectifiers, a nonlinear device, has been subject to significant research and improvements recently, especially at a low-power level, where rectifying efficiency is so limited. Current responsivity (the key rectification parameter describing the nonlinearity) is known to be impacted by the operating temperature, as predicted by William Shockley's law. However, no work has been carried out to quantify the impact of temperature in the RF rectification process, nor to relate existing diodes with their optimum operating temperature range. To address those missing links, this article first develops an analytical method to predict power conversion efficiency (PCE) of rectifiers from approximate milli-watt down to nano-watt level. Next, it identifies the optimum operating temperature of rectifiers corresponding to peak PCE. It also reports that the previous PCE ceiling of 15% (at an input power level below -30 dBm) can be broken when rectifiers operate at their optimum temperatures. Enhanced PCE results are then validated experimentally on SMS7630 and HSMS-2850-based rectifiers when operating at their optimum temperatures. Noticeably, the SMS7630-based rectifier delivers efficiency of 17.5% at -30 dBm and 41.7% at -20 dBm, showing respectively comparable and better PCE than that of tunnel diode-based counterparts at similar power levels. This article also indicates that rectifier design should consider the operating temperature when selecting diodes to maximize rectifying potential.

The age of central Yunnan fragment uplift has long been debated, with estimates ranging from the Late Eocene to about 1 Ma. To determine the central Yunnan fragment uplift time in the Cenozoic, apatite (U-Th)/He (AHe) was used to analyze the low-temperature thermochronology of samples from the Jiaozi Mountain area of the eastern central Yunnan fragment. The sampling area is located in the Dongchuan District of Kunming, Yunnan Province, near the Xiaojiang fault zone. The results show that AHe ages from the eastern part of central Yunnan fragment were mainly concentrated around 25.7–37.9 Ma, and intensive uplift had happened before 36.5 Ma. Together with previous low-temperature thermochronology research on the western and eastern central Yunnan fragment, we concluded that the Yunnan Plateau uplifted prior to 36.5 Ma, in a west to east sequence. The uplift caused a change in paleo-geographical terrain, which may have altered the ancient river systems of the southeast Tibetan Plateau.

In this article, the concept of radiative bandpass filter (RBPF) is proposed and investigated for developing a class of multifunctional filtering leaky-wave antennas (LWAs) which exhibit the simultaneous rapid frequency-dependent beam-scanning and frequency-selective characteristics. A substrate-integrated waveguide (SIW) is periodically loaded with closed (nonradiative) discontinuities acting as a bandpass filter, where the lower and higher stopbands are, respectively, stemmed from the SIW natural cutoff and the Bragg effect bandgap or bandstop caused by periodic discontinuities. By adequately adjusting the periodicity of filter unit cells and loading effects of closed discontinuities, filtering and dispersion behaviors of the periodic SIW can be flexibly engineered. Open (radiative) discontinuities are then deliberately introduced into the bandpass filter to generate a controllable radiation leakage, thereby accomplishing the design of the RBPF, i.e., the proposed LWA. With this concept, both filtering/dispersion and radiation tasks can be independently managed by different modules for LWAs. For demonstration purposes, two kinds of closed discontinuities, namely nonradiative longitudinal slot-pair (capacitive) and iris (inductive), are separately exploited for periodic SIWs with bandpass and high dispersion characteristics, whereas transverse slot (open discontinuity) is mainly aimed for radiation leakage. Two RBPF-based LWAs are simulated, fabricated, and measured. The simulated and measured results are in a reasonable agreement, and both demonstrate the rapid beam-scanning and filtering behaviors, thereby validating the proposed concept.

With the high spectral resolution, hyperspectral image (HSI) can provide a wealth of information for image classification. Many classification methods utilize the training samples to classify the ground materials. However, the small sample problem is still urgent to be solved when considering the cost of labeling training samples. In order to solve this problem, this letter proposes a semisupervised classification method based on the simple linear iterative cluster (SLIC) segmentation for HSI. This method improves the SLIC method to better explore the spectral characteristic of HSI. It explores the learned superpixel map and initial classification map to select the pseudo-labeled samples (PLSs), which is expected to increase the effectiveness of PLSs. The final classification map can be obtained with the integrated labeled training samples and PLSs. Experiments were carried out on three HSIs, and it was founded that the proposed method generally shows a better classification performance than the other methods.

An expression for the propagation constant, cutoff frequency, and associated fields of the first two modes in a waveguide filled with a tilted slab of the dielectric is derived using the variational analysis. The solution to such a problem is divided into two parts. First, the slab is assumed to be parallel with the walls of the waveguide with no tilt. In this part, the effective permittivities of the first two orthogonally polarized modes are derived from two different variational expressions for the transversal resonance frequencies. This results in a diagonal tensorial permittivity that represents an effective uniaxial anisotropic medium. Next, this tensorial permittivity is transformed into a tilted set of coordinates representing the required tilt angle. In the new set of coordinates, a variational expression for the propagation constant is solved using the Rayleigh–Ritz procedure. The resulting analytic expressions are verified using a full-wave analysis and a prototype measurement.

The flexible and conductive carbon dots (CDs)/MXene films with zero-dimensional (0D)/two-dimensional (2D) dot-sheet motif architectures are successfully fabricated via the Coulombic interaction between negatively charged Ti3C2Tx MXene nanosheets and positively charged CDs synthesized from biomass by a green and economic one-pot hydrothermal process. The interlayer spacing coupled with the type and content of doped heteroatoms of the hybrid films can be regulated by the selected CDs with various particle sizes and heteroatoms. These CDs/MXene films with enlarged interlayer spacing and doped heteroatoms accelerate the ion diffusion and charge transfer. The optimized freestanding film electrode from pomelo juice with suitable layer spacing and profuse heteroatom doping indicates a high volumetric capacitance of 984.5 F cm–3 at a scan rate of 2 mV s–1, and a excellent volumetric energy density of 19.42 Wh L–1 is obtained in the corresponding assembled asymmetric supercapacitor. This study sheds light on a facile self-assembly route to fabricate multitudinous low cost and high-performance flexible MXene-based electrode.

Calcium sulfoaluminate cement (CSA) is a low-carbon cementitious material that significantly reduces alkalinity and produces calcium hydroxide-free (CH-free) matrix environment in comparison to ordinary Portland cement (OPC). It might be, however, less efficient towards the passivation of steel in concrete and further investigation before widespread adoption is required. In this project, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) on polished samples was employed to provide the interfacial characterization of steel reinforced CSA concrete and study the relationship of interfacial quality and corrosion resistance of the embedded steel. The galvanostatic polarization behavior indicates that the steel embedded in CSA concrete remains passive for 28 days in absence of Cl− ions and carbonation. Microstructure analysis has shown that there is an Al-enriched layer at interfacial zone in CSA concrete with the main hydration product of AH3, which is also alkaline and is expected to improve the steel passivity. Furthermore, the interfacial zone has markedly reduced porosity compared to the bulk matrix, which leads to reduced possibility of current flow between anode and cathode and therefore improves the corrosion resistance of the embedded reinforcement.

In this letter, a class of rectangular waveguide filters with central-post resonators is introduced. By introducing a central post in an oversized rectangular cavity, the resonant frequency of TE301-mode can be brought close to that of TE201-mode. The two resonant modes are coupled to adjacent fundamental mode resonators by inductive irises. A doublet coupling topology can be used to model the physical configuration, and flexible filter responses with finite-position transmission zeros (TZs) can be realized. Four 4-pole filters with different TZ positions are designed and simulated. A seven-pole filter with two cascaded central-post resonators is fabricated and measured. In the seven-pole filter, each central-post resonator independently controls one TZ on the lower side and very close to the passband. The measurement results of the seven-pole filter agree with the simulated counterparts very well, thus validating this filter design technique.

Loading effects of radiating discontinuities have been explored to increase the phase constant’ frequency sensitivity of leaky-wave antennas (LWAs), based on which a quasi-uniform transversely slotted substrate integrated waveguide LWA featuring rapid beam-scanning and its hexagonal array have been proposed and investigated for millimeter-wave applications. The design concept is simply based on the use of a short period of unit cells and a long transverse slot with a sharp inductive reactance, and it has been theoretically elaborated and effectively validated by both full-wave and circuit-based simulations. A taper design with −25 dB Taylor amplitude distribution is implemented for the proposed LWA to have a low sidelobe radiation. For practical system applications, a hexagonal array consisting of six proposed LWAs is developed to provide an omnidirectional coverage in the azimuth plane while remaining the rapid frequency-driven beam-scanning in the elevation plane. Both the measured and simulated results are in an acceptable agreement with respect to the LWA block and the associated hexagonal array in terms of circuit and radiation performances. The proposed antenna will be a good candidate to be applied for prospective millimeter-wave systems such as autonomous driving and flying.

A dual-band filter of a large frequency ratio is proposed, studied, and developed in this article, which is based on mode composite coplanar waveguide (MCCPW). Both low and high bands of the dual-band filter can be designed independently with a high degree of design freedom. The filter can achieve more than ten times the frequency difference between the two bands, which is usually hard to accomplish by conventional dual-band filter design techniques. All harmonics between the two bands can be suppressed by a cascaded low-pass filter and impedance matching structure to form a qualified dual-band frequency response. The characteristic of the proposed MCCPW dual-band filter makes it a promising candidate for multiband systems, especially in 5G communication systems. The demonstrated MCCPW dual-band filter is fabricated with a single-layer substrate. Measured results are in good agreement with simulated results, which validate the feasibility and superiority of the proposed filtering technique.

In this article, a class of mode composite transmission line called mode composite sandwich slot line (MCSSL) is proposed, studied, and demonstrated. The MCSSL is composed of two substrate integrated waveguides (SIWs) and a sandwiched quasi-slot line. Structural parts of the two SIWs inherently serve as the two conductors of the quasi-slot line. The SIW supports the TE10 fundamental mode propagation, whereas the quasi-TEM mode is supported by the quasi-slot line. Two types of transition structures are proposed in this article, which enable an easier integration of the studied MCSSL with other transmission lines. An MCSSL-based antenna is designed and fabricated to theoretically and experimentally demonstrate its advantages and feasibility. It has been shown that the MCSSL features the physical and electrical characteristics of a joint structure (or structure sharing) in connection with a mode composite with planar structures, and it can find applications in broadband and multiband circuits and antenna developments.

Exploring cost-effective catalysts with high catalytic performance and long-term stability has always been a general concern for environment protection and energy conversion. Here, Au nanoparticles (NPs) embedded CuOx-CeO2 core/shell nanospheres (Au@CuOx-CeO2 CSNs) have been successfully prepared through a versatile one-pot method at ambient conditions. The spontaneous auto-redox reaction between HAuCl4 and Ce(OH)3 in aqueous solution triggered the self-assembly growth of micro-/ nanostructural Au@CuOx-CeO2 CSNs. Meanwhile, the CuOx clusters in Au@CuOx-CeO2 CSNs are capable of improving the anti-sintering ability of Au NPs and providing synergistic catalysis benefits. As a result, the confined Au NPs exhibited extraordinary thermal stability even at a harsh thermal condition up to 700 °C. In addition, before and after the severe calcination process, Au@CuOx-CeO2 CSNs can exhibit enhanced catalytic activity and excellent recyclability towards the hydrogenation of p-nitrophenol compared to previously reported nanocatalysts. The synergistic catalysis path between Au/CuOx/CeO2 triphasic interfaces was revealed by density functional theory (DFT) calculations. The CuOx clusters around the embedded Au NPs can provide moderate adsorption strength of p-nitrophenol, while the adjacent CeO2-supported Au NPs can facilitate the hydrogen dissociation to form H* species, which contributes to achieve the efficient reduction of p-nitrophenol. This study opens up new possibilities for developing high-efficient and sintering-resistant micro-/nanostructural nanocatalysts by exploiting multiphasic systems.

To test the effect of Banxia Xiexin Decoction (半夏泻心汤, BXD) on the contraction and relaxation of gastric smooth muscle (SM) in diabetic gastroparesis (DGP) model rats, and to explore the mechanism of BXD in the prevention and treatment of DGP through experiments of signal pathway both in vivo and in vitro. Sixty Sprague-Dawley rats were divided into 6 groups according to a random number table: control group, model group, high-, medium- and low-dose BXD groups (9.2, 4.6 and 1.8 g/(kg·d), respectively), and domperidone group (10 mg/(kg·d)), 10 rats per group. DGP model was established initially by a single intraperitoneal injection of streptozotocin (STZ), and was confirmed by recording gastric emptying, intestinal transport velocity and gastric myoelectric activity of rats after 2 months. Each group was treated with a corresponding drug for 4 weeks. The mRNA and protein expressions of phospholipase C (PLC), inositol triphosphate (IP3), neuronal nitric oxide synthase (nNOS), and cyclic guanosine monophosphate (cGMP) dependent protein kinase G (PKG) were detected by reverse transcription-polymerase chain reaction and Western blot, respectively, while nitric oxide (NO) and cGMP expressions were detected by enzyme-linked immunosorbent assay. Gastric tissues were obtained from rats for primary cell culture preparation. Gastric SM cells were treated with 0.8 µmol/L of STZ or STZ plus 1,000, 500 and 200 µg/mL of BXD or STZ plus 2.5 µmol/mL of domperidone for 24, 48, 72 or 96 h, respectively. The length of gastric SM cells and intracellular Ca2+ concentration ([Ca2+]i) before and after BXD treatment was measured. Compared with the model group, high- and medium-dose BXD and domperidone significantly increased the expressions of PLC, IP3, NO, nNOS, cGMP and PKG in rat’s gastric tissue (P

Implementation of the multifilament current method (MFCM) to analyze the scattering from homogeneous anisotropic cylinders is introduced. The ${z}$ -directed electric and magnetic line sources are used to associate with TM and TE polarizations, respectively. The radiation fields of a line source in unbounded space occupied with an anisotropic material are derived in detail. With the help of the derived fields, the application of the MFCM is expanded to anisotropic materials. The scattering field is then obtained in terms of these line sources. Monostatic and bistatic scattering widths of cylinders with and without sharp edge are investigated under different incident wave polarizations and material characteristics. Apart from homogeneous anisotropic cylinders, the scattering from an anisotropic shell-coated PEC cylinder is also straightforwardly analyzed without additional considerations in the formulation. The oscillation phenomenon of filament currents in representing the scattered fields and the ill-conditioned issue of the constructed matrix are also discussed in detail. Numerical results obtained with this proposed scheme are also in good agreement with published ones, whereas the proposed technique has its merits on simplicity and conciseness in comparison to the existing numerical methods.

In this paper, an ambient power harvester with a single-diode device is proposed for simultaneously scavenging both radiofrequency (RF) and thermal energy in a mixed and cooperative manner. This cooperative harvesting process is theoretically examined through a proposed model of the diode and then validated by simulation and measurement. In the proposed cooperative power harvester, the harvested dc voltage from a thermal source is used to bias the diode for improving the diode's RF-to-dc power conversion efficiency (PCE). An accurate analytical model of the Schottky diode is developed for specifying the constraining parameters of RF-to-dc PCE and accurately predicting diode's performances in a low RF power range $({ \leq - \text{25}\;{\text{dBm}}})$ , respectively. The calculated results are found to be in a good agreement with the simulated ones obtained by the harmonic balance simulator in the advanced design system. For demonstration and validation, the proposed mixed cooperative power harvester is designed and prototyped on the basis of diode SMS7630. A total measured output dc power around 0.8 μ W is obtained with an RF-to-dc PCE around 33.4%, when the two injecting power sources at the diode are both −30 dBm. In addition, rectennas with and without a matching network are both fabricated and tested. By eliminating the L matching network, the rectenna is found to offer a higher dc output power. The proposed mixed cooperative power harvester is hoped to find potential real-world applications in an ambient atmosphere with RF coverage and temperature gradient. It not only helps to produce a higher power but also provides a reliable way of improving the resilience of dc power production.

This letter introduces stepped-impedance bandpass filters based on the slab air-filled substrate integrated waveguide (SAFSIW), which provides a compromise in terms of loss and footprint between substrate integrated waveguide (SIW) and air-filled SIW (AFSIW). First, the theoretical unloaded quality factor of the SAFSIW guided-wave structure is presented. Then, a design procedure of SAFSIW stepped-impedance bandpass filters is introduced. Finally, for demonstration purposes, a third-order Chebyshev filter, centered at 30 GHz, is synthesized, optimized, fabricated, and measured. With a low-cost FR-4 to enclose the structure, a return loss better than 15 dB with a minimum insertion loss of 0.99 dB in the passband is obtained in experiments.

A self-embedded power-recycling technique in microwave mixers is proposed and presented for radio frequency (RF) and microwave multiple-input multiple-output (MIMO) systems. The novelty of the proposed power-recycling technique stems from a distinct concept of harnessing direct current (dc) signal rectified by mixing elements in the course of a frequency translation. The large-signal model of a nonlinear mixing element coupled with electromagnetic simulations is used to understand and examine the contribution of the dc signal in the overall transceiver energy efficiency. A single-balanced (SB) diode-switching mixer integrated with a diplexer bank is prototyped using off-the-shelf components to validate the power-recycling technique, which can be extended for an IC implementation. The measurement results show that about 30% of the driving signal power is directly present in the form of a dc signal at the power-recycling port under the maximum conversion efficiency condition. Furthermore, wide linear instantaneous bandwidth performance is shown with a resistive termination of sum–product signal in a downconverter.

This letter presents the integration of multiple active devices output port directly with the antenna for simultaneous active frequency multiplication and radiation. This eliminates the circuitry losses at the multiplied output frequency, which points to a significant advantage of the proposed unified integration space in addition to size reduction. Furthermore, active devices are configured in parallel to enhance the power handling capability of this unified module. Initially, the rectangular patch antenna is analyzed and presented as a potential design space for simultaneously accomplishing efficient radiation, output matching, and fundamental frequency suppression. Subsequently, a procedure to achieve the circuit–antenna unification is described through a prototype operating as a 14–28 GHz frequency doubler using two paralleled transistors. The fabricated prototype realizes the maximum conversion gain of 9 dB and fundamental frequency suppression of 14 dB from measurements.