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This paper proposes compact and wideband crossover and monopulse comparator based on the new multi-layer vertical transition of substrate integrated waveguide (SIW). Through etching slot lines in the internal layers and arranging vias to connect the top and bottom layers of the stacked SIW, the transition structure can excite the TE10-like mode and stacked TE10-like mode, simultaneously. By properly designing the physical size of the transition, good transmission and isolation characteristics of the dual-layer SIW crossover and quad-layer monopulse comparator are readily achieved. Finally, two samples are fabricated for demonstration. The bandwidth and size of the proposed crossover are 28.6% and 10.5λg2, and that of the comparator are 20% and 12.05λg2, respectively. Compared with the conventional prototypes, the bandwidths of proposed ones increased by nearly 50% at comparable dimensions, especially the comparator, which has tremendous potential utilization value in multi-port multilayer SIW beamforming networks and radar tracking systems.

When light passes through air–glass and glass–water interfaces, refraction occurs, which affects the accuracy of stereo vision three-dimensional measurements of underwater targets. To eliminate the impact of refraction, we developed a refractive stereo vision measurement model based on light propagation paths, utilizing the normalized coordinate of the underwater target. This model is rigorous in theory, and easy to understand and apply. Additionally, we established an underwater simulation imaging model based on the principle that light travels the shortest time between two points. Simulation experiments conducted using this imaging model verified the performance of the underwater stereo vision measurement model. The results demonstrate that the accuracy achieved by the new measurement model is comparable to that of the stereo vision measurement model in the air and significantly higher than that of the existing refractive measurement model. This is because the light rays from the camera’s optical center to the refraction point at the air–glass interface do not always intersect. The experiments also indicate that the deviation in the refractive index of water lead to corresponding systematic errors in the measurement results. Therefore, in real underwater measurements, it is crucial to carefully calibrate the refractive index of water and maintain the validity of the calibration results.

There has been substantial research on multi-medium visual measurement in fields such as underwater three-dimensional reconstruction and underwater structure monitoring. Addressing the issue where traditional air-based visual-measurement models fail due to refraction when light passes through different media, numerous studies have established refraction-imaging models based on the actual geometry of light refraction to compensate for the effects of refraction on cross-media imaging. However, the calibration of refraction parameters inevitably contains errors, leading to deviations in these parameters. To analyze the impact of refraction-parameter deviations on measurements in underwater structure visual navigation, this paper develops a dual-media stereo-vision measurement simulation model and conducts comprehensive simulation experiments. The results indicate that to achieve high-precision underwater-measurement outcomes, the calibration method for refraction parameters, the distribution of the targets in the field of view, and the distance of the target from the camera must all be meticulously designed. These findings provide guidance for the construction of underwater stereo-vision measurement systems, the calibration of refraction parameters, underwater experiments, and practical applications.

Abstract Blasting is widely used in mining, subway, demolition and groundwater-sealed tunnel, among them, the last one is widely concerned because of its many adjacent tunnels, high anti-seepage requirements, strict blasting control, etc. The identification of blasting characteristics is of great significance to the blasting construction and the safety evaluation of the groundwater-sealed tunnel. In view of the problem that conventional feature identification methods are less explored in groundwater-sealed tunnel, a complementary ensemble empirical mode decomposition with adaptive noise and multiscale permutation entropy and Hilbert–Huang transform (HHT) method was proposed. Then, the proposed method was verified by the numerical simulation and the Huangdao groundwater-sealed tunnel engineering. The results show that the proposed method can suppress modal aliasing and signal noise and identify the blasting characteristics of groundwater-sealed tunnel effectively. In addition, the blasting vibration energy which accounts for 94.7% in the frequency range of 0–200 Hz, 72.5% of 0–50 Hz was summarized. Furthermore, the safety status of each monitoring point was evaluated through HHT and the feasibility of millisecond blasting was identified. The method proposed can identify the vibration characteristics and safety status of groundwater-sealed tunnel from the perspective of time–frequency and energy effectively.

Bridges may undergo structural vibration responses when exposed to seismic waves. An analysis of structural vibration characteristics is essential for evaluating the safety and stability of a bridge. In this paper, a signal time-frequency feature extraction method (NTFT-ESVD) integrating standard time-frequency transformation, singular value decomposition, and information entropy is proposed to analyze the vibration characteristics of structures under seismic excitation. First, the experiment simulates the response signal of the structure when exposed to seismic waves. The results of the time-frequency analysis indicate a maximum relative error of only 1% in frequency detection, and the maximum relative errors in amplitude and time parameters are 5.9% and 6%, respectively. These simulation results demonstrate the reliability of the NTFT-ESVD method in extracting the time-frequency characteristics of the signal and its suitability for analyzing the seismic response of the structure. Then, a real seismic wave event of the Su-Tong Yangtze River Bridge during the Hengchun earthquake in Taiwan (2006) is analyzed. The results show that the seismic waves only have a short-term impact on the bridge, with the maximum amplitude of the vibration response no greater than 1 cm, and the maximum vibration frequency no greater than 0.2 Hz in the three-dimensional direction, indicating that the earthquake in Hengchun will not have any serious impact on the stability and security of the Su-Tong Yangtze River Bridge. Additionally, the reliability of determining the arrival time of seismic waves by extracting the time-frequency information from structural vibration response signals is validated by comparing it with results from seismic stations (SSE/WHN/QZN) at similar epicenter distances published by the USGS. The results of the case study show that the combination of dynamic GNSS monitoring technology and time-frequency analysis can be used to analyze the impact of seismic waves on the bridge, which is of great help to the manager in assessing structural seismic damage.

AbstractThe feature extraction of blasting and natural earthquake waves can effectively discriminate between the two, and is conducive to mastering the time–frequency distribution and failure mechanism. However, feature extraction and discrimination between the two are often subject to external interference. A complete ensemble empirical mode decomposition and multiscale permutation entropy and Hilbert–Huang transform method is proposed to extract features and discriminate for blasting and natural earthquake waves efficiently and accurately. Firstly, the simulation signals verify feasibility and applicability. Secondly, six scenarios for blasting and natural earthquakes are collected and compared. Thirdly, feature extraction and discrimination are performed. Results show that the proposed method can extract and discriminate features between the two effectively. Furthermore, the energy of the former is concentrated within 200 Hz, while the latter is within 3 Hz, and different scenarios or magnitudes have different characteristics. Moreover, the blasting earthquake has features such as short duration, peaks corresponding to the blasting initiation time and fast energy attenuation. The natural earthquake has features such as long duration, multiple peaks, and slow energy attenuation, resulting in more significant harm. This method can extract features and discriminate for blasting and natural earthquake waves from the perspective of time–frequency and energy effectively.

Abstract Driven by the urgent need for adaptive infrared (IR) electrochromic devices, the improvement in electrochromic performance based on polyaniline (PANI) conducting polymers has become an outstanding challenge. In recent years, the acid doping strategy has been proven to increase the IR modulation ability of PANI, in particular for the Bronsted acid doping. Herein, the effects of copper ions, a Lewis acid, on the structure and electrochromic properties of polyaniline were investigated. Compared to pure polyaniline, the Cu-doped PANI porous films show better IR modulation ability. With the increasing concentration of copper ions, the Cu-doped PANI porous films exhibit a trend in volcanic patterns for the emittance variation (∆ε), depending on the number of polarons and bipolarons. The optimal IR emissivity (ε) modulation obtained on Cu-doped PANI films shows the ∆ε modulation of 0.35 and 0.3 in the wavelength range of 8–14 µm and 2.5–25 µm, superior to previously reported pure sulfuric acid-doped PANI. Furthermore, a flexible IR electrochromic device was fabricated with the present Cu-doped PANI porous films. The modulation of the emittance variation varied between 0.513 and 0.834 (∆ε = 0.32 in ranges of wavelength 8–12 µm), suggesting the great potential for applications in military camouflage and intelligent IR thermal management. We believe that the results in this work will provide a novel perspective and avenue for improving the IR modulation ability of electrochromic devices based on polyaniline conducting polymers.

Abstract Due to the wide use of iron in all kinds of areas, the design and construction of direct, fast, and highly sensitive sensor for Fe3+ are highly desirable and important. In the present work, a kind of fluorescent MXene quantum dots (MQDs) was synthesized via an intermittent ultrasound process using N,N-dimethyl formamide as solvent. The prepared MQDs were characterized via a combination of UV–Vis absorption, fluorescence spectra, X-ray photoelectron energy spectra, and Fourier-transform infrared spectroscopy. Based on the electrostatic-induced aggregation quenching mechanism, the fluorescent MQDs probes exhibited excellent sensing performance for the detection of Fe3+, with a sensitivity of 0.6377 mM−1 and the detection limit of 1.4 μM, superior to those reported in studies. The present MQDs-based probes demonstrate the potential promising applications as the sensing device of Fe3+.

Abstract An accurate sensor to rapidly determine the glucose concentration is of significant importance for the human body health, as diabetes has become a very high incidence around the world. In this work, copper nanoparticles accommodated in porous carbon substrates (Cu NP@PC), synthesized by calcinating the filter papers impregnated with copper ions at high temperature, were designed as the electrode active materials for electrochemical sensing of glucose. During the formation of porous carbon, the copper nanoparticles spontaneously accommodated into the formed voids and constituted the half-covered composites. For the electrochemical glucose oxidation, the prepared Cu NP@PC composites exhibit much superior catalytic activity with the current density of 0.31 mA/cm2 at the potential of 0.55 V in the presence of 0.2 mM glucose. Based on the high electrochemical oxidation activity, the present Cu NP@PC composites also exhibit a superior glucose sensing performance. The sensitivity is determined to be 84.5 μA /(mmol.L) with a linear range of 0.01 ~ 1.1 mM and a low detection limit (LOD) of 2.1 μmol/L. Compared to that of non-porous carbon supported copper nanoparticles (Cu NP/C), this can be reasonable by the improved mass transfer and strengthened synergistic effect between copper nanoparticles and porous carbon substrates.

This paper proposes a dual-band linear polarization converter based on multi-mode metasurface. The converter consists of square-patch-resonator-based metasurface etched with cross-slot, which is beneficial to separate the degenerate modes of the patch resonator in the first band, as well as to generate additional resonant modes for the second conversion band. Different from the traditional method of using multiple resonators for dual-band polarization converters, the proposed one only utilizes one multi-mode resonator. Additionally, the two bands can be tuned relatively independently by appropriately changing the physical parameters of the resonator. To verify the design method, one sample is fabricated and measured. The proposed linear polarization converter works in the two frequency ranges of 3.16–3.52 GHz and 7.19–8.61 GHz with a polarization conversion rate (PCR) ≥ 90 %.

Camouflage plays a fundamental role in modern electrical confrontation. Two important elements of camouflage are camouflage colors and camouflage textures. Many methods were presented to extract the main colors of the background. However, there are few methods to extract the background textures at present. The traditional methods based on watershed segmentation or background contour segmentation are computationally complex and time-consuming, being difficult to meet the real-time requirements. In this paper, a camouflage generation algorithm based on rectangle blocks scrambling and Fuzzy C-Means (FCM) clustering method is proposed. The algorithm consists of three modules, namely (1) the rectangle blocks segmentation module, (2) the rectangle scrambling module, and (3) the extraction of background dominant colors. Firstly, the texture features of the background image are simulated by rectangle blocks segmentation and scrambling algorithm, which avoids the complex calculation process and the loss of textures information compared with traditional algorithms based on description operators for background textures extraction. Next, Fuzzy C-Means (FCM) method is used to extract the main colors of background image with high accuracy and fast speed. In addition, experiments show that the proposed algorithm reduces the computing time and presents better concealment effect by retaining the similar domain colors. Compared with the template traversal algorithm and the watershed segmentation algorithm, the proposed algorithm features reduced computing time by more than 50%, and an increased similarity between the generated texture and background texture to more than 90%.

The detection of chemical samples having close dielectric response is a big challenge as the detection principle is driven by the variations in the dielectric parameters of the investigated samples. In the current work, a new metamaterial-based sensor is designed and fabricated in order to be used for the detection of liquid chemicals in the frequency range from 8 to 12 GHz. Several designs were tested using genetic algorithm, which is embedded in the CST microwave studio, in order to optimize the desired dimensions of the resonator. The simulation and experimental results showed that the proposed sensor is working well to detect various liquids, including (i) clean and waste transformer oils, (ii) corn, cotton and olive oils, (iii) branded and unbranded diesels and (iv) aniline doped ethyl-alcohol and benzene doped carbon tetrachloride. This was made possible through the occurrence of a shift in the resonant frequency of about 250 MHz, 200 MHz, 250 MHz, 150 MHz and 50 MHz for the aforementioned samples, respectively. The sensing mechanism was interpreted through the surface current and electric field distributions. We believe that the proposed sensor is viable to be used in various applications including liquid chemicals detection and industrial applications.

Bridge dynamic monitoring based on GNSS has become an important means of monitoring bridge structure. GNSS dynamic monitoring signals are often overwhelmed by strong noises and multipath errors. Thus the conventional data processing methods such as Fourier transform, wavelet analysis, and others have poor denoising effect or obtain unconspicuous dynamic characteristics from weak vibration signals. To solve this problem, the present study proposes a new adaptive stochastic resonance method based on quantum genetic algorithm with known frequency as optimal parameter. Analyzing the simulation signals not only verifies the validity and scientificity of the method, but also analyzes its frequency extraction effect in the approximate error range of target frequency with different noise intensity. A notable bridge vibration frequency is obtained when the new method is applied to analyze the bridge dynamic monitoring data based on GNSS.

For ultra-long tunnels, the effective means of alignment and breakthrough accuracy optimization is to measure the gyro azimuths or transfer the coordinates of surface known points or the directions to the inside of the tunnel through vertical shafts or inclined shafts. Compared with bored tunnels, immersed tunnels have different engineering characteristics and construction environments, and have higher alignment control accuracy requirements. However, the immersed tunnel has no vertical shafts or inclined shafts that can be used for coordinate transfer to improve the measurement accuracy. In order to provide high-accuracy alignment control and breakthrough for long immersed tunnels, we put forward a new strategy after network stability analysis, and consistency analysis between the results of the element positioning system and the results of the control network. The results of the element positioning system are taken as constraints to improve the accuracy of the control network. The analysis on 100,000 simulations of a 20 km-long immersed tunnel shows that the accuracy of the last point pair of the traverse network with angle and distance observations is 60.8 mm, while the accuracy of the same point pair after adopting the new strategy in this paper is 11.8 mm. The results of a 7 km-long experimental traverse network show that the lateral breakthrough accuracy is improved by 73%. All of these indicate that the new strategy can effectively improve the measurement accuracy and the lateral errors can be kept at a small level. Following the new strategy, the high-accuracy alignment and breakthrough can be achieved for long immersed tunnels.

Magnetic nitrogen-doped carbon nanotubes have been recognized as promising microstructures for electromagnetic wave absorption, benefiting from the internal hollow structure, excellent electrical conductivity and easy functionalization. Herein, a new composite composed of the thin-wall carbon nanotubes coated with the cobalt nanoparticles (hereafter labelled as: Co@NCNTs) on the tip was designed and synthesized through high temperature pyrolysis process. Revealed by scanning electron microscopy and X-ray photoelectron spectroscopy, the geometric and electronic structures of product were susceptible to the carbonization temperature. With the multiple dielectric polarization relaxations, higher magnetism and good impedance matching, the flammulina velutipes-like Co@NCNTs-700 exhibited the strongest dielectric loss, magnetic loss and electromagnetic wave absorption performance. The minimum reflection loss value and effective absorption bandwidth was determined to be −21.0 dB at 4.96 GHz and 5.28 GHz, respectively, superior to the previous reports. Furthermore, the thickness is at 2 mm and the filler mass loading is only 10%. Therefore, our present Co@NCNTs materials will be an ultralight material as potential high-efficiency EMW absorber.

For large-area electronic applications, the mechanism of the leakage current in oxide-semiconductor thin-film transistors (TFTs) has become a critical issue. In this work, the impact of the irradiation location on the photo-leakage current of zinc oxide (ZnO) TFTs is investigated. The photo-leakage current of the ZnO TFTs is not only dependent on the light irradiation but it is also dependent on the parasitic capacitance between the drain electrode and the floating gate metal. The photo-leakage current of the source-half irradiation TFT is larger than that of the drain-half irradiation TFT. To explain this phenomenon, the profile of the electric potential and the electron concentration is analyzed by two-dimensional device simulation. It is found that the floating gate metal plays the dominant role in the photo-leakage current. This research provides insight into TFT structure optimization and high-performance TFT process development.

Laminated Ti3C2Tx MXene has been considered as a promising absorbing material. However, microwave absorption (MA) performance of single Ti3C2Tx MXene is always limited. The introduction of magnetic components has been proven to improve impedance matching and MA performance effectively. In this paper, a novel CoNi@Ti3C2Tx composites with various CoNi loading were in-situ fabricated via a simple and low-temperature hydrothermal method. By introducing different contents of CoNi nanoparticles, the electromagnetic (EM) parameters of CoNi@Ti3C2Tx composites are regulated to enhance magnetic loss and improve impedance matching. The CoNi@Ti3C2Tx composites with 40 wt% CoNi nanoparticles showed a strong reflection loss of −58.18 dB at 13.20 GHz as the thickness is only 1.55 mm and a broad effective absorption bandwidth of 5.68 GHz can be achieved. The superior MA performance can be attributed to natural resonance, multiple scattering and reflection of the laminated structure, dipole polarization and interfacial polarization. This low-cost, energy-saving and simple method is significative for microwave absorption applications of MXene-based composite materials.

The cost-effective copper (Cu) nanoparticles and core/shell derived architectures with novel physicochemical properties have received tremendous attention in recent years. Herein, the effect of nanoparticle geometry (including diameter and core/shell ratio) on optical scattering and absorption of Cu@C core/shell nanoparticles has been investigated through a combination of DDA-based simulation and experimental validation. Simulated results have shown that the localized surface plasmon resonance (LSPR) peaks of Cu@C core-shell nanoparticles present slightly blue-shift with the increase of core/shell ratio, the core/shell ratio play the dominant role in the shift of the LSPR peak. Moreover, scattering efficiencies factors are inclined to be increasing faster with particle size and core/shell ratio increase, corresponding to enhanced surface electric field intensity which originated from excessive electron concentration on the interface between Cu core and C shell. Finally, experimental optical absorption performance has been performed with the aim at confirmation of size-sensitive light scattering behaviors of Cu@C core-shell nanoparticles via metal organic chemical vapor deposition technology. Results have found that the light absorption coefficient of up to 99.4% could be achieved for nanoparticles with an average particle diameter of 10 nm, while 98.9% for 23 nm. Further decrease in diameter on the nanometer scale is demonstrated to promote optical absorption to a certain extent, which agrees well with simulated results. All these findings have demonstrated ultra-small Cu@C core-shell nanoparticle to be a promising candidate for efficient optical absorption, and are beneficial for design and development of Cu@C core-shell nanoparticles enabled optical-based devices.

In this work, a novel sensor based on printed circuit board (PCB) microstrip rectangular patch antenna is proposed to detect different ratios of ethanol alcohol in wines and isopropyl alcohol in disinfectants. The proposed sensor was designed by finite integration technique (FIT) based high-frequency electromagnetic solver (CST) and was fabricated by Proto Mat E33 machine. To implement the numerical investigations, dielectric properties of the samples were first measured by a dielectric probe kit then uploaded into the simulation program. Results showed a linear shifting in the resonant frequency of the sensor when the dielectric constant of the samples were changed due to different concentrations of ethanol alcohol and isopropyl alcohol. A good agreement was observed between the calculated and measured results, emphasizing the usability of dielectric behavior as an input sensing agent. It was concluded that the proposed sensor is viable for multipurpose chemical sensing applications.

Improvement in the antenna gain is usually achieved at the expense of bandwidth and vice versa. This is where the realization of this enhancement can be made through compromising the antenna profile. In this work, we propose a new design of incorporating periodic metasurface array to enhance the bandwidth and gain while keeping the antenna to a low-profile scheme. The proposed antenna was simulated and fabricated in order to validate the results in the operating frequency range from 10 MHz to 43.5 GHz. Computer simulation technology (CST) microwave studio software was used to design and simulate the proposed antenna, while LPKF prototyping PCB machine was utilized to fabricate the antenna. Results showed that the antenna generated a gain and bandwidth of 14.2 dB and 2.13 GHz, respectively. Following the good agreement between the numerical and measurement results, it is believed that the proposed antenna can be potentially attractive for the application of satellite communications in Ku-band electromagnetic wave.

A cross-shaped metamaterial absorber (CSMMA) has been introduced to integrate with two-layered polyurethane foam absorbers (PUFAs). By incorporating with CSMMA, microwave absorptive performance of the proposed PUFAs in 8–18 GHz has been remarkably improved for various oblique incident angles under the transverse electric (TE) and transverse magnetic (TM) waves. For the TE wave, the effective bandwidths of −10 dB reflection loss for the PUFAs incorporated with CSMMA increase by 0.85 GHz, 1.15 GHz, 1.25 GHz, 1.50 GHz and 1.70 GHz for 0°, 15°, 30°, 45° and 60°, respectively. As for the TM wave, the effective bandwidths of −10 dB reflection loss for the modified PUFAs by CSMMA rise by 0.85 GHz, 1.10 GHz, 1.20 GHz, 2.85 GHz and 2.90 GHz for 0°, 15°, 30°, 45° and 60°, respectively. The proposed PUFAs optimized by CSMMA could operate well at incident angles ranging from 0° to 60° for both TE and TM waves. In addition, the different variation rules of absorption peak intensity of CSMMA have been revealed through the magnetic field distributions under TE and TM waves. Results indicate that PUFAs combined with CSMMA can be utilized for microwave absorbers adapting to both TE and TM waves at various oblique incident angles. Keywords: Wide-angle absorption, Polyurethane foam, Metamaterial absorber, Electromagnetic field distribution

Abstract The detection of pruritic (itchy) stimuli is mediated by a variety of receptors and channels expressed by primary sensory neurons. The G protein-coupled receptor (GPCR) MRGPRD is selectively expressed by a subset of mouse non-peptidergic nociceptors and functions as the molecular receptor for the itch-inducing chemical β-alanine. However, the channels responsible for generating electrical signals downstream of MRGPRD remain unclear. Here, we found that a member of the canonical TRP channel family, TRPC3, is highly expressed in MRGPRD+ non-peptidergic nociceptors, raising the possibility of whether TRPC3 functions as a downstream channel in the MRGPRD signaling pathway. We tested TrpC3 null mice for β-alanine induced itch, and found that these mice exhibit normal responses to β-alanine. At the cellular level, calcium influx triggered by β-alanine is also unchanged in cultured DRG neurons from TrpC3 null mice compared to wild type. Together, our results demonstrate that mouse TrpC3 is dispensable for β-alanine-induced acute itch.

Incorporation of magnetic loss component is more favorable to high-performance microwave absorbing materials. In this paper, the NiFe2O4-decorated Ti3C2Tx MXene composites were synthesized by the in-situ chemical co-precipitation method. The magnetic NiFe2O4 nanoparticles were attached on the surfaces or inserted into the interlayers of Ti3C2Tx MXene. Interestingly, we reduced effectively complex permittivity and enhanced magnetic loss by increasing the NiFe2O4 content on Ti3C2Tx MXene. Stronger electromagnetic attenuation ability and preferable impedance matching property were achieved and considered to be responsible mainly for improving absorbing peaks as well as bandwidth of the NiFe2O4-Ti3C2Tx MXene composite. In particular, the NiFe2O4-Ti3C2Tx-20 sample exhibited an optimal effective absorption bandwidth (RL

Though impressive advances of the extension of effective working distance for magnetic resonant coupling wireless power transfer system have been made over past decades, their applications have been severely limited by the requirement of unidirectional coaxial distribution for the transmitter and receiver. In this paper, an omnidirectional magnetic resonant coupling wireless power transfer system is proposed. The cubic spiral transmitter requires only a single power source, and the receiver receives power in all directions. The power transfer efficiency of the system is derived through an equivalent circuit model. And an impedance matching circuit which includes a pair of parallel and series capacitors is proposed for better stability and higher efficiency. In addition, geometrical parameters of the single power driven spiral transmitter structure are optimized to improve distribution uniformity for different directions. Thus the power transfer efficiency of the system, which depends on the distance between the transmitter and the receiver, is almost the same for different receiving angles. Finally, the theoretical analysis is verified by practical experimental results, which shows the power transfer efficiency of 60% at 150 mm.

The microwave wireless power transfer (MWPT) technology has found a variety of applications in consumer electronics, medical implants and sensor networks. Here, instead of a magnetic resonant coupling wireless power transfer (MRCWPT) system, a novel MWPT system based on a frequency reconfigurable (covering the S-band and C-band) microstrip patch antenna array is proposed for the first time. By switching the bias voltage-dependent capacitance value of the varactor diode between the larger main microstrip patch and the smaller side microstrip patch, the working frequency band of the MWPT system can be switched between the S-band and the C-band. Specifically, the operated frequencies of the antenna array vary continuously within a wide range from 3.41 to 3.96 GHz and 5.7 to 6.3 GHz. For the adjustable range of frequencies, the return loss of the antenna array is less than −15 dB at the resonant frequency. The gain of the frequency reconfigurable antenna array is above 6 dBi at different working frequencies. Simulation results verified by experimental results have shown that power transfer efficiency (PTE) of the MWPT system stays above 20% at different frequencies. Also, when the antenna array works at the resonant frequency of 3.64 GHz, the PTE of the MWPT system is 25%, 20.5%, and 10.3% at the distances of 20 mm, 40 mm, and 80 mm, respectively. The MWPT system can be used to power the receiver at different frequencies, which has great application prospects and market demand opportunities.

In this work, a new design for a real-time noninvasive metamaterial sensor, based on a corona-shaped resonator, is proposed. The sensor was designed numerically and fabricated experimentally in order to be utilized for efficient detection of glucose in aqueous solutions such as water and blood. The sensor was inspired by a corona in-plane-shaped design with the presumption that its circular structure might produce a broader interaction of the electromagnetic waves with the glucose samples. A clear shift in the resonance frequency was observed for various glucose samples, which implies that the proposed sensor has a good sensitivity and can be easily utilized to distinguish any glucose concentration, even though their dielectric coefficients are close. Results showed a superior performance in terms of resonance frequency shift (1.51 GHz) and quality factor (246) compared to those reported in the literature. The transmission variation level ∆|S21| was investigated for glucose concentration in both water and blood. The sensing mechanism was elaborated through the surface current, electric field and magnetic field distributions on the corona resonator. The proposed metamaterials sensor is considered to be a promising candidate for biosensor and medicine applications in human glycaemia monitoring.

Immersed tunnel elements need to be exactly controlled during their immersion process. Position and attitude of the element should be determined quickly and accurately to navigate the element from the holding area to the final location in the tunnel trench. In this paper, a newly-developed positioning and attitude determination system, integrating a 3-antenna Global Navigation Satellite System (GNSS) system, an inclinometer and a range-measurement system, is presented. The system is designed to provide the absolute position of both ends of the element with sufficient accuracy in real time. Special attention in the accuracy analysis is paid to the influence of GNSS multipath error and sound speed profile. Simulations are conducted to illustrate the performance of the system in different scenarios. If both elements are very close, the accuracies of the system are higher than 0.02 m in the directions perpendicular to and along the tunnel axis.

When the dynamic characteristics of a bridge structure are analyzed though Hilbert–Huang transform (HHT), the noise contained in the bridge dynamic monitoring data may seriously affect the performance of the first natural frequency identification. A time-frequency analysis method that integrates wavelet threshold denoising and HHT is proposed to overcome this deficiency. The denoising effect of the experimental analysis on the simulated noisy signals proves the effectiveness of the proposed method. This method is used to perform denoising pre-processing on the dynamic monitoring data of Sutong Bridge, and the denoised results of different methods are compared and analyzed. Then, the best denoising data are selected as the input data of Hilbert spectrum analysis to identify the structural first natural frequency of the bridge. The results indicate that the wavelet-empirical mode decomposition (EMD) method effectively reduces the interference of random noise and eliminates useless intrinsic modal function (IMF) components, and the excellent properties of the signal evaluation index after denoising make the method suitable for processing non-stationary signals with noise. When Hilbert spectrum analysis is applied to the denoised data, the first natural frequency of the bridge structure can be identified clearly and is consistent with the theoretical calculation. The proposed method can effectively determine the natural vibration characteristics of the bridge structure.

Mass redistribution within the Earth system deforms the surface elastically. Loading theory allows us to predict loading induced displacement anywhere on the Earth’s surface using environmental loading models, e.g., Global Land Data Assimilation System. In addition, different publicly available loading products are available. However, there are differences among those products and the differences among the combinations of loading models cannot be ignored when precisions of better than 1 cm are required. Many scholars have applied these loading corrections to Global Navigation Satellite System (GNSS) time series from mainland China without considering or discussing the differences between the available models. Evaluating the effects of different loading products over this region is of paramount importance for accurately removing the loading signal. In this study, we investigate the performance of these different publicly available loading products on the scatter of GNSS time series from the Crustal Movement Observation Network of China. We concentrate on five different continental water storage loading models, six different non-tidal atmospheric loading models, and five different non-tidal oceanic loading models. We also investigate all the different combinations of loading products. The results show that the difference in RMS reduction can reach 20% in the vertical component depending on the loading correction applied. We then discuss the performance of different loading combinations and their effects on the noise characteristics of GNSS height time series and horizontal velocities. The results show that the loading products from NASA may be the best choice for corrections in mainland China. This conclusion could serve as an important reference for loading products users in this region.

Currently, the main remote sensing-based crop mapping methods are based on spectral-temporal features. However, there has been a lack research on the selection of the multi-temporal images, and most of the methods are based on the use of all the available images during the cycle of crop growth. In this study, in order to explore the optimal temporal window for crop mapping with limited remote sensing data, we tested all possible combinations of temporal windows in an exhaustive manner, and made a comprehensive consideration of the spatial accuracy and statistical accuracy as evaluation indices. We collected all the available cloud-free Sentinel-2 multi-spectral images for the winter wheat and rapeseed growth periods in the study area in southern China, and used the random forest (RF) method as the classifier to identify the optimal temporal window. The spatial and statistical accuracies of all the results were assessed by using ground survey data and local agricultural census data. The optimal temporal window for the mapping of winter wheat and rapeseed in the study area was obtained by identifying the best-performing set of results. In addition, the variable importance (VI) index was used to evaluate the importance of the different bands for crop mapping. The results of the spatial accuracy, statistical accuracy, and the VI showed that the combinations of images from the later stages of crop growth were more suitable for crop mapping.

Due to the drastic aerodynamic heating effect in supersonic aircrafts, the operational performance of wave-transmitting dielectric ceramics functionalized radomes strongly depends on the temperature and oxidation. In this paper, the evolution of microwave dielectric responses in Si3N4 ceramics via gelcasting over a wide temperature range (25°C∼800°C) is investigated experimentally and theoretically. Specifically, the relative increment rate of real permittivity over evaluated temperature range is 4.46% at 8.2GHz and 8.67% at 12.4GHz, while the imaginary permittivity remains less than 0.06. Taking temperature-dependent polarized bound charge and damping coefficient into consideration, a revised dielectric relaxation model with Lorentz correction for Si3N4 ceramics has been established, which agrees well with evolution of experimental results. Furthermore, the best fitting results indicate that the activation energy of electrons Ea (15.46 ∼17.49 KJ/mol) is less than that of lattice Eb (33.29∼40.40 KJ/mol), which could be ascribed to the binding force between the electrons and nucleus is lower than covalent bonding force of lattice. Besides, excellent restorable feature of permittivity after heat-treatment lays a solid foundation for radome materials serviced in high temperature circumstances.

In this study, an approach using ground control point-free unmanned aerial vehicle (UAV)-based photogrammetry is proposed to estimate the volume of stockpiles carried on barges in a dynamic environment. Compared with similar studies regarding UAVs, an indirect absolute orientation based on the geometry of the vessel is used to establish a custom-built framework that can provide a unified reference instead of prerequisite ground control points (GCPs). To ensure sufficient overlap and reduce manual intervention, the stereo images are extracted from a UAV video for aerial triangulation. The region of interest is defined to exclude the area of water in all UAV images using a simple linear iterative clustering algorithm, which segments the UAV images into superpixels and helps to improve the accuracy of image matching. Structure-from-motion is used to recover three-dimensional geometry from the overlapping images without assistance of exterior parameters obtained from the airborne global positioning system and inertial measurement unit. Then, the semi-global matching algorithm is used to generate stockpile-covered and stockpile-free surface models. These models are oriented into a custom-built framework established by the known distance, such as the length and width of the vessel, and they do not require GCPs for coordinate transformation. Lastly, the volume of a stockpile is estimated by multiplying the height difference between the stockpile-covered and stockpile-free surface models by the size of the grid that is defined using the resolution of these models. Results show that a relatively small deviation of approximately ±2% between the volume estimated by UAV photogrammetry and the volume calculated by traditional manual measurement was obtained. Therefore, the proposed approach can be considered the better solution for the volume measurement of stockpiles carried on barges in a dynamic environment because UAV-based photogrammetry not only attains superior density and spatial object accuracy but also remarkably reduces data collection time.