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The aerodynamic noise behavior of flow passing the simplified leading car and nose car scale models of a high-speed train is investigated through the vortex sound theory and acoustic analogy approach. The unsteady flow developed around the geometries is solved numerically and the data are applied to study the near-field quadrupole sound source and calculate the far-field noise radiated. It is found that the turbulent flow developed around the leading car is characterized by multi-scale vortices separated from the geometries. The intensity of volume dipole source is much larger than that of volume quadrupole source and the volume dipole source becomes the predominate source of the near-field quadrupole noise. The flow is separated noticeably in the regions of the nose, bogies, bogie cavities, and train tail of the leading car where the pressure fluctuations are generated largely upon the solid surfaces and correspondingly a dipole noise of high level is produced. By comparison, the noise contribution from the leading bogie and bogie cavity is larger than that from the other components. Moreover, the numerical and experimental results of train nose car model demonstrate that the flow around the bogie region is the dominant aerodynamic sound source. Therefore, the flow-induced noise generated from the leading cars may be reduced efficiently within a certain frequency range and specific direction by mitigating the flow interactions around the areas of leading bogie and bogie cavity.

A mild crystallization approach to MOF@TiO2 core–shell nanostructures for the efficient adsorption and photodegradation of anionic dyes.

The antenna array arrangement determines the rank of the transformation matrix in 1-D mirrored aperture synthesis (1-D MAS). Only when the transformation matrix is of full rank can cosine visibilities be precisely solved from the transformation equations. However, the existing literature states that full rank cannot be realized with the default perpendicular polarization of antennas. In this letter, the transformation matrices of arrays with various polarizations of antennas are discussed, and a type of full array with a full-rank transformation matrix is found. Based on these results, the existence conditions for an array with a full-rank transformation matrix are obtained. In addition, a search algorithm with a shorter search time than the existing algorithm is designed to find low-redundancy arrays with a full-rank transformation matrix. The simulations verify that cosine visibilities are precisely solved from the transformation equations for the array with a full-rank transformation matrix.

In this letter, 1-D mirrored aperture synthesis with two tilted reflectors (1-D MAS-T) is proposed to improve the spatial resolution of an antenna array without extending its size. The principle of 1-D MAS-T is given. The size of the reflector is analyzed, and detailed calculation formulae is derived. Numerical simulations and experiments are carried out to illustrate the performance of 1-D MAS-T. The results demonstrate that 1-D MAS-T can achieve a higher spatial resolution than conventional aperture synthesis with the same antenna array.

Some recent research reports that a dendritic neuron model (DNM) can achieve better performance than traditional artificial neuron networks (ANNs) on classification, prediction, and other problems when its parameters are well-tuned by a learning algorithm. However, the back-propagation algorithm (BP), as a mostly used learning algorithm, intrinsically suffers from defects of slow convergence and easily dropping into local minima. Therefore, more and more research adopts non-BP learning algorithms to train ANNs. In this paper, a dynamic scale-free network-based differential evolution (DSNDE) is developed by considering the demands of convergent speed and the ability to jump out of local minima. The performance of a DSNDE trained DNM is tested on 14 benchmark datasets and a photovoltaic power forecasting problem. Nine meta-heuristic algorithms are applied into comparison, including the champion of the 2017 IEEE Congress on Evolutionary Computation (CEC2017) benchmark competition effective butterfly optimizer with covariance matrix adapted retreat phase (EBOwithCMAR). The experimental results reveal that DSNDE achieves better performance than its peers.

Mirrored aperture synthesis (MAS) has been proposed as a novel interferometry to achieve higher spatial resolution in passive microwave remote sensing. The phase and amplitude errors for MAS are a crucial problem that has yet to be analyzed. In this letter, a model for the phase and amplitude errors is established. A correction method based on an external source is proposed to correct the phase and amplitude errors. An analysis of the position of the external source is performed by computing its impact on the radiometric accuracy of a reference scene. The imaginary parts of the cross correlations for MAS are analyzed for the first time. Simulations and experiments are carried out to demonstrate the effectiveness of the correction method.

Based on the theory of friction self-excited vibration and the measured data of rail corrugation, the cause of rail corrugation in metro straight section was analyzed. Then, using the stochastic finite element method, the sensitivity of each parameter to rail corrugation was studied by selecting the elastic modulus E1 and density ρ1 of the wheel-rail material, the elastic modulus E2 and density ρ2 of the track slab material, the wheel-rail coefficient of friction f, the fastener vertical stiffness K and vertical damping C, the wheel-rail longitudinal relative slip s as the random parameters. The results show that under the support of Cologne egg fastener track, the characteristic frequency of friction self-excited vibration of wheel-rail system is close to the characteristic frequency of measured corrugation, indicating that the occurrence of rail corrugation is related to the friction self-excited vibration of wheel-rail system under the condition of saturated creep force. The parameter sensitivity analysis illustrates that the influence degree of each random parameter on the real part αi of complex eigenvalue is E1>ρ1>C>E2>ρ2>f>K>s in turn. E1, C and s are positively correlated with the real part αi of complex eigenvalue, while the remaining 5 parameters are negatively correlated with the real part αi of complex eigenvalue. Therefore, appropriate decrease of E1, C and s, and increase of ρ1, E2, ρ2, f and K can play a positive role in the control of rail corrugation.

In order to ensure the normal use of a junction section of a modern tram, this paper mainly studied a trackside concrete reinforcement scheme. Firstly, the entire non-reinforcement system model with a small radius curve composed of rail, fastener, fastener cover, flexible material, asphalt layer and track slab was established using the ABAQUS finite element software, and the stress distribution and deformation state of the asphalt layers of the non-reinforcement system model under the social vehicle load were analyzed. Then, the whole system model of the concrete reinforcement scheme was founded, and the stress and deformation of the asphalt layers under the same load were investigated. Finally, the calculation results of the concrete reinforcement model were com-pared with those of the non-reinforcement model, and the reinforcement effect was studied. The results show that the concrete reinforcement scheme significantly reduces the stress and deformation of the asphalt layers and improves the stress distribution and deformation state of the asphalt layers.

In this work, phosphor-converted white laser diodes (pc-WLDs) with high color quality were fabricated by combining blue lasers and bicolor phosphor-in-glass (PiG) converters. The bicolor PiGs were prepared by printing and sintering green/red phosphor glass films on sapphire substrates, and then applied in the transmission type of pc-WLDs. The PiG-based white laser diodes (WLDs) display broadband emission and their optical performances were adjusted by varying the PiG film thickness. When the film thickness increases from 80 to $160~\mu \text{m}$ , the luminous flux and correlated color temperature (CCT) of PiG-based WLDs are gradually decreased, and they still have high color rendering index (CRI). At the film thickness of $160~\mu \text{m}$ , the PiG-based WLD achieves high color quality with a CRI of ${R}_{a} = {88}$ , ${R}_{{9}} = {91}$ , and ${R}_{{13}} = {93}$ , a CCT of 4571 K, and a chromaticity coordinate of (0.3525, 0.3541) at a laser power of 2.4 W. Furthermore, the PiG-based WLD has stable color quality at high laser power and the luminous flux reaches to 553 lm at a laser power of 5 W. The results indicate that the bicolor PiG-based WLDs realize high-quality white light, which can promote the practical applications of laser lighting in high-quality fields.

By using the transient finite element method, a three-dimensional wheelset-track coupled rolling contact model for high-speed rail is established, and the rationality and effectiveness of the model are verified by field measurements. Next, the wheel-rail contact stress states and relative slip characteristics are calculated and analyzed to reveal the cause of inner rail corrugation. Then, the vertical vibration acceleration of the rail/wheel is taken as the output variable to study the dynamic responses of the wheelset-track system. Finally, the parameter sensitivity analysis is carried out. The results show that the maximum normal/tangential contact stress between the inner wheel and inner rail is greater than that between outer wheel and outer rail due to the unbalanced load of inner rail caused by the excess superelevation of track structure, which indicates that the unbalanced load of the inner rail may aggravate the development of rail wear, and the rationality of the model established in this paper is verified. The wheel-rail relative slip region on the inner rail side appears periodically, and the distance between the two adjacent slip regions is close to the characteristic wavelength of the measured inner rail corrugation, which illustrates that the periodic variation of slip regions on the inner rail surface plays an important role in the formation of rail corrugation, and the validity of the model is verified. The periodic distribution of wheel-rail relative slip regions on the outer rail surface is not obvious, demonstrating that the outer rail tends to form uniform wear, which is consistent with the fact that the outer rail corrugation is slight in the measured section. The wheelset-track system has been in the process of unstable continuous oscillation in the analysis interval, combined with the analysis results of the wheel-rail relative slip characteristics, it can be concluded that the unstable self-excited vibration of wheelset-track system under the condition of tangential contact force reaching saturation is the main cause of rail corrugation. The dominant characteristic frequencies of vertical vibration accelerations of rail and wheel are all 561 Hz, the corresponding characteristic wavelength (148 mm) is close to the distance (150 mm) between the calculated adjacent slip regions, and is also close to the characteristic wavelengths (125 mm and 160 mm) of inner rail corrugation, which shows that the resonance phenomenon occurs in the wheelset-track system at the above frequency, thus leading to the increase of dynamic responses of wheelset-track system. The fastener vertical stiffness and wheel-rail coefficient of friction have significant effect on the development of rail corrugation, and the running speed determines the occurrence probability of inner/outer rail corrugation by affecting the track superelevation state.

There are few systematic researches on the dynamic characteristics of a wheelset–track system under different corrugation excitations. To study the influence of different corrugations on the wheelset–track dynamic characteristics, a three-dimensional wheelset–track rolling contact model is established, and the model rationality is analyzed. Then, the wavelength and wave depth of the initial corrugation irregularity for simulation analysis are determined according to the measured data. Finally, the wheel–rail vertical force and wheel vertical vibration acceleration are selected as the output variables, and the wheelset–track dynamic responses under excitations are studied. The results show that comparing with the middle/long-wavelength irregularity, the short-wavelength irregularity will not increase the amplitude of wheel–rail dynamic action but will increase the frequency of wheel–rail dynamic action. The initial irregularity wave depth will not affect the frequency of wheel–rail dynamic action but will affect the amplitude of wheel–rail dynamic action, and the greater the amplitude of the wave depth is, the greater the impact on the dynamic responses of the wheelset–track system is. The main characteristic frequencies of output variables are close to the initial irregularity passing frequency, and the other peak frequencies are in a frequency multiplication relationship with the initial irregularity passing frequency.

Based on the metro vehicle-track spatial coupled model, the wheel-rail dynamic responses of tangential track under different composite corrugation irregularities and the development characteristics of composite corrugation irregularities were studied by simplifying rail surface composite corrugation irregularities into superimposed harmonic corrugations. The time domain analysis results demonstrate that the short wavelength corrugation irregularity has obvious influence on wheel-rail dynamic characteristics. The frequency domain analysis results show that the existence of rail corrugation will also lead to wheel-rail dynamic responses at higher frequencies. The wear frequency spectrum curves contain characteristic frequencies corresponding to wavelengths of composite corrugation irregularities, and the peak values are high, showing that composite corrugation irregularities are in the process of continuous development, and the development speed of shorter wavelength corrugation is faster than that of longer wavelength corrugation. The peak values of wear frequency spectrum curves also appear at frequency multiple points of passing frequencies corresponding to wavelengths of composite corrugation irregularities, which illustrates that corresponding wavelength corrugations can be easily formed. Meantime, rail corrugation has the trend of developing into short-wavelength corrugation.

In order to study the waterproof performance of non-curable rubber modified asphalt material at deformation joints, the grouting situation of non-curable rubber modified asphalt material in the def...

In 2-D mirrored aperture synthesis (2-D MAS), the array configuration determines the rank of the transformation matrix, which can affect the accuracy of the solved cosine visibilities. Ultimately, errors in solved cosine visibilities degrade the quality of reconstructed brightness temperature images. In this letter, the maximum rank of the transformation matrix is analyzed and proven by mathematical induction. An array optimization model of 2-D MAS based on the “maximum-rank” criterion is established, and optimal arrays are presented. Finally, the simulations and experiments are carried out to demonstrate the effectiveness of the optimization model.

Developing highly efficient and durable eco-friendly heterogeneous catalysts for the Friedel–Crafts acylation (FCA) reaction has been a long-term and significant target, yet remains a great challenge. Herein, a series of Fe–Ni alloy nanoparticles (NPs) encapsulated inside N-doped carbon spheres (FexNi1−x@NC) was rationally fabricated by pyrolyzing the Fe–Ni bimetallic metal–organic frameworks (BMOFs-FexNi1−x) to this end. Various characterization results demonstrated that FeNi alloy NPs (25 nm) covered by a thin carbon shell (5 nm) were uniformly distributed throughout the entire carbon-based composite. A number of oxidized metal species (Fe3+, Ni2+) are present on the surface of the inner bimetallic core, which should be the main source of catalytically active centers of the carbon-wrapped metal NP catalysts. The composition-optimized Fe0.8Ni0.2@NC with relatively higher positive surface charges exhibited the highest catalytic activity and excellent stability for the acylation of aromatic compounds with acyl chlorides. The density functional theory calculations revealed that the catalytic activity of the FexNi1−x@NC catalysts could arise from the electron transfer, i.e., from the outermost layer of the carbon shell to the inner positively charged Fe-based metal NPs, which can lead to a positive charge distribution (by acting as weak Lewis acid sites) on the external surface of the carbon-encapsulated metal NP catalysts. In this case, the external carbon shell can function as ‘chainmail’ to transfer the Lewis acidity (positive charge), and also to protect the inner metal core from the destructive reaction environment, thus resulting in the formation of highly efficient and durable FCA catalysts.

Noise generated by trains running on elevated lines creates many disturbances to the normal lives of surrounding residents. Investigations have shown that people living along elevated lines complain that the noise is sometimes unbearable. To better control the noise and optimize the acoustic environment, noise spectrum characteristics were analyzed and compared with a field test and a numerical simulation. Through an energy analysis of the noise on the bridge side, the energy distribution characteristics of the noise at specific measuring points in different frequency bands were obtained. The influence of the Doppler effect on frequency shift was analyzed. Based on the partial coherence theory, a multi-input and single-output program was compiled to calculate the correlation and contribution degree of the bridge structure-borne noise and wheel/rail noise at the one-third octave center frequency. The results show that the peak noises of the bridge and the wheel/rail are concentrated at 31.5`-63 Hz and 400`-800 Hz, respectively. For environmental noise on the bridge side, the frequency band above 250 Hz is mainly affected by the wheel/rail noise. In areas of noise source strength, the relative ratio of noise energy above 250 Hz can reach 83.4%. Noise in the near ground and far bridge area is mainly low-frequency, and the relative energy ratio is about 8.9%. The Doppler effect has an influence of less than 6% on the frequency shift with a speed of 67.9 km/h. In the low-frequency band below 250 Hz, the noise in the acoustic shadow area near the bridge and the ground is mainly contributed to by the vibration-radiated noise of the bridge, of which the contribution of the bottom panel is the most prominent. The noise in the comprehensive noise area of the far bridge is mainly caused by the structure-borne noise of the bridge, and the contribution of each bridge panel is different. This study can provide a reference for finding the source of elevated rail noise in some challenging frequency ranges and for then determining optimal designs and measures for noise reduction.

In order to investigate the causes and development characteristics of rail corrugation on the tangential section, based on the finite element model of track structure and the vehicle-track space coupled dynamic model, modal analysis and dynamic analysis were carried out for detailed analysis. The results show that the line condition and passing frequency range of measured corrugation are close to those of roaring rail corrugation caused by Pinned-Pinned resonance of track structure, so it is preliminarily considered that corrugation occurring on this section is roaring rail corrugation. The modal analysis of track structure model shows that the vibration mode at the frequency of 513.7 Hz is the transverse Pinned-Pinned resonance of track structure and the vibration mode at the frequency of 1050.0 Hz is the vertical Pinned-Pinned resonance of track structure. The dynamic analysis of vehicle-track space coupled model shows that the amplitudes of rail vertical vibration acceleration levels are higher at the center frequencies of 500 Hz and 1000 Hz, and the one-third octave band widths corresponding to above center frequencies are in the frequency range of Pinned-Pinned resonance of track structure. Therefore, it can be determined that rail corrugation on the measured line is roaring rail corrugation. The changing trends of rail vertical vibration acceleration levels under different sleeper spacings and operating speeds are basically the same and amplitudes of rail vertical vibration acceleration levels at the center frequencies of 500 Hz and 1000 Hz are higher. With the increase of the sleeper spacing and operating speed, the variation trends of rail vertical vibration acceleration levels at 500 Hz and 1000 Hz are almost unanimous. By changing the sleeper spacing and operating speed, the rail vertical vibration acceleration levels can be changed significantly, which shows that the appropriate sleeper spacing (about 700 mm) and operating speed (about 80 km/h) can effectively control the occurrence and development of rail corrugation.

The mirrored aperture synthesis radiometer (MASR) has been proposed as a promising technique for Earth observation. However, considering the system imperfections, the cosine visibility function and the brightness temperature distribution do not constitute a cosine transform pair. The method to improve the quality of reconstructed brightness temperature images for a practical MASR has not yet been developed. In this article, the complete formulation of cosine visibility functions in a practical MASR is derived to better understand the measurement of a MASR with non-negligible effects of the system imperfections. The array factor of a practical MASR is analyzed. Then, the alias-free field of view (FOV) for a MASR is presented, and an iterative method is proposed to reconstruct the brightness temperature image in the alias-free FOV to reduce the computational burden. The numerical simulation and experimental results demonstrate that the proposed method can be applied to practical MASRs and that the reconstruction quality is significantly improved by the proposed method. Finally, the H-matrix inversion method is discussed as an alternative reconstruction method for a practical MASR. Compared with the H-matrix inversion method, the proposed method is more convenient for practical applications.

The typical passing frequencies of corrugation were obtained by analysing the measured corrugation data in small radius curve track with Cologne-egg fasteners. The three-dimensional solid element model of track structure was established with the software ABAQUS, and modal analysis was carried out to determine the relationship between natural frequencies of track structure and passing frequencies of corrugation. By using the material wear model based on friction work theory, the frequency characteristics of corrugation and the development law of wear under different speeds were studied, and the control measures of corrugation were analysed. The new point of this study is to implement the above dynamic analysis from the perspective of vehicle (with flexible wheelsets) track space coupling, which can consider the coupled relationship in three directions of space. The results show that the generation of corrugation is closely related to the mechanical characteristics of track structure. Passing frequencies do not change with speeds, reflecting the frequency-fixing characteristics of corrugation. The analysis of control measures of corrugation shows that the smaller the friction coefficient is, the less likely the rail is to produce corrugation. The existence of rail vibration absorber can eliminate the generation of some short wavelength corrugation and reduce the rail bending vibration, which has a significant effect on the control of corrugation.

To study the wheel–rail contact and creep characteristics and the evolution law of corrugation with different wavelengths, the wave-like wear is idealized as continuous harmonic excitations consisting of three wavelengths and wave depths, and the vehicle–track space coupled dynamic model is established for specific analysis. The results show that when the wavelength is fixed and the wave depth increases, the average values of rail/wheel vertical vibration acceleration and wheel–rail longitudinal creepage/creep force increase and the average value of transverse creepage/creep force decreases. But, when the wave depth is fixed and the wavelength increases, the average values of rail/wheel vertical vibration acceleration and longitudinal creepage/creep force decrease and the average value of transverse creepage/creep force increases. Both longitudinal and transverse creepages/creep forces contain the characteristic frequency consistent with the passing frequency of initial irregularity. The characteristic frequencies of longitudinal creepages/creep forces tend to develop in the high-frequency band with the increase of wave depth, whereas the characteristic frequencies of transverse creepages/creep forces concentrate in the low-frequency band and decrease with the increase of wave depth. Under the condition of the same wavelength, with the increase of operation times, the wear amount increases slightly in the low-frequency band but greatly in the middle- and high-frequency bands, which shows that rail corrugation will gradually develop toward short wavelength corrugation at the constant velocity. When rail corrugation is formed, its development speed will gradually slow down with the increase of vehicle running times, and the development speed of short wavelength corrugation is faster than that of long wavelength corrugation.

The fast Li-ion pathways in crystals contribute to superionic conductivity-extraordinarily high ionic conductivity-of the Li10GeP2S12 (LGPS) structure. Composition tuning is expected to improve the conductivity. The phase behavior, microstructure, and ion dynamics of a series of solid solutions of xLi4GeS4-yLi3PS4 (4/1 ≥ x/y ≥ 1/2) were studied by multiple 7Li and 31P solid-state NMR methods. Li10GeP2S12 (Ge/P = x/y = 1/2) is the smallest x/y of the disordered LGPS structure. When the Ge/P ratio increases, the room-temperature Li ionic conductivity first increases to a maximum around x/y = 1/1.2 and then decreases. Meanwhile, a disordered LGPS structure transforms into an ordered LGPS' structure synchronously with conductivity reduction. The Li4GeS4-Li3PS4 phase diagram with the order-disorder structure transition was reconstructed accordingly. Both ordered LGPS' and disordered LGPS exhibit similar two-dimensional (2D) and one-dimensional (1D) Li diffusion paths. But the disordered LGPS structure is conducive to fast ionic conductivity, rooted in its fast 2D Li+ diffusion in the ab-plane rather than 1D diffusion along the c-axis. Two high-temperature relaxation processes are observed in the LGPS' structure, suggesting heterogeneous 2D jumps of rapid and slow rates, whereas only a single homogeneous 2D jump process was found in the LGPS structure. Our findings provide insight into understanding the relationship between structure order (or disorder) and ionic conductivity of superionic materials, offering guidelines for optimizing ionic conductivity for extensive solid electrolyte materials rather than LGPS materials.

By establishing vehicle-track space coupled model and rail corrugation evaluation model, the generation mechanism of rail corrugation was analyzed in frequency domain and time domain, and development characteristics of corrugation were studied by using corrugation growth rate. Analysis based on frequency domain: through modal analysis and frequency response analysis on the finite element model of track structure, it is found that there are natural frequencies of track structure close to measured corrugation passing frequencies. It shows that the vibration modes corresponding to these frequencies can be more easily excited, which can cause the resonance phenomenon of track structure and form the rail corrugation at corresponding frequencies. Analysis based on time domain: the time-history curves of rail vertical vibration acceleration and rail vertical displacement are calculated by using vehicle-track coupled model and the frequency domain transformation of the time-history data is carried out. It is found that there are characteristic frequencies close to the measured corrugation passing frequencies, which indicates that the vibration of track structure at corresponding frequencies is an important reason to promote the formation of corrugation. The change of vehicle speed has no effect on characteristic frequencies of corrugation growth rate curves, which reflects the fixed frequency characteristic of corrugation. With the increase of train operation times, the corrugation corresponding to characteristic frequencies will gradually form and develop, and the increase of vehicle speed will increase the wavelength range and development speed of rail corrugation.

Fabrication of high-performance superconducting wires and tapes is essential for large-scale applications of superconducting materials. The powder-in-tube (PIT) method involves a series of cold processes and heat treatments and has been widely used for fabricating BSCCO, MgB2, and iron-based superconducting wires. The densification of the superconducting core is limited by traditional heat treatment under atmospheric pressure. The low density of the superconducting core and a large number of pores and cracks are the main factors limiting the current-carrying performance of PIT wires. Therefore, to improve the transport critical current density of the wires, it is essential to densify the superconducting core and eliminate pores and cracks to enhance grain connectivity. Hot isostatic pressing (HIP) sintering was employed to improve the mass density of superconducting wires and tapes. In this paper, we review the development and application of the HIP process in the manufacturing of BSCCO, MgB2, and iron-based superconducting wires and tapes. The development of HIP parameters and the performance of different wires and tapes are reviewed. Finally, we discuss the advantages and prospects of the HIP process for the fabrication of superconducting wires and tapes.

The Mooney–Rivlin hyperelastic model and Prony series viscoelastic constitutive model are used to verify the selected calculation parameters by finite element analysis compared with stress relaxation test data. Then, the ANSYS-PDS (ANSYS-probabilistic design system) module is used to analyze the sensitivity values of all random parameters to surface contact stress and the influence of hyperelastic and viscoelastic parameters on the surface contact stress relaxation. The results show that parameter values are reasonable. Random parameters that have great influence on the surface contact stress are α2 and C10, followed by α1, τ1 and C01, and the influence of τ2 is negligible, which shows that for the second-order viscoelastic model, the change in clay pot coefficient η2 has little effect on the surface contact stress. Moreover, with the increase in C10, the surface contact stress increases significantly; with the increase in α2, the surface contact stress decreases significantly, and the surface contact stress varies uniformly with C01. Stress relaxation mainly occurred on the first day of loading and remained basically stable within 1 year. The greater the values of hyperelastic parameters are, the smaller the stress attenuation is, and the opposite of viscoelastic parameters.

Low-cost hierarchical porous carbon materials with a controllable structure and high specific surface area as well as large pore volume were synthesized by a one-step route involving SnO2@chitosan precursor carbonization and subsequent SnO2 template removal. We found that when HPC CISC-29 is applied as the electrode in the supercapacitor device, it exhibits both high specific capacity (260.4 F g−1) and excellent rate capacitance retention (81.9%) from 0.1 A g−1 to 10 A g−1. CISC-29 shows superiority compared to conventional activated carbons for which specific capacitance and capacitance retention are 100–200 F g−1 and 60–70%, respectively. Solid-state NMR and NLDFT porosity distribution results reveal that the high specific capacitance is most likely associated with the optimized hierarchical porous structure, e.g. rich small-size micropores and their good connection with large-size mesopores. Finally, CISC-29 was complexed with Se to construct a cathode for lithium selenium batteries. Se@CISC-29 shows excellent performance with a specific capacity of 1207.0 mA h g−1 at 0.1 A g−1.

The concept, principle, and method of microwave radiometric imaging with mirrored aperture synthesis (MAS) were proposed by the Huazhong University of Science and Technology (HUST), Wuhan, China. MAS can achieve higher spatial resolution without extending the size of the antenna array. However, the MAS principle has not been sufficiently validated by practical experiments. To solve this problem, an innovative experiment system of MAS at the V-band (MAS-V) has been developed by HUST. Experiments on the interference fringe pattern, spatial resolution, as well as the imaging of an electric warmer and the absorbing material in the styrofoam box filled with liquid nitrogen are performed. The initial experimental results demonstrate that MAS can achieve higher spatial resolution with the same antenna array compared with the conventional AS. For MAS, the experimental results are consistent with theory and simulation results.

Vanadium hexacyanoferrate (VHCF) with an open-framework crystal structure is a promising cathode material for rechargeable aqueous metal-ion batteries owing to its high electrochemical performance and easy synthesis. In this paper, vanadium hexacyanoferrate cathodes were first used for constructing rechargeable aqueous sodium-ion batteries (VHCF/WO3) and tested in the new-type electrolyte (NaP-4.6) consisting of a polyethylene glycol (PEG)/H2O/NaClO4 electrolyte with a low H+ concentration (molar ratio of [H2O]/[Na+] is 4.6), which has high stability at a high current density as high as 1000 mA g-1 with a capacity retention of 90.3% after 2000 cycles at high coulombic efficiency (above 97.8%). To understand their outstanding performance, the proton-assisted sodium-ion storage mechanism and interphase chemistry of VHCF are investigated by solid-state NMR (ssNMR) technology. It is suggested that the H+ storage reaction is accompanied by the redox of vanadium atoms and Na+ intercalation is accompanied by the redox of iron atoms. It is also observed that the complex of polyethylene glycol (PEG) with Na+ (PEG-Na+) exists on the VHCF surface, which facilitates the stability of VHCF and promotes the alkali-ion transfer at a high current density. The results of the ssNMR study offer new insights into the intercalation chemistry of Prussian blue analogues with open-framework-structured compounds, which can greatly broaden our horizons for battery research.

Mirrored aperture synthesis (MAS) is a new method for passive microwave remote sensing after aperture synthesis (AS). In this paper, the relationship among the array factor (AF) for the two-dimensional (2-D) MAS, one-dimensional (1-D) MAS, and 1-D AS is established. Based on the relationship, the sidelobe level (SLL) of MAS is analyzed. The SLL of MAS is spatially variant compared to that of AS. Despite this, a set of directions can still be selected, in which the maximum SLLs of MAS are almost equal to those of AS. This is verified by the simulations and experiments based on a system working at 51.6GHz.