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Carbonyl rich conjugated polymer electrode materials for lithium‐ion batteries possessed the advantages of strong molecular design ability, abundance and high theoretical capacity. In this work, a Co2+ coordinated conjugated polymer using 2,3,5,6‐tetraamino‐p‐benzoquinone (TABQ) as building block was constructed and developed as electrode material for all organic symmetric lithium‐ion batteries, outputting a specific capacity of over 100 mAh g−1 after 50 cycles at 50 mA g−1. Performances of Co‐TABQ in half cells were explored. The Co‐TABQ cathode delivered a capacity of 133.3 mAh g−1 after 150 cycles at 20 mA g−1. When cycled at higher current density of 500 mA g−1, the capacity gradually increased to 109.4 mAh g−1 after 4000 cycles. The Co‐TABQ anode displayed a stable capacity of 568.6 mAh g−1 at 1 A g−1. The charge transfer within the electrode was greatly reduced due to the metallic centers in the extended conjugated skeleton, and the reversible Li+ storage was achieved by the active C=O and imine groups. This work showed the great potential of metal mediated conjugated polymer in Lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Summary: The large‐scale applications of energy storage system via lithium‐ion batteries (LIBs) put forward demands for high capacity, high safety, and low cost of materials. Covalent organic polymers have attracted extensive attention because of their high capacity, flexible structural design, high safety, abundance, and low cost. Here, 2,3,5,6‐tetraamino‐p‐benzoquinone and hexaketocyclohexane octahydrate were chosen as monomers to construct the covalent organic framework (TH‐COF) cathode materials with active C=O and C=N groups. The TH‐COF was further composed with reduced graphene oxide (rGO) and the prepared TH‐COF/rGO cathode provided a capacity of 135 mAh g−1 after 600 cycles at 1 C current density. In addition, after 100 cycles, the cathode delivered capacities of 118 and 73 mAh g−1 at the high current densities of 5 C and 20 C, respectively, displaying superior rate performances. The TH‐COF/rGO electrode exhibited high capacity and stability, making it a promising cathode material for the next generation LIBs. [ABSTRACT FROM AUTHOR]

In wet-chemistry processes, pH value is an important parameter that can be used to control the microstructures of the as-grown nanostructures. In this work, W 18 O 49 nanowires with crystalline@amorphous core-shell structures were synthesized by controlling the pH of the precursor solutions in a hydrothermal reaction. Due to surface functionalization by ethylene glycol (EG) groups, the hydrothermally grown W 18 O 49 nanowires could be easily dispersed in aqueous environment, thus enabling the fabrication of electrochromic thin films of W 18 O 49 nanowires by a simple spray-drying process. The optimized W 18 O 49 nanowire films showed a large optical modulation (ΔT) of 81.1% at 633 nm, short response time (coloring/bleaching time τ c /τ b = 7.9 s/3.9 s), good cycle stability (ΔT retention was 84.5% after 1000 cycles), and the excellent memory effect (the color withstood for 36000s after turning off the voltage). Furthermore, the electrochromic device (ECD) (4 × 4 cm2) based on the W 18 O 49 nanowires exhibits a large optical modulation of 56.6%, short response time (τ c = 7.6 s, τ b = 2.7 s), and superior coloration efficiency (CE) of 64 cm2 C−1. Finally, by simply amplifying the developed processes, a large-area electrochromic device (10 × 10 cm2) was successfully prepared, which implies the possibility of large-area spraying process for practical applications. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) has been considered as a key enabler for the fifth-generation (5G) communications. It is essential to design and test mmWave 5G devices under various realistic scenarios since the radio propagation channels pose intrinsic limitations on the performance. This requires emulating realistic dynamic mmWave channels in a reproducible manner in laboratories, which is the goal of this article. In this contribution, we first illustrate the dominant-cluster(s) concept, where the nondominant clusters in the mmWave channels are pruned, for mmWave 5G devices applying massive MIMO beamforming. This demonstrates the importance and necessity to accurately emulate the mmWave channels at a cluster level rather than the composite-channel level. Thus, an over-the-air (OTA) emulation strategy for dynamic mmWave channels is proposed based on the concept of the dominant cluster(s) in a sectored multiprobe anechoic chamber (SMPAC). The key design parameters, including the probe number and the angular spacing of probes, are investigated through comprehensive simulations. A cost-effective switch circuit is also designed for this purpose and validated in the simulation. Furthermore, a dynamic mmWave channel measured in an indoor scenario at 28–30 GHz is presented, where the proposed emulation strategy is also validated by reproducing the measured reality. [ABSTRACT FROM AUTHOR]

The reinforcement ratio of central column member has remarkable effect on the seismic behaviour of double-box stations. To investigate the effects of reinforcement ratio on seismic performance of hypothetical stations, hybrid simulations and quasi-static cyclic tests on five full-scale column specimens of various reinforcement ratios were presented in this paper. The five column specimens are comprised of a reference specimen and four specimens with the reduction in either longitudinal or transverse reinforcements. In the hybrid simulations, the physical specimen consisted of one central column, while the rest of the soil-structure system were modelled numerically using the OpenSEES software. Seismic loading to the columns was applied via displacement-controlled actuators to illustrate the drift demands of the station during hybrid simulations at three levels of ground motions. The hybrid simulation results showed that the column specimen with minimum longitudinal reinforcement ratio entered the yielding stage and the other four specimens were in the cracking stage. Furthermore, the quasi-static cyclic tests were carried out to investigate the strength and deformation capacity of tested columns. Results from both hybrid seismic tests and quasi-static cyclic tests indicate that central columns, with a high shear span-to-depth ratio and light transverse reinforcement, are prone to suffer brittle flexural-shear coupled failure. On the other hand, the columns of sufficient transverse reinforcement are likely to experience flexural failure. The safety margins between the seismic drift response and ultimate deformation capacity indicate that the drift ratio threshold of subway stations used by current code provisions is conservative for flexure-dominate columns. [ABSTRACT FROM AUTHOR]

Power control is becoming increasingly essential for the fifth-generation (5G) and beyond systems. An example use-case, among others, is the unmanned-aerial-vehicle (UAV) communications where the nearly line-of-sight (LoS) radio channels may result in very low signal-to-interference-plus-noise ratios (SINRs). The authors in (Chiang et al., 2007) proposed to efficiently and reliably solve this kind of non-convex problem via a series of geometrical programmings (GPs) using condensation approximation. However, it is only applicable for a small-scale network with several communication pairs and practically infeasible with more (e.g., tens of) nodes to be jointly optimized. We therefore in this paper aim to provide new insights into this problem. By properly introducing auxiliary variables, the problem is transformed to an equivalent form which is simpler and more intuitive for condensation. A novel condensation method with linear complexity is also proposed based on the form. The enhancements make the GP-based power control feasible for both small- and especially large-scale networks that are common in 5G and beyond. The algorithm is verified via simulations. A preliminary case study of uplink UAV communications also shows the potential of the algorithm. [ABSTRACT FROM AUTHOR]

Millimeter-wave with ultrawide bandwidth available and ability to pack massive number of antennas in a small area is considered the key enabler for future generation communication systems. Accurate understanding and modeling of the ultrawideband propagation channel with large-scale array configuration is essential. In this contribution, a realistic spherical-propagation signal model considering the spatial nonstationarity of path gain across the array elements is proposed. A novel trajectory-aided maximum-likelihood (TAMax) algorithm is proposed to extract propagation parameters from the measured data, since the existing high-resolution propagation parameter estimation algorithms are not applicable due to either prohibitively high computation loads or assumption violations. In the proposed TAMax algorithm, the high-dimensional maximum-likelihood estimation (MLE) problem is first decomposed into a subproblem where delays and amplitudes of multipath components (MPCs) are estimated at individual array elements. A novel transform is then proposed to identify multiple MPC trajectories in the delay-element domain. With interference cancellation and fast initialization obtained in the proposed transform, spherical propagation parameters are finally acquired via joint MLE with significantly decreased searching spaces. Moreover, a measurement campaign conducted at the frequency band of 27–29 GHz using a virtual uniform circular array is introduced, where the proposed TAMax algorithm is applied and validated. [ABSTRACT FROM AUTHOR]

In this contribution, a recently conducted measurement campaign for indoor millimeter-wave (mm-wave) propagation channels is introduced. A vector network analyzer (VNA)-based channel sounder was exploited to record the channel characteristics at the frequency band from 28–30 GHz. A virtual uniform circular array (UCA) with a radius of 0.25 m was formed using a rotator with 360 steps. Moreover, by taking advantage of fiber-optic technique applied in the channel sounder, measurements at 50 positions were performed from an indoor hall to an indoor corridor along a long pre-defined route. A low-complexity high-resolution propagation estimation (HRPE) algorithm is exploited to estimate the propagation parameters of multipath components (MPCs). Based on the HRPE estimation results, a novel clustering identification and tracking algorithm is proposed to trace clusters. Composite channel characteristics, cluster-level characteristics and dynamic (or birth-death) behaviours of the clusters are investigated, which constitute a dynamic model for the indoor mm-wave channel. [ABSTRACT FROM AUTHOR]

Millimeter wave (mm-wave) communication with large-scale antenna array configuration is seen as the key enabler of the next generation communication systems. Accurate knowledge of the mm-wave propagation channels is fundamental and essential. In this contribution, a novel complexity-efficient high resolution parameter estimation (HRPE) algorithm is proposed for the mm-wave channel with large-scale uniform circular array (UCA) applied. The proposed algorithm is able to obtain the high-resolution estimation results of the spherical channel propagation parameters. The prior channel information in the delay domain, i.e., the delay trajectories of individual propagation paths observed across the array elements, is exploited, by combining the high-resolution estimation principle and the phase mode excitation technique. Fast initializations, effective interference cancellations, and reduced searching spaces achieved by the proposed schemes significantly decrease the algorithm complexity. Furthermore, the channel spatial non-stationarity in path gain across the array elements is considered for the first time in the literature for propagation parameter estimation, which is beneficial to obtain more realistic results as well as to decrease the complexity. A mm-wave measurement campaign at the frequency band of 28–30GHz using a large-scale UCA is exploited to demonstrate and validate the proposed HRPE algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a recently conducted measurement campaign for unmanned-aerial-vehicle channels is introduced. The downlink signals of an in-service long-time-evolution network, which is deployed in a suburban scenario were acquired. Five horizontal and five vertical flight routes were considered. The channel impulse responses (CIRs) are extracted from the received data by exploiting the cell-specific signals, and the underlying physical propagation mechanisms are interpreted by exploiting the propagation graph modeling approach. Based on the CIRs, the parameters of multipath components are estimated by using a high-resolution algorithm derived according to the space-alternating generalized expectation-maximization (SAGE) principle. Based on the SAGE results, channel characteristics including the path loss, shadow fading, fast fading, delay spread, and Doppler frequency spread are thoroughly investigated for different heights and horizontal distances, which constitute a stochastic model. [ABSTRACT FROM AUTHOR]

In this paper, a recently conducted measurement campaign for vehicle-to-vehicle (V2V) propagation channel characterization is introduced. Two vehicles carrying a transmitter and a receiver, respectively, have been driven along an eight-lane road with heavy traffic. The measurement was conducted with 100 MHz signal bandwidth at a carrier frequency of 5.9 GHz. Channels are observed consisting of two kinds of channel components, i.e., time-evolving clusters and clutter paths. A novel approach based on Hough transform is proposed to identify the clusters. Based on the cluster identification results, channel characteristics in composite, intracluster, and time-variant levels are analyzed. The parameters investigated include the composite root-mean-square (RMS) delay spreads and power decay versus delay behaviors of clusters and clutter paths, cluster RMS delay spread, cluster RMS Doppler frequency spread, correlations of cluster parameters, and coherence time of parameters of interest. The statistics constitute an empirical stochastic clustered-delay-line channel model focusing on the wideband characteristics observed in the realistic time-variant V2V propagation scenario. [ABSTRACT FROM PUBLISHER]

Recently, a measurement campaign for characterizing the channels in underground subway environments was conducted in Shanghai, China. Downlink signals transmitted by 46 universal mobile telecommunication system cells deployed along a 34-km-long subway were collected. Channel impulse responses are extracted from the data received in the common pilot channels, based on which parameters of multipath components are estimated by using a high-resolution parameter algorithm derived using the space-alternating generalized expectation-maximization principle. Multiple time-evolving clusters are obtained, each representing the channel from a remote-radio-unit of a base station to the receiver. Based on a total of 98 time-evolving clusters, channels observed in the station scenario and the tunnel scenario are modeled separately for their distinctive behaviors in many aspects, particularly in the variations of clusters’ trajectories. Intracluster characteristics parameterized by cluster delay and Doppler frequency spreads, $K$ -factor, and dependences among these parameters are investigated. Intercluster parameters, including coexisting cluster number, delay offset, power offset, and cross correlations, are investigated for the station scenario. A path loss model is established for the tunnel scenario. [ABSTRACT FROM AUTHOR]

In order to capture global load redistribution in a structural system subjected to fire and fire induced local failure such as column buckling, this paper develops a dual-3D hybrid simulation scheme with multiple sub-structure models and a 3D structural system model to investigate structural fire responses. This hybrid simulation scheme is implemented with simulation models in OpenSees for fire and the naturally compatible middleware OpenFresco. A model of the Cardington plane-frame test was built and used to validate the presented approach regarding the performance of traditional thermo-mechanical model and test results. The modelling results demonstrate the necessity of modelling central columns in detailed models for local failure and the importance of including floor slabs in the structural system model. The effect of larger fire furnace area and the unprotected length of columns are studied using the dual-3D hybrid models, which warns the risk of floor failure following the column bucking and squashing. More importantly, the work in this paper paves the way for hybrid testing of structures in fire equipped with a 3D structural system model synchronized with multiple substructure models and in-laboratory tested specimen. • Hybrid fire simulation using 3D structural model and multiple sub-structure models. • Cardington plane-frame test is modelled for validation and demonstration. • Local buckling and squashing of columns are captured by the synchronized sub-structure models. • The effect of composite floors is considered in the 3D hybrid thermo-mechanical model. [ABSTRACT FROM AUTHOR]

Recommender system can provide users with items that meet their potential needs in mass information. Its development provides new ideas and supporting technologies for applications in online education scenarios. The previous recommendation methods usually only consider the enhancement of the item side, but ignore the importance of the user characteristics to the recommendation, and are not suitable for the online education scenario. To address this problem, we take knowledge graph as the auxiliary information source of collaborative filtering and propose an end-to-end framework using knowledge graph to enrich the semantics of the item representation. In particular, faced with the thorny problem of cold start, the framework makes use of the static features of users to personalize the modeling of new users. Experimenting with two public datasets and an industrial dataset, we demonstrate that the framework has significant performance improvements over the baseline and can maintain satisfactory performance with sparse user–item interactions. • A personalized KG-enhanced model is proposed for online course recommendation. • An attribute-level attention network is used in course modeling. • The user graph is constructed to find users with similar static features. • The interactions of similar users are used to simulate the preference of a new user. • The model can effectively alleviate data sparsity and cold start problems. [ABSTRACT FROM AUTHOR]

Joints are critical parts of structural members. In order to study the mechanical properties of beam-column joints improved by using UHPC after fire exposure, a series of tests have been conducted on reinforced concrete beam-column joints, with both conventional concrete and UHPC in the joint. Fire exposure tests were carried out on the specimens in the light of the designated heating curve, then followed by quasi-static loading tests. Measurements were respectively made on the temperature and load-displacement of the joints. Several significant parameters were analysed from the results of the loading tests, such as pinching width ratio, displacement ductility factor, energy dissipation, stiffness degradation and equivalent hysteretic damping ratio. The results show that high temperatures have a significant effect on the ultimate strength and initial stiffness of concrete beam-column joint specimens. The application of UHPC significantly improves the mechanical behaviour of beam-column joints. In addition, the energy-consuming capacity is enhanced. After fire exposure, the loading capacity of UHPC specimens is reduced correspondingly. [ABSTRACT FROM AUTHOR]

Transition metal oxides as anode materials for lithium‐ion batteries (LIBs) possess the advantages of high specific capacity and abundance. However, most reported transition metal oxides based active anode materials were coated on the copper current collector with the addition of inactive polymer binder and conductive agents, resulting in low utilization of active substances. To solve this problem, nanostructured CuO with different morphologies (CuO bunches, CuO nanosheets, CuO nanotubes) were in‐situ grown on the copper current collectors via a simple wet chemical oxidation method. The as‐obtained CuO@Cu foils were used directly as anode for LIBs. CuO nanotubes exhibited excellent electrochemical performance and sustained a reversible discharge specific capacity of 798 mA h g−1 after 60 cycles at 100 mA g−1. At current density of 1000 mA g−1, a high specific capacity of 758 mA h g−1 can be obtained after 200 cycles. The satisfying electrochemical performances of the CuO nanotubes anode indicated that a stable composite structure of CuO@Cu foils was achieved in the binder free electrode. This work demonstrated the feasibility of this binder free strategy in the development of electrode materials for high performance lithium‐ion batteries design. [ABSTRACT FROM AUTHOR]

Ultrathin all‐solid‐state electrolytes with an excellent Li+ transport behavior are highly desirable for developing high‐energy‐density solid‐state lithium metal batteries. However, how to balance the electrochemical performance and their mechanical properties remains a huge challenge. Herein, an ultrathin solid electrolyte membrane with a thickness of only 3 µm and a weight of 11.7 g m−2 is well constructed by integrating individual functionalized organic with inorganic modules. Impressively, the optimized hybrid electrolyte membrane shows a set of merits including a high room‐temperature ionic conductivity of 1.77 × 10−4 S cm−1, large Li+ transference number of 0.65, and strong mechanical strength (strength of 29 MPa, elongation of 95%), as well as negligible thermal shrink at 180 °C. The analysis results reveal that the lithium sulfonate‐functionalized mesoporous silica nanoparticles in the membrane play a crucial role in the selective transport of Li+ through anion trapping and cation exchange. The pouch full cell is further assembled with a high‐voltage NCM cathode and thin lithium anode, which exhibits excellent long‐term cycling stability, outstanding rate performance at room temperature, and high safety against abused conditions. The current work provides an innovative strategy for achieving lithium metal batteries with ultrathin all‐solid‐state electrolytes. [ABSTRACT FROM AUTHOR]

We propose a multivariate log-normal distribution to jointly model received power, mean delay, and root mean square (rms) delay spread of wideband radio channels, referred to as the standardized temporal moments. The model is validated using experimental data collected from five different measurement campaigns (four indoor scenarios and one outdoor scenario). We observe that the received power, the mean delay, and the rms delay spread are correlated random variables, and therefore, should be simulated jointly. Joint models are able to capture the structure of the underlying process, unlike the independent models considered in the literature. The proposed model of the multivariate log-normal distribution is found to be a good fit for a large number of wideband data sets. [ABSTRACT FROM AUTHOR]

Due to the decrease in cost, size, and weight, unmanned aerial vehicles (UAVs) are becoming more and more popular for general-purpose civil and commercial applications. Provision of communication services to UAVs both for user data and control messaging by using off-the-shelf terrestrial cellular deployments introduces several technical challenges. In this article, an approach to the air-to-ground channel characterization for low-height UAVs based on an extensive measurement campaign is proposed, giving special attention to the comparison of the results when a typical directional antenna for network deployments is used and when a quasi-omnidirectional one is considered. Channel characteristics, such as path loss, shadow fading, root-mean-square delay, Doppler frequency spreads, and the K-factor, are statistically characterized for different suburban scenarios. [ABSTRACT FROM AUTHOR]

In a wireless communication system, the radio propagation channel is a complicated component to characterise. Channel sounding equipment thus has to meet specific criteria to extract the desired channel parameters. In this study, the authors outline the development and validation of a vector network analyser (VNA) based channel sounder for the frequency range from 1 to 50 GHz using radio‐over‐fibre techniques. Three methods of de‐embedding phase errors due to hardware impairments are demonstrated and validated via back‐to‐back measurements. The bidirectional scheme utilising optical circulators is shown to have a superior performance over the two‐branch unidirectional and the two‐branch bidirectional schemes. Therefore, the bidirectional scheme utilising optical circulators is proposed to achieve a long‐range ultra‐channel sounder based on the VNA. [ABSTRACT FROM AUTHOR]

Reported studies on T-head Square-neck One-side Bolts (TSOBs) bolted I-beam to Hollow Section Square Column (HSSC) connections demonstrated the potential of TSOB applications in terms of mechanical properties, installation construction, and cost savings [11–14]. However, existing research was limited to the connection tests and lack a systematic and complete design approach. In this paper, the method for predicting the bending moment capacities and failure modes of the connections was proposed based on the existing test researches. Besides, the Finite Element Model (FEM) of the connections was established and validated by the reported test results. A sensitive analysis on the geometric parameters of the plastic hinge line pattern for calculating the bending moment capacity of the HSSC connecting face was carried out by the validated FEM. The proposed method was compared with the numerical simulation method in terms of the predicted results of the connection structural behavior. The results show that the prediction method proposed in this paper for the connection bending moment capacities and failure modes is accurate and reliable. Moreover, the mixed patterns of Type-H bolt holes and Type-V bolt holes are recommended for the TSOBC design because of the higher bending moment capacity than the unitary bolt hole patterns. • Method for predicting the bending moment capacity of TSOBC was proposed. • Failure mode of TSOBC was predicted based on design information. • Mixed patterns of Type-H and Type-V bolt holes are recommended for TSOBC. [ABSTRACT FROM AUTHOR]

The Elliptical-head one-side bolt (EOB) is a typical representative of the third generation for one-side bolts, relying on its elliptical head and bolt hole to achieve orthogonal anchorage, and the application scenario is mainly the bolted connection of closed-section members. Studies have been reported for the shear performance of EOBs bolted lap connections and the tensile behaviour of concrete-filled steel tubes, but there is still a lack of the tensile performance of EOBs connecting Hollow section columns (HSCs), which is necessary for the application of the component method for the beam-column joints design. Therefore, numerical simulation and theoretical analysis methods were employed in this paper to demonstrate the feasibility of adopting EOBs for this type of connection, including typical failure modes, novel yield line pattern in the HSC wall, comparison with the Conventional high-strength bolt (CHB) connections, analysis of the parameters related to the elliptical bolt head and hole, and the establishment and validation of the methodology for calculating the HSC bearing capacity. The results show that: The novel trapezoidal yield line pattern tended to show in the HSC wall with the smaller bolt pitch distance and larger gauge distance; The yield strength of the EOBs bolted T-stub to HSC connections was reduced by about 15% compared to the CHBs bolted ones; Vertical layout of bolt holes, accuracy of rough assembly, rotation deviation of bolt shank within 20° and avoidance of bolt offsets in bolt hole were recommended for EOB connections; The novel yield line pattern established in this paper predicted the yield strength of the connections, and the accuracy and stability were verified by comparing with finite element modelling (FEM) results. • Tensile performance of EOBs connecting HSC was carried out. • Trapezoidal yield line pattern was found in HSC connecting wall. • Strength of EOBs bolted connections was reduced by 15% compared to CHBs bolted ones. • Equations for predicting the strength of EOBs bolted connections were established. [ABSTRACT FROM AUTHOR]

Metal-doping is an effective method to adjust the physical and chemical properties of semiconductor metal oxides. This work adopts a simple solvothermal method to synthesize Mo-doped tungsten oxide nanoparticles. The high-performance electrochromic films can be homogenously formed on ITO glass without post-annealing. Compared with pure WO 3 films, the optimized Mo-doped WO 3 films show improved electrochromic properties with significant optical contrast (68.3% at 633 nm), the short response time (6.3 s and 3.9 s for coloring and bleaching, respectively), and excellent coloration efficiency (107.2 cm2 C−1). The improved electrochromic behavior is mainly due to the increasing diffusion rate of Li+ in Mo-doped WO 3 films (increased 20% than that of pure WO 3 films). The porous surface of Mo-doped WO 3 film shortens the diffusion path of Li+. Besides, Mo doping reduces the resistance and improves conductivity. Furthermore, 2at% Mo-doped WO 3 films indicate satisfactory energy-storage properties (the specific capacitance is 73.8 F g−1), resulting from the enhanced electrochemical activity and fast electrical conductivity. This work presents a practical and economical way of developing high-performance active materials for bifunctional electrochromic devices. [ABSTRACT FROM AUTHOR]

• Acetylacetone as surface passivator enhance device performance. • Larger grains and less traps of CsPbI 2 Br films with AA treatment. • High efficiency and stable perovskite solar cells have been fabricated at low temperature (90 °C). All inorganic perovskite solar cells (PSCs) have been demonstrated to get tremendous interest recently owing to their better thermal stability. Nevertheless, some CsPbI 2 Br films prepared at low temperature have lower quality compared to those annealing at high temperature. Herein, to obtain high performance PSCs, a simple post-treatment strategy is presented by spin coating acetylacetone (AA) solution on the CsPbI 2 Br films. The AA treatment can reduce the density traps on the CsPbI 2 Br films surface and enlarge the size of grains, resulting in enhanced performance PSCs. After optimizing surface treatment, the devices based on low-temperature-processed CsPbI 2 Br with AA treatment achieved a power conversion efficiency (PCE) of 14.43%. The better CsPbI 2 Br films quality and interface contact of hole transport layer (HTL)/CsPbI 2 Br result in better device stability. Therefore, it could be a promising post treatment method for enhancing the performance of PSCs by introducing AA on the perovskite surface. [ABSTRACT FROM AUTHOR]

In this article, a novel vector network analyzer (VNA)-based ultrawideband (UWB) channel sounder using radio-over-fiber (RoF) techniques is presented. Benefiting from the usage of optical fiber cable, the measurement range and the dynamic range are significantly increased compared with the conventional coaxial-based VNA system. Specifically, using RoF increases the dynamic range to a maximum of 112 dB at 30 GHz for the back-to-back connection with an optical fiber cable of length 300 m. Moreover, a state-of-the-art phase compensation scheme using optical circulators is proposed for the first time. The novel scheme renders the channel sounder immune to stochastic phase changes in the optical fiber cable due to thermal changes and mechanical stress, thus permitting the remoting of virtual antenna arrays. The proposed channel sounder is experimentally validated in back-to-back measurements, an anechoic chamber, and practical indoor scenarios. The indoor channel measurements are conducted using a virtual uniform rectangular array (URA) at the millimeter-wave (mm-wave) band from 26.5 to 30 GHz. The measured results demonstrate the developed channel sounder’s capability to perform UWB large-scale antenna array measurements with a long measurement range. [ABSTRACT FROM AUTHOR]

Purpose: The differential magnetic gradient tensor system is usually constructed from the three-axis magnetic sensor array. While the effects of measurement error, sensor performance and baseline distance on localization performance of such systems have been widely reported, the research about the effect of spatial design of sensor array is less presented. This paper aims to provide a spatial design method of sensor array and corresponding optimization strategy to localization based on magnetic tensor gradient to get the optimum design of the sensor array. Based on the results of simulation, magnetic localization systems constructed from the proposed array and the traditional array have been built to carry out a localization experiment. The results of experiment have verified the effectiveness of magnetic localization based on the proposed array. Design/methodology/approach: The authors focus on the localization of the magnetic target based on magnetic gradient by using three-axis magnetic sensor array and combine a design method with corresponding optimization strategy to get the optimum design of the sensor array. Findings: This paper provides an array design and optimization method for magnetic target localization based on magnetic gradient to improve the localization performance. Originality/value: In this paper, the authors focus on the magnetic localization based on magnetic gradient by using three-axis magnetic sensors and study the effect of the spatial design of sensor array on localization performance. [ABSTRACT FROM AUTHOR]

Recently, a measurement campaign for characterizing time-variant radio channels in city-canyon environments was conducted along a 2-km-long pedestrian shopping street in Shanghai. A passive sounding approach was adopted where a software-defined-radio platform is used as a receiver (Rx) to record downlink signals transmitted by base stations (BSs) in an in-service Universal Mobile Telecommunications System (UMTS). Channel impulse responses are calculated from the data received in common pilot channels, and a space-alternating generalized expectation–maximization (SAGE) algorithm is applied to estimate delays, Doppler frequencies, and complex attenuations of multipath, which are further grouped into clusters characterized by time-evolving parameters. Based on the observations from a total of 70 BSs, stochastic models are established for composite channel parameters, cluster-level characteristics, and the time variabilities of these parameters. The novelties of the models lie in the passive data acquisition, which leads naturally to superior model ergodicity and higher fidelity than the standard models constructed based on active sounding. Furthermore, the models proposed here also exploit a new channel categorization method that takes into account the realistic impact of system configurations, such as the usage of multiple remote radio units in a single BS. [ABSTRACT FROM PUBLISHER]

• Virtual hybrid simulation framework is established based on OpenSees and OpenFresco. • Nonlinear features of the soil-structure system are captured during emulation. • The Daikai station is applied to validate the effectiveness of the framework. • Two substructure schemes are presented under different levels of earthquake motion. Current knowledge on seismic analysis of underground structures is limited to analytical solutions, numerical methods and scaled model tests. Virtual hybrid simulation (VHS) is an efficient and economical analysis method that combines numerical approaches and experiment methods while taking the advantages of both. In this study, a VHS method employing a multi-axial experimental setup for seismic analysis of soil-structure systems is proposed and the corresponding VHS framework was developed using OpenFresco and OpenSees. To demonstrate the ability of the VHS method in accurately and efficiently capturing seismic behavior of underground structures, the proposed VHS method was applied to evaluate seismic response of the Daikai subway station, during which a good agreement was achieved when comparing the VHS results with those of the complete numerical simulation (CNS). Moreover, the advantages of the expanded multi-axial experimental setup in the proposed VHS method over the simplified single-DOF experimental setup are evaluated and discussed. [ABSTRACT FROM AUTHOR]