With the rapid development of flexible electronic device, yarn supercapacitors (YSCs) as one kind of flexible energy storage devices are attracting more and more attention. Carbon nanotube (CNT) and ...conductive polymers are widely investigated as potential active materials in energy storage field. Bacterial cellulose (BC) nanofiber is one of highly promising alternatives to the flexible substrates. Hence, an all-solid-state YSC is successfully fabricated via twisting CNT@BC membrane and electrochemically depositing polypyrrole. The proposed YSC demonstrates a high areal capacitance of 458 mF cm
−2
at a current density of 0.8 mA cm
−2
as well as a robust cycling stability (no significant degradation in capacitance after 2000 cycles). Moreover, the proposed YSC is comparatively flexible, confirming it as a promising power source candidate for portable and wearable electronics.
Graphic abstract
With the rapid development of flexible electronic devices, yarn supercapacitors (YSCs) as one kind of flexible energy storage devices are attracting more and more attention. Carbon nanotube (CNT) and ...conductive polymers (CPs) are widely investigated as potential active materials in energy storage field. Herein, an all-solid-state YSC was successfully fabricated via spinning CNT-coated cotton roving and in-situ polymerization of pyrrole. The proposed YSC demonstrated an areal specific capacitance of 421 mF cm
−2
at a current density of 0.57 mA cm
−2
as well as superior cycling performance. Moreover, the proposed YSC was comparatively flexible, confirming it as a promising power source candidate for portable and wearable electronics.
A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. ...Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation.
The equivalent-circuit model (ECM) is widely used in online estimating the parameters and states of lithium-ion batteries. However, the sampling delay between the voltage and current of a battery is ...generally overlooked, which is unavoidable in a modular battery management system (BMS) and would lead to wrong results in the estimation of battery parameters and states. In this paper, with the first-order resistor–capacitor (RC) model as our battery model, we analyze the influence mechanism of sampling delay and then propose an optimized method for online estimating battery parameters. The mathematical model derived from the first-order RC model and the approximation method of first-order derivative are optimized. The recursive least squares (RLS) algorithm is used for identifying the parameters of the model. In order to verify the proposed method, a modular battery test system with high sampling frequency and high synchronization accuracy is developed. The experiment results indicate that the sampling delay would cause the estimation process to fluctuate, and the optimized method effectively improves the tolerance range of sampling delay.
Human Activity Recognition(HAR) plays an important role in the field of ubiquitous computing, which can benefit various human-centric applications such as smart homes, health monitoring, and aging ...systems. Human Activity Recognition mainly leverages smartphones and wearable devices to collect sensory signals labeled with activity annotations and train machine learning models to recognize individuals’ activity automatically. In order to deploy the Human Activity Recognition model in real-world scenarios, however, there are two major barriers. Firstly, sensor data and activity labels are traditionally collected using special experimental equipment in a controlled environment, which means fitting models trained with these datasets may result in poor generalization to real-life scenarios. Secondly, existing studies focus on single or a few modalities of sensor readings, which neglect useful information and its relations existing in multimodal sensor data. To tackle these issues, we propose a novel activity recognition model for multimodal sensory data fusion: Marfusion, and an experimental data collection platform for HAR tasks in real-world scenarios: MarSense. Specifically, Marfusion extensively uses a convolution structure to extract sensory features for each modality of the smartphone sensor and then fuse the multimodal features using the attention mechanism. MarSense can automatically collect a large amount of smartphone sensor data via smartphones among multiple users in their natural-used conditions and environment. To evaluate our proposed platform and model, we conduct a data collection experiment in real-life among university students and then compare our Marfusion model with several other state-of-the-art models on the collected datasets. Experimental Results do not only indicate that the proposed platform collected Human Activity Recognition data in the real-world scenario successfully, but also verify the advantages of the Marfusion model compared to existing models in Human Activity Recognition.
In this paper, a novel T-channel field effect transistor with three input terminals (Ti-TcFET) is proposed. The channel of a Ti-TcFET consists of horizontal and vertical sections. The top gate is ...above the horizontal channel, while the front gate and back gate are on either side of the vertical channel. The T-shaped channel structure increases the coupling area between the top gate and the front and back gates, which improves the ability of the gate electrodes to control the channel. What’s more, it makes the top gate have almost the same control ability for the channel as the front gate and the back gate. This unique structure design brings a unique function in that the device is turned on only when two or three inputs are activated. Silvaco technology computer-aided design (TCAD) simulations are used to verify the current characteristics of the proposed Ti-TcFET. The current characteristics of the device are theoretically analyzed, and the results show that the theoretical analysis agrees with the TCAD simulation results. The proposed Ti-TcFET devices with three input terminals can be used to simplify the complex circuits in a compact style with reduced counts of transistors compared with the traditional complementary metal–oxide–semiconductor/ fin field-effect transistors (CMOS/FinFETs) with a single input terminal and thus provides a new idea for future circuit designs.
Crack sealing with hot-applied sealant is a widely used technology for asphalt pavement crack repair, but the sealant usually occurs bond failure at an early stage. Due to the research on the ...mechanical changing characteristics of crack sealant bonding interface is insufficient, the systematic analysis and explanation for the early failure phenomenon is lack. Based on this, a 3D finite element (FE) model of asphalt pavement with crack repair structure is established to study the dynamic behavior characteristic of crack sealant. Firstly, the dynamic response characteristics of the crack sealant bonding interface under different repair groove sizes and forms are systematically analyzed. Then the recommended repair groove size range is given accordingly. Secondly, the effects of different vehicle speeds and axle loads on the dynamic response of the crack sealant bonding interface are analyzed. The results show that lower vehicle speeds and higher axle loads result in higher stress levels at the crack sealant bonding interface, the sensitivity of tensile stress to vehicle speed and axle load is higher than that of shear stress. Finally, the temperature stress field of the repair structure is used as a predefined field and imported into the 3D FE model. The dynamic response of crack sealant bonding interface under thermal-mechanical coupling is analyzed. The results show that the tensile stress of bonding interface is mainly affected by temperature conditions, and the vehicle load is the primary factor affecting the level of shear stress. The research findings provide a scientific insights and guidance for the evaluation of crack sealant performance and the improvement of crack repair technology.
•The recommended repair groove size range was given.•The influence of thermal-mechanical coupling was evaluated.
The combination of pavement rutting, poor road alignment, and extreme adverse weather will seriously threaten the driving safety of vehicles, whereas only a few of these factors are commonly ...concerned. This study aims to efficiently evaluate the impacts of various driving conditions on the lateral stability of the vehicle and produce a practical recommendation for pavement maintenance in what concerns rutting. A systematic framework was, thus, developed to conduct a comprehensive evaluation of the lateral stability of the vehicle, which incorporates a single-factor test and multi-factor test based on the stability indicators obtained from Carsim simulations. The vehicle road weather model was established in the Carsim software by considering seven factors, including driving speed, width–height ratio (WHR) of rutting sidewall, radius of circular curve, superelevation, crosswind angle, crosswind speed, and friction coefficient, respectively. The results show that the established framework behaves with satisfactory performance, regarding evaluating the effect of various impact factors on the lateral stability of the vehicle while driving across rutting. Stability indicators suddenly fluctuate in a short time, due to the instantaneous wandering behavior of crossing rutting. Additionally, the sudden fluctuation phenomenon is greatly enlarged, and the vehicle is inclined to occur with lateral instability when WHR equals 5, particularly in roll-over instability. It is recommended to concurrently confine the WHR greater than 10 and friction coefficient greater than 0.4, in order to ensuring driving stability. The multi-factor test revealed that the vehicle speed and WHR of the rutting are leading factors that affect driving stability, followed by the radius of circular curve, superelevation, crosswind angle, crosswind speed and friction coefficient, respectively, which are both essential factors for driving stability. The outcomes of this study may contribute to supplying guidelines for controlling key adverse conditions and making decisions on pavement maintenance.
High-elasticity anti-rutting additives, one of the most promising modifiers of asphalt mixtures, were commonly utilized for mixtures by mixing with aggregates directly. However, their interaction ...with the asphalt binder and their modification mechanism remain unclear. Accordingly, to understand the rheological behavior of asphalt binder modified with high-elasticity anti-rutting additives, three additives were added into asphalt binder to prepare high-elasticity modified asphalts (HEMAs) via a high-speed shear mixer, and the typical attributes of viscoelastic properties were investigated by the rotational viscosity (RV) test, frequency sweep test, as well as bending beam rheometer test. Following that, the relation between the macro-rheological behavior and microscopic mechanism was incorporated by applying Fourier transform infrared spectroscopy (FTIR), atomic force microscope (AFM), and fluorescence microscopy (FM) analysis, respectively. Results indicate that the incorporation of high-elasticity additives into base asphalt causes a remarkable increase in RV along with a decline in temperature susceptibility. Likewise, a higher proportion of elasticity behavior is indicated for HEMAs, for which the wider temperature range of elasticity dominance also occurs. Regarding modification mechanism, the interaction between the asphalt and additives is physical co-blending, without new characteristic peaks appearing in FTIR spectrum. The AFM test reveals the grouping effect of “bee-structures” conduces the agglomeration of wax crystals and macromolecular components, thus increasing the elasticity and RV of HEMAs. However, the poor compatibility between the ARA-U additive and asphalt leads to unsatisfactory low-temperature performance. Significantly, a large area percentage of “sea-island structure” implies better compatibility of ARA-N, which strongly confirms the existence of the plateau region in master curve. It recommends employing anti-rutting additives that are compatible with the asphalt and enable moderately increase its elasticity, which ensure considerable entanglement and sufficient network in the asphalt-additive system, so that balanced performance can be achieved for the asphalt binder.
An electrothermochromic fabric triggered by electric voltages was prepared by combining the electric heating feature of conductive polypyrrole (PPy) and the temperature-response color-changing ...feature of thermochromic inks. PPy was deposited selectively on the carbon-coated side of the sailcloth fabric via electrochemical polymerization. Thermochromic inks were painted on the reverse side with white color. The obtained fabric could be heated to about 48 °C and change its color significantly under an applied voltage of 3 V.
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