Abstract
The expansion of the new media platform has further stimulated the diversified development of content production, with various media permeating each other and products merging with each ...other, thus broadening the depth of media. With the rapid popularization of the Internet and the wide application of social software, the social environment has become more free and efficient. People use mobile multimedia to realize free communication from space, express their right to speak effectively, and change the way people get information. With the continuous development of network economy, all kinds of short videos have gradually appeared in modern people’s life, adding fun to the people’s lifestyle and enriching the forms of people’s life and entertainment. Only by exploring the construction of short video communication mode can we better reveal the real veil of how short video is popular in the new media era. This paper starts with the phenomenon of mobile short video transmission, studies and analyzes the problems of mobile short video platform, and explores the coping strategies for its development.
Uniaxial compression tests were conducted on four groups of coal samples under dry condition and 0, 3, and 5 MPa water immersion pressure using acoustic emission, scanning electron microscopy, and a ...digital scattered spot deformation monitoring system to investigate the mechanical properties and damage characteristics of coal samples under the action of water pressure. The results showed that as the water immersion pressure increased, the water-rock interaction intensified and aggravated the internal damage of the samples. The uniaxial compressive strength, elastic modulus, and peak strain decreased by 71.4%, 43.3%, and 34.74%, respectively. The deformation localized zone of the samples first appeared at the original crack in the deformation and failure process. As the water immersion pressure increased, the coal sample deformation localization zone appeared earlier, the displacement dislocation momentum of the deformation localization zone increased, and the deformation failure gradually increased, furthermore, the samples transitioned from brittle to plastic failure, and their failure mode changed from tensile to tensile-shear hybrid failure. The acoustic emission activity of the samples corresponds to their failure processes. The initial compaction stage of the samples was prolonged as the water immersion pressure increased. In the stage before the peak point, the plastic damage to the samples caused a gradual increase in the intensity and frequency of the acoustic emission signal, and multiple sudden increase points appeared. After the peak point, the active degree of the acoustic emission decreased, and the signal changed from "single tremors" to "swarm tremors" type fluctuation. The water immersion pressure promoted the water-rock interaction in the samples, the water flow continuously eroded the samples, and many water marks appeared on the fracture surface. The average porosity of the fracture surface increased, and the defect size of the coal samples increased.
It is important to conduct research on the soil freeze⁻thaw process because concurrent adverse effects always occur during this process and can cause serious damage to engineering structures. In this ...paper, the variation of the impedance signature and the stress wave signal at different temperatures was monitored by using Lead Zirconate Titanate (PZT) transducers through the electromechanical impedance (EMI) method and the active sensing method. Three piezoceramic-based smart aggregates were used in this research. Among them, two smart aggregates were used for the active sensing method, through which one works as an actuator to emit the stress wave signal and the other one works as a sensor to receive the signal. In addition, another smart aggregate was employed for the EMI testing, in which it serves as both an actuator and a receiver to monitor the impedance signature. The trend of the impedance signature with variation of the temperature during the soil freeze⁻thaw process was obtained. Moreover, the relationship between the energy index of the stress wave signal and the soil temperature was established based on wavelet packet energy analysis. The results demonstrate that the piezoceramic-based electromechanical impedance method is reliable for monitoring the soil freezing and thawing process.
Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a ...bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li
ZrO
slabs into Li
MnO
domain in Li
Ni
Mn
O
, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal-oxygen band under a deep delithiation. This restrains cation reduction, metal-oxygen bond fracture, and the formation of localized O
molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability.
In recent years, piezoelectric-based transducers and technologies have made significant progress towards structural health monitoring and damage evaluation for various metal and concrete structures. ...Timber is still commonly used as a construction material in practical engineering; however, there is a lack of research on the health monitoring of timber-based structures using piezoelectric-based transducers and methods. This paper conducts a feasibility study on timber damage detection using surface-mounted piezoelectric patches, which enable the stress-wave-based active sensing approach. Typical damage modes in timber frame structures, such as surface cracks and holes, were investigated in this study. In the active sensing approach, one piezoceramic transducer is used as an actuator to generate stress waves, which propagate along the surface of the timber structure, and other piezoceramic transducers function as sensors to detect the propagating stress waves. Defects, such as a crack or a hole, induce additional attenuation to the propagating stress wave. Based on this attenuation, the proposed method can detect the defects using the wavelet-packet-based damage index, demonstrating its implementation potential for real-time timber damage detection.
The filling of thin-walled steel tubes with quartz sand can help to prevent the premature buckling of the steel tube at a low cost. During an impact, the internal stress of the quartz sand-filled ...steel tube column is subjected to not only axial force but also lateral confining force, resulting in complicated internal stress. A suitable sensor for monitoring the internal stress of such a structure under an impact is important for structural health monitoring. In this paper, piezoceramic Smart Aggregates (SAs) are embedded into a quartz Sand-Filled Steel Tube Column (SFSTC) to monitor the internal structural stress during impacts. The piezoceramic smart aggregates are first calibrated by an impact hammer. Tests are conducted to study the feasibility of monitoring the internal stress of a structure. The results reflect that the calibration value of the piezoceramic smart aggregate sensitivity test is in good agreement with the theoretical value, and the output voltage value of the piezoceramic smart aggregate has a good linear relationship with external forces. Impact tests are conducted on the sand-filled steel tube with embedded piezoceramic smart aggregates. By analyzing the output signal of the piezoceramic smart aggregates, the internal stress state of the structure can be obtained. Experimental results demonstrated that, under the action of impact loads, the piezoceramic smart aggregates monitor the compressive stress at different locations in the steel tube, which verifies the feasibility of using piezoceramic smart aggregate to monitor the internal stress of a structure.
High capacity and superlong cycle life of Li3VO4 have been actualized via carbon hybridization and N doping. The Li3VO4/N doped C (Li3VO4/N–C) that fabricated via an in situ carbonization method ...based on an intermedial solution phase delivers initial discharge and charge capacities of 686 and 540 mAh g−1 at a specific current of 0.15 A g−1, which maintain of 538 and 536 mAh g−1 after 800 cycles, showing excellent cycle stability. Meanwhile, the Li3VO4/N–C exhibits superior rate performance and long life performance. After 150 cycles at various specific currents from 0.1 to 2.0 A g−1, the discharge and charge capacities can restore 100% when reverting the specific current to 0.1 A g−1. After 1100 cycles at a specific current of 2.0 A g−1, the discharge and charge capacities can maintain of 340 and 337 mAh g−1, showing no capacity attenuation in cycling.
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•Li3VO4/N–C hybrids are successfully prepared via a facile way.•The Li3VO4/N–C shows homogeneous hybridization between Li3VO4 and N–C at nanoscale.•The Li3VO4/N–C exhibits ultrahigh reversible capacity of 536 mAh g−1.•The Li3VO4/N–C exhibits superlong cycle life over 1100 cycles without capacity attenuation.
Co substitution has been extensively used to improve the electrochemical performances of cathode materials for sodium-ion batteries (SIBs), but the role of Co has not been well understood. Herein, we ...have comprehensively investigated the effects of Co substitution for Ni on the structure and electrochemical performances of Na0.7Mn0.7Ni0.3-xCoxO2 (x = 0, 0.1, 0.3) as cathode materials for SIBs. In comparison with the Co-free sample, the high-rate capability and cycle performance have been greatly improved by the substitution of Co, and some new insights into the role of Co have been proposed for the first time. With the substitution of Co(3+) for Ni(2+) the lattice parameter a decreases; however, c increases, and the d-spacing of the sodium-ion diffusion layer has been enlarged, which enhances the diffusion coefficient of the sodium ion and the high-rate capability of cathode materials. In addition, Co substitution shortens the bond lengths of TM-O (TM = transition metal) and O-O due to the smaller size of Co(3+) than Ni(2+), which accounts for the decreased thickness and volume of the TMO6 octahedron. The contraction of TM-O and O-O bond lengths and the shrinkage of the TMO6 octahedron improve the structure stability and the cycle performance. Last but not least, the aliovalent substitution of Co(3+) for Ni(2+) can improve the electronic conductivity during the electrochemical reaction, which is also favorable to enhance the high-rate performance. This study not only unveils the role of Co in improving the high-rate capability and the cycle stability of layered Na0.7Mn0.7Ni0.3-xCoxO2 cathode materials but also offers some new insights into designing high performance cathode materials for SIBs.
Two novel polymers PTFBDT-BZS and PTFBDT-BZO with 4-alkyl-3,5-difluorophenyl substituted benzodithiophene as the donor unit, benzothiadiazole or benzooxadiazole as the acceptor unit, and thiophene as ...the spacer have been synthesized and used as donor materials for polymer solar cells (PSCs). These two polymers exhibited wide optical band gaps of about 1.8 eV. PSCs with the blend of PTFBDT-BZS:PC71BM (1:2, by weight) as the active layer fabricated without using any processing additive and any postannealing treatment showed power conversion efficiency (PCE) of 8.24% with an open circuit voltage (V oc) of 0.89 V, a short circuit current (J sc) of 12.67 mA/cm2, and a fill factor (FF) of 0.73 under AM 1.5G illumination, indicating that PTFBDT-BZS is a very promising donor polymer for PSCs. The blend of PTFBDT-BZO:PC71BM showed a lower PCE of 5.67% with a V oc of 0.96 V, a J sc of 9.24 mA/cm2, and an FF of 0.64. One reason for the lower PCE is probably due to that PTFBDT-BZO has a smaller LUMO offset with PC71BM, which cannot provide enough driving force for charge separation. And another reason is probably due to that PTFBDT-BZO has a lower hole mobility in comparison with PTFBDT-BZS.
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