关键词：
air decomposition pollutants;MoS2;ZnO;TiO2;gas sensor;DFT
摘要：
When partial discharges occur in air-insulated equipment, the air decomposes to produce a variety of contamination products, resulting in a reduction in the insulation performance of the insulated equipment. By monitoring the concentration of typical decomposition products (CO, NO, and NO(2)) within the insulated equipment, potential insulation faults can be diagnosed. MoS(2) has shown promising applications as a gas-sensitive semiconductor material, and doping metal oxides can improve the gas-sensitive properties of the material. Therefore, in this work, MoS(2) has been doped using the popular metal oxides (ZnO, TiO(2)) of the day, and its gas-sensitive properties to the typical decomposition products of air have been analyzed and compared using density functional theory (DFT) calculations. The stability of the doped system was investigated using molecular dynamics methods. The related adsorption mechanism was analyzed by adsorption configuration, energy band structure, density of states (DOS) analysis, total electron density (TED) analysis, and differential charge density (DCD) analysis. Finally, the practical application of related sensing performance is evaluated. The results show that the doping of metal oxide nanoparticles greatly improves the conductivity, gas sensitivity, and adsorption selectivity of MoS(2) monolayer to air decomposition products. The sensing response of ZnO-MoS(2) for CO at room temperature (25 °C) reaches 161.86 with a good recovery time (0.046 s). TiO(2)-MoS(2) sensing response to NO(2) reaches 3.5 × 10(6) at 25 °C with a good recovery time (0.108 s). This study theoretically solves the industrial challenge of recycling sensing materials and provides theoretical value for the application of resistive chemical sensors in air-insulated equipment.
摘要：
Two-dimensional transition metal disulfides (TMDs) heterojunction is a very promising non-precious metal catalyst that has been widely used as a catalyst for hydrogen evolution reactions. In this paper, the effects of different positions of Se vacancies on the electronic structure and hydrogen evolution reaction electrocatalyst of MoSe2/WSe2 heterojunction are investigated by first-principles calculations. After the introduction of vacancy, defect states appear between the conduction band bottom and the Fermi energy level of the heterojunction. This is more favorable for the electron transfer between H and the substrate. The results of the density of states calculations indicate that the defect states appear because the d orbitals of the transition metal atoms containing the Se vacancy layer hybridize with the p orbitals of the Se atoms. The differential charge density indicates that the Se vacancies promote the charge transfer of MoSe2/WSe2. In addition, calculations of the Gibbs free energy for the hydrogen evolution reaction of heterojunctions show that Se vacancies (especially the outer vacancies) enhance the electrocatalytic hydrogen precipitation performance of heterojunctions. The results provide a new way to regulate the hydrogen evolution properties of MoSe2/WSe2 heterojunctions.
摘要：
While highly sensitive elastic strain sensors have been widely investigated, the time-dependent stress sensitivity of viscoelastic MWCNT/polyethylene nanocomposite stress sensors remains to be explored. In this paper, we develop an electromechanically coupled homogenization scheme to reveal the time-dependent stress sensing performances of viscoelastic MWCNT/polyethylene nanocomposite sensors. In the time-dependent context, the complex moduli and electrical conductivity are selected as the dual homogenization parameters. The time-dependent stress sensitivity is illustrated through the viscoelastic imperfect interface connection and stress-induced tunneling distance. The predicted stress sensing capacities of viscoelastic MWCNT/polyethylene nanocomposite stress sensors are shown to be consistent with the experiments under the constant stress loading. It reveals that the stress sensitivity factor increases with the loading time under constant stress. The optimal MWCNT aspect ratio for high sensing capacities exhibits an increasing trend regarding the MWCNT volume fraction. The uncovered sensing characteristics can provide microstructural design guidance in high-performance nanocomposite stress sensors.
关键词：
Air discharge pollutants;Single-walled CNT;Geometric structure;Gas adsorption;DFT
摘要：
Air is a good insulating medium under normal conditions. The insulation performance of many electrical equipment is closely related to air. The detection of air decomposition pollutants is considered to be one of the effective ways to diagnose the fault of air insulated power equipment. Based on the first-principles, the adsorption and sensing characteristics of Single-walled CNT modified by transition metal clusters (Crn) for air discharge pollutants (CO, NOx) were analyzed. Firstly, through the modeling and analysis of different doping sites, four most stable models of Crn doped SWCNT are obtained, and their resistance is briefly analyzed. On the basis of these four configurations, the most stable adsorption configurations were found. The corresponding adsorption energy, adsorption distance and transfer charge are obtained. Then, the differential charge density, frontier molecular orbitals, adsorption selectivity and desorption properties of each system were analyzed. The result is that Crn-SWCNT surface has a good adsorption capacity for pollutants. The theoretical recovery time is not ideal at room temperature. However, CO can be rapidly desorbed from the surface of Crn-SWCNT at extremely high temperatures. Interestingly, Crn-SWCNT can be used as solid adsorption materials for purifying CO, NOx. This work provides a new idea for clean air to treat air discharge pollutants.
摘要：
This paper presents a stepped electromagnetic bandgap(EBG) hosted on the T-shaped stepped stub with an inverted H-shaped slot etched on the ground to enhance bandwidth and improve isolation for a compact UWB-MIMO antenna developed from our previous design. The characteristic mode analysis is used to offer physical insight into the operation phenomena taking place in the evolution of antenna. The proposed antenna has a compact size of $27\times 22\times 0.8$ mm and realize bandwidth from 3.07 GHz to 11.1 GHz, keeping the isolation more than 20 dB. Key parameters evaluating the antenna performance like radiation pattern, gain, radiation efficiency above 75% and envelope correlation coefficient below 0.05 are investigated. The simulated and measured results agree well, testifying the proposed MIMO antenna is a suitable candidate for UWB applications.
通讯机构：
[Fang, C ] W;Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Peoples R China.
关键词：
Flowering plants;Feature extraction;Image color analysis;Convolutional neural networks;Computational modeling;YOLO;Real-time systems;Image recognition;Agricultural products;Tomato flower fruit recognition;C3Faster;convolutional neural networks;lightweight
摘要：
In order to monitor the growth and development of tomatoes, and improve the efficiency of flower and fruit thinning and tomato picking, this paper constructs a tomato flower and fruit dataset and proposes a TF-YOLOv5s model for the detection of tomato flowers and fruits in natural environments. Based on the YOLOv5s model, a C3Faster module is introduced to reduce the number of parameters and calculations while maintaining detection accuracy. The regular convolution is replaced by depth-wise separable convolution (DWConv) to avoid parameter redundancy. To improve the convergence and accuracy of the model, this paper replaces Complete Intersection over Union (CIoU) loss with Efficient Intersection over Union (EIoU) loss. The Squeeze-and-Excitation (SE) module is added to improve the model’s sensitivity to the features of the tomato flowers and fruits. Compared with the baseline model, the number of parameters is reduced by 54.5%, the weight file is reduced by 52.8%, the Floating-point Operation Per second (FLOPs) is reduced by 48.7%. The detection accuracy of tomato flowers and fruits mAP@0.5 has improved by 1.4% and 1.2% respectively. TF-YOLOv5s is used to detect three types of targets: tomato flowers, red tomatoes, and green tomatoes, and mAP@0.5 of which can reach as high as 95.2%. Furthermore, the improved algorithm is deployed on two edge computing devices to verify its effectiveness. Experimental results show that the algorithm in this paper can achieve high detection with less computational resources. This algorithm has the potential value of application in practical tomato production.
期刊：
Digital Signal Processing,2024年144:104288 ISSN：1051-2004
通讯作者：
Ou, WH
作者机构：
[Xiong, Jiahao; Ou, Weihua; Ou, WH; Chen, Longbao; Han, Jie] Guizhou Normal Univ, Sch Big Data & Comp Sci, Guiyang 550025, Peoples R China.;[Zeng, Wu] Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430000, Peoples R China.;[Gou, Jianping] Southwest Univ, Coll Comp & Informat Sci, Coll Software, Chongqing 400715, Peoples R China.
通讯机构：
[Ou, WH ] G;Guizhou Normal Univ, Sch Big Data & Comp Sci, Guiyang 550025, Peoples R China.
关键词：
Face video;Heart rate;Remote photoplethysmography;Group sparse representation
摘要：
Non-contact heart rate measurement based on face video is rapidly developed due to its comfort and wide application. However, it is difficult to extract the pulse signals for non-contact heart rate measurement due to the various interference factors, such as illumination variation, head motion and face expression. In this paper, we propose group sparse representation to reconstruct the pulse signals, then estimate the heart rate based on the fact that the real heart rate is consistent at the same time from different sub-regions. Specifically, we formulate the reconstruction of pulse signals as group sparse representation problem and require the raw signals of all the sub-regions to be similar sparse representation. Firstly, we use the face detection algorithm to obtain the region of interest (ROI) and divide it into sub-regions, followed by the distortion compensation of color signals from different sub-regions. Then we extract the sub-region chrominance signals and select the high-quality chrominance signals to construct the raw pulse signals matrix. After that, we construct a mixed pulse dictionary containing discrete cosine bases and wavelet bases considering the periodicity and pulsatility of the pulse signals. Finally, we conduct group sparse representation to reconstruct the pulse signals and estimate the heart rate via spectral analysis based on the reconstructed pulse signals. Experimental results on three public datasets show that this method outperforms most existing heart rate measurement methods.
摘要：
The magnetization and magnetostriction properties of Mn1_xMgxV2O4 (x = 0.00, 0.10, 0.15, 0.20) single crystals have been investigated under both static and pulsed magnetic fields, in which the magnetization and magnetostriction behaviors exhibit field-sweep-rate dependence, which are related to the spin-orbital-lattice coupling in these systems. Especially, anomalous enhancement of spin-orbital correlation was observed for x = 0.15. We attribute this enhancement to the tuning on the canting angle of V3+ ions by Mg2+-ions substitution. Furthermore, while the inter-vanadium distance RV-V is important to determine the evolution of the properties in the doped cases proposed by many studies, our result suggests that RV-V is not always dominant, the spin-orbital correlation effect can survive from the disordering induced by the variation of RV-V and even be enhanced at proper doping level.
作者机构：
[Guo, Siqi; Cheng, Ningyan; Ge, Binghui; Zhang, Jialin] Anhui Univ, Inst Phys Sci & Informat Technol, Informat Mat & Intelligent Sensing Lab Anhui Prov, Key Lab Struct & Funct Regulat Hybrid Mat,Minist, Hefei 230601, Peoples R China.;[Ren, Long; Ji, Yuan] Wuhan Univ Technol, Int Sch Mat Sci & Engn, State Key Lab Adv Technol Mat Synth & Proc, Wuhan 430070, Peoples R China.;[Liu, Huating] Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Peoples R China.;[Yang, Ming] Beihang Univ, Sch Phys, Beijing 100191, Peoples R China.
通讯机构：
[Cheng, NY; Ge, BH ] A;[Ren, L ] W;Anhui Univ, Inst Phys Sci & Informat Technol, Informat Mat & Intelligent Sensing Lab Anhui Prov, Key Lab Struct & Funct Regulat Hybrid Mat,Minist, Hefei 230601, Peoples R China.;Wuhan Univ Technol, Int Sch Mat Sci & Engn, State Key Lab Adv Technol Mat Synth & Proc, Wuhan 430070, Peoples R China.
关键词：
carbothermal reduction;electrocatalysts;in situ;structure evolution;transmission electron microscopy
摘要：
Atomic understanding of a chemical reaction can realize the programmable design and synthesis of desired products with specific compositions and structures. Through directly monitoring the phase transition and tracking the dynamic evolution of atoms in a chemical reaction, in situ transmission electron microscopy (TEM) techniques offer the feasibility of revealing the reaction kinetics at the atomic level. Nevertheless, such investigation is quite challenging, especially for reactions involving multi-phase and complex interfaces, such as the widely adopted carbothermal reduction (CTR) reactions. Herein, in-situ TEM is applied to monitor the CTR of Co3O4 nanocubes on reduced graphene oxide nanosheets. Together with the first-principle calculation, the migration route of Co atoms during the phase transition of the CTR reaction is revealed. Meanwhile, the interfacial edge-dislocations/stress-gradient is identified as a result of the atomistic diffusion, which in turn can affect the morphology variation of the reactants. Accordingly, controllable synthesis of Co-based nanostructure with a desirable phase and structure has been achieved. This work not only provides atomic kinetic insight into CTR reactions but also offers a novel strategy for the design and synthesis of functional nanostructures for emerging energy technologies.
作者机构：
[Zhao, Xu; Li, Shaozhen] Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Peoples R China.;[Wu, Sujuan; Zhong, Shoudeng; Wu, SJ; Wang, Shuqi] South China Normal Univ, Inst Adv Mat, South China Acad Adv Optoelect, Guangzhou 510006, Peoples R China.;[Wu, Sujuan; Zhong, Shoudeng; Wu, SJ; Wang, Shuqi] South China Normal Univ, South China Acad Adv Optoelect, Guangdong Prov Key Lab Quantum Engn & Quantum Mat, Guangzhou 510006, Peoples R China.
通讯机构：
[Wu, SJ ] S;[Li, SZ ] W;Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Peoples R China.;South China Normal Univ, Inst Adv Mat, South China Acad Adv Optoelect, Guangzhou 510006, Peoples R China.;South China Normal Univ, South China Acad Adv Optoelect, Guangdong Prov Key Lab Quantum Engn & Quantum Mat, Guangzhou 510006, Peoples R China.
关键词：
potassium thiocyanate;diluted PEDOT:PSS solution;tin-based perovskite solar cells;photovoltaic performance
摘要：
The commercialized poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) is usually used as hole transport layers (HTLs) in tin-based perovskite solar cells (TPSCs). However, the further development has been restricted due to the acidity that could damage the stability of TPSCs. Although the PEDOT:PSS solution can be diluted by water to decrease acidity and reduce the cost of device fabrication, the electrical conductivity will decrease obviously in diluted PEDOT:PSS solution. Herein, potassium thiocyanate (KSCN) is selected to regulate the properties of PEDOT:PSS HTLs from the diluted PEDOT:PSS aqueous solution by water with a volume ratio of 1:1 to prepare efficient TPSCs. The effect of KSCN addition on the structure and photoelectrical properties of PEDOT:PSS HTLs and TPSCs have been systematically studied. At the optimal KSCN concentration, the TPSCs based on KSCN-doped PEDOT:PSS HTLs (KSCN-PSCs) demonstrate the champion power conversion efficiency (PCE) of 8.39%, while the reference TPSCs only show a champioan PCE of 6.70%. The further analysis demonstrates that the KSCN additive increases the electrical conductivity of HTLs prepared by the diluted PEDOT:PSS solution, improves the microstructure of perovskite film, and inhibits carrier recombination in TPSCs, leading to the reduced hysteresis effect and enhanced PCE in KSCN-PSCs. This work gives a low-cost and practical strategy to develop a high-quality PEDOT:PSS HTLs from diluted PE-DOT:PSS aqueous solution for efficient TPSCs.
摘要：
The structural, electronic and optical properties of MoSSe, PbS (111) and MoSSe/PbS (111) have been studied by the first-principles calculations, and the effect of V(S)on electronic and optical properties of MoSSe/PbS (111). When PbS (111) is stacked on MoSSe, an internal electric field and ohmic contact are formed at interlayer, and exhibited metal property. Compared with MoSSe and PbS (111) monolayer, MoSSe/PbS (111) heterostructure has higher absorption coefficients. Further analysis shows that this can be attributed to the orbital hybridization between the heterostructure layers. When V(S)is introduced, spin splitting occurs, making the spin-down channel below the Fermi level and inducing half-metallicity. What's more, Vs MoSSe/PbS (111) still performances better optical absorption coefficient. Based on these findings, the heterogeneous structures and defects not only affect the electronic properties, but also can be used as an effective method to regulate the electrical and optical properties, providing useful theoretical guidance for further experimental studies.
作者：
Fang, Chao;Chen, Xiqu;Zhang, Juanjuan;Xia, Xiaodong;Weng, George J.
期刊：
Journal of Physics D: Applied Physics,2023年56(4):045301 ISSN：0022-3727
通讯作者：
George J Weng
作者机构：
[Fang, Chao; Chen, Xiqu] Wuhan Polytech Univ, Dept Elect & Elect Engn, Wuhan 430023, Hubei, Peoples R China.;[Zhang, Juanjuan] Lanzhou Univ, Key Lab Mech Environm & Disaster Western China, Minist Educ China, Lanzhou 730000, Gansu, Peoples R China.;[Zhang, Juanjuan] Lanzhou Univ, Coll Civil Engn & Mech, Dept Mech & Engn Sci, Lanzhou 730000, Gansu, Peoples R China.;[Xia, Xiaodong] Cent South Univ, Sch Civil Engn, Changsha 410083, Peoples R China.;[Weng, George J.] Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA.
通讯机构：
[George J Weng] D;Department of Mechanical and Aerospace Engineering, Rutgers University, New Brunswick, NJ 08903, United States of America
关键词：
graphene films;EMI shielding;electromagnetic plane wave;path;wrinkles;Monte Carlo
摘要：
In this paper, the electromagnetic interference shielding effectiveness (EMI SE) of multilayer graphene films is studied by the Monte Carlo (MC) method. First, we use the transfer matrix method to study the transmission and reflection of electric fields of the incident light passing through the graphene plane and the dielectric interface, and then determine the reflection and transmission probability of the light. In this way, the path of light can be obtained by the MC method. From the distance and emission direction of a large number of lights passing through the film, the expected value of the emitted light field is calculated and the EMI SE is determined. The obtained results of SE are shown to be in good agreement with several sets of experimental data. This model also takes into account the influence of wrinkles of graphene. It is found that EMI SE first increases and then decreases with the increase of wrinkle. The effects of film thickness, conductivity, and dielectric constant on EMI SE in the X-band frequency range are also investigated.
通讯机构：
[Lei, C; Liu, S ] W;Wuhan Univ, Inst Technol Sci, Wuhan 430072, Peoples R China.;Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.
关键词：
RF compression cavity;dynamic atomic motion;ultrafast electron diffraction
摘要：
Ultrafast electron diffraction (UED) is a powerful tool for observing the evolution of transient structures at the atomic level. However, temporal resolution is a huge challenge for UEDs, mainly depending on the pulse duration. Unfortunately, the Coulomb force between electrons causes the pulse duration to increase continually when propagating, reducing the temporal resolution. In this paper, we theoretically design a radio frequency (RF) compression cavity using the finite-element method of electromagnetic-thermal coupling to overcome this limitation and obtain a high-brightness, short-pulse-duration, and stable electron beam. In addition, the cavity's size parameters are optimized, and a water-cooling system is designed to ensure stable operation. To the best of our knowledge, this is the first time that the electromagnetic-thermal coupling method has been used to study the RF cavity applied to UED. The results show that the RF cavity operates in TM010 mode with a resonant frequency of 2970 MHz and generates a resonant electric field. This mode of operation generates an electric field that varies periodically and transiently, compressing the electronic pulse duration. The electromagnetic-thermal coupling method proposed in this study effectively improves the temporal resolution of UED.
摘要：
Multipartite nonlocality is a measure of multipartite quantum correlations. In this paper we investigate the influence of symmetry-breaking perturbations upon ground-state nonlocality by considering several typical finite-size quantum models, including the transverse-field Ising chains, the XY ( XX ) chains, and the XXZ chains. We find that even a slight perturbation can reshape the nonlocality curve dramatically. For instance, in the XY chains, a perturbation can induce an oscillation behavior in the nonlocality curve. A clear microscopic mechanism for the results is proposed. Furthermore, we also connect the behaviors to the macroscopic symmetry properties of the chains and make some predictions on general models.
通讯机构：
[Liu, HT ] W;[Liu, HT; Huang, ZY ] X;Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Peoples R China.;Xiangtan Univ, Sch Phys & Optoelect, Hunan Key Lab Micronano Energy Mat & Devices, Xiangtan 411105, Hunan, Peoples R China.;Hunan Univ, Hunan Key Lab Two Dimens Mat, Changsha 410082, Peoples R China.
关键词：
Janus transition metal dichalcogenides;heterostructures;electronic structure;multilayer
摘要：
The structure and electronic properties of bilayer, trilayer, and multilayer vertical Janus heterostructures are studied by first-principles calculation. By comparing the electronic structure of monolayer SMoS, monolayer SeMoS, and SMoS/SeMoS heterostructures, it has been found that, when SMoS forms heterostructures with more than two layers of Janus SeMoS, the band gap of the system changes from direct to indirect. In the Janus heterostructure system, significant charge transfer occurs between layers and a certain built-in electric field occurs. Due to the different contribution of Mo-d orbital coupling to CBM in different SeMoS layers, the band gap oscillates periodically with three layers of SeMoS. As the number of SeMoS layers in the heterostructure increases, the electrostatic potential difference and built-in electric field of the system increases continuously, resulting in the band gap value decreasing slowly. At the same time, the valence band offset value of the heterostructure constructed by SMoS and multilayer SeMoS decreases, and the conduction band offset value increases. These properties enrich the research and application of transition metal dichalcogenide-related heterostructures as optoelectronic and nanoelectronic devices.
关键词：
UAV;artificial potential field method;virtual target points;adaptive step size;path planning
摘要：
The obstacle avoidance system of a drone affects the quality of its flight path. The artificial potential field method can react quickly when facing obstacles; however, the traditional artificial potential field method lacks consideration of the position information between drones and obstacles during flight, issues including local minima, unreachable targets, and unreasonable obstacle avoidance techniques that lengthen flight times and consume more energy get encountered. Therefore, an improved artificial potential field method is proposed. First, a collision risk assessment mechanism was introduced to avoid unreasonable obstacle avoidance actions and reduce the length of unmanned aerial vehicle flight paths. Then, to solve the problem of local minimum values and unreachable targets, a virtual sub-target was set up and the traditional artificial potential field model was modified to enable the drone to avoid obstacles and reach the target point. At the same time, a virtual sub-target evaluation factor was set up to determine the reasonable virtual sub-target, to achieve a reasonable obstacle avoidance path compared to the traditional artificial potential field method. The proposed algorithm can plan a reasonable path, reduce energy consumption during flight, reduce drone turning angle changes in the path, make the path smoother, and can also be applied in complex environments.
摘要：
The oscillatory potential well can cause the mass points in it to move chaotically, which can be considered as a physical mechanism of chaos generation. Based on this physical mechanism, the oscillatory multi-well potential with multi-concave is used to generate controllable multi-scroll chaotic attractors with multi-wing. These attractors have two kinds of topological units: scroll and wing. The topological structure of the attractor depends on the shape of the potential well, that is, the wells and the concaves correspond to the scrolls and wings of the attractor. By constructing potential wells with different shapes, we can obtain attractors with different topological structure. The number of scrolls and wings of the chaotic attractor can be controlled by the oscillation amplitude of the potential well and damping coefficient, that is, stronger oscillation or smaller damping allows the mass points to enter the higher potential wells or concaves, resulting in attractors with more scrolls or wings. As the number of scrolls or wings increases, the attractors become more complex, as expressed by Poincare & PRIME; maps and quantified by the Kaplan-Yorke dimensions. Kaplan-Yorke dimensions of attractors can be adjusted continuously from 2 to 3 by the two control parameters. Finally, the results are confirmed by Multisim simulation circuit and actual analog circuit.
摘要：
We investigate the many-body localization (MBL) transitions in a spin-1/2 Heisenberg chain with an on-site random magnetic field by employing global quantum discord (GQD). We use the disorder-averaged GQD to estimate the MBL critical point, which is found to be around at $W_{c}=3.8$ by making a finite-size scaling analysis. We further compare our results of GQD with those of half-chain entanglement entropy (EE) that is promising in the study of MBL. We show that GQD can exclude the finite-size interference under the same condition, which implies that GQD is more robust than the half-chain EE in characterizing MBL.
