摘要：
With the advancements in low-power and miniature electronics, various smart devices are deployed and interconnected as the Internet of Things (IoT), collecting a massive amount of data from surrounding environments. Despite the popularity of ZigBee for low-power communications in IoT, WiFi has recently been recommended for data collection in IoT for its high data rate, high reliability, native IP compatibility, and vastly-deployed infrastructures. However, it is well known that WiFi is energy-consuming. Although many schemes have been designed to reduce WiFi energy consumption, they usually suffer from the dilemma that a longer (shorter) sleep of WiFi gives a lower (higher) energy consumption but a larger (smaller) latency, hindering the use of WiFi in a wide range of IoT applications that require a certain level of quality of service (QoS). To this end, we propose a Heterogeneity-aware Dual-interface Scheduling (HDS) scheme to fully exploit the heterogeneity between ZigBee and WiFi to realize energy-efficient and delay-constrained data collection in a tree-based IoT network, where each device is equipped with a ZigBee and a WiFi interface. The low-power feature of ZigBee is utilized as much as possible for high energy efficiency, while the high-reliability advantage of WiFi is leveraged when the ZigBee link quality is low for delay guarantee. Under network dynamics, HDS jointly allocates ZigBee and WiFi schedules to strike a balance between energy and delay for optimized performance. A prototype system is built atop an IoT platform integrated with commercial off-the-shelf ZigBee and WiFi modules. Experiment results show that the energy consumption of HDS is 80.3% and 43.6% lower than the standard power saving protocol and a state-of-the-art dual-interface scheme, respectively, under a moderate delay constraint. Additionally, the percentage of data packets that satisfy the delay constraint is above 98.6%.
期刊：
EUROPEAN PHYSICAL JOURNAL C,2024年84(1):1-7 ISSN：1434-6044
通讯作者：
Chen, X
作者机构：
[Zhou, Jing] Hunan City Univ, Dept Phys, Yiyang 413000, Hunan, Peoples R China.;[Zhou, Jing] Hunan City Univ, All solid state Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.;[Zhou, Jing; Ping, Jialun] Nanjing Normal Univ, Dept Phys, Nanjing 210097, Jiangsu, Peoples R China.;[Chen, Jun] Hubei Minzu Univ, Dept Phys, Enshi 445000, Peoples R China.;[Zhang, Le] Hubei Normal Univ, Coll Phys & Elect Sci, Huangshi 435002, Peoples R China.
通讯机构：
[Chen, X ] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.
摘要：
According to gauge/gravity correspondence, we study the holographic Schwinger effect within an anisotropic background. Firstly, the separate length of the particle-antiparticle pairs is computed within the context of an anisotropic background which is parameterized by dynamical exponent nu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\nu $$\end{document}. It is found that the maximum separate length x increases with the increase of dynamical exponent nu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\nu $$\end{document}. By analyzing the potential energy, we find that the potential barrier increases with the dynamical exponent nu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\nu $$\end{document} at a small separate distance. This observation implies that the Schwinger effect within an anisotropic background is comparatively weaker when contrasted with its manifestation in an isotropic background. Finally, we also find that the Schwinger effect in the transverse direction is weakened compared to the parallel direction in the anisotropic background, which is consistent with the top-down model.
摘要：
Fatigue driving is a serious threat to road safety, which is why accurately identifying fatigue driving behavior and warning drivers in time are of great significance in improving traffic safety. However, accurately recognizing fatigue driving is still challenging due to large intra-class variations in facial expression, continuity of behaviors, and illumination conditions. A fatigue driving recognition method based on feature parameter images and a residual Swin Transformer is proposed in this paper. First, the face region is detected through spatial pyramid pooling and a multi-scale feature output module. Then, a multi-scale facial landmark detector is used to locate 23 key points on the face. The aspect ratios of the eyes and mouth are calculated based on the coordinates of these key points, and a feature parameter matrix for fatigue driving recognition is obtained. Finally, the feature parameter matrix is converted into an image, and the residual Swin Transformer network is presented to recognize fatigue driving. Experimental results on the HNUFD dataset show that the proposed method achieves an accuracy of 96.512%, thus outperforming state-of-the-art methods.
摘要：
Driver behavior is an essential factor affecting traffic safety, and driver behavior monitoring systems (DMSs) are widely exploited in intelligent transportation systems to reduce the risk of traffic accidents. However, understanding driver behavior is challenging because of the uncertainty of real driving scenarios. Most of the existing methods use deterministic models, which suffer from data uncertainty, for recognizing driver behaviors. In this paper, the fuzzy deep attention network (FDAN) method is proposed to improve driver behavior recognition. FDAN integrates fuzzy logic and an attention mechanism into deep neural networks, which enhances the representation ability of the model and reduces the uncertainty of the data. The attention mechanism with a lightweight squeeze -and -excitation block is embedded in the deep learning model for adaptively refining features. A DMS is designed, and the distracted driver dataset from the real scene is built. Experimental results confirm the proposed method performs better than the existing methods.
作者机构：
[Hu, Xiaojie; Dong, Fuxiao; Wang, Haiou; Zhao, Bojun; Huo, Dexuan; Wang, Yan] Hangzhou Dianzi Univ, Inst Mat Phys, Key Lab Novel Mat Sensor Zhejiang Prov, Hangzhou 310018, Peoples R China.;[Tan, Weishi] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413002, Peoples R China.;[Tan, Weishi] Nanjing Univ Sci & Technol, Dept Appl Phys, Key Lab Soft Chem & Funct Mat, Minist Educ, Nanjing 210094, Peoples R China.
通讯机构：
[Weishi Tan; Haiou Wang] A;Authors to whom correspondence should be addressed.<&wdkj&>All-Solid-State Energy Storage Materials and Devices Key Laboratory of Hunan Province, College of Information and Electronic Engineering, Hunan City University, Yiyang 413002, China<&wdkj&>Key Laboratory of Soft Chemistry and Functional Materials, Ministry of Education, Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094, China<&wdkj&>Authors to whom correspondence should be addressed.<&wdkj&>Key Laboratory of Novel Materials for Sensor of Zhejiang Province, Institute of Material Physics, Hangzhou Dianzi University, Hangzhou 310018, China
关键词：
magnetic properties;magnetocaloric;manganite;film;Pr0.7Sr0.3MnO3
摘要：
The magnetic behaviors and magnetocaloric effect (MCE) of Pr0.7Sr0.3MnO3 (PSMO-7) film grown on a (001) SrTiO3 single-crystal substrate by a pulsed laser deposition (PLD) were studied in this paper. X-ray diffraction with a high resolution (HRXRD) measurement shows that PSMO-7 film is grown with a (001) single orientation. The magnetic properties and the MCE related to the ferromagnetic (FM) phase transition of the PSMO-7 film are investigated using the temperature dependence of magnetization M(T) and the magnetic field dependence of magnetization M(H). The M(T) data suggest that with decreasing temperatures, the PSMO-7 film goes through the transition from the paramagnetic (PM) state to the FM state at around the Curie temperature (T-C). The T-C (about 193 K) can be obtained by the linear fit of the Curie law. Magnetic hysteresis loop measurements show that the PSMO-7 film exhibits the FM feature at temperatures of 10, 100, and 150 K (low magnetic hysteresis can be found), while the film reveals the PM feature with the temperature increased up to 200 and/or 300 K. The research results of M(H) data are consistent with the M(T) data. Furthermore, the magnetic entropy change (-delta S-M) of the PSMO-7 film was studied. It was found that the maximum value of (-delta S-M) near T-C reaches about 4.7 J/kg & BULL;K under the applied field change of 20 kOe, which is comparable to that of metal Gd (-delta S-M of 2.8 J/kg K under 10 kOe), indicating the potential applications of PSMO-7 film in the field of magnetic refrigeration.
关键词：
Semiconductors;Nanocomposites;Coaxial CdS@ZnO nanowire array;Photodegradation;Methylene blue
摘要：
Herein, a novel coaxial CdS@ZnO nanowire array catalyst was synthesized by magnetron sputtering and hy-drothermal method. The optimum photocatalytic composite was obtained by controlling the ratio of CdS and ZnO. Take methylene blue (MB) as the model, the CdS@ZnO nanowire array (CdS@ZnO-10) exhibited strong photocatalytic solid activity, and the highest adsorption and photodegradation rate of MB reached 90.38 % in 50 min and 99.13 % in 120 min under simulated sunlight illumination. The mechanism of the heterojunction interface affecting photocatalytic performance was studied. Therefore, the synthesis approach could offer new design and controllable construction of coaxial structure for organic dye pollutant degradation.
摘要：
In recent years, the provision of applications based on conferencing services over Software-Defined Networking (SDN) is increasing. So far, extensive studies have been conducted on improving conferencing services and supporting high-quality communication in SDN, and the importance of the issue has been understood by the research society. One of the challenges of guaranteeing conferencing services in SDN is the routing of network traffic taking into account Quality of Service (QoS) requirements. Most routing techniques in SDN guarantee end-to-end delay and bandwidth constraints. However, resource loss also plays a role in network performance, where it is clearly neglected in existing works. This study presents a guaranteed Latency-Bandwidth-Loss Routing algorithm based on Fuzzy approach to improve the performance of conference services in SDN (LBLRF). The purpose of the fuzzy-based approach is to increase the number of routed requests and improve the performance of conference services in SDN. LBLRF uses a postponement mechanism to improve the conference service, where it gives higher priority to the requests with low resource demand for connection. In addition, LBLRF is equipped with a hold time mechanism to release the reserved resources after satisfying the request requirements. This mechanism can increase the processing capacity of future requests by conserving network resources. Evaluations have been done by defining several scenarios on a synthetic SDN environment. The results of the experiments show that LBLRF provides a better request acceptance rate between 7% and 16% compared to the best results of existing algorithms.
摘要：
BiCuSeO compound is a promising thermoelectric material, which has attracted many experimental stud-ies through trial-and-error approaches to improve its thermoelectric performance by element doping, such that a fast and efficient prediction of thermoelectric property for unexplored and rarely explored doped-BiCuSeO is highly desired. In this work, a machine learning (ML) model for predicting the ZT value of M element doped-BiCuSeO (Bi1-xMxCuSeO) has been established via the correlation analysis for descriptors and the comparison among different ML approaches. The results show that Gradient Boosting Regressor is the most appropriate approach for our ML model, which is well validated by com-paring the predicted and experimental ZT values for the cases in the dataset. The ML model is also used to predict the ZT values of Bi1-xMxCuSeO with unexplored and rarely explored doping element M, and the optimal doping elements as well as their doping contents are screened out. The results indicate that the ZT of Bi0.86Po0.14CuSeO (Po-doped) and Bi0.88Cs0.12CuSeO (Cs-doped) are higher than that of pure BiCuSeO, and are improved by 104 % and 98 % at the 923 K, respectively. The enhancement is well explained by the first-principles calculations. The findings offer a guideline for exploring superior ther-moelectric performance in BiCuSeO.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
关键词：
Viscoelastic fluid;Activation energy;Stagnation point flow;Heat generation/absorption;Generalized Fourier and Fick ' s law;Stretching sheet
摘要：
This analysis describes the stagnation point and mixed convection flow of a viscoelastic micropolar fluid into a porous medium towards a stretchable sheet and magnetic field. Concentration and thermal stratification boundary conditions and activation energy are studied. For the flow of heat and mass transportation, Fourier and Fick's law is also accommodated into account. Suitable similarity variables are utilized to attain the dimen-sionless form of the governed equations. These dimensionless equations have been resolved numerically with the help of BVP4C approach. The velocity profile is reduced with the stronger estimations of eand M. The coefficient of skin friction has an increasing effect by improving values of K, fi, M, and SMALL ELEMENT OF. The velocity sketch has the opposite behavior for SMALL ELEMENT OF and fit. Stronger estimations of fi and Se lead to the decay of the temperature profile. The angular velocity of the fluid upsurges due to the stronger values of K.
摘要：
Through gravity/gauge duality, the string breaking and running coupling constant of heavy quarkantiquark pair are investigated in the rotating background. For the meson decay mode QQ -> Qq + Qq, we discuss the string breaking and running coupling in the parallel and transverse case. It is found that the parallel case has a more significant on string breaking and running coupling constant than the transverse case in the confined phase. The string-breaking distance and the maximum value of running coupling will decrease with the increase of angular velocity in the parallel case. Besides, we also investigate the running coupling and screening distance at finite angular velocity in the deconfined phase. It is found that the maximum values of the running coupling and screening distance are decreasing functions of angular velocity. The parallel case has a more significant influence on the running coupling and screening distance than the transverse case in the deconfined phase. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,2023年25(25):17034-17042 ISSN：1463-9076
通讯作者：
Xiong, CX
作者机构：
[Xiong, Cuixiu; Zhang, Saiwen; Tan, Meng; Wan, Can; Wei, Chengya; Wang, Jie; Xiong, CX] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.
通讯机构：
[Xiong, CX ] H;Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.
摘要：
A fully continuous geometric center symmetric cross-shaped graphene structure is proposed. Each cross-shaped graphene unit cell is composed of a central graphene region and four completely symmetric graphene chips, where each graphene chip acts as both bright and dark modes simultaneously, while the central graphene region always acts as the bright mode. Through destructive interference, the structure can realize the single plasmon-induced transparency (PIT) phenomenon, where the optical responses are independent of the polarization direction of the linearly polarized light due to the symmetry of the structure. Combining numerical simulations with coupled mode theory (CMT) calculations, the modulation of the Fermi energy of graphene to the optical spectra is investigated. The results show that the spectra are blue shifted as the Fermi energy increases, and the absorption of the two absorption peaks is basically equal (48.7%) when the Fermi energy increases to 0.667 eV. Theoretical calculations show that the slow light performance of the designed structure enhances with the increase of Fermi energy, where the maximum group index is high up to 424.73. Furthermore, it is worth noting that the electrode can be made very small due to its fully continuous structure. This work provides guidance in terms of terahertz modulators, tunable absorbers, and slow light devices.
期刊：
Journal of Network and Computer Applications,2023年217:103698 ISSN：1084-8045
通讯作者：
Qin, H
作者机构：
[Chen, Weimin; Li, Ni; Qin, Hua; Yang, Gelan; Qin, H; Wang, Tao; Chen, Hao] Hunan City Univ, Coll Informat & Elect Engn, Yiyang, Hunan, Peoples R China.;[Peng, Yang] Univ Washington Bothell, Div Comp & Software Syst, Bothell, WA USA.
通讯机构：
[Qin, H ] H;Hunan City Univ, Coll Informat & Elect Engn, Yiyang, Hunan, Peoples R China.
关键词：
QoS;Partitioning;Scheduling;Multimedia;IoT
摘要：
In the Internet of Things (IoT), multimedia traffic for audio, image, and video accounts for the largest proportion (over 78.7%) of the total traffic, bringing forward the vision of multimedia IoT (M-IoT). As part of the realization of loT, M-IoT is a general network paradigm that constitutes many smart objects equipped with the capability to collect multimedia data from the physical environment and deliver the data to other things. To satisfy a certain level of user experience, Quality of Service (QoS) is required to be regulated to ensure acceptable delivery of the multimedia content. As the most widely-used wireless technology, WiFi has been recommended for IoT communications for its high data rate, native IP compatibility, and good reusability of the existing infrastructures. However, WiFi suffers from channel contention, especially during multi-hop communications, which degrades the QoS performance and hinders its use for many M-IoT services. Although numerous protocols have been proposed to mitigate WiFi contention, they often consume much WiFi bandwidth for network control, lowering the level of achievable QoS performance. To address this issue, we propose a distributed Cross-interface network Partitioning and Scheduling (CPS) protocol, which leverages the co-existing ZigBee communications to divide the network into partitions and allows only one node in each partition to use its WiFi interface to transmit data at any time, for bandwidth-efficient and delay-constrained data flow delivery in M-IoT. A prototype node is implemented by integrating COTS ZigBee and WiFi interfaces into a BeagleBone Green wireless platform for IoT. Extensive field experiments are conducted in a multi-hop network of 24 prototype nodes that deliver real multimedia data (images and videos). The experiment results show that CPS outperforms the standard WiFi and a state-of-the-art contention control scheme (by 62.6% and 26.4% under high data traffic, respectively) in terms of a QoS metric capturing two basic performance metrics (i.e., bandwidth efficiency and end-to-end delay) of multi-hop communications, while retaining fair QoS performance and high energy efficiency.
摘要：
The propagation characteristics of Airy beams in an inhomogeneous medium with periodic potential are studied theoretically and numerically. The Gross-Pitaevskii equation was solved with periodic potential using the separating variables method, and a breathing soliton solution and the breathing period were obtained. Further, the propagation properties of an Airy beam, and the interaction between two Airy beams while considering the medium parameters and beam parameters were numerically simulated in detail. First, we discuss the influence of the initial medium parameters (modulation intensity P and modulation frequency ?) on the propagation characteristics. Then, we investigate the effect of the initial beam parameters (initial chirp C and position x(0)) on the propagation characteristics. Lastly, the interaction of two Airy beams with opposite spatial positions for different phase f, amplitude A, and initial interval x(0) is analyzed. The breathing period and central position of the breathing solitons could be controlled by changing the initial medium parameters. By varying the initial beam parameters, the deflection direction and size, and the maximal intensity of the breathing solitons were manipulated. The breathing solitons of different bound states were formed by changing the phase f, amplitude A, and initial interval x(0) of two Airy beams. The results provide a theoretical basis for the propagation and manipulation of Airy beams.
作者机构：
[Wang, Ke; An, Ying; Chen, Xianlai] Cent South Univ, Big Data Inst, Changsha 410083, Peoples R China.;[Long, Yuehong; Wang, Ke; Zhou, Jiancun] Hunan City Univ, Coll Informat & Elect Engn, Yiyang 413000, Peoples R China.;[Chen, Xianlai] Cent South Univ, Coll Hunan Prov, KeyLaboratory Med Informat Res, Changsha 410083, Peoples R China.
通讯机构：
[Xianlai Chen] B;Big Data Institute, Central South University, Changsha 410083, China<&wdkj&>KeyLaboratory of Medical Information Research (Central South University), College of Hunan Province, Changsha 410083, China
关键词：
Feature selection;Lasso coefficient;Quality of feature subset;Radiomics
摘要：
Radiomics is characterized by high-dimension and high redundancy. The existing Lasso-based feature selection does not consider features that are weakly correlated with the clas-sification results, which will have a certain impact on the quality of feature subset. A multi-level feature selection algorithm based on Lasso coefficient threshold (Coe-Thr-Lasso) was proposed. Firstly, t-test and variance were used to remove the features that had little correlation with the classification results. Secondly, the proposed algorithm was used to remove features with redun-dancy and weak correlation of classification results. Three machine learning algorithms, including Logistic regression (LR), random forest (RF) and support vector machine (SVM), were verify the performance of the proposed algorithm on the non-small cell lung cancer subtype classification dataset. When modeling based on the feature subset generated by the proposed method, the pro-posed method achieved the best classification performance compared with other publication methods. Therefore, Coe-Thr-Lasso algorithm can effectively remove redundant and irrelevant features in radiomics, so as to improve the quality of feature subset and the ability of model gen-eralization.CO 2022 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
期刊：
Journal of Materials Science: Materials in Electronics,2023年34(36):1-7 ISSN：0957-4522
通讯作者：
Wang, HO;Tan, WS
作者机构：
[Lu, Gefei; Dong, Fuxiao; Ma, Qinghua; Wang, Haiou; Wang, HO; Zhao, Bojun; Huo, Dexuan] Hangzhou Dianzi Univ, Inst Mat Phys, Key Lab Novel Mat Sensor Zhejiang Prov, Hangzhou 310018, Peoples R China.;[Tan, Weishi] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices, Key Lab Hunan Prov, Yiyang 413002, Peoples R China.;[Tan, Weishi] Nanjing Univ Sci & Technol, Key Lab Soft Chem & Funct Mat, Minist Educ, Dept Appl Phys, Nanjing 210094, Peoples R China.
通讯机构：
[Wang, HO ; Tan, WS ] H;Hangzhou Dianzi Univ, Inst Mat Phys, Key Lab Novel Mat Sensor Zhejiang Prov, Hangzhou 310018, Peoples R China.;Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices, Key Lab Hunan Prov, Yiyang 413002, Peoples R China.;Nanjing Univ Sci & Technol, Key Lab Soft Chem & Funct Mat, Minist Educ, Dept Appl Phys, Nanjing 210094, Peoples R China.
摘要：
The structure, magnetic, transport and magnetoresistance properties of SrMnO3 sample have been investigated. The SrMnO3 sample has single-phase structure with hexagonal symmetry, which is obtained by the X-ray diffraction. The scanning electron microscope reveals the particles of the sample are evenly distributed. The composition of the SrMnO3 sample is detected using the energy dispersive spectrometer, indicating the element ratio of Sr:Mn:O = 19.25:20.35:60.40. The magnetic, electrical transport and the magnetoresistance effect are studied via the temperature dependences of the magnetization, the resistivity and the magnetoresistance. An antiferromagnetic phase transition near 300 K appears in the SrMnO3 sample, and no significant entropy change can be found in the antiferromagnetic sample. The sample shows the insulator state since the resistance increases gradually with the decrease of temperature. Therefore, SrMnO3 is an antiferromagnetic insulator material. Moreover, the resistivity reduces significantly with the applied magnetic field, indicating an existence of magnetoresistance. Remarkably, the room-temperature magnetoresistance of the antiferromagnetic insulator SrMnO3 reaches 16.68% under 60 kOe field. This work opens our understanding of magneto-transport and magnetic properties of the antiferromagnetic SrMnO3. The discovery of magnetoresistance near room temperature in the antiferromagnetic insulator (SrMnO3) is of great significance for the development of antiferromagnetic spintronics.
作者机构：
[Wu, Yingying] Hunan Univ Sci & Technol, Sch Mat Sci & Engn, Xiangtan 411201, Peoples R China.;[Ou, Yun] Hunan Univ Sci & Technol, Hunan Prov Key Lab Hlth Maintenance Mech Equipment, Xiangtan 411201, Peoples R China.;[Peng, Jinlin] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413002, Peoples R China.;[Lei, CH; Lei, Chihou] St Louis Univ, Dept Aerosp & Mech Engn, St Louis, MO 63103 USA.
通讯机构：
[Lei, CH ] S;[Ou, Y ] H;Hunan Univ Sci & Technol, Hunan Prov Key Lab Hlth Maintenance Mech Equipment, Xiangtan 411201, Peoples R China.;St Louis Univ, Dept Aerosp & Mech Engn, St Louis, MO 63103 USA.
关键词：
non-equiaxed misfit strain;K0.5Na0.5NbO3;the Landau-Devonshire theory;ferroelectric thin films
摘要：
Environmentally friendly lead-free K1-xNaxNbO3 (KNN) ceramics possess electromechanical properties comparable to lead-based ferroelectric materials but cannot meet the needs of device miniaturization, and the corresponding thin films lack theoretical and experimental studies. To this end, we developed the nonlinear phenomenological theory for ferroelectric materials to study the effects of non-equiaxed misfit strain on the phase structure, electromechanical properties, and electrical response of K0.5Na0.5NbO3 epitaxial films. We constructed in-plane misfit strain (u(1)-u(2)) phase diagrams. The results show that K0.5Na0.5NbO3 epitaxial film under non-equiaxed in-plane strain can exhibit abundant phase structures, including orthorhombic a(1)c, a(2)c, and a(1)a(2) phases, tetragonal a1, a(2), and c phases, and monoclinic r(12) phases. Moreover, in the vicinity of a(2)c-r(12), a1c-c, and a(1)a(2)-a(2) phase boundaries, K0.5Na0.5NbO3 epitaxial films exhibit excellent dielectric constant epsilon(11), while at a(2)c-r(12) and a(1)c-c phase boundaries, a significant piezoelectric coefficient d15 is observed. It was also found that high permittivity epsilon 33 and piezoelectric coefficients d33 exist near the a(2)c-a(2), a(1)a(2)-r(12), and a(1)c-a(1) phase boundaries due to the existence of polymorphic phase boundary (PPB) in the KNN system, which makes it easy to polarize near the phase boundaries, and the polarizability changes suddenly, leading to electromechanical enhancement. In addition, the results show that the K0.5Na0.5NbO3 thin films possess a large electrocaloric response at the phase boundary at the a(1)a(2)-r(12) and a(1)c-a(1) phase boundaries. The maximum adiabatic temperature change Delta T is about 3.62 K when the electric field change is 30 MV/m at room temperature, which is significantly enhanced compared with equiaxed strain. This study provides theoretical guidance for obtaining K1-xNaxNbO3 epitaxial thin films with excellent properties.
期刊：
Journal of Materials Science: Materials in Electronics,2023年34(15):1-7 ISSN：0957-4522
通讯作者：
Wang, Haiou;Huo, DX
作者机构：
[Su, Kunpeng; Dong, Fuxiao; Hu, Xiaojie; Wang, Haiou; Huo, Dexuan; Zhao, Bojun; Yang, Dexin; Wang, HO; Wang, Yan] Hangzhou Dianzi Univ, Inst Mat Phys, Key Lab Novel Mat Sensor Zhejiang Prov, Hangzhou 310018, Peoples R China.;[Tan, Weishi] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413002, Peoples R China.;[Tan, Weishi] Nanjing Univ Sci & Technol, Dept Appl Phys, Key Lab Soft Chem & Funct Mat, Minist Educ, Nanjing 210094, Peoples R China.
通讯机构：
[Huo, DX ; Wang, HO] H;Hangzhou Dianzi Univ, Inst Mat Phys, Key Lab Novel Mat Sensor Zhejiang Prov, Hangzhou 310018, Peoples R China.
摘要：
The magnetocaloric and ferromagnetic properties of Pr0.7Sr0.3MnO3 film grown on (001) Pb(Mg1/3Nb2/3)(0.7)Ti0.3O3 (PMN-PT) using pulsed laser deposition technology have been investigated in this work. The X-ray diffraction measurement shows that the (001)-oriented film has been successfully deposited on PMN-PT substrate. The ferromagnetic properties and magnetocaloric effect resulted from ferromagnetic transition are explored via using the magnetic moment versus temperature plots, hysteresis loops, and the magnetic moment versus magnetic field curves. The magnetic moment versus temperature plots (M-T curves) show that with the decrease of temperature, the Pr0.7Sr0.3MnO3 film undergoes a transition from paramagnetic to ferromagnetic phase at temperature close to Curie-Weiss temperature (T-CW). T-CW (approximately 133 K) is determined by the Curie-Weiss law. The Pr0.7Sr0.3MnO3 film reveals the ferromagnetic feature below T-CW, while the film exhibits the paramagnetic state at temperature higher than T-CW. Hysteresis loops also confirm that the film reveals ferromagnetic feature at temperature lower than T-CW (e.g. ferromagnetic behaviors at 10 and 100 K). The result of hysteresis loops is in accordance with the M-T curves. Besides, entropy change has been investigated in our work. The maximum entropy change of Pr0.7Sr0.3MnO3 film reaches about 2.4 J/kg center dot K at around T-CW under 10 kOe field change, that is close to the entropy change of reference sample Gd (approximately 2.8 J/kg center dot K within the field change of 10 kOe), suggesting that the Pr0.7Sr0.3MnO3 film on PMN-PT has a great application prospect in magnetic refrigeration.
期刊：
Journal of Luminescence,2023年253:119443 ISSN：0022-2313
通讯作者：
Liezun Chen<&wdkj&>Jianxin Tang
作者机构：
[Zhu, Ying; Deng, Yanhong; Chen, Mo; Chen, Liezun; Mao, Liwei; Zhong, Liya; Wang, Jinjiang] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;[Chen, Liezun] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.;[Liu, Zui] Hengyang Normal Univ, Coll Life Sci, Hengyang 421000, Peoples R China.;[Tang, Jianxin] Soochow Univ, Inst Funct Nano & Soft Mat FUNSOM, Suzhou 215123, Peoples R China.
通讯机构：
[Liezun Chen] C;[Jianxin Tang] I;Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, China<&wdkj&>College of Physics and Electronics Engineering, Hengyang Normal University, Hengyang, 421002, China<&wdkj&>All-Solid-State Energy Storage Materials and Devices Key Laboratory of Hunan Province, College of Information and Electronic Engineering, Hunan City University, Yiyang, 413000, China
摘要：
Emission spectral shift has a significant influence on the color purity of organic light-emitting diodes (OLEDs) for the applications in full-color displays and solid-state lighting. However, the controllable shift of the emission spectra from one color to another provides a promising method to solve the problem in high-performance blue emitters. Here, we demonstrate the tunable emission colors from green to blue with the use of a green emitter of 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) with different doping concentrations. Upon an optimal 4CzIPN doping concentration of 1 wt%, the OLED achieves a blue emission at 488 nm with the maximum current efficiency of 41.69 cd/A, the maximum power efficiency of 43.66 lm/W, and Commission International de I'Eclairage (CIE) coordinates of (0.19, 0.39). By investigating the factors of the polarity of the host materials and the use of electron-transport layers, it has been clarified that the electroluminescence spectral shift arises from the synergistical effects of solid-state solvation and microcavity. These findings pave the way for the development of high-efficiency blue OLEDs without blue materials.
摘要：
The supercontinuum generation and manipulation of Airy-Gaussian pulses in a photonic crystal fiber with three zero-dispersion points are studied using the split-step Fourier method. Firstly, the spectral evolution of Airy-Gaussian pulses in four photonic crystal fibers with different barrier widths was discussed, and the optimal fiber was determined after considering the factors of width and flatness. By analyzing the mechanism of supercontinuum generation in photonic crystal fibers with single, double and three zero-dispersion points, it is found that the photonic crystal fiber with three zero-dispersion points have a larger spectral width due to the component of tunneling solitons. Then, the effects of four characteristic parameters (truncation factor a, distribution factor chi 0, initial chirp C and central wavelength lambda) on forming the supercontinuum spectrum of Airy-Gaussian pulses are analyzed in detail. The results show that the spectral width and energy intensity of the dispersive wave and tunneling soliton generation can be well controlled by adjusting the barrier width and initial parameters of the pulse. These research results provide a theoretical basis for generating and manipulating high-power mid-infrared supercontinuum sources.
