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61.
Xiaoyuan Sun Zixuan Liu Hao Qian Yunfei Liu Yinong Lyu 《Ceramics International》2021,47(17):24207-24217
A strategy that constructs the morphotropic phase boundary and manipulates the domain structure has been used to design the component of 0.96[Bi0.5(Na0.84K0.16)0.5Ti(1-x)NbxO3]-0.04SrTiO3 (BNKT-4ST-100xNb) to enhance the strain properties for actuator application. Non-equivalent Nb5+ donor doping modulates the phase transition from the mixture of rhombohedral and tetragonal phases to the pseudocubic phase and results in the coexistence of multiple phases. Moreover, the high-resolution TEM confirms the existence of polar nano regions that contribute to the macroscopic relaxor behaviour. The size of the domains is reduced with increasing Nb5+, resulting in an enhanced relaxor behaviour. The ferroelectric-relaxor transition temperature decreases from 85 to below 30 °C, implying a non-ergodic to ergodic relaxor transition. An improved strain of 0.56% and a giant normalized strain of 1120 pm/V were achieved for BNKT-4ST-1.5Nb, which were attributed to the unique domain structure in which nanodomains are embedded in an undistorted cubic matrix. Ferroelectric, antiferroelectric, and relaxor phases coexist. As the electric field is large enough, a reversible phase transition occurs. Furthermore, good temperature stability was obtained due to the stability of the nanodomains, and no degradation in strains was observed even after 104 cycles, which may originate from the reversible phase transition and dynamic domain wall. The results show that this design strategy offers a reference way to improve the strain behaviour and that BNKT-4ST-100xNb ceramics could be a potential material for high-displacement actuator applications. 相似文献
62.
Zihan Wang Qiao Yuan Yunfei Zhang Min Ma Daojiang Gao Jian Bi Jiangtao Wu 《Ceramics International》2021,47(13):17877-17882
Despite being difficult to identify, extremely dilute oxygen vacancies have been widely reported to play an important role in enhancing magnetism in ZnFe2O4. The mechanisms underlying this enhanced magnetism have not been well understood for a long time and remain controversial because the formation of oxygen vacancy-rich ZnFe2O4 can be accompanied by changes in the chemical/physical characteristics, especially the composition, particle size, surface morphology and cation distribution, which can significantly affect the magnetization. An open and important question is whether and to what extent the enhanced magnetization can be attributed only to oxygen vacancies. In this study, the relationship between the magnetization and oxygen vacancies in ZnFe2O4 was definitively determined by using a carefully designed “shake-and-heat” treatment to prepare vacancy-rich samples while keeping the other crystal/surface parameters constant. Compared to the nearly vacancy-free paramagnetism samples, the vacancy-rich samples exhibited a higher magnetization of approximately 5 emu/g at both 300 K and 2 K. The Fe3+-O2--Fe3+ superexchange paths broken by oxygen vacancies then resulting in the Fe3+-Fe3+ ferromagnetism configuration. Meanwhile, the oxygen vacancy is highly diluted then the ferromagnetism configuration is confined in a single super-cell, favoring a short-range magnetic ordering at room temperature. The concentration of oxygen vacancies was calculated to be 0.68% by magnetization measurement. Our results may shed a light on how oxygen vacancies affect magnetism. 相似文献
63.
Wang Yunfei Zheng Wang Zhang Xiaofei Shen Jinqing 《Multidimensional Systems and Signal Processing》2020,31(3):907-926
Multidimensional Systems and Signal Processing - Generalized coprime structure decomposes the interleaved subarrays in the conventional coprime array by introducing a displacement and the resulting... 相似文献
64.
Yunfei Chu Yijiao Cen Yanxi Song Zhenxiang Xu Luping Hu Hongqi Li Changling Yang 《Coloration Technology》2020,136(4):381-388
A coumarin‐based fluorescent probe containing both acrylate moiety and an allyl substituent was developed for distinguishing cysteine from homocysteine. The maximum absorption wavelength of the probe showed a bathochromic shift upon addition of cysteine and the colour changed from colourless to yellow. The maximum fluorescence emission at 462 nm of the probe was dramatically enhanced upon addition of cysteine in aqueous solution. In HEPES buffer (pH = 7.4, EtOH/H2O = 9:1, v/v), both of the fluorescence emission bands of the probe at ca. 390 and 462 nm were intensely enhanced upon the addition of cysteine, while other amino acids, namely, homocysteine, asparaginic acid, methionine, glycine, phenylalaninase, valine, tryptophan, serine, glutamic acid and glutathione, did not cause a remarkable change. The probe can be used for selectively colorimetric and ratiometric fluorescent detection of cysteine over homocysteine and other common amino acids in both organic media and aqueous solution. The concentration of cysteine can be estimated by titration of the probe in aqueous solution, and the detection limit of the probe towards cysteine was 2 μmol/L. 相似文献
65.
针对无线传感器网络拓扑快速变化、链路易拥塞断开,存在路由开销大、负载不均衡、网络生命周期短等问题,提出低开销负载均衡的改进型TORA(TORA-p)。通过定义网络变化率参数,自适应调整互联网封装协议(IMEP)中OBM包的最大重发次数,减少不必要的路由维护开销;同时,结合MAC层信息,定义链路可用性优化选路方式,自动平衡网络负载,避免关键路径和节点负载过重而过早死亡和断开。使用truetime2.0平台设定特定的仿真环境,对TORA-p算法的性能进行了详细比较分析,结果表明:TORA-p均衡了网络负载,提升了网络生命周期,同时也减少了路由开销和延时,展现出了较好的数据传输能力。 相似文献
66.
Controlling the morphology of poly(3‐hexylthiophene)/methanofullerene film through a dynamic‐cooling and freeze‐drying process 下载免费PDF全文
Ping‐Tsung Huang Cheng‐Wei Chou Bo‐Yu Lin Zhong‐En Shi Yu‐Jui Huang Chin‐Ti Chen Chao‐Han Cheng Juen‐Kai Wang 《Polymer International》2016,65(1):66-71
A dynamic‐cooling and freeze‐drying (DCFD) process has been applied to the fabrication of polymer solar cells. The dynamic‐cooling process allows poly(3‐hexylthiophene) molecules to aggregate in solution into a more organized structure during the cooling process; the freeze‐drying process prevents severe agglomeration of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) during the solvent removing process. Application of these two processes to the preparation of the poly(3‐hexylthiophene)/methanofullerene photoactive layer results in an enhanced poly(3‐hexylthiophene) aggregation and smaller PCBM agglomerates. Devices fabricated using the DCFD process generate 14% more in current density than those prepared by the spin‐coating process under AM1.5G illumination. © 2015 Society of Chemical Industry 相似文献
67.
68.
Abstract:Quantitative evaluations are of great importance in network security decision-making.In recent years,moving target defense (MTD) has appeared to be a promising defense approach that blocks asymmetrical advantage of attackers and favors the defender-notwithstanding,it has a limited deployment due to its uncertain efficiency and effectiveness in defense.In that case,quantitative metrics and evaluations of MTD are essential to prove its capability and impulse its further research.This article presents a comprehensive survey on state-of-the-art quantitative evaluations.First,taxonomy of MTD techniques is stated according to the software stack model.Then,a concrete review and comparison on existing quantitative evaluations of MTD is presented.Finally,notice-worthy open issues regarding this topic are proposed along with the conclusions of previous studies. 相似文献
69.
介绍大型空分装置出现的一次纯化器再生蒸汽加热器泄漏故障,分析泄漏故障对空分装置的不利影响,提出有效的不停机特护运行方法。 相似文献
70.
CUI Hua YUAN Chao WEI Zefa LI Pannong SONG Xinxin JI Yu LIU Yunfei 《西安电子科技大学学报(自然科学版)》2017,44(6):79-84
Accurate recognition of the traffic condition can proactively alert drivers who will enter the congested road to avoid congestion, so that the degree of congestion will not be increased. And it is also the basis to make scientific decision on active traffic managements, and conducive to alleviate congestion, improve the traffic efficiency, save energy and reduce emission. In this paper, the traffic surveillance videos are sampled every three minutes to build static image database, and the road area is marked as the region of interest (ROI), and then ROI images are normalized in terms of angle and scale. The three image features in ROI, i.e., average gradient, corner and long edge number, are then extracted. Finally, the fuzzy C-means clustering (FCM) method is used to classify the traffic condition into two classifications, i.e., flowing traffic and congestion. Experimental results show that the proposed algorithm can effectively identify the traffic condition involved in the image by the accuracy of 98%. Moreover, compared with the video-based approaches, this method greatly reduces the implementation cost. 相似文献