摘要：联邦学习使得多个移动参与者在不透露其本地隐私数据的情况下联合训练全局模型。通信计算代价和隐私保护性能是联邦学习的关键基础问题。现有的基于秘密共享的联邦学习安全聚合机制仍然存在引入显著额外计算代价、隐私保护性能不足和应对参与者掉线能力脆弱等问题。本文致力于通过引入灵活高效的秘密共享机制解决上述问题。本文提出了两种新颖的隐私保护联邦学习方案,分别是基于单向秘密共享的联邦学习(FLOSS)和基于多发秘密共享的联邦学习(FLMSS)。与当前的相关工作相比,FLOSS通过动态设计秘密共享的内容和对象,在显著降低通信代价的同时保证高强度的隐私保护性能。FLMSS进一步降低额外计算代价并且能够提高联邦学习应对参与者掉线的鲁棒性,从而在隐私保护和通信计算代价之间取得令人满意的平衡。安全性分析和基于真实数据集的性能评估证明了本文提出的方案在模型准确度、隐私保护性能和通信计算代价方面的优势。

摘要：石墨烯因其高载流子迁移率和宽光谱吸收范围而广泛应用于光电探测。然而,其低光吸收率导致的高暗电流严重限制了它的光电探测性能。钼基二硫族化合物(MoX_(2),X=S、Se和Te)具有高的吸收系数,能够弥补石墨烯基光电探测器中暗电流较高的劣势,因此基于石墨烯/MoX_(2)范德华异质结的光电探测器能够表现出优异的光电子特性。本综述首先回顾了光电探测器的工作原理、性能指标和结构。之后,从材料基础的角度突出了石墨烯/MoX_(2)范德华异质结光电探测器的重要性。接着,总结了石墨烯/MoX_(2)范德华异质结光电探测器的制备方法和性能增强策略。最后,强调了这类异质结光电探测器当前面临的挑战及未来的发展方向。本综述将为这类高性能范德华异质结光电探测器的设计提供一定的指导和参考。

摘要：临床上常用的广谱抗生素无法有效解决抗生素高度耐药ESKAPE菌感染的难题,ESKAPE耐药菌已经成为人类生命健康的重大威胁.抗生素与佐剂的联合治疗是解决抗生素耐药菌感染的重要途径,但是探索对所有ESKAPE耐药菌都具有广谱和高效抗菌活性的抗生素-佐剂组合仍然面临巨大挑战.在这里,我们提出了一种抗生素-佐剂的有效设计策略,将对ESKAPE中耐药阴性菌具有高活性的多粘菌素B(PMB)与模拟宿主防御肽的细菌膜靶向阳离子聚(2-噁唑啉)相结合.我们通过2-噁唑啉单体可控聚合,合成了一系列具有不同疏水性侧链的阳离子聚(2-噁唑啉).研究表明,聚(2-噁唑啉)和PMB的组合效果随着聚(2-噁唑啉)侧链疏水性的提高呈现出从拮抗效应到协同效应的逐渐变化.其中,优选的聚(2-噁唑啉)EACA-POX_(20)显著增强了PMB的抗菌活性,尤其是对于ESKAPE耐药阳性菌的抗菌活性增强了16–32倍.聚(2-噁唑啉)EACA-POX_(20)有效增强了PMB的抗菌活性并扩展了PMB的抗菌谱.聚(2-噁唑啉)和PMB的组合策略能够有效对抗所有耐药ESKAPE病原体,为解决ESKAPE耐药菌提供了新的思路.

摘要：跟踪注册是增强现实(Augmented reality,AR)中一项至关重要的技术。基于人工标识和基于图像的注册方法已广泛应用于增强装配系统中。然而,由于空间产品的弱纹理、结构对称、数据有限以及难以张贴标识等特点,空间站的跟踪注册仍面临挑战。本文提出了一种专门为中国空间站诱导维修应用设计的三维物体跟踪方法,旨在用AR技术取代传统的纸质手册,为宇航员提供更直观的操作指导。本文提出了一种无标记的中国空间站智能维护方法。采用点对特征方法来估计初始帧姿态,不需要手动调整来获得相应的姿态,这对宇航员来说至关重要,因为在微重力环境中精确运动是一项重大挑战,而且结合曲率信息可以提高采用点对特征方法估计初始帧姿态的效率。通过结合纹理和区域信息,消除了对宇航员位置的精确限制,进一步增强了空间对称产品的跟踪鲁棒性。该方法利用点云匹配来估计第一帧的初始姿态,并在失去跟踪后重新计算姿态。一旦获得了前一帧的姿态,则仅根据二维图像的区域和纹理信息来计算跟踪,以获得实时跟踪。实验结果表明:本文方法与基于标识的方法具有相同的姿态趋势;基于电子游标卡尺测量之间的误差在毫米级;使用专门为航天产品设计的专用工具成功更换过滤器,证明了在空间站上实施诱导维修程序的实用性和潜力。

摘要：准二维钙钛矿表现出独特的光物理性质,这使它们成为激光技术潜在进步的优秀候选材料.高性能纳秒脉冲激光和放大自发发射(ASE)是实现连续波抽运光电泵浦激光器的关键工艺.然而,在纳秒脉冲激光泵浦下发展准二维钙钛矿ASE或激光仍然存在一些困难,包括表面缺陷浓度高、俄歇复合和能量传递效率低.本文通过无添加剂的Cs^(+)阳离子掺杂策略,可以很好地控制准二维钙钛矿膜的形貌和相分布,从而解决了低n相导致的能量传递途径不足的问题.本文通过快速的能量传递过程揭示了增益性质和载流子复合.基于此,掺杂适当比例Cs^(+)阳离子的PEA_(2)(FA_(0.7)Cs_(0.3))_(2)Pb_(3)Br_(10)钙钛矿膜的净增益系数比原始钙钛矿薄膜提高了近3倍,从而将纳秒激光激发下的放大自发发射阈值降低到1/3.研究结果表明,在准二维钙钛矿中掺杂Cs^(+)可为实现高性能激光器件的相位分布设计提供见解.

摘要：Aiming at dealing with the difficulty for traditional emergency rescue vehicle(ECV)to enter into limited rescue scenes,the electro-hydraulic steer-by-wire(SBW)system is introduced to achieve the multi-mode steering of the *** overall structure and mathematical model of the SBW system are described at *** fractional order proportional-integral-derivative(FOPID)controller based on fractional calculus theory is designed to control the steering cylinder’s movement in SBW *** anti-windup problem is considered in the FOPID controller design to reduce the bad influence of *** parameters of the FOPID controller are optimized using the genetic algorithm by maximizing the fitness function which involves integral of time by absolute value error(ITAE),peak overshoot,as well as settling *** time-domain simulations are implemented to identify the performance of the raised FOPID *** simulation results indicate the presented FOPID controller possesses more effective control properties than classical proportional-integral-derivative(PID)controller on the part of transient response,tracking capability and robustness.

摘要：The design of metallic materials with high strength,high ductility,and high thermal stability has always been a long-sought goal for the materials science ***,the trade-off between strength and ductility remains a ***,we proposed a new strategy to design and fabricate bulk amorphous-crystalline dual-phase superior alloys out of the Al_(80)Li_(5)Mg_(5)Zn_(5)Cu_(5)multicomponent *** nano-amorphous phase revealed unexpected thermal stability during fabrication and mechanical testing above the crystallization *** true fracture strength of the Al_(80)Li_(5)Mg_(5)Zn_(5)Cu_(5)nano-amorphous-crystal dual-phase multicomponent alloy was increased from 528 to 657 MPa,and the true strain was increased from 18%to 48%.In addition,the alloy yielded a strength 1.5 times higher than that of the commonly used high-strength aluminum alloys at 250℃.This strategy provided a new approach and concept for the design of high-performance alloys to ensure strength-plasticity balance.

摘要：Reaction runaway has longtime been an issue in chemical industry as it often leads to severe accidents if not controlled and inhibited *** we have reviewed several key considerations and procedures to prevent such phenomena,including inherently safer reactor design,thermal risk assessment and early warning detection of runaway,and pointed out that the basic principle underlying is necessary heat management and construction of resilient *** inherently safer reactor design,important factors such as heat removal,heat capacitance,flow behaviors and explosive behaviors have been *** survey shows that heat exchanger(HEX) reactor and microreactor outperform traditional ***,we have looked into the effect of thermal risk ranking and safety operation region determining for thermal risk assessment,and the influence of runaway criteria and construction methods for early detection of reaction runaway as *** shows that thermal risk assessment plays a key role on process design,and early warning detection system(EWDS) is preferable on prevention of reaction *** the end,perspectives regarding inherently safer designs with the measures discussed above have been provided.

摘要：A large dual-polarization microstrip reflectarray with china-coverage patterns in two operating bands is *** sufficiently compensate for the spatial phase delay differences in two operating bands separately,a three-layer rectangular patch element is addressed,which is suitable for the large dual-polarization *** to the complexly shaped areas and high gain requirements,there are more than 25000 elements in the reflectarray,making it difficult to design,due to more than 150000 optimization ***,the discrete fast Fourier transform(DFFT)and the inverse DFFT are used to establish a one-to-one relationship between the aperture distribution and the far field,which lays a foundation for optimizing the shaped-beam *** intersection approach,based on the alternating projection,is used to obtain the desired reflection phases of all the elements at some sample frequencies,and a new method for producing a suitable initial solution is proposed to avoid undesired local *** validate the design method,a dual-polarization shaped-beam reflectarray with 7569 elements is fabricated and *** measurement results are in reasonable agreement with the simulation ***,for the large broadband reflectarray with the minimum differential spatial phase delays in the operating band,an approach for determining the optimal position of the feed is *** simultaneously find optimal dimensions of each element in two orthogonal directions,we establish a new optimization model,which is solved by the regular polyhedron ***,a dual-band dual-polarization microstrip reflectarray with 25305 elements is designed to cover the continent of *** results show that patterns of the reflectarray meet the china-coverage requirements in two operating bands,and that the proposed optimization method for designing large reflectarrays with complexly shaped patterns is reliable and efficient.

摘要：A stability analysis approach of tunnel face considering a longitudinally inclined tunnel angle and anisotropic purely cohesive soils based on a continuous velocity field (CVF) is investigated in this study. Based on the kinematic approach of limit analysis and the discretization technique, an improved three-dimensional CVF model for longitudinally inclined tunnels driven by pressurized shields is proposed. With the proposed model, the critical support pressure acted on tunnel face is determined by the work-balance equation. A serial of finite element numerical models are conducted to validate the proposed model. Finally, the effects of tunnel inclination angles, several dimensionless parameters as well as soil anisotropy on the critical support pressure are investigated. The numerical results show that the effects of the soil anisotropy and the tunnel inclination angle on tunnel faces should be considered in the actual design of tunneling engineering.