Pluggable multitask diffractive neural networks based on cascaded metasurfaces

Optical neural networks have significant advantages in terms of power consumption,parallelism,and high computing speed,which has intrigued extensive attention in both academic and engineering communities.It has been considered as one of the powerful tools in promoting the fields of imaging processing and object recognition.However,the existing optical system architecture cannot be reconstructed to the realization of multi-functional artificial intelligence systems simultaneously.To push the development of this issue,we propose the pluggable diffractive neural networks(P-DNN),a general paradigm resorting to the cascaded metasurfaces,which can be applied to recognize various tasks by switching internal plug-ins.As the proof-of-principle,the recognition functions of six types of handwritten digits and six types of fashions are numerical simulated and experimental demonstrated at near-infrared regimes.Encouragingly,the proposed paradigm not only improves the flexibility of the optical neural networks but paves the new route for achieving high-speed,low-power and versatile artificial intelligence systems.

Multi-dimensional multiplexing optical secret sharing framework with cascaded liquid crystal holograms

Secret sharing is a promising technology for information encryption by splitting the secret information into different shares.However,the traditional scheme suffers from information leakage in decryption process since the amount of available information channels is limited.Herein,we propose and demonstrate an optical secret sharing framework based on the multi-dimensional multiplexing liquid crystal(LC)holograms.The LC holograms are used as spatially separated shares to carry secret images.The polarization of the incident light and the distance between different shares are served as secret keys,which can significantly improve the information security and capacity.Besides,the decryption condition is also restricted by the applied external voltage due to the variant diffraction efficiency,which further increases the information security.In implementation,an artificial neural network(ANN)model is developed to carefully design the phase distribution of each LC hologram.With the advantage of high security,high capacity and simple configuration,our optical secret sharing framework has great potentials in optical encryption and dynamic holographic display.

Numerical investigation of hydro-morphodynamic characteristics of a cascading failure of landslide dams

A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the three-dimensional Reynoldsaveraged Navier-Stokes equations(RANS),the renormalization group(RNG)k-εturbulence model,suspended and bed load transport equations,and the instability discriminant formula of dam breach side slope,and the explicit finite volume method(FVM),a detailed numerical simulation model for calculating the hydro-morphodynamic characteristics of cascading dam breach process has been developed.The developed numerical model can simulate the breach hydrograph and the dam breach morphology evolution during the cascading failure process of landslide dams.A model test of the breaches of two cascading landslide dams has been used as the validation case.The comparison of the calculated and measured results indicates that the breach hydrograph and the breach morphology evolution process of the upstream and downstream dams are generally consistent with each other,and the relative errors of the key breaching parameters,i.e.,the peak breach flow and the time to peak of each dam,are less than±5%.Further,the comparison of the breach hydrographs of the upstream and downstream dams shows that there is an amplification effect of the breach flood on the cascading landslide dam failures.Three key parameters,i.e.,the distance between the upstream and the downstream dams,the river channel slope,and the downstream dam height,have been used to study the flood amplification effect.The parameter sensitivity analyses show that the peak breach flow at the downstream dam decreases with increasing distance between the upstream and the downstream dams,and the downstream dam height.Further,the peak breach flow at the downstream dam first increases and then decreases with steepening of the river channel slope.When the flood caused by the upstream dam failure flows to the downstream dam,it can produce a surge wave that overtops and erodes the dam crest,resulting in a lowering of the dam crest elevation.This has an impact on the failure occurrence time and the peak breach flow of the downstream dam.The influence of the surge wave on the downstream dam failure process is related to the volume of water that overtops the dam crest and the erosion characteristics of dam material.Moreover,the cascading failure case of the Xiaogangjian and Lower Xiaogangjian landslide dams has also been used as the representative case for validating the model.In comparisons of the calculated and measured breach hydrographs and final breach morphologies,the relative errors of the key dam breaching parameters are all within±10%,which verify the rationality of the model is applicable to real-world cases.Overall,the numerical model developed in this study can provide important technical support for the risk assessment and emergency treatment of failures of cascading landslide dams.

Phase-locked single-mode terahertz quantum cascade lasers array

We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.

Simulation and Analysis of Cascading Faults in Integrated Heat and Electricity Systems Considering Degradation Characteristics

Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.

Cascading multi-segment rupture process of the 2023 Turkish earthquake doublet on a complex fault system revealed by teleseismic P wave back projection method

In this study,the vertical components of broadband teleseismic P wave data recorded by China Earthquake Network are used to image the rupture processes of the February 6th,2023 Turkish earthquake doublet via back projection analysis.Data in two frequency bands(0.5-2 Hz and 1-3 Hz)are used in the imaging processes.The results show that the rupture of the first event extends about 200 km to the northeast and about 150 km to the southwest,lasting~90 s in total.The southwestern rupture is triggered by the northeastern rupture,demonstrating a sequential bidirectional unilateral rupture pattern.The rupture of the second event extends approximately 80 km in both northeast and west directions,lasting~35 s in total and demonstrates a typical bilateral rupture feature.The cascading ruptures on both sides also reflect the occurrence of selective rupture behaviors on bifurcated faults.In addition,we observe super-shear ruptures on certain fault sections with relatively straight fault structures and sparse aftershocks.

Model Predictive Control for Cascaded H-Bridge PV Inverter with Capacitor Voltage Balance

We designed an improved direct-current capacitor voltage balancing control model predictive control(MPC)for single-phase cascaded H-bridge multilevel photovoltaic(PV)inverters.Compared with conventional voltage balanc-ing control methods,the method proposed could make the PV strings of each submodule operate at their maximum power point by independent capacitor voltage control.Besides,the predicted and reference value of the grid-connected current was obtained according to the maximum power output of the maximum power point tracking.A cost function was con-structed to achieve the high-precision grid-connected control of the CHB inverter.Finally,the effectiveness of the proposed control method was verified through a semi-physical simulation platform with three submodules.

Inner Cascaded U^(2)-Net:An Improvement to Plain Cascaded U-Net

Deep neural networks are now widely used in the medical image segmentation field for their performance superiority and no need of manual feature extraction.U-Net has been the baseline model since the very beginning due to a symmetricalU-structure for better feature extraction and fusing and suitable for small datasets.To enhance the segmentation performance of U-Net,cascaded U-Net proposes to put two U-Nets successively to segment targets from coarse to fine.However,the plain cascaded U-Net faces the problem of too less between connections so the contextual information learned by the former U-Net cannot be fully used by the latter one.In this article,we devise novel Inner Cascaded U-Net and Inner Cascaded U^(2)-Net as improvements to plain cascaded U-Net for medical image segmentation.The proposed Inner Cascaded U-Net adds inner nested connections between two U-Nets to share more contextual information.To further boost segmentation performance,we propose Inner Cascaded U^(2)-Net,which applies residual U-block to capture more global contextual information from different scales.The proposed models can be trained from scratch in an end-to-end fashion and have been evaluated on Multimodal Brain Tumor Segmentation Challenge(BraTS)2013 and ISBI Liver Tumor Segmentation Challenge(LiTS)dataset in comparison to related U-Net,cascaded U-Net,U-Net++,U^(2)-Net and state-of-the-art methods.Our experiments demonstrate that our proposed Inner Cascaded U-Net and Inner Cascaded U^(2)-Net achieve better segmentation performance in terms of dice similarity coefficient and hausdorff distance as well as get finer outline segmentation.

装配式桥梁板玻璃纤维混凝土-U形钢筋湿接缝受力与变形分析

为解决装配式桥梁板体系湿接缝处力学性能不稳定、易变形的问题,提出采用玻璃纤维混凝土-U形钢筋加强方案优化湿接缝性能,以雄安新区荣乌高速荣乌主线桥为背景进行研究。选取主线桥2个试验段(试验段A湿接缝采用普通混凝土-U形钢筋方案,钢筋点焊;试验段B湿接缝采用玻璃纤维混凝土-U形钢筋加强方案,钢筋满焊)进行梁板体系湿接缝性能试验,监测湿接缝处搭接钢筋力学响应及混凝土接触面变形特征,同时对长期运载及强降雨影响下的钢筋受力与混凝土变形进行监测。结果表明:长期运载下,试验段B横筋受力约为试验段A的一半,其中部纵筋承受外力远大于试验段A,边缘纵筋承受外力较少,试验段B稳定性更优;试验段B较试验段A在湿接缝部位变形量小,其稳定性及耐久性更优;强降雨阶段,试验段B较试验段A变形及力学响应波动程度更低,其抗渗能力、耐久性更优。由此可知基于玻璃纤维混凝土-U形钢筋加强方案的湿接缝构造在外力传导、抵抗变形方面具有较强稳定性,不易受恶劣环境影响。

东昆仑大格勒农场南辉长岩锆石U-Pb年代学、地球化学特征及地质意义

东昆仑志留纪岩浆活动强烈,记录了东昆仑造山带原特提斯洋演化晚期大洋俯冲阶段与碰撞阶段转换地质过程。本次研究对东昆仑大格勒农场南志留纪基性侵入岩开展了详细的岩相学、岩石地球化学、锆石U-Pb年代学和Hf同位素研究,以确定其形成时代、岩石成因和构造环境。研究结果表明大格勒农场南辉长岩的结晶年龄为430.2±2.4 Ma,形成时代为中志留世。辉长岩SiO_(2)(51.40%~53.66%)含量较低,MgO(18.56%~22.16%)和FeO^(T)(7.54%~10.64%)含量高,Mg^(#)为79~82。微量元素富集Rb、Th、Ba、Cs等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),具有高Ni(276~973μg/g)、Cr(2152~3574μg/g)和Sc(35.5~53.1μg/g)含量,低Nb/Ta值(3.23~8.68)和εHf(t)值(-7.3~-3.6)。大格勒农场南辉长岩的地球化学组成具有岛弧基性岩特征,其成因可能是流体和俯冲沉积物加入的富尖晶石橄榄岩部分熔融的结果。综合区域资料表明,大格勒农场南辉长岩形成于东昆仑原特提斯洋俯冲晚期阶段,进一步限定原特提斯洋晚期俯冲与碰撞转换时限为中志留世,随后转入碰撞造山阶段。

引入上下文信息和Attention Gate的GUS-YOLO遥感目标检测算法

目前基于通用YOLO系列的遥感目标检测算法存在并未充分利用图像的全局上下文信息,在特征融合金字塔部分并未充分考虑缩小融合特征之间的语义鸿沟、抑制冗余信息干扰的缺点。在结合YOLO算法优点的基础上提出GUS-YOLO算法,其拥有一个能够充分利用全局上下文信息的骨干网络Global Backbone。除此之外,该算法在融合特征金字塔自顶向下的结构中引入Attention Gate模块,可以突出必要的特征信息,抑制冗余信息。另外,为Attention Gate模块设计了最佳的网络结构,提出了网络的特征融合结构U-Net。最后,为克服ReLU函数可能导致模型梯度不再更新的问题,该算法将Attention Gate模块的激活函数升级为可学习的SMU激活函数,提高模型鲁棒性。在NWPU VHR-10遥感数据集上,该算法相较于YOLOV7算法取得宽松指标mAP^(0.50)1.64个百分点和严格指标mAP^(0.75)9.39个百分点的性能提升。相较于目前主流的七种检测算法,该算法取得较好的检测性能。

体育锻炼与中国老年人生活满意度的倒U型关系:抑郁的中介作用

目的:探究体育锻炼与中国老年人生活满意度的关系以及抑郁的中介作用。方法:采用STATA 15.1软件对2018年中国健康与养老追踪调查数据中的60岁以上老年人生活满意度等基本情况进行描述性统计分析,运用基准回归模型与PSM(倾向得分匹配法)分析体育锻炼与老年人生活满意度的关系,通过建立中介模型考察抑郁在体育锻炼与生活满意度间的中介作用。结果:体育锻炼与老年人生活满意度呈倒U型关系(P<0.001),与抑郁呈U型关系(P<0.001),抑郁负向预测生活满意度(P<0.001),农村与城市老年人倒U型曲线出现拐点的阈值分别为3.133、3.455,在男女老年群体中倒U型曲线出现拐点的阈值分别为3.231、2.938,抑郁在体育锻炼与生活满意度间起中介作用。结论:体育锻炼在提升老年人生活满意度的过程中存在一定的剂量效应,体育锻炼对老年人生活满意度的影响具有异质性,老年人体育锻炼既可直接影响生活满意度,也可通过抑郁间接影响生活满意度。

基于土壤分层的双U型地埋管出口温度及土壤温度场研究

目的 探究在土壤分层和地下水渗流条件下地埋管的出口温度以及传热规律。方法 基于多孔介质理论建立分层岩土体瞬态三维模型,分析土壤的初始温度、地下水渗流、回填材料种类对地埋管出口温度及土壤温度场的影响。结果 土壤初始温度为290.15 K时,热泵运行30 d后地埋管的出口温度最高,达到280.43 K;三种常用的回填材料中沙土的换热效果最好,黏土作为回填材料时,地埋管附近出现明显的冷量堆积;地下水渗流速度达到200 m/a时,地埋管出口温度为280.85 K,相较于不存在地下水渗流时的出口温度增加了0.51 K。结论 土壤初始温度、地下水渗流速度均与地埋管出口温度呈正相关;土壤温度场的变化在一定程度上取决于回填材料的种类及热物性;地下水渗流的存在能够消除土壤冷量的堆积,在地埋管敷设时应适当增加沿着渗流方向管间距离。

基于BB-递归核函数SVR算法的U型折弯件模型参数优化研究

影响U型折弯件回弹的因素众多,工件尺寸、力学性能、负载条件、材料各向异性等相互耦合,表现出高度复杂的非线性,从而导致回弹预测结果的不确定性。本研究以板料折弯件回弹后的张开角(α)为目标函数,构建一个递归核函数支持向量回归(SVR)模型,并部署到分支界限法(BB)中,从而筛选出维度为4的最优的特征变量参数子集,其决定系数(R^(2))为0.982147,均方误差(MSE)为0.00433,模型预测精度相对较高。算法优化得到的折弯件参数为:厚度(t)为12 mm,上模宽度(d)为90 mm,上模圆角半径(r)为9 mm,载荷速度(v)为10 mm/s。BB递归核函数SVR算法、有限元模拟和实际测量的α分别为16.3°、17.5°和18.2°,尽管有限元结果更接近于实际值,但是BB递归核函数SVR算法可以为有限元模拟提供筛选出的参数(t,d,r,v)的数据,以快速进行模拟并预测张开角α,并实现回弹补偿装置的高效设计。

宽频小型化U形槽微带天线

针对微带贴片天线宽带化和小型化的设计需求,提出并设计了一种工作在S/C波段的改进的U形槽微带贴片天线。通过在辐射贴片中心开曲折U形槽,使缝隙和馈电探针偏离贴片中心,形成非对称曲折U形槽的层叠介质微带贴片天线。通过共面容性耦合馈电进一步提高天线的阻抗带宽。实测结果表明:该天线在3.11~5.40 GHz频率范围内回波损耗小于-10 dB,相对带宽可达53.8%,与仿真结果吻合,可为微带天线的小型化、宽带化设计提供参考。

U型卷积网络在乳腺医学图像分割中的研究综述

U-Net及其变体模型在乳腺医学图像分割领域展现了卓越的性能,U-Net采用全卷积网络(FCN)结构进行语义分割,U-Net对称结构的高度灵活性和适应性可以通过调整网络深度、引入新的模块来适应不同的图像分割任务和挑战,这种创新结构对后续网络设计产生了深远影响。深入探讨了基于U型卷积网络在乳腺医学图像分割中的应用,并对近年来用于乳腺医学图像分割的U型卷积网络进行了分类与归纳。针对U-Net网络结构改进的乳腺医学图像分割技术进行了如下总结。阐述了目前广泛使用的乳腺医学图像数据集及评价指标,陈述了常用的数据增强方法;详细介绍了U-Net模型的网络结构以及用于乳腺医学图像的传统分割方法;对用于乳腺医学图像分割方法的U型网络结构按照残差结构、多尺度特征、膨胀机制、注意力机制、跳跃连接机制、结合Transformer等方面改进进行归纳总结。讨论了当下乳腺医学图像分割所遇到的问题与挑战,对未来的研究走向做出了展望。

基于UNet3+生成对抗网络的视频异常检测

为解决传统视频异常检测方法在不同场景下多尺度特征提取不完全的问题,提出两种方法:一种是用于简单场景的基于UNet3+的生成对抗网络方法(简称U3P^(2)),另一种是用于复杂场景的基于UNet++的生成对抗网络方法(简称UP^(3))。两种方法分别对连续输入的视频帧生成预测,引入多种损失函数和光流模型学习其外观与运动信息,通过计算AUC进行性能评估。U3P^(2)方法以6.3 M参数量在Ped2数据集的AUC提升约0.6%,而UP^(3)方法在Avenue数据集的AUC提升约0.8%,验证其能够有效应对不同场景下的异常检测任务。

便捷填充U型管盐桥的制备与探索

Cu-Zn原电池实验是基础化学实验的重要组成部分,盐桥批量制备的品质是实验的关键,常规操作的温度高、消耗大、效率低。本文分别从U型管盐桥的填充材料和灌装方式两方面进行研究。针对盐桥的制作难度及功能特点进行探索,对琼脂和可溶性淀粉载体盐桥的导电能力、凝结时间进行分析。改进灌装方式,针对大批量盐桥制作需求,设计半自动式灌装机代替传统人力操作,提高盐桥的制作效率。为化学实验中盐桥的制备提供便捷高效的解决方案,提高相关实验数据的准确性和稳定性。

基于范数灰关联-动态功效系数法的机坪U型区空间效率评估

为了确定机坪U型区空间效率评估指标体系及其指标的重要程度,分别从机坪设计和机坪运行两个维度建立机坪U型区空间效率评估指标体系。基于此提出了基于范数灰关联-动态功效系数法的机坪U型区空间效率评估方法。并以10个国内大型运输机场航站楼对应的U型区机坪为例进行计算,得到了影响机坪U型区空间效率各指标的权重及各机场航站楼对应的U型区机坪的空间效率评分。提出在U型区设计时应着重考虑指廊边机位个数、U型区指廊纵深和U型区底边长度3个指标。结果表明,该方法能够较为科学地对机坪U型区空间效率影响因素进行综合分析,有效评判不同构型机坪U型区空间效率。

右江盆地大际山U-(Mo)矿床围岩蚀变特征及微量元素迁移规律——对区域内U、Au成生关系的指示

位于扬子地块西南缘的右江盆地,是全球第二大的卡林型Au矿(共伴生有Sb、Hg、Tl异常/矿化)矿集区,有着滇黔桂“金三角”的美誉。值得注意的是,该区除发育Au(-Sb-Hg-Tl)矿床外,还产有大量赋矿岩性和控矿构造相似的U矿床(点),成矿特色鲜明。前人对该区Au矿开展了大量研究,而U矿研究较少,对U、Au的成生关系尚不清楚。基于此,文章选取右江盆地内典型的U矿床——大际山U-(Mo)矿床为研究对象,通过开展岩矿相学研究和地球化学分析,厘定了矿化的围岩蚀变为硫化、沥青质化、磷铝锶石化、硅化和伊利石化,揭示了矿化过程中Re、Tl、Mo、U、Cd、Ni、Co、As、Sb、MREE的相对富集。蚀变矿物组合及元素迁移规律约束大际山U-(Mo)矿床中成矿物质可能来源于牛蹄塘组,成矿流体应为还原性有机流体与地表-近地表酸性、氧化性流体的混合,矿质沉淀发生在低温、酸性、还原环境中。综合分析认为,右江盆地内U、Au分布特征及矿床成因具有明显差异,二者应是不同成矿事件的产物。