Highly Stretchable and Sensitive Flexible Strain Sensor Based on Fe NWs/Graphene/PEDOT:PSS with a Porous Structure

With the rapid development of wearable smart electronic products, high-performance wearable flexible strain sensors are urgently needed. In this paper, a flexible strain sensor device with Fe NWs/Graphene/PEDOT:PSS material added under a porous structure was designed and prepared. The effects of adding different sensing materials and a different number of dips with PEDOT:PSS on the device performance were investigated. The experiments show that the flexible strain sensor obtained by using Fe NWs, graphene, and PEDOT:PSS composite is dipped in polyurethane foam once and vacuum dried in turn with a local linearity of 98.8%, and the device was stable up to 3500 times at 80% strain. The high linearity and good stability are based on the three-dimensional network structure of polyurethane foam, combined with the excellent electrical conductivity of Fe NWs, the bridging and passivation effects of graphene, and the stabilization effect of PEDOT:PSS, which force the graphene-coated Fe NWs to adhere to the porous skeleton under the action of PEDOT:PSS to form a stable three-dimensional conductive network. Flexible strain sensor devices can be applied to smart robots and other fields and show broad application prospects in intelligent wearable devices.     

盾构施工对临近桩基影响的数值模拟及参数分析

采用数值模拟软件对盾构隧道施工近距离下穿桩基进行三维仿真模拟,研究双线盾构动态掘进时桩基位移的变化。数值模拟实现了盾构施工时的步步掘进,考虑了土仓压力、注浆压力、盾构与土体摩擦力等施工参数的影响;利用PLAXIS 3D的固结计算,考虑盾构机自重对土体的固结作用引起的地层沉降,并由此考虑开挖速度对桩基位移的影响。计算结果表明:隧道开挖将导致桩基发生沉降、侧移以及倾斜,桩基的整体位移以及倾斜都随盾构施工的进行不断增加。施工参数敏感性分析表明:增大开挖速度可以有效控制桩基位移,但当开挖速度增大至一定程度时,开挖速度对桩基的影响逐渐减小;双线隧道同步开挖时对桩基的影响比双线分别开挖时小。     

3D‐printed cylindrical Luneburg lens antenna for millimeter‐wave applications

A 3D‐printed cylindrical Luneburg lens antenna working at 26 GHz is proposed in this article. The antenna consists of a feeding waveguide, a 3D‐printed cylinder, and a pair of printed metal grids which are stuck on the side faces of the cylinder. 3D‐printed structure ensures the convenience for processing and structural integrity of the Luneburg lens. Hole drilling technology is utilized for the design of the cylindrical lens. In the E‐plane, conversion of spherical waves into planar waves is achieved based on the gradient refractive index which is realized by the gradient equivalent relative dielectric constant. The main part of the lens contains a hole drilling region to realize the desired equivalent permittivity from 1.23 to 2, while another gradual‐thickness region realize the permittivity ranges from 1.23 to 1. H‐probe method is utilized for the optimization of the gradual‐thickness region in this article. And for the H‐plane, with the grids, H‐field distribution is optimized compared with the Luneburg lens antenna without the loading grids. Thus, the side lobe level (SLL) in H‐plane could be reduced. Meanwhile, a narrower half power beamwidth (HPBW) in H‐plane will be obtained due to the metal grids. Experiment results illustrate the feasibility and validity of the proposed 3D‐printed cylindrical Luneburg lens antenna.     

中文维基百科的实体分类研究

维基百科实体分类对自然语言处理和机器学习具有重要的作用。该文采用机器学习的方法对中文维基百科的条目进行实体分类,在利用维基百科页面中半结构化信息和无结构化文本作为基本特征的基础上,结合中文的特点使用扩展特征和语义特征来提高实体分类性能。在人工标注的语料库上的实验表明,这些额外特征有效地提高了ACE分类体系上的实体分类性能,总体F1值达到96%,同时在扩展实体分类上也取得了较好的效果,总体F1值达95%。
     

高度重叠社区的社区合并优化算法

当原图转换成边图后,在边图上进行社区发现可以天然地得到重叠社区,然而得到的社区往往相互大面积重叠,甚至相互包含,导致社区模块性质量较低.针对这一问题,在得到边图下重叠社区发现算法结果的基础上,我们将进一步以优化重叠社区模块化质量函数为标准进行社区合并,以获得高质量的重叠社区.本文首先提出一种描述社区间重叠程度的重叠系数,并基于此进一步提出一种构建带权社区图的启发式方法,能够快速有效地完成社区合并的过程.在人工生成网络与真实世界网络上的实验,进一步验证了该算法能够在不削弱边图方法速度优势的前提下,提高高度重叠社区的模块性.     

图卷积网络下牙齿种子点自动选取

目的 选取牙齿种子点是计算机正畸中常用牙齿分割方法的关键步骤。目前业内大部分牙齿正畸软件都采用需要交互标记的分割方法,通过人机交互在3维牙颌模型上选取每一颗牙齿的种子点,效率较低。针对这一问题,提出基于特征导向的图卷积网络（feature-steered graph convolutional network,FeaStNet）牙齿种子点自动选取方法。方法 通过分析每个牙齿类型的种子点位置和最终分割效果,设立统一的规则,建立了牙颌模型的种子点数据集;利用特征导向的图卷积构建了新的多尺度网络结构,用于识别3维牙颌模型上的特征信息,为了更好地拟合牙齿特征,加深网络模型的深度;再通过训练调整参数和多尺度网络结构,寻找特定的种子点,使用均值平方差损失函数对模型进行评估,以提高预测模型的精确度;把网络寻找出的特征点作为基础点,在牙颌模型上找出与基础点距离最近的点作为种子点,如果种子点位置准确,则根据种子点将牙齿与牙龈分割开。对于种子点位置不准确的结果,通过人工操作修正种子点位置,再进行分割。结果 实验在自建的数据集中测试,其中种子点全部准确的牙颌占88%,其余情况下只需要调整部分不准确种子点的位置。该方法简单快速,与现有方法相比,需要较少的人工干预,提高了工作效率。结论 提出的种子点自动选取方法,能够自动选取牙齿种子点,解决牙齿分割中需要进行交互标记的问题,基本实现了牙齿分割的自动化,适用于各类畸形牙患者模型的牙齿分割。     

Stochastic linear quadratic optimal control problem with terminal state constraints

This paper addresses the stochastic linear quadratic (LQ) control problem with first- and second-order moment constraints on the terminal state. The problem is a modified version of the optimal covariance control problem, where the terminal state is steered to a given probability distribution. Studying a multiplicative-noise stochastic system rather than an additive-noise system is a salient feature. Unlike the existing ideas in the optimal steering, by using the Lagrange multipliers method and establishing the stochastic maximum principle, our problem is converted into solving forward–backward stochastic difference equations (FBSDEs), which is a special stochastic two-point boundary-value problem (TPBVP). We provide the optimal closed-loop controller and necessary and sufficient solvability conditions by developing a nonhomogeneous relationship between the optimal state and costate in FBSDEs. Finally, numerical examples are given to demonstrate our results.     

H2+CO2 Synergistic Plasma Positioning Carboxyl Defects in g-C3N4 with Engineered Electronic Structure and Active Sites for Efficient Photocatalytic H2 Evolution

Defective functional-group-endowed polymer semiconductors, which have unique photoelectric properties and rapid carrier separation properties, are an emerging type of high-performance photocatalyst for various energy and environmental applications. However, traditional oxidation etching chemical methods struggle to introduce defects or produce special functional group structures gently and controllably, which limits the implementation and application of the defective functional group modification strategy. Here, with the surface carboxyl modification of graphitic carbon nitride (g-C₃N₄) photocatalyst as an example, we show for the first time the feasibility and precise modification potential of the non-thermal plasma method. In this method, the microwave plasma technique is employed to generate highly active plasma in a combined H₂+CO₂ gas environment. The plasma treatment allows for scalable production of high-quality defective carboxyl group-endowed g-C₃N₄ nanosheets with mesopores. The rapid H₂+CO₂ plasma immersion treatment can precisely tune the electronic and band structures of g-C₃N₄ nanosheets within 10 min. This conjoint approach also promotes charge-carrier separation and accelerates the photocatalyst-catalyzed H₂ evolution rate from 1.68 mmol h⁻¹g⁻¹ (raw g-C₃N₄) to 8.53 mmol h⁻¹g⁻¹ (H₂+CO₂-pCN) under Xenon lamp irradiation. The apparent quantum yield (AQY) of the H₂+CO₂-pCN with the presence of 5 wt.% Pt cocatalyst is 4.14% at 450 nm. Combined with density functional theory calculations, we illustrate that the synergistic N vacancy generation and carboxyl species grafting modifies raw g-C₃N₄ materials by introducing ideal defective carboxyl groups into the framework of heptazine ring g-C₃N₄, leading to significantly optimized electronic structure and active sites for efficient photocatalytic H₂ evolution. The 5.08-times enhancement in the photocatalytic H₂ evolution over the as-developed catalysts reveal the potential and maneuverability of the non-thermal plasma method in positioning carboxyl defects and mesoporous morphology. This work presents new understanding about the defect engineering mechanism in g-C₃N₄ semiconductors, and thus paves the way for rational design of effective polymeric photocatalysts through advanced defective functional group engineering techniques evolving CO₂ as the industrial carrier gas.     

稀土渣系电渣重熔H13钢铸锭的成分、组织及夹杂物特征

稀土(RE)微合金化是开发高品质模具钢的重要手段之一.采用稀土渣系结合电渣重熔实现H 13钢铸锭的稀土添加,重点对比研究了稀土氧化铝渣系和氧化铝渣系所制备H13钢铸锭的成分、组织及夹杂物特征,揭示了稀土氧化铝渣系对于H13钢铸态组织的稀土改性作用及机制.结果表明,采用稀土氧化铝渣系或稀土氧化钙渣系均可制备稀土质量分数约...     

感应电机压频比调节的模糊节能控制

根据三相感应电机的等效电路,推导出电机的损耗和输出功率与压频比之间的关系,提出了压频比调节的节能控制方法。考虑电机不同负载时损耗曲线的变化持点,引入基于电机转速和输入功率的比例算子,对电机输入功率的变化进行量化;电机稳态运行时进行模糊自寻优控制,动态调速时进行较高的恒压频比控制,提高了电机的效率并保持了一定的动态响应特性。仿真结果验证了运行控制方案的可行性和有效性。