制造发展的三个范式:制造发展规律的研究

基于对人类社会发展历史和科学技术发展内在规律的认识,本文详细分析了制造发展的三个范式,论证了原子及近原子尺度制造是制造范式III的核心使能技术。文章回顾了国内外各机构对原子级制造研发规划现状,指出我国目前处于原子级制造技术发展的重要战略机遇期,并从设计、材料、加工和检测等角度分析了原子级制造的技术体系内涵;梳理了原子级表面制造、原子级结构制造、原子级测量与表征等领域的研究进展,呈现了当前具有原子级制造能力的部分代表性技术,包括原子级切削、原子级抛光、电化学加工、等离子体原子级加工技术、原子精准操控以及原子分辨测量与表征技术,并对原子级制造战略规划提出发展建议。

原子级制造测量与表征研究现状综述

原子级制造是指将能量作用于原子,通过原子级材料的可控去除或者原子/分子级结构的大规模操控及组装,实现产品性能与功能跃迁的前沿制造技术,是一种可以大规模、批量化的先进制造技术。该过程需要在10-10m空间尺度下精确操控原子。同时,制造过程中原子的键合时间、电子动力学变化均发生在飞秒(10-15s)至阿秒(10-18s)量级。因此,只有具备超快时间和空间分辨在线检测与表征能力,才能够深入了解并利用原子级制造过程中原子尺度的新原理、新效应,保障原子级制造的可达性与可控性;只有实现原子级制造过程的高通量、大范围的在线监测,才能保障原子级制造的可靠性。基于此,原子级制造的测量与表征是指在原子级的时间、空间、能量尺度上对材料、结构或器件进行精确的测量和表征,以保障原子级制造的可达性、可控性与可靠性。本文介绍了原子级制造所需的测量表征手段的研究现状,从原子级超快动力学过程观测、原子结构演变原位表征、原子级制造过程在线质量监测三大方向进行系统梳理,总结了目前原子级制造测量与表征的挑战并针对未来发展给出建议。

NH_(2)-MOF-199@粘胶复合非织造材料的制备及有机染料吸附性能

采用原位溶剂热法在粘胶水刺非织造材料(VSN)表面合成了金属有机框架材料NH_(2)-MOF-199,制备了NH_(2)-MOF-199@粘胶水刺复合非织造材料(NH_(2)-MOF-199@VSN);然后,将NH_(2)-MOF-199@VSN经200℃高温煅烧,得到炭化后的NH_(2)-MOF-199@VSNC。结果表明,呈八面体结构的NH_(2)-MOF-199晶体粒子被均匀、致密地固定在VSN表面。高温炭化后,NH_(2)-MOF-199粒子的表面出现小孔和裂纹。与VSN和NH_(2)-MOF-199@VSN相比,NH_(2)-MOF-199@VSNC对亚甲基蓝(MB)的吸附效果最佳。当吸附溶液的温度为30℃,pH=7时,NH_(2)-MOF-199@VSNC对MB的吸附效率最高,为98.42%,经5次重复吸附使用后,NH_(2)-MOF-199@VSNC对MB的吸附效率仍有65.76%。NH_(2)-MOF-199@VSNC对MB的吸附是吸热、熵增且自发的过程,与准一级吸附动力学模型相比,其对MB的吸附过程更适合用准二级吸附动力学模型描述,吸附机理以化学吸附为主,伴随着物理吸附。

基于局部描述子的小样本轴承故障诊断方法

深度学习由于其在特征表示方面的优势,近年来已被应用于很多领域,但是在故障诊断领域很难获取大量的故障样本来训练模型。针对这一问题,提出了一种基于局部描述子的小样本轴承故障诊断方法,利用改进的深度最近邻神经网络(Deep Nearest Neighbor Neural Network,DN4)进行故障诊断。首先通过短时傅里叶变换将振动信号转换为二维时频图像,特征提取主干网络采用ResNet-12网络,引入高效多尺度注意力机制(Efficient Multi-scale Attention,EMA)来更好地提取故障特征,得到轴承故障的局部描述子,最后利用K近邻算法来得到故障类别。为验证所提方法的有效性,进行了不同样本数量、跨工况条件下的轴承故障诊断实验,实验结果表明,文章所提方法在小样本条件下具有较好的故障识别效果和泛化性能,具有一定的工程应用价值。

稳定界面助力石墨实现超长储钾性能

石墨作为锂离子电池的商业阳极材料,由于其高丰度、低成本和低电位的优势,在K离子电池中也显示出了的巨大潜力。然而,K离子半径(0.138 nm)大于Li离子半径(0.076 nm),会造成的明显结构损伤导致明显的容量衰减和不稳定的循环寿命。在这里,我们用简单有效的微波方法通过石墨烯涂层设计了石墨阳极的稳定界面。微波还原可以在10 s内有效地去除氧化石墨烯的氧基,这一点得到了X射线光电子能谱(XPS)的证实。石墨烯涂层不仅可以缓冲石墨的体积膨胀以抑制结构崩溃,还可以加速电子传输以提高倍率性能。石墨烯涂层负极(GCG)在3000次循环后表现出262 m Ah·g^(-1)的超级循环稳定性。与石墨相比GCG的倍率性能也更加优异(500 m A·g^(-1)的电流密度下容量为161.2 m Ah·g^(-1))。相反,在相同的电流密度下,石墨的容量在150次循环后衰减到小于150m Ah·g^(-1)。进一步的电化学阻抗(EIS)和恒电流间歇滴定(GITT)测试表明,与石墨相比,GCG表现出更快的电导率和离子扩散。循环后的拉曼光谱、扫描电镜(SEM)和透射电镜(TEM)图像验证了石墨烯作为缓冲界面有利于电极结构的完整性和固体电解质膜(SEI)的稳定性。这项工作为钾离子电池的大规模应用提供了新的希望。

面向激光雷达点云数据的多结构树种识别

针对由于树木种间相似性和种内差异性带来的识别困难,以及由于采集环境及设备的多样性导致的点云质量差异,提出面向激光雷达点云数据的多结构树种识别方法(MSTSR)。首先借助改进的组合采样策略,在有效降低数据冗余的同时,保留单木的主体枝干结构;其次通过内建的近邻感知与增强模块(NAE)层次化聚合点云属性,以形成高阶的语义描述;最后通过融合树冠、主干以及整树的多结构信息,生成跨尺度的树木点云表征。在地面激光雷达采集的树种点云数据集上验证该方法的有效性,该数据集由7个树种共690棵树组成的。结果表明:该方法的总体准确率达到94.2%。相比主流的PointNet和PointNet++深度点云分类网络,分别提升13.04和9.42个百分点;相比基于点云的多视图2D投影方法,提升8.19个百分点;相比基于多个测树因子的随机森林方法,提升24.63个百分点,从而证实采用深度网络直接进行树种点云识别的潜力。

Parental Educational Expectations,Academic Pressure,and Adolescent Mental Health:An Empirical Study Based on CEPS Survey Data

Background:This study aimed to investigate the relationship between parental educational expectations and adolescent mental health problems,with academic pressure as a moderating variable.Methods:This study was based on the baseline data of the China Education Panel Survey,which was collected within one school year during 2013–2014.It included 19,958 samples from seventh and ninth graders,who ranged from 11 to 18 years old.After removing missing values and conducting relevant data processing,the effective sample size for analysis was 16344.The OLS(Ordinary Least Squares)multiple linear regression analysis was used to examine the relationship between parental educational expectations,academic pressure,and adolescents’mental health problems.In addition,we established an interaction term between parents’educational expectations and academic pressure to investigate the moderating effect of academic stress.Results:The study found that adolescents whose parents had high educational expectations reported less mental health problems.(β=−0.195;p<0.001).Additionally,adolescents who had high academic pressure reported more mental health problems.(β=0.649;p<0.001).Furthermore,the study found that academic pressure had a significant moderating effect on the relationship between parental educational expectations and adolescents’mental health problems(β=0.082;p<0.001).Conclusion:Parental educational expectations had a close relationship with adolescents’mental health problems,and academic pressure moderated this relationship.For those adolescents with high levels of academic pressure,the association between high parental educational expectations and mental health problems became stronger.On the contrary,for those adolescents with low levels of academic pressure,the association between high parental educational expectations and mental health problems became weaker.These findings shed new light on how parental educational expectations affected adolescent mental health problems and had significant implications for their healthy development.

骨科住院医师在运动医学专科轮转期间微创临床思维及内镜手术能力培训实践

随着全民健身运动的兴起,运动人群和运动类型快速增加导致运动损伤发病率增高及病种类型增多,运动医学这门新兴临床学科近年来也得到了快速发展,作为骨科住院医师规范化培训(简称住培)包含的一门亚专业,微创临床思维和内镜手术能力是运动医学临床诊疗的两大核心。骨科住院医师在运动医学专科轮转阶段,如何在指导医师指导下提高微创临床思维及内镜手术能力是本阶段培训的目的和难点。该文总结了骨科住院医师在运动医学专科轮转期间微创临床思维及内镜手术能力的培训实践。

Primary frequency control considering communication delay for grid-connected offshore wind power systems

Offshore wind farms are becoming increasingly distant from onshore centralized control centers,and the communication delays between them inevitably introduce time delays in the measurement signal of the primary frequency control.This causes a deterioration in the performance of the primary frequency control and,in some cases,may even result in frequency instability within the power system.Therefore,a frequency response model that incorporates communication delays was established for power systems that integrate offshore wind power.The Padéapproximation was used to model the time delays,and a linearized frequency response model of the power system was derived to investigate the frequency stability under different time delays.The influences of the wind power proportion and frequency control parameters on the system frequency stability were explored.In addition,a Smith delay compensation control strategy was devised to mitigate the effects of communication delays on the system frequency dynamics.Finally,a power system incorporating offshore wind power was constructed using the MATLAB/Simulink platform.The simulation results demonstrate the effectiveness and robustness of the proposed delay compensation control strategy.

Anisotropic metal–insulator transition in strained VO_(2)(B) single crystal

Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide, imparting substantial scientific importance to both the exploration of phase transitions and the development of potential technological applications. Unlike the traditional rutile(R) phase, bronze-phase vanadium dioxide [VO_(2)(B)] exhibits an in-plane anisotropic structure. When subjected to stretching along distinct crystallographic axes, VO_(2)(B) may further manifest the axial dependence in lattice–electron interactions, which is beneficial for gaining insights into the anisotropy of electronic transport.Here, we report an anisotropic room-temperature metal–insulator transition in single-crystal VO_(2)(B) by applying in-situ uniaxial tensile strain. This material exhibits significantly different electromechanical responses along two anisotropic axes.We reveal that such an anisotropic electromechanical response mainly arises from the preferential arrangement of a straininduced unidirectional stripe state in the conductive channel. This insulating stripe state could be attributed to the in-plane dimerization within the distorted zigzag chains of vanadium atoms, evidenced by strain-modulated Raman spectra. Our work may open up a promising avenue for exploiting the anisotropy of metal–insulator transition in vanadium dioxide for potential technological applications.

柔性双工网络功率分配:边剪枝加速的GNN计算

由于用户间干扰的存在,无线通信网络中的功率分配问题往往是非凸的、计算量巨大。当前图神经网络(graph neural network,GNN)成为一种有效的计算方法被用来解决该问题。为了最大限度地提高网络传输速率的同时降低计算复杂度,提出一种将设备属性和通信连接属性纳入GNN的柔性双工网络图表示方法,并构建了相应的柔性双工图神经网络(flexible duplex GNN,FD-GNN)模型,首次将节点对之间的距离、信道增益和邻居作为动态阈值引入到FD-GNN中,以适应动态环境。排除GNN中邻居的信道状态信息,通过修剪FD-GNN中的边来减少计算时间降低网络时间复杂度。仿真表明,所提出的基于信道增益邻居的阈值设定方法,性能最优且达到加权最小均方误差(weighted minimum mean square error,WMMSE)的97%,相较于Full-GNN所需的训练时间下降24%。提出的基于阈值的边剪枝有效降低了GNN运算的时间复杂度,提高了算法有效性。

Analysis and verification of electrodynamic force,thermal stress and current sharing for CRAFT converter structure design

In the design realm of fusion power supplies,structural components play a pivotal role in ensuring the safety of fusion devices.To verify the reliability of the converter structure design at the Comprehensive Research Facility for Fusion Technology(CRAFT),meticulous analysis of the converter's dynamic impact is carefully performed based on the worst fault current(400k A),firstly.Subsequently,the thermal stress analysis based on the maximum allowable steadystate temperature is finished,and the equivalent thermal stress,thermal deformation,maximum shear stress of a single bridge arm and the whole converter are studied.Furthermore,a simple research method involving the current-sharing characteristics of a bridge arm with multithyristor parallel connection is proposed using a combination of Simplorer with Q3D in ANSYS.The results show that the current-sharing characteristics are excellent.Finally,the structural design has been meticulously tailored to meet the established requirements.

Ultrasensitive Mechanical Sensor Using Tunable Ordered Array of Metallic and Insulating States in Vanadium Dioxide

Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO_(2)(B)] quantum material. It is shown that the initial metallic state in the VO_(2)(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO_(2)(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.

Studies on the motion and radiation of interior plasmas in gas-filled hohlraums with different laser entrance hole sizes

An experiment on 100 k J laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums.These hohlraums are designed to possess one open end and one laser entrance hole(LEH)with different diameters,which would or not result in the blocking of the LEH.An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the timeresolved x-ray images from the open end.Based on the images,we can study the evolutions of the wall plasma,corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior.Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes.In order to understand these characteristics,our two-dimensional radiation hydrodynamic code is used to simulate the experimental results.For the accuracy of reproduction,dielectronic recombination and two parameter corrections are applied in our code.Based on the comparison between experiments and simulations,we quantitatively understand the blocking process of LEH and the motion effects of other plasmas.The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space,especially the limit size of LEH.

The seismicity in the middle section of the Altyn Tagh Fault system revealed by a dense nodal seismic array

The left-lateral Altyn Tagh Fault(ATF) system is the northern boundary of the Qinghai-Xizang Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes since1598 AD, so the potential seismic hazard is unclear. We develope an earthquake catalog using continuous waveform data recorded by the Tarim-Altyn-Qaidam dense nodal seismic array from September 17 to November23, 2021 in the middle section of ATF. With the machine learning-based picker, phase association, location, match and locate workflow, we detecte 233 earthquakes with M_L-1–3, far more than 6 earthquakes in the routine catalog. Combining with focal mechanism solutions and the local fault structure, we find that seismic events are clustered along the ATF with strike-slip focal mechanisms and on the southern secondary faults with thrusting focal mechanisms. This overall seismic activity in the middle section of the ATF might be due to the northeastward transpressional motion of the Qinghai-Xizang Plateau block at the western margin of the Qaidam Basin.

异构网络中基于深度强化学习的用户关联与资源分配策略

由于异构网络非凸性和组合性的特点,联合用户关联和资源分配来实现能量效率(energy efficiency, EE)和频谱效率(spectral efficiency, SE)同时最大化的最优全局策略仍然是非常具有挑战性的。基于深度强化学习(deep reinforcement learning, DRL)的方法成为在保证异构网络下行链路用户设备(user equipments, UEs)服务质量(quality of service, QoS)的同时实现联合EE-SE性能最大化的必要解决方案。此外,为解决状态-动作空间下计算量大的问题,引入了多智能体架构的深度强化学习算法(MAD3QN)来获得近乎最优控制策略。仿真结果表明,MAD3QN算法在系统容量方面比DDQN算法和DQN算法分别提高了9.2%和18.2%,在联合EE-SE性能方面分别提高了8.5%和16.6%,提升了系统的有效性。

大型铬铁矿热炉渣中Cr_(2)O_(3)含量影响因素研究与实践

介绍了通过研究铬矿特性、冶炼渣型、炉渣碱度、镁铝比以及合金中硅含量等参数与渣中Cr_(2)O_(3)含量的关系,借助Mintab数据分析软件明确了各参数和相关影响因素的优先级,从而有针对性的对原有工艺参数进行优化调整,有效的降低了渣中Cr_(2)O_(3)含量并提高了铬综合收得率。

基于扩张状态观测器的双永磁同步电机同步抗扰控制

对于双永磁同步电机系统中由于参数摄动和随机摩擦扰动引发的转速失同步现象,提出了一种新的双永磁同步电机滑模控制方法。首先,设计了扩张状态观测器去估计系统状态与实时扰动,并结合滑模跟踪控制器来提高电机在扰动作用下的跟踪性能;其次,将交叉耦合结构与滑模同步控制器结合,对电机转速的同步误差进行抗扰控制并且提升系统的同步性能。仿真结果表明,扩张状态观测器能准确估计电机系统机械角、转速及系统总扰动;设计的滑模控制器能够有效提高电机系统在扰动作用下的跟踪与同步控制性能。

Phenomenology of plume-surface interactions and preliminary results from the Tianwen-1 landing crater on Mars

The plume-surface interaction(PSI)is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies.The PSI will cause obscuration,erosion of the planetary surface,and high-speed spreading of dust or high-energy ejecta streams,which will induce risks to a safe landing and cause damage to payloads on the landers or to nearby assets.Safe landings and the subsequent scientific goals of deep-space exploration in China call for a comprehensive understanding of the PSI process,including the plume flow mechanics,erosion mechanism,and ejecta dynamics.In addition,the landing crater caused by the plume provides a unique and insightful perspective on the understanding of PSI.In particular,the PSI can be used directly to constrain the composition,structure,and mechanical properties of the surface and subsurface soil.In this study,we conducted a systematic review of the phenomenology and terrestrial tests of PSI:we analyzed the critical factors in the PSI process and compared the differences in PSI phenomena between lunar and Martian conditions;we also reviewed the main erosion mechanisms and the evolution and development of terrestrial tests on PSI.We discuss the problems with PSI,challenges of terrestrial tests,and prospects of PSI,and we show the preliminary results obtained from the landing crater caused by the PSI of Tianwen-1.From analysis of the camera images and digital elevation model reconstructions,we concluded that the landing of Tianwen-1 caused the deepest crater(depth>40 cm)on a planetary surface reported to date and revealed stratigraphic layers in the subsurface of Martian soil.We further constrained the lower bounds of the mechanical properties of Martian soil by a slope stability analysis of the Tianwen-1 landing crater.The PSI may offer promising opportunities to obtain greater insights into planetary science,including the subsurface structure,mineral composition,and properties of soil.

Self-absorption effects of laser-induced breakdown spectroscopy under different gases and gas pressures

The self-absorption effect is one of the main factors affecting the quantitative analysis accuracy of laser-induced breakdown spectroscopy.In this paper,the self-absorption effects of laserinduced 7050 Al alloy plasma under different pressures in air,Ar,and N2have been studied.Compared with air and N2,Ar significantly enhances the spectral signal.Furthermore,the spectral self-absorption coefficient is calculated to quantify the degree of self-absorption,and the influences of gas species and gas pressure on self-absorption are analyzed.In addition,it is found that the spectral intensity fluctuates with the change of pressure of three gases.It can also be seen that the fluctuation of spectral intensity with pressure is eliminated after correcting,which indicates that the self-absorption leads to the fluctuation of spectral intensity under different pressures.The analysis shows that the evolution of optical thin spectral lines with pressure in different gases is mainly determined by the gas properties and the competition between plasma confinement and Rayleigh–Taylor instability.