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Physics package based on intracavity laser cooling ^(87)Rb atoms for space cold atom microwave clock

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Chinese Physics B 2024年第7期33卷 22-26页

作者：邓思敏达任伟项静峰赵剑波李琳张迪万金银孟艳玲蒋小军李唐刘亮吕德胜 Aerospace Laser Technology and System Department Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China mechanics Chinese Academy of SciencesShanghai 201800China Center of Materials Science and Optoelectronics engineering University of Chinese Academy of SciencesBeijing 100049China

This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation,microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of 1.2×10^(-􀀀12) τ^(-1/2) with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.

关键词： atomic clock microgravity microwave cavity space station frequency stability

Customizable multifunctional metasurface absorber based on bidirectional deep neural networks covering the quasi-entire terahertz band

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Chinese Optics Letters 2024年第6期 187-195页

作者：丁志鹏苏巍叶李鹏安周远航李文龙 Riaz Ali 唐斌姚红兵 College of mechanics and engineering Science Hohai University School of Microelectronics and Control engineering Changzhou University

In this work, we propose a novel approach that combines a bidirectional deep neural network(BDNN) with a multifunctional metasurface absorber(MMA) for inverse design, which can effectively address the challenge of on-demand customization for absorbers. The inverse design of absorption peak frequencies can be achieved from 0.5 to 10 terahertz(THz), covering the quasi-entire THz band. Based on this, the BDNN is extended to broadband absorption, and the inverse design yields an MMA at the desired frequency. This work provides a broadly applicable approach to the custom design of multifunctional devices that can facilitate the evaluation and design of metasurfaces in electromagnetic absorption.

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Energy absorption behaviors of a novel buffer lander-leg with Yoshimura core

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Chinese Journal of Aeronautics 2024年第4期37卷 333-342页

作者： Yan XU He HUANG Chao ZHANG Rongji FU School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China School of mechanics Civil engineering and Architecture Northwestern Polytechnical UniversityXi’an 710072China

In the current soft-landing system,the lander-leg and the buffer are two independent parts which may cause weight *** traditional mechanical buffers also have their own shortcomings such as small buffer stroke and being non-reusable.A Novel Buffer Lander-leg with Yoshimura core (NBLY) is proposed in this paper,inspired by the Buckling Restrained Brace(BRB).The design details of NBLY and parameter definitions of the core are *** finite element analysis modes have been employed to analyze the nonlinear mechanical behaviors of NBLY subjected to the cyclic *** with four different core styles of hexagon,octagon,dodecagon and hexadecagon are analyzed and *** restraining ratio and cumulative dissipation energy ratio have been obtained to evaluate the energy absorption *** results show that the origami pattern has significant influences on the deformation ductility,plastic energy absorbing and axial load transferring to the *** NBLY with octagon core has outstanding properties,especially the hysteretic energy dissipation and enhancement of compression *** interaction mechanism between the core and encasing member constrains the deformation extensions and contributes to the frictional energy dissipation of the *** paper provides a new conceptual design of buffer lander-leg for soft-landing *** can realize the reuse function as a buffer lander-leg with better loading-bearing and energy absorption behaviors.

关键词： Lander-leg structure Origami Energy absorption Cyclic loading Finite element analysis

Energy Absorption by 3D-Printed Mesh Structures with a Negative Poisson’s Ratio

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 205-212页

作者： Wenyu Li Weiming Yang Mingze Li Xiang Zhang Ping Zhang Yucheng Zhao Peijian Chen Haishun Liu School of mechanics and Civil engineering China University of Mining and TechnologyXuzhou221116China School of Materials Sciences and Physics China University of Mining and TechnologyXuzhou221116China

A negative Poisson's ratio(NPR)structure represents optimal impact-resistance with applications in various fields,including the crash box in vehicles,which absorbs impact kinetic *** crash box is designed to deform in response to impact,increasing local structural density,which enhances impact resistance *** studies have only focused on the NPR effect in the plane dimension at low-speed *** studies have considered high-speed impact loads on three-dimensional NPR *** have developed two types of AlSi10Mg alloy energy-absorbing structures with NPR using three-dimensional printing technology,and have compared our systems with a conventional hexagonal mesh *** testing involved split-Hopkinson pressure bar measurements,which showed good agreement with dynamic numerical *** subjected to an impact load,the NPR structure exhibited better impact resistance and energy absorption compared with the positive Poisson's ratio *** proposed dual-layer hexagonal structure ensures an NPR effect while exhibiting higher strength and improved stability relative to the conventional concave hexagon structure.

关键词： Negative Poisson’s ratio Energy absorption 3D printing Split-Hopkinson pressure bar Numerical simulation

Fourth-order phase-field modeling for brittle fracture in piezoelectric materials

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Applied Mathematics and mechanics(English Edition) 2024年第5期45卷 837-856页

作者： Yu TAN Fan PENG Chang LIU Daiming PENG Xiangyu LI State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China College of Science Chang'an UniversityXi'an 710064China Applied mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Failure analyses of piezoelectric structures and devices are of engineering and scientific *** this paper,a fourth-order phase-field fracture model for piezoelectric solids is developed based on the Hamilton *** typical electric boundary conditions are involved in the present model to characterize the fracture behaviors in various physical situations.A staggered algorithm is used to simulate the crack *** polynomial splines over hierarchical T-meshes(PHT-splines)are adopted as the basis function,which owns the *** numerical simulations are performed to study the influence of the electric boundary conditions and the applied electric field on the fracture behaviors of piezoelectric *** electric boundary conditions may influence crack paths and fracture loads *** present research may be helpful for the reliability evaluation of the piezoelectric structure in the future applications.

关键词： isogeometric analysis(IGA) brittle fracture fourth-order phase-field model piezoelectric solid

Crack identification in concrete, using digital image correlation and neural network

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Frontiers of Structural and Civil engineering 2024年第4期18卷 536-550页

作者： Jingyi WANG Dong LEI Kaiyang ZHOU Jintao HE Feipeng ZHU Pengxiang BAI College of mechanics and Materials Hohai UniversityNanjing 211100China

In engineering applications,concrete crack monitoring is very *** methods are of low efficiency,low accuracy,have poor timeliness,and are applicable in only a limited number of ***,more comprehensive detection of concrete damage under different scenarios is of high value for practical engineering *** image correlation(DIC)technology can provide a large amount of experimental data,and neural network(NN)can process very rich ***,NN,including convolutional neural networks(CNN)and back propagation neural networks(BP),can be combined with DIC technology to analyze experimental data of three-point bending of plain concrete and four-point bending of reinforced *** addition,strain parameters can be used for training,and displacement parameters can be added for comprehensive *** data obtained by DIC technology are grouped for training,and the recognition results of NN show that the combination of strain and displacement parameters,i.e.,the response of specimen surface and whole body,can make results more objective and *** identification results obtained by CNN and BP show that these technologies can accurately identify *** identification results for reinforced concrete specimens are less affected by noise than those of plain concrete *** is more convenient because it can identify some features directly from images,recognizing the cracks formed by macro *** can issue early warning of the microscopic cracks,but it requires a large amount of data and *** can be seen that CNN is more intuitive and efficient in image processing,and is suitable when low accuracy is adequate,while BP is suitable for occasions with greater accuracy *** two tools have advantages in different situations,and together they can play an important role in engineering monitoring.

关键词： digital image correlation convolutional neural network back propagation neural neural network damage detection concrete

A thermo-mechanical damage constitutive model for deep rock considering brittleness-ductility transition characteristics

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Journal of Central South University 2024年第7期31卷 2379-2392页

作者： FENG Chen-chen WANG Zhi-liang WANG Jian-guo LU Zhi-tang LI Song-yu School of Civil and Hydraulic engineering Hefei University of TechnologyHefei 230009China School of mechanics and Civil engineering China University of Mining and TechnologyXuzhou 221116China School of Resources and Environmental engineering Hefei University of TechnologyHefei 230009China

This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion *** model parameters were determined through the extremum features of stress−strain ***,the model predictions were compared with experimental results of marble *** is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution *** a constant temperature,confining pressure can suppress the expansion of *** the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic *** model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining ***,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high *** relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.

关键词： deep rock crack initiation threshold thermo-mechanical coupling statistical damage model distortion energy theory

Uncertainty quantification of inverse analysis for geomaterials using probabilistic programming

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Journal of Rock mechanics and Geotechnical engineering 2024年第3期16卷 895-908页

作者： Hongbo Zhao Shaojun Li Xiaoyu Zang Xinyi Liu Lin Zhang Jiaolong Ren School of Civil engineering and Geomatics Shandong University of TechnologyZibo255000China State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

Uncertainty is an essentially challenging for safe construction and long-term stability of geotechnical *** inverse analysis is commonly utilized to determine the physico-mechanical ***,conventional inverse analysis cannot deal with uncertainty in geotechnical and geological *** this study,a framework was developed to evaluate and quantify uncertainty in inverse analysis based on the reduced-order model(ROM)and probabilistic *** ROM was utilized to capture the mechanical and deformation properties of surrounding rock mass in geomechanical *** programming was employed to evaluate uncertainty during construction in geotechnical engineering.A circular tunnel was then used to illustrate the proposed framework using analytical and numerical *** results show that the geomechanical parameters and associated uncertainty can be properly obtained and the proposed framework can capture the mechanical behaviors under ***,a slope case was employed to demonstrate the performance of the developed *** results prove that the proposed framework provides a scientific,feasible,and effective tool to characterize the properties and physical mechanism of geomaterials under uncertainty in geotechnical engineering problems.

关键词： Geological engineering Geotechnical engineering Inverse analysis Uncertainty quantification Probabilistic programming

Bioinspired anti-freezing 3D-printable conductive hydrogel microfibers for highly-sensitive and wide-range detection of ultralow and high strains

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Green Chemical engineering 2024年第1期5卷 132-143页

作者： Yi-Min Yang Ting-Yuan Hu Haidong Fan Lu Shi Shi-Yuan Zhang Zhuang Liu Xiao-Jie Ju Rui Xie Wei Wang Liang-Yin Chu School of Chemical engineering Sichuan UniversityChengdu610065China Department of mechanics Sichuan UniversityChengdu610065China State Key Laboratory of Polymer Materials engineering Sichuan UniversityChengdu610065China

Soft strain sensors that can transduce stretch stimuli into electrical readouts are promising as sustainable wearable ***,most strain sensors cannot achieve highly-sensitive and wide-range detection of ultralow and high *** by bamboo structures,anti-freezing microfibers made of conductive poly(vinyl alcohol)hydrogel with poly(3,4-ethylenedioxythiphene)-poly(styrenesulfonate)are developed via continuous microfluidic *** microfibers provide unique bamboo-like structures with enhanced local stress to improve both their length change and resistance change upon stretching for efficient signal *** microfibers allow highlysensitive(detection limit:0.05%strain)and wide-range(0%-400%strain)detection of ultralow and high strains,as well as features of good stretchability(485%strain)and anti-freezing property(freezing temperature:-41.1°C),fast response(200 ms),and good *** experimental results,together with theoretical foundation analysis and finite element analysis,prove their enhanced length and resistance changes upon stretching for efficient signal *** integrating microfluidic spinning with 3D-printing technique,the textiles of the microfibers can be flexibly *** microfibers and their 3D-printed textiles enable highperformance monitoring of human motions including finger bending and throat vibrating during *** work provides an efficient and general strategy for developing advanced conductive hydrogel microfibers as highperformance wearable strain sensors.

关键词： Conductive hydrogel microfibers Microfluidics Sensitive detection Wide detection range Anti-freezing