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Nonreciprocal thermal metamaterials:Methods and applications

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1678-1693页

作者： Zhengjiao Xu Chuanbao Liu Xueqian wang yongliang Li Yang Bai Institute for Advanced Material and Technology University of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

Nonreciprocity of thermal metamaterials has significant application prospects in isolation protection,unidirectional transmission,and energy ***,due to the inherent isotropic diffusion law of heat flow,it is extremely difficult to achieve nonreciprocity of heat *** review presents the recent developments in thermal nonreciprocity and explores the fundamental theories,which underpin the design of nonreciprocal thermal metamaterials,i.e.,the Onsager reciprocity ***,three methods for achieving nonreciprocal metamaterials in the thermal field are elucidated,namely,nonlinearity,spatiotemporal modulation,and angular momentum bias,and the applications of nonreciprocal thermal metamaterials are *** also discuss nonreciprocal thermal ***,the potential applications of nonreciprocity to other Laplacian physical fields are ***,the prospects for advancing nonreciprocal thermal metamaterials are highlighted,including developments in device design and manufacturing techniques and machine learning-assisted material design.

关键词： thermal metamaterials nonreciprocity nonlinearity spatiotemporal modulation

Research on Theoretical Model of Linear Frequency Modulation Interferometry

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Chinese Journal of Lasers 2000年第3期9卷 28-34页

作者： CHEN Yan ZHAO Yang (State Key Laboratory of precision Measurement Technology and instruments, Department of precision instruments,tsinghua university, beijing 100084,china) 清华大学精密测试技术及仪器国家重点实验室北京 100084

In this paper, the principle of linear frequency-modulation (LFM) with an external microcavity laser is analyzed mathematically and a method to establish the math model of LFM heterodyne interference is presented. The expression of LFM heterodyne interference is deduced by an illustration of a triangular frequency modulation. At present, one application of the LFM technique is non-guide absolute distance measurement. Experimental results of a system for absolute distance measurement based on a microchip solid laser and LFM technique are given. Based on the precisely theoretical model some effective approaches to improve the performance of LFM and decrease the measuring error are discussed.

关键词： linear frequency modulation heterodyne interference absolute distance measurement

Orthogonally linear polarized lasers (I)——principle and devices

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Progress in Natural Science:Materials International 2005年第7期15卷 586-595页

作者： ZHANG Shulian and XU Ting (State Key Laboratory of precision Measurement Technology and instruments, Department of precision instruments, tsinghua university, beijing 100084, china) State Key Laboratory of precision Measurement Technology and instruments Department of Precision Instruments Tsinghua University Beijing 100084 China

Two kinds of orthogonally polarized lasers, i. e. Zeeman dual-frequency lasers and four-frequency ring lasers (laser gyros) have been developed since the invention of lasers, in which circularly polarized lights oscillate. This paper summarizes recent progress of the study on orthogonally linear polarized lasers with the standing wave cavity. Firstly, the expression of producing orthogonally linear polarized lights in standing wave cavity, i. e. laser frequency splitting, is given. Almost all the birefringence effects made in laser cavity are used to produce orthogonally linear polarized lights. The effect includes quartz crystal birefringence effect, calcite birefringence effect, stress (photo-elastic) birefringence effect and electro-optical birefringence effect. Secondly, several physical phenomena of orthogonally linear polarized lasers are discovered such as aberrance of frequency splitting curves caused by optical activity of quartz crystal, order-passing of longitudinal modes with frequency splitting and strong modes competition. Finally, because the traditional Zeeman dual frequency laser cannot output frequency difference larger than 3 MHz, the approaches of obtaining larger frequency difference are studied. The sequential results, several kinds of orthogonally polarized lasers, are described, such as birefringence dual frequency lasers outputting a frequency difference from 40 MHz to hundreds of megahertz, birefringence-Zeeman dual frequency lasers outputting a frequency difference from 1 MHz to hundreds of megahertz, the LD pumped YAG birefringence dual frequency laser outputting frequency difference of several gigahertz, and the lasers whose longitudinal mode spacing is c/4L instead of c/2. .

关键词： orthogonally polarized laser dual frequency laser intra-cavity birefringence Zeeman effect photo-elastic birefringence electro-optical birefringence frequency splitting.

Improved Particle Swarm Optimization for Parameter Identification of Permanent Magnet Synchronous Motor

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Computers, Materials & Continua 2024年第5期79卷 2187-2207页

作者： Shuai Zhou Dazhi wang yongliang Ni Keling Song Yanming Li School of Information Science and Engineering Northeastern UniversityShenyang110819China china Northern Vehicle Research Institute Beijing100072China

In the process of identifying parameters for a permanent magnet synchronous motor,the particle swarm optimization method is prone to being stuck in local optima in the later stages of iteration,resulting in low parameter *** work proposes a fuzzy particle swarm optimization approach based on the transformation function and the filled *** approach addresses the topic of particle swarmoptimization in parameter identification from two ***,the algorithm uses a transformation function to change the form of the fitness function without changing the position of the extreme point of the fitness function,making the extreme point of the fitness function more prominent and improving the algorithm’s search ability while reducing the algorithm’s computational ***,on the basis of themulti-loop fuzzy control systembased onmultiplemembership functions,it is merged with the filled function to improve the algorithm’s capacity to skip out of the local optimal *** approach can be used to identify the parameters of permanent magnet synchronous motors by sampling only the stator current,voltage,and speed *** simulation results show that the method can effectively identify the electrical parameters of a permanent magnet synchronous motor,and it has superior global convergence performance and robustness.

关键词： Transformation function filled function fuzzy particle swarm optimization algorithm permanent magnet synchronous motor parameter identification

Detection Algorithm of Laboratory Personnel Irregularities Based on Improved YOLOv7

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Computers, Materials & Continua 2024年第2期78卷 2741-2765页

作者： yongliang Yang Linghua Xu Maolin Luo Xiao wang Min Cao School of Electrical Engineering Guizhou UniversityGuiyang550025China

Due to the complex environment of the university laboratory,personnel flow intensive,personnel irregular behavior is easy to cause security *** using mainstream detection algorithms suffers from low detection accuracy and slow ***,the current management of personnel behavior mainly relies on institutional constraints,education and training,on-site supervision,etc.,which is time-consuming and *** the above situation,this paper proposes an improved You Only Look Once version 7(YOLOv7)to achieve the purpose of quickly detecting irregular behaviors of laboratory personnel while ensuring high detection ***,to better capture the shape features of the target,deformable convolutional networks(DCN)is used in the backbone part of the model to replace the traditional convolution to improve the detection accuracy and ***,to enhance the extraction of important features and suppress useless features,this paper proposes a new convolutional block attention module_efficient channel attention(CBAM_E)for embedding the neck network to improve the model’s ability to extract features from complex ***,to reduce the influence of angle factor and bounding box regression accuracy,this paper proposes a newα-SCYLLA intersection over union(α-SIoU)instead of the complete intersection over union(CIoU),which improves the regression accuracy while increasing the convergence *** experiments on public and homemade datasets show that the improved algorithm outperforms the original algorithm in all evaluation indexes,with an increase of 2.92.in the precision rate,4.14%in the recall rate,0.0356 in the weighted harmonic mean,3.60%in the mAP@0.5 value,and a reduction in the number of parameters and *** with the mainstream algorithm,the improved algorithm has higher detection accuracy,faster convergence speed,and better actual recognition effect,indicating the effectiveness of the improved algorithm in this p

关键词： university laboratory personnel behavior YOLOv7 deformable convolutional networks attention module intersection over union

Orthogonal linear polarized lasers (Ⅲ)——Applications in self-sensing

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Progress in Natural Science:Materials International 2005年第11期15卷 961-971页

作者： ZHANG Shulian, DU Wenhua and LIU Gang (The State Key Laboratory of precision Measurement Technology and instruments, Department of precision instruments, tsinghua university, beijing 100084, china) The State Key Laboratory of precision Measurement Technology and instruments Department of Precision Instruments Tsinghua University Beijing 100084 China

In this paper, the applications of orthogonal linear polarized lasers in self-sensing are reviewed. The properties for such a laser include the production of a new frequency in one longitudinal mode spacing, the tuning of frequency difference, the change of polarization states as cavity tuning, the control of mode competition intensity, the optical feedback, and so on. The orthogonal polarized lasers have been used as a laser nanometer ruler based on competition between two polarized lights in a HeNe laser and as a displacement measurement tool based on the optical feedback in the orthogonal polarized lasers. They are also used in the phase retardation measurement of a waveplate, the angle measurement, the vibration measurement, the pressure/force measurement, the weak magnetic field measurement, and so on. The structures of these new devices are simple and compact with the great advantages of high resolution and high accuracy. Some of these devices can trace to the source of the laser wavelength. The nanometer laser ruler is an example whose measurement range is 12.mm, resolution is 79 nm and linearity is less than 5×10-5. The repeatability of the phase retardation measuring system of waveplate can reach 3’.

关键词： orthogonal polarized laser frequency splitting optical feedback vibration measurement displacement measurement waveplate measurement angle measurement.

Holographic Storage Parametric Optimization of the Crystal LiNbO3∶Fe Based on One-center Model

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Chinese Journal of Lasers 2002年第1期11卷 28-34页

作者： wang Jiangang HE Qingsheng JIN Guofan WU Minxian (State Key Laboratory of precision Measurement Technology and {2., Department of precision {2., tsinghua university, beijing 100084, china) Department of precision instruments Tsinghua University State Key Laboratory of Precision Measurement Technology and Instruments 北京 100084

Based on one-center model, the effects of the doping amount and the degrees of reduction and oxidation on the dynamic range M, the response time and the photorefractive sensitivity in the crystal LiNbO 3∶Fe are analyzed in detail. The principle of material optimization is discussed. The best crystal thickness (about 1.4～2.6 mm) for the maximum dynamic range M is calculated for the different doping amounts. The results show that the more the doping amount, the lighter the reduction of the crystal should be chosen, and that the heavier the reduction of the crystal, the less effect the doping amount has on the response time. The dynamic range M is in conflict with the response time. Due to the difficulty of processing crystals, the thickness is increased to 5 mm at the cost of decreasing the dynamic range M by 0.3～0.5.

关键词： holographic storage materials parametric optimization LiNbO 3∶Fe crystals

Effects of cement content, polypropylene fiber length and dosage on fluidity and mechanical properties of fiber-toughened cemented aeolian sand backfill

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International Journal of Minerals,Metallurgy and Materials 2024年第11期31卷 2404-2416页

作者： Shushuai wang Renshu Yang yongliang Li Zhongwen Yue School of Mechanics and Civil Engineering China University of Mining and Technolog(Beijing)Beijing 100083China School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China School of Energy and Mining Engineering China University of Mining and Technology(Beijing)Beijing 100083China

Using aeolian sand(AS)for goaf backfilling allows coordination of green mining and AS *** AS backfill(CASB)exhibits brittle ***(PP)fibers are good toughening *** the toughening effect of fibers is analyzed,their influence on the slurry conveying performance should also be ***,cement affects the interactions among the hydration products,fibers,and *** this study,the effects of cement content(8wt%,9wt%,and 10wt%)and PP fiber length(6,9,and 12.mm)and dosage(0.05wt%,0.1wt%,0.15wt%,0.2.t%,and 0.2.wt%)on fluidity and mechanical properties of the fibertoughened CASB(FCASB)were *** results indicated that with increases in the three aforementioned factors,the slump flow decreased,while the rheological parameters *** compressive strength(UCS)increased with the increase of cement content and fiber length,and with an increase in fiber dosage,it first increased and then *** strain increased with the increase of fiber dosage and *** effect of PP fibers became more pronounced with the increase of cement *** image correlation(DIC)test results showed that the addition of fibers can restrain the peeling of blocks and the expansion of fissure,and reduce the stress concentration of the *** electron microscopy(SEM)test indicated that the functional mechanisms of fibers mainly involved the interactions of fibers with the hydration products and matrix and the spatial distribution of *** the basis of single-factor analysis,the response surface method(RSM)was used to analyze the effects of the three aforementioned factors and their interaction terms on the *** influence surface of the two-factor interaction terms and the three-dimensional scatter plot of the three-factor coupling were *** conclusion,the response law of the FCASB properties under the effects of cement and PP fibers were obtained,which provides theoretical and engineerin

关键词： polypropylene fibers fiber-toughened cemented aeolian sand backfill digital image correlation scanning electron microscopy response surface method

Step kinematic calibration of a 3-DOF planar parallel kinematic machine tool

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Science china(Technological Sciences) 2008年第12期51卷 2155-2167页

作者： CHANG Peng,wang JinSong,LI TieMin,LIU XinJun & GUAN LiWen Department of precision {2. and Mechanology,tsinghua university,beijing 100084,china 1. Department of precision instruments and Mechanology Tsinghua University Beijing 100084 China

This paper presents a novel step kinematic calibration method for a 3 degree-of-freedom(DOF) planar parallel kinematic machine tool,based on the minimal linear combinations(MLCs) of error *** method using mapping of linear combinations of parameters in error transfer multi-parameters coupling system changes the modeling,identification and error compensation of geometric parameters in the general kinematic calibration into those of linear combinations of *** using the four theorems of the MLCs,the sets of the MLCs that are respectively related to the relative precision and absolute precision are *** simple and feasible measurement methods in practice are given,and identification analysis of the set of the MLCs for each measurement is carried *** to the identification analysis results,a step calibration including step measurement,step identification and step error compensation is determined by taking into account both measurement costs and *** experiment shows that the proposed method has the following merits:(1) the parameter errors that cannot influence precision are completely avoided;(2. it reflects the mapping of linear combinations of parameters more accurately and enhances the precision of identification;and(3) the method is robust,efficient and effective,so that the errors in position and orientation are kept at the same order of the measurement *** to these merits,the present method is attractive for the 3-DOF planar parallel kinematic machine tool and can be also applied to other parallel kinematic machine tools with weakly nonlinear kinematics.

关键词： parallel kinematic machine tools kinematic calibration parameter identification minimal linear combinations