bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of helium bubbles in FeCoNiCr-based high-entropy alloys containing γ′ nanoprecipitates
Authors: Feng 冯 Ting 婷 , Jiang 蒋 Sheng-Ming 胜明 , Hu 胡 Xiao-Tian 潇天 , Zhang 张 Zi-Jun 子骏 , Huang 黄 Zi-Jing 子敬 , Dong 董 Shi-Gang 士刚 , Zhang 张 Jian 建
Published: March 2024

A series of high-entropy alloys (HEAs) containing nanoprecipitates of varying sizes is successfully prepared by a non-consuming vacuum arc melting method. In order to study the irradiation evolution of helium bubbles in the FeCoNiCr-based HEAs with γ′ precipitates, these samples are irradiated by 100-keV helium ions with a fluence of 5×1020 ions/m2 at 293 K and 673 K, respectively. And the samples irradiated at room temperature are annealed at different temperatures to examine the diffusion behavior of helium bubbles. Transmission electron microscope (TEM) is employed to characterize the structural morphology of precipitated nanoparticles and the evolution of helium bubbles. Experimental results reveal that nanosized, spherical, dispersed, coherent, and ordered L12-type Ni3Ti γ′ precipitations are introduced into FeCoNiCr(Ni3Ti)0.1 HEAs by means of ageing treatments at temperatures between 1073 K and 1123 K. Under the ageing treatment conditions adopted in this work, γ′ nanoparticles are precipitated in FeCoNiCr(Ni3Ti)0.1 HEAs, with average diameters of 15.80 nm, 37.09 nm, and 62.50 nm, respectively. The average sizes of helium bubbles observed in samples after 673-K irradiation are 1.46 nm, 1.65 nm, and 1.58 nm, respectively. The improvement in the irradiation resistance of FeCoNiCr(Ni3Ti)0.1 HEAs is evidenced by the diminution in bubbles size. Furthermore, the FeCoNiCr(Ni3Ti)0.1 HEAs containing γ′ precipitates of 15.8 nm exhibits the minimum size and density of helium bubbles, which can be ascribed to the considerable helium trapping effects of heterogeneous coherent phase boundaries. Subsequently, annealing experiments conducted after 293-K irradiation indicate that HEAs containing precipitated phases exhibits smaller apparent activation energy (E
a) for helium bubbles, resulting in larger helium bubble size. This study provides guidance for improving the irradiation resistance of L12-strengthened high-entropy alloy.
A package to bridge experimental tokamak data to modelling workflows for heating and transport
Authors: Tardini G. , Odstrcil T. , Poli E. , Weiland M. ,   the ASDEX Upgrade Team
Published: March 2024

The comprehensive visual tool TRVIEW is presented, a software to read and fit experimental measurements and equilibrium reconstruction in the frame of nuclear fusion research. At the same time, TRVIEW provides a framework to setup physics workflows, especially those related to heating and transport. The TRVIEW package was originally created in order to provide file input to transport codes such as ASTRA and TRANSP. However, having a comprehensive set of python classes for the experimental plasma parameters, it allows direct coupling to several modules, such as the heating and current-drive codes RABBIT and TORBEAM and the equilibrium codes FEQIS and NEMEC. The direct coupling allows also direct visualisation of the input and output parameters and profiles in TRVIEW. The option of storing equilibrium files in the standard gEQDSK format is also enabled in TRVIEW. Special algorithms have been developed or adapted for TRVIEW: a class for fitting the plasma separatrix contour with Fourier moments, a recursive procedure for spline fits of the experimental kinetic profiles. Finally, TRVIEW includes the option to read, visualise and write integrated modelling and analysis system (IMAS) files with a comprehensive set of integrated data structures, covering most of the discharge and plasma parameters and several source profiles, calculated with the TORBEAM and RABBIT codes. This enables users to setup workflows for code validation and physics investigations using the world-wide established IMAS environment. TRVIEW can take the experimental input from the shotfile system of the ASDEX Upgrade tokamak or from IMAS files. Since the algorithms and the coupled codes are device-agnostic, TRVIEW is portable to any other fusion devices.
Seasonal variation of Marine Heat Wave in the East China Sea
Authors: Li Yifan , He Hailun , Zhao Liang , Li Yiwen , Lin Pengfei
Published: March 2024

The satellite-based daily sea surface temperature was used to study the Marine Heat Wave (MHW) in the East China Sea. The seasonal variation of MHW is significant. In winter, the 200 m isobath on the shelf is identified as a section with high-frequency MHW. The duration of MHW is relatively long on the slope and deep basin, and mean intensity of MHW is obviously high in the central Taiwan Strait. In summer, the frequency of MHW is relatively high near the coast of the China Mainland. Meanwhile, the shelf section of the 200 m isobath is also high in frequency. Otherwise, the duration of MHW on the shelf is short. In the northern shelf, the mean intensity of MHW is obviously higher. The total days and maximum intensity of MHW are also discussed, aiming at giving near-fully description of MHW in the East China Sea.
Temporal and spatial distribution characteristics of ocean temperature front in Antarctic Circumpolar Current waters
Authors: Dou Hongyu , Guo Hailong , Wu Jiawei , Xi Shengjun
Published: March 2024

This article uses satellite data and reanalysis data to study the spatiotemporal distribution characteristics of ocean temperature fronts in the Antarctic Circumpolar Current (ACC) waters under the proposed new classification standard using an optimized dynamic gradient threshold method based on Bayesian decision theory. The permanent oceanic front is mainly distributed between 40°S-65°S, with an average intensity of 1.5 °C per 100 kilometers; The average intensity of a semi permanent ocean front is 1.2 °C per 100 kilometers; The average intensity of the short-term oceanic front is around 1 °C per 100 kilometers. The determination of the optimal threshold in the ocean front recognition method adopted in this article is adaptive to the temperature distribution of the studied sea area, effectively reducing the subjectivity of threshold selection.
Statistical Analysis of Mesoscale Eddy Characteristics in the northwestern Pacific Ocean
Authors: Shang Longquan , Han Kaifeng , Chen Feng , Wang Ning , Lu Jiaqing
Published: March 2024

In this paper, the mesoscale eddy data set established by Professor Chelton in Oregon State University is used to analyse the statistical characteristics of mesoscale eddies in the Northwest Pacific Ocean. Mesoscale eddies in this region are divided into short-lived, Mid-lived, and long-lived eddies according to their life cycle with the aim of exploring the characteristics of eddies with different life cycles. Those with a life cycle of less than 6 weeks, 6-9 weeks, and more than 9 weeks are defined as short-lived eddies, mid-lived eddies, and long-lived eddies, respectively. The results show that most of the eddies are short lived eddies with a lifetime of 6 weeks or less. Both short-lived eddies and Mid-lived eddies have more cyclonic eddies than anticyclonic eddies. But long-lived eddies have more anticyclonic eddies than cyclonic eddies. In addition, the number of short-lived eddies in the Subtropical Ocean is more than those in the Kuroshio Extension, while the number of long-lived eddies is the opposite.
Numerical simulation study on hydrodynamics of Xisha Islands and Reefs driven by tide levels, sea surface heights and ocean currents
Authors: Cao Yonggang , Zeng Cansheng , Liao Shizhi , Chen Yizhan , Ma Yu , Zhang Yan , Ma Lei , Zhou Dongsheng , Zhou Runsheng
Published: March 2024

This study employs the FVCOM numerical model to investigate tide flow and hydrodynamics in the marine region surrounding Yongxing Island. The HYCOM model is utilized to obtain sea surface height and ocean current data at the boundary. Additionally, the astronomical tide level predicted by the TPXO9 global tide model is incorporated into the analysis. Through numerical simulation research, the paper aims to examine the aforementioned phenomena. The findings indicate a strong concurrence between the outcomes of the FVCOM numerical simulation and the observed data. The winter and summer tidal patterns in the seas around Yongxing Island exhibit a high degree of similarity. In winter, the current speed of rapid flood and ebb process, exhibits somewhat higher than that in summer. The maximum current speed occurs in the northern marine region of Yongxing Island, during the rapid flood process, whereas it occurs in the northwest marine region of Yongxing Island during the rapid ebb process.
A Deep Learning Method for Arctic Sea Ice Type Classification Based on Active-Passive Microwave Data
Authors: Huang Rui , Xie Tao , Wang Changying
Published: March 2024

The Arctic-scale classification of sea ice type is important in the fields of macro-monitoring in the Arctic, climate change assessment, and long time-series interannual variability of sea ice. To date, a lack of deep learning-based algorithms for detecting Arctic sea ice types from microwave sensors is comparatively rare. In this study, a sea ice type classification algorithm based on the U-Net-CBAM deep learning semantic segmentation network was developed by carrying out research on sea ice type classification algorithms in the Arctic through the integrated use of ASCAT scatterometer and AMSR2 radiometer data. The results of the study show that the proposed method achieves an impressive average accuracy of 94.1% in extracting sea ice categories using AARI ice maps. The results of the algorithm show a high degree of agreement with the OSI-SAF sea ice type daily products.
A Water Quality Prediction Method Based on Deep LSTM Network
Authors: Jiang Nian , Hu Zechen , Huang Yifeng , Li Lulu , Xu Chongyang
Published: March 2024

Water quality parameters are key factors affecting marine ranching. The water quality parameters are not consistent, which are usually complex and variable. The traditional water quality prediction methods have problems such as low long-term prediction accuracy and weak generalization ability. In order to solve the above problems, this paper proposes a multivariate water quality prediction model based on WT-LSTM, which is compared with the BP neural network model for short-term prediction and long-term prediction of dissolved oxygen water quality parameters, and the experimental results show that the WT-LSTM model has good accuracy and generalization in both short-term and long-term prediction, and the short-term prediction accuracy can be up to 98.47% and the long-term prediction accuracy can be up to 98.28%.
Global Sea Surface Temperature Analysis Based on Domestic Ocean Satellite Data. Part II: Comparative Analysis of Multiple Sets of Global Sea Surface Temperature Products in 2022
Authors: Yu Qinglong , Qin Yinghao , Wan Liying
Published: March 2024

With more and more global gap-free fusion products of the sea surface temperature, understanding the consistency and discrepancy of the different SST fusion products will not only help data providers to improve their algorithms, but also help them to select the one that may better suit their applications. In this article, we have compared and analysed 10 sets of global gap-free fusion products of sea surface temperature in 2022, with different fusion techniques and related configurations. It is found that each SST analysis product has the same spatial distribution, with the minimum NMEFC mean value (20.11) and the maximum MGDSST mean value (20.31). Compared with ARGO in-situ data, the RMSE ranges are from 0.3233 (OSTIA) to 0.5180 (MGDSST). The RMSE between NMEFC fusion products and Argo in-situ data is 0.3861, ranked fifth out of 10 sets of fusion products. Compared with GMPE analysis among 9 sets of fusion products, the RMSE ranges are from 0.1579 (CMC) to 0.3199 (K10), and the NMEFC fusion product has a RMSE of 0.3040, which is at the intermediate level, ranked sixth out of 9 fusion products.
Three-dimension holographic numerical simulation of gravity anomalies
Authors: Zhu Dexiang , Dai Shikun , Chen Qingrui , Tian Hongjun
Published: March 2024

In gravity-anomaly-based prospecting, it is difficult to achieve large-scale and high-precision inversion imaging of complex geological models. To address this issue, this paper proposes a three-dimensional holographic numerical simulation method for gravity anomalies. This method transforms the 3D partial differential equation of gravity potential into many independent 1D differential equations with different wavenumbers by performing a 2D Fourier transform along the horizontal direction. It decomposes a large-scale 3D numerical modeling problem into many 1D numerical modeling problems, which greatly reduces the computation and memory requirements of modeling, and each 1D differential equation is independent, so it has high parallelism. The vertical direction is reserved as the spatial domain, which has strict upper and lower boundary conditions; The horizontal 2D Fourier transform uses a holographic Fourier transform (Holo-FT) with a full interval of integration, consistent with the physical boundary in the horizontal direction, thus the physical information of the gravity potential described by the three-dimensional partial differential equation is fully and accurately simulated. Using the high parallelism of the algorithm, the CPU is used for parallel solving ordinary differential equations, while the GPU is used for parallel computing of Holo-FT, which implements the CPU-GPU parallel acceleration scheme and further improves the efficiency of this algorithm.
Research on reconstruction of diffraction tomography based on prior information
Authors: Liang Peihui , Tang Wusheng , Han Jingqi , Wang Jun , Zhang Peng , Lou Kang , Xu Pan
Published: March 2024

Under coherent light illumination, several approaches need either angle scanning or diffuser rotating to reconstruct the image through opaque scattering media. We propose a linear model to restore the hidden object through the actual power spectrum with disturbance of the scattering layer. The experimental results confirm that, the algorithm quickly converge to the only correct reconstruction solution with the accuracy power spectrum pattern of Fourier transform, and the method can reconstruct the high accuracy image of the object hidden by the scattering media with one-shot power spectrum.
Three-dimensional modeling of Marine Controlled Source Electromagnetic field using a space-wavenumber domain method
Authors: Chen Qingrui , Ma Shuqing , Zhang Lilun , Dai Shikun , Ling Jiaxuan
Published: March 2024

Under complex conditions, the three-dimensional modeling of Marine Controlled Source Electromagnetic field requires a significant amount of computation, resulting in slow calculation speed and high storage requirements. To solve these problems, we propose a 3D numerical simulation method of electromagnetic field in the space-wavenumber domain under the Lorenz gauge. Firstly, the new method utilizes the two-dimensional Fourier transform in the horizontal direction to transform the 3D partial differential equations of the Lorenz vector potentials into multiple independent ordinary differential equations. Secondly, the finite element method is used to solve the ordinary differential equations. The fields in the spatial domain are then obtained by using the inverse Fourier transform, and finally, an iterative method with a compact operator is applied to approximate the true solution. The approach requires less computation and storage, and the algorithm is highly parallel, which effectively improves the efficiency of 3D forward modeling of electromagnetic fields. The correctness, effectiveness, and computational efficiency of the method are verified by the design model.
Three-dimensional temperature field inversion in the northern South China Sea
Authors: Li Jingshi , Kuang Xiaodi , Liu Guimei
Published: March 2024

A Swin Transformer oceanic three-dimensional temperature field inversion model is established for the northern South China Sea and its surrounding waters based on satellite observation data and ocean reanalysis data from 1993 to 2018. The inversion results are tested using Argo observation data. The root-mean-square errors of the monthly average temperature fields for 2017 and 2018 are 0.10 to 1.98°C and 0.11 to 1.92°C, respectively, with the maximum values mainly located near the mixing layer. The temperature inversion root-mean-square errors are generally less than 1 °C. Additionally, this article analyzes the three-dimensional structural characteristics and evolution process of a typical anticyclone eddy in the study area. The results show that the inversion results can clearly demonstrate the three-dimensional structure of the eddy and continuously and completely reproduce the process of eddy persistence and movement.
Compression AutoEncoder for High-Resolution Ocean Sound Speed Profile Data
Authors: Liang Zhenyu , Chen Letian , Xiao Wenbin
Published: March 2024

High-resolution ocean sound speed profile (HROSSP) data is essential for ocean acoustic modeling and sonar performance evaluation. However, the large volume and storage requirements of this data severely restrict its practical application in ocean acoustics. In this paper, we propose a compression autoencoder specifically designed for managing HROSSP data (CAE-HROSSP) and investigate the optimal network structure. Experimental results demonstrate that by using the min-max normalization method for input data and the corresponding inverse normalization for output data, along with employing the LeakyReLU function as the final activation layer, the accuracy of decompressed data reconstruction can be significantly improved. To tackle the challenges of fitting the distribution of surface sound speed data caused by significant variations and noise, we propose two loss functions: slice mean square error and elemental mean square error. These loss functions are combined with mean squared error through weighted summation to enhance CAE-HROSSP’s ability to fit the distribution of surface sound speed values and minimize the reconstruction errors of compressed data. Performance evaluation experiments reveal that CAE-HROSSP outperforms two existing methods in compressing HROSSP data, achieving superior performance with smaller data reconstruction errors at higher compression ratios. Furthermore, transfer learning is utilized to enhance the training of CAE-HROSSP, employing HROSSP data from the area where the mesoscale eddy is situated, as well as at the convergence of cold and warm ocean currents. The compression performance of both the training set and the validation set is comparable in the sea, where the structure of the sound speed profile varies greatly. This indicates that CAE-HROSSP can compress highly variable sound speed profile data in more sea areas using transfer learning, and has the potential to be extended globally. The findings and insights obtained from this study provide guidance for future endeavors in utilizing autoencoders to compress HROSSP data.
Study of the strength characteristics of particle velocity at the seabed interface
Authors: Xie Jinhuai , Cao Dejin , Zhang Haigang
Published: March 2024

When studying the propagation characteristics of the acoustic vector field, the law that the horizontal particle velocity intensity is stronger than the vertical particle velocity intensity does not apply near the seabed interface. To verify this characteristic, a sea experiment was conducted in the South China Sea to obtain the long-range propagation data of particle velocity at the seabed interface. Then, based on the normal mode method, the particle velocity intensity distribution of different types of seabed is theoretically simulated and compared with the experimental data, and the intensity characteristics of particle velocity at the seabed interface are verified. The results show that the particle velocity strength of the elastic seabed is mainly influenced by the submarine shear wave, which leads to the phenomenon that the vertical particle velocity is stronger than the horizontal particle velocity strength, and the relative strength of the two is determined by the compression wave velocity, the shear wave velocity and the seabed density.
Phenomenon of reverberation intensity oscillation observed in shallow-water reverberation experiment
Authors: Li Gongyun , Gao Bo , Pang Jie
Published: March 2024

Reverberation has always been a disturbance for active sonar. In the Yellow Sea reverberation experiment conducted in July 2014, the motion of the soliton internal wave was recorded by the temperature sensor attached to the vertical array. The effect of the soliton internal wave on reverberation was investigated from both the temperature chain and the reverberation static experiment. Through the processing of the data in this section, it is found that the soliton internal wave can cause the generation of clutter and the oscillation phenomenon of the average reverberation intensity, and the subsequent research can realize the acoustic telemetry to forecast the internal wave and further improve the performance of the active sonar.
Study on the inductively coupled high rate system and long-distance transmission
Authors: Wu Sheng , Huang Yifeng , Zhang Pingping , Jiang Nian , Liu Chao , Li Lulu , Zhang Cheng , Hu Zechen
Published: March 2024

The inductively coupled transmission chain can carry multiple Marine sensors, which is an important means to obtain Marine data, but the current transmission rate of inductively coupled data is low, which can not meet the needs of future Marine data transmission. The induction coupling system designed in this paper adopts the structure of double magnetic loop and a double-winding, and adopts the new single frequency different code algorithm to realize the data transmission rate of 150kbps. Different water environments were set up in the laboratory for testing, and the lower bit error rate was found in the water environment with the ion concentration of 10%-35%, which met the requirements of inductive coupling data transmission in a multi-water environment. It is of great significance to establish the research of underwater inductively coupled long-distance transmission for the subsequent design of a new inductively coupled transmission chain and the improvement of the data transmission rate.
Frequency estimation of underwater acoustic targets based on improved FRI method
Authors: Wang Xin , Guo Longxiang , Sun Hui
Published: March 2024

The line spectrum information of a ship’s radiated noise signal is often regarded as an important feature used to distinguish between targets. In this paper, an improved FRI (finite rate of innovation) method is proposed to estimate the low-frequency line spectra of the radiated noise from underwater acoustic passive targets under the condition of finite sampling points. First, a preliminary rough estimation of the frequency is performed using the Fourier transform. Then, the multichannel signal data are iteratively fitted based on the polynomial-ratio form model. The optimal estimation results are finally determined based on the residuals between the data and the model in the fitting process. Simulation experiments prove that compared with the original FRI algorithm, the method proposed in this paper can estimate line spectral frequency more efficiently under the condition of low signal-to-noise ratio (SNR), and can achieve fast convergence with shorter operation time. The experimental data processing results prove that the method can realize high-precision extraction of line spectrum information of ship noise.
Research on rapid detection of characteristic parameters of aeroengine blade surface based on laser scanning
Authors: Song Junfang , Sun Bin , Wang Tengjiao , Deng Huauyou
Published: March 2024

How to detect and evaluate the profile quality of aeroengine blades and provide technical support for blade manufacturing has become one of the key technical problems in the field of aviation manufacturing quickly and effectively. This paper studies the evaluation criteria of medium surface quality in the processing and manufacturing process of aeroengine blades, optimizes and innovates the fast extraction algorithms of various geometric parameters such as aeroengine blade section line, middle arc, front/rear edge center, front/rear edge radius, blade chord length, and chord angle, and establishes the evaluation criteria of aeroengine blade surface. According to the geometric relationship of blade chord length and front/rear edge radius in the blade section profile, the parameters are solved one by one through an optimization algorithm, combined with non-contact laser scanning measurement, and the blade detection efficiency is improved by more than 40%.
Research on the UOSM four-port Calibration algorithm and determination method of the Transmission error term
Authors: Du Jinghui , Chen Xiaolong , Wu Jianqiu , Wang Yingquan
Published: March 2024

As one of the key techniques for vector network analyzers to achieve high precision measurement, calibration, and error correction technology has always been the focus of continuous exploration and innovation. UOSM calibration algorithm uses unknown straight-through transmission standards that do not need to be defined and known open-circuit standards, short-circuit standards, and matching standards to calibrate microwave and millimeter wave bands. Based on the study of the mature UOSM calibration algorithm, this paper proposes a method of self-calibration and comparison of the measurement data based on the unknown cut-through standard, which no longer needs the group delay parameters of the unknown straight-through standard and reduces the dependence on the calibrator. The accuracy of the algorithm and error item determination method is verified by ADS simulation and instrument actual test, and a good calibration effect is achieved. It is proved that the algorithm has the ability of accurate calibration. Due to the reduction of parameters, the stability and applicability of the algorithm are improved.
Simulation and experimental study of die-casting pickup robot
Authors: Chen Chaoda , Lv Zhisheng , Yu Zhuoyuan , Xu Biaoqing , Xie Junxian , Luo Yayuan
Published: March 2024

To improve the efficiency of die-casting machine pickup, the combination of SolidWorks and RobotStudio is proposed to establish a simulation workstation. In this paper, the key mechanism analysis and design of the die-casting machine pickup robot are used to determine the robot body and end-effector. SolidWorks three-dimensional software is used for die-casting pickup robot’s overall mechanical structure and workstation peripheral equipment modeling. The RobotStudio software is used for the corresponding model planning layout and Smart components to write to achieve die-casting robot workstation efficient pickup work program writing and simulation debugging. Experimental results show that the die-casting machine pickup robot completed the pickup behavior. The system has the advantages of fast response speed, high positioning accuracy, and reliable operation, effectively improving the efficiency of the production line.
Research on extremely weak remanence measurement system
Authors: Xu Chaoqun , Sun Tian , Huang Kui , Xiao Qi
Published: March 2024

To accurately obtain the extremely weak magnetic field information of the test piece, this article first introduces the basic principles of the extremely weak residual magnetic field measurement technology. Then, an ultra-high precision magnetic shielding system has been developed, which is made of high permeability materials and equipped with a demagnetization coil system, and it can regularly eliminate the inductance of the entire shielding system. The effective shielding inner diameter of the magnetic shielding system is 0.8 m, the length is 1.6 m, and the magnetic field resolution is 0.0015 nT. This system can provide strong support for the measurement of extremely weak magnetic fields in materials and biomedical magnetic research.
Hydraulic fault prediction of integrated transmission system based on LSTM
Authors: Liu Xiongjun , Jin Yuwen , Yao Shuai , Hao Chuangbo , Zhang Jinle , Xu Yi
Published: March 2024

Integrated drive-line fluids play a role in transmitting torque, providing control pressure, lubrication, and cleaning in the integrated drive-train. The increase of oil abrasive particles will accelerate the wear rate of rotating parts, while insufficient oil will lead to rapid ablation and gluing of rotating parts. According to statistics, more than 75% of hydraulic equipment failure is caused by oil pollution. Oil pollution leads to filter blockage which will cause fatal failure so that the entire transmission system cannot work. Therefore, it is extremely important to predict the fault and health management of the hydraulic system. This paper studies the oil fault of the integrated transmission system, proposes a data preprocessing method, and solves the problem of difficult extraction of deterioration index in the multichannel strong noise signal of the hydraulic system through the information fusion algorithm and the mean smoothing algorithm. According to the abnormal data judgment criterion based on the sliding window, the identification of the early fault starting point of the hydraulic system is realized, which provides a basis for the start-up fault prediction and the division of normal and degraded states. A multi-channel fusion fault prediction algorithm for hydraulic systems based on a Long-Short Term Memory (LSTM) deep network is proposed, which realizes long-term and high-precision fault prediction of hydraulic systems. Finally, the oil failure prediction algorithm of the integrated transmission system is verified by using real vehicle fault data.
A robust estimation method of GNSS/IMU fusion kalman filter
Authors: Pu Yanyan , Liu Shihuan
Published: March 2024

Aiming at the traditional gross error detection method of GNSS/IMU fusion Kalman filter, which simply retains or eliminates abnormal observation data and does not make full use of useful observation information, a new robust estimation method of Kalman filter is proposed. Based on the chi-square statistical hypothesis test, this method constructs continuous change measurement using weight coefficient, fully excavates measurable innovation between normal value and abnormal value, and establishes a new measurement update equation of Kalman filter robust estimation. Finally, through GNSS/IMU integrated navigation simulation, the advantages of the new Kalman filter are verified: no parameter adjustment is required, and the statistical error fluctuation is smaller than that of the traditional adaptive filter.
Experimental research on instrumentation for measuring automotive exhaust particle concentrations
Authors: Li Yuanhao , Li Guangze , Chang Liuyong , Zhou Quan
Published: March 2024

Due to the absence of domestic automotive exhaust measurement methods, this paper, based on the principle of condensation nucleus growth counting, has developed a nanoparticle counter suitable for automotive exhaust detection. The paper incorporates the peak value counting method and conducts comparative experiments between different counting methods of the nanoparticle counter and the results obtained by electrostatic counting, as well as parallel experiments with a TSI CPC. The following results were obtained: (1) Compared to the traditional rising edge counting method, the peak value counting method significantly improves counting accuracy. (2) When the concentration is below 12, 500 P/cc, the peak value counting method can count more particle signals. (3) In the testing of complex particle clusters in automotive exhaust, the nanoparticle counter can be used for measuring automotive exhaust emissions.
A method of liquid refractive index measurement based on image correlation coefficient
Authors: Xie Xinxin , Chen Junyi , Zhou Mengna , Xu Junjiang , Zheng Zijian , Yang Jiayao , Luo Jinming , Zhong Yuancong
Published: March 2024

According to the difference of speckle image caused by the axial displacement due to the refraction of a transparent medium, the liquid refractive index is measured by using the image correlation coefficient. An optical measurement system based on laser speckle is built into the experiment. Firstly, the CCD camera is adjusted to move along the optical axis in air, and multiple speckle images at different positions are collected, which are correlated with the speckle image at zero position to obtain the image correlation coefficients, and then the exponential calibration relation between the correlation coefficient and the axial displacement can be obtained. Secondly, two speckle images are collected when the laser speckle spreads respectively through the liquid to be measured and water as the internal standard, and the correlation coefficient between them is calculated. Finally, according to the above calibration relation, the corresponding axial displacement between the liquid to be measured and water can be derived, and then the refractive index of the liquid to be measured is calculated using the axial displacement formula. The results show that this method can realize the measurement of liquid refractive index, and the optical structure is simple and easy to operate.
Geometric calibration of the linear-array whiskbroom optical satellites based on look-angle corrections
Authors: Sun Yuanyuan
Published: March 2024

Linear-array whiskbroom optical satellites are equipped with scanning mirrors and compensation mirrors. They rotate and scan imaging with the satellite flight orbit as the rotation axis, and geometrically splice the scanned images along the orbit, achieving a balance between large width and high resolution of remote sensing images. The addition of scanning mirrors and compensation mirrors necessitates multiple reflections for the imaging ray to reach the focal plane. Hence, the calibration of the geometric aspects for linear-array whiskbroom optical satellites will be an intricate procedure. A geometric calibration model based on look-angle corrections is established according to the imaging characteristics of linear-array whiskbroom optical satellites. All errors are corrected using correction quantities, and cubic polynomial surfaces are used to fit correction quantities. The proposed geometric calibration method based on the look-angle corrections has a sensor positioning precision of better than 1.0 pixels for the calibrated image.
Application of particle filter algorithm in satellite positioning and navigation system
Authors: Ye Fangbin , Xiang Yingjie , Jiang Chi , Wang Jinrong , Wang Taoyue
Published: March 2024

To understand the application of satellite positioning and navigation system, the application of a particle filter algorithm in satellite positioning and navigation system is studied. In this paper, firstly, the state equation of the system is established according to the correlation between the parameters of GPS output, and the particle filter algorithm is applied to filter the GPS-received data. In the CPS navigation system, DSP is used to decode and filter the output signal of the CPS receiver. The results show that when the GPS signal is disturbed, the particle filter algorithm can deal with the abnormal observation samples well, which shows that it can reduce the computational complexity and improve the GPS positioning accuracy, and have a certain robustness.
The effect of crystal phase noise on the proton precession magnetometer magnetic field measurement accuracy
Authors: Zhang Cheng , Bo Tao , Chen Aimin , Luo Wang , Dong Haobin
Published: March 2024

The proton precession magnetometer is a crucial piece of equipment for measuring magnetic fields because it can determine the value of the magnetic field by measuring the frequency of the Free Induction Decay (FID) signal. The frequency source, one of the crucial parts of the frequency measurement system, has a direct impact on how well the system works as a whole. The communication quality and detection accuracy of the frequency measuring system are directly influenced by phase noise, which is a crucial indicator of frequency stability. By acquiring various output frequencies of crystal oscillators using the Phase Locked Loop (PLL) frequency doubling technique, this study investigates the extent to which crystal phase noise impacts the accuracy of magnetometer frequency measurement.
Thermal error modelling of gear measuring instrument based on principal component regression
Authors: He Dongfeng , Wang Jianhua , Ren Yanping
Published: March 2024

As gear measuring instruments (GMI) are frequently used at the production site, the influence of temperature on their accuracy and stability becomes non-negligible. The existing standards and technologies only consider the error modelling and compensation problem when the GMI is in a uniform temperature field and is not suitable for the production site environment with a large temperature change rate and large temperature gradient. The paper delves into the problems of GMI thermal error modelling at the production site. First, the temperatures of the GMI and its surroundings were measured using multiple temperature sensors. The parallelism thermal errors between centres and the Z-axis (referred to as parallelism thermal errors) and the y-direction spatial thermal errors (referred to as spatial thermal errors) were also measured by the probe and laser interferometer synchronously. Then, the models of them were established based on principle component regression (PCR). As evidenced by the experimental results, the fitting determination coefficient of the models are both greater than 97%, and the prediction determination coefficient is greater than 90%, demonstrating that the models are precise and robust.
A multifunctional reference torque standard machine
Authors: Yi Wei , Qiu Dongli , Liu Ying , Yuan Guihong , Dai Hua , Li Shiqian
Published: March 2024

In response to the problem of using different single machines to achieve measurement and detection of existing torque instruments, this article introduces a multifunctional reference torque standard and proposes specific steps for torque measurement and detection. This standard machine can be used to detect various existing torque instruments and can solve the problem of using a single machine to achieve the detection of a certain type of torque equipment. After adopting this standard machine and its detection method, experimental data shows that the measurement of the torque transducer can meet the requirements of JJG995-2005 “Static Torque Measuring Machines” and the measurement of the reference torque wrench can meet the requirements of JJG1103-2014 “Reference torque wrench Verification Regulations”.
Testability evaluation of radar equipment with improved matter-element extension method
Authors: Chen Jiajun , Hu Bing , Shi Duanyang , Min Zhuo
Published: March 2024

In response to the problems of many influencing factors and different indexes, a radar equipment testability assessment index system is constructed based on the characteristics of equipment and testability connotation requirements. The Criteria Importance Though the Intercrieria Correlation (CRITIC) method is improved by using the variance coefficient to replace standard deviation and conflict coefficient to calculate the absolute value, and the objective weights of evaluation indexes are determined. An improved matter-element extension model is established, and the testability evaluation of different types of radar equipment is obtained by calculating the asymmetric close degree of the extension set. The effectiveness of the model is verified by an example analysis.
Dynamic characteristics for 2 μm-self-similar pulse thulium-doped fiber laser
Authors: Liu Weici , Li Xingxing , Lin Zhenguo
Published: March 2024

A passive mode-locked thulium-doped fiber laser is a generator for 2 μm ultra-short laser pulses. In addition, mode-locked self-similar pulses also exhibit rich nonlinear dynamic characteristics in thulium-doped fiber lasers. Therefore, this article studies the dynamic characteristics of self-similar pulses for the 2 μm passive mode-locked thulium-doped fiber laser. The research results also indicate that as the gain coefficient increases, the peak power of self-similar pulses increases, pulse width widens, and the linearity of chirp increases.
THz Near-field spectroscopy of metamaterial resonators
Authors: Degl’Innocenti R , Lu Y , Hale L L , Zaman A M , Addamane S J , Brener I , Mitrofanov O
Published: March 2024

Terahertz near-field spectroscopy is a powerful technique for the investigation of metamaterial resonators with subwavelength resolution. Here, we used an a-SNOM THz time domain spectroscopic system for the direct study of all the modes supported by individual D-split ring resonators, their E-field distributions and relative Q factors. A cross-polarized excitation and detection technique is also demonstrated, yielding a modes’ mapping by the resonators with unprecedented resolution and sharpness.
Summer drought weakens land surface cooling of tundra vegetation
Authors: Rietze Nils , Assmann Jakob J , Plekhanova Elena , Naegeli Kathrin , Damm Alexander , Maximov Trofim C , Karsanaev Sergey V , Hensgens Geert , Schaepman-Strub Gabriela
Published: March 2024

Siberia experienced a prolonged heatwave in the spring of 2020, resulting in extreme summer drought and major wildfires in the North-Eastern Siberian lowland tundra. In the Arctic tundra, plants play a key role in regulating the summer land surface energy budget by contributing to land surface cooling through evapotranspiration. Yet we know little about how drought conditions impact land surface cooling by tundra plant communities, potentially contributing to high air temperatures through a positive plant-mediated feedback. Here we used high-resolution land surface temperature and vegetation maps based on drone imagery to determine the impact of an extreme summer drought on land surface cooling in the lowland tundra of North-Eastern Siberia. We found that land surface cooling differed strongly among plant communities between the drought year 2020 and the reference year 2021. Further, we observed a decrease in the normalized land surface cooling (measured as water deficit index) in the drought year 2020 across all plant communities. This indicates a shift towards an energy budget dominated by sensible heat fluxes, contributing to land surface warming. Overall, our findings suggest significant variation in land surface cooling among common Arctic plant communities in the North-Eastern Siberian lowland tundra and a pronounced effect of drought on all community types. Based on our results, we suggest discriminating between functional tundra plant communities when predicting the drought impacts on energy flux related processes such as land surface cooling, permafrost thaw and wildfires.
First principles study of electronic structure and transport in graphene grain boundaries
Authors: Bach Lorentzen Aleksander , Gao Fei , Bøggild Peter , Jauho Antti-Pekka , Brandbyge Mads
Published: March 2024

Grain boundaries play a major role for electron transport in graphene sheets grown by chemical vapor deposition. Here we investigate the electronic structure and transport properties of idealized graphene grain boundaries (GBs) in bi-crystals using first principles density functional theory (DFT) and non-equilibrium Greens functions. We generated 150 different grain boundaries using an automated workflow where their geometry is relaxed with DFT. We find that the GBs generally show a quasi-1D bandstructure along the GB. We group the GBs in four classes based on their conductive properties: transparent, opaque, insulating, and spin-polarizing and show how this is related to angular mismatch, quantum mechanical interference, and out-of-plane buckling. Especially, we find that spin-polarization in the GB correlates with out-of-plane buckling. We further investigate the characteristics of these classes in simulated scanning tunnelling spectroscopy and diffusive transport along the GB which demonstrate how current can be guided along the GB.
Apparent color and Raman vibrational modes of the high-temperature superconductor Bi2Sr2CaCu2O
8+δ
exfoliated flakes
Authors: Figueruelo-Campanero Ignacio , del Campo Adolfo , Nieva Gladys , González Elvira M , Serrano Aida , Menghini Mariela
Published: March 2024

Studying and controlling the properties of individual exfoliated materials is one of the first steps towards the fabrication of complex van der Waals systems. In this work, we present a systematic study of optical properties and micro-Raman spectroscopy on exfoliated flakes of the high-temperature superconductor Bi2Sr2CaCu2O

8
+
δ

(BSCCO-2212). We demonstrate that these are quick and non-invasive techniques for studying air sensitive materials. The apparent color of BSCCO-2212 exfoliated flakes on SiO2/Si has allowed a rough and fast identification of the number of layers. By analyzing the optical contrast of different flakes we determined the complex refractive index in the visible range and found the optimal combination of illumination wavelength and substrate properties for the identification of flakes with different thickness. In addition, we report the hardening of the most characteristic Raman modes as flake thickness decreases, possibly caused by strain in the BiO and CuO2 planes. Moreover, the evolution of the Raman modes establishes a second approach to determine the thickness of BSCCO-2212 thin flakes. As BSCCO-2212 is a challenging material due to its sensitivity to ambient conditions, the present work provides a guide for the fabrication and characterization of complex van der Waals systems paving the way for studying heterostructures based on unconventional superconductors in the 2D limit.
Anomalous redshift in interlayer exciton emission with increasing twist angle in WSe2/MoSe2 heterostructures
Authors: Palekar Chirag Chandrakant , Hagel Joakim , Rosa Barbara , Brem Samuel , Shih Ching-Wen , Limame Imad , von Helversen Martin , Tongay Sefaattin , Malic Ermin , Reitzenstein Stephan
Published: March 2024

Van der Waals heterostructures utilizing semiconducting transition metal dichalcogenide (TMDC) monolayers have surfaced as compelling candidates due to their intriguing optical characteristics, which can be effectively controlled by the manipulation of the stacking twist angle. This study investigates the intricate correlation between twist angle, band offset, and interlayer exciton emission within twisted WSe2/MoSe2 heterostructures. Our findings suggest a crucial influence of monolayer stacking order on the band offset and the dipole orientation in twisted heterostructures that leads to either blueshift or redshift in emission energy. Herein, we fabricate heterobilayers with twist angles varying from 1

∘

to 56

∘

and observe an anomalous redshift energy of 100 meV in the interlayer exciton emission. Additionally, photoluminescence excitation spectroscopy measurements highlight the systematic twist angle dependence of intralayer exciton resonances, indicating significant angle dependent effects on individual monolayer bandgaps and on the interlayer coupling strength. Our fundamental study of exciton resonances provides comprehensive insights into the nuanced interplay between twist angle, dipole orientation, and dielectric asymmetry, providing a deeper understanding of the factors governing the optical properties of layered TMDC heterostructures.