bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of AR injection on shielding layer properties and surface protection from transient high heat loads under the QSPA plasma exposures
Authors: Garkusha I.E. , Makhlai V.A. , Herashchenko S.S. , Ladygina M.S. , Aksenov N.N. , Byrka O.V. , Petrov Yu.V. , Volkova Y.E. , Kulik N.V. , Staltsov V.V. , Yelisyeyev D.V.
Published: March 2024

The paper presents experimental studies of a shielding plasma layer formation in front of a tungsten surface exposed with hydrogen plasma in the QSPA-M test-bed facility under the conditions of additional seeding of argon (Ar) along the target surface into the zone of plasma-surface interaction. A pulsed gas injector on the base of a fast electromagnetic valve has been developed for the local injection of Ar. The injector is capable of generating a homogeneous argon gas flow with a maximum concentration above n
Ar = 6 × 1023 m−3 and a pulse duration of 0.5 ms. It is shown that the increase in the argon gas density in front of the surface leads to an essential decrease (in 1.5–2 times) in the energy load delivered to the target surface. In the presence of a strong magnetic field (up to 1 T), both the thickness of the shielding layer and the fraction of energy dissipated by the shield increase further. Even for moderate energy densities of the QSPA plasma streams in the experiments with Ar gas injection, less than 40% of the impacting plasma load is absorbed by the tungsten surface. The results demonstrate that this additional shielding attributed to the formation of a dense Ar plasma layer in front of the exposed W surface would be favourable for the divertor armour performance, causing the decreasing erosion of plasma-facing components in the course of transient events in a fusion reactor.
Overview of advances in ASDEX Upgrade plasma control to support critical physics research for ITER and beyond
Authors: Kudlacek O. , David P. , Gomez I. , Gräter A. , Sieglin B. , Treutterer W. , Weiland M. , Zehetbauer T. , Van Berkel M. , Bernert M. , Bosman T. , Felici F. , Giannone L. , Illerhaus J. , Kropackova D. , Lang P.T. , Maraschek M. , Ploeckl B. , Reich M. , Vedl Kubincova A. ,   the ASDEX Upgrade Team,   EUROfusion Tokamak Exploitation Team
Published: March 2024

The successful operation of fusion reactors requires plasma scenarios with good core confinement and acceptable first wall heat loads that are stable and robust to external perturbations. This poses both physical and technological challenges. One of the technologies that addresses these challenges is a complex feedback control system that supports advances in physical understanding and helps to ensure stable operating conditions. The operation of marginally stable plasmas often leads to off-normal events (such as disruptions) and feedback control can prevent these to some extent. This contribution gives an overview of the main results of the development and operation of the feedback control algorithms on ASDEX Upgrade (AUG). Fueling actuators, using a combination of gas valves and pellet injection, can simultaneously control neutral density of the divertor and the density of the plasma core above the Greenwald limit. Impurity injection is employed to control the position of the X-point radiator, allowing the creation of an ELM-suppressed H-mode with high radiation fraction. Heating actuators are used to control the plasma energy content, which supports advanced tokamak experiments and enables stable I-mode operation, and the electron temperature control, which supports turbulence studies. In control technology, AUG has pioneered the use of virtual actuators, which allow effective use of the limited number of heating actuators, adaptive control policies, and exception handling. Such technologies will also be used in ITER. Advanced nonlinear state observers (RAPTOR, RAPDENS) and codes to evaluate the power deposition properties (RABBIT, TORBEAM) are available for routine use in the AUG feedback controllers. Extensive use of the AUG discharge control system further enhances the research capabilities of this machine.
Numerical research on internal solitary waves in stratified fluid
Authors: Huang Miaomiao , Li Yinghua , Pan Ziying
Published: March 2024

Internal solitary waves are a common nonlinear large amplitude internal wave in nature, which can cause strong divergence and sudden strong currents in seawater during propagation, thus having great destructive effects on marine structures. The paper focuses on numerical wave generation based on three types of internal solitary wave theories. The waves are numerical simulated by RANS method in the paper. The numerical results of internal solitary wave theories are compared and analyzed. It shows that under the same numerical water tank scale and calculation conditions, the mKdV theory can obtain the largest wave amplitude, followed by the eKdV theory and the KdV theory. In addition, background currents will accelerate the propagation speed of internal solitary waves and increase their amplitude slightly.
A Scheme for Credibility of Surface Currents Derived From High Frequency Radars
Authors: Wang Li , Wu Xiongbin , Ai Weihua
Published: March 2024

Large amount of real-time ocean currents measured by HF radar have been included into the ocean observation database in many countries and regions, in support of applications for various marine activities such as marine research, Oil spill detection, tsunami warning, search and rescue. However, due to the performance of inversion algorithms and radar antennas, and other reasons, there are differences in the credibility of ocean current results at different times and locations, which brings on difficulties to applications of ocean currents. This letter proposes a method for developing a credibility model of ocean current results, mainly for all-digital multi-input and multi-output (MIMO) HF radar. By comparing the model with field experimental results, it is confirmed that the method is feasible. It will be very beneficial for radar users to select and use ocean current results, greatly reducing the work of verification of newly installed radars, and will be an innovation in the application technology of over-the-horizon marine radars.
Quality assessment of the mapping of satellite ocean altimeter data
Authors: Lv Xianyu , Ren Kaijun , Liu Lei , Wang Huizan , Bao Senliang , Zhang Xiaoya
Published: March 2024

Based on the orbital data of the Jason3 satellite, the absolute dynamic topography (ADT) of 1/8°×1/8° and 1/4°×1/4° products distributed by AVISO (hereinafter referred to as AVISO1/8° and AVISO1/4°) was interpolated into the Jason3 orbit, and the effective resolution and merged product error of the two products were evaluated with the Northwest Pacific Ocean as the target area. In addition, combined with independent SST data and drifting buoy data, the ground conversion field in the merged data was tested, and the results showed that although the spatial resolution of AVISO1/8° was doubled compared with AVISO1/4°, its effect was not significantly improved, and the error in some areas was even slightly greater than that of AVISO1/4°. Finally, these two merged datasets were used to identify mesoscale vortices. AVISO1/8° have higher precision and make identifying vortex structures easier. The two products are consistent in identifying vortices with relatively large radius, while there are differences in identifying vortices with relatively small radius.
Atmospheric correction based on the optimal solution of aerosol mix ratio: A case study for Pearl River Estuary
Authors: Wu Jie , Chen Chuqun , Shi Jian
Published: March 2024

In ocean color remote sensing, the presence of absorbing aerosols and turbid waters will lead to increased errors in atmospheric correction (AC) for coastal regions. In order to reduce these errors, an alternative AC algorithm has been proposed based on the in situ measurements of the Pearl River Estuary (PRE) and the candidate aerosol models including continental, maritime, and absorbing urban aerosols. The new AC algorithm optimally solved the equation set which is constructed by the multi-spectral relationships of remote sensing reflectance (Rrs
) and the aerosol reflectance of each aerosol model. The performances of the new AC were evaluated using the simulated dataset and the in situ Rrs
. The results indicated that this algorithm can effectively reduce the overestimation of aerosol reflectance caused by absorbing aerosols, and can retrieve reasonable Rrs
values in PRE.
Three DOF Rotation Compensation in Floating HFSWR for Ocean Current Inversion
Authors: Yi Xianzhou
Published: March 2024

High-frequency surface wave radar (HFSWR) has been widely used for ocean surface current inversion. Floating this radar can realize the ocean surface inversion among large areas far away from the coastline. However, six degree-of-freedom (DOF) movements will set the barrier for the ocean current inversion on its radial velocity estimation and direction of arrival estimation. Among these movements, three DOF rotations can cause both Doppler modulation and azimuth modulation while three DOF translations only cause Doppler modulation which is dependent on the arrival direction of echoes. Hence, the analysis and compensation for three DOF rotations are first to be solved. In this paper, we analyse the Doppler modulation and azimuth modulation of three DOF rotations and further develop the global adaptive beamforming method to compensate for these rotations. Adaptive beamforming is used to compensate for rotations to make the real-time beams fixed to the ground when the platform is rotating. Simulations indicate that the global adaptive beamforming can perfectly compensate for the reasonable rotations, among which the yaw rotation is the dominant factor for both Doppler spectrum modulation and azimuth modulation. The rotation compensation using global adaptive beamforming can greatly improve the precision of ocean surface inversion.
Global Sea Surface Temperature Analysis Based on Domestic Ocean Satellite Data. Part I: Methods and Results
Authors: Yu Qinglong , Wan Liying , Qin Yinghao
Published: March 2024

Sea surface temperature is widely used in research and applications such as upper ocean processes, air-sea heat exchange, numerical simulation and prediction of the ocean and atmosphere. In this article, the global gap-free fusion data of sea surface temperature has been developed using optimal interpolation (OI) method which is commonly used by international operational institution, merging satellite remote sensed H1C, H2B, AVHRR, AMSR data and GTS in-situ data. According to three data fusion experiments, it is found that the fusion results of domestic satellite remote sensed data during the test period are qualitatively better than those of foreign satellites in the Northwest Pacific region. Further quantitative analysis is compared with Argo surface SST data, a total of 41842 data pairs are matched in 2022, with a deviation of -0.0756 and a root mean square error of 0.4283.
A Global Coupled Atmosphere-Wave Model System Based on C-Coupler2. Part I: Model Description
Authors: Peng Wei , Zhang Yunfei , Wang Yi , Chen Li , Liu Kewei
Published: March 2024

This study presents a global coupled atmosphere-wave model system (MPAS-NWW3) and its verification. The Community Coupler2 (C-Coupler2), a developed coupler, is used to couple the global wave configuration of the NWW3 (WAVEWATHCH III) with the global atmosphere configuration of the MPAS-Atmosphere model. Surface wind at 10 meters above sea level, temperature and specific humidity at 2 meters above sea level are the coupled variables for atmospheric component model, and significant wave height, average wave length and peak frequency are for wave component model. Some codes are added to the surface layer scheme and the effect of momentum flux induced by sea waves is taken into consideration in this paper. All the coupled variables, input or output the coupler are demonstrated their consistency in the MPAS-NWW3 coupled model.
Removing the systematic errors of the model in operational oceanography forecasting system using data assimilation method
Authors: Zu Ziqing , Zhu Xueming , Ren Shihe , Zhou Qian , Zhang Yunfei , Li Ang , Yang Qing , Li Xiang
Published: March 2024

For the operational oceanography forecast, the synoptic forecast error is partly from the long-term systematic bias of the model, which can be partly counteracted by adjusting the values of the physical parameters. To this end, a four-dimensional optimization system is implemented into the South China Sea operational oceanography forecasting system, to adjust the values of multi-parameters using data assimilation method. By assimilating Argo temperature profiles of 51 days in the model domain, five physical parameters (coefficients of horizontal/vertical diffusion/viscosity and linear bottom drag) of the model have been adjusted simultaneously, and then the optimal values are obtained. The RMSE of temperature simulations in the assimilation window decreases from 1.17 to 0.97 K, when using the optimal values. The validation of the freerun experiments shows that the temperature RMSE decreases from 0.97 to 0.88 K, which indicates that the optimal values are still valid in a longer and independent period. Finally, the validation of the hindcast experiments shows that at the synoptic scale the temperature RMSE decreases from 0.90 to 0.80 K and other variables also present improvements. It hints that it is feasible to reduce the synoptic forecast errors by adjusting the parameter values at the climatological scale to partly counteract the systematic bias of the model. Therefore, it also provides a potential pathway to improve the synoptic forecast skill for the operational oceanography forecasting system.
Numerical Simulation of the Northwest Pacific Based on the MaCOM
Authors: Feng Boyu , Wang Zhaoyi , Zhang Yu , Wan Liying
Published: March 2024

Based on the GLORY reanalysis data, the simulation results of the two versions of MaCOM volume conservation and mass conservation in the Northwest Pacific Ocean for 8 years (1993-2000) are tested. In this paper, the sea surface height, sea surface flow field, sea surface temperature, salinity, vertical profile structures of sea temperature, sea salinity are evaluated respectively. The results show that the average absolute deviation of sea surface temperature is about 0.3 °C, the average absolute deviation of sea surface salinity is about 0.5 psu, the average absolute deviation of sea surface height is about 0.06 m, and the average absolute deviation of see surface current velocity is about 0.08 m/s. Among them, the difference between volume conservation and mass conservation is not large, about from percentile to thousandth percentile. In the vertical direction, the temperature profiles of the two versions are generally consistent, and The maximum deviation from GLORY data is about 0.5°C at depths of 100-400m. In terms of salinity profile, the deviation between the two versions and GLORY mainly exists in the depth range of 200-800 meters, and the deviation is 0.1-0.3 psu. On the whole, MaCOM runs stably and the results are good. It can well reproduce the temperature and salinity characteristics, ocean current field and dynamic environment of the ocean, and is consistent with the internationally recognized high-precision reanalysis data. It is suitable as another powerful tool for studying the ocean.
Spatial-temporal characteristics of temperature in Indonesian Sea based on a high-resolution reanalysis data
Authors: Li Aojie , Zhang Yongchui , Hong Mei , Wang Ning , Hu Wangjiang , Yan Hengqian , Chen Zhentao
Published: March 2024

Influenced by both the Pacific and Indian Oceans, the temperature field in the Indonesian Sea are complicated. In order to reveal the spatial-temporal variability, the surface, thermocline and intermediate layers of the temperature field are studied based on the global ocean reanalysis data of Copernicus Marine Environment Monitoring Service (CMEMS) from 1993 to 2019 and the Empirical Orthogonal Function (EOF) analysis method. The results show that there is a warming trend of 1.36×10−2 °C /year in the surface layer. The first two modes both show reverse changes close to the Pacific and Indian Oceans. The correlation coefficients between the first and second modal time coefficients and the Niño 3.4 index are 0.62 and 0.48, respectively. And the correlation coefficient between the second modal time coefficient and the ITF inflow is -0.45. In the thermocline, there is a warmer trend, which is 4.78×10−2 °C /year. The correlation index of the first and second modal time coefficient with the Niño 3.4 and DMI indices are 0.87 and 0.43, respectively. The correlation index between the first and second modal time coefficient and the ITF inflow are -0.60 and 0.38, respectively. In the intermediate layer, the warming trend is 2.18×10−2 °C /year. From 1993 to 1999, from 2000 to 2016 and from 2017 to 2019, the Sulu Sea and northern Halmahera Sea experienced three periods of warming, cooling and warming, respectively. The study is helpful for further understanding the variation of the temperature field in the Indonesian Sea.
Research on magnetic localization and tracking algorithm based on total magnetic field
Authors: Yi Chuanchuan , Tong Qingshan , Liu Shuang
Published: March 2024

There are few studies on the total magnetic field localization and tracking algorithm based on the domestic magnetic dipole model, and the scalar magnetometer’s measurement of magnetic targets is not affected by its own posture. Therefore, a magnetic localization and tracking algorithm based on the total magnetic field is proposed., this method is based on the magnetic dipole model and uses the particle swarm algorithm and the extended Kalman auxiliary algorithm to achieve magnetic localization and tracking. The effectiveness of this method has been verified through simulation experiments. The relative localization error is small and maintained in the range of about 10%.
Research on the classification of seabed sediments sonar images based on MoCo self-supervised learning
Authors: Yang Y , Wang Y B , Yang Z Y , Yang J , Deng L
Published: March 2024

The discrimination of seafloor substrate type is an extremely important part of seafloor science, and the substrate information is of great significance for the development of marine science and the protection of the marine environment. Current sonar equipment can efficiently generate seafloor images and present seafloor information visually, so the seafloor substrate classification technology based on sonar images has become a hot research topic. Convolutional neural network, as one of the most important classification algorithms in seabed substrate sonar image classification, has excellent performance in most cases. However, the size of the convolutional kernel of convolutional neural network limits the global feature extraction ability, and the ability to discriminate global features in sonar images is weak. In addition, seabed substrate sonar images have labelled data acquisition difficulty and high cost, and acoustic seabed substrate classification in practice generally belongs to small sample classification scenarios. Aiming at the above problems, this thesis selects Swin Transformer, which has strong global feature extraction ability, as the classifier, and uses MoCo self-supervised learning to pre-train the unlabeled data in order to achieve better results.
Research on optimization method of evaporation duct prediction model based on particle swarm algorithm
Authors: Cui Yingxue , Hu Tong , Zhang Cheng , Qiu Zhijin , Zou Jing , Qi Ke , Wang Bo
Published: March 2024

The sea surface roughness parameterization and universal stability functions, as key components of the evaporation duct prediction models rooted in the Monin-Obukhov similarity theory, dictate the model performance which further impacts the efficiency and accuracy of offshore electromagnetic applications. In this paper, layered meteorological and hydrological observations are collected during two cruises and processed to obtain the reference modified refractivity profiles close to the sea surface, and then particle swarm algorithm is utilized to optimize the parameters of the sea surface roughness parameterization and universal stability functions. The results show that compared with the pre-optimization model, the prediction accuracy of the optimized model is improved by 5.09% and 8.12% under stable conditions, and by 9.97% and 31.51% under unstable conditions for observation dataset from each cruise, which proves the feasibility of the proposed method for evaporation duct prediction model optimization.
Multi-frame non-coherent track-before-detect method for weak tones in passive sonar
Authors: Zhang Liu , Piao Shengchun , Guo Junyuan , Wang Xiaohan
Published: March 2024

In order to solve the problem of performance degradation of track-before-detect (TBD) methods using single frame information when received signals exhibit a large fluctuation. A TBD method utilizing multi-frame information is proposed. Specifically, the novel measurement model and likelihood ratio function based on the non-coherent accumulation of multi-frame data are established. Multi-frame integration greatly improves the signal-to-noise ratio (SNR) of measurements. Furthermore, the derived likelihood ratio function can more effectively describe the statistical characteristics of the spectrum measurements. Combining these two advantages can improve the detection performance of weak tones for passive sonar. The simulation and experimental data results both demonstrate the advantages of the proposed method.
The impact of shallow waveguides on the spectral characteristics of modulated spectral lines in underwater radiated noise produced by ships
Authors: Li Na , Zhang Jiling , Lin Jianheng , Yi Xuejuan , Jiang Pengfei , Sun Junping
Published: March 2024

The modulation spectrum line spectrum of undersea radiated noise from ships is a significant characteristic in the identification of ship targets. This research presents an analysis of the impact of waveguide dispersion effect and demodulation bandwidth on the intensity of modulation line spectrum, based on the theoretical framework of square demodulation method. The physical mechanism underlying this influence is derived and discussed. The examination of collected data and numerical simulations demonstrates that the extracted modulated line spectrum intensity in an unobstructed environment effectively utilizes the carrier’s energy and generally does not exhibit any abnormal loss during propagation. However, in a shallow sea dispersive waveguide, as the propagation distance increases, a transimission loss anomaly of over 3dB occurs in the modulated line spectrum. The theoretical derivation yields implications that can offer theoretical backing for the reduction of vibration and noise in underwater targets, extraction of faint signals from high-order line spectra in the distant field, and identification of targets.
Virtual array element beamforming algorithm based on LSTM neural network
Authors: Lyu Yaohui , Xu Yuan , Tang Shengyu , Zhang Yanmin , Zhai Yucheng
Published: March 2024

Virtual array element beamforming technology can improve the angular resolution of conventional beamforming algorithm. However, when the number of real array elements is limited, the beam pattern of the virtual array element beamforming algorithm based on linear prediction(the VAEBF-LP) is slightly distorted, the root mean square error(RMSE) of Direction of Arrival(DOA) is larger and so is the main lobe width. In response to this problem, A virtual array element beamforming algorithm based on the LSTM neural network(the VAEBF-LSTM) is proposed. This algorithm uses the LSTM neural network to learn the temporal characteristics between the received data of real array elements and the virtual array elements. Obtaining the received data of virtual array elements, this algorithm enables the beam pattern to be free of distortion and achieve higher angular resolution detection of targets with a relatively low RMSE of DOA in this context. The simulation results show that the VAEBF-LSTM not only makes the beam pattern distortion disappear but also makes the main lobe smaller in width than that of the conventional beamforming algorithm with the guarantee that the RMSE of DOA remains considerably low when the number of real array elements is limited.
Passive localization using horizontal dual-array acoustic intensity striations
Authors: Pan Xiefan , Du Xuanmin , Han Yina , Liu Liang
Published: March 2024

The formation of interference striations is closely related to channel structure and target location, which has attracted extensive attention from scholars at home and abroad. In this paper, the passive localizing method using observed interference striations of horizontal dual-arrays will be studied. The relationship between interference phenomena and target motion is discussed firstly, then the basic principle of the passive positioning method by using horizontal dual-array acoustic intensity striations is derived mathematically. Meanwhile, it can be seen that the shape of the interference striations is related to the parameters, which reflects the motion parameters of the target. This provides mathematical theory support for extracting the the target motion state parameters carried out by Hough transformation according to these acoustic interference striations.The simulation results show that the proposed method can effectively obtain the targets’ range. Meanwhile, comparing the ranging results of different groups of parameters, we can see that the more accurate the target motion parameters are, the smaller the estimated target distance error is. Finally, the performance of the algorithm under different noise conditions is discussed. The simulation results show that the error of extracted parameters is larger under the condition of low SNR, which leads to a larger passive positioning error. However, at high SNR, the range estimation performance is good, within 10%.
Source localization by Matching the Multipath Arrival Angles based on Sparse Bayesian Learning
Authors: Cui Mengda , Shen Tongsheng , Yang Zhikai
Published: March 2024

In the deep-sea direct arrival region, a significant multipath characteristic is presented by the propagation of acoustic signals. This characteristic is closely linked to the distance and depth of the sound source and can be utilized for source localization. In this study, the changes in incidence angle characteristics of multipath signals at different distances and depths are analysed initially. Subsequently, the high-resolution azimuthal spectra are obtained using the Sparse Bayesian Learning (SBL) method. The azimuthal spectra are then matched with multiple incidence angles using the Gaussian kernel function, facilitating the localization of sound sources. Throughout this paper, the impacts of different distance, depth, and SNR conditions on the model are assessed through simulations. Furthermore, the model’s validity is confirmed by utilizing experimental data from an explosion sound source.
Surface and Underwater Acoustic Source Recognition Using Array Feature Extraction Based on Machine Learning
Authors: Yu Qiankun , Zhang Wen , Zhu Min , Shi Jian , Liu Yan , Liu Shuo
Published: March 2024

Sound source recognition is an important application of passive sonar. How to distinguish between surface and underwater sound sources is always a difficult problem. In order to solve the problem of S/U sound source identification, this paper proposes a machine learning method based on array feature extraction, which has certain innovative value. Firstly, according to the experimental environment of SACLANT 1993, simulation data is generated based on KRAKEN. Secondly, the simulation data and experimental data are used to extract the array features. Thirdly, the accuracy, recall rate, F1 and accuracy of GBDT classifier in three different frequency bands are evaluated. The results show that the training model established by using the array feature extraction method can effectively solve the problem of poor accuracy of some channels in the single channel classification, and obtain good experimental accuracy. Finally, the experimental accuracy of the three bandwidths is 0.9920, 0.9857 and 0.9713, respectively.
Mechanism of Seebeck coefficient variation at the output of NiCr/NiSi thin film thermocouple with different wires
Authors: Liu Zhihui , Guo Tengda , Cheng Yongjun , Wang Bi , Shen Kai , Hu Kai , Zhou Jiankang , Zhang Chuanbing , Wang Zixi , Ding Wanyu
Published: March 2024

In this paper, by using magnetron sputtering to prepare NiCr/NiSi thin film thermocouples, the static calibration method is used for NiCr/NiSi thermocouples with rapid temperature calibration experiments. Different temperature calibration curves are obtained. The Seebeck coefficient of NiCr/NiSi thin film thermocouples connected to NiCr/NiSi wires is significantly higher (41.39 μV/°C) than that of NiCr/NiSi wires (0 μV/°C). The Seebeck coefficient (41.39 μV/°C) of the NiCr/NiSi thin-film thermocouple connected to copper wire is significantly higher than that of the thermocouple connected to copper wire (0 μV/°C). The problem of the Seebeck coefficient of the K-type thermocouple is analyzed by experimental data, which provides the relevant parameter basis for the use of the K-type thermocouple. The method has the advantages of simple equipment, convenient operation, accurate and reliable data, and provides a basis for the sensor to measure the temperature measurement.
Research on high precision flow control technology of low speed wind tunnel air supply system
Authors: Tang Ling , Ye Jian , Kang Hongming
Published: March 2024

Aiming at the shortcomings of traditional analog control valves and digital valves, a high-pressure air supply system with accurate flow control is designed. Firstly, the ER5000 controller and pilot proportional valve drive several diaphragm reducing valves to achieve the preliminary adjustment of air pressure. Secondly, a needle valve based on the PCM digital valve and equal percentage flow characteristics is used to achieve accurate control of gas flow. Then, the Venturi flow meter with a honeycomb and damping network is used to accurately measure the airflow. Finally, a PID flow control algorithm based on nonlinear self-tuning is proposed. The results show that the flow regulation range of the system reaches 0.1∼8 kg/s, the absolute control accuracy is better than ±3 g/s, and the relative control accuracy is better than ±0.04%. Moreover, the system has the characteristics of short regulation time, small overshoot, and good dynamic performance, which can achieve strong support for wind tunnel air supply tests.
Design of a non-invasive blood pressure simulator based on oscillographic method
Authors: Wang Yaohong , Zeng Cheng , Fang Meina , Yan Yu , Wang Zhonghao , Deng Bowen
Published: March 2024

In this article, a non-invasive blood pressure simulation system based on the oscillographic method is proposed, and a piston-connecting rod-type variable air chamber is designed and installed in the system as the pulse waveform generation mechanism. It uses PWM constant current control and ultra-small subdivision technology to control the linear stepping motor to achieve stable and accurate displacement and to reproduce the pulse wave according to the blood pressure envelope, to simulate ambulatory blood pressure. In this article, a hardware circuit design scheme is also put forward, including a power supply circuit, pressure acquisition feedback circuit, stepping motor drive circuit, and so on. The experimental results show that the simulator can meet the requirements of JJF 1626-2017 Calibration Specification for NIBP Simulators and can be used as a calibration standard with efficiency and accuracy.
Design and implementation of control software for radar antenna performance index test system
Authors: Deng Bin , Liang Chaohua , Wang Jingjing , Lv Wei
Published: March 2024

According to the actual requirements of radar antenna performance testing, focusing on the design of the instrument control software of the test system, in this paper, the functional requirement of the instrument control software of the system is analyzed, the basic framework of the software design is put forward, and the design ideas and implementation methods of the instrument and equipment management as well as the specific design methods of the instrument and equipment control are given. Practical applications have shown that the control software has advantages such as an intuitive interface, convenient operation, and good interactivity. Combined with system hardware, it can achieve fast and accurate measurement of radar antenna performance and has high practical value.
Design of differential probe with harmonic magnetic field and its data process method
Authors: Yang Lin , Wang Xinhua , Sun Tao , Hu Naixiang , Guo Zisheng
Published: March 2024

To identify the condition of steel pipelines beyond the line of sight during operation, this study presents a design methodology for a differential probe, along with a harmonic magnetic field excitation technique and its corresponding data processing methodology. The coaxial arrangement of the excitation coils in a planar configuration generates a potent induced magnetic field, ensuring a sufficient standoff distance. Under the influence of harmonic excitation, the magnetic permeability of the pipeline surface decreases, resulting in an increased detection depth. Periodic alterations in the magnetic permeability of the pipeline surface enhance the amplitude of defects. Adjusting the position of the induction coil minimizes interference from the excitation magnetic field, thereby obtaining a pure induced magnetic field. Differential processing is applied to the two induction coils to counteract interference from the background magnetic field. Finally, the effectiveness and reliability of this probe are validated through three experiments: pipeline positioning, weld seam inspection, and damage detection.
Feature optimization combined with UPerNet-Twins model for eucalyptus extraction from Sentinel-2A image
Authors: Huang Wenchao , Wei Bo , Wei Chang
Published: March 2024

To improve the extraction accuracy of eucalyptus from Sentinel-2A image, two key factors of feature construction and extraction model are considered. The original band spectrum, custom vegetation index, red edge spectral index, and texture features are obtained from the image. The Relief F-PSO-SVM model is used to screen out the best feature subset. A UPerNet-Twins combination model is used to realize the high-precision extraction of eucalyptus for the study area. The experiments show that the original spectrum plays a significant role in the extraction of eucalyptus. In addition, the texture features, vegetation index, and red edge spectral index are helpful to the extraction of eucalyptus, which are increased by about 5.84%, 3.81%, and 3.00%, respectively, compared with the IOU of the original spectrum. Moreover, the IOU of the optimal feature subset obtained by feature selection is increased by about 2.22% compared with the original feature set. The UPerNet-Twins combination model has the highest extraction accuracy of eucalyptus with an IOU of 0.8496 compared with DeeplabV3+, PspNet-UNet, FCN, UperNet, and UperNet-Vision Transformers models.
State of health estimation for lithium battery based on multi-source transfer learning
Authors: Jiang Tianhao , Wu Youyu
Published: March 2024

Aiming at the problem that the state of health estimation accuracy decreases when the lithium battery in training and testing sets has different charging conditions, we proposed a solution based on the transfer learning with the multi-source method. This scheme uses the complete aging test data of 16 batteries under different charging conditions as the source domain and extracts aging characteristics respectively to train the basic model. The similarity coefficient was obtained by the similarity evaluation of the first 200 cycles of each source and target battery, and the learning weight of each source battery model was weighted by the similarity coefficient. The experimental results show that the MAE and RMSE of the transfer learning with a multi-source model decreased by 53.63% and 54.97% compared with the single-source estimation model under new charging conditions.
Study on calibration of surface temperature source
Authors: Feng Li , Gong Wei , Li Xianhong , Yang Xuemei , Zhang Qiuquan , Ren Tingting
Published: March 2024

Surface temperature source is widely used to provide adjustable, stable and uniform temperature fields to calibrate surface thermometers. Parameters such as temperature deviation, temperature uniformity, and temperature fluctuation can directly decide the metrological performance of the instrument. At present, there is no relevant calibration specification for surface temperature sources in China. This article presents a novel calibration method for surface temperature sources by determining corresponding environmental conditions, calibration standards and calculation equations. The calibration results show that the calibration method is scientific and practical for the metrological performance evaluation of surface temperature sources.
Research on denoising the temperature monitoring signal of a distributed optical fiber downhole cable
Authors: Zhao Xiaowei , Wang Dong , Liu Kang , Guo Jianqiao , Zhao Hongfu , Tan Liangxiao
Published: March 2024

Aiming at the noise mixed in the downhole cable skin temperature signal measured by the BOTDR distributed fiber optic sensing temperature measurement system, a new improved wavelet threshold function is proposed, and denoising experiments are completed based on the MATLAB platform for the measured cable skin temperature signal. The denoising results of several threshold function methods are compared and analyzed from the aspects of graphical intuitive comparison as well as quantitative evaluation indicators. The results show that the improved threshold function denoising fiber optic temperature monitoring signal has a higher SNR and lower RMSE, there is no obvious distortion phenomenon, and the denoising performance is significantly improved compared with the traditional threshold function, which has a high application value.
Different responses of surface air temperature over Eurasia in early and late winter to the autumn Kara–Laptev Sea ice
Authors: Guo Haichen , Yin Zhicong , Xu Tianbao , Zhou Botao
Published: March 2024

The Arctic climate is changing rapidly, along with intensified melting of sea ice, which has significant impacts on surface air temperature (SAT) in Eurasia. This study reveals that the subseasonal response of SAT to the autumn Kara–Laptev Sea ice (KLSIC) differs significantly between early and late winter. The response of SAT to KLSIC forms a warm Arctic–cold Eurasia pattern in early winter. Conversely, the negative anomaly response of SAT to KLSIC in late winter is only distributed in the band range of Eurasia, without significant positive SAT anomaly over the Arctic Ocean. After further examination of the separate physical mechanisms involved in early and late winter, it is found that a decrease in KLSIC in autumn can lead to a strengthened Ural high and Siberian high in the Arctic–Eurasia region, which is conducive to cold events in the mid-latitudes of Eurasia in early winter. For late winter, a westward shift in the response of atmospheric circulation to KLSIC leads to a negative anomaly feedback of North Sea surface temperature, which triggers the propagation of Rossby waves to the Sea of Japan through the wave activity flux. Meanwhile, the deep trough of East Asia is strengthened and extends to the southeast, guiding northern cold air to the western Pacific. Our results highlight that different subseasonal effects of sea ice should be considered in Eurasian climate prediction, rather than only consider the effects in winter mean.
Probing the account of phase transition upon electrochemical cycling of the P2-Na0.67Ni0.15Fe0.2Mn0.65O2 layered oxide cathodes for sodium-ion batteries
Authors: Li Shiyou , Fan Xiaoqi , Wang Shimin , Wang Mengya , Tong Yifan , Zhou Junfei , Li Xin , Zhao Dongni , Zhang Ningshuang
Published: March 2024

Layered P2-Na0.67Ni0.15Fe0.2Mn0.65O2 (P2-NFM) cathode material has attracted great attention in sodium-ion batteries due to its high theoretical capacity, low cost, and environmental friendliness. However, P2-NFM exhibits irreversible phase transition and slip of transition metal layers in the high voltage range during charging process, leading to a gradually declined performance of the cathode material. It is therefore necessary to investigate the mechanism of phase transition of P2-NFM as well as the effect of phase transition on its performance. Herein, utilizing ex situ x-ray diffraction spectroscopy and x-ray photoelectron spectroscopy, the crystal structure and TM (transition-metal) bonding changes caused by phase transition are elucidated. It is found that P2-NFM is prone to undergo an irreversible P2-O2 phase transition at high voltage, causing changes in lattice parameters and rapid capacity decay. The irreversible phase transition is mainly due to he dynamic transformation of valence states of Fe and Ni in P2-NFM materials at high voltage. It is this process that results in irreversible fluctuations in the bond lengths between these elements and oxygen, consequently instigating interlayer slip within the material. Besides, the charge compensation mechanism of P2-NFM has been elucidated based on the study of its initial charging process. Results show that the charge compensation is mainly contributed by Ni and Fe in the high voltage range, while by a small amount of Mn in the low voltage range. It reveals the essential cause of the adverse phase transition of P2-NFM materials and points out the direction for improving the cycling stability of these layered oxide materials.
A study of the tribological properties of Mo-S-Ti composite films prepared by magnetron sputtering
Authors: Bai Xu , Xue Xiangyang , Lu Feng , Wu Yuhou , Hao Tianen
Published: March 2024

Pure MoS2 films exhibit disadvantages such as low densities, poor mechanical properties, and weak wear resistance under atmospheric environments. For this reason, Ti was chosen as the doping element in this work. Mo-S-Ti composite films with different Ti contents were deposited using the magnetron sputtering system, and the effects of Ti content on the chemical composition, mechanical and tribological properties of these films were analyzed by numerous characterization methods to determine the doping content of Ti elements. The results show that the tribological performance of Mo-S-Ti composite film under atmospheric environments reaches the best when the Ti content is 13.48 at%. In addition, the present work also found that longitudinal load and reciprocating frequency have a significant effect on the tribological properties of this film. It is easier to form high quality transfer film on GCr15 balls under higher longitudinal load and lower reciprocating frequency, thus transforming the friction between film and GCr15 ball into the friction between film and transfer film, resulting in excellent tribological performance.
Land–atmosphere coupling exacerbates the moisture-associated heterogeneous impacts of compound extreme events on maize yield in China
Authors: Li Zitong , Liu Weihang , Ye Tao , Chen Shuo , Liu Yiqing , Sun Ran , Zhan Ning
Published: March 2024

Compound climate events are major threats to crop production under climate change. However, the heterogeneity in the impact of compound events on crop yield and its drivers remain poorly understood. Herein, we used empirical approach to evaluate the impact of compound hot–dry (HD) and cold–wet (CW) events on maize yield in China at the county level from 1990 to 2016, with a special focus on the spatial heterogeneity. Our findings indicate comparable impact of extremely compound CW events (−12.8 ± 3.6%) on maize yield loss to extremely compound HD events (−11.3 ± 2.1%). The spatial pattern of compound HD and CW events impacts on maize yield was dominantly associated with moisture regime, followed by management practices and soil properties. Specifically, drier counties and counties with less fraction of clay soil and organic carbon tend to experience greater yield loss due to compound HD events, and wet condition, excessive fertilizer, clay soil and rich organic carbon aggravate the maize yield loss due to compound CW events. Moreover, the land–atmosphere coupling exacerbated the heterogeneous yield impact through divergent heat transfer. In drier regions, the greater proportion of sensible heat creates a positive feedback between drier land and hotter atmosphere. In contrast, the greater proportion of latent heat in wetter regions results in a positive feedback between wetter land and colder atmosphere. Our results highlighted a critical element to explore in further studies focused on the land–atmosphere coupling in agricultural risk under climate change.
Least-cost and 2 °C-compliant mitigation pathways robust to physical uncertainty, economic paradigms, and intergenerational cost distribution
Authors: Bossy Thomas , Gasser Thomas , Lecocq Franck , Bednar Johannes , Tanaka Katsumasa , Ciais Philippe
Published: March 2024

Each run of an integrated assessment models produces a single mitigation pathway consistent with stated objectives (e.g. maximum temperature) and optimizing some objective function (e.g. minimizing total discounted costs of mitigation). Even though models can be run thousands of times, it is unclear how built-in assumptions constrain the final set of pathways. Here we aim at broadly exploring the space of possible mitigation scenarios for a given mitigation target, and at characterizing the sets of pathways that are (near-)optimal, taking uncertainties into account. We produce an extensive set of CO2 emission pathways that stay below 2 °C of warming using a reduced-form climate-carbon model with a 1000 different physical states. We then identify 18 sets of quasi ‘least-cost’ mitigation pathways, under six assumptions about cost functions and three different cost minimization functions embarking different visions of intergenerational cost distribution. A first key outcome is that the absence or presence of inertia in the cost function plays a pivotal role in the resulting set of least-cost pathways. Second, despite inherent structural differences, we find common pathways across the 18 combinations in 96% of the physical states studied. Interpreting these common pathways as robust economically and in terms of intergenerational distribution, we shed light on some of their characteristics, even though these robust pathways differ for each physical state.