bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.