• 中国科技核心期刊
  • JST收录期刊
  • Scopus收录期刊
  • DOAJ收录期刊

2024 Vol. 32, No. 4

Display Method:
2024, 32(4): 591-591.
Abstract:
Research Progress and Development Trend of Air-Sea Cross-domain Communication
SHANG Zhigang, ZHANG Hongyu, LIU Songzuo, QIAO Gang, YU Han, MIAO Bailu, MA Lu, WANG Zhe
2024, 32(4): 592-610. doi: 10.11993/j.issn.2096-3920.2024-0115
Abstract:
At present, there is an increasing demand for real-time communication and data transmission between the air and the sea. Therefore, it is important to study robust and reliable air-sea cross-domain communication technologies. However, due to the different characteristics of the two media and the impact of harsh environments, air-sea cross-domain communication channels are complex and varied, making it difficult to smoothly pass through the air-water interface. In order to better understand the development of air-sea cross-domain communication technologies, the current research on air-sea cross-domain communication was comprehensively summarized, and its working environment and development of communication technologies were explained. The technologies were divided into two categories: air-sea cross-domain link-level direct communication and air-sea cross-domain relay communication. Then, the research status, difficulties, and proposed solutions were summarized. Finally, future research directions were discussed. The research can help to promote the development of air-sea cross-domain communication technologies.
Review of Underwater Acoustic Communication Based on Metamaterials
ZHOU Ping, JIA Han, YANG Jun
2024, 32(4): 611-620. doi: 10.11993/j.issn.2096-3920.2024-0103
Abstract:
In recent years, acoustic metamaterials, as a sort of novel artificial composite materials, have demonstrated the ability to surpass the limitations of traditional materials through their exceptional acoustic parameter manipulation capabilities. Thus, acoustic metamaterials have shown promising applications in numerous areas such as underwater detection, underwater target identification, acoustic imaging, navigation, and underwater communication. The advancements in metamaterial-based underwater acoustic communication were reviewed, focusing primarily on multiplex communication based on acoustic orbital angular momentum, underwater acoustic communication between specific transmitter and receiver based on beam steering of acoustic metasurface, and water-air trans-medium acoustic communication. The key technologies were summarized, and the current challenges and future prospects of metamaterial-based underwater acoustic communication were outlined.
2FSK Communication System Demodulation Algorithm for Novel Acoustically Excited SLF Antennas
ZHANG Xiayu, ZHANG Jiahao, JIAO Jie, LIU Yi
2024, 32(4): 621-627. doi: 10.11993/j.issn.2096-3920.2024-0106
Abstract:
There exist some problems for acoustically excited super low frequency(SLF) antennas, such as low transmission power and low received signal-to-noise ratio. In addition, it is difficult to design a narrow-band filter in traditional binary frequency-shift keying(2FSK) non-coherent demodulation. Therefore, a 2FSK weak signal demodulation method based on a Duffing chaotic oscillator was proposed. Because the Duffing oscillator itself was sensitive to the phase, a phase synchronization method of “coarse synchronization + fine synchronization” was designed. The coarse synchronization was accomplished through the short-time Fourier transform, while the fine synchronization was achieved through the Duffing chaotic oscillator. Then, the properties of the chaotic oscillator, such as being sensitive to the same-frequency periodic signal and being immune to noise signals, were utilized, and the signal passed through two Duffing oscillators in parallel, with the built-in signal frequency of the two being consistent with the two carrier frequencies. At a certain moment when one system must be in the large-scale periodic state and the other in the chaotic state, the two systems could be discriminated to realize signal demodulation. The simulation results show that the proposed Duffing oscillator demodulation algorithm outperforms the non-coherent and coherent demodulation algorithms by 5 dB and 4 dB in bit error rate, respectively.
Experimental Study of Trans-Medium Communication of Millimeter-Wave Radar in Wave Tank
ZENG Yuming, ZHANG Kun, LE Nanyan, SONG Chunyi, XU Zhiwei
2024, 32(4): 628-636, 643. doi: 10.11993/j.issn.2096-3920.2024-0109
Abstract:
Wireless cross-medium communication for underwater equipment may be possible by using millimeter-wave radar to detect the micro-wave vibration on the water surface excited by sound waves of underwater equipment. Studying the effect of water surface waves is of great value for achieving trans-medium communication based on micro-wave vibration detection by millimeter-wave radar. Therefore, experiments were carried out on the trans-medium communication of binary phase-shift keying(BPSK) and binary frequency-shift keying(BFSK) modulation signals in a wave tank. The influence of different water surface wave vibrations on trans-medium communication was tested and analyzed, and the communication performance based on spatial diversity technology was evaluated. The experimental results show that moderate water surface wave vibrations have the least impact on the trans-medium communication performance of millimeter-wave radar, and the spatial diversity technology based on multi-channel data merging can improve trans-medium communication performance on wavy water surfaces. The research results can provide a reference for practical applications of trans-medium communication technology based on micro-wave vibration detection by millimeter-wave radar on wavy water surfaces.
Laser-Induced Acoustic Air-Water Trans-Medium Communication Based on PWM
CHEN Yingnan, ZHAO Yang, ZHOU Zhiquan, CAO Yifei, ZHANG Faxiang
2024, 32(4): 637-643. doi: 10.11993/j.issn.2096-3920.2024-0019
Abstract:
Laser-induced acoustic communication has emerged as a critical technology for facilitating air-water trans-medium nodeless communication, garnering increasing attention in research and application. At higher repetition frequencies, traditional modulation and demodulation techniques based on single-pulse recognition face challenges due to exacerbated interference among pulses, significantly disrupting code element determination and leading to high error rates that impede effective communication. To address this issue, a novel laser-induced acoustic communication method employing pulse width modulation (PWM) was proposed. Experiments utilized an Nd:YAG pulsed laser with a maximum repetition frequency of 500 Hz, and the number of laser pulses was adjusted to generate PWM signals of varying widths, with code element recognition achieved at the receiving end based on pulse width. The experiment results show that the PWM-based communication method effectively minimizes decoding errors due to inter-pulse interference, achieving commendable performance at the highest repetition frequency of 400 Hz with an error rate of just 8%. This improvement significantly enhances the reliability and effectiveness of laser-induced acoustic communication at high repetition frequencies.
Algorithm of Water-Air Trans-Medium Communication Based on Acousto-Optic System
ZHOU Zhiquan, ZHAO Xingkang, CHEN Yingnan, HUANG Jinxin, ZHAO Yang
2024, 32(4): 644-649, 658. doi: 10.11993/j.issn.2096-3920.2024-0098
Abstract:
To achieve underwater-aerial trans-medium uplink wireless communication, based on the laser interference detection of underwater acoustic signals, attenuation curves of acoustic signals at various water depths to the water surface and micro-vibration curves on the water surface caused by different underwater acoustic power frequency signals were obtained through simulation calculations. A quantitative relationship between underwater sound source characteristics and disturbances on the water surface was established. Code elements for trans-medium communication were designed, and various demodulation methods were compared. The impact of parameter variations on the transmission error rate was analyzed, and modulation and demodulation simulations of acoustic-laser communication were achieved.
Cross-Domain Communication Buoy System Based on Optimal Communication Link Selection
XING Minghan, SHANG Zhigang, QIAO Gang, ZHOU Feng, NIE Donghu, ZHANG Tong, LI Tianshui, XIE Jiaxuan
2024, 32(4): 650-658. doi: 10.11993/j.issn.2096-3920.2024-0113
Abstract:
The existing marine buoy communication mode is single, with low reliability, high packet loss rate, and poor real-time performance, which cannot meet the needs of large-scale marine data acquisition and cross-domain communication. In order to further strengthen the construction of marine global interconnection, a cross-domain communication buoy system with multi-source communication as the core was designed and manufactured. The system could complete the switching of multiple communication modes, multi-source information acquisition, and multi-link real-time cross-domain communication. An optimal communication link selection algorithm was designed for the system. According to the real-time signal quality of each communication module, the optimal communication link was selected to improve the reliability of communication. At the same time, the communication module with poor signal quality was closed to reduce the problem of large redundancy and power consumption of system communication that may occur when multiple communication methods are used at the same time. The experimental results show that the system realizes the cross-domain transmission of water surface and underwater data, and the multi-source communication design is feasible. The communication links are stable and reliable, and the comprehensive communication success rate is more than 99%. It provides a reference for the construction of a marine global observation network and communication network.
Progress and Prospect of Underwater Information Acquisition Technique for Trans-Medium Vehicles during Water Exit
ZHANG Xu, LI Wanpeng
2024, 32(4): 659-667. doi: 10.11993/j.issn.2096-3920.2024-0044
Abstract:
The water exit process of trans-medium vehicles involves multiphase flow, unsteady evolution of cavitation, strong transient effect, and varying load environments, which significantly affects the motion stability, water exit attitude, and structural strength of the vehicles. To fully understand and verify the performance of the vehicle during water exit in the marine environment, underwater information acquisition techniques adapting to the corresponding working conditions are urgently required. In this paper, the research on underwater information acquisition techniques for the water exit test of the trans-medium vehicle was summarized, such as target localization, phenomena observation, environmental measurement, and trans-medium information transmission. Meanwhile, the new requirements for underwater information acquisition techniques to adapt to the modern trans-medium vehicles with high dynamics and large depth were analyzed, and its development trend towards systematization, multimodality, and digitalization was prospected, which may provide an idea and technical support for obtaining the high-value underwater information, understanding the complex underwater environments, and interpreting key underwater motion process.
Traffic Measurement Optimization for Cross-Domain Ad Hoc Networks Based on Meta-Learning and Reinforcement Learning
SONG Jian, NIE Laisen, TAO Zui, YUAN Qiendong
2024, 32(4): 668-677. doi: 10.11993/j.issn.2096-3920.2024-0094
Abstract:
Cross-domain Ad Hoc network is a network that self-organizes nodes on different media and adapts to network topology. In cross-domain communication networks, direct measurement technology helps obtain accurate end-to-end network traffic information. However, the low computational power and low storage characteristics of some nodes in the cross-domain network hinder all nodes from running the network traffic measurement process. To address this issue, a network traffic measurement optimization method based on meta-learning and proximal policy optimization(PPO) was proposed. This method determined the set of nodes that performed network traffic measurement in the next time slot according to the network operating environment of the previous time slot, so as to perform the measurement process on as few nodes as possible to obtain as much network traffic information as possible. Three network datasets were used to verify the proposed method. The experimental results show that the traffic measurement optimization algorithm for cross-domain Ad Hoc networks based on meta-learning and reinforcement learning can effectively select the nodes with large traffic flow, with faster convergence speed and higher measurement efficiency.
Clock Synchronization Algorithm of UAV-USV-UUV Cross-Domain Cooperation
YU Jianyu, LIN Jingsheng, YAN Jing, CAO Wenqiang, ZHANG Shihang, YANG Xian
2024, 32(4): 678-687. doi: 10.11993/j.issn.2096-3920.2024-0097
Abstract:
With the development of marine science and technology, underwater missions have placed greater emphasis on the collaboration of cross-platform systems. However, different application scenarios have varying requirements for clock synchronization. Due to the weak communication and high time delay of underwater communication, a new synchronization method is required for heterogeneous systems involving multiple scenarios. With regard to the problem of global time synchronization under the influence of random time delay, a neural network-based time synchronization algorithm for cross-domain cooperation of unmanned aerial vehicles(UAVs), unmanned surface vessels(USVs), and unmanned undersea vehicles(UUVs) was proposed. First, the impact of random time delay was considered, and the clock of USVs was used as the reference clock. The clock offset of UAVs was corrected through recursive filtering and a neural network. Finally, with the assistance of USVs, the underwater long time delay was estimated by UUVs, and a neural network algorithm was designed to estimate clock drift and clock skew. The effectiveness of the proposed algorithm was verified through simulation.
Cross-Domain Communication System with Cloud-Based Software-Defined Acoustic
YAO Kexing, GUAN Quansheng, XIE Jiaxuan, ZHAO Hao, WANG Yan
2024, 32(4): 688-694. doi: 10.11993/j.issn.2096-3920.2024-0075
Abstract:
Due to the restriction of acoustic communication performance, the performance of data transmission across the water-air interface is difficult to further improve. In this paper, a cross-domain communication system architecture with cloud-based software-defined acoustic(C-SDA) was proposed. C-SDA moved the underwater acoustic receiver from the surface relay to the cloud (i.e., the monitoring center) and used the radio communication bandwidth to exchange the computing resources of the cloud to demodulate and decode the acoustic signal. In this case, the acoustic-radio dual-stack protocol of the relay gateway was simplified to a single-stack structure, which avoided packet capsulation and re-capsulation and saved hardware costs. The C-SDA not only enabled advanced communication signal processing but also promoted rapid updates and iteration of acoustic communication technology. The field test results show that C-SDA can be applied to equalizers with higher performance and achieve a significant improvement in bit error rate compared with the self-developed embedded underwater acoustic receiver.
A Task-Oriented Routing Protocol for Sea-Air Cross-Domain Networks
ZHANG Haobo, WANG Biao, HAN Zhaoyue
2024, 32(4): 695-702. doi: 10.11993/j.issn.2096-3920.2024-0015
Abstract:
Sea-air cross-domain networks consist of underwater and surface subnets. In order to fully utilize resources, enable multiple applications to share the same physical infrastructure, and make different data packets coexist within the same network, differentiated transmission strategies are needed to meet application demands. However, existing routing protocols often fail to provide personalized services based on application requirements. To address this issue, a task-oriented routing protocol for sea-air cross-domain networks was proposed. The protocol adjusted the calculation method of forwarding factors based on the types of tasks, thereby selecting the most suitable next-hop node for specific task types. Furthermore, a preprocessing layer was added to the protocol to facilitate communication between heterogeneous networks. Simulation results show that compared to other typical protocols, the proposed protocol achieves optimal transmission strategies based on specific task requirements.
Opportunistic Routing Protocol for Underwater Optical Sensor Networks Based on Fuzzy Logic
SHEN Rui, HAO Jiqiang, FU Dongmin, YANG Ming, HAN Shuo, YUE Peng, SUN Cheng
2024, 32(4): 703-712. doi: 10.11993/j.issn.2096-3920.2024-0110
Abstract:
Underwater optical sensor networks offer significant advantages over traditional acoustic sensor networks, such as high bandwidth and low latency, making them a research hotspot to realize high-speed and real-time transmission of underwater data in sea-air cross-domain communication. However, traditional routing protocols for underwater sensor networks often encounter problems such as routing holes and redundant data transmission due to the transmission obstruction and directional alignment of underwater optical nodes. To address these issues, a fuzzy logic-based opportunistic routing protocol for underwater optical sensor networks was proposed. Firstly, a fuzzy logic-based algorithm was proposed to evaluate the underwater optical channel links. Combined with the modeling of an underwater complex communication environment, the multi-factor fusion evaluation of routing metrics was designed. Additionally, a dynamic mechanism was designed to set the node data forwarding probability and data packet retention time based on real-time link evaluation data. Finally, a probabilistic redundant suppression forwarding algorithm was proposed. Simulation results demonstrate that the proposed routing protocol effectively improves transmission efficiency and reduces end-to-end latency in typical marine communication environments, exhibiting good network dynamic adaptability.
Multi-Base Active Location Based on Cross-Domain Information Synchronization
WANG Yongfeng, LIN Jinmei, DONG Lei, QIU Sai
2024, 32(4): 713-717. doi: 10.11993/j.issn.2096-3920.2024-0085
Abstract:
The information synchronization problem is one of the difficulties in the application of multi-base active sonar systems. In existing research and application, it is usually assumed that the receiving station knows the pulse transmission time of the transmitting station, the spatial location information of the sound source, and the transmission waveform parameters, thus can calculate the echo sound path, locate the target, and obtain the time processing gain of the echo signal. However, these conditions may not be met in practice. The obstacles and possible solutions for information synchronization in different application scenarios were first discussed. A multi-base active location method based on cross-domain information synchronization was then proposed for the situation where there is an external communication link between the receiving and transmitting stations, but the link is unreliable, or the delay is uncertain. This method used the basic physical law that the direct wave arrives at the receiving station before the target echo. The receiving station first obtained the position and waveform parameter information of the transmitting station through the external link and then estimated the transmission time according to the direct wave arrival time and the distance between stations. It had high engineering feasibility. Finally, the factors affecting the accuracy of time and position synchronization and the target positioning error caused by the time and space information error were discussed and simulated.
Communication Technology of Far-Sea Cross-Domain Buoys Based on High Frequency Sky-Wave Propagation
XIAO Longzhong, ZHANG Song, LIU Zhenji, ZHAO Yi
2024, 32(4): 718-723. doi: 10.11993/j.issn.2096-3920.2024-0033
Abstract:
High frequency(HF) sky-wave propagation is limited by the working frequency, and the antenna size meeting high gain and adapting to high sea conditions is large, so the application scenario is seriously limited. For the demand of cross-domain long-distance transmission of far-sea science detection information, a cross-domain buoy communication technology integrating HF communication, underwater acoustic communication and unmanned buoy characteristic was proposed. The composition and working principle of far-sea cross-domain transmission buoy devices were introduced, and the working flow was designed. Through the design of a flexible HF antenna with variable length and integrated power amplifier components for water cooling and heat dissipation, the advantages of high antenna gain, strong adaptation to sea conditions, and cross-medium transmission were ensured. The simulation analysis shows that the proposed communication method can effectively guarantee the communication effect and achieve reliable cross-domain long-distance communication of HF signals in high sea conditions and complex interference environments, providing certain technical support for the development of maritime long-distance cross-domain communication.
Design of a Low-Power Cross-Domain Communication Buoy System
ZHANG Rui
2024, 32(4): 724-729. doi: 10.11993/j.issn.2096-3920.2024-0035
Abstract:
To meet the cross-domain surfaced communication requirements of underwater information in cross-domain cooperative operations, a low-power cross-domain communication buoy system was designed by taking advantage of the buoy’s flexible deployment, long-term concealment, and flexible payload characteristics. This system mainly supported deep-sea deployment at great depths and long-term silent watch and concealed cross-domain communication upon activation. Additionally, it could autonomously destruct critical components according to preset instructions, thus avoiding the exposure risk of surfaced communication on underwater platforms such as submarines, and it is relatively easy to deploy and sustain. Test results indicate that the designed system features high pressure resistance, low power consumption, and certain scalability, offering good prospects for application.
Cooperative Hunting Method for Multiple ASVs Using Differential Games Based on Escape Angle
YANG Huizhen, LI Jianguo, WU Tianyu, WANG Zijiang, YANG Jun
2024, 32(4): 730-738. doi: 10.11993/j.issn.2096-3920.2023-0142
Abstract:
In the scenario where multi-autonomous surface vehicles(ASVs) round up an actively escaped adversarial target, a game model of the multi-ASV cooperative hunting problem was established using differential game theory. A surround term consisting of the escape angle was introduced into the payment function which included the distance cost so that the escape probability of the target was reduced. At the same time, the hunting problem was converted into an optimization problem for solving achievable strategies, and the particle swarm optimization(PSO) algorithm was used to solve the optimal strategy that satisfied the Nash equilibrium. The simulation and lake test results show the effectiveness of the hunting algorithm based on differential game and PSO.
Deep Learning-Based Method for Key Signal Recognition during Underwater Explosions
ZHOU Zhenxian, HONG Feng, XU Weijie, ZHANG Tao, CHEN Feng
2024, 32(4): 739-748. doi: 10.11993/j.issn.2096-3920.2023-0146
Abstract:
The amount of data collected from underwater explosion tests is enormous, which is mixed with a large amount of useless data. To protect the data from the effects of the explosion, it is crucial to prioritize the recognition and storage of key data during the test. In response to this, a key signal recognition model that combined feature extraction methods with deep learning models was proposed to improve the accuracy of key signal recognition. Firstly, different preprocessing methods for removing trend components from underwater explosion acceleration signals were studied. Existing test results demonstrated that wavelet packet decomposition, empirical mode decomposition, and high-pass filtering could significantly enhance the model’s recognition performance. Secondly, to make the extracted features more conducive to distinguishing between explosion and non-explosion segments, a feature extraction method based on the inter-class variance ratio for underwater explosion acceleration signals was proposed. According to the actual measured underwater explosion acceleration signal data, it was found that compared to Log Mel features, the proposed features improved classification accuracy by approximately 4.92% using the K-means method. Finally, the ECAPA-TDNN model incorporating the SE-Res2Block module was introduced, ensuring better recognition accuracy. With the proposed features as input, the recognition accuracy reached 99.31%.
Analysis of Induced Current and Electromagnetic Safety of Bridge-Wire Electric Explosive Device
ZHU Xiaonan, PAN Jin, YANG Jinhou, WANG Kaiguo, LIN Xiaochuan
2024, 32(4): 749-756. doi: 10.11993/j.issn.2096-3920.2023-0134
Abstract:
Based on the basic theory of electromagnetic fields, the formation of the equivalent antenna of an electric explosive device(EED) and its energy conversion process were analyzed, and CST software was used to simulate and model the formation of induced current in the EED under the action of strong electromagnetic pulses. After validating the model, the influence of factors such as incident wave signal, lead wire layout, and bridge-wire resistance on the induced current was studied. According to the results, the strength, frequency, and the direction of incident wave, as well as the inductive receiving area of the equivalent antenna of the EED were major factors determining induced current. Bridge-wire resistance and induced current jointly determine the induced energy coupled to the EED. From the perspective of electromagnetic safety, the duration of continuous electromagnetic pulse action on EED shall not exceed 178 μs. The research content has certain reference significance for the safety protection of EEDs in weapon systems.
Control Method of Deep-Sea Vector Propulsion Motors Based on Position-Sensorless and Variable Carrier Frequency
HUANG Xiaoyan, LIU Yabing, GU Yujie, ZHANG Qiang, WANG Yuankui
2024, 32(4): 757-764. doi: 10.11993/j.issn.2096-3920.2023-0129
Abstract:
In order to improve the stability and stealth of vector propulsion motors in deep-sea exploration, a control method of deep-sea vector propulsion motors based on the position-sensorless and variable carrier frequency was derived from surface-mounted permanent magnet synchronous motors by using periodic spread spectrum modulation technology and position-sensorless control technology of improved sliding mode observer. Through simulations of motors’ variable carrier frequency, motor start-up speed variation, and sudden load change, the control effects of the proposed method were analyzed. The simulation results show that the rotation speed estimation of the studied control method is accurate, and the method has good dynamic tracking performance for rotation speed. The estimation error rate at the rated rotation speed is only 0.32%, and the estimation error rate at 0.5 times the rated rotation speed is only 0.09%. In addition, the proposed control method has an obvious high frequency harmonic spread spectrum suppression effect and good dynamic anti-interference performance. Combined with the simplification effect of reducing the motor structure brought by the position sensor, the control method proposed in this paper can effectively lower the failure rate of the deep-sea vector propulsion motor during operation, reduce the high-order fixed frequency harmonics that are easy to be detected, improve the reliability and stealth of the deep-sea vector propulsion motor, and provide efficient and reliable power guarantee for deep-sea unmanned undersea vehicles.
Calculation Method of Torpedo Discovery Probability by Combining Analytical and Simulation Methods
DAI Zhen, YAN Yong, SHEN Xiangzhong
2024, 32(4): 765-769. doi: 10.11993/j.issn.2096-3920.2023-0128
Abstract:
The analytical method and simulation method are commonly used to calculate the discovery probability of acoustic homing torpedoes. The analytical method is fast but only applicable to some parameter error types. The simulation method is applicable to all parameter error types, but its calculation efficiency is low. To address this issue, a torpedo discovery probability calculation method combining analytical and simulation methods was proposed. Firstly, the parameter masking interval was solved based on the simulation method. Then, the discovery probability was calculated using the analytical method, which significantly improved calculation efficiency while ensuring accuracy. Finally, the effectiveness of the proposed algorithm was verified through simulation.
Construction and Assessment of Quality Evaluation System for Solving Target Motion Elements
ZHANG Hongrui, LI Bin, CHENG Shuai, KOU Xiaoming
2024, 32(4): 770-778. doi: 10.11993/j.issn.2096-3920.2023-0109
Abstract:
Target tracking is an important part of the anti-submarine warfare process of surface ships. In the process of target tracking, the four elements of targets are obtained through the target motion element solving, and the hit probability is calculated through the result. The solution results of the target motion elements are affected by many factors, such as battlefield situation, detection method, and solution model. In order to associate the separated factor, a quality evaluation system for solving target motion elements was constructed from the four aspects of completeness, availability, timeliness, and accuracy of the solved data. In order to minimize the total deviation, the analytic hierarchy method and entropy weight method were effectively combined to determine the index weight. The quality evaluation value of the target motion elements was obtained by weighted summation and compared with the simulation result of hit probability. The simulation results show that the error between the approximate hit probability and the actual hit probability calculated by using the solved mass is less than 9.2%. The evaluation system constructed in this paper can effectively combine all information, reasonably and fully express the hit probability, and is conducive to the decision-making of the engagement.
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