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Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the continuous reforms of low-altitude economy, the advancement of low-altitude aircraft are presenting a new landscape characterized by high density, heterogeneity, autonomy, and mixed manned/ unmanned operations. Low-altitude surveillance, as an important safeguard for the safety of low-altitude operations, can ensure the safe and efficient operation of aircraft at low altitudes. To address current issues of inadequate low-altitude surveillance means, it is necessary to construct a low-altitude surveillance technology system with no blind spots, covering mixed manned/unmanned operations, based on the characteristics of the complex low-altitude environment. Firstly, current difficulties in low-altitude surveillance are analyzed from the perspectives of the concept of low-altitude surveillance and its development trends, including weight, size and power limitations of airborne equipment, tight channel resources, and significant differences among aircraft. Secondly, from the perspectives of the cooperative surveillance technology and the non-cooperative surveillance technology, the current status of key surveillance technologies worldwide is elaborated, and a systematic comparison and summary of the relevant characteristics of each technology are provided. Finally, facing the development of a new generation of low-altitude surveillance, the development directions of future cooperative surveillance, non-cooperative surveillance, and integrated surveillance technologies are discussed, with the expectation of providing certain guidance for the safe operation of low-altitude aircraft in the future. [ABSTRACT FROM AUTHOR]

To address the increasing number of low-altitude aerial vehicles and meet the surveillance and tracking needs of the aviation industry for future urban air mobility (UAM) vehicles, an investigation about the encoding and modulation technologies of the UAT2 data link transmitter was conducted. The system structure of the UAT2 data link transmitter was designed. Aiming at the surveillance needs of UAM vehicles, an addressable data uplink communication encoding and a vehicle health status monitoring downlink encoding algorithm are proposed to cover the safety operation requirements of UAM. A high-speed reed solomon (RS) encoding algorithm for UAT2 messages was developed, which significantly reduced execution time and memory usage. CPFSK modulation was implemented based on direct digital synthesizer (DDS) technology. The signal requirements of the UAT2 data link were met and the spectral energy distribution was ensured to be concentrated. The encoding and modulation key technologies were tested and evaluated for performance. The results verified their effectiveness and applicability to the UAT2 data link transmitter. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bridging the digital divide provides a new way to alleviate the imbalance in family education investment. Based on the 2020 China Family Panel Studies (CFPS) database, and from the perspective of micro-families, this paper constructs a comprehensive evaluation system of digital divide from the aspects of digital access, digital use and digital awareness, and introduces family economic capital, family cultural capital and family social capital to empirically test the impact and mechanism of digital divide on family education investment. The results show that the digital divide has a significant negative impact of widening the family education investment gap, and the impact is more obvious in the developed areas and urban areas in east China. Mechanism analysis shows that family capital is an important transmission channel for the evolution of the digital divide into the "family education investment divide". Further extended analysis demonstrates that the educational equity has a significant role in promoting common prosperity and is conducive to the overall prosperity of the social economy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Changzhou University (Social Science Edition) is the property of Editorial Department of Journal of Changzhou University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central China Normal University is the property of Huazhong Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the security monitoring problem of general aviation flight activities， a reasonable automatic dependent surveillance-broadcast （ADS‑B） ground station location planning can improve the airspace surveillance scope. This paper proposes a surveillance signal coverage analysis method of the true height and its location analysis of ADS‑B ground station based on grid division. First，considering the influence of earth curvature and terrain shading on the signal propagation distance， we establish the geographic model by the digital elevation model（DEM），and divide the airspace into grids. Second，the grid coverage is calculated by the Xdraw algorithm，and the maximum theoretical coverage of ADS-B ground station at the true height is determined. Third，the maximum coverage model of the ground station is constructed for spatial planning and layout. Finally，the signal coverage of ADS‑B ground station is simulated as Hubei Province is taken as an example. The layout of ground stations that meet the coverage requirements of this area is calculated. The results demonstrate that the proposed method can provide a foundation the layout planning of ground stations in practice. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

【 Objective/Meaning】 Analyzing the impact of financial support on the performance of farmers ’ professional cooperatives is conducive to investigating the effect of the expenditure allocation of financial support funds and has practical significance for the effective implementation of financial support policies for the high-quality development of farmers’ professional cooperatives.【 Methods/Procedures】 Based on the questionnaire survey of 128 farmers ’ professional cooperatives in Fujian Province, the multiple regression model was used to empirically analyze the impact of financial support on the performance of farmers’ professional cooperatives.【Results/Conclusions】The results showed that obtaining the financial support had a significant promoting effect in improving the comprehensive performance of farmers’ professional cooperatives, which was mainly reflected in the improvement of economic performance and social performance, while the improvement of ecological performance was not obvious. In addition, the amount of financial support had a positive promoting effect on the comprehensive performance and all aspects of performance of cooperatives, but the amount of financial support had no obvious promoting effect on the ecological performance. [ABSTRACT FROM AUTHOR]

As air traffic has become increasingly congested，the effective mining of abnormal flight behaviors can assist controllers to make decisions. Current methods can only identify abnormal spatial positions with limited horizontal scalability. This paper incorporates four abnormal characteristics，position，speed，altitude and heading，and improves the density-based spatial clustering of applications with noise（DBSCAN）by the altitude level division strategy，the local outlier factor and the faster cover tree. Then，the density clustering algorithm named density-based spatial clustering considering speed，direction and high level improved by local outlier factor（LOFDBSC-SDH） is proposed to effectively extract the normal track patterns of airplanes. Next，based on the normal track patterns，a track matching algorithm is designed to mine abnormal flight behavior patterns，including flights’cross-point time and above abnormal features. Finally，the effectiveness of the proposed scheme is verified by the experimental simulation. [ABSTRACT FROM AUTHOR]

Copyright of Modern Food Science & Technology is the property of Editorial Office of Modern Food Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To predict aircraft taxiing estimated time of arrival（ETA），reduce conflicts，and improve the efficiency of the airport，this paper uses the Kalman filter algorithm to preprocess historical trajectory data of an airport. In order to measure the distance between trajectory samples， three kinds of features are synthesized for clustering of airport historical trajectory data，including the aircraft taxiing period and the number of surface aircraft. In addition ，we refer to the dynamic time warp（DTW）algorithm to extract the difference features of the trajectory. The Euclidean distance of two sample features is taken as their similarity. Initial clustering center is determined based on the divided difference maximum principle. The K⁃means algorithm is used to cluster samples，and the cluster with the highest matching degree is selected according to the time period of the aircraft to be planned and the number of aircraft operating on the surface. The trajectory sequence of the cluster’s center sample and the static path planned by the tower are combined to predict the aircraft taxiing ETA. By comparing and analyzing the actual trajectory data with the predicted taxiing ETA， the good performance of predicting the aircraft taxiing ETA in this paper is verified. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Image & Graphics is the property of Editorial Office of Journal of Image & Graphics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nursing of Integrated Traditional Chinese & Western Medicine is the property of Journal of Clinical Nursing in Practice (Editorial Board, Shanghai Jiao Tong University Press) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the problem of separation assurance between two aircraft under the sequential flying conditions when the leading aircraft decelerating，the hybrid separation assurance strategy combined heading adjustment and true airspeed adjustment based on receding horizon control was proposed considering the random disturbance factors on the route. Three separation assurance strategies， including static offline optimization without counting the random disturbance，dynamic optimization of speed adjustment and hybrid separation assurance control law，were compared. In the simulation，an aircraft that adopted static offline strategy without considering the random disturbance did not return to the route centerline after the end of the predicted maneuver time；an aircraft that adopted speed adjustment separation assurance strategy completed the maneuver in 254 s；and an aircraft that adopted hybrid separation assurance strategy with speed adjustment and heading adjustment completed maneuver in 97 s，a maneuvering efficiency increased by 61.8%. The results show the effectiveness，efficiency and robustness of the hybrid separation assurance strategy. [ABSTRACT FROM AUTHOR]

For the multiple aircraft strategic trajectory planning under the conditions of great traffic flow， high density and small separation， the single-segment and multi-segment traffic flow control models are proposed by applying the air traffic control separation constraints under the framework of max-plus theory. Regarding the single aircraft as a batch， the relationship among input variable， state variable and output variable is established with buffer time parameter based on the air route conflict point competition mechanism as well as the space layout structure . From the spatial logic structure of various sub-models， the airspace multi-aircraft max-algebra coupled model and the robust optimization model are proposed. Moreover， the trajectory robust optimization model is formulated based on the proposed multiple optimization objective functions by adjusting the time of aircraft arrival and departure. Finally， the simulation shows the feasibility of the robust optimization model. [ABSTRACT FROM AUTHOR]