Rapid and accurate extraction of shoreline is of great significance for the use and management of sea area. Remote sensing has a strong ability to obtain data and has obvious advantages in shoreline survey. Compared with visible-light remote sensing, synthetic aperture radar (SAR) has the characteristics of all-weather and all-day working. It has been well-applied in shoreline extraction. However, due to the influence of natural conditions there is a problem of weak boundary in extracting shoreline from SAR images. In addition, the complex micro topography near the shoreline makes it difficult for traditional visual interpretation and image edge detection methods based on edge information to obtain a continuous and complete shoreline in SAR images. In order to solve these problems, this paper proposes a method to detect the land–sea boundary based on a geometric active contour model. In this method, a new symbolic pressure function is used to improve the geometric active-contour model, and the global regional smooth information is used as the convergence condition of curve evolution. Then, the influence of different initial contours on the number and time of iterations is studied. The experimental results show that this method has the advantages of fewer iteration times, good stability and high accuracy.

The detection performance of high-frequency surface-wave radar (HFSWR) is closely related to the suppression effect of sea clutter. To effectively suppress sea clutter, a sea clutter suppression method based on radial basis function neural network (RBFNN) optimized by improved gray wolf optimization (IGWO) algorithm is proposed. Firstly, according to shortcomings of the standard gray wolf optimization (GWO) algorithm, such as slow convergence speed and easily getting into local optimum, an adaptive division of labor search strategy is proposed, which makes the population have abilities of both large-scale search and local exploration in the entire optimization process. Then, the IGWO algorithm is used to optimize RBFNN, finally, establishing a sea clutter prediction model (IGWO-RBFNN) and realizing the prediction and suppression of sea clutter. Experiments show that the IGWO algorithm has significantly improved convergence speed and optimization accuracy. Compared with the particle swarm algorithm with linear decreasing weight strategy (LDWPSO) and the GWO algorithm, the RBFNN prediction model optimized by the IGWO algorithm has higher prediction accuracy and has a better suppression effect on sea clutter of HFSWR.

Aerospace electromagnetic relay (EMR) is one of the key electromechanical components used for signal transmission, load switching, circuit protection and control and system isolation. At present, concern for the storage reliability of Aerospace EMR is respectively light although it comes to the highly-dependable and long-life electrical components. And the corresponding research still faces a series of problems, such as low level experiment and test detection, unclear law of performance parameters changing, ambiguous about failure mode and failure mechanism, and lack of effective evaluating and predicting means. Therefore, how to evaluate the storage reliability of aerospace EMR has become the important subject that demanding prompt solution at present. This study used aerospace EMR as research object. A new method for testing storage reliability is proposed by performance parameters degradation. The test and analysis system of aerospace electromagnetic relay storage parameters under temperature-accelerated stress was designed and developed. Based on the analysis of parameters changing in storage degradation testing, the modeling storage reliability method of aerospace EMR is extensively investigated. Prediction parameters preprocessing method is proposed which combines time series analysis with one-dimensional wavelet transform method. This reduces the random signal's influence on the prediction precision in prediction parameters. Parameters of the storage degradation model are estimated through regression theory. And the storage life of aerospace EMR under normal stress is predicted. These studies provide the necessary theoretical method and basis for studying storage reliability of the aerospace EMR. Its key techniques and methods could be also applied to other electromechanical components storage reliability studies.

In HFSWR (high-frequency surface-wave radar) system, the detection performance is impacted seriously by ionospheric clutter. Frequency selection is an effective method to avoid the effect of ionospheric clutter. The key to the method is the stationarity of ionospheric clutter over a period of time. This paper mainly researches the stationary time statistical property of the ionospheric clutter. A large number of real data including ionospheric clutter in HFSWR are processed and analyzed. It shows that ionospheric clutter in HFSWR has the characteristics of approximate stationarity within a period of time.

In order to evaluate the electrical contact performances of contact materials in relays, a new type of electrical contact simulation test system was designed and developed, in which contact materials of dynamic and static contacts can easily be replaced. The electrical contact characteristics of AgSnO ₂ with regard to the physical phenomenon of material surface adhesion was analyzed. Contact adhesion is divided into cold adhesion and hot adhesion. Cold adhesion occurs under the condition that no current passes the contact pair. This article mainly studies the hot adhesion phenomenon under the condition of resistive load current. The failure process of the contact pair due to dynamic welding of the contact during the experiment was analyzed. Firstly, the experimental process of hot adhesion was researched through the testing system, and then the relationship between the adhesion force and the contact resistance under adhesion condition is analyzed theoretically. Secondly, observing the microscopic morphology of the contact surface, and experimental data of other electrical performance degradation parameters in the experiment, the physical degradation mechanism of the adhesion characteristics was analyzed. Finally, the influencing factors of adhesion characteristics were explored through experiments, and the relationship between contact force, load conditions and adhesion characteristics were discussed.