The degradation of aeroengines can be divided into two stages: the healthy stage and the unhealthy stage. Remain useful life (RUL) prediction should be triggered from the start time of the unhealthy stage to ensure safe operation. Nevertheless, many existing RUL prediction methods simply assign a fixed DSP to any aeroengine, limiting further improvement as the DSP is uncertain and varies with individual differences of aeroengines. To address this issue, a novel two-stage deep residual long-short term memory (Dual-DRLSTM) is developed, which integrates DSP detection and RUL prediction into one framework, and associates them through degradation health index (HI). First, DRLSTM is employed as the backbone to extract representative degradation features from multi-dimensional time-series monitoring data. Second, the Dual-DRLSTM relaxes the strong assumption of the fixed degradation start point (DSP) and performs DSP detection for each aeroengine. Then, the Dual-DRLSTM predicts the RUL of the aeroengine beyond the DSP in the unhealthy stage. Finally, the outstanding performance of Dual-DRLSTM is validated through a series of experiments on a public C-MAPSS dataset.

Space missions have become diversified in recent years, where connection and separation devices play a crucial role as key components of various spacecraft. Traditional pyrotechnic devices have the advantages of large carrying capacity, rapid motion and functional reliability. However, their shortcomings such as great release shock, poor safety, unrepeatability and other prominent defects make them unsuitable for new generation spacecraft such as microsatellites to separate at low shock or lock repeatedly, etc. Therefore, it is necessary to develop space non-pyrotechnic low-shock connection and separation devices (SNLD) which are required for advanced aerospace missions. In this paper, the progress of the research on space non-pyrotechnic low-shock connection and separation technology (SNLT) is summarized and reviewed. Proceed from the principle of reducing shock for non-pyrotechnic devices, present studies are classified from the perspective of actuating technology and systematic designing methods. For non-pyrotechnic actuating techniques, according to different driving sources, the separation devices are classified into several main categories: electric, magnetic, gas and thermal actuating devices. The actuation principle and application prospect of separation techniques are introduced and the working process, dimension and mechanical properties of typical devices are compared and evaluated. For the systematic designing method, the common mechanism types of SNLDs are summarized according to the designing concept of reducing shock. Then connection configurations are classified according to the structural forms of connection devices, of which the principles, bearing capacities and general applications are discussed. This paper systematically summarizes the key problems, puts forward the future development trend of SNLT, and points out the breakthrough direction for related scholars.