No abstract

2016-11-02T18:49:00

Sleep-disordered breathing (SDB), a common sleep disorder, shows symptoms of shallow breathing or paused breathing during sleep called respiratory events. SDB was conventionally diagnosed based on overnight multi-channel polysomnography (PSG) in clinical treatment. However, this process requires experienced sleep technicians to annotate and is quite labour-intensive. In this study, a novel one-dimensional signal based object detection network was proposed for automatic, high efficiency detection and classification of different kinds of respiratory events from continuous PSG signals. Our method can locate respiratory events in PSG signal data and classify them into four categories for further clinical treatment. The method was further validated on a PSG clinical dataset collected from Beijing Tongren Hospital. Precision, recall and F1-score of 84.9%, 85.1%, 85.0% were achieved for events detection with total accuracy rate reaching 74.9% in classification of detected events. The result shows that one-dimensional signal object detection is a promising method to locate the characteristic waveform and extract signal features. Such method can be applied in other signal feature detection field.

Cast austenitic stainless steels (CASSs) are used in the cooling system of light water reactors (LWRs) for components with complex shapes, such as pump casings, valve bodies, coolant piping, etc. The CF grades of CASS alloys are the cast equivalents of 300-series stainless steels (SSs) and show excellent mechanical properties and corrosion resistance. In contrast to the fully austenitic microstructure of wrought SSs, CASS alloys consist of a dual-phase microstructure of delta ferrite and austenite and are vulnerable to thermal aging embrittlement. The service performance of CASS alloys is of concern after long-term exposure to high-temperature coolant. In this work, we studied the effects of thermal aging and ferrite content on the fracture resistance of CASS alloys. Crack growth rate and fracture toughness J–R curve tests were performed on aged and unaged CASS alloys in simulated light water reactor environments. The impact of thermal aging on the cracking susceptibility was investigated and the effect of ferrite content was evaluated. Significant embrittlement was observed in the CASS alloys after aging at 400°C. To understand the embrittlement mechanism, microstructural characterizations were performed with transmission electron microscope. The thermal aging produced G-phase precipitates and phase separation in the ferrite, but did not affect the microstructure of austenite. Consequently, the ferrite was hardened considerably after thermal aging while the hardness of austenite phase remained unchanged. The difference in hardness created a high incompatible strain at the interface between ferrite and austenite, leading to fracture at phase boundaries.

No abstract