Ikeda and Mizuno1 first indicated theoretically that frustration instability and frequency locking exist in optical bistability with two delayed feedback signals. Zhang and Dai2 have experimentally observed the instability in a hybrid liquid crystal optical bistable device and also observed frequency locking, jumps between locking steps, hysteresis, and a beating pattern. In this paper we discuss the influence of feedback strength on the oscillation patterns studied by means of power spectra and phase portrait. The hybrid optical bistable device is described by the delayed differential equation:
The discharge structure is one of the key parts of water control project,because it not only plays the functions of spillway and diversion tunnel,but also is charge of bottom outlet for flood discharge,sediment discharge,and to drainage out all the water,so that it has different characteristics for different operation periods.Based on analysis of its features,the tasks and effects of different type and scale were studied to determine the reasonable type and scale,and a case study was provided in this paper.
ABSTRACT Objective Modic changes (MCs) classification system is the most widely used method in magnetic resonance imaging (MRI) for characterizing subchondral vertebral marrow changes. However, it shows a high degree of sensitivity to variations in MRI because of its semiquantitative nature. In 2021, the authors of this classification system further proposed a quantitative and reliable MC grading method. However, automated tools to grade MCs are lacking. This study developed and investigated the performance of convolutional neural network (CNN) in detecting and grading MCs based on their maximum vertical extent. In order to verify performance, we tested CNNs' generalization performance, the performance of CNN with that of junior doctors, and the consistency of junior doctors after AI assistance. Methods A retrospective analysis of 139 patients' MRIs with MCs was conducted and annotated by a spine surgeon. Of the 139 patients, MRIs from 109 patients were acquired using Philips scanners from June 2020 to June 2021, constituting Dataset 1. The remaining 30 patients had MRIs obtained from both Philips and United Imaging scanners from June 2022 to March 2023, forming Dataset 2. YOLOv8 and YOLOv5 were developed in PyCharm using the Python language and based on the PyTorch deep learning framework, data enhancement and transfer learning were applied to enhance model generalization. The model's performance was compared with precision, recall, F1 score, and mAP50. It also tested generalizability and compared it with the junior doctor's performance on the second data set (Dataset 2). Post hoc, the junior doctor graded Dataset 2 with CNN assistance. In addition, the region of interest was displayed using the class activation mapping heat map. Results On the unseen test set, the YOLOv8 and YOLOv5 models achieved precision of 81.60% and 61.59%, recall of 80.90% and 67.16%, mAP50 of 84.40% and 68.88%, and F1 of 0.81 and 0.60 respectively. On Dataset 2, YOLOv8 and junior doctor achieved precision of 95.1% and 72.5%, recall of 68.3% and 60.6%. In the AI‐assisted experiment, agreement between the junior doctor and the senior spine surgeon significantly improved from Cohen's kappa of 0.368–0.681. Conclusions YOLOv8 in detecting and grading MCs was significantly superior to that of YOLOv5. The performance of YOLOv8 is superior to that of junior doctors, and it can enhance the capabilities of junior doctors and improve the reliability of diagnoses.
Microstructures of Inconel 740, a new type nickel-based superalloy for advanced ultra supercritical steam boiler tubing, at different heat treatment conditions including solution treatment, precipitation treatment and ageing at 750 ℃ for 300, 1 000 and 3 000 h were investigated by using SEM (scanning electron microscope), FEG-SEM(field emission gun scanning electron microscope), TEM(transmission electron microscope) and EDS(X-ray energy dispersion spectroscopy). The results indicate that the grain size is about ASTM No.3 to 4, many large primary (Nb,Ti)C and TiN precipitate in the matrix randomly and gamma prime phase nucleate after solution treatment. After precipitation treatment, a lot of M23C6 carbide and a little of G phase precipitate at grain boundaries, gamma prime phases precipitate coherently in the grains. Gamma prime phases grow with Ostwald ripening rule during ageing at 750 ℃, G phase become dominant on grain boundary after long term exposure, eta phase begin to precipitate along gamma grain boundary at 300 h, grow with ageing time and tend to show Widmanstatten pattern after 3 000 h. Microstructure stability of Inconel 740 requires further improvement.
The application of crown wheel to the 6-axes AC high-speed bogie hollow shaft transmission was introduced.The choose of main parameters,the fix of minimum pretightening force,the calculation of tooth strength,the contact strees of tooth,and so on,were described.It was pointed out that the shrink trapeziform tooth model is preferred.3D finite element model for the crown wheel was built.By analyzing contact stresscurves,it is concluded that the maximum contact stress occurred on the inner tooth tip.
R&D of high field accelerator magnets is ongoing at the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP, CAS) for pre-study of the next-generation high energy colliders like Super Proton-Proton Collider (SPPC), Future Circular Collider (FCC) and etc. A 12.47-T main field at 4.2 K has been attained in 2021 within two 14-mm apertures of LPF1-U, a superconducting model dipole magnet with Nb3Sn & NbTi combined common-coil configuration. Based on the experiences mastered in the LPF1 series magnets, a 16-T high field dipole magnet named LPF3 has been designed, fabricated and is in the performance test process. LPF3 is also a combined magnet with six racetrack Nb3Sn coils outside, expected to provide a 13-T main field within two 50-mm apertures, and with inserted HTS coils to enhance the field up to 16 T or even higher. The 13-T Nb3Sn dipole magnet, named LPF3-LTS, incorporates a graded common-coil configuration to enhance superconductor efficiency. The optimization of coil layouts includes varying bending radii (BR) and lengths of straight sections (LSS) to mitigate field accumulation in the outer four coils near the central posts and coil ends, respectively. Several Rutherford cables over 200 meters were fabricated for the coils winding, and with the maximum strands count of 42. The support structure for LPF3-LTS has adopted a shell-based design, with an improved "Bladder & Key" technology. Dedicated hydraulic pistons were investigated and utilized to replace the traditional bladders. The main design characteristics, fabrication process and some preliminary test results of the magnet are presented in this paper.
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