Search

Objective To explore the feasibility of deep learning reconstruction (DLR) in shortening the scanning time through water phantom experiments. Methods The control variable method based on phantom, was adopted to depict the curves of scanning time varying with the number of excitation (NEX) ，matrix，and resolution. The signal-to-noise ratio (SNR) and subjective image quality of different DLR with high, medium and low noise reduction levels (DLR_H, DLR_M, DLR_L) and traditional reconstruction (ConR) were analyzed, including the four-point assessment of sharpness and detail clarity, and distortion degree, and the curves of changes were depicted and the fitting curves were calculated. Results The positive correlation between NEX and resolution with MRI scanning time and SNR was consistent in ConR and DLR reconstructions with different noise reduction levels. Specifically, under the same NEX and resolution conditions, the SNR of ConR, DLR_L, DLR_M, and DLR_H increased sequentially. When the matrix was fixed at 512×512 while images with subjective evaluation score of 3 or 4 were taken as satisfactory ones, the images reconstructed by DLR can obtain satisfactory sharpness, distortion degree and detail display, and when NEX were 3, 4, 5 and 7 and 11, image details were displayed best while scanning time was significantly reduced. Meanwhile, the distortion of images achieved satisfactory results with NEX of 2, 4, 5, and 6. Also, satisfactory detail display was obtained when NEX was 3, 5, 7 and 11. All the above combinations of NEX and resolution saved scanning time from 31 to 244 seconds. Similarly, as the resolution increased, the image scores of the sharpness and detail display gradually increased and. distortion degree decreased. When NEX was fixed at 6, the images reconstructed by DLR_H, DLR_M, DLR_L and ConR obtained satisfactory sharpness ；When the matrix was 320×320, 384×384, 448×448 and 640×640,, the scanning time was 141 seconds, 141 seconds, 187 seconds and 232 seconds, respectively. DLR_H and DLR_M achieved a smaller distortion degree at the 512×512 matrix, while DLR_L and ConR required a higher imaging matrix and longer scanning time to obtain similar image quality. For detail clarity, DLR_H achieved satisfactory detail display when the matrix was 512×512, and the scanning time was less than that of DLR_M, DLR_L and ConR. Conclusions DLR, especially DLR_H, while reducing NEX and resolution to shorten the MRI scanning time, may not only maintain a satisfactory SNR and image detail clarity, but also achieve higher image clarity and lower distortion degree.

The tooth surface friction has an important impact on the tooth surface contact stress and the tooth surface contact fatigue life. In the estimation of the contact fatigue life of the tooth surface, the influence of the friction force of the tooth surface is often ignored, which is not conducive to the accurate prediction of the contact fatigue life of the tooth surface. In order to accurately predict the contact fatigue life of the tooth surface, the R-S-N curves are fitted based on the three-parameter Weibull distribution and the nominal stress method according to the tooth surface contact fatigue test data of 18CrNiMo7-6 gear material. By calculating the contact stress on the tooth surface, the time-varying friction factor is introduced, and the influence of the time-varying friction factor on the contact fatigue life of the tooth surface is analyzed. Finally, the tooth surface contact fatigue test is used to verify the validity. The results show that the contact fatigue limit of tooth surface estimated by the traditional nominal stress method is large due to the influence of the time-varying friction factor, and the influence of the friction factor on contact fatigue life of tooth surfaces decreases with the increase of stress.

Objective: To explore application value of iterative metal artifact reduction (iMAR) algorithm in reducing the artifacts from abdominal metal implants. Methods: The CT images of 32 patients with abdominal metal implants were reconstructed with both iMAR and filtered back projection (FBP) algorithm, respectively. Subjective image quality was assessed by two independent radiologists. Objective image quality indic including signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and artifact index (AI) were calculated by the noise values measured at the most severe level of artifacts near metal implants on images of both iMAR and FBP algorithms. Difference in subjective and objective image quality assessment between iMAR and FBP algorithms was compared. Results: The overall subjective quality score of iMAR images was significantly higher than FBP images (3.656±0.475 vs. 2.156±0.618, P

In this study, the thermoforming formability of continuous glass fiber-reinforced polypropylene (CGFRPP) laminates below the melting temperature were investigated. The forming limits of CGFRPP laminates were explored using flexural tests, Erichsen tests and deep drawing tests. The failure mechanism of CGFRPP in thermoforming was investigated by observing typical failure specimens using a microscope. The results show that the flexural performance and Erichsen performance are optimal at 130 °C and 2 mm/min. At 160 °C and 100 mm/min, the deep drawing performance is optimal. The restriction of fibers by the matrix is affected by the deformation temperature, and the creation of defects is affected by the deformation rate. During forming, the CGFRPP laminates undergo shear and extrusion deformations, resulting in wrinkles, delamination, and fiber aggregation. [ABSTRACT FROM AUTHOR]

Hydrogen is increasingly recognized as a clean and reliable energy vector for decarbonization in the future. In the marine sector, marine solid oxide fuel cells (SOFCs) that employ hydrogen as an energy source have already been developed. In this study, a multi-channel plate-anode-loaded SOFC was taken as the research object. A three-dimensional steady-state computational fluid dynamics (CFD) model for anode-supported SOFC was established, which is based on the mass conservation, energy conservation, momentum conservation, electrochemical reactions, and charge transport equations, including detailed geometric shapes, model boundary condition settings, and the numerical methods employed. The polarization curves calculated from the numerical simulation were compared with experimental results from the literature to verify the model's accuracy. The curved model was applied by enlarging the flow channels or adding blocks. Numerical calculations were employed to obtain the current density, temperature distribution, and component concentration distribution under the operating conditions of the SOFC. Subsequently, the distribution patterns of various physical parameters during the SOFC operation were analyzed. Compared to the classical model, the temperature of the curved model was reduced by 1.3%, and the velocities of the cathode and anode were increased by 4.9% and 5.0%, respectively, with a 2.42% enhancement in performance. The findings of this study provide robust support for research into and the application of marine SOFCs, and offer they insights into how we may achieving "dual carbon" goals. [ABSTRACT FROM AUTHOR]

BackgroundIn the injection and extraction Kicker power supply system of High Intensity Heavy-ion Accelerator Facility (HIAF), the transmission efficiency and stability of the control event directly affect the working performance of the power supply.PurposeThis study aims to develop the Kicker power supply communication system for precise control of hundreds of IGBT (insulated gate bipolar transistor) switches in the bipolar solid-state PFN-Marx generator of HIAF-Kicker power supply, hence to provide a gigabit readback path for the waveform data obtained by the high-speed acquisition system.MethodsBased on a digital controller with kernel Xilinx Kintex-7 FPGA (field programmable gate array) chip, the UDP (user datagram protocol) stack described by hardware language as the core of data communication was employed by the system. The scheme of intercepting waveform pulse and its front and back parts for transmission was adopted to improve the communication efficiency and save the system resources. The optical control signals required by the multi-channel power supply were provided by the controller via the connecting optical fiber daughter boards. The shielding case was added to reduce electromagnetic interference and enhance the stability of data transmission.ResultsThe data transmission test shows that the system meets the precise control demand of hundreds of IGBT switches, and the data transmit speed satisfies the needs of gigabit data readback.ConclusionsThe performance of designed system meets the communication requirements of Kicker power supply.