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Purpose: The paper aims to solve the problem of personnel intrusion identification within the limits of high-speed railways. It adopts the fusion method of millimeter wave radar and camera to improve the accuracy of object recognition in dark and harsh weather conditions. Design/methodology/approach: This paper adopts the fusion strategy of radar and camera linkage to achieve focus amplification of long-distance targets and solves the problem of low illumination by laser light filling of the focus point. In order to improve the recognition effect, this paper adopts the YOLOv8 algorithm for multi-scale target recognition. In addition, for the image distortion caused by bad weather, this paper proposes a linkage and tracking fusion strategy to output the correct alarm results. Findings: Simulated intrusion tests show that the proposed method can effectively detect human intrusion within 0–200 m during the day and night in sunny weather and can achieve more than 80% recognition accuracy for extreme severe weather conditions. Originality/value: (1) The authors propose a personnel intrusion monitoring scheme based on the fusion of millimeter wave radar and camera, achieving all-weather intrusion monitoring; (2) The authors propose a new multi-level fusion algorithm based on linkage and tracking to achieve intrusion target monitoring under adverse weather conditions; (3) The authors have conducted a large number of innovative simulation experiments to verify the effectiveness of the method proposed in this article.

Magnetic particle imaging (MPI) is a tracer-based imaging modality known for its high sensitivity and temporal resolution. It makes the quantitative visualization of the concentration and spatial location of magnetic nanoparticles (MNPs) possible. The $x$ -space method is widely used in MPI for high-speed image reconstruction. In this method, the received signal is mapped directly onto the corresponding spatial position. However, the anisotropic 2-D point spread function (PSF) in the $x$ -space method introduces artifacts and blur in the reconstructed images. In this study, an isotropic MPI method, transverse MNP signal-based isotropic imaging (TSI), was developed. It makes isotropic imaging possible in 2-D unidirectional Cartesian MPI. Unlike conventional methods that rely on MNP signals registered from the same direction as the excitation, TSI only utilizes MNP signals received perpendicular to the excitation direction. In TSI, the velocity of the time domain signal is first normalized to obtain a “raw-image.” The raw-image is then integrated, differentiated, and added to generate an isotropic MPI image. Because all the operations in TSI are analytical, it preserves the real-time imaging characteristics of the $x$ -space while isotropic imaging is performed. The PSF of TSI was calculated through analytical derivation and the resolution isotropy was validated through simulation and imaging experiments on an in-house-built MPI system. The simulation and experimental results demonstrate that, by improving the isotropy, TSI achieves an approximately 2.5- $\times $ increase in resolution in the nonexcitation direction compared with the conventional $x$ -space method. The proposed TSI algorithm does not increase hardware complexity and requires only half the scanning time of the previously proposed multichannel method. In addition, the transverse MNP signal used in TSI is geometrically decoupled from the excitation magnetic field, eliminating the need for a special compensation design for the receiving coils. This shows promise for future MPI designs with flexible surface coils.

In this study, a coupled computational fluid dynamics and discrete element method (CFD-DEM) model is constructed to deal with the motion of flexible fibers in molten thermoplastic during fused deposition modeling (FDM) 3D printing process. The effects of fiber stiffness and length on fiber bridging and nozzle clogging are investigated. Numerical results show that fiber deformation has a clear influence on nozzle clogging even when the fibers are as short as 0.24 mm for the printing of short carbon fiber reinforced polyamide-6 (sCF/PA6) composite with a fiber volume fraction of 13.34%. Through a particle-scale analysis on the fiber architecture in terms of coordinate number, contact force, and fiber orientation, the influence of fiber deformation is identified. It is found that the flexible fibers are more sensitive to the geometry and profile changes of the nozzle internal walls, which leads to a larger inclination of the flexible fiber in the nozzle. Complex interlocking structures are formed by flexible fibers in the printer nozzle, promoting the fiber bridges. The results of this paper provide insights for the development and optimization of printer nozzles to enable the printing of longer fibers without potential nozzle clogging.

AbstractAimsTo examine the effectiveness of Self-Help Plus (SH+) as an intervention for alleviating stress levels and mental health problems among healthcare workers.MethodsThis was a prospective, two-arm, unblinded, parallel-designed randomised controlled trial. Participants were recruited at all levels of medical facilities within all municipal districts of Guangzhou. Eligible participants were adult healthcare workers experiencing psychological stress (10-item Perceived Stress Scale scores of ≥15) but without serious mental health problems or active suicidal ideation. A self-help psychological intervention developed by the World Health Organization in alleviating psychological stress and preventing the development of mental health problems. The primary outcome was psychological stress, assessed at the 3-month follow-up. Secondary outcomes were depression symptoms, anxiety symptoms, insomnia, positive affect (PA) and self-kindness assessed at the 3-month follow-up.ResultsBetween November 2021 and April 2022, 270 participants were enrolled and randomly assigned to either SH+ (n= 135) or the control group (n= 135). The SH+ group had significantly lower stress at the 3-month follow-up (b= −1.23, 95% CI = −2.36, −0.10, p= 0.033) compared to the control group. The interaction effect indicated that the intervention effect in reducing stress differed over time (b= −0.89, 95% CI = −1.50, −0.27, p= 0.005). Analysis of the secondary outcomes suggested that SH+ led to statistically significant improvements in most of the secondary outcomes, including depression, insomnia, PA and self-kindness.ConclusionsThis is the first known randomised controlled trial ever conducted to improve stress and mental health problems among healthcare workers experiencing psychological stress in a low-resource setting. SH+ was found to be an effective strategy for alleviating psychological stress and reducing symptoms of common mental problems. SH+ has the potential to be scaled-up as a public health strategy to reduce the burden of mental health problems in healthcare workers exposed to high levels of stress.

Photodynamic therapy (PDT) has received extensive attention in tumor treatment due to its advantages in overcoming drug resistance for chemotherapy. In this work, we prepared a nanoplatform generated from graphene quantum dots capped in hollow mesoporous silica nanoparticles (GQDs/hMSN). The singlet oxygen (1O2) generation efficiency and photodynamic therapy effect of GQDs/hMSN were studied in vitroand in vivo. GQDs/hMSN had good 1O2generation yield in water. Based on the findings from cellular experiments, we concluded that doxorubicin (DOX) loaded GQDs/hMSN (GQDs/hMSN(DOX)) had synergistic chemo-photodynamic therapeutic effect. From in vivotherapy on HeLa tumor-bearing mice, GQDs/hMSN exhibited significant accumulation in the tumor site, where DOX was also released from the nanoplatform due to the unique tumor microenvironment. This work further confirmed the usefulness of GQDs/hMSN nanoplatform as a potentially useful vector for combinational therapy of cancer.