Institute Of Mechanics,Chinese Academy of Sciences
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Improving computed tomography of chemiluminescence under projection angle limitations via camera layout optimization
No full textHigh-quality bulk tomography imaging under limited projection angle conditions is an important challenge in complex flow and combustion diagnostics. Aiming at the problem that only a few high-speed cameras can usually be deployed in supersonic wind tunnel experiments due to limited optical access, this paper proposes a camera layout optimization method that combines computed tomography of chemiluminescence (CTC) technology with fiber-optic endoscopes (FBEs). The method reduces the correlation of the projected weight matrix and data redundancy by maximizing the angle between the subspaces of the rows of the weight matrix, thus improving the reconstruction accuracy and stability. Combined with the geometric characteristics of the wind tunnel with multiple windows, the simulated annealing algorithm is used to optimize the projection angle and spatial distribution of the camera to maximize the capture of effective information. Numerical simulation and experimental results show that, compared with the traditional circular plane uniform layout, the average cross-correlation coefficient of the verified projections is above 0.98, which is about 2.1% higher than that of a uniform layout, effectively suppressing reconstruction artifacts caused by limited projections. This optimization method reduces the reconstruction error of finite projection angles and exhibits good adaptability and robustness to changes in flame direction. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI)training, and similar technologies, are reserved
太极计划中的测温电桥激励源设计与验证
No full text热扰动是空间引力波探测最重要的干扰来源之一，为满足空间引力波探测太极计划的需求，需要保证探测器光学干涉平台所在区域温度波动优于10μK/Hz1/2 @ 0.1mHz~1Hz，这需要μK/Hz1/2的温度测量技术。本文针对空间引力波探测对高分辨率温度测量技术的需求，研制了一套基于惠斯通电桥的多激励源的测温电桥实验装置。讨论了测温电桥的激励源及其他组件的设计方案，并进行了恒压源、恒流源和交流源激励下的测温电桥本底噪声的实验验证。实验结果表明：在三种激励源分别激励电桥时，交流源结合锁相读出技术相较其他两种激励源能够达到更低的本底噪声，且在30mHz~1Hz频率范围内噪声优于10μK/Hz1/2，基本能满足太极探路者的指标要求。为太极计划后续μK级温度测量系统的研制，奠定了坚实的理论和实验基础。</p
一种水泥窑协同的煤矸石气化系统及方法
No full text本发明公开了煤矸石气化技术领域的一种水泥窑协同的煤矸石气化系统，包括设置于分解炉旁的气化炉，所述气化炉的侧面设置有用于通入煤矸石粉的进料口；所述气化炉于所述进料口的下部设置有与水泥窑的三次风管连通的进气管，以向所述气化炉内通入高温三次风，气化煤矸石粉；所述气化炉于所述进料口的上部设置有与分解炉连通的出气管，以将煤矸石粉气化产生的煤气通入所述分解炉中
一种渗氮模具钢的激光熔覆复合涂层的制备方法
No full text本发明提供了一种渗氮模具钢的激光熔覆复合涂层的制备方法，是先选择Ti合金粉末和H13钢合金粉末进行均匀混粉后得到含Ti的H13钢粉末，其中Ti合金粉末属于微米级粉末；同时，选择Stellite合金粉末和H13钢混合粉末进行均匀混粉后得到含Stellite合金的H13钢粉末；然后分别将含Ti的H13钢粉末和含Stellite合金的H13钢粉末进行烘粉处理；接着在渗氮钢表层上熔覆烘粉处理后的含Ti的H13钢粉末作为打底层，再在打底层上继续熔覆含Stellite合金的H13钢粉末作为工作层，以最终获得含有打底层和工作层的复合涂层。本发明构思合理、流程简单，在渗氮钢表面进行激光熔覆的复合涂层，可以制备出界面无明显孔洞、裂纹缺陷且性能优良的熔覆层
Are sutural structures in biology the optimal topological design?
No full textSutural structures are widely observed in biology and attract lots of attention. However, the majority of current research focuses on understanding the characteristics of sutural structures, with little research investigating whether sutural structures in biology are the optimal topological design. To disclose this mystery, this paper summarizes the characteristics of sutural structures found in nature and characterizes their shapes by several important geometric parameters. By establishing analytical models and finite element models of sutural structures, we investigate the stiffness, strength, and damping energy dissipation properties of sutural structures in biomaterials and optimized the sutural shapes based on genetic algorithm (GA) under static tensile and shear loading, as well as dynamic uniaxial loading. Under static loading, sutural structures with interlocking features demonstrate great stiffness and strength. Under dynamic loading, the frequency of the external excitation and the sutural shapes jointly determine the energy dissipation performance. We find that the sutural shapes in typical biomaterials evolve to optimal shapes to achieve certain optimal mechanical properties. Additionally, genetic algorithms provide a paradigm for the design of materials with multi-objectives, allowing for the design of sutural structures that balance various mechanical properties
Numerical study of relationships between flows and structural characteristics of the rotor in a rim-driven hubless thruster using a strongly-coupling FSI algorithm
No full textThe shaftless rim-driven thruster (RDT), as a new type of ship propulsion method, has attracted more and more attention in recent years. In this study, RDT was employed. Firstly, the open water performance of RDT with rigid blade was numerically studied based on the Detached Eddy Simulation (DES). Subsequently, A two-way fluid- structure interaction (FSI) method was adopted to simulate the effects of four flexible blades on the hydrodynamic performance and pulsating pressure. The differences between the hydrodynamic coefficients, flow fields, von Mises stress (VMS), blade deformation, and excitation forces of the flexible and rigid RDT were analyzed. The results show that the blade deformation leads to the loss of thrust and overall efficiency, and the smaller the Young's modulus, the greater the loss of thrust and overall efficiency. As the Young's modulus decreases, the blade deformation in the axial, tangential and radial directions increases, and blade deformation in the axial plays a dominant role in the three directions. Compared with the rigid RDT, blade deformation increases the pulsating pressure of the upstream freestream of blade and weakens the pulsating pressure of the downstream freestream of blade. These findings will provide a reference for the design and optimization of RDT rotor
Revisiting viscoelastic liquid films flowing down a slippery substrate: Linear and nonlinear viscoelastic waves
No full textThis paper revisits the flow of a viscoelastic film on a slippery substrate (Phys. Rev. Fluids 7 (6), 064007, 2022) using the Navier-slip boundary condition, tau xz = lambda u (lambda represents the friction coefficient of the substrate). Here, tau xz represents the total tangential shear stress, comprised of both a viscous and an elastic component. A model equation for the film thickness is derived based on the long-wave theory. The study investigates both the linear and nonlinear dynamics of the film flow. It reveals that the presence of a slippery substrate and viscoelasticity promote the instability of linear viscoelastic waves. Additionally, they affect the speed and height of nonlinear viscoelastic waves. Our present study suggests that neglecting the elastic component of tau xz at the slippery wall could result in an overestimation of the linear stability threshold while underestimating the speed and height of nonlinear waves
Multi-resolution reconstruction of longitudinal streambed footprints using embedded sparse convolutional autoencoders
No full textThis study introduces an embedded convolutional autoencoder (CAE) architecture designed for the multiresolution reconstruction of longitudinal streambed footprints as sparse heatmaps. Three standalone but interrelated CAEs are trained to achieve double-upsampling, enhancing the heatmaps' spatial resolution and data measurement resolution simultaneously. Transfer learning improves model training efficiency by incorporating a trained model into a larger model at the next level. Cascading the CAEs facilitates a direct pathway for enhancing data quality from the coarsest inputs and recovering fine-grained patterns. Systematic evaluations prove the CAEs' reliability in working individually and collectively. Robustness analyses demonstrate the model's ability to retain field reconstructive quality when subjected to various corrupted inputs, including bulk data loss and spiky noise interference with local measurements at different streambed sections. The model's capacity benefitted from including attention mechanisms (convolutional block attention modules, CBAM) and the adaptive training strategy using crafted loss functions, ensuring efficient extraction and learning of sparse dense patterns and fast reconstruction of physically sound fields. The model architecture's flexibility and scalability are highlighted, proving it suitable for more complex geophysical systems with higher dimensions. The proposed embedded CAE architecture provides a foundational tool for creating digital surrogates of river courses and similar entities, which often involve inherently sparsely distributive data in both spatial and temporal domains
掺氢天然气环境下管线钢氢致疲劳裂纹扩展研究进展
No full text天然气掺氢输送是实现氢能长距离、低成本、大规模输运的重要途经，但管线因疲劳载荷作用可能发生氢致疲劳损伤，严重威胁掺氢天然气管线的服役安全。因此，本文首先介绍了管线钢氢致疲劳裂纹扩展的机理和模型，重点论述了微观组织结构及焊接、载荷和服役环境等因素对掺氢天然气环境下管线钢氢致疲劳裂纹扩展的影响，最后对该领域的未来研究方向提出了展望。</p
Reproducing the thermal effects induced by aging in La-based amorphous alloy
No full textPhysical aging intrinsically exists in amorphous materials and refers to the evolution of the nonequilibrium structure toward an equilibrium state. The aging process can significantly affect the thermomechanical properties of the amorphous materials, thereby influencing their macroscopic responses. Aging models not only help in understanding the underlying physical mechanisms of the relaxation behavior but also may provide an effective tool for predicting the physical and mechanical properties of metastable nonequilibrium materials in practical applications. In the current work, based on the measurement of calorimetric data and shear modulus during the heating process of amorphous metallic alloys, we obtained the mechanical and thermal property changes caused by physical aging. By incorporating the characteristic time of their alpha relaxation into a first-order kinetic equation and considering the coupled evolution between the characteristic time and the structural order parameter, we derived an aging kinetics model based on the hierarchically constrained atomic dynamics theory. This model effectively reproduces the thermal effects in the aging region and the supercooled liquid region observed in the calorimetric data. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/)</p