The estimation of workspace for parallel kinematic machines (PKMs) typically relies on geometric considerations, which is suitable for PKMs operating under light load conditions. However, when subjected to heavy load, PKMs may experience significant deformation in certain postures, potentially compromising their stiffness. Additionally, heavy load conditions can impact motor loading performance, leading to inadequate motor loading in specific postures. Consequently, in addition to geometric constraints, the workspace of PKMs under heavy load is also constrained by mechanism deformation and motor loading performance.

This paper aims at developing a new heavy load 6-PSS PKM for multi-degree of freedom forming process. Additionally, it proposes a new method for estimating the workspace, which takes into account both mechanism deformation and motor loading performance. Initially, the geometric workspace of the machine is predicted based on its geometric configuration. Subsequently, the workspace is predicted while considering the effects of mechanism deformation and motor loading performance separately. Finally, the workspace is synthesized by simultaneously accounting for both mechanism deformation and motor loading performance, and a new index of workspace utilization rate is proposed. The results indicate that the synthesized workspace of the machine diminishes as the load magnitude and load arm increase. Specifically, under a heavy load magnitude of 6000 kN and a load arm of 200 mm, the utilization rate of the synthesized workspace is only 9.9% of the geometric workspace.

This study presents a dual-channel vortex generator (VG) that leverages the snap-through behaviour of flexible sheets. The VG outperforms a similar-sized rigid VG in generating vortices within dual-channel flows while minimizing pressure loss. Numerical simulations using the immersed boundary-lattice Boltzmann method analyse the dynamics and vortex generation performance of the sheet under various system parameters. Two distinct modes are identified for the elastic sheet: a sustained snap-through mode (SSTM) and a dormant mode (DM). The sheet's mode is predominantly influenced by its length ratio (L*), bending stiffness $(K_b^\ast )$ and flow strength, with the mass ratio having a minimal impact. The sheet exhibiting regular SSTM can effectively generate vortices in both channels and the vortex generation performance can be conveniently tuned by altering the sheet's initial buckling (i.e. L*). An increase in $K_b^\ast $ results in a higher critical Reynolds number (Rec) required for mode transition. An increase in L*, however, initially raises Rec and then lowers it, suggesting an optimal length ratio (approximately 0.7 for our considered system) for minimizing the Rec necessary to trigger SSTM. Furthermore, a disparity in the flow strength between channels is found to suppress the snap-through of the sheet; a greater disparity, however, is permissible to induce the SSTM of more compliant sheets. These findings underscore the potential of snap-through behaviour for enhanced flow manipulation in dual-channel systems.

Cryo-electron tomography (cryo-ET) is a powerful technique that can provide unprecedented insight into protein-protein interactions and molecular machinery in a near-native state. The adoption of cryo-ET by life science research groups is hampered by the challenges associated with cryo-ET sample preparation. The current sample preparation process has many steps at which ice contamination may occur to negatively affect the final sample and data quality. A survey was conducted to better understand the effects and impact of ice contamination to the cryo-ET outcome. Over 80 cryo-electron microscopy users worldwide participated in our survey. The results are presented in this article. We furthermore discussed the currently available solutions that can alleviate the ice contamination problems to increase the sample yield and cryo-ET data output.

Although scanning transmission electron microscopy (STEM) images of individual heavy atoms were reported 50 years ago, the applications of atomic-resolution STEM imaging became wide spread only after the practical realization of aberration correctors on field-emission STEM/TEM instruments to form sub-Ångstrom electron probes. The innovative designs and advances of electron optical systems, the fundamental understanding of electron–specimen interaction processes, and the advances in detector technology all played a major role in achieving the goal of atomic-resolution STEM imaging of practical materials. It is clear that tremendous advances in computer technology and electronics, image acquisition and processing algorithms, image simulations, and precision machining synergistically made atomic-resolution STEM imaging routinely accessible. It is anticipated that further hardware/software development is needed to achieve three-dimensional atomic-resolution STEM imaging with single-atom chemical sensitivity, even for electron-beam-sensitive materials. Artificial intelligence, machine learning, and big-data science are expected to significantly enhance the impact of STEM and associated techniques on many research fields such as materials science and engineering, quantum and nanoscale science, physics and chemistry, and biology and medicine. This review focuses on advances of STEM imaging from the invention of the field-emission electron gun to the realization of aberration-corrected and monochromated atomic-resolution STEM and its broad applications.

Nanosized Platinum (Pt) nanocrystals (NCs) have been extensively investigated in catalytic fields because of their high reactivity due to the unique electron structure. However, the rarity and the high cost of Pt limit its applications in industry. To reduce the usage of Pt in catalytic industry, research interests have been extended to Pt-based nanoalloys. Among various nanostructures, nanoframes (NFs) showed promising catalytic performance even with a lower metallic loading dose. Herein, we report a facile and robust method to transfer the Pt-Ni tetrahexahedral (THH) NCs into THH NFs in which carbon monoxide (CO) plays a role of the “etching reagent”. The driving force of the etching is a formation of gaseous metallic complex, Ni(CO)4, known as Mond Process, preferentially dealloying nickel atoms along <100> directions of the Pt-Ni THH NCs. It is determined that the resultant Pt-Ni THH NFs possess an open, stable and high-index preserved nanostructure, in which the outside atomic layers are composed of only Pt atoms with surface strains. Compared to a solution-based etching process, this approach requires less etching time and generates a well-defined structure. The associated thermal annealing operation also releases extra internal stress, making the NFs more stable with fewer surface defects. Such Pt-Ni THH NFs show interesting potentials in the improvement of stability and activity as advanced catalysts.