Tianjin Hi-Tech Superconducting Electronic Technology (China)

The polishing pad is a key consumable in chemical–mechanical planarization (CMP), and its groove structure significantly regulates the slurry transport capacity and debris removal efficiency. This study establishes a Computational Fluid Dynamics model to systematically analyze, for the first time, the flow field characteristics of radial groove (RG), concentric groove, and eccentric groove (EG) polishing pads (with different eccentricity distances). The effects of groove structure on process performance are further investigated experimentally. Furthermore, based on mixed lubrication theory, the mechanisms by which groove width, depth, and spacing affect flow field characteristic parameters are revealed, thereby clarifying the dimensional optimization directions for different groove structures. The results indicate that the EG pad exhibits the highest slurry saturation degree; the periodic fluctuation in its flow field helps optimize the slurry distribution state, thereby improving global planarity. Appropriately increasing the groove width can improve the problem of low slurry saturation degree. The RG pad exhibits a higher slurry mass flow rate, which enhances the chemical corrosion effect and improve debris removal efficiency. Appropriately increasing the groove spacing can ameliorate the problem of low slurry saturation degree. By constructing a multi-scale correlation model, this study reveals the intrinsic relationship between polishing pad structure and its flow field characteristics, along with the parameter regulation rules, providing theoretical support for optimizing polishing pad structure design and enhancing CMP process controllability.

This article provides an overview of the design and verification of a 1.0-T ultrashort-cavity intraoperative head magnetic resonance imaging (MRI) superconducting magnet. We proposed a linear programming method with repeated iterations for the electromagnetic design of superconducting magnets in MRI, referred to as repeated iterative linear programming (RILP). By employing RILP, we first investigated the influence of axial length on the maximum magnetic induction intensity, the number of coils, and the cost of superconducting material. The rectangularization of current clusters during the linear programming phase of the electromagnetic design was then completed. The electromagnetic force, stress, and strain were also analyzed. Finally, passive shimming within linear programming was performed on the superconducting magnet, resulting in magnetic field inhomogeneity within 20-cm diameter of spherical volume being below 8 ppm. The designed superconducting magnet meets the technical requirements for intraoperative head MRI, with a total length of 960 mm and a bore size of 650 mm.

In order to verify the feasibility of key technologies in the proposed prototype of 10-Mvar high temperature superconducting (HTS) dynamic synchronous condenser (DSC), This paper focuses on the design of HTS rotor magnets, damping shield and screening that affect the performance of the system. The HTS rotor coils consisting of three double-pancake coils were designed. 6061 aluminum alloy is selected for the prototype. The stator output voltage has no significant harmonic component. By calculating the V-curve, the strong reactive power compensation capability of HTS DSC is verified. At rated gap field 1.4 T and no-load excitation current 434 A, the maximum flux density on the YBCO coils is 3.28 T. At the full-load excitation current 475 A, this prototype can output 10-Mvar reactive power. Furthermore, this paper deals with short-circuit accident of 10-Mvar class superconducting condenser. The most serious fault is three phase short-circuit, where the impact current reaches more than 52 times of the rated armature current. There results show that the design the 10-Mvar class superconducting synchronous condenser considers not only normal operational performances but also fault conditions.

Front cover image: Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase (SEI)-film growth. In article number 10.1002/cey2.141, Tao et al. demonstrate that the gradient regulation of Si-valence can eliminate the local stress and enhance the lithium-ion transport dynamics for SiOx anode, effectively boosting the cycle life and output power for batteries, and thus strongly driving electric vehicles.

To develop and validate a fast dynamic MR imaging scheme. A novel approach termed K-T ARTificial Sparsity enhanced GROWL (K-T ARTS-GROWL) is proposed that integrates dynamic artificial sparsity and GROWL-based parallel imaging (PI). Golden-angle radial k-space data are acquired with the free-breathing sampling scheme and then sorted into a time series by grouping consecutive spokes into temporal frames. The reconstruction framework sequentially applies PI and dynamic artificial sparsity. In the implementation, GROWL is taken as a special PI instance for its high computational efficiency and the K-T sparse is exploited to improve the PI reconstruction performance, because the dynamic MR images are often sparse in the x-f domain. In the final reconstruction procedure, artificial sparsity is constructed and fed back to the previous reconstruction. The K-T ARTS-GROWL results in high spatial and temporal resolution reconstructions. By exploiting dynamic artificial sparsity, the acceleration capability is further improved compared to the PI alone. The experimental results demonstrate that K-T ARTS-GROWL leads to significantly better image quality (P<0.05) than the frame-by-frame GROWL and frame-by-frame ARTS-GROWL for invivo liver imaging. Compared with the tested K-T reconstruction algorithms, the K-T ARTS-GROWL results in a better or comparable image quality and temporal resolution with greatly decreased computational costs. The proposed technique enables sparse, fast imaging of high spatial, high temporal resolutions for dynamic MRI.

Most HTS (high-temperature superconductor) coils will quench due to defects in the winding. Some of these defects come from tape manufacturing, but more commonly are generated in the process of making a coil, especially for the YBCO racetrack coils that use epoxy resin to solidify the winding. In order to find out defects, chemical solutions are used to dissolve epoxy resin of three damaged YBCO racetrack coils. YBCO tapes reclaimed from these coils are scanned by MCorder, a continuous critical current measurement device that can tell amplitude of defects and distribution of defects in a high speed and high resolution. The scan result shows severe defects everywhere in the winding. However, during the solidification process, outer turns are more vulnerable to the defects than the inner turns. We believe that the delamination of YBCO tape caused by contraction of the epoxy resin contributes to the defects.

Graphene/hexagonal boron nitride (h‐BN) monolayer in‐plane heterostructure offers a novel material platform for both fundamental research and device applications. To obtain such a heterostructure in high quality via controllable synthetic approaches is still challenging. In this work, in‐plane epitaxy of graphene/h‐BN heterostructure is demonstrated on Cu–Ni substrates. The introduction of nickel to copper substrate not only enhances the capability of decomposing polyaminoborane residues but also promotes graphene growth via isothermal segregation. On the alloy surface partially covered by h‐BN, graphene is found to nucleate at the corners of the as‐formed h‐BN grains, and the high growth rate for graphene minimizes the damage of graphene‐growth process on h‐BN lattice. As a result, high‐quality graphene/h‐BN in‐plane heterostructure with epitaxial relationship can be formed, which is supported by extensive characterizations. Photodetector device applications are demonstrated based on the in‐plane heterostructure. The success will have important impact on future research and applications based on this unique material platform.