| 1. |
- Du, Hao, et al.
(författare)
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Side reactions/changes in lithium-ion batteries : mechanisms and strategies for creating safer and better batteries
- 2024
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Ingår i: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095.
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Forskningsöversikt (refereegranskat)abstract
- Abstract Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and overdischarge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.
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| 2. |
- He, Song, et al.
(författare)
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Notes on Worldsheet : Like Variables for Cluster Configuration Spaces
- 2023
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Ingår i: Symmetry, Integrability and Geometry. - : SIGMA (Symmetry, Integrability and Geometry: Methods and Application). - 1815-0659. ; 19, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- We continue the exploration of various appearances of cluster algebras in scattering amplitudes and related topics in physics. The cluster configuration spaces generalize the familiar moduli space M0,n to finite-type cluster algebras. We study worldsheet-like variables, which for classical types have also appeared in the study of the symbol alphabet of Feynman integrals. We provide a systematic derivation of these variables from Y-systems, which allows us to express the dihedral coordinates in terms of them and to write the corresponding cluster string integrals in compact forms. We mainly focus on the Dn type and show how to reach the boundaries of the configuration space, and write the saddle-point equations in terms of these variables. Moreover, these variables make it easier to study various topological properties of the space using a finite-field method. We propose conjectures about quasi-polynomial point count, dimensions of cohomology, and the number of saddle points for the Dn space up to n = 10, which greatly extend earlier results.
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| 3. |
- Jing, Zhao, et al.
(författare)
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Effect of Multistep Processing Technique on the Formation of Micro-defects and Residual Stresses in Zirconia Dental Restorations
- 2014
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Ingår i: Journal of Prosthodontics. - : Wiley. - 1059-941X .- 1532-849X. ; 23:3, s. 206-212
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The clinical failures of zirconia dental restorations are often caused by extrinsic artifacts introduced by processing. The aim of this study was to investigate the micro-defects and residual stresses generated during the multistep process of zirconia dental restorations. Materials and Methods Thermal spray granulated 3Y-TZP powders were dry pressed by two tools exhibiting distinctly different Young's moduli, cold isostatic pressed (CIP-ed), and pressure-less fully sintered. The green bodies pressed by a stiff tool were treated with different procedures: direct milling (green milling) followed by fully sintering; half-sintering and milling (raw milling) with or without fully sintering; and fully sintering followed by grinding. The fully sintered 3Y-TZP crowns were clinically adjusted using both a diamond bur and SiC bur, respectively. Phase composition and microstructure of the pressed, milled, and ground surfaces were studied by XRD and SEM. Results Tetragonal phase was the main phase of all detected 3Y-TZP specimens. Excessive residual stresses introduced by raw milling and grinding were confirmed by a strained T (111) peak, monoclinic phase, and obviously changed I(002)(t)/I(200)(t) ratio. The residual stresses would form a compressive stress layer, while it was too shallow to inhibit crack propagation even for ground specimens. Large voids with high-coordination numbers were the common packing micro-defects. Once formed, they were barely healed by CIP-ing and sintering. A stiff pressing tool was confirmed to be useful for reducing the surface packing voids. Milling removed the surface voids, but was no help for the interior ones. Raw milling introduced more serious chippings, most originating from the existing packing voids, than green milling due to its brittle failure and was less recommended for production. Grinding dense 3Y-TZP caused surface grain refinement and much more severe micro-defects, especially when clinical adjustment was applied by diamond bur compared to SiC bur. Conclusions Micro-defects and residual stresses are introduced and accumulated through the entire production chain and determine the final microstructure of zirconia dental restorations. Several procedural improvements are offered and expected to reduce processing micro-defects.
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| 4. |
- Qin, Changliang, et al.
(författare)
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Process optimizations to recessed e-SiGe source/drain for performance enhancement in 22 nm all-last high-k/metal-gate pMOSFETs
- 2016
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Ingår i: Solid-State Electronics. - : Elsevier. - 0038-1101 .- 1879-2405. ; 123, s. 38-43
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the technology of recessed embedded SiGe (e-SiGe) source/drain (S/D) module is optimized for the performance enhancement in 22 nm all-last high-k/metal-gate (HK/MG) pMOSFETs. Different Si recess-etch techniques were applied in S/D regions to increase the strain in the channel and subsequently, improve the performance of transistors. A new recess-etch method consists of a two-step etch method is proposed. This process is an initial anisotropic etch for the formation of shallow trench followed by a final isotropic etch. By introducing the definition of the upper edge distance (D) between the recessed S/D region and the channel region, the process advantage of the new approach is clearly presented. It decreases the value of D than those by conventional one-step isotropic or anisotropic etch of Si. Therefore, the series resistance is reduced and the channel strain is increased, which confirmed by the simulation results. The physical reason of D reducing is analyzed in brief. Applying this recess design, the implant conditions for S/D extension (SDE) are also optimized by using a two-step implantation of BF2 in SiGe layers. The overlap space between doping junction and channel region has great effect on the device's performance. The designed implantation profile decreases the overlap space while keeps a shallow junction depth for a controllable short channel effect. The channel resistance as well as the transfer ID-VG curves varying with different process conditions are demonstrated. It shows the drive current of the device with the optimized SDE implant condition and Si recess-etch process is obviously improved. The change trend of on-off current distributions extracted from a series of devices confirmed the conclusions. This study provides a useful guideline for developing high performance strained PMOS SiGe technology.
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| 5. |
- Shen, Zhijian, et al.
(författare)
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Fractography of self-glazed zirconia with improved reliability
- 2017
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 37:14, s. 4339-4345
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Tidskriftsartikel (refereegranskat)abstract
- The fractography of a new grade of zirconia ceramics, known as self-glazed zirconia, was investigated. The as-sintered intact top surface was made with superior smoothness that mimicked the optical appearances of the natural teeth enamel. The beneath surface opposite to this was made hierarchically rough with microscopic pits of the size up to 60. μm together with grain-level roughness of about 2. μm. The three-point bending test of the samples made with the hierarchically rough surface being tensile one demonstrated an average bending strength of 1120. ±. 70. MPa and a Weibull modulus of as high as 18 ascribed to the improved structural homogeneity. Surface topography was found the main origins of crack initiation leading to fracture. The observed unusually predominant transgranular fracture mode of submicron-sized grains disclosed a possible toughening mechanism of disassembling of mesocrystalline grains that differs significantly from the commonly quoted phase transformation toughening of this category of ceramics.
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| 6. |
- Yan, Shiyang, et al.
(författare)
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Arch-related alteration in foot loading patterns affected by the increasing extent of body mass index in children : A follow-up study
- 2023
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Ingår i: Gait & Posture. - : Elsevier BV. - 0966-6362 .- 1879-2219. ; 100, s. 247-253
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Tidskriftsartikel (refereegranskat)abstract
- Background: A high load on children 's feet can cause arch deformation and negatively affect their normal development. Studies have yet to document how the foot arch varied with different body mass index (BMI) increments and its influence on foot loading patterns.Methods: Barefoot walking trails were conducted using a Footscan (R) plate system. A follow-up check was per-formed after twenty-four months. Participants were selected with an initial BMI between 14.5 kg/m2 and 16.5 kg/m2. Totally 75 participants were classified into groups 0-7 according to the BMI increment levels of 0-0.49 kg/m2, 0.50-1.49 kg/m2, 1.50-2.49 kg/m2, 2.50-3.49 kg/m2, 3.50-4.49 kg/m2, 4.50-5.49 kg/m2, 5.50-6.49 kg/m2, 6.50-7.49 kg/m2, respectively. Paired t-tests and effect sizes were used to compare the data.Results: The arch index significantly decreased when the BMI reached 20.8 kg/m2. Significantly increased normalized maximum forces were found in the great toe and 1st MTPJ in groups 4-5. Meanwhile, the absence of significance showed under the 3rd-5th, midfoot, and rearfoot in those groups. The normalized maximum force increments under the 3rd-5th MTPJs, midfoot and rearfoot regions in groups 4-5 after the follow-up study were significantly decreased compared with the increments found in groups 0-3, followed by a sudden increase arising under those regions in group 6. It indicates a transition period that leads to alteration in gait pattern charac-teristics when BMI increases to 18.6-19.9 kg/m2 (between group 3 and group 4). Group 6 displayed significantly increased peak pressure amplitudes under the great toe, 1st-3rd MTPJs, midfoot, and medial rearfoot compared to other groups.Significance: There was a transition period when the BMI of normal-weighted children increased to a certain extent and failed to reach the obesity level, resulting in changes in foot arch structure and loading patterns.
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