Purpose
Through‐time spiral GRAPPA is a real‐time imaging technique that enables ungated, free‐breathing evaluation of the left ventricle. However, it requires a separate fully‐sampled calibration ...scan to calculate GRAPPA weights. A self‐calibrated through‐time spiral GRAPPA method is proposed that uses a specially designed spiral trajectory with interleaved arm ordering such that consecutive undersampled frames can be merged to form calibration data, eliminating the separate fully‐sampled acquisition.
Theory and Methods
The proposed method considers the time needed to acquire data at all points in a GRAPPA calibration kernel when using interleaved arm ordering. Using this metric, simulations were performed to design a spiral trajectory for self‐calibrated GRAPPA. Data were acquired in healthy volunteers using the proposed method and a comparison electrocardiogram‐gated and breath‐held cine scan. Left ventricular functional values and image quality are compared.
Results
A 12‐arm spiral trajectory was designed with a temporal resolution of 32.72 ms/cardiac phase with an acceleration factor of 3. Functional values calculated using the proposed method and the gold‐standard method were not statistically significantly different (paired t‐test, p < 0.05). Image quality ratings were lower for the proposed method, with statistically significantly different ratings (Wilcoxon signed rank test, p < 0.05) for two of five image quality aspects rated (level of artifact, blood‐myocardium contrast).
Conclusions
A self‐calibrated through‐time spiral GRAPPA reconstruction can enable ungated, free‐breathing evaluation of the left ventricle in 71 s. Functional values are equivalent to a gold‐standard cine technique, although some aspects of image quality may be inferior due to the real‐time nature of the data collection.
Constructing an artificial solid electrolyte interphase (SEI) layer is an effective strategy for solving uncontrolled Li dendrite growth resulting from an unstable and heterogeneous Li/electrolyte ...interface. Herein, we develop a hybrid layer of a LiZn alloy and a polyethylene oxide (PEO) polymer to protect the Li metal anode for achieving a Li dendrite-free Li metal anode surface. The LiZn alloy is advantageous for fast Li
+
transport, and is uniformly dispersed in the PEO matrix to regulate electronic and Li
+
ion flux distributions homogeneously. Furthermore, the flexible PEO network can alleviate the volume change during cycling. The synergistic effect enables Li deposition underneath the hybrid film. Hence, the hybrid protection film results in significantly improved cycling stability with respect to the pristine Li metal anode. A symmetric Li/Li cell with a composite protective layer can be cycled for over 1000 h at a current density of 1 mA cm
−2
with a fixed capacity of 1 mA h cm
−2
, and a full cell with a high areal capacity of the LiFePO
4
(2.45 mA h cm
−2
) cathode exhibits an outstanding cycling performance.
A hybrid film that is constructed using a composite of LiZn-LiCl-PEO on the Li metal surface can achieve a dendrite-free Li deposition morphology and lead to uniform Li deposition under the hybrid layer instead of the top surface.
Although deep face recognition benefits significantly from large-scale training data, a current bottleneck is the labelling cost. A feasible solution to this problem is semi-supervised learning, ...exploiting a small portion of labelled data and large amounts of unlabelled data. The major challenge, however, is the accumulated label errors through auto-labelling, compromising the training. In this paper, we present an effective solution to semi-supervised face recognition that is robust to the label noise aroused by the auto-labelling. Specifically, we introduce a multi-agent method, named GroupNet (GN), to endow our solution with the ability to identify the wrongly-labelled samples and preserve the clean samples. We show that GN alone achieves the leading accuracy in traditional supervised face recognition even when the noisy labels take over 50% of the training data. Further, we develop a semi-supervised face recognition solution, named Noise Robust Learning-Labelling (NRoLL), which is based on the robust training ability empowered by GN. It starts with a small amount of labelled data and consequently conducts high-confidence labelling on a large amount of unlabelled data to boost further training. The more data is labelled by NRoLL, the higher confidence is with the label in the dataset. To evaluate the competitiveness of our method, we run NRoLL with a rough condition that only one-fifth of the labelled MSCeleb is available and the rest is used as unlabelled data. On a wide range of benchmarks, our method compares favorably against the state-of-the-art methods.
•LiF headspace affixed Li composite accommodates Li deposition perfectly.•LiF array as the framework on the surface provides fast Li+ diffusion paths.•The LZLF anode renders a prolongated cyclic ...lifetime.
Lithium (Li) metal composite with three-dimensional (3D) skeleton is regarded as the promising anode material for next generation rechargeable high energy batteries. Currently, most of the commercial cathodes are compounds rich of Li elements. In the initial operation of the as-assembled full cell, Li atoms are released from the cathode and directly deposited on the anode surface. The absence of the storage space in the conventional Li composite anode makes Li growth in an uncontrolled way and serious volume fluctuation of the electrode. Herein, LiF headspace affixed Li composite anode is prepared for the first time via a facile one-step thermal fusion method. The storage space constructed by LiF particles is formed on the top surface of 3D Li-LiZn-LiF (LZLF) composite anode, which can accommodate Li deposition from the cathode maintaining structural stability of the anode. Additionally, the LiF particles array on the surface can benefit for fast Li+ diffusion, suppressing Li dendrites growth and inducing uniform Li deposition. In a consequence, the LiF headspace affixed LZLF composite anode shows significantly improved electrochemical performance, i.e., more than 1000 h in symmetrical cell at 1 mA cm−2 and 1 mAh cm−2, or capacity retention of 88.9% after 800 cycles for the full cell at 1C with 2.45 mAh cm−2 in carbonate ester-based electrolyte.
Li metal is considered as the preferred anode material to replace graphite in next generation of Li metal battery. However, the shortages including Li dendrite growth are hindering its practical ...application. In addition, Li metal is unstable in ambient air, which brings safety risk for assembling and operating of Li metal battery. Herein, we deposit Al thin film on Li foil as the protective layer by magnetron sputtering. The Al-coated Li metal electrode shows higher stability in the air and carbonate-based electrolyte. Moreover, the Li electrode with Al coating layer exhibits metallic luster even after 200 cycles, and the cycling lifetime is expanded over 950 h at 0.5 mA cm−2 and 0.5 mAh cm−2. The improved electrochemical performance is attributed to the formation of a stable Li-Al alloy layer on the electrode surface, where the reduced Li atoms can diffuse into the alloy layer resulting in the formation of dense and compact Li metal anode.
Abstract
Dolomite@Al
2
O
3
spherical particles with core–shell structure were fabricated by using the dolomite powders as the core and wrapping corundum powders on their surface. The phase evolution ...and microstructure of the dolomite@Al
2
O
3
spherical particles with different firing temperatures were studied. As the spherical particles fired at different temperatures, the dolomite in the spherical core decomposed into MgO and CaO. Due to the Kirkendall effect, MgO and CaO diffused into the shell of the spherical particle and left Kirkendall holes in the core. The holes produced by the Kirkendall effect and the decomposition of dolomite act together to form a hollow structure in the center. And during the diffusion process, MgO and CaO reacted with corundum to generate spinel and calcium hexaaluminate. A small amount of spinel and calcium hexaaluminate can form a ternary compound Ca
2
Mg
2
Al
28
O
46
. Moreover, simulation software Factsage and Abaqus were used separately to help prove the phase evolution and the introduction of spherical particles to the properties of refractories. To test the lightweight effect of dolomite@Al
2
O
3
spherical particles on refractories, it was introduced into spinel–corundum refractories as medium particles in different content and fired at different temperatures. The results show that after firing at 1650°C for 3 h with introducing 30% dolomite@Al
2
O
3
spherical particles, the samples can reach a high compressive strength (128 MPa), high refractoriness under load (1683°C), and low thermal conductivity (1.79 W (m K)
−1
).
This paper investigated the effects of Z-pin content and insertion angle on the deformation and failure of quasi-isotropic laminates in the thickness direction by tensile pull-out tests and ...out-of-plane tensile tests. Local defect characteristics of the composite laminates when carbon fiber pin needle arrays are inserted were reproduced to analyze the Z-pin pull-out stresses and failure mechanism. Experimental results demonstrate that with the increase of Z-pin insertion angle, the maximum pull-out force and the maximum friction force which reflects the strength between Z-pins and matrix are reduced and interfacial debonding gradually dominated the failure. Z-pin insertion has little effect on the global failure mode of laminates. Compared with the unpinned laminates, the out-of-plane tensile strength of composite laminates decreased by 20.2% when the Z-pin insertion density is 1.4%. FEA results demonstrate that the decrease can be attributed to the resin-rich zone defect caused by Z-pin insertion and was not significantly associated with local in-plane fibre buckling.
Rational design and facile synthesis of highly active and stable electrocatalysts for oxygen reduction reaction (ORR) are crucial in the field of metal-air batteries. Here, we present a facile ...two-stage thermal synthesis of Fe-N codoped porous carbon (Fe-N/C) with abundant Fe-N x active sites and mesopores from Fe-doped ZIF-8 precursors. The first-stage preheating treatment of the Fe-doped ZIF-8 precursors before the second-stage carbonization is the key to boost the coordination between the doped Fe and N-containing ligands, which contributes to a higher N content and more Fe-N x sites in the final carbonized product. Besides, the preheating and Fe-doping both affect the morphology, porous structure, and catalytic performance of the fabricated Fe-N/C. The optimized Fe-N/C catalyst exhibits an outstanding ORR catalytic performance with a half-wave potential of 0.88 V and limiting current density of 6.0 mA cm–2 in 0.1 M KOH. A Mg-air battery assembled with a neutral electrolyte using the optimized Fe-N/C catalyst as the cathode exhibits an excellent power density of 72 mW cm–2 at 0.72 V. This developed two-stage synthesis strategy is facile, and the preheating stage could be integrated into any carbonization process as an intermediate step for the fabrication of various metal, N codoped carbon materials with enhanced electrocatalytic performance.
Combined modified lithium metal composite anode with multilevel micro-nano structure was synthesized by infusion of molten lithium into Cu foam and coating with zinc fluoride. The lithium metal ...composite anode was used for lithium batteries, the electrochemical performances reveal that surface modification reduces interfacial side reaction and multilevel micro-nano structure suppresses the growth of lithium dendrite.
Display omitted
•The strategy of combining bulk and surface modification is proposed.•The multilevel micro-nano structure of lithium metal composite is formed.•The excellent performance of symmetric cell is achieved.
Lithium (Li) metal has extremely high theoretical specific capacity and low redox potential, which can greatly improve energy density of Li battery. Nevertheless, some troubles including Li dendrite, parasitic reaction and volumetric change extremely restrict its practical application. Herein, a strategy of combining 3D composite lithium metal and surface modification is proposed for solving these issues simultaneously. The 3D composite lithium metal electrode is synthesized by infusing molten Li into Cu foam, and multilevel micro-nano structure is obtained by alloying reaction between Li and surface part of Cu foam, which can be used as three-dimensional (3D) scaffold with high specific surface area. The surface modification of coating zinc fluoride (ZnF2) is used as artificial solid electrolyte interphase (SEI). The symmetric cell using modified composite Li anode exhibits stable electrochemical performance and long cycling lifespan. And the excellent performance of LiCoO2 (LCO) cell (average 121 mAh g−1) is achieved, compared to pristine Li of 114 mAh g−1.
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