155,631 research outputs found
Interfacial “Single-Atom-in-Defects” Catalysts Accelerating Li+ Desolvation Kinetics for Long-Lifespan Lithium-Metal Batteries
No full textThe lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li+, Li0 nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co1−xS embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li+ solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO4 cathode, the full cell (10.7 mg cm−2) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications
Thermodynamic Modeling of the Li-H and Ca-H Systems
No full textThe phase diagram and thermodynamic properties of the Li-H and Ca-H systems in the literature are critically reviewed. The Gibbs energy functions of individual phases in these two systems are modeled by the CALPHAD approach. The associate solution model and substitutional model are employed to represent the thermodynamic properties of the liquid phase in the Li-H and Ca-H systems, respectively. The available experimental data are well reproduced by the present modeling. With the obtained Gibbs energy functions, the phase relationships in the Li-H and Ca-H systems at high pressures are also predicted
Characterization of an alternatively spliced G(M2) activator protein, G(M2A) protein - An activator protein which stimulates the enzymatic hydrolysis of N-acetylneuraminic acid, but not N-acetylgalactosamine, from G(M2)
No full textG(M2) activator protein is a protein cofactor which stimulates the enzymatic hydrolysis of both GalNAc and NeuAc from G(M2). We have previously isolated two cDNA clones, G(M2) activator cDNA and G(M2A) cDNA, for human G(M2) activator protein (Nagarajan, S., Chen, H.-C., Li, S.-C., Li, Y.-T., and Lockyer, J. M. (1992) Biochem. J. 282, 807-813). G(M2A) mRNA is an RNA alternative splicing product that contains exons 1, 2, 3, and intron 3 of the genomic DNA sequence of G(M2) activator protein (Klima, H., Tanaka, A., Schnabel, D., Nakano, T., Schroder, M., Suzuki, K., and Sandhoff, K. (1991) FEES Left. 289, 260-264). G(M2A) cDNA encodes a protein (G(M2A) protein) containing 1-109 of the 160 amino acids of human G(M2) activator protein, plus a tripeptide (VST) encoded by intron 3 at the COOH terminus. Thus, G(M2A) protein can be regarded as a form (truncated version) of G(M2) activator protein. We have expressed G(M2A) cDNA in Escherichia coli using pT7-7 as the vector. The recombinant G(M2A) protein was purified to an electrophoretically homogeneous form and was found to stimulate the hydrolysis of NeuAc from G(M2) by clostridial sialidase, but not the hydrolysis of GalNAc from G(M2) by beta-hexosaminidase A. Like G(M2) activator protein, G(M2A) protein also specifically recognized the terminal G(M2) epitope in GalNAc-GD1a and stimulated the hydrolysis of only the external NeuAc from this ganglioside by clostridial sialidase. These results enabled us to discern the enzymatic hydrolyses of GalNAc and NeuAc from the G(M2) epitope and established that the NeuAc recognition domain of G(M2) activator protein is located within amino acids 1-109. The presence of G(M2A) mRNA in human tissues and the selective stimulation of NeuAc hydrolysis by G(M2A) protein indicate that this activator protein may be involved in the catabolism of G(M2) through the asialo-G(M2) pathway
The effects of sintering temperature and time on the structure and electrochemical performance of LiNi0.8Co0.2O2 cathode materials derived from sol-gel method
No full textLiNi0.8Co0.2O2 cathode materials were synthesized by the sol-gel method using citric acid as a chelating agent. The effects of sintering temperature and time on the structure and electrochemical performance of the materials were investigated. The materials were characterized by X-ray diffraction, together with refinement analysis by the Rietveld method. The results showed that sintering temperature and time had significant influence on the structure of the materials. The lattice parameters (a, c, c/a and volume) and the amount of Ni in the Li 3a site showed a peak shape change with sintering temperature and time. The sample sintering at 998 K for 24 h showed the best ordering layered structure with the maximum c/a ratio and the least amount of Ni on the Li 3a site. The charge-discharge experiments also indicated that the sample had the best electrochemical properties, with an initial capacity of 181 mA h/g and a capacity retention of 82.9% after 50 cycles at a 0.1 C rate between 3.0 V and 4.2 V. In addition, the compositional homogeneity of these cathode materials derived using the sol-gel method was demonstrated by scanning electron microscopy/energy dispersive analysis
Li-rich cathodes for rechargeable Li-based batteries: Reaction mechanisms and advanced characterization techniques
No full textDue to their high specific capacities beyond 250 mA h g-1, lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional layered-oxide based lithium-ion batteries and future lithium metal batteries such as lithium sulfur and lithium air batteries. However, the practical application of Li-rich oxides has been hindered by formidable challenges. To address these challenges, the understanding of their electrochemical behaviors becomes critical and is expected to offer effective guidance for both materials and cell development. This review aims to provide fundamental insights into the reaction mechanisms, electrochemical challenges and modification strategies of lithium-rich oxides. We first summarize the research history, the pristine structures, and the classification of lithium-rich oxides. Then we review the critical reaction mechanisms that are closely related to their electrochemical features and performances, such as lattice oxygen oxidation, oxygen vacancy formation, transition-metal migration, layered to spinel transitions, 'two-phase mechanism', and lattice evolution. These discussions are coupled with state-of-the-art characterization techniques. As a comparison, the anionic redox reactions of layered sodium transition metal oxides are also discussed. Finally, after a brief overview of the correlation among the aforementioned mechanisms, we provide perspectives on the rational design of lithium-rich oxides with high energy densities and long-term cycling stability. This journal i
H∞ consensus and synchronization of nonlinear systems based on a novel fuzzy model
No full textThis paper investigates the H∞ consensus control problem of nonlinear multiagent systems under an arbitrary topological structure. A novel Takagi-Sukeno (T-S) fuzzy modeling method is proposed to describe the problem of nonlinear follower agents approaching a time-varying leader, i.e., the error dynamics between the follower agents and the leader, whose dynamics is evolving according to an isolated unforced nonlinear agent model, is described as a set of T-S fuzzy models. Based on the model, a leader-following consensus algorithm is designed so that, under an arbitrary network topology, all the follower agents reach consensus with the leader subject to external disturbances, preserving a guaranteed H∞ performance level. In addition, we obtain a sufficient condition for choosing the pinned nodes to make the entire multiagent network reach consensus. Moreover, the fuzzy modeling method is extended to solve the synchronization problem of nonlinear systems, and a fuzzy H∞ controller is designed so that two nonlinear systems reach synchronization with a prescribed H∞ performance level. The controller design procedure is greatly simplified by utilization of the proposed fuzzy modeling method. Finally, numerical simulations on chaotic systems and arbitrary nonlinear functions are provided to illustrate the effectiveness of the obtained theoretical results. © 2013 IEEE
H ∞ fault detection filter design for discrete-time nonlinear Markovian jump systems with missing measurements
No full textFault detection filter (FDF) design problem for a class of discrete-time nonlinear Markovian jump systems subject to unreliable communication channel is addressed in this study. The considered system nonlinearity is assumed to satisfy global Lipschitz condition and the missing measurement phenomenon is modeled by Bernoulli binary distribution. By constructing an observer-based FDF as a residual generator, the fault detection issue is cast into a stochastic H ∞ filtering framework. Sufficient existence conditions of the H ∞ -FDF are derived via matrix inequalities. Two cases for the Markovian parameters, one is completely known transition probabilities and the other is partially known transition probabilities, have been considered in the filter design procedure, respectively. Furthermore, parameter matrices of the FDF are obtained by solving a set of linear matrix inequalities. An illustrative example is addressed to show the efficacy of the proposed filter
Platinum-group elements and geochemical characteristics of the Permian continental flood basalts in the Tarim Basin, northwest China: Implications for the evolution of the Tarim Large Igneous Province
No full textAbstract not availableYin-Qi Li, Zi-Long Li, Ya-Li Sun, M. Santosh, Charles H. Langmuir, Han-Lin Chen, Shu-Feng Yang, Zhong-Xing Chen, Xing Y
Improved 3D printed silica ceramics impregnated with an alumina sol by controlling atmosphere, vacuum pressure and holding time
No full textWhen the content of cristobalite is in the appropriate range, the mechanical properties of silica ceramics can be improved. The formation and growth of cristobalite in silica ceramics can be promoted by introducing alumina into silica ceramics by vacuum impregnation. In this study, the influence of different conditions on the impregnation of silica ceramics by alumina sol was studied by controlling the impregnation atmosphere, vacuum impregnation pressure and vacuum impregnation time. The results proved that the impregnation atmosphere has a great influence on the impregnation effect. The flexural strength of vacuum impregnated sample increased by 278.8 % compared with that of air impregnated sample. The smaller the pressure, the greater the difference between the pressure and the external pressure, and the better the impregnation effect of the sample. The flexural strength of the sample with vacuum impregnation pressure of 0.015 MPa was 138.1 % higher than that of the sample with vacuum impregnation pressure of 0.065 MPa. The increase of vacuum impregnation holding time can improve the performance of the sample, but the improvement effect has an upper limit. When the vacuum impregnation time was 3.0 h, the strength of the sample improved by 98.3 % compared with that of the sample with vacuum impregnation time of 1.5 h. Based on the mechanical properties and economic benefits, the best mechanical properties of silica ceramics were obtained by impregnating 3.0 h with 25 wt% alumina sol at a temperature of 60 °C and a vacuum pressure of 0.015 MPa. In these conditions, the flexural strength of the samples was 19.9 ± 0.4 MPa, the bulk density was 1.68 ± 0.02 g/cm3, and the porosity was 25.9 ± 0.9 %
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