Lithium metal is an ideal anode for lithium batteries due to its low electrochemical potential and high theoretical capacity. However, safety issues arising from lithium dendrite growth have ...significantly reduced the practical applicability of lithium metal batteries. Here, we report the addition of octaphenyl polyoxyethylene as an electrolyte additive to enable a stable complex layer on the surface of the lithium anode. This surface layer not only promotes uniform lithium deposition, but also facilitates the formation of a robust solid-electrolyte interface film comprising cross-linked polymer. As a result, lithium|lithium symmetric cells constructed using the octaphenyl polyoxyethylene additive exhibit excellent cycling stability over 400 cycles at 1 mA cm
, and outstanding rate performance up to 4 mA cm
. Full cells assembled with a LiFePO
cathode exhibit high rate capability and impressive cyclability, with capacity decay of only 0.023% per cycle.
Voltage feedback flux-weakening control has the advantages of simplicity and robustness against parameter variation. However, due to less voltage control margin in the flux-weakening region, the ...increased feedback voltage ripple could deteriorate the system performance in the flux-weakening region and may even cause oscillation. In this article, based on a nonsalient permanent magnet synchronous machine, the steady-state feedback voltage ripple in the flux-weakening region are analyzed first. It shows that the feedback voltage ripple caused by the current command ripple could dominate in some flux-weakening regions. Consequently, the speed bandwidth based on the conventional speed proportional-integral (PI) controller in the flux-weakening region can be hardly increased, which leads to poor dynamic performance. In order to obtain both fast speed dynamics and less steady-state ripple, especially in the flux-weakening region, an adaptive fuzzy logic (FLC) speed controller is designed and compared with the conventional speed PI controller. With the adaptive FLC, the dc-link voltage utilization can be increased and better flux-weakening capability can be obtained. Finally, the improved performances are verified by the experimental results.
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•We present vibrational partition function for the improved Manning-Rosen potential.•Analytical expressions of four thermodynamic functions are given.•Behaviors of the thermodynamic ...functions for the Na2 molecule are discussed.
We present a closed-form expression of the classical vibrational partition function for the improved Rosen-Morse potential energy model. We give explicit expressions for the vibrational mean energy, vibrational specific heat, vibrational free energy, and vibrational entropy for diatomic molecule systems. The properties of these thermodynamic functions for the Na2 dimer are discussed in detail. We find that the improved Rosen-Morse potential model is superior to the harmonic oscillator in calculating the heat capacity for the Na2 molecules.
It is of great significance to develop highly efficient and superior stable oxygen evolution reaction (OER) electrocatalysts for upcoming electrochemical conversion technologies and clean energy ...systems. Here, an assembled 3D electrode is synthesized by a one‐step solvothermal process using such an original OER electrocatalyst. During the solvothermal process, Ni ions released from Ni foam in acidic solution and Fe ions added exogenously act as metal centers and coordinate with terephthalic acid (TPA) organic molecules by robust coordinate bonds, and finally, NiFe‐based metal–organic framework (MOF) nanosheets in situ grown on Ni foam, i.e., MIL‐53(FeNi)/NF, are prepared. This binder‐free 3D electrode shows superior OER activity with high current density (50 mA cm−2) at an overpotential of 233 mV, a Tafel slope of 31.3 mV dec−1, and excellent stability in alkaline aqueous solution (1 m KOH). It is discovered that introduction of Fe into MIL‐53 structure increases electrochemically‐active areas as well as reaction sites, accelerated electron transport capability, and modulated electronic structure to enhance catalytic performance. Besides, first principles calculations show that MIL‐53(FeNi) is more favorable for foreign atoms' adsorption and has increased 3d orbital electron density boosting intrinsic activity. This work elucidates a promising electrode for electrocatalysts and enriches direct application of MOF materials.
Metal–organic framework nanosheets are successfully grown on a conductive Ni foam surface, as a binder‐free 3D electrode and applied to catalyzing the oxygen evolution reaction. This electrode delivers excellent catalytic activity and superior stability with a current density of 50 mA cm−2 at an overpotential as low as 233 mV. The reaction mechanism is explored with the assistance of density functional theory calculations.
In this paper, a transmission protocol is studied for a two relay wireless network in which simple repetition coding is applied at the relays. Information-theoretic achievable rates for this ...transmission scheme are given, and a space-time V-BLAST signalling and detection method that can approach them is developed. It is shown through the diversity multiplexing tradeoff analysis that this transmission scheme can recover the multiplexing loss of the half-duplex relay network, while retaining some diversity gain. This scheme is also compared with conventional transmission protocols that exploit only the diversity of the network at the cost of a multiplexing loss. It is shown that the new transmission protocol offers significant performance advantages over conventional protocols, especially when the interference between the two relays is sufficiently strong.
Hong Kong presents a test case of China’s willingness to adapt Western liberal values of individual freedom and the rule of law in a corner of China. The Western model of governance, along with its ...common law system and capitalist economic system, has been permitted to operate side by side with the Chinese socialist system within the framework of Chinese sovereignty and the People’s Republic of China’s (PRC) political and legal system. The formation and implementation of the policy of ‘one country, two systems’ (OCTS) entail Chinese law-makers’ selective integration of international and Western rules of governance into the Hong Kong and China context to serve the interests of the PRC party regime. This article explores the approaches taken by the PRC to the governance of Hong Kong in light of the regime’s political and economic goals and how the Western concept of rule of law and autonomy is perceived and substantiated in terms of the communist ideology. The author argues that the intrinsic value of OCTS lies in seeking complementarity and coexistence between the Western liberal norms of governance and Chinese communist ideology, and that this intrinsic value should be upheld and remain in full force to serve as a normative consensus between China and the West.
Oxygen evolution reaction (OER) is a pivotal reaction in many technologies for renewable energy, such as water splitting, metal–air batteries, and regenerative fuel cells. However, this reaction is ...known to be kinetically sluggish and proceeds at rather high overpotential due to the universal scaling relationship, namely, the adsorption energies of intermediates are linearly correlated and cannot be optimized simultaneously. Several approaches have been proposed to break the scaling relationship by introducing additional active sites; however, positive experimental results are still absent. Herein, a different solution is suggested on the basis of dynamic tridimensional adsorption of the OER intermediates at NiO/NiFe layered double hydroxide intersection, by which the adsorption energy of each intermediate can be adjusted independently, so as to bypass the scaling relationship and achieve high catalytic performance. Experimentally, the OER overpotential is reduced to ≈205 mV at current density of 30 mA cm−2, which represents the best performance achieved by state‐of‐the‐art OER catalysts.
The oxygen evolution reaction (OER), a key reaction for energy conversion and storage, is kinetically sluggish due to the limits of the scaling relationship. A strategy to bypass the scaling relationship through dynamic tridimensional adsorption of OER intermediates is reported, and OER overpotential is reduced to 205 mV at current density of 30 mA cm−2.
Monodisperse dumbbell-like Pt−Fe3O4 nanoparticles are synthesized by epitaxial growth of Fe onto Pt nanoparticles followed by Fe oxidation. The nanoparticle size in the structure is tunable from 2 to ...8 nm for Pt and 6 to 20 nm for Fe3O4. Pt nanoparticles in the Pt−Fe3O4 structure show a 20-fold increase in mass activity toward oxygen reduction reaction compared with the single component Pt nanoparticles and the commercial 3 nm Pt particles. The work proves that it is possible to maximize catalytic activity of the Pt nanoparticle catalyst through the control not only of Pt size and shape but also of its interaction with Fe3O4 nanoparticles.
Livestock grazing is an important component and driver of biodiversity in grassland ecosystems. While numerous studies and a few meta-analyses had been conducted on the response of single taxon ...diversity to grazing in grasslands, a synthesis of how multi-taxa diversity is affected has been largely missing, especially reflecting its changes along a grazing intensity gradient. We performed a comprehensive meta-analyses of 116 published studies on the species richness (SR) and Shannon−Wiener index (H′) of plants, arthropods, and microbes to examine the response of biodiversity to grazing intensity in temperate grasslands globally. This quantitative assessment showed that the response of SR and H′ to grazing intensity agreed with the intermediate disturbance hypothesis in grasslands; SR and H′ increased with light and moderate grazing intensities, while they decreased at heavy intensity. In addition, plant SR increased markedly with light and moderate grazing and declined with heavy grazing intensity; however, H′ increased at light intensity and declined at moderate and heavy intensities. Moreover, the SR and H′ of microbes were enhanced at light and moderate grazing and were significantly reduced with heavy intensity. The SR and H′ of arthropods monotonously declined with increasing grazing intensity. Importantly, structural equation modeling showed that grazing resulted in enhanced plant SR mainly through its negative effects on plant biomass. Grazing had negative effects on plant coverage and arthropod abundance so that arthropod SR declined with increased grazing intensity. Moreover, increased grazing intensity caused an increase in soil pH, decrease in soil moisture, and then a decrease in microbe SR. Our findings confirm that different taxa exhibit diverse responses to changes in grazing intensity, and the way that grazing intensity affects diversity also varied with different taxa. We strongly recommend considering the requirements of multi-taxa diversity when applying grazing management and including arthropods and microbes in monitoring schemes.
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