New steel-concrete-steel sandwich composite structure using novel enhanced C-channels (ECs) and ultra-high performance concrete (UHPC) was firstly proposed. The ECs offered strong tension separation ...resistance of faceplates from UHPC core as well as faceplate-UHPC interfacial shear resistance. Then, two-point loading tests on nine steel-UHPC-steel sandwich beams with ECs (SUSSB-ECs) were performed to study their ultimate strength behaviour. The studied parameters are thickness of steel faceplate, spacing of ECs, shear span, and strength of core. From the tests, though the shear span had quite significant influences on the ultimate strength of SUSSB-ECs, but all SUSSB-ECs failed in flexure mode even for the SUSSB-EC with short shear span ratio of 2.41, which confirms the bonding efficiency of ECs and high performance of this novel sandwich composite structures. The faceplate thickness exhibited significant, but the spacing of ECs has marginal influences on ultimate strength behaviour of SUSSB-ECs. Besides the tests, theoretical models were also developed to predict the initial stiffness, elastic stiffness, cracking load, yielding load, and ultimate load of the SUSSB-ECs. The validations of the predictions on stiffness and strength show that the developed theoretical models offer reasonable estimations on the stiffness and strength of SUSSB-ECs with limited errors.
•Enhanced C-channels (ECs) offer effective bonding for steel-UHPC-steel sandwich beam (SUSSB).•SUSSB with novel ECs fails in ductile flexure mode even for SUSSB with short shear span.•Spacing of ECs has marginal influences on failure mode of SUSSB under four-point bending.•Parameters influencing flexural behavior of SUSSB are revealed and discussed.•Developed theoretical models predict well stiffness and strength of SUSSB with ECs.
Dendrite growth of alkali metal anodes limited their lifetime for charge/discharge cycling. Here, we report near-perfect anodes of lithium, sodium, and potassium metals achieved by electrochemical ...polishing, which removes microscopic defects and creates ultra-smooth ultra-thin solid-electrolyte interphase layers at metal surfaces for providing a homogeneous environment. Precise characterizations by AFM force probing with corroborative in-depth XPS profile analysis reveal that the ultra-smooth ultra-thin solid-electrolyte interphase can be designed to have alternating inorganic-rich and organic-rich/mixed multi-layered structure, which offers mechanical property of coupled rigidity and elasticity. The polished metal anodes exhibit significantly enhanced cycling stability, specifically the lithium anodes can cycle for over 200 times at a real current density of 2 mA cm
with 100% depth of discharge. Our work illustrates that an ultra-smooth ultra-thin solid-electrolyte interphase may be robust enough to suppress dendrite growth and thus serve as an initial layer for further improved protection of alkali metal anodes.
The ideal magnetocaloric material would lay at the borderline of a first-order and a second-order phase transition. Hence, it is crucial to unambiguously determine the order of phase transitions for ...both applied magnetocaloric research as well as the characterization of other phase change materials. Although Ehrenfest provided a conceptually simple definition of the order of a phase transition, the known techniques for its determination based on magnetic measurements either provide erroneous results for specific cases or require extensive data analysis that depends on subjective appreciations of qualitative features of the data. Here we report a quantitative fingerprint of first-order thermomagnetic phase transitions: the exponent n from field dependence of magnetic entropy change presents a maximum of n > 2 only for first-order thermomagnetic phase transitions. This model-independent parameter allows evaluating the order of phase transition without any subjective interpretations, as we show for different types of materials and for the Bean-Rodbell model.
Axially chiral styrenes bearing a chiral axis between a sterically non-congested acyclic alkene and an aryl ring are difficult to prepare due to low rotational barrier of the axis. Disclosed here is ...an N-heterocyclic carbene (NHC) catalytic asymmetric solution to this problem. Our reaction involves ynals, sulfinic acids, and phenols as the substrates with an NHC as the catalyst. Key steps involve selective 1,4-addition of sulfinic anion to acetylenic acylazolium intermediate and sequential E-selective protonation to set up the chiral axis. Our reaction affords axially chiral styrenes bearing a chiral axis as the product with up to > 99:1 e.r., > 20:1 E/Z selectivity, and excellent yields. The sulfone and carboxylic ester moieties in our styrene products are common moieties in bioactive molecules and asymmetric catalysis.
AbstractThis paper first proposes a high-strength (HS) steel-moment frame structure with replaceable damage-control fuses, which utilized the very large elastic deformation capacity of HS steel and ...damage-control functions of fuses. The damage is basically concentrated to fuses even under very rare earthquakes, and the damaged fuses can be easily replaced after earthquakes. A test program including 11 full-scale specimens was carried out to study the seismic behavior of HS steel beam-to-column joints either with or without fuses. The investigated parameters include different types of fuses, different thickness of the fuse plate, and different ways to strengthen the out-of-plane stiffness of fuse plates. The failure mode, deformation progress, hysteretic responses, skeleton curves, bending strengths, and energy-dissipation capacity of these full-scale tests were reported, analyzed, and discussed. Test results showed that the HS steel joints with fuses were able to provide large damage-free deformation. The application of proposed fuses in the HS steel-moment frame effectively shifted the damage from beam-to-column welds to replaceable fuse plates. Meanwhile, the shape of fuse plate exhibited marginal influence, but its thickness has significant influence on the T-joint. Formulas were proposed to estimate the yielding and ultimate bending strength of T-joint with fuses. Finally, a step-by-step procedure is given to design the proposed fuses.
Perovskite solar cells are strong competitors for silicon-based ones, but suffer from poor long-term stability, for which the intrinsic stability of perovskite materials is of primary concern. ...Herein, we prepared a series of well-defined cesium-containing mixed cation and mixed halide perovskite single-crystal alloys, which enabled systematic investigations on their structural stabilities against light, heat, water, and oxygen. Two potential phase separation processes are evidenced for the alloys as the cesium content increases to 10% and/or bromide to 15%. Eventually, a highly stable new composition, (FAPbI3)0.9(MAPbBr3)0.05(CsPbBr3)0.05, emerges with a carrier lifetime of 16 μs. It remains stable during at least 10 000 h water–oxygen and 1000 h light stability tests, which is very promising for long-term stable devices with high efficiency. The mechanism for the enhanced stability is elucidated through detailed single-crystal structure analysis. Our work provides a single-crystal-based paradigm for stability investigation, leading to the discovery of stable new perovskite materials.
We present a first-principles study of effects of small biaxial strain (varepsilon < or = 5%) and perpendicular electric field (E-field) on the electronic and phonon properties of low-buckled ...silicene and germanene. With an increase of the biaxial strain, the conduction bands at the high-symmetric Gamma and M points of the first Brillouin zone shift significantly towards the Fermi level in both silicene and germanene. In contrast, the E-field changes the band dispersions near the Gamma and open a small band gap at the K point in silicene. We found that the field-induced gap opening in silicene could be enhanced by a compressive strain while mitigated by a tensile strain. This result highlights the tunability of the electronic structure of silicene by combining mechanical strain and electric field.
Layered Ni‐rich lithium transition metal oxides are promising battery cathodes due to their high specific capacity, but their poor cycling stability due to intergranular cracks in secondary particles ...restricts their practical applications. Surface engineering is an effective strategy for improving a cathode's cycling stability, but most reported surface coatings cannot adapt to the dynamic volume changes of cathodes. Herein, a self‐adaptive polymer (polyrotaxane‐co‐poly(acrylic acid)) interfacial layer is built on LiNi0.6Co0.2Mn0.2O2. The polymer layer with a slide‐ring structure exhibits high toughness and can withstand the stress caused by particle volume changes, which can prevent the cracking of particles. In addition, the slide‐ring polymer acts as a physicochemical barrier that suppresses surface side reactions and alleviates the dissolution of transition metallic ions, which ensures stable cycling performance. Thus, the as‐prepared cathode shows significantly improved long‐term cycling stability in situations in which cracks may easily occur, especially under high‐rate, high‐voltage, and high‐temperature conditions.
A slide‐ring polymer featuring high elasticity and self‐adaptive ability is designed to improve the performance of lithium‐ion batteries via relieving the cracks of cathode particles and retarding parasitic interfacial side reactions during cycling.
Provided with mobile edge computing (MEC) services, wireless devices (WDs) no longer have to experience long latency in running their desired programs locally, but can pay to offload computation ...tasks to the edge server. Given its limited storage space, it is important for the edge server at the base station (BS) to determine which service programs to cache by meeting and guiding WDs' offloading decisions. In this article, we propose an MEC service pricing scheme to coordinate with the service caching decisions and control WDs' task offloading behavior in a cellular network. We propose a two-stage dynamic game of incomplete information to model and analyze the two-stage interaction between the BS and multiple associated WDs. Specifically, in Stage I, the BS determines the MEC service caching and announces the service program prices to the WDs, with the objective to maximize its expected profit under both storage and computation resource constraints. In Stage II, given the prices of different service programs, each WD selfishly decides its offloading decision to minimize individual service delay and cost, without knowing the other WDs' desired program types or local execution delays. Despite the lack of WD's information and the coupling of all the WDs' offloading decisions, we derive the optimal threshold-based offloading policy that can be easily adopted by the WDs in Stage II at the Bayesian equilibrium. In particular, a WD is more likely to offload when there are fewer WDs competing for the edge server's computation resource, or when it perceives a good channel condition or low MEC service price. Then, by predicting the WDs' offloading equilibrium, we jointly optimize the BS' pricing and service caching in Stage I via a low-complexity algorithm. In particular, we first study the differentiated pricing scheme and prove that the same price should be charged to the cached programs of the same workload. Motivated by this analysis, we further propose a low-complexity uniform pricing heuristics.
Since the outbreak of coronavirus disease 2019 (COVID-19), the National Health Commission of the People's Republic of China has issued a series of timely updated guidelines. 5–8 Type II alveolar ...epithelial cells show extensive hyperplasia, with some necrosis and desquamation. ...latest research has confirmed the postmortem persistence of 2019-nCoV in the lung tissue of the patients who experienced diffuse alveolar damage followed by rapidly evolving pulmonary fibrosis and respiratory failure. ...several complications, such as acute cardiac injury, acute kidney injury, abnormal coagulation function, shock, and even multi-organ dysfunction, tend to develop in critically ill patients. The previous clinical experience suggests that some patients with mild and moderate disease would inevitably evolve into critically ill states or may even die during hospitalization. ...the prognostic factors for patients at risk of developing more severe disease are of paramount importance in strengthening surveillance and enabling timely initiation of appropriate treatment.
PDF
