In order to solve the basic problem of high-temperature sintering of molybdenum carbide restricting the efficient construction of molybdenum carbide nanostructures and the full play of hydrogen ...evolution performance, this article studies the preparation of nano molybdenum carbide/boron nitrogen codoped two-dimensional carbon composite structure catalysts and the electrochemical hydrogen evolution reaction performance. Based on the self-assembly process of gelatin molecules on the surface of a two-dimensional layered boric acid crystal template, a new strategy for constructing a high-performance electrochemical hydrogen evolution reaction catalyst based on molybdenum carbide/boron nitrogen codoped two-dimensional nanocarbon composite structure (η-MoC@ BN-CSs) was established. The experimental results show that the overpotential of hydrogen evolution reaction based on molybdenum carbide/boron nitrogen codoped two-dimensional nanocarbon composite structure catalyst is 159 mV, which is slightly higher than 67 mV of commercial Pt/C catalyst, but lower than the reported literature value in the list. The Tafel slope is 68 mV·dec−1, which is slightly higher than that of the commercial Pt/C catalyst (40 mV·dec−1) and the reference value (58 mV·dec−1), but lower than those of other reported literature values in the list, indicating that the molybdenum carbide/boron nitrogen codoped two-dimensional carbon nanocomposites have excellent catalytic performance under alkaline conditions. Conclusion. This kind of two-dimensional nanocomposite structure shows platinum-like catalytic activity when used as an electrochemical hydrogen evolution catalyst in alkaline electrolyte. It has better reaction kinetics and better stability.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Blending a certain proportion of basalt fiber into concrete improves the toughness of concrete, which prevents cracking and avoids the brittle behaviors. In this paper, the compressive, tensile, and ...flexural tests of concrete with different basalt fiber contents were carried out. Then the test phenomena, failure modes, and mechanical properties were compared and analyzed to derive the relationship between the basalt fiber contents and mechanical properties. The toughness and crack resistance performance of basalt fiber reinforced concrete were evaluated by the fracture energy, advanced toughness parameters, and characteristic length proposed by Hillerborg. The correlation coefficient of basalt fiber was introduced to establish the calculation formula for mechanical properties of basalt fiber reinforced concrete. The results indicated that basalt fiber significantly improved the toughness and crack resistance performance of concrete. The enhancing effect of the basalt fiber on the compressive strength of concrete is lower than that of tensile strength and flexural strength. Moreover, the improvement effect was the highest with the basalt fiber content was 0.3% and 0.4%.
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Complex concentrated solutions of multiple principal elements are being widely investigated as high- or medium-entropy alloys (HEAs or MEAs)
, often assuming that these materials have the high ...configurational entropy of an ideal solution. However, enthalpic interactions among constituent elements are also expected at normal temperatures, resulting in various degrees of local chemical order
. Of the local chemical orders that can develop, chemical short-range order (CSRO) is arguably the most difficult to decipher and firm evidence of CSRO in these materials has been missing thus far
. Here we discover that, using an appropriate zone axis, micro/nanobeam diffraction, together with atomic-resolution imaging and chemical mapping via transmission electron microscopy, can explicitly reveal CSRO in a face-centred-cubic VCoNi concentrated solution. Our complementary suite of tools provides concrete information about the degree/extent of CSRO, atomic packing configuration and preferential occupancy of neighbouring lattice planes/sites by chemical species. Modelling of the CSRO order parameters and pair correlations over the nearest atomic shells indicates that the CSRO originates from the nearest-neighbour preference towards unlike (V-Co and V-Ni) pairs and avoidance of V-V pairs. Our findings offer a way of identifying CSRO in concentrated solution alloys. We also use atomic strain mapping to demonstrate the dislocation interactions enhanced by the CSROs, clarifying the effects of these CSROs on plasticity mechanisms and mechanical properties upon deformation.
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GEOZS, IJS, IMTLJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Manganese oxides are the strongest natural oxidants in our environments aside from oxygen. Most natural manganese oxides are produced through the Mn(II) oxidation process driven by microbes. Biogenic ...manganese oxides (BioMnOx) are usually amorphous and rich in defects and possess large surface areas, resulting in high oxidative reactivity and strong absorption capacity for many emerging pollutants. Up to date, numerous of Mn(II) oxidation microbes (MnOM) have been isolated and characterized. Both directly enzymatic or indirectly abiotic Mn(II) oxidation processes were found in MnOM, but a systemic summarization about the Mn(II) oxidation mechanism is still lack. Moreover, the differentiation among BioMnOx produced by different MnOM needs to compare. As a potential oxidant and catalyst for pollutants removal, the role of BioMnOx in environmental remediation is also rarely mentioned. In this review, we focus on the Mn(II) oxidation process mediated by different MnOM, including their Mn(II) oxidation characterization and putative mechanism, as well as characterization of BioMnOx, and BioMnOx-related environmental remediation processes.
•Backbone neighborhood distribution points are reduced to facilitate classification.•Dual-scale backbone features are combined for accurate width measurement direction.•A detailed visual measurement ...process of crack width is proposed.•A visual measurement method of crack width that is closer to reality is used to obtain more accurate results.
State-of-the-art machine-vision systems have limitations associated with crack width measurements. The sample points used to describe the crack width are often subjectively defined by experimenters, which obscures the crack width ground truth. Consequently, in most related studies, the uncontrollable system errors of vision modules result in unsatisfactory measurement accuracy. In this study, the cracks of a reservoir dam are taken as objects, and a new crack backbone refinement algorithm and width-measurement scheme are proposed. The algorithm simplifies the redundant data in the crack image and improves the efficiency of crack-shape estimation. Further, an effective definition of crack width is proposed that combines the macroscale and microscale characteristics of the backbone to obtain accurate and objective sample points for width description. Compared with classic methods, the average simplification rate of the crack backbone and the average error rate of direction determination are all improved. The results of a series of experiments validate the efficacy of the proposed method by showing that it can improve detection automation and has potential engineering application.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Motivated by the implications from a stylized self-contained general equilibrium model incorporating the effects of time-varying economic uncertainty, we show that the difference between implied and ...realized variation, or the variance risk premium, is able to explain a nontrivial fraction of the time-series variation in post-1990 aggregate stock market returns, with high (low) premia predicting high (low) future returns. Our empirical results depend crucially on the use of "model-free," as opposed to Black-Scholes, options implied volatilities, along with accurate realized variation measures constructed from high-frequency intraday as opposed to daily data. The magnitude of the predictability is particularly strong at the intermediate quarterly return horizon, where it dominates that afforded by other popular predictor variables, such as the P/E ratio, the default spread, and the consumption-wealthratio.
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BFBNIB, INZLJ, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK, ZRSKP
Despite the recent success of deep learning in video-related tasks, deep models typically focus on the most discriminative features, ignoring other potentially non-trivial and informative contents. ...Such characteristic heavily constrains their capability to learn implicit visual grammars in sign videos behind the collaboration of different visual cues (i.e., hand shape, facial expression and body posture). To this end, we approach video-based sign language understanding with multi-cue learning and propose a spatial-temporal multi-cue (STMC) network to solve the vision-based sequence learning problem. Our STMC network consists of a spatial multi-cue (SMC) module and a temporal multi-cue (TMC) module. The SMC module learns to spatial representation of different cues with a self-contained pose estimation branch. The TMC module models temporal corrections from intra-cue and inter-cue perspectives to explore the collaboration of multiple cues. A joint optimization strategy and a segmented attention mechanism are designed to make the best of multi-cue sources for SL recognition and translation. To validate the effectiveness, we perform experiments on three large-scale sign language benchmarks: PHOENIX-2014, CSL and PHOENIX-2014-T. Experimental results demonstrate that the proposed method achieves new state-of-the-art performance on all three benchmarks.
Positron emission tomography (PET) imaging is an imaging modality for diagnosing a number of neurological diseases. In contrast to Magnetic Resonance Imaging (MRI), PET is costly and involves ...injecting a radioactive substance into the patient. Motivated by developments in modality transfer in vision, we study the generation of certain types of PET images from MRI data. We derive new flow-based generative models which we show perform well in this small sample size regime (much smaller than dataset sizes available in standard vision tasks). Our formulation, DUAL-GLOW, is based on two invertible networks and a relation network that maps the latent spaces to each other. We discuss how given the prior distribution, learning the conditional distribution of PET given the MRI image reduces to obtaining the conditional distribution between the two latent codes w.r.t. the two image types. We also extend our framework to leverage ``side'' information (or attributes) when available. By controlling the PET generation through ``conditioning'' on age, our model is also able to capture brain FDG-PET (hypometabolism) changes, as a function of age. We present experiments on the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset with 826 subjects, and obtain good performance in PET image synthesis, qualitatively and quantitatively better than recent works.
In this letter, we propose a generalized nested array (GNA) with two flexible co-prime factors for enlarging the inter-element spacing of two concatenated uniform linear subarrays. It is shown that ...both the prototype nested array and generalized co-prime array can be interpreted as special cases. The closed-form expressions for the range of consecutive lags and the number of unique lags are derived for any given factors. After optimization, GNA has the same number of degrees of freedom as (super) nested array but with reduced mutual coupling. Numerical simulations prove the superiority of proposed configuration using compressed sensing algorithm.
Mesoporous Zn4O(−COO)6-based metal–organic frameworks (MOFs), including UMCM-1, MOF-205, MUF-7a, and the newly synthesized MOFs, termed ST-1, ST-2, ST-3, and ST-4 (ST = ShanghaiTech University), ...have been systematically investigated for ultrahigh capacity methane storage. Exceptionally, ST-2 was found to have the highest deliverable capacity of 289 cm3 STP/cm3 (567 mg/g) at 298 K and 5–200 bar, which surpasses all previously reported records held by porous materials. We illustrate that the fine-tuned mesoporosity is critical in further improving the deliverable capacities at ultrahigh pressure.
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