Surrogate models are often used as surrogates for computationally intensive simulations. And there are a variety of surrogate models which are widely used in aerospace engineering–related ...investigation and design. In general, there is an optimal individual surrogate for a certain research object. However, the behavior of an individual surrogate is unknown in advance. Building an ensemble of surrogates by combining different individual surrogates into a weighted-sum formulation is an efficient method to enhance the accuracy and robustness of the surrogate model. Motivated by the previous researches on the ensemble of surrogates, we propose an optimal pointwise weighted ensemble (OPWE) method, wherein the optimal pointwise weight factors are obtained based on the minimization of the local mean square error which is constructed by the global-local error (GLE). By using six well-known mathematical problems and four engineering problems, it is proved that the OPWE proposed in this paper is better than the other ensembles of surrogates in terms of both accuracy and robustness.
Hydrogenation reactions are industrially important reactions that typically require unfavorably high H2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong ...size‐dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size‐dependent d‐band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28‐fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal‐nanoparticle‐based catalysts for a broad range of organic syntheses.
Cat. size: The activity of Pt nanoparticles (PtNPs) in catalyzing the regioselective hydrogenation of quinoline (see picture) is strongly dependent on the size of the PtNPs. This dependence is rationalized by the size‐dependent d‐band electron structure of the PtNPs and thus their interactions with the reactants and the products.
Nitrogen-doped graphene (NG) is a promising conductive matrix material for fabricating high-performance Li/S batteries. Here we report a simple, low-cost, and scalable method to prepare an ...additive-free nanocomposite cathode in which sulfur nanoparticles are wrapped inside the NG sheets (S@NG). We show that the Li/S@NG can deliver high specific discharge capacities at high rates, that is, ∼1167 mAh g–1 at 0.2 C, ∼1058 mAh g–1 at 0.5 C, ∼971 mAh g–1 at 1 C, ∼802 mAh g–1 at 2 C, and ∼606 mAh g–1 at 5 C. The cells also demonstrate an ultralong cycle life exceeding 2000 cycles and an extremely low capacity-decay rate (0.028% per cycle), which is among the best performance demonstrated so far for Li/S cells. Furthermore, the S@NG cathode can be cycled with an excellent Coulombic efficiency of above 97% after 2000 cycles. With a high active S content (60%) in the total electrode weight, the S@NG cathode could provide a specific energy that is competitive to the state-of-the-art Li-ion cells even after 2000 cycles. The X-ray spectroscopic analysis and ab initio calculation results indicate that the excellent performance can be attributed to the well-restored C–C lattice and the unique lithium polysulfide binding capability of the N functional groups in the NG sheets. The results indicate that the S@NG nanocomposite based Li/S cells have a great potential to replace the current Li-ion batteries.
Abstract
Promoting the formation of high-oxidation-state transition metal species in a hydroxide catalyst may improve its catalytic activity in the oxygen evolution reaction, which remains difficult ...to achieve with current synthetic strategies. Herein, we present a synthesis of single-layer NiFeB hydroxide nanosheets and demonstrate the efficacy of electron-deficient boron in promoting the formation of high-oxidation-state Ni for improved oxygen evolution activity. Raman spectroscopy, X-ray absorption spectroscopy, and electrochemical analyses show that incorporation of B into a NiFe hydroxide causes a cathodic shift of the Ni
2+
(OH)
2
→ Ni
3+δ
OOH transition potential. Density functional theory calculations suggest an elevated oxidation state for Ni and decreased energy barriers for the reaction with the NiFeB hydroxide catalyst. Consequently, a current density of 100 mA cm
–2
was achieved in 1 M KOH at an overpotential of 252 mV, placing it among the best Ni-based catalysts for this reaction. This work opens new opportunities in electronic engineering of metal hydroxides (or oxides) for efficient oxygen evolution in water-splitting applications.
Converting carbon dioxide (CO
) into liquid fuels and synthesis gas is a world-wide priority. But there is no experimental information on the initial atomic level events for CO
electroreduction on ...the metal catalysts to provide the basis for developing improved catalysts. Here we combine ambient pressure X-ray photoelectron spectroscopy with quantum mechanics to examine the processes as Ag is exposed to CO
both alone and in the presence of H
O at 298 K. We find that CO
reacts with surface O on Ag to form a chemisorbed species (O = CO
). Adding H
O and CO
then leads to up to four water attaching on O = CO
and two water attaching on chemisorbed (b-)CO
. On Ag we find a much more favorable mechanism involving the O = CO
compared to that involving b-CO
on Cu. Each metal surface modifies the gas-catalyst interactions, providing a basis for tuning CO
adsorption behavior to facilitate selective product formations.
Photoelectrochemical (PEC) water splitting promises a solution to the problem of large-scale solar energy storage. However, its development has been impeded by the poor performance of photoanodes, ...particularly in their capability for photovoltage generation. Many examples employing photovoltaic modules to correct the deficiency for unassisted solar water splitting have been reported to-date. Here we show that, by using the prototypical photoanode material of haematite as a study tool, structural disorders on or near the surfaces are important causes of the low photovoltages. We develop a facile re-growth strategy to reduce surface disorders and as a consequence, a turn-on voltage of 0.45 V (versus reversible hydrogen electrode) is achieved. This result permits us to construct a photoelectrochemical device with a haematite photoanode and Si photocathode to split water at an overall efficiency of 0.91%, with NiFeOx and TiO2/Pt overlayers, respectively.
The sulfur cathode in traditional lithium–sulfur batteries suffers from poor cyclability due to polysulfide shuttling effect as well as large volume change during charge/discharge processes. Gum ...arabic (GA), a low cost, nontoxic, and sustainable natural polymer from Acacia senegal, is adopted as a binder for the sulfur cathode to address these issues. The excellent mechanical properties of GA endow the cathode with high binding strength and suitable ductility to buffer volume change, while the functional groups chemically and physically confine sulfur species within the cathode to inhibit the shuttling effect of polysulfides. Additionally, GA shifts the electrode fabrication process from the organic solvent process to an aqueous process, eliminates the use of toxic organic solvents, and achieves uniformly distributed electrode with lower impedance. A remarkable cycling performance, i.e., 841 mAh g−1 at low current rate of C/5, is achieved throughout 500 cycles due to the bifunctions of the GA binder.
The gum arabic (GA) binder‐based sulfur cathode (75 wt% sulfur) is evaluated under long‐term cycling at C/5. The excellent mechanical properties of GA endow the S@GA cathode with high binding strength and suitable ductility to buffer volume change, while the functional groups chemically and physically confine sulfur species within the cathode to inhibit the shuttling effect of the polysulfides.
The electrochemical CO2 reduction reaction (CO2RR) using Cu-based catalysts holds great potential for producing valuable multi-carbon products from renewable energy. However, the chemical and ...structural state of Cu catalyst surfaces during the CO2RR remains a matter of debate. Here, we show the structural evolution of the near-surface region of polycrystalline Cu electrodes under in situ conditions through a combination of grazing incidence X-ray absorption spectroscopy (GIXAS) and X-ray diffraction (GIXRD). The in situ GIXAS reveals that the surface oxide layer is fully reduced to metallic Cu before the onset potential for CO2RR, and the catalyst maintains the metallic state across the potentials relevant to the CO2RR. We also find a preferential surface reconstruction of the polycrystalline Cu surface toward (100) facets in the presence of CO2. Quantitative analysis of the reconstruction profiles reveals that the degree of reconstruction increases with increasingly negative applied potentials, and it persists when the applied potential returns to more positive values. These findings show that the surface of Cu electrocatalysts is dynamic during the CO2RR, and emphasize the importance of in situ characterization to understand the surface structure and its role in electrocatalysis.
As a prerequisite for pollution control, monitoring air pollutants is crucial. In recent years, all walks of life are developing toward intelligence, and the concept of intelligent ports is also the ...development direction of current port planning. A lot of work such as loading and unloading of port cargo and planning has now achieved intellectual development, and the monitoring of air pollutants in ports also needs to be developed towards intelligence. However, at present, there are not many air pollutant monitoring systems for ports. In order to find monitoring equipment and models that are better suited to the port environment, this paper focuses on the main components of air pollutants in ports (SO2, NOX, PM, etc.) and their sources and describes the monitoring methods and principles for these pollutants in ports and on ships, respectively. Regarding monitoring methods, the current application of DOAS (Differential Optical Absorption Spectroscopy) equipment and the monitoring system based on various gas sensors have great development prospects and advantages, based on the monitoring system being more intelligent. At the same time, the use of the same monitoring principle for a variety of pollutants monitoring equipment to a certain extent can save the cost and efficiency of monitoring. In terms of monitoring mode, the combination of manual analysis and automatic analysis will be perfect for the port’s air pollutant monitoring system. This mode can alleviate the embarrassment of the low life of the sensor-based monitoring system to a certain extent, and the data monitored by this mode will be more accurate.
Clinical studies have shown that miRNAs are closely related to human health. The study of potential associations between miRNAs and diseases will contribute to a profound understanding of the ...mechanism of disease development, as well as human disease prevention and treatment. MiRNA-disease associations predicted by computational methods are the best complement to biological experiments.
In this research, a federated computational model KATZNCP was proposed on the basis of the KATZ algorithm and network consistency projection to infer the potential miRNA-disease associations. In KATZNCP, a heterogeneous network was initially constructed by integrating the known miRNA-disease association, integrated miRNA similarities, and integrated disease similarities; then, the KATZ algorithm was implemented in the heterogeneous network to obtain the estimated miRNA-disease prediction scores. Finally, the precise scores were obtained by the network consistency projection method as the final prediction results. KATZNCP achieved the reliable predictive performance in leave-one-out cross-validation (LOOCV) with an AUC value of 0.9325, which was better than the state-of-the-art comparable algorithms. Furthermore, case studies of lung neoplasms and esophageal neoplasms demonstrated the excellent predictive performance of KATZNCP.
A new computational model KATZNCP was proposed for predicting potential miRNA-drug associations based on KATZ and network consistency projections, which can effectively predict the potential miRNA-disease interactions. Therefore, KATZNCP can be used to provide guidance for future experiments.
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