Compressive surface strains have been necessary to boost oxygen reduction reaction (ORR) activity in core/shell M/platinum (Pt) catalysts (where M can be nickel, cobalt, or iron). We report on a ...class of platinum-lead/platinum (PtPb/Pt) core/shell nanoplate catalysts that exhibit large biaxial strains. The stable Pt (110) facets of the nanoplates have high ORR specific and mass activities that reach 7.8 milliampere (mA) per centimeter squared and 4.3 ampere per milligram of platinum at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. Density functional theory calculations reveal that the edge-Pt and top (bottom)-Pt (110) facets undergo large tensile strains that help optimize the Pt-O bond strength. The intermetallic core and uniform four layers of Pt shell of the PtPb/Pt nanoplates appear to underlie the high endurance of these catalysts, which can undergo 50,000 voltage cycles with negligible activity decay and no apparent structure and composition changes.
Developing highly effective and stable counter electrode (CE) materials to replace rare and expensive noble metals for dye‐sensitized and perovskite solar cells (DSC and PSC) is a research hotspot. ...Carbon materials are identified as the most qualified noble metal‐free CEs for the commercialization of the two photovoltaic devices due to their merits of low cost, excellent activity, and superior stability. Herein, carbonaceous CE materials are reviewed extensively with respect to the two devices. For DSC, a classified discussion according to the morphology is presented because electrode properties are closely related to the specific porosity or nanostructure of carbon materials. The pivotal factors influencing the catalytic behavior of carbon CEs are also discussed. For PSC, an overview of the new carbon CE materials is addressed comprehensively. Moreover, the modification techniques to improve the interfacial contact between the perovskite and carbon layers, aiming to enhance the photovoltaic performance, are also demonstrated. Finally, the development directions, main challenges, and coping approaches with respect to the carbon CE in DSC and PSC are stated.
Carbon counter electrode materials for dye‐sensitized and perovskite solar cells are summarized extensively. The specific morphology and structure design of the carbon counter electrode in dye‐sensitized solar cells and the intrinsic features, energy level alignment, and interface engineering of the perovskite/carbon interface in perovskite solar cells are emphasized.
Lanthanide MOFs (Ln-MOFs), {Ln2(L)2(H2O)2·5H2O·6DMAC}n, Ln||| = Eu(1) and Tb(2); H3L = 4,4′-(((5-carboxy-1,3-phenylene)bis(azanediyl))bis(carbonyl)) dibenzoic acid, DMAC = N,N′-dimethylacetamide, ...with a new topology type have been isolated. Single crystal X-ray diffraction indicates that complexes 1 and 2 are isostructural with binuclear Eu2(COO)7n secondary building units as 7-connected nodes and H3L ligands as 3-connected nodes and can be viewed as a (5,7)-connected 3D framework with a new topological point symbol of {32·44·54} {34·46·56·65}. Complexes 1 and 2 exhibit an excellent luminescence sensing response to inorganic ions Fe3+, Cr2O72−, MnO4− and 4-nitrophenol, with a low detection limit and high Ksv value. Interestingly, when the MnO4− ions are detected, the color of the solid sample is observed to change from yellow to brown, visually indicating luminescence induction, which makes the process of detecting MnO4− ions simpler and more practical. Moreover, by using time-resolved photoluminescence techniques, complex 1 can effectively eliminate background fluorescence interference during detection and improve detection accuracy. Solvent luminescence studies, pH stability and PXRD data indicate that complexes 1 and 2 can be used as excellent water-stable multi-response luminescent sensors for detecting a wide variety of toxic substances. In addition, the mechanism of selective detection is explained by the energy competition between the excitation of complexes 1 and 2 and the ultraviolet absorption of the responsive substance.
In the airborne or spaceborne radar applications, prolonging the coherent integration time is one of the effective methods to improve the radar detection ability of a weak maneuvering target, whereas ...the coherent integration performance may degrade due to the complex range migration (RM) and Doppler frequency migration (DFM) effects. In this paper, detection and motion parameter estimation for a weak maneuvering target with the third-order RM and DFM are considered. Firstly, Keystone transform is applied to compensate the linear range walk. Then, the matched filtering processing is performed in the range-frequency and azimuth-time domain to eliminate the residual coupling effects between range and azimuth. Finally, a well-focused image of a moving target is obtained, and three motion parameters, i.e., velocity, acceleration, and acceleration rate, are effectively estimated. In addition, as for a fast-moving target with Doppler ambiguity, two cases, i.e., target azimuth spectrum within a pulse repetition frequency (PRF) and spanning over neighboring PRF bands, are analyzed. Compared with the generalized Radon Fourier transform (GRFT), the proposed method can acquire a close integration performance but with lower computational complexity since the parameter searching dimension is reduced. Simulated processing results are provided to validate the effectiveness of the proposed method.
Urbanization has eco-environmental consequences; among which are effects on the urban thermal environment, which have drawn extensive attention especially in metropolitan regions having intensive ...population and high building density. In this study, the variation of the thermal environment during the urbanization process from 2001 to 2009 in the Beijing metropolitan region was evaluated using the spatial Lorenz curve and distribution index. In addition, the effects of landscape composition and spatial configuration on the thermal environment were investigated using correlation analysis and piecewise linear regression. The urban heat island (UHI) was found to be much more significant in summer than in spring, autumn and winter. Furthermore, the magnitude of the urban thermal environment in Beijing has increased during the process of urbanization. The suburban areas of Beijing, including the new urban development zone and ecological conservation zone, have increased the magnitude of the thermal environment. However, the opposite effect has occurred in the center of Beijing, including the core functional zone and urban function extended zone. Landscape types such as built-up areas and barren land make the most significant contribution to the thermal environment, whereas ecological land plays a significant role in mitigating the UHI. When the coverage of ecological land exceeded 70% (25km2) of the total land area, the cooling efficiency of this landscape type was relatively obvious, and the shape index and fragmentation index of landscape configuration both had a significantly positive correlation (0.594 and 0.510 Pearson's coefficients, respectively) with average land surface temperature. The Pearson's coefficient between the ecological land proportion and the average land surface temperature was 0.614 (P<0.01); this value was higher than that for the effects of the spatial configuration, indicating that landscape composition affects the thermal environment more than does spatial configuration.
•LST dynamic was examined in Beijing during 2001–2009.•LST increased averagely in the whole metropolitan area but decreased in city center.•Built-up areas and barren land contribute most to UHI.•Cooling effects of ecological land is obvious with the proportion above 70%.•LST is determined more by landscape composition than spatial configuration.
Recently, the newly emerging lead-halide perovskites have received tremendous attention in the photodetection field because of their intrinsic large light absorption and high well-balanced carrier ...transport characteristics. Unfortunately, the issue of instability and the existence of toxic lead cations have greatly restricted their practical applications and future commercialization. Furthermore, the previous studies on perovskite photodetectors mainly operate in visible and near-infrared light region, and there are practically no relevant reports aimed at the deep-ultraviolet (DUV) region. In this study, an air-stable and DUV-sensitive photoconductive detector was demonstrated with a solution-processed ternary copper halides Cs
3
Cu
2
I
5
thin films as the light absorber. The proposed photodetector is very sensitive to wavelengths of light below 320 nm and unresponsive to the visible light. Because of the high material integrity and large surface coverage of the Cs
3
Cu
2
I
5
thin films, the detector presents an outstanding photodetection performance with a photoresponsivity of ∼17.8 A W
−1
, specific detectivity of 1.12 × 10
12
Jones, and fast response speed of 465/897 μs, superior to previously reported DUV photodetectors based on other material systems. Unlike traditional lead-halide perovskites, the lead-free Cs
3
Cu
2
I
5
shows remarkable stability against heat, UV light, and environmental oxygen/moisture. Thus, the unsealed photodetector demonstrates good operation stability for 11 h of continuous running in open air. Even after 80-day storage in ambient air, its photodetection capability can nearly be maintained. The results suggest that non-toxic Cs
3
Cu
2
I
5
could be a potential candidate for stable and environment friendly DUV detectors, enabling an assembly of optoelectronic systems in the future.
An air-stable and deep-ultraviolet-sensitive photodetector was fabricated using a solution-processed ternary copper halide Cs
3
Cu
2
I
5
thin film as the light absorber.
The 2019 novel coronavirus (2019-nCoV) causing an outbreak of pneumonia in Wuhan, Hubei province of China was isolated in January 2020. This study aims to investigate its epidemiologic history, and ...analyze the clinical characteristics, treatment regimens, and prognosis of patients infected with 2019-nCoV during this outbreak.
Clinical data from 137 2019-nCoV-infected patients admitted to the respiratory departments of nine tertiary hospitals in Hubei province from December 30, 2019 to January 24, 2020 were retrospectively collected, including general status, clinical manifestations, laboratory test results, imaging characteristics, and treatment regimens.
None of the 137 patients (61 males, 76 females, aged 20-83 years, median age 57 years) had a definite history of exposure to Huanan Seafood Wholesale Market. Major initial symptoms included fever (112/137, 81.8%), coughing (66/137, 48.2%), and muscle pain or fatigue (44/137, 32.1%), with other, less typical initial symptoms observed at low frequency, including heart palpitations, diarrhea, and headache. Nearly 80% of the patients had normal or decreased white blood cell counts, and 72.3% (99/137) had lymphocytopenia. Lung involvement was present in all cases, with most chest computed tomography scans showing lesions in multiple lung lobes, some of which were dense; ground-glass opacity co-existed with consolidation shadows or cord-like shadows. Given the lack of effective drugs, treatment focused on symptomatic and respiratory support. Immunoglobulin G was delivered to some critically ill patients according to their conditions. Systemic corticosteroid treatment did not show significant benefits. Notably, early respiratory support facilitated disease recovery and improved prognosis. The risk of death was primarily associated with age, underlying chronic diseases, and median interval from the appearance of initial symptoms to dyspnea.
The majority of patients with 2019-nCoV pneumonia present with fever as the first symptom, and most of them still showed typical manifestations of viral pneumonia on chest imaging. Middle-aged and elderly patients with underlying comorbidities are susceptible to respiratory failure and may have a poorer prognosis.
Temperature can govern morphologies, structures and properties of products from synthesis in solution. A reaction in solution at low temperature may result in different materials than at higher ...temperature due to thermodynamics and kinetics of nuclei formation. Here, we report a low-temperature solution synthesis of atomically dispersed cobalt in a catalyst with superior performance. By using a water/alcohol mixed solvent with low freezing point, liquid-phase reduction of a cobalt precursor with hydrazine hydrate is realized at -60 °C. A higher energy barrier and a sluggish nucleation rate are achieved to suppress nuclei formation; thus atomically dispersed cobalt is successfully obtained in a catalyst for oxygen reduction with electrochemical performance superior to that of a Pt/C catalyst. Furthermore, the atomically dispersed cobalt catalyst is applied in a microbial fuel cell to obtain a high maximum power density (2550 ± 60 mW m
) and no current drop upon operation for 820 h.
Amidst the rapid evolution of the digital economy, this research positions fuzzy rough set theory at the forefront of industrial economic modeling, acknowledging its profound capability to manage ...uncertain information. This theory’s analytical precision facilitates a deep dive into the dynamics of industrial economic growth, enabling the refinement of industrial structures for sustainable development. Our empirical investigation into region A’s grain industry showcases a remarkable output growth of 272.88% from 2008 to 2018, with a model accuracy exceeding 95%. Analysis on cost inputs further demonstrates how innovation in science and technology plays a crucial role in cost reduction. By leveraging fuzzy rough set theory, this work contributes significantly to the strategic development of industrial economics, offering a robust methodology for data-driven analysis and forecasting in industrial sectors.
This paper first analyzes the effective application of web platforms and information technology in college teaching and constructs a web-based teaching aid platform for college courses based on the ...open Web. Secondly, the A3C algorithm is used to implement adaptive coding decisions to improve the performance of the platform by adaptive network coding. Finally, the performance test analysis is conducted for the web teaching aid platform built in this paper. The results show that the average response time of the system using the communication function with 2000 concurrent users is 1.807s, and the CPU and memory usage are 1146MHz and 1486MB, respectively, after running for 25s. This shows that adaptive network coding can effectively improve the performance of the supplementary teaching platform.
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