Intensification of short‐duration rainfall extremes contributes to increased urban flood risk. Yet, it remains unclear how upper‐tail rainfall statistics could change with regional warming. Here, we ...characterize the non‐stationarity of rainfall extremes over durations of 1–24 hr for the rapidly developing coastal megalopolis of the Greater Bay Area, China. Using high‐resolution, multi‐source, merged and gridded data we observe greater increases in rainfall intensities over the north‐central part of the region compared with the southern coastal region. Our results show, for the first time, that urbanization nonlinearly increases rainfall intensities at different durations and return periods. Over short durations (≤3‐hr) and short return periods (2‐yr), urban areas have the greatest scaling rates (≥19.9%/°C). However, over longer durations (≥9‐hr) rural areas have greater scaling rates, with a lower degree of dependency on both durations and return periods.
Plain Language Summary
Short‐duration (sub‐daily) rainfall extremes are major drivers of flash floods and hence significant disruptions to society. Previous modeling and statistical studies show that urbanization intensifies short‐duration rainfall extremes. However, there has been less attention to regional variations in rates of rainfall intensification under a warming climate, particularly for extreme events with return periods that are comparable to or longer than the years of record. In this study, we investigate changes in rainfall extremes over the Greater Bay Area, China using long records of high‐resolution data merged from gauge networks, satellite observations, and reanalysis products. This enables us to evaluate changes in low‐frequency rainfall extremes (2‐ to 100‐yr return periods) over different land surfaces, under a warming climate. We find that increases in rainfall extremes significantly depend on the duration and return period of events, with the largest scaling occurring for short‐duration “nuisance” rainfall intensities over urban areas.
Key Points
Non‐stationarities of sub‐daily rainfall extremes over a coastal megalopolis exhibit marked land cover and duration dependencies
Urban areas show more prominent intensification of events over short durations and short return periods compared with rural areas
Rural areas show smaller nonstationary variabilities across durations and return periods and a lower peak scaling rate than urban areas
Flexible, slit, and rigid barriers are common countermeasures to mitigate natural geophysical mass flows, but presently, quantitative comparisons of their performance are lacking, due to the ...challenges involved in accurately representing the multi‐body and multi‐phase interactions. This study presents a numerical appraisal on this issue using a physics‐based coupled computational fluid dynamics and discrete element method (CFD‐DEM). A geophysical flow is considered as a mixture of discrete gap‐graded particles (DEM) and a continuous viscous slurry (CFD), whereas a permeable and deformable barrier structure can be modeled by DEM. The in‐flow multiphase interactions and flow‐barrier interactions can be rigorously modeled by a coupling scheme between DEM and CFD. Our numerical simulations reasonably capture both field and experimental observations on key features of flow‐barrier interactions and barrier responses. The different intercepting mechanisms of three barriers via pile‐up and runup modes are revealed by qualitative and quantitative characterizations. Flexible barriers perform the best under runup mode regarding much larger peak load reduction ratios (up to 89%) due to their high permeability and Fr‐dependent load‐deflection behavior. We further compile a barrier‐specific design diagram that suggests existing analytical models calibrated by limited experiments may underestimate the peak impact for slit and rigid barriers due to their neglect of large solid particles in the impinging flows while leading to overestimations for flexible barriers owing to inappropriate representations of barrier permeability and structural deformability. Our findings may offer a basis for model improvements and developments in practical barrier selection and design.
Plain Language Summary
Engineers commonly use flexible, open‐type, and closed‐type barriers to reduce the adverse impacts of natural geophysical mass flows. However, the selection and design of barriers mainly rely on engineering experience and simplified models. We present a numerical study based on the coupled fluid‐solid modeling to offer quantitative reference on this issue. The numerical framework employed enables a unified description of a geophysical flow as a mixture of solid particles and a continuous viscous slurry and any of the three barrier types, offering a consistent comparison basis. We compare the different intercepting mechanisms of three types of barriers in resisting an impinging flow and identify their intertwined dependence of incoming flow characteristics, barrier deformability and passing ability, and peak impact loads. A flexible barrier is found to outperform the other two in achieving better peak load reduction ratios (up to 89%) with a runup mode, due to its high passing ability and load‐deflection behavior. The compilation of a unified barrier‐specific design diagram highlights the influences of barrier passing ability, structure deformability, and large solid particles on the peak impacts. This work could help for developing better analytical models on specific barrier design to mitigate natural geohazards caused by geophysical mass flows.
Key Points
Coupled fluid‐solid simulations of geophysical flows against flexible, slit and rigid barriers reveal their distinct intercepting mechanisms
The flexible barrier performs the best under runup mode owing to its high permeability and Fr‐dependent load‐deflection behavior
Compilation of a barrier‐specific design diagram highlights the effects of large particles, barrier permeability, and structure deformability
Impact of outdoor and household air pollution on physical function remains unelucidated. This study examined the influence of various ambient particulate sizes (PM1, PM2.5, and PM10) and household ...fuel usage on physical function.
Data from the China Health and Retirement Longitudinal Study (CHARLS) spanning 2011 and 2015 were utilized. The physical functional score was computed by summing scores from four tests: grip strength, gait speed, chair stand test, and balance. Multivariate linear and linear mixed-effects models were used to explore the separate and combined effects of PM1, PM2.5, PM10 and household fuel use on physical function in the cross-sectional and longitudinal analyses, respectively, and to further observe the effects of fuel cleanup on physical function in the context of air pollution exposure.
Both cross-sectional and longitudinal analyses revealed negative correlations between PM1 (β = −0.044; 95% CI: −0.084, −0.004), PM2.5 (β = −0.024; 95% CI: −0.046, −0.001), PM10 (β = −0.041; 95% CI: −0.054, −0.029), and physical function, with a more pronounced impact observed for fine particulate matter (PM1). Cleaner fuel use was associated with enhanced physical function compared to solid fuels (β = 0.143; 95% CI: 0.070, 0.216). The presence of air pollutants and use of solid fuels had a negative impact on physical function, while cleaner fuel usage mitigated the adverse effects of air pollutants, particularly in areas with high exposure.
This study underscores the singular and combined detrimental effects of air pollutants and solid fuel usage on physical function. Addressing fine particulate matter, specifically PM1, and prioritizing efforts to improve household fuel cleanliness in regions with elevated air pollution levels are crucial for preventing physical disability.
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•Negative correlations among PM1, PM2.5, and PM10 and physical function are identified.•Beneficial effects of clean fuels use on physical function are observed.•Among various air pollutant sizes, PM1 causes greatest harm to physical function.•Air pollutants and solid fuel use have combined adverse effects on physical function.
The growing amount of social media data is an invaluable and rapidly accessible source of information for flood response and recovery. In this study, a workflow framework is developed to assess urban ...flood impacts by extracting and analysing social media data, as well as identifying the intensive public response areas, using the case of 2020 China Chengdu rainstorm-induced flooding. A crawler-algorithm is applied to extract and filter the social media data from the commonly used social platforms, namely Weibo (static data) and Tiktok (dynamic data). Based on the spatiotemporal analysis, 232 flood sites with geological locations are identified. The study shows that, social media activities and precipitation are temporally correlated in a significant and positive way. The temporal evolution analysis of social media topics reveals the process of flooding and enables quick determination of severely affected areas. Spatially, social media data can provide spatial flood information and social media activities are typically connected with user demographics. Based on a flood simulation, the framework can generate valuable data sources of urban flooding from social media, which can enhance flood risk modelling with the aid of a hydrodynamic model. This study demonstrates the utility of social media in urban flooding impact assessment.
•We develop an optimized workflow to identify flood data from social media dataset.•Temporally, social media activities are positively correlated with precipitation.•Spatially, flood-points data concentration characterizes flood severity.•232 flood sites are identified and validated by numerical simulation.
Superconducting nanocircuits, which are usually fabricated from superconductor films, are the core of superconducting electronic devices. While emerging transition-metal dichalcogenide ...superconductors (TMDSCs) with exotic properties show promise for exploiting new superconducting mechanisms and applications, their environmental instability leads to a substantial challenge for the nondestructive preparation of TMDSC nanocircuits. Here, we report a universal strategy to fabricate TMDSC nanopatterns via a topotactic conversion method using prepatterned metals as precursors. Typically, robust NbSe
meandering nanowires can be controllably manufactured on a wafer scale, by which a superconducting nanowire circuit is principally demonstrated toward potential single photon detection. Moreover, versatile superconducting nanocircuits, e.g., periodical circle/triangle hole arrays and spiral nanowires, can be prepared with selected TMD materials (NbS
, TiSe
, or MoTe
). This work provides a generic approach for fabricating nondestructive TMDSC nanocircuits with precise control, which paves the way for the application of TMDSCs in future electronics.
A tin dioxide/reduced graphene oxide composite (SnO2/RGO) is synthesized using combined methods, including in-situ metal tin reduction, spray drying and thermal treatment. Under mild hydrothermal ...condition, metal tin works as both reducing agent for few-layered graphene oxide (GO) to prepare restacked 2-dimensional (2D) reduced graphene oxide (RGO) sheets and metal source for homogeneously distributed nanostructured Sn and Sn oxides (Sn/SnO/SnO2). The 2D precursors are shrunk to a micro-sized dried blueberry shape via a spray drying process. After further thermal treatment, SnO2/RGO composite is obtained, in which Sn and SnO species are converted to SnO2 and the nano-sized SnO2 is well stabilized by the micro-sized 3D porous RGO supporting framework. The 3D SnO2/RGO composite exhibits not only a higher reversible capacity of 708 mAh·g−1 under a current density of 500 mA·g−1 over 150 cycles compared with 2D counterpart, but also a long and stable cycling life under a high current density of 1000 mA·g−1. This synthesis route can be considered as simple, economic and environmental-friendly, and it has great potential to find applications in other fields.
•Metal tin works as a reducing agent for few-layered graphene oxide (GO) to prepare restacked 2-dimensional (2D) reduced graphene oxide (RGO).•It is the first time observed that metal tin can be converted to homogeneously distributed nanostructured Sn and Sn oxides (Sn/SnO/SnO2) with GO reduction process.•The 2D Sn/SnO/SnO2 and RGO precursor is transformed to 3D dried blueberry shape SnO2/RGO composite after spray drying and thermal treatment.•As an anode material for lithium ion batteries, the 3D SnO2/RGO composite exhibits highe reversible capacity and stable cycling life.•The synthesis route can be considered as simple, economic and environmental-friendly.
In this work, Ti3C2, was obtained by selective etching of Al in Ti3AlC2 by hydrofluoric and VS2 was modified on two-dimensional Ti3C2 by solvothermal process to prepare VS2/Ti3C2 composites. In the ...three-electrode system, the prepared VS2/Ti3C2 composites were compared with VS2 and Ti3C2, respectively, and it was found that the electrochemical properties of VS2/Ti3C2 composites were better. The intercalated VS2 nanosheets expanded the distance between Ti3C2 sheets, leading to a wide ion-accessible surface region and fast ionic/electric transport, resulting in the improved the electrochemical performance of the Ti3C2/VS2 composites. Density functional theory (DFT) analysis shows that the prepared VS2/Ti3C2 composite material has high electrical conductivity. Under the current density of 1 A∙g−1, the specific capacity of VS2/Ti3C2 composite is 191.3mAh∙g−1, which is much higher than that of VS2 and Ti3C2. The asymmetric supercapacitors were assembled with VS2/Ti3C2 composites as positive electrodes, and the electrochemical performance was tested when the power density was 1288 W·kg−1 and the energy density was 24 Wh·kg−1. The initial capacity retention is 82.2% after 5000 cycles of constant current charge and discharge at the current density of 2 A·g−1. In short, VS2/Ti3C2 composites show excellent supercapacitor performance in terms of capacity, stability, energy density and power density. It shows that VS2/Ti3C2 is a promising electrode material for supercapacitors.
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•VS2 was modified on two-dimensional Ti3C2 by solvothermal process to prepare VS2/Ti3C2 composites.•The VS2/Ti3C2 heterostructure achieves greatly enhanced electrochemical performance of composite materials.•The DFT is used to clarify the electron transfer mechanism.
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•Seven CQAs were determined during extraction process of XXZOL.•The extraction process of XXZOL were monitored by fusing NIR and MIR spectroscopy.•Data fusion is feasible for model ...performance in multivariate calibration.
The traditional Chinese medicine (TCM) extraction process is a complicated dynamic system with many variables and disturbance. Therefore, multi critical quality attributes (CQAs) monitoring is of great significance to understand the whole process. Spectroscopy is a powerful process analytical tool used for process understanding. However, single senor sometimes could not provide comprehensive information. Sensor fusion is a very practical method to overcome this deficiency. In this study, the extraction process of Xiao’er Xiaoji Zhike Oral Liquid (XXZOL) was carried out in pilot scale, where near infrared (NIR) spectroscopy and mid infrared (MIR) spectroscopy were collected to determine the concentrations of seven CQAs (synephrine, arecoline, chlorogenic acid, forsythoside A, naringin, hesperidin and neohesperidin) during extraction process. Based on fused data blocks, fusion partial least squares (PLS) models were established. Two fusion data blocks are obtained from the concatenation of original spectra (low-level data fusion) and the concatenation of characteristic variables based on band selection (mid-level data fusion) respectively. The results indicated that for all seven analytes, the mid-level data fusion models were superior to the single spectral models, with the prediction performance significantly improved. Specifically, the coefficients of determination (Rp2 and Rt2) of NIR, MIR and fusion quantitative models were all higher than 0.95. The relative standard errors of prediction (RSEP) values were all within 10%, except for models of neohesperidin, which were 10.76%, 12.39%, 12.05%, 10.03% for NIR, MIR, low-level and mid-level models respectively. These results demonstrate that it is feasible to monitor the extraction process of Xiao’er Xiaoji Zhike Oral Liquid more accurately and rapidly by fusing NIR and MIR spectroscopy, and the proposed approach also has vital and valuable reference value for the rapid monitoring of the mixed decoction process of other TCM.
•SNSPD maintains excellent comprehensive performance in near infrared.•SNSPD-based Lidar maintains high depth accuracy and long detection range.•Enhanced SNSPD will promote the development of Lidar.
...Lidar has already achieved long-distance and high-accuracy detection due to the improved sensitivity and timing accuracy of single-photon detectors (SPDs). However, single-photon Lidar systems based on semiconductor detectors are usually susceptible to dark counts and afterpulsing. Recently, superconducting nanowire single-photon detectors (SNSPDs) have shown promise toward single-photon Lidar systems owing to their high detection efficiency, high maximum count rate, low dark count rate and low timing jitter. An in-depth understanding of SNSPD Lidar can promote its further rational development and application. This article reviews the advantages of SNSPDs in single-photon Lidar systems and corresponding developments and introduces and prospects its related applications. In the future, the development of SNSPD working bands and array sizes may promote the next generation of single-photon Lidar systems with a longer detection range, higher depth accuracy and shorter acquisition time.
Geophysical mass flows impacting flexible barriers can create complex flow patterns and multiway solid‐fluid‐structure interactions, wherein estimates of impact loads rely predominantly on analytical ...or simplified solutions. However, an examination of the fundamental relations, applicability, and underlying mechanisms of these solutions has been so far elusive. Here, using a coupled continuum‐discrete method, we systematically examine the physical laws of multiphase, multiway interactions between geophysical flows of variable natures, and a permeable flexible ring net barrier system. This model well captures the essential physics observed in experiments and field investigations. Our results reveal for the first time that unified bi‐linear laws underpin widely used analytical and simplified solutions, with inflection points caused by the transitions from trapezoid‐shaped to triangle‐shaped dead zones. Specifically, the peak impact load increases bi‐linearly with increasing Froude number, peak cable force, or maximum barrier deformation. Flow materials (wet vs. dry) and impact dynamics (slow vs. fast) jointly drive the patterns of identified bi‐linear correlations. These findings offer a physics‐based, significant improvement over existing solutions to impact problems for geophysical flows.
Plain Language Summary
Flexible barriers are increasingly used worldwide to mitigate debris flows, debris/rock/snow avalanches, and rockfalls. Although many methods exist to estimate critical design factors of flexible barriers, a systematic examination of their applicability and underlying relations remains elusive. The status quo has been largely caused by the challenges of capturing and quantifying the multiphase, multiway flow‐barrier interactions. Here, we perform a series of hybrid solid‐fluid simulations to explore the impact of debris flows/avalanches and rock avalanches on a flexible barrier system. Our numerical predictions of critical physical processes show reasonable consistency with experimental and field observations. For the first time, the physics‐based numerical measures of the flow‐barrier forces, in‐barrier forces, and barrier load‐deformation relations reveal the unified bi‐linear laws behind widely used methods. We find that the flow‐specific turning points of the bi‐linear laws are due to the changes from trapezoid‐shaped to triangle‐shaped jammed regions formed upstream of the barrier. Our findings quantitatively explain how flow properties (e.g., wet vs. dry and slow vs. fast) control the obtained bi‐linear laws. This study provides a crucial improvement over widely used methods for geohazard scientists and engineers to impact problems for geophysical flows.
Key Points
We present numerical measures of the impact loads of debris flows/avalanches and rock avalanches on a flexible ring net barrier system
Bi‐linear laws relate peak impact to Fr, peak cable force, or maximum barrier deformation with turning points due to shifts of dead zones
Flow materials and dynamics jointly control the obtained bi‐linear laws, which underpin widely used analytical and simplified solutions
