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SnO2 nanorods were grown on two kinds of seed layers formed from SnCl2·2H2O and SnO2 nanoparticles precursors, respectively, and used as one-dimensional electron transport materials to fabricate perovskite solar cell (PSCs). Effects of the seed layers on morphology, structure, optical properties of SnO2 nanorods and perovskite films, charge transfer at SnO2/perovskite interfaces as well as device performance were investigated by utilizing field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible-near infrared spectroscopy(UV-vis), steady-state photoluminescence spectroscopy (PL) and volt-ampere characteristic curves (J-V). The results show that more dense seed layers can be formed from SnO2 nanoparticles and SnO2 nanorods films formed from SnO2 nanoparticles are more smooth and uniform relative to those grown from SnCl2·2H2O. The perovskite films deposited on the former show better crystallization quality and higher light absorption. The maximum efficiency of the device based on the SnO2 nanorods is 12.93%. This work demonstrates that SnO2 nanoparticles are a kind of excellent seed layer material for growing SnO2 nanorods films, and lays foundation for the preparation of high-performance perovskite solar cells based on one-dimensional electron transport materials.

This paper investigates the anti-icing effect of hydrophobic coating, which has similar characteristics with a superhydrophobic surface. First, the factors affecting the wettability of water droplets on a solid surface were theoretically analyzed. Using hydrolytic condensation reaction, low-surface-energy materials were prepared based on a modified vulcanized silicone resin. Different sizes of silica particles were added in a fluorinated silicone resin to prepare the superhydrophobic coatings, considering the fractal theory. In the coating test characterization phase, the microstructure of the particles-doped coating surface and the contact angle of water droplets on different coating surfaces were investigated and analyzed. To visually analyze the effect of coating anti-icing property, icing tests were carried out in an icing wind tunnel after coating the test pieces by different coatings. The results show that the surface of the hydrophobic coating mixed with particles of different sizes forms a composite microstructure, which has a better roughness. The contact angle test result shows that the contact angle of water droplets on the fluorinated silicone resin-coated surface is 10° higher than that on the ordinary silicone resin-coated surface, and increases by nearly 20° in the coating with different particle sizes compared with the uniformly sized particles coating, thus achieving a superhydrophobic surface effect. The different coated test pieces were set in an icing wind tunnel to test their anti-icing abilities, and the results indicate that the superhydrophobic coating with a fractal structure after being cured does not only have a lower icing weight, which is reduced by 35.6% and 25.9% at the wind speed of 5 m·s-1 and 15 m·s-1, respectively, compared with the uncoated surface, but also has longer anti-icing effect than the uniformly rough surface. Therefore, the designed superhydrophobic coating has an outstanding anti-icing ability. In conclusion, the designed superhydrophobic coating achieves a superhydrophobic surface and has a better anti-icing performance, as confirmed through a series of performance tests.

During an on-orbit refueling mission, the liquid fuel partially filling in the tanks will slosh and produce coupled motion with the servicer-to-client transfer, which may bring dangers to the spacecraft and even lead to attitude divergence. To effectively simulate the motion and the inertia of liquid fuel in a cylindrical tank during refueling, equivalent dynamic modeling of liquid fuel sloshing coupled with mass transfer is developed in this paper. A spring-mass-damper model with time-varying elastic and damping coefficients is implemented in the axial direction to equal the motion of the liquid mass center, while a pendulum model with time-varying pendulum length is adopted in the radial direction. An equivalent liquid elliptical cylinder is developed to approximate the inertia of dispersed liquid while sloshing. A series of computational fluid dynamics simulations are carried out to observe the liquid behaviors in the fuel tanks and to verify the proposed equivalent dynamic model. Finally, three-dimensional sloshing is theoretically and numerically analyzed. [ABSTRACT FROM AUTHOR]

Groundwater withdrawal can cause localized and rapid poroelastic subsidence, spatially broad elastic uplift of low amplitude, and changes in the gravity field. Constraining groundwater loss in Mexico City, we analyze data from the Gravity Recovery and Climate Experiment and its follow‐on mission (GRACE/FO) and Synthetic Aperture Radar (SAR) Sentinel‐1A/B images between 2014 and 2021. GRACE/FO observations yield a groundwater loss of 0.85–3.87 km3/yr for a region of ∼300 × 600 km surrounding Mexico City. Using the high‐resolution interferometric SAR data set, we measure >35 cm/yr subsidence within the city and up to 2 cm/yr of uplift in nearby areas. Attributing the long‐term subsidence to poroelastic aquifer compaction and the long‐term uplift to elastic unloading, we apply respective models informed by local geology, yielding groundwater loss of 0.86–12.57 km3/yr. Our results suggest Mexico City aquifers have been depleting at faster rates since 2015, exacerbating the socioeconomic and health impacts of long‐term groundwater overdrafts. Plain Language Summary: Groundwater overdraft in Mexico City results from excessive freshwater demand and unsustainable water resource management in a subtropical environment with warm summers and dry winters. Groundwater depletion can result in ground surface deformation and changes in the gravity field, observable by Sentinel‐1 and GRACE satellites. Here, we examine data from both satellite missions between November 2014 and October 2021 to determine groundwater volume loss. Using GRACE, which has a footprint of ∼350 km, we quantify groundwater volume loss to a rate of 0.85–3.87 km3 per year in the broader area surrounding Mexico City. Analysis of high‐resolution Sentinel‐1 synthetic aperture radar images shows land sinks at a rate of 35 cm/yr within the city and surrounding areas uplifts at a rate of ∼2 cm/yr. While the subsidence is a consequence of aquifer compaction, the uplift represents an elastic unloading response of the Earth's crust to water mass loss. Using geophysical models informed by local geology, we show that the region loses groundwater at rates of 0.86–12.57 km3/yr. Our results emphasize the need for groundwater monitoring in Mexico City to assist with managing freshwater resources. Key Points: A subsidence rate of >35 cm/yr within Mexico City, surrounded by ∼2 cm/yr of uplift, is observed using space‐borne synthetic aperture radarGroundwater loss of 0.86–12.57 km3/yr in Mexico City causes poroelastic subsidence, a broad‐scale elastic uplift, and gravity field changeMexico City aquifers have been depleting at least since 2015, exacerbating groundwater overdrafts' socioeconomic and health impacts [ABSTRACT FROM AUTHOR]

Sign language recognition has been utilized in human–machine interactions, improving the lives of people with speech impairments or who rely on nonverbal instructions. Thanks to its higher temporal resolution, less visual redundancy information and lower energy consumption, the use of an event camera with a new dynamic vision sensor (DVS) shows promise with regard to sign language recognition with robot perception and intelligent control. Although previous work has focused on event camera-based, simple gesture datasets, such as DVS128Gesture, event camera gesture datasets inspired by sign language are critical, which poses a great impediment to the development of event camera-based sign language recognition. An effective method to extract spatio-temporal features from event data is significantly desired. Firstly, the event-based sign language gesture datasets are proposed and the data have two sources: traditional sign language videos to event stream (DVS_Sign_v2e) and DAVIS346 (DVS_Sign). In the present dataset, data are divided into five classification, verbs, quantifiers, position, things and people, adapting to actual scenarios where robots provide instruction or assistance. Sign language classification is demonstrated in spike neuron networks with a spatio-temporal back-propagation training method, leading to the best recognition accuracy of 77%. This work paves the way for the combination of event camera-based sign language gesture recognition and robotic perception for the future intelligent systems. [ABSTRACT FROM AUTHOR]

During soft landing on asteroids, the weak gravity and rugged terrain put the spacecraft at risk of crashing and bouncing, such that a safe and accurate landing is essential for the spacecraft. In this paper, a new flexible spacecraft, composed of three thrust units and connecting airbags, is designed for asteroid landing. To estimate the flexible deformation of the spacecraft, an equivalent system model consisting of three spring-damping components and three thrust units is developed. Based on this model, a control scheme including path planning, tracking control, and control allocation is proposed. Considering double-zero constraints and flexible connection constraints, the trajectories of three thrust units are planned with the Gaussian pseudospectral method and then fitted into the trajectory of the flexible spacecraft mass center. Then, a nonsingular terminal sliding mode control law considering flexible body disturbances and thruster saturation problems is designed. To solve the control allocation problem, an active set algorithm considering the time-varying installation matrix caused by the flexible deformation is applied. Two simulation cases are provided to demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Production of more than 20 million tons of epoxides per year from olefins suffers from low atom economy due to the use of oxidants and complex catalysts with unsatisfactory selectivity, leading to huge environmental and economic costs. We present a proof‐of‐concept application of electron‐rich RuO2 nanocrystals to boost the highly selective epoxidation of cyclooctene via direct oxygen transfer from water as the sole oxygen source under mild conditions. The enhanced electron enrichment of RuO2 nanocrystals via the Schottky effect with nitrogen‐doped carbons largely promotes the capture and activation of cyclooctene to give a high turnover frequency (260 h−1) of cyclooctene oxide, far surpassing the reported values (<20 h−1) of benchmarked catalysts at room temperature with oxidants. Our electron‐rich RuO2 electrocatalysts enable efficient and durable hydrogen production (Faradaic efficiency >90 %) on the cathode without impacting on the selectivity to epoxide (>99 %) on the anode. [ABSTRACT FROM AUTHOR]

The low orbit and high density satellilte constellation attracts increaring attention due to its wide coverage and Its capablilty of tracking ballistic targets throughout their traces. To cope with the problem of multiple balidtic targets cooperaiive tracking, this paper proposes a multistarget cooperative tracking filter based on Chi-square distribution and unscented Kalman filter (UKF). Under the assumption of a Chi-square distribution, this paper develops an indicator function of dala association on the measurement plane to assiign measurements. And based on the assignment, the variable filter structure is adopted to update the states of multi-target. Finally, the evaluation index of multi-larget slate estimation performance is given. The numerical simulations show that the algorithm proposed in this paper can effectively realize data association on measurement plane and estimate the state of multiple maneuvering targets (MTT) accurately with less computational load. [ABSTRACT FROM AUTHOR]

Platinum (Pt) is the most effective bench‐marked catalyst for producing renewable and clean hydrogen energy by electrochemical water splitting. There is demand for high HER catalytic activity to achieve efficient utilization and minimize the loading of Pt in catalysts. In this work, we significantly boost the HER mass activity of Pt nanoparticles in Ptx/Co to 8.3 times higher than that of commercial Pt/C by using Co/NC heterojunctions as a heterogeneous version of electron donors. The highly coupled interfaces between Co/NC and Pt metal enrich the electron density of Pt nanoparticles to facilitate the adsorption of H+, the dissociation of Pt−H bonds and H2 release, giving the lowest HER overpotential of 6.9 mV vs. RHE at 10 mA cm−2 in acid among reported HER electrocatalysts. Given the easy scale‐up synthesis due to the stabilization of ultrafine Pt nanoparticles by Co/NC solid ligands, Ptx/Co can even be a promising substitute for commercial Pt/C for practical applications. [ABSTRACT FROM AUTHOR]

Objective: We aimed to evaluate the diagnostic value of soluble interleukin-2 receptor (sIL-2R), tumor necrosis factor-α (TNF-α), procalcitonin (PCT), and combined detection for sepsis infection in patients with closed abdominal injury complicated with severe multiple abdominal injuries. Patients and Methods: One hundred forty patients with closed abdominal injury complicated with severe multiple abdominal injuries who were diagnosed and treated from 2015 to 2020 were divided into a sepsis group (n = 70) and an infection group (n = 70). Results: The levels of sIL-2R, TNF-α, and PCT in the sepsis group were higher than those in the infection group (p < 0.05). The receiver operating characteristic (ROC) curve showed that the areas under the ROC curve (AUCs) of sIL-2R, TNF-α, PCT and sIL-2R+TNF-a+PCT were 0.827, 0.781, 0.821, and 0.846, respectively, which were higher than those of white blood cells (WBC, 0.712), C-reactive protein (CRP, 0.766), serum amyloid A (SAA, 0.666), and IL-6 (0.735). The AUC of the three combined tests was higher than that of TNF-α, and the difference was statistically significant (p < 0.05). There was no significant difference in the AUCs of sIL-2R and TNF-α, sIL-2R and PCT, TNF-α and PCT, the three combined tests and sIL-2R, and the three combined tests and PCT (p > 0.05). When the median was used as the cut point, the corrected sIL-2R, TNF-α, and PCT of the high-level group were not better than those of the low-level group (p > 0.05). When the four groups were classified by using quantile as the cut point, the OR risk values of high levels of TNF-α and PCT (Q4) and the low level of PCT (Q1) after correction were 7.991 and 21.76, respectively, with statistical significance (p < 0.05). Conclusions: The detection of sIL-2R, TNF-α, and PCT has good value in the diagnosis of sepsis infection in patients with closed abdominal injury complicated with severe multiple abdominal injuries. The high concentrations of PCT and TNF-α can be used as predictors of the risk of septic infection. [ABSTRACT FROM AUTHOR]