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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]

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]

The M5 Mentone earthquake that occurred on March 26, 2020, was the largest event recorded over the last 2 decades in West Texas within the Delaware Basin, a U.S. major petroleum‐producing area. Also, numerous hydrofracturing and wastewater disposal wells are spread across this region. Within a 30 km distance to mainshock, eight class‐II injection wells for industrial wastewater disposal target the deep porous Ellenburger aquifer at an average rate of 1.36 × 106 barrel (BBL) per month during 2012–2020. Poroelastic models of fluid diffusion show these nearby injectors collectively imparted up to 80.5 kPa of Coulomb stress at the mainshock location, capable of triggering this M5 event. Assuming the Mentone event occurs when pore‐pressure increase is maximum, the time delay between peak injection and the M5 occurrence corresponds with an optimal permeability of 6.76 × 10‐14 m2 for the Ellenburger aquifer layer, in agreement with independent estimates. Plain Language Summary: On March 26, 2020, a M5 earthquake took place near the town Mentone in West Texas, located within one of the largest petroleum‐producing areas in the United States. This area also contains injection sites designated for disposing of wastewater coproduced from unconventional hydrocarbon production processes. Our study found that this earthquake could be triggered by fluid diffusion from the nearby disposal wells. Seismicity's timing and location are consistent with injection occurring in an intermediately permeable aquifer and are indicators for individual wells' operation. These provide essential information to help industrial practitioners and regulatory agencies to assess the associated seismic hazard, implement mitigation measures, and draft policies or guidelines for disposal well management. Key Points: Fluid diffusion from nearby injection wells is likely the primary triggering mechanism for the M5 Mentone earthquakeTwo nearby injectors could individually impart adequate Coulomb stress to induce the M5 eventTime delay between injection and seismicity is used to constrain the mechanical properties of the aquifer unit [ABSTRACT FROM AUTHOR]

Doping the host materials with either electron‐rich heteroatoms or electron‐deficient heteroatoms have been applied as a straightforward and main‐stream method to modify the electronic structures and boost the electrochemical activity for various reactions, including nitrogen reduction reactions (NRR). As the third type of dopants, isoelectric heteroatoms (exemplified with Si atoms in carbon framework in this work) have been designed as highly efficient active centers for NRR. As the same group element with a different size and electronegativity to carbon support, the isoelectric Si heteroatom (Iso‐e Si) creates localized singularities with a lone orbital that can act as an electron trap for pre‐adsorbed N2 molecules through coulomb interaction and thus facilitates the following activation process for NRR. Iso‐e Si atom thus functions as a special type of metal‐free single atom‐based electrocatalyst to largely boost the faradaic efficiency of pristine carbon support for NRR by a factor of 12, giving a remarkably high turnover frequency value of 0.52 h−1, comparable to atomically dispersed transition metal‐based electrocatalysts. [ABSTRACT FROM AUTHOR]

Induced seismicity has expanded into south‐central Kansas, an area with rare damaging natural earthquakes, leading to the second‐highest seismicity rate in the central United States after Oklahoma. Here we assess the mechanical effects of large‐scale injection in the combined area of western Oklahoma and southern Kansas during 2010–2018 and its link to the observed seismicity using physics‐based hydromechanical and seismicity rate models. Such models link injection operations to seismic hazards and allow solving for the spatially variable distribution of background seismic productivity that yields an acceptable match between the observed and modeled seismicity. We show that injection in Oklahoma amplifies the total Coulomb stress change and seismicity rate by 1.5‐fold and threefold, respectively, in south‐central Kansas. This cross‐border interaction modulates the annual earthquake probability in Kansas. We conclude that the issue of induced seismicity is not a local problem due to the far‐reaching effects of fluid diffusion. Key Points: Unified hydromechanical model to reproduce and forecast induced seismicity for western Oklahoma and southern KansasThe state of stress and seismicity rate in Kansas are modulated by injection in OklahomaThe probability of large earthquakes in Kansas is exacerbated by the hydromechanical interaction with fluid injection in Oklahoma [ABSTRACT FROM AUTHOR]

Abstract: The Barnett Shale in Texas experienced an increase in seismicity since 2008, coinciding with high‐volume deep fluid injection. Despite the spatial proximity, the lack of a first‐order correlation between seismic records and the total volume of injected fluid requires more comprehensive geomechanical analysis, which accounts for local hydrogeology. Using time‐varying injections at 96 wells and employing a coupled linear poroelastic model, we simulate the spatiotemporal evolution of pore pressure and poroelastic stresses during 2007–2015. The overall contribution of poroelastic stresses to Coulomb failure stress change is ~10% of that of pore pressure; however, both can explain the spatiotemporal distribution of earthquakes. We use a seismicity rate model to calculate earthquake magnitude exceedance probability due to stress changes. The obtained time‐dependent seismic hazard is heterogeneous in space and time. Decreasing injection rates does not necessarily reduce probabilities immediately. [ABSTRACT FROM AUTHOR]

Abstract: Geodetic observations of surface deformation associated with volcanic activities can be used to constrain volcanic source parameters and their kinematics. Simple analytical models, such as point and spherical sources, are widely used to model deformation data. The inherent nature of oversimplified model geometries makes them unable to explain fine details of surface deformation. Current nonparametric, geometry‐free inversion approaches resolve the distributed volume change, assuming it varies smoothly in space, which may detect artificial volume change outside magmatic source regions. To obtain a physically meaningful representation of an irregular volcanic source, we devise a new sparsity‐promoting modeling scheme assuming active magma bodies are well‐localized melt accumulations, namely, outliers in the background crust. First, surface deformation data are inverted using a hybrid L1‐ and L2‐norm regularization scheme to solve for sparse volume change distributions. Next, a boundary element method is implemented to solve for the displacement discontinuity distribution of the reservoir, which satisfies a uniform pressure boundary condition. The inversion approach is thoroughly validated using benchmark and synthetic tests, of which the results show that source dimension, depth, and shape can be recovered appropriately. We apply this modeling scheme to deformation observed at Kilauea summit for periods of uplift and subsidence leading to and following the 2007 Father's Day event. We find that the magmatic source geometries for these periods are statistically distinct, which may be an indicator that magma is released from isolated compartments due to large differential pressure leading to the rift intrusion. [ABSTRACT FROM AUTHOR]

This paper presents the deployment strategies for planar multi-tethered satellite formation that spins in orbit plane. By using Lagrange principles, the deployment dynamics, which treat the parent satellite as a finite sized rigid body, are established under gravity gradient perturbation. Comparing with the simplified dynamics that take the parent satellite as mass point, the model in this work enables the investigation on dynamical coupling between parent satellite and tethers. To achieve successful deployment, typical strategies are developed firstly with active gravity gradient compensation, both the tether deployment rate and parent satellite spinning profile are derived under specific motion constraints, after that, the deployment strategy capable of compensating the gravity gradient perturbation is also developed. For the fully deployed system, the minimum spinning rate that ensures the configuration stabilization is mathematically analyzed by employing Jacobi Integrator. Finally, series numerical simulations are performed to validate the proposed deployment strategies. [ABSTRACT FROM AUTHOR]

Since tertiary amines (C-H) can be oxidized by peroxides and transition metal cations in high oxidation states into C· radicals to initiate vinylic polymerizations of methacrylates, Cu and 2-( N,N-dimethylamino)ethyl methacrylate (DMAEMA) form a polymerizable redox initiating pair, in which DMAEMA serves as an intrinsically reducing inimer. CuSO-catalyzed aqueous self-initiated radical polymerizations of DMAEMA were successfully performed at ambient temperature via a continuous Cu-tertiary amine redox initiation based on catalyst regeneration in the presence of O. The polymerization kinetics was monitored by gas chromatography and the structure of PDMAEMA was characterized by gelpermeation chromatography, nuclear magnetic resonance spectroscopy, laser light scattering and online intrinsic-viscosity analysis. Both the monomer conversion and the molecular weight of PDMAEMA increase with the reaction while the molecular weight distribution maintains rather broad, as the Cu-DMAEMA redox-initiation leads to linear PDMAEMA chains with terminal methacryloxyl moieties, and the Cu-PDMAEMA redox-initiation results in branched chains. The branched topology forms and develops only for the high-MW components of the PDMAEMA. Our results provide a facile strategy to prepare branched polymers from such commercially available intrinsically reducing inimers using a negligible concentration of regenerative air-stable catalysts. [ABSTRACT FROM AUTHOR]

In order to probe CO2-coal interactions, differential scanning calorimetry(DSC) experiment was carried out in the atmosphere of He, N2 and CO2 with coals from Huozhou and Jincheng area in Shanxi Province. The results show that, in a He atmosphere, the curves are straightforward, the curves in the N2 atmosphere are smooth and upward compared with curves in the He atmosphere, however, in a CO2 atmosphere, all the three curves show exothermic peaks and endothermic peaks are irreversible. It is proposed that, as an inert gas, He can't be adsorbed on coal surface, hence no enthalpy released. For N2, physical adsorption occurs, charactered with lower enthalpy releasing. The larger enthalpy variation in a CO2 atmosphere indicates that, except for physical reactions, chemical reactions may also occur. Based on the analysis of coal interactions, CO2 interactions and molecular-scale interactions of CO2 with substances other than coal, the CO2-coal interactions were explained as follows: the C atom of CO2 accepted electrons from coal molecular, and formed an "electron donor-acceptor complex" ( i. e. , an "EDA complex" ), in other words, chemical reactions occurred, hence exothermic peaks occurred. The interconnections of the active sites to other groups in coal molecular are weakened due to the formation of EDA complex, so to be easily broken during heating, hence endothermic peaks occurred. The irreversibility of the curves indicates that coal structure is changed. [ABSTRACT FROM AUTHOR]

Abstract: A new concept using flexible tether–net system to perform on-orbit capture is presented in this paper. As a promising on-orbit capture strategy, the tether–net system has many exciting advantages by contrast with the existing orbital capture system. However, under the disturbance of orbital dynamics an attitude libration, which leads to a capture error, will be presented when the capture net is ejected towards the target aiming at investigating the relationship between the capture error and initial capture conditions, the governing equations of the tether–net system in orbital frame is developed by applying Lagrange equations. In order to optimize capture operation, the in-plane capture constraints are studied by numerical simulations with an effort to damp the in-plane libration and compensate the capture error, the control scheme based on tether tension is investigated firstly, after that an integrated control scheme is proposed by introduced the thrusters into the system, the nonlinear closed-loop dynamics is linearized by feedforward strategy, the simulation results show that feedforward controller is effective for in-plane libration damping and enable the capture net to track an expected trajectory. [Copyright &y& Elsevier]

Stille cross-coupling reactions catalysed by an ideal catalyst combining the high activity of homogeneous catalysts and the reusability of heterogeneous catalysts are of great interest for C–C bond formation, which is a widely used reaction in fine chemistry. Despite great effort to increase the utilization ratio of surface metal atoms, the activity of heterogeneous catalysts under mild conditions remains unsatisfactory. Herein, we design a proof-of-concept strategy to trigger the room-temperature activity of heterogeneous Au catalysts by decreasing the electron density at the interface of a rationally designed Schottky heterojunction of Au metals and boron-doped carbons. The electron-deficient Au nanoparticles formed as a result of the rectifying contact with boron-doped carbons facilitate the autocleavage of C–Br bonds for highly efficient C–C coupling reactions of alkylbromides and allylstannanes with a TOF value of 5199 h−1 at room temperature, surpassing that of the state-of-the-art homogeneous catalyst. [ABSTRACT FROM AUTHOR]

The detailed mechanism of induced seismicity associated with salt mining remains elusive. Herein we compile the geological, industrial data, and seismic records within the Changning salt mining zone, China, and simulate the changes in crustal stresses and seismicity rate based on the physics-based poroelastic model and rate-and-state earthquake nucleation model. Our models reveal that the regional induced seismicity, including the 2019 Ms. 6.0 Changning earthquake, which might be one of the largest induced events by industrial exploitation ever recorded, is mainly driven by the pore-pressure diffusion, but suppressed by pumping operations. Motivated by the injection-extraction scenario, we further investigate the effect of wells' locations on stress changes, which could be potentially used for well site optimization to minimize the poroelastic response. A simple mode of setting extraction wells around the injection well could reduce the seismicity rate by a factor of two. These results collectively advance the understanding of physics and hazards associated with injection-extraction-induced earthquakes, and help design or guide industrial well deployment. • The state of stress and seismicity rate in Changning salt mining zone, China, are modulated by injection and extraction. • The induced seismicity in Changning salt mining zone, including the Ms 6.0 earthquake, is driven by pore-pressure diffusion. • Seismicity rate is sensitive to the rate of Coulomb stress change and wells' position. • The induced seismic hazard could be potentially reduced by adjusting the extraction wells' position. [ABSTRACT FROM AUTHOR]

Pore pressure in aquifers confined below a cryosphere will increase as Mars cools and the cryosphere thickens. Increased pore pressure decreases the effective stress and hence promotes seismicity. We calculate the rate of pore pressure change from cooling of Mars's interior and the modulation of pore pressure from solar and Phobos tides and barometric loading. Using the time‐varying pressure and tidal stresses, we compute Coulomb stress changes and the expected seismicity rate from a rate‐and‐state friction model. Seismicity rate will vary by several tens of percent to 2 orders of magnitude if the mean pore pressure is within 0.2 and 0.01 MPa of lithostatic, respectively. Seismic events promoted by high pore pressure may be tremor‐like. Documenting (or not) tidally modulated shallow seismicity would provide evidence for (or against) water‐filled confined aquifers, that pore pressure is high, and that the state of stress is close to failure—with implications for processes that can deliver water to the Martian surface. Key Points: Freezing aquifers become pressurizedHigh pore pressure promotes seismicityTides from the Sun and Phobos and barometric loading can modulate seismicity if pore pressure is high [ABSTRACT FROM AUTHOR]

Wastewater injection over the past decade has increased seismicity in the central USA, in some cases accompanied by detectable surface uplift. Here, we use this uplift to constrain subsurface properties and pore pressure evolution. We apply an advanced multitemporal interferometric algorithm to 35 synthetic aperture radar images acquired by ALOS satellite over four years before the 2012 earthquake sequence in east Texas, where large volumes of wastewater are disposed at depths of ∼800 m and ∼1800 m. To solve for the hydraulic diffusivity of the injection layers, we jointly inverted the injected volume and uplift data, considering a poroelastic layered half space. We find diffusivity values of 0.3 ± 0.1 m2/s and 0.7 ± 0.15 m2/s for shallow and deep injection layers, respectively, which combined with seismically-derived bulk moduli yields permeability values of 5.5 ± 2.6 × 10 − 14 m2 and 1.9 ± 0.25 × 10 − 13 m2 for these layers, consistent with permeability range reported for Rodessa formation and well test values. Hydraulic conductivity determines the evolution of pore pressure and thus the origin and location of induced seismicity. This study highlights the value of geodetic observations to constrain key hydrogeological properties of injection layers and to monitor the evolution of the subsurface pressure change. • Fluid injection near Timpson, East Texas caused an uplift detectable by InSAR. • Surface deformation data are inverted to solve for hydraulic diffusivity of injection layer. • Pore pressure increase due to injection has triggered the 2012 M w 4.8 earthquake. [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the performance of active learning algorithm for detecting blueberry damage using hyperspectral transmittance data with the very low labeling cost. A hyperspectral transmittance imaging system was first applied to collect the hyperspectral transmittance data of blueberries. Subsequently, the mean hyperspectral transmittance data was extracted. With only 9 labeled berries, the estimated error reduction could achieve the accuracy, precision and recall of 0.87, 0.93 and 0.78 respectively, and it consistently improved or maintained the performance of classifier for the remainder of the queries. In contrast to the SOM and SVM models, the classifier based on estimated error reduction also provided higher accuracy, precision and recall with the much fewer labeled samples. The active learning algorithms can be extended to the large scale applications in which the labeled samples are very limited or expensive and the models are required to be frequently transferred. In our case, due to the significant biological variations existing among blueberry samples, the classifier required frequent updates in practical applications, and the active learning algorithms could remarkably reduce label effort during the model updating processes. [ABSTRACT FROM AUTHOR]

Recent years, docetaxel (DTX)-loaded intelligent polymeric micelles have been regarded as a promising vehicle for DTX for the reason that compared with conventional DTX-loaded micelles, DTX-loaded intelligent micelles not only preserve the basic functions of micelles such as DTX solubilization, enhanced accumulation in tumor tissue, and improved bioavailability and biocompatibility of DTX, but also possess other new properties, for instance, tumor-specific DTX delivery and series of responses to endogenous or exogenous stimulations. In this paper, basic theories and action mechanism of intelligent polymeric micelles are discussed in detail, especially the related theories of DTX-loaded stimuli-responsive micelles. The relevant examples of stimuli-responsive DTX-loaded micelles are also provided in this paper to sufficiently illustrate the advantages of relevant technology for the clinical application of anticancer drug, especially for the medical application of DTX. [ABSTRACT FROM AUTHOR]

A simple hydride system is fabricated to measure the superconducting transition temperature Tc under high pressure using a diamond anvil cell (DAC). The system is designed with centrosymetric coils around the diamond that makes it easy to keep balance between the pick-up coil and the inductance coil, while the superconducting states can be modulated with a low-frequency small external magnetic field. Using the device we successfully obtain the Tc evolution as a function of applied pressure up to 10 GPa for YBa2Cu3O6+d superconductor single crystal. [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]

Background: The need for intraoperative endoscopic nasobiliary drainage during laparoscopic cholecystectomy and laparoscopic common bile duct exploration with primary closure is controversial in the treatment of cholecystolithiasis combined with choledocholithiasis. The aim of this study was to evaluate the safety and efficacy of laparoscopic cholecystectomy + laparoscopic common bile duct exploration + intraoperative endoscopic nasobiliary drainage + primary closure (LC + LCBDE + IO-ENBD + PC). The safety of different intubation methods in IO-ENBD was also evaluated. Method: From January 2018 to January 2022, 168 consecutive patients with cholecystolithiasis combined with choledocholithiasis underwent surgical treatment in our institution. Patients were divided into two groups: group A (n = 96) underwent LC + LCBDE + IO-ENBD + PC and group B (n = 72) underwent LC + LCBDE + PC. Patient characteristics, perioperative indicators, complications, stone residual, and recurrence rates were analyzed. Group A was divided into two subgroups. In group A1, the nasobiliary drainage tube was placed in an anterograde way, and in group A2, nasobiliary drainage tube was placed in an anterograde–retrograde way. Perioperative indicators and complications were analyzed between subgroups. Results: No mortality in the two groups. The operation success rates in groups A and B were 97.9% (94/96) and 100% (72/72), respectively. In group A, two patients were converted to T-tube drainage. The stone clearance rates of group A and group B were 100% (96/96) and 98.6% (71/72), respectively. Common bile duct diameter was smaller in group A [10 vs. 12 mm, P < 0.001] in baseline data. In perioperative indicators, group A had a longer operation time [165 vs.135 min, P < 0.001], but group A had a shorter hospitalization time [10 vs.13 days, P = 0.002]. The overall complications were 7.3% (7/96) in group A and 12.5% (9/72) in group B. Postoperative bile leakage was less in group A [0% (0/96) vs. 5.6% (4/72), P = 0.032)]. There were no residual and recurrent stones in group A. And there were one residual stone and one recurrent stone in group B (all 1.4%). The median follow-up time was 12 months in group A and 6 months in group B. During the follow-up period, 2 (2.8%) patients in group B had a mild biliary stricture. At subgroup analysis, group A1 had shorter operation time [150 vs. 182.5 min, P < 0.001], shorter hospitalization time [9 vs. 10 days, P = 0.002], and fewer patients with postoperative elevated pancreatic enzymes [32.6% (15/46) vs. 68% (34/50), P = 0.001]. Conclusion: LC + LCBDE + IO-ENBD + PC is safer and more effective than LC + LCBDE + PC because it reduces hospitalization time and avoids postoperative bile leakage. In the IO-ENBD procedure, the antegrade placement of the nasobiliary drainage tube is more feasible and effective because it reduces the operation time and hospitalization time, and also reduces injury to the duodenal papilla. [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]

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]

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]

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]

NOx− reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx− reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple‐electron NOx−‐to‐NH3 process. Here, we utilize the Schottky barrier‐induced surface electric field, by the construction of high density of electron‐deficient Ni nanoparticles inside nitrogen‐rich carbons, to facilitate the enrichment and fixation of all NOx− anions on the electrode surface, including NO3− and NO2−, and thus ensure the final selectivity to NH3. Both theoretical and experimental results demonstrate that NOx− anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3− and NO2− reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h−1 cm−2 in electrocatalytic NO2− reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx− pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology. [ABSTRACT FROM AUTHOR]

NOx− reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx− reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple‐electron NOx−‐to‐NH3 process. Here, we utilize the Schottky barrier‐induced surface electric field, by the construction of high density of electron‐deficient Ni nanoparticles inside nitrogen‐rich carbons, to facilitate the enrichment and fixation of all NOx− anions on the electrode surface, including NO3− and NO2−, and thus ensure the final selectivity to NH3. Both theoretical and experimental results demonstrate that NOx− anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3− and NO2− reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h−1 cm−2 in electrocatalytic NO2− reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx− pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology. [ABSTRACT FROM AUTHOR]

Imaging quality is a critical component of compressive imaging in real applications. In this study, we propose a compressive imaging method based on multi-scale modulation and reconstruction in the spatial frequency domain. Theoretical analysis and simulation show the relation between the measurement matrix resolution and compressive sensing (CS) imaging quality. The matrix design is improved to provide multi-scale modulations, followed by individual reconstruction of images of different spatial frequencies. Compared with traditional single-scale CS imaging, the multi-scale method provides high quality imaging in both high and low frequencies, and effectively decreases the overall reconstruction error. Experimental results confirm the feasibility of this technique, especially at low sampling rate. The method may thus be helpful in promoting the implementation of compressive imaging in real applications. [ABSTRACT FROM AUTHOR]

A stable artificial solid electrolyte interphase (ASEI) containing P hosphazene and perfluoroalkoxy groups was designed to protect Li anodes. The ASEI with high ionic conductivity and mechanical robustness successfully suppressed the growth of Li dendrites, significantly enhancing the electrochemical performance of the Li–O2 batteries. [ABSTRACT FROM AUTHOR]

A traditional single-pixel camera needs a large number of measurements to reconstruct the object with compressive sensing computation. Compared with the 1/0 matrices in classical measurement, the 1/−1 matrices in the complementary measurement has better property for reconstruction computation and returns better reconstruction results. However, each row of the 1/−1 matrices needs two measurements with the traditional single-pixel camera which results into double measurements compared with the 1/0 matrices. In this paper, we consider the pseudo complementary measurement which only takes the same amount of measurements with the row number of some properly designed 1/0 matrix to compute the total luminous flux of the objective and derives the measurement data of the corresponding 1/−1 matrix in a mathematical way. The numerical simulation and experimental result show that the pseudo complementary measurement is an efficient tool for the traditional single-pixel camera imaging under low measurement rate, which can combine the advantages of the classical and complementary measurements and significantly improve the peak signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

Ghost imaging, which is an indirect imaging technique that uses correlations between two beams to retrieve the information of an object, is applicable to any wavelength. It has been performed with a growing range of light sources, including x-rays, the visible, and the infrared, and has also been extended to atoms and electrons recently. In this Letter, we demonstrate acoustical ghost imaging using the correlation between random acoustic patterns, which are generated by the phase and delaying manipulation of a transducer array and the total transmitted intensity signals. Furthermore, the reconstruction quality and resolution can be further improved by compressed sensing. This study shows a demonstration of ghost imaging using mechanical waves. Moreover, this approach requires fewer computational resources and offers great promise for high-speed and high-resolution acoustical imaging. [ABSTRACT FROM AUTHOR]

Computed-tomography imaging spectrometry (CTIS) can achieve non-scanning and high speed imaging recording of spatial and spectral data of a rapidly changing target scene. However, it has the problem of missing cone, which means the projection data cannot be fully sampled. This limits its practicality due to the ill-posed spectral reconstruction from limited angles of projection tomography. This paper proposes a compressed sensing (CS) sampling model for the CTIS, or CSCTIS in short, with the under sampling advantage of CS to improve the problem. The simulation results validates that the CS model is more effective than the traditional computed-tomography (CT) one, and further experimental results prove that the CSCTIS performs more accurate spectral reconstruction than the traditional CTIS. • Introduced the compressed sensing (CS) sampling in improving the computed-tomography imaging spectrometry (CTIS) to establish the CSCTIS. • The proposed CSCTIS enables instantaneous or snapshotting acquisition of spatial and spectral information of a moving scene with accurate and high-throughput measurement. • It provides promising application prospects in medical diagnosis, remote sensing, material detection. [ABSTRACT FROM AUTHOR]

A nitrogen-thermal approach via the reaction between transition metal species and N dopants affords us the ability to optimize the tradeoff between the number of exposed transition metal/carbon (exemplified by cobalt in this work) boundaries and the most pronounced interfacial rectifying contact to achieve the highly efficient and selective hydrogenation and dehydrogenation of N-heterocycle compounds in a reversible manner. [ABSTRACT FROM AUTHOR]

We described an effective way to generate a Co3O4 mesocrystal array with well-developed porosity, simply by uniting a coupled interface with hydrazine treatment. Due to the fast electron transfer and sufficient active sites, the Ti mesh-supported Co3O4 nanoneedles electrode could provide a current density of 49.9 mA cm−2 at 570 mV OER overpotential and has exceptionally high stability. [ABSTRACT FROM AUTHOR]

As a new type of heterogeneous catalyst with "homogeneous‐like" activity, single‐site transition‐metal materials are usually treated as integrated but separate active centers. A novel grouping effect is reported for single Ni−N4 sites in nitrogen‐doped carbon (Ni/NC), where an effective ligand‐stabilized polycondensation method endows Ni/NC nanocatalysts with a high content of single‐site Ni up to 9.5 wt %. The enhanced electron density at each single Ni−N4 site promotes a highly efficient hydrogen transfer, which is exemplified by the coupling of benzyl alcohol and aniline into N‐benzylaniline with a turnover frequency (TOF) value of 7.0 molN‐benzylaniline molmetal−1 h−1; this TOF outpaces that of reported stable non‐noble‐metal‐based catalysts by a factor of 2. [ABSTRACT FROM AUTHOR]

As a new type of heterogeneous catalyst with "homogeneous‐like" activity, single‐site transition‐metal materials are usually treated as integrated but separate active centers. A novel grouping effect is reported for single Ni−N4 sites in nitrogen‐doped carbon (Ni/NC), where an effective ligand‐stabilized polycondensation method endows Ni/NC nanocatalysts with a high content of single‐site Ni up to 9.5 wt %. The enhanced electron density at each single Ni−N4 site promotes a highly efficient hydrogen transfer, which is exemplified by the coupling of benzyl alcohol and aniline into N‐benzylaniline with a turnover frequency (TOF) value of 7.0 molN‐benzylaniline molmetal−1 h−1; this TOF outpaces that of reported stable non‐noble‐metal‐based catalysts by a factor of 2. Herd instinct: A grouping effect is observed for single Ni−N4 sites in a Ni catalyst supported by nitrogen‐doped carbon (NC). A high 9.5 wt % Ni content was achieved with a ligand‐stabilized polycondensation method. An enhanced electron density effect manifests at each single Ni−N4 site, which decreases the binding energy of H radicals to Ni and promotes efficient coupling of benzyl alcohol and aniline to form N‐benzylaniline. [ABSTRACT FROM AUTHOR]

This paper presents a trajectory-optimization method for a chaser spacecraft operating in ultra-close proximity to a failed satellite. Based on the combination of active and passive trajectory protection, the constraints in the optimization framework are formulated for collision avoidance and successful docking in the presence of any thruster failure. The constraints are then handled by an adaptive Gauss pseudospectral method, in which the dynamic residuals are used as the metric to determine the distribution of collocation points. A finite-time feedback control is further employed in tracking the optimized trajectory. In particular, the stability and convergence of the controller are proved. Numerical results are given to demonstrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Thermal imaging is an essential tool in a wide variety of research areas. In this work we demonstrate high-throughput double-wavelength temperature distribution imaging using a modified single-pixel camera without the requirement of a beam splitter (BS). A digital micro-mirror device (DMD) is utilized to display binary masks and split the incident radiation, which eliminates the necessity of a BS. Because the spatial resolution is dictated by the DMD, this thermal imaging system has the advantage of perfect spatial registration between the two images, which limits the need for the pixel registration and fine adjustments. Two bucket detectors, which measures the total light intensity reflected from the DMD, are employed in this system and yield an improvement in the detection efficiency of the narrow-band radiation. A compressive imaging algorithm is utilized to achieve under-sampling recovery. A proof-of-principle experiment was presented to demonstrate the feasibility of this structure. [ABSTRACT FROM AUTHOR]

This paper discusses the noisy phase retrieval problem: recovering a complex image signal with independent noise from quadratic measurements. Inspired by the dark fringes shown in the measured images of the array detector, a novel phase retrieval approach is proposed and demonstrated both theoretically and experimentally to apply the information of extracted dark fringes and its relationship with designed phase patterns. Here the dark fringes are extracted from the image plane, rather than the Fourier/focal plane, and the invalid extracted fringes can be tactfully bypassed to improve the anti-noise capability. A more accurate relative phase ratio between arbitrary two pixels is achieved by calculating the multiplicative ratios (or the sum of phase difference) on the path between them. Then the object phase image can be reconstructed precisely. Our approach is a good choice for retrieving high-quality phase images from noisy signals and has broad prospects in practical applications such as X-ray crystallography, diffractive imaging, and so on. [ABSTRACT FROM AUTHOR]

We present a new technique to denoise a single-pixel camera, in which complementary compressive imaging and a threshold strategy have been combined to improve image quality. The number of measurements recorded by the detector is reduced by setting a threshold. With an appropriate choice of threshold value, the quality of the reconstructed image is enhanced with a small number of measurements. This denoising method thus offers a very effective approach to promote the implementation of single-pixel camera in real applications. [ABSTRACT FROM AUTHOR]

The aim of this study was to use mid-infrared spectroscopy coupled with multiple model population analysis based on Monte Carlo-uninformative variable elimination for rapidly estimating the copper content of Tegillarca granosa . Copper-specific wavelengths were first extracted from the whole spectra, and subsequently, a least square-support vector machine was used to develop the prediction models. Compared with the prediction model based on full wavelengths, models that used 100 multiple MC-UVE selected wavelengths without and with bin operation showed comparable performances with Rp (root mean square error of Prediction) of 0.97 (14.60 mg/kg) and 0.94 (20.85 mg/kg) versus 0.96 (17.27 mg/kg), as well as ratio of percent deviation (number of wavelength) of 2.77 (407) and 1.84 (45) versus 2.32 (1762). The obtained results demonstrated that the mid-infrared technique could be used for estimating copper content in T. granosa . In addition, the proposed multiple model population analysis can eliminate uninformative, weakly informative and interfering wavelengths effectively, that substantially reduced the model complexity and computation time. [ABSTRACT FROM AUTHOR]

An experiment on compressive microscopic imaging with single-pixel detector and single-arm has been performed on the basis of “positive–negative” (differential) light modulation of a digital micromirror device (DMD). A magnified image of micron-sized objects illuminated by the microscope's own incandescent lamp has been successfully acquired. The image quality is improved by one more orders of magnitude compared with that obtained by conventional single-pixel imaging scheme with normal modulation using the same sampling rate, and moreover, the system is robust against the instability of light source and may be applied to very weak light condition. Its nature and the analysis of noise sources is discussed deeply. The realization of this technique represents a big step to the practical applications of compressive microscopic imaging in the fields of biology and materials science. [ABSTRACT FROM AUTHOR]

A new type of compressive spectroscopy technique employing a complementary sampling strategy is reported. In a single sequence of spectral compressive sampling, positive and negative measurements are performed, in which sensing matrices with a complementary relationship are used. The restricted isometry property condition necessary for accurate recovery of compressive sampling theory is satisfied mathematically. Compared with the conventional single-pixel spectroscopy technique, the complementary compressive sampling strategy can achieve spectral recovery of considerably higher quality within a shorter sampling time. We also investigate the influence of the sampling ratio and integration time on the recovery quality. [ABSTRACT FROM AUTHOR]

An experimental demonstration of spectral imaging with measurement dimensions compressed has been performed. With the method of dual compressed sensing (CS) we derive, the spectral image of a colored object can be obtained with only a single point detector, and sub-sampling is achieved in both spatial and spectral domains. The performances of dual CS spectral imaging are analyzed, including the effects of dual modulation numbers and measurement noise on the imaging quality. Our scheme provides a stable, high-flux measurement approach of spectral imaging. [ABSTRACT FROM AUTHOR]

We report an experimental demonstration of spectral imaging with a spectrometer without any scanning. The spatial resolution is provided by spatial light modulation based on the theory of compressed sensing. Objects with both continuous and discrete spectrum are used to demonstrate the performance of our system, which shows wide-spectrum and high efficient spectral imaging ability. The spatial and spectral resolutions of our imaging system are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the hovering control operation of a target in an elliptical orbit based on frozen parameter. The relative dynamics of spacecraft in eccentric orbits can be described as linear time-varying systems with periodic parameters. Those periodic parameters are the orbital radius, angular velocity and angular acceleration. The time-varying characteristics of these periodic parameters were analyzed via a performance index which is obtained analytically with small fixed time interval. Then, the frozen time interval was obtained with a fixed performance index using a numerical method. A series of constant coefficient linear systems are then obtained to represent the periodic linear system, namely the relative motion dynamics. In the frozen time interval, the hovering control scheme was designed based on a Linear Quadratic Regulator (LQR). Numerical simulations showed that the hovering control performance is good, except the vicinity near the apogee and perigee, both of which exhibit a relative large performance index. Decreasing the performance index from 0.01 to 0.001 reduces the position errors from 5 m to 0.5 m during steady state. It is shown that this approach can save propellant and eliminate chatter during the convergence compared to Control Lyapunov Functions (CLF) approach. [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]

A single-photon imaging system based on compressed sensing has been developed to image objects under ultra-low illumination. With this system, we have successfully realized imaging at the single-photon level with a single-pixel avalanche photodiode without point-by-point raster scanning. From analysis of the signal-to-noise ratio in the measurement we find that our system has much higher sensitivity than conventional ones based on point-by-point raster scanning, while the measurement time is also reduced. [ABSTRACT FROM AUTHOR]