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A vibration absorption meta-structure with strong nonlinear stiffness is proposed by combining concepts of the vibration absorber and meta-structure. An experimental setup comprising the meta-structure and a primary oscillator is designed. The results of ultraslow linear sweep and fixed-frequency harmonic excitation tests show that the meta-structure can suppress the vibrations of the primary oscillator with different stiffnesses. Moreover, the meta-structure changes the resonance frequency band of the test system to an acceptable range when softer springs are used in the primary oscillator. The primary oscillator and meta-structure have almost the same phase when the resonance occurs, resulting in an acceptable change. Another meta-structure mode is activated as its frequency increases, inducing an additional resonance band when a harder spring is attached. Furthermore, permanent magnets are installed in the meta-structure to form a bistable characteristic, and the influences of the number of magnets on the vibration reduction are analyzed. When the meta-structure has twelve magnets, the high-frequency resonance peak is eliminated because the magnets can suppress the second mode of the meta-structure. The wavelet analysis is conducted to detect the frequency components. The meta-structure results in energy spread from the excitation frequency to the other frequencies. [ABSTRACT FROM AUTHOR]

It was shown in [A. Mondino and G. Wei, On the universal cover and the fundamental group of an RCD * ⁢ (K , N) -space, J. reine angew. Math. 753 2019, 211–237] that any RCD * ⁢ (K , N) space (X , d , 픪) has a universal cover. We prove that for any point x ∈ X and R > 0 , there exists r < R such that any loop in B r ⁢ (x) is contractible in B R ⁢ (x) ; in particular, X is semi-locally simply connected and the universal cover of X is simply connected. This generalizes the earlier work in [J. Wang, Ricci limit spaces are semi-locally simply connected, preprint 2021] that any Ricci limit space is semi-locally simply connected. [ABSTRACT FROM AUTHOR]

We study the topology of a Ricci limit space (X,p), which is the Gromov-Hausdorff limit of a sequence of complete n-manifolds (M_i, p_i) with \mathrm {Ric}\ge -(n-1). Our first result shows that, if M_i has Ricci bounded covering geometry, i.e. the local Riemannian universal cover is non-collapsed, then X is semi-locally simply connected. In the process, we establish a slice theorem for isometric pseudo-group actions on a closed ball in the Ricci limit space. In the second result, we give a description of the universal cover of X if M_i has a uniform diameter bound; this improves a result by Ennis and Wei [Differential Geom. Appl. 24 (2006), pp. 554-562]. [ABSTRACT FROM AUTHOR]

• Wear mechanisms of gear with initial defects of bearing inner ring. • Monitoring and fault diagnosis of gear condition. • Employs a multi-analytical approach including vibration signal analysis, wear debris concentration analysis, qualitative analysis of the wear debris, and tooth surface analysis. • The combination of experimental research and simulation analysis. This study investigated the wear characteristics and operational condition of gears with initial defects of the bearing inner ring. The working states of gears were evaluated through a combination of vibration signal analysis, wear debris concentration analysis, qualitative analysis of the wear debris, and tooth surface analysis. Based on the Hertz contact theory, a dynamic model for the gear drive system was constructed, enabling the simulation and comparison of vibration acceleration signals under normal and fault conditions. The research results revealed that bearing defects induced irregularities in vibration frequency and amplitude, adversely affecting the performance and stability of the gear system. Furthermore, these defects trigger the creation of substantial wear debris, which exacerbates gear wear and reduces the gear lifespan by about 15%. Additionally, bearing defects induced intermittent load spikes and uneven stress distribution across tooth contacts, resulting in localized high shear stresses, material flaking, and surface spalling. Consequently, initial defects of the bearing will accelerate gear wear progression and lead to abnormal wear patterns, potentially resulting in the premature failure of the gear train system. The study investigates the underlying mechanisms of gear wear evolution influenced by these defects and offers practical guidelines for the engineering, manufacturing, and maintenance of gear systems. [ABSTRACT FROM AUTHOR]

The dealing/recycling of Ni‐containing wastewater pollution has aroused great attention both from environmental science and resource utilization perspectives. Herein, a classic CaFe‐layered double hydroxide (CaFe‐LDH) stabilizer, which exhibits a super‐stable mineralization efficiency for removing Ni2+ ions with a maximum saturated removal capacity of 321 mg g−1 is prepared. This stabilizer can remove not only 10 000 mg L−1 Ni2+ ions to a few mg L−1, but also 1 mg L−1 Ni2+ ions to 2 µg L−1. Moreover, the CaFe‐LDH shows great mineralization capability for the real Ni‐containing electroplating solution. It is demonstrated by ex situ X‐ray diffraction and extended X‐ray absorption fine structure characterization that the isomorphous substitution of Ca2+ by Ni2+ in the laminate of LDH dominates the mineralization process, and the CaFe‐LDH is transformed to the corresponding NiCaFe‐LDH accordingly. Further application of the resultant NiCaFe‐LDH shows improved electrocatalytic oxygen evolution reaction and photocatalytic CO2 reduction activities. This work paves great way for Ni2+ ion removal from wastewater and utilization of the recycled Ni resource. [ABSTRACT FROM AUTHOR]

Hydrazine (N2H4) is considered as one of the most potential energy storage materials in liquid fuel cells, as it contains high energy and power density, and the high‐efficiency oxidation of N2H4 in fuel cells has drawn great attention. However, the most used catalysts are expensive noble metal catalysts, thus the development of highly efficient non‐noble metal catalysts is crucial to reduce the cost of hydrazine oxidation in practical industry. Herein, we synthesized a series of CoFe‐layered double hydroxides (CoFe‐LDHs) intercalated with different anions via a simple one‐step co‐precipitation method for the electrooxidation of hydrazine. Through altering the intercalated anions of CoFe‐LDHs, the defects and the electronic structure can be well controlled, and the catalytic performance for the electrooxidation of hydrazine were well promoted by using NO3− intercalated into CoFe‐LDH compared with other anions (like Cl−, BO33−, CO32−). This work developed a series of hydrazine electrooxidation catalysts and established the relationship between the intercalated anions, the fine structure of the catalyst and the electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Improving the operating temperature to >1573 K is promising to enhance the generating efficiency of solar thermal power. However, such extremely ultra-high temperature inevitably brings severe challenges to solar-thermal conversion. Therefore, a cavity receiver with a simple flat absorber was designed and optimized in this study. Firstly, the receiver cavity was designed to be made of machinable insulation material, and its crucial absorbing surface was a flat absorber assembled from individual tungsten panels to simplify the structure. Then, an optical-thermal-mechanical model was established to identify the suggested configuration. It was found the partially coated receiver with a 130-mm-depth cavity and a down-in flow pattern can operate safely and efficiently under ultra-high temperatures, which was regarded as the optimized design. Finally, the performance of the optimized receiver was evaluated when the mass flow rate was within 22.0–32.0 g·s−1 and the inlet temperature was within 623∼873 K. The results indicated the highest outlet temperature reached 1579.2 K with receiver efficiency ranging from 69.9%–80.8%. Additionally, the maximum thermal losses from the glass and the insulation reached 860.2 W and 365.9 W, respectively, pointing out the crucial adiabatic directions for ultra-high-temperature receivers. The obtained results can offer promising insights to ultra-high-temperature solar receivers. • An ultra-high-temperature cavity receiver with a simple flat absorber is designed. • An optical-thermal-mechanical model is built to evaluate the receiver performance. • The suggested receiver operates safely and efficiently under ultra-high temperature. • The highest outlet temperature is 1579.2 K with efficiencies within 69.9%–80.8%. [ABSTRACT FROM AUTHOR]

Dihydroxybenzenes (DHB) are one of the most important fine chemicals used as raw materials or intermediates in industries. One-step selective phenol hydroxylation using a photo-Fenton system is an attractive and challenging strategy, especially under long-wavelength irradiation. Herein, we report that a highly selective photo-driven Fenton hydroxylation reaction of phenol to DHB can be achieved over NiFe-layered double hydroxide nanosheets (NiFe-NS) under visible-light irradiation with 70% phenol conversion and ∼99% DHB selectivity. A more interesting finding is that a high phenol conversion (∼40%) activity can be maintained even under monochromatic irradiation at 550 nm. The superior photocatalytic activity was attributed to the abundant defects in NiFe-NS, which facilitated the adsorption of hydrogen peroxide (H2O2) onto the catalyst surface and promoted the transfer efficiency of photoinduced electrons from the catalyst to H2O2, generating ˙OH radicals to participate in the hydroxylation of phenol. [ABSTRACT FROM AUTHOR]

• A high-performance simulator pursuing high flux and fine uniformity is designed. • Design and optimization processes are illustrated to provide universal guidelines. • A 30 kW e realistic simulator is fabricated and measured experimentally. • The simulator improves 10% uniformity while reaching a peak flux of 8.6 × 106 W·m−2. The high flux solar simulator is a significant experimental tool in concentrated solar power applications. For a simulator, the uniformity of its light spot is as vital as high flux, since uneven light spots may result in the thermal-stress failure of the solar receiver. However, most constructed simulators have only pursued extremely high flux but ignored uniformity, thus degrading the simulator's overall performance. Considering that improving uniformity comes at the expense of decreasing the flux, a high-performance solar simulator must meet a reasonable compromise between high flux and fine uniformity. In this paper, a simulator whose input power reached 30 kW e was designed and optimized using an in-house Monte Carlo Ray Tracing (MCRT) model, and corresponding processes were demonstrated to provide universal guidelines. To improve the uniformity while maintaining satisfying high flux, a non-coaxial reflector with optimized parameters was implemented. Based on the design and optimization results, a realistic solar simulator was manufactured and calibrated through experimental methods. The results demonstrate that the manufactured simulator achieved an about 10% reduction in non-uniformity while reaching a peak flux of 8.6 × 106 W·m−2, meeting the design expectation for a high-performance simulator. [ABSTRACT FROM AUTHOR]

The assessment of hemostasis and fibrinolysis is essential in emergency settings to make timely medical decisions. While conventional thromboelastography (TEG) analyzers provide comprehensive information on blood clotting, their long test times are often unsuitable for emergency patients. In this study, we propose an innovative method of microfluidic thromboelastography (μ-TEG) that rapidly measures the viscoelastic properties of blood coagulation in oscillating flow through circular tubes. Our μ-TEG system moves a blood sample back and forth through a circular tube subjected to sinusoidal pressure, generating shear rates ranging from 1.2 to 20 s−1, higher than those of conventional TEGs. The movements are monitored by a pressure sensor and converted to a conventional TEG. Key parameters such as MA and Ly30 can be acquired within 10–12 min for normal samples. Our study showed that the increased shear rate in the μ-TEG system alters the coagulation mechanism, resulting in increased coagulation strength and rapid fibrinolysis. Despite the short test time, the μ-TEG showed good agreement with the TEG5000. The rapid measurement of μ-TEG makes it a useful tool for analyzing hemostasis and fibrinolysis in emergency and operating rooms. [Display omitted] • The μ-TEG system can measure the viscoelastic properties of blood clots within 10 min. • Oscillatory flow monitoring of blood coagulation successfully translated into TEG-equivalent results. • Elevated shear rate accelerates the coagulation and fibrinolysis processes, while also enhancing clot strength and fibrinolytic capacity. [ABSTRACT FROM AUTHOR]

Detecting the optical vortices of darkness hidden in an ultra-weak background is a difficult task. Here we report an experiment demonstrating that the optical vortices can be directly visualized and identified with a smaller number of photons. Our method is based on the extension of the spiral phase contrast technique to incorporate vortex phase plates (VPP) of high-order topological charges. In our experiment, we prepare optical vortex arrays of interesting structures such as Arabic numerals and the wings carrying various topological charges. By placing various VPP filters in the Fourier plane of a 4f imaging system, the embedded vortices of an incident ultra-weak light field can be visualized, revealing both their positions and topological charges. It is found that a higher order vortex generally requires a smaller number of photons to be detected. Our method may find potential application in the fields of astronomical optics and biosensing in an ultra-weak light environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The atomic economical synthesis of CaCr-LDH and the rapid purification of wastewater containing high concentration of Cr3+ are realized by super-stable mineralization. • Through multistage super-stable mineralization, using CaCr-LDH to treat multiple divalent heavy metal ions can reduce costs by about 50% and sludge by about 10%. • The product showed excellent performance in photocatalytic CO 2 reduction and precious metal (Au) recovery from printed circuit board leaching wastewater. The treatment and recycling of heavy metal pollutants are vital for the restoration of the ecological environment and the recovery and reuse of resources. Herein, we report an atomic-economic method to synthesize a novel CaCr-layered double hydroxide (LDH) by extracting toxic Cr3+ (more than 1000 mg/L) from industrial wastewater, by which the wastewater can be purified to discharge standards. The obtained CaCr-LDH can be reused for the super-stable mineralization of multiple heavy metal ions with a high capacity, and the removal capacities of Ni, Co, Cu and Zn ions are 306.7 mg/g, 578.0 mg/g, 657.9 mg/g, and 352.1 mg/g, respectively. Furthermore, CaCr-LDH has the advantages of a large treatment range, anti-interference, alkali corrosion resistance, low cost, and less sludge. In the above mineralization process, CaCr-LDH converts to MCaCr-LDH (M = Co, Ni, Cu, and Zn) through an isomorphous substitution process. The obtained NiCaCr-LDH products show excellent performance in photocatalytic CO 2 reduction with a high CH 4 selectivity of 34.8% under visible light. The MCaCr-LDH products can selectively adsorb gold ions with approximately 90% adsorption efficiency and reduce them with approximately 80% reduction efficiency from printed circuit board leaching wastewater, offering promising functionalities for improving environmental pollution, resource waste, and energy crises. [ABSTRACT FROM AUTHOR]

• A lab-scale ultra-high-temperature tungsten solar receiver is designed. • Optical-thermal-mechanical performance of the receiver is evaluated. • High receiver efficiency of 81.88–89.08% is achieved under different conditions. • The receiver can work safely at ultra-high outlet temperature of above 1573 K. The key to raising the cycle efficiency of the solar power tower plant is to improve the operating temperature of the solar receiver. However, only a few receivers can operate at a temperature above 1573 K, and it is still very challenging to harvest solar energy safely and efficiently under such ultra-high temperatures. In this paper, firstly, a lab-scale tungsten receiver with the designed thermal power of 7 kW th was designed for ultra-high-temperature solar energy harvesting. Then, an optical-thermal–mechanical coupling model was constructed and validated with experimental data. Based on this model, the receiver performance under different cylinder lengths was evaluated. It is found that the solar receiver with a 150 mm length cylinder was able to operate safely and efficiently under the most extreme condition, which was suggested as the optimized design. Then, the effects of key operating parameters on the performance of the optimized receiver were analyzed, finding that the receiver efficiency increases with increasing inlet mass flow rate, decreasing inlet temperature, or increasing incident power. Moreover, performance evaluation indicates that high receiver efficiency of 81.88%-89.08% can be achieved by the optimized receiver while the inlet mass flow rate is within 0.07–0.12 kg·s−1, the average fluid temperature is within 833.9–1384.7 K, and the incident power is within 5.5–8.0 kW. Results from the present study can provide a reliable and useful reference for developing ultra-high-temperature solar receivers. [ABSTRACT FROM AUTHOR]

In this study, the source-relationships were established for surface nitrate concentrations in Northeast Asia, using the Particulate Matter Source Apportionment Technology (PSAT) in the CAMx (a regional chemical transport model). Both of the local emissions and Chinese emissions were important among the sources of the particle nitrate in Japan and South Korea, accounting for 27.9–62.9% and 22.9–50.5% respectively. The local contributions of nitrate were 4–20% higher than the figures of sulfate, and this was caused by the different chemical processes and emissions involved. The seasonal variation of the nitrate concentration in East Asia led to different amounts of nitrate being attributed to long-range transport, and was higher in winter (>53%) than in summer (<41%). The interactions between ammonia/ammonium, sulfate and nitrate were also discussed. The distribution of degree of sulfate neutralization (DSN) and the adjusted gas ratio (AdjGR) in East Asia suggested that the particle nitrate concentration was most sensitive to changes in the total ammonia in most parts of Japan and some regions of South Korea. And that was different in most parts of East Asia, where there were large quantities of ammonia. The ammonia from local emissions were most likely responsible for some particulate nitrate being transformed from trans-boundary gaseous nitric, which signified that local emissions of ammonia increased the contribution of China to the nitrate concentrations in Japan and South Korea. [ABSTRACT FROM AUTHOR]

The power quality of hydrogen production converters is related to the characteristics of electrolytic hydrogen production, which is crucial to efficiency, power loss and other performance factors of hydrogen production. In order to explore the influence of the output voltage ripple of a hydrogen production converter on the hydrogen production performance of a proton exchange membrane electrolyzer, a proton exchange membrane electrolyzer model was established according to the principles of material conservation and electrochemistry. The performance characteristics of the proton exchange membrane electrolyzer and the effects of three kinds of ripple voltage with different frequencies and amplitudes on the hydrogen production efficiency and power consumption of the proton exchange membrane electrolyzer were explored. The effects of the three kinds of ripple were consistent. For example, when the ripple coefficient of the sinusoidal ripple voltage was increased by 45%, the average power consumption increased by 61%. When the ripple coefficient was constant, the frequency increased by 1000%, and the average power consumption increased by only 0.033%. In the range of low ripple coefficient (0~35%), the hydrogen production rate was reduced by 2% at most. When the ripple coefficient was in the range of 35~70%, the hydrogen production rate was reduced by 12% at most. The results showed that the ripple coefficient had a greater impact on the power consumption and hydrogen production rate of the electrolyzer, but the frequency was smaller. Among the three kinds of ripple, the triangular wave had the least influence on the power consumption and hydrogen production rate of the electrolytic cell. This study provides reference and theoretical support for the subsequent engineering application, precise control and dynamic characteristics of proton exchange membrane electrolyzer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Monolayer layered double hydroxides (LDHs) have been synthesised successfully by scale-up and used as mineralizers for heavy metal ions. • The monolayer MgAl-LDH exhibited excellent removal efficiency of more than 99% for Cu2+, Ni2+ and Cd2+, and can rapidly lower a low concentration of 1 ppm to ppb level. • The mineralisation mechanism was confirmed based on X-ray absorption fine structure (EXAFS) and Density functional theory (DFT) calculations. • The mineralized products can efficiently convert CO 2 into fuel through photocatalysis and quickly remove organic dyes from sewage. Exploring a sustainable route for the efficient treating/recycling of heavy metal (like Ni2+, Cd2+, Cu2+) contamination of water is highly desirable both from the environment and resource view. Herein, we reported the scale-up synthesis of monolayer magnesium-aluminium layered double hydroxide (m-MgAl-LDH) nanosheets, which showed exceptional ability to mineralize Ni2+, Cd2+ and Cu2+ rapidly and efficiently. Furthermore, m-MgAl-LDH can purify 1 ppm Cu2+, Ni2+ and Cd2+ to safe levels. The sorption sites of heavy metal ions were revealed. Ni2+ and Cd2+ substitute for the Mg2+ sites within the MgAl-LDH layers, while Cu2+ ions anchor on the surface of MgAl-LDH with high dispersion. The mineralized products from Ni2+ and Cu2+ cations further showed excellent performance in visible-light-induced photocatalytic reduction of CO 2 and removal of anions (like PO 4 3- and toxic AsO 2 - ions) efficiently, providing an alternative for the mitigation of energy and resource crisis. [ABSTRACT FROM AUTHOR]

Northern China experienced a severe sand and dust storm (SDS) on 14/15 March 2021. It was difficult to simulate this severe SDS event accurately. This study compared the performances of three dust-emission schemes on simulating PM10 concentration during this SDS event by implementing three vertical dust flux parameterizations in the Comprehensive Air-Quality Model with Extensions (CAMx) model. Additionally, a statistical gusty-wind model was implemented in the dust-emission scheme, and it was used to quantify the gusty-wind contribution to dust emissions and peak PM10 concentration. As a result, the LS scheme (Lu and Shao 1999) produced the minimum errors for peak PM10 concentrations, the MB scheme (Marticorena and Bergametti 1995) underestimated the PM10 concentrations by 70–90%, and the KOK scheme (Kok et al. 2014) overestimated PM10 concentrations by 10–50% in most areas. The gusty-wind model could reasonably reproduce the probability density function of 2-min wind speeds. There were 5–40% more dust-emission flux and 5–40% more peak PM10 concentrations generated by the gusty wind than the hourly wind in the dust-source regions. The increase of peak PM10 concentration caused by gusty wind in the non-dust-source regions was higher than in the dust-source regions, with 10–50%. Implementing the gusty-wind model could help improve the LS scheme's performance in simulating PM10 concentrations of this severe SDS event. More work is still needed to investigate the reliability of the gusty-wind model and LS scheme on various SDS events. [ABSTRACT FROM AUTHOR]

Sand and dust storms occur frequently in East Asia, and the dust particles could be transported to most areas of East Asia. To quantify the dust emissions in 18 dust source regions in China and Mongolia and their contributions to PM 10 concentrations over East Asia, 10 sand and dust storms (SDSs) episodes in 2020 were simulated using the Comprehensive Air Quality Model with Extensions (CAMx). A dust emission scheme and a tagged method were incorporated. The model well captured the variations of PM 10 concentrations during the SDSs episodes. The Gobi deserts in Mongolia were the most important sources of sand and dust in East Asia, with the highest dust emissions, contributing more than 60% to the PM 10 concentrations over East-Central China, Japan, and South Korea. The dust emission from Inner Mongolia was about 1/3 of that in Mongolia, and contributed 20–30% to PM 10 concentrations over East-Central China, Japan, and South Korea. However, more than 50% of the PM 10 concentrations in Inner Mongolia originated from Mongolia in the SDSs events. Few dust aerosols from Taklimakan and Eastern Xinjiang could be transported to the areas further than its surrounding area. Because of the larger contribution of Mongolia to Northern China, the variation of the dust storm frequency in Northern China correlated well with the surface conditions in Mongolia. Anthropogenic emissions contributed less than 5% to the PM 10 concentrations over most part of East Asia during the SDSs events. • Source apportionment of PM 10 during SDSs events over East Asia were done using a tagged method. • Mongolia contributed more than 60% of Dust aerosols over east-central China, Japan, and Korea. • Taklimakan and Eastern Xinjiang rarely affected or were affected by other regions. • Anthropogenic emissions contributed less than 5% to PM 10 concentrations during the SDSs events. [ABSTRACT FROM AUTHOR]

To further make a compromise among the accuracy, convenience, safety, and measuring power range of the flux mapping in the high-flux solar simulator, a modified indirect flux mapping system that combines a water-cooled Lambertian target and a gray spot superposition method was firstly designed. Then, measuring errors of the modified system were analyzed, which were found to be acceptable. Then, a comparison between the modified system and a reference indirect system was conducted, indicating that the modified system is reliable. Then, based on the modified system, the flux distributions of a 30 kWe high-flux solar simulator were measured, finding the modified system can exceed the upper limit of the reference indirect system which burned a target under a relatively small power value. In addition, more analysis pointed out that the modified system can reduce the system complexity and improve the mapping accuracy compared with the direct or traditional indirect flux mapping systems. Results from current study indicated the modified system is reliable and suitable for wide-range flux mapping of the solar simulator. [Display omitted] • A modified system was presented for flux mapping of high-flux solar simulators. • A cooled Lambertian target and a gray spot superposition method are employed. • Measuring uncertainties of the flux and power are ±7.94% and ±7.96%, respectively. • The system was found to be reliable by comparing with an existing system. • The modified system is effective for extending the measuring power range. [ABSTRACT FROM AUTHOR]

Aiming at the energy-saving of water heater, a novel technology which can enhance thermal insulation and improve energy efficiency simultaneously has been proposed, and its source-sink matching strategy has been investigated in this study. A source-sink heat transfer device is designed, and the optimal installment position of this device has been determined through theoretical and experimental methods, besides that, the rationality of matching strategy is also evaluated. Experimental results and exergy analysis show that the optimal installment position and suitable source-sink matching strategy facilitate to boost the energy-saving effect, lower production cost and conform to the miniaturization trend of water heater. In addition, the experimental results reveal that although adiabatic measures and energy efficiency improvement measures adopted by this technology are different, the ultimate direction is the same, both of which are to directly or indirectly reduce the temperature of heat source, which can provide significant reference for practical engineering application. • A novel energy-saving technology of water heater is proposed. • The rationality of its source-sink matching strategy is evaluated. • The energy efficiency and adiabatic effect are improved simultaneously. • Significant references for practical engineering application are provided. [ABSTRACT FROM AUTHOR]

The optical vortices embedded in a light field scattered by an object may contain abundant information from the object. However, their identification becomes very challenging when the detected light field is ultra‐weak. Based on the development of spiral phase filtering technique with high‐order vortex phase plates, the researchers from China and Canada present a high‐efficiency scheme to illuminate these vortices with only a small number of photons. In their demonstration, both the topological charge and location of each hidden vortex can be well visualized then revealed by a bright focused spot after scanning the high‐order vortex phase plates. This easy‐to‐implement filtering technique might be integrated into telescopes to detect optical vortices of weak signals from distant astronomical objects. (Picture: Wuhong Zhang et al., article number 1600163, in this issue) [ABSTRACT FROM AUTHOR]

[Display omitted] • The CaAl-LDH exhibited excellent removal efficiency with the removal capacity of Cu2+, Zn2+, Ni2+, and Co2+ exceeding 400 mg/g. • For actual electroplating wastewater, CaAl-LDH showed outperforming mineralization performance to meet the WHO drinking water standard. • The mineralisation mechanism in LDH was confirmed based on X-ray absorption fine structure (EXAFS) and Density functional theory (DFT) calculations. • The Ni2+ mineralized products can efficiently convert CO 2 into fuel (CH 4 , CO) through photocatalysis with excellent selectivity and stability. From an environmental and resource management perspective, it is preferable to recover and reuse heavy metal ions found in electroplating wastewater. The discharge of electroplating wastewater has caused serious environmental pollution and resource waste. Ca-based layered double hydroxides (LDHs) stabilizers are designed, which show a rapid, effective, and adequate capacity exceeding 400 mg/g against solutions of Cu2+, Zn2+, Co2+, and Ni2+ ions through an isomorphous substitution mechanism. The needs of plant development were met by the use of CaAl-LDH in soil remediation. While Cu resources can be recovered from the CuAl-LDH products by electrolysis, the final mineralization products from Ni2+ and Zn2+ ions showed exceptional performance in visible-light-induced photocatalytic reduction of CO 2 with excellent selectivity (98.7% toward CO and CH 4) and the removal of arsenite ions (99.97%). The results of this investigation revealed a feasible new approach to the removal, recycling, and reutilization of heavy metal ions. [ABSTRACT FROM AUTHOR]

In the spiral phase contrast imaging, the integer spiral phase plate (SPP) are generally employed to perform the radial Hilbert transform on the object. Here we introduce fractional SPP filters, instead of the integer ones, to investigate the gradual formation of edge enhancement for pure phase objects. Two spatial light modulators are used in our experimental configuration. One is addressed to display the pure phase object of a five-pointed star, while the other serves as a dynamic filter of fractional topological charge Q. Of interest is the observation of the complete reversal of the edge and background brightness by gradually changing the fractional vortices from Q = 0 to 1. The experimental results were well interpreted based on the OAM spectra of fractional SPP, which indicates that the filtered output image can be considered as a coherent superposition of all possible images that are individually resulted from the integer OAM filtering. Besides, we show that the spiral phase contrast effect can still be observed in real time for a rotating three-leaf clover. Our results may find potential applications in the optical microscopic imaging. [ABSTRACT FROM AUTHOR]

• We have obtained the mixed metal oxides as the outstanding heavy metal mineraliser for Pb2+ irons. • The mineralization mechanisms towards different concentrations of Pb2+ were fully demonstrated by XAFS and DFT calculation. • The mineralized Pb2+ could be recycled by electrolysis to obtain the metallic lead. Lead (Pb) as one of the most widespread toxic heavy metals in both water distribution systems and in surface water, it still remains a challenge to quickly and completely remove/recycle Pb ions from these systems. Herein, the obtained Mg 2 Fe-mixed metal oxides (Mg 2 Fe-MMO) through calcination of Mg 2 Fe-Cl-layered double hydroxide (Mg 2 Fe-Cl-LDH) showed extremely high mineralized capacity for Pb ions with removal figures of 2406 mg/g. This performance is superior to most reported materials, and can rapidly purify Pb2+ at 1 ppm to safe levels (12 ppb). X-ray absorption fine structure (XAFS) studies revealed a transformation from MgFe-MMO to defective Mg 2 Fe-CO 3 -LDH with the Pb ions sequestering OH− from Mg 2 Fe-CO 3 -LDH to form a solid precipitate. Moreover, the mineralized products could be recycled by electrolysis to obtain metallic lead, providing a new opportunity for pollution remediation and the recovery of metal lead. This work provides a new route for Pb ions removal from wastewater and the potential for utilization of the recycled Pb resource. [ABSTRACT FROM AUTHOR]

• The multi-metallic LDHs provide exciting electronic property than traditional binary LDHs. • The transformation from binary LDH to LMMH (layered multi-metallic hydroxides) is accompanied by changes in electronic or morphological structure. • The prepared LDHs exhibit enhanced photo/electrocatalytic performance. The development of efficient photo/electrocatalysis using sustainable renewable resources to prepare high value-added products is now a major goal to achieve new environmentally friendly technologies. However, existing solutions still offer unsatisfied catalytic efficiency and low energy utilization. Therefore, it is paramount to develop new strategies to control the morphology and structure of functional materials to improve their photo/electrocatalytic activity. Layered double hydroxides (LDHs), as a kind of two-dimensional (2D) materials, have been largely explored in photo/electrocatalytic reactions due to their extensive tenability of elemental composition and interlayered anions. Furthermore, the intrinsic feature of atomic dispersion has been utilized to introduce more active sites to further improve the reaction performance. Herein, we review strategies that have been developed for introducing more active sites into or onto the LDH layer for the construction of multi-metallic LDHs based photo/electrocatalytic material. The accompanied structure and electronic changes that are pivotal for modulation for catalytic activity are proposed, such as, improving carrier transportation, and optimizing molecular activation energy. We review the catalytic performance of multi-metallic LDHs for photo/electrocatalytic water splitting, CO 2 photoreduction, CO hydrogenation, heavy metal mineralization/reutilization and beyond. We highlight future challenges and opportunities to design multi-metallic LDHs to address future photo/electrocatalysis research challenges. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple solar absorber with regular hexagonal tungsten nanopores is proposed. • Near-ideal spectral selectivity is achieved, and relevant mechanisms are revealed. • The absorber can capture solar energy efficiently within 673 K–1573 K. • A high photothermal efficiency of 89.39 % is obtained at 1573 K and 2000 suns. • The absorber is insensitive to the variations of its geometry and incident light. An efficient and simple spectral selective solar absorber is vital for solar-thermal systems that operate under a wide temperature range (673–1573 K). However, few absorbers are competent for this wide temperature range due to their suboptimal spectral selectivity under specific conditions or complex structures that are difficult to be fabricated. Here, we proposed a near-ideal spectral selective solar absorber consisting of simple regular hexagonal tungsten nanopores filled with silicon dioxide. A strong solar absorptivity up to 0.9632 and a reduced total emissivity down to 0.0961 were realized due to its good spectral selectivity. Meanwhile, the near-ideal spectral selective solar absorber obtains high photothermal efficiencies of 95.25 % at 673 K, 95.84 % at 873 K, and 89.38 % at 1573 K when the concentration ratios are 100, 1000, and 2000 suns, respectively. Subsequently, mechanism analysis implies that the excellent performance of the near-ideal absorber results from the electromagnetic field enhanced by the cavity resonances, localized surface plasmon resonances, and surface plasmon polaritons. Further, the impedance matching also plays an important role in achieving the excellent performance. In addition, the near-ideal absorber also shows insensitivity to incident angle and polarization angle with both TE and TM waves. All the above positive properties presented by the near-ideal absorber indicate that it is a good option for solar energy capture in the wide temperature range of 673–1573 K. [ABSTRACT FROM AUTHOR]

The Beijing–Tianjin–Hebei (BTH) region has encountered increasingly severe and frequent haze pollution during recent decades. This study reveals that El Niño–Southern Oscillation (ENSO) has distinctive impacts on interannual variations of haze pollution over BTH in early and late winters. The impact of ENSO on the haze pollution over the BTH is strong in early winter, but weak in late winter. In early winter, ENSO-related sea surface temperature anomalies generate double-cell Walker circulation anomalies, with upward motion anomalies over the tropical central-eastern Pacific and tropical Indian Ocean, and downward motion anomalies over the tropical western Pacific. The ascending motion and enhanced atmospheric heating anomalies over the tropical Indian Ocean trigger atmospheric teleconnection propagating from the north Indian Ocean to East Asia, and result in the generation of an anticyclonic anomaly over Northeast Asia. The associated southerly anomalies to the west side lead to more serious haze pollution via reducing surface wind speed and increasing low-level humidity and the thermal inversion. The strong contribution of the Indian Ocean heating anomalies to the formation of the anticyclonic anomaly over Northeast Asia in early winter can be confirmed by atmospheric model numerical experiments. In late winter, vertical motion and precipitation anomalies are weak over the tropical Indian Ocean related to ENSO. As such, ENSO cannot induce a clear anticyclonic anomaly over Northeast Asia via atmospheric teleconnection, and thus has a weak impact on the haze pollution over BTH. Further analysis shows that stronger ENSO-induced atmospheric heating anomalies over the tropical Indian Ocean in early winter are partially due to higher mean SST and precipitation there. Significance Statement: There exist large discrepancies regarding the contribution of El Niño–Southern Oscillation (ENSO) events to the wintertime haze pollution over North China. Several studies have indicated that ENSO has a weak impact on the haze pollution over North China. However, some studies have argued that ENSO events can exert impacts on the occurrence of haze pollution over North China. In this study, we present evidence to demonstrate that ENSO has distinctive impacts on interannual variations of the haze pollution over the Beijing–Tianjin–Hebei (BTH) region in North China in early and late winters. Specifically, ENSO has a strong impact on the haze pollution over BTH in early winter, whereas the impact of ENSO on the haze pollution over BTH is fairly weak in late winter. Results of this study could reconcile the discrepancy of previous studies about the impact of ENSO on the haze pollution over North China. [ABSTRACT FROM AUTHOR]

The environmental meteorological services in China are concerned with atmospheric environmental quality, which is directly related to human activities and affects human health. In recent years, air pollution and other environmental problems have attracted nationwide attention in China, so the environmental meteorological services have been developed rapidly. To provide better meteorological monitoring and forecasting services, the Environmental Meteorological Centre of China Meteorological Administration was established in March 2014 by integrating the resources of various national service units. We review the development of China’s national environmental meteorological services and highlight their current status including major technological capabilities. We also explore future trends of the national environmental meteorological services by analysing deficiencies, gaps in supply and demand, and capabilities of the current environmental meteorological services. [ABSTRACT FROM AUTHOR]

Air-breathing hypersonic flight vehicles are highly airframe/propulsion integrated, especially the outer and inner flows of the flight vehicles are very complicated and interact strongly with each other, considerable difficulties should be solved rationally in ground testing. Therefore, it is of great necessity to conduct researches on the related experimental methodology. This paper presents a brief analysis of main aerodynamic issues concerned with air-breathing hypersonic flight vehicles as well as associated experimental testing requirements, in which three typical types of experimental testing are focused on, they are performance testing of airframe/propulsion integrated vehicles, experiment of boundary layer transition with trips, and arc-heated facility testing of sharp leading edges. Besides, an overview of wind tunnel research methodologies both in China and abroad is included. This paper also provides critical similarity parameters that need to be ensured for the three types of experiments mentioned above, followed by an influence analysis of those key parameters that are difficult to achieve in ground testing. Based on the testing capability of the current test facilities, three typical wind tunnel experimental methods have been put forward, along with an effective method of acquiring accurate aerodynamic performance of the airframe/propulsion integrated vehicles in particular. The research materials presented should provide a useful guideline on the aerothermal and aerodynamic experimental research on hypersonic flight vehicles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four new He-SCO 2 Brayton cycles are designed for ultra-high-temperature solar power. • Thermal efficiency & fluid temperature difference cannot be maximized concurrently. • The four He-SCO 2 cycles are optimized successfully by multi-objective optimizations. • The He-SCO 2 cycles can be flexibly selected under different requirements. • Efficiency of 60.5% and temperature difference of 906 °C are obtained concurrently. In this study, to improve the power cycle performance of the ultra-high-temperature (1300 °C) concentrating solar power, four novel He-SCO 2 combined Brayton cycles are conceptually designed. After the design, firstly, parameter analysis of the cycles is conducted by developing a thermodynamic model. It is found that two key performance criteria, including the thermal efficiency of the cycle and the temperature difference of the heat transfer fluid, are affected by many parameters, where the temperature difference represents the capability to couple with the thermal energy storage. Moreover, it is found that the two criteria cannot be maximized concurrently by an identical group of operating parameters. Then, multi-objective optimizations are employed to optimize the cycles, where the thermal efficiency and the temperature difference are regarded as the objective functions. The results suggest that the He-SCO 2 cycles can achieve better performance than a typical He cycle. Moreover, comparisons of the Pareto optimal fronts of the four He-SCO 2 cycles show that the combined cycle with more components can achieve superior performance than those with fewer components. The cycle 4 can yield the highest optimized thermal efficiency of 64.72%, and the cycle 3 can yield the highest temperature difference of 1014.7 °C. Moreover, it is found different cycles can be recommended under different requirements. If the thermal efficiency is required to be as high as possible, the cycles 3 and 4 should be suggested. If the temperature difference is required to be as large as possible, the cycle 1 that needs the fewest components should be recommended. Comparisons among the optimal solutions of the four He-SCO 2 cycles show that the cycles 3 and 4 should be recommended when the thermal efficiency and temperature difference are required to be balanced. The optimal cycles 3 and 4 can provide quite high thermal efficiencies of 60.49% and 60.74%, respectively. And their corresponding temperature differences reach 906.1 °C and 899.7 °C, respectively. The above results suggest the designed He-SCO 2 cycles are promising for improving the power cycle performance under ultra-high-temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • A modified trough receiver with two solar mirrors and a hot mirror is proposed. • An optical-thermal coupled model is developed to analyze the collector performance. • The receiver can reduce the heat loss and improve the efficiency effectively. • Heat loss of the absorber can be reduced by 13.5% at the fluid temperature of 823 K. • The best improvement in the collector efficiency of 4.70% is achieved. Parabolic trough collector is an up-and-coming technology for urban energy supply. To further enhance the optical-thermal efficiency of the collector, a modified receiver enhanced by solar and hot mirrors was proposed. In this receiver, two symmetrical solar mirrors were designed to collect more solar irradiance, and a transparent hot-mirror shield was employed to lessen the thermal loss. After the design, the collector performance was studied by developing an optical-thermal coupled model. Based on the model, firstly, the proposed receiver was compared with the conventional receiver and two existing modified receivers. Results indicate the proposed receiver can achieve an optical efficiency of 78.02%, which is higher than those of the existing modified receivers and is just 0.22% lower than that of the conventional one. Moreover, compared with the conventional receiver, the two existing modified receivers cannot improve the optical-thermal efficiency at sufficiently high direct normal irradiance or relatively low fluid temperature, which can be overcome by the proposed receiver. Furthermore, compared with the conventional receiver, the proposed receiver can lessen the thermal loss by 11.2–89.6 W·m−1, thus improving the receiver efficiency and the optical-thermal efficiency by 0.03–5.26% and 0.03–4.70%, respectively, under the typical ranges of the inlet temperature (573–823 K) and the direct normal irradiance (0.3–1 kW·m−2). Then, parameter analysis indicates the hot mirror with low emissivity is necessary for efficiently improving the optical-thermal efficiency. Finally, the proposed receiver can improve the optical-thermal efficiency more effectively at higher fluid temperature or larger coating emissivity. The above results signify that the proposed receiver can be helpful for enhancing the efficiency of the trough collector. [ABSTRACT FROM AUTHOR]

For many years, Beijing has suffered from severe air pollution. At present, fine particulate matter (PM2.5) pollution in the winter and ozone (O3) pollution in the summer constitute serious environmental problems. In this study, the combination of a comprehensive air quality model with particulate matter source apportionment technology (CAMx-PAST) and monitoring data was used for the high-spatial resolution source apportionment of secondary inorganic components (SNA: SO42−, NO3−, and NH4+) in PM2.5; their corresponding precursor gases (SO2, NO2, and NH3); and O3 in the winter and summer over Beijing. Emissions from residents, industry, traffic, agriculture, and power accounted for 54%, 25%, 14%, 5%, and 2% of PM2.5 in the winter, respectively. In the summer, the emissions from industry, traffic, residents, agriculture, and power accounted for 42%, 24%, 20%, 10%, and 4% of PM2.5, respectively. The monthly transport ratio of PM2.5 was 27% and 46% in the winter and summer, respectively. The regional transport of residential and industrial emissions accounted for the highest proportion of PM2.5. The regional transport of emissions had a significant effect on the SO42− and NO3− concentrations, whereas SO2 and NO2 pollution were mainly affected by local emissions, and NH4+ and NH3 were mainly attributed to agricultural emissions. Industrial and traffic sources were two major emission sectors that contributed to O3 pollution in Beijing. The monthly transport ratios of O3 were 31% and 65% in the winter and summer, respectively. The high-spatial resolution regional source apportionment results showed that emissions from Langfang, Baoding, and Tangshan had the greatest impact on Beijing's air pollution. This work's methods and results will provide scientific guidance to support the government in its decision-making processes to manage the PM2.5 and O3 pollution issues. [ABSTRACT FROM AUTHOR]

• A trough receiver with a spectral-selective cover & rabbit-ear mirrors is proposed. • Receiver efficiency can be improved at any solar irradiance or temperature. • Receiver optical loss can be reduced by 13 W per meter length receiver. • Absorber thermal loss can be reduced by 3.3–41.6 W per meter length receiver. • Increase in the receiver efficiency of 0.30–2.72% is gained at typical conditions. Improving the efficiency of the evacuated receiver, which is a vital element of the parabolic trough solar plant, can increase the plant performance significantly. To improve the receiver efficiency, four novel modified receivers were designed. In each modified receiver, a spectral-selective glass cover partially coated by a heat-reflecting film on its top half was designed to decrease the thermal loss from the absorber. Meanwhile, two rabbit-ear mirrors were employed to concentrate some solar rays lost by the traditional receiver. After the design, the optical and thermal characteristics of the modified receivers were analyzed by using ray tracing method and computational fluid dynamics. Results indicate that the mirrors are effective for improving the optical efficiency. Furthermore, the heat-reflecting film on the cover inner wall was found to be effective to lessen the thermal loss, but the film on the cover outer wall not only cannot lessen the thermal loss but also causes additional optical loss. Moreover, it was found the modified receiver that only employs the inner film and the mirrors can obtain higher optical and thermal efficiencies than other modified receivers and the traditional receiver. Therefore, it was suggested as the optimal design. Then, simulation indicates the optimal design can enhance the receiver efficiency under any fluid temperature or solar irradiance compared with the traditional receiver. When the inlet fluid temperature is within 573–823 K, and the direct normal irradiance is within 300–1000 W·m−2, the optimal modified receiver could increase the receiver optical efficiency by 0.23% and reduce the thermal loss by 3.3–41.6 W·m−1(3.1–6.1%). As a result, it can improve the receiver efficiency and the collector efficiency by 0.30–2.72% and 0.28–2.56%, respectively. In addition, parameter study indicates the emittance of the heat-reflecting film has significant effects on the relative reduction in the thermal loss. Therefore, it is expected to be as low as possible for improving the efficiency to the best extent possible. The proposed receiver and results from this study should be useful for promoting the performance of the trough plant. [ABSTRACT FROM AUTHOR]