Stable Air Research Articles

LSTM-Cubic A*-based auxiliary decision support system in air traffic management

Airports, pilots and geographical environment contribute a lot to stable and safe air traffic, especially during the climbing and descending phases. Accidents occur frequently in these two phases, even small errors can lead to serious consequences. Modern equipment has made great progress in monitoring the airspace. However, when encountering strong external interference or blind zones, potential risks will be raised. With the assistance of newly developed technologies and equipment, flight trajectories can be recorded at high frequency, which enhances capabilities of Air Traffic Management systems. A four-dimensional flight trajectory prediction model is put forward in this paper. Combined with sliding windows, Long Short-Term Memory network maintains the long-term features and manages to predict accurate trajectories. Massive data contributes a lot for forecasting, but cannot guarantee better decisions. Decision-making is closely related to threat assessment. Taking the geographical environment into consideration, the static threat is involved in the current work. The experimental scenario is set to be an aircraft takes off from Hong Kong International Airport, which is located close to mountains. Characteristics of terrains are introduced to our system by digital elevation model. The proposed cubic A* search algorithm provides reasonable path by considering the ultimate dynamic performance of an aircraft. Threat is assessed during the path planning process. Finally, the auxiliary decision support system is developed based on ArcGIS 10.0, to graphically provide the intuitive and quick assistance. Multiple sets of experimental results indicate that this system is able to provide timely decision support.

Ambient Air Stability of Hybrid Perovskite Thin‐Film Transistors by Ambient Air Processing

AbstractDespite the widespread research on organic–inorganic hybrid perovskites, the ambient air instability and ion migration‐induced hysteresis in the current–voltage characteristics of their devices remain unsolved. Here, it is shown that stable ambient air operation of methylammonium lead iodide (MAPbI3) thin‐film transistors can be achieved by solution processing of the MAPbI3 film in ambient air via solvent engineering. N,N‐dimethylformamide (DMF), mixed with dimethyl sulfoxide (DMSO) and hydroiodic acid (HI), is found to be the most suitable solvent for one‐step deposition in ambient air. While the HI promotes homogeneous nucleation, the low boiling point of DMF and the high vapor pressure and strong Lewis base property of DMSO lead to fast crystallization and consequent large grain size. The oxygen in air passivates grain boundary defects, thereby improving lateral conduction and minimizing grain boundary defect‐mediated ion migration. This approach paves the way for the simple fabrication of hybrid perovskites by eliminating the need for well‐controlled inert environments and provides a solution for the problem of ambient air stability in perovskite devices.

Nickel Integrated Carbon Electrodes for Improved Stability

The development of an efficient, stable and low cost air electrode is a necessity in metal-air battery for oxygen reduction and oxygen evolution reaction. Carbon based air electrodes are conventionally used in metal-air batteries due its high electrical conductivity, high specific surface area and porosity. However, the highly oxidative environment of metal-air batteries during charging, corrodes the carbon air electrodes which lead to poor cyclic stability. The current study develops a hybrid air electrode with a nickel interlayer between carbon and electrocatalyst. This approach protects the carbon from corrosion and also provides an enhanced electocatalytic activity for silver catalyst by improving the electron conduction pathway through metallic nickel interlayer. The electroless deposition of nickel interlayer was optimized by deposition time. The electrochemical performances of the electrodes with Zn as anode were investigated to study the stability during cycling. The C–Ni–Ag electrode exhibited a round trip efficiency of 55%, a voltage gap of about 0.9 V over the entire cycle life of more than 1300 cycles and ∼350 h of operation with capacity retention of 98%. These results prove that the Ni interlayer circumvents the carbon corrosion at higher oxidative/charging potentials during oxygen evolution reaction.

Spatio-temporal variability of atmospheric impurities over Lake Baikal during the expeditions to the SRV V.A. Koptyug in 2019

Route observations were carried out aboard the SRV Akademik V.A. Koptyug on study of the spatio-temporal variability of small gas impurities (O3, NO2, SO2) at Lake Baikal. The spatio-temporal variability of O3, NO2, SO2 is extremely heterogeneous over the lake. Under conditions of the formation of a stable air mass in the warm sector of cyclone, high daytime air temperatures and elevated concentrations of surface ozone up to 120 g/m3, sulfur dioxide (up to 30 g/m3) were observed. The concentrations of nitrogen oxides (NO, NO2) did not exceed the background values. It is shown that in the water area of the lake the content of nitrogen dioxide is much lower than that of sulfur dioxide. A comparative analysis of the results of measurements of small gas impurities SO2, NO2 over the water area of the lake and at the coastal station showed that with long-distance transport of anthropogenic impurities, gaseous nitrogen oxides usually transform into nitrates due to a higher rate of NO2 oxidation than SO2.

Non-invasive arterial pressure monitoring by a new pneumatic sensor and on-line analysis of pulse waveforms for a modern medical home care systems.

The development of the third-generation devices for medical home care systems is in the center of discussion. The results of developing non-invasive arterial pressure monitoring channel on the basis of the unique pneumatic sensor are discussed in detail. In particular, the main principles of operation, design features and testing results of a pneumatic sensor are considered. Namely, the issues of the stable air flow regime in the sensor’s working chamber are discussed. It is shown that the miniature size of the sensor and the possibility of its precise positioning directly in the measurement zone on small (< 1 mm) areas of the skin elastic surfaces result in improved quality of pulse wave shape recovery, the parameters continuity measured and the disturbances reduction. Measurement examples for some human superficial arteries are given. The possibility of continuous measurement of the actual value of blood pressure for radial and temporal arteries is confirmed.

Durable superhydrophobic surface prepared by designing “micro-eggshell” and “web-like” structures

A durable superhydrophobic PVDF/FAC-SiO 2 /CNF coating with stable superhydrophobicity was prepared by designing “egg-shell” and “web-like” structures. Combined with the eggshell and web-like structure, the stable air cushion trapped on the PVDF/FAC-SiO 2 /CNF SHC surface can provide excellent hydrophobic stability, even for slurry, hot water or 98% H 2 SO 4 . • A novel superhydrophobic coating was successfully prepared by designing ‘micro-eggshell’ and ‘web-like’ structures. • The locked gas of “egg-shell” and “web-like” can enhance the hydrophobic stability of the coating surface. • The PVDF/FAC-SiO 2 /CNF coating can withstand hot water immersion or 98% H 2 SO 4 dumped. • The prepared coating possesses high charge transfer resistance (1.44 × 10 10 Ω cm 2 ) after 30 d immersion. Superhydrophobic surfaces (SHSs) have drawn a lot of interest in both academic and industry by its special wettability, but most artificial SHSs suffer from their poor hydrophobic and mechanical durability. Here, a durable PVDF/FAC-SiO 2 /CNF superhydrophobic coating (SHC) was successfully fabricated by designing “egg-shell” and “web-like” structures. We have in situ loaded nano-SiO 2 particles on the azodicarbonamide (AC) surface to provide a layer of barrier, which can prompt the formation of a special egg-shell structure after AC thermal decomposition. Moreover, CNF divided the pore structure to smaller spaces by forming web-like structure in the coating surface. Cooperation of the egg-shell and web-like structures, the PVDF/FAC-SiO 2 /CNF SHC surface can lock the gas stably and block the diffusion of corrosive media into the coating. Therefore, the prepared PVDF/FAC-SiO 2 /CNF coating can withstand 250 kPa water flow impact and possesses high charge transfer resistance (1.44 × 10 10 Ω cm 2 ) after 30 d immersion in 3.5 wt% NaCl solution. Furthermore, the prepared coating also exhibited outstanding mechanical and hydrophobic stability, which can maintain its superhydrophobicity even after 1000 abrasion cycles, hot water immersion, or dealing with 98% H 2 SO 4 . This fabrication process is scalable and provides a new avenue for the fabrication of robust superhydrophobic coatings.

Mesoscale precipitation systems and their role in the rapid development of a monsoon depression over the Bay of Bengal

AbstractThe structure of mesoscale precipitation within monsoon depressions is still not as well‐known as the synoptic‐scale composite cloud and precipitation structure. Here, using observational data from multi‐satellite sensors and a cloud‐resolving regional model, we investigate the three‐dimensional structure of mesoscale precipitation systems in the different stages of the life cycle of a monsoon depression. Effects of latent heating from the precipitation systems and the Bay of Bengal (BoB) on the development of the monsoon depression are also evaluated in sensitivity experiments with the model. A typical monsoon depression developed on 17 August 2016 over the BoB. In the rapid development phase, satellite observations reveal mesoscale convective systems with deep convective precipitation cells and stratiform precipitation near the head of the BoB. Extremely deep and intense convective cells appear along a ring‐like rain band when a closed cyclonic circulation becomes obvious around the northernmost part of the BoB. The deep convection appears frequently, particularly along the western‐to‐southwestern side of the low, a convergence‐prone area between northerlies with air masses of large convective available potential energy (CAPE) that makes up the western–southwestern part of the closed cyclonic circulation, and strong monsoon westerlies with relatively stable air masses to the south of the low. Sensitivity experiments reveal that both cloud/precipitation processes and evaporation from the BoB are essential for the rapid development of the monsoon depression over the BoB. Evaporation from the BoB adds a large amount of moisture to the atmospheric boundary layer near the low. Southwesterlies and southerlies on the eastern side of the low draw in warm, humid boundary‐layer air to the closed cyclonic circulation, which maintains a large‐CAPE environment in the low and enhances deep convection. A possible positive feedback process including moist convection that leads to the rapid intensification of monsoon depressions over the BoB is discussed.

Investigation of the dust control performance of a new transverse-flow air curtain soft-sealing system

On account of certain technological requirements, it is difficult for some industrial processes that generate dust to be sealed in a fixed pattern and ventilated for dust discharge, mainly automatic welding, pressure casting, wood processing, and crop production, which has become a significant bottleneck in dust control. The present study developed a transverse-flow soft-sealing dust control system, in which four novel air curtain generators were arranged in a square pattern within the region where dust was generated to create end-to-end planar transverse-flow air curtains and achieve soft sealing. The air suction inlet was placed centrally above the area where dust was generated; under the suction airflow, the dusty air was gradually diluted and driven away to effectively suppress dust escape. The flow field characteristics in the area where dust was generated and the performance of the developed sealing system in controlling fine smoke dust were qualitatively analyzed using a tracing experiment with smoke dust. Tracing experimental results on leaf powder qualitatively reveal directional dust control of large dust particles. Moreover, the dust control efficiency was evaluated under different conditions to quantitatively investigate the effects of air curtain outlet velocity, exhaust-to-pressure ratio, and jet angle. The results show that with a greater air supply and air suction rate, the airflow exhibited a more obvious entrainment effect and stronger dust exhaust and discharge, and simultaneously, the formed tracing smoke column had a clearer boundary. At an air curtain outlet velocity of 6.27–8.39 m/s and a corresponding air supply rate of 17.00–22.57 m3/min, a stable air curtain was formed, which achieved remarkable dust control at an exhaust-to-pressure ratio of 0.8–1.0. With an increase in the air curtain jet angle, the dust control efficiency of the system first increased but subsequently decreased. In the present study, the appropriate air curtain jet angle was 10–20° for the developed soft-sealing system. In conclusion, when the air curtain outlet velocity, exhaust-to-pressure ratio, and jet angle were 6.27 m/s, 0.6, and 15°, respectively, the dust control efficiency of the developed soft-sealing system reached 92.6%.

Synergism effects of coconut diethanol amide and anionic surfactants for entraining stable air bubbles into concrete

Entraining tiny and stable bubbles into cement and concrete is becoming more and more important with the complex composition of cement and concrete. In this work, multi-component surfactants are compounded to improve the air-void stability in fresh concrete. The surface tensions, foam properties of their solutions, and the air contents and air-void parameters of the fresh and hardened cement mortars were tested. The results show that there are strong interactions on the interface of multi-components by calculating the important parameters of surface activity. When coconut diethanol amide molecules are introduced into the interface for co-assembly, the electrostatic repulsion between the anionic surfactant molecules is effectively diminished, thereby decreasing the interfacial free energy and making the interface more stable. The multi-component surfactants induced smaller bubbles with larger amounts in aqueous solutions, which also have higher stability of air bubbles in both cement mortars and concretes. So it is of great practical significance to compound nonionic and anionic surfactants to improve the air-void stability in concrete.

Practical application of nonaqueous foam in the preparation of a novel aerated reduced-fat sauce

This study aims to develop a new formulation of a sauce by incorporation of air in the oil phase. First, the effect of mono- and diglyceride (MDG) concentration (2, 6, and 10wt.%), whipping speed (1100, 3200, and 5400rpm) and time (up to 60min) on foam properties were studied. The desired foam (overrun≥60%) achieved by oil containing 10wt.% MDG at 3200rpm for 10min. Optical micrographs showed stable air bubbles (20–25μm) even after six months of storage. Then this foam was used to produce an aerated reduced-fat sauce. For purposes of comparison, aerated sauce, along with commercial full- and reduced-fat sauces, was analyzed by measuring the rheological properties, stability, and color. The power-law equation was used to model the behavioral features (R2=0.99). Compared with the full-fat sauce, the consistency coefficient (K) of aerated and reduced-fat sauces was more close to each other, and their flow behavior index (n) was higher. Overall samples showed shear-thinning thixotropic flow behavior. Also, aerated sauce showed acceptable stability and lightness (L*). These findings affirm the potential of nonaqueous foam for the production of reduced-fat sauces, which could be meet consumers’ and marketing requirements.

Tropical Cyclone as a Possible Remote Controller of Air Quality over South Korea through Poleward-Propagating Rossby Waves

AbstractAir quality depends as much on large-scale tropospheric circulation as on the amount of pollutant emissions. Many studies have found a relationship between air quality and midlatitude synoptic weather systems. A stable low-level troposphere and airflow from polluted areas are conditions that favor air pollution in a region. However, few studies have focused on the possible remote effect of tropical cyclone (TC) activity in the tropics on air quality in the midlatitude East Asian countries. Here, we found that TCs in the South China Sea (SCS) can increase the concentration of particulate matter with aerodynamic diameters less than 10 μm (PM10) over South Korea through poleward-propagating Rossby waves. According to our analyses, intense divergence due to a TC causes a barotropic Rossby wave train from the SCS to the North Pacific Ocean. Anomalous highs over the Korean Peninsula (part of the Rossby wave train) result in stable air conditions and cause polluted air inflow to increase the PM10 concentration up to 65 μg m−3. Our finding suggests that TC activity in the tropics should be considered for more accurate forecasts of air quality in South Korea.

Cobalt‐Doped Tungsten Sulfides as Stable and Efficient Air Electrodes for Rechargeable Zinc‐Air Batteries

AbstractStable and efficient air electrode are significantly important for the industrial applications of rechargeable zinc‐air batteries (ZABs). In this work, we introduce approximately 1 at % cobalt to tungsten sulfides nanosheets (Co−WS2) to create a bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A boosted ORR activity with half‐wave potential of 840 mV vs. RHE is achieved for Co−WS2 compared to that of WS2 (776 mV vs. RHE). Meanwhile, the overpotential for delivering 10 mA cm−2 in OER catalysis is decreased from 492 to 303 mV after doping with Co atoms. The excellent ORR and OER activities are ascribed to the presence of Co2+ and Co3+ species in Co−WS2, enabling OOH* intermediate formation and strong binding ability to O2, respectively. The assembled liquid rechargeable ZAB from Co−WS2 exhibits a threefold higher power density than commercial Pt/C−IrO2; moreover, a stable discharge‐charge performance (100 cycles) is recorded. Finally, the fabricated all‐solid‐sate ZAB exhibits a reasonably high power density of 58 mW cm−2 and good stability, implying the potential application of Co−WS2 as an air electrode for rechargeable ZABs.

Microstructure and Isothermal Oxidation of Ir-Rh Spark Plug Electrodes.

High-temperature oxidation tests were performed on pure iridium, rhodium, and the iridium alloys, IrRh10, IrRh25, and IrRh40, at 1100 °C in a stable air environment for 60 h. The results of the oxidation were analyzed by X-ray photoelectron spectroscopy (XPS). Microstructural changes of the Ir–Rh alloys were characterized by scanning electron microscopy (SEM). XPS analysis results show that the main oxide of the Ir–Rh alloy in a 1100 °C environment was Rh2O3, and SEM analysis shows that the surfaces of the Ir–Rh alloys after oxidation formed both linear and ellipse-shaped corrosion pits, and had the same direction with the wire-drawing process. The oxidation behavior of Ir–Rh alloys, including the mass change, the reason for the mass loss, and the role of Rh in improving oxidation resistance performance, are discussed.

ZIF-8 Membrane Separation Performance Tuning by Vapor Phase Ligand Treatment.

Vapor phase ligand treatment (VPLT) of 2-aminobenzimidazole (2abIm) for 2-methylimidazole (2mIm) in ZIF-8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut-off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O2 /N2 ; 2.2 to 32 for CO2 /CH4 ; 2.4 to 24 for CO2 /N2 ; 4.8 to 140 for H2 /CH4 and 5.2 to 126 for H2 /N2 . Stable (based on a one-week test) oxygen-selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep-free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10-3 mol m-2 s-1 is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm-VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT-LIPS membranes can be recovered upon 2mIm-VPLT.

Saharan air intrusions as a relevant mechanism for Iberian heatwaves: The record breaking events of August 2018 and June 2019

The summers of 2018 and 2019 were characterized by unusually warm conditions over Europe. Here, we describe the intense heatwaves striking the Iberian Peninsula in early August 2018 and late June 2019. The 2018 episode was relatively short-lived but outstanding in amplitude, particularly in western Iberia. Similar to previous mega-heatwaves, the 2019 event was long-lasting and affected large areas of western and central Europe, including eastern Iberia. During these events, many absolute temperature records were broken in western and eastern Iberia, respectively (some of them standing since 2003). In both cases, a cyclonic circulation off the coast in the northeastern Atlantic and a strong subtropical ridge pattern over the affected area promoted the advection of an anomalously warm air mass. This paper highlights the role of these very warm, stable and dry air intrusions of Saharan origin in the western and eastern Iberia heatwave events. Using a thermodynamical classification based on the geopotential height thickness and potential temperature, we show how the magnitude and poleward extension of these Saharan intrusions were unprecedented in the period since 1948. The relationship between Iberian heatwaves and Saharan warm air intrusions is discussed in the long-term context, showing a closer link in southern sectors of the Peninsula. However, a consistent poleward trend in the latitudinal extension of these subtropical intrusions reveals their increasing relevance for heatwaves in northern sectors of Iberia and western Europe. This overall trend is accompanied by an apparent “see-saw” in the occurrence of subtropical intrusions between eastern and western Iberia on multi-decadal scales.

Microbial composition in seasonal time series of free tropospheric air and precipitation reveals community separation

Primary biological aerosols are transported over large distances, are traveling in various media such as dry air masses, clouds or fog, and eventually deposited with dry deposition, especially for larger particles, or precipitation like rain, hail or snow. To investigate relative abundance and diversity of airborne bacterial and fungal communities, samples have been collected with a liquid impinger (Coriolis µ) from the top of Mount Sonnblick (3106 m asl, Austrian Alps) from the respective sources under a temporal aspect over four seasons over the year to include all climatic conditions. Bacterial and fungal samples (16S rRNA and ITS) were sequenced using Illumina MiSeq paired-end sequencing, investigated for relative abundance by qPCR(16S rRNA and 18S rRNA) and ice nucleation activity. Results show that there is no stable free tropospheric air microbial community and air mass origin was different for the four sampling periods which exerted influence on the microbial composition of the atmosphere although a core microbiome could be identified consisting of 61 bacterial OTUs and eight fungal genera. Differentiation between seasons was stronger pronounced in air than in precipitation, with rain being most different and variable of precipitation types, indicating distinct forces driving microbial fate in the air. Microorganisms precipitated with snow, hail or rain or being transported by clouds differ in their species composition from free tropospheric air masses and do not mirror the air community structure. They were more diverse, distinct in composition, 16S:18S ratio and abundance from free-floating PBA. Hence, snow or cloud samples are not suitable proxies for free tropospheric air microbiome composition, since separation processes in aerosolization, transport and scavenging occur. The microbial composition of arriving precipitation or clouds represents only a part of the microbial air composition communities of the cumulative sources of origin. Relative abundance and composition of ice nucleation-active bacteria showed a higher share of relative % reads of known ice nucleation-active bacteria present in all wet phases compared to air. Results propose a separation of IN-active reads with higher shares occurring in precipitation. This study presents the first comparison of free tropospheric bacterial and fungal abundance and diversity in time series of air over several seasons in contrast to various precipitation forms in the free troposphere.

Experimental study of the effectiveness of water-air suspension to prevent an explosion

For many countries where mining facilities exist, the importance of the mining sector is steadily increasing. Also, the mining sector is central to the global economy. However, the environment is adversely affected by explosions of finely dispersed coal dust and methane-air mixture in the mine. Dust deposited on the surface of the mine workings is as dangerous as hovering dust. The use of a water suspension system is effective for reducing the concentration of coal dust because dispersion increases. To ensure technological and environmental safety during combustion, release, mixing and distribution of gas impurities in the atmosphere (including in multiply connected areas with complex terrain or in closed spaces), an adequate mathematical description of the processes of creating and maintaining multiphase dispersed structures is required. The creation of such a mathematical model is possible only using the system of unsteady Navier–Stokes equations for compressible gas. For the practical implementation of this mathematical model, experimental studies are needed, which will confirm the possibility to create a water suspension with the necessary dispersion, the area of irrigated surface and at the required distance by the atomizer. The maximum range (in the extreme drops) of the jet was measured from the projection of the atomizer barrel onto the test site using pre-installed beacons. The size of the water droplets was determined by sampling from a stream on small glass slides coated with a thin layer of paraffin. Glass slides were photographed under a microscope and the diameter of the drop was determined using software. It was established experimentally that spraying a liquid with a mass flow rate of 1.0 l/s through square cells measuring 150 μm ensures the formation of a stable water-air dispersed suspension at a distance of 10 m. This is the most effective range where a stable air-dispersed air curtain was formed. By numerical simulation, it was established that the presence of water droplets provides not only complete deposition of coal dust, but also an additional decrease in the overpressure and temperature of the high-temperature cloud of the combustion products of the methane-air mixture. This is due to the transition of the liquid phase to the vapor state. From the analysis of the simulation results it can be seen that the effectiveness of water curtains decreases when extinguishing explosions of only methane-air mixture (that is, without participation in the explosion of coal dust).

2018년 11월 광주 지역에서 발생한 미세먼지 고농도 사례 시 수용성 성분의 크기 분포 조사

In this study, mass size distributions of ambient aerosol particles and their water-soluble organic and inorganic species were investigated under high pollution episode. To achieve the aim of this study, 24-hr integrated size-segregated aerosol samples were collected at an ubran site of Gwangju between November 02 and 16, 2018, and analyzed for mass, water-soluble organic carbon (WSOC), and ionic species. During study period, a high pollution episode of fine particulate matter (PM) occurred between November 02 and 07, possibly due to high pressure developed around Korean peninsula, extremely stable air conditions, and long-range transportation of aerosol particles from North Korea and northeastern China region. On November 02~03 when influence of local pollution dominated, ambient aerosol particles, WSOC, NO3-, SO₄2-, and NH4+ exhibited bi-modal size distributions with a condensation mode at a particle size of 0.32 μm and a droplet mode at a particle size of 1.0 μm in PM1.8. While, between November 05 and 07 when long-range transportation of PM was mixed with locally-produced pollution, they showed very pronounced droplet mode size distributions at 1.0 μm, without a condensation mode. NO3- concentration in PM1.8 during pollution episode increased significantly from 5.9 μg/m³ on November 02 to 21.5μg/m³ on November 06, while SO₄2- in PM1.8 increased from 1.6 to 5.8 μg/m³, indicating the dominance of local pollution during pollution episode. Furthermore, for WSOC, NO3-, SO₄2-, and NH4+, fraction of droplet mode size (PM0.55-1.8) to PM1.8 increased gradually as PM pollution got increased, while the condensation mode (PM0.17-0.32) contribution decreased. In addition, it was demonstrated that relative humidity could be an important factor promoting formation of droplet mode WSOC, NO3-, and SO₄2-.

A self-supported electrode as a high-performance binder- and carbon-free cathode for rechargeable hybrid zinc batteries

Developing highly efficient and flexible air-breathing electrodes is of significant importance for various energy conversion and storage technologies. In this work, we report the synthesis of the self-supported sandwich-structured electrode with Co3-xNixO4/Co3O4 nanowire arrays (NS@Co3-xNixO4/Co3O4). This novel nanostructure demonstrates very high reversible Faradaic redox reaction of CoNi−O ↔ CoNi−O−OH and excellent bifunctional activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, the air cathode, prepared by pressing the stainless steel (SS)@Co3O4 sandwiched between two Ni foam (NF)@Co3-xNixO4, possesses a dense and interconnected structure with a high loading of active catalyst. The Ni foam in this work not only acts as a substrate, but also serves as a nickel precursor for the formation of the Co3-xNixO4 catalyst. Meanwhile, combining the 3D porous structure of NF and intrinsic high OER activity of SS, the assembled porous air electrode can take full advantage of the sandwich structure to promote the electrocatalytic reaction kinetics of NS@Co3xNixO4/Co3O4. Rechargeable battery system assembled from this NS@Co3-xNixO4/Co3O4 electrode based on both Zn−Co3-xNixO4 and Zn−air electrochemical reactions exhibits much higher energy efficiency and durability than those of commercial Pt/C and RuO2 electrocatalysts. This protocol opens a new avenue for the rational design of highly efficient and stable self-supported air electrode for metal-air batteries.

Interactions between a Nocturnal MCS and the Stable Boundary Layer as Observed by an Airborne Compact Raman Lidar during PECAN

Abstract Small-scale variations within the low-level outflow and inflow of an MCS can either support or deter the upscale growth and maintenance of the MCS. However, these small-scale variations, in particular in the thermodynamics (temperature and humidity), remain poorly understood, due to a lack of detailed measurements. The compact Raman lidar (CRL) deployed on the University of Wyoming King Air aircraft directly sampled temperature and water vapor profiles at unprecedented vertical and along-track resolutions along the southern margin of a series of mature nocturnal MCSs traveling along a frontal boundary on 1 July 2015 during the Plains Elevated Convection at Night (PECAN) campaign. Here, the capability of the airborne CRL to document interactions between the MCS inflow and outflow currents is illustrated. The CRL reveals the well-defined boundary of a cooler current. This is interpreted as the frontal boundary sharpened by convectively induced cold pools, in particular by the outflow boundary of the downstream MCS. In one CRL transect, the frontal/outflow boundary appeared as a distinct two-layer structure of moisture and aerosols formed by moist stable boundary layer air advected above the boundary. The second transect, one hour later, reveals a single sloping boundary. In both cases, the lofting of the moist stably stratified air over the boundary favors MCS maintenance, through enhanced elevated CAPE and reduced CIN. The CRL data are sufficiently resolved to reveal Kelvin–Helmholtz (KH) billows and the vertical structure of the outflow boundary, which in this case behaved as a density current rather than an undular bore.