High Low Pressure Research Articles

Design and Development of Flow Fields with Multiple Inlets or Outlets in Vanadium Redox Flow Batteries

In vanadium redox flow batteries, the flow field geometry plays a dramatic role on the distribution of the electrolyte and its design results from the trade-off between high battery performance and low pressure drops. In the literature, it was demonstrated that electrolyte permeation through the porous electrode is mainly regulated by pressure difference between adjacent channels, leading to the presence of under-the-rib fluxes. With the support of a 3D computational fluid dynamic model, this work presents two novel flow field geometries that are designed to tune the direction of the pressure gradients between channels in order to promote the under-the-rib fluxes mechanism. The first geometry is named Two Outlets and exploits the splitting of the electrolyte flow into two adjacent interdigitated layouts with the aim to give to the pressure gradient a more transverse direction with respect to the channels, raising the intensity of under-the-rib fluxes and making their distribution more uniform throughout the electrode area. The second geometry is named Four Inlets and presents four inlets located at the corners of the distributor, with an interdigitated-like layout radially oriented from each inlet to one single central outlet, with the concept of reducing the heterogeneity of the flow velocity within the electrode. Subsequently, flow fields performance is verified experimentally adopting a segmented hardware in symmetric cell configuration with positive electrolyte, which permits the measurement of local current distribution and local electrochemical impedance spectroscopy. Compared to a conventional interdigitated geometry, both the developed configurations permit a significant decrease in the pressure drops without any reduction in battery performance. In the Four Inlets flow field the pressure drop reduction is more evident (up to 50%) due to the lower electrolyte velocities in the feeding channels, while the Two Outlets configuration guarantees a more homogeneous current density distribution.

Study of essential oil extraction from Moroccan Rosmarinus officinalis L. by distillation based on quantum chemical calculation and molecular dynamics simulation

In this work, essential oils were extracted from rosemary leaves (Rosmarinus officinalis L.) from the eastern region of Morocco using hydrodistillation (Hd) and steam distillation (Sd). The yield, chemical composition, thermal stability, and antioxidant activity of the essential oils obtained by the two methods were compared. Determining the chemical composition of rosemary essential oil, with GC-MS, showed a significant qualitative and quantitative difference in certain components. The Sd method improved the extraction of sesquiterpene compounds with high molecular weight and low vapour pressure. The findings reveal that sesquiterpene and oxygenated monoterpenes in essential oils improved the antioxidant activity and thermal stability. Determining antioxidant activity using DPPH and the β-carotene bleaching assay showed that the Sd and Hd oils presented good radical scavenging activity (IC50 = 4960 μg/mL for Hd oil and 4570 μg/mL for Sd oil), capable of delaying β-carotene discolouration with 16.3 and 9.71% inhibition for Sd and Hd respectively. Thermal stability analysis of the oil products was performed using TGA/DTG analysis, and the results showed that the decomposition points of Hd oil and Sd oil were 362 and 368 K respectively. Furthermore, to identify intermolecular interactions and develop better knowledge of phenomena occurring during the extraction of the family of sesquiterpene compounds by water, quantum chemical calculation and molecular simulation by molecular dynamics (MD) were performed. The results suggested the relative stability of caryophyllene-water and the development of intermolecular bonding interactions of van der Walls and steric effect, improving extraction of the substance studied under steam distillation conditions.

Synoptic and planetary-scale dynamics modulate antarctic atmospheric river precipitation intensity

Although rare, atmospheric rivers substantially influence the interannual variability of Antarctic surface mass balance. Here we use MERRA-2 reanalysis to identify characteristics unique to atmospheric river environments by comparing (1) Analog (environments that feature high-low pressure couplets, similar to Atmospheric River environments, but no Atmospheric River), (2) Atmospheric River, and (3) Top Atmospheric River (highest precipitation) timesteps during 1980–2019 around Antarctica. We find significant differences between Atmospheric River and Analog environments including more intense and poleward-shifted mid-tropospheric geopotential height couplets as well as larger atmospheric moisture anomalies. We find similar significant enhancement in synoptic-scale dynamic drivers of Top Atmospheric Rivers compared to all Atmospheric River environments, but no significant difference in local integrated water vapor anomalies. Instead, our results highlight the importance of large-scale dynamic drivers during Top Atmospheric River timesteps, including amplified Rossby waves excited by tropical convection.

Interannual variations in ozone pollution with a dipole structure over Eastern China associated with springtime thermal forcing over the Tibetan Plateau

The Tibetan Plateau (TP) is essential in modulating climate change in downstream Eastern China (EC). As a meteorology-sensitive pollutant, changes in ozone (O3) in connection with the TP have received limited attention. In this study, using climate analysis of the China High Air Pollutants O3 product and ERA5 reanalysis data of meteorology for 1980–2020, the effect of springtime TP thermal forcing on the warm season (April–September) O3 pollution over EC was investigated. The strong TP thermal effect significantly modulates the interannual variations in O3 pollution with a dipole pattern over EC, inducing more O3 pollution in northern EC regions and alleviating O3 pollution in the southern regions. In northern (southern) EC, strong TP thermal forcing triggers a significant anomalous high (low) pressure center accompanied by anticyclonic (cyclonic) anomalies, resulting in decreased (increased) total cloud cover, increased (reduced) surface downward solar radiation and air temperature, which are conducive to the anomalous increase (decrease) in surface O3 concentrations. Moreover, the key sources of springtime thermal forcing over the TP influence the major O3 pollution regions over southern and northern EC with an inverse pattern, depending on their locations and orientations to the large topography of the TP. This research reveals an important driving factor for the dipole interannual variation in O3 pollution over EC, providing a new prospect for the effect of the TP on atmospheric environmental change.

Characteristics and Outcomes of Coronavirus Disease- 2019 Among Pregnant Women in Saudi Arabia; a Retrospective Study.

Pregnancy-related coronavirus disease 2019 infection ranges from asymptomatic to very serious illness. This study aimed to determine the impact of the COVID-19 infection on pregnant women in the Jazan region of Saudi Arabia. Retrospective observational study of women who had COVID-19 positive test in pregnancy admitted in King Fahd Hospital, Abu Arish General Hospital, and Sabya General Hospital, Jazan, Saudi Arabia during the period between March 2020 and March 2022. Data were extracted from the patient's records. Frequency and percentage distributions were calculated for categorical variables. Descriptive studies and regression analysis were conducted to evaluate the association between selected variables and pregnancy outcomes. Of the 33 pregnant women with confirmed infection, the majority were in their second and third trimester, with approximately 42.4% requiring intensive care unit (ICU) admission and oxygen therapy. The most prevalent symptoms were high respiratory rate and low blood pressure, often accompanied by fever, cough, and shortness of breath. Live births resulted in 54.5% of the cases, while two maternal deaths were reported. Significant associations were found between the need for non-invasive ventilation and timing of infection (p = 0.026), the mode of delivery and timing of infection (p = 0.036), and the mode of delivery and body mass index (BMI) (p = 0.007). COVID-19 poses significant risks to pregnant women, particularly in the third trimester, and emphasized the importance of early identification of high-risk pregnancies, strategic planning, and enhanced monitoring during antenatal care.

An efficient framework for controllable micromixer design through the fusion of data-driven modeling and machine learning insights: Numerical and experimental analysis

Micromixers are inevitable components in microfluidics, micro-electro-mechanical devices, and numerous bio-chemical assays. By assays, we mean diverse analytical procedures encompassing gene engineering, the manipulation of genetic material; nanoparticle synthesis, focusing on the controlled creation of nanoparticles; and cell lysis, involving cell membranes disruption for the release of intracellular substances for diagnostic purposes. In these assays, the homogeneous mixture of two or more fluids is crucial. However, designing an efficient micromixer providing high homogeneity and low pressure drop, while maintaining controllability, is challenging. Controllability refers to the design of a micro-system tailored to meet the specific requirements of a given assay. This study proposes a controllable framework, combining machine learning and statistical modeling. The framework begins with the generation of a reference parametric micro-structure, herein a microchannel with L-shaped baffles and featuring seven variables. A response surface method, a data-driven modeling scheme, is used to establish functional relationships between design variables and objective functions. The study reveals that the baffle height significantly impacts the system functionality, increasing the mixing index by over 40% and the pressure drop by more than 220% when reaching its upper limit. Dean-like secondary vortexes are generated in the microchannel at Re = 10, demonstrating the efficiency of the implemented baffles. Subsequently, multi-objective optimization methods, non-dominated sorting genetic algorithm (NSGA-II) and differential evolution (DE), are employed, with adaptable variable constraints. Comparative analysis of the methods shows that DE finds superior optimum solutions in fewer iterations. Finally, an optimum structure is fabricated using soft lithography, and experimental tests are conducted for validation.

Constraints on uranium mineralization by chronology and microgeochemical characteristics of monazite in the Datian area of the Kangdian region, China

Monazite, a common U-containing ore-rich mineral found in association with U minerals, has excellent sealing properties after its formation, making it a promising tool for determining the age and genetic type of U mineralization. The Datian area in the Kangdian region of China is an important Neoproterozoic U ore-forming region. It has garnered the attention of researchers owing to the presence of megacrystalline uraninite with well-developed crystal forms. However, most studies conducted on U mineralization in the Datian area have focused on macroscopic observations and uraninite, with limited reports on accessory minerals. In this study, LA-ICP-MS U-Pb chronology and in-situ major and trace element analyses were performed on monazite associated with megacrystalline uraninite in the Datian area metallogenic belt I. The research yielded the following insights: 1) U mineralization in the Datian area was estimated to have occurred approximately 770 million years ago. This age demonstrates a potential correlation with the assembly and fracturing of the Rodinia supercontinent, suggesting a geodynamic context for the mineralization event. 2) The geochemical characteristics of the monazite indicate an igneous rock origin for its genetic type. Combined with previous research findings, it is postulated that U mineralization in the Datian area may be closely linked to the partial melting of deep crustal materials within a metamorphic environment characterized by high temperature and low pressure.

Transitioning from Methanol to Olefins (MTO) toward a Tandem CO2 Hydrogenation Process: On the Role and Fate of Heteroatoms (Mg, Si) in MAPO-18 Zeotypes.

The tandem CO2 hydrogenation to hydrocarbons over mixed metal oxide/zeolite catalysts (OXZEO) is an efficient way of producing value-added hydrocarbons (platform chemicals and fuels) directly from CO2via methanol intermediate in a single reactor. In this contribution, two MAPO-18 zeotypes (M = Mg, Si) were tested and their performance was compared under methanol-to-olefins (MTO) conditions (350 °C, PCH3OH = 0.04 bar, 6.5 gCH3OH h-1 g-1), methanol/CO/H2 cofeed conditions (350 °C, PCH3OH/PCO/PH2 = 1:7.3:21.7 bar, 2.5 gCH3OH h-1 g-1), and tandem CO2 hydrogenation-to-olefin conditions (350 °C, PCO2/PH2 = 7.5:22.5 bar, 1.4-12.0 gMAPO-18 h molCO2-1). In the latter case, the zeotypes were mixed with a fixed amount of ZnO:ZrO2 catalyst, well-known for the conversion of CO2/H2 to methanol. Focus was set on the methanol conversion activity, product selectivity, and performance stability with time-on-stream. In situ and ex situ Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), sorption experiments, and ab initio molecular dynamics (AIMD) calculations were performed to correlate material performance with material characteristics. The catalytic tests demonstrated the better performance of MgAPO-18 versus SAPO-18 at MTO conditions, the much superior performance of MgAPO-18 under methanol/CO/H2 cofeeds, and yet the increasingly similar performance of the two materials under tandem conditions upon increasing the zeotype-to-oxide ratio in the tandem catalyst bed. In situ FT-IR measurements coupled with AIMD calculations revealed differences in the MTO initiation mechanism between the two materials. SAPO-18 promoted initial CO2 formation, indicative of a formaldehyde-based decarboxylation mechanism, while CO and ketene were the main constituents of the initiation pool in MgAPO-18, suggesting a decarbonylation mechanism. Under tandem CO2 hydrogenation conditions, the presence of high water concentrations and low methanol partial pressure in the reaction medium led to lower, and increasingly similar, methanol turnover frequencies for the zeotypes. Despite both MAPO-18 zeotypes showing signs of activity loss upon storage due to the interaction of the sites with ambient humidity, they presented a remarkable stability after reaching steady state under tandem reaction conditions and after steaming and regeneration cycles at high temperatures. Water adsorption experiments at room temperature confirmed this observation. The faster activity loss observed in the Mg version is assigned to its harder Mg2+-ion character and the higher concentration of CHA defects in the AEI structure, identified by solid-state NMR and XRD. The low stability of a MgAPO-34 zeotype (CHA structure) upon storage corroborated the relationship between CHA defects and instability.

Close-Space Sublimation as a Scalable Method for Perovskite Solar Cells.

Vacuum techniques for perovskite photovoltaics (PV) are promising for their scalability but are rarely studied with techniques readily adaptable for industry. In this work, we study the use of close-space sublimation (CSS) for making perovskite solar cells, a technique that has seen widespread use in industry, including in PV, and benefits from high material-transfer and low working pressures. A pressed pellet of formamidinium iodide (FAI) can be used multiple times as an organic source, without needing replacement. Using CSS at a rough vacuum (10 mbar), efficient cesium formamidinium lead iodide perovskite based solar cells are obtained reaching a maximum photoconversion efficiency (PCE) of 18.7%. They maintain their performance for >650 h when thermally stressed at 85 °C in a nitrogen environment. To explain the initial rise in PCE upon heating, we used drift-diffusion simulations and identified a reduction in bulk trap density as the primary factor.

A Study for Estimating the Overall Heat Transfer Coefficient in a Pilot-Scale Indirect Rotary Dryer

An experimental study and dimensional analysis of the effective heat transfer coefficient in a continuous-indirect rotatube dryer using forest biomass as the granular material isare developed in the present work. The study employed a factorial design 33 to investigate the effects of feed flow frequency (20–35–50 (Hz)), drum rotational velocity (6–8–10 (rpm)), and saturated vapor pressure (4–5–6 (bar)) on the heat transfer coefficient. During steady state conditions, the moisture content profiles and inlet and outlet temperatures were measured within the experimental region, and parameters, such as the effective heat transfer coefficient, solid retention change, and moisture content ratio were studied. The results showed that heat transfer was optimized with high solid feeding rates, low pressure, and low rotation, with solid feeding being the predominant factor. The moisture content profiles revealed a change in the hydrodynamic behavior, with the center point of the experimental region being the least optimal. The dimensional analysis yielded a Nu number as a function of Pe, Fr, and the feeding dimensionless number. A new dimensionless energy efficiency number improved the coefficient correlation from 85.88 (%) to 94.46 (%), indicating the developed model potential to predict dimensionless variables and scale continuous-indirect rotatube dryers.

An Analysis of the Instability Conditions and Water Vapor Transport Characteristics during a Typical Rainstorm in the Tarim Basin

In order to deepen the understanding of the occurrence mechanism and water vapor transport characteristics of the heavy rain process in the extreme arid region of Xinjiang, a rare heavy rain process in the Tarim Basin during the period of 18–22 July 2021 was comprehensively analyzed by using multi-source data. The results show that the upper tropospheric South Asian high was distributed in a “west-high-east-low” pattern during the rainstorm process, and the rainstorm area was located on the right side of the upper jet stream entrance area, while the middle-level Iranian high pressure, Baikal high pressure and Central Asian low pressure formed a “two-highs and one-low” circulation situation. The coupling of the high and low air jets and the strong vertical upward motion provided favorable dynamic conditions. Rainstorm water vapor mainly comes from the Mediterranean Sea, Central Asia and the Indian Ocean, and it enters the basin in four paths: west, east to west, west to east, and southwest and south. The water vapor mainly flows into the middle layer of the western boundary and the southern boundary and the lower layer of the eastern boundary, and it flows out from the middle and upper layer of the eastern boundary. The negative moist potential vorticity region at a low level has a strong indicator significance for the occurrence and development of heavy rain, and the superposition of positive and negative moist potential vorticity regions at vertical height is conducive to the occurrence and development of heavy rain.

Diagnosing Flavors of Tropospheric Rossby Wave Breaking and Their Associated Dynamical and Sensible Weather Features

Abstract Rossby wave breaking (RWB) can be manifested by the irreversible overturning of isentropes on constant potential vorticity (PV) surfaces. Traditionally, the type of breaking is categorized as anticyclonic (AWB) or cyclonic (CWB) and can be identified using the orientation of streamers of high potential temperature (θ) and low θ air on a PV surface. However, an examination of the differences in RWB structure and their associated tropospheric impacts within these types remains unexplored. In this study, AWB and CWB are identified from overturning isentropes on the dynamic tropopause (DT), defined as the 2 potential vorticity unit (PVU; 1 PVU = 10−6 K kg−1 m2 s−1) surface, in the ERA5 dataset during December, January, and February 1979–2019. Self-organizing maps (SOM), a machine learning method, is used to cluster the identified RWB events into archetypal patterns, or “flavors,” for each type. AWB and CWB flavors capture variations in the θ minima/maxima of each streamer and the localized meridional θ gradient (∇θ) flanking the streamers. Variations in the magnitude and position of ∇θ between flavors correspond to a diversity of jet structures leading to differences in vertical motion patterns and troposphere-deep circulations. A subset of flavors of AWB (CWB) events are associated with the development of strong surface high (low) pressure systems and the generation of extreme poleward moisture transport. For CWB, many events occurred in similar geographical regions, but the precipitation and moisture patterns were vastly different between flavors. Our findings suggest that the location, type, and severity of the tropospheric impacts from RWB are strongly dictated by RWB flavor. Significance Statement Large-scale atmospheric waves ∼15 km above Earth’s surface are responsible for the daily weather patterns that we experience. These waves can undergo wave breaking, a process that is analogous to ocean waves breaking along the seashore. Wave breaking events have been linked to extreme weather impacts at the surface including cold and heat waves, strong low pressure systems, and extreme precipitation events. Machine learning is used to identify and analyze different flavors, or patterns, of wave breaking events that result in differing surface weather impacts. Some flavors are able to generate notable channels of moisture that result in extreme high precipitation events. This is a crucial insight as forecasting of extreme weather events could be improved from this work.

Improved perovskite crystallization by antisolvent engineering in tin-perovskite photovoltaics.

Tin-based perovskites are considered the candidate with the most potential as lead-free perovskites because of their excellent optoelectronic properties. As a conventional precursor solvent for the fabrication of tin-based perovskite films, dimethyl sulfoxide (DMSO) can form intermediates with SnI2, which slows down the crystal growth and thus induces a smooth surface. However, the DMSO solvent exhibits a high donor number and low vapor pressure, whereas the typical anti-solvent chlorobenzene displays a low donor number, resulting in a lack of solvent-cleaning ability and excess DMSO remaining in the perovskite film. Here, we used dimethyl sulfide as an anti-solvent to prepare tin-based perovskite film; it has a high donor number and high vapor pressure. It was found that the introduction of dimethyl sulfide greatly improved the morphology and quality of the perovskite films. In addition, the crystallinity of the thin film improves the transport of charge carriers and reduces defects, resulting in a champion device efficiency of 5.3%.

A semi-packed gas chromatographic column with staggered elliptic cylindrical post arrays.

A semi-packed gas chromatographic column has the advantages of high specific surface area and low column pressure. We report that the stagnation regions formed in the adjacent posts along the channel of the semi-packed columns can decrease the area and height of chromatographic peaks, which makes it difficult to detect low-concentration mixed gases. A semi-packed column with staggered elliptic cylindrical post arrays (SC-S) made using a micro-electro-mechanical system technique is presented, and the separation performance of SC-S is compared with that of a semi-packed column with aligned elliptic cylindrical post arrays (SC-A). The simulation results show that the width of stagnation regions in SC-S is 86.89% smaller than that in SC-A. The experimental results indicate that the area and height of chromatographic peaks increased as stagnation regions reduced. In the separation of the alkane mixture from C8 through C10 with 10 ppm concentration, the chromatographic peak of decane was hardly identified in SC-A while the chromatographic peak in SC-S was still clearly visible. The chromatographic peak heights of octane and nonane were increased by 65.06% and 130.00%, respectively, in SC-S. The peak areas of octane and nonane were increased by 120.45% and 168.18%, respectively.

Current Situation and Engineering Application Prospect of Liquid Air Energy Storage Technology

Liquid air energy storage (LAES)technology is a new-coming energy storage method using cryogenic technology as basic theory. It managed to reach consumption of new energy in a grid-connected way, absorbing low power properly, and stable output of many other forms of energy like industrial gas and electricity. This paper introduces the technical principle and advantages of LAES, analyzes and discusses the problems faced by the development of LAES technology and the corresponding solutions, summarizes the applied fields of LAES technology. It also looks forward to the development direction of LAES technology. LAES has the advantages of high energy storage density and low storage pressure, and is less restricted by geographical conditions. It can store the remaining or discontinuous power for a certain time and produce stable power output. LAES technology has a wide range of application prospects in the power system, providing a variety of energy storage services and market opportunities for the power system, the industrial field, providing a variety of energy recovery, peak-valley balance, emergency backup and energy conversion services for industrial production, and urban gas systems, providing a variety of energy reserve, peak load emergency, emergency backup and auxiliary services for urban gas systems. It is of great significance to improve the phenomenon of "wind abandonment" and "light abandonment" in the power generation industry and meet the demand of "peak cutting and valley filling" in the power grid system.

Effect of modified method based on recoil motion on interior ballistic performance of ultralight high-low pressure artillery

Light gun is of unique application prospect for its low body mass and projectile initial velocity. In order to solve the problem of calculation error caused by the large free recoil velocity of light artillery in traditional interior ballistic model, a more suitable internal ballistic model for ultralight artillery was proposed through the design and test of a light gun, the accuracy of the algorithm was verified. The model described the effect of the recoil motion of the gun on chamber pressure and projectile acceleration travel, which made the calculation result more accurate when the gun mass was lighter. Compared with the experimental data, the errors of the calculation results using the improved algorithm were 2.90 % and 0.33 % respectively, while that using the traditional algorithm were 20.38 % and 10.02 % respectively. At the same time, the extended calculation was carried out to analyze the impact of the buffer device on the interior ballistic performance. The result showed that the lighter the gun, the greater the improvement brought by the buffer device under the same mass and recoil resistance. When the mass of the projectile and the gun was both 3 kg, the resistance of 70 kN could increase the velocity of projectile by 16.2 %. Furthermore, the internal ballistic elements of the traditional algorithm and the improved algorithm were calculated respectively under the same working conditions. It was found that when the mass of the gun is 8.567 times the mass of the bullet, the error of the two algorithms was less than 1 %, and the error increased gradually with the mass ratio of gun and projectile decreasing.

Structures and reactivity of monomeric MoO[formula omitted] moieties supported on ZrO[formula omitted] (111) slab: A DFT study

Supported molybdenum oxides have been widely employed as catalysts for variety of reactions including upgrading of bio-oil via hydrodeoxygenation. Herein, we perform spin-polarized density functional theory calculations to investigate the structures and reactivity of monomeric MoOx species supported on ZrO2 in the absence and presence of hydroxyl(s). Monomeric molybdenum moieties were found to have a mono-oxo (one molybdenyl), di-oxo (two molybdenyls) or a pero-oxo (one molybdenyl and Mo coordinated to a peroxide) configuration. Based on the formation energies, we find that mono-oxo moieties are the most stable among the three. This is also true for the moieties in the presence of hydroxyls on the support. Further, the computed vibrational frequencies of a mono-oxo moiety on a hydroxylated support is a closer match to the peaks observed in experiments. A thermodynamic analysis of the molybdenum oxide moieties on a hydroxylated support indicated that the dehydroxylation is favoured at high temperatures and low partial pressures of water. On adsorption of hydrogen on the oxygen of the support, hydrogen loses its electron and reduces Mo of the monomeric moiety without making an oxygen vacancy. We studied the activity of this reduced site for deoxygenation of anisole to benzene. The overall barriers for this reaction are comparable to previously computed barriers for deoxygenation of bio-oil model compounds on an oxygen-vacant molybdenum oxide surfaces, suggesting that this may be an important mechanistic pathway during a hydro-deoxygenation process.

Relationship between the AMOC and the Multidecadal Variability of the Midlatitude Southern Indian Ocean

Abstract Air–sea coupling system in the southwestern Indian Ocean (SWIO; 35°–55°S, 40°–75°E) exhibits predominant multidecadal variability that is the strongest during austral summer. It is characterized by an equivalent barotropic atmospheric high (low) pressure over warm (cold) sea surface temperature (SST) anomalies and a poleward (equatorward) shift of the westerlies during the positive (negative) phase. In this study, physical processes of this multidecadal variability are investigated by using observations/reanalysis and CMIP6 model simulations. Results suggest that the multidecadal fluctuation can be explained by the modulation of the Atlantic meridional overturning circulation (AMOC) and the local air–sea positive feedback in the SWIO. In both observations/reanalysis and CMIP6 model simulations, the AMOC fluctuation presents a significantly negative correlation with the multidecadal SST variation in the SWIO when the AMOC is leading by about a decade. The mechanisms are that the preceding AMOC variation can cause an interhemispheric dipolar pattern of SST anomalies in the Atlantic Ocean. Subsequently, the SST anomalies in the midlatitudes of the South Atlantic can propagate to the SWIO by the oceanic Rossby wave under the influence of the Antarctic Circumpolar Current (ACC). Once the SST anomalies reach the SWIO, these SST anomalies in the oceanic front can affect the baroclinicity in the lower troposphere to influence the synoptic transient eddy and then cause the atmospheric circulation anomaly via the eddy–mean flow interaction. Subsequently, the anomalous atmospheric circulation over the SWIO can significantly strengthen the SST anomalies through modifying the oceanic meridional temperature advection and latent and sensible heat flux.

Atmospheric-pressure CVD-grown h-BN for the detector with deep ultraviolet response

Hexagonal boron nitride (h-BN) has a wide range of applications, especially as a protective coating, dielectric layer/substrate, transparent film, or deep ultraviolet detectors. High-quality h-BN thick films are indispensable for practical deep-ultraviolet (DUV) photodetector applications. However, the controlled synthesis of h-BN films in terms of thicknesses and crystallinity often requires high growth temperatures, low pressures, and catalytic transition metal substrates, which will ultimately hinder their applicability. In this work, we conducted a detailed study of h-BN films with thickness ranging from 50 nm to 160 nm directly synthesized by chemical vapor deposition (CVD) on SiO2/Si substrate under atmospheric pressure. The synthesized h-BN is clean, uniform, and exhibits excellent optical and photoelectrical properties for ultraviolet light in the range of 210 nm-280 nm. This sensitive h-BN photodetector has a high repulsion rate (R220nm/R280nm > 102 and R220nm/ R290nm > 103), a large detection rate (2.8 × 1010 Jones). This work presented here demonstrates the great potential of this h-BN thick film for the development of DUV photodetectors.

Fluid dynamic analysis and lift enhancement of material transport and mixing around airfoil through Lagrangian coherent structures

Flow separation around an airfoil can be effectively controlled by appropriately positioning a synthetic jet (SJ) on the airfoil surface, subsequently enhancing the airfoil's lift. This study conducts a fluid dynamics analysis of material transport and mixing related to momentum transport and mixing around an airfoil. The detailed analysis of the corresponding effects on lift improvement aids in understanding fluid dynamics through Lagrange Coherent Structures (LCSs) and their nonlinear dynamics. An additional SJ is introduced in the airfoil's rear section, combined with a high-speed, low-frequency SJ in the front section to form a combined SJ. The flow around the airfoil with this combined SJ is simulated. LCSs surrounding the SJs are identified and utilized to analyze the complex material transport and mixing processes. The impact of material transport and mixing on lift enhancement is explored through the evolution of LCSs and pressure distribution on the airfoil surface. Results demonstrate that the combined SJs further improve the airfoil's lift coefficient compared to single SJs, with the enhanced material transport and mixing of SJs playing a vital role in lift enhancement. The rear jet accumulates downstream of the rear slot, forming a tail vortex with high momentum and low pressure. The vortex generated by the front jet carries the tail vortex, continuing to move downstream when it reaches the rear slot. A pressure drop forms where the two vortices flow, enhancing the airfoil's lift. The rear jet can absorb fluid downstream and upstream of the jet slot, reducing pressure on the suction surface near the jet slot and significantly contributing to lift improvement.