Annular Structure Research Articles

Electromagnetic Design and Performance Analysis of a Hybrid-Type Superconducting Fault Current Limiter in Shipboard MVDC IPS

As medium voltage dc-based (MVDC) technology is widely considered in the shipboard power system (SPS), the short fault protection of shipboard IPS is urgent. Superconducting fault current limiter (SFCL) is an efficient way to solve the short fault problems in shipboard MVDC IPS. A hybrid type SFCL (H-SFCL) based on a non-quenching inductor and two resistors is electromagnetic designed in this study. The H-SFCL can limit short fault current with no quenching and little heating. In this study, the short fault mechanism and mathematical model of MVDC SPS bipolar short fault is analyzed. According to current limiting performance requirements in MVDC SPS, components parameters of H-SFCL are optimized matching. The scheme of annular structure inductors is proposed and electromagnetic design of a 10 kV/6 kA H-SFCL is completed based on a genetic algorithm. The ac loss and thermal stress of the designed magnet are evaluated. The simulation results show that the H-SFCL with optimized electromagnetic parameters meets the design requirements.

Shape optimization method for wheel rim of automobile wheels based on load path analysis

The wheel rim is an annular and thin-walled structure with complex structural features and working conditions. Guaranteeing its safety and lightweight are two major concerns in wheel rim design. In this study, a shape optimization method based on load path analysis is proposed to evaluate and optimize the structure of the wheel rim. The load-transfer law of the wheel rim is identified based on the load path visualization. Two design criteria are put forward to evaluate the load-bearing performance and give the improvement suggestions. Then, the shape optimization problem is simplified to a parameter optimization problem, and the optimal size combination performance-oriented is obtained using the non-dominated sorting genetic algorithm II (NSGA-II). As a case study, a wheel rim is redesigned and the optimization result shows that the stiffness and strength are improved under bending and radial fatigue simulation, while the weight is reduced by 3.78%. Two stages of experimental studies are carried out to verify the optimization method. The static pressure test shows that the bending resistance performance of the wheel rim is improved by 4.57%, and the load transfer is more uniform. The radial impact test shows that the impact deformation at a high energy level is reduced by 13.77%, indicating that the impact resistance performance is significantly improved.

Field-controlled flow and shape of a magnetorheological fluid annulus.

We investigate the behavior of a magnetorheological (MR) fluid annulus, bounded by a nonmagnetic fluid and confined in a Hele-Shaw cell, under the simultaneous effect of in-plane, external radial and azimuthal magnetic fields. A second-order mode-coupling theory is used to study the early nonlinear stage of the pattern-forming dynamics. We examine changes in the morphology of the MR fluid annular structure as a function of its magnetic-field-tunable rheological properties, as well as the combined magnetic field's intensities, and thickness of the ring. Our weakly nonlinear perturbative results show that, depending on the system control parameters, the MR fluid annulus adopts various stationary shapes. These equilibrium annular structures present slightly bent, asymmetric fingered protrusions which may emerge on the inner, outer, or even on both boundaries of the magnetic fluid ring. On top of these morphological changes, we find that the resulting permanent shape patterns rotate with a well defined angular velocity. We focus on analyzing how the overall shape of the fingered patterns, in particular their sharpness and asymmetric form, as well as the number of resulting fingers are impacted by the magnetic-field-dependent yield stress of the MR fluid annulus. The influence of the magnetically controlled rheological properties of the MR fluid on the angular velocity of the rotating annulus is also scrutinized.

Microstructural evolution and mechanical properties of TiC-containing WC-based cemented carbides prepared by pressureless melt infiltration

WC-based cemented carbides with different amounts of TiC (0.9, 1.2, 1.5, 1.8 and 2.1 wt%) were synthesized by pressureless melt infiltration at 1200 °C for 90 min in vacuum furnace using Cu–10Ni–5Mn–3Sn binder alloy and cast WC, Ni and TiC powders. The microstructural evolution, new phase formation, and related mechanical properties of melt infiltrated alloys were investigated. Results revealed that partially-cast WC and TiC decomposed and formed Ni2W4C, W, (Ti,W)C1-x and annular-structured solid solution when the content of TiC was in the range of 1.2–2.1 wt%, whereas Ni2W4C and W were not observed in the alloy with 0.9 wt% TiC. Annular-structured solid solution was characterized by high carbon with relatively small amounts of W and/or Ti. An increase in TiC content promoted the formation and growth of Ni2W4C and (Ti,W)C1-x phases. However, the annular structure with a continuous network developed into discontinuous net-like distribution and gradually disappeared. Addition of an appropriate amount of TiC improved the Rockwell hardness (HRA) and transverse rupture strength (TRS); however, the impact toughness always decreased with the addition of more amount of TiC. The alloys with 1.8 wt% TiC, 1.5 wt% TiC, and 0.9 wt% TiC exhibited the best mechanical properties with Rockwell hardness of 93.6 HRA, TRS of 1823.4 MPa, and impact toughness of 6.33 J cm−2, respectively.

An Annular Fresnel Zone Plate without Central Spots Fabricated by Femtosecond Laser Direct Writing.

In recent years, micro-annular beams have been widely used, which has expanded the possibilities for laser processing. However, the current method of generating an annular beam still has shortcomings, such as spot energy at the center of the produced beam. In this study, a Fresnel zone plate with an annular structure was machined using a femtosecond laser. After focusing, an annular laser beam without a spot in the center was obtained, and the radius and focal length of the annular beam could be easily adjusted. In addition, two annular Fresnel zone plates were concentrically connected to obtain a concentric double-ring beam in the same focal plane. The simulation and experimental results were consistent, providing effective potential for applications related to nontraditionally shaped laser beams.

Study on Marangoni- and buoyancy-driven convection in smaller Reynolds number flow field of electrochemical machining

In order to study the Marangoni- and buoyancy-driven convection in smaller Reynolds number flow field, a new electrochemical machining model was established by coupling various physical fields, in which the machining gap was defined as 20 mm and the electrolyte conductivity was equal to 8.74 S/m. Through the numerical simulation and experiments, the mechanisms of convection formation, diffusion and instability were investigated. The results indicated that the convection cells had a strong correlation with the current density, and the convection driven by buoyancy and Marangoni forces existed in the flow field. With the accumulation of the heat in the processing area, the transition region gradually became the main channel for the heat transfer. The convection cell gradually changed from a stable and symmetrically distributed structure to an annular convection structure, when the processing voltage exceeded the critical voltage (12 V). The convection cells in the processing region were mainly driven by the Marangoni force, which eventually formed the Marangoni convection. The convection cells near the upper surface of the electrolyte were induced by the buoyancy force, which formed the buoyancy convection. The convection cells in the transition region were gradually compressed and destroyed by the progressively increasing buoyancy effect and the bubble flow. Near the anode-electrolyte interface, the boundary layer thickness of the velocity was more important than the boundary layer thickness of the thermal, and the convection transportation was significantly larger than the diffusion transportation. These characteristics provide application potential for the thin film self-assembly process in ECM.

Compression Deformation Prediction of Chiral Metamaterials: A Compression–Shear Coupling Model

A category of metamaterials consisting of chiral cytosolic elements assembled periodically, in which the introduction of a rotatable annular structure gives metamaterials the ability to deform in compression–shear, has been a focus of research in recent years. In this paper, a compression–shear coupling model is developed to predict the compressive deformation behaviour of chiral metamaterials. This behaviour will be analysed by coupling the rotation of the annular node and the bending characteristics of ligament beam, which are obtained as a function of the length of ligament beam and the angle of rotation at the end of the beam. The shape function of the ligament beam under large deformation is obtained based on the elliptic integral theory; the function characterises the potential relationship between key parameters such as displacement and rotation angle at any point on the ligament beam. By simulating the deformation of cells under uniaxial compression, the reasonableness of the large deformation model of the ligament beam is verified. On this basis, a chiral cell-compression mechanical model considering the ductile deformation of the annular node is established. The compression–shear deformation of two-dimensional planar chiral metamaterials and three-dimensional cylindrical-shell chiral metamaterials was predicted; the offset displacements and torsion angles agreed with the experimental and finite element simulation results with an error of less than 10%. The developed compression–shear coupling model provides a theoretical basis for the design of chiral metamaterials, which meet the need for the precise control of shapes and properties.

A Biodegradable Polymeric Matrix for the Repair of Annulus Fibrosus Defects in Intervertebral Discs.

Tissue defects in the annulus fibrosus (AF) due to intervertebral disc (IVD) degeneration or after nucleodiscectomy have little self-healing capacity. To prevent progressive degeneration of the IVD, the AF must be repaired. Biological closure has not yet been achieved and is a challenge for the research community. In this study, a scaffold made of absorbable poly (glycolic acid) (PGA) and hyaluronan (HA) that exhibit excellent biocompatibility and cell colonization properties was used to repair AF defects in an ovine model. A partial resection was performed in AF in L3/4 or L4/5 of 10 sheep and PGA-HA scaffolds were implanted on the defects (n = 5), while defects in the control group were left untreated (n = 5). Three months post-operation, the lumbar discs were sectioned and stained with hematoxylin and eosin and safranin-O/fast-green. Histological features including proteoglycan content, annular structure, cellular morphology, blood vessel ingrowth and tear/cleft formation were scored using a modified scoring scheme by 3 investigators and evaluated by a pathologist independently. The treated AF exhibited significantly enhanced repair tissue structure with signs of proteoglycan formation compared to the untreated group. The median scores were 4.3 for the treated and 9.8 for the untreated group. Cystic degeneration, perivascular infiltration, inflammation and necrosis were only present in the untreated group. Blood vessel ingrowth and tear/cleft formation were increased, though not significant, in the untreated group while cell morphology was comparable in both groups. PGA-HA scaffolds used for AF closure support repair tissue formation in an ovine lumbar disc defect model.

A novel hydrocyclone for use in underground DNAPL phase separation

Halogenated organic solvents are the most commonly detected pollutants in groundwater and are particularly toxic and harmful. How to separate these dense nonaqueous phase liquid (DNAPL) pollutants efficiently from groundwater has become an important research question. Here, a novel hydrocyclone with annular overflow structure was designed, which eliminated the short-circuit flow of the traditional hydrocyclone and solved the problem of overflow entrainment caused by the enrichment of droplets near the locus of zero vertical velocities (LZVV) into turbulence. The flow field characteristics of this novel hydrocyclone were studied using Computational Fluid Dynamics (CFD) simulation and compared with the traditional hydrocyclone. It was found that the annular gap structure of the novel hydrocyclone increased the tangential velocity of the outer vortex. Moreover, the radius of the LZVV was expanded outward by 0.17 mm, which reduced the possibility of droplets with small particle sizes in the second phase escaping from the overflow pipe. The collective effect was to eliminate the short-circuit flow. This novel hydrocyclone was able to separate DNAPL pollutants with low consumption and high efficiency, across a range of inlet velocity from 4 to 6 m/s. The maximum separation efficiency was 99.91 %. In addition, with trichloroethylene (TCE) as the target pollutant, the maximum volume fraction of the dispersed phase in the hydrocyclone was located on the side wall of the hydrocyclone. Taken together, we believe that this work will provide a low-cost, efficient separation method for the separation of groundwater- contaminated liquid mixtures. Furthermore, it has broad application prospects in the field of heterotopic remediation of groundwater.

Flow characteristics of air separation in VPSA process with radial flow adsorber

Radial flow adsorbers are widely applied to large-scale air separation. The low pressure drops and flow uniformity in radial flow adsorbers (RFAs) are of great importance for high quality O2 enrichment. However, the insufficient consideration of annular channel structure and simplification of perforated plate distributor in existing methods limit a further optimization of uneven flow in the RFAs. In this study, the detailed perforated plate distributor configuration (hole arrangement and porosity) is adopted to investigate the flow field in the RFAs more deeply. In addition, the effects of three types of annular channels on pressure drop profiles rarely studied intensively in previous publications are also discussed. The simulated results agree well with static and dynamic experiments in terms of N2 adsorbed amount and breakthrough time, indicating the feasibility of proposed model for RFAs simulation. Thereafter, it can be found that for the adsorber with a convergent annular channel, the utilization ratio of the adsorbent and desorption efficiency can reach up to 27.58% and 91.64% respectively, accompanied by average 96.61% pressure drop uniformity. Moreover, the impact of hole arrangement is insignificant in the case of a regular arranged cylindrical holes on the distributor. However, the nonuniform porosity makes the adsorption area shift from the bottom to upper of the adsorber by changing the flow resistance. For the adsorber with convergent annular channel and optimized arrangement of distributor, the whole flow uniformity can be improved by 24.69%.

Synthesis of tung oil-based vinyl ester resin and its application for anti-corrosion coatings

Anti-corrosion coatings are of great significance for marine equipment and engineering on account of the harsh marine environment. Vinyl ester resin is widely used as a resin material for anti-corrosion coating because of its excellent hardness and protective performance. However, the intrinsic brittleness of vinyl ester resin causes the resulting coating film with poor toughness. In this study, the tung oil-based toughen modifier (TOAMA) with a long carbon chain and annular structure is firstly prepared by Diels-Alder reaction of tung oleic acid and maleic anhydride under solvent-free conditions, and then used as a reactive toughening agent to synthesize toughened vinyl ester resin. The characterization results of Fourier transform infrared and hydrogen nuclear magnetic resonance spectroscopies reveal the successful synthesis of the TOAMA-toughened vinyl ester resin. Furthermore, the toughened vinyl ester resin is used in the anti-corrosion coatings, and the properties of the related cured coating films including thermostability, mechanical performance and corrosion resistance are systematically studied. The related results display that TOAMA can effectively toughen vinyl ester resin, and the toughened vinyl ester resin prepared with the optimized TOAMA content can effectively improve the mechanical properties including mechanical strength, elongation at break and fracture toughness, and achieve favorable thermal stability and excellent corrosion resistance of the cured coating films. Grafting tung oil-based toughening modifier TOAMA into the backbone of vinyl ester resin effectively provides a significant promising method to toughen vinyl ester resin, which is beneficial to the application of vinyl ester resin in the marine anti-corrosion coating field.

Performance Analysis of Magnetorheological Damper with Folded Resistance Gaps and Bending Magnetic Circuit

The traditional magnetorheological (MR) damper subject to the limited space has shortcomings such as small damping force, narrow dynamic range and low adaptability. In this study, a new MR damper with folded resistance gaps and bending magnetic circuit was proposed for improving the damping performance. The length of the resistance gap was increased by configuring the multi-stage folded annular gap structure, and the magnetic circuit was established to activate the non-flux region. The mathematical model was established for the MR damper to analyze the damper force, magnetic circuit and dynamic performance. Subsequently, the finite element analysis (FEA) methodology was utilized to investigate the changes of magnetic flux densities in the folded resistance gaps. The test rig was setup to explore and verify the dynamic performance of the proposed MR damper under different excitation conditions. The results indicate the maximum damping force is approximately 4346 N at the current of 1.5 A, frequency of 0.25 Hz and amplitude of 7.5 mm. The damping force and dynamic range of the proposed MR damper are enhanced by 55.82% and 62.21% compared to that of the traditional MR damper at the applied current of 1.5 A, respectively, thus highlighting its high vibration control ability.

Numerical study of singlet delta oxygen (O2(a1Δg)) generation and transport in the He/O2 atmospheric pressure plasma jet

This paper investigates the spatial-temporal evolution and the transport of the singlet delta oxygen (O2(a1Δg)) of an atmospheric pressure plasma jet using a 2D fluid modeling. The plasma jet is produced in pure helium or helium with small oxygen admixtures (no bigger than 2%), by applying a constant DC voltage of +5 kV on the annular electrode. It is found that, at the 0.7% O2 admixture, a higher O2(a1Δg) density is obtained inside the tube before the jet impacts the substrate. After the jet propagates along the substrate surface, the peak O2(a1Δg) density is transferred from the tube to the gap. Varying the O2 admixtures percentage in the working gas changes the O2(a1Δg) spatial distribution. The O2(a1Δg) with two thinner edges is dominantly produced in the helium–air mixing layer for pure helium. The addition of O2 in the working gas leads to O2(a1Δg) production in the tube. Meanwhile, the thickness of the O2(a1Δg) edges increases in the helium–air mixing layer. But the radius of the O2(a1Δg) density channel continuously reduces with the O2 admixture. The O2(a1Δg) density and its surface flux first increase within the 0.7% O2 admixture and then decreases with the further augment of the O2 admixture. The influence of the gas flow velocity on the production and transport of O2(a1Δg) is also studied. Increasing the gas flow velocity changes the spatial distribution of the O2(a1Δg) density from the solid structure to the annular structure in the gap. At the same time, lower volume average density and instantaneous flux are obtained at larger gas flow velocity.

Research on multi-motor coordinated control under load disturbance

With the iterative development of industrialization and automation, more and more mechanical and electrical equipment rely on the joint operation of multiple motors, and the efficient operation of mechanical and electrical equipment benefits from the reliable cooperative control of multiple motors. Therefore, to ensure the stability of multi-motor coordination control and improve the precision of multi-motor coordination control has important practical significance. In this paper, the multi-motor master-slave controls structure and ring-coupling control structure with random disturbance are simulated and analyzed, and it is verified that the annular coupling control structure has stronger anti-interference ability and higher control accuracy under random load disturbance in the case of four-motor coordinated control.

Spectrum sampling optimization for quantitative phase imaging based on Kramers-Kronig relations.

Annular-illumination quantitative phase imaging based on space-domain Kramers-Kronig relations (AIKK) is a newly developed technique that is object-independent and non-iterative reconstructed inherently. Only capturing four low-resolution images, the AIKK system gains a resolution enhancement of nearly twofold. Under matching constraints between the illumination wave vector and pupil function aperture, we set a spectrum sampling criterion and establish a spectrum effective utilization model to search for the optimal solution of spectrum distribution for the specific annular structure. In view of the square spectrum structure, a diagonal-expanded sampling based AIKK method (DES-AIKK) is presented to get rid of the pixel aliasing problem. It is worth noting that the space-bandwidth-time product (SBP-T) further increases to 439.51 megapixels (1.8× of AIKK). Our work provides the guidelines and insights for designing the most suitable AIKK platform for high-throughput microscopic applications in pathology and real-time dynamic observation.

Unveiling topological order through multipartite entanglement

It is well known that the topological entanglement entropy (${S}_{\mathrm{topo}}$) of a topologically ordered ground state in two spatial dimensions can be captured efficiently by measuring the tripartite quantum information (${I}^{3}$) of a specific annular arrangement of three subsystems. However, the nature of the general $N$-partite information (${I}^{N}$) and correlation of a topologically ordered ground state remains unknown. In this work, we study such ${I}^{N}$ measure and its nontrivial dependence on the arrangement of $N$ subsystems. For the collection of subsystems (CSS) forming a closed annular structure, the ${I}^{N}$ measure ($N\ensuremath{\ge}3$) is a topological invariant equal to the product of ${S}_{\mathrm{topo}}$ and the Euler characteristic of the CSS embedded on a planar manifold, $|{I}^{N}|=\ensuremath{\chi}{S}_{\mathrm{topo}}$. Importantly, we establish that ${I}^{N}$ is robust against several deformations of the annular CSS, such as the addition of holes within individual subsystems and handles between nearest-neighbor subsystems. While the addition of a handle between further neighbor subsystems causes ${I}^{N}$ to vanish, the multipartite information measures of the two smaller annular CSS emergent from this deformation again yield the same topological invariant. For a general CSS with multiple holes (${n}_{h}>1$), we find that the sum of the distinct, multipartite information measured on the annular CSS around those holes is given by the product of ${S}_{\mathrm{topo}}, \ensuremath{\chi}$ and ${n}_{h}, {\ensuremath{\sum}}_{{\ensuremath{\mu}}_{i}=1}^{{n}_{h}}|{I}_{{\ensuremath{\mu}}_{i}}^{{N}_{{\ensuremath{\mu}}_{i}}}|={n}_{h}\ensuremath{\chi}{S}_{\mathrm{topo}}$. This constrains the concomitant measurement of several multipartite information on any complicated CSS. The $N\text{th}$ order irreducible correlations for an annular CSS of $N$ subsystems is also found to be bounded from above by $|{I}^{N}|$, which shows the presence of correlations among subsystems arranged in the form of closed loops of all sizes. Thus, our results offer important insight into the nature of the many-particle entanglement and correlations within a topologically ordered state of matter.

Sperm morphology and some aspects of acrosomal complex development in four species of Heteronemertea (Pilidiophora, Nemertea)

The ultrastructure of sperm morphology and some aspects of acrosomal complex development were examined in Kulikovia alborostrata, K. torquata, Kulikovia sp., and Micrura bella using transmission and scanning electron microscopy. The studied Kulikovia species have spermatozoa with a bullet-shaped head consisting of an acrosomal complex with a single cup-like acrosomal vesicle, a cone-shaped nucleus, and a short midpiece that are characteristic of the ect-aquasperm type. Despite the general similarity in spermatozoon organization, an ultrastructural analysis has revealed some species-specific size differences. M. bella is distinguished by an elongated curved sperm head with an acrosomal complex containing one large electron-dense and a few small, moderately electron-dense acrosomal vesicles. As a rule, five mitochondria are located in the midpiece in all the studied species. According to data published in literature and the present findings, all Pilidiophora have spermatozoa with several (three, four or five) mitochondria, and they never contain a single mitochondrion. We suggest this trait to be a synapomorphy for the class Pilidiophora, while the posterior acrosomal ring component, an annular structure formed by the basal part of the acrosomal vesicle, to be a synapomorphy for Heteronemertea. Acrosomal vesicles develop from numerous proacrosomal vesicles that are synthesized in spermatocytes I and fuse (or partly fuse in M. bella) at the spermatid stage. We regard the separate small acrosomal vesicles in the acrosomal complex of M. bella spermatozoa as the retention of an ancient trait in the sperm structure via “progenetic spermatogenesis” during the sperm cell development.

Visualization and Quantification of the Unrepaired Complete Atrioventricular Canal Valve Using Open-Source Software

Repair of complete atrioventricular canal (CAVC) is often complicated by residual left atrioventricular valve regurgitation. The structure of the mitral and tricuspid valves in biventricular hearts has previously been shown to be associated with valve dysfunction. However, the three-dimensional (3D) structure of the entire unrepaired CAVC valve has not been quantified. Understanding the 3D structure of the CAVC may inform optimized repair. Novel open-source work flows were created in SlicerHeart for the modeling and quantification of CAVC valves on the basis of 3D echocardiographic images. These methods were applied to model the annulus, leaflets, and papillary muscle (PM) structure of 35 patients (29 with trisomy 21) with CAVC using transthoracic 3D echocardiography. The mean leaflet and annular shapes were calculated and visualized using shape analysis. Metrics of the complete native CAVC valve structure were compared with those of normal mitral valves using the Mann-Whitney U test. Associations between CAVC structure and atrioventricular valve regurgitation were analyzed. CAVC leaflet metrics varied throughout systole. Compared with normal mitral valves, the left CAVC PMs were more acutely angled in relation to the annular plane (P<.001). In addition, the anterolateral PM was laterally and inferiorly rotated in CAVC, while the posteromedial PM was more superiorly and laterally rotated, relative to normal mitral valves (P<.001). Lower native CAVC atrioventricular valve annular height and annular height-to-valve width ratio before repair were both associated with moderate or greater left atrioventricular valve regurgitation after repair (P<.01). It is feasible to model and quantify 3D CAVC structure using 3D echocardiographic images. The results demonstrate significant variation in CAVC structure across the cohort and differences in annular, leaflet, and PM structure compared with the mitral valve. These tools may be used in future studies to catalyze future research intended to identify structural associations of valve dysfunction and to optimize repair in this vulnerable and complex population.

Can current reanalyses accurately portray changes in Southern Annular Mode structure prior to 1979?

Early reanalyses are less than optimal for investigating the regional effects of ozone depletion on Southern Hemisphere (SH) high-latitude climate because the availability of satellite sounder data from 1979 significantly improved their accuracy in data sparse regions, leading to a coincident inhomogeneity. To determine whether current reanalyses are better at SH high-latitudes in the pre-satellite era, here we examine the capabilities of the European Centre for Medium-range Weather Forecasts (ECMWF) fifth generation reanalysis (ERA5), the Twentieth Century Reanalysis version 3 (20CRv3), and the Japanese Meteorological Agency (JMA) 55-year reanalysis (JRA-55) to reproduce and help explain the pronounced change in the relationship between the Southern Annular Mode (SAM) and Antarctic near-surface air temperatures (SAT) between 1950 and 1979 (EARLY period) and 1980–2020 (LATE period). We find that ERA5 best reproduces Antarctic SAT in the EARLY period and is also the most homogeneous reanalysis across the EARLY and LATE periods. ERA5 and 20CRv3 provide a good representation of SAM in both periods with JRA-55 only similarly skilful in the LATE period. Nevertheless, all three reanalyses show the marked change in Antarctic SAM-SAT relationships between the two periods. In particular, ERA5 and 20CRv3 demonstrate the observed switch in the sign of the SAM-SAT relationship in the Antarctic Peninsula: analysis of changes in SAM structure and associated meridional wind anomalies reveal that in these reanalyses positive SAM is linked to cold southerly winds during the EARLY period and warm northerly winds in the LATE period, thus providing a simple explanation for the regional SAM-SAT relationship reversal.

Numerical study of atmospheric-pressure argon plasma jet propagating into ambient nitrogen

A 2D axial symmetry fluid model is applied to study the features of an atmospheric-pressure argon (Ar) plasma jet propagating into ambient nitrogen (N2) driven by a pulsed voltage, emphasizing the influence of gas velocity on the dynamic characteristics of the jet. The results show that the Ar jet exhibits a cylindrical-shaped channel and the jet channel gradually shrinks with the increase in propagation length. The jet propagation velocity varies with time. Inside the dielectric tube, the plasma jet accelerates propagation and reaches its maximum value near the nozzle. Exiting the tube, its velocity quickly decreases and when approaching the metal plane, the decrease in jet velocity slows down. The increase in gas speed results in the variation of jet spatial distribution. The electron density presents a solid structure at lower gas flow speeds, whereas an annular structure can be observed under the higher gas flow velocity in the ionization head. The jet length increases with the flow velocity. However, when the flow velocity exceeds a critical value, the increase in the rate of the plasma jet length slows down. In addition, the gas velocity effect on the generation and transport of the reactive particles is also studied and discussed.