Outer Rings Research Articles

Extensive reduction in choroidal thickness after photodynamic therapy in eyes with central serous chorioretinopathy

We examined the effect of reduced fluence (rf)-photodynamic therapy (PDT) of the macular area on the wide-field choroidal thickness in 20 eyes with central serous chorioretinopathy (CSC) and 20 age- and sex-matched control eyes. The choroidal thickness at the posterior pole was measured before and after rf-PDT, using a grid with inner and outer rings, each divided into superotemporal, inferotemporal, superonasal, and inferonasal quadrants, respectively, making up a total of nine subfields including the central 3 mm ring. Before treatment, all eyes showed wide-field choroidal thickening from the dilated vortex vein ampulla to the fovea, along the course of the vein. After rf-PDT of the macular area, the choroidal thickness significantly decreased, not only in the irradiated macular area but also outside the arcade vessels in all quadrants (p < 0.001 for all inner subfields; p = 0.035 and p = 0.024 for the outer superonasal and inferonasal subfields, respectively; p < 0.001 and p = 0.004 for the outer superotemporal and inferotemporal subfields, respectively). For control eyes, the choroidal thickness did not differ between the initial visit and follow-up 1.2 ± 0.7 months after the initial visit (p > 0.05 for all subfields). These findings provide new insights into the pathogenesis of CSC and explain the reasons for the effectiveness of rf-PDT for this condition.

Optimization of three-dimensional traveling wave drive for a PZT thin-film micro-motor based on stiffness tuning of the supporting structure

This paper is based on the analysis of the three-dimensional motion of the PZT (lead zirconate titanate) thin-film traveling wave micro-motor and presents an optimization study of the effect of the radial component on the output torque and maximum speed. Based on theoretical analysis, it is proposed that the inconsistency of the equivalent constraint stiffness of the inner and outer rings is the main factor in the radial component of the traveling wave drive. Considering the large computational and time costs of 3D (three-dimensional) transient simulation, the residual stress-relieved deformation state in a steady state is used to equivalently characterize the inner and outer ring constraint stiffness of the micro-motor, and then the outer ring support stiffness is adjusted to achieve the consistency of the inner and outer ring constraint stiffness and the optimization of the radial component reduction, as well as to improve the flatness of the micro-motor interface under residual stress and optimize the contact state between the stator and rotor. Finally, performance testing of the device prepared by the MEMS process showed that the output torque of the PZT traveling wave micro-motor increased by 21% (14.89 μN*m), the maximum speed increased by 18% (>12000 rpm), and the speed instability was optimally reduced by a factor of 3 (<10%).

Optimization of cooling water jacket structure of high-speed electric spindle based on response surface method

In high-precision machining machine tools, the high-speed electric spindle is the fundamental transmission component. Nonetheless, the electric spindle's small and tightly sealed internal structure may result in insufficient heat dissipation, resulting in significant heat accumulation during continuous operation. This might induce thermal displacement of the spindle and reduce machine tool machining precision. A response surface was established by a 2-factor 3-level interaction experiment utilizing Design-expert software to reduce the heat displacement of the electric spindle. The electric spindle cooling water jacket was optimized and front and rear bearing cooling water channels were added based on the response surface results. The thermal-solid coupling simulation was carried out using ANSYS, and the optimized data for the front and rear bearing temperature, as well as spindle thermal displacement, were obtained through simulation analysis. Comparing the simulation with the experimental data, it was found that the front and rear bearing temperature decreased by 4.34 °C and 8.97 °C, respectively, and the spindle thermal displacement was reduced by 16.57 μm, resulting in improved machining accuracy. The service life of the bearings was further prolonged by the decreased thermal stress between the inner and outer rings and the balls of the front and rear bearings.

PEDS13: Systemic force evaluation of Magnetic Bearings Design for a Pediatric LVAD Study

Study: A miniature magnetic levitation bearing system (maglev) was proposed for an implantable pediatric LVAD. The maglev bearing system is comprised passive radial bearings made of permanent magnet (PM) rings, and an active axial bearing. The study evaluates the passive bearing’s ability to radially stabilize the rotor within a moveable range of radial and axial displacements, and characterizes the axial forces produced. Methods: A stacked pair of concentric PM rings was placed on each side of the rotor and stator for the radial bearings. The PM rings were placed with like poles facing each other. The outer PM rings and stator were mounted on a six-axis force sensor attached to an xyz micrometer driven stage to set the position, and a rotational stage for alignment. The rotor and inner PM rings were inserted in the stator and held in place by both ends. The forces produced were measured at a combination of radial (0mm to 0.35mm with 0.05mm steps) and axial (0mm to 0.25mm with 0.05mm steps) displacements away from the center for a combination of 48 points. The measurements were taken three times and the average was taken. A finite element simulation was conducted by combining previously validated models of the motor, and the PM ring bearings to calculate radial and axial displacement forces. Results: As radial displacement increases, bearing force towards the center increases. Axial displacement decreases the force magnitude, but the direction towards the center remains. This shows the bearing’s ability to radially stabilize the rotor at a range of different radial and axial displacement combinations. As you increase axial displacement, the axial force away from the center increases. The radial position has little effect on axial force. This study quantifies the passive bearing’s axial forces to use in future work of developing the active axial bearing. The simulation results are in accordance with the experimental results. Variation is likely due to rotor-stator alignment error, holder manufacturing tolerances, and rotor rod flexing.Figure 1. Experimental Force Test SetupFigure 2. Axial and radial forces produced. Points are experimental results, dashed lines are simulation results.

Coming of Age in Faith: The Rite of Confirmation after the English Reformation

This article explores confirmation as a ritual of Christian initiation in the context of the English Reformation. It examines how this rite of passage, which was demoted from its traditional status as a sacrament, survived and evolved in the wake of the theological, liturgical and ecclesiological changes associated with the advent of Protestantism. It traces the permutations of the practice of laying on of hands that both united and fractured people within the Church of England and its evangelical outer rings between the sixteenth and eighteenth centuries. It also considers the social history of a ritual that increasingly coincided with the transition from childhood to puberty, and its capacity to shed light on the formation of collective religious identity, bodily habitus and lived experience. Finally, it briefly discusses the Counter-Reformation of confirmation and its transformation into a marker of the confessional militancy of a minority faith.

Application of circuit analog optimization method in fast optimization of dynamically tunable terahertz metamaterial sensor

The simulation design of terahertz metamaterial sensors with dynamically tunable parameters typically relies on manual parameter tuning for structural optimization. However, this method is often prone to subjective factors and suffer from issues such as frequent reconstruction of simulations, high computational costs, long processing times, and suboptimal optimization results. In this paper, we propose a circuit analog optimization method (CAOM), which constructs equivalent RLC parameters to achieve a highly fitted terahertz transmission spectrum frequency obtained from CST full-wave numerical simulation. To validate the effectiveness of the proposed model, we use a typical periodic structure unit, a double-nested split ring resonator (DSRR) terahertz metamaterial sensor, as the simulation object. Both the inner and outer open resonant rings of the sensor are made of graphene, as a result, the opening size and Fermi level of the resonant rings are dynamically tunable. The results of the validation demonstrate that the adjustments of the sensor parameters can be effectively mapped by the changes of the equivalent RLC parameters. And the proposed equivalent circuit model has parameter substitutability in the simulation modeling of split ring resonator type sensors. The proposed equivalent circuit model exhibits parameter substitution in the simulation modeling of open resonant ring-type sensors. To achieve optimal sensing performance for the electromagnetically induced transparency (EIT)-like resonant peak (with a resonant frequency of f 2) of the sensor under constrained conditions, we introduce the genetic algorithm (GA) into the equivalent circuit model to enable fast optimization of the opening sizes of the inner and outer resonant rings, as well as the Fermi level of the sensor. Moreover, the accuracy of the optimization results is verified by CST simulations. Finally, the optimization results show that the optimal FOM of the EIT-like resonant peak within the given parameter range is 0.712, which is greater than that of any randomly combined parameters. This numerical result demonstrates the effectiveness of the proposed CAOM. The proposed model and optimization method have potentials to inspire further research in device design, performance optimization, theoretical modeling, etc.

Spreading Characteristics of Volatile Liquid Film on the Liquid-solid Substrates

The spreading characteristics of volatile liquid film on the liquid-solid substrate have been experimentally investigated. Unlike the liquid film spreading on the liquid substrate, there exists a dip at the top of the solid substrate, as a result, the spreading behaviors are inhibited. It is found that dip characteristics of R’/ R slightly decrease at the beginning then it keeps constant R’/ R=0.83 until the end. Moreover, the comparison of spreading behaviors on two different substrates is investigated. When the volatile film spreads on the liquid-solid substrate, the maximum radii of the outer and inner rings are smaller, but the process lasts longer. Although the evolutions of radii are different, the variation trend of nondimensional ring width is consistent. We further study the spreading rate; results show there exist three stages due to the relative importance of different forces. Our results provide important missing pieces to the rich mechanisms of the multiple-phase flow driven by the Marangoni effect.

Three-dimensional fretting and sliding contact model in planetary gear system: Theoretical analysis and experiments

The failure of the interference fit between the planetary gear and the bearing outer rings in planetary gear systems has received increasing attention from researchers. In this study, a three-dimensional model for determining the fretting and sliding contacts between planetary gears and these outer rings is presented. A three-dimensional fretting numerical model under oblique forces was established to investigate the fretting contact between planetary gears and bearings, and an experiment was conducted to study the relative sliding between them. The results showed that if the torque generated by the difference between two meshing forces exceeded the limit torque of the interference fit, overall relative sliding would occur. Otherwise, fretting contact would occur in some regions of the interference fit surface under oblique forces. The relative sliding between the planetary gear and outer rings of the bearings can be reproduced experimentally; the relative sliding value decreased with an increase in the size of the interference fit.

Defects Detection Method Based on Programmable Spoof Surface Plasmon Polaritons in Non-Metallic Composites

Microwave nondestructive testing (NDT) offers promising application prospects due to its advantages of non-contact inspection in detecting defects in non-metallic composites. However, the detection sensitivity of this technology is generally affected by the lift-off effect. To reduce this effect and highly concentrate electromagnetic fields on defects, a defect detection method using scanning instead of moving sensors in the microwave frequency range was proposed. Additionally, a novel sensor based on the programmable spoof surface plasmon polaritons (SSPPs) was designed for non-destructive detection in non-metallic composites. The unit structure of the sensor was made up of a metallic strip and a split ring resonator (SRR). A varactor diode was loaded between the inner and outer rings of the SRR, and by changing the capacitance of this diode using electronic scanning, the field concentration phenomenon of the SSPPs sensor can be moved along a specific direction for defect detection. By using this proposed method and sensor, the location of a defect can be analyzed without moving the sensor. The experimental results demonstrated that the proposed method and designed SSPPs sensor can be effectively applied in detecting defects in non-metallic materials.

Piecewise Hybrid System with Cross-Correlation Spectral Kurtosis for Fault Diagnosis in Rolling Bearing of Wind Power Generator

As the core equipment of wind turbines, rolling bearings affect the normal operation of wind power generators, resulting in huge economic losses and significant social impacts in the case of faults. Most faults are not easily found because of the small vibration response of these rolling bearings that operate in harsh conditions. To address the problem that the fault identifications of rolling bearings are disturbed by the strong noise in wind power generators, an adaptive nonlinear method based on a piecewise hybrid stochastic resonance system with a novel cross-correlation spectral kurtosis is proposed. Then, the vibration signals collected from the fault point of the outer and inner rings are used to clarify the outstanding capability of the proposed method when compared with the maximum cross-correlation-kurtosis-based unsaturated stochastic resonance method. Furthermore, the machine learning method based on the medium tree was adopted to further prove the excellent performance of the piecewise hybrid stochastic resonance system with a novel cross-correlation spectral kurtosis for realizing the efficient detection of rolling bearing faults in wind power generators, which has important innovation significance and practical engineering value for ensuring the safe and stable operation of wind turbines.

Study of spatter net forming mechanism and penetration mode under flexible ring mode laser welding

Flexible ring mode (FRM) laser technology can generate different powers by adjusting the power ratio of the inner and outer rings, and has great potential for welding copper and its alloys with high reflectivity. This paper used a high-speed photographic camera to monitor the behavior and spatter-forming process of molten pool on the front of red copper plate. The spattering behavior in different penetration modes and net forming mechanisms under FRM are revealed. The results show that full penetration causes the high-temperature vapor to escape from the upper and lower openings. More energy is absorbed by the molten pool and keyhole in the semi-penetration mode, forming an expansion zone and increasing the pool's instability. The outer ring laser of FRM reduces the temperature gradient, which can lower the surface tension gradient, making the flow of the molten pool smoother and the height and formation times of the liquid column lower and less, thereby reducing the spatter. Moreover, FRM laser produces a larger and more stable keyhole, making the escape of metal vapor easier and minimizing the kinetic energy. The reasons above bring the sound result of high yield rate, improved by 75%, comparing with pure Gaussian laser. This paper provides theoretical guidance for engineering researchers to understand the role of shaping laser beams in the welding of highly reflective materials.

Dynamic Service Mechanism of Double-Row Spherical Roller Bearings Due to Self-Aligning Behavior

Spherical roller bearings (SRBs) are widely used under self-aligning operating conditions, such as rotor bending or an angular misalignment between inner and outer rings due to their self-aligning function. However, the characterization of SRBs’ self-aligning function is often ignored in the present models. The reason for this is that the self-aligning condition is essentially a fault condition, and many scholars have assumed SRBs are in an ideal operating condition. Although there is nothing wrong with this analysis theoretically, it is incapable of characterizing SRBs’ service behavior comprehensively. In this work, the Lagrange equation was introduced to model the relationship among the rollers and the inner and outer rings. The contact region in particular was characterized in detail in order to solve the problems of undetermined contact status (UCS) and the varying law of the self-aligning contact angle (SAC angle). For the experiment, a novel SRBs pedestal with a self-aligning operating condition was designed, and the relevant self-aligning function testing was carried out. A good agreement was shown between the theoretical and experimental results. The results pointed out that, if taking no account of the self-aligning function, SRBs can be regarded as angular contact ball bearings or cylinder roller bearings. The amplitude of the inner-ring motion orbit is determined by the external load, but the shape is influenced by the direction and magnitude of the SAC angle. In the example of this paper, the values of the main frequency equal 136.8 Hz. Some additional frequencies are clearly aroused under the self-aligning operating condition, whose value is approximately equal to 8.3 Hz or its integer multiples. The dynamic performance of SRBs will be substantially improved by a light axial load plus an anticlockwise self-aligning contact angle rather than a large axial preload.

A novel air core electromagnetic fault current limiter with rotational motion

AbstractThe authors deal with design and analysis of an air‐core electromagnetic fault current limiter (FCL) with rotary motion. The proposed device is characterised by a simple structure, fast operating speed and reversible operation. It consists of two movable concentric air core spherical reactor rings (i.e. inner and outer rings) with variable mutual angular displacement. At normal condition, reactors are approximately aligned, and subsequently, the effective inductance/impedance of the equipment and the respective voltage drop are low. At faulty conditions, the short circuit current exerts a repulsive rotary electromagnetic torque on the reactors, which results in a fast and steady increase of the reactors angular displacement. During this process, the effective inductance of the equipment rapidly rises up to a level that effectively limits the short circuit current. To determine the effectiveness of the proposed topology in limiting the network's fault current, the inductance profile of the proposed rotary FCL and the respective fault current characteristic are compared with similar case studies (a) with linear FCL and (b) without FCL. The analysis is carried out via a finite element (FE) and supported via analytical and theoretical discussion. Finally, a down‐scale prototype of the proposed FCL was built and tested to verify the functionality of the device in the lab environment.

Plasmonic Metasurfaces for Superposition of Profile-Tunable Tightly Focused Vector Beams and Generation of the Structured Light

Vector beams (VBs) and their superposition have found important applications in versatile fields such as optical communications, super-resolution microscopy and quantum information, and metasurfaces have enabled the miniaturization and integration of the optical systems manipulating the vector beams, providing potential applications to subwavelength regimes. In this work, we propose a metasurface to realize the superposition of profile-tunable tightly focused VBs, with the novel structured light fields generated. The metasurface is composed of two sets of orthogonal-nanoslit pairs arranged on the inner and outer rings. By realizing the chiral conversion of circularly polarized light with the slit-pairs which act as half-wave plates, and by creating helical phase profiles of optical vortices with the geometrical phase of rotational nano-slit pairs, two focused Bessel VBs are formed. By finely varying the diameters of two sets of rings, the doughnuts of the two Bessel VBs of different orders are tuned to be of the same size, and the superposition of the two VBs is realized. The theoretical analyses of the superimposed fields were presented, the FDTD simulations were performed to optimize the designed metasurfaces, and the experimental measurements were carried out to validate feasibility of the metasurface. The novel and interesting characteristics of the superposed fields different from those of the conventional VBs were demonstrated. This work will be of significance for classical and quantum applications of VBs in various fields.

The ‘old wood’ effect and problems of dating iron smelting sites

The paper is aimed at the analysis of the ‘old wood’ effect in radiocarbon chronology of iron smelting com-plexes of South Siberia. The production sites are here set outside the settlements, and radiocarbon dating re-mains the only means of their chronological attribution. With the example of Kuyahtanar metallurgical site in the Mountain Altai, we show that the range of a series of radiocarbon dates obtained for the same iron-smelting fur-naces can span a thousand years. It has been established that such a chronological range can be explained by the use of wood from long-lived tree species for charcoal production and the resulting significant apparent age due to the ‘old wood’ effect. The essence of the effect consists in that as a tree grows, its inner annual rings die out and stop exchanging carbon with the environment, while the tree is still alive. Therefore, the pith of a long-lived tree is much older than its outer rings, and radiocarbon analysis determines not the age of the archaeologi-cal object, or time when the tree was cut, but the date of the death of that part of the tree which was sampled for the dating. Methodological recommendations have been drawn up capable of minimizing the impact of the ‘old wood’ effect in the dating of iron metallurgy sites. During the sampling, it is recommended to collect fragments of char-coal from the tree outer rings. In a case, where this is not possible, it is necessary to obtain a series of at least three dates for one site. In such a series, the latest of the three dates will be the closest to the age of the archaeological object. It is also necessary to determine the tree species used for burning the charcoal for smelting. After the tree species is identified, it becomes possible to infer its average and maximum life expectancy in the specific natural and climatic conditions, and, consequently, possible average and maximum impact of the ‘old wood’ effect. Since in the case of dating metallurgical sites the impact of the ‘old wood’ effect is virtually unavoidable, it is suggested that, in the future, the chronology of the complexes radiocarbon dated with a single sample of charcoal is revisited.

Analysis of Circulation Characteristics and Heat Balance of High-Speed Rolling Bearing under Oil-Air Lubrication

Aiming to solve the problem of oil-air lubrication failure caused by the high working temperature of high-speed rolling bearings, this study proposes a method, based on the theory of gas-solid two-phase flow and bearing tribology, of predicting the dynamic temperature rise of nonlinear high-speed rolling bearings under oil-air lubrication conditions. The accuracy of the fluid–structure coupling model is verified by comparing the temperature rise test results of angular contact ball bearing at different speeds. The characteristics of oil-air lubrication circulation and the relationship between the lubrication parameters and the heat balance of the high-speed rolling bearings have been studied. The results show that the gas supply pressure of the system has a significant influence on the continuity and fluctuation of the oil film in the oil pipe nozzle. The initial rise in temperature of the inner and outer rings of the bearing and the fluid domain has a speed threshold value, and the temperature increases linearly with the bearing speed. With the increase in the oil supply and lube oil viscosity of the system, the temperature rise of the outer ring of the bearing increases first, then decreases, and finally increases again. There is an optimal oil supply 5.5 mL and optimize viscosity 68 cSt for the bearing in the work condition.

Characterization of thylakoid division using chloroplast dividing mutants in Arabidopsis.

Chloroplasts are double membrane bound organelles that are found in plants and algae. Their division requires a number of proteins to assemble into rings along the center of the organelle and to constrict in synchrony. Chloroplasts possess a third membrane system, the thylakoids, which house the majority of proteins responsible for the light-dependent reactions. The mechanism that allows chloroplasts to sort out and separate the intricate thylakoid membrane structures during organelle division remain unknown. By characterizing the sizes of thylakoids found in a number of different chloroplast division mutants in Arabidopsis, we show that thylakoids do not divide independently of the chloroplast division cycle. More specifically, we show that thylakoid division requires the formation of both the inner and the outer contractile rings of the chloroplast.

What can analysis of Space-Time of Action tell us about medium-term changes in adults’ and children’s access to place of activity? The example of Bogotá

This article draws on the space-time prism as formalized in time-geography (Hägerstrand 1970) and on spatial analysis methods to examine medium-term changes to household members’ access to place of activity, against the backdrop of urban change. The analytical framework thus uses the concept of Space-Time of Action (Demoraes et al. 2020a), referring to the combination of all the places of work or study that individuals go to, and the time taken to reach them from home. The analysis is based on two surveys conducted in Bogotá (Colombia) in 1993 and 2009 to apprehend individuals’ spatial mobilities. Two groups at different stages in their life course and co-residing in the same households are studied: schoolchildren and working adults. First, Space-Times of Action are calculated and mapped using kernel outer rings delineating the concentration of destinations for the two groups and the nine survey zones at each date. Second, the statistical significance of the discrepancies between Space-Times of Action is assessed using a bivariate colocation test. The test indicates overall stability in children’s access to place of schooling, but a more contrasting situation for adults.

Structural evolution and electronic properties of doped boron clusters Ta2Bn (n = 10 ∼ 20): Ta2B16 and Ta2B18 with strong aromaticity

In this work, we combine the CALYPSO method with DFT calculations to conduct a comprehensive structural search of Ta2Bn (n = 10 ∼ 20) clusters. Among all the candidate structures obtained by CALYPSO searching, the structures of ground state Ta2Bn clusters at each size are determined according to their total energy and symmetry. The relative stability analysis indicates that the ground state Ta2B16 and Ta2B18 clusters with the unique bicyclic boron ring and two Ta atoms as axes exhibit excellent stability in the studied range, with their HOMO-LUMO gaps of 2.374 and 2.640 eV, respectively. The bonding analyses reveal that the strong interaction between two Ta atoms and the outer B16/18 bicyclic ring dominates their significant stability, especially the interaction between Ta-d AOs and B-s/p AOs. It is confirmed that both Ta2B16 and Ta2B18 have strong aromaticity by examining the isochemical shielding surface (ICSS). Finally, the strong coupling between their outer boron rings (B16/18) and two Ta atoms inside the structures of Ta2B16 and Ta2B18 is further elucidated by the electronic absorption spectrum (UV–vis and CTS).

“Home away from home” in pandemic times: how has COVID-19 changed the Airbnb market in Melbourne?

PurposeThis study aims to investigate how the COVID-19 pandemic has impacted and changed Airbnb market in the Greater Melbourne area in terms of its temporal and spatial patterns and identify possible shifts in underlying trends in travel activities.Design/methodology/approachA panel data set of Airbnb listings in Melbourne is analysed to compare temporal patterns, spatial distribution and lengths of stay of Airbnb users before and after the COVID outbreak.FindingsThis study found that the COVID disruption did not fundamentally change the temporal cycle of the Airbnb market. Month-to-month fluctuations peaked at different levels from pre-pandemic times mainly because of lockdowns and other restrictive measures. The impact of COVID-19 disruptions on neighbourhood-level Airbnb revenues is associated with distance to CBD rather than number of COVID cases. Inner city suburbs suffered major loss during the pandemic, whereas outer suburbs gained popularity due to increased domestic travel and long stays. Long stays (28 days or more, as defined by Airbnb) were the fastest growing segment during the pandemic, which indicates the Airbnb market was adapting to increasing demand for purposes like remote working or lifestyle change. After easing of COVID-related restrictions, demand for short-term accommodation quickly recovered, but supply has not shown signs of strong recovery. Spatial distribution of post-pandemic supply recovery shows a similar spatial variation. Neighbourhoods in the inner city have not shown signs of significant recovery, whereas those in the middle and outer rings are either slowly recovering or approaching their pre-COVID levels.Practical implicationsThe COVID-19 pandemic has significantly impacted short-term rental markets and in particular the Airbnb sector during the phase of its rapid development. This paper helps inform in- and post-pandemic housing policy, market opportunity and investment decision.Originality/valueTo the best of the authors’ knowledge, this is one of the first attempts to empirically examine both temporal and spatial patterns of the COVID-19 impact on Airbnb market in one of the most severely impacted major cities. It is one of the first attempts to identify shifts in underlying trends in travel based on Airbnb data.