Velocity Amplitude Research Articles

Instabilities in Models of Supergiants MWC 137 and MWC 314

In several B-type supergiants, photometric and spectroscopic variabilities together with episodes of enhanced mass-loss have been observed. Here we present the preliminary results of a linear stability analysis followed by nonlinear numerical simulations in two B-type supergiants MWC 137 and MWC 314. All the considered models of MWC 137 having mass in the range of 30M⊙ to 70M⊙ are unstable while for the case of MWC 314 models with mass below 31M⊙ are unstable. The instabilities have been followed into the nonlinear regime for selected models of these two supergiants. During the nonlinear numerical simulations, instabilities lead to a finite pulsation amplitude with a well defined saturation level in the considered models of MWC 137 with mass greater than 42M⊙. The model of MWC 314 with mass of 40M⊙ - the suggested mass for the primary star - does not show any instabilities both in linear stability analysis and nonlinear numerical simulations. The velocity amplitude reaches to 107 cm s−1 in the nonlinear regime for the model of MWC 314 with mass of 30M⊙. Further extensive numerical simulations and observations are required to understand the origin of the observed variabilities in these stars.

Non-intrusive measurements of wave nonlinearity over movable bed of sediment with different beach slopes

A series of laboratory experiments were undertaken to qualitatively investigate the evolution of wave nonlinearity over a movable bed of sediment with five different beach slopes under regular waves in a medium-scale wave flume. An innovative non-intrusive data collecting system, which mainly consists of three side-looking high-speed cameras, was developed to collect high-resolution and synchronous data on free-surface water elevation of waves and bed level changes without causing any disturbances to wave motions and the movable bed of sediment. On analyzing the collected experimental data, it is found that regular waves become nonlinear when they propagate to the shoaling zone and start breaking, and linear wave theory is quite accurate for calculating wave parameters such as orbital velocity with the correlation coefficient r2 = 0.8–0.95 before the waves break, but becomes less accurate after the waves break or are in the breaking zone with the smaller correlation coefficient r2 = 0.4–0.6. Four parameters, wave skewness Skη, asymmetry Ayη, Ursell number Ur, and Rocha number NP0, are introduced to describe the wave nonlinearity, of which Skη and Ayη are found to be of largest amplitudes at the wave breaking point and then start to decrease in the breaking zone and are almost unchanged for different beach slopes, while Ur further increases in the breaking zone and exceed the first larger value as waves approach to shoreline, but NP0 is almost linearly proportional to wave orbital velocity amplitude and quite sensitive to beach slope. The location of sandbar is found close to the wave breaking point in the wave flume and may be also considered as the point where wave nonlinearity becomes important for sediment transport in the surf zone, and the linear wave theory becomes less accurate.

Research on Tremor Suppression Strategies Under a Constant Current Peripheral Electrical Stimulation Device for Parkinson's Disease.

Tremor, a prevalent symptom in Parkinson's patients, is conventionally treated with medications and craniotomy. However, the associated side effects and high surgical costs pose challenges for some individuals. In this study, a lightweight constant current electrical stimulator was developed, which is driven by the FPGA to control the underlying logic and has multiple programmable stimulation parameters. Clinical experiments involving patients with Parkinson's-related resting tremor symptoms were conducted to assess the efficacy of peripheral electrical stimulation. Two Co-contraction Avoidance Stimulation (CAS) strategies targeting nerves and muscles were proposed to reduce tremors. Four Parkinson's disease (PD) patients were recruited to verify the effectiveness of these strategies. Kinematic data recorded by inertial sensors showed that the radial nerve and muscle intervention strategies reduced the average angular velocity amplitude of finger joints during resting tremor by 75.92% and 82.41%, respectively. Notably, under low-frequency pulse stimulation (100 Hz) focused on muscle interference, a low-intensity current of no more than 8 mA maintained a tremor suppression rate of 59.91% even 5 minutes post-stimulation. Based on the experimental results, it is concluded that the constant current electrical stimulator developed in this study can effectively suppress tremor under specific stimulation strategies. These findings have significant implications for the development of lightweight, wearable tremor suppression devices. The stimulator's adaptability, coupled with its precise control parameters, demonstrates promise for advancing non-invasive and cost-effective tremor management in Parkinson's patients.

Movement of and drag force on slender flat plates in an array exposed to combinations of unidirectional and oscillatory flow

When flexible structures deflect under unidirectional flow or sway under oscillatory flow, their hydrodynamic drag forces are reduced. The flow-induced motion of a structure is governed by the balance between hydrodynamic forces and restoring forces due to stiffness (a ratio known as the Cauchy number, Ca). Movement of and drag on structures under unidirectional (current) and oscillatory (wave) flow have often been studied separately, but such flows frequently coexist. In this study, a simple numerical model of a slender flexible plate, which can represent a seagrass blade, was used to investigate how the posture of and drag on the plate in oscillatory flow was impacted by collinear currents moving in the same (following) and opposite (opposing) directions, relative to the wave propagation. The rate of work done against hydrodynamic drag forces defines the rate of wave energy dissipation, ED,w. The velocity acting on the blade was modeled as if the blade existed in a canopy of blades. For conditions in which blade motion was observed, added currents influenced ED,w in two ways. When the ratio of the time-averaged velocity within the canopy, U1, to the wave velocity amplitude, Uw, was less than 0.33±0.05, ED,w was reduced relative to the pure wave condition, which was attributed to current-induced deflection. However, when U1/Uw exceeded 0.33±0.05, ED,w increased. While the blade increasingly deflected with increasing current, higher currents also limited unsteady wave-induced reconfiguration, increasing the relative motion between the blade and fluid and therefore increasing drag. While Ca can predict the drag reduction associated with weak current, it cannot predict the increase in drag for U1/Uw>0.33. Finally, the model was used to explore the influence of current on wave amplitude evolution across a seagrass meadow. Relative to pure wave conditions, opposing currents enhanced wave damping, but following currents had little impact on wave damping.

Simulation Research on Non-Bevel Gear Transmission Mechanism

Abstract: There are problems with vibration and impact in the meshing transmission process of non-bevel gear. Therefore, a simulation control method of non-bevel gear transmission based on ADAMS and MATLAB is proposed. First of all, the design modeling of non-bevel gear is briefly described, and the influence of order and eccentricity on its transmission ratio is analyzed; Then, the established non-bevel gear model is imported into ADAMS, and the constraint, motion pair, driving force, input and output variables are set. The data transfer relationship is established by using the ADAMS/Control module and MATLAB/Simulink interface, and the non-bevel gear mechanical system module is generated in MATLAB/Simulink; Finally, its joint simulation control system is built in the MATLAB/Simulink module, and its control simulation analysis is carried out. The research results show that by comparing and analyzing the simulation results of only constant value input and adding the PI control module, the amplitude, and frequency of the angular velocity and angular acceleration curves of the driven wheel are significantly reduced, that is, the vibration and impact in the non-bevel gear transmission are reduced, which verifies the correctness and feasibility of the control strategy, It provides a new method for the control design and development of the vibration reduction performance of non-bevel gear transmission; The result is beneficial to the application and popularization of non-bevel gears.

Nystagmus Characteristics in Albinism: Unveiling the Link to Foveal Hypoplasia and Visual Acuity.

The purpose of this study was to describe the association among nystagmus characteristics, foveal hypoplasia, and visual acuity in patients with albinism. We studied nystagmus recordings of 50 patients with albinism. The nystagmus waveform was decomposed into two types: dominantly pendular and dominantly jerk. We correlated the nystagmus type, amplitude, frequency, and percentage of low velocity (PLOV) to Snellen visual acuity and foveal hypoplasia grades. The grade of foveal hypoplasia and visual acuity showed a strong correlation (r = 0.87, P < 0.0001). Nystagmus type and PLOV had the strongest significant (P < 0.0001) correlation with visual acuity (r = 0.70 and r = -0.56, respectively) and with foveal hypoplasia (r = 0.76 and r = -0.60, respectively). Patients with pendular nystagmus type had the lowest PLOV, and the highest grade of foveal hypoplasia (P < 0.0001). Severe foveal hypoplasia (grade 4), was almost invariably associated with pendular nystagmus (86%). Foveal hypoplasia grade 4 is associated with pendular nystagmus, lower PLOV, and worse visual acuity. Based on these results, nystagmus recordings at a young age may contribute to predicting visual outcomes.

Dynamic Topology Optimization of Constrained Layer Damping Structure Considering Non-Uniform Blast Load

The non-uniform distributed pressure of impact wave is usually simplified into concentrated or uniform load equivalently in the optimization design of constrained layer damping structure. However, for the thin-walled structure, it becomes necessary to regard the load as a non-uniform distribution. In this paper, a topology optimization approach is proposed considering the blast load with non-uniform distribution, aiming to unveil its impact on optimization layouts and dynamic responses. Initially, the smoothed particle hydrodynamics (SPH) algorithm is used to obtain the blast pressure what are extracted and integrated into the optimization model. Subsequently, the relative density is regarded as design variable. The construction of material penalty model and the topology optimization model are based on polynomial interpolation scheme (PIS). The sensitivity of objective function is deduced employing an improved adjoint variable method (AVM) to fit the load forms, and the Newmark-[Formula: see text] method is used to calculate the dynamic response. The optimization criterion (OC) is adopted to update the design variables. Finally, two numerical examples are used to exhibit the validity and accuracy of the presented methodology. The findings indicate that the distributed form, spread velocity, excited position and excited amplitude of the blast load all exert a notable influence on optimization results and dynamic response. These results underscore the valuable engineering application of this research and introduce a fresh perspective to the challenge of topology optimization under the blast case.

Alternating Current Electroosmotic Flow of Maxwell Fluid in a Parallel Plate Microchannel with Sinusoidal Roughness.

The EOF of a viscoelastic Maxwell fluid driven by an alternating pressure gradient and electric field in a parallel plate microchannel with sinusoidal roughness has been investigated within the Debye-Hückel approximation based on boundary perturbation expansion and separation of variables. Perturbation solutions were obtained for the potential distribution, the velocity and the mean velocity, and the relation between the mean velocity and the roughness. There are significant differences in the velocity amplitudes of the Newtonian and Maxwell fluids. It is shown here that the velocity distribution of the viscoelastic fluid is significantly affected by the roughness of the walls, which leads to the appearance of fluctuations in the fluid. Also, the velocity is strongly dependent on the phase difference θ of the roughness of the upper and lower plates. As the oscillation Reynolds number ReΩ increases, the velocity profile and the average velocity um(t) of AC EOF oscillate rapidly but the velocity amplitude decreases. The Deborah number De plays a similar role to ReΩ, which makes the AC EOF velocity profile more likely to oscillate. Meanwhile, phase lag χ (representing the phase difference between the electric field and the mean velocity) decreases when G and θ are increased. However, for larger λ (e.g., λ > 3), it almost has no phase lag χ.

Enhanced interfacial boiling of impacting droplets upon vibratory surfaces

HypothesisDespite the flourishing studies of droplet interfacial boiling, the boiling upon vibratory surfaces, which may cause vigorous liquid–vapor-solid interactions, has rarely been investigated. Enhanced boiling normally can be gained from rapid removal of vapor and disturbance of liquid–vapor interface. We hypothesize that the vibratory surfaces enhance both effects with new intriguing phenomena and thus, attain an enhanced boiling heat transfer. ExperimentsWe experimentally investigated the impacting fluid dynamics and coupled heat transfer patterns of multiple droplets and a single droplet impinging on still and vibratory surfaces of various materials and different wettability. FindingsThe boiling under vibratory surfaces with increased vibration velocity amplitude and enhanced wettability can be enhanced by 80% in heat transfer coefficient and Nusselt number, which is attributed to several reasons: shortened bubble lifespan, thinner and smaller bubbles, and enhanced disturbances in liquid–vapor interfaces. The vibration also delays the Leidenfrost point when the droplet impacts a descending surface, which shows that the droplet impact moment (vibration phase angle) is particularly crucial. The descending surface releases the generated vapor actively and facilitates liquid–solid contact, thereby delaying the Leidenfrost. From fundamentals to application, this article strengthens our understanding of vibrated interfacial boiling in scenarios closer to multiple natural processes and practical industries.

Resonance, Velocity, Dispersion, and Attenuation of Ultrasound-Induced Shear Wave Propagation in Blood Clot In Vitro Models.

Improve the characterization of mechanical properties of blood clots. Parameters derived from shear wave (SW) velocity and SW amplitude spectra were determined for gel phantoms and in vitro blood clots. Homogeneous phantoms and phantoms with gel or blood clot inclusions of different diameters and mechanical properties were analyzed. SW amplitude spectra were used to observe resonant peaks. Parameters derived from those resonant peaks were related to mimicked blood clot properties. Three regions of interest were tested to analyze where resonances occurred the most. For blood experiments, 20 samples from different pigs were analyzed over time during a 110-minute coagulation period using the Young modulus, SW frequency dispersion, and SW attenuation. The mechanical resonance was manifested by an increase in the number of SW spectral peaks as the inclusion diameter was reduced (P < .001). In blood clot inclusions, the Young modulus increased over time during coagulation (P < .001). Descriptive spectral parameters (frequency peak, bandwidth, and distance between resonant peaks) were linearly correlated with clot elasticity values (P < .001) with R2 = .77 for the frequency peak, .60 for the bandwidth, and .48 for the distance between peaks. The SW dispersion and SW attenuation reflecting the viscous behavior of blood clots decreased over time (P < .001), mainly in the early stage of coagulation (first minutes). The confined soft inclusion configuration favored SW mechanical resonances potentially challenging the computation of spectral-based parameters, such as the SW attenuation. The impact of resonances can be reduced by properly selecting the region of interest for data analysis.

Vibroacoustics Analysis of Plates with Bioinspired Surface Modifications

This study presents a simplified semi-analytical model to analyze the dynamic behavior of a plate with shark skin biomimetic surface modifications. The base plate is considered to be thin isotropic homogeneous and modeled using a Kirchhoff–Love plate theory, whereas the dermal denticles are modeled as a distributed array of point mass and replicated using a Dirac delta function. A semi-analytical formulation, which takes into account closed-form beam mode shapes, with the Galerkin technique to minimize errors is utilized to study the free and forced vibration response of modified plates. Harmonic analysis is carried out to understand the dynamic behavior of the modified plate both quantitatively as well as qualitatively. A parametric study varying the array spacing and the boundary conditions is carried out to understand the effect of surface modification on power radiation characteristics. It appears that adding dermal denticles reduces the peak velocity amplitude and peak radiated power at all resonance frequencies. A separate study by varying the base plate material reveals that a higher reduction in the dynamic response and the radiated power can be achieved by increasing the mass ratio. Hence, surface modification using such a shark skin layer may prove beneficial to reduce acoustic radiation and dynamic response and to optimize the design.

High-Accuracy Simulation of Rayleigh Waves Using Fractional Viscoelastic Wave Equation

The propagation of Rayleigh waves is usually accompanied by dispersion, which becomes more complex with inherent attenuation. The accurate simulation of Rayleigh waves in attenuation media is crucial for understanding wave mechanisms, layer thickness identification, and parameter inversion. Although the vacuum formalism or stress image method (SIM) combined with the generalized standard linear solid (GSLS) is widely used to implement the numerical simulation of Rayleigh waves in attenuation media, this type of method still has its limitations. First, the GSLS model cannot split the velocity dispersion and amplitude attenuation term, thus limiting its application in the Q-compensated reverse time migration/full waveform inversion. In addition, GSLS-model-based wave equation is usually numerically solved using staggered-grid finite-difference (SGFD) method, which may result in the numerical dispersion due to the harsh stability condition and poses complexity and computational burden. To overcome these issues, we propose a high-accuracy Rayleigh-waves simulation scheme that involves the integration of the fractional viscoelastic wave equation and vacuum formalism. The proposed scheme not only decouples the amplitude attenuation and velocity dispersion but also significantly suppresses the numerical dispersion of Rayleigh waves under the same grid sizes. We first use a homogeneous elastic model to demonstrate the accuracy in comparison with the analytical solutions, and the correctness for a viscoelastic half-space model is verified by comparing the phase velocities with the dispersive images generated by the phase shift transformation. We then simulate several two-dimensional synthetic models to analyze the effectiveness and applicability of the proposed method. The results show that the proposed method uses twice as many spatial step sizes and takes 0.6 times that of the GSLS method (solved by the SGFD method) when achieved at 95% accuracy.

Properties of Short-Period Internal Waves in the Kara Gates Strait Revealed from Spaceborne SAR Data

This paper presents the results of identification of surface manifestations (SM) of short-period internal waves (SIW) in Sentinel-1 A/B synthetic aperture radar (SAR) images of the Kara Gates Strait in August–September 2021. 44 SM of SIW trains were detected in 47 SAR images. Statistics of occurrence, propagation direction and spatial characteristics of SIWs in the study area are given. During two months, satellite observations cover almost all phases of spring-neap tidal cycle. The use of a detailed topography of the study area made it possible to identify certain regions with a more frequent presence of the SIW leading crests with a particular focus made on the shallow (&lt; 100 m) part of the strait. Each identified region is then described in terms of water depth, dimensionless slope, amplitudes of tidal current velocity and properties of SIWs. The obtained results were then compared with the results of previous studies.

Interactive Errors Analysis and Scale Factor Nonlinearity Reduction Methods for Lissajous Frequency Modulated MEMS Gyroscope.

Although the Lissajous frequency modulated (LFM) mode can improve the long-term and temperature stability of the scale factor (SF) for mode mismatch MEMS gyroscopes, its SF nonlinearity poses a significant limitation for full-scale accuracy maintenance. This paper examines the interaction effects among stiffness coupling, system phase delay, readout demodulation phase shift, and velocity amplitude mismatch within the control process. Based on the completion of frequency difference control and demodulation phase matching, we clarify that the remaining stiffness coupling and residual system phase error are the primary factors influencing SF nonlinearity. Furthermore, SF nonlinearity is reduced through error compensation. On one hand, this paper suppresses stiffness coupling through the observation of the instantaneous frequency difference and the application of the quadrature voltage. On the other hand, system phase error is compensated by observing the amplitude control force and tuning the reference in the Phase-Locked Loops (PLLs). Subsequent simulations of these methods demonstrated a remarkable 97% reduction in SF nonlinearity within the measurement range of ±500°/s. In addition, an observed rule dictates that maintaining a sufficiently large frequency split effectively constrains the SF nonlinearity.

Primitive and gravity modulation of periodical heat transfer along magnetic-driven porous cone with thermal conductivity and surface heat flux

The significant goal of present problem is to evaluate oscillating frequency and amplitude in heat and magnetic flux with thermal conductivity and heat flux effects across magnetized porous cone under lower gravitational region. To maintain heat transport efficiency, the thermal conductivity of conducting fluid is assumed as temperature dependent. The magnetic-driven cone is placed in lower gravitational region. To improve the heating rate across the magnetic-driven porous cone, the convective heating conditions are applied. The implications of thermal conductivity, surface heat flux, and reduced gravity on the periodic behavior of convective heat transfer characteristics of conducting fluid across porous gravity-driven cone is the novelty of this research. Using the appropriate non-dimensional variables, the model's nonlinear governing partial differential has been converted into a dimensionless form. The proposed model is solved later with the help of finite difference approach. The dimensionless form of the equations is reduced to the convenient form for numerical algorithm. The influence of adjusting parameters, such as thermal conductivity parameter ζ, reduced gravity parameter Rg, Biot number Bi, Prandtl number Pr, mixed convection parameter λ, porosity parameter Ω, magnetic prandtl number γ and some others stationary parameters has been highlighted. By using FORTRAN tool, the numerical outcomes are explored in graphs and tabular form. It is depicted that magnetic field enhances as Biot number decreases because magnetic field insulates the excessive heating across the magnetic-driven porous cone. It is noticed that significant amplitude in fluid velocity is noticed with prominent changes as reduced gravity increases. It is concluded that fluctuations in heat transport increases as parameter γ decreases under thermal conductivity because magnetic material insulates the extreme heat across the porous cone. The recent thermal conductivity and lowered gravity problem is significant in the fields of radioactive waste, cooling electronic components, storing nuclear, catalysts, heat exchangers, the underground storage of radioactive or nonnuclear materials, aircrafts and space vehicles.

Simultaneous Horizontal and Vertical Oscillation of a Quiescent Filament Observed by CHASE and SDO

In this paper, we present the imaging and spectroscopic observations of the simultaneous horizontal and vertical large-amplitude oscillation of a quiescent filament triggered by an extreme-ultraviolet (EUV) wave on 2022 October 2. Particularly, the filament oscillation involved winking phenomenon in Hα images and horizontal motions in EUV images. Originally, a filament and its overlying loops across AR 13110 and 13113 erupted with a highly inclined direction, resulting in an X1.0 flare and a non-radial coronal mass ejection. The fast lateral expansion of loops excited an EUV wave and the corresponding Moreton wave propagating northward. Once the EUV wave front arrived at the quiescent filament, the filament began to oscillate coherently along the horizontal direction, and the “winking filament” appeared concurrently in Hα images. The horizontal oscillation involved an initial amplitude of ∼10.2 Mm and a velocity amplitude of ∼46.5 km s−1, lasting for ∼3 cycles with a period of ∼18.2 minutes and a damping time of ∼31.1 minutes. The maximum Doppler velocities of the oscillating filament are 18 km s−1 (redshift) and −24 km s−1 (blueshift), which were derived from the spectroscopic data provided by the Chinese Hα Solar Explorer/Hα Imaging Spectrograph. The three-dimensional velocity of the oscillation is determined to be ∼50 km s−1 at an angle of ∼50° to the local photosphere plane. Based on the wave–filament interaction, the minimum energy of the EUV wave is estimated to be 2.7 × 1020 J. Furthermore, this event provides evidence that Moreton waves should be excited by the highly inclined eruptions.

Heat source/sink impact on wave oscillations of thermal and concentration boundary layer along inclined plate under lower gravitational region

The force of attraction between two masses increases as gravity increases. Gravity is very important mechanism for mass transfer characteristics across the inclined shape. The significant purpose of current study is to examine amplitude in mass transfer under reduced gravity-driven flow. The impact of heat source/sink on periodic mixed convective gravity-driven flow across the inclined plate has been evaluated. The oscillatory characteristics of heat rate and mass transmission are explored at three inclined angles π/6, π/4 and π/3. The gravity is assumed under maximum temperature difference. The governing dimensional model is transformed into non-dimensional equations with appropriate scaling variables. The non-dimensional equations are again reduced in non-oscillatory, real and imaginary parts. For smooth coding, the primitive formulation is used with finite difference method to change non-dimensional forms in algebraic system. The algebraic equations are solved with Gaussian elimination scheme to display velocity field, temperature distribution and rate of concentration numerically. The impact of heat source/sink ±δ, reduced gravity Rg, buoyancy variable λT, modified buoyancy factor λC, Prandtl factor Pr, reduced gravitation factor Rg, and Schmidt variable Sc on the oscillating behavior of shear stress, rate of fluctuating heat transfer, and rate of fluctuating mass transfer is secured. It is found that the amplitude of fluid velocity and temperature increases for each parameter under heat source +δ=0.4. It can be seen that concentration distribution increases as reduced gravity Rg increases under heat sink −δ=0.3. It can be seen that amplitude of shearing stress and heat transfer increases as heat source +δ increases. It is obtained that oscillation in mass transfer increases as heat source/sink ±δ increases under reduced gravitation Rg=1.2.

Deep learning with soft attention mechanism for small-scale ground roll attenuation

Ground roll is a type of coherent noise with low frequency, low velocity, and high amplitude, which masks useful signals and decreases the quality of subsequent seismic data processing. It is a challenge for traditional signal processing methods to separate useful signals effectively when the ground roll and useful reflected signals overlap seriously in the low-frequency band. We develop a supervised-learning-based framework with soft attention residual learning mechanisms for suppressing the ground roll noise. To reduce the cost of manual labeling, the 2D patching technique is used to segment large-scale seismic data into a large number of small-scale patches for training. Our network includes a multibranch attention block that uses multiple branches with different kernel sizes to extract waveform features at different scales from input noisy patches. Then, we use the soft attention mechanism to select and fuse the feature maps of different branches. Our network can achieve encouraging ground roll attenuation performance by using a small number of training samples, which is demonstrated by synthetic and field data examples. Compared with one traditional method and two advanced deep-learning frameworks, our network has better abilities in preserving low-frequency useful signals and removing ground roll.

The magnetically quiet solar surface dominates HARPS-N solar RVs during low activity

ABSTRACT Using images from the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory, we extract the radial velocity (RV) signal arising from the suppression of convective blueshift and from bright faculae and dark sunspots transiting the rotating solar disc. We remove these rotationally modulated magnetic-activity contributions from simultaneous RVs observed by the HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) solar feed to produce an RV time series arising from the magnetically quiet solar surface (the ‘inactive-region RVs’). We find that the level of variability in the inactive-region RVs remains constant over the almost 7-yr baseline and shows no correlation with well-known activity indicators. With an root-mean-square scatter of roughly 1 ${\rm m\, s}^{-1}$, the inactive-region RV time series dominates the total RV variability budget during the decline of solar cycle 24. Finally, we compare the variability amplitude and time-scale of the inactive-region RVs with simulations of supergranulation. We find consistency between the inactive-region RV and simulated time series, indicating that supergranulation is a significant contribution to the overall solar RV variability, and may be the main source of variability towards solar minimum. This work highlights supergranulation as a key barrier to detecting Earth twins.

Visual attention predictive model of built colonial heritage based on visual behaviour and subjective evaluation

Although physiological measurements, subjective evaluation and other methods have been applied to visual attention research, architects still lack a systematic quantitative classification method when assessing the visual attention to built colonial heritage. This study aimed to investigate the relationship between people’s visual behaviour and subjective evaluation when observing built colonial heritage and to construct a prediction model based on eye-movement metrics and subjective evaluation indicators to distinguish the visual attention to built colonial heritage. This study recorded data from 54 participants while observing five scenes of built colonial heritage, and the results showed that participants had different visual behaviours and subjective evaluations when viewing built colonial heritage in different scenes. And visual attention to built colonial heritage was negatively correlated with the average saccades peak velocity and average saccades amplitude and positively correlated with the average pupil diameter; visual attention was correlated with 12 subjective evaluation indicators. The eye-movement metrics and subjective evaluation indicators with correlation to visual attention were used as input variables to construct a prediction model of visual attention to built colonial heritage based on the BP neural network. Different built colonial heritage’s low, middle and high visual attention were identified with high accuracy (74.46%). This quantitative method can help architects to measure the visual attention to built colonial heritage to develop conservation and renewal strategies.