Inversion Technique Research Articles

Significant variations in the structure and composition of the crust beneath northwestern India: Imprints of magmatism

Northwestern India was affected by the Neoproterozoic Malani and Erinpura magmatism, Cretaceous rifting, and magmatism associated with the Deccan precursors. Receiver function analysis was done using 1704 RFs from 18 stations to image and decipher the imprints of the magmatic events and comprehend the crustal modifications in terms of variations in structure and composition. The H-κ grid search and neighbourhood inversion techniques are used to retrieve the crustal structure and Vp/Vs ratios (κ). The study reveals significant variations in the crustal thickness (H = 34 km to 43 km), composition (κ=1.74 to 1.92) and shear wave velocity structure across northwestern India. The terrains encompassing the Erinpura granite and the Malani igneous suite in the vicinity of the Barmer rift are characterized by a thick (H ≥ 41 km) crust with felsic to intermediate composition (κ ≤ 1.81). The crust beneath the southern part of the Marwar basin is ≈ 38–40 km thick with mafic composition (κ> 1.81). The region around the Barmer rift has a thin crust (H = 34–36 km) with intermediate to mafic composition. The region hosting the Early Cretaceous to Paleogene alkaline complexes exhibits a high Vp/Vs ratio (κ= 1.91) that may be associated with mafic cumulates emplaced by magmatic events that overprint the signatures of the Malani event. The crust is heterogeneous with low/high velocity intracrustal layers that reflect the fractionation of magma at different depths. The mafic residue, together with magmatic intrusions, results in a mafic lowermost crust with high shear velocities of 3.9–4.0 km/s beneath most stations. Overall, northwestern India is characterized by a thick crust with intermediate crustal composition and intracrustal layering resulting from large scale magmatic events linked to the Neoproterozoic reorganization of plates and younger magmatic events.

HiStyle: Reinventing historic portraits via 3D generative model

Recreating historical portraits with accuracy and artistic diversity has always been a challenge in the field of computer vision. To ensure faithful reinvention of portrait images, it is essential to not only restore colors and reconstruct 3D geometry but also incorporate various artistic styles. Although significant progress has been made in individual tasks, existing methods often struggle with a trade-off between low-quality yet accurate restoration, limiting their ability to meet all criteria within a unified model. To address these challenges, we propose HiStyle, a generative model that simultaneously supports 2D to 3D reconstruction, grayscale to RGB conversion, and photo-to-stylized image transformation. HiStyle first introduces a GAN inversion technique, restoring the lost color information of input historic portraits while elevating 2D images to 3D representation. Additionally, we integrate the powerful CLIP model into 3D-aware GANs to achieve zero-shot text-driven style transfer. To further enhance the range of styles, we leverage the latent diffusion model to synthesize multiple 2D style extensions of the colorized images. Experiment results demonstrate improved quality and diversity of generated images. Our HiStyle reveals the potential of 3D-aware GANs in preserving cultural heritage.

Feedforward decoupling vibration control of an unbalanced maglev rotor subjected to base excitation

ABSTRACT The maglev rotor installed on a moving base is subjected to both the unbalanced force of the rotor itself and the base excitation caused by external interferences. The interaction between the maglev rotor and the moving base gives rise to a combination of challenges. Specifically, the base excitation can propagate to the rotor, inducing vibration, while the unbalanced vibration can reciprocally transmit to the base, thereby augmenting the complexity of the base vibration. This paper introduces a feedforward decoupling control approach to address the base excitation vibration of the maglev rotor, utilising the base acceleration as the reference signal. The foundation of the feedforward controller model for countering base excitation vibration is constructed through the utilisation of inverse system principles and system identification techniques. The resultant decoupling model is engineered to facilitate decentralised control of the rotor across four radial directions. Simultaneously, to mitigate the impact of rotor unbalance on the base acceleration reference signal used by the feedforward controller, the least mean square (LMS) adaptive filtering algorithm is employed. This strategy facilitates unconstrained rotation of the rotor around its inertial axis, thereby reducing the unbalanced inertial forces and enabling isolated control of both base excitation vibration and rotor unbalance-induced vibration in the maglev system. An experimental device is constructed to validate the effectiveness of the proposed control methodology. The experimental results show that the maximum vibration amplitude of the maglev rotor decreases by 47% ~71% after the control method is applied.

Site-Specific Ground-Motion Waveform Generation Using a Conditional Generative Adversarial Network and Generalized Inversion Technique

ABSTRACT Accurate ground-motion simulations are essential for seismic hazard assessments and engineering practices. Herein, we propose a novel method combining conditional generative adversarial networks (cGANs) and the generalized inversion technique (GIT) to generate site-specific and variability-controlled strong-motion seismograms. The cGANs calculate synthetic seismogram without amplitude scales. The GIT is to separate the source, path, and site characteristics from the Fourier amplitude spectrum (FAS) of the observed seismograms. This method is applied to plate boundary earthquakes off the Pacific coast of Tohoku, Japan. It successfully generates a set of strong-motion seismograms at a given magnitude, distance, and observation station. The output waveforms reproduce the P and S waves as well as coda waves. We validate the method through a quantitative comparison with observed seismograms in terms of both time-domain duration and frequency-domain amplitude characteristics, using metrics of peak ground acceleration (PGA), peak ground velocity, FASs, response spectra, and waveform duration time. The validation results show that the variation in the PGA of the observed seismograms and the synthetic seismograms has a standard deviation of 0.643, and the duration of the seismograms has a standard deviation of 0.346, comparable to the standard deviations seen in the previous studies. Our approach offers high accuracy in stochastic finite-source modeling for a period of 1 s or shorter. The two features of the method, site-specificity and variability control, can contribute to further improvements in seismic hazard assessment by incorporating empirical information based on observed seismograms.

Zeolite-Based Poly(vinylidene fluoride) Ultrafiltration Membrane: Characterization and Molecular Weight Cut-Off Estimation with Support Vector Regression Modelling.

Zeolite serves as a promising additive for enhancing the hydrophilicity of polymeric membranes, yet its utilization for bolstering the mechanical strength of the membrane remains limited. In this study, poly(vinylidene fluoride) (PVDF) membranes were modified by incorporating various concentrations of zeolite (0.5-2 wt%) to improve not only their mechanical properties, but also other features for water filtration. Membranes with and without zeolite incorporation were fabricated via a dry-wet phase inversion technique, followed by the application of a series of characterization techniques in order to study their morphological structure, mechanical strength, and hydrophilicity. The membrane filtration performance for each membrane was evaluated based on pure water flux and Bovine Serum Albumin (BSA) rejection. Field-Emission Scanning Electron Microscopy (FESEM) images revealed a dense, microvoid-free structure across all of the PVDF membranes, contributing to a high pristine PVDF membrane tensile strength of 14 MPa. The addition of 0.5 wt% zeolite significantly improved the tensile strength up to 19.4 MPa. Additionally, the incorporation of 1 wt% zeolite into PVDF membrane yielded improvements in membrane hydrophilicity (contact angle of 67.84°), pure water flux (63.49% increase), and high BSA rejection (95.76%) compared to pristine PVDF membranes. To further improve the characterization of the zeolite-modified PVDF membranes, the Support Vector Regression (SVR) model was adopted to estimate the molecular weight cut off (MWCO) of the membranes. A coefficient of determination (R2) value of 0.855 was obtained, suggesting that the SVR model predicted the MWCO accurately. The findings of this study showed that the utilization of zeolite is promising in enhancing both the mechanical properties and separation performance of PVDF membranes for application in ultrafiltration processes.

Chromospheric and coronal heating in an active region plage by dissipation of currents from braiding

The question of what heats the outer solar atmosphere remains one of the longstanding mysteries in astrophysics. Statistical studies of Sun-like stars reveal a correlation between global chromospheric and coronal emissions, constraining theoretical models of potential heating mechanisms. However, spatially resolved observations of the Sun have surprisingly failed to show a similar correlation on small spatial scales. Here we use unique coordinated observations of the chromosphere (from the IRIS satellite) and the low corona (from the Hi-C 2.1 sounding rocket), and machine-learning-based inversion techniques, to show a strong correlation on spatial scales of a few hundred kilometres between heating in the chromosphere and emission in the upper transition region in strong magnetic field regions (‘plage’). Our observations are compatible with an advanced three-dimensional magnetohydrodynamic simulation in which the dissipation of current sheets caused by magnetic field braiding is responsible for heating the plasma simultaneously to chromospheric and coronal temperatures. Our results provide deep insight into the nature of the heating mechanism in solar active regions.

Rock characterization of rupelian-chatian Asmari carbonate formation using the simultaneous pre-stack inversion technique and lame parameters in the Kopal oilfield, Dezful embayment, Zagros basin

Rock characterization of rupelian-chatian Asmari carbonate formation using the simultaneous pre-stack inversion technique and lame parameters in the Kopal oilfield, Dezful embayment, Zagros basin

High performance and antifouling zeolite@polyethersulfone/cellulose acetate asymmetric membrane for efficient separation of oily wastewater

Microfiltration membranes have emerged as a promising alternative for oily wastewater treatment due to their high efficiency, low cost, and ease of operation. In this study, polyethersulfone (PES), cellulose acetate (CA), and 4A zeolite were blended to fabricate asymmetric membranes by the phase inversion technique and examined in oily wastewater treatment. Kerosene was chosen as a model polluting oil. The fabricated pure PES membrane (P), PES membranes incorporating 4A zeolite (ZP), PES membrane blended with CA (PC), and PES/CA blended membranes with 4A zeolite (ZPC) were characterized using field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, porosity, and contact angle to study the structure properties of these membranes. The performance of membranes was examined by water permeation, oil permeation flux, oil rejection, flux recovery ratio, and relative flux reduction. The ZPC membranes showed the highest performance in comparison with other prepared membranes. Incorporating 4A zeolite nanoparticles with 0.5 wt% into the PES/CA blended membrane significantly enhanced the microfiltration performance and decreased the contact angle of the P membrane from 70° to 29.8°. The effect of operation parameters such as transmembrane pressure (1–4 bar), feed temperature (25–50 ºC), and concentration of oil feed solution (250–1000 mg/L) on the permeation flux and oil rejection was studied on the PES/CA blended membrane containing 0.5 wt% 4A zeolite (0.5%ZPC). The 0.5%ZPC membrane showed improved porosity of 87.7% and it gave the highest value of pure water flux of 91.1 L/m2.h, oil permeation flux of 75.55 L/m2.h, maximum oil rejection of 98.8%, flux recovery ratio of 97.7%, and relative flux reduction of 21.8%. The permeation flux given by the 0.5%ZPC membrane was improved by about 8 times that of the P membrane. Re-usability studies verified the durability of the blended membranes and their performance in oily wastewater treatment.

2D/2D nanohybrid of MoS2/g-C3N4 engineered polysulfone (PSF) membrane with enhanced filtration and anti-fouling performance

The rational design of 2D hybrid materials has gained substantial attention in the field of membrane-based water treatment. In this study, a hierarchical flower-like MoS2/g-C3N4 (Hf-MoCN) hybrid has been reported as a modifier for antifouling and performance enhancement of polysulfone (PSF) membranes. PSF membranes modified with 0.1, 0.3, and 0.5 wt% of Hf-MoCN were prepared by phase inversion technique. The prepared membranes were examined for their morphology, contact angle, pore size, and porosity. Further, the ultrafiltration performance and antifouling ability of the PSF/ Hf-MoCN were examined through BSA filtration studies. The contact angle dropped from 78° to 55° when 0.3 wt% of Hf-MoCN was incorporated into the PSF matrix. Moreover, the pure water and BSA fluxes of this modified membrane were improved by 2.1 and 3.6 folds, respectively, compared to the bare membrane. Besides, all Hf-MoCN modified membranes showed higher BSA rejection efficiency than the unmodified membrane. Flux recovery ratio studies showed that the membrane modified with 0.3 wt% of Hf-MoCN had better antifouling ability than the other membranes. Thus, the study showed that the incorporation of Hf-MoCN provided the membrane with a versatile transport pathway and desirable surface properties, thus improving its wettability, filtration performance and antifouling ability.

Long-Term Ampacity Prediction Method for Cable Intermediate Joints Based on the Prophet Model

The development of power grids is hindered by the limited transmission capacity of cable equipment, necessitating the accurate prediction of dynamic ampacity for cable expansion. This study focuses on the 110 kV cable intermediate joint, employing radial and axial inversion techniques for real-time conductor temperature inversion. Utilizing the Prophet time series model, we predict environmental changes and propose a dynamic ampacity evaluation method for cable intermediate joints. Experimental validation confirms the model’s accuracy, with prediction errors under 10 K, demonstrating its potential for enhancing cable system reliability and power grid development.

Geoelectrical image of the Sabalan geothermal reservoir from magnetotelluric studies

The magnetotelluric (MT) survey of the Sabalan geothermal zone, which includes 22 stations along three traverse profiles across the main prospect zone, was conducted in 2007. The geophysical investigation utilized sharp boundary inversion of processed MT data due to the high contrast of electrical resistivity between embedded layers. This method was preferred to suppress the smeared-out impact of the smooth inversion algorithm on retrieving geological layering. The analysis of MT data led to the use of a 2D inversion algorithm to visualize the geothermal reservoir. Additionally, the geoelectrical strike of the main geothermal target was determined, showing some inconsistency across the profiles. The simulation of synthetic numerical models is conducted to evaluate the effectiveness of sharp boundary inversion compared to a smooth algorithm in sharp gradient mediums, specifically in terms of electrical characteristics, for plausible geothermal scenarios. The Finite Element method (FEM) was employed to construct these models, followed by running the 2D forward and inversion processes. The meshing and initial parameters of the modeling were set based on information obtained from prior geological and geophysical investigations. A sharp boundary inversion can be accurately implemented by introducing layering constraints along each profile surrounding the probable sought geothermal reservoir target. These layering constraints encompass the conductive cap, topsoil, and basement rocks, which are the key components of a plausible geothermal configuration. The results of the comparison indicate that the sharp boundary inversion technique effectively restored the boundary between neighboring layers that had significant differences in electrical resistivity. This was achieved when the smoothing algorithm failed to produce an accurate representation of the layered model. Ultimately, conceptual geological models were developed to illustrate the plausible structures corresponding to each profile, focusing on the sought geothermal reservoir targets. It can be deduced that many misunderstandings in the smoothing inversion algorithm will be omitted if the sharp boundary algorithm is used in highly electrical gradient structures. Based on the outcomes, a trachyandesite, andesite, and altered andesite reservoir exists at an elevation of 1600 to −2000 m. The reservoirs were recovered precisely with sharp and discriminable interfaces. Therefore, accurate interfaces led us to determine the conductive cap, heat source, and topsoil stacking as the main components of the geothermal system.

Toward Atmospheric Retrievals of Panchromatic Light Curves: ExPLOR-ing Generalized Inversion Techniques for Transiting Exoplanets with JWST and Ariel

Conventional atmospheric retrieval codes are designed to extract information, such as chemical abundances, thermal structures, and cloud properties, from fully “reduced” spectra obtained during transit or eclipse. Reduced spectra, however, are assembled by fitting a series of simplified light curves to time-series observations, wavelength by wavelength. Thus, spectra are postprocessed summary statistics of the original data, which by definition do not encode all the available information (i.e., astrophysical signal, model covariance, and instrumental noise). Here, we explore an alternative inversion strategy where the atmospheric retrieval is performed on the light curve directly, i.e., closer to the data. This method is implemented in EXoplanet Panchromatic Light curve Observation and Retrieval (ExPLOR), a novel atmospheric retrieval code inheriting from the TauREx project. By explicitly considering time in the model, ExPLOR naturally handles transits, eclipses, phase curves, and other complex geometries for transiting exoplanets. In this paper, we have validated this new technique by inverting simulated panchromatic light curves. The model was tested on realistic simulations of a WASP-43 b-like exoplanet as observed with the James Webb Space Telescope (JWST) and Ariel telescope. By comparing our panchromatic light-curve approach against conventional spectral retrievals on mock scenarios, we have identified key breaking points in information and noise propagation when employing past literature techniques. Throughout the paper, we discuss the importance of developing “closer-to-data” approaches such as the method presented in this work, and highlight the inevitable increase in model complexity and computing requirements associated with the recent JWST revolution.

Combining magneto-hydrostatic constraints with Stokes profile inversions. IV. Imposing divB =0 condition

Inferences of the magnetic field in the solar atmosphere by means of spectropolarimetric inversions (i.e., Stokes inversion codes) yield magnetic fields that are non-solenoidal ($ B 0$). Because of this, results obtained by such methods are sometimes put into question. We aim to develop and implement a new technique that, in conjunction with Stokes inversion codes, can retrieve magnetic fields that are simultaneously consistent with observed polarization signals and with the null divergence condition. The method used in this work strictly imposes $ B =0$ by determining the vertical component of the magnetic field ($B_ z $) from the horizontal ones ($B_ x B_ y $). We implement this technique, which we refer to as solenoidal inversion, into the FIRTEZ Stokes inversion code and apply it to spectropolarimetric observations of a sunspot observed with the Hinode/SP instrument. We show that the solenoidal inversion retrieves a vertical component of the magnetic field that is consistent in 80<!PCT!> of the analyzed three-dimensional $(x,y,z )$ domain, with the vertical component of the magnetic field inferred from the non-solenoidal inversion. We demonstrate that the solenoidal inversion is capable of a better overall fitting to the observed Stokes vector than the non-solenoidal inversion. In fact, the solenoidal magnetic field fits Stokes $V$ worse, but this is compensated by a better fit to Stokes $I$. We find a direct correlation between the worsening in the fit to the circular polarization profiles by the solenoidal inversion and the deviations in the inferred $B_ z $ with respect to the non-solenoidal inversion. Finally, we also show that the spatial distribution of the electric currents given by $ B $ does not change significantly after imposing the null divergence condition. In spite of being physically preferable, solenoidal magnetic fields are topologically very similar in 80<!PCT!> of the analyzed three-dimensional domain to the non-solenoidal fields obtained from spectropolarimetric inversions. These results support the idea that common Stokes inversion techniques fail to reproduce $ B =0$ mainly as a consequence of the uncertainties in the determination of the individual components of the magnetic field. In the remaining 20<!PCT!> of the analyzed domain, where the $B_ z $ inferred by the solenoidal and non-solenoidal inversions disagree, it remains to be proven that the solenoidal inversion is to be preferred because even though the overall fit to the Stokes parameters improves, the fit to Stokes $V$ worsens. It is in these regions where the application of the Stokes inversion constrained by the null divergence condition can yield new insights about the topology of the magnetic field in the solar photosphere.

Li+ EXTRACTION FROM AQUEOUS SOLUTIONS BY PVDF-BASED MEMBRANES CONTAINING PARTIALLY PROTONATED POTASSIUM POLYTITANATE

Extraction of lithium from natural aqueous solutions as alternative source of this chemical element becomes the actual and demanded task. Among the variety of known methods, ion exchange adsorption is considered to be suitable both in terms of the final product purity and economic efficiency of the technological operations. Compounds with layered and tunnel structures are promising ion-exchange materials. In this study, the partially protonated potassium polytitanate is investigated as the Li+ ions adsorbent. This amorphous substance characterized with the K1.3H0.7Ti4.1O9 chemical composition is synthesized by acid treatment of X-ray amorphous layered potassium polytitanate K2O·nTiO2 (n = 4.1). The PVDF-based membranes filled with the K1.3H0.7Ti4.1O9 powder are prepared by the phase inversion technique. Using the kinetic and isotherm technique, it is shown that a use of the pseudo-first order model (qe = 0.5 mg/cm2; k1 = 0.014 min-1) and the Freundlich adsorption model (KF = 0.028 (L)1/n(mg)1-1/n/cm2; n = 1.595) are the best models to describe the interaction of the obtained membranes with lithium ions. The calculated parameters of the adsorption capacity, distribution coefficient (Kd), separation factor (α) and concentration factor (CF) confirm a high lithium ions selectivity of the investigated ion-exchange composite in the presence of sodium and potassium ions. The obtained results show that the PVDF-based membrane with partially protonated potassium polytitanate is a good candidate for selective lithium extraction from natural aqueous solution. For citation: Vikulova M.A., Maximova L.A., Rudyh V.Yu., Gorokhovsky A.V. Li+ extraction from aqueous solutions by PVDF-based membranes containing partially protonated potassium polytitanate. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 62-69. DOI: 10.6060/ivkkt.20246705.6969.

Inverse Modelling Techniques as Dynamic Digital Pre-Distortion for Broadband Systems for CS-DACs Based on Volterra Series Expansion

Inverse Modelling Techniques as Dynamic Digital Pre-Distortion for Broadband Systems for CS-DACs Based on Volterra Series Expansion

The Radial Orbits of Ram-pressure-stripped Galaxies in Clusters from the GASP Survey

We analyze a sample of 244 ram-pressure-stripped candidate galaxy members within the virial radius of 62 nearby clusters to determine their velocity anisotropy profile β(r). We use previously determined mass profiles for the 62 clusters to build an ensemble cluster by stacking the 62 cluster samples in projected phase space. We solve the Jeans equation for dynamical equilibrium by two methods, MAMPOSSt and the Jeans inversion technique, and determine β(r) both in parametric form and nonparametrically. The two methods consistently indicate that the orbits of the ram-pressure-stripped candidates are increasingly radial with distance from the cluster center, from almost isotropic (β ≃ 0) at the center, to very radial at the virial radius (β ≃ 0.7). The orbits of cluster galaxies undergoing ram pressure stripping are similar to those of spiral cluster galaxies but more radially elongated at large radii.

A new method for accurate inversion of Forel-Ule index using MODIS images - revealing the water color evolution in China's large lakes and reservoirs over the past two decades

The Forel Ule water color index (FUI) based on satellite inversion can characterize the comprehensive characteristics of water quality on a large spatiotemporal scale. The high-frequency observations and rich historical data of the MODIS surface reflectance product (MODIS-500 m) provide important data support for monitoring the FUI of inland lakes. However, MODIS-500 m has only three bands in the visible light range, resulting in significant uncertainty in FUI inversion. To address this problem, this study developed an improved FUI inversion model using 500 synthetic spectra covering natural waters. The model, with a performance threshold set at 170° (FUI = 8), used a segmented algorithm across the entire color space. Validated with on-site measurement datasets (3500 samples), the model exhibited excellent performance, with mean relative error (MRE) and root mean square error (RMSE) of 1.71 % and 3.63°, respectively. Compared to existing models, it was more suitable for long-term FUI inversion in various types of lakes, particularly in eutrophic regions. Subsequently, the model was applied to MODIS-500 m observations from 2000 to 2022, revealing the spatiotemporal dynamics of FUI in 180 large lakes and reservoirs (hereinafter referred to as lakes) in China. The results indicated that the long-term mean FUI in the study area was 9, with 7 and 12 in the western and eastern regions, respectively, showing a distinct spatial distribution of "blue in the west and green in the east." The mean change rate of hue angle for all lakes was -0.085°/yr, showing an overall decreasing trend. Environmental factors' relative contributions to long-term water color changes in each lake region were quantified using the multiple general linear model (GLM). Although each lake region exhibited different driving forces, they were primarily influenced by vegetation, lake surface area, and anthropogenic factors. Additionally, the seasonal types of lake water color were analyzed, with the west and east showing opposite patterns, reflecting the significant influence of topographic features and seasonal changes in climate on water color. The research results provide techniques for accurate inversion of FUI using MODIS-500 m data, while deepening the understanding of long-term water color changes in inland lakes in China.

Photocatalytic bio‐inspired PDA‐RGO/g‐C3N4 nanocomposite incorporated PES membrane for removal of environmental antibiotic pollutants

AbstractBACKGROUNDMembrane technology makes it more suitable for the treatment of environmental polluted organic wastewater. Membrane fouling is one of the major concerns in commercial membranes. To overcome this issue, photocatalytic nanomaterials are embedded into the membrane to enhance its surface nature and reusability. In this investigation, polydopamine functionalized graphene oxide (PDA‐RGO), graphite carbon nitride (g‐C3N4) and PDA‐RGO/g‐C3N4 nanomaterials were incorporated within polyethersulfone membrane fabricated via a phase inversion technique. These as‐prepared membranes’ functional groups and surface morphologies were investigated by Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and field emission electron microscopy (FESEM). These as‐prepared membranes were investigated for photocatalytic activity under visible‐light‐driven photodegradation by environmental pollutants such as Rhodamine B (RhB) and Norfloxacin (NOR).RESULTSCompared with pristine PES membrane, the PDA‐RGO/g‐C3N4‐PES nanocomposite membrane showed higher photocatalytic activity for Rhodamine B 94.6% and Norfloxacin 96.8%, also reached greater water flux 189 L m−2 h−1. Therefore, the bio‐inspired nanocomposite‐modified PDA‐RGO/g‐C3N4 photocatalytic membrane could have huge potential in processing environmentally polluted water.CONCLUSIONSPDA‐RGO/g‐C3N4‐PES nanocomposite membrane improved the membrane hydrophilicity, water flow, anti‐fouling performance, rejection studies and photocatalytic degradation than the pristine membrane. The synergistic result of PDA‐RGO and g‐C3N4 exhibits better photodegradation efficiency of the membrane towards environmental pollutants. © 2024 Society of Chemical Industry (SCI).

A MCMC method based on surrogate model and Gaussian process parameterization for infinite Bayesian PDE inversion

This work focuses on an inversion problem derived from parametric partial differential equations (PDEs) with an infinite-dimensional parameter, represented as a coefficient function. The objective is to estimate this coefficient function accurately despite having only noisy measurements of the PDE solution at sparse input points. Conventional methods for inversion require numerous calls to a refined PDE solver, resulting in significant computational complexity, especially for challenging PDE problems, making the inference of the coefficient function practically infeasible. To address this issue, we propose a MCMC method that combines an deep learning-based surrogate and Gaussian process parameterization to efficiently infer the posterior of the coefficient function. The surrogate model is a combination of a cost-effective coarse PDE solver and a neural network-based transformation which provides an approximate solution derived from the refined PDE solver but based on the coarse PDE solution. The coefficient function is represented by Gaussian process with finite number of spatially dependent parameters and this parametric representation will be beneficial for the preconditioned Crank-Nicolson (pCN) Markov chain Monte Carlo method to sample efficiently from the posterior distribution. Approximate Bayesian computation method is used for constructing an informative dataset for the transformation learning. Our numerical examples demonstrate the effectiveness of this approach in accurately estimating the coefficient function while significantly reducing the computational burden associated with traditional inversion techniques.

Improved Approaches for 3D Gravity and Gradient Imaging Based on Potential Field Separation: Application to the Magma Chamber in Wudalianchi Volcanic Field, Northeastern China

The gravity and gradient anomalies contain valuable information about the underground geological structures at various depths. Deep and shallow buried source bodies are able to be identified through multi-scale field separation processes, and visual comprehensions of geological structures can be obtained via 3D density inversion techniques. In this study, we propose an improved 3D imaging strategy based on gravitational field separation using the preferential continuation filter. This strategy incorporates the relationship between spectral features and buried depths of source bodies, allowing for a one-step transformation from planar gravity and full-tensor gradient field observations to a 3D density structure in the wave-number domain. Synthetic tests validate the effectiveness and robustness of the gravity and gradient imaging approaches, highlighting their advantages in high vertical resolution and low computational requirements. Nonetheless, it should be noted that the imaging effects of horizontal gradients Γxx and Γyy are unsatisfactory due to their weak noise resistance. Thus, they are not suitable for real data applications. The other imaging approaches are further applied to recover the subsurface 3D density structure beneath the Weishan cone in Wudalianchi Volcanic Field, Northeastern China. Our results provide insights into the possible location and shape of the low-density magma chamber. Also, the potential presence of partial melts is inferred and supported from a gravity perspective. The primary advantage of these approaches is their ability to generate a reasonable geological model in scenarios with limited prior information and physical property constraints. As a result, they have significant practical value in the field of applied geophysics, including mineral exploration and volcanology studies.