Retraction to: Shear strength of extremely altered serpentinites based on degree of saturation (Ankara, Turkey)

The Editor in Chief has retracted this article.After publication,concerns were raised over potentially inconsistent data-for example,the author mentioned residual soil with silt fraction,but Fig.5 shows even the smallest grains are beyond silt grains.Further analysis showed that Fig.6 and Fig.9 show both loose and dense soils exhibiting very similar dilatance behaviour,which is not typical.The author shared raw data,but it was incomplete and could not be verified.The Editor in Chief,therefore,has lost confidence in the findings of this article.The author does not agree to this retraction.

Nested Saturated Control of Uncertain Complex Cascade Systems Using Mixed Saturation Levels

This study addresses the problem of global asymptotic stability for uncertain complex cascade systems composed of multiple integrator systems and non-strict feedforward nonlinear systems. To tackle the complexity inherent in such structures, a novel nested saturated control design is proposed that incorporates both constant saturation levels and state-dependent saturation levels. Specifically, a modified differentiable saturation function is proposed to facilitate the saturation reduction analysis of the uncertain complex cascade systems under the presence of mixed saturation levels. In addition, the design of modified differentiable saturation function will help to construct a hierarchical global convergence strategy to improve the robustness of control design scheme. Through calculation of relevant inequalities, time derivative of boundary surface and simple Lyapunov function,saturation reduction analysis and convergence analysis are carried out, and then a set of explicit parameter conditions are provided to ensure global asymptotic stability in the closed-loop systems. Finally, a simplified system of the mechanical model is presented to validate the effectiveness of the proposed method.

Theoretical characterization of the temperature-dependent saturation magnetization of magnetic metallic materials

Based on the force-heat equivalence energy density principle,a theoretical model for magnetic metallic materials is developed,which characterizes the temperature-dependent magnetic anisotropy energy by considering the equivalent relationship between magnetic anisotropy energy and heat energy;then the relationship between the magnetic anisotropy constant and saturation magnetization is considered.Finally,we formulate a temperature-dependent model for saturation magnetization,revealing the inherent relationship between temperature and saturation magnetization.Our model predicts the saturation magnetization for nine different magnetic metallic materials at different temperatures,exhibiting satisfactory agreement with experimental data.Additionally,the experimental data used as reference points are at or near room temperature.Compared to other phenomenological theoretical models,this model is considerably more accessible than the data required at 0 K.The index included in our model is set to a constant value,which is equal to 10/3 for materials other than Fe,Co,and Ni.For transition metals(Fe,Co,and Ni in this paper),the index is 6 in the range of 0 K to 0.65T_(cr)(T_(cr) is the critical temperature),and 3 in the range of 0.65T_(cr) to T_(cr),unlike other models where the adjustable parameters vary according to each material.In addition,our model provides a new way to design and evaluate magnetic metallic materials with superior magnetic properties over a wide range of temperatures.

Analysis and Design of Time-Delay Impulsive Systems Subject to Actuator Saturation

This paper investigates the exponential stability and performance analysis of nonlinear time-delay impulsive systems subject to actuator saturation. When continuous dynamics is unstable, under some conditions, it is shown that the system can be stabilized by a class of saturated delayed-impulses regardless of the length of input delays. Conversely, when the system is originally stable, it is shown that under some conditions, the system is robust with respect to sufficient small delayed-impulses. Moreover, the design problem of the controller with the goal of obtaining a maximized estimate of the domain of attraction is formulated via a convex optimization problem. Three examples are provided to demonstrate the validity of the main results.

Deep learning-based inpainting of saturation artifacts in optical coherence tomography images

Limited by the dynamic range of the detector,saturation artifacts usually occur in optical coherence tomography(OCT)imaging for high scattering media.The available methods are difficult to remove saturation artifacts and restore texture completely in OCT images.We proposed a deep learning-based inpainting method of saturation artifacts in this paper.The generation mechanism of saturation artifacts was analyzed,and experimental and simulated datasets were built based on the mechanism.Enhanced super-resolution generative adversarial networks were trained by the clear–saturated phantom image pairs.The perfect reconstructed results of experimental zebrafish and thyroid OCT images proved its feasibility,strong generalization,and robustness.

Event-based nonfragile state estimation for memristive recurrent neural networks with stochastic cyber-attacks and sensor saturations

This paper addresses the issue of nonfragile state estimation for memristive recurrent neural networks with proportional delay and sensor saturations. In practical engineering, numerous unnecessary signals are transmitted to the estimator through the networks, which increases the burden of communication bandwidth. A dynamic event-triggered mechanism,instead of a static event-triggered mechanism, is employed to select useful data. By constructing a meaningful Lyapunov–Krasovskii functional, a delay-dependent criterion is derived in terms of linear matrix inequalities for ensuring the global asymptotic stability of the augmented system. In the end, two numerical simulations are employed to illustrate the feasibility and validity of the proposed theoretical results.

Modelling rapid non-destructive test using light weight deflectometer on granular soils across different degrees of saturation

This study introduces an advanced finite element model for the light weight deflectometer(LWD),which integrates contact mechanics with fully coupled models.By simulating LWD tests on granular soils at various saturation levels,the model accurately reflects the dependence of the LWD modulus on dry density,water content,and effective stress.This model addresses and overcomes the limitations of previous finite element models for this specific problem.Simultaneously,this research presents the first experimentally validated fully coupled contact impact model.Furthermore,the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-tosegment method(developed in this study)with the more precise mortar technique for contact mechanics.These comparisons reveal unique advantages and challenges for each method.Moreover,the study underscores the importance of careful application of the LWD modulus,emphasising the need for sophisticated tools to interpret soil behaviour accurately.

Effect of Skeleton Grain Size on the Saturation of Gas Hydrate in Natural Sediments

Natural gas hydrate is prospected as a new and promising,highly clean energy resource that mainly occurs in perma-frost or at continental margins.Its formation is subject to many soil conditions,such as grain size,matrix materials,pore morphology,and permeability.In this study,we propose that grain size is the most decisive parameter that affects the saturation of gas hydrate in sediments based on data from Ocean Drilling Program Leg 164 and Mallik 5L-38,which represent marine sediments and terrestrial sediments,respectively.Our study reveals that high gas hydrate saturation generally occurs in coarse-grained sand,regardless of whether sediment formation is homogeneous or inhomogeneous,and the sorting of sediments may affect the hydrate saturation to a certain degree.Using grain size and sorting of sediments may be the most intuitive proxy method for a rough estimation of hydrate saturation.Further study is necessary to fully understand the relationship between hydrate morphology and sediment grain size,even though massive hydrates are typically found in fine clayey-rich sediments.

Saturation Estimation with Complex Electrical Conductivity for Hydrate-Bearing Clayey Sediments:An Experimental Study

Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.

Adaptive Sensor-Fault Tolerant Control of Unmanned Underwater Vehicles With Input Saturation

This paper investigates the tracking control problem for unmanned underwater vehicles(UUVs)systems with sensor faults,input saturation,and external disturbance caused by waves and ocean currents.An active sensor fault-tolerant control scheme is proposed.First,the developed method only requires the inertia matrix of the UUV,without other dynamic information,and can handle both additive and multiplicative sensor faults.Subsequently,an adaptive fault-tolerant controller is designed to achieve asymptotic tracking control of the UUV by employing robust integral of the sign of error feedback method.It is shown that the effect of sensor faults is online estimated and compensated by an adaptive estimator.With the proposed controller,the tracking error and estimation error can asymptotically converge to zero.Finally,simulation results are performed to demonstrate the effectiveness of the proposed method.

Oil Saturation Is Determined by Different Experimental Methods

Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the original oil saturation of the study area was studied by using the comprehensive experimental method. The original oil saturation of tight oil in the study area was determined by J function method, rock electricity method and oil-based mud coring method. The results showed that through the comparison of three experimental methods, it could be concluded that the J function method leads to the low value of oil saturation in the study area. The oil-based mud coring method was more suitable for the determination of oil saturation in this area than the other two methods because it needs to meet too many conditions and the calculation results were also low. G area was located in Qili Village, Ordos Basin.

Noninvasive Characterization of Metabolic Changes in Ischemic Stroke Using Z-spectrum-fitted Multiparametric Chemical Exchange Saturation Transfer-weighted Magnetic Resonance Imaging

Objective This study aimed to noninvasively characterize the metabolic alterations in ischemic brain tissues using Z-spectrum-fitted multiparametric chemical exchange saturation transfer-weighted magnetic resonance imaging(CEST-MRI).Methods Three sets of Z-spectrum data with saturation power(B_(1))values of 1.5,2.5,and 3.5µT,respectively,were acquired from 17 patients with ischemic stroke.Multiple contrasts contributing to the Z-spectrum,including fitted amide proton transfer(APT_(fitted)),+2 ppm peak(CEST@2ppm),concomitantly fitted APT_(fitted) and CEST@2ppm(APT&CEST@2ppm),semisolid magnetization transfer contrast(MT),aliphatic nuclear Overhauser effect(NOE),and direct saturation of water(DSW),were fitted with 4 and 5 Lorentzian functions,respectively.The CEST metrics were compared between ischemic lesions and contralateral normal white matter(CNWM),and the correlation between the CEST metrics and the apparent diffusion coefficient(ADC)was assessed.The differences in the Z-spectrum metrics under varied B1 values were also investigated.Results Ischemic lesions showed increased APTfitted,CEST@2ppm,APT&CEST@2ppm,NOE,and DSW as well as decreased MT.APT&CEST@2ppm,MT,and DSW showed a significant correlation with ADC[APT&CEST@2ppm at the 3 B_(1) values:R=0.584/0.467/0.551;MT at the 3 B_(1) values:R=−0.717/−0.695/−0.762(4-parameter fitting),R=−0.734/−0.711/−0.785(5-parameter fitting);DSW of 4-/5-parameter fitting:R=0.794/0.811(2.5µT),R=0.800/0.790(3.5µT)].However,the asymmetric analysis of amide proton transfer(APT_(asym))could not differentiate the lesions from CNWM and showed no correlation with ADC.Furthermore,the Z-spectrum contrasts varied with B_(1).Conclusion The Z-spectrum-fitted multiparametric CEST-MRI can comprehensively detect metabolic alterations in ischemic brain tissues.

Maximum Correntropy Kalman Filtering for Non-Gaussian Systems With State Saturations and Stochastic Nonlinearities

This paper tackles the maximum correntropy Kalman filtering problem for discrete time-varying non-Gaussian systems subject to state saturations and stochastic nonlinearities. The stochastic nonlinearities, which take the form of statemultiplicative noises, are introduced in systems to describe the phenomenon of nonlinear disturbances. To resist non-Gaussian noises, we consider a new performance index called maximum correntropy criterion(MCC) which describes the similarity between two stochastic variables. To enhance the “robustness” of the kernel parameter selection on the resultant filtering performance, the Cauchy kernel function is adopted to calculate the corresponding correntropy. The goal of this paper is to design a Kalman-type filter for the underlying systems via maximizing the correntropy between the system state and its estimate. By taking advantage of an upper bound on the one-step prediction error covariance, a modified MCC-based performance index is constructed. Subsequently, with the assistance of a fixed-point theorem, the filter gain is obtained by maximizing the proposed cost function. In addition, a sufficient condition is deduced to ensure the uniqueness of the fixed point. Finally, the validity of the filtering method is tested by simulating a numerical example.

Visual Feedback Disturbance Rejection Control for an Amphibious Bionic Stingray Under Actuator Saturation

Dear Editor,This letter is concerned with visual feedback disturbance rejection control for an amphibious bionic stingray subject to actuator saturation with internal and external disturbances. A visual feedback control method is designed for a dynamic nonlinear system on yaw angle of the amphibious bionic stingray via a finite-time extended-stateobserver,which is proved to achieve finite-time stability via a Lyapunov method. Finally, simulation results verify the effectiveness on the visual feedback control method.

Route to Stabilize Cubic Gauche Polynitrogen to Ambient Conditions via Surface Saturation by Hydrogen

Cubic gauche polynitrogen(cg-N)is an attractive high-energy density material.However,high-pressure synthesized cg-N will decompose at low pressure and cannot exist under ambient conditions.Here,the stabilities of cg-N surfaces with and without saturations at different pressures and temperatures are systematically investigated based on first-principles calculations and molecular dynamics simulations.Pristine surfaces at 0 GPa are very brittle and will decompose at 300 K,especially(110)surface will collapse completely just after structural relaxation,whereas the decompositions of surfaces can be suppressed by applying pressure,indicating that surface instability causes the cg-N decomposition at low pressure.Due to the saturation of dangling bonds and transferring electrons to the surfaces,saturation with H can stabilize surfaces under ambient conditions,while it is impossible for OH saturation to occur solely from obtaining electrons from surfaces.This suggests that polynitrogen is more stable in an acidic environment or when the surface is saturated with less electronegative adsorbates.

Path Following of Underactuated Autonomous Surface Vessels With Surge Velocity Constraint and Asymmetric Saturation

Dear Editor, This letter is concerned with the path following of underactuated autonomous surface vessels(ASV) in the presence of surge velocity constraint and asymmetric saturation as well as unknown dynamics.To cope with velocity constraints both magnitude and rate and asymmetric saturation as well as unknown dynamics, an adaptive finitetime sliding mode control scheme(AFTSM) is designed.

Semi-analytical steady-state response prediction for multi-dimensional quasi-Hamiltonian systems

The majority of nonlinear stochastic systems can be expressed as the quasi-Hamiltonian systems in science and engineering. Moreover, the corresponding Hamiltonian system offers two concepts of integrability and resonance that can fully describe the global relationship among the degrees-of-freedom(DOFs) of the system. In this work, an effective and promising approximate semi-analytical method is proposed for the steady-state response of multi-dimensional quasi-Hamiltonian systems. To be specific, the trial solution of the reduced Fokker–Plank–Kolmogorov(FPK) equation is obtained by using radial basis function(RBF) neural networks. Then, the residual generated by substituting the trial solution into the reduced FPK equation is considered, and a loss function is constructed by combining random sampling technique. The unknown weight coefficients are optimized by minimizing the loss function through the Lagrange multiplier method. Moreover, an efficient sampling strategy is employed to promote the implementation of algorithms. Finally, two numerical examples are studied in detail, and all the semi-analytical solutions are compared with Monte Carlo simulations(MCS) results. The results indicate that the complex nonlinear dynamic features of the system response can be captured through the proposed scheme accurately.

A Posteriori Stabilized Sixth-Order Finite Volume Scheme with Adaptive Stencil Construction:Basics for the 1D Steady-State Hyperbolic Equations

We propose an adaptive stencil construction for high-order accurate finite volume schemes a posteriori stabilized devoted to solve one-dimensional steady-state hyperbolic equations.High accuracy(up to the sixth-order presently)is achieved,thanks to polynomial recon-structions while stability is provided with an a posteriori MOOD method which controls the cell polynomial degree for eliminating non-physical oscillations in the vicinity of dis-continuities.We supplemented this scheme with a stencil construction allowing to reduce even further the numerical dissipation.The stencil is shifted away from troubles(shocks,discontinuities,etc.)leading to less oscillating polynomial reconstructions.Experimented on linear,Burgers',and Euler equations,we demonstrate that the adaptive stencil technique manages to retrieve smooth solutions with optimal order of accuracy but also irregular ones without spurious oscillations.Moreover,we numerically show that the approach allows to reduce the dissipation still maintaining the essentially non-oscillatory behavior.

Giant saturation absorption of tungsten trioxide film prepared based on the seedless layer hydrothermal method

Nonlinear materials have gained wide interest as saturable absorbers and pulse compression for pulsed laser applications due to their unique optical properties.This work investigates the third-order nonlinear phenomenon of tungsten trioxide(WO_(3))thin films.The giant nonlinear absorption and nonlinear refractive index of WO_(3)thin films were characterized by Z-scan method at 800 nm.We experimentally observed the giant saturable absorption(SA)and nonlinear refractive index of WO_(3)thin films prepared by the seedless layer hydrothermal method,with SA coefficient being as high as-2.59×105cm·GW^(-1).The SA coefficient is at least one order of magnitude larger than those of the conventional semiconductors.The nonlinear refractive index n_(2)of WO_(3)film has been observed for the first time in recent studies and the corresponding coefficient can be up to 1.793 cm^(2)·GW^(-1).The large third-order nonlinear optical(NLO)response enables WO_(3)thin films to be promising candidates for optoelectronic and photonic applications in the near-infrared domain.

Enhancing the elastoplastic damage constitutive model for clayey rocks: Incorporating anisotropy, saturation, time-dependent, and debonding effects

This paper introduced a novel microstructure-based constitutive model designed to comprehensively characterize the intricate mechanical behavior of anisotropic clay rocks under the influence of water saturation.The proposed model encompasses elastoplastic deformation,time-dependent behavior,and induced damage.A two-step homogenization process incorporates mineral compositions and porosity to determine the macroscopic elastic tensor and plastic yield criterion.The model also considers interfacial debonding between the matrix and inclusions to capture rock damage.The application of the proposed model is demonstrated through an analysis of Callovo-Oxfordian clayey rocks,specifically in the context of radioactive waste disposal in France.Model parameters are determined,followed by numerical simulations of various laboratory tests including lateral decompression tests with constant mean stress,triaxial compression tests under different water saturation conditions,and creep tests.The numerical results are compared with corresponding experimental data to assess the efficacy of the proposed model.