Modeling Geometrically Nonlinear FG Plates: A Fast and Accurate Alternative to IGA Method Based on Deep Learning

Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.

A perspective on regression and Bayesian approaches for system identification of pattern formation dynamics

We present two approaches to system identification, i.e. the identification of partial differentialequations (PDEs) from measurement data. The first is a regression-based variational systemidentification procedure that is advantageous in not requiring repeated forward model solves andhas good scalability to large number of differential operators. However it has strict data typerequirements needing the ability to directly represent the operators through the available data.The second is a Bayesian inference framework highly valuable for providing uncertaintyquantification, and flexible for accommodating sparse and noisy data that may also be indirectquantities of interest. However, it also requires repeated forward solutions of the PDE modelswhich is expensive and hinders scalability. We provide illustrations of results on a model problemfor pattern formation dynamics, and discuss merits of the presented methods.

Isogeometric Boundary Element Analysis for 2D Transient Heat Conduction Problem with Radial Integration Method

This paper presents an isogeometric boundary element method(IGABEM)for transient heat conduction analysis.The Non-Uniform Rational B-spline(NURBS)basis functions,which are used to construct the geometry of the structures,are employed to discretize the physical unknowns in the boundary integral formulations of the governing equations.Bezier extraction technique is employed to accelerate the evaluation of NURBS basis functions.We adopt a radial integration method to address the additional domain integrals.The numerical examples demonstrate the advantage of IGABEM in dimension reduction and the seamless connection between CAD and numerical analysis.

Bayesian Optimization for Field-Scale Geological Carbon Storage

We present a framework that couples a high-fidelity compositional reservoir simulator with Bayesian optimization(BO)for injection well scheduling optimization in geological carbon sequestration.This work represents one of the first at tempts to apply BO and high-fidelity physics models to geological carbon storage.The implicit parallel accurate reservoir simulator(IPARS)is utilized to accurately capture the underlying physical processes during CO_(2)sequestration.IPARS provides a framework for several flow and mechanics models and thus supports both stand-alone and coupled simulations.In this work,we use the compositional flow module to simulate the geological carbon storage process.The compositional flow model,which includes a hysteretic three-phase relative permeability model,accounts for three major CO_(2)trapping mechanisms:structural trapping,residual gas trapping,and solubility trapping.Furthermore,IPARS is coupled to the International Business Machines(IBM)Corporation Bayesian Optimization Accelerator(BOA)for parallel optimizations of CO_(2)injection strategies during field-scale CO_(2)sequestration.BO builds a probabilistic surrogate for the objective function using a Bayesian machine learning algorithm-the Gaussian process regression,and then uses an acquisition function that leverages the uncertainty in the surrogate to decide where to sample.The IBM BOA addresses the three weaknesses of standard BO that limits its scalability in that IBM BOA supports parallel(batch)executions,scales better for high-dimensional problems,and is more robust to initializations.We demonstrate these merits by applying the algorithm in the optimization of the CO_(2)injection schedule in the Cranfield site in Mississippi,USA,using field data.The optimized injection schedule achieves 16%more gas storage volume and 56%less water/surfactant usage compared with the baseline.The performance of BO is compared with that of a genetic algorithm(GA)and a covariance matrix adaptation(CMA)-evolution strategy(ES).The results demonstrate the superior performance of BO,in that it achieves a competitive objective function value with over 60%fewer forward model evaluations.

BOUNDARY PROCEDURES FOR THE TIME-DEPENDENT BURGERS' EQUATION UNDER UNCERTAINTY

The Burgers'equation with uncertain initial and boundary conditions is approximated using a Polynomial Chaos Expansion(PCE)approach where the solution is represented as a series of stochastic,orthogonal polynomials.The resulting truncated PCE system is solved using a novel numerical discretization method based on spatial derivative operators satisfying the summation by parts property and weak boundary conditions to ensure stability.The resulting PCE solution yields an accurate quantitative description of the stochastic evolution of the system,provided that appropriate boundary conditions are available.The specification of the boundary data is shown to influence the solution;we will discuss the problematic implications of the lack of precisely characterized boundary data and possible ways of imposing stable and accurate boundary conditions.

Isogeometric Collocation:A Mixed Displacement-Pressure Method for Nearly Incompressible Elasticity Dedicated to Professor Karl Stark Pister for his 95th birthday

We investigate primal and mixed u−p isogeometric collocation methods for application to nearly-incompressible isotropic elasticity.The primal method employs Navier’s equations in terms of the displacement unknowns,and the mixed method employs both displacement and pressure unknowns.As benchmarks for what might be considered acceptable accuracy,we employ constant-pressure Abaqus finite elements that are widely used in engineering applications.As a basis of comparisons,we present results for compressible elasticity.All the methods were completely satisfactory for the compressible case.However,results for low-degree primal methods exhibited displacement locking and in general deteriorated in the nearly-incompressible case.The results for the mixed methods behaved very well for two of the problems we studied,achieving levels of accuracy very similar to those for the compressible case.The third problem,which we consider a“torture test”presented a more complex story for the mixed methods in the nearly-incompressible case.

Damage in hybrid corrugated core sandwich structures under high velocity hail ice impact:A numerical study

Potential damage in composite structures caused by hail ice impact is an essential safety threat to the aircraft in flight.In this study,a nonlinear finite element(FE)model is developed to investigate the dynamic response and damage behavior of hybrid corrugated sandwich structures subjected to high velocity hail ice impact.The impact and breaking behavior of hail are described using the FE-smoothed particle hydrodynamics(FE-SPH)method.A rate-dependent progressive damage model is employed to capture the intra-laminar damage response;cohesive element and surface-based cohesive contact are implemented to predict the inter-laminar delamination and sheet/core debonding phenomena respectively.The transient processes of sandwich structure under different hail ice impact conditions are analyzed.Comparative analysis is conducted to address the influences of core shape and impact position on the impact performance of sandwich structures and the corresponding energy absorption characteristics are also revealed.

Light-Induced Phonon-Mediated Magnetization in Monolayer MoS_(2)

Light-induced ultrafast spin dynamics in materials is of great importance for developments of spintronics and magnetic storage technology.Recent progresses include ultrafast demagnetization,magnetic switching,and magnetic phase transitions,while the ultrafast generation of magnetism is hardly achieved.Here,a strong lightinduced magnetization(up to 0.86μBper formula unit)is identified in non-magnetic monolayer molybdenum disulfide(MoS_(2)).With the state-of-the-art time-dependent density functional theory simulations,we demonstrate that the out-of-plane magnetization can be induced by circularly polarized laser,where chiral phonons play a vital role.The phonons strongly modulate spin-orbital interactions and promote electronic transitions between the two conduction band states,achieving an effective magnetic field~380 T.Our study provides important insights into the ultrafast magnetization and spin-phonon coupling dynamics,facilitating effective light-controlled valleytronics and magnetism.

Resolving Domain Integral Issues in Isogeometric Boundary Element Methods via Radial Integration:A Study of Thermoelastic Analysis

The paper applied the isogeometric boundary element method(IGABEM)to thermoelastic problems.The Non-Uniform Rational B-splines(NURBS)used to construct geometric models are employed to discretize the boundary integral formulation of the governing equation.Due to the existence of thermal stress,the domain integral term appears in the boundary integral equation.We resolve this problem by incorporating radial integration method into IGABEM which converts the domain integral to the boundary integral.In this way,IGABEM can maintain its advantages in dimensionality reduction and more importantly,seamless integration of CAD and numerical analysis based on boundary representation.The algorithm is verified by numerical examples.

Analysis of lattices with non-linear interphases

Anti-plane deformation of square lattices containing interphases is analyzed. It is assumed that lattices are linear elastic but not necessarily isotropic, whereas interphases exhibit non-linear elastic behavior. It is demonstrated that such problems can be treated effectively using Green's functions, which allow to eliminate the degrees of freedom outside of the interphase. Illustrative numerical examples focus on the determination of applied stresses leading to lattice instability.

Noise Pollution Reduction through a Novel Optimization Procedure in Passive Control Methods

This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build gap-free Computer-Aided Design models and meanwhile tackle the extraordinary points that are commonly encountered in geometricmodelling.The acoustic fields are simulated using the isogeometric boundary elementmethod,and a density-based topology optimization is conducted to optimize distribution of sound-absorbing materials adhered to structural surfaces.The approach enables one to perform acoustic optimization from Computer-Aided Design models directly without needingmeshing and volume parameterization,thereby avoiding the geometric errors and time-consuming preprocessing steps in conventional simulation and optimization methods.The effectiveness of the present method is demonstrated by three dimensional numerical examples.

A Study of Water Supercooling

The objective of this paper is to investigate water supercooling. Supercooling occurs when a liquid does not freeze although its temperature is below its freezing point. In general, supercooling is an unstable condition and occurs under special conditions. The parameters that influence supercooling stability and probability of occurrence include freezer temperature and water’s initial temperature. In this paper, it is shown that with a freezer temperature range of -3℃ to -8℃, supercooling is most likely to happen and is independent of the water’s initial temperature. Furthermore, as the freezer temperature decreases, the probability of nucleation increases, causing instant freezing. Finally, it is concluded that the Mpemba effect, in which initially hot water freezes faster than initially cold water, is due to the supercooling instability in initially hot water in which nucleation agents are more active.

High-entropy alloy nanoparticles as a promising electrocatalyst to enhance activity and durability for oxygen reduction

Developing efficient platinum-based electrocatalysts with super durability for the oxygen reduction reaction(ORR)is highly desirable to promote the large-scale commercialization of fuel cells.Although progress has been made in this aspect,the electrochemical kinetics and stability of platinum-based catalysts are still far from the requirements of the practical applications.Herein,PtPdFeCoNi high-entropy alloy(HEA)nanoparticles were demonstrated via a high-temperature injection method.PtPdFeCoNi HEA nanocatalyst exhibits outstanding catalytic activity and stability towards ORR due to the high entropy,lattice distortion,and sluggish diffusion effects of HEA,and the HEA nanoparticles delivered a mass activity of 1.23 A/mgPt and a specific activity of 1.80 mA/cmPt 2,which enhanced by 6.2 and 4.9 times,respectively,compared with the values of the commercial Pt/C catalyst.More importantly,the high durability of PtPdFeCoNi HEA/C was evidenced by only 6 mV negativeshifted half-wave potential after 50,000 cycles of accelerated durability test(ADT).

Direct synthesis of tin spheres/nitrogen-doped porous carbon composite by self-formed template method for enhanced lithium storage

To inhibit the agglomeration of tin-based nanomaterials and simplify the complicated synthesis process,a facile and eco-friendly self-formed template method is reported to synthesize tin submicron spheres dispersed in nitrogen-doped porous carbon(Sn/NPC)by pyrolysis of a mixture of disodium stannous citrate and urea.The vital point of this strategy is the formation of Na_(2)CO_(3)templates during pyrolysis.This self-formed Na_(2)CO_(3)acts as porous templates to support the formation of NPC.The obtained NPC provides good electronic conductivity,ample defects,and more active sites.Serving as anode for Li-ion batteries,the Sn/NPC electrode obtains a stable discharge capacity of 674.1 mAh/g after 150 cycles at 0.1 A/g.Especially,a high discharge capacity of 331.2 mAh/g can be achieved after 1100 cycles at 3 A/g.Additionally,a full cell coupled with LiCoO_(2)as cathode yields a discharge capacity of 524.8 mAh/g after 150 cycles at 0.1 A/g.In-situ XRD is implemented to investigate the alloying/dealloying reaction mechanisms.Density functional theory calculation ulteriorly explicates that NPC heightens intrinsic electronic conductivity,and NPC especially pyrrolic-N and pyridinic-N doping facilitates the Li-adsorption ability.Climbing image nudged elastic band method reveals low Li~+diffusion energy barrier in presence of N atoms,which accounts for the terrific electrochemical properties of Sn/NPC electrode.

Combined subsampling and analytical integration for efficient large-scale GW calculations for 2D systems

Accurate and efficient predictions of the quasiparticle properties of complex materials remain a major challenge due to the convergence issue and the unfavorable scaling of the computational cost with respect to the system size.Quasiparticle GW calculations for two-dimensional(2D)materials are especially difficult.The unusual analytical behaviors of the dielectric screening and the electron self-energy of 2D materials make the conventional Brillouin zone(BZ)integration approach rather inefficient and require an extremely dense k-grid to properly converge the calculated quasiparticle energies.In this work,we present a combined nonuniform subsampling and analytical integration method that can drastically improve the efficiency of the BZ integration in 2D GW calculations.

ON THE QUASI-RANDOM CHOICE METHOD FOR THE LIOUVILLE EQUATION OF GEOMETRICAL OPTICS WITH DISCONTINUOUS WAVE SPEED

我们以不连续的本地波浪速度为几何光学的 Liouville 方程学习伪随机选择方法(QRCM ) 。这个方程通过接口在高频率波浪的阶段空格计算产生，在波浪经历部分传播和 re ections 的地方。数字挑战包括接口，接触 discon- tinuities，和珍视措施的答案。所谓的 QRCM 基于伪随机采样(随机的采样的一种确定的选择) 是一个随机的选择方法。方法不仅是没有粘性的而且提供更快的集中率。因此，它确实在是的学习下面正在恳求这个问题 Hamiltonian 嗷。我们的分析和计算结果证明 QRCM 1 ) 是几乎一阶的甚至与上述的断绝精确；2 ) 为处于这个问题遇到的所有断绝给锋利的分辨率；并且 3 ) 为珍视措施的答案，不与数字粘性为 funite 差别 / 卷方法需要水平集合分解。[从作者抽象]

Conservative Residual Distribution Method for Viscous Double Cone Flows in Thermochemical Nonequilibrium

Amulti-dimensionally upwind conservative ResidualDistribution algorithm for simulating viscous axisymmetric hypersonic flows in thermo-chemical nonequilibrium on unstructured grids is presented and validated in the case of the complex flowfield over a double cone configuration.The resulting numerical discretization combines a state-of-the-art nonlinear quasi-monotone second order blended scheme for distributing the convective residual and a standard Galerkin formulation for the diffusive residual.The physical source terms are upwinded together with the convective fluxes.Numerical results show an excellent agreement with experimental measurements and available literature.

A Numerical Scheme for the Quantum Fokker-Planck-Landau Equation Efficient in the Fluid Regime

We construct an efficient numerical scheme for the quantum Fokker-Planck-Landau(FPL)equation that works uniformly from kinetic to fluid regimes.Such a scheme inevitably needs an implicit discretization of the nonlinear collision operator,which is difficult to invert.Inspired by work[9]we seek a linear operator to penalize the quantum FPL collision term QqFPL in order to remove the stiffness induced by the small Knudsen number.However,there is no suitable simple quantum operator serving the purpose and for this kind of operators one has to solve the complicated quantum Maxwellians(Bose-Einstein or Fermi-Dirac distribution).In this paper,we propose to penalize QqFPL by the”classical”linear Fokker-Planck operator.It is based on the observation that the classicalMaxwellian,with the temperature replaced by the internal energy,has the same first five moments as the quantum Maxwellian.Numerical results for Bose and Fermi gases are presented to illustrate the efficiency of the scheme in both fluid and kinetic regimes.

A VASUALIZATION FOR THE DYNAMIC BEHAVIORS OF THE MIXTURE OF WATER MASS FOR NORTHWESTERN PACIFIC NEAR JAPAN

Recent studies are focusing on the distribution of water mass because the mixture region of water mass is highly related to the rich fishing grounds[Yasuda I.,Watanabe Y.,Fish.Oceanogr.3(3):172–181,1994].Due to the large data size and time-varying property,efficient exploration and visualization of the ocean data is always extremely challenging.To extract the dynamic behaviors of the water mass and its mixture from a large-scale simulated ocean dataset,we developed an efficient visualization system by applying our volume compression method and our volume rendering method.This system allows us to investigate the time-varying distributions of ocean physical properties,additionally from the user’s perspective and requirements.In the experiments,we show the generality and expressiveness by applying our system for single-and multi-property visualizations to find some significant ocean water mass.Consequently,we could obtain a clear visualization result to show the dynamic behaviors of the mixture of water mass for simulation data regarding a location in the northwestern Pacific near Japan.

A visualization for the dynamic behaviors of the mixture of water mass for northwestern pacific near Japan

(1)This article,published on 20 June 2013,had the following title:A VASUALIZATION FOR THE DYNAMIC BEHAVIORS OF THE MIXTURE OF WATER MASS FOR NORTHWESTERN PACIFIC NEAR JAPAN Here“VASUALIZATION”should be“VISUALIZATION”.