Reference Solution Research Articles

Monte Carlo Workflow Unification for Nuclear Reactor Analysis with Metamodel-Driven Modeling

Monte Carlo (MC) transport codes are a cornerstone of nuclear reactor analysis frameworks, providing reference solutions and multigroup cross sections, and even as core components in multiphysics couplings. These applications can be seen in toolkits from the Nuclear Energy Advanced Modeling and Simulation program and the U.S. Nuclear Regulatory Commission’s BlueCRAB (Comprehensive Reactor Analysis Bundle). Contrary to their ubiquitousness in reactor physics modeling and simulation, popular MC codes, such as MCNP, Serpent, and KENO, are still reliant on antiquated textual input formats. These input languages use a plethora of keywords with terse syntax to specify all facets of a model, including its geometry, materials, physics settings, and tally options. This poses a steep learning curve and a poor user experience. Being tied to unique text-based input formats also significantly complicates programmatic input generation or modification that may be desired and/or required within a multiphysics framework. This work demonstrates how the development of programmatic interfaces for MC codes can support model unification and translation activities. Building on the Python application program interface (API) development of MCNPy, similar capabilities are being implemented for Serpent that are able to support model translation. In future work, the Serpent API capabilities will be made more robust and the work will be further expanded to include translations with KENO.

A Benchmark for Neutron Kinetics Methods in Hexagonal Geometry

A new benchmark solution has been developed to aid in the development of neutron kinetics solvers for hexagonal geometries, such as those in water-water energetic reactors. This benchmark problem is based on the two-dimensional, two-group, International Atomic Energy Agency–Hex steady-state benchmark problem. Two transient problems are presented: a ramp and a step transient. To create a benchmark-quality solution to this transient problem, a basic neutron kinetics model was added to the computer program LUPINE (Liquid metal–cooled fast reactor Utility for Physics Informed Nuclear Engineering). LUPINE solves neutron kinetics equations in general unstructured mesh. First, the LUPINE kinetics solvers are verified using the TWIGL benchmark problems. Then the methods in LUPINE are used to perform a spatiotemporal convergence analysis to ensure that the solutions are sufficiently converged. Finally, Richardson extrapolation is performed to obtain the reference solutions for these new kinetics benchmark problems.

SBFEM with perturbation method for solving the Reynolds equation

AbstractRotordynamic simulations with nonlinear hydrodynamic bearing forces require a solution of the Reynolds equation at every time step. As a computationally efficient alternative to the standard numerical methods, a semi‐analytical solution based on the scaled boundary finite element method (SBFEM) was developed recently. Through a discretization of the hydrodynamic pressure (dependent variable) along the circumferential but not the axial coordinate, the partial differential equation is transformed into a system of ordinary differential equations. This system of differential equations is referred to as SBFEM equation and can be solved exactly if the influence of shaft tilting is neglected. In common numerical models, this influence can be taken into account without difficulties, but as far as this semi‐analytical approach is concerned, shaft tilting complicates the equations substantially. Therefore, previous studies on the SBFEM solution of the Reynolds equation were conducted without consideration of this effect. The formulation presented in the work at hand no longer requires this simplification. The terms representing the influence of shaft tilting in the SBFEM equation are handled by the perturbation method. The pressure field is expressed by a series expansion, where the solution of order correlates to the power of a perturbation parameter chosen proportional to the tilting angle. The differential equation governing the solution contains lower‐order solutions on its right‐hand side, implying a recursive computation of the series from lowest to highest order. A universal expression for the general solution is formulated, where only the coefficients and the maximum power of the axial coordinate differ for every . This allows the implementation of a general algorithm with no inherent limitation regarding the maximum order of perturbation. For verification, the pressure fields computed by the proposed method are compared to a numerical reference solution, showing that the series converges to the correct result for the investigated set of parameters.

An overset-grid finite-difference algorithm for seismic wavefield propagations modelling in the polar coordinate system with a complex free-surface topography

Summary Nowadays, finite-difference method has been widely applied to simulate seismic wavefield propagation in a local seismic model with a complex topography by utilizing curvilinear grids and traction image method in Cartesian coordinates system. For a global seismic model in polar coordinate system, it is still a challenge for the conventional finite-difference method to deal with the grid singularity at the center and the topographic free surface at the top. In this study, we develop a finite-difference method in polar coordinates for seismic wavefield propagation in the 2D global model. In the proposed finite-difference method, the overset-grid algorithm is used to handle the grid singularity at the center, and the curvilinear grid technique as well as the traction image method are applied to implement free-surface boundary condition on the complex topography. The proposed finite-difference method is validated in flat and topographic free-surface models by comparing synthetic waveforms with reference solutions. The seismic wavefield propagation in a realistic Mars profile is computed by the proposed finite-difference method. The proposed finite-difference method is an efficient and accurate method for seismic wave modeling in the polar coordinate system with a complex free-surface topography.

Copper ions-photo dual-crosslinked alginate hydrogel for angiogenesis and osteogenesis.

Early healing of bone defects is still a clinical challenge. Many bone-filling materials have been studied, among which photocrosslinked alginate has received significant attention due to its good biocompatibility and morphological plasticity. Although it has been confirmed that photocrosslinked alginate can be used as an extracellular matrix for 3D cell culture, it lacks osteogenesis-related biological functions. This study constructed a copper ions-photo dual-crosslinked alginate hydrogel scaffold by controlling the copper ion concentration. The scaffolds were shaped by photocrosslinking and then endowed with biological functions by copper ions crosslinking. According to in vitro research, the dual-crosslinked hydrogel increased the compressive strength and favored copper dose-dependent osteoblast differentiation and cell surface adherence of rat bone marrow mesenchymal stem cells and the expression of type I collagen (Col1), runt-related transcription factor 2 (Runx2), osteocalcin (OCN), vascular endothelial growth factor (VEGF). In addition, hydrogel scaffolds were implanted into rat skull defects, and more angiogenesis and osteogenesis could be observed in in vivo studies. The above results show that the copper-photo-crosslinked hydrogel scaffold has excellent osseointegration properties and can potentially promote angiogenesis and early healing of bone defects, providing a reference solution for bone tissue engineering materials.

Stochastic Dynamic Buckling Analysis of Cylindrical Shell Structures Based on Isogeometric Analysis

In this paper, we extend our previous work on the dynamic buckling analysis of isogeometric shell structures to the stochastic situation where an isogeometric deterministic dynamic buckling analysis method is combined with spectral-based stochastic modeling of geometric imperfections. To be specific, a modified Generalized-α time integration scheme combined with a nonlinear isogeometric Kirchhoff–Love shell element is used to simulate the buckling and post-buckling problems of cylindrical shell structures. Additionally, geometric imperfections are constructed based on NURBS surface fitting, which can be naturally incorporated into the isogeometric analysis framework due to its seamless CAD/CAE integration feature. For stochastic analysis, the method of separation is adopted to model the stochastic geometric imperfections of cylindrical shells based on a set of measurements. We tested the accuracy and convergence properties of the proposed method with a cylindrical shell example, where measured geometric imperfections were incorporated. The ABAQUS reference solutions are also presented to demonstrate the superiority of the inherited smooth and high-order continuous properties of the isogeometric approach. For stochastic dynamic buckling analysis, we evaluated the buckling load variability and reliability functions of the cylindrical shell with 500 samples generated based on seven nominally identical shells reported in the geometric imperfection data bank. It is noted that the buckling load variability in the cylindrical shell obtained with static nonlinear analysis is also presented to show the differences between dynamic and static buckling analysis.

A pore-scale lattice Boltzmann model for solute transport coupled with heterogeneous surface reactions and mineral dissolution

In this paper, we propose a pore-scale lattice Boltzmann model to simulate fluid flow coupled with heterogeneous surface reactions and mineral dissolution. The primary innovation lies in the transformation of surface reactions, originally treated as a boundary condition, into a volume-source term through dimensional augmentation within the framework of sharp liquid–solid interfaces. This significantly simplifies the implementation, particularly for reactions occurring in porous media with intricate geometric structures. Several benchmark tests were performed to validate the accuracy of this model, including a reaction–diffusion problem in a rectangular domain, a two-dimensional reaction and dissolution of a circular grain, as well as a three-dimensional calcite crystal dissolution in a micro-channel. All the obtained simulation results agree well with the reference solutions. In addition, a dissolution problem in a three-dimensional porous medium built with the sand pack is then investigated. Cases with different Péclet numbers (Pe) and Damköhler numbers (Da) were simulated, and five dissolution modes were obtained, which were finally summarized in a diagram of Pe and Da.

The use of a hypromellose based sorbent for a solid-phase extraction in the quantitative determination of procaine in combination drugs

Aim – to assess the selectivity and metrological characteristics of the spectrophotometric method for procaine determination in combination drugs using a solid-phase extraction sorbent based on hypromellose. Material and methods. The solid-phase extraction sorbent was obtained with hypromellose and ethyl cyanoacrylate; the procaine hydrochloride and sodium hydroxide formed the active centers. The sorbent was prepared using a standard method. The sorption capacity of the obtained sorbent samples for procaine was 10.2 ± 1.0 µg/g. For the study, we selected the combination drugs containing procaine and its salts, such as "Menovazin", "Sulfocamphocaine", and "Otolorin". The eluate optical density was registered using a SF-56 spectrophotometer (OKB SPECTR LLC) at an analytical wavelength of 292 nm in a cuvette with an optical layer thickness of 1 cm. The reference solution was a 0.1 M hydrochloric acid solution. To calculate the procaine content in the eluates, a calibration graph (dependence of eluate optical density on procaine concentration) was plotted in the concentration range of 1–20 mcg/ml. To evaluate the selectivity (specificity) of sample preparation in chromatographic separation of the combination drugs, the absorption spectra were registered in the wavelength range of 200–400 nm for eluates obtained using purified water and a 0.1 M hydrochloric acid solution. The procaine and benzocaine were identified in the eluate by the presence of absorption maxima at wavelengths of 222 and 286 nm for benzocaine, and 228 and 292 nm for procaine. For statistical processing of the experimental results and determination of metrological characteristics of the analysis method, we followed the GPM.1.1.0013 "Statistical processing of results of physical, physicochemical, and chemical tests". Results. We have demonstrated the selectivity of the spectrophotometric determination of procaine in certain combination drugs using a solid-phase extraction sorbent based on hypromellose. The selective binding of the analyzed substance with active centers in the sorbent and stepwise elution with purified water and a 0.1 M hydrochloric acid solution during solid-phase extraction eliminated the interfering effect of drug components during the UV-spectrophotometry of procaine. The use of a hypromellose based sorbent improved the metrological characteristics and reduced the systematic error of the quantitative determination method by an average of 14.4%. The proposed methodological approach using a selective sorbent might be recommended as the quality control for combination drugs containing procaine and its salts.

Development of Multigroup Monte Carlo Neutron Transport Method with Regionwise Even-Parity Discontinuity Factor

The multigroup Monte Carlo (MC) neutron transport method with a regionwise even-parity discontinuity factor (REPDF), i.e. the discontinuity factor (DF)–MC method, is developed with the aim to provide a reference solution for deterministic transport calculations with DF. Applying the analogy with optics, neutrons are transmitted or reflected at a region surface during random walks. The probability of transmission or reflection is determined by REPDFs in adjacent regions. The DF is traditionally used in deterministic neutron transport methods to reduce the discretization error due to spatial homogenization and energy condensation. The DF-MC method can treat DF in the framework of the multigroup MC method. In this paper, the weight cancellation technique based on the closest pair of points using the divide-and-conquer algorithm is used because negative weights appear due to the neutron reflection. The REPDF is calculated by the method of characteristics (MOC). The verification calculations are carried out in the pin-by-pin homogenized and assembly homogenized KAIST-2A core geometry. The DF-MC calculation can reproduce the results of the MOC with the REPDF. These results demonstrate the principle of the DF-MC method and extend the application of the DF to the probabilistic neutron transport method.

Sour, but acceptable: Taste responsiveness to five food-associated acids in zoo-housed white-faced sakis, Pithecia pithecia

White-faced sakis (Pithecia pithecia) are commonly considered as frugivores but are unusual among primates as they do not specialize on ripe fruits but rather include a high proportion of unripe fruits into their diet, even during seasons when ripe fruits are available. Using a two-bottle preference test of short duration we therefore assessed whether this dietary specialization affects the taste responsiveness and sour-taste tolerance of four adult white-faced sakis for five food-associated acids. We found taste preference thresholds of the sakis to be 1-10 mM for citric acid, 0.5-20 mM for ascorbic acid, 2-10 mM for malic acid, 0.1-1 mM for tannic acid, and 2-20 mM for acetic acid, respectively. When given the choice between a reference solution of 50 mM sucrose and mixtures containing varying concentrations of sucrose plus citric acid, the sakis displayed a high sour-taste tolerance and required only 100 mM of sucrose (when mixed with 10 mM citric acid) or 200 mM of sucrose (when mixed with 30 or 50 mM citric acid), respectively, to prefer the sweet-sour mixture over the purely sweet 50 mM sucrose reference solution. These results demonstrate that white-faced sakis have a well-developed taste sensitivity for food-associated acids which is not inferior to that of primates specializing on ripe fruits. Compared to other platyrrhine primates, the sakis displayed a markedly higher sour-taste tolerance. These results may therefore reflect an evolutionary adaptation to the dietary specialization of the white-faced sakis to sour-tasting unripe fruits.

T-stress extraction in arbitrarily cracked orthotropic composites with the numerical manifold method and Stroh formalism

The escalating utilization of composites over the past decades has necessitated the fracture investigation of orthotropic materials. The T-stress, namely, the first non-singular term of the normal stress parallel to the crack in William’s expansion, is of great significance for fracture analysis. In this work, the numerical manifold method (NMM) is advanced to assess the T-stress of arbitrary-shaped cracks (including non-intersecting cracks and multi-branched cracks) in two-dimensional orthotropic composites. Attributing to the bi-cover systems, the NMM can conveniently discretize the physical domain and naturally accommodate the discontinuity across crack surface. Meanwhile, the singularity at crack tip can be well captured by the wise choice of local approximation function. Through the application of interaction integral technology in the NMM postprocessing, the T-stress is extracted with the Stroh-form auxiliary fields. The accuracy of the proposed method is verified by comparing with reference solutions and then applied to arbitrarily branched and intersecting cracks. The results indicate that the present approach has convincing accuracy and also considerable convenience in T-stress evaluation. Additionally, the impacts of material orientations, crack geometries and loading conditions on the T-stress are also investigated.

Model-free chemomechanical interfaces: History-dependent damage under transient mass diffusion

This paper presents a data-driven framework based on distance functional for chemo-mechanical cohesive interfaces to capture transient diffusion and resulting interfacial damage evolution. The framework eliminates reliance on complex constitutive models and phenomenological assumptions, especially avoiding the coupling tangent terms with a given material database. The interfacial chemical potential and its jumps are used to expand the phase space for describing the chemical states of interfaces. Subsequently, a novel chemo-mechanical distance norm, including traction-separation pair, interfacial chemical potential-concentration pair and corresponding chemical potential jump-flux pair, is presented. Momentum conservation law for interfacial tractions and mass conservation law for interfacial concentration are enforced via Lagrange multipliers. For tracking the history-dependent state of the interface damage, an internal variable, termed interface integrity, is introduced to condition the interfacial database and manage the subsets mapping strategies, following physically motivated evolution constraints. Numerical examples are conducted to investigate the efficiency and capability of the present framework. A monotonic loading test validates a good numerical convergence relative to the number of data points. Subsequent cyclic loading simulations, compared with the reference solutions, show that the algorithm is well suitable to predict the history-dependent interface damage evolution under complex loading paths. Finally, the chemo-mechanically coupled examples capture phenomena such as interfacial swelling and interface degradation induced by transient diffusion and stress-driven diffusion. The current work provides a promising tool for understanding chemo-mechanical behaviors of interfaces within heterogeneous composites.

Analysis of okadaic acid using electrochemiluminescence imaging on microfluidic biosensing chip

The sensitivity and specificity of electrochemiluminescence (ECL)-based biosensor directly rely on the property of luminophor, the type of sensing carriers and the effectiveness of signal amplification used in the sensor design, which poses a major challenge to manage these elements simultaneously. In this work, an aggregation-induced electrochemiluminescence (AIECL) microfluidic sensing chip using 4′,4″,4‴,4‴'-(ethene-1,1,2,2-tetrayl)tetrabiphenyl-4-carboxylic acid (TPE)-derived hafnium-based metal-organic framework (Hf-MOF) as emitter was developed. An easily overlooked marine pollutant, okadaic acid (OA) with different concentrations ranging from 5.00 ng/mL to 1.50 × 104 ng/mL at the electrode is visualized imaging benefit from high luminescence efficiency of Hf-MOF coupled the rolling circle amplification strategy assisted by trans-cleavage activity of CRISPR/Cas12a. These highlights will solve the long-lasting task in the accurate analysis of small molecule pollutants, which can be able to provide more worthy reference solution about construction of novel ECL luminophor and signal extraction of low-abundance disease-related biomarkers.

A new seismic wave input method for canyon sites based on the finite element method-indirect boundary integral equation method

The seismic input is the basis for the seismic safety analysis of dams, but current seismic input methods have not reasonably considered the influence of canyon scattering effects on the dynamic response of dams. In this paper, the total motion field of the canyon is deconstructed into the free field of a uniform half space and the scattering field of the canyon and they are obtained separately. The indirect boundary integral equation method (IBIEM) is used to determine the scattering field of the canyon, which is superimposed with the free field to obtain the seismic ground motion field (total motion field) of the canyon. The accuracy of the total motion field of the canyon is verified through reference solutions. In the finite element analysis of seismic ground motion field in the canyon, the total motion field at the truncation boundary of the canyon foundation is transformed into the equivalent seismic input loads and the interior of the canyon are simulated using the finite element method (FEM). Then, based on the wave input for the free field combined with the viscoelastic artificial boundary, a new wave input method for the total motion field combined with the viscoelastic artificial boundary is established. The seismic wave input method based on the finite element-indirect boundary integral equation method is applied to numerically determine the seismic response of a trapezoidal canyon. The differences in the seismic response of the canyon under free-field input and total motion field input are discussed. The results show that there is a certain deviation between the displacement and waveform obtained from the free-field input and the solutions obtained from the indirect boundary integral equation method. There is a large error for a large angle of incidence, and the errors increase with increasing seismic wave frequency. When the incident angle is 60°, the maximum error in the frequency domain reaches 92.3 %, and the maximum error in the time domain reaches 250 %. The displacement amplitude and waveform of the canyon obtained from the total motion field input showed agreement with the results of the indirect boundary integral equation method. The wave input method established in this paper has high calculation accuracy and reasonably considers the scattering effect of canyons, which provides a basis for more accurate predictions of the seismic response of dams on canyon foundations.

RealTimeTransport: An open-source C++ library for quantum transport simulations in the strong coupling regime.

The description of quantum transport in the strong system-reservoir coupling regime poses a significant theoretical and computational challenge that demands specialized tools for accurate analysis. RealTimeTransport is a new open-source C++ library that enables the computation of both stationary and transient transport observables for generic quantum systems connected to metallic reservoirs. It computes the Nakajima-Zwanzig memory kernels for both dynamics and transport in real-time, going beyond traditional expansions in the bare system-reservoir couplings. Currently, several methods are available as follows: (i) A renormalized perturbation theory in leading and next-to-leading order, which avoids the low-temperature breakdown that limits the traditional theory. (ii) Starting from this well-behaved reference solution, a two- and three-loop, self-consistent renormalization-group transformation of the memory kernels is implemented. This allows refined quantitative predictions even in the presence of many body resonances, such as the Kondo enhancement of cotunneling. This paper provides an overview of the theory, the architecture of RealTimeTransport, and practical demonstrations of the currently implemented methods. In particular, we analyze the stationary transport through a serial double quantum dot and showcase for the T = 0 interacting Anderson model the complete time-development of single-electron tunneling (SET), cotunneling-assisted SET, and inelastic cotunneling resonances throughout the entire gate-bias stability diagram. We discuss the range of applicability of the implemented methods and benchmark them against other advanced approaches.

A Bayesian approach to modeling finite element discretization error

In this work, the uncertainty associated with the finite element discretization error is modeled following the Bayesian paradigm. First, a continuous formulation is derived, where a Gaussian process prior over the solution space is updated based on observations from a finite element discretization. To avoid the computation of intractable integrals, a second, finer, discretization is introduced that is assumed sufficiently dense to represent the true solution field. A prior distribution is assumed over the fine discretization, which is then updated based on observations from the coarse discretization. This yields a posterior distribution with a mean that serves as an estimate of the solution, and a covariance that models the uncertainty associated with this estimate. Two particular choices of prior are investigated: a prior defined implicitly by assigning a white noise distribution to the right-hand side term, and a prior whose covariance function is equal to the Green’s function of the partial differential equation. The former yields a posterior distribution with a mean close to the reference solution, but a covariance that contains little information regarding the finite element discretization error. The latter, on the other hand, yields posterior distribution with a mean equal to the coarse finite element solution, and a covariance with a close connection to the discretization error. For both choices of prior a contradiction arises, since the discretization error depends on the right-hand side term, but the posterior covariance does not. We demonstrate how, by rescaling the eigenvalues of the posterior covariance, this independence can be avoided.

Efficient Taste Analysis via Single-Channel Hybrid Electronic Tongue

The prospective applications of electronic tongues (e-tongues) in the food, water, beverage, and pharmaceutical industries have long been hampered by the inconvenient nature of series measurements using expensive and specialised sensor arrays. A cost-efficeint and easier solution to this problem arises in the shape of a single-channel hybrid e-tongue, presenting a novel approach to overcoming restrictions. This progress uses data fusion from potentiometry and impedimetry to combine these measures into a single channel made up of unfunctionalized metal electrodes supported by a pH electrode.The hybrid e-tongue combines potentiometric response, which includes pH and open circuit potential, with impedimetric response, which takes into account comparable electric circuit parameters such as charge transfer resistance and double-layer capacitance. The taste discriminability of this low-cost single-channel hybrid e-tongue is validated using two metal electrodes, Pt and Ni, and two separate sample preparations of basic taste analytes, each at concentrations around the human tongue threshold.Principal component analysis (PCA) plots are used to test qualitative discrimination by reducing dimensionality and clustering analytes. Silhouette coefficients (SC) and hierarchical cluster analysis are used to assess clustering quality. Even without particular sample preparation, the Pt and Ni electrodes exhibit substantial clustering with SC values of 0.83 and 0.74, respectively. This significant outcome highlights the efficacy of the hybrid e-tongue in improving taste discriminability.Comparisons with potentiometric and impedimetric measurements performed independently show that the hybrid e-tongue, assisted by data fusion at a single channel, improves accuracy and clustering significantly. This finding not only speeds up the analysis process, but it also improves the overall effectiveness of taste discrimination.Correlations between taste analytes and physicochemical factors are formed using heatmap plots and PCA loading plots to provide a fuller knowledge of the hybrid e-tongue's mechanics. These visualisations provide vital insights into the complex interplay of several physicochemical processes, offering insight into the mechanism underlying the hybrid e-tongue's excellent performance.discrimination.Despite its remarkable capabilities, the study acknowledges that taste discriminability diminishes due to the buffer activity of the standard reference solution used for sample preparation. This recognition prompts further exploration and optimization of the solution to ensure the broad applicability of the hybrid e-tongue across various scenarios.In conclusion, the reported single-channel hybrid e-tongue represents a significant advancement in taste analysis technology. By addressing the challenges associated with series measurements on complex sensor arrays, this innovation opens new avenues for commercial e-tongues in diverse industries. The amalgamation of potentiometry and impedimetry in a single channel not only enhances accuracy and clustering but also provides valuable mechanistic insights. As the research community continues to refine and optimize this technology, the future holds great promise for the widespread adoption of single-channel hybrid e-tongues in analytical applications, advancing how we perceive and understand taste.

Intelligent Fault Diagnosis Method for Rotating Machinery Based on Recurrence Binary Plot and DSD-CNN.

To tackle the issue of the traditional intelligent diagnostic algorithm's insufficient utilization of correlation characteristics within the time series of fault signals and to meet the challenges of accuracy and computational complexity in rotating machinery fault diagnosis, a novel approach based on a recurrence binary plot (RBP) and a lightweight, deep, separable, dilated convolutional neural network (DSD-CNN) is proposed. Firstly, a recursive encoding method is used to convert the fault vibration signals of rotating machinery into two-dimensional texture images, extracting feature information from the internal structure of the fault signals as the input for the model. Subsequently, leveraging the excellent feature extraction capabilities of a lightweight convolutional neural network embedded with attention modules, the fault diagnosis of rotating machinery is carried out. The experimental results using different datasets demonstrate that the proposed model achieves excellent diagnostic accuracy and computational efficiency. Additionally, compared with other representative fault diagnosis methods, this model shows better anti-noise performance under different noise test data, and it provides a reliable and efficient reference solution for rotating machinery fault-classification tasks.

An improved peridynamics topology optimization formulation for compliance minimization

This work proposes an improved peridynamics density-based topology optimization framework for compliance minimization. One of the main advantages of using a peridynamics discretization relies in the fact that it provides a consistent regularization of classical continuum mechanics into a nonlocal continuum, thus containing an inherent length scale called the horizon. Furthermore, this reformulation allows for discontinuities and is highly suitable for treating fracture and crack propagation. Partial differential equations are rewritten as integrodifferential equations and its numerical implementation can be straightforwardly done using meshfree collocation, inheriting its advantages. In the optimization formulation, Solid Isotropic Material with Penalization (SIMP) is used as interpolation for the design variables. To improve the peridynamic formulation and to evaluate the objective function in a energetically consistent manner, surface correction is implemented. Moreover, a detailed sensitivity analysis reveals an analytical expression for the objective function derivatives, different from an expression commonly used in the literature, providing an important basis for gradient-based topology optimization with peridynamics. The proposed implementation is studied with two examples illustrating different characteristics of this framework. The analytical expression for the sensitivities is validated against a reference solution, providing an improvement over the referred expression in the literature. Also, the effect of using the surface correction is evidenced. An extensive analysis of the horizon size and sensitivity filter radius indicates that the current method is mesh-independent, i.e. a sensitivity filter is redundant since peridynamics intrinsically filters length scales with the horizon. Different optimization methods are also tested for uncracked and cracked structures, demonstrating the capabilities and robustness of the proposed framework.

Fluid-structure coupling analysis in liquid-filled containers using scaled boundary finite element method

In this study, a semi-analytical model is developed to investigate the fluid-structure coupling characteristics of liquid sloshing in an elastic rectangular container subjected to horizontal external excitation based on the scaled boundary finite element method (SBFEM) for the first time. The fluid inside the container is assumed to be incompressible, inviscid and irrotational, with the hydrodynamic pressure chosen as independent nodal variable in the governing equations. The container walls are considered as cantilever beams. The coupled fluid-structure system is initially divided into the structural domain and fluid domain, after which the SBFEM is employed to obtain the governing equations for each sub-domain. In the framework of the SBFEM, only the boundary of each sub-domain, rather than the entire computational domain, needs to be meshed and discretized. This method reduces the spatial dimension of the problem by one and offers an efficient approach to model the computational domain, while allowing for analytical formulations to be derived for the internal of the domain, resulting in an accurate description of the field variables. The fundamental equation of the entire coupled fluid-structure system is then assembled by performing the equilibrium condition and compatibility condition to ensure the balance of interaction forces at the interface between container walls and the liquid. The free vibrations analysis of the fluid-structure coupling system is solved by utilizing the generalized eigenvalue problem, and the transient dynamic response is determined using the synchronous solution algorithm in conjunction with the implicit-implicit scheme of the Newmark method. To validate the excellent accuracy and stability of the proposed formulation, several numerical examples are presented to investigate the free vibration and transient dynamic characteristics for the fluid-structure coupling problem. The obtained results show good agreement with reference solutions available in the literature. Additionally, the effects of geometrical and material parameters on the system responses are examined and discussed.