Point Method Research Articles

Coupling transport equations to mechanics in the material point method using an approximate full capacity matrix inverse

Coupling solutions of one or more transport equations to mechanics modeling in the material point method (MPM), extends MPM to a platform for solving multi-physics problems. Unfortunately, the standard MPM approach to transport equations using a lumped transport capacity matrix is prone to large oscillations in particle values especially near interfaces, cracks, or rapid changes in transport value. Switching from lumped capacity matrix methods to an approximate full capacity matrix approach can eliminate those oscillations. Although this switch can cause unwanted numerical diffusion, that problem can be suppressed using periodic or blending options. Several examples illustrate the new methods for heat conduction, solvent transport, poroelasticity, and phase field fracture simulations. In thermal calculations, the new methods improve accuracy for tracking thermodynamics state functions.

Automatic History Matching for Adjusting Permeability Field of Fractured Basement Reservoir Simulation Model Using Seismic, Well Log, and Production Data

Developing automatic history matching (AHM) methods to replace the traditional manual history matching (MHM) approach in adjusting the permeability distribution of the reservoir simulation model has been studied by many authors. Because permeability values need to be evaluated at hundreds of thousands of grid cells in a typical reservoir simulation model, it is necessary to apply a reparameterization technique to allow the optimization algorithms to be implemented with fewer variables. In basic reparameterization techniques including zonation and pilot point methods, the calibrations are usually based solely on the production data with no systematic link to the geological and geophysical data, and therefore, the obtained permeability distribution may be not geologically consistent. Several other reparameterization techniques have attempted to preserve geological consistency by incorporating 4D seismic data; however, these techniques cannot be applied to our fractured basement reservoirs (FBRs) as they do not have 4D seismic data. Taking into account these challenges, in this study, an AHM methodology and workflow have been developed using a new reparameterization technique. This approach attempts to minimize the potential for geological nonconsistency of the calibrated results by linking the permeability to geophysical data. The proposed methodology can be applied to fields with only traditional geophysical data (3D seismic and conventional well logs). In the proposed workflow, the spatial distributions of seismic attributes and geomechanical properties were calculated and estimated from 3D seismic data and well logs, respectively. After that, a feed-forward artificial neural network (ANN) model trained by the back-propagation algorithm of the relationship between initial permeability with seismic attributes and geomechanical properties of their grid cell values is developed. Then, the calibration of the permeability distribution is performed by adjustment of the ANN model. Modification of the ANN model is performed using the simultaneous perturbation stochastic approximation (SPSA) algorithm to calibrate transmission coefficients in the ANN model to minimize the discrepancy between the simulated results and observed data. The developed methodology is applied to calibrate the permeability distribution of a simulation model of Bach Ho FBR in Vietnam. The effectiveness of the methodology is evident by comparing the historical matches with an available manually history-matched simulation model. The application shows that the proposed methodology could be considered as a suitable practical approach for adjusting the permeability distribution for FBR reservoir simulation models.

A Simplified Approach of Analytical Seismic Fragility Analysis Using the Endurance Time Method

ABSTRACT The endurance time (ET) method is an effective dynamic analysis method for seismic response analysis of structures. It has been recently used for analytical fragility analysis. However, the available ET-based fragility analysis methods have two limitations: 1) the prediction error of the structural median responses estimated by the ET method is ignored; and 2) the record-to-record variability inherent earthquake ground motions is not well considered. To overcome the above limitations, another ET-based fragility analysis method is proposed, where only three times of ET nonlinear analyses are required. To do this, three specific endurance time excitation functions (ETEFs) are generated in correspondence to the mean and 16% and 84% percentile of response spectra of a selected suite of ground motion records (i.e. ETE F m , ETE F v 1 and ETE F v 2 , respectively). The structural response under ETE F m is used to estimate the median response of structures under the selected suite of ground motion. Moreover, the structural responses under ETE F v 1 and ETE F v 2 are used to quantify the record-to-record variability in earthquake ground motions. The fragility relationships are developed by both point and interval estimate methods since another logarithmic standard deviation is introduced to account for the difference between the median responses predicted using ETE F m and those predicted by the dynamic analysis. To validate the proposed method, two RC frame structures with six and nine stories are taken as the study cases. The fragility results based on the proposed ET-based method and those based on the cloud method are compared. It is found that the proposed ET-based fragility analysis method could generate reliable fragility estimation, whereas requiring limited computation cost. The proposed method would provide another simplified way for the rapid fragility assessment of structures.

Study on copper-stainless steel explosive welding for nuclear fusion by generalized interpolated material point method and experiments

The thick copper stainless steel composite plate is an important component of the cooling coil terminal box of international nuclear fusion reactors. The composite rate, tensile strength, shear strength, and interface waveform of the metal plate are also far higher than the requirements of conventional explosive welding technology. It is difficult to obtain the best technical process parameters in a short time solely relying on conventional explosive welding tests. In order to solve the above-mentioned technical difficulties in explosive welding, this article applies the generalized interpolation material point method (GIMP) based on the explosive welding window, metal elastic-plastic mechanics, and explosive detonation theory to conduct macroscopic three-dimensional and microscopic two-dimensional numerical simulations of the copper stainless steel explosive welding process and the composite interface wave formation process, respectively. The experimental results demonstrate that the GIMP has significant advantages in numerical calculation and analysis for the explosive welding problem of high-speed impact collision of metal plates driven by explosive detonation, and it can effectively solve the technical problems of high technical specifications, low explosive processing composite rate, and low interface strength of large thickness copper stainless steel composite plates used in nuclear fusion.

B-spline convected particle domain interpolation method

The B-spline material point method (BSMPM) has been shown to be a promising approach to effectively mitigate the cell-crossing instability by using high-order B-spline basis functions. However, the BSMPM still suffers from the quadrature error, another well-known source of inaccuracy in the material point methods. On the other hand, the convected particle domain interpolation (CPDI) method effectively reduces the quadrature error by using alternative basis functions. The B-spline basis functions can be naturally used within the CPDI formulation, here called the BSCPDI method. The BSCPDI may be prone to the cell-crossing instability since the alternative basis functions in the BSCPDI are always C0-continuous despite the high-continuity of the B-spline basis functions used as the original grid basis functions. In this paper, the reproducibility of the BSCPDI effective basis function gradients and the susceptibility of the method to the cell-crossing instability are investigated analytically and numerically. The effectiveness of the BSCPDI in mitigating the quadrature error is also investigated through numerical simulations.

Measurement of a Freeform Surface by Dragging Three Point Method Along with a Circular Path

Freeform surfaces can realize optical systems with a wide field of view, high throughput, and high contrast. For constructing optical systems with freeform surfaces, measuring technology is essential. However, it is difficult to measure freeform surfaces by existing measurement methods. We have developed a new measurement method of the dragging three-point method (DTPM). To realize further improvement in the accuracy of the DTPM, we propose the DTPM with a circular path. Since the circular path is closed, the measurement error can be reduced by the boundary condition that the height and slope agree with at the start and end points of the measurement. To evaluate this method, we conducted the circular path measurement of an off-axis asphere. The measurement repeatability was RMS = 1.5 nm, and the result agreed well with that of an interferometric test; the difference was RMS = 17.2 nm.

A stable implicit nodal integration-based particle finite element method (N-PFEM) for modelling saturated soil dynamics

In this study, we present a novel nodal integration-based particle finite element method (N-PFEM) designed for the dynamic analysis of saturated soils. Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner (HR) variational principle, creating an implicit PFEM formulation. To mitigate the volumetric locking issue in low-order elements, we employ a node-based strain smoothing technique. By discretising field variables at the centre of smoothing cells, we achieve nodal integration over cells, eliminating the need for sophisticated mapping operations after re-meshing in the PFEM. We express the discretised governing equations as a min-max optimisation problem, which is further reformulated as a standard second-order cone programming (SOCP) problem. Stresses, pore water pressure, and displacements are simultaneously determined using the advanced primal-dual interior point method. Consequently, our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation. Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy, obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches. This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.

Global Existence and Uniqueness of Solutions of Integral Equations with Multiple Variable Delays and Integro Differential Equations: Progressive Contractions

In this work, we delve into a nonlinear integral equation (IEq) with multiple variable time delays and a nonlinear integro-differential equation (IDEq) without delay. Global existence and uniqueness (GEU) of solutions of that IEq with multiple variable time delays and IDEq are investigated by the fixed point method using progressive contractions, which are due to T.A. Burton. We prove four new theorems including sufficient conditions with regard to GEU of solutions of the equations. The results generalize and improve some related published results of the relevant literature.

DETECTION OF A SEISMIC SIGNAL BY A THREE-COMPONENT SEISMIC STATION AND DETERMINATION OF THE SEISMIC EVENT CENTER

Context. The work is devoted on the development of theoretical foundations aimed at automating process of determining location at the seismic event center.
 Objective. The purpose of the work is to develop a method for determining the center of a seismic event based on the use of the features of the angular characteristics of the constituent volume waves of a seismic signal obtained with the help of a threecomponent seismic station. The proposed method will reduce the time it takes to provide users with preliminary information about the fact of a seismic event and its parameters.
 Method. The method of automatic detection focal point is based on features of orthogonality in the angular characteristics volume waves registered sample of three-component seismic recordings from a certain direction. Implementation of the proposed approaches makes it possible to reduce the processing time of the seismic record with appropriate reliability compared to processing in manual mode.An example application of the proposed method (algorithm) for processing a seismic signal in the Vrancea zone on 27.10.2004 with magnitude M=5.7 is considered.
 Results. The proposed approach to processing the measured data of a separate seismic three-component seismic station using a polarization analysis device allows detecting the arrival of a seismic signal, identifying the main components of a seismic signal, and estimating the location of the epicenter of a seismic event.Experimental research on the use of the proposed algorithm for determining the location of the epicenter of a seismic event showed that the time of establishing an emergency event within the borders of Ukraine was reduced five times (from 15 to 3 minutes), and the detection error was 37 km.
 Conclusions. The formed basis and proposed approach to detecting a seismic signal, identifying its components and determining a seismic event focal point based on results of processing a three-component seismic record are effective. Proposed method (algorithm) should be used to automate process of seismic signal detection by a three-component seismic station and to determine the seismic event center.

A nonsmooth modified symplectic integration scheme for frictional contact dynamics of rigid–flexible multibody systems

Constructing an efficient high-order nonsmooth time-stepping integration scheme for rigid–flexible multibody systems with frictional contacts and impacts is a challenging task. This paper presents a nonsmooth modified symplectic integration scheme that can automatically achieve second-order convergence if possible. This scheme is obtained in three main steps. Firstly, the position coordinates are used to interpolate midpoint approximated integrals, which include velocity jumps implicitly; Secondly, a two-timestep central difference scheme is formulated to approximate the measure differential inclusions; Thirdly, composing two half-condensed two-timestep schemes leads to a one-timestep scheme, which retains the structure of a second-order scheme. Furthermore, while bilateral constraints are satisfied at the position level, unilateral constraints at the velocity level are subject to constraint drifts. To alleviate this issue, a classified cone complementarity problem is formulated to restrain penetration from deteriorating and sticking contacts from fictitious slipping. After time discretization, a set of nonlinear equations with cone complementarity conditions at each timestep is solved by a two-layer iterative computational strategy, where the outer layer is Newton iteration and the inner layer is a primal–dual interior point method. Several numerical examples demonstrate the high accuracy attained by the proposed method. Nonsmooth dynamics of a rigid–flexible robot involving high-speed and high-friction impacts can be simulated faster than real-time.

A Comparative Analysis of UAV Photogrammetric Software Performance for Forest 3D Modeling: A Case Study Using AgiSoft Photoscan, PIX4DMapper, and DJI Terra.

Three-dimensional (3D) modeling of trees has many applications in various areas, such as forest and urban planning, forest health monitoring, and carbon sequestration, to name a few. Unmanned Aerial Vehicle (UAV) photogrammetry has recently emerged as a low cost, rapid, and accurate method for 3D modeling of urban and forest trees replacing the costly traditional methods such as plot measurements and surveying. There are numerous commercial and open-source software programs available, each processing UAV data differently to generate forest 3D modeling and photogrammetric products, including point clouds, Digital Surface Models (DSMs), Canopy Height Models (CHMs), and orthophotos in forest areas. The objective of this study is to compare the three widely-used commercial software packages, namely, AgiSoft Photoscan (Metashape) V 1.7.3, PIX4DMapper (Pix4D) V 4.4.12, and DJI Terra V 3.7.6 for processing UAV data over forest areas from three perspectives: point cloud density and reconstruction quality, computational time, DSM assessment for height accuracy (z) and ability of tree detection on DSM. Three datasets, captured by UAVs on the same day at three different flight altitudes, were used in this study. The first, second, and third datasets were collected at altitudes of 60 m, 100 m, and 120 m, respectively over a forested area in Tully, New York. While the first and third datasets were taken horizontally, the second dataset was taken 20 degrees off-nadir to investigate the impact of oblique images. Results show that Pix4D and AgiSoft generate 2.5 times denser point clouds than DJI Terra. However, reconstruction quality evaluation using the Iterative Closest Point method (ICP) shows DJI Terra has fewer gaps in the point cloud and performed better than AgiSoft and Pix4D in generating a point cloud of trees, power lines and poles despite producing a fewer number of points. In other words, the outperformance in key points detection and an improved matching algorithm are key factors in generating improved final products. The computational time comparison demonstrates that the processing time for AgiSoft and DJI Terra is roughly half that of Pix4D. Furthermore, DSM elevation profiles demonstrate that the estimated height variations between the three software range from 0.5 m to 2.5 m. DJI Terra's estimated heights are generally greater than those of AgiSoft and Pix4D. Furthermore, DJI Terra outperforms AgiSoft and Pix4D for modeling the height contour of trees, buildings, and power lines and poles, followed by AgiSoft and Pix4D. Finally, in terms of the ability of tree detection, DJI Terra outperforms AgiSoft and Pix4D in generating a comprehensive DSM as a result of fewer gaps in the point cloud. Consequently, it stands out as the preferred choice for tree detection applications. The results of this paper can help 3D model users to have confidence in the reliability of the generated 3D models by comprehending the accuracy of the employed software.

Instabilities and Stabilities of Additive Functional Equation in Paranormed Spaces

In this paper, we solve the general solution in vector space and prove the Hyers-Ulam stability of the following additive functional equationin paranormed spaces by using the direct and fixed point methods. Also we present its pertinent counter examples for instabilities.

A Unified MPM Framework Supporting Phase-field Models and Elastic-viscoplastic Phase Transition

Recent years have witnessed the rapid deployment of numerous physics-based modeling and simulation algorithms and techniques for fluids, solids, and their delicate coupling in computer animation. However, it still remains a challenging problem to model the complex elastic-viscoplastic behaviors during fluid–solid phase transitions and facilitate their seamless interactions inside the same framework. In this article, we propose a practical method capable of simulating granular flows, viscoplastic liquids, elastic-plastic solids, rigid bodies, and interacting with each other, to support novel phenomena all heavily involving realistic phase transitions, including dissolution, melting, cooling, expansion, shrinking, and so on. At the physics level, we propose to combine and morph von Mises with Drucker–Prager and Cam–Clay yield models to establish a unified phase-field-driven EVP model, capable of describing the behaviors of granular, elastic, plastic, viscous materials, liquid, non-Newtonian fluids, and their smooth evolution. At the numerical level, we derive the discretization form of Cahn–Hilliard and Allen–Cahn equations with the material point method to effectively track the phase-field evolution, so as to avoid explicit handling of the boundary conditions at the interface. At the application level, we design a novel heuristic strategy to control specialized behaviors via user-defined schemes, including chemical potential, density curve, and so on. We exhibit a set of numerous experimental results consisting of challenging scenarios to validate the effectiveness and versatility of the new unified approach. This flexible and highly stable framework, founded upon the unified treatment and seamless coupling among various phases, and effective numerical discretization, has its unique advantage in animation creation toward novel phenomena heavily involving phase transitions with artistic creativity and guidance.

The effect of the Almalyk-Akhangaran industrial zone on changes in the groundwater level of the Ahangaran river basin

This article describes the state of groundwater and surface waters in the Akhangaran River basin, around the Almalyk Mining and Metallurgical Combine (AMMC), the amount of water consumed by the population of the city of Almalyk, the amount of precipitation in the region, and the annual flow regime of existing canals in the region. Comprehensive research methods, include the analysis of scientific and technical information on the geographical, hydrogeological, geomechanical and mineralogical compositions of the Almalyk-Akhangaran industrial zone, underground and surface waters, as well as the study of all valuable components by chemical, and X-ray structural methods, and atomic emission spectroscopy. Integration and point methods are used for measuring current velocity. Basic, detailed, abbreviated and graphical methods for measuring water flow are perfomed by electric metrs. Experimental filtration studies are carried out and systems of observation wells are organized. Additionally water temperature is measured with thermocouples and water density, salt concentration and water pH are measured using ionomers.

ЦИФРОВИЙ МЕНЕДЖМЕНТ ЯК СУЧАСНИЙ ТРЕНД РОЗВИТКУ ПІДПРИЄМСТВА

The article highlights the concept of digital management as a modern trend in the development of enterprise. The authors of the study noted that digital management is based on aspects of modern technical and economic development of society, on modern creative approaches to managing business processes of enterprise. The main directions of development of digital management are outlined. In order to study the possibility of improving the digital management system at the enterprise, it is recommended to carry out an assessment by the point method. Attention is focused on the fact that the assessment of digital management should be carried out in the context of management functions: planning, organization, coordination, motivation, control. The analysis showed that the functions of planning, organization and coordination of the accounting system of the studied enterprise function better than motivation and control. It is established that digital management is formed on the basis of a knowledge society, information use of components used in the so-called "smart society". In turn, the information and digital development of enterprises is based on information resources. The importance of information and digital management lies in its emphasis on digitalization, which is determined by the competence, qualifications and ability of specialists to solve complex computerization problems. It is determined that the main problems of digital management are that it is not sufficiently automated and developed to function independently, without the participation of managers. In addition, any changes in digitalization algorithms require the involvement of a large number of specialists, which makes the automation process even more complex than business processes without its participation. Insufficient level of qualification and insufficient number of specialists who can solve these problems promptly, do not allow you to create perfect software shells for business management. The publication identifies the tasks that need to be solved in order to create a unified system for automating business processes, as well as the parameters that allow compiling algorithms for digitalization of business management.

A Novel Method of Maximum Power Point Reaching for Magnetic Field Energy Harvesting Based on a Low-Power Analog Control Circuit

A Novel Method of Maximum Power Point Reaching for Magnetic Field Energy Harvesting Based on a Low-Power Analog Control Circuit

Selection method for observation points using Bayesian LASSO at estimating radiation source distribution from air dose rates

When we decommission a reactor building, it is essential to identify the radiation source distribution for safety. It has been reported that the source distribution can be predicted from the measured air dose rates at appropriate observation points by minimizing an evaluation function using the Least Absolute Shrinkage and Selection Operator (LASSO). However, it is challenging to decide on suitable points in advance. Therefore, we estimate the posterior distribution from the prior distribution of the source amounts, calculated by the standard LASSO, using the Bayesian LASSO. We then assess the predictive distribution of the air dose rates at the candidate observation points from the posterior distribution. We select the additional observation points based on the variances of the predictive distributions. We confirmed that the method can estimate the source distribution with fewer additional observation points than when adding them randomly in most cases.

Calculation method of equilibrium points for OCL in the longitudinal degrees of freedom

Calculation method of equilibrium points for OCL in the longitudinal degrees of freedom

A semi-probabilistic approach for assessing material and model uncertainty in the out-of-plane response of URM structures

A procedure tailored for a practical calibration of partial safety factors (PSF) related to input material properties is presented. The methodology addresses the propagation of material and model uncertainty through a FORM-based calibration, resulting in a noteworthy reduction in computation time compared to full probabilistic approaches. The novelty lies on the introduction of the Star Design with Central Point (SDCP) method for the computation of sensitivity coefficients and corresponding partial safety factors for material uncertainty. A calibration example is reported with reference to unreinforced masonry structures under out-of-plane failure. The effect of considering different geometries, failure modes, and modelling approaches is explored. A comparative analysis involving different approaches to propagate uncertainties emphasize the promising potential of the proposed procedure.

Data-driven revision of coal spontaneous combustion risk classification for prevailing methods used in Australian mining industry

Spontaneous combustion poses persistent hazards in underground coal mining operations, threatening personnel and operations. To assess this risk, in Australia small-scale laboratory tests are being conducted using Adiabatic Oxidation (R70), Crossing Point (CPT) and Minimum Self-Heating Temperature (SHTmin) methods. The intrinsic spontaneous combustion propensity classification (ISCP) utilizes R70 results to establish a risk rating. This risk ranking provides guidance on the severity of spontaneous combustion ranging from low to extremely high, aiding in the implementation of preventive measures. However, The ISCP lacks supporting literature, and there is no existing literature on correlation between laboratory tests or risk matrix for CPT. This paper presents the results of a Spearman correlation study among R70, CPT and SHTmin based on a large historical database (n = 318) showing that only R70 and CPT can be used to reliably rank spontaneous combustion risk. It was found that CPT is strongly correlated with R70 (ρ = -0.8875), but SHTmin shows a weaker correlation with R70 (ρ = -0.7265). The hierarchical clustering analysis resulted in a revised risk ranking: Low (R70 < 0.4 °C/h, CPT > 156 °C), Medium (0.4 °C/h < R70 < 3 °C/h, 132 °C < CPT < 156 °C), High (3 °C/h < R70 < 11 °C/h, 102 °C < CPT < 132 °C), and Very High (R70 > 11 °C/h, CPT < 102 °C).