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MJIDILA, Ahmed, Salah Eddine JALAL, Lahbib BOUSSHINE, and Zakaria EL LASKAOUI. "Nodal Integration Technique in Meshless Method." IOSR Journal of Mechanical and Civil Engineering 11, no. 1 (2014): 18–26. http://dx.doi.org/10.9790/1684-11141826.
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FENG, HUI, XIANGYANG CUI, and GUANGYAO LI. "STATIC AND DYNAMIC ANALYSIS OF TIMOSHENKO BEAM USING NODAL INTEGRATION TECHNIQUE." International Journal of Applied Mechanics 04, no. 04 (2012): 1250045. http://dx.doi.org/10.1142/s1758825112500457.
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In this paper, a nodal integration method (NIM) is presented to deal with the static and dynamic problems of Timoshenko beam. In the present method, linear-shape functions are employed to approximate the displacement field, and smoothing domains based on the nodes are further formed for computing the stiffness matrix. Through a smoothing operation, the shear locking is effectively avoided and the computation gets much simpler. For static problems, the upper bounds for a set of benchmark examples are obtained by nodal integration. For dynamic problems, while keeping the shear stiffness matrix the same as NIM, integration based on elements is adopted to construct the bending stiffness matrix to improve the stability and diminish singular modes caused by pure nodal integration. Results computed in this way prove to be much better than pure nodal integration method for free vibration and forced vibration problems. Numerical examples indicate that very accurate results can be obtained when a reasonable number of nodes is used. Both computational efficiency and accuracy are achieved by above formulations.
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Greco, Francesco, Domenico Umbrello, Serena Di Renzo, Luigino Filice, I. Alfaro, and E. Cueto. "Application of the Nodal Integrated Finite Element Method to Cutting: a Preliminary Comparison with the “Traditional” FEM Approach." Advanced Materials Research 223 (April 2011): 172–81. http://dx.doi.org/10.4028/www.scientific.net/amr.223.172.
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FEM implicit formulation shows specific limitations in processes such as cutting, where large deformation results in a heavy mesh distortion. Powerful rezoning-remeshing algorithms strongly reduce the effects of such a limitation but the computational times are significantly increased and additional errors are introduced. Nodal Integration is a recently introduced technique that allows finite element method to provide more reliable results when mesh becomes distorted in traditional FEMs. Furthermore, volumetric locking phenomenon seems to be avoided by using this integration technique instead of other methods, such as the coupled formulations. In this paper, a comparison between a “classical” FEM simulation and the Nodal Integration one is carried out taking into account a simple orthogonal cutting process.
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Liu, G. R., G. Y. Zhang, Y. Y. Wang, Z. H. Zhong, G. Y. Li, and X. Han. "A nodal integration technique for meshfree radial point interpolation method (NI-RPIM)." International Journal of Solids and Structures 44, no. 11-12 (2007): 3840–60. http://dx.doi.org/10.1016/j.ijsolstr.2006.10.025.
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Patel, Bhavana S. S., Babu K. S. Narayan, and Katta Venkataramana. "Strategy for refinement of nodal densities and integration cells in EFG technique." Structural Engineering and Mechanics 59, no. 5 (2016): 901–20. http://dx.doi.org/10.12989/sem.2016.59.5.901.
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Canales, Diego, Adrien Leygue, Francisco Chinesta, et al. "Efficient Updated-Lagrangian Simulations in Forming Processes." Key Engineering Materials 651-653 (July 2015): 1294–300. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.1294.
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A new efficient updated-Lagrangian strategy for numerical simulations of material forming processes is presented in this work. The basic ingredients are the in-plane-out-of-plane PGD-based decomposition and the use of a robust numerical integration technique (the Stabilized Conforming Nodal Integration). This strategy is of general purpose, although it is especially well suited for plateshape geometries. This paper is devoted to show the feasibility of the technique through some simple numerical examples.
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Horst, Vernon D., Hetal D. Patel, and Stan C. Hewlett. "Robotic Transhiatal Esophagectomy in a Community Hospital: Evolution of Technique." American Surgeon 82, no. 8 (2016): 730–32. http://dx.doi.org/10.1177/000313481608200832.
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Esophageal cancer is an uncommon but highly lethal disease. Surgical resection is the gold standard of treatment for early-stage disease. Traditional surgical approach entailed significant convalescence, hospital stay, and morbidity and mortality. Transhiatal esophagectomy (THE) involves blind dissection of the esophagus with minimal mediastinal lymphadenectomy. Integration of robotic surgery is an alternate platform for minimally invasive approach while maintaining safety and following oncologic principles. We review our technique for minimally invasive THE using robotic technology, demonstrating the safety and efficacy of robotic technology surgery. We present a retrospective review of a single surgeon's data of patients treated with robotic-assisted THE, with a chart review to evaluate pathology, adequacy of surgical resection, nodal harvest, and perioperative course. Robotic THE (rTHE) shows promise as a valid option for esophageal resection, including premalignant and advanced stages of cancer. Adequate transhiatal mediastinal nodal resection can be performed with the robot.
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Sun, Tingting, Peng Wang, Guanjun Zhang, and Yingbin Chai. "A Modified Radial Point Interpolation Method (M-RPIM) for Free Vibration Analysis of Two-Dimensional Solids." Mathematics 10, no. 16 (2022): 2889. http://dx.doi.org/10.3390/math10162889.
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The classical radial point interpolation method (RPIM) is a powerful meshfree numerical technique for engineering computation. In the original RPIM, the moving support domain for the quadrature point is usually employed for the field function approximation, but the local supports of the nodal shape functions are always not in alignment with the integration cells constructed for numerical integration. This misalignment can result in additional numerical integration error and lead to a loss in computation accuracy. In this work, a modified RPIM (M-RPIM) is proposed to address this issue. In the present M-RPIM, the misalignment between the constructed integration cells and the nodal shape function supports is successfully overcome by using a fixed support domain that can be easily constructed by the geometrical center of the integration cell. Several numerical examples of free vibration analysis are conducted to evaluate the abilities of the present M-RPIM and it is found that the computation accuracy of the original RPIM can be markedly improved by the present M-RPIM.
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Zhou, J. X., J. B. Wen, H. Y. Zhang, and L. Zhang. "A nodal integration and post-processing technique based on Voronoi diagram for Galerkin meshless methods." Computer Methods in Applied Mechanics and Engineering 192, no. 35-36 (2003): 3831–43. http://dx.doi.org/10.1016/s0045-7825(03)00376-1.
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CUI, X. Y., S. LIN, and G. Y. LI. "NODAL INTEGRATION THIN PLATE FORMULATION USING LINEAR INTERPOLATION AND TRIANGULAR CELLS." International Journal of Computational Methods 08, no. 04 (2011): 813–24. http://dx.doi.org/10.1142/s0219876211002848.
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This paper presents a thin plate formulation with nodal integration for bending analysis using three-node triangular cells and linear interpolation functions. The formulation was based on the classic thin plate theory, in which only deflection field was required and dealt with as the field variables. They were assumed to be piecewisely linear and expressed using a set of three-node triangular cells. Based on each node, the integration domain has been further derived, where the curvature in the domain was computed using a gradient smoothing technique (GST). As a result, the curvature in each integration domain is a constant whereby the deflection is compatible in the whole problem domain. The generalized smoothed Galerkin weak form is then used to create the discretized system equations where the system stiffness is obtained using simple summation operation. The essential rotational boundary conditions are imposed in the process of constructing the curvature field in conjunction with imposing the translational boundary conditions in the same way as undertaken in the standard FEM. A number of numerical examples were studied using the present formulation, including both static and free vibration analyses. The numerical results were compared with the reference ones together with those shown in the state-of-art literatures published. Very good accuracy has been achieved using the present method.
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Darbani, Mohsen. "The Meshfree Finite Element Method for Fluids with Large Deformations." Defect and Diffusion Forum 326-328 (April 2012): 176–80. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.176.
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The shallow water equations (SWE) is often simulated by using Eulerian descriptions. These phenomena may give rise to strong gradients and lead to large distortion of grids meshes. Hence classical finite elements methods may fall in simulating such problems. In this paper we present a meshless method, based on the natural element nethod (NEM). In a geometrical domain of a cloud of nodes, NEM uses the Voronoi cells and then its dual, namely Delaunay triangulation. Its main advantage lies in shape function of the natural neighbour interpolation, such that the position of natural neighbours is enough to its construction. To avoid the nonlinear term, the time material derivative term is discretized by a Lagrangian procedure. We also used an appropriate nodal integration technique to estimate integrals related to the diffusion, pressure and Coriolis terms because NEM shape functions are not polynomials and they are rational. For the diffusion term, the method of stabilized conforming nodal integration (SCNI) is proposed while for pressure and Coriolis terms a geometrical method will transform the integration over the cells domain to the integration over the edges. The method was successfully used to simulate dam-break flows by solving the fully 2D shallow water equations (SWE) by using an implicit scheme under a transient flow.
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Du, Yi Xian, Jin Run Hu, and Yi Zhang. "An Adaptive Element-Free Galerkin Method Based on the Strain Energy Density." Advanced Materials Research 677 (March 2013): 225–29. http://dx.doi.org/10.4028/www.scientific.net/amr.677.225.
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In practical study, an adaptive procedure based on the gradient of the strain energy density is developed for element-free Galerkin method using moving least-squares (MLS) approximation and global Galerkin formulation require a background mesh for domain integration. It comprises nodal strain energy density and a local domain refinement technique. The numerical experiments in this paper show that this adaptive element-free Galerkin method is simple, effective and efficient.
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Belinha, J., J. M. C. Azevedo, L. M. J. S. Dinis, and R. M. Natal Jorge. "The Natural Neighbor Radial Point Interpolation Method in Computational Fracture Mechanics: A 2D Preliminary Study." International Journal of Computational Methods 14, no. 04 (2017): 1750045. http://dx.doi.org/10.1142/s0219876217500451.
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In this work, the natural neighbor radial point interpolation method (NNRPIM) is extended to the numeric analysis of crack propagation problems. Here, the advanced discretization meshless technique is combined with a linear elastic crack growth algorithm. The algorithm simulates the crack propagation by displacing iteratively the crack tip, which consequently requires a local remeshing. In each iteration, it is estimated the stress state in the crack tip and afterwards the direction of the crack propagation is obtained considering the maximum circumferential stress criterion.The required local remeshing does not represent a numeric difficulty for the NNRPIM. The main advantage of the NNRPIM is its capability to fully discretize the problem domain using only an unstructured nodal distribution. Being a truly meshless method, the NNRPIM is able to define autonomously the nodal connectivity and the background integration mesh.The classic NNRPIM formulation permits to enforce the nodal connectivity by means of two kind of influence-cells: first degree influence-cells or second degree influence-cells. This work investigates the influence of the nodal connectivity on the simulated crack propagation path. Thus, demanding benchmark crack propagation examples are studied and the obtained results are compared with reference solutions available in the literature.
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Rathod, H. T., Md Shafiqul Islam, Bharath Rathod, and K. Sugantha Devi. "Finit element solution of Poisson Equation over Polygonal Domains using a novel auto mesh generation technique and an explicit integration scheme for linear convex quadrilaterals of cubic order Serendipity and Lagrange families." International Journal Of Engineering And Computer Science 7, no. 01 (2018): 23329–482. http://dx.doi.org/10.18535/ijecs/v7i1.01.
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This paper presents an explicit integration scheme to compute the stiffness matrix of twelve node and sixteen node linear convex quadrilateral finite elements of Serendipity and Lagrange families using an explicit integration scheme and discretisation of polygonal domain by such finite elements using a novel auto mesh generation technique, In finite element analysis, the boundary value problems governed by second order linear partial differential equations, the element stiffness matrices are expressed as integrals of the product of global derivatives over the linear convex quadrilateral region. These matrices can be shown to depend on the material properties matrices and the matrix of integrals with integrands as rational functions with polynomial numerator and the linear denominator (4+) in the bivariates over a 2-square (-1 ) with the nodes on the boundary and in the interior of this simple domain. The finite elements up to cubic order have nodes only on the boundary for Serendipity family and the finite elements with boundary as well as some interior nodes belong to the Lagrange family. The first order element is the bilinear convex quadrilateral finite element which is an exception and it belongs to both the families. We have for the present ,the cubic order finite elements which havee 12 boundary nodes at the nodal coordinates {(-1,-1),(1,-1),(1,1),(-1,1),(-1/3,-1), (1/3,-1),(1,-1/3),(1,1/3),(1/3,1),(-1/3,1),(-1,1/3),(-1,-1/3)} and the four interoior nodal coordinates at the points (-1/3,-1/3),(1/3,-1/3),(1/3,1/3),(-1/3,1/3)} in the local parametric space ( In this paper, we have computed the integrals of local derivative products with linear denominator (4+) in exact forms using the symbolic mathematics capabilities of MATLAB. The proposed explicit finite element integration scheme can be then applied to solve boundary value problems in continuum mechanics over convex polygonal domains. We have also developed a novel auto mesh generation technique of all 12-node and 16-node linear(straight edge) convex quadrilaterals for a polygonal domain which provides the nodal coordinates and the element connectivity. We have used the explicit integration scheme and this novel auto mesh generation technique to solve the Poisson equation u ,where u is an unknown physical variable and in with Dirichlet boundary conditions over the convex polygonal domain.
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Poirier, D., and M. Salcudean. "On Numerical Methods Used in Mathematical Modeling of Phase Change in Liquid Metals." Journal of Heat Transfer 110, no. 3 (1988): 562–70. http://dx.doi.org/10.1115/1.3250529.
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The work presents an analysis and comparative evaluation of different methods used for the numerical solution of heat conduction with phase change problems. Both freezing (melting) water as well as solidifying liquid metal problems are examined. Emphasis is placed on weak formulations as they tend to be simple to program and easily implemented in existing single-phase codes. A new method based on the apparent capacity technique is proposed. In this technique an “effective capacity” is computed, based on the integration of temperature profiles over the nodal volumes. This method shows significantly better performance when compared with other methods for the numerical analysis of solidifying metals.
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Jannesari, Zahra, and Mehdi Tatari. "A Meshfree Technique for Numerical Simulation of Reaction-Diffusion Systems in Developmental Biology." Advances in Applied Mathematics and Mechanics 9, no. 5 (2017): 1225–49. http://dx.doi.org/10.4208/aamm.2015.m1085.
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AbstractIn this work, element free Galerkin (EFG) method is posed for solving nonlinear, reaction-diffusion systems which are often employed in mathematical modeling in developmental biology. A predicator-corrector scheme is applied, to avoid directly solving of coupled nonlinear systems. The EFG method employs the moving least squares (MLS) approximation to construct shape functions. This method uses only a set of nodal points and a geometrical description of the body to discretize the governing equation. No mesh in the classical sense is needed. However a background mesh is used for integration purpose. Numerical solutions for two cases of interest, the Schnakenberg model and the Gierer-Meinhardt model, in various regions is presented to demonstrate the effects of various domain geometries on the resulting biological patterns.
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Tomashevskyi, Andrii. "NUMERICAL-ANALYTICAL TECHNIQUE FOR DETERMINING INTERNAL FORCES IN CROSS-SECTIONS OF BUILDING STRUCTURES." Collection of Scientific Works of the Ukrainian State University of Railway Transport, no. 211 (April 22, 2025): 101–12. https://doi.org/10.18664/1994-7852.211.2025.327330.
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This paper presents a numerical-analytical technique for determining internal forces in cross-sections of building structures that are modeled using finite element methods (FEM). The study focuses on structural components that, despite being represented by a set of finite elements of different dimensions (beam, plate, and volumetric elements), exhibit behavior similar to bar-like structures: pilons, short piers, lintels, deep beams, prefabricated floor slabs, wall panels, diaphragms, core walls.The methodology is based on summing nodal reactions from selected finite elements over a defined cross-section and transforming these forces into a chosen coordinate system. The proposed approach allows for determining internal forces in sections composed of multiple nodes and adjacent finite elements, ensuring consistency with engineering analysis and design principles. The results obtained through this approach can be used as standalone data for evaluating structural behavior or as input for further design calculations, including load-bearing capacity assessments, serviceability limit state verification, reinforcement calculation, and cross-section parameter determination.The implementation of this method in the LIRA-SAPR software system is discussed in detail. It is integrated into two subsystems: "Stone and Reinforced Masonry Structures" and "Bar Analogues". To validate the accuracy and applicability of the method, several verification problems are presented. These include structural models analyzed using beam elements, shell elements, and solid finite elements, with the computed internal forces being compared against theoretical values derived from classical mechanics of materials. The study demonstrates that the numerical-analytical approach produces results that are highly consistent with traditional beam theory calculations, confirming its validity for practical engineering applications.One of the key advantages of this approach is its ability to keep the structural integrity of the original finite element model while allowing engineers to obtain results in a format that aligns with standard design practices. Unlike traditional stress integration methods, which can be affected by local stress concentrations and numerical inaccuracies, the use of nodal reactions provides a more robust and reliable means of extracting internal forces from FEM models. Despite its advantages, the method requires careful selection of finite elements and nodal regions to ensure accurate force summation. The automation of this process within the LIRA-SAPR software significantly simplifies the task, providing engineers with an efficient tool for evaluating internal forces in complex structures.In conclusion, this numerical-analytical technique offers a powerful tool for engineers and researchers involved in structural analysis using finite element methods. Its integration into commercial structural engineering software ensures practical usability and efficiency, making it an essential advancement for modern engineering practice.
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Vacu, Malizukiswe Vincent, Chunjiao Jiang, Haojie Sun, et al. "Nodal Injection of Agrobacterium tumefaciens for Gene Functional Analysis in Peanut: An Appraisal." Agronomy 15, no. 2 (2025): 384. https://doi.org/10.3390/agronomy15020384.
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Peanut is a key cash crop worldwide, yet the limited availability of functional genes and markers for breeding hinders further progress, largely due to the lack of an efficient and user-friendly transformation system. This study aimed to comprehensively evaluate the effectiveness of nodal agroinjection, a novel transformation technique we developed for peanut, by introducing the soybean cold-tolerance gene SCTF-1. Putative transgenic seeds and seedlings were screened using genomic DNA PCR, while transgene expression was analyzed via qRT-PCR and phenotypic assessments. Southern blotting confirmed the stable integration of SCTF-1. The transgenic seedlings displayed enhanced chilling tolerance, characterized by increased proline accumulation, reduced malondialdehyde (MDA), and elevated peroxidase (POD) activity. These findings demonstrate that nodal agroinjection is an efficient and reliable approach for generating transgenic peanut and analyzing gene function. This method offers a promising alternative to conventional tissue culture-based transformation strategies.
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Ghoreishi, Farideh, and Elena Farahbakhsh-Tooli. "The Laguerre Collocation Method for Third Kind Integral Equations on Unbounded Domains." Computational Methods in Applied Mathematics 16, no. 2 (2016): 245–56. http://dx.doi.org/10.1515/cmam-2015-0038.
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AbstractThe aim of this paper is to approximate the solution of a class of integral equations of the third kind on an unbounded domain. For computing such approximation, the collocation method based on the generalized Laguerre abscissas is considered. In this method, the unknown function is interpolated at the nodal points ${\lbrace t_i\rbrace _{i=1}^{n+1}}$, where ${\lbrace t_i\rbrace _{i=1}^{n}}$ are the zeros of generalized Laguerre polynomials and ${t_{n+1}=4n}$. Then, the given equation is transformed to the Fredholm integral equation of the second kind. In the sequel, according to the integration interval, we apply the Gauss–Laguerre collocation method on the interval ${[0,\infty )}$ by using the given nodal points. Therefore, the solution of the third kind integral equation is reduced to the solution of a system of linear equations. Convergence analysis of the method in some Sobolev-type space is studied. Illustrative examples are included to demonstrate the validity and applicability of the technique.
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ALI, FARHAD, and M. A. KASSAR. "HYPERBOLIC CONSERVATION LAWS HAVING SOURCE TERMS AND DONOR CELL DIFFERENCING." International Journal of Modern Physics C 05, no. 03 (1994): 519–36. http://dx.doi.org/10.1142/s0129183194000702.
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Modifications in the integration of the source terms in hyperbolic conservation laws such as those governing combustion, detonation and radiative transport, with a first order upwind differencing technique are proposed and analysed. The von Neuman stability and phase error analysis for a linear scalar equation, together with a few test problems is presented in order to compare the performance of the resulting variants of the donor cell scheme. It is established that when the source term is integrated using higher order formulae, the resulting scheme gives better resolution and has better stability limit and phase accuracy, compared to the standard single nodal value replacement. It is shown that integration by the trapezoidal rule gives sufficient accuracy and further improvement may not necessarily be achieved using better methods, such as the Simpson’s rule.
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Diachuk, Maksym, and Said M. Easa. "Using Inverse Dynamics Technique in Planning Autonomous Vehicle Speed Mode Considering Physical Constraints." Highlights of Vehicles 1, no. 1 (2023): 29–53. http://dx.doi.org/10.54175/hveh1010003.
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The study aims at improving the technique of planning the autonomous vehicles’ (AV) speed mode based on a kinematic model with physical restrictions. A mathematical model relates the derivatives of kinematic parameters with ones of the trajectory’s curvature. The inverse approach uses an expanded vehicle model considering the distribution of vertical reactions, wheels’ longitudinal reactions according to a drive type, and lateral forces ensuring motion stability. For analysis of the drive type, four options are proposed: front-wheel drive (FWD), rear-wheel drive (RWD), permanent engaged all-wheel drive (AWD), and 4-wheel drive with torque vectoring (4WD-TV). The optimization model is also built by the inverse scheme. The longitudinal speed’s higher derivatives are modeled by the finite element (FE) functions with nodal unknowns. The sequential integrations ensure the optimality and smoothness of the third derivative. The kinematic restrictions are supplemented by the tire-road critical slip states. Sequential quadratic programming (SQP) and the Gaussian N-point scheme for quadrature integration are used to minimize the objective function. The simulation results show a significant difference in the mode forecasts between four types of AV drives at the same initial conditions. This technique allows redistributing the traction forces strictly according to the wheels’ adhesion potentials and increases the optimization performance by about 40% compared to using the kinematic model based on the same technique without physical constrains.
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Binesh, S. M., and A. Gholampour. "Mesh-Free Lower Bound Limit Analysis." International Journal of Computational Methods 12, no. 01 (2015): 1350105. http://dx.doi.org/10.1142/s0219876213501053.
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A novel numerical approach is developed for computing lower bound limit load in soil mechanics problems under plane strain condition. In the presented technique, there is no need to mesh in the traditional sense, and a lower bound solution is obtained. To develop the lower bound optimization problem, a statically admissible stress field is constructed by Shepard's shape functions in conjunction with the stabilized nodal integration scheme. The linearized Mohr–Coulomb criterion is adopted to satisfy the plastic admissibility of the generated stress field. The obtained optimization problem with a considerable reduced number of constraints has been solved by the linear programming technique. Based on the derived formulations, a computer code has been developed and the accuracy and efficiency of proposed method is demonstrated by solving some examples at the end of the paper.
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Oliveira, Carlos, Ana Pais, and Jorge Belinha. "Structural Optimisation of a Suspension Control Arm Using a Bi-Evolutionary Bone Remodelling Inspired Algorithm and the Radial Point Interpolation Method." Applied Sciences 15, no. 2 (2025): 502. https://doi.org/10.3390/app15020502.
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Today, topological structural optimisation is a valuable computational technique for designing mechanical components with optimal mass-to-stiffness ratios. Thus, this work aims to assess the performance of the Radial Point Interpolation Method (RPIM) when compared with the well-established Finite Element Method (FEM) within the context of a vehicle suspension control arm’s structural optimisation process. Additionally, another objective of this work is to propose an optimised design for the suspension control arm. Being a meshless method, RPIM allows one to discretise the problem’s domain with an unstructured nodal distribution. Since RPIM relies on a weak form equation to establish the system of equations, it is necessary to additionally discretise the problem domain with a set of background integration points. Then, using the influence domain concept, nodal connectivity is established for each integration point. RPIM shape functions are constructed using polynomial and radial basis functions with interpolating properties. The RPIM linear elastic formulation is then coupled with a bi-evolutionary bone remodelling algorithm, allowing for non-linear structural optimisation analyses and achieving solutions with optimal stiffness/mass ratios. In this work, a vehicle suspension control arm is analysed. The obtained solutions were evaluated, revealing that RPIM allows better solutions with enhanced truss connections and a higher number of intermediate densities. Assuming the obtained optimised solutions, four models are investigated, incorporating established design principles for material removal commonly used in vehicle suspension control arms. The proposed models showed a significant mass reduction, between 18.3% and 31.5%, without losing their stiffness in the same amount. It was found that the models presented a stiffness reduction between 5.4% and 9.8%. The obtained results show that RPIM is capable of delivering solutions similar to FEM, confirming it as an alternative numerical technique.
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Truong, Thien Tich, Nha Thanh Nguyen, Dinh Kien Nguyen, and Vay Siu Lo. "A novel nodal integration technique for meshfree methods based on the Cartesian transformation approach in the analysis of curved shells." Engineering Analysis with Boundary Elements 163 (June 2024): 69–83. http://dx.doi.org/10.1016/j.enganabound.2024.02.018.
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Shao, Weidong, and Jun Li. "An Absorbing Boundary Condition Based on Perfectly Matched Layer Technique Combined with Discontinuous Galerkin Boltzmann Method for Low Mach Number Flow Noise." Journal of Theoretical and Computational Acoustics 26, no. 04 (2018): 1850011. http://dx.doi.org/10.1142/s2591728518500111.
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For flow noise simulations, the nonreflecting boundary condition (NRBC) is significant to confine the computational domain to a small domain. Lattice Boltzmann method (LBM) has advantages for noise because of its low dissipation, but is limited to the uniform grid. In this paper, an absorbing boundary condition (ABC) based on perfectly matched layer (PML) technique is introduced to LBM. Then PML stability is analyzed and a new strategy is developed to achieve robustness. Invoking the decoupling time integration, the underlying equation for streaming is solved with the nodal discontinuous Galerkin method. Benchmark acoustic problems were used to demonstrate the PML absorption. Moreover, PML parameters, long time behavior and inhomogeneous pseudo mean flow are discussed. The methodology appears to work very well and would be hoped for practical flow noise computation.
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Shabana, A. "Dynamics of Inertia-Variant Flexible Systems Using Experimentally Identified Parameters." Journal of Mechanisms, Transmissions, and Automation in Design 108, no. 3 (1986): 358–66. http://dx.doi.org/10.1115/1.3258740.
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In this investigation modal parameters (frequency, damping, and mode shapes) which are determined experimentally using parameter estimation techniques are employed to simulate and predict the dynamic behavior of flexible multibody systems which consist of interconnected rigid and flexible components. The system differential equations of motion and algebraic constraint equations describing mechanical joints in the system are first identified using analytical techniques. Dynamic parameters such as mass, damping, and stiffness coefficients that appear in the system differential equations are then identified using a set of experimentally measured data. Mode shapes which are the result of the experimental identification are used to write the physical elastic coordinates of selected nodal points on the flexible body in terms of a reduced set of modal coordinates. The nonlinear differential and algebraic constraint equations are then written in terms of mixed sets of coupled reference and modal coordinates. These equations are integrated numerically using a direct numerical integration technique coupled with Newton–Raphson type iterations in order to check on constraint violations. The formulation developed is numerically exemplified using a three-dimensional dune buggy vehicle model.
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Isobe, Daigoro, Daisaku Imaizumi, Youichi Chikugo, and Shunsuke Sato. "A Parallel Solution Scheme for Inverse Dynamics and its Application in Feed-forward Control of Link Mechanisms." Journal of Robotics and Mechatronics 15, no. 1 (2003): 1–7. http://dx.doi.org/10.20965/jrm.2003.p0001.
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This paper describes a three-dimensional parallel solution scheme for inverse dynamics of link mechanisms, which has already been proposed for the two-dimensional case and applied in several in-plane motions. In this theory, the entire system is subdivided into finite elements and evaluated as a continuum. A single-link structure of a pin joint and a rigid bar is expressed using the Shifted Integration (SI) technique, which is conventionally used in finite element analyses of framed structures. This scheme calculates nodal forces by evaluating equations of motion in a matrix form, and thus information from the entire system can be handled in parallel, which is a very useful characteristic when applied in closed-loop or continuously transforming mechanisms. The obtained nodal forces are then converted into the joint torque in the system. Simple numerical tests on two-dimensional and threedimensional open-loop link mechanisms are carried out for comparison with other schemes. The proposed scheme is implemented in a control system to evaluate the performance in actual control with dynamics compensation, and some control experiments are carried out on an open-loop link mechanism. The results reveal the possibility of using the proposed solution scheme in feed-forward control, independently to the system configuration of link mechanisms.
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Huang, Yuan Mao, and Yung-Shane Liaw. "The Impact of Sliding Blades in a Rotary Compressor." Journal of Mechanical Design 123, no. 4 (1999): 583–89. http://dx.doi.org/10.1115/1.1416150.
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The purpose of this study was to analyze the impact of blades with slots in a rotary compressor. The equations for contact forces were derived from Newton’s law. Updated moving Lagrangian descriptions with the hybrid technique and the Newark time integration method were used to determine the nodal displacement vectors. The finite element method was used to analyze the contact forces and the stresses of blades. The maximum blade contact force of 2.3 KN was larger than the maximum static force of 1 KN. The maximum blade impact Von Mises stress of 12.3 Mpa that occurred at the contact point was greater than the previous calculated static stress of 5.15 Mpa. Hence, the impact effect was significant. Experimental modal analysis was also used to determine the first and second natural frequencies of blades.
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Pígl, Jan, and Radoslav Cipín. "Dynamic Model of Medium Voltage Vacuum Circuit Breaker and Induction Motor for Switching Transients Simulation Using Clark Transformation." Energies 16, no. 3 (2023): 1020. http://dx.doi.org/10.3390/en16031020.
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A derivation of the dynamic model of a medium voltage vacuum circuit breaker and induction motor in space vectors in coordinates allow us to model switching transients in various dynamic states of the motor. In the case of the Clark transformation, the corresponding numerical integration technique can be selected including variable time-step integration techniques to avoid numerical instabilities due to the stiffness of the system. Assymetrical operations such as switching cause the power system to become unbalanced and the transformed equations , and are not uncoupled. Therefore, it is necessary to derive a coupling matrix between circuit breaker voltages and currents in the coordinate system . The subject of our interest is switching overvoltages that arise when turning off small inductive currents by a vacuum circuit breaker. When deriving the model of a vacuum circuit breaker, all its properties encountered during this action are taken into account, i.e., current chop, virtual current chop, dielectric barrier in the circuit breaker and its recovery rate, and the ability of the vacuum circuit breaker to extinguish high frequency currents. Simulation results are compared with the measured results on a medium voltage motor as well as with the simulation results of the mathematical model of the test circuit according to IEC 62271-110 resolved using the nodal method (EMTP algorithm). Models are implemented in the MATLAB/Simulink programming environment.
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Kumar, Sushil, and Lionel Fourment. "Remapping Method for Transferring Data between Two Meshes Using a Modified Iterative SPR Approach for Parallel Resolution." Key Engineering Materials 504-506 (February 2012): 455–60. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.455.
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In metal forming simulations, the transfer of data from one mesh to another can be very often required such as, in ALE formulation at each time step or in Lagrangian formulation at each remeshing step. Its accuracy is one of the main concerns for researchers, since the accumulation of generated diffusion can lead to larger numerical error and create convergence problems. Since 1992, the Super convergent Patch Recovery method (SPR) introduced by Zienkiewicz & Zhu [1], was a major breakthrough for the methods to estimate errors in FE solution. Later, it has also been used to recover nodal fields from integration points, in order to transfer data between two meshes [10]. The original method raises some difficulties to treat the domain boundaries. They have not quite properly been handled, in particular in the frame of parallel implementation, despite the fact that, surface phenomena, such as contact and friction, play such an important role in metal forming applications. In the present paper, it is presented a modified iterative SPR method which deals with boundary points with the same order of accuracy as the interior points. It does not require increasing the patch size and it is easier to implement in parallel environment. Also, when interpolating the field on new mesh, a new and consistent technique (P0+ transport) of enriched field has been used. It involves building a P1+ field by mixing the recovered SPR nodal field with the known field at integration points. Results are presented in form of convergence rate and L2 error norm, for several analytical functions for a SPR based transfer operator against a simple volumetric based transfer operator, before being applied to an actual metal forming problem. All computations presented here have been done by using four processors in parallel environment.
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Hidayat, Mas Irfan Purbawanto, Bambang Ariwahjoedi, and Setyamartana Parman. "A new meshless local B-spline basis functions-FD method for two-dimensional heat conduction problems." International Journal of Numerical Methods for Heat & Fluid Flow 25, no. 2 (2015): 225–51. http://dx.doi.org/10.1108/hff-05-2013-0169.
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Purpose – The purpose of this paper is to present a new approach of meshless local B-spline based finite difference (FD) method for solving two dimensional transient heat conduction problems. Design/methodology/approach – In the present method, any governing equations are discretized by B-spline approximation which is implemented in the spirit of FD technique using a local B-spline collocation scheme. The key aspect of the method is that any derivative is stated as neighbouring nodal values based on B-spline interpolants. The set of neighbouring nodes are allowed to be randomly distributed thus enhanced flexibility in the numerical simulation can be obtained. The method requires no mesh connectivity at all for either field variable approximation or integration. Time integration is performed by using the Crank-Nicolson implicit time stepping technique. Findings – Several heat conduction problems in complex domains which represent for extended surfaces in industrial applications are examined to demonstrate the effectiveness of the present approach. Comparison of the obtained results with solutions from other numerical method available in literature is given. Excellent agreement with reference numerical method has been found. Research limitations/implications – The method is presented for 2D problems. Nevertheless, it would be also applicable for 3D problems. Practical implications – A transient two dimensional heat conduction in complex domains which represent for extended surfaces in industrial applications is presented. Originality/value – The presented new meshless local method is simple and accurate, while it is also suitable for analysis in domains of arbitrary geometries.
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Mendonça, Flávio dos Ramos de Sousa, Wilber Humberto Vélez Gómez, and Artur Antônio de Almeida Portela. "A local meshless analysis of dynamics problems / Uma análise local desordenada dos problemas dinâmicos." Brazilian Journal of Development 7, no. 10 (2021): 96793–812. http://dx.doi.org/10.34117/bjdv7n10-134.
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This paper is concerned with new formulations of local meshfree numerical method, for the solution of dynamic problems in linear elasticity, Integrated Local Mesh Free (ILMF) method. The key attribute of local numerical methods is the use of a modeling paradigm based on a node-by-node calculation, to generate the rows of the global system of equations of the body discretization. In the local domain, assigned to each node of a discretization, the work theorem is kinematically formulated, leading thus to an equation of mechanical equilibrium of the local node, that is used by local meshfree method as the starting point of the formulation. The main feature of this paper is the use of a linearly integrated local form of the work theorem. The linear reduced integration plays a key role in the behavior of local numerical methods, since it implies a reduction of the nodal stiffness which, in turn, leads to an increase of the solution accuracy. As a consequence, the derived meshfree and finite element numerical methods become fast and accurate, which is a feature of paramount importance, as far as computational efficiency of numerical methods is concerned. The cantilever beam was analyzed with this technique, in order to assess the accuracy and efficiency of the new local numerical method for dynamic problems with regular and irregular nodal configuration. The results obtained in this work are in perfect agreement with Mesh-Free Local Petrov-Galerkin (MLPG) and the Finite Element Method (FEM) solutions.
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I. Jurić-Grgić, M. Kurtović, and R. Lucić. "Numerical Analysis of Power System Electromechanical and Electromagnetic Transients based on the Finite Element Technique." Journal of Energy - Energija 59, no. 1-4 (2022): 38–45. http://dx.doi.org/10.37798/2010591-4276.
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This paper presents a novel technique for numerical analysis of electromagnetic transients and electromechanical oscillations in a power system. The proposed method is based on the finite element method (FEM). The finite element technique so far used for numerical analysis of continuum field problems here has been adopted to analyse electromagnetic and electromechanical transients in a power system. According to the finite element technique in the field problem, where the region of interest is divided into finite elements, in the proposed method power system is also divided into electric power system (finite) elements. Each finite element (generator, transformer, transmission line, load etc.) is characterized by a system of governing differential equations. Using generalized trapezoidal rule, also known as thetamethod for time integration, the system of differential equations of each electric power system (finite) element can be transformed to the system of algebraic equations for every time step. Once when a system of algebraic equations of each electric power system element is obtained, assembly procedure has to be done. The main contribution of the proposed approach is in an assembly procedure. With the proposed approach, in case of any disturbances in power system or in a part of power system, nodal voltage and branch currents will be obtained, as well as all other interesting variables. The proposed method will be tested on the example of the single-phase short circuit in the power system.
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Quarta, Leonardo, Donato Cannoletta, Francesco Pellegrino, et al. "The Role of Robot-Assisted, Imaging-Guided Surgery in Prostate Cancer Patients." Cancers 17, no. 9 (2025): 1401. https://doi.org/10.3390/cancers17091401.
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Emerging imaging-guided technologies, such as prostate-specific membrane antigen radioguided surgery (PSMA-RGS) and augmented reality (AR), could enhance the precision and efficacy of robot-assisted prostate cancer (PCa) surgical approaches, maximizing the surgeons’ ability to remove all cancer sites and thus patients’ outcomes. Sentinel node biopsy (SNB) represents an imaging-guided technique that could enhance nodal staging accuracy by leveraging lymphatic mapping with tracers. PSMA-RGS uses radiolabeled tracers with the aim to improve intraoperative lymph node metastases (LNMs) detection. Several studies demonstrated its feasibility and safety, with promising accuracy in nodal staging during robot-assisted radical prostatectomy (RARP) and in recurrence setting during salvage lymph node dissection (sLND) in patients who experience biochemical recurrence (BCR) after primary treatment and have positive PSMA positron emission tomography (PET). Near-infrared PSMA tracers, such as OTL78 and IS-002, have shown potential in intraoperative fluorescence-guided surgery, improving positive surgical margins (PSMs) and LNMs identification. Finally, augmented reality (AR), which integrates preoperative imaging (e.g., multiparametric magnetic resonance imaging [mpMRI] of the prostate and computed tomography [CT]) onto the surgical field, can provide a real-time visualization of anatomical structures through the creation of three-dimensional (3D) models. These technologies may assist surgeons during intraoperative procedures, thus optimizing the balance between oncological control and functional outcomes. However, challenges remain in standardizing these tools and assessing their impact on long-term PCa control. Overall, these advancements represent a paradigm shift toward personalized and precise surgical approaches, emphasizing the integration of innovative strategies to improve outcomes of PCa patients.
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Boscheri, Walter, and Raphaël Loubère. "High Order Accurate Direct Arbitrary-Lagrangian-Eulerian ADER-MOOD Finite Volume Schemes for Non-Conservative Hyperbolic Systems with Stiff Source Terms." Communications in Computational Physics 21, no. 1 (2016): 271–312. http://dx.doi.org/10.4208/cicp.oa-2015-0024.
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AbstractIn this paper we present a 2D/3D high order accurate finite volume scheme in the context of direct Arbitrary-Lagrangian-Eulerian algorithms for general hyperbolic systems of partial differential equations with non-conservative products and stiff source terms. This scheme is constructed with a single stencil polynomial reconstruction operator, a one-step space-time ADER integration which is suitably designed for dealing even with stiff sources, a nodal solver with relaxation to determine the mesh motion, a path-conservative integration technique for the treatment of non-conservative products and ana posterioristabilization procedure derived from the so-called Multidimensional Optimal Order Detection (MOOD) paradigm. In this work we consider the seven equation Baer-Nunziato model of compressible multi-phase flows as a representative model involving non-conservative products as well as relaxation source terms which are allowed to become stiff. The new scheme is validated against a set of test cases on 2D/3D unstructured moving meshes on parallel machines and the high order of accuracy achieved by the method is demonstrated by performing a numerical convergence study. Classical Riemann problems and explosion problems with exact solutions are simulated in 2D and 3D. The overall numerical code is also profiled to provide an estimate of the computational cost required by each component of the whole algorithm.
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Phuc, Ho Le Huy, Le Van Canh, and Phan Duc Hung. "A computational homogenization analysis of materials using the stabilized mesh-free method based on the radial basis functions." Journal of Science and Technology in Civil Engineering (STCE) - NUCE 14, no. 1 (2020): 65–76. http://dx.doi.org/10.31814/stce.nuce2020-14(1)-06.
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This study presents a novel application of mesh-free method using the smoothed-radial basis functions for the computational homogenization analysis of materials. The displacement field corresponding to the scattered nodes within the representative volume element (RVE) is split into two parts including mean term and fluctuation term, and then the fluctuation one is approximated using the integrated radial basis function (iRBF) method. Due to the use of the stabilized conforming nodal integration (SCNI) technique, the strain rate is smoothed at discreted nodes; therefore, all constrains in resulting problems are enforced at nodes directly. Taking advantage of the shape function satisfies Kronecker-delta property, the periodic boundary conditions well-known as the most appropriate procedure for RVE are similarly imposed as in the finite element method. Several numerical examples are investigated to observe the computational aspect of iRBF procedure. The good agreement of the results in comparison with those reported in other studies demonstrates the accuracy and reliability of proposed approach.
 Keywords:
 homogenization analysis; mesh-free method; radial point interpolation method; SCNI scheme.
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Olivier, Gerrit, Braeden Borg, Lawrence Trevor, et al. "Fleet’s Geode: A Breakthrough Sensor for Real-Time Ambient Seismic Noise Tomography over DtS-IoT." Sensors 22, no. 21 (2022): 8372. http://dx.doi.org/10.3390/s22218372.
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As most of the outcropping and shallow mineral deposits have been found, new technology is imperative to finding the hidden critical mineral deposits required to transition to renewable energy. One such new technique, called ambient seismic noise tomography, has shown promise in recent years as a low-cost, low environmental impact method that can image under cover and at depth. Wireless and compact nodal seismic technology has been instrumental to enable industry applications of ambient noise tomography, but these devices are designed for the active seismic reflection method and do not have the required sensitivity at low frequencies for ambient noise tomography, and real-time data transmission in remote locations requires significant infrastructure to be installed. In this paper, we show the development and testing of the Geode—a real-time seismic node purpose-built by Fleet Space Technologies for ambient seismic noise tomography on exploration scales. We discuss the key differences between current nodal technology and the Geode and show results of a field trial where the performance of the Geode is compared with a commercially popular nodal geophone. The use of a 2 Hz high sensitivity geophone and low noise digitiser results in an instrument noise floor that is more than 30 dB lower below 5 Hz than nodes that are commonly used in the industry. The increased sensitivity results in signal-to-noise ratios in the cross-correlation functions in the field trial that are more than double that of commercially available nodal geophone at low frequencies. When considering the full bandwidth of retrievable correlations in our study, using the Geode would reduce the required recording time from 75 h to 32 h to achieve an average signal-to-noise ratio in the cross-correlation functions of 10. We also discuss the integration of a real-time direct-to-satellite Internet of Things (DtS-IoT) modem in the Geode, which, together with edge processing of seismic data directly on the Geode, enables us to image the subsurface in real-time. During the field trial, the Geodes successfully transmitted more than 90% of the available preprocessed data packets. The Geode is compact enough so that several devices can be carried and installed by one field technician, whilst the array of stations do not require a base station to transmit data to the cloud for further processing. We believe this is the future of passive seismic surveys and will result in faster and more dynamic seismic imaging capabilities analogous to the medical imaging community, increasing the pace at which new mineral deposits are discovered.
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Belinha, Jorge. "Multiscale Analysis of Sandwich Beams with Polyurethane Foam Core: A Comparative Study of Finite Element Methods and Radial Point Interpolation Method." Materials 17, no. 18 (2024): 4466. http://dx.doi.org/10.3390/ma17184466.
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This study presents a comprehensive multiscale analysis of sandwich beams with a polyurethane foam (PUF) core, delivering a numerical comparison between finite element methods (FEMs) and a meshless method: the radial point interpolation method (RPIM). This work aims to combine RPIM with homogenisation techniques for multiscale analysis, being divided in two phases. In the first phase, bulk PUF material was modified by incorporating circular holes to create PUFs with varying volume fractions. Then, using a homogenisation technique coupled with FEM and four versions of RPIM, the homogenised mechanical properties of distinct PUF with different volume fractions were determined. It was observed that RPIM formulations, with higher-order integration schemes, are capable of approximating the solution and field smoothness of high-order FEM formulations. However, seeking a comparable field smoothness represents prohibitive computational costs for RPIM formulations. In a second phase, the obtained homogenised mechanical properties were applied to large-scale sandwich beam problems with homogeneous and approximately functionally graded cores, showing RPIM’s capability to closely approximate FEM results. The analysis of stress distributions along the thickness of the beam highlighted RPIM’s tendency to yield lower stress values near domain edges, albeit with convergence towards agreement among different formulations. It was found that RPIM formulations with lower nodal connectivity are very efficient, balancing computational cost and accuracy. Overall, this study shows RPIM’s viability as an alternative to FEM for addressing practical elasticity applications.
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Katib, Yousef, Steven Tisseverasinghe, Ian J. Gerard, et al. "Evaluating the Effects of Prostate Radiotherapy Intensified with Pelvic Nodal Radiotherapy and Androgen Deprivation Therapy on Myelosuppression: Single-Institution Experience." Current Oncology 31, no. 9 (2024): 5439–51. http://dx.doi.org/10.3390/curroncol31090402.
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Background: Prostate cancer (PCa) management commonly involves the utilization of prostate radiotherapy (PRT), pelvic nodal radiotherapy (PNRT), and androgen deprivation therapy (ADT). However, the potential association of these treatment modalities with bone marrow (BM) suppression remains inadequately reported in the existing literature. This study is designed to comprehensively evaluate the risk of myelosuppression associated with PRT, shedding light on an aspect that has been underrepresented in prior research. Materials and Methods: We conducted a retrospective analysis of 600 patients with prostate cancer (PCa) treated with prostate radiotherapy (PRT) at a single oncology center between 2007 and 2017. Patients were categorized into four cohorts: PRT alone (n = 149), PRT + ADT, (n = 91), PRT + PNRT (n = 39), and PRT + PNRT + ADT (n = 321). To assess the risk of myelosuppression, we scrutinized specific blood parameters, such as hemoglobin (HGB), white blood cells (WBCs), neutrophils (NEUT), lymphocytes (LYM), and platelets (PLT) at baseline, mid-treatment (mRT), immediately post-RT (pRT), 1 month post-RT (1M-pRT), and 1 year post-RT (1Y-pRT). The inter-cohort statistical significance was evaluated with further stratification based on the utilized RT technique {3D conformal radiotherapy (3D-CRT), and intensity-modulated radiation therapy (IMRT)}. Results: Significant statistical differences at baseline were observed in HGB and LYM values among all cohorts (p < 0.05). Patients in the PRT + PNRT + ADT cohort had significantly lower HGB at baseline and 1M-pRT. In patients undergoing ADT, BMS had a significant impact at 1M-pRT {odds ratio (OR) 9.1; 95% Confidence Interval (CI) 4.8–17.1} and at 1Y-pRT (OR 2.84; CI 1.14–7.08). The use of 3D-CRT was linked to reduced HGB levels in the PRT + PNRT + ADT group at 1 month pRT (p = 0.015). Similarly, PNRT significantly impacted BMS at 1M-pRT (OR 6.7; CI 2.6–17.2). PNRT increased the odds of decreased WBC counts at 1Y-pRT (OR 6.83; CI: 1.02–45.82). Treatment with any RT techniques (3D-CRT or IMRT), particularly in the PRT + PNRT and PRT + PNRT + ADT groups, significantly increased the odds of low LYM counts at all time points except immediately pRT (p < 0.05). Furthermore, NEUT counts were considerably lower at 1M-pRT (p < 0.05) in the PRT + PNRT + ADT group. PLT counts were significantly decreased by PRT + PNRT + ADT at mRT (OR 2.57; 95% CI: 1.42–4.66) but were not significantly impacted by the RT technique. Conclusions: Treatment with PRT, ADT, PNRT, and 3D-CRT is associated with BMS. Despite this statistically significant risk, no patient required additional interventions to manage the outcome. While its clinical impact appears limited, its importance cannot be underestimated in the context of increased integration of novel systemic agents with myelosuppressive properties. Longer follow-up should be considered in future studies.
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Chen, Cheng, Kai Yuan, Winnie Chiu-wing Chu, and Raymond Kai-yu Tong. "The Effects of 10 Hz and 20 Hz tACS in Network Integration and Segregation in Chronic Stroke: A Graph Theoretical fMRI Study." Brain Sciences 11, no. 3 (2021): 377. http://dx.doi.org/10.3390/brainsci11030377.
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Transcranial alternating current stimulation (tACS) has emerged as a promising technique to non-invasively modulate the endogenous oscillations in the human brain. Despite its clinical potential to be applied in routine rehabilitation therapies, the underlying modulation mechanism has not been thoroughly understood, especially for patients with neurological disorders, including stroke. In this study, we aimed to investigate the frequency-specific stimulation effect of tACS in chronic stroke. Thirteen chronic stroke patients underwent tACS intervention, while resting-state functional magnetic resonance imaging (fMRI) data were collected under various frequencies (sham, 10 Hz and 20 Hz). The graph theoretical analysis indicated that 20 Hz tACS might facilitate local segregation in motor-related regions and global integration at the whole-brain level. However, 10 Hz was only observed to increase the segregation from whole-brain level. Additionally, it is also observed that, for the network in motor-related regions, the nodal clustering characteristic was decreased after 10 Hz tACS, but increased after 20 Hz tACS. Taken together, our results suggested that tACS in various frequencies might induce heterogeneous modulation effects in lesioned brains. Specifically, 20 Hz tACS might induce more modulation effects, especially in motor-related regions, and they have the potential to be applied in rehabilitation therapies to facilitate neuromodulation. Our findings might shed light on the mechanism of neural responses to tACS and facilitate effectively designing stimulation protocols with tACS in stroke in the future.
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Karpyn, A. B., N. G. Orlova, T. M. Rozhnova, and Yu L. Orlov. "Computer reconstruction of the interaction of genes associated with Angelman syndrome." Russian Journal of Telemedicine and E-Health 10, no. 4 (2024): 7–19. https://doi.org/10.29188/2712-9217-2024-10-4-7-19.
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Reconstruction of the structure of the gene network for a set of genes associated with the disease makes it possible to determine the effectiveness of diagnosis and therapy, and to study the possibilities of targeted drug effects on target genes. The study of Angelman syndrome, a hereditary disorder of the development of the nervous system by modern means of bioinformatics, involves the search for associated genes as targets for medicinal effects. Angelman syndrome is characterized by developmental delay, severe learning difficulties, ataxia, convulsive disorder, and changes in character and behavior. Based on database queries, a set of genes was built and the gene network of this disease was reconstructed (graphical representation). Gene ontologies for genes associated with Angelman syndrome are considered, their connection with hormones and the development of the nervous system is shown. The structure of the network is investigated, nodal genes are found, and their functional annotation is presented. Network clusters are highlighted. The technique of using online bioinformatics tools for the reconstruction of gene networks of rare and complex diseases is shown. A network of related diseases has been built for Angelman syndrome, and the role of the UBE3A gene has been described. Using the example of Angelman syndrome, the role of database integration for gene search for therapy is discussed.
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Diachuk, Maksym, and Said M. Easa. "Improved Technique for Autonomous Vehicle Motion Planning Based on Integral Constraints and Sequential Optimization." Vehicles 4, no. 4 (2022): 1122–57. http://dx.doi.org/10.3390/vehicles4040060.
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The study is dedicated to elaborating and analyzing a technique for autonomous vehicle (AV) motion planning based on sequential trajectory and kinematics optimization. The proposed approach combines the finite element method (FEM) basics and nonlinear optimization with nonlinear constraints. There were five main innovative aspects introduced in the study. First, a 7-degree polynomial was used to improve the continuity of piecewise functions representing the motion curves, providing 4 degrees of freedom (DOF) in a node. This approach allows using the irregular grid for roadway segments, increasing spans where the curvature changes slightly, and reducing steps in the vicinity of the significant inflections of motion boundaries. Therefore, the segment length depends on such factors as static and moving obstacles, average road section curvature, camera sight distance, and road conditions (adhesion). Second, since the method implies splitting the optimization stages, a strategy for bypassing the moving obstacles out of direct time dependency was developed. Thus, the permissible area for maneuvering was determined using criteria of safety distance between vehicles and physical limitation of tire–road adhesion. Third, the nodal inequality constraints were replaced by the nonlinear integral equality constraints. In contrast to the generally distributed approach of restricting the planning parameters in nodes, the technique of integral equality constraints ensures the disposition of motion parameters’ curves strictly within the preset boundaries, which is especially important for quite long segments. In this way, the reliability and stability of predicted parameters are improved. Fourth, the seamless continuity of both the sought parameters and their derivatives is ensured in transitional nodes between the planning phases and adjacent global coordinate systems. Finally, the problem of optimization rapidity to match real-time operation requirements was addressed. For this, the quadrature integration approach was implemented to represent and keep all the parameters in numerical form. The study considered cost functions, limitations stipulated by the vehicle kinematics and dynamics, as well as initial and transient conditions between the planning stages. Simulation examples of the predicted trajectories and curves of kinematic parameters are demonstrated. The advantages and limitations of the proposed approach are highlighted.
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Choi, S. J., F. X. Giraldo, J. Kim, and S. Shin. "Verification of a non-hydrostatic dynamical core using the horizontal spectral element method and vertical finite difference method: 2-D aspects." Geoscientific Model Development 7, no. 6 (2014): 2717–31. http://dx.doi.org/10.5194/gmd-7-2717-2014.
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Abstract. The non-hydrostatic (NH) compressible Euler equations for dry atmosphere were solved in a simplified two-dimensional (2-D) slice framework employing a spectral element method (SEM) for the horizontal discretization and a finite difference method (FDM) for the vertical discretization. By using horizontal SEM, which decomposes the physical domain into smaller pieces with a small communication stencil, a high level of scalability can be achieved. By using vertical FDM, an easy method for coupling the dynamics and existing physics packages can be provided. The SEM uses high-order nodal basis functions associated with Lagrange polynomials based on Gauss–Lobatto–Legendre (GLL) quadrature points. The FDM employs a third-order upwind-biased scheme for the vertical flux terms and a centered finite difference scheme for the vertical derivative and integral terms. For temporal integration, a time-split, third-order Runge–Kutta (RK3) integration technique was applied. The Euler equations that were used here are in flux form based on the hydrostatic pressure vertical coordinate. The equations are the same as those used in the Weather Research and Forecasting (WRF) model, but a hybrid sigma–pressure vertical coordinate was implemented in this model. We validated the model by conducting the widely used standard tests: linear hydrostatic mountain wave, tracer advection, and gravity wave over the Schär-type mountain, as well as density current, inertia–gravity wave, and rising thermal bubble. The results from these tests demonstrated that the model using the horizontal SEM and the vertical FDM is accurate and robust provided sufficient diffusion is applied. The results with various horizontal resolutions also showed convergence of second-order accuracy due to the accuracy of the time integration scheme and that of the vertical direction, although high-order basis functions were used in the horizontal. By using the 2-D slice model, we effectively showed that the combined spatial discretization method of the spectral element and finite difference methods in the horizontal and vertical directions, respectively, offers a viable method for development of an NH dynamical core.
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Jia, Xichun, Xuebing Jiang, Jun Huang, Shunchao Yu, and Bingjun Liu. "Slope Stability Analysis Based on the Explicit Smoothed Particle Finite Element Method." Sustainability 16, no. 2 (2024): 702. http://dx.doi.org/10.3390/su16020702.
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A landslide is a common natural disaster that causes environmental damage, casualties and economic losses, which seriously affects the sustainable development of society. In geomechanics, it is one of the largest deformation problems. Herein, the GPU-accelerated explicit smoothed particle finite element method (eSPFEM) for large deformation analysis in geomechanics was developed on the CUDA platform based on high-performance computing using a self-designed eSPFEM program code. The eSPFEM combines the strain smoothing nodal integration techniques found in the particle finite element method (PFEM) framework, which allows for the use of low-order triangular elements without volume locking and avoids frequent information transfer and mapping errors between Gaussian points and particles in PFEM. A numerical simulation of slope instability using the eSPFEM and based on a strength reduction technique was conducted using various examples, including a cohesive homogeneous slope, a non-cohesive homogeneous slope, a non-homogeneous slope and a slope with a thin soft band. The calculation results show that the eSPFEM can be applied to slope stability analysis under different working conditions, simulating the entire process of slope instability initiation, sliding and reaccumulation, and obtaining reliable FOS values. A numerical simulation was conducted to analyse a landslide that occurred in the Zhangjiazhuang tunnel on the Lanzhou–Xinjiang high-speed railway line on 18 January 2016. A natural unsaturated soil slope, a soil slope with a high moisture content and a soil slope with a high moisture content subjected to an earthquake were analysed. The findings of this study are in good agreement with the actual slope failure conditions. The primary triggers identified for the landslide were heavy rainfall and earthquakes. The verification results indicate that the eSPFEM can effectively simulate an actual landslide case, showcasing high accuracy and applicability in simulating the large deformation behaviour of landslides.
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Bazhenov, V. G., A. I. Kibets, A. V. Demareva, and Yu A. Kalinina. "ALGORITHM FOR CONSERVATIVE SMOOTHING OF STRESS WAVES IN FEM." Problems of Strength and Plasticity 84, no. 3 (2022): 331–42. http://dx.doi.org/10.32326/1814-9146-2022-84-3-331-342.
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Three-dimensional geometrically and physically nonlinear problems of nonstationary deformation of structures are considered. The defining system of equations is formulated in Lagrange variables. The equation of motion is derived from the balance of virtual work capacities. The elastic-plastic deformation of structural materials is described by the relations of the flow theory with isotropic hardening. The solution of the problem is based on the moment scheme of the finite element method. The discretization of the problem by spatial variables is carried out by eight nodal finite elements with multilinear functions of the approximation form of the displacement velocity. Time integration is performed according to an explicit finite-difference scheme of the “cross” type, which does not have the monotonicity property. Due to the dispersion in the vicinity of the gap, it generates non-physical oscillations, which significantly limits the scope of its applicability. In this paper, to suppress high-frequency oscillations, it is proposed to use an algorithm for conservative smoothing of a numerical solution with a space-time monotony analyzer. Based on it, software modules have been developed for the “Dynamics-3” computing complex. Verification of the developed technique and its software implementation was carried out by solving a one-dimensional problem in a three-dimensional formulation of the compression wave passing through a fixed elastic layer. For comparison, the results of numerical solution of the problem according to the “cross” scheme without smoothing, with linear viscosity, with conservative smoothing using spatial and spatiotemporal monotonicity analyzers are obtained. The problem of penetration of an elastic cylinder into a round steel plate is solved in a three-dimensional formulation. It is shown that the developed technique not only suppresses high-frequency oscillations, but also prevents the occurrence of zero-energy modes. So, in the second problem, without using the procedure of conservative smoothing of the numerical solution, the final elements of the plate in the collision zone are significantly distorted, which leads to an early interruption of the calculation.
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Pi, Jun, and Xi Peng Xu. "Design of Integration Tool-Holder System for Ultrasonic Vibration Machining Using Contactless Inductive Power Transfer." Advanced Materials Research 69-70 (May 2009): 520–24. http://dx.doi.org/10.4028/www.scientific.net/amr.69-70.520.
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Contactless inductive power transfer system with conventional inductive technology was studied and a design method was presented after applying it to ultrasonic vibration machining systems. The compensation techniques are used for piezoelectricity transducer. Nodal plane support of transducer is researched and models of different structures for nodal plane support are got. Influence of rotary precision for different support due to centrifugal force and displacement vibration of nodal plane support to toolholder are analyzed. The system integrated with ultrasonic-vibration toolholder based on contactless inductive power transfer is designed. Power transfer and dynamic tests show that the design procedures and result based on theoretical analysis are comparative.
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Carpenter, Chris. "Rate Transient Analysis Transforms Exploitation of Mature and Tight Fields." Journal of Petroleum Technology 77, no. 01 (2025): 64–67. https://doi.org/10.2118/0125-0064-jpt.
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_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 23731, “Unleashing the Potential of Rate Transient Analysis: Transforming the Exploitation of Mature and Tight Fields, 40-Year Mature Field Case Study,” by Amr Gharieb Ali, Apache; Mohamed A. Gabry, SPE, University of Houston; and Ahmed Algarhy, SPE, Marietta College, et al. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ The objective of this paper is to address the power of old, cheap data integration with the rate transient analysis (RTA) technique in the development of mature and tight fields. The absence of sophisticated reservoir modeling data further complicates the situation. However, the paper intends to explore the potential of diverse sets of production data over an extended period, available for interpretation and integration with production operations data, to revolutionize the exploitation of mature and tight fields. Introduction Mature oil fields, such as the subject Field X, which commenced production approximately 40 years ago from late Cretaceous reservoirs, often are repositories of untapped information and potential. Field X in particular stands as a testament to the enduring vitality of such mature assets. Even after decades of exploitation, it continues to demonstrate robust production potential, making it a remarkable case study within the industry. During the past 10 years, production in Field X has been primarily driven by the ATC reservoir, albeit at a reduced rate. This recent phase of extraction, aided by hydraulic fracturing, has revealed inefficiencies. Most notably, a lack of optimization in well spacing and hydraulic fracture design has been noted. Against this backdrop, this paper delves into the application of RTA in mature fields. The authors propose an innovative workflow that leverages historical data sources often overlooked, highlighting the transformative potential of RTA in reinvigorating development strategies for aging tight reservoirs. The goal is to understand, optimize, and revolutionize operational strategies in mature fields by use of a synergy between RTA, hydraulic fracturing, and simulation studies. Methodology Field X, encompassing approximately 100 producing wells spread across 22 distinct zones, initially tapped into 22 separate reservoirs, achieving a notable start of more than 10,000 STB/D. This study concentrates on the development of the northern area of Field X, specifically targeting the ATC reservoir. The focus is on exploiting tight oil reservoirs through the application of hydraulic fracturing techniques. To enhance the efficacy of these fracturing treatments, nodal analysis was used. The optimization process faced challenges, however, because of the uncertainties surrounding the drainage area and permeability characteristics of the ATC reservoir. In the authors’ approach, the drainage area was conservatively estimated to be half the well spacing. The permeability values were derived from porosity logs. This led to a wide permeability range of 0.5–5 md, introducing complexities in the fracture-optimization process. Post-fracturing, the wells exhibited production rates ranging between 100 and 200 STB/D, using sucker rod pumps (SRPs) for artificial lift. The production profiles showed a steep initial decline, stabilizing at approximately 50 BOPD over a 7-year period. This production behavior indicated substantial reserve potential.
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Thai, Chien H., and H. Nguyen-Xuan. "A Moving Kriging Interpolation Meshfree Method Based on Naturally Stabilized Nodal Integration Scheme for Plate Analysis." International Journal of Computational Methods 16, no. 04 (2019): 1850100. http://dx.doi.org/10.1142/s0219876218501001.
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A moving Kriging interpolation (MKI) meshfree method based on naturally stabilized nodal integration (NSNI) scheme is presented to study static, free vibration and buckling behaviors of isotropic Reissner–Mindlin plates. Gradient strains are directly computed at nodes similar to the direct nodal integration (DNI). Outstanding features of the current approach are to alleviate instability solutions in the DNI and to decrease computational cost significantly when compared with the traditional high-order Gauss quadrature scheme. The NSNI is a naturally implicit gradient expansion and does not employ a divergence theorem for strain fields as addressed in the stabilized conforming nodal integration method. The present formulation is derived from the Galerkin weak form and avoids a naturally shear-locking phenomenon without using any other techniques. Thanks to satisfied Kronecker delta function property of MKI shape function, essential boundary conditions (BCs) are easily and directly enforced similar to the finite element method. A variety of numerical examples with various geometries, stiffness ratios and BCs are studied to verify the effectiveness of the present approach.
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Gianto, Rudy, and Purwoharjono Purwoharjono. "A new method to incorporate three-phase power transformer model into distribution system load flow analysis." International Journal of Applied Power Engineering (IJAPE) 10, no. 3 (2021): 262. http://dx.doi.org/10.11591/ijape.v10.i3.pp262-270.
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This paper proposes a new and simple method to incorporate three-phase power transformer model into distribution system load flow (DSLF) analysis. The objective of the present work is to find a robust and efficient technique for modeling and integrating power transformer in the DSLF analysis. The proposed transformer model is derived based on nodal admittance matrix and formulated by using the symmetrical component theory. Load flow formulation in terms of branch currents and nodal voltages is also proposed in this paper to enable integrating the model into the DSLF analysis. Singularity that makes the calculations in forward/backward sweep (FBS) algorithm is difficult to be carried out. It can be avoided in the method. The proposed model is verified by using the standard IEEE test system.
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Rudy, Gianto, and Purwoharjono. "A new method to incorporate three-phase power transformer model into distribution system load flow analysis." International Journal of Applied Power Engineering (IJAPE) 10, no. 3 (2021): 262–70. https://doi.org/10.11591/ijape.v10.i3.pp262-270.
Full textAbstract:
This paper proposes a new and simple method to incorporate three-phase power transformer model into distribution system load flow (DSLF) analysis. The objective of the present work is to find a robust and efficient technique for modeling and integrating power transformer in the DSLF analysis. The proposed transformer model is derived based on nodal admittance matrix and formulated by using the symmetrical component theory. Load flow formulation in terms of branch currents and nodal voltages is also proposed in this paper to enable integrating the model into the DSLF analysis. Singularity that makes the calculations in forward/backward sweep (FBS) algorithm is difficult to be carried out. It can be avoided in the method. The proposed model is verified by using the standard IEEE test system.