EFFICIENCY ASSESSMENT OF THE DIRECT INTEGRATION METHOD BY CENTRAL DIFFERENCES (DIMCD)

The direct integration method by central differences (DIMCD) is an explicit method of order two for integrating the equations governing the dynamic analysis of multibody systems. So far, development has focused only on verifying the quality of the results. In this paper, it is shown that in addition to providing optimal results, it is also competitive from the point of view of computational efficiency, at least for systems with up to six bodies. For this purpose, an appropriate implementation of the method in a compiled language is presented. In turn, it is shown that the methodology is suitable for modeling in sparse matrices, although the proposed implementation is based on dense matrices. The resulting code is applied to different benchmark examples. Results from various commercial software are also included. Keywords: Computational efficiency, multibody dynamics, central differences, null space, dense matrices, quaternions

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Bright and dark optical solitons for the generalized variable coefficients nonlinear Schrödinger equation

International Journal of Nonlinear Sciences and Numerical Simulation ◽

10.1515/ijnsns-2019-0054 ◽

2020 ◽

Vol 21 (7-8) ◽

pp. 675-681

Author(s):

Rehab M. El-Shiekh ◽

Mahmoud Gaballah

Keyword(s):

Schrödinger Equation ◽

Nonlinear Schrödinger Equation ◽

Schrodinger Equation ◽

Integration Method ◽

Variable Coefficients ◽

Nonlinear Schrodinger Equation ◽

Equation Method ◽

Direct Integration ◽

Wave Solutions ◽

Direct Integration Method

AbstractIn this paper, the generalized nonlinear Schrödinger equation with variable coefficients (gvcNLSE) arising in optical fiber is solved by using two different techniques the trail equation method and direct integration method. Many different new types of wave solutions like Jacobi, periodic and soliton wave solutions are obtained. From this study we have concluded that the direct integration method is more easy and straightforward than the trail equation method. As an application in optic fibers the propagation of the frequency modulated optical soliton is discussed and we have deduced that it's propagation shape is affected with the different values of both the amplification increment and the group velocity (GVD).

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Direct integration method and first integrals for three-dimensional Lotka–Volterra systems

Physics Letters A ◽

10.1016/s0375-9601(99)00193-0 ◽

1999 ◽

Vol 255 (4-6) ◽

pp. 253-258 ◽

Cited By ~ 9

Author(s):

Puyun Gao

Keyword(s):

Integration Method ◽

Three Dimensional ◽

First Integrals ◽

Direct Integration ◽

Volterra Systems ◽

Direct Integration Method

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Piecewise Polynomial Fitting with Trend Item Removal and Its Application in a Cab Vibration Test

Journal of Sensors ◽

10.1155/2018/3417692 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Wu Ren ◽

Qiongqiong Ren ◽

Lin Han ◽

Ying Liu ◽

Bo Peng

Keyword(s):

Integration Method ◽

Vibration Signal ◽

Vibration Test ◽

Measured Signal ◽

Direct Integration ◽

Piecewise Polynomial ◽

Modal Parameter ◽

Polynomial Fitting ◽

Special Equipment ◽

Direct Integration Method

The trend item of a long-term vibration signal is difficult to remove. This paper proposes a piecewise integration method to remove trend items. Examples of direct integration without trend item removal, global integration after piecewise polynomial fitting with trend item removal, and direct integration after piecewise polynomial fitting with trend item removal were simulated. The results showed that direct integration of the fitted piecewise polynomial provided greater acceleration and displacement precision than the other two integration methods. A vibration test was then performed on a special equipment cab. The results indicated that direct integration by piecewise polynomial fitting with trend item removal was highly consistent with the measured signal data. However, the direct integration method without trend item removal resulted in signal distortion. The proposed method can help with frequency domain analysis of vibration signals and modal parameter identification for such equipment.

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Stabilization of chaotic systems via act-and-wait delayed feedback control using a high-precision direct integration method

SN Applied Sciences ◽

10.1007/s42452-020-2310-6 ◽

2020 ◽

Vol 2 (4) ◽

Author(s):

Dasheng Liu ◽

Guozheng Yan

Keyword(s):

Feedback Control ◽

High Precision ◽

Chaotic Systems ◽

Integration Method ◽

Delayed Feedback ◽

Delayed Feedback Control ◽

Direct Integration ◽

Direct Integration Method

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An Improved Transfer Matrix-Direct Integration Method for Rotor Dynamics

Journal of Vibration and Acoustics ◽

10.1115/1.3269320 ◽

1986 ◽

Vol 108 (2) ◽

pp. 182-188 ◽

Cited By ~ 12

Author(s):

Jialiu Gu

Keyword(s):

Transfer Matrix ◽

Integration Method ◽

Equations Of Motion ◽

Rotor Dynamics ◽

Direct Integration ◽

Rotating System ◽

Direct Integration Method ◽

Mass Moment ◽

Mass Moment Of Inertia ◽

Matrix Iteration

A transfer matrix-direct integration combined method is proposed, which employs the transfer matrix method to derive the equations of motion of a “characteristic disk,” and uses the direct integration method to determine the critical speeds, modes and unbalance response of a rotor-bearing system, and to analyze its stability. Despite the complexity of the system, the number of governing equations is not greater than eight. For a single-spool rotating system, the number of equations is only four. A transfer matrix for a uniform shaft is derived to consider its distributed mass, moment of inertia and the effect of shearing force. An impedance matrix iteration method is proposed to consider the effect of a complicated bearing-supporting system on the rotor dynamics. Two examples are given, and the results agree satisfactorily with the experiments.

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Analysis of Infinitely Short and Infinitely Long Hydrodynamic Journal Bearings Under Micro-Polar Fluid by Direct Integration Method

Volume 2: Structures and Dynamics; Renewable Energy (Solar, Wind); Inlets and Exhausts; Emerging Technologies (Hybrid Electric Propulsion, UAV, ...); GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2017-4852 ◽

2017 ◽

Author(s):

Bikash Routh

Keyword(s):

Finite Difference ◽

Finite Difference Method ◽

Reynolds Equation ◽

Journal Bearing ◽

Integration Method ◽

Pressure Profile ◽

Journal Bearings ◽

Direct Integration ◽

Polar Fluid ◽

Direct Integration Method

In the present paper Reynolds equation of lubrication under micro-polar fluid for journal bearing is solved by direct-integration method under infinitely long and infinitely short journal bearing assumptions [1]. Infinitely long-bearing and infinitely short bearing solutions are the two available approximate closed form solutions for journal bearings. In the present investigation, solution of Reynolds equation i.e. pressure profile is compared with pressure profile obtained by previously used approximate method like finite difference method (FDM). Mentionable here that any approximation method needs lots of calculation and computer programing to get the result. In the present work it has been found that direct-integration method leads the almost same result as the conventionally used complex finite difference method. CFD analysis is also presented in the present work to justify the profile obtained by direct numerical method. It has seen here that theoretical and simulation results are in good agreement to each other’s.

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