The Generation of 3D Trimmed Elements for NURBS-Based Isogeometric Analysis

2018 ◽  
Vol 15 (07) ◽  
pp. 1850065 ◽  
Author(s):  
Chan-Kyung Im ◽  
Sung-Kie Youn
Keyword(s):  
Isogeometric Analysis ◽  
3D Model ◽  
Integration Scheme ◽  
Complex Objects ◽  
Surface Information ◽  
Cad System ◽  
Integration Schemes ◽  
Tetrahedral Cells ◽  
Difference Operation ◽  
Integration Rules

In conventional 3D NURBS-based isogeometric analysis (IGA), it is required to generate a discretized 3D model from the imported CAD model. Since a CAD file only contains surface information of the 3D object, generation of 3D mesh and trivariate basis functions are required for the IGA. In CAD system, the Boolean difference operation, so-called “trimming” is frequently employed for creating complex objects. To directly utilize the trimming information into analysis, trimmed elements need to be defined and their integration schemes are also needed. In this paper, trimmed elements searching, classification, decomposition and integration rules are presented. In the process, seven types of generalized trimmed elements are defined. Since covering all possible 3D geometries is not possible, three out of seven types of trimmed elements formed by extrusion are treated. The decomposition rule of trimmed elements is introduced and curved tetrahedral cells are adopted to integrate the trimmed elements. For numerical integration of curved tetrahedral cells, 3D NEFEM-like integration scheme has been developed. For the demonstration of the usage of the developed elements, two numerical examples of trimmed volume are treated.

Investigation and Implementation of a Web-Based CAD System for Fabric Appearance

2010 ◽  
Vol 129-131 ◽  
pp. 645-647
Author(s):  
Fan Lei Yan ◽  
Lian He Yang ◽  
Hai Feng Chang
Keyword(s):  
Data Exchange ◽  
3D Model ◽  
Texture Mapping ◽  
Future Research ◽  
Web Browser ◽  
Research Directions ◽  
Web Based ◽  
Cad System ◽  
Key Technologies ◽  
Future Research Directions

The area of web-based CAD system has grown since the mid-1990s. This paper introduces a new web-based CAD system for fabric appearance. The system uses the Browser/Server structure, and the designer can employ this system installed on the server to build a 3D model of fabric appearance through the Web browser. The basic architecture is discussed in this paper. Some key technologies, such as graphics display, texture mapping and the data exchange, are also investigated. In the last, some future research directions are presented.

3D Model Registration Based on Feature Extraction

2011 ◽  
Vol 299-300 ◽  
pp. 1091-1094 ◽  
Author(s):  
Jiang Zhu ◽  
Yuichi Takekuma ◽  
Tomohisa Tanaka ◽  
Yoshio Saito
Keyword(s):  
Feature Extraction ◽  
Point Cloud ◽  
3D Model ◽  
Point Cloud Data ◽  
Coordinate Systems ◽  
High Precision Measurement ◽  
Registration Method ◽  
Cloud Data ◽  
Cad System ◽  
Complicated Model

Currently, design and processing of complicated model are enabled by the progress of the CAD/CAM system. In shape measurement, high precision measurement is performed using CMM. In order to evaluate the machined part, the designed model made by CAD system the point cloud data provided by the measurement system are analyzed and compared. Usually, the designed CAD model and measured point cloud data are made in the different coordinate systems, it is necessary to register those models in the same coordinate system for evaluation. In this research, a 3D model registration method based on feature extraction and iterative closest point (ICP) algorithm is proposed. It could efficiently and accurately register two models in different coordinate systems, and effectively avoid the problem of localized solution.

scholarly journals Investigation of Air Pocket Behavior in Pipelines Using Rigid Column Model and Contributions of Time Integration Schemes

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 785
Author(s):  
Arman Rokhzadi ◽  
Musandji Fuamba
Keyword(s):  
Transient Flow ◽  
Time Integration ◽  
Driving Pressure ◽  
Implicit Time ◽  
Numerical Dissipation ◽  
Integration Scheme ◽  
Time Step ◽  
Column Model ◽  
Integration Schemes ◽  
Backward Euler

This paper studies the air pressurization problem caused by a partially pressurized transient flow in a reservoir-pipe system. The purpose of this study is to analyze the performance of the rigid column model in predicting the attenuation of the air pressure distribution. In this regard, an analytic formula for the amplitude and frequency will be derived, in which the influential parameters, particularly, the driving pressure and the air and water lengths, on the damping can be seen. The direct effect of the driving pressure and inverse effect of the product of the air and water lengths on the damping will be numerically examined. In addition, these numerical observations will be examined by solving different test cases and by comparing to available experimental data to show that the rigid column model is able to predict the damping. However, due to simplified assumptions associated with the rigid column model, the energy dissipation, as well as the damping, is underestimated. In this regard, using the backward Euler implicit time integration scheme, instead of the classical fourth order explicit Runge–Kutta scheme, will be proposed so that the numerical dissipation of the backward Euler implicit scheme represents the physical dissipation. In addition, a formula will be derived to calculate the appropriate time step size, by which the dissipation of the heat transfer can be compensated.

scholarly journals A Semi-Implicit Version of the MPAS-Atmosphere Dynamical Core

2015 ◽  
Vol 143 (9) ◽  
pp. 3838-3855 ◽  
Author(s):  
Steven Sandbach ◽  
John Thuburn ◽  
Danail Vassilev ◽  
Michael G. Duda
Keyword(s):  
Time Integration ◽  
Standard Test ◽  
Newton Iteration ◽  
Atmospheric Modeling ◽  
Implicit Time ◽  
Integration Scheme ◽  
Baroclinic Wave ◽  
Time Step ◽  
Integration Schemes ◽  
Helmholtz Problem

Abstract An important question for atmospheric modeling is the viability of semi-implicit time integration schemes on massively parallel computing architectures. Semi-implicit schemes can provide increased stability and accuracy. However, they require the solution of an elliptic problem at each time step, creating concerns about their parallel efficiency and scalability. Here, a semi-implicit (SI) version of the Model for Prediction Across Scales (MPAS) is developed and compared with the original model version, which uses a split Runge–Kutta (SRK3) time integration scheme. The SI scheme is based on a quasi-Newton iteration toward a Crank–Nicolson scheme. Each Newton iteration requires the solution of a Helmholtz problem; here, the Helmholtz problem is derived, and its solution using a geometric multigrid method is described. On two standard test cases, a midlatitude baroclinic wave and a small-planet nonhydrostatic gravity wave, the SI and SRK3 versions produce almost identical results. On the baroclinic wave test, the SI version can use somewhat larger time steps (about 60%) than the SRK3 version before losing stability. The SI version costs 10%–20% more per step than the SRK3 version, and the weak and strong scalability characteristics of the two versions are very similar for the processor configurations the authors have been able to test (up to 1920 processors). Because of the spatial discretization of the pressure gradient in the lowest model layer, the SI version becomes unstable in the presence of realistic orography. Some further work will be needed to demonstrate the viability of the SI scheme in this case.

Energy-Momentum Conserving Time Integration of Modally Reduced Flexible Multibody Systems

2013 ◽  
Author(s):  
Alexander Humer ◽  
Johannes Gerstmayr
Keyword(s):  
Angular Momentum ◽  
Multibody Systems ◽  
Mass Matrix ◽  
Time Integration ◽  
Flexible Multibody Dynamics ◽  
Integration Scheme ◽  
Integration Schemes ◽  
Flexible Multibody ◽  
Floating Frame ◽  
Energy And Momentum

Many conventional time integration schemes frequently adopted in flexible multibody dynamics fail to retain the fundamental conservation laws of energy and momentum of the continuous time domain. Lack of conservation, however, in particular of angular momentum, may give rise to unexpected, unphysical results. To avoid such problems, a scheme for the consistent integration of modally reduced multibody systems subjected to holonomic constraints is developed in the present paper. As opposed to the conventional approach, in which the floating frame of reference formulation is combined with component mode synthesis for approximating the flexible deformation, an alternative, recently proposed formulation based on absolute coordinates is adopted in the analysis. Owing to the linear relationship between the generalized coordinates and the absolute displacement, the inertia terms in the equations of motion attain a very simple structure. The mass matrix remains independent of the current state of deformation and the velocity dependent term known from the floating frame approach vanishes due to the absence of relative coordinates. These advantageous properties facilitate the construction of an energy and momentum consistent integration scheme. By the mid-point rule, algorithmic conservation of both linear and angular momentum is achieved. In order to consistently integrate the total energy of the system, the discrete derivative needs to be adopted when evaluating the strain energy gradient and the derivative of the algebraic constraint equations.

scholarly journals Efficient Approximate Techniques for Integrating Stochastic Differential Equations

2006 ◽  
Vol 134 (10) ◽  
pp. 3006-3014 ◽  
Author(s):  
James A. Hansen ◽  
Cecile Penland
Keyword(s):  
Time Series ◽  
Differential Equations ◽  
Stochastic Differential Equations ◽  
Deterministic Model ◽  
Probability Distributions ◽  
Approximate Solutions ◽  
Integration Scheme ◽  
Time Step ◽  
Integration Schemes ◽  
Runge Kutta

Abstract The delicate (and computationally expensive) nature of stochastic numerical modeling naturally leads one to look for efficient and/or convenient methods for integrating stochastic differential equations. Concomitantly, one may wish to sensibly add stochastic terms to an existing deterministic model without having to rewrite that model. In this note, two possibilities in the context of the fourth-order Runge–Kutta (RK4) integration scheme are examined. The first approach entails a hybrid of deterministic and stochastic integration schemes. In these examples, the hybrid RK4 generates time series with the correct climatological probability distributions. However, it is doubtful that the resulting time series are approximate solutions to the stochastic equations at every time step. The second approach uses the standard RK4 integration method modified by appropriately scaling stochastic terms. This is shown to be a special case of the general stochastic Runge–Kutta schemes considered by Ruemelin and has global convergence of order one. Thus, it gives excellent results for cases in which real noise with small but finite correlation time is approximated as white. This restriction on the type of problems to which the stochastic RK4 can be applied is strongly compensated by its computational efficiency.

The Impact of Ecowas on Intraregional Trade Flows: An Empirical Investigation

1995 ◽  
Vol 23 (3) ◽  
pp. 113-129 ◽  
Author(s):  
Mamit Deme
Keyword(s):  
Economic Integration ◽  
Regional Integration ◽  
Empirical Investigation ◽  
West African ◽  
Trade Flows ◽  
Integration Scheme ◽  
General View ◽  
Economic Community ◽  
Integration Schemes ◽  
The Impact

There is a scarcity of published statistical analysis that examines the impact of economic integration schemes in Africa. This study fills the gap in the literature. The impact of Economic Community of West African States (ECOWAS) on trade flows of its member countries is examined applying an econometric analysis. The parameters of a multivariate trade-flows model are estimated using a panel data of the 1975 to 1991 period. The results suggest that the regional integration scheme has succeeded in increasing trade flows between member countries. The general view in the literature is that African integration schemes have failed to increase trade flows.

Parametric Modeling CAD-CAM of the Ankle and Pathological Related Situations

2014 ◽  
Vol 657 ◽  
pp. 740-744
Author(s):  
Iulia Huzu ◽  
Nicolae Florin Cofaru
Keyword(s):  
Healthy Subject ◽  
3D Model ◽  
Treatment Strategies ◽  
Parametric Modeling ◽  
Cad System ◽  
Primary Object ◽  
Graphic Modeling ◽  
The Status ◽  
Modeling Software ◽  
Cad Cam

It is primary object of the present study to create a 3D model of the human ankle and an axis system that will show the position the tibia and the foot on a healthy subject. Regarding this scope of the study, the first step in obtaining the 3D model of the bones is scanning. The graphic modeling software used is Catia V5 R20. It is another object of the present study to create an axis system that will be very easy to maneuver and on which we can show different pathological situations, not only on a healthy subject, creating their assembly reference systems considering the mechanical and anatomical axes existing and creating prerequisites for the study of different possible pathological situations. For this scope, was used a triorthogonal axis system called skeleton that is defined as a system of axes Euler. This means that the angles can change the grid, in the desire to analyze different situations. In this study the focus is on the situation of varus equinus, in which the foot leg is not aligned with the tibia, as it is on a healthy subject. It was realized an important element: the incorporation of geometric and dimensional references. The last object in this study is to determine the status of CAE, in order to study the stress and the strain. Creating the CAD system is very important because it can be used to study the osteoarticular system, treatment strategies and related surgery.

INNOVATIVE INTEGRATION BASED ON SILICON-CORE TECHNOLOGIES FOR SENSOR AND COMMUNICATIONS APPLICATIONS

2000 ◽  
Vol 10 (01) ◽  
pp. 205-215 ◽  
Author(s):  
TADAO NAGATSUMA ◽  
KATSUYUKI MACHIDA ◽  
HIROMU ISHII ◽  
NABIL SAHRI ◽  
MITSURU SHINAGAWA ◽  
...  
Keyword(s):  
Low Power ◽  
System Integration ◽  
Lower Cost ◽  
Photonic Devices ◽  
Integration Scheme ◽  
Heterogeneous Integration ◽  
Integration Schemes ◽  
Semiconductor Electronics ◽  
Innovative System ◽  
Technology Trends

This paper describes an innovative system integration scheme wherein heterogeneous materials and devices, including photonic devices as well as electronics, are organically integrated on silicon-core circuitry to achieve better performance, higher functionality and lower cost. First, some general integration technology trends in semiconductor electronics are described. Then, after a discussion of new heterogeneous integration schemes based on silicon-core technologies, recent attempts and applications are shown such as low power LSIs, sensors and micromachine switches on silicon and milimeter-wave photonics.

Isogeometric analysis of boundary integral equations: High-order collocation methods for the singular and hyper-singular equations

2016 ◽  
Vol 26 (08) ◽  
pp. 1447-1480 ◽  
Author(s):  
Matthias Taus ◽  
Gregory J. Rodin ◽  
Thomas J. R. Hughes
Keyword(s):  
Integral Equations ◽  
Isogeometric Analysis ◽  
Computer Aided Design ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
High Order ◽  
Collocation Methods ◽  
Algebraic Equations ◽  
Integration Schemes ◽  
Linear Algebraic Equations

Isogeometric analysis is applied to boundary integral equations corresponding to boundary-value problems governed by Laplace’s equation. It is shown that the smoothness of geometric parametrizations central to computer-aided design can be exploited for regularizing integral operators to obtain high-order collocation methods involving superior approximation and numerical integration schemes. The regularization is applicable to both singular and hyper-singular integral equations, and as a result one can formulate the governing integral equations so that the corresponding linear algebraic equations are well-conditioned. It is demonstrated that the proposed approach allows one to compute accurate approximate solutions which optimally converge to the exact ones.

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