Enriched goal-oriented error estimation for fracture problems solved by continuum-based shell extended finite element method

An enriched goal-oriented error estimation method with extended degrees of freedom is developed to estimate the error in the continuum-based shell extended finite element method. It leads to high quality local error bounds in three-dimensional fracture mechanics simulation which involves enrichments to solve the singularity in crack tip. This enriched goal-oriented error estimation gives a chance to evaluate this continuum- based shell extended finite element method simulation. With comparisons of reliability to the stress intensity factor calculation in stretching and bending, the accuracy of the continuum-based shell extended finite element method simulation is evaluated, and the reason of error is discussed.

Goal-oriented error estimation applied to direct solution of steady-state analysis with frequency-domain finite element method

Based on the concept of the constitutive relation error along with the residuals of both the origin and the dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed. It leads to the high quality locM error bounds in the problem of the direct-solution steady-state dynamic analysis with a frequency-domain finite element, which involves the enrichments with plural variable basis functions. The solution of the steady-state dynamic procedure calculates the harmonic response directly in terms of the physical degrees of freedom in the model, which uses the mass, damping, and stiffness matrices of the system. A three-dimensional finite element example is carried out to illustrate the computational procedures.

ENRICHED GOAL-ORIENTED ERROR ESTIMATION APPLIED TO FRACTURE MECHANICS PROBLEMS SOLVED BY XFEM

Based on the concept of constitutive relation error along with the residual of both origin and dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed in this paper. It leads to high quality local error bounds in the problem of fracture mechanics simulation with extended finite element method （XFEM）, which involves enrichment to solve a stress singularity in the crack. Since goal-oriented error estimation with enriched degrees of freedom gives us a chance to evaluate the XFEM simulation, the stress intensity factor calculated by two kinds of XFEM programs developed by ourselves and by commercial code ABAQUS are compared in this work. By comparing the reliability of the stress intensity factor calculation, the accuracy of two programs in different cases is evaluated and the source of error is discussed. A 2-dimensional XFEM example is given to illustrate the computational procedure.

ANURBS-Enhanced Finite Volume Method for Steady Euler Equations with Goal-Oriented h-Adaptivity

In[A NURBS-enhanced finite volume solver for steady Euler equations,X.C.Meng,G.H.Hu,J.Comput.Phys.,Vol.359,pp.77–92],aNURBS-enhanced finite volume method was developed to solve the steady Euler equations,in which the desired high order numerical accuracy was obtained for the equations imposed in the domain with a curved boundary.In this paper,the method is significantly improved in the following ways:(i)a simple and efficient point inversion technique is designed to compute the parameter values of points lying on a NURBS curve,(ii)with this new point inversion technique,the h-adaptive NURBS-enhanced finite volume method is introduced for the steady Euler equations in a complex domain,and(iii)a goal-oriented a posteriori error indicator is designed to further improve the efficiency of the algorithm towards accurately calculating a given quantity of interest.Numerical results obtained from a variety of numerical experiments with different flow configurations successfully show the effectiveness and robustness of the proposed method.

Reliability Analysis of Repairable System with Multiple Closed-Loop Feedbacks Based on GO Method

In order to solve the problem of reliability modeling and the analysis of complex systems with multiple closed-loop feedbacks,a new reliability analysis method for repairable systems with multiple closed-loop feedbacks is proposed based on the goal-oriented(GO)methodology.Firstly,the basic theories and advantages of GO method are introduced.Secondly,a type-24B multiple closed-loop feedback structure operator is proposed through GO method with its operation formula given,which expands the types of GO method operators and the application scope of their reliability analysis.Finally,taking a certain type of diesel engine fuel supply system an example,the quantitative and qualitative analysis is carried out through GO method,Monte Carlo simulation as well as FTA respectively.The availability results verify the availability of the proposed type-24B operator in the reliability analysis of multiple closed-loop feedback systems.The qualitative analysis results indicate the accuracy and usability of the GO method as a qualitative analysis method.

＂Winning Is Everything＂ as the Basis of Academic Misconduct Among Indonesian Students

Unethical behavior among university students such as cheating and plagiarism has weakened the character of honesty in education. This fact has challenged those who perceived education as a holistic process of internalizing values and norms that lead to the formation of students＇ moral principles and moral behaviour. Educators have played the role of ensuring the students to internalize and realized moral values and norms. A study of 360 students of the second semester who enrolled at the course of ＂ethical and personal development＂ at Atma Jaya Catholic University in Indonesia showed that unethical behavior such as cheating and plagiarism were rarely done. However, a deep look at the reason the students did academic dishonesty has prompted the permissiveness of student＇s moral life. This study proves that academic integrity among university students is worrisome, and it is worsened by the fact that they were enrolled in the course of ＂ethical and personal development＂. Seriously taking into consideration the strong desire of students to change the culture of academic misconduct, the authors argue that an educational model which is not oriented excessively to cognitive performance is needed. The authors argue that this position has to be practiced in line with the involvement of ＂clean＂ students who are involved as role models in influencing the formation of student awareness and ethical behavior.

Automatically multi-paradigm requirements modeling and analyzing:An ontology-based approach

There are several purposes for modeling and analyzing the problem domain before starting the software requirements analysis. First, it focuses on the problem domain, so that the domain users could be involved easily. Secondly, a comprehensive description on the problem domain will advantage getting a comprehensive software requirements model. This paper proposes an ontology-based approach for mod- eling the problem domain. It interacts with the domain users by using terminology that they can under- stand and guides them to provide the relevant information. A multiple paradigm analysis approach, with the basis of the description on the problem domain, has also been presented. Three criteria, i.e. the ra- tionality of organization structure, the achievability of organization goals, and the feasibility of organiza- tion process, have been proposed. The results of the analysis could be used as feedbacks for guiding the domain users to provide further information on the problem domain. And those models on the problem domain could be a kind of document for the pre-requirements analysis phase. They also will be the basis for further software requirements modeling.

Nonconforming Finite Element Methods for the Constrained Optimal Control Problems Governed by Nonsmooth Elliptic Equations

In this paper,nonconforming finite element methods(FEMs)are proposed for the constrained optimal control problems(OCPs)governed by the nonsmooth elliptic equations,in which the popular EQr1 ot element is employed to approximate the state and adjoint state,and the piecewise constant element is used to approximate the control.Firstly,the convergence and superconvergence properties for the nonsmooth elliptic equation are obtained by introducing an auxiliary problem.Secondly,the goal-oriented error estimates are obtained for the objective function through establishing the negative norm error estimate.Lastly,the methods are extended to some other well-known nonconforming elements.

Model Adaptation Enriched with an Anisotropic Mesh Spacing for Nonlinear Equations: Application to Environmental and CFD Problems

Goal of this paper is to suitably combine a model with an anisotropic mesh adaptation for the numerical simulation of nonlinear advection-diffusion-reaction systems and incompressible flows in ecological and environmental applications.Using the reduced-basis method terminology,the proposed approach leads to a noticeable computational saving of the online phase with respect to the resolution of the reference model on nonadapted grids.The search of a suitable adapted model/mesh pair is to be meant,instead,in an offline fashion.