Interactive boundary element analysis for engineering design.

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the eciency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. The re-meshing algorithm must accommodate these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. For this problem, a GMRES solver has been shown to provide the fastest convergence rate. Further time savings can be made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for 3D simulations; for 2D models such real-time performance has already been demonstrated

On the solvability of euler graphene beam subject to axial compressive load

In this paper we formulate the equilibrium equation for a beam made of graphene sub- jected to some boundary conditions and acted upon by axial compression and nonlinear lateral constrains as a fourth-order nonlinear boundary value problem. We first study the nonlinear eigenvalue problem for buckling analysis of the beam. We show the solvability of the eigen- value problem as an asymptotic expansion in a ratio of the elastoplastic parameters. We verify that the spectrum is a closed set bounded away from zero and contains a discrete in- finite sequence of eigenvalues. In particular, we prove the existence of a minimal eigenvalue for the graphene beam corresponding to a Lipschitz continuous eigenfunction, providing a lower bound for the critical buckling load of the graphene beam column. We also proved that the eigenfunction corresponding to the minimal eigenvalue is positive and symmetric. For a certain range of lateral forces, we demonstrate the solvability of the general equation by using energy methods and a suitable iteration scheme

Rapid re-meshing and re-solution of three-dimensional boundary element problems for interactive stress analysis

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. It is becoming increasingly possible to make significant improvements in the efficiency of this process by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. A key part of such a strategy is the ability to accommodate changes in geometry with minimal perturbation to an existing mesh. This work introduces a new re-meshing algorithm that can generate and update a boundary element mesh in real-time as a series of small changes are sequentially applied to the associated model. The algorithm is designed to make minimal updates to the mesh between each step whilst preserving a suitable mesh quality that retains accuracy in the stress results. This significantly reduces the number of terms that need to be updated in the system matrix, thereby reducing the time required to carry out a re-analysis of the model. A range of solvers are assessed to find the most efficient and robust method of re-solving the system. The GMRES algorithm, using complete approximate LU preconditioning, is found to provide the fastest convergence rate

Evaluation of angiotensin II receptor blockers for drug formulary using objective scoring analytical tool

Drug selection methods with scores have been developed and used worldwide for formulary purposes. These tools focus on the way in which the products are differentiated from each other within the same therapeutic class. Scoring Analytical Tool (SAT) is designed based on the same principle with score and is able to assist formulary committee members in evaluating drugs either to add or delete in a more structured, consistent and reproducible manner. Objective: To develop an objective SAT to facilitate evaluation of drug selection for formulary listing purposes. Methods: A cross-sectional survey was carried out. The proposed SAT was developed to evaluate the drugs according to pre-set criteria and sub-criteria that were matched to the diseases concerned and scores were then assigned based on their relative importance. The main criteria under consideration were safety, quality, cost and efficacy. All these were converted to questionnaires format. Data and information were collected through self-administered questionnaires that were distributed to medical doctors and specialists from the established public hospitals. A convenient sample of 167 doctors (specialists and non-specialists) were taken from various disciplines in the outpatient clinics such as Medical, Nephrology and Cardiology units who prescribed ARBs hypertensive drugs to patients. They were given a duration of 4 weeks to answer the questionnaires at their convenience. One way ANOVA, Kruskal Wallis and post hoc comparison tests were carried out at alpha level 0.05. Results: Statistical analysis showed that the descending order of ARBs preference was Telmisartan or Irbesartan or Losartan, Valsartan or Candesartan, Olmesartan and lastly Eprosartan. The most cost saving ARBs for hypertension in public hospitals was Irbesartan. Conclusion: SAT is a tool which can be used to reduce the number of drugs and retained the most therapeutically appropriate drugs in the formulary, to determine most cost saving drugs and has the potential to complement the conventional method of drug selection as it is effective in aiding decision making process through the pre-established criteria and increasing scientific ground of decisions and transparency.Scopu

Numerical study of viscous dissipation effect on free convection heat and mass transfer of MHD non-Newtonian fluid flow through a porous medium

AbstractThe problem of free convection heat with mass transfer for MHD non-Newtonian Eyring–Powell flow through a porous medium, over an infinite vertical plate is studied. Taking into account the effects of both viscous dissipation and heat source. The temperature and concentration are of periodic variation. The governing non-linear partial differential equations of this phenomenon are transformed into non-linear algebraic system utilizing finite difference method. Numerical results for the velocity, temperature and concentration distributions as well as the skin friction, heat and mass transfer are obtained and reported in tabular form and graphically for different values of physical parameters of the problem. Also, the stability condition is studied

Analysis of global and local stress changes in a longwall gateroad

A numerical-model-based approach was recently developed for estimating the changes in both the hor- izontal and vertical loading conditions induced by an approaching longwall face. In this approach, a sys- tematic procedure is used to estimate the model’s inputs. Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements. Coal is modeled with a newly developed coal mass model. The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments. The model results were verified with the sub- sidence and stress data recently collected from a longwall mine in the eastern United States

Analysis of global and local stress changes in a longwall gateroad

A numerical-model-based approach was recently developed for estimating the changes in both the hor- izontal and vertical loading conditions induced by an approaching longwall face. In this approach, a sys- tematic procedure is used to estimate the model’s inputs. Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements. Coal is modeled with a newly developed coal mass model. The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments. The model results were verified with the sub- sidence and stress data recently collected from a longwall mine in the eastern United States

Interactive three-dimensional boundary element stress analysis of components in aircraft structures

Computer aided design of mechanical components is an iterative process that often involves multiple stress analysis runs; this can be time consuming and expensive. Significant efficiency improvements can be made by increasing interactivity at the conceptual design stage. One approach is through real-time re-analysis of models with continuously updating geometry. Thus each run can benefit from an existing mesh and governing boundary element matrix that are similar to the updated geometry. For small problems, amenable to real-time analysis, re-integration accounts for the majority of the re-analysis time. This paper assesses how efficiency can be achieved during re-integration through both algorithmic and hardware based methods. For models with fewer than 10,000 degrees of freedom, the proposed algorithm performs up to five times faster than a standard integration scheme. An additional six times speed is achieved on eight cores over the serial implementation. By combining this work with previously addressed meshing and solution schemes, real-time re-analysis becomes a reality for small three-dimensional problems. Significant acceleration of larger systems is also achieved. This work demonstrates the viability of application in the aerospace industry where rapid validation of a range of similar models is an essential tool for optimising aircraft designs

Interactive Boundary Element Analysis for Engineering Design

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the eciency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. The re-meshing algorithm must accommodate these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. For this problem, a GMRES solver has been shown to provide the fastest convergence rate. Further time savings can be made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for 3D simulations; for 2D models such real-time performance has already been demonstrated

General Fuzzy Graphs

Fuzzy graphs have many applications in database theory,neural networks and decision making problems.Literature survey shows that in the exisiting definition of fuzzy graph the membership value on links is always less than or equal to the minimum of membership values on the corresponding nodes.This restriction brings a difficulty to address some practical problems where the membership value on links does not depend on that of corresponding nodes.So there exists a gap in literature of fuzzy graphs.In this article we have developed general fuzzy graph and general weak fuzzy graphs and have proved some properties of general weak fuzzy graphs