Lot Of Computational Effort Research Articles

Preserving mesh quality in shape optimization

AbstractIn PDE‐constrained shape optimization, a lot of computational effort is used to update the geometry at every iteration step. This iterative process can result in loss of element quality and degeneracy of the underlying mesh, which is particularly relevant for applications involving large deformations of some parts of the domain. To avoid remeshing, we model the mesh deformation using the method of mappings. We use an extension equation that maps a boundary control variable to a deformation field defined over the entire domain. By using the nonlinear extension operator proposed in our previous work, we increase the set of reachable shapes, allowing us to model large deformations. We discuss how the choice of parameters of the extension equations affects the mesh quality and we study the influence of the extension factor on the convergence properties of the iterative solvers.

Remarks on coupled multi‐scale simulations and high performance computation

AbstractTo describe material behaviour more precisely than nowadays, tomorrows simulation software will include multi‐scale homogenisation techniques. State of the art are various scale bridging strategies, like FE‐ODE, FE‐Phasefield or FE2‐Method. We are dealing with the FE2‐Method, see [3], [4], which gives us the possibility to take the geometric, discrete micro‐structure of a material into account. Furthermore, it allows to integrate enhanced continuum mechanical models. Here, we are researching on two‐scale approach with poro‐mechanical coupling based on the Theory of Porous Media (TPM), for more details see [1] or [2]. The framework is demanding and need a lot of computational effort. In order to receive industrial recognition, it is necessary to decrease the computation runtime. One way to go is definitely using high performance cluster. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

An Optimization Tool for Impact Analysis of Composite Structures

Composite materials exhibit complex failure behavior under impact loading especially such as that for composite landing gear structure. Possible failure modes in composites may include matrix cracking, fiber breakage, kinking, fiber-matrix debonding or delamination between composite plies. In order to better understand the damage mechanisms and non-linear response of composite structures under impact, complex geometries, materials, ply orientations and stacking sequence need to be considered. However, general drop test analysis for composite structures usually takes a lot of computational efforts, and it may be even more expensive for failure analysis and optimization when various structural geometries and design configurations are taken into account. This paper proposes a new methodology for evaluation and optimization of failure behavior of composite structures subjected to impact loading, whereby drop test analysis of composite structures is modeled by explicitly dynamics analysis of two-dimensional structures and implicit analysis of three-dimensional solid structures to predict delamination or out-of-plane failure. The above-mentioned modeling strategy helps speed up the optimization process and considerably save computational time and efforts. The proposed methodology together with reliable optimization algorithms and failure theory criteria are integrated and coded into a FE optimization tool by Python script. It is shown that the optimization tool effectively helps engineers and researchers perform optimization of general composite structures and fully take into account of various geometries, materials, loading configurations, composite stack-up and sequences and individual ply's orientation.

Closed Form Solution for Deflection of Flexible Composite Bridges

Simply supported steel-concrete composite beams are widely used in bridge construction. Deflection is the significant parameter for serviceability limit state of bridges. A lot of computational effort is required for finite element analysis of bridges considering flexibility of shear connectors and shear leg effects. Neural network is presented for prediction of deflections, at service load, in simply supported steel-concrete composite bridges incorporating flexibility of shear connectors and shear lag effect. The training, testing and validation data sets for neural network are generated using finite element models. The finite element models have been developed using ABAQUS software. These models have been validated with available experimental results. Closed form solution is also proposed based on the developed neural network. The use of the neural network requires a computational effort almost equal to that required for the simple beam analysis (neglecting flexibility of shear connectors and shear lag effect). The neural network has been validated for number of bridges and the errors are found to be small. The network/closed form solution can be used for rapid prediction of deflection for everyday design.

Posicast control of a class of fractional-order processes

AbstractThe number of studies on the control of fractional-order processes—processes having dynamics described by differential equations of arbitrary order—has been increasing in the past two decades and it is now ubiquitous. Various methods have emerged and have been proven to effectively control such processes—usually resulting in fractional-order controllers similar to their conventional integer-order counterparts, which include, but are not limited to fractional PID and fractional lead-lag controllers. However, such methods require a lot of computational effort and fractional-order controllers could be challenging when it comes to their synthesis and implementation. In this paper, we propose a simple yet effective delay-based controller with the use of the Posicast control methodology in controlling the overshoot of a fractional-order process of the class $$\mathcal{P}:\left\{ {P\left( s \right) = {1 \mathord{\left/ {\vphantom {1 {\left( {as^\alpha + b} \right)}}} \right. \kern-\nulldelimiterspace} {\left( {as^\alpha + b} \right)}}} \right\}$$ having orders 1 < α < 2. Such controllers have proven to be easy to implement because they only require delays and summers. In this paper, the Posicast control methodology introduced in the past few years is modified to minimize the overshoot of the processes step response to a level that is acceptable in control engineering and automation practices. Furthermore, proof of the existence of overshoot for such class of processes, as well as the determination of the peak-time of the open-loop response of a fractional-order process of the class P is presented. Validation through numerical simulations for a class of fractional-order processes are presented in this paper.

Assessing the stirred mill design space

In the context of the mining industry, smaller grain size and other mineralogical characteristics have motivated the need to grind finer. In order to address this need, the interest in fine grinding technologies has grown over the last 20years as is illustrated by a growing body of knowledge on stirred milling. Emphasis in recent years has been on the use of computationally intensive modeling and simulation methods such as the discrete element method (DEM) and computational fluid dynamics (CFDs). However, due to the computational requirements of these two methods, initiating a study that spans the stirred mill design space would take a lot of computational effort and time. Therefore the goal of this paper is to propose and apply a simplified stirred mill model that will then be used to assess configurations in the stirred mill design space.To this end, a stirred mill model was proposed based on the assumption that the main if not only mechanism of ore breakage is shear. As the basis of this model is the fluid mechanics definition of shear stress, the stirred mill power model became a function of viscosity, mill speed and a new parameter called shear volume. An initial validation using published data indicated the shear based power model correlated well with measured power.Establishing a morphological chart to delimit the stirred mill design space indicated that 24 design and operating conditions can be assess using the established shear volume measure. The results indicated for the mill configurations tested that a change in stirred mill liner design can potentially increase shear volume and power from 14% to 290% as compared to smooth chamber liners.

REMEDY FOR LOAD DISCONTINUITY IN TIME HISTORY ANALYSIS

Discontinuity at the end of an impulse will lead to an amplitude distortion in a time history analysis. This amplitude distortion can be effectively reduced, if a very small time step is used to perform a complete step-by-step integration procedure. As a result, a lot of computational effort is involved. In this study, it will be shown that a significant amplitude distortion may also occur for a dynamic loading, which is not classified as an impulse. Furthermore, a remedy is proposed to overcome the difficulty caused by the load discontinuity. This remedy is very simple and it involves adjusting the input load at the time instant of discontinuity. In fact, the average of the two discontinuity values at the load discontinuity is taken to be the adjusting input load for the time instant of load discontinuity. The feasibility of this remedy is analytically verified and confirmed with numerical examples not only for impulses but also for dynamic loadings. Apparently, there is no extra computational effort needed for the remedy and it will not complicate the programming of dynamic analysis codes.

Design Space Exploration of Deeply Nested Loop 2D Filtering and 6 Level FSBM Algorithm Mapped onto Systolic Array

The high integration density in today′s VLSI chips offers enormous computing power to be utilized by the design of parallel computing hardware. The implementation of computationally intensive algorithms represented by n‐dimensional (n‐D) nested loop algorithms, onto parallel array architecture is termed as mapping. The methodologies adopted for mapping these algorithms onto parallel hardware often use heuristic search that requires a lot of computational effort to obtain near optimal solutions. We propose a new mapping procedure wherein a lower dimensional subspace (of the n‐D problem space) of inner loop is identified, in which lies the computational expression that generates the output or outputs of the n‐D problem. The processing elements (PE array) are assigned to the identified sub‐space and the reuse of the PE array is through the assignment of the PE array to the successive sub‐spaces in consecutive clock cycles/periods (CPs) to complete the computational tasks of the n‐D problem. The above is used to develop our proposed modified heuristic search to arrive at optimal design and the complexity comparisons are given. The MATLAB results of the new search and the design space trade‐off analysis using the high‐level synthesis tool are presented for two typical computationally intensive nested loop algorithms—the 6D FSBM and the 4D edge detection alternatively known as the 2D filtering algorithm.

FluDetWeb: an interactive web-based system for the early detection of the onset of influenza epidemics

BackgroundThe early identification of influenza outbreaks has became a priority in public health practice. A large variety of statistical algorithms for the automated monitoring of influenza surveillance have been proposed, but most of them require not only a lot of computational effort but also operation of sometimes not-so-friendly software.ResultsIn this paper, we introduce FluDetWeb, an implementation of a prospective influenza surveillance methodology based on a client-server architecture with a thin (web-based) client application design. Users can introduce and edit their own data consisting of a series of weekly influenza incidence rates. The system returns the probability of being in an epidemic phase (via e-mail if desired). When the probability is greater than 0.5, it also returns the probability of an increase in the incidence rate during the following week. The system also provides two complementary graphs. This system has been implemented using statistical free-software (ℝ and WinBUGS), a web server environment for Java code (Tomcat) and a software module created by us (Rdp) responsible for managing internal tasks; the software package MySQL has been used to construct the database management system. The implementation is available on-line from: http://www.geeitema.org/meviepi/fludetweb/.ConclusionThe ease of use of FluDetWeb and its on-line availability can make it a valuable tool for public health practitioners who want to obtain information about the probability that their system is in an epidemic phase. Moreover, the architecture described can also be useful for developers of systems based on computationally intensive methods.

Nonlocal collisionless power absorption using effective viscosity model in inductively coupled plasma discharges

Effective viscosity model for inductively coupled plasma (ICP) discharges has been used to calculate the power absorbed inside ICP discharges. It is found that it can be used to calculate collisionless heating, which is a warm plasma effect. The validity of effective viscosity model has been checked by comparing it with kinetic model for warm ICP discharges. For very small plasma lengths, the results of both models are the same. At intermediate lengths where bounce resonance heating is important, results of the two models are not the same. Bounce resonance length given by effective viscosity model does not match very well with that given by the kinetic model. It shows that bounce resonance heating cannot be taken care of accurately using the effective viscosity model. For large plasma length, when driving frequencies are low, power absorbed calculated using the kinetic model is more than that calculated by the effective viscosity model. For high driving frequencies, power absorbed calculated using the kinetic model is less than that calculated by the effective viscosity model. The best match between the results of two models (for large plasma length) is obtained if the combination of plasma density, electron temperature, driving frequency, and speed of light is such that the relation K=ωpvth/ωc≃1 holds. It is concluded that computationally less extensive effective viscosity model can be used to estimate power absorption in ICP discharges by calibrating it with the help of computationally intensive kinetic model. Once calibration is done a lot of computational effort can be avoided by using effective viscosity model instead of kinetic model.

Real–Time Correction of Cameras’ Geometric Distortions using GPGPU

Lens distortion correction is very important for machine vision applications. Estimation of internal camera parameters is necessary for precise 2D or 3D scene measurements. Nonlinear image warping operation needs a lot of computational effort and is critical for real–time systems. Modern GPGPU devices give the possibility processing such data but needs fast algorithm for calculations result. In this paper optimized coalescence algorithm for best GPGPU performance is proposed.

Load Discontinuity in Step-by-step Integration

In this article, both analytical and numerical studies show that a load discontinuity will lead to an amplitude distortion in performing the step-by-step integration. It is also found that the relative amplitude error caused by load discontinuity is closely related to, but not proportional to, the value of the load discontinuity. In general, this amplitude distortion can be reduced if a very small time step is used for a whole step-by-step integration procedure. Hence, a lot of computational efforts will be involved. In order to reduce these computational efforts a remedy is proposed herein. The remedy is proposed to perform a very small single time step immediately after the load discontinuity to reduce amplitude distortion. Since only a very small time step is performed in the step-by-step integration, many computational efforts can be saved. The feasibility of this remedy is analytically proved and numerically confirmed.

Bias Reduction in European Option Pricing

Pricing European options using price estimates of the underlying security that contain noise, create a bias in the option price. We present a technique to reduce this bias. Using ideas from the Longstaff and Schwartz (2001) algorithm, we prove that when the price of the underlying security belongs to a space spanned by a set of basis functions, the bias reduction technique can effectively remove the option price bias. In this setting we prove (i) the option price bias can be controlled by increasing the computational burden (ii) the proposed estimator for the price of the underlying security is less volatile than the crude Monte Carlo estimate and (iii) the resulting option price estimator is consistent. The technique is particular efficient when a lot of computational effort has to be allocated to reduce the option price bias.

An efficient modeling technique for floor vibration in multi-story buildings

Analysis of a framed structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic responses. This paper presents an efficient modeling technique for vertical vibration utilizing substructuring technique and super elements. To simplify the modeling procedure each floor in a structure is modeled as a substructure. Only the vertical translational degrees of freedom are selected as master degrees of freedom in the inside of each substructure. At the substructure-column interface, horizontal and rotational degrees of freedom are also included considering the compatibility condition of slabs and columns. For further simplification, the repeated parts in a substructure are modeled as super elements, which reduces computation time required for the construction of system matrices in a substructure. Finally, the Guyan reduction technique is applied to enhance the efficiency of dynamic analysis. In numerical examples, the efficiency and accuracy of the proposed method are demonstrated by comparing the response time histories and the analysis time.

Gradient estimate for parameter design of threshold controllers in a failure-prone production system

A manufacturing system, with n failure-prone machines in tandem and n internal buffers, is considered. Two threshold control policies, which can be interpreted as the noted PULL and PUSH policies, are used to regulate the system. To optimize the threshold values, the key problem is to find the available gradient information of objective functional with respect to threshold values. We apply the perturbation analysis technique to this system. By defining the machine states and events in the evolution of the system, general perturbation rules are presented. Then simple algorithms are developed to derive the gradient estimates based on a single sample process, which may save a lot of computational efforts and simulation/ experiment times. The unbiasedness and consistency of the gradient estimates are proved. Simulation examples are given to demonstrate the effectiveness of the results

Saturable reactor controlled parallel resonant load

This paper develops a model for a saturable reactor with a parallel tuned tank circuit. From this model the characteristics of the circuit are derived and compared with measured data. Saturable reactors are used to control power to various loads. In the case of an induction furnace the load is a tuned tank circuit. This combination of reactors and load has demonstrated resonances at low load, "Q". The phenomenon is hard to predict. Solutions, using a continuous function to model the, "B-H" curve, usually require a great deal of computational effort. The sharp saturation, typical of these reactors, requires a high order polynomial to model the, "B-H" curve. In solving the equations with such a polynomial, a lot of computational effort must be spent in expanding the polynomial in order to produce a set of non-linear equations.