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Realistic Problems (realistic + problem)
Selected AbstractsHybrid approach with an expert system and a genetic algorithm to production management in the supply netINTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 1-2 2006awrynowicz A new approach to solving production management problems in the supply net is proposed. An expert system designed to help companies in medium-term and short-term production planning is discussed. The proposed expert system considers alternative process plans for a job and outsourcing, when a bottleneck exists in the machine. The proposed hybrid system uses the output of the expert system as the input of the genetic algorithm. The output of the genetic algorithm is a near optimal schedule. The proposed method does not require any unrealistic assumptions. It can be used to solve highly complicated and non-linear functions of a realistic problem. Copyright © 2007 John Wiley & Sons, Ltd. [source] Computer programs for estimating substrate flux into steady-state biofilms from pseudoanalytical solutionsCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2002Chetan T. Goudar Abstract Fixed-film processes employing microorganisms attached to an inert surface (biofilms) are widely used for biological treatment of municipal and industrial wastewater. For optimal design and analysis of these processes, mathematical models are necessary that describe the dynamics of contaminant transport within these biofilms and the associated contaminant utilization by the microorganisms. However, these governing equations that typically involve Fickian diffusion for contaminant transport and Monod kinetics for contaminant utilization are inherently nonlinear and have no closed form solutions except under special conditions. This can restrict their use in the classroom as cumbersome numerical techniques must be used for their solution. This problem is well documented in the literature and several authors have presented pseudoanalytical solutions that replace numerical solutions with algebraic equations. In the present study, we present pseudoanalytical solution-based computer programs for estimating substrate flux and biofilm thickness for a steady-state biofilm. Depending upon the intended end use, these programs can either partially or totally automate the solution process. In the partial automation mode, they can serve to enhance student understanding of important concepts related to steady-state biofilms, while complete automation can help bring more challenging and realistic problems associated with steady-state biofilms into the classroom. The programs have been tested on MATLAB version 5.0 and are available as freeware for educational purposes. © 2002 Wiley Periodicals, Inc. Comput Appl Eng Educ 10: 26,32, 2002; Published online in Wiley InterScience (www.interscience.wiley.com.); DOI 10.1002/cae.10017 [source] GPU-accelerated boundary element method for Helmholtz' equation in three dimensionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2009Toru Takahashi Abstract Recently, the application of graphics processing units (GPUs) to scientific computations is attracting a great deal of attention, because GPUs are getting faster and more programmable. In particular, NVIDIA's GPUs called compute unified device architecture enable highly mutlithreaded parallel computing for non-graphic applications. This paper proposes a novel way to accelerate the boundary element method (BEM) for three-dimensional Helmholtz' equation using CUDA. Adopting the techniques for the data caching and the double,single precision floating-point arithmetic, we implemented a GPU-accelerated BEM program for GeForce 8-series GPUs. The program performed 6,23 times faster than a normal BEM program, which was optimized for an Intel's quad-core CPU, for a series of boundary value problems with 8000,128000 unknowns, and it sustained a performance of 167,Gflop/s for the largest problem (1 058 000 unknowns). The accuracy of our BEM program was almost the same as that of the regular BEM program using the double precision floating-point arithmetic. In addition, our BEM was applicable to solve realistic problems. In conclusion, the present GPU-accelerated BEM works rapidly and precisely for solving large-scale boundary value problems for Helmholtz' equation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Parallel multipole implementation of the generalized Helmholtz decomposition for solving viscous flow problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2003Mary J. Brown Abstract The evaluation of a domain integral is the dominant bottleneck in the numerical solution of viscous flow problems by vorticity methods, which otherwise demonstrate distinct advantages over primitive variable methods. By applying a Barnes,Hut multipole acceleration technique, the operation count for the integration is reduced from O(N2) to O(NlogN), while the memory requirements are reduced from O(N2) to O(N). The algorithmic parameters that are necessary to achieve such scaling are described. The parallelization of the algorithm is crucial if the method is to be applied to realistic problems. A parallelization procedure which achieves almost perfect scaling is shown. Finally, numerical experiments on a driven cavity benchmark problem are performed. The actual increase in performance and reduction in storage requirements match theoretical predictions well, and the scalability of the procedure is very good. Copyright © 2003 John Wiley Sons, Ltd. [source] On accurate boundary conditions for a shape sensitivity equation methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2006R. Duvigneau Abstract This paper studies the application of the continuous sensitivity equation method (CSEM) for the Navier,Stokes equations in the particular case of shape parameters. Boundary conditions for shape parameters involve flow derivatives at the boundary. Thus, accurate flow gradients are critical to the success of the CSEM. A new approach is presented to extract accurate flow derivatives at the boundary. High order Taylor series expansions are used on layered patches in conjunction with a constrained least-squares procedure to evaluate accurate first and second derivatives of the flow variables at the boundary, required for Dirichlet and Neumann sensitivity boundary conditions. The flow and sensitivity fields are solved using an adaptive finite-element method. The proposed methodology is first verified on a problem with a closed form solution obtained by the Method of Manufactured Solutions. The ability of the proposed method to provide accurate sensitivity fields for realistic problems is then demonstrated. The flow and sensitivity fields for a NACA 0012 airfoil are used for fast evaluation of the nearby flow over an airfoil of different thickness (NACA 0015). Copyright © 2005 John Wiley & Sons, Ltd. [source] Blur-generated non-separable space,time modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 4 2000Patrick E. Brown Statistical space,time modelling has traditionally been concerned with separable covariance functions, meaning that the covariance function is a product of a purely temporal function and a purely spatial function. We draw attention to a physical dispersion model which could model phenomena such as the spread of an air pollutant. We show that this model has a non-separable covariance function. The model is well suited to a wide range of realistic problems which will be poorly fitted by separable models. The model operates successively in time: the spatial field at time t +1 is obtained by ,blurring' the field at time t and adding a spatial random field. The model is first introduced at discrete time steps, and the limit is taken as the length of the time steps goes to 0. This gives a consistent continuous model with parameters that are interpretable in continuous space and independent of sampling intervals. Under certain conditions the blurring must be a Gaussian smoothing kernel. We also show that the model is generated by a stochastic differential equation which has been studied by several researchers previously. [source] Decentralized control strategies for dynamic routingOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 6 2002ftar Abstract The routing problem in multi-destination data communication networks is considered. A dynamic model, which can incorporate arbitrary, different, time-varying processing delays at different nodes, is developed to describe the network dynamics. Based on this model, controllers for routing control are proposed. The structures of the proposed controllers are motivated by an optimal control problem. These proposed controllers are completely decentralized in the sense that all necessary on-line computations are done locally at each node. Furthermore, the information needed for these computations is related only to the queue lengths at the present node and the adjacent downstream nodes. Both cases when the controls can be continuously changed and when the controls are updated at discrete time instants are considered. In the latter case the controls at different nodes may be updated at different time instants (i.e. the network is not necessarily synchronous). It is shown that the controllers enjoy many desirable properties; in particular, they clear all the queues of the network in the absence of external message arrivals, in finite time. Furthermore, the controllers do not direct messages around a loop. They also have certain robustness properties. Some simulation results relating to a number of realistic problems are presented to illustrate various features of the controllers. Copyright © 2002 John Wiley & Sons, Ltd. [source] Type 1, tents, take-aways and toilets: how to manage at a music festivalPRACTICAL DIABETES INTERNATIONAL (INCORPORATING CARDIABETES), Issue 7 2010J Charlton BSc, PgCTLHE Abstract Maintaining optimal glycaemic control in people with type 1 diabetes is challenging. Attending a weekend music festival encompasses lifestyle activities that increase the challenge. These include: increased exercise, and changes in eating and alcohol consumption. The practicalities of blood glucose monitoring and insulin injections are also a consideration. The aim of this project was to identify realistic problems for people with type 1 diabetes attending a music festival, and to review current written advice and available literature in order to provide relevant information. No literature was identified. Fifty people with type 1 diabetes aged 18,40 years were randomly selected and sent a questionnaire enquiring about experiences. Thirteen responded (26%). The mean duration of diabetes was 11.7 years (range 1.5,28 years). All 13 respondents had attended a music festival; of these, 46% had attended one for the first time. Some of the concerns included: hypoglycaemia (31%), lack of food (23%), losing insulin and equipment (23%), and maintaining blood glucose levels (23%). Anxieties regarding hypoglycaemia resulted in 38% running blood glucose levels higher than normal. Thirty-eight percent experienced hypoglycaemia, the reasons being: increased activity (38%), eating less carbohydrate (8%), and reduced blood glucose testing (8%). Twenty-three percent attended the first aid tent: 15% regarding injections and 8% for non-diabetic reasons. An information leaflet regarding managing diabetes when attending a festival has been designed which includes feedback and tips from patients. The leaflet was evaluated by 50 people with type 1 diabetes, and 20 health care professionals. Currently, negotiations are underway with Diabetes UK, T in the Park festival organisers and the St Andrew's Ambulance Service to have an advice stand at the festival. Copyright © 2010 John Wiley & Sons. [source] | ||||||||||