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Continuous System (continuous + system)
Selected AbstractsStochastic Response of a Continuous System with Stochastic Surface Irregularities to an Accelerated LoadPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003C.A. Schenk The problem of calculating the second moment characteristics of the response of a general class of nonconservative linear distributed parameter systems with stochastically varying surface roughness, excited by a moving concentrated load, is investigated. In particular the case of an accelerated load is discussed. The surface roughness is modeled as a Gaussian stationary second order process. For the stochastic representation of the surface roughness a orthogonal series expansion of the covariance kernel, the so called Karhunen-Loéve expansion, is applied. The resulting initial/boundary value problem is transformed by eigenfunction expansion into the modal state space. Second moment characteristics of the response are determined numerically by direct integration using a Runge-Kutta method. [source] Modeling and simulation of bioheat transfer in the human eye using the 3D alpha finite element method (,FEM)INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2010Eric Li Abstract Computational modeling is an effective tool for the detection of eye abnormalities and a valuable assistant to hyperthermia treatments. In all these diagnoses and treatments, predicting the temperature distribution accurately is very important. However, the standard finite element method (FEM) currently used for such purposes has strong reliance on element meshes and the discretized system exhibits the so-called ,overly stiff' behavior. To overcome this shortcoming, this paper formulates an alpha finite element method (,FEM) to compute two-dimensional (2D) and three-dimensional (3D) bioheat transfer in the human eyes. The ,FEM can produce much more accurate results using triangular (2D) and tetrahedron (3D) elements that can be generated automatically for complicated domains and hence is particularly suited for modeling human eyes. In the ,FEM, a scaling factor ,,[0, 1] is introduced to combine the ,overly stiff' FEM model and ,overly soft' node-based finite element method (NS-FEM) model. With a properly chosen ,, the ,FEM can produce models with very ,close-to-exact' stiffness of the continuous system. Numerical results have shown that the present method gives much more accurate results compared with the standard FEM and the NS-FEM. Copyright © 2010 John Wiley & Sons, Ltd. [source] Reduced order state-space models from the pulse responses of a linearized CFD schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2003Ann L. Gaitonde This paper describes a method for obtaining a time continuous reduced order model (ROM) from a system of time continuous linear differential equations. These equations are first put into a time discrete form using a finite difference approximation. The unit sample responses of the discrete system are calculated for each system input and these provide the Markov parameters of the system. An eigenvalue realization algorithm (ERA) is used to construct a discrete ROM. This ROM is then used to obtain a continuous ROM of the original continuous system. The focus of this paper is on the application of this method to the calculation of unsteady flows using the linearized Euler equations on moving meshes for aerofoils undergoing heave or linearized pitch motions. Applying a standard cell-centre spatial discretization and taking account of mesh movement a continuous system of differential equations is obtained which are continuous in time. These are put into discrete time form using an implicit finite difference approximation. Results are presented demonstrating the efficiency of the system reduction method for this system. Copyright © 2003 John Wiley & Sons, Ltd. [source] Roman Navigation in Venice Lagoon: the Results of Underwater ResearchINTERNATIONAL JOURNAL OF NAUTICAL ARCHAEOLOGY, Issue 2 2010Marco D'Agostino Venice lagoon formed part of a network of inland waterways used for navigation in the northern Adriatic, an almost continuous system of lakes, river-mouths and canals, at least partly pre-Roman in origin. The fossae which cross the present lagoon are the continuation of a complex system of natural watercourses and artificial canals between Ravenna and Aquileia. Two Roman buildings discovered on the present San Felice canal could be interpreted as providing navigational assistance at points linking the sea and inland routes. © 2009 The Authors [source] Inactivation Kinetics of Foodborne Spoilage and Pathogenic Bacteria by OzoneJOURNAL OF FOOD SCIENCE, Issue 3 2000J.-G. Kim ABSTRACT: Ozone was tested against Pseudomonas fluorescens, Escherichia coli O157:H7, Leuconostoc mesenteroides, and Listeria monocytogenes. When kinetic data from a batch reactor were fitted to a dose-response model, a 2-phased linear relationship was observed. A continuous ozone reactor was developed to ensure a uniform exposure of bacterial cells to ozone and a constant concentration of ozone during the treatment. Survivors plots in the continuous system were linear initially, followed by a concave downward pattern. Exposure of bacteria to ozone at 2.5 ppm for 40 s caused 5 to 6 log decrease in count. Resistance of tested bacteria to ozone followed this descending order: E. coli O157:H7, P. fluorescens, L. mesenteroides, and L. monocytogenes. [source] Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modelingBIOTECHNOLOGY PROGRESS, Issue 5 2009S. Jaisankar Abstract Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m3 as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe2+ concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Utilization of semi-natural grassland through integrated generation of solid fuel and biogas from biomass.GRASS & FORAGE SCIENCE, Issue 4 2009Abstract A procedure (Integrated Generation of Solid Fuel and Biogas from Biomass, IFBB) was developed which uses a screw press to separate the readily digestible constituents of mature grassland biomass into a press fluid for conversion into biogas and a fibrous press cake for processing into a solid fuel. Effects of mechanical dehydration and prior hydrothermal conditioning at different temperatures (5, 60 and 80°C) on concentrations of organic compounds in the press fluid and on methane production in batch experiments were evaluated for five semi-natural grasslands typical of mountain areas of Germany. Results show that the crude protein concentration of the press fluids was higher and crude fibre concentration was lower than that of the parent material (herbage conserved as silage). Digestion tests in batch fermenters showed that the methane yield of the press fluids was double [397,426 normal litre (NL) kg,1 volatile solids (VS) after 13 d] that of the whole-crop grassland silage (218 NL kg,1 VS after 27 d) but no consistent effect of higher temperature during conditioning was observed. Within 13 d of fermentation the decomposition of the organic matter (OM) that occurred in the press fluids was 0·90, whereas after 27 d of fermentation more than 0·40 of the OM remained undigested in the whole-crop silage, pointing at a marked reduction in retention time for anaerobic digestion of press fluids in continuous systems. Press fluids produced 0·90 of the maximum methane yield after 4 to 7 d compared with 19 days for the whole-crop silage. [source] Stability and accuracy of the iterative differential quadrature methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2003Stefania Tomasiello Abstract In this paper the stability and accuracy of an iterative method based on differential quadrature rules will be discussed. The method has already been proposed by the author in a previous work, where its good performance has been shown. Nevertheless, discussion about stability and accuracy remained open. An answer to this question will be provided in this paper, where the conditional stability of the method will be pointed out, in addition to an examination of the possible errors which arise under certain conditions. The discussion will be preceded by an overview of the method and its foundations, i.e. the differential quadrature rules, and followed by a numerical case which shows how the method behaves when applied to reduce continuous systems to two-degree-of-freedom systems in the non-linear range. In particular, here the case of oscillators coupled in non-linear terms will be treated. The numerical results, used to draw Poincaré maps, will be compared with those obtained by using the Runge,Kutta method with a high precision goal. Copyright © 2003 John Wiley & Sons, Ltd. [source] Assessment of airflow patterns inside six industrial beef carcass chillersINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2001Pierre-Sylvain Mirade Airflow patterns determine process efficiency in beef carcass chilling. An experimental study of air velocity in six industrial chillers (three batch and three continuous systems) afforded a diagnosis of their overall operation. However, the original experimental method did not provide an ideal chiller design: only configurations that were a priori more favourable for carcass chilling than others were identified. To complete the study, calculations were performed using computational fluid dynamics techniques. Applied to a continuous beef carcass chiller, this helped correct a dysfunction revealed in the experimental diagnosis, resulting in a marked lack of ventilation throughout about half the volume of the plant. [source] | |||||||||||||