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General Equation (general + equation)
Selected AbstractsPerformance analysis and interoperability issue of consolidation algorithms in point-to-multipoint ABR servicesINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2002Naris Rangsinoppamas Abstract In this paper we propose a performance analysis of the consolidation algorithms in point-to-multipoint ABR services in ATM network. We also present a new efficient consolidation algorithm, which overcomes some drawbacks of the previous works. The performance of the previous works and our proposed consolidation algorithms are analysed mathematically. General equations for calculating the response time and allowed cell rate of the source are derived. The derived equations show relatively good agreement with simulation results and can be applied for using in various network topologies. In addition, the interoperability issue in multicast available bit rate (ABR) is investigated. It is found that the branch points implemented with different consolidation algorithms can work interoperably. It is concluded from the simulation results that the performance of the point-to-multipoint ABR services is dominated by the most upper stream branch point (the nearest one to the source), therefore, in order to avoid the consolidation noise and get a faster response in the network, the most upper stream branch point has to be implemented with a high accuracy consolidation algorithm while the lower stream branch point(s) should be implemented with a fast response consolidation algorithm with a less degree of complexity. Copyright © 2002 John Wiley & Sons, Ltd. [source] Carbon dioxide generation calorimetry,Errors induced by the simplifying assumptions in the standard test methodsFIRE AND MATERIALS, Issue 2 2009S. Brohez Abstract Carbon dioxide generation (CDG) calorimetry is commonly used for measuring heat release rates of materials. Calorimetric equation provided in the ASTM E 2058 and the NFPA code 287 is a simplified equation since the water content in the ambient air and the fumes as well as the expansion factor of the combustion gases are neglected. This paper provides general equation for CDG calorimetry based on the Tewarson formulation. A comparison is proposed between the Standard test methods (simplified equation) and the general one. It is shown that the errors induced by the simplifying assumptions are negligible for oxygen depletion factor values commonly encountered in the Fire Propagation Apparatus (where large dilution factors of the combustion gases are used before the measurements of species concentrations). Copyright © 2009 John Wiley & Sons, Ltd. [source] Sea surface shape derivation above the seismic streamerGEOPHYSICAL PROSPECTING, Issue 6 2006Robert Laws ABSTRACT The rough sea surface causes perturbations in the seismic data that can be significant for time-lapse studies. The perturbations arise because the reflection response of the non-flat sea perturbs the seismic wavelet. In order to remove these perturbations from the received seismic data, special deconvolution methods can be used, but these methods require, as input, the time varying wave elevation above each hydrophone in the streamer. In addition, the vertical displacement of the streamer itself must also be known at the position of each hydrophone and at all times. This information is not available in conventional seismic acquisition. However, it can be obtained from the hydrophone measurements provided that the hydrophones are recorded individually (not grouped), that the recording bandwidth is extended down to 0.05 Hz and that data are recorded without gaps between the shot records. The sea surface elevation, and also the wave-induced vertical displacement of the streamer, can be determined from the time-varying pressure that the sea waves cause in the hydrophone measurements. When this was done experimentally, using a single sensor seismic streamer without a conventional low cut filter, the wave induced pressure variations were easily detected. The inversion of these experimental data gives results for the sea surface elevation that are consistent with the weather and sea state at the time of acquisition. A high tension approximation allows a simplified solution of the equations that does not demand a knowledge of the streamer tension. However, best results at the tail end of the streamer are obtained using the general equation. [source] Studies on pyrolysis of vegetable market wastes in presence of heat transfer resistance and deactivationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Ruby Ray Abstract In the present investigation, the pyrolysis of predried vegetable market waste (dp=5.03 mm) has been studied using a cylindrical pyrolyser having diameter of 250 mm under both isothermal and non-isothermal conditions within the temperature range of 523,923 K with an intention to investigate the effective contribution of different heat transfer controlling regime namely intra-particle, external along with kinetically control regime on the overall global rate of pyrolysis. Thermogravimetric method of analysis was utilized to obtain experimental data for both isothermal and non-isothermal cases by coupling a digital balance with the pyrolyser. The pyrolysis of vegetable market waste has been observed to exhibit deactivated concentration independent pyrolysis kinetics, analogous to catalytic poisoning, throughout the entire range of study. The deactivation is of 1st order up to 723 K and follows the 3rd order in the temperature range of 723 Using the general equation of a conic for the calculation of the instrument function of a Bragg,Brentano diffractometerJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2008A. D. Zuev The general equation of the conic representing the intersection of the receiving-slit plane with the diffraction cone as well as with the reflection cone of a plane crystal monochromator are given for a diffractometer in Bragg,Brentano geometry. Apart from the fact that this equation can be easily used to calculate the total instrument function as well as specific instrument functions for diffractometers in Bragg,Brentano geometry, it also provides tools for elucidating different aberrations of the diffractometer in Bragg,Brentano geometry. [source] Validation of SAPS 3 Admission Score and comparison with SAPS IIACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2009M. CAPUZZO Background: The objective of this study was to validate the Simplified Acute Physiology Score SAPS 3 Admission Score (SAPS 3) and to compare its fit with that of SAPS II in an independent sample of patients admitted to a single-centre intensive care unit (ICU). Methods: The data for all adult patients consecutively admitted to an eight-bed ICU of a 700-bed university hospital between 1 January 2006 and 2 September 2007 were collected. SAPS II and SAPS 3 were computed, as well as the predicted hospital mortality. The calibration of SAPS II and SAPS 3, according to the general equation (GE), and equations for Southern Europe and Mediterranean countries (SE&MC), and Central and Western Europe (C&WE), were assessed by the goodness-of-fit Hosmer,Lemeshow ? and , statistics. Standardized mortality ratios (SMR) with 95% confidence interval (95% CI) were computed for SAPS II and SAPS 3 equations. Results: Six hundred and eighty-four patients were studied (males 63%). The median age was 73 (quartiles 65,80) years. The fit of SAPS 3 using the C&WE equation (? 13.49, P=0.095; , 12.73, P=0.121) as well as that of SAPS II was acceptable (? 6.02, P=0.644; ,12.08, P=0.147), while SAPS 3 GE (? 23.36, P=0.002; , 22.37, P=0.004) and S&MC (? 25.73, P=0.001; , 26.19, P=0.001) did not fit well. SAPS 3 GE, SAPS 3 SE&M Countries and the SAPS II significantly over estimated the mortality. Only 95% CI of SMR for SAPS 3 C&WE included 1 (SMR 0.97; 95% CI 0.89,1.05). Conclusion: Each ICU should identify the SAPS 3 equation most suitable for its case mix. The SAPS II model tended to overestimate the mortality. [source] Studies on Jacobi,Davidson, Rayleigh quotient iteration, inverse iteration generalized Davidson and Newton updatesNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 8 2006Yunkai Zhou Abstract We study Davidson-type subspace eigensolvers. Correction equations of Jacobi,Davidson and several other schemes are reviewed. New correction equations are derived. A general correction equation is constructed, existing correction equations may be considered as special cases of this general equation. The main theme of this study is to identify the essential common ingredient that leads to the efficiency of a diverse form of Davidson-type methods. We emphasize the importance of the approximate Rayleigh-quotient-iteration direction. Copyright © 2006 John Wiley & Sons, Ltd. [source] Prediction of oxygen transmission rate for thermoformed traysPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2004Marit KvalvÅg Pettersen Abstract There is a desire in the food industry to be able to estimate the oxygen transmission rate (OTR) of packages by knowing the permeability data of unconverted sheet/film, instead of measuring the OTR of packages. Due to thermoforming, the permeability of a material changes and therefore it is difficult to estimate the permeability (OTR) of converted trays from the OTR values of unconverted material. This paper evaluates the possibilities and limitations of predicting the OTR of thermoformed trays. Different methods for the calculation of OTR due to thickness measurements were compared. The use of theoretical thickness was satisfactory in the calculation of OTR of trays based on the OTR of unconverted sheet, area and thickness. Both linear and quadratic regression models were evaluated. Validation of the regression models was made by comparing the measured and calculated OTR of trays made of PS/EVOH/PE, A-PET/PE, PS/PE and PP/PE. These trays were manufactured on different thermoforming machines, different processing parameters and different sizes of mould. None of the models (linear and quadratic) were suitable for the calculation of OTR of trays made of PS/PE and PP/PE. Both linear and quadratic models gave satisfactory agreement with measured values for trays made of both PS/EVOH/PE and A-PET/PE. This case study indicates that a general equation for the calculation of OTR for different polymer combinations was not possible to generate. The equations presented in this paper are strictly applicable only for the polymer combinations used in this experiment, and can not be considered as general equations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Urea interactions with protein groups: A volumetric study,BIOPOLYMERS, Issue 10 2010Soyoung Lee Abstract We determined the partial molar volumes and adiabatic compressibilities of N -acetyl amino acid amides, N -acetyl amino acid methylamides, N -acetyl amino acids, and short oligoglycines as a function of urea concentration. We analyze these data within the framework of a statistical thermodynamic formalism to determine the association constants for the reaction in which urea binds to the glycyl unit and each of the naturally occurring amino acid side chains replacing two waters of hydration. Our determined association constants, k, range from 0.04 to 0.39M. We derive a general equation that links k with changes in free energy, ,Gtr, accompanying the transfer of functional groups from water to urea. In this equation, ,Gtr is the sum of a change in the free energy of cavity formation, ,,GC, and the differential free energy of solute,solvent interactions, ,,GI, in urea and water. The observed range of affinity coefficients, k, corresponds to the values of ,,GI ranging from highly favorable to slightly unfavorable. Taken together, our data support a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. Our derived equation linking k to ,Gtr suggests that ,,GI and, hence, the net transfer free energy, ,Gtr, are both strongly influenced by the concentration of a solute used in the experiment. We emphasize the need to exercise caution when two solutes differing in solubility are compared to determine the ,Gtr contribution of a particular functional group. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 866,879, 2010. [source] Epidermal kinetic alterations required to generate the psoriatic phenotype: a reappraisalCELL PROLIFERATION, Issue 3 2010T. Simonart Objectives:, Although there have been major advances in understanding immunopathogenesis of psoriasis, the basic processes causing psoriatic morphology remain to be identified. Materials and methods:, Our group has designed a systematic review of studies (1962,2009) on keratinocyte kinetics in psoriasis. We obtained data from MEDLINE, PubMed, Current Contents, reference lists and specialist textbooks. A general equation for evolution of the differentiated epidermis has been analysed. Necessary conditions for observed qualitative change in homeostasis between normal skin and established psoriatic lesions were determined. Results and discussion:, Increase in the number of cell divisions (or imbalance in symmetric division rates of committed progenitor cells) and/or decrease in physiological apoptosis in the germinative compartment, together with feedback loops that limit thickening of the skin, are required to generate psoriatic morphology, that is, to increase the absolute size but decrease relative size of the differentiated cell compartment with respect to the germinative compartment. [source] Efficient reduction of fault current through the grounding grid of a substation supplied by an overhead lineEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006Ljubivoje M. Popovi Abstract The paper presents a directly applicable and reasonably accurate method for the evaluation of the effects of the counterpoise, the measure for the reduction of the fault current through the substation grounding grid. Under practical conditions the magnitude of the current diverted from a substation grounding grid by the counterpoise conductor is a very complex function of the self and mutual impedances of overhead and underground conductors, substation grounding impedance, transmission line towers resistance, proximity effect between the grounding grid and the counterpoise conductor, as well as on many other factors of lower order. Therefore certain idealizations and simplification of the real physical model were indispensable to develop the mathematical model presented here. The obtained expressions are mostly based on the general equations of a line represented by its lumped parameters and the general equations of uniform ladder circuits. Copyright © 2006 John Wiley & Sons, Ltd. [source] Leakage field distribution of a transformer for conventional and superconducting conditionsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2002P. Raitsios The overall distribution of leakage field and current density in a transformer model with cylindrical windings in proximity to the core yokes is investigated from a different viewpoint than that of Kapp or Rogowski, i.e. by taking into consideration the conductivity of the conductive material. Using Maxwell's differential equations and the vector potential and by considering the conductivity of the conductive material, general equations are obtained for the components of the magnetic induction in a two dimensional space. From these components the leakage inductance is calculated and its application for conventional and superconducting conditions is examined. The distribution of current density in the windings is obtained from the vector potential. [source] An arbitrary Lagrangian,Eulerian method based on the adaptive Riemann solvers for general equations of stateINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2009Baolin Tian Abstract Approximate or exact Riemann solvers play a key role in Godunov-type methods. In this paper, three approximate Riemann solvers, the MFCAV, DKWZ and weak wave approximation method schemes, are investigated through numerical experiments, and their numerical features, such as the resolution for shock and contact waves, are analyzed and compared. Based on the analysis, two new adaptive Riemann solvers for general equations of state are proposed, which can resolve both shock and contact waves well. As a result, an ALE method based on the adaptive Riemann solvers is formulated. A number of numerical experiments show good performance of the adaptive solvers in resolving both shock waves and contact discontinuities. Copyright © 2008 John Wiley & Sons, Ltd. [source] Hierarchic multigrid iteration strategy for the discontinuous Galerkin solution of the steady Euler equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9-10 2006Koen Hillewaert Abstract We study the efficient use of the discontinuous Galerkin finite element method for the computation of steady solutions of the Euler equations. In particular, we look into a few methods to enhance computational efficiency. In this context we discuss the applicability of two algorithmical simplifications that decrease the computation time associated to quadrature. A simplified version of the quadrature free implementation applicable to general equations of state, and a simplified curved boundary treatment are investigated. We as well investigate two efficient iteration techniques, namely the classical Newton,Krylov method used in computational fluid dynamics codes, and a variant of the multigrid method which uses interpolation orders rather than coarser tesselations to define the auxiliary coarser levels. Copyright © 2005 John Wiley & Sons, Ltd. [source] Pressure relaxation procedures for multiphase compressible flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2005M.-H. Lallemand Abstract This paper deals with pressure relaxation procedures for multiphase compressible flow models. Such models have nice mathematical properties (hyperbolicity) and are able to solve a wide range of applications: interface problems, detonation physics, shock waves in mixtures, cavitating flows, etc. The numerical solution of such models involves several ingredients. One of those ingredients is the instantaneous pressure relaxation process and is of particular importance. In this article, we present and compare existing and new pressure relaxation procedures in terms of both accuracy and computational efficiency. Among these procedures we enhance an exact one in the particular case of fluids governed by the stiffened gas equation of state, and approximate procedures for general equations of state, which are particularly well suited for problems with large pressure variations. We also present some generalizations of these procedures in the context of multiphase flows with an arbitrary number of fluids. Some tests are provided to illustrate these comparisons. Copyright © 2005 John Wiley & Sons, Ltd. [source] Numerical simulation of dense gas flows on unstructured grids with an implicit high resolution upwind Euler solverINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2004P. Colonna Abstract The study of the dense gas flows which occur in many technological applications demands for fluid dynamic simulation tools incorporating complex thermodynamic models that are not usually available in commercial software. Moreover, the software mentioned can be used to study very interesting phenomena that usually go under the name of ,non-classical gasdynamics', which are theoretically predicted for high molecular weight fluids in the superheated region, close to saturation. This paper presents the numerical methods and models implemented in a computer code named zFlow which is capable of simulating inviscid dense gas flows in complex geometries. A detailed description of the space discretization method used to approximate the Euler equations on unstructured grids and for general equations of state, and a summary of the thermodynamic functions required by the mentioned formulation are also given. The performance of the code is demonstrated by presenting two applications, the calculation of the transonic flow around an airfoil computed with both the ideal gas and a complex equation of state and the simulation of the non-classical phenomena occurring in a supersonic flow between two staggered sinusoidal blades. Non-classical effects are simulated in a supersonic flow of a siloxane using a Peng,Robinson-type equation of state. Siloxanes are a class of substances used as working fluids in organic Rankine cycles turbines. Copyright © 2004 John Wiley & Sons, Ltd. [source] Prediction of oxygen transmission rate for thermoformed traysPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2004Marit KvalvÅg Pettersen Abstract There is a desire in the food industry to be able to estimate the oxygen transmission rate (OTR) of packages by knowing the permeability data of unconverted sheet/film, instead of measuring the OTR of packages. Due to thermoforming, the permeability of a material changes and therefore it is difficult to estimate the permeability (OTR) of converted trays from the OTR values of unconverted material. This paper evaluates the possibilities and limitations of predicting the OTR of thermoformed trays. Different methods for the calculation of OTR due to thickness measurements were compared. The use of theoretical thickness was satisfactory in the calculation of OTR of trays based on the OTR of unconverted sheet, area and thickness. Both linear and quadratic regression models were evaluated. Validation of the regression models was made by comparing the measured and calculated OTR of trays made of PS/EVOH/PE, A-PET/PE, PS/PE and PP/PE. These trays were manufactured on different thermoforming machines, different processing parameters and different sizes of mould. None of the models (linear and quadratic) were suitable for the calculation of OTR of trays made of PS/PE and PP/PE. Both linear and quadratic models gave satisfactory agreement with measured values for trays made of both PS/EVOH/PE and A-PET/PE. This case study indicates that a general equation for the calculation of OTR for different polymer combinations was not possible to generate. The equations presented in this paper are strictly applicable only for the polymer combinations used in this experiment, and can not be considered as general equations. Copyright © 2004 John Wiley & Sons, Ltd. [source]
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