Theory of steady state plasma flow and confinement in a periodic magnetic field

International Nuclear Information System (INIS)

Brown, M.G.

1981-02-01

The steady flow of plasmas through spatially periodic magnetic fields is examined, and a theoretical model is developed for the case of axisymmetric geometry. The externally applied magnetic fields can be cusps or mirrors joined end to end; electrons are then localised by these fields because of their small Larmor radius, while the ions can traverse the magnetic mirrors. The properties of the model equations are studied and dimensionless parameters which appear are interpreted. Numerical methods used in steady flow applications are reviewed, and some techniques of solution for the model equations are discussed. A solution method involving numerical integration of time-dependent equations is described, which approaches the steady state asymptotically; results from this method are presented and compared with the results from perturbation theory. (author)

Customized Steady-State Constraints for Parameter Estimation in Non-Linear Ordinary Differential Equation Models.

Science.gov (United States)

Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel

2016-01-01

Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization.

Numerical investigation of steady-state thermal behavior of an infrared detector cryo chamber

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Singhal Mayank

2017-01-01

Full Text Available An infrared (IR detector is simply a transducer of radiant energy, converting radiant energy into a measurable form. Since radiation does not rely on visible light, it offers the possibility of seeing in the dark or through obscured conditions, by detecting the IR energy emitted by objects. One of the prime applications of IR detector systems for military use is in target acquisition and tracking of projectile systems. The IR detectors also have great potential in commercial market. Typically, IR detectors perform best when cooled to cryogenic temperatures in the range of nearly 120 K. However, the necessity to operate in such cryogenic regimes makes the application of IR detectors extremely complex. Further, prior to proceeding on to a full blown transient thermal analysis it is worthwhile to perform a steady-state numerical analysis for ascertaining the effect of variation in viz., material, gas conduction coefficient, h, emissivity, ε, on the temperature profile along the cryo chamber length. This would enable understanding the interaction between the cryo chamber and its environment. Hence, the present work focuses on the development of steady-state numerical models for thermal analysis of IR cryo chamber using MATLAB. The numerical results show that gas conduction coefficient has marked influence on the temperature profile of the cryo chamber whereas the emissivity has a weak effect. The experimental validation of numerical results has also been presented.

On the application of finite element method in the solution of steady state diffusion equation

International Nuclear Information System (INIS)

Ono, S.

1982-01-01

The solution of the steady state neutron diffusion equation is obtained by using the finite element method. Specifically the variational approach is used for one dimensional problems and the weighted residual method (Galerkin) for one and two dimensional problems. The spatial domain is divided into retangular elements and the neutron flux is approximated by linear (one dimensional case), and bilinear (two-dimensional case) functions. Numerical results are obtained with a FORTRAN IV computer program and compared with those obtained by the finite difference CITATION code. The results show that linear or bilinear functions, do not satisfactorily describe the differential parameters in highly heterogeneous reactor cases, but provide good results for integral parameters such as multiplication factor. (Author) [pt

Numerical analysis of Markov-perfect equilibria with multiple stable steady states : A duopoly application with innovative firms

NARCIS (Netherlands)

Dawid, H.; Keoula, M.Y.; Kort, Peter

2017-01-01

This paper presents a numerical method for the characterization of Markov-perfect equilibria of symmetric differential games exhibiting coexisting stable steady states. The method relying on the calculation of ‘local value functions’ through collocation in overlapping parts of the state space, is

Optimal control of transitions between nonequilibrium steady states.

Directory of Open Access Journals (Sweden)

Patrick R Zulkowski

Full Text Available Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines.

Existence and instability of steady states for a triangular cross-diffusion system: A computer-assisted proof

Science.gov (United States)

Breden, Maxime; Castelli, Roberto

2018-05-01

In this paper, we present and apply a computer-assisted method to study steady states of a triangular cross-diffusion system. Our approach consist in an a posteriori validation procedure, that is based on using a fixed point argument around a numerically computed solution, in the spirit of the Newton-Kantorovich theorem. It allows to prove the existence of various non homogeneous steady states for different parameter values. In some situations, we obtain as many as 13 coexisting steady states. We also apply the a posteriori validation procedure to study the linear stability of the obtained steady states, proving that many of them are in fact unstable.

Numerical solution of High-kappa model of superconductivity

Energy Technology Data Exchange (ETDEWEB)

Karamikhova, R. [Univ. of Texas, Arlington, TX (United States)

1996-12-31

We present formulation and finite element approximations of High-kappa model of superconductivity which is valid in the high {kappa}, high magnetic field setting and accounts for applied magnetic field and current. Major part of this work deals with steady-state and dynamic computational experiments which illustrate our theoretical results numerically. In our experiments we use Galerkin discretization in space along with Backward-Euler and Crank-Nicolson schemes in time. We show that for moderate values of {kappa}, steady states of the model system, computed using the High-kappa model, are virtually identical with results computed using the full Ginzburg-Landau (G-L) equations. We illustrate numerically optimal rates of convergence in space and time for the L{sup 2} and H{sup 1} norms of the error in the High-kappa solution. Finally, our numerical approximations demonstrate some well-known experimentally observed properties of high-temperature superconductors, such as appearance of vortices, effects of increasing the applied magnetic field and the sample size, and the effect of applied constant current.

Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

International Nuclear Information System (INIS)

Yu Tsvelodub, O

2016-01-01

The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically. (paper)

Stability of periodic steady-state solutions to a non-isentropic Euler-Poisson system

Science.gov (United States)

Liu, Cunming; Peng, Yue-Jun

2017-06-01

We study the stability of periodic smooth solutions near non-constant steady-states for a non-isentropic Euler-Poisson system without temperature damping term. The system arises in the theory of semiconductors for which the doping profile is a given smooth function. In this stability problem, there are no special restrictions on the size of the doping profile, but only on the size of the perturbation. We prove that small perturbations of periodic steady-states are exponentially stable for large time. For this purpose, we introduce new variables and choose a non-diagonal symmetrizer of the full Euler equations to recover dissipation estimates. This also allows to make the proof of the stability result very simple and concise.

The steady state solutions of radiatively driven stellar winds for a non-Sobolev, pure absorption model

International Nuclear Information System (INIS)

Poe, C.H.; Owocki, S.P.; Castor, J.I.

1990-01-01

The steady state solution topology for absorption line-driven flows is investigated for the condition that the Sobolev approximation is not used to compute the line force. The solution topology near the sonic point is of the nodal type with two positive slope solutions. The shallower of these slopes applies to reasonable lower boundary conditions and realistic ion thermal speed v(th) and to the Sobolev limit of zero of the usual Castor, Abbott, and Klein model. At finite v(th), this solution consists of a family of very similar solutions converging on the sonic point. It is concluded that a non-Sobolev, absorption line-driven flow with a realistic values of v(th) has no uniquely defined steady state. To the extent that a pure absorption model of the outflow of stellar winds is applicable, radiatively driven winds should be intrinsically variable. 34 refs

Basis adaptation and domain decomposition for steady-state partial differential equations with random coefficients

Energy Technology Data Exchange (ETDEWEB)

Tipireddy, R.; Stinis, P.; Tartakovsky, A. M.

2017-12-01

We present a novel approach for solving steady-state stochastic partial differential equations (PDEs) with high-dimensional random parameter space. The proposed approach combines spatial domain decomposition with basis adaptation for each subdomain. The basis adaptation is used to address the curse of dimensionality by constructing an accurate low-dimensional representation of the stochastic PDE solution (probability density function and/or its leading statistical moments) in each subdomain. Restricting the basis adaptation to a specific subdomain affords finding a locally accurate solution. Then, the solutions from all of the subdomains are stitched together to provide a global solution. We support our construction with numerical experiments for a steady-state diffusion equation with a random spatially dependent coefficient. Our results show that highly accurate global solutions can be obtained with significantly reduced computational costs.

Steady state magnetic field configurations for the earth's magnetotail

Science.gov (United States)

Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.

1989-01-01

A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

Analytical solution and simplified analysis of coupled parent-daughter steady-state transport with multirate mass transfer

Science.gov (United States)

R. Haggerty

2013-01-01

In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the ratio of concentrations, In (daughter...

Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

Science.gov (United States)

Tsvelodub, O. Yu; Bocharov, A. A.

2017-09-01

The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. The paper studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. The periodic and soliton steady-state traveling solutions of this equation have been numerically found. The analysis of branching of new families of steady-state traveling solutions has been performed. In particular, it is shown that this model equation has solutions in the form of solitons-humps.

Steady-state solution growth of microcrystalline silicon on nanocrystalline seed layers on glass

Science.gov (United States)

Bansen, R.; Ehlers, C.; Teubner, Th.; Boeck, T.

2016-09-01

The growth of polycrystalline silicon layers on glass from tin solutions at low temperatures is presented. This approach is based on the steady-state solution growth of Si crystallites on nanocrystalline seed layers, which are prepared in a preceding process step. Scanning electron microscopy and atomic force microscopy investigations reveal details about the seed layer surfaces, which consist of small hillocks, as well as about Sn inclusions and gaps along the glass substrate after solution growth. The successful growth of continuous microcrystalline Si layers with grain sizes up to several ten micrometers shows the feasibility of the process and makes it interesting for photovoltaics. Project supported by the German Research Foundation (DFG) (No. BO 1129/5-1).

Limitations of steady state solutions to a two-state model of population oscillations and hole burning

International Nuclear Information System (INIS)

Payne, M. G.; Deng, L.; Jiang, K. J.

2006-01-01

We consider a two-state system driven by an on-resonance, continuous wave pump laser and a much weaker pulsed probe laser that is slightly detuned from the pump laser frequency (usually this detuning is about ω p -ω P =Δ≅1 kHz). The upper state population is assumed to be slowly decaying, but the off-diagonal element of the density matrix decays rapidly due to homogeneous broadening. This model has been solved by others in rare-earth-element-doped fibers and crystals in a usual steady state approximation for slow optical wave propagation. We show that in general the usual steady state approximation does not apply unless either Δτ>>1 or (2S+1)γ 2 τ>>1 where γ 2 is the decay rate of the excited state population, τ is the pulse length of the probe field, and 2S is the saturation parameter. Both conditions, however, are not satisfied in many population-oscillation- and corresponding group-velocity-reduction-related studies. Our theory and corresponding numerical simulations have indicated that for probe pulses that are much shorter than the lifetime of the upper state, there is no analytical theory for the amplitude, pulse shape, and group velocity of the probe field. In addition, there is no reason to assume that the group velocity remains small when γ 2 τ<<1 and there is no reason to believe that many pulse length decays can be obtained for such short pulses

Adaptive solution of some steady-state fluid-structure interaction problems

International Nuclear Information System (INIS)

Etienne, S.; Pelletier, D.

2003-01-01

This paper presents a general integrated and coupled formulation for modeling the steady-state interaction of a viscous incompressible flow with an elastic structure undergoing large displacements (geometric non-linearities). This constitutes an initial step towards developing a sensitivity analysis formulation for this class of problems. The formulation uses velocity and pressures as unknowns in a flow domain and displacements in the structural components. An interface formulation is presented that leads to clear and simple finite element implementation of the equilibrium conditions at the fluid-solid interface. Issues of error estimation and mesh adaptation are discussed. The adaptive formulation is verified on a problem with a closed form solution. It is then applied to a sample case for which the structure undergoes large displacements induced by the flow. (author)

Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil

Science.gov (United States)

Kryštůfek, P.; Kozel, K.

2015-05-01

The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.

Steady state magnetic field configurations for the earth's magnetotail

International Nuclear Information System (INIS)

Hau, L.N.; Wolf, R.A.; Voigt, G.H.; Wu, C.C.

1989-01-01

The authors present a two-dimensional, force-balanced magnetic field model in which flux tubes have constant pVγ throughout an extended region of the nightside plasma sheet, between approximately 36 R E geocentric distance and the region of the inner edge of the plasma sheet. They have thus demonstrated the theoretical existence of a steady state magnetic field configuration that is force-balanced and also consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD (isotropic pressure, perfect conductivity). The numerical solution was constructed for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The primary characteristics of the steady state convection solution are (1) a pressure maximum just tailward of the inner edge of the plasma sheet and (2) a deep, broad minimum in equatorial magnetic field strength B ze , also just tailward of the inner edge. The results are consistent with Erickson's (1985) convection time sequences, which exhibited analogous pressure peaks and B ze minima. Observations do not indicate the existence of a B ze minimum, on the average. They suggest that the configurations with such deep minima in B ze may be tearing-mode unstable, thus leading to substorm onset in the inner plasma sheet

Assessing Quasi-Steady State in Evaporation of Sessile Drops by Diffusion Models

Science.gov (United States)

Martin, Cameron; Nguyen, Hoa; Kelly-Zion, Peter; Pursell, Chris

2017-11-01

The vapor distributions surrounding sessile drops of methanol are modeled as the solutions of the steady-state and transient diffusion equations using Matlab's PDE Toolbox. The goal is to determine how quickly the transient diffusive transport reaches its quasi-steady state as the droplet geometry is varied between a Weber's disc, a real droplet shape, and a spherical cap with matching thickness or contact angle. We assume that the only transport mechanism at work is diffusion. Quasi-steady state is defined using several metrics, such as differences between the transient and steady-state solutions, and change in the transient solution over time. Knowing the vapor distribution, the gradient is computed to evaluate the diffusive flux. The flux is integrated along the surface of a control volume surrounding the drop to obtain the net rate of diffusion out of the volume. Based on the differences between the transient and steady-state diffusive fluxes at the discrete points along the control-volume surface, the time to reach quasi-steady state evaporation is determined and is consistent with other proposed measurements. By varying the dimensions of the control volume, we can also assess what regimes have equivalent or different quasi-steady states for different droplet geometries. Petroleum Research Fund.

Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil

Science.gov (United States)

Kryštůfek, P.; Kozel, K.

2014-03-01

The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.

Numerical Solution of Compressible Steady Flows around the NACA 0012 Airfoil

Directory of Open Access Journals (Sweden)

Kozel K

2013-04-01

Full Text Available The article presents results of a numerical solution of subsonic and transonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the NACA 0012 airfoil. Authors used Runge-Kutta method to numerically solve the flows around the NACA 0012 airfoil.

Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil

Directory of Open Access Journals (Sweden)

Kryštůfek P.

2014-03-01

Full Text Available The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.

Steady state neutral beam injector

International Nuclear Information System (INIS)

Mattoo, S.K.; Bandyopadhyay, M.; Baruah, U.K.; Bisai, N.; Chakbraborty, A.K.; Chakrapani, Ch.; Jana, M.R.; Bajpai, M.; Jaykumar, P.K.; Patel, D.; Patel, G.; Patel, P.J.; Prahlad, V.; Rao, N.V.M.; Rotti, C.; Singh, N.P.; Sridhar, B.

2000-01-01

Learning from operational reliability of neutral beam injectors in particular and various heating schemes including RF in general on TFTR, JET, JT-60, it has become clear that neutral beam injectors may find a greater role assigned to them for maintaining the plasma in steady state devices under construction. Many technological solutions, integrated in the present day generation of injectors have given rise to capability of producing multimegawatt power at many tens of kV. They have already operated for integrated time >10 5 S without deterioration in the performance. However, a new generation of injectors for steady state devices have to address to some basic issues. They stem from material erosion under particle bombardment, heat transfer > 10 MW/m 2 , frequent regeneration of cryopanels, inertial power supplies, data acquisition and control of large volume of data. Some of these engineering issues have been addressed to in the proposed neutral beam injector for SST-1 at our institute; the remaining shall have to wait for the inputs of the database generated from the actual experience with steady state injectors. (author)

Light diffusion in N-layered turbid media: steady-state domain.

Science.gov (United States)

Liemert, André; Kienle, Alwin

2010-01-01

We deal with light diffusion in N-layered turbid media. The steady-state diffusion equation is solved for N-layered turbid media having a finite or an infinitely thick N'th layer. Different refractive indices are considered in the layers. The Fourier transform formalism is applied to derive analytical solutions of the fluence rate in Fourier space. The inverse Fourier transform is calculated using four different methods to test their performance and accuracy. Further, to avoid numerical errors, approximate formulas in Fourier space are derived. Fast solutions for calculation of the spatially resolved reflectance and transmittance from the N-layered turbid media ( approximately 10 ms) with small relative differences (<10(-7)) are found. Additionally, the solutions of the diffusion equation are compared to Monte Carlo simulations for turbid media having up to 20 layers.

Quasi-steady state natural convection in a tilted porous layer

Energy Technology Data Exchange (ETDEWEB)

Robillard, L.; Vasseur, P. (Ecole Polytechnique, Montreal, PQ (Canada))

1992-12-01

Natural convection in an inclined porous layer heated or cooled on one side, when its other walls are insulated, has several important engineering applications. These include solar power collection, regenerative heat exchangers, and high performance insulation for buildings and cold storage. Although the problem is basically an unsteady state one, it is known that if the heating (or cooling) process is maintained for a sufficiently long time, a quasi-steady state is approached. Quasi-steady state laminar natural convection in an inclined porous layer is studied analytically and numerically. On the basis of the Darcy-Oberbeck-Boussinesq equations, the problem is solved analytically in the limit of a thin porous layer heated on one side by a heat flux while the other boundaries are maintained adiabatic. For quasi-steady state, the flow and temperature fields overall heat transfer rates are obtained in terms of the controlling parameters and the onset of convection in a bottom heated horizantal system is predicted. It is also demonstrated for the case of a bottom-heated layer that for sufficiently small inclinations, multiple unicellular quasi-steady states exist, some of which are unstable. A numerical study of the same phenomenon, obtained by solving the complete set of governing equations, is conducted. Good agreement is found between the analytical predictions and the numerical simulation. 22 refs., 6 figs.

Active ideal sedimentation: exact two-dimensional steady states.

Science.gov (United States)

Hermann, Sophie; Schmidt, Matthias

2018-02-28

We consider an ideal gas of active Brownian particles that undergo self-propelled motion and both translational and rotational diffusion under the influence of gravity. We solve analytically the corresponding Smoluchowski equation in two space dimensions for steady states. The resulting one-body density is given as a series, where each term is a product of an orientation-dependent Mathieu function and a height-dependent exponential. A lower hard wall is implemented as a no-flux boundary condition. Numerical evaluation of the suitably truncated analytical solution shows the formation of two different spatial regimes upon increasing Peclet number. These regimes differ in their mean particle orientation and in their variation of the orientation-averaged density with height.

Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers

Science.gov (United States)

de S. Teixeira, Renan; S. de B. Alves, Leonardo

2017-12-01

Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases

Steady-state numerical modeling of size effects in micron scale wire drawing

DEFF Research Database (Denmark)

Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof

2017-01-01

Wire drawing processes at the micron scale have received increased interest as micro wires are increasingly required in electrical components. It is well-established that size effects due to large strain gradient effects play an important role at this scale and the present study aims to quantify...... these effects for the wire drawing process. Focus will be on investigating the impact of size effects on the most favourable tool geometry (in terms of minimizing the drawing force) for various conditions between the wire/tool interface. The numerical analysis is based on a steady-state framework that enables...... convergence without dealing with the transient regime, but still fully accounts for the history dependence as-well as the elastic unloading. Thus, it forms the basis for a comprehensive parameter study. During the deformation process in wire drawing, large plastic strain gradients evolve in the contact region...

Numerical simulation of steady cavitating flow of viscous fluid in a Francis hydroturbine

Science.gov (United States)

Panov, L. V.; Chirkov, D. V.; Cherny, S. G.; Pylev, I. M.; Sotnikov, A. A.

2012-09-01

Numerical technique was developed for simulation of cavitating flows through the flow passage of a hydraulic turbine. The technique is based on solution of steady 3D Navier—Stokes equations with a liquid phase transfer equation. The approch for setting boundary conditions meeting the requirements of cavitation testing standard was suggested. Four different models of evaporation and condensation were compared. Numerical simulations for turbines of different specific speed were compared with experiment.

A semi-analytical solution to accelerate spin-up of a coupled carbon and nitrogen land model to steady state

Directory of Open Access Journals (Sweden)

J. Y. Xia

2012-10-01

Full Text Available The spin-up of land models to steady state of coupled carbon–nitrogen processes is computationally so costly that it becomes a bottleneck issue for global analysis. In this study, we introduced a semi-analytical solution (SAS for the spin-up issue. SAS is fundamentally based on the analytic solution to a set of equations that describe carbon transfers within ecosystems over time. SAS is implemented by three steps: (1 having an initial spin-up with prior pool-size values until net primary productivity (NPP reaches stabilization, (2 calculating quasi-steady-state pool sizes by letting fluxes of the equations equal zero, and (3 having a final spin-up to meet the criterion of steady state. Step 2 is enabled by averaged time-varying variables over one period of repeated driving forcings. SAS was applied to both site-level and global scale spin-up of the Australian Community Atmosphere Biosphere Land Exchange (CABLE model. For the carbon-cycle-only simulations, SAS saved 95.7% and 92.4% of computational time for site-level and global spin-up, respectively, in comparison with the traditional method (a long-term iterative simulation to achieve the steady states of variables. For the carbon–nitrogen coupled simulations, SAS reduced computational cost by 84.5% and 86.6% for site-level and global spin-up, respectively. The estimated steady-state pool sizes represent the ecosystem carbon storage capacity, which was 12.1 kg C m⁻² with the coupled carbon–nitrogen global model, 14.6% lower than that with the carbon-only model. The nitrogen down-regulation in modeled carbon storage is partly due to the 4.6% decrease in carbon influx (i.e., net primary productivity and partly due to the 10.5% reduction in residence times. This steady-state analysis accelerated by the SAS method can facilitate comparative studies of structural differences in determining the ecosystem carbon storage capacity among biogeochemical models. Overall, the

Natural equilibria in steady-state neutron diffusion with temperature feedback

International Nuclear Information System (INIS)

Pounders, J. M.; Ingram, R.

2013-01-01

The critical diffusion equation with feedback is investigated within the context of steady-state multiphysics. It is proposed that for critical configurations there is no need to include the multiplication factor k in the formulation of the diffusion equation. This is notable because exclusion of k from the coupled system of equations precludes the mathematically tenuous notion of a nonlinear eigenvalue problem. On the other hand, it is shown that if the factor k is retained in the diffusion equation, as is currently common practice, then the resulting problem is equivalent to the constrained minimization of a functional representing the critical equilibrium of neutron and temperature distributions. The unconstrained solution corresponding to k = 1 represents the natural equilibrium of a critical system at steady-state. Computational methods for solving the constrained problem (with k) are briefly reviewed from the literature and a method for the unconstrained problem (without k) is outlined. A numerical example is studied to examine the effects of the constraint in the nonlinear system. (authors)

Implications of steady-state operation on divertor design

International Nuclear Information System (INIS)

Sevier, D.L.; Reis, E.E.; Baxi, C.B.; Silke, G.W.; Wong, C.P.C.; Hill, D.N.

1996-01-01

As fusion experiments progress towards long pulse or steady state operation, plasma facing components are undergoing a significant change in their design. This change represents the transition from inertially cooled pulsed systems to steady state designs of significant power handling capacity. A limited number of Plasma Facing Component (PFC) systems are in operation or planning to address this steady state challenge at low heat flux. However in most divertor designs components are required to operate at heat fluxes at 5 MW/m 2 or above. The need for data in this area has resulted in a significant amount of thermal/hydraulic and thermal fatigue testing being done on prototypical elements. Short pulse design solutions are not adequate for longer pulse experiments and the areas of thermal design, structural design, material selection, maintainability, and lifetime prediction are undergoing significant changes. A prudent engineering approach will guide us through the transitional phase of divertor design to steady-state power plant components. This paper reviews the design implications in this transition to steady state machines and the status of the community efforts to meet evolving design requirements. 54 refs., 5 figs., 2 tabs

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

DEFF Research Database (Denmark)

Koestel, J. K.; Nørgaard, Trine; Loung, N. M.

2013-01-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables......, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field...... to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column...

An efficient and general numerical method to compute steady uniform vortices

Science.gov (United States)

Luzzatto-Fegiz, Paolo; Williamson, Charles H. K.

2011-07-01

Steady uniform vortices are widely used to represent high Reynolds number flows, yet their efficient computation still presents some challenges. Existing Newton iteration methods become inefficient as the vortices develop fine-scale features; in addition, these methods cannot, in general, find solutions with specified Casimir invariants. On the other hand, available relaxation approaches are computationally inexpensive, but can fail to converge to a solution. In this paper, we overcome these limitations by introducing a new discretization, based on an inverse-velocity map, which radically increases the efficiency of Newton iteration methods. In addition, we introduce a procedure to prescribe Casimirs and remove the degeneracies in the steady vorticity equation, thus ensuring convergence for general vortex configurations. We illustrate our methodology by considering several unbounded flows involving one or two vortices. Our method enables the computation, for the first time, of steady vortices that do not exhibit any geometric symmetry. In addition, we discover that, as the limiting vortex state for each flow is approached, each family of solutions traces a clockwise spiral in a bifurcation plot consisting of a velocity-impulse diagram. By the recently introduced "IVI diagram" stability approach [Phys. Rev. Lett. 104 (2010) 044504], each turn of this spiral is associated with a loss of stability for the steady flows. Such spiral structure is suggested to be a universal feature of steady, uniform-vorticity flows.

Steady states of a diode with counterstreaming electron and positron beams

Energy Technology Data Exchange (ETDEWEB)

Ender, A. Ya.; Kuznetsov, V. I., E-mail: victor.kuznetsov@mail.ioffe.ru; Gruzdev, A. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation)

2016-10-15

Steady states of a plasma layer with counterstreaming beams of oppositely charged particles moving without collisions in a self-consistent electric field are analyzed. The study is aimed at clarifying the mechanism of generation and reconstruction of pulsar radiation. Such a layer also models the processes occurring in Knudsen plasma diodes with counterstreaming electron and ion beams. The steady-state solutions are exhaustively classified. The existence of several solutions at the same external parameters is established.

Steady-state and dynamic models for particle engulfment during solidification

Science.gov (United States)

Tao, Yutao; Yeckel, Andrew; Derby, Jeffrey J.

2016-06-01

Steady-state and dynamic models are developed to study the physical mechanisms that determine the pushing or engulfment of a solid particle at a moving solid-liquid interface. The mathematical model formulation rigorously accounts for energy and momentum conservation, while faithfully representing the interfacial phenomena affecting solidification phase change and particle motion. A numerical solution approach is developed using the Galerkin finite element method and elliptic mesh generation in an arbitrary Lagrangian-Eulerian implementation, thus allowing for a rigorous representation of forces and dynamics previously inaccessible by approaches using analytical approximations. We demonstrate that this model accurately computes the solidification interface shape while simultaneously resolving thin fluid layers around the particle that arise from premelting during particle engulfment. We reinterpret the significance of premelting via the definition an unambiguous critical velocity for engulfment from steady-state analysis and bifurcation theory. We also explore the complicated transient behaviors that underlie the steady states of this system and posit the significance of dynamical behavior on engulfment events for many systems. We critically examine the onset of engulfment by comparing our computational predictions to those obtained using the analytical model of Rempel and Worster [29]. We assert that, while the accurate calculation of van der Waals repulsive forces remains an open issue, the computational model developed here provides a clear benefit over prior models for computing particle drag forces and other phenomena needed for the faithful simulation of particle engulfment.

Reliable and Efficient Procedure for Steady-State Analysis of Nonautonomous and Autonomous Systems

Directory of Open Access Journals (Sweden)

J. Dobes

2012-04-01

Full Text Available The majority of contemporary design tools do not still contain steady-state algorithms, especially for the autonomous systems. This is mainly caused by insufficient accuracy of the algorithm for numerical integration, but also by unreliable steady-state algorithms themselves. Therefore, in the paper, a very stable and efficient procedure for the numerical integration of nonlinear differential-algebraic systems is defined first. Afterwards, two improved methods are defined for finding the steady state, which use this integration algorithm in their iteration loops. The first is based on the idea of extrapolation, and the second utilizes nonstandard time-domain sensitivity analysis. The two steady-state algorithms are compared by analyses of a rectifier and a C-class amplifier, and the extrapolation algorithm is primarily selected as a more reliable alternative. Finally, the method based on the extrapolation naturally cooperating with the algorithm for solving the differential-algebraic systems is thoroughly tested on various electronic circuits: Van der Pol and Colpitts oscillators, fragment of a large bipolar logical circuit, feedback and distributed microwave oscillators, and power amplifier. The results confirm that the extrapolation method is faster than a classical plain numerical integration, especially for larger circuits with complicated transients.

Steady state in a gas of inelastic rough spheres heated by a uniform stochastic force

Energy Technology Data Exchange (ETDEWEB)

Vega Reyes, Francisco, E-mail: fvega@unex.es; Santos, Andrés, E-mail: andres@unex.es [Departamento de Física and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, 06071 Badajoz (Spain)

2015-11-15

We study here the steady state attained in a granular gas of inelastic rough spheres that is subject to a spatially uniform random volume force. The stochastic force has the form of the so-called white noise and acts by adding impulse to the particle translational velocities. We work out an analytical solution of the corresponding velocity distribution function from a Sonine polynomial expansion that displays energy non-equipartition between the translational and rotational modes, translational and rotational kurtoses, and translational-rotational velocity correlations. By comparison with a numerical solution of the Boltzmann kinetic equation (by means of the direct simulation Monte Carlo method), we show that our analytical solution provides a good description that is quantitatively very accurate in certain ranges of inelasticity and roughness. We also find three important features that make the forced granular gas steady state very different from the homogeneous cooling state (attained by an unforced granular gas). First, the marginal velocity distributions are always close to a Maxwellian. Second, there is a continuous transition to the purely smooth limit (where the effects of particle rotations are ignored). And third, the angular translational-rotational velocity correlations show a preference for a quasiperpendicular mutual orientation (which is called “lifted-tennis-ball” behavior)

Efficient steady-state solver for hierarchical quantum master equations

Science.gov (United States)

Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing

2017-07-01

Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.

ATC calculation with steady-state security constraints using Benders decomposition

International Nuclear Information System (INIS)

Shaaban, M.; Yan, Z.; Ni, Y.; Wu, F.; Li, W.; Liu, H.

2003-01-01

Available transfer capability (ATC) is an important indicator of the usable amount of transmission capacity accessible by assorted parties for commercial trading, ATC calculation is nontrivial when steady-state security constraints are included. In hie paper, Benders decomposition method is proposed to partition the AC problem with steady-state security constraints into a base case master problem and a series of subproblems relevant to various contingencies to include their impacts on ATC. The mathematical model is formulated and the two solution schemes are presented. Computer testing on the 4-bus system and IEEE 30-bus system shows the effectiveness of the proposed method and the solution schemes. (Author)

Steady-state oxygen-solubility in niobium

International Nuclear Information System (INIS)

Schulze, K.; Jehn, H.

1977-01-01

During annealing of niobium in oxygen in certain temperature and pressure ranges steady states are established between the absorption of molecular oxygen and the evaporation of volatile oxides. The oxygen concentration in the niobium-oxygen α-solid solution is a function of oxygen pressure and temperature and has been redetermined in the ranges 10 -5 - 10 -2 Pa O 2 and 2,070 - 2,470 K. It follows differing from former results the equation csub(o) = 9.1 x 10 -6 x sub(po2) x exp (502000/RT) with csub(o) in at.-ppm, sub(po2) in Pa, T in K, R = 8.31 J x mol -1 x K -1 . The existence of steady states is limited to a temperature range from 1870 to 2470 K and to oxygen concentrations below the solubility limit given by solidus and solvus lines in the T-c diagram. In the experiments high-purity niobium wires with a specific electrical ratio rho (273 K)/rho(4.2 K) > 5,000 have been gassed under isothermal-isobaric conditions until the steady state has been reached. The oxygen concentration has been determined analytically by vacuum fusion extraction with platinum-flux technique as well as by electrical residual resistivity measurements at 4.2 K. (orig.) [de

Iterative Observer-based Estimation Algorithms for Steady-State Elliptic Partial Differential Equation Systems

KAUST Repository

Majeed, Muhammad Usman

2017-07-19

Steady-state elliptic partial differential equations (PDEs) are frequently used to model a diverse range of physical phenomena. The source and boundary data estimation problems for such PDE systems are of prime interest in various engineering disciplines including biomedical engineering, mechanics of materials and earth sciences. Almost all existing solution strategies for such problems can be broadly classified as optimization-based techniques, which are computationally heavy especially when the problems are formulated on higher dimensional space domains. However, in this dissertation, feedback based state estimation algorithms, known as state observers, are developed to solve such steady-state problems using one of the space variables as time-like. In this regard, first, an iterative observer algorithm is developed that sweeps over regular-shaped domains and solves boundary estimation problems for steady-state Laplace equation. It is well-known that source and boundary estimation problems for the elliptic PDEs are highly sensitive to noise in the data. For this, an optimal iterative observer algorithm, which is a robust counterpart of the iterative observer, is presented to tackle the ill-posedness due to noise. The iterative observer algorithm and the optimal iterative algorithm are then used to solve source localization and estimation problems for Poisson equation for noise-free and noisy data cases respectively. Next, a divide and conquer approach is developed for three-dimensional domains with two congruent parallel surfaces to solve the boundary and the source data estimation problems for the steady-state Laplace and Poisson kind of systems respectively. Theoretical results are shown using a functional analysis framework, and consistent numerical simulation results are presented for several test cases using finite difference discretization schemes.

Steady-state solidification of aqueous ammonium chloride

Science.gov (United States)

Peppin, S. S. L.; Huppert, Herbert E.; Worster, M. Grae

We report on a series of experiments in which a Hele-Shaw cell containing aqueous solutions of NH4Cl was translated at prescribed rates through a steady temperature gradient. The salt formed the primary solid phase of a mushy layer as the solution solidified, with the salt-depleted residual fluid driving buoyancy-driven convection and the development of chimneys in the mushy layer. Depending on the operating conditions, several morphological transitions occurred. A regime diagram is presented quantifying these transitions as a function of freezing rate and the initial concentration of the solution. In general, for a given concentration, increasing the freezing rate caused the steady-state system to change from a convecting mushy layer with chimneys to a non-convecting mushy layer below a relatively quiescent liquid, and then to a much thinner mushy layer separated from the liquid by a region of active secondary nucleation. At higher initial concentrations the second of these states did not occur. At lower concentrations, but still above the eutectic, the mushy layer disappeared. A simple mathematical model of the system is developed which compares well with the experimental measurements of the intermediate, non-convecting state and serves as a benchmark against which to understand some of the effects of convection. Movies are available with the online version of the paper.

An implicit steady-state initialization package for the RELAP5 computer code

International Nuclear Information System (INIS)

Paulsen, M.P.; Peterson, C.E.; Odar, F.

1995-08-01

A direct steady-state initialization (DSSI) method has been developed and implemented in the RELAP5 hydrodynamic analysis program. It provides a means for users to specify a small set of initial conditions which are then propagated through the remainder of the system. The DSSI scheme utilizes the steady-state form of the RELAP5 balance equations for nonequilibrium two-phase flow. It also employs the RELAP5 component models and constitutive model packages for wall-to-phase and interphase momentum and heat exchange. A fully implicit solution of the linearized hydrodynamic equations is implemented. An implicit coupling scheme is used to augment the standard steady-state heat conduction solution for steam generator use. It solves the primary-side tube region energy equations, heat conduction equations, wall heat flux boundary conditions, and overall energy balance equation as a coupled system of equations and improves convergence. The DSSI method for initializing RELAP5 problems to steady-state conditions has been compared with the transient solution scheme using a suite of test problems including; adiabatic single-phase liquid and vapor flow through channels with and without healing and area changes; a heated two-phase test bundle representative of BWR core conditions; and a single-loop PWR model

Statistical steady states in turbulent droplet condensation

Science.gov (United States)

Bec, Jeremie; Krstulovic, Giorgio; Siewert, Christoph

2017-11-01

We investigate the general problem of turbulent condensation. Using direct numerical simulations we show that the fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. This leads to propose a Lagrangian stochastic model consisting of a set of integro-differential equations for the joint evolution of the squared radius and the supersaturation along droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution.

The steady-state tokamak program

International Nuclear Information System (INIS)

Politzer, D.A.; Nevins, W.M.

1992-01-01

This paper reports on a steady-state tokamak experiment (STE) needed to develop the technology and physics data base required for construction of a steady-state fusion power demonstration reactor in the early 21st century. The STE will provide an integrated facility for the development and demonstration of steady-state and particle handling, low-activation high-heat-flux components and materials, efficient current drive, and continuous plasma performance in steady-state, with reactor-like plasma conditions under severe conditions of heat and particle bombardment of the wall. The STE facility will also be used to develop operation and control scenarios for ITER

Molecular control of steady-state dendritic cell maturation and immune homeostasis.

Science.gov (United States)

Hammer, Gianna Elena; Ma, Averil

2013-01-01

Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.

Algorithm for determining two-periodic steady-states in AC machines directly in time domain

Directory of Open Access Journals (Sweden)

Sobczyk Tadeusz J.

2016-09-01

Full Text Available This paper describes an algorithm for finding steady states in AC machines for the cases of their two-periodic nature. The algorithm enables to specify the steady-state solution identified directly in time domain despite of the fact that two-periodic waveforms are not repeated in any finite time interval. The basis for such an algorithm is a discrete differential operator that specifies the temporary values of the derivative of the two-periodic function in the selected set of points on the basis of the values of that function in the same set of points. It allows to develop algebraic equations defining the steady state solution reached in a chosen point set for the nonlinear differential equations describing the AC machines when electrical and mechanical equations should be solved together. That set of those values allows determining the steady state solution at any time instant up to infinity. The algorithm described in this paper is competitive with respect to the one known in literature an approach based on the harmonic balance method operated in frequency domain.

Feasibility study for improved steady-state initialization algorithms for the RELAP5 computer code

International Nuclear Information System (INIS)

Paulsen, M.P.; Peterson, C.E.; Katsma, K.R.

1993-04-01

A design for a new steady-state initialization method is presented that represents an improvement over the current method used in RELAP5. Current initialization methods for RELAP5 solve the transient fluidflow balance equations simulating a transient to achieve steady-state conditions. Because the transient solution is used, the initial conditions may change from the desired values requiring the use of controllers and long transient running times to obtain steady-state conditions for system problems. The new initialization method allows the user to fix thermal-hydraulic values in volumes and junctions where the conditions are best known and have the code compute the initial conditions in other areas of the system. The steady-state balance equations and solution methods are presented. The constitutive, component, and specialpurpose models are reviewed with respect to modifications required for the new steady-state initialization method. The requirements for user input are defined and the feasibility of the method is demonstrated with a testbed code by initializing some simple channel problems. The initialization of the sample problems using, the old and the new methods are compared

Toroidal visco-resistive magnetohydrodynamic steady states contain vortices

International Nuclear Information System (INIS)

Bates, J.W.; Montgomery, D.C.

1998-01-01

Poloidal velocity fields seem to be a fundamental feature of resistive toroidal magnetohydrodynamic (MHD) steady states. They are a consequence of force balance in toroidal geometry, do not require any kind of instability, and disappear in the open-quotes straight cylinderclose quotes (infinite aspect ratio) limit. If a current density j results from an axisymmetric toroidal electric field that is irrotational inside a torus, it leads to a magnetic field B such that ∇x(jxB) is nonvanishing, so that the Lorentz force cannot be balanced by the gradient of any scalar pressure in the equation of motion. In a steady state, finite poloidal velocity fields and toroidal vorticity must exist. Their calculation is difficult, but explicit solutions can be found in the limit of low Reynolds number. Here, existing calculations are generalized to the more realistic case of no-slip boundary conditions on the velocity field and a circular toroidal cross section. The results of this paper strongly suggest that discussions of confined steady states in toroidal MHD must include flows from the outset. copyright 1998 American Institute of Physics

Exact steady state manifold of a boundary driven spin-1 Lai–Sutherland chain

International Nuclear Information System (INIS)

Ilievski, Enej; Prosen, Tomaž

2014-01-01

We present an explicit construction of a family of steady state density matrices for an open integrable spin-1 chain with bilinear and biquadratic interactions, also known as the Lai–Sutherland model, driven far from equilibrium by means of two oppositely polarizing Markovian dissipation channels localized at the boundary. The steady state solution exhibits n+1 fold degeneracy, for a chain of length n, due to existence of (strong) Liouvillian U(1) symmetry. The latter can be exploited to introduce a chemical potential and define a grand canonical nonequilibrium steady state ensemble. The matrix product form of the solution entails an infinitely-dimensional representation of a non-trivial Lie algebra (semidirect product of sl 2 and a non-nilpotent radical) and hints to a novel Yang–Baxter integrability structure

Exact steady state manifold of a boundary driven spin-1 Lai–Sutherland chain

Energy Technology Data Exchange (ETDEWEB)

Ilievski, Enej; Prosen, Tomaž

2014-05-15

We present an explicit construction of a family of steady state density matrices for an open integrable spin-1 chain with bilinear and biquadratic interactions, also known as the Lai–Sutherland model, driven far from equilibrium by means of two oppositely polarizing Markovian dissipation channels localized at the boundary. The steady state solution exhibits n+1 fold degeneracy, for a chain of length n, due to existence of (strong) Liouvillian U(1) symmetry. The latter can be exploited to introduce a chemical potential and define a grand canonical nonequilibrium steady state ensemble. The matrix product form of the solution entails an infinitely-dimensional representation of a non-trivial Lie algebra (semidirect product of sl{sub 2} and a non-nilpotent radical) and hints to a novel Yang–Baxter integrability structure.

A quasilinear model for solute transport under unsaturated flow

International Nuclear Information System (INIS)

Houseworth, J.E.; Leem, J.

2009-01-01

We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to the effective hydraulic conductivity. This leads to a quasilinear form for the transport problem in terms of a scalar potential that is analogous to the Kirchhoff potential for quasilinear flow. The solutions for both flow and transport scalar potentials take the form of Fourier series. The particular solution given here is for two sources of flow, with one source containing a dissolved solute. The solution method may easily be extended, however, for any combination of flow and solute sources under steady-state conditions. The analytical results for multidimensional solute transport problems, which previously could only be solved numerically, also offer an additional way to benchmark numerical solutions. An analytical solution for two-dimensional, steady-state solute transport under unsaturated flow conditions is presented. A specific case with two sources is solved but may be generalized to any combination of sources. The analytical results complement numerical solutions, which were previously required to solve this class of problems.

Well balancing of the SWE schemes for moving-water steady flows

Science.gov (United States)

Caleffi, Valerio; Valiani, Alessandro

2017-08-01

In this work, the exact reproduction of a moving-water steady flow via the numerical solution of the one-dimensional shallow water equations is studied. A new scheme based on a modified version of the HLLEM approximate Riemann solver (Dumbser and Balsara (2016) [18]) that exactly preserves the total head and the discharge in the simulation of smooth steady flows and that correctly dissipates mechanical energy in the presence of hydraulic jumps is presented. This model is compared with a selected set of schemes from the literature, including models that exactly preserve quiescent flows and models that exactly preserve moving-water steady flows. The comparison highlights the strengths and weaknesses of the different approaches. In particular, the results show that the increase in accuracy in the steady state reproduction is counterbalanced by a reduced robustness and numerical efficiency of the models. Some solutions to reduce these drawbacks, at the cost of increased algorithm complexity, are presented.

The quasi-steady state of the valley wind system

Directory of Open Access Journals (Sweden)

Juerg eSchmidli

2015-12-01

Full Text Available The quasi-steady-state limit of the diurnal valley wind system is investigated overidealized three-dimensional topography. Although this limit is rarely attained inreality due to ever-changing forcings, the investigation of this limit canprovide valuable insight, in particular on the mass and heat fluxes associatedwith the along-valley wind. We derive a scaling relation for the quasi-steady-state along-valleymass flux as a function of valley geometry, valley size, atmospheric stratification,and surface sensible heat flux forcing. The scaling relation is tested by comparisonwith the mass flux diagnosed from numerical simulations of the valleywind system. Good agreement is found. The results also provide insight into the relationbetween surface friction and the strength of the along-valley pressure gradient.

Poiseuille flow of soft glasses in narrow channels: from quiescence to steady state.

Science.gov (United States)

Chaudhuri, Pinaki; Horbach, Jürgen

2014-10-01

Using numerical simulations, the onset of Poiseuille flow in a confined soft glass is investigated. Starting from the quiescent state, steady flow sets in at a time scale which increases with a decrease in applied forcing. At this onset time scale, a rapid transition occurs via the simultaneous fluidization of regions having different local stresses. In the absence of steady flow at long times, creep is observed even in regions where the local stress is larger than the bulk yielding threshold. Finally, we show that the time scale to attain steady flow depends strongly on the history of the initial state.

Improved Dyson series expansion for steady-state quantum transport beyond the weak coupling limit: Divergences and resolution

International Nuclear Information System (INIS)

Thingna, Juzar; Zhou, Hangbo; Wang, Jian-Sheng

2014-01-01

We present a general theory to calculate the steady-state heat and electronic currents for nonlinear systems using a perturbative expansion in the system-bath coupling. We explicitly demonstrate that using the truncated Dyson-series leads to divergences in the steady-state limit, thus making it impossible to be used for actual applications. In order to resolve the divergences, we propose a unique choice of initial condition for the reduced density matrix, which removes the divergences at each order. Our approach not only allows us to use the truncated Dyson-series, with a reasonable choice of initial condition, but also gives the expected result that the steady-state solutions should be independent of initial preparations. Using our improved Dyson series we evaluate the heat and electronic currents up to fourth-order in system-bath coupling, a considerable improvement over the standard quantum master equation techniques. We then numerically corroborate our theory for archetypal settings of linear systems using the exact nonequilibrium Green's function approach. Finally, to demonstrate the advantage of our approach, we deal with the nonlinear spin-boson model to evaluate heat current up to fourth-order and find signatures of cotunnelling process

Steady-state equations of even flux and scattering

International Nuclear Information System (INIS)

Verwaerde, D.

1985-11-01

Some mathematical properties of steady-state equation of even flux are shown in variational formalism. This theoretical frame allows to study the existence of a solution and its asymptotical behavior in opaque media (i.e. the relation with scattering equation). At last it allows to qualify the convergence velocity of resolution iterative processes used practically [fr

Numerical analysis of steady state and transient analysis of high temperature ceramic plate-fin heat exchanger

International Nuclear Information System (INIS)

Nagarajan, Vijaisri; Chen, Yitung; Wang, Qiuwang; Ma, Ting

2014-01-01

Highlights: • Rip saw fin design is considered to be the best because it has thin fins and has higher heat transfer coefficient. • Minimum principal stress and maximum safety factor are obtained for the inverted bolt fin design. • Maximum principal stress and minimum safety factor are obtained for triangular fin design. • Thermal stress has significant impact than mechanical stress. • High principal stress is found at the startup and shutdown stage. - Abstract: In this study three-dimensional model of ceramic plate-fin high temperature heat exchanger with different fin designs and arrangements is analyzed numerically using ANSYS FLUENT and ANSYS structural module. The ability of ceramics to withstand high temperature and corrosion makes silicon carbide (SiC) suitable candidate material to be used in high temperature heat exchanger. The operating temperature of heat exchanger is 950 °C and the operating pressure is 1.5 MPa. The working fluids are helium, sulfur trioxide, sulfur dioxide, oxygen and the water vapor. Fluid flow and heat transfer analysis are carried out for steady and transient state in FLUENT. The obtained thermal and pressure load for the steady and transient state from ANSYS FLUENT are imported to ANSYS structural module to obtain the principal stress and the factor of safety. Different arrangements of rectangular fins, triangular fins, inverted bolt fins and ripsaw fins are studied. From the results it is found that the minimum stress and the maximum safety factor are obtained for inverted bolt fins. The triangular fins have the maximum principal stress and minimum factor of safety. However, the fluid flow and heat transfer analysis show inverted bolt fins and triangular fins produce higher pressure drop and friction factor. The steady state maximum principal stress is 10.08 MPa, 9.90 MPa and 11.43 MPa for straight, staggered and top and bottom ripsaw fin arrangement. The corresponding safety factors are 21.80, 21.95 and 19

An implicit scheme with memory reduction technique for steady state solutions of DVBE in all flow regimes

Science.gov (United States)

Yang, L. M.; Shu, C.; Yang, W. M.; Wu, J.

2018-04-01

High consumption of memory and computational effort is the major barrier to prevent the widespread use of the discrete velocity method (DVM) in the simulation of flows in all flow regimes. To overcome this drawback, an implicit DVM with a memory reduction technique for solving a steady discrete velocity Boltzmann equation (DVBE) is presented in this work. In the method, the distribution functions in the whole discrete velocity space do not need to be stored, and they are calculated from the macroscopic flow variables. As a result, its memory requirement is in the same order as the conventional Euler/Navier-Stokes solver. In the meantime, it is more efficient than the explicit DVM for the simulation of various flows. To make the method efficient for solving flow problems in all flow regimes, a prediction step is introduced to estimate the local equilibrium state of the DVBE. In the prediction step, the distribution function at the cell interface is calculated by the local solution of DVBE. For the flow simulation, when the cell size is less than the mean free path, the prediction step has almost no effect on the solution. However, when the cell size is much larger than the mean free path, the prediction step dominates the solution so as to provide reasonable results in such a flow regime. In addition, to further improve the computational efficiency of the developed scheme in the continuum flow regime, the implicit technique is also introduced into the prediction step. Numerical results showed that the proposed implicit scheme can provide reasonable results in all flow regimes and increase significantly the computational efficiency in the continuum flow regime as compared with the existing DVM solvers.

Advanced numerical methods for three dimensional two-phase flow calculations

Energy Technology Data Exchange (ETDEWEB)

Toumi, I. [Laboratoire d`Etudes Thermiques des Reacteurs, Gif sur Yvette (France); Caruge, D. [Institut de Protection et de Surete Nucleaire, Fontenay aux Roses (France)

1997-07-01

This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses an extension of Roe`s method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations.

Advanced numerical methods for three dimensional two-phase flow calculations

International Nuclear Information System (INIS)

Toumi, I.; Caruge, D.

1997-01-01

This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses an extension of Roe's method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations

A steady-state fluid model of the coaxial plasma gun

International Nuclear Information System (INIS)

Herziger, G.; Krompholz, H.; Schneider, W.; Schoenbach, K.

1979-01-01

The plasma layer in a coaxial plasma gun is considered as a shock front driven by expanding magnetic fields. Analytical steady-state solutions of the fluid equations yield the plasma properties, allowing the scaling of plasma focus devices. (Auth.)

Three-dimensional stellarator equilibrium as an ohmic steady state

International Nuclear Information System (INIS)

Park, W.; Monticello, D.A.; Strauss, H.; Manickam, J.

1985-07-01

A stable three-dimensional stellarator equilibrium can be obtained numerically by a time-dependent relaxation method using small values of dissipation. The final state is an ohmic steady state which approaches an ohmic equilibrium in the limit of small dissipation coefficients. We describe a method to speed up the relaxation process and a method to implement the B vector . del p = 0 condition. These methods are applied to obtain three-dimensional heliac equilibria using the reduced heliac equations

Existence of non-unique steady state solutions to the RMF current drive equations

Energy Technology Data Exchange (ETDEWEB)

Hugrass, W N [Flinders Univ. of South Australia, Bedford Park. School of Physical Sciences

1985-05-04

It is shown that the value of the d.c. current driven in a plasma cylinder by means of a rotating magnetic field (RMF) is not unique for R/delta >= 6 and eBsub(..omega..)/..nu..sub(ei)m approx.R/delta, where R is the radius of the plasma cylinder, delta is the classical skin depth, ..nu..sub(ei) is the electron-ion momentum transfer collision frequency, Bsub(..omega..) is the magnitude of the rotating magnetic field, e is the electron charge and m is the electron mass. This effect is predicted using three distinct approaches: (i) a steady state anaysis which ignores the second and higher harmonics of the fields and currents; (ii) a qualitative model which utilizes the analogy between the RMF current drive technique and the operation of the induction motor; (iii) a solution of the initial boundary value equations describing the RMF current drive in cylindrical plasmas.

How should we understand non-equilibrium many-body steady states?

Science.gov (United States)

Maghrebi, Mohammad; Gorshkov, Alexey

: Many-body systems with both coherent dynamics and dissipation constitute a rich class of models which are nevertheless much less explored than their dissipationless counterparts. The advent of numerous experimental platforms that simulate such dynamics poses an immediate challenge to systematically understand and classify these models. In particular, nontrivial many-body states emerge as steady states under non-equilibrium dynamics. In this talk, I use a field-theoretic approach based on the Keldysh formalism to study nonequilibrium phases and phase transitions in such models. I show that an effective temperature generically emerges as a result of dissipation, and the universal behavior including the dynamics near the steady state is described by a thermodynamic universality class. In the end, I will also discuss possibilities that go beyond the paradigm of an effective thermodynamic behavior.

Steady-state and transient heat transfer through fins of complex geometry

Directory of Open Access Journals (Sweden)

Taler Dawid

2014-06-01

Full Text Available Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.

The non-local Fisher–KPP equation: travelling waves and steady states

International Nuclear Information System (INIS)

Berestycki, Henri; Nadin, Grégoire; Perthame, Benoit; Ryzhik, Lenya

2009-01-01

We consider the Fisher–KPP equation with a non-local saturation effect defined through an interaction kernel φ(x) and investigate the possible differences with the standard Fisher–KPP equation. Our first concern is the existence of steady states. We prove that if the Fourier transform φ-circumflex(ξ) is positive or if the length σ of the non-local interaction is short enough, then the only steady states are u ≡ 0 and u ≡ 1. Next, we study existence of the travelling waves. We prove that this equation admits travelling wave solutions that connect u = 0 to an unknown positive steady state u ∞ (x), for all speeds c ≥ c * . The travelling wave connects to the standard state u ∞ (x) ≡ 1 under the aforementioned conditions: φ-circumflex(ξ) > 0 or σ is sufficiently small. However, the wave is not monotonic for σ large

Exact and Numerical Solutions of a Spatially-Distributed Mathematical Model for Fluid and Solute Transport in Peritoneal Dialysis

Directory of Open Access Journals (Sweden)

Roman Cherniha

2016-06-01

Full Text Available The nonlinear mathematical model for solute and fluid transport induced by the osmotic pressure of glucose and albumin with the dependence of several parameters on the hydrostatic pressure is described. In particular, the fractional space available for macromolecules (albumin was used as a typical example and fractional fluid void volume were assumed to be different functions of hydrostatic pressure. In order to find non-uniform steady-state solutions analytically, some mathematical restrictions on the model parameters were applied. Exact formulae (involving hypergeometric functions for the density of fluid flux from blood to tissue and the fluid flux across tissues were constructed. In order to justify the applicability of the analytical results obtained, a wide range of numerical simulations were performed. It was found that the analytical formulae can describe with good approximation the fluid and solute transport (especially the rate of ultrafiltration for a wide range of values of the model parameters.

Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection.

Science.gov (United States)

Kitazumi, Yuki; Hamamoto, Katsumi; Noda, Tatsuo; Shirai, Osamu; Kano, Kenji

2015-01-01

The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.

A Theoretical Study of Steady State and Transient Condensation on Axisymmetric Fins Under Combined Capillary and Gravitational Forces

Science.gov (United States)

Kostoglou, M.; Karapantsios, T. D.; Buffone, C.; Glushchuk, A.; Iorio, C.

2016-10-01

The present work attempts to model the case of combined gravitational and capillary motion of condensate for an axisymmetric fin under steady and transient fin operation conditions. The focus here is to examine the structure of the mathematical problem and to develop suitable numerical techniques rather than yield information on the macroscopic condensate flow rate and fin efficiency. The problem is formulated starting from general conditions and is simplified step by step by introducing corresponding assumptions. The particular fin shape of a paraboloid from revolution is chosen and the equations are properly non-dimensionalized. A vast reduction of the number of problem parameters is achieved in this way. The cases of isothermal fin, steady state operation and dynamic operation are treated separately using specialized numerical solution techniques developed for each case in order to improve computational efficiency and accuracy. Typical results of fin temperature and condensate film thickness are presented and discussed.

Multiple solutions and stability of the steady transonic small-disturbance equation

Directory of Open Access Journals (Sweden)

Ya Liu

2017-09-01

Full Text Available Numerical solutions of the steady transonic small-disturbance (TSD potential equation are computed using the conservative Murman−Cole scheme. Multiple solutions are discovered and mapped out for the Mach number range at zero angle of attack and the angle of attack range at Mach number 0.85 for the NACA 0012 airfoil. We present a linear stability analysis method by directly assembling and evaluating the Jacobian matrix of the nonlinear finite-difference equation of the TSD equation. The stability of all the discovered multiple solutions are then determined by the proposed eigen analysis. The relation of stability to convergence of the iterative method for solving the TSD equation is discussed. Computations and the stability analysis demonstrate the possibility of eliminating the multiple solutions and stabilizing the remaining unique solution by adding a sufficiently long splitter plate downstream the airfoil trailing edge. Finally, instability of the solution of the TSD equation is shown to be closely connected to the onset of transonic buffet by comparing with experimental data.

A numerical technique for enhanced efficiency and stability for the solution of the nuclear reactor equation

International Nuclear Information System (INIS)

Khotylev, V.A.; Hoogenboom, J.E.

1996-01-01

The paper presents new techniques for the solution of the nuclear reactor equation in diffusion approximation, that has enhanced efficiency and stability. The code system based on the new technique solves a number of steady-state and/or transient problems with coupled thermal hydraulics in one-, two-, or three dimensional geometry with reduced CPU time as compared to similar code systems of previous generations if well-posed neutronics problems are considered. Automated detection of ill-posed problem and selection of the appropriate numerical method makes the new code system capable of yielding a correct solution for wider range of problems without user intervention. (author)

A numerical technique for enhanced efficiency and stability for the solution of the nuclear reactor equation

Energy Technology Data Exchange (ETDEWEB)

Khotylev, V.A.; Hoogenboom, J.E. [Delft Univ. of Technology, Interfaculty Reactor Inst., Delft (Netherlands)

1996-07-01

The paper presents new techniques for the solution of the nuclear reactor equation in diffusion approximation, that has enhanced efficiency and stability. The code system based on the new technique solves a number of steady-state and/or transient problems with coupled thermal hydraulics in one-, two-, or three dimensional geometry with reduced CPU time as compared to similar code systems of previous generations if well-posed neutronics problems are considered. Automated detection of ill-posed problem and selection of the appropriate numerical method makes the new code system capable of yielding a correct solution for wider range of problems without user intervention. (author)

steady – state performance of induction and transfer state

African Journals Online (AJOL)

eobe

This paper presents paper presents paper presents the steady the steady the steady–state performance state performance state performance comparison comparison comparison between polyphase induction motor and polyphase between polyphase induction motor and polyphase. TF motor operating in. TF motor ...

Green's theorem and Green's functions for the steady-state cosmic-ray equation of transport

International Nuclear Information System (INIS)

Webb, G.M.; Gleeson, L.J.

1977-01-01

Green's Theorem is developed for the spherically-symmetric steady-state cosmic-ray equation of transport in interplanetary space. By means of it the momentum distribution function F 0 (r,p), (r=heliocentric distance, p=momentum) can be determined in a region rsub(a) 0 . Examples of Green's functions are given for the case rsub(a)=0, rsub(b)=infinity and derived for the cases of finite rsub(a) and rsub(b). The diffusion coefficient kappa is assumed of the form kappa=kappa 0 (p)rsup(b). The treatment systematizes the development of all analytic solutions for steady-state solar and galactic cosmic-ray propagation and previous solutions form a subset of the present solutions. (Auth.)

Temperature prediction in a coal fired boiler with a fixed bed by fuzzy logic based on numerical solution

International Nuclear Information System (INIS)

Biyikoglu, A.; Akcayol, M.A.; Oezdemir, V.; Sivrioglu, M.

2005-01-01

In this study, steady state combustion in boilers with a fixed bed has been investigated. Temperature distributions in the combustion chamber of a coal fired boiler with a fixed bed are predicted using fuzzy logic based on data obtained from the numerical solution method for various coal and air feeding rates. The numerical solution method and the discretization of the governing equations of two dimensional turbulent flow in the combustion chamber and one dimensional coal combustion in the fixed bed are explained. Control Volume and Finite Difference Methods are used in the discretization of the equations in the combustion chamber and in the fixed bed, respectively. Results are presented as contours within the solution domain and compared with numerical ones. Comparison of the results shows that the difference between the numerical solution and fuzzy logic prediction throughout the computational domain is less than 1.5%. The statistical coefficient of multiple determinations for the investigated cases is about 0.9993 to 0.9998. This accuracy degree is acceptable in predicting the temperature values. So, it can be concluded that fuzzy logic provides a feasible method for defining the system properties

Computing the stability of steady-state solutions of mathematical models of the electrical activity in the heart.

Science.gov (United States)

Tveito, Aslak; Skavhaug, Ola; Lines, Glenn T; Artebrant, Robert

2011-08-01

Instabilities in the electro-chemical resting state of the heart can generate ectopic waves that in turn can initiate arrhythmias. We derive methods for computing the resting state for mathematical models of the electro-chemical process underpinning a heartbeat, and we estimate the stability of the resting state by invoking the largest real part of the eigenvalues of a linearized model. The implementation of the methods is described and a number of numerical experiments illustrate the feasibility of the methods. In particular, we test the methods for problems where we can compare the solutions with analytical results, and problems where we have solutions computed by independent software. The software is also tested for a fairly realistic 3D model. Copyright © 2011 Elsevier Ltd. All rights reserved.

History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

Science.gov (United States)

Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen

2013-11-01

It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

Steady-state and pre-steady-state kinetic analysis of halopropane conversion by a Rhodococcus haloalkane dehalogenase

NARCIS (Netherlands)

Bosma, T; Pikkemaat, MG; Kingma, Jacob; Dijk, J; Janssen, DB

2003-01-01

Haloalkane dehalogenase from Rhodococcus rhodochrous NCIMB 13064 (DhaA) catalyzes the hydrolysis of carbon-halogen bonds in a wide range of haloalkanes. We examined the steady-state and pre-steady-state kinetics of halopropane conversion by DhaA to illuminate mechanistic details of the

Pseudo Steady-State Free Precession for MR-Fingerprinting.

Science.gov (United States)

Assländer, Jakob; Glaser, Steffen J; Hennig, Jürgen

2017-03-01

This article discusses the signal behavior in the case the flip angle in steady-state free precession sequences is continuously varied as suggested for MR-fingerprinting sequences. Flip angle variations prevent the establishment of a steady state and introduce instabilities regarding to magnetic field inhomogeneities and intravoxel dephasing. We show how a pseudo steady state can be achieved, which restores the spin echo nature of steady-state free precession. Based on geometrical considerations, relationships between the flip angle, repetition and echo time are derived that suffice to the establishment of a pseudo steady state. The theory is tested with Bloch simulations as well as phantom and in vivo experiments. A typical steady-state free precession passband can be restored with the proposed conditions. The stability of the pseudo steady state is demonstrated by comparing the evolution of the signal of a single isochromat to one resulting from a spin ensemble. As confirmed by experiments, magnetization in a pseudo steady state can be described with fewer degrees of freedom compared to the original fingerprinting and the pseudo steady state results in more reliable parameter maps. The proposed conditions restore the spin-echo-like signal behavior typical for steady-state free precession in fingerprinting sequences, making this approach more robust to B 0 variations. Magn Reson Med 77:1151-1161, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Chemical-specific screening criteria for interpretation of biomonitoring data for volatile organic compounds (VOCs)--application of steady-state PBPK model solutions.

Science.gov (United States)

Aylward, Lesa L; Kirman, Chris R; Blount, Ben C; Hays, Sean M

2010-10-01

The National Health and Nutrition Examination Survey (NHANES) generates population-representative biomonitoring data for many chemicals including volatile organic compounds (VOCs) in blood. However, no health or risk-based screening values are available to evaluate these data from a health safety perspective or to use in prioritizing among chemicals for possible risk management actions. We gathered existing risk assessment-based chronic exposure reference values such as reference doses (RfDs), reference concentrations (RfCs), tolerable daily intakes (TDIs), cancer slope factors, etc. and key pharmacokinetic model parameters for 47 VOCs. Using steady-state solutions to a generic physiologically-based pharmacokinetic (PBPK) model structure, we estimated chemical-specific steady-state venous blood concentrations across chemicals associated with unit oral and inhalation exposure rates and with chronic exposure at the identified exposure reference values. The geometric means of the slopes relating modeled steady-state blood concentrations to steady-state exposure to a unit oral dose or unit inhalation concentration among 38 compounds with available pharmacokinetic parameters were 12.0 microg/L per mg/kg-d (geometric standard deviation [GSD] of 3.2) and 3.2 microg/L per mg/m(3) (GSD=1.7), respectively. Chemical-specific blood concentration screening values based on non-cancer reference values for both oral and inhalation exposure range from 0.0005 to 100 microg/L; blood concentrations associated with cancer risk-specific doses at the 1E-05 risk level ranged from 5E-06 to 6E-02 microg/L. The distribution of modeled steady-state blood concentrations associated with unit exposure levels across VOCs may provide a basis for estimating blood concentration screening values for VOCs that lack chemical-specific pharmacokinetic data. The screening blood concentrations presented here provide a tool for risk assessment-based evaluation of population biomonitoring data for VOCs and

Multimode optical fibers: steady state mode exciter.

Science.gov (United States)

Ikeda, M; Sugimura, A; Ikegami, T

1976-09-01

The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.

Simulation of steady-state natural convection using CFD

Energy Technology Data Exchange (ETDEWEB)

Zitzmann, T.; Pfrommer, P. [Univ. of Applied Sciences, Coberg (Germany); Cook, M.; Rees, S.; Marjanovic, L. [De Montfort Univ., Leicester (United Kingdom). Inst. of Energy and Sustainable Development

2005-07-01

Building materials play an important role in the creation of comfortable indoor environments and can reduce dependence on high energy use mechanical systems. Correct predictions between building structure and heat transfer are needed in order to achieve optimal conditions. Heat transfer is dependent on the velocity and temperature distribution in a room, particularly in the wall boundary layer. This paper discussed the modeling of air flow and heat transfer over a heated vertical plate in a differentially-heated cavity using Computational Fluid Dynamics (CFD). Guidelines on the use of CFD with unstructured meshes to model buoyancy-driven flow in a cavity were presented. Benchmark CFD results were compared with published analytical data. The finite volume method was employed using an unstructured mesh containing tetrahedral and prism elements, so that local numerical diffusion was reduced and therefore suitable for complex flows. The code was based on a couple solver for solving the differential equations using the fully implicit discretization method. Hydrodynamic equations were treated as one single system. A false time stepping method was used to reduce the number of iterations required for convergence, which also guided the solutions to a steady-state solution. It was concluded that the methodology achieves accurate predictions, and is suitable for the modeling of heat transfer optimizations. 13 refs., 7 figs.

Homogenization of steady-state creep of porous metals using three-dimensional microstructural reconstructions

DEFF Research Database (Denmark)

Kwok, Kawai; Boccaccini, Dino; Persson, Åsa Helen

2016-01-01

The effective steady-state creep response of porous metals is studied by numerical homogenization and analytical modeling in this paper. The numerical homogenization is based on finite element models of three-dimensional microstructures directly reconstructed from tomographic images. The effects ...... model, and closely matched by the Gibson-Ashby compression and the Ramakrishnan-Arunchalam creep models. [All rights reserved Elsevier]....

Analytical solutions of steady-state conjugate heat transfer in ducts with turbulent flow

International Nuclear Information System (INIS)

Cerqueira, Djane R.; Jian Su

2007-01-01

In this work, we present an approximate analytical solution of the steady-state conjugate heat transfer of turbulent forced convection in a circular pipe with wall axial heat conduction and external convective boundary conditions. Improved lumped differential approach based on two points Hermite approximation for integrals was applied to reduce the heat conduction equation in the solid into a second-order ordinary differential equation for the radially averaged solid temperature. The energy equation in the fluid was solved by applying the generalized integral transform technique (GITT). The Sturm-Lioville eigenproblem for fluid energy equation in the cylindrical coordinate system was solved by the sign-count method. The truncated system of N ordinary differential equations for transformed potentials of the fluid temperature and the second-order ordinary differential equation for radially averaged solid temperature formed a homogeneous system of N+2 ordinary differential equations, which was solved analytically. The effects of the fluid-solid thermal conductivity ratio on the Nusselt number, the average fluid and solid temperatures, and the fluid-solid interface temperature were investigated. (author)

Direct numerical simulation of steady state, three dimensional, laminar flow around a wall mounted cube

Science.gov (United States)

Liakos, Anastasios; Malamataris, Nikolaos

2014-11-01

The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experimental conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horse-shoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000. Financial support of author NM from the Office of Naval Research Global (ONRG-VSP, N62909-13-1-V016) is acknowledged.

Advanced numerical methods for three dimensional two-phase flow calculations in PWR

International Nuclear Information System (INIS)

Toumi, I.; Gallo, D.; Royer, E.

1997-01-01

This paper is devoted to new numerical methods developed for three dimensional two-phase flow calculations. These methods are finite volume numerical methods. They are based on an extension of Roe's approximate Riemann solver to define convective fluxes versus mean cell quantities. To go forward in time, a linearized conservative implicit integrating step is used, together with a Newton iterative method. We also present here some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. This kind of numerical method, which is widely used for fluid dynamic calculations, is proved to be very efficient for the numerical solution to two-phase flow problems. This numerical method has been implemented for the three dimensional thermal-hydraulic code FLICA-4 which is mainly dedicated to core thermal-hydraulic transient and steady-state analysis. Hereafter, we will also find some results obtained for the EPR reactor running in a steady-state at 60% of nominal power with 3 pumps out of 4, and a thermal-hydraulic core analysis for a 1300 MW PWR at low flow steam-line-break conditions. (author)

Tailored parameter optimization methods for ordinary differential equation models with steady-state constraints.

Science.gov (United States)

Fiedler, Anna; Raeth, Sebastian; Theis, Fabian J; Hausser, Angelika; Hasenauer, Jan

2016-08-22

Ordinary differential equation (ODE) models are widely used to describe (bio-)chemical and biological processes. To enhance the predictive power of these models, their unknown parameters are estimated from experimental data. These experimental data are mostly collected in perturbation experiments, in which the processes are pushed out of steady state by applying a stimulus. The information that the initial condition is a steady state of the unperturbed process provides valuable information, as it restricts the dynamics of the process and thereby the parameters. However, implementing steady-state constraints in the optimization often results in convergence problems. In this manuscript, we propose two new methods for solving optimization problems with steady-state constraints. The first method exploits ideas from optimization algorithms on manifolds and introduces a retraction operator, essentially reducing the dimension of the optimization problem. The second method is based on the continuous analogue of the optimization problem. This continuous analogue is an ODE whose equilibrium points are the optima of the constrained optimization problem. This equivalence enables the use of adaptive numerical methods for solving optimization problems with steady-state constraints. Both methods are tailored to the problem structure and exploit the local geometry of the steady-state manifold and its stability properties. A parameterization of the steady-state manifold is not required. The efficiency and reliability of the proposed methods is evaluated using one toy example and two applications. The first application example uses published data while the second uses a novel dataset for Raf/MEK/ERK signaling. The proposed methods demonstrated better convergence properties than state-of-the-art methods employed in systems and computational biology. Furthermore, the average computation time per converged start is significantly lower. In addition to the theoretical results, the

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

Science.gov (United States)

Koestel, J. K.; Norgaard, T.; Luong, N. M.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandé, M.; Iversen, B. V.; Wollesen de Jonge, L.

2013-02-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m × 165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger.

Steady State Crack Propagation in Layered Material Systems Displaying Visco-plastic Behaviour

DEFF Research Database (Denmark)

Nielsen, Kim Lau

2012-01-01

The steady state fracture toughness of elastic visco-plastic materials is studied numerically, using both a conventional and a higher order model. Focus is on the combined effect of strain hardening, strain gradient hardening and strain rate hardening on cracking in layered material systems...

Steady-State Creep of Asphalt Concrete

Directory of Open Access Journals (Sweden)

Alibai Iskakbayev

2017-02-01

Full Text Available This paper reports the experimental investigation of the steady-state creep process for fine-grained asphalt concrete at a temperature of 20 ± 2 °С and under stress from 0.055 to 0.311 MPa under direct tension and was found to occur at a constant rate. The experimental results also determined the start, the end point, and the duration of the steady-state creep process. The dependence of these factors, in addition to the steady-state creep rate and viscosity of the asphalt concrete on stress is satisfactorily described by a power function. Furthermore, it showed that stress has a great impact on the specific characteristics of asphalt concrete: stress variation by one order causes their variation by 3–4.5 orders. The described relations are formulated for the steady-state of asphalt concrete in a complex stressed condition. The dependence is determined between stress intensity and strain rate intensity.

Reactor kinetics - pulse and steady state

Energy Technology Data Exchange (ETDEWEB)

Estes, B F; Morris, F M [Sandia Laboratories (United States)

1974-07-01

An analytical model has been developed which couples the nuclear and thermal characteristics of the Annular Core Pulse Reactor (ACPR) into a solution which describes both the neutron kinetics of the reactor and the temperature behavior of a fuel-moderator element. The model describes both pulse and steady state operations. This paper describes the important aspects of the reactor, the fuel- moderator elements, the neutron kinetic equations of the reactor, and the time-temperature behavior of a fuel-moderator element that is being subjected to the maximum power density in the core. The parameters which are utilized in the equations are divided into two classes, those that can be measured directly and those that are assumed to be known (each is described briefly). Some of the solutions which demonstrate the versatility of the analytical model are described. (author)

Importance sampling large deviations in nonequilibrium steady states. I

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T.

2018-03-01

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Importance sampling large deviations in nonequilibrium steady states. I.

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T

2018-03-28

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Asynchronous and corrected-asynchronous numerical solutions of parabolic PDES on MIMD multiprocessors

Science.gov (United States)

Amitai, Dganit; Averbuch, Amir; Itzikowitz, Samuel; Turkel, Eli

1991-01-01

A major problem in achieving significant speed-up on parallel machines is the overhead involved with synchronizing the concurrent process. Removing the synchronization constraint has the potential of speeding up the computation. The authors present asynchronous (AS) and corrected-asynchronous (CA) finite difference schemes for the multi-dimensional heat equation. Although the discussion concentrates on the Euler scheme for the solution of the heat equation, it has the potential for being extended to other schemes and other parabolic partial differential equations (PDEs). These schemes are analyzed and implemented on the shared memory multi-user Sequent Balance machine. Numerical results for one and two dimensional problems are presented. It is shown experimentally that the synchronization penalty can be about 50 percent of run time: in most cases, the asynchronous scheme runs twice as fast as the parallel synchronous scheme. In general, the efficiency of the parallel schemes increases with processor load, with the time level, and with the problem dimension. The efficiency of the AS may reach 90 percent and over, but it provides accurate results only for steady-state values. The CA, on the other hand, is less efficient, but provides more accurate results for intermediate (non steady-state) values.

Comparing Interval Management Control Laws for Steady-State Errors and String Stability

Science.gov (United States)

Weitz, Lesley A.; Swieringa, Kurt A.

2018-01-01

Interval Management (IM) is a future airborne spacing concept that leverages avionics to provide speed guidance to an aircraft to achieve and maintain a specified spacing interval from another aircraft. The design of a speed control law to achieve the spacing goal is a key aspect in the research and development of the IM concept. In this paper, two control laws that are used in much of the contemporary IM research are analyzed and compared to characterize steady-state errors and string stability. Numerical results are used to illustrate how the choice of control laws gains impacts the size of steady-state errors and string performance and the potential trade-offs between those performance characteristics.

Practical steady-state enzyme kinetics.

Science.gov (United States)

Lorsch, Jon R

2014-01-01

Enzymes are key components of most biological processes. Characterization of enzymes is therefore frequently required during the study of biological systems. Steady-state kinetics provides a simple and rapid means of assessing the substrate specificity of an enzyme. When combined with site-directed mutagenesis (see Site-Directed Mutagenesis), it can be used to probe the roles of particular amino acids in the enzyme in substrate recognition and catalysis. Effects of interaction partners and posttranslational modifications can also be assessed using steady-state kinetics. This overview explains the general principles of steady-state enzyme kinetics experiments in a practical, rather than theoretical, way. Any biochemistry textbook will have a section on the theory of Michaelis-Menten kinetics, including derivations of the relevant equations. No specific enzymatic assay is described here, although a method for monitoring product formation or substrate consumption over time (an assay) is required to perform the experiments described. © 2014 Elsevier Inc. All rights reserved.

Numerical investigation of the recruitment process in open marine population models

International Nuclear Information System (INIS)

Angulo, O; López-Marcos, J C; López-Marcos, M A; Martínez-Rodríguez, J

2011-01-01

The changes in the dynamics, produced by the recruitment process in an open marine population model, are investigated from a numerical point of view. The numerical method considered, based on the representation of the solution along the characteristic lines, approximates properly the steady states of the model, and is used to analyze the asymptotic behavior of the solutions of the model

Steady ablation on the surface of a two-layer composite

Energy Technology Data Exchange (ETDEWEB)

Lin, Wen-Shan [Chung Shan Institute of Science and Technology, P.O. Box 90008-15-3, Lung-Tan, Tao-Yuan, 32526 Taiwan (China)

2005-12-01

Discovered is a quasi-steady ablation phenomenon on the surface of a two-layer composite which is formed by a layer of ablative material and another layer of non-ablative substrate. Theoretical exact solutions of quasi-steady ablation rate, the associated temperature distribution and end-of-ablation time of this two-layer composite are derived. A criterion for the occurrence of quasi-steady ablation is presented also. A one-dimensional transient numerical model is developed to perform a number of numerical experiments and hence to verify the correctness of the above theoretical solutions for the current quasi-steady ablation phenomenon. Based on the current results, a new method of measuring the ablation (or sublimation) heat is also proposed. (author)

Steady state drift vortices in plasmas with shear flow in equilibrium

DEFF Research Database (Denmark)

Chakrabarti, N.

1999-01-01

The Hasegawa-Mima equation in the presence of sheared poloidal flow is solved for two-dimensional steady state vortex. It is shown that when the phase velocity of the vortex is the same as the diamagnetic drift velocity, an exact solution in the form of counter-rotating vortices may appear...

Quasi-steady state thermal performances of a solar air heater with ...

African Journals Online (AJOL)

Quasi-steady state thermal performance of a solar air heater with a combined absorber is studied. The whole energy balance equations related to the system were articulated as a linear system of temperature equations. Solutions to this linear system were assessed from program based on an iterative process. The mean ...

Steady-State Performance of Kalman Filter for DPLL

Institute of Scientific and Technical Information of China (English)

QIAN Yi; CUI Xiaowei; LU Mingquan; FENG Zhenming

2009-01-01

For certain system models, the structure of the Kalman filter is equivalent to a second-order vari-able gain digital phase-locked loop (DPLL). To apply the knowledge of DPLLs to the design of Kalman filters, this paper studies the steady-state performance of Kalman filters for these system models. The results show that the steady-state Kalman gain has the same form as the DPLL gain. An approximate simple form for the steady-state Kalman gain is used to derive an expression for the equivalent loop bandwidth of the Kalman filter as a function of the process and observation noise variances. These results can be used to analyze the steady-state performance of a Kalman filter with DPLL theory or to design a Kalman filter model with the same steady-state performance as a given DPLL.

Boundary Element Analysis of the Steady-state Response of an Elastic Half-Space to a Moving Force on its Surface

DEFF Research Database (Denmark)

Andersen, Lars; Nielsen, Søren R. K.

2003-01-01

The paper deals with the boundary element method formulation of the steady-state wave propagation through elastic media due to a source moving with constant velocity. The Greens' function for the three-dimensional full-space is formulated in a local frame of reference following the source...... is approximated, but the error which is introduced in this way is insignificant. Numerical examples are given for a moving rectangular load on an elastic half-space. The result from a boundary element code based on the derived Green's function are compared with a semi-analytic solution....

New Tore Supra steady state operating scenario

International Nuclear Information System (INIS)

Martin, G.; Parlange, F.; van Houtte, D.; Wijnands, T.

1995-01-01

This document deals with plasma control in steady state conditions. A new plasma control systems enabling feedback control of global plasma equilibrium parameters has been developed. It also enables to operate plasma discharge in steady state regime. (TEC). 4 refs., 5 figs

A mathematical model and numerical solution of interface problems for steady state heat conduction

Directory of Open Access Journals (Sweden)

Z. Muradoglu Seyidmamedov

2006-01-01

(isolation Ωδ tends to zero. For each case, the local truncation errors of the used conservative finite difference scheme are estimated on the nonuniform grid. A fast direct solver has been applied for the interface problems with piecewise constant but discontinuous coefficient k=k(x. The presented numerical results illustrate high accuracy and show applicability of the given approach.

Some Considerations on the Fundamentals of Chemical Kinetics: Steady State, Quasi-Equilibrium, and Transition State Theory

Science.gov (United States)

Perez-Benito, Joaquin F.

2017-01-01

The elementary reaction sequence A ? I ? Products is the simplest mechanism for which the steady-state and quasi-equilibrium kinetic approximations can be applied. The exact integrated solutions for this chemical system allow inferring the conditions that must fulfill the rate constants for the different approximations to hold. A graphical…

Steady-State-Preserving Simulation of Genetic Regulatory Systems

Directory of Open Access Journals (Sweden)

Ruqiang Zhang

2017-01-01

Full Text Available A novel family of exponential Runge-Kutta (expRK methods are designed incorporating the stable steady-state structure of genetic regulatory systems. A natural and convenient approach to constructing new expRK methods on the base of traditional RK methods is provided. In the numerical integration of the one-gene, two-gene, and p53-mdm2 regulatory systems, the new expRK methods are shown to be more accurate than their prototype RK methods. Moreover, for nonstiff genetic regulatory systems, the expRK methods are more efficient than some traditional exponential RK integrators in the scientific literature.

Measurement of non-steady-state free fatty acid turnover

International Nuclear Information System (INIS)

Jensen, M.D.; Heiling, V.; Miles, J.M.

1990-01-01

The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with [ 14 C]-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra [( 14 C]oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra

Numerical bifurcation analysis of delay differential equations arising from physiological modeling.

Science.gov (United States)

Engelborghs, K; Lemaire, V; Bélair, J; Roose, D

2001-04-01

This paper has a dual purpose. First, we describe numerical methods for continuation and bifurcation analysis of steady state solutions and periodic solutions of systems of delay differential equations with an arbitrary number of fixed, discrete delays. Second, we demonstrate how these methods can be used to obtain insight into complex biological regulatory systems in which interactions occur with time delays: for this, we consider a system of two equations for the plasma glucose and insulin concentrations in a diabetic patient subject to a system of external assistance. The model has two delays: the technological delay of the external system, and the physiological delay of the patient's liver. We compute stability of the steady state solution as a function of two parameters, compare with analytical results and compute several branches of periodic solutions and their stability. These numerical results allow to infer two categories of diabetic patients for which the external system has different efficiency.

The impact of the form of the Euler equations for radial flow in cylindrical and spherical coordinates on numerical conservation and accuracy

Science.gov (United States)

Crittenden, P. E.; Balachandar, S.

2018-03-01

The radial one-dimensional Euler equations are often rewritten in what is known as the geometric source form. The differential operator is identical to the Cartesian case, but source terms result. Since the theory and numerical methods for the Cartesian case are well-developed, they are often applied without modification to cylindrical and spherical geometries. However, numerical conservation is lost. In this article, AUSM^+ -up is applied to a numerically conservative (discrete) form of the Euler equations labeled the geometric form, a nearly conservative variation termed the geometric flux form, and the geometric source form. The resulting numerical methods are compared analytically and numerically through three types of test problems: subsonic, smooth, steady-state solutions, Sedov's similarity solution for point or line-source explosions, and shock tube problems. Numerical conservation is analyzed for all three forms in both spherical and cylindrical coordinates. All three forms result in constant enthalpy for steady flows. The spatial truncation errors have essentially the same order of convergence, but the rate constants are superior for the geometric and geometric flux forms for the steady-state solutions. Only the geometric form produces the correct shock location for Sedov's solution, and a direct connection between the errors in the shock locations and energy conservation is found. The shock tube problems are evaluated with respect to feature location using an approximation with a very fine discretization as the benchmark. Extensions to second order appropriate for cylindrical and spherical coordinates are also presented and analyzed numerically. Conclusions are drawn, and recommendations are made. A derivation of the steady-state solution is given in the Appendix.

STRANGE ATTRACTORS ON PSEUDOSPECTRAL SOLUTIONS FOR DISSIPATIVE ZAKHAROV EQUATIONS

Institute of Scientific and Technical Information of China (English)

马书清; 常谦顺

2004-01-01

In this paper, the pseudospcctral method to solve the dissipative Zakharov equations is used. Its convergence is proved by priori estinates. The existence of the global attractors and the estimates of dimension are presented. A class of steady state solutions is also disscussed. The numerical results show that if the steady state solutions satisfy some special conditions, they become unstable and limit cycles and strange attractors will occur for very small perturbations.The largest Lyapunov exponent and analysis of the lincarized system are applied to explain these phenomena.

Numerical solution of the Schrodinger equation for stationary bound states using nodel theorem

International Nuclear Information System (INIS)

Chen Zhijiang; Kong Fanmei; Din Yibin

1987-01-01

An iterative procedure for getting the numerical solution of Schrodinger equation on stationary bound states is introduced. The theoretical foundtion, the practical steps and the method are presented. An example is added at the end. Comparing with other methods, the present one requires less storage, less running time but posesses higher accuracy. It can be run on the personal computer or microcomputer with 256 K memory and 16 bit word length such as IBM/PC, MC68000/83/20, PDP11/23 etc

Evaluating Hydrologic Transience in Watershed Delineation, Numerical Modeling and Solute Transport in the Great Basin. Clayton Valley, Nevada

Science.gov (United States)

Underdown, C. G.; Boutt, D. F.; Hynek, S. A.; Munk, L. A.

2017-12-01

Importance of transience in managed groundwater systems is generally determined by timeframe of management decisions. Watersheds with management times shorter than the aquifer (watershed) response time, or the time it takes a watershed to recover from a change in hydrologic state, would not include the new state and are treated as steady-state. However, these watersheds will experience transient response between hydrologic states. Watershed response time is a function of length. Therefore flat, regional watersheds characteristic of the Great Basin have long response times. Defining watershed extents as the area in which the water budget is balanced means inputs equal outputs. Steady-state budgets in the Great Basin have been balanced by extending watershed boundaries to include more area for recharge; however, the length and age of requisite flow paths are poorly constrained and often unrealistic. Inclusion of stored water in hydrologic budget calculations permits water balance within smaller contributing areas. As groundwater flow path lengths, depths, and locations differ between steady-state and transient systems, so do solute transport mechanisms. To observe how transience affects response time and solute transport, a refined (transient) version of the USGS steady-state groundwater flow model of the Great Basin is evaluated. This model is used to assess transient changes in contributing area for Clayton Valley, a lithium-brine producing endorheic basin in southwestern Nevada. Model runs of various recharge, discharge and storage bounds are created from conceptual models based upon historical climate data. Comparing results of the refined model to USGS groundwater observations allows for model validation and comparison against the USGS steady-state model. The transient contributing area to Clayton Valley is 85% smaller than that calculated from the steady-state solution, however several long flow paths important to both water and solute budgets at Clayton Valley

Nonlinear dynamics and numerical uncertainties in CFD

Science.gov (United States)

Yee, H. C.; Sweby, P. K.

1996-01-01

The application of nonlinear dynamics to improve the understanding of numerical uncertainties in computational fluid dynamics (CFD) is reviewed. Elementary examples in the use of dynamics to explain the nonlinear phenomena and spurious behavior that occur in numerics are given. The role of dynamics in the understanding of long time behavior of numerical integrations and the nonlinear stability, convergence, and reliability of using time-marching, approaches for obtaining steady-state numerical solutions in CFD is explained. The study is complemented with spurious behavior observed in CFD computations.

Numerical analysis of steady and transient natural convection in an enclosed cavity

Science.gov (United States)

Mehedi, Tanveer Hassan; Tahzeeb, Rahat Bin; Islam, A. K. M. Sadrul

2017-06-01

The paper presents the numerical simulation of natural convection heat transfer of air inside an enclosed cavity which can be helpful to find out the critical width of insulation in air insulated walls seen in residential buildings and industrial furnaces. Natural convection between two walls having different temperatures have been simulated using ANSYS FLUENT 12.0 in both steady and transient conditions. To simulate different heat transfer and fluid flow conditions, Rayleigh number ranging from 103 to 105 has been maintained (i.e. Laminar flow.) In case of steady state analysis, the CFD predictions were in very good agreement with the reviewed literature. Transient simulation process has been performed by using User Defined Functions, where the temperature of the hot wall varies with time linearly. To obtain and compare the heat transfer properties, Nusselt number has been calculated at the hot wall at different conditions. The buoyancy driven flow characteristics have been investigated by observing the flow pattern in a graphical manner. The characteristics of the system at different temperature differences between the wall has been observed and documented.

Data system design considerations for a pseudo-steady-state device

International Nuclear Information System (INIS)

Wing, W.R.

1981-01-01

The Advanced Toroidal Facility is being designed to run in a steady state. This places stringent requirements on a data system, since it must provide steady-state support that is equivalent to the support users are accustomed to from pulsed experiments; i.e., enough capacity to reduce diagnostic data for live presentation. Parameters such as density, position, and temperature must be presented live (i.e., within 0.1 s). Quantities such as plasma shape or internal structure should be available with a minimum of delay. The traditional solution to providing such capabilities is to use distributed processing to off-load data acquisition from the analysis computers. However, this suffers in a real-time environment because of the necessity of moving large quantities of data from acquisition to analysis. We expect to solve the problem by using a pipelined design that will acquire data directly into shared memory, where any one of four CPU's (VAX 11/780's) can proceed with analysis

Numerical solutions of several reflected shock-wave flow fields with nonequilibrium chemical reactions

Science.gov (United States)

Hanson, R. K.; Presley, L. L.; Williams, E. V.

1972-01-01

The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values.

Steady-State Process Modelling

DEFF Research Database (Denmark)

Cameron, Ian; Gani, Rafiqul

2011-01-01

illustrate the “equation oriented” approach as well as the “sequential modular” approach to solving complex flowsheets for steady state applications. The applications include the Williams-Otto plant, the hydrodealkylation (HDA) of toluene, conversion of ethylene to ethanol and a bio-ethanol process....

Numerical analysis of flow fields generated by accelerating flames

Energy Technology Data Exchange (ETDEWEB)

Kurylo, J.

1977-12-01

Presented here is a numerical technique for the analysis of non-steady flow fields generated by accelerating flames in gaseous media. Of particular interest in the study is the evaluation of the non-steady effects on the flow field and the possible transition of the combustion process to detonation caused by an abrupt change in the burning speed of an initially steady flame propagating in an unconfined combustible gas mixture. Optically recorded observations of accelerating flames established that the flow field can be considered to consist of non-steady flow fields associated with an assembly of interacting shock waves, contact discontinuities, deflagration and detonation fronts. In the analysis, these flow fields are treated as spatially one-dimensional, the influence of transport phenomena is considered to be negligible, and unburned and burned substances are assumed to behave as perfect gases with constant, but different, specific heats. The basis of the numerical technique is an explicit, two step, second order accurate, finite difference scheme employed to integrate the flow field equations expressed in divergence form. The burning speed, governing the motion of the deflagration, is expressed in the form of a power law dependence on pressure and temperature immediately ahead of its front. The steady wave solution is obtained by the vector polar interaction technique, that is, by determining the point of intersection between the loci of end states in the plane of the two interaction invariants, pressure and particle velocity. The technique is illustrated by a numerical example in which a steady flame experiences an abrupt change in its burning speed. Solutions correspond either to the eventual reestablishment of a steady state flow field commensurate with the burning speed or to the transition to detonation. The results are in satisfactory agreement with experimental observations.

Adaptively locating unknown steady states: Formalism and basin of attraction

International Nuclear Information System (INIS)

Wu, Yu; Lin, Wei

2011-01-01

The adaptive technique, which includes both dynamical estimators and coupling gains, has been recently verified to be practical for locating the unknown steady states numerically. This Letter, in the light of the center manifold theory for dynamical systems and the matrix spectrum principle, establishes an analytical formalism of this adaptive technique and reveals a connection between this technique and the original adaptive controller which includes only the dynamical estimator. More interestingly, in study of the well-known Lorenz system, the selections of the estimator parameters and initial values are found to be crucial to the successful application of the adaptive technique. Some Milnor-like basins of attraction with fractal structures are found quantitatively. All the results obtained in the Letter can be further extended to more general dynamical systems of higher dimensions. -- Highlights: → Establishing a new and rigorous formalism for the adaptive stabilization technique. → Showing a close connection between the adaptive technique and the original controller. → Providing feasible algorithms for simultaneous stabilization of multiple steady states. → Finding Milnor-like basins of attraction with fractal structures in adaptive control.

Pellet injectors for steady state plasma fuelling

International Nuclear Information System (INIS)

Vinyar, I.; Geraud, A.; Yamada, H.; Lukin, A.; Sakamoto, R.; Skoblikov, S.; Umov, A.; Oda, Y.; Gros, G.; Krasilnikov, I.; Reznichenko, P.; Panchenko, V.

2005-01-01

Successful steady state operation of a fusion reactor should be supported by repetitive pellet injection of solidified hydrogen isotopes in order to produce high performance plasmas. This paper presents pneumatic pellet injectors and its implementation for long discharge on the LHD and TORE SUPRA, and a new centrifuge pellet injector test results. All injectors are fitted with screw extruders well suited for steady state operation

Steady state analysis of Boolean molecular network models via model reduction and computational algebra.

Science.gov (United States)

Veliz-Cuba, Alan; Aguilar, Boris; Hinkelmann, Franziska; Laubenbacher, Reinhard

2014-06-26

A key problem in the analysis of mathematical models of molecular networks is the determination of their steady states. The present paper addresses this problem for Boolean network models, an increasingly popular modeling paradigm for networks lacking detailed kinetic information. For small models, the problem can be solved by exhaustive enumeration of all state transitions. But for larger models this is not feasible, since the size of the phase space grows exponentially with the dimension of the network. The dimension of published models is growing to over 100, so that efficient methods for steady state determination are essential. Several methods have been proposed for large networks, some of them heuristic. While these methods represent a substantial improvement in scalability over exhaustive enumeration, the problem for large networks is still unsolved in general. This paper presents an algorithm that consists of two main parts. The first is a graph theoretic reduction of the wiring diagram of the network, while preserving all information about steady states. The second part formulates the determination of all steady states of a Boolean network as a problem of finding all solutions to a system of polynomial equations over the finite number system with two elements. This problem can be solved with existing computer algebra software. This algorithm compares favorably with several existing algorithms for steady state determination. One advantage is that it is not heuristic or reliant on sampling, but rather determines algorithmically and exactly all steady states of a Boolean network. The code for the algorithm, as well as the test suite of benchmark networks, is available upon request from the corresponding author. The algorithm presented in this paper reliably determines all steady states of sparse Boolean networks with up to 1000 nodes. The algorithm is effective at analyzing virtually all published models even those of moderate connectivity. The problem for

Steady state compact toroidal plasma production

Science.gov (United States)

Turner, William C.

1986-01-01

Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.

Description of a stable scheme for steady-state coupled Monte Carlo–thermal–hydraulic calculations

International Nuclear Information System (INIS)

Dufek, Jan; Eduard Hoogenboom, J.

2014-01-01

Highlights: • A stable coupling scheme for steady-state MC–TH calculations is described. • The coupling scheme is based on the stochastic approximation method. • The neutron flux (or power) distribution is relaxed using a variable step-size. - Abstract: We provide a detailed description of a numerically stable and efficient coupling scheme for steady-state Monte Carlo neutronic calculations with thermal–hydraulic feedback. While we have previously derived and published the stochastic approximation based method for coupling the Monte Carlo criticality and thermal–hydraulic calculations, its possible implementation has not been described in a step-by-step manner. As the simple description of the coupling scheme was repeatedly requested from us, we have decided to make it available via this note

Non steady-state descriptions of drug permeation through stratum corneum. I. The biphasic brick-and-mortar model.

Science.gov (United States)

Heisig, M; Lieckfeldt, R; Wittum, G; Mazurkevich, G; Lee, G

1996-03-01

The diffusion equation should be solved for the non-steady-state problem of drug diffusion within a two-dimensional, biphasic stratum corneum membrane having homogeneous lipid and corneocyte phases. A numerical method was developed for a brick-and-mortar SC-geometry, enabling an explicit solution for time-dependent drug concentration within both phases. The lag time and permeability were calculated. It is shown how the barrier property of this model membrane depends on relative phase permeability, corneocyte alignment, and corneocyte-lipid partition coefficient. Additionally, the time-dependent drug concentration profiles within the membrane can be observed during the lag and steady-state phases. The model SC-membrane predicts, from purely morphological principles, lag times and permeabilities that are in good agreement with experimental values. The long lag times and very small permeabilities reported for human SC can only be predicted for a highly-staggered corneocyte geometry and corneocytes that are 1000 times less permeable than the lipid phase. Although the former conclusion is reasonable, the latter is questionable. The elongated, flattened corneocyte shape renders lag time and permeability insensitive to large changes in their alignment within the SC. Corneocyte/lipid partitioning is found to be fundamentally different to SC/donor partitioning, since increasing drug lipophilicity always reduces both lag time and permeability.

Transient productivity index for numerical well test simulations

Energy Technology Data Exchange (ETDEWEB)

Blanc, G.; Ding, D.Y.; Ene, A. [Institut Francais du Petrole, Pau (France)] [and others

1997-08-01

The most difficult aspect of numerical simulation of well tests is the treatment of the Bottom Hole Flowing (BHF) Pressure. In full field simulations, this pressure is derived from the Well-block Pressure (WBP) using a numerical productivity index which accounts for the grid size and permeability, and for the well completion. This productivity index is calculated assuming a pseudo-steady state flow regime in the vicinity of the well and is therefore constant during the well production period. Such a pseudo-steady state assumption is no longer valid for the early time of a well test simulation as long as the pressure perturbation has not reached several grid-blocks around the well. This paper offers two different solutions to this problem: (1) The first one is based on the derivation of a Numerical Transient Productivity Index (NTPI) to be applied to Cartesian grids; (2) The second one is based on the use of a Corrected Transmissibility and Accumulation Term (CTAT) in the flow equation. The representation of the pressure behavior given by both solutions is far more accurate than the conventional one as shown by several validation examples which are presented in the following pages.

STEADY STATE AND PSEUDO-TRANSIENT ELECTRIC POTENTIAL USING THE POISSONBOLTZMANN EQUATION

Directory of Open Access Journals (Sweden)

L. C. dos Santos

2015-03-01

Full Text Available A method for analysis of the electric potential profile in saline solutions was developed for systems with one or two infinite flat plates. A modified Poisson-Boltzmann equation, taking into account nonelectrostatic interactions between ions and surfaces, was used. To solve the stated problem in the steady-state approach the finite-difference method was used. For the formulated pseudo-transient problem, we solved the set of ordinary differential equations generated from the algebraic equations of the stationary case. A case study was also carried out in relation to temperature, solution concentration, surface charge and salt-type. The results were validated by the stationary problem solution, which had also been used to verify the ionic specificity for different salts. The pseudo-transient approach allowed a better understanding of the dynamic behavior of the ion-concentration profile and other properties due to the surface charge variation.

Steady State Shift Damage Localization

DEFF Research Database (Denmark)

Sekjær, Claus; Bull, Thomas; Markvart, Morten Kusk

2017-01-01

The steady state shift damage localization (S3DL) method localizes structural deterioration, manifested as either a mass or stiffness perturbation, by interrogating the damage-induced change in the steady state vibration response with damage patterns cast from a theoretical model. Damage is, thus...... the required accuracy when examining complex structures, an extensive amount of degrees of freedom (DOF) must often be utilized. Since the interrogation matrix for each damage pattern depends on the size of the system matrices constituting the FE-model, the computational time quickly becomes of first......-order importance. The present paper investigates two sub-structuring approaches, in which the idea is to employ Craig-Bampton super-elements to reduce the amount of interrogation distributions while still providing an acceptable localization resolution. The first approach operates on a strict super-element level...

Quantum thermodynamics of nanoscale steady states far from equilibrium

Science.gov (United States)

Taniguchi, Nobuhiko

2018-04-01

We develop an exact quantum thermodynamic description for a noninteracting nanoscale steady state that couples strongly with multiple reservoirs. We demonstrate that there exists a steady-state extension of the thermodynamic function that correctly accounts for the multiterminal Landauer-Büttiker formula of quantum transport of charge, energy, or heat via the nonequilibrium thermodynamic relations. Its explicit form is obtained for a single bosonic or fermionic level in the wide-band limit, and corresponding thermodynamic forces (affinities) are identified. Nonlinear generalization of the Onsager reciprocity relations are derived. We suggest that the steady-state thermodynamic function is also capable of characterizing the heat current fluctuations of the critical transport where the thermal fluctuations dominate. Also, the suggested nonequilibrium steady-state thermodynamic relations seemingly persist for a spin-degenerate single level with local interaction.

Numerical Asymptotic Solutions Of Differential Equations

Science.gov (United States)

Thurston, Gaylen A.

1992-01-01

Numerical algorithms derived and compared with classical analytical methods. In method, expansions replaced with integrals evaluated numerically. Resulting numerical solutions retain linear independence, main advantage of asymptotic solutions.

Numerical calculation of impurity charge state distributions

International Nuclear Information System (INIS)

Crume, E.C.; Arnurius, D.E.

1977-09-01

The numerical calculation of impurity charge state distributions using the computer program IMPDYN is discussed. The time-dependent corona atomic physics model used in the calculations is reviewed, and general and specific treatments of electron impact ionization and recombination are referenced. The complete program and two examples relating to tokamak plasmas are given on a microfiche so that a user may verify that his version of the program is working properly. In the discussion of the examples, the corona steady-state approximation is shown to have significant defects when the plasma environment, particularly the electron temperature, is changing rapidly

HEXNOD23, 2-D, 3-D Coarse Mesh Solution of Steady State Diffusion Equation in Hexagonal Geometry

International Nuclear Information System (INIS)

Grundmann, Ulrich

1986-01-01

1 - Description of program or function: Two- or three dimensional coarse mesh solution of steady state two group neutron diffusion equation in arrays of regular hexagons or hexagonal subassemblies. 2 - Method of solution: The neutron flux in a hexagonal node is expanded in a series of Bessel functions in the hexagonal plane. Polynomials up to the 4. order are used for the approximation of neutron flux in axial direction of three dimensional cases. Resulting relations between node averaged fluxes and mean partial currents of node faces in connection with the neutron balance of nodes are used to calculate the eigenvalue Keff, mean fluxes and mean powers of nodes. The iterations process is divided into inner and outer iterations. The iterations are accelerated by Ljusternik and Tschebyscheff extrapolation schemes. The power densities in the nodes and subassembly powers are computed for given reactor power in three dimensional cases. 30 degree reflectional, 60 and 120 degree rotational core symmetry and the whole core can be treated. 3 - Restrictions on the complexity of the problem: If the problem size designated by LIAR and LRAR exceeds 3000 and 50000 respectively, the lengths of the working array MIAR and MRAR in the main program can be increased. External sources are not permitted

Steady states in conformal theories

CERN Multimedia

CERN. Geneva

2015-01-01

A novel conjecture regarding the steady state behavior of conformal field theories placed between two heat baths will be presented. Some verification of the conjecture will be provided in the context of fluid dynamics and holography.

Applications of mixed Petrov-Galerkin finite element methods to transient and steady state creep analysis

International Nuclear Information System (INIS)

Guerreiro, J.N.C.; Loula, A.F.D.

1988-12-01

The mixed Petrov-Galerkin finite element formulation is applied to transiente and steady state creep problems. Numerical analysis has shown additional stability of this method compared to classical Galerkin formulations. The accuracy of the new formulation is confirmed in some representative examples of two dimensional and axisymmetric problems. (author) [pt

Differences between automatically detected and steady-state fractional flow reserve.

Science.gov (United States)

Härle, Tobias; Meyer, Sven; Vahldiek, Felix; Elsässer, Albrecht

2016-02-01

Measurement of fractional flow reserve (FFR) has become a standard diagnostic tool in the catheterization laboratory. FFR evaluation studies were based on pressure recordings during steady-state maximum hyperemia. Commercially available computer systems detect the lowest Pd/Pa ratio automatically, which might not always be measured during steady-state hyperemia. We sought to compare the automatically detected FFR and true steady-state FFR. Pressure measurement traces of 105 coronary lesions from 77 patients with intermediate coronary lesions or multivessel disease were reviewed. In all patients, hyperemia had been achieved by intravenous adenosine administration using a dosage of 140 µg/kg/min. In 42 lesions (40%) automatically detected FFR was lower than true steady-state FFR. Mean bias was 0.009 (standard deviation 0.015, limits of agreement -0.02, 0.037). In 4 lesions (3.8%) both methods lead to different treatment recommendations, in all 4 cases instantaneous wave-free ratio confirmed steady-state FFR. Automatically detected FFR was slightly lower than steady-state FFR in more than one-third of cases. Consequently, interpretation of automatically detected FFR values closely below the cutoff value requires special attention.

Steady State versus Pulsed Tokamak DEMO

Energy Technology Data Exchange (ETDEWEB)

Orsitto, F.P., E-mail: francesco.orsitto@enea.it [Associazione EURATOM-ENEA Unita Tecnica Fusione, Frascati (Italy); Todd, T. [CCFE/Fusion Association, Culham Science Centre, Abingdon (United Kingdom)

2012-09-15

Full text: The present report deals with a Review of problems for a Steady state(SS) DEMO, related argument is treated about the models and the present status of comparison between the characteristics of DEMO pulsed versus a Steady state device.The studied SS DEMO Models (SLIM CS, PPCS model C EU-DEMO, ARIES-RS) are analyzed from the point of view of the similarity scaling laws and critical issues for a steady state DEMO. A comparison between steady state and pulsed DEMO is therefore carried out: in this context a new set of parameters for a pulsed (6 - 8 hours pulse) DEMO is determined working below the density limit, peak temperature of 20 keV, and requiring a modest improvement in the confinement factor(H{sub IPBy2} = 1.1) with respect to the H-mode. Both parameters density and confinement parameter are lower than the DEMO models presently considered. The concept of partially non-inductive pulsed DEMO is introduced since a pulsed DEMO needs heating and current drive tools for plasma stability and burn control. The change of the main parameter design for a DEMO working at high plasma peak temperatures T{sub e} {approx} 35 keV is analyzed: in this range the reactivity increases linearly with temperature, and a device with smaller major radius (R = 7.5 m) is compatible with high temperature. Increasing temperature is beneficial for current drive efficiency and heat load on divertor, being the synchrotron radiation one of the relevant components of the plasma emission at high temperatures and current drive efficiency increases with temperature. Technology and engineering problems are examined including efficiency and availability R&D issues for a high temperature DEMO. Fatigue and creep-fatigue effects of pulsed operations on pulsed DEMO components are considered in outline to define the R&D needed for DEMO development. (author)

Dynamical and technological consequences of multiple isolas of steady states in a catalytic fluidised-bed reactor

Directory of Open Access Journals (Sweden)

Bizon Katarzyna

2017-09-01

Full Text Available Steady-state characteristics of a catalytic fluidised bed reactor and its dynamical consequences are analyzed. The occurrence of an untypical steady-state structure manifesting in a form of multiple isolas is described. A two-phase bubbling bed model is used for a quantitative description of the bed of catalyst. The influence of heat exchange intensity and a fluidisation ratio onto the generation of isolated solution branches is presented for two kinetic schemes. Dynamical consequences of the coexistence of such untypical branches of steady states are presented. The impact of linear growth of the fluidisation ratio and step change of the cooling medium temperature onto the desired product yield is analyzed. The results presented in this study confirm that the identification of a region of the occurrence of multiple isolas is important due to their strong impact both on the process start-up and its control.

Series Solution for Steady Three-Dimensional Flow due to Spraying on Inclined Spinning Disk by Homotopy Perturbation Method

Directory of Open Access Journals (Sweden)

Saeed Dinarvand

2012-01-01

Full Text Available The steady three-dimensional flow of condensation or spraying on inclined spinning disk is studied analytically. The governing nonlinear equations and their associated boundary conditions are transformed into the system of nonlinear ordinary differential equations. The series solution of the problem is obtained by utilizing the homotopy perturbation method (HPM. The velocity and temperature profiles are shown and the influence of Prandtl number on the heat transfer and Nusselt number is discussed in detail. The validity of our solutions is verified by the numerical results. Unlike free surface flows on an incline, this through flow is highly affected by the spray rate and the rotation of the disk.

LANSCE steady state unperturbed thermal neutron fluxes at 100 μA

International Nuclear Information System (INIS)

Russell, G.J.

1989-01-01

The ''maximum'' unperturbed, steady state thermal neutron flux for LANSCE is calculated to be 2 /times/ 10 13 n/cm 2 -s for 100 μA of 800-MeV protons. This LANSCE neutron flux is a comparable entity to a steady state reactor thermal neutron flux. LANSCE perturbed steady state thermal neutron fluxes have also been calculated. Because LANSCE is a pulsed neutron source, much higher ''peak'' (in time) neutron fluxes can be generated than at a steady state reactor source. 5 refs., 5 figs

The Asymptotic Solution for the Steady Variable-Viscosity Free ...

African Journals Online (AJOL)

Under an arbitrary time-dependent heating of an infinite vertical plate (or wall), the steady viscosity-dependent free convection flow of a viscous incompressible fluid is investigated. Using the asymptotic method of solution on the governing equations of motion and energy, the resulting Ordinary differential equations were ...

STEADY STATE DUST DISTRIBUTIONS IN DISK VORTICES: OBSERVATIONAL PREDICTIONS AND APPLICATIONS TO TRANSITIONAL DISKS

International Nuclear Information System (INIS)

Lyra, Wladimir; Lin, Min-Kai

2013-01-01

The Atacama Large Millimeter Array has returned images of transitional disks in which large asymmetries are seen in the distribution of millimeter sized dust in the outer disk. The explanation in vogue borrows from the vortex literature and suggests that these asymmetries are the result of dust trapping in giant vortices, excited via Rossby wave instabilities at planetary gap edges. Due to the drag force, dust trapped in vortices will accumulate in the center and diffusion is needed to maintain a steady state over the lifetime of the disk. While previous work derived semi-analytical models of the process, in this paper we provide analytical steady-steady solutions. Exact solutions exist for certain vortex models. The solution is determined by the vortex rotation profile, the gas scale height, the vortex aspect ratio, and the ratio of dust diffusion to gas-dust friction. In principle, all of these quantities can be derived from observations, which would validate the model and also provide constrains on the strength of the turbulence inside the vortex core. Based on our solution, we derive quantities such as the gas-dust contrast, the trapped dust mass, and the dust contrast at the same orbital location. We apply our model to the recently imaged Oph IRS 48 system, finding values within the range of the observational uncertainties

Calculation analysis on steady state natural circulation characteristics

International Nuclear Information System (INIS)

Wang Fei; Nie Changhua; Huang Yanping

2005-01-01

The calculation results of single-phase steady state natural circulation characteristics by using Retran02 code have been presented, good agreement is achieved between the verified calculation result and the experimental data which were conducted at a test facility. Based on the calculation model, some sensibility analyses were made and much deeper understanding for single-phase steady state natural circulation characteristics was obtained. (author)

Selection of steady states in planar Darcy convection

International Nuclear Information System (INIS)

Tsybulin, V.G.; Karasoezen, B.; Ergenc, T.

2006-01-01

The planar natural convection of an incompressible fluid in a porous medium is considered. We study the selection of steady states under temperature perturbations on the boundary. A selection map is introduced in order to analyze the selection of a steady state from a continuous family of equilibria which exists under zero boundary conditions. The results of finite-difference modeling for a rectangular enclosure are presented

Introduction to the numerical solutions of Markov chains

CERN Document Server

Stewart, Williams J

1994-01-01

A cornerstone of applied probability, Markov chains can be used to help model how plants grow, chemicals react, and atoms diffuse - and applications are increasingly being found in such areas as engineering, computer science, economics, and education. To apply the techniques to real problems, however, it is necessary to understand how Markov chains can be solved numerically. In this book, the first to offer a systematic and detailed treatment of the numerical solution of Markov chains, William Stewart provides scientists on many levels with the power to put this theory to use in the actual world, where it has applications in areas as diverse as engineering, economics, and education. His efforts make for essential reading in a rapidly growing field. Here, Stewart explores all aspects of numerically computing solutions of Markov chains, especially when the state is huge. He provides extensive background to both discrete-time and continuous-time Markov chains and examines many different numerical computing metho...

Steady-state entanglement activation in optomechanical cavities

Science.gov (United States)

Farace, Alessandro; Ciccarello, Francesco; Fazio, Rosario; Giovannetti, Vittorio

2014-02-01

Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of nonclassical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.

Two-Dimensional Steady-State Boundary Shape Inversion of CGM-SPSO Algorithm on Temperature Information

Directory of Open Access Journals (Sweden)

Shoubin Wang

2017-01-01

Full Text Available Addressing the problem of two-dimensional steady-state thermal boundary recognition, a hybrid algorithm of conjugate gradient method and social particle swarm optimization (CGM-SPSO algorithm is proposed. The global search ability of particle swarm optimization algorithm and local search ability of gradient algorithm are effectively combined, which overcomes the shortcoming that the conjugate gradient method tends to converge to the local solution and relies heavily on the initial approximation of the iterative process. The hybrid algorithm also avoids the problem that the particle swarm optimization algorithm requires a large number of iterative steps and a lot of time. The experimental results show that the proposed algorithm is feasible and effective in solving the problem of two-dimensional steady-state thermal boundary shape.

Steady States in SIRS Epidemical Model of Mobile Individuals

International Nuclear Information System (INIS)

Zhang Duanming; He Minhua; Yu Xiaoling; Pan Guijun; Sun Hongzhang; Su Xiangying; Sun Fan; Yin Yanping; Li Rui; Liu Dan

2006-01-01

We consider an epidemical model within socially interacting mobile individuals to study the behaviors of steady states of epidemic propagation in 2D networks. Using mean-field approximation and large scale simulations, we recover the usual epidemic behavior with critical thresholds δ c and p c below which infectious disease dies out. For the population density δ far above δ c , it is found that there is linear relationship between contact rate λ and the population density δ in the main. At the same time, the result obtained from mean-field approximation is compared with our numerical result, and it is found that these two results are similar by and large but not completely the same.

Steady-State Ion Beam Modeling with MICHELLE

Science.gov (United States)

Petillo, John

2003-10-01

There is a need to efficiently model ion beam physics for ion implantation, chemical vapor deposition, and ion thrusters. Common to all is the need for three-dimensional (3D) simulation of volumetric ion sources, ion acceleration, and optics, with the ability to model charge exchange of the ion beam with a background neutral gas. The two pieces of physics stand out as significant are the modeling of the volumetric source and charge exchange. In the MICHELLE code, the method for modeling the plasma sheath in ion sources assumes that the electron distribution function is a Maxwellian function of electrostatic potential over electron temperature. Charge exchange is the process by which a neutral background gas with a "fast" charged particle streaming through exchanges its electron with the charged particle. An efficient method for capturing this is essential, and the model presented is based on semi-empirical collision cross section functions. This appears to be the first steady-state 3D algorithm of its type to contain multiple generations of charge exchange, work with multiple species and multiple charge state beam/source particles simultaneously, take into account the self-consistent space charge effects, and track the subsequent fast neutral particles. The solution used by MICHELLE is to combine finite element analysis with particle-in-cell (PIC) methods. The basic physics model is based on the equilibrium steady-state application of the electrostatic particle-in-cell (PIC) approximation employing a conformal computational mesh. The foundation stems from the same basic model introduced in codes such as EGUN. Here, Poisson's equation is used to self-consistently include the effects of space charge on the fields, and the relativistic Lorentz equation is used to integrate the particle trajectories through those fields. The presentation will consider the complexity of modeling ion thrusters.

Development of synchronous generator saturation model from steady-state operating data

Energy Technology Data Exchange (ETDEWEB)

Jadric, Martin; Despalatovic, Marin; Terzic, Bozo [FESB University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split (Croatia)

2010-11-15

A new method to estimate and model the saturated synchronous reactances of hydroturbine generators from operating data is presented. For the estimation process, measurements of only the generator steady-state variables are required. First, using a specific procedure, the field to armature turns ratio is estimated from measured steady-state variables at constant power generation and various excitation conditions. Subsequently, for each set of steady-state operating data, saturated synchronous reactances are identified. Fitting surfaces, defined as polynomial functions in two variables, are later used to model these saturated reactances. It is shown that the simpler polynomial functions may be used to model saturation at the steady-state than at the dynamic conditions. The developed steady-state model is validated with measurements performed on the 34 MVA hydroturbine generator. (author)

Steady state and transient critical heat flux examinations

International Nuclear Information System (INIS)

Szabados, L.

1978-02-01

In steady state conditions within the P.W.R. parameter range the critical heat flux correlations based on local parameters reproduce the experimental data with less deviations than those based on system parameters. The transient experiments were restricted for the case of power transients. A data processing method for critical heat flux measurements has been developed and the applicability of quasi steady state calculation has been verified. (D.P.)

Theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor

International Nuclear Information System (INIS)

Gou Junli; Qiu Suizheng; Su Guanghui; Jia Dounan

2006-01-01

This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single-phase conservative equations for the primary circuit and the steady-state two-phase drift-flux conservative equations for the secondary side of the steam generator, the natural circulation characteristics were studied. On the basis of the preliminary calculation analysis, it was found that natural circulation mass flow rate was proportional to the exponential function of the power and that the value of the exponent is related to the operating conditions of the secondary side of the steam generator. The higher the outlet pressure of the secondary side of the steam generator, the higher the primary natural circulation mass flow rate. The larger height difference between the core center and the steam generator center is favorable for the heat removal capacity of the natural circulation. (authors)

The Markov process admits a consistent steady-state thermodynamic formalism

Science.gov (United States)

Peng, Liangrong; Zhu, Yi; Hong, Liu

2018-01-01

The search for a unified formulation for describing various non-equilibrium processes is a central task of modern non-equilibrium thermodynamics. In this paper, a novel steady-state thermodynamic formalism was established for general Markov processes described by the Chapman-Kolmogorov equation. Furthermore, corresponding formalisms of steady-state thermodynamics for the master equation and Fokker-Planck equation could be rigorously derived in mathematics. To be concrete, we proved that (1) in the limit of continuous time, the steady-state thermodynamic formalism for the Chapman-Kolmogorov equation fully agrees with that for the master equation; (2) a similar one-to-one correspondence could be established rigorously between the master equation and Fokker-Planck equation in the limit of large system size; (3) when a Markov process is restrained to one-step jump, the steady-state thermodynamic formalism for the Fokker-Planck equation with discrete state variables also goes to that for master equations, as the discretization step gets smaller and smaller. Our analysis indicated that general Markov processes admit a unified and self-consistent non-equilibrium steady-state thermodynamic formalism, regardless of underlying detailed models.

Exact partial solution to the steady-state, compressible fluid flow problems of jet formation and jet penetration

International Nuclear Information System (INIS)

Karpp, R.R.

1980-10-01

This report treats analytically the problem of the symmetric impact of two compressible fluid streams. The flow is assumed to be steady, plane, inviscid, and subsonic and that the compressible fluid is of the Chaplygin (tangent gas) type. In the analysis, the governing equations are first transformed to the hodograph plane where an exact, closed-form solution is obtained by standard techniques. The distributions of fluid properties along the plane of symmetry as well as the shapes of the boundary streamlines are exactly determined by transforming the solution back to the physical plane. The problem of a compressible fluid jet penetrating into an infinite target of similar material is also exactly solved by considering a limiting case of this solution. This new compressible flow solution reduces to the classical result of incompressible flow theory when the sound speed of the fluid is allowed to approach infinity. Several illustrations of the differences between compressible and incompressible flows of the type considered are presented

A study on the steady-state solutions of a relativistic Bursian diode in the presence of a transverse magnetic field

Energy Technology Data Exchange (ETDEWEB)

Pramanik, Sourav; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Kuznetsov, V. I.; Bakaleinikov, L. A. [Ioffe Institute, St. Petersburg 194021 (Russian Federation)

2016-08-15

A comprehensive study on the steady states of a planar vacuum diode driven by a cold relativistic electron beam in the presence of an external transverse magnetic field is presented. The regimes, where no electrons are turned around by the external magnetic field and where they are reflected back to the emitter by the magnetic field, are both considered in a generalized way. The problem is solved by two methods: with the Euler and the Lagrange formulation. Taking non-relativistic limit, the solutions are compared with the similar ones which were obtained for the Bursian diode with a non-relativistic electron beam in previous work [Pramanik et al., Phys. Plasmas 22, 112108 (2015)]. It is shown that, at a moderate value of the relativistic factor of the injected beam, the region of the ambiguous solutions located to the right of the SCL bifurcation point (space charge limit) in the non-relativistic regime disappears. In addition, the dependencies of the characteristic bifurcation points and the transmitted current on the Larmor frequency as well as on the relativistic factor are explored.

Contour analysis of steady state tokamak reactor performance

International Nuclear Information System (INIS)

Devoto, R.S.; Fenstermacher, M.E.

1990-01-01

A new method of analysis for presenting the possible operating space for steady state, non-ignited tokamak reactors is proposed. The method uses contours of reactor performance and plasma characteristics, fusion power gain, wall neutron flux, current drive power, etc., plotted on a two-dimensional grid, the axes of which are the plasma current I p and the normalized beta, β n = β/(I p /aB 0 ), to show possible operating points. These steady state operating contour plots are called SOPCONS. This technique is illustrated in an application to a design for the International Thermonuclear Experimental Reactor (ITER) with neutral beam, lower hybrid and bootstrap current drive. The utility of the SOPCON plots for pointing out some of the non-intuitive considerations in steady state reactor design is shown. (author). Letter-to-the-editor. 16 refs, 3 figs, 1 tab

Numerical solution of viscous and viscoelastic fluids flow through the branching channel by finite volume scheme

Science.gov (United States)

Keslerová, Radka; Trdlička, David

2015-09-01

This work deals with the numerical modelling of steady flows of incompressible viscous and viscoelastic fluids through the three dimensional channel with T-junction. The fundamental system of equations is the system of generalized Navier-Stokes equations for incompressible fluids. This system is based on the system of balance laws of mass and momentum for incompressible fluids. Two different mathematical models for the stress tensor are used for simulation of Newtonian and Oldroyd-B fluids flow. Numerical solution of the described models is based on cetral finite volume method using explicit Runge-Kutta time integration.

Stationary Distribution and Thermodynamic Relation in Nonequilibrium Steady States

KAUST Repository

Komatsu, Teruhisa S.; Nakagawa, Naoko; Sasa, Shin-ichi; Tasaki, Hal; Ito, Nobuyasu

2010-01-01

We describe our recent attempts toward statistical mechanics and thermodynamics for nonequilibrium steady states (NESS) realized, e.g., in a heat conducting system. Our first result is a simple expression of the probability distribution (of microscopic states) of a NESS. Our second result is a natural extension of the thermodynamic Clausius relation and a definition of an accompanying entropy in NESS. This entropy coincides with the normalization constant appearing in the above mentioned microscopic expression of NESS, and has an expression similar to the Shannon entropy (with a further symmetrization). The NESS entropy proposed here is a clearly defined measurable quantity even in a system with a large degrees of freedom. We numerically measure the NESS entropy in hardsphere fluid systems with a heat current, by observing energy exchange between the system and the heat baths when the temperatures of the baths are changed according to specified protocols.

Steady-state spheromak reactor studies

International Nuclear Information System (INIS)

Krakowski, R.A.; Hagenson, R.L.

1985-01-01

After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design points is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported

Application of quasi-steady state methods to molecular motor transport on microtubules in fungal hyphae.

Science.gov (United States)

Dauvergne, Duncan; Edelstein-Keshet, Leah

2015-08-21

We consider bidirectional transport of cargo by molecular motors dynein and kinesin that walk along microtubules, and/or diffuse in the cell. The motors compete to transport cargo in opposite directions with respect to microtubule polarity (towards the plus or minus end of the microtubule). In recent work, Gou et al. (2014) used a hierarchical set of models, each consisting of continuum transport equations to track the evolution of motors and their cargo (early endosomes) in the specific case of the fungus Ustilago maydis. We complement their work using a framework of quasi-steady state analysis developed by Newby and Bressloff (2010) and Bressloff and Newby (2013) to reduce the models to an approximating steady state Fokker-Plank equation. This analysis allows us to find analytic approximations to the steady state solutions in many cases where the full models are not easily solved. Consequently, we can make predictions about parameter dependence of the resulting spatial distributions. We also characterize the overall rates of bulk transport and diffusion, and how these are related to state transition parameters, motor speeds, microtubule polarity distribution, and specific assumptions made. Copyright © 2015 Elsevier Ltd. All rights reserved.

Steady state of tapped granular polygons

International Nuclear Information System (INIS)

Carlevaro, Carlos M; Pugnaloni, Luis A

2011-01-01

The steady state packing fraction of a tapped granular bed is studied for different grain shapes via a discrete element method. Grains are monosized regular polygons, from triangles to icosagons. Comparisons with disc packings show that the steady state packing fraction as a function of the tapping intensity presents the same general trends in polygon packings. However, better packing fractions are obtained, as expected, for shapes that can tessellate the plane (triangles, squares and hexagons). In addition, we find a sharp transition for packings of polygons with more than 13 vertices signaled by a discontinuity in the packing fraction at a particular tapping intensity. Density fluctuations for most shapes are consistent with recent experimental findings in disc packing; however, a peculiar behavior is found for triangles and squares

Stochastic Galerkin methods for the steady-state Navier–Stokes equations

Energy Technology Data Exchange (ETDEWEB)

Sousedík, Bedřich, E-mail: sousedik@umbc.edu [Department of Mathematics and Statistics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Elman, Howard C., E-mail: elman@cs.umd.edu [Department of Computer Science and Institute for Advanced Computer Studies, University of Maryland, College Park, MD 20742 (United States)

2016-07-01

We study the steady-state Navier–Stokes equations in the context of stochastic finite element discretizations. Specifically, we assume that the viscosity is a random field given in the form of a generalized polynomial chaos expansion. For the resulting stochastic problem, we formulate the model and linearization schemes using Picard and Newton iterations in the framework of the stochastic Galerkin method, and we explore properties of the resulting stochastic solutions. We also propose a preconditioner for solving the linear systems of equations arising at each step of the stochastic (Galerkin) nonlinear iteration and demonstrate its effectiveness for solving a set of benchmark problems.

Probabilistic Steady-State Operation and Interaction Analysis of Integrated Electricity, Gas and Heating Systems

Directory of Open Access Journals (Sweden)

Lun Yang

2018-04-01

Full Text Available The existing studies on probabilistic steady-state analysis of integrated energy systems (IES are limited to integrated electricity and gas networks or integrated electricity and heating networks. This paper proposes a probabilistic steady-state analysis of integrated electricity, gas and heating networks (EGH-IES. Four typical operation modes of an EGH-IES are presented at first. The probabilistic energy flow problem of the EGS-IES considering its operation modes and correlated uncertainties in wind/solar power and electricity/gas/heat loads is then formulated and solved by the Monte Carlo method based on Latin hypercube sampling and Nataf transformation. Numerical simulations are conducted on a sample EGH-IES working in the “electricity/gas following heat” mode to verify the probabilistic analysis proposed in this paper and to study the effects of uncertainties and correlations on the operation of the EGH-IES, especially uncertainty transmissions among the subnetworks.

Steady-state propagation of interface corner crack

DEFF Research Database (Denmark)

Veluri, Badrinath; Jensen, Henrik Myhre

2013-01-01

Steady-state propagation of interface cracks close to three-dimensional corners has been analyzed. Attention was focused on modeling the shape of the interface crack front and calculating the critical stress for steady-state propagation of the crack. The crack propagation was investigated...... on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stresses as a function of the fracture criterion and corner angles. The implication of the results on the delamination is discussed in terms of crack front profiles and the critical stresses...... for propagation and the angle of intersection of the crack front with the free edge....

Steady-state leaching of tritiated water from silica gel

DEFF Research Database (Denmark)

Das, H.A.; Hou, Xiaolin

2009-01-01

Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion.......Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion....

Quasi steady-state aerodynamic model development for race vehicle simulations

Science.gov (United States)

Mohrfeld-Halterman, J. A.; Uddin, M.

2016-01-01

Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.

Realizing steady-state tokamak operation for fusion energy

International Nuclear Information System (INIS)

Luce, T. C.

2011-01-01

Continuous operation of a tokamak for fusion energy has clear engineering advantages but requires conditions beyond those sufficient for a burning plasma. The fusion reactions and external sources must support both the pressure and the current equilibrium without inductive current drive, leading to demands on stability, confinement, current drive, and plasma-wall interactions that exceed those for pulsed tokamaks. These conditions have been met individually, and significant progress has been made in the past decade to realize scenarios where the required conditions are obtained simultaneously. Tokamaks are operated routinely without disruptions near pressure limits, as needed for steady-state operation. Fully noninductive sustainment with more than half of the current from intrinsic currents has been obtained for a resistive time with normalized pressure and confinement approaching those needed for steady-state conditions. One remaining challenge is handling the heat and particle fluxes expected in a steady-state tokamak without compromising the core plasma performance.

Improving the steady-state loading margin to voltage collapse in the North-West Control Area of the Mexican Power System

Energy Technology Data Exchange (ETDEWEB)

Calderon-Guizar, J.G.; Inda-Ruiz, G.A.; Tovar, G.E. [Gerencia de Analisis de Redes, Temixco, Morelos (Mexico). Inst. de Investigaciones Eleectricas

2003-10-01

This paper reports the application of a static approach for assessing the steady-state loading margin to voltage collapse of the North-West Control Area (NWCA) of the Mexican Power System. The approach uses both optimal load flow (OLF) and conventional load flow (LF) solutions, and singular value decomposition of the load flow Jacobian matrix (J). Additionally, the approach allows to determine suitable locations for corrective actions such as, the addition of new equipment or load shedding. The results shows that the combination of OLF and LF resulted in a steady-state loading margin to voltage collapse of the NWCA 7.2% higher than the case when only conventional load flow solutions were considered. (author)

Steady State Advanced Tokamak (SSAT): The mission and the machine

International Nuclear Information System (INIS)

Thomassen, K.; Goldston, R.; Nevins, B.; Neilson, H.; Shannon, T.; Montgomery, B.

1992-03-01

Extending the tokamak concept to the steady state regime and pursuing advances in tokamak physics are important and complementary steps for the magnetic fusion energy program. The required transition away from inductive current drive will provide exciting opportunities for advances in tokamak physics, as well as important impetus to drive advances in fusion technology. Recognizing this, the Fusion Policy Advisory Committee and the US National Energy Strategy identified the development of steady state tokamak physics and technology, and improvements in the tokamak concept, as vital elements in the magnetic fusion energy development plan. Both called for the construction of a steady state tokamak facility to address these plan elements. Advances in physics that produce better confinement and higher pressure limits are required for a similar unit size reactor. Regimes with largely self-driven plasma current are required to permit a steady-state tokamak reactor with acceptable recirculating power. Reliable techniques of disruption control will be needed to achieve the availability goals of an economic reactor. Thus the central role of this new tokamak facility is to point the way to a more attractive demonstration reactor (DEMO) than the present data base would support. To meet the challenges, we propose a new ''Steady State Advanced Tokamak'' (SSAT) facility that would develop and demonstrate optimized steady state tokamak operating mode. While other tokamaks in the world program employ superconducting toroidal field coils, SSAT would be the first major tokamak to operate with a fully superconducting coil set in the elongated, divertor geometry planned for ITER and DEMO

Steady-State Diffusion of Water through Soft-Contact LensMaterials

Energy Technology Data Exchange (ETDEWEB)

Fornasiero, Francesco; Krull, Florian; Radke, Clayton J.; Prausnitz, JohnM.

2005-01-31

Water transport through soft contact lenses (SCL) is important for acceptable performance on the human eye. Chemical-potential gradient-driven diffusion rates of water through soft-contact-lens materials are measured with an evaporation-cell technique. Water is evaporated from the bottom surface of a lens membrane by impinging air at controlled flow rate and humidity. The resulting weight loss of a water reservoir covering the top surface of the contact-lens material is recorded as a function of time. New results are reported for a conventional hydrogel material (SofLens{trademark} One Day, hilafilcon A, water content at saturation W{sub 10} = 70 weight %) and a silicone hydrogel material (PureVision{trademark}, balafilcon A, W{sub 10} = 36 %), with and without surface oxygen plasma treatment. Also, previously reported data for a conventional HEMA-SCL (W{sub 10} = 38 %) hydrogel are reexamined and compared with those for SofLens{trademark} One Day and PureVision{trademark} hydrogels. Measured steady-state water fluxes are largest for SofLens{trademark} One Day, followed by PureVision{trademark} and HEMA. In some cases, the measured steady-state water fluxes increase with rising relative air humidity. This increase, due to an apparent mass-transfer resistance at the surface (trapping skinning), is associated with formation of a glassy skin at the air/membrane interface when the relative humidity is below 55-75%. Steady-state water-fluxes are interpreted through an extended Maxwell-Stefan diffusion model for a mixture of species starkly different in size. Thermodynamic nonideality is considered through Flory-Rehner polymer-solution theory. Shrinking/swelling is self-consistently modeled by conservation of the total polymer mass. Fitted Maxwell-Stefan diffusivities increase significantly with water concentration in the contact lens.

Dynamics from a mathematical model of a two-state gas laser

Science.gov (United States)

Kleanthous, Antigoni; Hua, Tianshu; Manai, Alexandre; Yawar, Kamran; Van Gorder, Robert A.

2018-05-01

Motivated by recent work in the area, we consider the behavior of solutions to a nonlinear PDE model of a two-state gas laser. We first review the derivation of the two-state gas laser model, before deriving a non-dimensional model given in terms of coupled nonlinear partial differential equations. We then classify the steady states of this system, in order to determine the possible long-time asymptotic solutions to this model, as well as corresponding stability results, showing that the only uniform steady state (the zero motion state) is unstable, while a linear profile in space is stable. We then provide numerical simulations for the full unsteady model. We show for a wide variety of initial conditions that the solutions tend toward the stable linear steady state profiles. We also consider traveling wave solutions, and determine the unique wave speed (in terms of the other model parameters) which allows wave-like solutions to exist. Despite some similarities between the model and the inviscid Burger's equation, the solutions we obtain are much more regular than the solutions to the inviscid Burger's equation, with no evidence of shock formation or loss of regularity.

Instabilities in fluid layers and in reaction-diffusion systems: Steady states, time-periodic solutions, non-periodic attractors, and related convective and otherwise non-linear phenomena

Energy Technology Data Exchange (ETDEWEB)

Garcia Velarde, M

1977-07-01

Thermo convective instabilities in horizontal fluid layers are discussed with emphasis on the Rayleigh-Bernard model problem. Steady solutions and time-dependent phenomena (relaxation oscillations and transition to turbulence) are studied within the nonlinear Boussinesq-Oberbeck approximation. Homogeneous steady solutions, limit cycles, and inhomogeneous (ordered) spatial structures are also studied in simple reaction-diffusion systems. Lastly, the non-periodic attractor that appears at large Rayleigh numbers in the truncated Boussinesq-Oberbeck model of Lorenz, is constructed, and a discussion of turbulent behavior is given. (Author) 105 refs.

Instabilities in fluid layers and in reaction-diffusion systems: Steady states, time-periodic solutions, non-periodic attractors, and related convective and otherwise non-linear phenomena

International Nuclear Information System (INIS)

Garcia Velarde, M.

1977-01-01

Thermoconvective instabilities in horizontal fluid layers are discussed with emphasis on the Rayleigh-Benard model problem. Steady solutions and time-dependent phenomena (relaxation oscillations and transition to turbulence) are studied within the nonlinear Boussinesq-Oberbeck approximation. Homogeneous steady solutions, limit cycles, and inhomogeneous (ordered) spatial structures are also studied in simple reaction-diffusion systems. Lastly, the non-periodic attractor that appears at large Rayleigh numbers in the truncated Boussinesq-Oberbeck model of Lorenz, is constructed, and a discussion of turbulent behavior is given. (author) [es

Instabilities in fluid layers and in reaction-diffusion systems: Steady states, time-periodic solutions, non-periodic attractors, and related convective and otherwise non-linear phenomena

International Nuclear Information System (INIS)

Garcia Velarde, M.

1977-01-01

Thermo convective instabilities in horizontal fluid layers are discussed with emphasis on the Rayleigh-Bernard model problem. Steady solutions and time-dependent phenomena (relaxation oscillations and transition to turbulence) are studied within the nonlinear Boussinesq-Oberbeck approximation. Homogeneous steady solutions, limit cycles, and inhomogeneous (ordered) spatial structures are also studied in simple reaction-diffusion systems. Lastly, the non-periodic attractor that appears at large Rayleigh numbers in the truncated Boussinesq-Oberbeck model of Lorenz, is constructed, and a discussion of turbulent behavior is given. (Author) 105 refs

VARI-QUIR-3, 2-D Multigroup Steady-State Neutron Diffusion in X-Y R-Z or R-Theta Geometry

International Nuclear Information System (INIS)

Collier, George

1984-01-01

1 - Nature of physical problem solved: The steady-state, multigroup, two-dimensional neutron diffusion equations are solved in x-y, r-z, and r-theta geometry. 2 - Method of solution: A Gauss-Seidel type of solution with inner and outer iterations is used. The source is held constant during the inner iterations

Stability, accuracy and numerical diffusion analysis of nodal expansion method for steady convection diffusion equation

International Nuclear Information System (INIS)

Zhou, Xiafeng; Guo, Jiong; Li, Fu

2015-01-01

Highlights: • NEMs are innovatively applied to solve convection diffusion equation. • Stability, accuracy and numerical diffusion for NEM are analyzed for the first time. • Stability and numerical diffusion depend on the NEM expansion order and its parity. • NEMs have higher accuracy than both second order upwind and QUICK scheme. • NEMs with different expansion orders are integrated into a unified discrete form. - Abstract: The traditional finite difference method or finite volume method (FDM or FVM) is used for HTGR thermal-hydraulic calculation at present. However, both FDM and FVM require the fine mesh sizes to achieve the desired precision and thus result in a limited efficiency. Therefore, a more efficient and accurate numerical method needs to be developed. Nodal expansion method (NEM) can achieve high accuracy even on the coarse meshes in the reactor physics analysis so that the number of spatial meshes and computational cost can be largely decreased. Because of higher efficiency and accuracy, NEM can be innovatively applied to thermal-hydraulic calculation. In the paper, NEMs with different orders of basis functions are successfully developed and applied to multi-dimensional steady convection diffusion equation. Numerical results show that NEMs with three or higher order basis functions can track the reference solutions very well and are superior to second order upwind scheme and QUICK scheme. However, the false diffusion and unphysical oscillation behavior are discovered for NEMs. To explain the reasons for the above-mentioned behaviors, the stability, accuracy and numerical diffusion properties of NEM are analyzed by the Fourier analysis, and by comparing with exact solutions of difference and differential equation. The theoretical analysis results show that the accuracy of NEM increases with the expansion order. However, the stability and numerical diffusion properties depend not only on the order of basis functions but also on the parity of

Stability, accuracy and numerical diffusion analysis of nodal expansion method for steady convection diffusion equation

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xiafeng, E-mail: zhou-xf11@mails.tsinghua.edu.cn; Guo, Jiong, E-mail: guojiong12@tsinghua.edu.cn; Li, Fu, E-mail: lifu@tsinghua.edu.cn

2015-12-15

Highlights: • NEMs are innovatively applied to solve convection diffusion equation. • Stability, accuracy and numerical diffusion for NEM are analyzed for the first time. • Stability and numerical diffusion depend on the NEM expansion order and its parity. • NEMs have higher accuracy than both second order upwind and QUICK scheme. • NEMs with different expansion orders are integrated into a unified discrete form. - Abstract: The traditional finite difference method or finite volume method (FDM or FVM) is used for HTGR thermal-hydraulic calculation at present. However, both FDM and FVM require the fine mesh sizes to achieve the desired precision and thus result in a limited efficiency. Therefore, a more efficient and accurate numerical method needs to be developed. Nodal expansion method (NEM) can achieve high accuracy even on the coarse meshes in the reactor physics analysis so that the number of spatial meshes and computational cost can be largely decreased. Because of higher efficiency and accuracy, NEM can be innovatively applied to thermal-hydraulic calculation. In the paper, NEMs with different orders of basis functions are successfully developed and applied to multi-dimensional steady convection diffusion equation. Numerical results show that NEMs with three or higher order basis functions can track the reference solutions very well and are superior to second order upwind scheme and QUICK scheme. However, the false diffusion and unphysical oscillation behavior are discovered for NEMs. To explain the reasons for the above-mentioned behaviors, the stability, accuracy and numerical diffusion properties of NEM are analyzed by the Fourier analysis, and by comparing with exact solutions of difference and differential equation. The theoretical analysis results show that the accuracy of NEM increases with the expansion order. However, the stability and numerical diffusion properties depend not only on the order of basis functions but also on the parity of

Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.

Science.gov (United States)

Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P

2010-06-07

The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Dynamics and non-equilibrium steady state in a system of coupled harmonic oscillators

Energy Technology Data Exchange (ETDEWEB)

Ghesquière, Anne, E-mail: Anne.Ghesquiere@nithep.ac.za; Sinayskiy, Ilya, E-mail: sinayskiy@ukzn.ac.za; Petruccione, Francesco, E-mail: petruccione@ukzn.ac.za

2013-10-15

A system of two coupled oscillators, each of them coupled to an independent reservoir, is analysed. The analytical solution of the non-rotating wave master equation is obtained in the high-temperature and weak coupling limits. No thermal entanglement is found in the high-temperature limit. In the weak coupling limit the system converges to an entangled non-equilibrium steady state. A critical temperature for the appearance of quantum correlations is found.

Stability of racemic and chiral steady states in open and closed chemical systems

Energy Technology Data Exchange (ETDEWEB)

Ribo, Josep M. [Departament de Quimica Organica, Universitat de Barcelona, c. Marti i Franques 1, Barcelona (Spain); Hochberg, David [Centro de Astrobiologia (CSIC-INTA), Ctra. Ajalvir Km. 4, 28850 Torrejon de Ardoz, Madrid (Spain)], E-mail: hochbergd@inta.es

2008-12-22

The stability properties of models of spontaneous mirror symmetry breaking in chemistry are characterized algebraically. The models considered here all derive either from the Frank model or from autocatalysis with limited enantioselectivity. Emphasis is given to identifying the critical parameter controlling the chiral symmetry breaking transition from racemic to chiral steady-state solutions. This parameter is identified in each case, and the constraints on the chemical rate constants determined from dynamic stability are derived.

Stability of racemic and chiral steady states in open and closed chemical systems

International Nuclear Information System (INIS)

Ribo, Josep M.; Hochberg, David

2008-01-01

The stability properties of models of spontaneous mirror symmetry breaking in chemistry are characterized algebraically. The models considered here all derive either from the Frank model or from autocatalysis with limited enantioselectivity. Emphasis is given to identifying the critical parameter controlling the chiral symmetry breaking transition from racemic to chiral steady-state solutions. This parameter is identified in each case, and the constraints on the chemical rate constants determined from dynamic stability are derived

Numerical Investigation on the Propagation Mechanism of Steady Cellular Detonations in Curved Channels

International Nuclear Information System (INIS)

Li Jian; Ning Jian-Guo; Zhao Hui; Wang Cheng; Hao Li

2015-01-01

The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism. The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where detonation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression. (paper)

Steady state theta pinch concept for slow formation of FRC

International Nuclear Information System (INIS)

Hirano, K.

1987-05-01

A steady state high beta plasma flow through a channel along the magnetic field increasing downstream can be regarded as a ''steady state theta pinch'', because if we see the plasma riding on the flow we should observe very similar process taking place in a theta pinch. Anticipating to produce an FRC without using very high voltage technics such as the ones required in a conventional theta pinch, we have studied after the analogy a ''steady state reversed field theta pinch'' which is brought about by steady head-on collision of counter plasma streams along the channel as ejected from two identical co-axial plasma sources mounted at the both ends of the apparatus. The ideal Poisson and shock adiabatic flow models are employed for the analysis of the steady colliding process. It is demonstrated that an FRC involving large numbers of particles is produced only by the weak shock mode which is achieved in case energetic plasma flow is decelerated almost to be stagnated through Poisson adiabatic process before the streams are collided. (author)

A new perspective on steady-state cosmology: from Einstein to Hoyle

OpenAIRE

O'Raifeartaigh, Cormac; Mitton, Simon

2015-01-01

We recently reported the discovery of an unpublished manuscript by Albert Einstein in which he attempted a 'steady-state' model of the universe, i.e., a cosmic model in which the expanding universe remains essentially unchanged due to a continuous formation of matter from empty space. The manuscript was apparently written in early 1931, many years before the steady-state models of Fred Hoyle, Hermann Bondi and Thomas Gold. We compare Einstein’s steady-state cosmology with that of Hoyle, Bondi...

The non-steady state oceanic CO2 signal: its importance, magnitude and a novel way to detect it

Directory of Open Access Journals (Sweden)

B. I. McNeil

2013-04-01

Full Text Available The role of the ocean has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering nearly half of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960s (~1 Pg C yr−1 and 2000s (~2 Pg C yr−1, with expectations that it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent CO2 outgassing signal represents a significant shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in a steady state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady state CO2 signal from observations. Over the entire industrial era, the non-steady state CO2 outgassing signal (~13 ± 10 Pg C is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C. However, between 1989 and 2007, the non-steady state CO2 outgassing signal (~6.3 Pg C has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C. The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady state CO2 signal, however with more data and better certainty estimates across a range of diverse methods, this important and growing CO2 signal could be better constrained in the future.

BR2 reactor core steady state transient modeling

International Nuclear Information System (INIS)

Makarenko, A.; Petrova, T.

2000-01-01

A coupled neutronics/hydraulics/heat-conduction model of the BR2 reactor core is under development at SCK-CEN. The neutron transport phenomenon has been implemented as steady state and time dependent nodal diffusion. The non-linear heat conduction equation in-side fuel elements is solved with a time dependent finite element method. To allow coupling between functional modules and to simulate subcooled regimes, a simple single-phase hydraulics has been introduced, while the two-phase hydraulics is under development. Multiple tests, general benchmark cases as well as calculation/experiment comparisons demonstrated a good accuracy of both neutronic and thermal hydraulic models, numerical reliability and full code portability. A refinement methodology has been developed and tested for better neutronic representation in hexagonal geometry. Much effort is still needed to complete the development of an extended cross section library with kinetic data and two-phase flow representation. (author)

Unsteady State Two Phase Flow Pressure Drop Calculations

OpenAIRE

Ayatollahi, Shahaboddin

1992-01-01

A method is presented to calculate unsteady state two phase flow in a gas-liquid line based on a quasi-steady state approach. A computer program for numerical solution of this method was prepared. Results of calculations using the computer program are presented for several unsteady state two phase flow systems

Steady State Analysis of Stochastic Systems with Multiple Time Delays

Science.gov (United States)

Xu, W.; Sun, C. Y.; Zhang, H. Q.

In this paper, attention is focused on the steady state analysis of a class of nonlinear dynamic systems with multi-delayed feedbacks driven by multiplicative correlated Gaussian white noises. The Fokker-Planck equations for delayed variables are at first derived by Novikov's theorem. Then, under small delay assumption, the approximate stationary solutions are obtained by the probability density approach. As a special case, the effects of multidelay feedbacks and the correlated additive and multiplicative Gaussian white noises on the response of a bistable system are considered. It is shown that the obtained analytical results are in good agreement with experimental results in Monte Carlo simulations.

Numerical Simulation of Cyclic Thermodynamic Processes

DEFF Research Database (Denmark)

Andersen, Stig Kildegård

2006-01-01

This thesis is on numerical simulation of cyclic thermodynamic processes. A modelling approach and a method for finding periodic steady state solutions are described. Examples of applications are given in the form of four research papers. Stirling machines and pulse tube coolers are introduced...... and a brief overview of the current state of the art in methods for simulating such machines is presented. It was found that different simulation approaches, which model the machines with different levels of detail, currently coexist. Methods using many simplifications can be easy to use and can provide...... models flexible and easy to modify, and to make simulations fast. A high level of accuracy was achieved for integrations of a model created using the modelling approach; the accuracy depended on the settings for the numerical solvers in a very predictable way. Selection of fast numerical algorithms...

Transient and steady-state currents in epoxy resin

International Nuclear Information System (INIS)

Guillermin, Christophe; Rain, Pascal; Rowe, Stephen W

2006-01-01

Charging and discharging currents have been measured in a diglycidyl ether of bisphenol-A epoxy resin with and without silica fillers, below and above its glass transition temperature T g = 65 deg. C. Both transient and steady-state current densities have been analysed. The average applied fields ranged from 3 to 35 kV mm -1 with a sample thickness of 0.5 mm. Above T g , transient currents suggested a phenomenon of charge injection forming trapped space charges even at low fields. Steady-state currents confirmed that the behaviour was not Ohmic and suggested Schottky-type injection. Below T g , the current is not controlled by the metal-dielectric interface but by the conduction in the volume: the current is Ohmic at low fields and both transient and steady-state currents suggest a phenomenon of space-charge limited currents at high fields. The field threshold is similar in the filler-free and the filled resin. Values in the range 12-17 kV mm -1 have been measured

Transient and steady-state currents in epoxy resin

Energy Technology Data Exchange (ETDEWEB)

Guillermin, Christophe [Schneider Electric Industries S.A.S., 37 quai Paul-Louis Merlin, 38050 Grenoble Cedex 9 (France); Rain, Pascal [Laboratoire d' Electrostatique et de Materiaux Dielectriques (LEMD), CNRS, 25 avenue des Martyrs, 38042 Grenoble Cedex 9 (France); Rowe, Stephen W [Schneider Electric Industries S.A.S., 37 quai Paul-Louis Merlin, 38050 Grenoble Cedex 9 (France)

2006-02-07

Charging and discharging currents have been measured in a diglycidyl ether of bisphenol-A epoxy resin with and without silica fillers, below and above its glass transition temperature T{sub g} = 65 deg. C. Both transient and steady-state current densities have been analysed. The average applied fields ranged from 3 to 35 kV mm{sup -1} with a sample thickness of 0.5 mm. Above T{sub g}, transient currents suggested a phenomenon of charge injection forming trapped space charges even at low fields. Steady-state currents confirmed that the behaviour was not Ohmic and suggested Schottky-type injection. Below T{sub g}, the current is not controlled by the metal-dielectric interface but by the conduction in the volume: the current is Ohmic at low fields and both transient and steady-state currents suggest a phenomenon of space-charge limited currents at high fields. The field threshold is similar in the filler-free and the filled resin. Values in the range 12-17 kV mm{sup -1} have been measured.

Spurious solutions in few-body equations. II. Numerical investigations

International Nuclear Information System (INIS)

Adhikari, S.K.

1979-01-01

A recent analytic study of spurious solutions in few-body equations by Adhikari and Gloeckle is here complemented by numerical investigations. As proposed by Adhikari and Gloeckle we study numerically the spurious solutions in the three-body Weinberg type equations and draw some general conclusions about the existence of spurious solutions in three-body equations with the Weinberg kernel and in other few-body formulations. In particular we conclude that for most of the potentials we encounter in problems of nuclear physics the three-body Weinberg type equation will not have a spurious solution which may interfere with the bound state or scattering calculation. Hence, if proven convenient, the three-body Weinberg type equation can be used in practical calculations. The same conclusion is true for the three-body channel coupling array scheme of Kouri, Levin, and Tobocman. In the case of the set of six coupled four-body equations proposed by Rosenberg et al. and the set of the Bencze-Redish-Sloan equations a careful study of the possible spurious solutions is needed before using these equations in practical calculations

Numerical Study on Several Stabilized Finite Element Methods for the Steady Incompressible Flow Problem with Damping

Directory of Open Access Journals (Sweden)

Jilian Wu

2013-01-01

Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.

Steady state flow evaluations for passive auxiliary feedwater system of APR

International Nuclear Information System (INIS)

Park, Jongha; Kim, Jaeyul; Seong, Hoje; Kang, Kyoungho

2012-01-01

This paper briefly introduces a methodology to evaluate steady state flow of APR+ Passive Auxiliary Feedwater System (PAFS). The PAFS is being developed as a safety grade passive system to completely replace the existing active Auxiliary Feedwater System (AFWS). Natural circulation cooling can be generally classified into the single-phase, two-phase, and boiling-condensation modes. The PAF is designed to be operated in a boiling-condensation natural circulation mode. The steady-state flow rate should be equal to the steady-state boiling/condensation rate determined by the steady-state energy and momentum balances in the PAFS. The determined steady-state flow rate can be used in the design optimization for the natural circulation loop of the PAFS through the steady-state momentum balance. Since the retarding force, which is to be balanced by the driving force in the natural circulation system design depends on the reliable evaluation of the success of a natural circulation system design depends on the reliable evaluation of the pressure loss coefficients. In PAFS, the core decay heat is released by natural circulation flow between the S G secondary side and the Passive Condensation Heat Exchanger (PCHX) that is immersed in the Passive Condensation Cooling Tank (PCCT). The PCCT is located on the top of Auxiliary building The driving force is determined by the difference between the S/G (heat Source) secondary water level and condensation liquid (heat sink) level. It will overcome retarding force at flowrate in the system, which is determined by vaporization and condensation of the steam which is generated at the S/G by the latent heat in system. In this study, the theoretical method to estimate the steady state flow rate in boiling-condensation natural circulation system is developed and compared with test results

SYNTH-C, Steady-State and Time-Dependent 3-D Neutron Diffusion with Thermohydraulic Feedback

Energy Technology Data Exchange (ETDEWEB)

Brega, E [ENEL-CRTN, Bastioni di Porta Volta 10, Milan (Italy); Salina, E [A.R.S. Spa, Viale Maino 35, Milan (Italy)

1980-04-01

1 - Description of problem or function: SYNTH-C-STEADY and SYNTH-C- TRANS solve respectively the steady-state and time-dependent few- group neutron diffusion equations in three dimensions x,y,z in the presence of fuel temperature and thermal-hydraulic feedback. The neutron diffusion and delayed precursor equations are approximated by a space-time (z,t) synthesis method with axially discontinuous trial functions. Three thermal-hydraulic and fuel heat transfer models are available viz. COBRA-3C/MIT model, lumped parameter (WIGL) model and adiabatic fuel heat-up model. 2 - Method of solution: The steady-state and time-dependent synthesis equations are solved respectively by the Wielandt's power method and by the theta-difference method (in time), both coupled with a block factorization technique and double precision arithmetic. The thermal-hydraulic model equations are solved by fully implicit finite differences (WIGL) or explicit-implicit difference techniques with iterations (COBRA-EC/MIT). 3 - Restrictions on the complexity of the problem: Except for the few- group limitation, the programs have no other fixed limitation so the ability to run a problem depends only on the available computer storage.

Einstein's steady-state theory: an abandoned model of the cosmos

Science.gov (United States)

O'Raifeartaigh, Cormac; McCann, Brendan; Nahm, Werner; Mitton, Simon

2014-09-01

We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a `steady-state' model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein's steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.

Numerical investigation of the 3-dimensional steady-state temperature- and flow distribution in the core of a pebble bed high temperature reactor

International Nuclear Information System (INIS)

Verfondern, K.

1983-01-01

This work presents a computer model determining the steady-state temperature- and flow field in 3 dimensions in the core of a pebble bed high temperature reactor. The numerical sprinkler method, basind on the Thermix-model, allows to describe the thermo-hydraulics of a non-rotational-symmetric core-geometry. The AVR-reactor in Juelich, in operation since 1967, represents a suitable investigation-object for the computer model of Thermix-3D. It is in a 3D-mesh-structure to reproduce very precisely the so called ''graphite noses'', in which the shut-down rods are conducted as well as the filling cones in the inner and outer area. The results of the final calculation of the normal operation condition for the AVR-reactor unambiguously show, that within the core reproduced in 3 dimensions there are evident deviations in the flow profile and in the temperatures of the cooling gas in contrast to a 2D-handling. (orig.) [de

Simulations of KSTAR high performance steady state operation scenarios

International Nuclear Information System (INIS)

Na, Yong-Su; Kessel, C.E.; Park, J.M.; Yi, Sumin; Kim, J.Y.; Becoulet, A.; Sips, A.C.C.

2009-01-01

We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; β N above 3, H 98 (y, 2) up to 2.0, f BS up to 0.76 and f NI equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of q min is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work

Superconducting magnets and cryogenics for the steady state superconducting tokamak SST-1

International Nuclear Information System (INIS)

Saxena, Y.C.

2000-01-01

SST-1 is a steady state superconducting tokamak for studying the physics of the plasma processes in tokamak under steady state conditions and to learn technologies related to the steady state operation of the tokamak. SST-1 will have superconducting magnets made from NbTi based conductors operating at 4.5 K temperature. The design of the superconducting magnets and the cryogenic system of SST-1 tokamak are described. (author)

Characteristics of steady vibration in a rotating hub-beam system

Science.gov (United States)

Zhao, Zhen; Liu, Caishan; Ma, Wei

2016-02-01

A rotating beam features a puzzling character in which its frequencies and modal shapes may vary with the hub's inertia and its rotating speed. To highlight the essential nature behind the vibration phenomena, we analyze the steady vibration of a rotating Euler-Bernoulli beam with a quasi-steady-state stretch. Newton's law is used to derive the equations governing the beam's elastic motion and the hub's rotation. A combination of these equations results in a nonlinear partial differential equation (PDE) that fully reflects the mutual interaction between the two kinds of motion. Via the Fourier series expansion within a finite interval of time, we reduce the PDE into an infinite system of a nonlinear ordinary differential equation (ODE) in spatial domain. We further nondimensionalize the ODE and discretize it via a difference method. The frequencies and modal shapes of a general rotating beam are then determined numerically. For a low-speed beam where the ignorance of geometric stiffening is feasible, the beam's vibration characteristics are solved analytically. We validate our numerical method and the analytical solutions by comparing with either the past experiments or the past numerical findings reported in existing literature. Finally, systematic simulations are performed to demonstrate how the beam's eigenfrequencies vary with the hub's inertia and rotating speed.

Steady-state models in electrophoresis: from isotachophoresis to capillary zone electrophoresis

NARCIS (Netherlands)

Beckers, J.L.

1995-01-01

Although all electrophoretic techniques are closely allied and controlled by the same rules, we often distinguish between steady-state and dynamic models in the modeling of electrophoretic processes, whereby steady-state models are applied for isotachophoresis (ITP) and dynamic models are applied

Mathematical Modeling and Simulation of the Dehydrogenation of Ethyl Benzene to Form Styrene Using Steady-State Fixed Bed Reactor

Directory of Open Access Journals (Sweden)

Zaidon M. Shakoor

2013-05-01

Full Text Available In this research, two models are developed to simulate the steady state fixed bed reactor used for styrene production by ethylbenzene dehydrogenation. The first is one-dimensional model, considered axial gradient only while the second is two-dimensional model considered axial and radial gradients for same variables.The developed mathematical models consisted of nonlinear simultaneous equations in multiple dependent variables. A complete description of the reactor bed involves partial, ordinary differential and algebraic equations (PDEs, ODEs and AEs describing the temperatures, concentrations and pressure drop across the reactor was given. The model equations are solved by finite differences method. The reactor models were coded with Mat lab 6.5 program and various numerical techniques were used to obtain the desired solution.The simulation data for both models were validated with industrial reactor results with a very good concordance.

X-Ray Spectral Analysis of the Steady States of GRS1915+105

Science.gov (United States)

Peris, Charith S.; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa D.; Varnière, Peggy; Rodriguez, Jerome; Pooley, Guy

2016-05-01

We report on the X-ray spectral behavior within the steady states of GRS1915+105. Our work is based on the full data set of the source obtained using the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to these regions as steady-soft and steady-hard. GRS1915+105 displays significant curvature in the coronal component in both the soft and hard data within the RXTE/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius ({R}{{in}}), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations, we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes η ˜ 0.68+/- 0.35 and η ˜ 1.12+/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of the model parameters to the state definitions shows that almost all of the steady-soft observations match the criteria of either a thermal or steep power-law state, while a large portion of the steady-hard observations match the hard-state criteria when the disk fraction constraint is neglected.

NASA Lewis Steady-State Heat Pipe Code Architecture

Science.gov (United States)

Mi, Ye; Tower, Leonard K.

2013-01-01

NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given

New Approaches for Very Short-term Steady-State Analysis of An Electrical Distribution System with Wind Farms

Directory of Open Access Journals (Sweden)

Antonio Bracale

2010-04-01

Full Text Available Distribution networks are undergoing radical changes due to the high level of penetration of dispersed generation. Dispersed generation systems require particular attention due to their incorporation of uncertain energy sources, such as wind farms, and due to the impacts that such sources have on the planning and operation of distribution networks. In particular, the foreseeable, extensive use of wind turbine generator units in the future requires that distribution system engineers properly account for their impacts on the system. Many new technical considerations must be addressed, including protection coordination, steady-state analysis, and power quality issues. This paper deals with the very short-term, steady-state analysis of a distribution system with wind farms, for which the time horizon of interest ranges from one hour to a few hours ahead. Several wind-forecasting methods are presented in order to obtain reliable input data for the steady-state analysis. Both deterministic and probabilistic methods were considered and used in performing deterministic and probabilistic load-flow analyses. Numerical applications on a 17-bus, medium-voltage, electrical distribution system with various wind farms connected at different busbars are presented and discussed.

Details of the general numerical solutions of the Friedberg-Lee soliton model for ground and exited states

International Nuclear Information System (INIS)

Koeppel, T.; Harvey, M.

1984-06-01

A new numerical method is applied to solving the equations of motion of the Friedberg-Lee Soliton model for both ground and spherically symmetric excited states. General results have been obtained over a wide range of parameters. Critical coupling constants and critical particle numbers have been determined below which soliton solutions cease to exist. The static properties of the proton are considered to show that as presently formulated the model fails to fit all experimental data for any set of parameters

Diffusion in coronas around clinopyroxene: modelling with local equilibrium and steady state, and a non-steady-state modification to account for zoned actinolite-hornblende

Science.gov (United States)

Ashworth, J. R.; Birdi, J. J.; Emmett, T. F.

1992-01-01

Retrograde coronas of Caledonian age, between clinopyroxene and plagioclase in the Jotun Nappe Complex, Norway, illustrate the effects of diffusion kinetics on mineral distributions among layers and on the compositions of hornblende-actinolite. One corona type comprises a symplectite of epidote + quartz adjacent to plagioclase, and a less well-organized intergrowth of amphibole + quartz replacing clinopyroxene. The observed mineral proportions imply an open-system reaction, but the similarity of Al/Si ratios in reactant plagioclase and product symplectite indicates approximate conservation of Al2O3 and SiO2. The largest inferred open-system flux is a loss of CaO, mostly derived from consumption of clinopyroxene. The approximate layer structure, Pl|Ep + Qtz|Hbl + Qtz|Act±Hbl + Qtz|Cpx, is modelled using the theory of steady-state diffusion-controlled growth with local equilibrium. To obtain a solution, it is necessary to use a reactant plagioclase composition which takes into account aluminous (epidote) inclusions. The results indicate that, in terms of Onsager diffusion coefficients L ii , Ca is more mobile than AL ( L CaCa/ L AlAl≳3.) (where ≳ means greater than or approximately equal to). This behaviour of Ca is comparable with that of Mg in previously studied coronas around olivine. Si is non-diffusing in the present modelling, because of silica saturation. Oxidation of some Fe2+ to Fe3+ occurs within the corona. Mg diffuses towards its source (clinopyroxene) to maintain local equilibrium. Other coronas consist of two layers, hornblende adjacent to plagioclase and zoned amphibole + quartz adjacent to clinopyroxene. In the zoned layer, actinolitic hornblende forms relict patches, separated from quartz blebs by more aluminous hornblende. A preliminary steady-state, local-equilibrium model of grain-boundary diffusion explains the formation of low-Al and high-Al layers as due to Al immobility. Zoning and replacement are qualitatively explained in terms of

Physical design of MW-class steady-state spherical tokamak, QUEST

International Nuclear Information System (INIS)

Hanada, K.; Sato, K.N.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Higashizono, Y.; Yoshida, N.; Takase, Y.; Ejiri, A.; Ogawa, Y.; Ono, Y.; Yoshida, Z.; Mitarai, O.; Maekawa, T.; Kishimoto, Y.; Ishiguro, M.; Yoshinaga, T.; Igami, H.; Hirooka, Y.; Komori, A.; Motojima, O.; Sudo, S.; Yamada, H.; Ando, A.; Asakura, Nobuyuki; Matsukawa, Makoto; Ishida, A.; Ohno, N.; Peng, M.

2008-10-01

QUEST (R=0.68 m, a=0.4 m) focuses on the steady state operation of the spherical tokamak (ST) by controlled PWI and electron Bernstain wave (EBW) current drive (CD). The QUEST project will be developed along two phases, phase I: steady state operation with plasma current, I p =20-30 kA on open divertor configuration and phase II: steady state operation with I p = 100 kA and β of 10% in short pulse on closed divertor configuration. Feasibility of the missions on QUEST was investigated and the suitable machine size of QUEST was decided based on the physical view of plasma parameters. Electron Bernstein wave (EBW) current drive are planned to establish the maintenance of plasma current in steady state. Mode conversion efficiency to EBW was calculated and the conversion of 95% will be expected. A new type antenna for QUEST has been fabricated to excite EBW effectively. The situation of heat and particle handling is challenging, and W and high temperature wall is adopted. The start-up scenario of plasma current was investigated based on the driven current by energetic electron and the most favorable magnetic configuration for start-up is proposed. (author)

Basin stability measure of different steady states in coupled oscillators

Science.gov (United States)

Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

2017-04-01

In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.

Small-angle scattering at a pulsed neutron source: comparison with a steady-state reactor

Energy Technology Data Exchange (ETDEWEB)

Borso, C S; Carpenter, J M; Williamson, F S; Holmblad, G L; Mueller, M H; Faber, J Jr; Epperson, J E; Danyluk, S S [Argonne National Lab., IL (USA)

1982-08-01

A time-of-flight small-angle diffractometer employing seven tapered collimator elements and a two-dimensional gas proportional counter was successfully utilized to collect small-angle scattering data from a solution sample of the lipid salt cetylpyridinium chloride, C/sub 21/H/sub 38/N/sup +/.Cl/sup -/, at the Argonne National Laboratory prototype pulsed spallation neutron source, ZING-P'. Comparison of the small-angle scattering observed from the same compound at the University of Missouri Research Reactor corroborated the ZING-P' results. The results are used to compare the neutron flux available from the ZING-P' source relative to the well characterized University of Missouri source. Calculations based on experimentally determined parameters indicated the time-averaged rate of detected neutrons at the ZING-P' pulsed spallation source to have been at least 33% higher than the steady-state count rate from the same sample. Differences between time-of-flight techniques and conventional steady-state techniques are discussed.

Analysis of steady-state creep of Fe-Mo alloys from the viewpoint of recovery

International Nuclear Information System (INIS)

Maruyama, K.; Karashima, S.; Oikawa, H.

1979-01-01

A theoretical equation to d evaluate the steady-state creep-rates, d epsilon/dtsub(s), based on a recovery creep model is derived: epsilonsub(s)/dt proportional to r/sigma 2 sub(a) x lambda 2 , where r is the recovery rate, which can be determined from results of stress-reduction tests, deltasub(a) the applied stress, and lambda the dislocation link-length. Two cases of recovery are considered, i.e., recovery of dislocation networks at sub-boundaries and that of three-dimensional networks within subgrains. The high-temperature steady-state creep of Fe-Mo solid solutions, creep characteristics of which have been reported to be well rationalized as viscous glide creep, is analyzed using this equation. It is shown that stress dependence of d epsilon/dtsub(s) is well explained from the viewpoint of recovery, in which the activation and the annihilation of dislocations at sub-boundaries are considered to take place. (orig.) [de

A model on valence state evaluation of TRU nuclides in reprocessing solutions

International Nuclear Information System (INIS)

Uchiyama, Gunzo; Fujine, Sachio; Yoshida, Zenko; Maeda, Mitsuru; Motoyama, Satoshi.

1998-02-01

A mathematical model was developed to evaluate the valence state of TRU nuclides in reprocessing process solutions. The model consists of mass balance equations, Nernst equations, reaction rate equations and electrically neutrality equations. The model is applicable for the valence state evaluation of TRU nuclides in both steady state and transient state conditions in redox equilibrium. The valence state which is difficult to measure under high radiation and multi component conditions is calculated by the model using experimentally measured data for the TRU nuclide concentrations, nitric acid and redox reagent concentrations, electrode potential and solution temperature. (author)

Dark Entangled Steady States of Interacting Rydberg Atoms

DEFF Research Database (Denmark)

Dasari, Durga; Mølmer, Klaus

2013-01-01

their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly...

Numerical solution of non-linear dual-phase-lag bioheat transfer equation within skin tissues.

Science.gov (United States)

Kumar, Dinesh; Kumar, P; Rai, K N

2017-11-01

This paper deals with numerical modeling and simulation of heat transfer in skin tissues using non-linear dual-phase-lag (DPL) bioheat transfer model under periodic heat flux boundary condition. The blood perfusion is assumed temperature-dependent which results in non-linear DPL bioheat transfer model in order to predict more accurate results. A numerical method of line which is based on finite difference and Runge-Kutta (4,5) schemes, is used to solve the present non-linear problem. Under specific case, the exact solution has been obtained and compared with the present numerical scheme, and we found that those are in good agreement. A comparison based on model selection criterion (AIC) has been made among non-linear DPL models when the variation of blood perfusion rate with temperature is of constant, linear and exponential type with the experimental data and it has been found that non-linear DPL model with exponential variation of blood perfusion rate is closest to the experimental data. In addition, it is found that due to absence of phase-lag phenomena in Pennes bioheat transfer model, it achieves steady state more quickly and always predict higher temperature than thermal and DPL non-linear models. The effect of coefficient of blood perfusion rate, dimensionless heating frequency and Kirchoff number on dimensionless temperature distribution has also been analyzed. The whole analysis is presented in dimensionless form. Copyright © 2017 Elsevier Inc. All rights reserved.

Sensitivity analysis of numerical solutions for environmental fluid problems

International Nuclear Information System (INIS)

Tanaka, Nobuatsu; Motoyama, Yasunori

2003-01-01

In this study, we present a new numerical method to quantitatively analyze the error of numerical solutions by using the sensitivity analysis. If a reference case of typical parameters is one calculated with the method, no additional calculation is required to estimate the results of the other numerical parameters such as more detailed solutions. Furthermore, we can estimate the strict solution from the sensitivity analysis results and can quantitatively evaluate the reliability of the numerical solution by calculating the numerical error. (author)

Steady-State Crack Growth in Rate-Sensitive Single Crystals

DEFF Research Database (Denmark)

Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof

2016-01-01

The characteristics of the active plastic zone surrounding a crack growingin a single crystal (FCC, BCC, and HCP) at constant velocity is investigated for ModeI loading under plane strain assumptions. The framework builds upon a steady-state relation bringing the desired solution out in a frame...... translating with the crack tip. In the study, the shielding of the crack tip that follows from plastic slip is investigated by adopting the SSV-model. High resolution plots of the plastic zones are obtained and a detailed study confirms the existence of analytically determined velocity discontinuities from...... the literature. The plastic zone is found to be smallest for the FCC structure andlargest for the HCP structure, which is also reected in the shielding ratio, where FCC crystals show the smallest shielding and HCP the largest shielding....

Experimental and Numerical Investigation of Local Scour Around Submarine Piggyback Pipeline Under Steady Current

Science.gov (United States)

Zhao, Enjin; Shi, Bing; Qu, Ke; Dong, Wenbin; Zhang, Jing

2018-04-01

As a new type of submarine pipeline, the piggyback pipeline has been gradually adopted in engineering practice to enhance the performance and safety of submarine pipelines. However, limited simulation work and few experimental studies have been published on the scour around the piggyback pipeline under steady current. This study numerically and experimentally investigates the local scour of the piggyback pipe under steady current. The influence of prominent factors such as pipe diameter, inflow Reynolds number, and gap between the main and small pipes, on the maximum scour depth have been examined and discussed in detail. Furthermore, one formula to predict the maximum scour depth under the piggyback pipeline has been derived based on the theoretical analysis of scour equilibrium. The feasibility of the proposed formula has been effectively calibrated by both experimental data and numerical results. The findings drawn from this study are instructive in the future design and application of the piggyback pipeline.

Exact solutions, numerical relativity and gravitational radiation

International Nuclear Information System (INIS)

Winicour, J.

1986-01-01

In recent years, there has emerged a new use for exact solutions to Einstein's equation as checks on the accuracy of numerical relativity codes. Much has already been written about codes based upon the space-like Cauchy problem. In the case of two Killing vectors, a numerical characteristic initial value formulation based upon two intersecting families of null hypersurfaces has successfully evolved the Schwarzschild and the colliding plane wave vacuum solutions. Here the author discusses, in the context of exact solutions, numerical studies of gravitational radiation based upon the null cone initial value problem. Every stage of progress in the null cone approach has been associated with exact solutions in some sense. He begins by briefly recapping this history. Then he presents two new examples illustrating how exact solutions can be useful

A design of steady state fusion burner

International Nuclear Information System (INIS)

Hasegawa, Akira; Hatori, Tadatsugu; Itoh, Kimitaka; Ikuta, Takashi; Kodama, Yuji.

1975-01-01

We present a brief design of a steady state fusion burner in which a continuous burning of nuclear fuel may be achieved with output power of a gigawatt. The laser fusion is proposed to ignite the fuel. (auth.)

Analysis of numerical solutions for Bateman equations

International Nuclear Information System (INIS)

Loch, Guilherme G.; Bevilacqua, Joyce S.

2013-01-01

The implementation of stable and efficient numerical methods for solving problems involving nuclear transmutation and radioactive decay chains is the main scope of this work. The physical processes associated with irradiations of samples in particle accelerators, or the burning spent nuclear fuel in reactors, or simply the natural decay chains, can be represented by a set of first order ordinary differential equations with constant coefficients, for instance, the decay radioactive constants of each nuclide in the chain. Bateman proposed an analytical solution for a particular case of a linear chain with n nuclides decaying in series and with different decay constants. For more complex and realistic applications, the construction of analytical solutions is not viable and the introduction of numerical techniques is imperative. However, depending on the magnitudes of the decay radioactive constants, the matrix of coefficients could be almost singular, generating unstable and non convergent numerical solutions. In this work, different numerical strategies for solving systems of differential equations were implemented, the Runge-Kutta 4-4, Adams Predictor-Corrector (PC2) and the Rosenbrock algorithm, this last one more specific for stiff equations. Consistency, convergence and stability of the numerical solutions are studied and the performance of the methods is analyzed for the case of the natural decay chain of Uranium-235 comparing numerical with analytical solutions. (author)

The non-differentiable solution for local fractional Laplace equation in steady heat-conduction problem

Directory of Open Access Journals (Sweden)

Chen Jie-Dong

2016-01-01

Full Text Available In this paper, we investigate the local fractional Laplace equation in the steady heat-conduction problem. The solutions involving the non-differentiable graph are obtained by using the characteristic equation method (CEM via local fractional derivative. The obtained results are given to present the accuracy of the technology to solve the steady heat-conduction in fractal media.

Spurious Solutions Of Nonlinear Differential Equations

Science.gov (United States)

Yee, H. C.; Sweby, P. K.; Griffiths, D. F.

1992-01-01

Report utilizes nonlinear-dynamics approach to investigate possible sources of errors and slow convergence and non-convergence of steady-state numerical solutions when using time-dependent approach for problems containing nonlinear source terms. Emphasizes implications for development of algorithms in CFD and computational sciences in general. Main fundamental conclusion of study is that qualitative features of nonlinear differential equations cannot be adequately represented by finite-difference method and vice versa.

Steady State Dynamic Operating Behavior of Universal Motor

Directory of Open Access Journals (Sweden)

Muhammad Khan Burdi

2015-01-01

Full Text Available A detailed investigation of the universal motor is developed and used for various dynamic steady state and transient operating conditions of loads. In the investigation, output torque, motor speed, input current, input/output power and efficiency are computed, compared and analyzed for different loads. While this paper discusses the steady-state behavior of the universal motor, another companion paper, ?Transient dynamic behavior of universal motor?, will discuss its transient behavior in detail. A non-linear generalized electric machine model of the motor is considered for the analysis. This study was essential to investigate effect of output load on input current, power, speed and efficiency of the motor during operations. Previously such investigation is not known

On Steady-State Tropical Cyclones

Science.gov (United States)

2014-01-01

Press: London. Marks FD, Black PG, Montgomery MT, Burpee RW. 2008. Structure of the eye and eyewall of Hurricane Hugo (1989). Mon. Weather Rev. 136: 1237... hurricanes ; tropical cyclones; typhoons; steady-state Received 18 April 2013; Revised 25 November 2013; Accepted 29 December 2013; Published online in Wiley...the concept of the ‘mature stage’ of a hurricane vortex. The definition of the ‘mature stage’ is commonly based on the time period in which the maximum

STEADY-STATE RELATIVISTIC STELLAR DYNAMICS AROUND A MASSIVE BLACK HOLE

Energy Technology Data Exchange (ETDEWEB)

Bar-Or, Ben; Alexander, Tal [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 (Israel)

2016-04-01

A massive black hole (MBH) consumes stars whose orbits evolve into the small phase-space volume of unstable orbits, the “loss cone,” which take them into the MBH, or close enough to interact strongly with it. The resulting phenomena, e.g., tidal heating and disruption, binary capture and hyper-velocity star ejection, gravitational wave (GW) emission by inspiraling compact remnants, or hydrodynamical interactions with an accretion disk, can produce observable signatures and thereby reveal the MBH, affect its mass and spin evolution, test strong gravity, and probe stars and gas near the MBH. These continuous stellar loss and resupply processes shape the central stellar distribution. We investigate relativistic stellar dynamics near the loss cone of a non-spinning MBH in steady state, analytically and by Monte Carlo simulations of the diffusion of the orbital parameters. These take into account Newtonian mass precession due to enclosed stellar mass, in-plane precession due to general relativity, dissipation by GW, uncorrelated two-body relaxation, correlated resonant relaxation (RR), and adiabatic invariance due to secular precession, using a rigorously derived description of correlated post-Newtonian dynamics in the diffusion limit. We argue that general maximal entropy considerations strongly constrain the orbital diffusion in steady state, irrespective of the relaxation mechanism. We identify the exact phase-space separatrix between plunges and inspirals, and predict their steady-state rates. We derive the dependence of the rates on the mass of the MBH, show that the contribution of RR in steady state is small, and discuss special cases where unquenched RR in restricted volumes of phase-space may affect the steady state substantially.

Analysis of the steady state hydraulic behaviour of the ITER blanket cooling system

Energy Technology Data Exchange (ETDEWEB)

Di Maio, P.A., E-mail: pietroalessandro.dimaio@unipa.it [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Dell’Orco, G.; Furmanek, A. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Garitta, S. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Merola, M.; Mitteau, R.; Raffray, R. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Spagnuolo, G.A.; Vallone, E. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

2015-10-15

Highlights: • Nominal steady state hydraulic behaviour of ITER blanket standard sector cooling system has been investigated. • Numerical simulations have been run adopting a qualified thermal-hydraulic system code. • Hydraulic characteristic functions and coolant mass flow rates, velocities and pressure drops have been assessed. • Most of the considered circuits are able to effectively cool blanket modules, meeting ITER requirements. - Abstract: The blanket system is the ITER reactor component devoted to providing a physical boundary for plasma transients and contributing to thermal and nuclear shielding of vacuum vessel, magnets and external components. It is expected to be subjected to significant heat loads under nominal conditions and its cooling system has to ensure an adequate cooling, preventing any risk of critical heat flux occurrence while complying with pressure drop limits. At the University of Palermo a study has been performed, in cooperation with the ITER Organization, to investigate the steady state hydraulic behaviour of the ITER blanket standard sector cooling system. A theoretical–computational approach based on the finite volume method has been followed, adopting the RELAP5 system code. Finite volume models of the most critical blanket cooling circuits have been set-up, realistically simulating the coolant flow domain. The steady state hydraulic behaviour of each cooling circuit has been investigated, determining its hydraulic characteristic function and assessing the spatial distribution of coolant mass flow rates, velocities and pressure drops under reference nominal conditions. Results obtained have indicated that the investigated cooling circuits are able to provide an effective cooling to blanket modules, generally meeting ITER requirements in term of pressure drop and velocity distribution, except for a couple of circuits that are being revised.

Simulation and Experimental Study on the Steady Conduction Solution for Continuous Rheo-Casting for A356 Alloy

Energy Technology Data Exchange (ETDEWEB)

Duc, Do Minh; Hai, Nguyen Hong; Quang, Pham [Hanoi University of Science and Technology (HUST), Hanoi (Viet Nam)

2017-03-15

Computational fluid dynamic modeling of a continuous rheo-casting technology was conducted, consistent with the manufacturing of 3 {sup mm-thin} plates made of aluminum alloy A356. The A numerical simulation on of the stabilizing time of the material crystallization was carried out using the ANSYS FLUENT code. Solidification and melting models were simulated with heat transfer and solid-liquid phase transformation involving the latent heat of crystallization were simulated. The calculated temperature distribution and the evolution of cooling rate through the material were examined and used to clarify their influence on microstructure, and further investigated with hardness testing. The thickness of the mushy zone was determined for the steady conduction solution of the continuous rheo-casting process.

'Memory' and sustention of microdischarges in a steady-state DBD: volume plasma or surface charge?

International Nuclear Information System (INIS)

Akishev, Yuri; Aponin, Gregory; Balakirev, Anton; Grushin, Mikhail; Karalnik, Vladimir; Petryakov, Alexander; Trushkin, Nikolay

2011-01-01

The results of a numerical study on the spatio-temporal behavior of transient microdischarges (MDs) in a steady-state dielectric barrier discharge (DBD) excited by a sinusoidal voltage are presented. MDs have a spatial 'memory'-every subsequent MD appears at exactly the same location occupied by the MD at the preceding half-period (HP). In the majority of cases each MD appears at its location only once during every HP. For such a case, the memory effect is not attributed to the residual surface charge deposited by the preceding MD but determined by the residual MD plasma column shunting the gap right up to the beginning of the next HP. In contrast to good memory in space, each individual MD has a large scatter with time in its appearance within every HP, i.e. there is no 'memory' concerning the phase of an applied voltage. This MD jittering within the period is attributed to the stochastic nature of partial surface breakdowns around the bases of the MD plasma column. Numerical calculations show that surface breakdown provides an MD current splash at every HP. Hence, in the steady-state DBD, the volume plasma is responsible for the existence of MD spatial 'memory' (i.e. where the MD appears), and the deposited surface charge is responsible for MD jittering in time (i.e. when the MD appears).

40 CFR Appendix II to Part 1039 - Steady-State Duty Cycles

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix... Appendix II to Part 1039—Steady-State Duty Cycles (a) The following duty cycles apply for constant-speed engines: (1) The following duty cycle applies for discrete-mode testing: D2 mode number Engine speed...

Analysis of steady state creep of southeastern New Mexico bedded salt

International Nuclear Information System (INIS)

Herrmann, W.; Wawersik, W.R.; Lauson, H.S.

1980-03-01

Steady state creep rates have been obtained from a large suite of existing experimental creep data relating to bedded rock salt from the Salado formation of S.E. New Mexico. Experimental conditions covered an intermediate temperature range from 22 0 C to 200 0 C, and shear stresses from 1000 psi (7 MPa) to 6000 psi (31 MPa). An expression, based on a single diffusion controlled dislocation climb mechanism, has been found to fit the observed dependence of steady state creep rate on shear stress and temperature, yielding an activation energy of 12 kcal/mole (50 kJ/mole) and a stress exponent of 4.9. Multiple regression analysis revealed a dependence on stratigraphy, but no statistically significant dependence on pressure of specimen size. No consistent dilatancy or compaction associated with steady state creep was found, although some individual specimens dilated or compacted during creep. The steady state creep data were found to agree very well with creep data for both bedded and dome salt from a variety of other locations

Chlorine decay under steady and unsteady-state hydraulic conditions

DEFF Research Database (Denmark)

Stoianov, Ivan; Aisopou, Angeliki

2014-01-01

This paper describes a simulation framework for the scale-adaptive hydraulic and chlorine decay modelling under steady and unsteady-state flows. Bulk flow and pipe wall reaction coefficients are replaced with steady and unsteady-state reaction coefficients. An unsteady decay coefficient is defined...... which depends upon the absolute value of shear stress and the rate of change of shear stress for quasi-unsteady and unsteady-state flows. A preliminary experimental and analytical investigation was carried out in a water transmission main. The results were used to model monochloramine decay...... and these demonstrate that the dynamic hydraulic conditions have a significant impact on water quality deterioration and the rapid loss of disinfectant residual. © 2013 The Authors....

On the calculation of steady-state loss probabilities in the GI/G/2/0 queue

Directory of Open Access Journals (Sweden)

Igor N. Kovalenko

1994-01-01

Full Text Available This paper considers methods for calculating the steady-state loss probability in the GI/G/2/0 queue. A previous study analyzed this queue in discrete time and this led to an efficient, numerical approximation scheme for continuous-time systems. The primary aim of the present work is to provide an alternative approach by analyzing the GI/ME/2/0 queue; i.e., assuming that the service time can be represented by a matrix-exponential distribution. An efficient computational scheme based on this method is developed and some numerical examples are studied. Some comparisons are made with the discrete-time approach, and the two methods are seen to be complementary.

Steady-state heat transfer in an inverted U-tube steam generator

International Nuclear Information System (INIS)

Boucher, T.J.

1986-01-01

Experimental results are presented involving U-tube steam generator tube bundle local heat transfer and fluid conditions during steady-state, full-power operations performed at high temperatures and pressures with conditions typical of a pressurized water reactor (15.0 MPa primary pressure, 600 K hot-leg fluid temperatures, 6.2 MPa secondary pressure). The MOD-2C facility represents the state-of-the-art in measurement of tube local heat transfer data and average tube bundle secondary fluid density at several elevations, which allows an estimate of the axial heat transfer and void distributions during steady-state and transient operations. The method of heat transfer data reduction is presented and the heat flux, secondary convective heat transfer coefficient, and void fraction distributions are quantified for steady-state, full-power operations

40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix..., App. II Appendix II to Part 1042—Steady-State Duty Cycles (a) The following duty cycles apply as specified in § 1042.505(b)(1): (1) The following duty cycle applies for discrete-mode testing: E3 mode No...

Spatially distributed characterization of hyporheic solute transport during baseflow recession in a headwater mountain stream using electrical geophysical imaging

Science.gov (United States)

Adam S. Ward; Michael N. Gooseff; Michael Fitzgerald; Thomas J. Voltz; Kamini Singha

2014-01-01

The transport of solutes along hyporheic flowpaths is recognized as central to numerous biogeochemical cycles, yet our understanding of how this transport changes with baseflow recession, particularly in a spatially distributed manner, is limited. We conducted four steady-state solute tracer injections and collected electrical resistivity data to characterize hyporheic...

Emergence of advance waves in a steady-state universe

Energy Technology Data Exchange (ETDEWEB)

Hobart, R.H.

1979-10-01

In standard Wheeler-Feynman electrodynamics advanced waves from any source are absolutely canceled by the advanced waves from the absorber responding to that source. The present work shows this cancellation fails over cosmic distances in a steady-state universe. A test of the view proposed earlier, in a paper which assumed failure of cancellation ad hoc, that zero-point fluctuations of the electromagnetic field are such emergent advanced waves, is posed. The view entails anomalous slowing of spontaneous transition rates at longer emission wavelengths; available data go against this, furnishing additional argument against the suspect assumption that the universe is steady-state.

Emergence of advance waves in a steady-state universe

International Nuclear Information System (INIS)

Hobart, R.H.

1979-01-01

In standard Wheeler-Feynman electrodynamics advanced waves from any source are absolutely canceled by the advanced waves from the absorber responding to that source. The present work shows this cancellation fails over cosmic distances in a steady-state universe. A test of the view proposed earlier, in a paper which assumed failure of cancellation ad hoc, that zero-point fluctuations of the electromagnetic field are such emergent advanced waves, is posed. The view entails anomalous slowing of spontaneous transition rates at longer emission wavelengths; available data go against this, furnishing additional argument against the suspect assumption that the universe is steady-state

Decay Properties of Axially Symmetric D-Solutions to the Steady Navier-Stokes Equations

Science.gov (United States)

Weng, Shangkun

2018-03-01

We investigate the decay properties of smooth axially symmetric D-solutions to the steady Navier-Stokes equations. The achievements of this paper are two folds. One is improved decay rates of u_{θ } and \

Mechanism for multiplicity of steady states with distinct cell concentration in continuous culture of mammalian cells.

Science.gov (United States)

Yongky, Andrew; Lee, Jongchan; Le, Tung; Mulukutla, Bhanu Chandra; Daoutidis, Prodromos; Hu, Wei-Shou

2015-07-01

Continuous culture for the production of biopharmaceutical proteins offers the possibility of steady state operations and thus more consistent product quality and increased productivity. Under some conditions, multiplicity of steady states has been observed in continuous cultures of mammalian cells, wherein with the same dilution rate and feed nutrient composition, steady states with very different cell and product concentrations may be reached. At those different steady states, cells may exhibit a high glycolysis flux with high lactate production and low cell concentration, or a low glycolysis flux with low lactate and high cell concentration. These different steady states, with different cell concentration, also have different productivity. Developing a mechanistic understanding of the occurrence of steady state multiplicity and devising a strategy to steer the culture toward the desired steady state is critical. We establish a multi-scale kinetic model that integrates a mechanistic intracellular metabolic model and cell growth model in a continuous bioreactor. We show that steady state multiplicity exists in a range of dilution rate in continuous culture as a result of the bistable behavior in glycolysis. The insights from the model were used to devise strategies to guide the culture to the desired steady state in the multiple steady state region. The model provides a guideline principle in the design of continuous culture processes of mammalian cells. © 2015 Wiley Periodicals, Inc.

Chaotic and steady state behaviour of a nonlinear controlled gyro subjected to harmonic disturbances

International Nuclear Information System (INIS)

Perez Polo, Manuel F.; Perez Molina, Manuel

2007-01-01

Chaotic and steady state motions of a nonlinear controlled gimbals suspension gyro used to stabilize an external body are studied in this paper. The equations of the gyro without nonlinear control are deduced from the Euler-Lagrange equations by using the nutation theory. The equations of the system show that a cyclic variable appears. Its elimination allows us to find an auxiliary nonlinear system from which it is possible to deduce a nonlinear control law in order to obtain a desired equilibrium point. From the analysis of the nonlinear control law it is possible to show that due to both harmonic disturbances in the platform of the gyro and in the body to stabilize, regular and chaotic motions can appear. The chaotic motion is researched by means of chaos maps, bifurcation diagrams, sensitivity to initial conditions, Lyapunov exponents and Fourier spectrum density. The transition from chaotic to steady state motion by eliminating the harmonic disturbances from the modification of the initial nonlinear control law is also researched. Next, the paper shows how to use the chaotic motion in order to obtain small input signals so that the desired equilibrium state of the gyro can be reached. The developed methodology and its compared performance are evaluated through analytical methods and numerical simulations

Chaotic and steady state behaviour of a nonlinear controlled gyro subjected to harmonic disturbances

Energy Technology Data Exchange (ETDEWEB)

Perez Polo, Manuel F. [Department of Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Escuela Politecnica Superior, Campus de San Vicente, 03071 Alicante (Spain)]. E-mail: manolo@dfists.ua.es; Perez Molina, Manuel [Facultad de Ciencias Matematicas, Universidad Nacional de Educacion a Distancia, UNED, C/Boyero 12-1A, Alicante 03007 (Spain)]. E-mail: ma_perez_m@hotmail.com

2007-07-15

Chaotic and steady state motions of a nonlinear controlled gimbals suspension gyro used to stabilize an external body are studied in this paper. The equations of the gyro without nonlinear control are deduced from the Euler-Lagrange equations by using the nutation theory. The equations of the system show that a cyclic variable appears. Its elimination allows us to find an auxiliary nonlinear system from which it is possible to deduce a nonlinear control law in order to obtain a desired equilibrium point. From the analysis of the nonlinear control law it is possible to show that due to both harmonic disturbances in the platform of the gyro and in the body to stabilize, regular and chaotic motions can appear. The chaotic motion is researched by means of chaos maps, bifurcation diagrams, sensitivity to initial conditions, Lyapunov exponents and Fourier spectrum density. The transition from chaotic to steady state motion by eliminating the harmonic disturbances from the modification of the initial nonlinear control law is also researched. Next, the paper shows how to use the chaotic motion in order to obtain small input signals so that the desired equilibrium state of the gyro can be reached. The developed methodology and its compared performance are evaluated through analytical methods and numerical simulations.

A numerical study of the eigenvalues in the neutron diffusion theory

International Nuclear Information System (INIS)

Lima Bezerra, J. de.

1982-12-01

A systematic numerical study for the eigenvalue problem in one dimension was carried out. A computer code RED2G was developed to obtain and to discuss a number of numerical solutions concerning eigenvalues problems originating from the discretization of the two groups neutron diffusion equation in one dimension and steady state. The problem of eigenvalues was created from the discretization by the method of finite differences. The solutions were obtained by four different iterative methods, i.e. Power, Wielandt-1, Wielandt-2 and accelerated Power with the Chebyshev polinomials. The numerical results given by the solution of the two test-problems indicate that the RED2G code is fast and efficient in these calculations and the Wielandt-2 method has been found to be the best both in respect of rapidity of calculations as well as programation effort required. (E.G.) [pt

Nonequilibrium steady states of ideal bosonic and fermionic quantum gases.

Science.gov (United States)

Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

2015-12-01

We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013)]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

Nonequilibrium steady states of ideal bosonic and fermionic quantum gases

Science.gov (United States)

Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

2015-12-01

We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

Effect of the poloidal current from the classical diffusion in the steady-state neo-classical transport

International Nuclear Information System (INIS)

Igna Junior, A.D.

1984-01-01

The relevant parameters of two steady-state models of a plasma column, in fusion regime, were analyzed for an ideal Tokamak. The neo-classical transport theory was considered in the banana regime and in the Pfirsch-Schlueter regime. The first model proposes a correction in the numerical coefficients of the transport equations. In the other one, a poloidal current from Pfirsch-Schlueter classical diffusion is considered aiming to satisfy the pressure balance. (M.C.K.) [pt

A neural basis for the visual sense of number and its development: A steady-state visual evoked potential study in children and adults

Directory of Open Access Journals (Sweden)

Joonkoo Park

2018-04-01

Full Text Available While recent studies in adults have demonstrated the existence of a neural mechanism for a visual sense of number, little is known about its development and whether such a mechanism exists at young ages. In the current study, I introduce a novel steady-state visual evoked potential (SSVEP technique to objectively quantify early visual cortical sensitivity to numerical and non-numerical magnitudes of a dot array. I then examine this neural sensitivity to numerical magnitude in children between three and ten years of age and in college students. Children overall exhibit strong SSVEP sensitivity to numerical magnitude in the right occipital sites with negligible SSVEP sensitivity to non-numerical magnitudes, the pattern similar to what is observed in adults. However, a closer examination of age differences reveals that this selective neural sensitivity to numerical magnitude, which is close to absent in three-year-olds, increases steadily as a function of age, while there is virtually no neural sensitivity to other non-numerical magnitudes across these ages. These results demonstrate the emergence of a neural mechanism underlying direct perception of numerosity across early and middle childhood and provide a potential neural mechanistic explanation for the development of humans’ primitive, non-verbal ability to comprehend number. Keywords: Numerosity, Steady-state visual evoked potential, Child development, Visual cortex, Approximate number system

On the theoretical–numerical study of the ITER Upper Port Plug structure hydraulic behaviour under steady state and draining and drying transient conditions

International Nuclear Information System (INIS)

Di Maio, P.A.; Paradiso, D.; Dell’Orco, G.; Pitcher, C.S.; Kalish, M.

2011-01-01

Highlights: ► UPP TS hydraulic behaviour has been investigated under steady state and D and D transient conditions. ► A thermal–hydraulic system code has been adopted and a UPP TS model has been set-up and validated against results of steady state CFD analyses. ► The TS steady state hydraulic characteristic functions have been derived for two coolant flow paths showing that right plate inlet one is the most promising. ► Draining simulations indicate that the 4 MPa injection pressure is high enough to drain almost completely the circuit in a reasonable time (∼6 s). ► Results indicate that right plate inlet flow path allows the TS complete draining, eliminating the need for the drying procedure. - Abstract: The ITER diagnostic Upper Port Plug (UPP) is a water-cooled stainless steel structure aimed to integrate within vacuum vessel the plasma diagnostic systems, shielding them from neutron and photon irradiation. Due to the very intense heat loads expected, a proper cooling circuit has been designed to ensure an adequate UPP cooling with an acceptable thermal rise and an unduly high pumping power and to perform its draining and drying procedure by injection of pressurized nitrogen. A theoretical research activity has been launched at the Department of Nuclear Engineering of the University of Palermo aiming to investigate the hydraulic behaviour of the UPP Trapezoid Section cooling circuit under steady state conditions and during its draining and drying transient procedure. The research activity has been performed following a theoretical–computational approach and adopting the RELAP5 thermal–hydraulic system code. The Trapezoid Section cooling circuit characteristic functions have been derived under steady state conditions at various coolant temperatures for both the coolant flow paths at the present under consideration for this circuit. The distributions of coolant mass flow rates along the channels of the cooling circuit have been calculated too

Steady-state Operational Characteristics of Ghana Research ...

African Journals Online (AJOL)

Steady state operational characteristics of the 30 kW tank-in-pool type reactor named Ghana Research Reactor-1 were investigated after a successful on-site zero power critical experiments. The steadystate operational character-istics determined were the thermal neutron fluxes, maximum period of operation at nominal ...

Numerical modelling of two-layer shallow water flow in microtidal salt-wedge estuaries: Finite volume solver and field validation

Directory of Open Access Journals (Sweden)

Krvavica Nino

2017-03-01

Full Text Available A finite volume model for two-layer shallow water flow in microtidal salt-wedge estuaries is presented in this work. The governing equations are a coupled system of shallow water equations with source terms accounting for irregular channel geometry and shear stress at the bed and interface between the layers. To solve this system we applied the Q-scheme of Roe with suitable treatment of source terms, coupling terms, and wet-dry fronts. The proposed numerical model is explicit in time, shock-capturing and it satisfies the extended conservation property for water at rest. The model was validated by comparing the steady-state solutions against a known arrested salt-wedge model and by comparing both steady-state and time-dependant solutions against field observations in Rječina Estuary in Croatia. When the interfacial friction factor λi was chosen correctly, the agreement between numerical results and field observations was satisfactory.

Evidence for forcing-dependent steady states in a turbulent swirling flow.

Science.gov (United States)

Saint-Michel, B; Dubrulle, B; Marié, L; Ravelet, F; Daviaud, F

2013-12-06

We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems.

Constructive interference in steady-state/FIESTA-C clinical applications in neuroimaging

International Nuclear Information System (INIS)

Kulkami, Makarand

2011-01-01

Full text: High spatial resolution is one of the major problems in neuroimaging, par ticularly in cranial and spinal nerve imaging. Constructive interference in steady-state/fast imaging employing steady-state acquisition with phase cycling is a robust sequence in imaging the cranial and spinal nerve patholo gies. This pictorial review is a concise article about the applications of this sequence in neuroimaging with clinical examples.

INS3D - NUMERICAL SOLUTION OF THE INCOMPRESSIBLE NAVIER-STOKES EQUATIONS IN THREE-DIMENSIONAL GENERALIZED CURVILINEAR COORDINATES (DEC RISC ULTRIX VERSION)

Science.gov (United States)

Biyabani, S. R.

1994-01-01

INS3D computes steady-state solutions to the incompressible Navier-Stokes equations. The INS3D approach utilizes pseudo-compressibility combined with an approximate factorization scheme. This computational fluid dynamics (CFD) code has been verified on problems such as flow through a channel, flow over a backwardfacing step and flow over a circular cylinder. Three dimensional cases include flow over an ogive cylinder, flow through a rectangular duct, wind tunnel inlet flow, cylinder-wall juncture flow and flow through multiple posts mounted between two plates. INS3D uses a pseudo-compressibility approach in which a time derivative of pressure is added to the continuity equation, which together with the momentum equations form a set of four equations with pressure and velocity as the dependent variables. The equations' coordinates are transformed for general three dimensional applications. The equations are advanced in time by the implicit, non-iterative, approximately-factored, finite-difference scheme of Beam and Warming. The numerical stability of the scheme depends on the use of higher-order smoothing terms to damp out higher-frequency oscillations caused by second-order central differencing. The artificial compressibility introduces pressure (sound) waves of finite speed (whereas the speed of sound would be infinite in an incompressible fluid). As the solution converges, these pressure waves die out, causing the derivation of pressure with respect to time to approach zero. Thus, continuity is satisfied for the incompressible fluid in the steady state. Computational efficiency is achieved using a diagonal algorithm. A block tri-diagonal option is also available. When a steady-state solution is reached, the modified continuity equation will satisfy the divergence-free velocity field condition. INS3D is capable of handling several different types of boundaries encountered in numerical simulations, including solid-surface, inflow and outflow, and far

Simulation and Experimental Study on the Steady Conduction Solution for Continuous Rheo-Casting for A356 Alloy

International Nuclear Information System (INIS)

Duc, Do Minh; Hai, Nguyen Hong; Quang, Pham

2017-01-01

Computational fluid dynamic modeling of a continuous rheo-casting technology was conducted, consistent with the manufacturing of 3 "m"m"-"t"h"i"n plates made of aluminum alloy A356. The A numerical simulation on of the stabilizing time of the material crystallization was carried out using the ANSYS FLUENT code. Solidification and melting models were simulated with heat transfer and solid-liquid phase transformation involving the latent heat of crystallization were simulated. The calculated temperature distribution and the evolution of cooling rate through the material were examined and used to clarify their influence on microstructure, and further investigated with hardness testing. The thickness of the mushy zone was determined for the steady conduction solution of the continuous rheo-casting process.

Current drive efficiency requirements for an attractive steady-state reactor

Energy Technology Data Exchange (ETDEWEB)

Tonon, G

1994-12-31

The expected values of the figure of merit and the electrical efficiency of various non-inductive current drive methods are considered. The main experimental results achieved today with neutral beams and radiofrequency systems are summarized. Taking into account the simplified energy flow diagram of a steady state reactor, the figure of merit and the electrical efficiency values which are necessary in order to envisage an attractive steady-state reactor are determined. These values are compared to the theoretical predictions. (author). 16 refs., 11 figs., 2 tabs.

Current drive efficiency requirements for an attractive steady-state reactor

International Nuclear Information System (INIS)

Tonon, G.

1994-01-01

The expected values of the figure of merit and the electrical efficiency of various non-inductive current drive methods are considered. The main experimental results achieved today with neutral beams and radiofrequency systems are summarized. Taking into account the simplified energy flow diagram of a steady state reactor, the figure of merit and the electrical efficiency values which are necessary in order to envisage an attractive steady-state reactor are determined. These values are compared to the theoretical predictions. (author). 16 refs., 11 figs., 2 tabs

Determination of Solution Accuracy of Numerical Schemes as Part of Code and Calculation Verification

Energy Technology Data Exchange (ETDEWEB)

Blottner, F.G.; Lopez, A.R.

1998-10-01

This investigation is concerned with the accuracy of numerical schemes for solving partial differential equations used in science and engineering simulation codes. Richardson extrapolation methods for steady and unsteady problems with structured meshes are presented as part of the verification procedure to determine code and calculation accuracy. The local truncation error de- termination of a numerical difference scheme is shown to be a significant component of the veri- fication procedure as it determines the consistency of the numerical scheme, the order of the numerical scheme, and the restrictions on the mesh variation with a non-uniform mesh. Genera- tion of a series of co-located, refined meshes with the appropriate variation of mesh cell size is in- vestigated and is another important component of the verification procedure. The importance of mesh refinement studies is shown to be more significant than just a procedure to determine solu- tion accuracy. It is suggested that mesh refinement techniques can be developed to determine con- sistency of numerical schemes and to determine if governing equations are well posed. The present investigation provides further insight into the conditions and procedures required to effec- tively use Richardson extrapolation with mesh refinement studies to achieve confidence that sim- ulation codes are producing accurate numerical solutions.

Numerical solution of the transport equation describing the radon transport from subsurface soil to buildings

International Nuclear Information System (INIS)

Savovic, S.; Djordjevich, A.; Ristic, G.

2012-01-01

A theoretical evaluation of the properties and processes affecting the radon transport from subsurface soil into buildings is presented in this work. The solution of the relevant transport equation is obtained using the explicit finite difference method (EFDM). Results are compared with analytical steady-state solution reported in the literature. Good agreement is found. It is shown that EFDM is effective and accurate for solving the equation that describes radon diffusion, advection and decay during its transport from subsurface to buildings, which is especially important when arbitrary initial and boundary conditions are required. (authors)

Numerical integration of asymptotic solutions of ordinary differential equations

Science.gov (United States)

Thurston, Gaylen A.

1989-01-01

Classical asymptotic analysis of ordinary differential equations derives approximate solutions that are numerically stable. However, the analysis also leads to tedious expansions in powers of the relevant parameter for a particular problem. The expansions are replaced with integrals that can be evaluated by numerical integration. The resulting numerical solutions retain the linear independence that is the main advantage of asymptotic solutions. Examples, including the Falkner-Skan equation from laminar boundary layer theory, illustrate the method of asymptotic analysis with numerical integration.

Burn cycle requirements comparison of pulsed and steady-state tokamak reactors

International Nuclear Information System (INIS)

Brooks, J.N.; Ehst, D.A.

1983-12-01

Burn cycle parameters and energy transfer system requirements were analyzed for an 8-m commercial tokamak reactor using four types of cycles: conventional, hybrid, internal transformer, and steady state. Not surprisingly, steady state is the best burn mode if it can be achieved. The hybrid cycle is a promising alternative to the conventional. In contrast, the internal transformer cycle does not appear attractive for the size tokamak in question

40 CFR 1033.515 - Discrete-mode steady-state emission tests of locomotives and locomotive engines.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Discrete-mode steady-state emission... Procedures § 1033.515 Discrete-mode steady-state emission tests of locomotives and locomotive engines. This... a warm-up followed by a sequence of nominally steady-state discrete test modes, as described in...

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1987-01-01

The steady state behaviour of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is shown that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed in light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (author)

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1986-06-01

The steady state behavior of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is showm that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed on light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (Author) [pt

Controlling Unknown Saddle Type Steady States of Dynamical Systems with Latency in the Feedback Loop

DEFF Research Database (Denmark)

Tamasevicius, Arunas; Bumeliene, Skaidra; Tamaseviciute, Elena

2009-01-01

We suggest an adaptive control technique for stabilizing saddle type unstable steady states of dynamical systems. The controller is composed of an unstable and a stable high-pass filters operating in parallel. The mathematical model is considered analytically and numerically. The conjoint...... controller is sufficiently robust to time latencies in the feedback loop. In addition, it is not sensitive to the damping parameters of the system and is relatively fast. Experiments have been performed using a simplified version of the electronic Young-Silva circuit imitating behavior of the Duffing...

TRUMP, Steady-State and Transient 1-D, 2-D and 3-D Potential Flow, Temperature Distribution

International Nuclear Information System (INIS)

Elrod, D.C.; Turner, W.D.

1981-01-01

1 - Description of problem or function: TRUMP solves a general non- linear parabolic partial differential equation describing flow in various kinds of potential fields, such as fields of temperature, pressure, or electricity and magnetism; simultaneously, it will solve two additional equations representing, in thermal problems, heat production by decomposition of two reactants having rate constants with a general Arrhenius temperature dependence. Steady- state and transient flow in one, two, or three dimensions are considered in geometrical configurations having simple or complex shapes and structures. Problem parameters may vary with spatial position, time, or primary dependent variables--temperature, pressure, or field strength. Initial conditions may vary with spatial position, and among the criteria that may be specified for ending a problem are upper and lower limits on the size of the primary dependent variable, upper limits on the problem time or on the number of time-steps or on the computer time, and attainment of steady state. 2 - Method of solution: Solutions may be obtained by use of explicit- or implicit-difference equations, or by an optimized combination of both. 3 - Restrictions on the complexity of the problem: The program currently provides for maxima of: 40 materials, 5 reactants, 105 surface conditions, 20 boundary nodes, 16 entries per tabulated function (table-length)

Influence of longitudinal position on the evolution of steady-state signal in cardiac cine balanced steady-state free precession imaging.

Science.gov (United States)

Spear, Tyler J; Stromp, Tori A; Leung, Steve W; Vandsburger, Moriel H

2017-11-01

Emerging quantitative cardiac magnetic resonance imaging (CMRI) techniques use cine balanced steady-state free precession (bSSFP) to measure myocardial signal intensity and probe underlying physiological parameters. This correlation assumes that steady-state is maintained uniformly throughout the heart in space and time. To determine the effects of longitudinal cardiac motion and initial slice position on signal deviation in cine bSSFP imaging by comparing two-dimensional (2D) and three-dimensional (3D) acquisitions. Nine healthy volunteers completed cardiac MRI on a 1.5-T scanner. Short axis images were taken at six slice locations using both 2D and 3D cine bSSFP. 3D acquisitions spanned two slices above and below selected slice locations. Changes in myocardial signal intensity were measured across the cardiac cycle and compared to longitudinal shortening. For 2D cine bSSFP, 46% ± 9% of all frames and 84% ± 13% of end-diastolic frames remained within 10% of initial signal intensity. For 3D cine bSSFP the proportions increased to 87% ± 8% and 97% ± 5%. There was no correlation between longitudinal shortening and peak changes in myocardial signal. The initial slice position significantly impacted peak changes in signal intensity for 2D sequences ( P  cine bSSFP that is only restored at the center of a 3D excitation volume. During diastole, a transient steady-state is established similar to that achieved with 3D cine bSSFP regardless of slice location.

Progress and prospect of true steady state operation with RF

Directory of Open Access Journals (Sweden)

Jacquinot Jean

2017-01-01

Full Text Available Operation of fusion confinement experiments in full steady state is a major challenge for the development towards fusion energy. Critical to achieving this goal is the availability of actively cooled plasma facing components and auxiliary systems withstanding the very harsh plasma environment. Equally challenging are physics issues related to achieving plasma conditions and current drive efficiency required by reactor plasmas. RF heating and current drive systems have been key instruments for obtaining the progress made until today towards steady state. They hold all the records of long pulse plasma operation both in tokamaks and in stellarators. Nevertheless much progress remains to be made in particular for integrating all the requirements necessary for maintaining in steady state the density and plasma pressure conditions of a reactor. This is an important stated aim of ITER and of devices equipped with superconducting magnets. After considering the present state of the art, this review will address the key issues which remain to be solved both in physics and technology for reaching this goal. They constitute very active subjects of research which will require much dedicated experimentation in the new generation of superconducting devices which are now in operation or becoming close to it.

Gravity currents in rotating channels. Part 1. Steady-state theory

Science.gov (United States)

Hacker, J. N.; Linden, P. F.

2002-04-01

A theory is developed for the speed and structure of steady-state non-dissipative gravity currents in rotating channels. The theory is an extension of that of Benjamin (1968) for non-rotating gravity currents, and in a similar way makes use of the steady-state and perfect-fluid (incompressible, inviscid and immiscible) approximations, and supposes the existence of a hydrostatic ‘control point’ in the current some distance away from the nose. The model allows for fully non-hydrostatic and ageostrophic motion in a control volume V ahead of the control point, with the solution being determined by the requirements, consistent with the perfect-fluid approximation, of energy and momentum conservation in V, as expressed by Bernoulli's theorem and a generalized flow-force balance. The governing parameter in the problem, which expresses the strength of the background rotation, is the ratio W = B/R, where B is the channel width and R = (g[prime prime or minute]H)1/2/f is the internal Rossby radius of deformation based on the total depth of the ambient fluid H. Analytic solutions are determined for the particular case of zero front-relative flow within the gravity current. For each value of W there is a unique non-dissipative two-layer solution, and a non-dissipative one-layer solution which is specified by the value of the wall-depth h0. In the two-layer case, the non-dimensional propagation speed c = cf(g[prime prime or minute]H)[minus sign]1/2 increases smoothly from the non-rotating value of 0.5 as W increases, asymptoting to unity for W [rightward arrow] [infty infinity]. The gravity current separates from the left-hand wall of the channel at W = 0.67 and thereafter has decreasing width. The depth of the current at the right-hand wall, h0, increases, reaching the full depth at W = 1.90, after which point the interface outcrops on both the upper and lower boundaries, with the distance over which the interface slopes being 0.881R. In the one-layer case, the wall

Steady-state spheromak

International Nuclear Information System (INIS)

Jarboe, T.R.

1982-01-01

A major effort is being made in the national program to make the operation of axisymmetric, toroidal confinement systems steady state by the application of expensive rf current drive. Described here is a method by which such a confinement system, the spheromak, can be refluxed indefinitely through the application of dc power. As a step towards dc sustainment we have operated the present CTX source in the slow source mode with a longer power application time (approx. 0.1 ms) and successfully generated long-lived spheromaks. If the erosion of the electrodes can be controlled as well as it is with MPD arcs then dc operation should be very clean. If only a small fraction (approx. 10% for an experiment) of the poloidal flux of the spheromak connects to the source then the dc sustainment can be very efficient. The amount of connecting flux that is necessary for sustainment needs to be determined experimentally

Numerical solution of problems concerning the thermal convection of a variable-viscosity liquid

Science.gov (United States)

Zherebiatev, I. F.; Lukianov, A. T.; Podkopaev, Iu. L.

A stabilizing-correction scheme is constructed for integrating the fourth-order equation describing the dynamics of a viscous incompressible liquid. As an example, a solution is obtained to the problem of the solidification of a liquid in a rectangular region with allowance for convective energy transfer in the liquid phase as well as temperature-dependent changes of viscosity. It is noted that the proposed method can be used to study steady-state problems of thermal convection in ingots obtained through continuous casting.

The Steady State Calculation for SMART with MIDAS/SMR

International Nuclear Information System (INIS)

Park, Jong Hwa; Kim, Dong Ha; Chung, Young Jong; Park, Sun Hee; Cho, Seong Won

2010-01-01

KAERI is developing a new concept of reactor that all the main components such as the steam generator, the coolant pumps and the pressurizer are located inside the reactor vessel. Before the severe accident sequences are estimated, it is prerequisite that MIDAS code predicts the steady state conditions properly. But MIDAS code does not include the heat transfer model for the helical tube. Therefore, the heat transfer models for the helical tube from TASS/SMR-S were implemented into MIDAS code. To estimate the validity of the implemented heat transfer correlations for the helical tube and the input data, the steady state was recalculated with MIDAS/SMR based on design level 2 and compared with the design values

On the optimization of a steady-state bootstrap-reactor

International Nuclear Information System (INIS)

Polevoy, A.R.; Martynov, A.A.; Medvedev, S.Yu.

1993-01-01

A commercial fusion tokamak-reactor may be economically acceptable only for low recirculating power fraction r 0 ≡ P CD /P α BS ≡I BS /I > 0.9 to sustain the steady-state operation mode for high plasma densities > 1.5 10 20 m -3 , fulfilled the divertor conditions. This paper presents the approximate expressions for the optimal set of reactor parameters for r BS /I∼1, based on the self-consistent plasma simulations by 1.5D ASTRA code. The linear MHD stability analysis for ideal n=1 kink and ballooning modes has been carried out to determine the conditions of stabilization for bootstrap steady state tokamak reactor BSSTR configurations. (author) 10 refs., 1 tab

Computational issues of solving the 1D steady gradually varied flow equation

Directory of Open Access Journals (Sweden)

Artichowicz Wojciech

2014-09-01

Full Text Available In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.

Numerical Simulation of Steady Supercavitating Flows

OpenAIRE

Ali Jafarian; Ahmad-Reza Pishevar

2016-01-01

In this research, the Supercavitation phenomenon in compressible liquid flows is simulated. The one-fluid method based on a new exact two-phase Riemann solver is used for modeling. The cavitation is considered as an isothermal process and a consistent equation of state with the physical behavior of the water is used. High speed flow of water over a cylinder and a projectile are simulated and the results are compared with the previous numerical and experimental results. The cavitation bubble p...

Computation of Effective Steady-State Creep of Porous Ni–YSZ Composites with Reconstructed Microstructures

DEFF Research Database (Denmark)

Kwok, Kawai; Jørgensen, Peter Stanley; Frandsen, Henrik Lund

2015-01-01

This paper investigates the effective steady-state creep response of porous Ni–YSZ composites used in solid oxide fuel cell applications by numerical homogenization based on three-dimensional microstructural reconstructions and steadystate creep properties of the constituent phases. The Ni phase...... is found to carry insignificant stress in the composite and has a negligible role in the effective creep behavior. Thus, when determining effective creep, porous Ni–YSZ composites can be regarded as porous YSZ in which the Ni phase is counted as additional porosity. The stress exponents of porous YSZ...... are the same as that of dense YSZ, but the effective creep rate increases by a factor of 8–10 due to porosity. The relationship of creep rate and volume fraction of YSZ computed by numerical homogenization is underestimated by most existing analytical models. The Ramakrishnan–Arunchalam creep model provides...

Steady-state creep of discontinuous fibre composites

International Nuclear Information System (INIS)

Boecker Pedersen, O.

1975-07-01

A review is given of the relevant literature on creep of composites, including a presentation of existing models for the steady-state creep of composites containing aligned discontinuous fibres where creep of the matrix and fibres is assumed to follow a power law. A model is suggested for predicting the composite creep law from a matrix creep law given in a general form, in the case where the fibres do not creep. The composite creep law predicted by this model is compared with those predicted by previous models, when these are extended to comprise a general matrix creep law. Experimentally, pure copper and composites consisting of aligned discontinuous tungsten fibres in a copper matrix were creep tested at a temperature of 500 deg C. The results indicate a relatively low stress sensitivity of the steady-state creep-rate for pure copper and relatively high stress sensitivity for the composites. This may be explained by the creep models based upon a general matrix creep law. A quantitative prediction shows promising agreement with the present experimental results. (author)

Numerical solution of the Navier--Stokes equations at high Reynolds numbers

International Nuclear Information System (INIS)

Shestakov, A.I.

1974-01-01

A numerical method is presented which is designed to solve the Navier-Stokes equations for two-dimensional, incompressible flow. The method is intended for use on problems with high Reynolds numbers for which calculations via finite difference methods have been unattainable or unreliable. The proposed scheme is a hybrid utilizing a time-splitting finite difference method in areas away from the boundaries. In areas neighboring the boundaries, the equations of motion are solved by the newly proposed vortex method by Chorin. The major accomplishment of the new scheme is that it contains a simple way for merging the two methods at the interface of the two subdomains. The proposed algorithm is designed for use on the time-dependent equations but can be used on steady state problems as well. The method is tested on the popular, time-independent, square cavity problem, an example of a separated flow with closed streamlines. Numerical results are presented for a Reynolds number of 10 3 . (auth)

Steady state statistical correlations predict bistability in reaction motifs.

Science.gov (United States)

Chakravarty, Suchana; Barik, Debashis

2017-03-28

Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.

Understanding void fraction in steady state and dynamic environments

International Nuclear Information System (INIS)

Chexal, B.; Maulbetsch, J.; Harrison, J.; Petersen, C.; Jensen, P.; Horowitz, J.

1997-01-01

Understanding void fraction behavior in steady-state and dynamic environments is important to accurately predict the thermal-hydraulic behavior of two-phase or two-component systems. The Chexal-Lellouche (C-L) void fraction mode described herein covers the full range of pressures, flows, void fractions, and fluid types (steam-water, air-water, and refrigerants). A drift flux model formulation is used which covers the complete range of concurrent and countercurrent flows. The (1996) model revises the earlier C-L void fraction correlation, improves the capability of the model in countercurrent flow based on the incorporation of additional data, and improves the characteristics of the correlation that are important in transient programs. The model has been qualified with data from a number of steady state two-phase and two-component tests, and has been incorporated into the transient analysis code RELAP5 and RETRAN-3D and evaluated with a variety of transient and steady state tests. A 'plug-in' module for the void fraction correlation has been developed and implemented in RELAP5 and RETRAN-3D. The module is available as source code for inclusion into other thermal-hydraulic programs and can be used in any program that utilizes the same interface variables

Numerical modelling of random walk one-dimensional diffusion

International Nuclear Information System (INIS)

Vamos, C.; Suciu, N.; Peculea, M.

1996-01-01

The evolution of a particle which moves on a discrete one-dimensional lattice, according to a random walk low, approximates better the diffusion process smaller the steps of the spatial lattice and time are. For a sufficiently large assembly of particles one can assume that their relative frequency at lattice knots approximates the distribution function of the diffusion process. This assumption has been tested by simulating on computer two analytical solutions of the diffusion equation: the Brownian motion and the steady state linear distribution. To evaluate quantitatively the similarity between the numerical and analytical solutions we have used a norm given by the absolute value of the difference of the two solutions. Also, a diffusion coefficient at any lattice knots and moment of time has been calculated, by using the numerical solution both from the diffusion equation and the particle flux given by Fick's low. The difference between diffusion coefficient of analytical solution and the spatial lattice mean coefficient of numerical solution constitutes another quantitative indication of the similarity of the two solutions. The results obtained show that the approximation depends first on the number of particles at each knot of the spatial lattice. In conclusion, the random walk is a microscopic process of the molecular dynamics type which permits simulations precision of the diffusion processes with given precision. The numerical method presented in this work may be useful both in the analysis of real experiments and for theoretical studies

Extracting Steady State Components from Synchrophasor Data Using Kalman Filters

Directory of Open Access Journals (Sweden)

Farhan Mahmood

2016-04-01

Full Text Available Data from phasor measurement units (PMUs may be exploited to provide steady state information to the applications which require it. As PMU measurements may contain errors and missing data, the paper presents the application of a Kalman Filter technique for real-time data processing. PMU data captures the power system’s response at different time-scales, which are generated by different types of power system events; the presented Kalman Filter methods have been applied to extract the steady state components of PMU measurements that can be fed to steady state applications. Two KF-based methods have been proposed, i.e., a windowing-based KF method and “the modified KF”. Both methods are capable of reducing noise, compensating for missing data and filtering outliers from input PMU signals. A comparison of proposed methods has been carried out using the PMU data generated from a hardware-in-the-loop (HIL experimental setup. In addition, a performance analysis of the proposed methods is performed using an evaluation metric.

Reliability importance analysis of Markovian systems at steady state using perturbation analysis

Energy Technology Data Exchange (ETDEWEB)

Phuc Do Van [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France); Barros, Anne [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)], E-mail: anne.barros@utt.fr; Berenguer, Christophe [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)

2008-11-15

Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies.

Reliability importance analysis of Markovian systems at steady state using perturbation analysis

International Nuclear Information System (INIS)

Phuc Do Van; Barros, Anne; Berenguer, Christophe

2008-01-01

Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies

Analysis of physical properties controlling steady-state infiltration rates on tropical savannah soils

International Nuclear Information System (INIS)

Mbagwu, J.S.C.

1993-10-01

A knowledge of physical properties influencing the steady-state infiltration rates (ic) of soils is needed for the hydrologic modelling of the infiltration process. In this study evidence is provided to show that effective porosity (Pe) (i.e. the proportion of macro pore spaces with equivalent radius of > 15 μm) and dry bulk density are the most important soil physical properties controlling the steady-state infiltration rates on a tropical savannah with varying land use histories. At a macro porosity value of ≤ 5.0% the steady-state infiltration rate is zero. Total porosity and the proportion of water-retaining pores explained only a small fraction of the variation in this property. Steady-state infiltration rates can also be estimated from either the saturated hydraulic conductivity (Ks) by the equation, i c = 31.1 + 1.06 (Ks), (R 2 = 0.8104, p ≤ 0.001) or the soil water transmissivity (A) by the equation, i c = 30.0 + 29.9(A), (R 2 = 0.8228, ρ ≤ 0.001). The Philip two-parameter model under predicted steady-state infiltration rates generally. Considering the ease of determination and reliability it is suggested that effective porosity be used to estimate the steady-state infiltration rates of these other soils with similar characteristics. The model is, i c 388.7(Pe) - 10.8(R 2 = 0.7265, p ≤ 0.001) where i c is in (cm/hr) and Pe in (cm 3 /cm 3 ). (author). 20 refs, 3 figs, 4 tabs

Full transmission modes and steady states in defect gratings,

NARCIS (Netherlands)

van Groesen, Embrecht W.C.; Sopaheluwakan, A.; Andonowati, A.; de Ridder, R.M; Altena, G; Geuzebroek, D.H.; Dekker, R

2003-01-01

For a symmetric grating structure with a defect, we show that a fully transmitted defect mode in the band gap can be obtained as a superposition of two steady states: an amplified and an attenuated defect state. Without scanning the whole band gap by transmission calculations, this simplifies the

Bioaccumulation factors and the steady state assumption for cesium isotopes in aquatic foodwebs near nuclear facilities.

Science.gov (United States)

Rowan, D J

2013-07-01

Steady state approaches, such as transfer coefficients or bioaccumulation factors, are commonly used to model the bioaccumulation of (137)Cs in aquatic foodwebs from routine operations and releases from nuclear generating stations and other nuclear facilities. Routine releases from nuclear generating stations and facilities, however, often consist of pulses as liquid waste is stored, analyzed to ensure regulatory compliance and then released. The effect of repeated pulse releases on the steady state assumption inherent in the bioaccumulation factor approach has not been evaluated. In this study, I examine the steady state assumption for aquatic biota by analyzing data for two cesium isotopes in the same biota, one isotope in steady state (stable (133)Cs) from geologic sources and the other released in pulses ((137)Cs) from reactor operations. I also compare (137)Cs bioaccumulation factors for similar upstream populations from the same system exposed solely to weapon test (137)Cs, and assumed to be in steady state. The steady state assumption appears to be valid for small organisms at lower trophic levels (zooplankton, rainbow smelt and 0+ yellow perch) but not for older and larger fish at higher trophic levels (walleye). Attempts to account for previous exposure and retention through a biokinetics approach had a similar effect on steady state, upstream and non-steady state, downstream populations of walleye, but were ineffective in explaining the more or less constant deviation between fish with steady state exposures and non-steady state exposures of about 2-fold for all age classes of walleye. These results suggest that for large, piscivorous fish, repeated exposure to short duration, pulse releases leads to much higher (137)Cs BAFs than expected from (133)Cs BAFs for the same fish or (137)Cs BAFs for similar populations in the same system not impacted by reactor releases. These results suggest that the steady state approach should be used with caution in any

The Completion of Non-Steady-State Queue Model on The Queue System in Dr. Yap Eye Hospital Yogyakarta

Science.gov (United States)

Helmi Manggala Putri, Arum; Subekti, Retno; Binatari, Nikenasih

2017-06-01

Dr Yap Eye Hospital Yogyakarta is one of the most popular reference eye hospitals in Yogyakarta. There are so many patients coming from other cities and many of them are BPJS (Badan Penyelenggara Jaminan Sosial, Social Security Administrative Bodies) patients. Therefore, it causes numerous BPJS patients were in long queue at counter C of the registration section so that it needs to be analysed using queue system. Queue system analysis aims to give queue model overview and determine its effectiveness measure. The data collecting technique used in this research are by interview and observation. After getting the arrival data and the service data of BPJS patients per 5 minutes, the next steps are investigating steady-state condition, examining the Poisson distribution, determining queue models, and counting the effectiveness measure. Based on the result of data observation on Tuesday, February 16th, 2016, it shows that the queue system at counter C has (M/M/1):(GD/∞/∞) queue model. The analysis result in counter C shows that the queue system is a non-steady-state condition. Three ways to cope a non-steady-state problem on queue system are proposed in this research such as bounding the capacity of queue system, adding the servers, and doing Monte Carlo simulation. The queue system in counter C will reach steady-state if the capacity of patients is not more than 52 BPJS patients or adding one more server. By using Monte Carlo simulation, it shows that the effectiveness measure of the average waiting time for BPJS patients in counter C is 36 minutes 65 seconds. In addition, the average queue length of BPJS patients is 11 patients.

Experimental and numerical study of a printed circuit heat exchanger

International Nuclear Information System (INIS)

Chen, Minghui; Sun, Xiaodong; Christensen, Richard N.; Shi, Shanbin; Skavdahl, Isaac; Utgikar, Vivek; Sabharwall, Piyush

2016-01-01

temperature increase and the other for helium inlet temperature decrease, were experimentally carried out to assess the applicability of the dynamic model. Comparisons of the numerical results with the experimental data show that the dynamic model is successful in predicting the experimental transient scenarios. Although difference was observed between the numerical results and experimental data, the comparisons suggest that the numerical solutions are sufficiently accurate and conservative and that the applicability of the dynamic model proposed for predicting the steady-state and transient performance of the straight-channel PCHE has been confirmed. Furthermore, both the numerical and experimental studies provide insights into the dynamic performance of the PCHE.

Vacuum system problems of EBT: a steady-state fusion experiment

International Nuclear Information System (INIS)

Livesey, R.L.

1981-01-01

Many of the vacuum problems faced by EBT will soon be shared by other plasma devices as high-power microwave systems and long pulse lengths become more common. The solutions used on EBT (such as the raised lip with elastomer seal) are not unique; however, experience has shown that microwave-compatible designs must be carefully thought out. All details of the vacuum must be carefully thought out. All details of the vacuum must be carefully screened in advance to insure that microwaves do not leak into pumps or diagnostics where they can cause major damage. Sputter coating, which even now is noticeably present in most pulsed plasma systems, becomes much worse as systems approach steady state. And finally, radiation degradation of components which is presently a minor problem will become significant on high-power microwave-fed devices, such as EBT-P

Time Reversibility, Correlation Decay and the Steady State Fluctuation Relation for Dissipation

Directory of Open Access Journals (Sweden)

Denis J. Evans

2013-04-01

Full Text Available Steady state fluctuation relations for nonequilibrium systems are under intense investigation because of their important practical implications in nanotechnology and biology. However the precise conditions under which they hold need clarification. Using the dissipation function, which is related to the entropy production of linear irreversible thermodynamics, we show time reversibility, ergodic consistency and a recently introduced form of correlation decay, called T-mixing, are sufficient conditions for steady state fluctuation relations to hold. Our results are not restricted to a particular model and show that the steady state fluctuation relation for the dissipation function holds near or far from equilibrium subject to these conditions. The dissipation function thus plays a comparable role in nonequilibrium systems to thermodynamic potentials in equilibrium systems.

Efficient decoding with steady-state Kalman filter in neural interface systems.

Science.gov (United States)

Malik, Wasim Q; Truccolo, Wilson; Brown, Emery N; Hochberg, Leigh R

2011-02-01

The Kalman filter is commonly used in neural interface systems to decode neural activity and estimate the desired movement kinematics. We analyze a low-complexity Kalman filter implementation in which the filter gain is approximated by its steady-state form, computed offline before real-time decoding commences. We evaluate its performance using human motor cortical spike train data obtained from an intracortical recording array as part of an ongoing pilot clinical trial. We demonstrate that the standard Kalman filter gain converges to within 95% of the steady-state filter gain in 1.5±0.5 s (mean ±s.d.). The difference in the intended movement velocity decoded by the two filters vanishes within 5 s, with a correlation coefficient of 0.99 between the two decoded velocities over the session length. We also find that the steady-state Kalman filter reduces the computational load (algorithm execution time) for decoding the firing rates of 25±3 single units by a factor of 7.0±0.9. We expect that the gain in computational efficiency will be much higher in systems with larger neural ensembles. The steady-state filter can thus provide substantial runtime efficiency at little cost in terms of estimation accuracy. This far more efficient neural decoding approach will facilitate the practical implementation of future large-dimensional, multisignal neural interface systems.

Numerical solution of one-dimensional transient, two-phase flows with temporal fully implicit high order schemes: Subcooled boiling in pipes

Energy Technology Data Exchange (ETDEWEB)

López, R., E-mail: ralope1@ing.uc3m.es; Lecuona, A., E-mail: lecuona@ing.uc3m.es; Nogueira, J., E-mail: goriba@ing.uc3m.es; Vereda, C., E-mail: cvereda@ing.uc3m.es

2017-03-15

Highlights: • A two-phase flows numerical algorithm with high order temporal schemes is proposed. • Transient solutions route depends on the temporal high order scheme employed. • ESDIRK scheme for two-phase flows events exhibits high computational performance. • Computational implementation of the ESDIRK scheme can be done in a very easy manner. - Abstract: An extension for 1-D transient two-phase flows of the SIMPLE-ESDIRK method, initially developed for incompressible viscous flows by Ijaz is presented. This extension is motivated by the high temporal order of accuracy demanded to cope with fast phase change events. This methodology is suitable for boiling heat exchangers, solar thermal receivers, etc. The methodology of the solution consist in a finite volume staggered grid discretization of the governing equations in which the transient terms are treated with the explicit first stage singly diagonally implicit Runge-Kutta (ESDIRK) method. It is suitable for stiff differential equations, present in instant boiling or condensation processes. It is combined with the semi-implicit pressure linked equations algorithm (SIMPLE) for the calculation of the pressure field. The case of study consists of the numerical reproduction of the Bartolomei upward boiling pipe flow experiment. The steady-state validation of the numerical algorithm is made against these experimental results and well known numerical results for that experiment. In addition, a detailed study reveals the benefits over the first order Euler Backward method when applying 3rd and 4th order schemes, making emphasis in the behaviour when the system is subjected to periodic square wave wall heat function disturbances, concluding that the use of the ESDIRK method in two-phase calculations presents remarkable accuracy and computational advantages.

The Numerical Solution of the Equilibrium Problem for a Stretchable Elastic Beam

Science.gov (United States)

Mehdiyeva, G. Y.; Aliyev, A. Y.

2017-08-01

The boundary value problem under consideration describes the equilibrium of an elastic beam that is stretched or contracted by specified forces. The left end of the beam is free of load, and the right end is rigidly lapped. To solve the problem numerically, an appropriate difference problem is constructed. Solving the difference problem, we obtain an approximate solution of the problem. We estimate the approximate solution of the stated problem.

Computer simulation of the steam--graphite reaction under isothermal and steady-state conditions

International Nuclear Information System (INIS)

Joy, D.S.; Stem, S.C.

1975-05-01

A mathematical model was formulated to describe the isothermal, steady-state diffusion and reaction of steam in a graphite matrix. A generalized Langmuir-Hinshelwood equation is used to represent the steam-graphite reaction rate. The model also includes diffusion in the gas phase adjacent to the graphite matrix. A computer program, written to numerically integrate the resulting differential equations, is described. The coupled nonlinear differential equations in the graphite phase are solved using the IBM Continuous System Modeling Program. Classical finite difference techniques are used for the gas-phase calculations. An iterative procedure is required to couple the two sets of calculations. Several sample problems are presented to demonstrate the utility of the model. (U.S.)

A Review of Fusion and Tokamak Research Towards Steady-State Operation: A JAEA Contribution

Directory of Open Access Journals (Sweden)

Mitsuru Kikuchi

2010-11-01

Full Text Available Providing a historical overview of 50 years of fusion research, a review of the fundamentals and concepts of fusion and research efforts towards the implementation of a steady state tokamak reactor is presented. In 1990, a steady-state tokamak reactor (SSTR best utilizing the bootstrap current was developed. Since then, significant efforts have been made in major tokamaks, including JT-60U, exploring advanced regimes relevant to the steady state operation of tokamaks. In this paper, the fundamentals of fusion and plasma confinement, and the concepts and research on current drive and MHD stability of advanced tokamaks towards realization of a steady-state tokamak reactor are reviewed, with an emphasis on the contributions of the JAEA. Finally, a view of fusion energy utilization in the 21st century is introduced.

Finite element modelling of creep process - steady state stresses and strains

Directory of Open Access Journals (Sweden)

Sedmak Aleksandar S.

2014-01-01

Full Text Available Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.

Optimal estimation of spatially variable recharge and transmissivity fields under steady-state groundwater flow. Part 2. Case study

Science.gov (United States)

Graham, Wendy D.; Neff, Christina R.

1994-05-01

The first-order analytical solution of the inverse problem for estimating spatially variable recharge and transmissivity under steady-state groundwater flow, developed in Part 1 is applied to the Upper Floridan Aquifer in NE Florida. Parameters characterizing the statistical structure of the log-transmissivity and head fields are estimated from 152 measurements of transmissivity and 146 measurements of hydraulic head available in the study region. Optimal estimates of the recharge, transmissivity and head fields are produced throughout the study region by conditioning on the nearest 10 available transmissivity measurements and the nearest 10 available head measurements. Head observations are shown to provide valuable information for estimating both the transmissivity and the recharge fields. Accurate numerical groundwater model predictions of the aquifer flow system are obtained using the optimal transmissivity and recharge fields as input parameters, and the optimal head field to define boundary conditions. For this case study, both the transmissivity field and the uncertainty of the transmissivity field prediction are poorly estimated, when the effects of random recharge are neglected.

Nonlinear reaction-diffusion equations with delay: some theorems, test problems, exact and numerical solutions

Science.gov (United States)

Polyanin, A. D.; Sorokin, V. G.

2017-12-01

The paper deals with nonlinear reaction-diffusion equations with one or several delays. We formulate theorems that allow constructing exact solutions for some classes of these equations, which depend on several arbitrary functions. Examples of application of these theorems for obtaining new exact solutions in elementary functions are provided. We state basic principles of construction, selection, and use of test problems for nonlinear partial differential equations with delay. Some test problems which can be suitable for estimating accuracy of approximate analytical and numerical methods of solving reaction-diffusion equations with delay are presented. Some examples of numerical solutions of nonlinear test problems with delay are considered.

Numerical solution of non-linear diffusion problems

International Nuclear Information System (INIS)

Carmen, A. del; Ferreri, J.C.

1998-01-01

This paper presents a method for the numerical solution of non-linear diffusion problems using finite-differences in moving grids. Due to the presence of steep fronts in the solution domain and to the presence of advective terms originating in the grid movement, an implicit TVD scheme, first order in time and second order in space has been developed. Some algebraic details of the derivation are given. Results are shown for the pure advection of a scalar as a test case and an example dealing with the slow spreading of viscous fluids over plane surfaces. The agreement between numerical and analytical solutions is excellent. (author). 8 refs., 3 figs

40 CFR 86.1363-2007 - Steady-state testing with a discrete-mode cycle.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Steady-state testing with a discrete-mode cycle. 86.1363-2007 Section 86.1363-2007 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Exhaust Test Procedures § 86.1363-2007 Steady-state testing with a discrete-mode cycle. This section...

Steady-state groundwater recharge in trapezoidal-shaped aquifers: A semi-analytical approach based on variational calculus

Science.gov (United States)

Mahdavi, Ali; Seyyedian, Hamid

2014-05-01

This study presents a semi-analytical solution for steady groundwater flow in trapezoidal-shaped aquifers in response to an areal diffusive recharge. The aquifer is homogeneous, anisotropic and interacts with four surrounding streams of constant-head. Flow field in this laterally bounded aquifer-system is efficiently constructed by means of variational calculus. This is accomplished by minimizing a properly defined penalty function for the associated boundary value problem. Simple yet demonstrative scenarios are defined to investigate anisotropy effects on the water table variation. Qualitative examination of the resulting equipotential contour maps and velocity vector field illustrates the validity of the method, especially in the vicinity of boundary lines. Extension to the case of triangular-shaped aquifer with or without an impervious boundary line is also demonstrated through a hypothetical example problem. The present solution benefits from an extremely simple mathematical expression and exhibits strictly close agreement with the numerical results obtained from Modflow. Overall, the solution may be used to conduct sensitivity analysis on various hydrogeological parameters that affect water table variation in aquifers defined in trapezoidal or triangular-shaped domains.

Herd-Level Modeling and Steady-State Livestock Productivity ...

African Journals Online (AJOL)

... an outline of the scope for applications and addresses the prospects for refinement and model extensions. The algorithms for use in development of steady state derivations include transition of matrices in a Markov Chain approach, continuous differential equations and actuarial approach built on life and fecundity tables.

Principle of Entropy Maximization for Nonequilibrium Steady States

DEFF Research Database (Denmark)

Shapiro, Alexander; Stenby, Erling Halfdan

2002-01-01

The goal of this contribution is to find out to what extent the principle of entropy maximization, which serves as a basis for the equilibrium thermodynamics, may be generalized onto non-equilibrium steady states. We prove a theorem that, in the system of thermodynamic coordinates, where entropy...

Steady-state operation of spheromaks by inductive techniques

International Nuclear Information System (INIS)

Janos, A.

1984-04-01

A method to maintain a steady-state spheromak configuration inductively using the S-1 Spheromak device is described. The S-1 Spheromak formation apparatus can be utilized to inject magnetic helicity continuously (C.W., not pulsed or D.C.) into the spheromak configuration after equilibrium is achieved in the linked mode of operation. Oscillation of both poloidal- and toroidal-field currents in the flux core (psi-phi Pumping), with proper phasing, injects a net time-averaged helicity into the plasma. Steady-state maintenance relies on flux conversion, which has been earlier identified. Relevant experimental data from the operation of S-1 are described. Helicity flow has been measured and the proposed injection scheme simulated. In a reasonable time practical voltages and frequencies can inject an amount of helicity comparable to that in the initial plasma. Plasma currents can be maintained or increased. This pumping technique is similar to F-THETA Pumping of a Reversed-Field-Pinch but is applied to this inverse-pinch formation

Numerical simulation of flow fields and particle trajectories

DEFF Research Database (Denmark)

Mayer, Stefan

2000-01-01

. The time-dependent flow is approximated with a continuous sequence of steady state creeping flow fields, where metachronously beating ciliary bands are modelled by linear combinations of singularity solutions to the Stokes equations. Generally, the computed flow fields can be divided into an unsteady......A model describing the ciliary driven flow and motion of suspended particles in downstream suspension feeders is developed. The quasi-steady Stokes equations for creeping flow are solved numerically in an unbounded fluid domain around cylindrical bodies using a boundary integral formulation...... in the simulated unsteady ciliary driven flow. A fraction of particles appear to follow trajectories, that resemble experimentally observed particle capture events in the downstream feeding system of the polycheate Sabella penicillus, indicating that particles can be captured by ciliary systems without mechanical...

Steady 3D Numerical Simulation of the Evaporator and Compensation Chamber of a Loop Heat Pipe

Directory of Open Access Journals (Sweden)

A. V. Nedayvozov

2017-01-01

Full Text Available The paper presents results of a steady three-dimensional numerical simulation of a flat evaporator and compensation chamber (CC of a loop heat pipe (LHP and describes a procedure of the thermal state calculation of the evaporator and the compensation chamber.The LHP is an efficient heat transfer device operating on the principle of evaporation-condensation cycle. It is successfully used in space technology and also to cool the heat-stressed components of electronic devices and computer equipment. The authors carried out a numerical study of the influence of the condensate pipeline length, immersed in water, on the thermal state of the evaporator and the compensation chamber.  The paper shows the influence of the mass forces field on the calculation results. Presents all the numerical studies carried out by the authors for a brass flat evaporator with a thermal load of 80 W. Water is used as a LHP heat-transfer fluid. Fields of temperature, pressure and velocity are presented for each design option.Based on the calculation results, the authors came to the following conclusions:Influence of the mass forces field for the LHP of this type is significant and leads to arising water vortex flow in the condensate pipeline and CC, thereby mixing and equalizing the water temperature in the CC and in the porous element, reducing the maximum temperature of the porous element;The increasing section length of the condensate pipeline in the CC leads to increasing velocity of the heat-transfer fluid in the CC and in the porous element, decreasing mixing zone of the condensate in the CC, and increasing temperature non-uniformity of the porous element.

Time-dependent inelastic analysis of metallic media using constitutive relations with state variables

Energy Technology Data Exchange (ETDEWEB)

Kumar, V; Mukherjee, S [Cornell Univ., Ithaca, N.Y. (USA)

1977-03-01

A computational technique in terms of stress, strain and displacement rates is presented for the solution of boundary value problems for metallic structural elements at uniform elevated temperatures subjected to time varying loads. This method can accommodate any number of constitutive relations with state variables recently proposed by other researchers to model the inelastic deformation of metallic media at elevated temperatures. Numerical solutions are obtained for several structural elements subjected to steady loads. The constitutive relations used for these numerical solutions are due to Hart. The solutions are discussed in the context of the computational scheme and Hart's theory.

Finite-State Mean-Field Games, Crowd Motion Problems, and its Numerical Methods

KAUST Repository

Machado Velho, Roberto

2017-09-10

In this dissertation, we present two research projects, namely finite-state mean-field games and the Hughes model for the motion of crowds. In the first part, we describe finite-state mean-field games and some applications to socio-economic sciences. Examples include paradigm shifts in the scientific community and the consumer choice behavior in a free market. The corresponding finite-state mean-field game models are hyperbolic systems of partial differential equations, for which we propose and validate a new numerical method. Next, we consider the dual formulation to two-state mean-field games, and we discuss numerical methods for these problems. We then depict different computational experiments, exhibiting a variety of behaviors, including shock formation, lack of invertibility, and monotonicity loss. We conclude the first part of this dissertation with an investigation of the shock structure for two-state problems. In the second part, we consider a model for the movement of crowds proposed by R. Hughes in [56] and describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an Eikonal equation with Dirichlet or Neumann data. We first establish a priori estimates for the solutions. Next, we consider radial solutions, and we identify a shock formation mechanism. Subsequently, we illustrate the existence of congestion, the breakdown of the model, and the trend to the equilibrium. We also propose a new numerical method for the solution of Fokker-Planck equations and then to systems of PDEs composed by a Fokker-Planck equation and a potential type equation. Finally, we illustrate the use of the numerical method both to the Hughes model and mean-field games. We also depict cases such as the evacuation of a room and the movement of persons around Kaaba (Saudi Arabia).

General Unified Integral Controller with Zero Steady-State Error for Single-Phase Grid-Connected Inverters

DEFF Research Database (Denmark)

Guo, Xiaoqiang; Guerrero, Josep M.

2016-01-01

Current regulation is crucial for operating single-phase grid-connected inverters. The challenge of the current controller is how to fast and precisely tracks the current with zero steady-state error. This paper proposes a novel feedback mechanism for the conventional PI controller. It allows...... done indicates that the widely used PR (P+Resonant) control is just a special case of the proposed control solution. The time-domain simulation in Matlab/Simulink and experimental results from a TMS320F2812 DSP based laboratory prototypes are in good agreement, which verify the effectiveness...

A numerical solution to an inverse unsteady-state heat transfer problem involving the Trefftz functions

Directory of Open Access Journals (Sweden)

Maciejewska Beata

2017-01-01

Full Text Available This paper shows the results concerning flow boiling heat transfer in an asymmetrically heated vertical minichannel. The heated element for FC-72 Fluorinert flowing in that minichannel was a thin foil. The foil surface temperature was monitored continuously at 18 points by K-type thermocouples from the outer foil surface. Fluid temperature and pressure in the minichannel inlet and outlet, current supplied to the foil and voltage drop were also monitored. Measurements were carried out at 1 s intervals. The objective was to determine the heat transfer coefficient on the heated foil–fluid contact surface in the minichannel. It was obtained from the Robin boundary condition. The foil temperature was the result of solving the nonstationary two-dimensional inverse boundary problem in the heated foil. Using the FEM combined with Trefftz functions as basis functions solved the problem. The unknown temperature values at nodes were calculated by minimising the adequate functional. The values of local heat transfer coefficients were consistent with the results obtained by the authors in their previous studies when steady-state conditions were analysed. This time, however, these values were analysed as time dependent, which facilitated observation of coefficient changes that were impossible to observe under the steady-state conditions.

Hybrid diffusion-P3 equation in N-layered turbid media: steady-state domain.

Science.gov (United States)

Shi, Zhenzhi; Zhao, Huijuan; Xu, Kexin

2011-10-01

This paper discusses light propagation in N-layered turbid media. The hybrid diffusion-P3 equation is solved for an N-layered finite or infinite turbid medium in the steady-state domain for one point source using the extrapolated boundary condition. The Fourier transform formalism is applied to derive the analytical solutions of the fluence rate in Fourier space. Two inverse Fourier transform methods are developed to calculate the fluence rate in real space. In addition, the solutions of the hybrid diffusion-P3 equation are compared to the solutions of the diffusion equation and the Monte Carlo simulation. For the case of small absorption coefficients, the solutions of the N-layered diffusion equation and hybrid diffusion-P3 equation are almost equivalent and are in agreement with the Monte Carlo simulation. For the case of large absorption coefficients, the model of the hybrid diffusion-P3 equation is more precise than that of the diffusion equation. In conclusion, the model of the hybrid diffusion-P3 equation can replace the diffusion equation for modeling light propagation in the N-layered turbid media for a wide range of absorption coefficients.

Computational multiple steady states for enzymatic esterification of ethanol and oleic acid in an isothermal CSTR.

Science.gov (United States)

Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya

2005-05-01

The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.

A quaternionic map for the steady states of the Heisenberg spin-chain

Energy Technology Data Exchange (ETDEWEB)

Mehta, Mitaxi P., E-mail: mitaxi.mehta@ahduni.edu.in [IICT, Ahmedabad University, Opp. IIM, Navrangpura, Ahmedabad (India); Dutta, Souvik; Tiwari, Shubhanshu [BITS-Pilani, K.K. Birla Goa campus, Goa (India)

2014-01-17

We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.

A quaternionic map for the steady states of the Heisenberg spin-chain

International Nuclear Information System (INIS)

Mehta, Mitaxi P.; Dutta, Souvik; Tiwari, Shubhanshu

2014-01-01

We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.

The primary results for the mixed carbon material used for high flux steady-state tokamak operation in China

International Nuclear Information System (INIS)

Guo, Q.G.; Li, J.G.; Zhai, G.T.; Liu, L.; Song, J.R.; Zhang, L.F.; He, Y.X.; Chen, J.L.

2001-01-01

Several types of carbon mixed materials have been developed in China to be used for high flux steady-state tokamak operation. Performance evaluation of these materials is necessary to determine their applicability as PFCs for high flux steady state. This paper describes the primary results of carbon mixed materials and the effects of dopants on properties are primarily discussed. Test results reveal that bulk boronized graphite has excellent physical and mechanical properties while their thermal conductivity is no more than 73 W/m K due to the formation of a uniform boron-carbon solid solution. In case of multi-element doped graphite, titanium dopant or a decreased boron content is favorable to enhance thermal conductivity. A kind of doped graphite has been developed with thermal conductivity as high as 278 W/m K by optimizing the compositions. Correlations among compositions, microstructure and properties of such doped graphite are discussed

Numerical Diffusion Effect in Dynamic Simulation of Thermohydraulic Systems

International Nuclear Information System (INIS)

Zanocco, Pablo; Gimenez, Marcelo; Delmastro, Dario

2003-01-01

In this work, the behavior of the explicit - up-wind method is studied in two phase natural convection circuit, near the instabilities boundaries.The effect of the numerical diffusion of the scheme upon the system stability is evaluated by means of linearization by small perturbations.The results are compared with a non-diffusive method, in the frequency domain, that solves analytically the linearized equations around a steady state condition.Moreover, a conservation equation transport model using the method of characteristics is implemented and studied.This method is compared with the explicit - up-wind scheme and it is found that it significantly reduces numerical diffusion in the equations solution. Several advantages are visualized for particular cases

Isotope partitioning for NAD-malic enzyme from Ascaris suum confirms a steady-state random kinetic mechanism

International Nuclear Information System (INIS)

Chen, C.Y.; Harris, B.G.; Cook, P.F.

1988-01-01

Isotope partitioning studies beginning with E-[ 14 C]NAD, E-[ 14 C] malate, E-[ 14 C] NAD-Mg 2+ , and E-Mg-[ 14 C]malate suggest a steady-state random mechanism for the NAD-malic enzyme. Isotope trapping beginning with E-[ 14 C]NAD and with varying concentrations of Mg 2+ and malate in the chase solution indicates that Mg 2+ is added in rapid equilibrium and must be added prior to malate for productive ternary complex formation. Equal percentage trapping from E-[ 14 C]NAD-Mg and E-Mg-[ 14 C] malate indicates the mechanism is steady-state random with equal off-rates for NAD and malate from E-NAD-Mg-malate. The off-rates for both do not change significantly in the ternary E-Mg-malate and E-NAD-Mg complexes, nor does the off-rate change for NAD from E-NAD. No trapping of malate was obtained from E-[ 14 C] malate, suggesting that this complex is nonproductive. A quantitative analysis of the data allows an estimation of values for a number of the rate constants along the reaction pathway

Washout and non-washout solutions of a system describing microbial fermentation process under the influence of growth inhibitions and maximal concentration of yeast cells.

Science.gov (United States)

Kasbawati; Gunawan, Agus Yodi; Sidarto, Kuntjoro Adjie

2017-07-01

An unstructured model for the growth of yeast cell on glucose due to growth inhibitions by substrate, products, and cell density is discussed. The proposed model describes the dynamical behavior of fermentation system that shows multiple steady states for a certain regime of operating parameters such as inlet glucose and dilution rate. Two types of steady state solutions are found, namely washout and non-washout solutions. Furthermore, different numerical impositions to the two parameters put in evidence three results regarding non-washout solution: a unique locally stable non-washout solution, a unique locally stable non-washout solution towards which other nearby solutions exhibit damped oscillations, and multiple non-washout solutions where one is locally stable while the other is unstable. It is also found an optimal inlet glucose which produces the highest cell and ethanol concentration. Copyright © 2017 Elsevier Inc. All rights reserved.

Efficient determination of the Markovian time-evolution towards a steady-state of a complex open quantum system

Science.gov (United States)

Jonsson, Thorsteinn H.; Manolescu, Andrei; Goan, Hsi-Sheng; Abdullah, Nzar Rauf; Sitek, Anna; Tang, Chi-Shung; Gudmundsson, Vidar

2017-11-01

Master equations are commonly used to describe time evolution of open systems. We introduce a general computationally efficient method for calculating a Markovian solution of the Nakajima-Zwanzig generalized master equation. We do so for a time-dependent transport of interacting electrons through a complex nano scale system in a photon cavity. The central system, described by 120 many-body states in a Fock space, is weakly coupled to the external leads. The efficiency of the approach allows us to place the bias window defined by the external leads high into the many-body spectrum of the cavity photon-dressed states of the central system revealing a cascade of intermediate transitions as the system relaxes to a steady state. The very diverse relaxation times present in the open system, reflecting radiative or non-radiative transitions, require information about the time evolution through many orders of magnitude. In our approach, the generalized master equation is mapped from a many-body Fock space of states to a Liouville space of transitions. We show that this results in a linear equation which is solved exactly through an eigenvalue analysis, which supplies information on the steady state and the time evolution of the system.

Steady state ion acceleration by a circularly polarized laser pulse

International Nuclear Information System (INIS)

Zhang Xiaomei; Shen Baifei; Cang Yu; Li Xuemei; Jin Zhangying; Wang Fengchao

2007-01-01

The steady state ion acceleration at the front of a cold solid target by a circularly polarized flat-top laser pulse is studied with one-dimensional particle-in-cell (PIC) simulation. A model that ions are reflected by a steady laser-driven piston is used by comparing with the electrostatic shock acceleration. A stable profile with a double-flat-top structure in phase space forms after ions enter the undisturbed region of the target with a constant velocity

Non-equilibrium transport in the quantum dot: quench dynamics and non-equilibrium steady state

Science.gov (United States)

Culver, Adrian; Andrei, Natan

We present an exact method of calculating the non-equilibrium current driven by a voltage drop across a quantum dot. The system is described by the two lead Anderson model at zero temperature with on-site Coulomb repulsion and non-interacting, linearized leads. We prepare the system in an initial state consisting of a free Fermi sea in each lead with the voltage drop given as the difference between the two Fermi levels. We quench the system by coupling the dot to the leads at t = 0 and following the time evolution of the wavefunction. In the long time limit a new type of Bethe Ansatz wavefunction emerges, which satisfies the Lippmann-Schwinger equation with the two Fermi seas serving as the boundary conditions. This exact, non-perturbative solution describes the non-equilibrium steady state of the system. We describe how to use this solution to compute the infinite time limit of the expectation value of the current operator at a given voltage, which would yield the I-V characteristic of the dot. Research supported by NSF Grant DMR 1410583.

A Novel Chronic Opioid Monitoring Tool to Assess Prescription Drug Steady State Levels in Oral Fluid.

Science.gov (United States)

Shaparin, Naum; Mehta, Neel; Kunkel, Frank; Stripp, Richard; Borg, Damon; Kolb, Elizabeth

2017-11-01

Interpretation limitations of urine drug testing and the invasiveness of blood toxicology have motivated the desire for the development of simpler methods to assess biologically active drug levels on an individualized patient basis. Oral fluid is a matrix well-suited for the challenge because collections are based on simple noninvasive procedures and drug concentrations better correlate to blood drug levels as oral fluid is a filtrate of the blood. Well-established pharmacokinetic models were utilized to generate oral fluid steady state concentration ranges to assess the interpretive value of the alternative matrix to monitor steady state plasma oxycodone levels. Paired oral fluid and plasma samples were collected from patients chronically prescribed oxycodone and quantitatively analyzed by liquid chromatography tandem mass spectrometry. Steady state plasma concentration ranges were calculated for each donor and converted to an equivalent range in oral fluid. Measured plasma and oral fluid oxycodone concentrations were compared with respective matrix-matched steady state ranges, using each plasma steady state classification as the control. A high degree of correlation was observed between matrices when classifying donors according to expected steady state oxycodone concentration. Agreement between plasma and oral fluid steady state classifications was observed in 75.6% of paired samples. This study supports novel application of basic pharmacokinetic knowledge to the pain management industry, simplifying and improving individualized drug monitoring and risk assessment through the use of oral fluid drug testing. Many benefits of established therapeutic drug monitoring in plasma can be realized in oral fluid for patients chronically prescribed oxycodone at steady state. © 2017 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Nonequilibrium fluctuation-dissipation relations for one- and two-particle correlation functions in steady-state quantum transport

International Nuclear Information System (INIS)

Ness, H.; Dash, L. K.

2014-01-01

We study the non-equilibrium (NE) fluctuation-dissipation (FD) relations in the context of quantum thermoelectric transport through a two-terminal nanodevice in the steady-state. The FD relations for the one- and two-particle correlation functions are derived for a model of the central region consisting of a single electron level. Explicit expressions for the FD relations of the Green's functions (one-particle correlations) are provided. The FD relations for the current-current and charge-charge (two-particle) correlations are calculated numerically. We use self-consistent NE Green's functions calculations to treat the system in the absence and in the presence of interaction (electron-phonon) in the central region. We show that, for this model, there is no single universal FD theorem for the NE steady state. There are different FD relations for each different class of problems. We find that the FD relations for the one-particle correlation function are strongly dependent on both the NE conditions and the interactions, while the FD relations of the current-current correlation function are much less dependent on the interaction. The latter property suggests interesting applications for single-molecule and other nanoscale transport experiments

Computation of tokamak equilibria with steady flow

International Nuclear Information System (INIS)

Kerner, W.; Tokuda, Shinji

1987-08-01

The equations for ideal MHD equilibria with stationary flow are reexamined and addressed as numerically applied to tokamak configurations with a free plasma boundary. Both the isothermal (purely toroidal flow) and the poloidal flow cases are treated. Experiment-relevant states with steady flow (so far only in the toroidal direction) are computed by the modified SELENE40 code. (author)

Steady-state bifurcations of the three-dimensional Kolmogorov problem

Directory of Open Access Journals (Sweden)

Zhi-Min Chen

2000-08-01

Full Text Available This paper studies the spatially periodic incompressible fluid motion in $mathbb R^3$ excited by the external force $k^2(sin kz, 0,0$ with $kgeq 2$ an integer. This driving force gives rise to the existence of the unidirectional basic steady flow $u_0=(sin kz,0, 0$ for any Reynolds number. It is shown in Theorem 1.1 that there exist a number of critical Reynolds numbers such that $u_0$ bifurcates into either 4 or 8 or 16 different steady states, when the Reynolds number increases across each of such numbers.

Steady-state heat transfer in an inverted U-tube steam generator

International Nuclear Information System (INIS)

Boucher, T.J.

1987-01-01

Experimental results are presented involving U-tube steam generator tube bundle local heat transfer and fluid conditions during stead-state, full-power operations performed at high temperatures and pressures with conditions typical of a pressurized water reactor (15.0 MPa primary pressure, 600 K steam generator inlet plenum fluid temperatures, 6.2 MPa secondary pressure). The Semiscale (MOD-2C facility represents the state-of-the-art in measurement of tube local heat transfer data and average tube bundle secondary fluid density at several elevations, which allows an estimate of the axial heat transfer and void distributions during steady-state and transient operations. The method of heat transfer data reduction is presented and the heat flux, secondary convective heat transfer coefficient, and void fraction distributions are quantified for steady-state, full-power operations

PACE-90 water and solute transport calculations for 0.01, 0.1, and 0. 5 mm/yr infiltration into Yucca Mountain

International Nuclear Information System (INIS)

Dykhuizen, R.C.; Eaton, R.R.; Hopkins, P.L.; Martinez, M.J.

1991-12-01

Numerical results are presented for the Performance Assessment Calculational Exercise (PACE-90). One- and two-dimensional water and solute transport are presented for steady infiltration into Yucca Mountain. Evenly distributed infiltration rates of 0.01, 0.1, and 0.5 mm/yr were considered. The calculations of solute transport show that significant amounts of radionuclides can reach the water table over 100,000 yr at the 0.5 mm/yr rate. For time periods less than 10,000 yr or infiltrations less than 0.1 mm/yr very little solute reaches the water table. The numerical simulations clearly demonstrate that multi-dimensional effects can result in significant decreases in the travel time of solute through the modeled domain. Dual continuum effects are shown to be negligible for the low steady state fluxes considered. However, material heterogeneities may cause local amplification of the flux level in multi-dimensional flows. These higher flux levels may then require modeling of a dual continuum porous medium

On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

Energy Technology Data Exchange (ETDEWEB)

Shaha, Poly Rani; Poddar, Nayan Kumar; Mondal, Rabindra Nath, E-mail: rnmondal71@yahoo.com [Department of Mathematics, Jagannath University, Dhaka-1100 (Bangladesh); Rudro, Sajal Kanti [Department of Mathematics, Notredame Colleage, Motijheel, Dhaka (Bangladesh)

2016-07-12

The study of flows through coiled ducts and channels has attracted considerable attention not only because of their ample applications in Chemical, Mechanical, Civil, Nuclear and Biomechanical engineering but also because of their ample applications in other areas, such as blood flow in the veins and arteries of human and other animals. In this paper, a numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a loosely coiled rectangular duct of large aspect ratio. Numerical calculations are carried out by using a spectral method, and covering a wide range of the Dean number, Dn, for two types of curvatures of the duct. The main concern of the present study is to find out effects of curvature as well as formation of secondary vortices on unsteady solutions whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if Dn is increased. Time evolution calculations as well as their phase spaces are performed with a view to study the non-linear behavior of the unsteady solutions, and it is found that the steady-state flow turns into chaotic flow through various flow instabilities, if Dn is increased no matter what the curvature is. It is found that the unsteady flow is a steady-state solution for small Dn’s and oscillates periodically or non-periodically (chaotic) between two- and twelve-vortex solutions, if Dn is increased. It is also found that the chaotic solution is weak for small Dn’s but strong as Dn becomes large. Axial flow distribution is also investigated and shown in contour plots.

On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

International Nuclear Information System (INIS)

Shaha, Poly Rani; Poddar, Nayan Kumar; Mondal, Rabindra Nath; Rudro, Sajal Kanti

2016-01-01

The study of flows through coiled ducts and channels has attracted considerable attention not only because of their ample applications in Chemical, Mechanical, Civil, Nuclear and Biomechanical engineering but also because of their ample applications in other areas, such as blood flow in the veins and arteries of human and other animals. In this paper, a numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a loosely coiled rectangular duct of large aspect ratio. Numerical calculations are carried out by using a spectral method, and covering a wide range of the Dean number, Dn, for two types of curvatures of the duct. The main concern of the present study is to find out effects of curvature as well as formation of secondary vortices on unsteady solutions whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if Dn is increased. Time evolution calculations as well as their phase spaces are performed with a view to study the non-linear behavior of the unsteady solutions, and it is found that the steady-state flow turns into chaotic flow through various flow instabilities, if Dn is increased no matter what the curvature is. It is found that the unsteady flow is a steady-state solution for small Dn’s and oscillates periodically or non-periodically (chaotic) between two- and twelve-vortex solutions, if Dn is increased. It is also found that the chaotic solution is weak for small Dn’s but strong as Dn becomes large. Axial flow distribution is also investigated and shown in contour plots.

An accelerator based steady state neutron source

International Nuclear Information System (INIS)

Burke, R.J.; Johnson, D.L.

1985-01-01

Using high current, c.w. linear accelerator technology, a spallation neutron source can achieve much higher average intensities than existing or proposed pulsed spallation sources. With about 100 mA of 300 MeV protons or deuterons, the Accelerator Based Neutron Research Facility (ABNR) would initially achieve the 10 16 n/cm 2 .s thermal flux goal of the advanced steady state neutron source, and upgrading could provide higher steady state fluxes. The relatively low ion energy compared to other spallation sources has an important impact on R and D requirements as well as capital cost, for which a range of $300-450M is estimated by comparison to other accelerator-based neutron source facilities. The source is similar to a reactor source in most respects. It has some higher energy neutrons but fewer gamma rays, and the moderator region is free of many of the design constraints of a reactor, which helps to implement sources for various neutron energy spectra, many beam tubes, etc. With the development of multi-beam concept and the basis for currents greater than 100 mA that is assumed in the R and D plan, the ABNR would serve many additional uses, such as fusion materials development, production of proton-rich isotopes, and other energy and defense program needs

Numerical solution of singularity-perturbed two-point boundary-value problems

International Nuclear Information System (INIS)

Masenge, R.W.P.

1993-07-01

Physical processes which involve transportation of slowly diffusing substances in a fast-flowing medium are mathematically modelled by so-called singularly-perturbed second order convection diffusion differential equations in which the convective first order terms dominate over the diffusive second order terms. In general, analytical solutions of such equations are characterized by having sharp solution fronts in some sections of the interior and/or the boundary of the domain of solution. The presence of these (usually very narrow) layer regions in the solution domain makes the task of globally approximating such solutions by standard numerical techniques very difficult. In this expository paper we use a simple one-dimensional prototype problem as a vehicle for analysing the nature of the numerical approximation difficulties involved. In the sequel we present, without detailed derivation, two practical numerical schemes which succeed in varying degrees in numerically resolving the layer of the solution to the prototype problem. (author). 3 refs, 1 fig., 1 tab

Analysing bifurcations encountered in numerical modelling of current transfer to cathodes of dc glow and arc discharges

International Nuclear Information System (INIS)

Almeida, P G C; Benilov, M S; Cunha, M D; Faria, M J

2009-01-01

Bifurcations and/or their consequences are frequently encountered in numerical modelling of current transfer to cathodes of gas discharges, also in apparently simple situations, and a failure to recognize and properly analyse a bifurcation may create difficulties in the modelling and hinder the understanding of numerical results and the underlying physics. This work is concerned with analysis of bifurcations that have been encountered in the modelling of steady-state current transfer to cathodes of glow and arc discharges. All basic types of steady-state bifurcations (fold, transcritical, pitchfork) have been identified and analysed. The analysis provides explanations to many results obtained in numerical modelling. In particular, it is shown that dramatic changes in patterns of current transfer to cathodes of both glow and arc discharges, described by numerical modelling, occur through perturbed transcritical bifurcations of first- and second-order contact. The analysis elucidates the reason why the mode of glow discharge associated with the falling section of the current-voltage characteristic in the solution of von Engel and Steenbeck seems not to appear in 2D numerical modelling and the subnormal and normal modes appear instead. A similar effect has been identified in numerical modelling of arc cathodes and explained.

Effect of vadose zone on the steady-state leakage rates from landfill barrier systems

International Nuclear Information System (INIS)

Celik, B.; Rowe, R.K.; Unlue, K.

2009-01-01

Leakage rates are evaluated for a landfill barrier system having a compacted clay liner (CCL) underlain by a vadose zone of variable thickness. A numerical unsaturated flow model SEEP/W is used to simulate the moisture flow regime and steady-state leakage rates for the cases of unsaturated zones with different soil types and thicknesses. The results of the simulations demonstrate that harmonic mean hydraulic conductivity of coarse textured vadose zones is 3-4 orders of magnitude less than saturated hydraulic conductivity; whereas, the difference is only one order of magnitude for fine textured vadose zones. For both coarse and fine textured vadose zones, the effective hydraulic conductivity of the barrier system and the leakage rate to an underlying aquifer increases with increasing thickness of the vadose zone and ultimately reaches an asymptotic value for a coarse textured vadose zone thickness of about 10 m and a fine textured vadose zone thickness of about 5 m. Therefore, the fine and coarse textured vadose zones thicker than about 5 m and 10 m, respectively, act as an effective part of the barrier systems examined. Although the thickness of vadose zone affects the effective hydraulic conductivity of the overall barrier system, the results demonstrated that the hydraulic conductivity of the CCL is the dominant factor controlling the steady-state leakage rates through barrier systems having single low permeability clay layers

Exploration of one-dimensional plasma current density profile for K-DEMO steady-state operation

Energy Technology Data Exchange (ETDEWEB)

Kang, J.S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Jung, L. [National Fusion Research Institute, Daejeon (Korea, Republic of); Byun, C.-S.; Na, D.H.; Na, Y.-S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Hwang, Y.S., E-mail: yhwang@snu.ac.kr [Seoul National University, Seoul 151-742 (Korea, Republic of)

2016-11-01

Highlights: • One-dimensional current density and its optimization for the K-DEMO are explored. • Plasma current density profile is calculated with an integrated simulation code. • The impact of self and external heating profiles is considered self-consistently. • Current density is identified as a reference profile by minimizing heating power. - Abstract: Concept study for Korean demonstration fusion reactor (K-DEMO) is in progress, and basic design parameters are proposed by targeting high magnetic field operation with ITER-sized machine. High magnetic field operation is a favorable approach to enlarge relative plasma performance without increasing normalized beta or plasma current. Exploration of one-dimensional current density profile and its optimization process for the K-DEMO steady-state operation are reported in this paper. Numerical analysis is conducted with an integrated plasma simulation code package incorporating a transport code with equilibrium and current drive modules. Operation regimes are addressed with zero-dimensional system analysis. One-dimensional plasma current density profile is calculated based on equilibrium, bootstrap current analysis, and thermal transport analysis. The impact of self and external heating profiles on those parameters is considered self-consistently, where thermal power balance and 100% non-inductive current drive are the main constraints during the whole exploration procedure. Current and pressure profiles are identified as a reference steady-state profile by minimizing the external heating power with desired fusion power.

Trade-offs between forest carbon stocks and harvests in a steady state - A multi-criteria analysis.

Science.gov (United States)

Pingoud, Kim; Ekholm, Tommi; Sievänen, Risto; Huuskonen, Saija; Hynynen, Jari

2018-03-15

This paper provides a perspective for comparing trade-offs between harvested wood flows and forest carbon stocks with different forest management regimes. A constant management regime applied to a forest area with an even age-class distribution leads to a steady state, in which the annual harvest and carbon stocks remain constant over time. As both are desirable - carbon stocks for mitigating climate change and harvests for the economic use of wood and displacing fossil fuels - an ideal strategy should be chosen from a set of management regimes that are Pareto-optimal in the sense of multi-criteria decision-making. When choosing between Pareto-optimal alternatives, the trade-off between carbon stock and harvests is unavoidable. This trade-off can be described e.g. in terms of carbon payback times or carbon returns. As numerical examples, we present steady-state harvest levels and carbon stocks in a Finnish boreal forest region for different rotation periods, thinning intensities and collection patterns for harvest residues. In the set of simulated management practices, harvest residue collection presents the most favorable trade-off with payback times around 30-40 years; while Pareto-optimal changes in rotation or thinnings exhibited payback times over 100 years, or alternatively carbon returns below 1%. By extending the rotation period and using less-intensive thinnings compared to current practices, the steady-state carbon stocks could be increased by half while maintaining current harvest levels. Additional cases with longer rotation periods should be also considered, but were here excluded due to the lack of reliable data on older forest stands. Copyright © 2018 Elsevier Ltd. All rights reserved.

Steady-state hydrodynamic instabilities of active liquid crystals: hybrid lattice Boltzmann simulations.

Science.gov (United States)

Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M

2007-09-01

We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.

The effects of intrinsic noise on the behaviour of bistable cell regulatory systems under quasi-steady state conditions.

Science.gov (United States)

de la Cruz, Roberto; Guerrero, Pilar; Spill, Fabian; Alarcón, Tomás

2015-08-21

We analyse the effect of intrinsic fluctuations on the properties of bistable stochastic systems with time scale separation operating under quasi-steady state conditions. We first formulate a stochastic generalisation of the quasi-steady state approximation based on the semi-classical approximation of the partial differential equation for the generating function associated with the chemical master equation. Such approximation proceeds by optimising an action functional whose associated set of Euler-Lagrange (Hamilton) equations provides the most likely fluctuation path. We show that, under appropriate conditions granting time scale separation, the Hamiltonian can be re-scaled so that the set of Hamilton equations splits up into slow and fast variables, whereby the quasi-steady state approximation can be applied. We analyse two particular examples of systems whose mean-field limit has been shown to exhibit bi-stability: an enzyme-catalysed system of two mutually inhibitory proteins and a gene regulatory circuit with self-activation. Our theory establishes that the number of molecules of the conserved species is order parameters whose variation regulates bistable behaviour in the associated systems beyond the predictions of the mean-field theory. This prediction is fully confirmed by direct numerical simulations using the stochastic simulation algorithm. This result allows us to propose strategies whereby, by varying the number of molecules of the three conserved chemical species, cell properties associated to bistable behaviour (phenotype, cell-cycle status, etc.) can be controlled.

The effects of intrinsic noise on the behaviour of bistable cell regulatory systems under quasi-steady state conditions

Energy Technology Data Exchange (ETDEWEB)

Cruz, Roberto; Alarcón, Tomás de la [Centre de Recerca Matemàtica. Edifici C, Campus de Bellaterra, 08193 Bellaterra (Barcelona) (Spain); Departament de Matemàtiques, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Guerrero, Pilar [Department of Mathematics, University College London, Gower Street, London WC1E 6BT (United Kingdom); Spill, Fabian [Department of Biomedical Engineering, Boston University, 44 Cummington Street, Boston, Massachusetts 02215 (United States); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)

2015-08-21

We analyse the effect of intrinsic fluctuations on the properties of bistable stochastic systems with time scale separation operating under quasi-steady state conditions. We first formulate a stochastic generalisation of the quasi-steady state approximation based on the semi-classical approximation of the partial differential equation for the generating function associated with the chemical master equation. Such approximation proceeds by optimising an action functional whose associated set of Euler-Lagrange (Hamilton) equations provides the most likely fluctuation path. We show that, under appropriate conditions granting time scale separation, the Hamiltonian can be re-scaled so that the set of Hamilton equations splits up into slow and fast variables, whereby the quasi-steady state approximation can be applied. We analyse two particular examples of systems whose mean-field limit has been shown to exhibit bi-stability: an enzyme-catalysed system of two mutually inhibitory proteins and a gene regulatory circuit with self-activation. Our theory establishes that the number of molecules of the conserved species is order parameters whose variation regulates bistable behaviour in the associated systems beyond the predictions of the mean-field theory. This prediction is fully confirmed by direct numerical simulations using the stochastic simulation algorithm. This result allows us to propose strategies whereby, by varying the number of molecules of the three conserved chemical species, cell properties associated to bistable behaviour (phenotype, cell-cycle status, etc.) can be controlled.

An Analytical Solution for Probabilistic Guarantees of Reservation Based Soft Real--Time Systems

OpenAIRE

Palopoli, Luigi; Fontanelli, Daniele; Abeni, Luca; Villalba Frias, Bernardo

2015-01-01

We show a methodology for the computation of the probability of deadline miss for a periodic real-time task scheduled by a resource reservation algorithm. We propose a modelling technique for the system that reduces the computation of such a probability to that of the steady state probability of an infinite state Discrete Time Markov Chain with a periodic structure. This structure is exploited to develop an efficient numeric solution where different accuracy/computation time trade-offs can be...

Compact tokamak reactors part 2 (numerical results)

International Nuclear Information System (INIS)

Wiley, J.C.; Wootton, A.J.; Ross, D.W.

1996-01-01

The authors describe a numerical optimization scheme for fusion reactors. The particular application described is to find the smallest copper coil spherical tokamak, although the numerical scheme is sufficiently general to allow many other problems to be solved. The solution to the steady state energy balance is found by first selecting the fixed variables. The range of all remaining variables is then selected, except for the temperature. Within the specified ranges, the temperature which satisfies the power balance is then found. Tests are applied to determine that remaining constraints are satisfied, and the acceptable results then stored. Results are presented for a range of auxiliary current drive efficiencies and different scaling relationships; for the range of variables chosen the machine encompassing volume increases or remains approximately unchanged as the aspect ratio is reduced

Efficient Numerical Solution of Coupled Radial Differential Equations in Multichannel Scattering Problems

International Nuclear Information System (INIS)

Houfek, Karel

2008-01-01

Numerical solution of coupled radial differential equations which are encountered in multichannel scattering problems is presented. Numerical approach is based on the combination of the exterior complex scaling method and the finite-elements method with the discrete variable representation. This method can be used not only to solve multichannel scattering problem but also to find bound states and resonance positions and widths directly by diagonalization of the corresponding complex scaled Hamiltonian. Efficiency and accuracy of this method is demonstrated on an analytically solvable two-channel problem.

Strain gradient effects on steady state crack growth in rate-sensitive materials

DEFF Research Database (Denmark)

Nielsen, Kim Lau; Niordson, Christian Frithiof; Hutchinson, John W.

2012-01-01

, a characteristic velocity, at which the toughness becomes independent of the rate-sensitivity, has been observed. It is the aim to bring forward a similar characteristic velocity for the current strain gradient visco-plastic model, as-well as to signify its use in future visco-plastic material modeling.......Steady state crack propagation produce substantial plastic strain gradients near the tip, which are accompanied by a high density of geometrically necessary dislocations and additional local strain hardening. Here, the objective is to study these gradient effects on Mode I toughness...... of a homogeneous rate-sensitive metal, using a higher order plasticity theory. Throughout, emphasis is on the toughness rate-sensitivity, as a recent numerical study of a conventional material (no gradient effects) has indicated a significant influence of both strain rate hardening and crack tip velocity. Moreover...

A steady-state stomatal model of balanced leaf gas exchange, hydraulics and maximal source-sink flux.

Science.gov (United States)

Hölttä, Teemu; Lintunen, Anna; Chan, Tommy; Mäkelä, Annikki; Nikinmaa, Eero

2017-07-01

Trees must simultaneously balance their CO2 uptake rate via stomata, photosynthesis, the transport rate of sugars and rate of sugar utilization in sinks while maintaining a favourable water and carbon balance. We demonstrate using a numerical model that it is possible to understand stomatal functioning from the viewpoint of maximizing the simultaneous photosynthetic production, phloem transport and sink sugar utilization rate under the limitation that the transpiration-driven hydrostatic pressure gradient sets for those processes. A key feature in our model is that non-stomatal limitations to photosynthesis increase with decreasing leaf water potential and/or increasing leaf sugar concentration and are thus coupled to stomatal conductance. Maximizing the photosynthetic production rate using a numerical steady-state model leads to stomatal behaviour that is able to reproduce the well-known trends of stomatal behaviour in response to, e.g., light, vapour concentration difference, ambient CO2 concentration, soil water status, sink strength and xylem and phloem hydraulic conductance. We show that our results for stomatal behaviour are very similar to the solutions given by the earlier models of stomatal conductance derived solely from gas exchange considerations. Our modelling results also demonstrate how the 'marginal cost of water' in the unified stomatal conductance model and the optimal stomatal model could be related to plant structural and physiological traits, most importantly, the soil-to-leaf hydraulic conductance and soil moisture. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Pre-steady-state Kinetics for Hydrolysis of Insoluble Cellulose by Cellobiohydrolase Cel7A

DEFF Research Database (Denmark)

Cruys-Bagger, Nicolaj; Olsen, Jens Elmerdahl; Præstgaard, Eigil

2012-01-01

The transient kinetic behavior of enzyme reactions prior to the establishment of steady state is a major source of mechanistic information, yet this approach has not been utilized for cellulases acting on their natural substrate, insoluble cellulose. Here, we elucidate the pre-steady-state regime...... for the exo-acting cellulase Cel7A using amperometric biosensors and an explicit model for processive hydrolysis of cellulose. This analysis allows the identification of a pseudo-steady-state period and quantification of a processivity number as well as rate constants for the formation of a threaded enzyme...... to unveil fundamental reasons for the distinctive variability in hydrolytic activity found in different cellulase-substrate systems....

Dust remobilization in fusion plasmas under steady state conditions

NARCIS (Netherlands)

Tolias, P.; Ratynskaia, S.; de Angeli, M.; De Temmerman, G.; Ripamonti, D.; Riva, G.; I. Bykov,; Shalpegin, A.; Vignitchouk, L.; Brochard, F.; Bystrov, K.; Bardin, S.; Litnovsky, A.

2016-01-01

The first combined experimental and theoretical studies of dust remobilization by plasma forces are reported. The main theoretical aspects of remobilization in fusion devices under steady state conditions are analyzed. In particular, the dominant role of adhesive forces is highlighted and generic

Combined Steady-State and Dynamic Heat Exchanger Experiment

Science.gov (United States)

Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

2009-01-01

This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…

Nonlinear steady-state coupling of LH waves

International Nuclear Information System (INIS)

Ko, K.; Krapchev, V.B.

1981-02-01

The coupling of lower hybrid waves at the plasma edge by a two waveguide array with self-consistent density modulation is solved numerically. For a linear density profile, the governing nonlinear Klein-Gordon equation for the electric field can be written as a system of nonlinearly modified Airy equations in Fourier k/sub z/-space. Numerical solutions to the nonlinear system satisfying radiation condition are obtained. Spectra broadening and modifications to resonance cone trajectories are observed with increase of incident power

Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

Science.gov (United States)

Yeh, Wei-Ting; Chen, Hsuan-Yi

2016-05-01

A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

Theory of minimum dissipation of energy for the steady state

International Nuclear Information System (INIS)

Chu, T.K.

1992-02-01

The magnetic configuration of an inductively driven steady-state plasma bounded by a surface (or two adjacent surfaces) on which B·n = 0 is force-free: ∇xB = 2αB, where α is a constant, in time and in space. α is the ratio of the Poynting flux to the magnetic helicity flux at the boundary. It is also the ratio of the dissipative rates of the magnetic energy to the magnetic helicity in the plasma. The spatial extent of the configuration is noninfinitesimal. This global constraint is a result of the requirement that, for a steady-state plasma, the rate of change of the vector potential, ∂A/∂t, is constant in time and uniform in space

Monotone numerical methods for finite-state mean-field games

KAUST Repository

Gomes, Diogo A.; Saude, Joao

2017-01-01

Here, we develop numerical methods for finite-state mean-field games (MFGs) that satisfy a monotonicity condition. MFGs are determined by a system of differential equations with initial and terminal boundary conditions. These non-standard conditions are the main difficulty in the numerical approximation of solutions. Using the monotonicity condition, we build a flow that is a contraction and whose fixed points solve the MFG, both for stationary and time-dependent problems. We illustrate our methods in a MFG modeling the paradigm-shift problem.

Monotone numerical methods for finite-state mean-field games

KAUST Repository

Gomes, Diogo A.

2017-04-29

Here, we develop numerical methods for finite-state mean-field games (MFGs) that satisfy a monotonicity condition. MFGs are determined by a system of differential equations with initial and terminal boundary conditions. These non-standard conditions are the main difficulty in the numerical approximation of solutions. Using the monotonicity condition, we build a flow that is a contraction and whose fixed points solve the MFG, both for stationary and time-dependent problems. We illustrate our methods in a MFG modeling the paradigm-shift problem.

Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations

Directory of Open Access Journals (Sweden)

D. Pumo

2008-02-01

Full Text Available The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from a stochastic differential equation describing the soil water balance, where the unknown quantity, the soil moisture, depends both on spaces and time. Most of the solutions existing in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the same problem by subtracting generalities from it.

The steady-state hypothesis, appears perfectly applicable in arid and semiarid climatic areas like those of African's or middle American's savannas, but it seems to be no more valid in areas with Mediterranean climate, where, notoriously, the wet season foregoes the growing season, recharging water into the soil. This moisture stored at the beginning of the growing season (known as soil moisture initial condition has a great importance, especially for deep-rooted vegetation, by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during the first period of the same season.

The aim of this paper is to analyze the soil moisture dynamics using a simple non-steady numerical ecohydrological model. The numerical model here proposed is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climates and soils in steady-state conditions; consequently it can be used to compute both the soil moisture time-profile and the vegetation static water stress time-profile in non-steady conditions.

Here the differences between the steady-analytical and the non-steady numerical probability density functions are analyzed, showing how the proposed numerical model is able to capture the effects of winter recharge on the soil moisture. The dynamic

Integration of steady-state and temporal gene expression data for the inference of gene regulatory networks.

Science.gov (United States)

Wang, Yi Kan; Hurley, Daniel G; Schnell, Santiago; Print, Cristin G; Crampin, Edmund J

2013-01-01

We develop a new regression algorithm, cMIKANA, for inference of gene regulatory networks from combinations of steady-state and time-series gene expression data. Using simulated gene expression datasets to assess the accuracy of reconstructing gene regulatory networks, we show that steady-state and time-series data sets can successfully be combined to identify gene regulatory interactions using the new algorithm. Inferring gene networks from combined data sets was found to be advantageous when using noisy measurements collected with either lower sampling rates or a limited number of experimental replicates. We illustrate our method by applying it to a microarray gene expression dataset from human umbilical vein endothelial cells (HUVECs) which combines time series data from treatment with growth factor TNF and steady state data from siRNA knockdown treatments. Our results suggest that the combination of steady-state and time-series datasets may provide better prediction of RNA-to-RNA interactions, and may also reveal biological features that cannot be identified from dynamic or steady state information alone. Finally, we consider the experimental design of genomics experiments for gene regulatory network inference and show that network inference can be improved by incorporating steady-state measurements with time-series data.

Numerical identifiability of the parameters of induction machines

Energy Technology Data Exchange (ETDEWEB)

Corcoles, F.; Pedra, J.; Salichs, M. [Dep. d' Eng. Electrica ETSEIB. UPC, Barcelona (Spain)

2000-08-01

This paper analyses the numerical identifiability of the electrical parameters of induction machines. Relations between parameters and the impossibility to estimate all of them - when only external measures are used: voltage, current, speed and torque - are shown. Formulations of the single and double-cage induction machine, with and without core losses in both models, are developed. The proposed solution is the formulation of machine equations by using the minimum number of parameters (which are identifiable parameters). As an application example, the parameters of a double-cage induction machine are identified using steady-state measurements corresponding to different angular speeds. (orig.)

Numerical Study on Deformation and Interior Flow of a Droplet Suspended in Viscous Liquid under Steady Electric Fields

Directory of Open Access Journals (Sweden)

Zhentao Wang

2014-07-01

Full Text Available A model based on the volume of fluid (VOF method and leaky dielectric theory is established to predict the deformation and internal flow of the droplet suspended in another vicious fluid under the influence of the electric field. Through coupling with hydrodynamics and electrostatics, the rate of deformation and internal flow of the single droplet are simulated and obtained under the different operating parameters. The calculated results show that the direction of deformation and internal flow depends on the physical properties of fluids. The numerical results are compared with Taylor's theory and experimental results by Torza et al. When the rate of deformation is small, the numerical results are consistent with theory and experimental results, and when the rate is large the numerical results are consistent with experimental results but are different from Taylor's theory. In addition, fluid viscosity hardly affects the deformation rate and mainly dominates the deformation velocity. For high viscosity droplet spends more time to attain the steady state. The conductivity ratio and permittivity ratio of two different liquids affect the direction of deformation. When fluid electric properties change, the charge distribution at the interface is various, which leads to the droplet different deformation shapes.

Semi-analytical solutions of the Schnakenberg model of a reaction-diffusion cell with feedback

Science.gov (United States)

Al Noufaey, K. S.

2018-06-01

This paper considers the application of a semi-analytical method to the Schnakenberg model of a reaction-diffusion cell. The semi-analytical method is based on the Galerkin method which approximates the original governing partial differential equations as a system of ordinary differential equations. Steady-state curves, bifurcation diagrams and the region of parameter space in which Hopf bifurcations occur are presented for semi-analytical solutions and the numerical solution. The effect of feedback control, via altering various concentrations in the boundary reservoirs in response to concentrations in the cell centre, is examined. It is shown that increasing the magnitude of feedback leads to destabilization of the system, whereas decreasing this parameter to negative values of large magnitude stabilizes the system. The semi-analytical solutions agree well with numerical solutions of the governing equations.

Numerically satisfactory solutions of Kummer recurrence relations

NARCIS (Netherlands)

J. Segura (Javier); N.M. Temme (Nico)

2008-01-01

textabstractPairs of numerically satisfactory solutions as $n\\rightarrow \\infty$ for the three-term recurrence relations satisfied by the families of functions $_1\\mbox{F}_1(a+\\epsilon_1 n; b +\\epsilon_2 n;z)$, $\\epsilon_i \\in {\\mathbb Z}$, are given. It is proved that minimal solutions always

Volume of the steady-state space of financial flows in a monetary stock-flow-consistent model

Science.gov (United States)

Hazan, Aurélien

2017-05-01

We show that a steady-state stock-flow consistent macro-economic model can be represented as a Constraint Satisfaction Problem (CSP). The set of solutions is a polytope, which volume depends on the constraints applied and reveals the potential fragility of the economic circuit, with no need to study the dynamics. Several methods to compute the volume are compared, inspired by operations research methods and the analysis of metabolic networks, both exact and approximate. We also introduce a random transaction matrix, and study the particular case of linear flows with respect to money stocks.

Numerical simulation on coolant flow and heat transfer in core

International Nuclear Information System (INIS)

Yao Zhaohui; Wang Xuefang; Shen Mengyu

1997-01-01

To simulate the coolant flow and the heat transfer characteristics of a core, a computer code, THAPMA (Thermal Hydraulic Analysis Porous Medium Analysis) has been developed. In THAPMA code, conservation equations are based on a porous-medium formulation, which uses four parameters, i.e, volume porosity, directional surface porosity, distributed resistance, and distributed heat source (sink), to model the effects of fuel rods and other internal solid structures on flow and heat transfer. Because the scheme and the solution are very important in accuracy and speed of calculation, a new difference scheme (WSUC) has been used in the energy equation, and a modified PISO solution method have been employed to simulate the steady/transient states. The code has been proved reliable and can effectively solve the transient state problem by several numerical tests. According to the design of Qinshan NPP-II, the flow and heat transfer phenomena in reactor core have been numerically simulated. The distributions of the velocity and the temperature can provide a theoretical basis for core design and safety analysis

Numerical benchmarking of SPEEDUP trademark against point kinetics solutions

International Nuclear Information System (INIS)

Gregory, M.V.

1993-02-01

SPEEDUP trademark is a state-of-the-art, dynamic, chemical process modeling package offered by Aspen Technology. In anticipation of new customers' needs for new analytical tools to support the site's waste management activities, SRTC has secured a multiple-user license to SPEEDUP trademark. In order to verify both the installation and mathematical correctness of the algorithms in SPEEDUP trademark, we have performed several numerical benchmarking calculations. These calculations are the first steps in establishing an on-site quality assurance pedigree for SPEEDUP trademark. The benchmark calculations consisted of SPEEDUP trademark Version 5.3L representations of five neutron kinetics benchmarks (each a mathematically stiff system of seven coupled ordinary differential equations), whose exact solutions are documented in the open literature. In all cases, SPEEDUP trademark solutions to be in excellent agreement with the reference solutions. A minor peculiarity in dealing with a non-existent discontinuity in the OPERATION section of the model made itself evident

Constructing exact symmetric informationally complete measurements from numerical solutions

Science.gov (United States)

Appleby, Marcus; Chien, Tuan-Yow; Flammia, Steven; Waldron, Shayne

2018-04-01

Recently, several intriguing conjectures have been proposed connecting symmetric informationally complete quantum measurements (SIC POVMs, or SICs) and algebraic number theory. These conjectures relate the SICs to their minimal defining algebraic number field. Testing or sharpening these conjectures requires that the SICs are expressed exactly, rather than as numerical approximations. While many exact solutions of SICs have been constructed previously using Gröbner bases, this method has probably been taken as far as is possible with current computer technology (except in special cases where there are additional symmetries). Here, we describe a method for converting high-precision numerical solutions into exact ones using an integer relation algorithm in conjunction with the Galois symmetries of an SIC. Using this method, we have calculated 69 new exact solutions, including nine new dimensions, where previously only numerical solutions were known—which more than triples the number of known exact solutions. In some cases, the solutions require number fields with degrees as high as 12 288. We use these solutions to confirm that they obey the number-theoretic conjectures, and address two questions suggested by the previous work.

Analysis on the steady-state coherent synchrotron radiation with strong shielding

International Nuclear Information System (INIS)

Li, R.; Bohn, C.L.; Bisognano, J.J.

1997-01-01

There are several papers concerning shielding of coherent synchrotron radiation (CSR) emitted by a Gaussian line charge on a circular orbit centered between two parallel conducting plates. Previous asymptotic analyses in the frequency domain show that shielded steady-state CSR mainly arises from harmonics in the bunch frequency exceeding the threshold harmonic for satisfying the boundary conditions at the plates. In this paper the authors extend the frequency-domain analysis into the regime of strong shielding, in which the threshold harmonic exceeds the characteristic frequency of the bunch. The result is then compared to the shielded steady-state CSR power obtained using image charges

Steady-state entanglement and thermalization of coupled qubits in two common heat baths

Science.gov (United States)

Hu, Li-Zhen; Man, Zhong-Xiao; Xia, Yun-Jie

2018-03-01

In this work, we study the steady-state entanglement and thermalization of two coupled qubits embedded in two common baths with different temperatures. The common bath is relevant when the two qubits are difficult to be isolated to only contact with their local baths. With the quantum master equation constructed in the eigenstate representation of the coupled qubits, we have demonstrated the variations of steady-state entanglement with respect to various parameters of the qubits' system in both equilibrium and nonequilibrium cases of the baths. The coupling strength and energy detuning of the qubits as well as the temperature gradient of the baths are found to be beneficial to the enhancement of the entanglement. We note a dark state of the qubits that is free from time-evolution and its initial population can greatly influence the steady-state entanglement. By virtues of effective temperatures, we also study the thermalization of the coupled qubits and their variations with energy detuning.

The technology and science of steady-state operation in magnetically confined plasmas

International Nuclear Information System (INIS)

Becoulet, A; Hoang, G T

2008-01-01

The steady-state operation of magnetically confined fusion plasmas is considered as one of the 'grand challenges' of future decades, if not the ultimate goal of the research and development activities towards a new source of energy. Reaching such a goal requires the high-level integration of both science and technology aspects of magnetic fusion into self-consistent plasma regimes in fusion-grade devices. On the physics side, the first constraint addresses the magnetic confinement itself which must be made persistent. This means to either rely on intrinsically steady-state configurations, like the stellarator one, or turn the inductively driven tokamak configuration into a fully non-inductive one, through a mix of additional current sources. The low efficiency of the external current drive methods and the necessity to minimize the re-circulating power claim for a current mix strongly weighted by the internal 'pressure driven' bootstrap current, itself strongly sensitive to the heat and particle transport properties of the plasma. A virtuous circle may form as the heat and particle transport properties are themselves sensitive to the current profile conditions. Note that several other factors, e.g. plasma rotation profile, magneto-hydro-dynamics activity, also influence the equilibrium state. In the present tokamak devices, several examples of such 'advanced tokamak' physics research demonstrate the feasibility of steady-state regimes, though with a number of open questions still under investigation. The modelling activity also progresses quite fast in this domain and supports understanding and extrapolation. This high level of physics sophistication of the plasma scenario however needs to be combined with steady-state technological constraints. The technology constraints for steady-state operation are basically twofold: the specific technologies required to reach the steady-state plasma conditions and the generic technologies linked to the long pulse operation of a

A displacement based FE formulation for steady state problems

NARCIS (Netherlands)

Yu, Y.

2005-01-01

In this thesis a new displacement based formulation is developed for elasto-plastic deformations in steady state problems. In this formulation the displacements are the primary variables, which is in contrast to the more common formulations in terms of the velocities as the primary variables. In a

Dissipative preparation of steady Greenberger-Horne-Zeilinger states for Rydberg atoms with quantum Zeno dynamics

Science.gov (United States)

Shao, X. Q.; Wu, J. H.; Yi, X. X.; Long, Gui-Lu

2017-12-01

Inspired by a recent work [F. Reiter, D. Reeb, and A. S. Sørensen, Phys. Rev. Lett. 117, 040501 (2016), 10.1103/PhysRevLett.117.040501], we present a simplified proposal for dissipatively preparing a Greenberger-Horne-Zeilinger (GHZ) state of three Rydberg atoms in a cavity. The Z pumping is implemented under the action of the spontaneous emission of Λ -type atoms and the quantum Zeno dynamics induced by strong continuous coupling. In the meantime, a dissipative Rydberg pumping breaks up the stability of the state | GHZ+〉 in the process of Z pumping, making | GHZ-〉 the unique steady state of the system. Compared with the former scheme, the number of driving fields acting on atoms is greatly reduced and only a single-mode cavity is required. The numerical simulation of the full master equation reveals that a high fidelity ˜98 % can be obtained with the currently achievable parameters in the Rydberg-atom-cavity system.

A novel multivariate STeady-state index during general ANesthesia (STAN).

Science.gov (United States)

Castro, Ana; de Almeida, Fernando Gomes; Amorim, Pedro; Nunes, Catarina S

2017-08-01

The assessment of the adequacy of general anesthesia for surgery, namely the nociception/anti-nociception balance, has received wide attention from the scientific community. Monitoring systems based on the frontal EEG/EMG, or autonomic state reactions (e.g. heart rate and blood pressure) have been developed aiming to objectively assess this balance. In this study a new multivariate indicator of patients' steady-state during anesthesia (STAN) is proposed, based on wavelet analysis of signals linked to noxious activation. A clinical protocol was designed to analyze precise noxious stimuli (laryngoscopy/intubation, tetanic, and incision), under three different analgesic doses; patients were randomized to receive either remifentanil 2.0, 3.0 or 4.0 ng/ml. ECG, PPG, BP, BIS, EMG and [Formula: see text] were continuously recorded. ECG, PPG and BP were processed to extract beat-to-beat information, and [Formula: see text] curve used to estimate the respiration rate. A combined steady-state index based on wavelet analysis of these variables, was applied and compared between the three study groups and stimuli (Wilcoxon signed ranks, Kruskal-Wallis and Mann-Whitney tests). Following institutional approval and signing the informed consent thirty four patients were enrolled in this study (3 excluded due to signal loss during data collection). The BIS index of the EEG, frontal EMG, heart rate, BP, and PPG wave amplitude changed in response to different noxious stimuli. Laryngoscopy/intubation was the stimulus with the more pronounced response [Formula: see text]. These variables were used in the construction of the combined index STAN; STAN responded adequately to noxious stimuli, with a more pronounced response to laryngoscopy/intubation (18.5-43.1 %, [Formula: see text]), and the attenuation provided by the analgesic, detecting steady-state periods in the different physiological signals analyzed (approximately 50 % of the total study time). A new multivariate approach for

From magma-poor Ocean Continent Transitions to steady state oceanic spreading: the balance between tectonic and magmatic processes

Science.gov (United States)

Gillard, Morgane; Manatschal, Gianreto; Autin, Julia; Decarlis, Alessandro; Sauter, Daniel

2016-04-01

The evolution of magma-poor rifted margins is linked to the development of a transition zone whose basement is neither clearly continental nor oceanic. The development of this Ocean-Continent Transition (OCT) is generally associated to the exhumation of serpentinized mantle along one or several detachment faults. That model is supported by numerous observations (IODP wells, dredges, fossil margins) and by numerical modelling. However, if the initiation of detachment faults in a magma-poor setting tends to be better understood by numerous studies in various area, the transition with the first steady state oceanic crust and the associated processes remain enigmatic and poorly studied. Indeed, this latest stage of evolution appears to be extremely gradual and involves strong interactions between tectonic processes and magmatism. Contrary to the proximal part of the exhumed domain where we can observe magmatic activity linked to the exhumation process (exhumation of gabbros, small amount of basalts above the exhumed mantle), in the most distal part the magmatic system appears to be independent and more active. In particular, we can observe large amounts of extrusive material above a previously exhumed and faulted basement (e.g. Alps, Australia-Antarctica margins). It seems that some faults can play the role of feeder systems for the magma in this area. Magmatic underplating is also important, as suggested by basement uplift and anomalously thick crust (e.g. East Indian margin). It results that the transition with the first steady state oceanic crust is marked by the presence of a hybrid basement, composed by exhumed mantle and magmatic material, whose formation is linked to several tectonic and magmatic events. One could argue that this basement is not clearly different from an oceanic basement. However, we consider that true, steady state oceanic crust only exists, if the entire rock association forming the crust is created during a single event, at a localized

Fundamental structure of steady plastic shock waves in metals

OpenAIRE

Molinari, A.; Ravichandran, G.

2004-01-01

The propagation of steady plane shock waves in metallic materials is considered. Following the constitutive framework adopted by R. J. Clifton [Shock Waves and the Mechanical Properties of Solids, edited by J. J. Burke and V. Weiss (Syracuse University Press, Syracuse, N.Y., 1971), p. 73] for analyzing elastic–plastic transient waves, an analytical solution of the steady state propagation of plastic shocks is proposed. The problem is formulated in a Lagrangian setting appropriate for large de...

Nodal methods in numerical reactor calculations

International Nuclear Information System (INIS)

Hennart, J.P.; Valle, E. del

2004-01-01

The present work describes the antecedents, developments and applications started in 1972 with Prof. Hennart who was invited to be part of the staff of the Nuclear Engineering Department at the School of Physics and Mathematics of the National Polytechnic Institute. Since that time and up to 1981, several master theses based on classical finite element methods were developed with applications in point kinetics and in the steady state as well as the time dependent multigroup diffusion equations. After this period the emphasis moved to nodal finite elements in 1, 2 and 3D cartesian geometries. All the thesis were devoted to the numerical solution of the neutron multigroup diffusion and transport equations, few of them including the time dependence, most of them related with steady state diffusion equations. The main contributions were as follows: high order nodal schemes for the primal and mixed forms of the diffusion equations, block-centered finite-differences methods, post-processing, composite nodal finite elements for hexagons, and weakly and strongly discontinuous schemes for the transport equation. Some of these are now being used by several researchers involved in nuclear fuel management. (Author)

Nodal methods in numerical reactor calculations

Energy Technology Data Exchange (ETDEWEB)

Hennart, J P [UNAM, IIMAS, A.P. 20-726, 01000 Mexico D.F. (Mexico); Valle, E del [National Polytechnic Institute, School of Physics and Mathematics, Department of Nuclear Engineering, Mexico, D.F. (Mexico)

2004-07-01

The present work describes the antecedents, developments and applications started in 1972 with Prof. Hennart who was invited to be part of the staff of the Nuclear Engineering Department at the School of Physics and Mathematics of the National Polytechnic Institute. Since that time and up to 1981, several master theses based on classical finite element methods were developed with applications in point kinetics and in the steady state as well as the time dependent multigroup diffusion equations. After this period the emphasis moved to nodal finite elements in 1, 2 and 3D cartesian geometries. All the thesis were devoted to the numerical solution of the neutron multigroup diffusion and transport equations, few of them including the time dependence, most of them related with steady state diffusion equations. The main contributions were as follows: high order nodal schemes for the primal and mixed forms of the diffusion equations, block-centered finite-differences methods, post-processing, composite nodal finite elements for hexagons, and weakly and strongly discontinuous schemes for the transport equation. Some of these are now being used by several researchers involved in nuclear fuel management. (Author)

Diffusion-driven steady states of the Z-pinch

International Nuclear Information System (INIS)

Lehnert, B.

1988-01-01

Steady states of a Z-pinch where no electric field is imposed along the pinch axis by external means are investigated. In this case, diffusion-driven states become possible when imposed volume sources of particles and heat drive a radial diffusion velocity that, in its turn, generates the electric plasma current. The particle sources can be from pellet injection or a neutral gas blanket, and the heat sources provided by thermonuclear reactions or auxiliary heating. The present analysis and associated kinetic considerations indicate that steady diffusion-driven operation should become possible for certain classes of plasma profiles, without running into singularity problems at the pinch axis. Such operation leads to higher axial currents in a Z-pinch without an axial magnetic field than in a tokamaklike case under similar plasma conditions. The technical difficulty in realizing a volume distribution of particle sinks introduces certain constraints on the plasma and current profiles. This fact has to be taken into account in a stability analysis. Neoclassical or anomalous diffusion will increase the diffusion velocity of the plasma but is not expected to affect the main physical features of the present results

Steady state minority carrier lifetime and defect level occupation in thin film CdTe solar cells

International Nuclear Information System (INIS)

Cheng, Zimeng; Delahoy, Alan E.; Su, Zhaoqian; Chin, Ken K.

2014-01-01

A model consisting of Shockley Read Hall (SRH) recombination under steady state conditions of constant photon injection is proposed in this work to study the steady state minority carrier lifetime in CdS/CdTe thin film solar cells. The SRH recombination rate versus optical injection level is analytically approximated in the junction and neutral regions. In the neutral region, it is found that the recombination rate through certain defect levels has one constant value under lower optical injection conditions and another constant value under higher optical injection conditions with the transition occurring at a critical optical injection level. By simultaneously solving the equations of charge neutrality, charge conservation and SRH recombination in the neutral region, it is found that the compensation of doping and the reduction of minority carrier lifetime by donors in the p-type semiconductor can each be remedied by optical injection. It is also demonstrated that this optical-dependent SRH recombination is significant in large bandgap thin films. The measured minority carrier diffusion length in a CdS/CdTe solar cells, as determined from the steady-state photo-generated carrier collection efficiency, shows the predicted transition of minority carrier lifetime versus optical injection level. A numerical fitting of the indirectly-measured minority carrier lifetime by assuming the minority carrier mobility gives a non-intuitive picture of the p–n junction with a low free hole concentration but a narrow depletion region width. - Highlights: • Minority carrier lifetimes under different optical injections are solved. • Simplifications of Shockley–Read–Hall recombination equation are discussed. • The compensation of donor can be remedied with optical injection. • The recombination efficiency of donor can be remedied with optical injection. • The minority carrier lifetime transition under illumination was experimentally observed

Numerical solution of Boltzmann's equation

International Nuclear Information System (INIS)

Sod, G.A.

1976-04-01

The numerical solution of Boltzmann's equation is considered for a gas model consisting of rigid spheres by means of Hilbert's expansion. If only the first two terms of the expansion are retained, Boltzmann's equation reduces to the Boltzmann-Hilbert integral equation. Successive terms in the Hilbert expansion are obtained by solving the same integral equation with a different source term. The Boltzmann-Hilbert integral equation is solved by a new very fast numerical method. The success of the method rests upon the simultaneous use of four judiciously chosen expansions; Hilbert's expansion for the distribution function, another expansion of the distribution function in terms of Hermite polynomials, the expansion of the kernel in terms of the eigenvalues and eigenfunctions of the Hilbert operator, and an expansion involved in solving a system of linear equations through a singular value decomposition. The numerical method is applied to the study of the shock structure in one space dimension. Numerical results are presented for Mach numbers of 1.1 and 1.6. 94 refs, 7 tables, 1 fig

Asymptotic solution for heat convection-radiation equation

Energy Technology Data Exchange (ETDEWEB)

Mabood, Fazle; Ismail, Ahmad Izani Md [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Khan, Waqar A. [Department of Engineering Sciences, National University of Sciences and Technology, PN Engineering College, Karachi, 75350 (Pakistan)

2014-07-10

In this paper, we employ a new approximate analytical method called the optimal homotopy asymptotic method (OHAM) to solve steady state heat transfer problem in slabs. The heat transfer problem is modeled using nonlinear two-point boundary value problem. Using OHAM, we obtained the approximate analytical solution for dimensionless temperature with different values of a parameter ε. Further, the OHAM results for dimensionless temperature have been presented graphically and in tabular form. Comparison has been provided with existing results from the use of homotopy perturbation method, perturbation method and numerical method. For numerical results, we used Runge-Kutta Fehlberg fourth-fifth order method. It was found that OHAM produces better approximate analytical solutions than those which are obtained by homotopy perturbation and perturbation methods, in the sense of closer agreement with results obtained from the use of Runge-Kutta Fehlberg fourth-fifth order method.

Steady squares and hexagons on a subcritical ramp

International Nuclear Information System (INIS)

Hoyle, R.B.

1995-01-01

Steady squares and hexagons on a subcritical ramp are studied, both analytically and numerically, within the framework of the lowest-order amplitude equations. On the subcritical ramp, the external stress or control parameter varies continuously in space from subcritical to supercritical values. At the subcritical end of the ramp, pattern formation is suppressed, and patterns fade away into the conduction solution. It is shown that three-dimensional patterns may change shape on a subcritical ramp. A square pattern becomes a pattern of rolls as it fades, with the roll axes aligned in the direction orthogonal to that in which the control parameter varies. Hexagons in systems with horizontal midplane symmetry become a pattern of rectangles before reaching the conduction solution. There is a suggestion that hexagons in systems which lack this symmetry might fade away through a roll pattern. Numerical simulations are used to illustrate these phenomena

Experimental and theoretical comparison of fuel temperature and bulk coolant characteristics in the Oregon State TRIGA reactor during steady state operation

Energy Technology Data Exchange (ETDEWEB)

Marcum, W.R., E-mail: marcumw@engr.orst.ed [Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97330 (United States); Woods, B.G.; Reese, S.R. [Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97330 (United States)

2010-01-15

In September of 2008 Oregon State University (OSU) completed its core conversion analysis as part of the Reduced Enrichment for Research and Test Reactors (RERTR) Program. Experimental bulk coolant temperatures were collected in various locations throughout the Oregon State TRIGA Reactor (OSTR) core in order to supplement the validity of the numerical thermal hydraulic results produced in RELAP5-3D Version 2.4.2. Axial bulk coolant temperature distributions were collected by acquiring discrete thermocouple measurements in individual subchannel locations during steady state operation at 1.0 MW{sub th}. The experimental axial temperature distribution collected was compared to one-channel, two-channel, and eight-channel RELAP5-3D models and found to match within 11.94%, 11.69%, and 8.78%, respectively, on average. Comparisons to similar studies were made based on a dimensional analysis of fluid body forces in the discrete core locations, indicating that the chosen approach produces conservative results for use in the OSTR safety analysis.

A Data Filter for Identifying Steady-State Operating Points in Engine Flight Data for Condition Monitoring Applications

Science.gov (United States)

Simon, Donald L.; Litt, Jonathan S.

2010-01-01

This paper presents an algorithm that automatically identifies and extracts steady-state engine operating points from engine flight data. It calculates the mean and standard deviation of select parameters contained in the incoming flight data stream. If the standard deviation of the data falls below defined constraints, the engine is assumed to be at a steady-state operating point, and the mean measurement data at that point are archived for subsequent condition monitoring purposes. The fundamental design of the steady-state data filter is completely generic and applicable for any dynamic system. Additional domain-specific logic constraints are applied to reduce data outliers and variance within the collected steady-state data. The filter is designed for on-line real-time processing of streaming data as opposed to post-processing of the data in batch mode. Results of applying the steady-state data filter to recorded helicopter engine flight data are shown, demonstrating its utility for engine condition monitoring applications.

Comparison of pulsed three-dimensional CEST acquisition schemes at 7 tesla : steady state versus pseudosteady state

NARCIS (Netherlands)

Khlebnikov, Vitaly; Geades, Nicolas; Klomp, DWJ; Hoogduin, Hans; Gowland, Penny; Mougin, Olivier

PURPOSE: To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time. METHODS: Both schemes were optimized for maximum sensitivity to amide

Analytical solution and numerical study on water hammer in a pipeline closed with an elastically attached valve

Science.gov (United States)

Henclik, Sławomir

2018-03-01

The influence of dynamic fluid-structure interaction (FSI) onto the course of water hammer (WH) can be significant in non-rigid pipeline systems. The essence of this effect is the dynamic transfer of liquid energy to the pipeline structure and back, which is important for elastic structures and can be negligible for rigid ones. In the paper a special model of such behavior is analyzed. A straight pipeline with a steady flow, fixed to the floor with several rigid supports is assumed. The transient is generated by a quickly closed valve installed at the end of the pipeline. FSI effects are assumed to be present mainly at the valve which is fixed with a spring dash-pot attachment. Analysis of WH runs, especially transient pressure changes, for various stiffness and damping parameters of the spring dash-pot valve attachment is presented in the paper. The solutions are found analytically and numerically. Numerical results have been computed with the use of an own computer program developed on the basis of the four equation model of WH-FSI and the specific boundary conditions formulated at the valve. Analytical solutions have been found with the separation of variables method for slightly simplified assumptions. Damping at the dash-pot is taken into account within the numerical study. The influence of valve attachment parameters onto the WH courses was discovered and it was found the transient amplitudes can be reduced. Such a system, elastically attached shut-off valve in a pipeline or other, equivalent design can be a real solution applicable in practice.

Tore-Supra infrared thermography system, a real steady-state diagnostic

International Nuclear Information System (INIS)

Guilhem, D.; Bondil, J.L.; Bertrand, B.; Desgranges, C.; Lipa, M.; Messina, P.; Missirlian, M.; Portafaix, C.; Reichle, R.; Roche, H.; Saille, A.

2005-01-01

Tore-Supra Tokamak (I p = 1.5 MA, B t = 4 T) has been constructed with a steady-state magnetic field using super-conducting magnets and water-cooled plasma facing components (PFCs) for high-performance long pulse plasma discharges. When not actively cooled, plasma facing components can only accumulate a limited amount of energy since the temperature increases continuously during the discharge until radiation cooling equals the incoming heat flux. Such an environment is found in the JET Tokamak [JET Team, IAEA-CN-60/A1-3, Seville, 1994] and on TRIAM [M. Sakamoto, H. Nakashima, S. Kawasaki, A. Iyomasa, S.V. Kulkarni, M. Hasegawa, E. Jotaki, H. Zushi, K. Nakamura, K. Hanada, S. Itoh, Static and dynamic properties of wall recycling in TRIAM-1M, J. Nucl. Mater. 313-316 (2003) 519-523] [Y. Kamada, et al., Nucl. Fusion 3 (1999) 1845]. In Tore-Supra, the surface temperature of the actively cooled plasma facing components reach steady state within a second. We present here the Tore-Supra thermographic system, made of seven endoscope bodies equipped so far with eight infrared (IR) cameras. It has to be noted that this diagnostic is the first diagnostic to be actively cooled, as required for steady state. The main purpose of such a diagnostic is to prevent the plasma to damage the actively cooled plasma facing components (ACPFCs), which consist of the toroidal pumped limiter (TPL), 7 m 2 , and of five radio-frequency antennae, 1.5 m 2 each

NESTLE: Few-group neutron diffusion equation solver utilizing the nodal expansion method for eigenvalue, adjoint, fixed-source steady-state and transient problems

International Nuclear Information System (INIS)

Turinsky, P.J.; Al-Chalabi, R.M.K.; Engrand, P.; Sarsour, H.N.; Faure, F.X.; Guo, W.

1994-06-01

NESTLE is a FORTRAN77 code that solves the few-group neutron diffusion equation utilizing the Nodal Expansion Method (NEM). NESTLE can solve the eigenvalue (criticality); eigenvalue adjoint; external fixed-source steady-state; or external fixed-source. or eigenvalue initiated transient problems. The code name NESTLE originates from the multi-problem solution capability, abbreviating Nodal Eigenvalue, Steady-state, Transient, Le core Evaluator. The eigenvalue problem allows criticality searches to be completed, and the external fixed-source steady-state problem can search to achieve a specified power level. Transient problems model delayed neutrons via precursor groups. Several core properties can be input as time dependent. Two or four energy groups can be utilized, with all energy groups being thermal groups (i.e. upscatter exits) if desired. Core geometries modelled include Cartesian and Hexagonal. Three, two and one dimensional models can be utilized with various symmetries. The non-linear iterative strategy associated with the NEM method is employed. An advantage of the non-linear iterative strategy is that NSTLE can be utilized to solve either the nodal or Finite Difference Method representation of the few-group neutron diffusion equation

Comparison of Steady-State SVC Models in Load Flow Calculations

DEFF Research Database (Denmark)

Chen, Peiyuan; Chen, Zhe; Bak-Jensen, Birgitte

2008-01-01

This paper compares in a load flow calculation three existing steady-state models of static var compensator (SVC), i.e. the generator-fixed susceptance model, the total susceptance model and the firing angle model. The comparison is made in terms of the voltage at the SVC regulated bus, equivalent...... SVC susceptance at the fundamental frequency and the load flow convergence rate both when SVC is operating within and on the limits. The latter two models give inaccurate results of the equivalent SVC susceptance as compared to the generator model due to the assumption of constant voltage when the SVC...... is operating within the limits. This may underestimate or overestimate the SVC regulating capability. Two modified models are proposed to improve the SVC regulated voltage according to its steady-state characteristic. The simulation results of the two modified models show the improved accuracy...

Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

Science.gov (United States)

Petrone, Chiara Maria; Braschi, Eleonora; Francalanci, Lorella; Casalini, Martina; Tommasini, Simone

2018-06-01

Steady-state volcanic activity implies equilibrium between the rate of magma replenishment and eruption of compositionally homogeneous magmas, lasting for tens to thousands of years in an open conduit system. The Present-day activity of Stromboli volcano (Aeolian Islands, Southern Italy) has long been recognised as typical of a steady-state volcano, with a shallow magmatic reservoir (highly porphyritic or hp-magma) continuously refilled by more mafic magma (with low phenocryst content or lp-magma) at a constant rate and accompanied by mixing, crystallisation and eruption. Our aim is to clarify the timescale and dynamics of the plumbing system at the establishment of the Present-day steady-state activity (volcanoes.

Comparing Non-Steady State Emissions under Start-Up and Shut-Down Operating Conditions with Steady State Emissions for Several Industrial Sectors: A Literature Review

Directory of Open Access Journals (Sweden)

Juwairia Obaid

2017-02-01

Full Text Available This study investigates the emissions of various industrial facilities under start-up, shut-down, and normal operations. The industries that have been investigated include power and/or heat generation, energy-from-waste generation, nuclear power generation, sulphuric acid production, ethylene production, petrochemical production, and waste incineration. The study investigated multiple facilities worldwide for each of these industrial categories. The different potential contaminants characteristic of each industry type have been investigated and the emissions of these contaminants under non-steady state have been compared to the steady state emissions. Where available, trends have been developed to identify the circumstances, i.e., the industrial sector and contaminant, under which the assessment and consideration of emissions from start-up and shut-down events is necessary for each industry. These trends differ by industrial sector and contaminant. For example, the study shows that sulphur dioxide (SO2 emissions should be assessed for the start-up operations of sulphuric acid production plants, but may not need to be assessed for the start-up operations of a conventional power generation facility. The trends developed as part of this research paper will help air permit applicants to effectively allocate their resources when assessing emissions related to non-steady state operations. Additionally, it will ensure that emissions are assessed for the worst-case scenario. This is especially important when emissions under start-up and shut-down operations have the potential to exceed enforceable emission limits. Thus, assessing emissions for the worst-case scenario can help in preventing the emissions from adversely impacting public health and the environment.

On the analytic solution of the steady flow of a fourth grade fluid

International Nuclear Information System (INIS)

Sajid, M.; Hayat, T.; Asghar, S.

2006-01-01

The steady flow of a fourth grade fluid is a problem belonging to non-Newtonian fluid mechanics and deserves to be more widely studied than it has been to date. In the non-linear regime the literature is scarce. We develop a formulation suitable for solution of hydrodynamic equation containing non-linear rheological effects of fourth grade fluids. The homotopy analysis method (HAM) is used to investigate the flow of a fourth grade fluid past a porous plate. Explicit analytic solution is given. The non-linear effects on the velocity distribution is shown and discussed. Comparison of the present analysis is also made with the existing results in the literature

Development of repetitive railgun pellet accelerator and steady-state pellet supply system

International Nuclear Information System (INIS)

Oda, Y.; Onozuka, M.; Azuma, K.; Kasai, S.; Hasegawa, K.

1995-01-01

A railgun system for repetitive high-speed pellet acceleration and steady-state pellet supply system has been developed and investigated. Using a 2m-long railgun system, the hydrogen pellet was accelerated to 2.6km/sec by the supplied energy of 1.7kJ. It is expected that the hydrogen pellet can be accelerated to 3km/sec using the present pneumatic pellet accelerator and a 2m-long augment railgun. Screw-driven hydrogen-isotope filament extruding system has been fabricated and will be tested to examine its applicability to the steady-state extrusion of the solid hydrogen-isotope filament

Development of repetitive railgun pellet accelerator and steady-state pellet supply system

Energy Technology Data Exchange (ETDEWEB)

Oda, Y.; Onozuka, M.; Azuma, K. [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Kasai, S.; Hasegawa, K. [Japan Atomic Energy Research Inst., Naka (Japan)

1995-12-31

A railgun system for repetitive high-speed pellet acceleration and steady-state pellet supply system has been developed and investigated. Using a 2m-long railgun system, the hydrogen pellet was accelerated to 2.6km/sec by the supplied energy of 1.7kJ. It is expected that the hydrogen pellet can be accelerated to 3km/sec using the present pneumatic pellet accelerator and a 2m-long augment railgun. Screw-driven hydrogen-isotope filament extruding system has been fabricated and will be tested to examine its applicability to the steady-state extrusion of the solid hydrogen-isotope filament.

Local wettability reversal during steady-state two-phase flow in porous media.

Science.gov (United States)

Sinha, Santanu; Grøva, Morten; Ødegården, Torgeir Bryge; Skjetne, Erik; Hansen, Alex

2011-09-01

We study the effect of local wettability reversal on remobilizing immobile fluid clusters in steady-state two-phase flow in porous media. We consider a two-dimensional network model for a porous medium and introduce a wettability alteration mechanism. A qualitative change in the steady-state flow patterns, destabilizing the percolating and trapped clusters, is observed as the system wettability is varied. When capillary forces are strong, a finite wettability alteration is necessary to move the system from a single-phase to a two-phase flow regime. When both phases are mobile, we find a linear relationship between fractional flow and wettability alteration.

An equation oriented approach to steady state flowsheeting of methanol synthesis loop

International Nuclear Information System (INIS)

Fathikalajahi, J.; Baniadam, M.; Rahimpour, M.R.

2008-01-01

An equation-oriented approach was developed for steady state flowsheeting of a commercial methanol plant. The loop consists of fixed bed reactor, flash separator, preheater, coolers, and compressor. For steady sate flowsheeting of the plant mathematical model of reactor and other units are needed. Reactor used in loop is a Lurgi type and its configuration is rather complex. Previously reactor and flash separator are modeled as two important units of plant. The model is based on mass and energy balances in each equipment and utilizing some auxiliary equations such as rate of reaction and thermodynamics model for activity coefficients of liquid. In order to validate the mathematical model for the synthesis loop, some simulation data were performed using operating conditions and characteristics of the commercial plant. The good agreement between the steady state simulation results and the plant data shows the validity of the model

Comparison of Models for the Steady-State Analysis of Tilting-Pad Thrust Bearings

DEFF Research Database (Denmark)

Heinrichson, Niels; Santos, Ilmar

2005-01-01

Prediction of the minimum oil film thickness and the maximum temperature on the surface of the bearing pad is crucial in the design and dimensioning of bearings. Friction loss, oil bath temperature and pad deflection are other parameters of interest. Depending on the desired information a numerical...... for the groove between pads and the oil bath temperature from energy equilibrium for the entire bearing. The main theoretical contribution of this paper is the elaboration and comparison of 7 different mathematical models of increasing complexity. The results are compared to experimental data for steady......-state operation of a 228 mm outer diameter bearing. It is found that for the given bearing a two dimensional model is sufficient to estimate the minimum oil film thickness and the maximum temperature on the pad surface. Three dimensional modelling does not improve the quality of the results....

Coagulation profile of children with sickle cell anemia in steady state ...

African Journals Online (AJOL)

Background: Sickle cell anemia is associated with a hypercoagulable state that may lead to alterations in a coagulation profile. Measurements of coagulation factors are known to have some predictive value for clinical outcome. Objectives: To determine the coagulation profile of children with SCA in steady state and crisis ...

Reduction of numerical diffusion in three-dimensional vortical flows using a coupled Eulerian/Lagrangian solution procedure

Science.gov (United States)

Felici, Helene M.; Drela, Mark

1993-01-01

A new approach based on the coupling of an Eulerian and a Lagrangian solver, aimed at reducing the numerical diffusion errors of standard Eulerian time-marching finite-volume solvers, is presented. The approach is applied to the computation of the secondary flow in two bent pipes and the flow around a 3D wing. Using convective point markers the Lagrangian approach provides a correction of the basic Eulerian solution. The Eulerian flow in turn integrates in time the Lagrangian state-vector. A comparison of coarse and fine grid Eulerian solutions makes it possible to identify numerical diffusion. It is shown that the Eulerian/Lagrangian approach is an effective method for reducing numerical diffusion errors.

Cycle kinetics, steady state thermodynamics and motors-a paradigm for living matter physics

International Nuclear Information System (INIS)

Qian, Hong

2005-01-01

An integration of the stochastic mathematical models for motor proteins with Hill's steady state thermodynamics yields a rather comprehensive theory for molecular motors as open systems in the nonequilibrium steady state. This theory, a natural extension of Gibbs' approach to isothermal molecular systems in equilibrium, is compared with other existing theories with dissipative structures and dynamics. The theory of molecular motors might be considered as an archetype for studying more complex open biological systems such as biochemical reaction networks inside living cells

Determination of the Steady State Leakage Current in Structures with Ferroelectric Ceramic Films

Science.gov (United States)

Podgornyi, Yu. V.; Vorotilov, K. A.; Sigov, A. S.

2018-03-01

Steady state leakage currents have been investigated in capacitor structures with ferroelectric solgel films of lead zirconate titanate (PZT) formed on silicon substrates with a lower Pt electrode. It is established that Pt/PZT/Hg structures, regardless of the PZT film thickness, are characterized by the presence of a rectifying contact similar to p-n junction. The steady state leakage current in the forward direction increases with a decrease in the film thickness and is determined by the ferroelectric bulk conductivity.

A homotopy method based on WENO schemes for solving steady state problems of hyperbolic conservation laws

Science.gov (United States)

2012-09-03

27] introduced a new smoothness indicator, which removed the slight post- shock oscillations and improved the convergence . A Newton- iteration method... Gauss - Seidel algorithm for steady Euler equation on unstructured grids, Numer. Math. Theor. Meth. Appl., Vol. 1, pp. 92–112, (2008). [14] G.-S. Jiang...was adopted to solve the steady two dimensional Euler equations [10, 11, 13]. The matrix-free Squared Preconditioning is applied to a Newton iteration

steady and dynamic states analysis of induction motor: fea approach

African Journals Online (AJOL)

HOD

The flux levels at these loading conditions were also monitored. Key words: Three phase Induction Motor, Steady state and Dynamic Response, Flux Levels, FEA, Loading conditions. 1. INTRODUCTION ..... Boston: Computational Mechanics Publications;. New York: ... for Electrical Engineers, Cambridge University. Press ...

Post-CHF heat transfer during steady-state and transient conditions

International Nuclear Information System (INIS)

Fung, K.K.

1978-06-01

This review extends previous reviews of steady-state post-CHF literature by Groeneveld, Gardiner, and Fung by including more recent data. A review of the literature on transient post-CHF data is also included by extending the work of Yadigaroglu

Paracetamol decreases steady-state exposure to lamotrigine by induction of glucuronidation in healthy subjects

DEFF Research Database (Denmark)

Gastrup, Sandra; Stage, Tore Bjerregaard; Fruekilde, Palle Bach Nielsen

2016-01-01

AIM: Patients receiving lamotrigine therapy frequently use paracetamol concomitantly. While one study suggests a possible, clinically relevant drug-drug interaction, practical recommendations of the concomitant use are inconsistent. We performed a systematic pharmacokinetic study in healthy...... volunteers to quantify the effect of 4-day treatment of paracetamol on the metabolism of steady-state lamotrigine. METHODS: Twelve healthy, male volunteers participated in an open-label, sequential interaction study. Lamotrigine was titrated to steady state (100 mg daily) over 36 days, and blood and urine...... sampling was performed in a non-randomised order with and without paracetamol (1 g four times daily). The primary endpoint was change in steady-state area under the plasma concentration-time curve of lamotrigine. Secondary endpoints were changes in total apparent oral clearance, renal clearance...

Distraction task rather than focal attention modulates gamma activity associated with auditory steady-state responses (ASSRs)

DEFF Research Database (Denmark)

Griskova-Bulanova, Inga; Ruksenas, Osvaldas; Dapsys, Kastytis

2011-01-01

To explore the modulation of auditory steady-state response (ASSR) by experimental tasks, differing in attentional focus and arousal level.......To explore the modulation of auditory steady-state response (ASSR) by experimental tasks, differing in attentional focus and arousal level....

Quasi-Steady Simulations for the Efficient Generation of Static Aerodynamic Coefficients at Subsonic Velocity

Science.gov (United States)

2016-09-01

10 Fig. 5 Pitching-moment coefficient for BF comparing dα variation to steady-state results, CFL = 10 and N = 50...11 Fig. 6 Roll-torque coefficient for BF comparing dα variation to steady-state results, CFL = 10 and N = 50...compute the flow solution. The Goldberg 3-equation k-ε-Rt turbulence model ( Goldberg et. al. 1998) was implemented in this study based on the findings

Spatial variability of steady-state infiltration into a two-layer soil system on burned hillslopes

Science.gov (United States)

Kinner, D.A.; Moody, J.A.

2010-01-01

Rainfall-runoff simulations were conducted to estimate the characteristics of the steady-state infiltration rate into 1-m2 north- and south-facing hillslope plots burned by a wildfire in October 2003. Soil profiles in the plots consisted of a two-layer system composed of an ash on top of sandy mineral soil. Multiple rainfall rates (18.4-51.2 mm h-1) were used during 14 short-duration (30 min) and 2 long-duration simulations (2-4 h). Steady state was reached in 7-26 min. Observed spatially-averaged steady-state infiltration rates ranged from 18.2 to 23.8 mm h-1 for north-facing and from 17.9 to 36.0 mm h-1 for south-facing plots. Three different theoretical spatial distribution models of steady-state infiltration rate were fit to the measurements of rainfall rate and steady-state discharge to provided estimates of the spatial average (19.2-22.2 mm h-1) and the coefficient of variation (0.11-0.40) of infiltration rates, overland flow contributing area (74-90% of the plot area), and infiltration threshold (19.0-26 mm h-1). Tensiometer measurements indicated a downward moving pressure wave and suggest that infiltration-excess overland flow is the runoff process on these burned hillslope with a two-layer system. Moreover, the results indicate that the ash layer is wettable, may restrict water flow into the underlying layer, and increase the infiltration threshold; whereas, the underlying mineral soil, though coarser, limits the infiltration rate. These results of the spatial variability of steady-state infiltration can be used to develop physically-based rainfall-runoff models for burned areas with a two-layer soil system. ?? 2010 Elsevier B.V.

MARS input data for steady-state calculation of ATLAS

International Nuclear Information System (INIS)

Park, Hyun Sik; Euh, D. J.; Choi, K. Y.; Kwon, T. S.; Jeong, J. J.; Baek, W. P.

2004-12-01

An integral effect test loop for Pressurized Water Reactors (PWRs), the ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), is under construction by Thermal-Hydraulics Safety Research Division in Korea Atomic Energy Research Institute (KAERI). This report includes calculation sheets of the input for the best-estimate system analysis code, the MARS code, based on the ongoing design features of ATLAS. The ATLAS facility has been designed to have the length scale of 1/2 and area scale of 1/144 compared with the reference plant, APR1400. The contents of this report are divided into three parts: (1) core and reactor vessel, (2) steam generator and steam line, and (3) primary piping, pressurizer and reactor coolant pump. The steady-state analysis for the ATLAS facility will be performed based on these calculation sheets, and its results will be applied to the detailed design of ATLAS. Additionally, the calculation results will contribute to getting optimum test conditions and preliminary operational test conditions for the steady-state and transient experiments

Advanced control scenario of high-performance steady-state operation for JT-60 superconducting tokamak

International Nuclear Information System (INIS)

Tamai, H.; Kurita, G.; Matsukawa, M.; Urata, K.; Sakurai, S.; Tsuchiya, K.; Morioka, A.; Miura, Y.M.; Kizu, K.; Kamada, Y.; Sakasai, A.; Ishida, S.

2004-01-01

Plasma control on high-β N steady-state operation for JT-60 superconducting modification is discussed. Accessibility to high-β N exceeding the free-boundary limit is investigated with the stabilising wall of reduced-activated ferritic steel and the active feedback control of the in-vessel non-axisymmetric field coils. Taking the merit of superconducting magnet, advanced plasma control for steady-state high performance operation could be expected. (authors)

Steady-state pharmacokinetics of pravastatin in children with familial hypercholesterolaemia

NARCIS (Netherlands)

Wiersma, Heleen E.; Wiegman, Albert; Koopmans, Richard P.; Bakker, Henk D.; Kastelein, John J. P.; van Boxtel, Chris J.

2004-01-01

Objective: To determine pharmacokinetic data for pravastatin in children, since current data are insufficient in this age group. Subjects and methods: A 2-week, multiple-dose, steady-state pharmacokinetic study was carried out with pravastatin 20mg daily in 24 children with familial

Optimising performance in steady state for a supermarket refrigeration system

DEFF Research Database (Denmark)

Green, Torben; Kinnaert, Michel; Razavi-Far, Roozbeh

2012-01-01

Using a supermarket refrigeration system as an illustrative example, the paper postulates that by appropriately utilising knowledge of plant operation, the plant wide performance can be optimised based on a small set of variables. Focusing on steady state operations, the total system performance...

Progress towards Steady State on NSTX

International Nuclear Information System (INIS)

Gates, D.A.; Kessel, C.; Menard, J.; Taylor, G.; Wilson, J.R.

2005-01-01

In order to reduce recirculating power fraction to acceptable levels, the spherical torus concept relies on the simultaneous achievement of high toroidal β and high bootstrap fraction in steady state. In the last year, as a result of plasma control system improvements, the achievable plasma elongation on the National Spherical Torus Experiment (NSTX) has been raised from κ ∼ 2.1 to κ ∼ 2.6--approximately a 25% increase. This increase in elongation has lead to a doubling increase in the toroidal β for long-pulse discharges. The increase in β is associated with an increase in plasma current at nearly fixed poloidal β, which enables higher β t with nearly constant bootstrap fraction. As a result, for the first time in a spherical torus, a discharge with a plasma current of 1 MA has been sustained for 1 second. Data is presented from NSTX correlating the increase in performance with increased plasma shaping capability. In addition to improved shaping, H-modes induced during the current ramp phase of the plasma discharge have been used to reduce flux consumption during and to delay the onset of MHD instabilities. A modeled integrated scenario, which has 100% non-inductive current drive with very high toroidal β, will also be presented. The NSTX poloidal field coils are currently being modified to produce the plasma shape which is required for this scenario, which requires high triangularity ((delta) ∼ 0.8) at elevated elongation (κ ∼ 2.5). The other main requirement for steady state on NSTX is the ability to drive a fraction of the total plasma current with radio-frequency waves. The results of High Harmonic Fast Wave heating and current drive studies as well as electron Bernstein Wave emission studies will be presented

Flt3 ligand-receptor interaction is important for maintenance of early thymic progenitor numbers in steady-state thymopoiesis.

Science.gov (United States)

Kenins, Linda; Gill, Jason W; Holländer, Georg A; Wodnar-Filipowicz, Aleksandra

2010-01-01

T-cell production throughout life depends on efficient colonization and intrathymic expansion of BM-derived hematopoietic precursors. After irradiation-induced thymic damage, thymic recovery is facilitated by Flt3 ligand (FL), expressed by perivascular fibroblasts surrounding the thymic entry site of Flt3 receptor-positive progenitor cells. Whether intrathymic FL-Flt3 interactions play a role in steady-state replenishment of T cells remains unknown. Here, using competitive BM transplantation studies and fetal thymic organ cultures we demonstrated the continued numerical advantage of Flt3+ intrathymic T-cell precursors. Sub-kidney capsule thymic transplantation experiments, in which WT and FL-/- thymic lobes were grafted into FL-/- recipients, revealed that FL expression by the thymic microenvironment plays a role in steady-state thymopoiesis. The deficiency of the most immature thymic T-cell precursors correlated to upregulation of FL by thymic MTS15+ fibroblasts, suggesting that the number of Flt3+ progenitor cells may regulate the thymic expression of this cytokine. Together, these results show that FL expression by thymic stromal fibroblasts interacting with Flt3+ T-cell progenitors is important for the physiological maintenance of early T-cell development.

Numerical Solution of Stochastic Nonlinear Fractional Differential Equations

KAUST Repository

El-Beltagy, Mohamed A.

2015-01-07

Using Wiener-Hermite expansion (WHE) technique in the solution of the stochastic partial differential equations (SPDEs) has the advantage of converting the problem to a system of deterministic equations that can be solved efficiently using the standard deterministic numerical methods [1]. WHE is the only known expansion that handles the white/colored noise exactly. This work introduces a numerical estimation of the stochastic response of the Duffing oscillator with fractional or variable order damping and driven by white noise. The WHE technique is integrated with the Grunwald-Letnikov approximation in case of fractional order and with Coimbra approximation in case of variable-order damping. The numerical solver was tested with the analytic solution and with Monte-Carlo simulations. The developed mixed technique was shown to be efficient in simulating SPDEs.

Numerical Solution of Stochastic Nonlinear Fractional Differential Equations

KAUST Repository

El-Beltagy, Mohamed A.; Al-Juhani, Amnah

2015-01-01

Using Wiener-Hermite expansion (WHE) technique in the solution of the stochastic partial differential equations (SPDEs) has the advantage of converting the problem to a system of deterministic equations that can be solved efficiently using the standard deterministic numerical methods [1]. WHE is the only known expansion that handles the white/colored noise exactly. This work introduces a numerical estimation of the stochastic response of the Duffing oscillator with fractional or variable order damping and driven by white noise. The WHE technique is integrated with the Grunwald-Letnikov approximation in case of fractional order and with Coimbra approximation in case of variable-order damping. The numerical solver was tested with the analytic solution and with Monte-Carlo simulations. The developed mixed technique was shown to be efficient in simulating SPDEs.

Theoretical analysis of steady state operating forces in control valves

Directory of Open Access Journals (Sweden)

Basavaraj Hubballi

2018-01-01

Full Text Available The controlling components, such as valves are used to regulate controlled fluid power. It is not always possible to calculate valve forces accurately, and with some types of valves even the existence of certain types of forces cannot be predicted with certainty. In many cases, however, the analysis can be made fairly completely and accurately. The assumption of steady state conditions is valid for the valve alone, but transient effects in the rest of the system may be large. These effects are particularly important with regard to the instability of valves, where the system may react on the valve in such a way as to make it squeal or oscillate, sometimes with large amplitude. The origin of the steady state flow force understood from a brief qualitative explanation. The following paper will summarize much of what is known about valve forces in the spool type controlling element.

Is steady-state capitalism viable? A review of the issues and an answer in the affirmative.

Science.gov (United States)

Lawn, Philip

2011-02-01

Most ecological economists believe that the transition to a steady-state economy is necessary to ensure ecological sustainability and to maximize a nation's economic welfare. While some observers agree with the necessity of the steady-state economy, they are nonetheless critical of the suggestion made by ecological economists-in particular, Herman Daly-that a steady-state economy is compatible with a capitalist system. First, they believe that steady-state capitalism is based on the untenable assumption that growth is an optional rather than in-built element of capitalism. Second, they argue that capitalist notions of efficient resource allocation are too restrictive to facilitate the transition to an "ecological" or steady-state economy. I believe these observers are outright wrong with their first criticism and, because they misunderstand Daly's vision of a steady-state economy, are misplaced with their second criticism. The nature of a capitalist system depends upon the institutional framework that supports and shapes it. Hence, a capitalist system can exist in a wide variety of forms. Unfortunately, many observers fail to recognize that the current "growth imperative" is the result of capitalist systems everywhere being institutionally designed to grow. They need not be designed this way to survive and thrive. Indeed, because continued growth is both existentially undesirable and ecologically unsustainable, redesigning capitalist systems through the introduction of Daly-like institutions would prove to be capitalism's savior. What's more, it would constitute humankind's best hope of achieving sustainable development. © 2011 New York Academy of Sciences.

Ideal MHD stability and performance of ITER steady-state scenarios with ITBs

Science.gov (United States)

Poli, F. M.; Kessel, C. E.; Chance, M. S.; Jardin, S. C.; Manickam, J.

2012-06-01

Non-inductive steady-state scenarios on ITER will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. The large pressure gradients at the location of the internal barrier are conducive to the development of ideal MHD instabilities that may limit the plasma performance and may lead to plasma disruptions. Fully non-inductive scenario simulations with five combinations of heating and current drive sources are presented in this work, with plasma currents in the range 7-10 MA. For each configuration the linear, ideal MHD stability is analysed for variations of the Greenwald fraction and of the pressure peaking factor around the operating point, aiming at defining an operational space for stable, steady-state operations at optimized performance. It is shown that plasmas with lower hybrid heating and current drive maintain the minimum safety factor above 1.5, which is desirable in steady-state operations to avoid neoclassical tearing modes. Operating with moderate ITBs at 2/3 of the minor radius, these plasmas have a minimum safety factor above 2, are ideal MHD stable and reach Q ≳ 5 operating above the ideal no-wall limit.

Coherent control of long-distance steady-state entanglement in lossy resonator arrays

Science.gov (United States)

Angelakis, D. G.; Dai, L.; Kwek, L. C.

2010-07-01

We show that coherent control of the steady-state long-distance entanglement between pairs of cavity-atom systems in an array of lossy and driven coupled resonators is possible. The cavities are doped with atoms and are connected through waveguides, other cavities or fibers depending on the implementation. We find that the steady-state entanglement can be coherently controlled through the tuning of the phase difference between the driving fields. It can also be surprisingly high in spite of the pumps being classical fields. For some implementations where the connecting element can be a fiber, long-distance steady-state quantum correlations can be established. Furthermore, the maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the establishment of coherence between otherwise uncoupled atomic levels using classical coherent fields. We suggest a method to measure this entanglement by analyzing the correlations of the emitted photons from the array and also analyze the above results for a range of values of the system parameters, different network geometries and possible implementation technologies.

Producing a steady-state population inversion

International Nuclear Information System (INIS)

Richards, R.K.; Griffin, D.C.

1986-03-01

An observed steady-state transition at 17.5 nm is identified as the 2p 5 3s3p 4 S/sub 3/2/ → 2p 6 3p 2 P/sub 3/2/ transition in Na-like aluminum. The upper level is populated by electron inner shell ionization of metastable Mg-like aluminum. From the emission intensity, the rate coefficient for populating the upper level is calculated to be approximately 5 x 10 -10 ) cm 3 /sec. Since the upper level is quasimetastable with a lifetime 22 times longer than the lower level, it may be possible to produce a population inversion, if a competing process to populate the lower level can be reduced

Steady-state oxidation of cholesterol catalyzed by cholesterol oxidase in lipid bilayer membranes on platinum electrodes

International Nuclear Information System (INIS)

Bokoch, Michael P.; Devadoss, Anando; Palencsar, Mariela S.; Burgess, James D.

2004-01-01

Cholesterol oxidase is immobilized in electrode-supported lipid bilayer membranes. Platinum electrodes are initially modified with a self-assembled monolayer of thiolipid. A vesicle fusion method is used to deposit an outer leaflet of phospholipids onto the thiolipid monolayer forming a thiolipid/lipid bilayer membrane on the electrode surface. Cholesterol oxidase spontaneously inserts into the electrode-supported lipid bilayer membrane from solution and is consequently immobilized to the electrode surface. Cholesterol partitions into the membrane from buffer solutions containing cyclodextrin. Cholesterol oxidase catalyzes the oxidation of cholesterol by molecular oxygen, forming hydrogen peroxide as a product. Amperometric detection of hydrogen peroxide for continuous solution flow experiments are presented, where flow was alternated between cholesterol solution and buffer containing no cholesterol. Steady-state anodic currents were observed during exposures of cholesterol solutions ranging in concentration from 10 to 1000 μM. These data are consistent with the Michaelis-Menten kinetic model for oxidation of cholesterol as catalyzed by cholesterol oxidase immobilized in the lipid bilayer membrane. The cholesterol detection limit is below 1 μM for cholesterol solution prepared in buffered cyclodextrin. The response of the electrodes to low density lipoprotein solutions is increased upon addition of cyclodextrin. Evidence for adsorption of low density lipoprotein to the electrode surface is presented

The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity.

Science.gov (United States)

Foster, Carl; Farland, Courtney V; Guidotti, Flavia; Harbin, Michelle; Roberts, Brianna; Schuette, Jeff; Tuuri, Andrew; Doberstein, Scott T; Porcari, John P

2015-12-01

High intensity interval training (HIIT) has become an increasingly popular form of exercise due to its potentially large effects on exercise capacity and small time requirement. This study compared the effects of two HIIT protocols vs steady-state training on aerobic and anaerobic capacity following 8-weeks of training. Fifty-five untrained college-aged subjects were randomly assigned to three training groups (3x weekly). Steady-state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of ventilatory threshold (VT). Tabata (n = 21) completed eight intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15) completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s recovery, average PO = 90% VT. Each subject did 24 training sessions during 8 weeks. There were significant (p Tabata protocol was significantly less enjoyable (p HIIT protocols are time efficient, they are not superior to conventional exercise training in sedentary young adults. Key pointsSteady state training equivalent to HIIT in untrained studentsMild interval training presents very similar physiologic challenge compared to steady state trainingHIIT (particularly very high intensity variants were less enjoyable than steady state or mild interval trainingEnjoyment of training decreases across the course of an 8 week experimental training program.

Iterative Observer-based Estimation Algorithms for Steady-State Elliptic Partial Differential Equation Systems

KAUST Repository

Majeed, Muhammad Usman

2017-01-01

the problems are formulated on higher dimensional space domains. However, in this dissertation, feedback based state estimation algorithms, known as state observers, are developed to solve such steady-state problems using one of the space variables as time

Rotationally symmetric numerical solutions to the sine-Gordon equation

DEFF Research Database (Denmark)

Olsen, O. H.; Samuelsen, Mogens Rugholm

1981-01-01

We examine numerically the properties of solutions to the spherically symmetric sine-Gordon equation given an initial profile which coincides with the one-dimensional breather solution and refer to such solutions as ring waves. Expanding ring waves either exhibit a return effect or expand towards...

Analysis of steady state and transient two-phase flows in downwardly inclined lines

International Nuclear Information System (INIS)

Crawford, T.J.

1983-01-01

A study of steady-state and transient two-phase flows in downwardly inclined lines is described. Steady-state flow patterns maps are presented using Freon-113 as the working fluid to provide new high density vapors. These flow maps with high density vapor serve to significantly extend the investigations of steady-state downward two-phase flow patterns. Physical models developed which successfully predicted the onset or location of various flow pattern transitions. A new simplified criterion that would be useful to designers and experimenters is offered for the onset of dispersed flow. A new empirical holdup correlation and a new bubble diameter/flow rate correlation are also proposed. Flow transients in vertical downward lines were studied to investigate the possible formation of intermediate or spurious flow patterns that would not be seen at steady-state conditions. Void fraction behavior during the transients was modeled by using the dynamic slip equation from the transient analysis code RETRAN. Physical models of interfacial area were developed and compared with models and data from literature. There was satisfactory agreement between the models of the present study and the literature models and data. The concentration parameter of the drift flux model was evaluated for vertical downward flow. These new values of the flow dependent parameter were different from those previously proposed in the literature for use in upward flows, and made the drift flux model suitable for use in upward or downward flow lines

An integral equation-based numerical solver for Taylor states in toroidal geometries

Science.gov (United States)

O'Neil, Michael; Cerfon, Antoine J.

2018-04-01

We present an algorithm for the numerical calculation of Taylor states in toroidal and toroidal-shell geometries using an analytical framework developed for the solution to the time-harmonic Maxwell equations. Taylor states are a special case of what are known as Beltrami fields, or linear force-free fields. The scheme of this work relies on the generalized Debye source representation of Maxwell fields and an integral representation of Beltrami fields which immediately yields a well-conditioned second-kind integral equation. This integral equation has a unique solution whenever the Beltrami parameter λ is not a member of a discrete, countable set of resonances which physically correspond to spontaneous symmetry breaking. Several numerical examples relevant to magnetohydrodynamic equilibria calculations are provided. Lastly, our approach easily generalizes to arbitrary geometries, both bounded and unbounded, and of varying genus.

On numerical solution of Burgers' equation by homotopy analysis method

International Nuclear Information System (INIS)