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Madžar, Dominik, Christian Maihöfner, Rüdiger Zimmermann, Stefan Schwab, Johannes Kornhuber, and Piotr Lewczuk. "Cerebrospinal fluid under non-steady state condition caused by plasmapheresis." Journal of Neural Transmission 118, no. 2 (November 16, 2010): 219–22. http://dx.doi.org/10.1007/s00702-010-0519-z.
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Przekop, Rafał, and Leon Gradoń. "Non-steady-state aerosol filtration in nanostructured fibrous media." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1945 (June 28, 2011): 2476–84. http://dx.doi.org/10.1098/rsta.2011.0063.
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The filtration of aerosol particles using composites of nano- and microsized fibrous structures is a promising method for the effective separation of nanoparticles from gases. A multi-scale physical system describing the flow pattern and particle deposition at a non-steady-state condition requires an advanced method of modelling. The combination of lattice Boltzmann and Brownian dynamics was used for analysis of the particle deposition pattern in a fibrous system. The dendritic structures of deposits for neutral and charged fibres and particles are present. The efficiency of deposition, deposit morphology, porosity and fractal dimension were calculated for a selected operational condition of the process.
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Abidat, M., M. Hachemi, M. K. Hamidou, and N. C. Baines. "Prediction of the steady and non-steady flow performance of a highly loaded mixed flow turbine." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 212, no. 3 (May 1, 1998): 173–84. http://dx.doi.org/10.1243/0957650981536844.
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This paper describes a method for predicting the performance under both turbine inlet steady state and non-steady state flow conditions of a mixed flow turbine used for turbocharged internal combustion engines. The mixed flow turbine steady state performances computed with the steady state performance prediction method are in good agreement with the experimental results obtained in the Imperial College turbocompressor cold air test rig. The unsteady state performance is computed using a one-dimensional model based on the solution of the unsteady one-dimensional flow equations. These equations are solved in the volute by a finite difference method using a four-step explicit Runge—Kutta scheme. The instantaneous volute exit condition is provided by the steady state rotor performance prediction model with the assumption of a quasi-steady state flow in the rotor. The computed instantaneous performances are in reasonable agreement with published experimental data for the same mixed flow turbine. The unsteady flow model is also used to study the effects of the frequency and the amplitude of the pulse on the performances of the mixed flow turbine.
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Sudi Mungkasi. "Modelling And Simulation of Topical Drug Diffusion in The Dermal Layer of Human Body." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 86, no. 2 (August 24, 2021): 39–49. http://dx.doi.org/10.37934/arfmts.86.2.3949.
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We consider the problem of drug diffusion in the dermal layer of human body. Two existing mathematical models of the drug diffusion problem are recalled. We obtain that the existing models lead to inconsistent equations for the steady state condition. We also obtain that solutions to the existing models are unrealistic for some cases of the unsteady state condition, because negative drug concentrations occur due to the inappropriate assumption of the model. Therefore, in this paper, we propose a modified mathematical model, so that the model is consistent, and the solution is nonnegative for both steady and unsteady state conditions of the drug diffusion problem in the dermal layer of human body. For the steady state condition, the exact solution to the proposed model is given. For unsteady state condition, we use a finite difference method for solving the models numerically, where the discretisation is centred in space and forward in time. Simulation results confirm that our proposed model and method preserve the non-negativity of the solution to the problem, so the solution is more realistic than that of the old model.
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Radrizzani, Danilo, Riccardo Giudici, Barbara DeToffol, Simone Fracassi, Matteo Lucchelli, Giorgio Musazzi, Luisa Santambrogio, and Cristian Leva. "Evaluation of oxygen consumption and energy expenditure after cardiac surgery in non-steady-state condition." Nutritional Therapy & Metabolism 31, no. 1 (December 20, 2012): 45–51. http://dx.doi.org/10.5301/ntm.2012.10447.
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Tuvdendorj, Demidmaa, David L. Chinkes, David N. Herndon, Xiao-Jun Zhang, and Robert R. Wolfe. "A novel stable isotope tracer method to measure muscle protein fractional breakdown rate during a physiological non-steady-state condition." American Journal of Physiology-Endocrinology and Metabolism 304, no. 6 (March 15, 2013): E623—E630. http://dx.doi.org/10.1152/ajpendo.00552.2012.
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The measurement of the fractional breakdown rate (FBR) of muscle proteins during physiological non-steady state of amino acids (AAs) presents some challenges. Therefore, the goal of the present experiment was to modify the bolus stable isotope tracer injection approach to determine both fractional synthesis rate (FSR) and FBR of leg muscle protein during a physiological non-steady state of AAs. The approach uses the traditional precursor-product principle but is modified with the assumption that inward transport of AAs is proportional to their plasma concentrations. The FBR value calculated from the threonine tracer served as a reference to evaluate the validity of the FBR measurement from the phenylalanine tracer, which was under a non-steady-state condition due to the concomitant injection of unlabeled phenylalanine. Plasma phenylalanine concentration increased more than fourfold after the bolus injection, and thereafter it decreased exponentially, whereas the threonine concentration remained stable. FBR values were similar with the two tracers [0.133 ± 0.003 and 0.148 ± 0.003%/h (means ± SE) for the phenylalanine and threonine tracers, respectively, P > 0.05]. In addition, FSR values for the two tracers were similar (0.069 ± 0.002 and 0.067 ± 0.001%/h for the phenylalanine and threonine tracers, respectively, P > 0.05), indicating that the traditional FSR approach can also be used in the non-steady state. Accordingly, net balance (NB) values were similar (−0.065 ± 0.002 and −0.081 ± 0.002%/h for the phenylalanine and threonine tracers, respectively, P > 0.05). This new method of measuring muscle protein FBR during physiological non-steady state gives reliable results and allows simultaneous measurement of muscle protein FSR and thus a calculation of NB.
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Pumo, D., F. Viola, and L. V. Noto. "Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations." Hydrology and Earth System Sciences 12, no. 1 (February 27, 2008): 303–16. http://dx.doi.org/10.5194/hess-12-303-2008.
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Abstract. 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 water stress is also numerically evaluated, implicitly taking into account the soil moisture condition at the beginning of the growing season. It is also shown the role of different annual climatic parameterizations on the soil moisture probability density function and on the vegetation water stress evaluation. The proposed model is applied to a case study characteristic of Mediterranean climate: the watershed of Eleuterio in Sicily (Italy).
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Higashimori, Mitsuo, Kiyoshi Yamaoka, and Terumichi Nakagawa. "Dose‐Dependency in Local Disposition of 5‐Fluorouracil under Non‐Steady‐State Condition in Rat Liver." Journal of Pharmaceutical Sciences 89, no. 1 (January 2000): 100–107. http://dx.doi.org/10.1002/(sici)1520-6017(200001)89:1<100::aid-jps10>3.0.co;2-l.
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Higashimori, Mitsuo, Kiyoshi Yamaoka, and Terumichi Nakagawa. "Dose-dependency in local disposition of 5-fluorouracil under non-steady-state condition in rat liver." Journal of Pharmaceutical Sciences 89, no. 1 (January 2000): 100. http://dx.doi.org/10.1002/(sici)1520-6017(200001)89:1<100::aid-jps10>3.3.co;2-c.
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Venturini, Elisa, Ivano Vassura, Cristian Zanetti, Andrea Pizzi, Giuseppe Toscano, and Fabrizio Passarini. "Evaluation of non-steady state condition contribution to the total emissions of residential wood pellet stove." Energy 88 (August 2015): 650–57. http://dx.doi.org/10.1016/j.energy.2015.05.105.
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Rodríguez, Nancy, and Yi Hu. "On the steady-states of a two-species non-local cross-diffusion model." Journal of Applied Analysis 26, no. 1 (June 1, 2020): 1–19. http://dx.doi.org/10.1515/jaa-2020-2003.
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AbstractWe investigate the existence and properties of steady-state solutions to a degenerate, non-local system of partial differential equations that describe two-species segregation in homogeneous and heterogeneous environments. This is accomplished via the analysis of the existence and non-existence of global minimizers to the corresponding free energy functional. We prove that in the spatially homogeneous case global minimizers exist if and only if the mass of the potential governing the intra-species attraction is sufficiently large and the support of the potential governing the interspecies repulsion is bounded. Moreover, when they exist they are such that the two species have disjoint support, leading to complete segregation. For the heterogeneous environment we show that if a sub-additivity condition is satisfied then global minimizers exists. We provide an example of an environment that leads to the sub-additivity condition being satisfied. Finally, we explore the bounded domain case with periodic conditions through the use of numerical simulations.
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SARGSYAN, K. G. "TWO TEMPERATURE DESCRIPTION OF RNA-LIKE POLYMER." Modern Physics Letters B 22, no. 10 (April 20, 2008): 785–90. http://dx.doi.org/10.1142/s021798490801519x.
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The two-temperature description of the RNA-like molecule is invented. Instead of equilibrium treatment of the polymer state, the steady state viewpoint is proposed. The molecule is considered as being in an adiabatic steady state, which is a non-equilibrium one. The general approach to the molecule in such a steady state is discussed and the simple model with saturating bonds is considered. The relation between mean square end-to-end distance and the number of monomers is derived for the simple system under condition T>Θ. The obtained relation depends on additional so-called disorder temperature.
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Katsube, N., and M. M. Carroll. "The Modified Mixture Theory for Fluid-Filled Porous Materials: Applications." Journal of Applied Mechanics 54, no. 1 (March 1, 1987): 41–46. http://dx.doi.org/10.1115/1.3172992.
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The recently established modified mixture theory for fluid-filled porous materials is applied to two steady state boundary value problems; also, how the newly developed theory provides more general solution than Biot’s theory is examined. The velocity profiles in steady state boundary value problems are found to depend on the ratio of a characteristic length of the microstructure to a characteristic length defined by the boundary conditions. As opposed to Biot’s theory, the zero fluid velocity condition on the boundary are satisfied and the existence of a non-Darcy flow closer to the boundary are shown.
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Jia, De Li, Rui Jia Wang, and Chun Sheng Wang. "Simulation Research of Inverted Plasma Cutting Power Supply Based on Fuzzy Control." Advanced Materials Research 179-180 (January 2011): 1229–34. http://dx.doi.org/10.4028/www.scientific.net/amr.179-180.1229.
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Focusing on load characteristics of inverted plasma cutting power supply, this paper puts forward a nonlinear control method. This method integrates fuzzy control technology into the controller of power supply, thereby optimizing dynamic characteristics of power supply. The SIMULINK simulation technology is also used. To compare steady-state precision, robustness, response speed and other control indexes between fuzzy control and conventional PI control, the comparative simulation experiments were made respectively under constant non-disturbance steady-state condition, aperiodic load disturbance condition, and periodic load disturbance condition. The simulation results show that power supply with fuzzy controller has perfect steady robustness, fast system response and strong harmonic suppression ability. The simulation model is accurate and reliable, and it can be an efficient tool for further studying mechanism and algorithm optimization of plasma cutting power supply.
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Chang, Na Na, and Hai Bao. "The Influence of Time Truncation on Phase Angle Measurement Principle." Applied Mechanics and Materials 668-669 (October 2014): 957–60. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.957.
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Real-time accurate voltage phase angle measurement data has a very important significance to monitor and analyze the power system, and phase angle measurement principle of Fourier transform plays an important role in the theoretical calculations and engineering applications. The dynamic sinusoidal voltage signal contains two parts of the sinusoidal steady-state component and decaying DC component, and the decaying DC component having a continuous spectrum, at the frequency corresponding to the sinusoidal steady-state component must have a non-zero value, making dynamic signal phase than steady signal phase has one extra deviation angle. Considering Fourier transform method and theory of engineering application are different, this paper only considered the application conditions of time truncation, analyzes continuous Fourier transform under a real eigenvalue and a pair of conjugate complex roots condition, then compared with the theoretical calculation, for the two case of limited time integration and theoretical calculation condition, the phase angle difference and influencing factors are given.
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Chen, Zhigang, Rongwei Xu, and Yongxi Yi. "Dynamic Optimal Control of Transboundary Pollution Abatement under Learning-by-Doing Depreciation." Complexity 2020 (June 9, 2020): 1–17. http://dx.doi.org/10.1155/2020/3763684.
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This paper analyzes a dynamic Stackelberg differential game model of watershed transboundary water pollution abatement and discusses the optimal decision-making problem under non-cooperative and cooperative differential game, in which the accumulation effect and depreciation effect of learning-by-doing pollution abatement investment are taken into account. We use dynamic optimization theory to solve the equilibrium solution of models. Through numerical simulation analysis, the path simulation and analysis of the optimal trajectory curves of each variable under finite-planning horizon and long-term steady state were carried out. Under the finite-planning horizon, the longer the planning period is, the lower the optimal emission rate is in equilibrium. The long-term steady-state game under cooperative decision can effectively reduce the amount of pollution emission. The investment intensity of pollution abatement in the implementation of non-cooperative game is higher than that of cooperative game. Under the long-term steady state, the pollution abatement investment trajectory of the cooperative game is relatively stable and there is no obvious crowding out effect. Investment continues to rise, and the optimal equilibrium level at steady state is higher than that under non-cooperative decision making. The level of decline in pollution stock under finite-planning horizon is not significant. Under the condition of long-term steady state, the trajectories of upstream and downstream pollution in the non-cooperative model and cooperative model are similar, but cooperative decision-making model is superior to the non-cooperative model in terms of the period of stabilization and steady state.
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Li, Y. G. "A gas turbine diagnostic approach with transient measurements." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 217, no. 2 (January 1, 2003): 169–77. http://dx.doi.org/10.1243/09576500360611317.
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Most gas turbine performance analysis based diagnostic methods use the information from steady state measurements. Unfortunately, steady state measurement may not be obtained easily in some situations, and some types of gas turbine fault contribute little to performance deviation at steady state operating conditions but significantly during transient processes. Therefore, gas turbine diagnostics with transient measurement is superior to that with steady state measurement. In this paper, an accumulated deviation is defined for gas turbine performance parameters in order to measure the level of performance deviation during transient processes. The features of the accumulated deviation are analysed and compared with traditionally defined performance deviation at a steady state condition. A non-linear model based diagnostic method, combined with a genetic algorithm (GA), is developed and applied to a model gas turbine engine to diagnose engine faults by using the accumulated deviation obtained from transient measurement. Typical transient measurable parameters of gas turbine engines are used for fault diagnostics, and a typical slam acceleration process from idle to maximum power is chosen in the analysis. The developed diagnostic approach is applied to the model engine implanted with three typical single-component faults and is shown to be very successful.
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Glynn, Peter W., and Ward Whitt. "Logarithmic asymptotics for steady-state tail probabilities in a single-server queue." Journal of Applied Probability 31, A (1994): 131–56. http://dx.doi.org/10.2307/3214953.
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We consider the standard single-server queue with unlimited waiting space and the first-in first-out service discipline, but without any explicit independence conditions on the interarrival and service times. We find conditions for the steady-state waiting-time distribution to have asymptotics of the form x–1 log P(W> x) → –θ ∗as x → ∞for θ ∗ > 0. We require only stationarity of the basic sequence of service times minus interarrival times and a Gärtner–Ellis condition for the cumulant generating function of the associated partial sums, i.e. n–1 log E exp (θSn) → ψ (θ) as n → ∞, plus regularity conditions on the decay rate function ψ. The asymptotic decay rate θ is the root of the equation ψ (θ) = 0. This result in turn implies a corresponding asymptotic result for the steady-state workload in a queue with general non-decreasing input. This asymptotic result covers the case of multiple independent sources, so that it provides additional theoretical support for a concept of effective bandwidths for admission control in multiclass queues based on asymptotic decay rates.
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Glynn, Peter W., and Ward Whitt. "Logarithmic asymptotics for steady-state tail probabilities in a single-server queue." Journal of Applied Probability 31, A (1994): 131–56. http://dx.doi.org/10.1017/s002190020010703x.
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We consider the standard single-server queue with unlimited waiting space and the first-in first-out service discipline, but without any explicit independence conditions on the interarrival and service times. We find conditions for the steady-state waiting-time distribution to have asymptotics of the form x –1 log P(W > x) → –θ ∗as x → ∞for θ ∗ > 0. We require only stationarity of the basic sequence of service times minus interarrival times and a Gärtner–Ellis condition for the cumulant generating function of the associated partial sums, i.e. n –1 log E exp (θSn ) → ψ (θ) as n → ∞, plus regularity conditions on the decay rate function ψ. The asymptotic decay rate θ is the root of the equation ψ (θ) = 0. This result in turn implies a corresponding asymptotic result for the steady-state workload in a queue with general non-decreasing input. This asymptotic result covers the case of multiple independent sources, so that it provides additional theoretical support for a concept of effective bandwidths for admission control in multiclass queues based on asymptotic decay rates.
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Gastaldelli, A., A. R. Coggan, and R. R. Wolfe. "Assessment of methods for improving tracer estimation of non-steady-state rate of appearance." Journal of Applied Physiology 87, no. 5 (November 1, 1999): 1813–22. http://dx.doi.org/10.1152/jappl.1999.87.5.1813.
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The most common approach for estimating substrate rate of appearance (Ra) is use of the single-pool model first proposed by R. W. Steele, J. S. Wall, R. C. DeBodo, and N. Altszuler. ( Am. J. Physiol. 187: 15–24, 1956). To overcome the model error during highly non-steady-state conditions due to the assumption of a constant volume of distribution (V), two strategies have been proposed: 1) use of a variable tracer infusion rate to minimize tracer-to-tracee ratio (TTR) variations (fixed-volume approach) or 2) use of two tracers of the same substrate with one infused at a constant rate and the other at a variable rate (variable-volume approach or approach of T. Issekutz, R. Issekutz, and D. Elahi. Can. J. Physiol. Pharmacol. 52: 215–224, 1974). The goal of this study was to compare the results of these two strategies for the analysis of the kinetics of glycerol and glucose under the non-steady-state condition created by a constant infusion of epinephrine (50 ng ⋅ kg−1 ⋅ min−1) with the traditional approach of Steele et al., which uses a constant infusion and fixed volume. The results showed that for glucose and glycerol the estimates of Raobtained with the constant and the variable tracer infusion rate and the equation of Steele et al. were comparable. The variable tracer infusion approach was less sensitive to the choice of V in estimating Ra for glycerol and glucose, although the advantage of changing the tracer infusion rate was greater for glucose than for glycerol. The model of Issekutz et al. showed instability when the ratio TTR1/TTR2approaches a constant value, and the model is more sensitive to measurement error than the constant-volume model for glucose and glycerol. We conclude that the one-tracer constant-infusion technique is sufficient in most cases for glycerol, whereas the one-tracer variable-infusion technique is preferable for glucose. Reasonable values for glucose Ra can be obtained with the constant-infusion technique if V = 145 ml/kg.
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Guha, Anirban, and Gregory A. Lawrence. "A wave interaction approach to studying non-modal homogeneous and stratified shear instabilities." Journal of Fluid Mechanics 755 (August 18, 2014): 336–64. http://dx.doi.org/10.1017/jfm.2014.374.
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AbstractHomboe (Geophys. Publ., vol. 24, 1962, pp. 67–112) postulated that resonant interaction between two or more progressive, linear interfacial waves produces exponentially growing instabilities in idealized (broken-line profiles), homogeneous or density-stratified, inviscid shear layers. Here we have generalized Holmboe’s mechanistic picture of linear shear instabilities by (i) not initially specifying the wave type, and (ii) providing the option for non-normal growth. We have demonstrated the mechanism behind linear shear instabilities by proposing a purely kinematic model consisting of two linear, Doppler-shifted, progressive interfacial waves moving in opposite directions. Moreover, we have found a necessary and sufficient (N&S) condition for the existence of exponentially growing instabilities in idealized shear flows. The two interfacial waves, starting from arbitrary initial conditions, eventually phase-lock and resonate (grow exponentially), provided the N&S condition is satisfied. The theoretical underpinning of our wave interaction model is analogous to that of synchronization between two coupled harmonic oscillators. We have re-framed our model into a nonlinear autonomous dynamical system, the steady-state configuration of which corresponds to the resonant configuration of the wave interaction model. When interpreted in terms of the canonical normal-mode theory, the steady-state/resonant configuration corresponds to the growing normal mode of the discrete spectrum. The instability mechanism occurring prior to reaching steady state is non-modal, favouring rapid transient growth. Depending on the wavenumber and initial phase-shift, non-modal gain can exceed the corresponding modal gain by many orders of magnitude. Instability is also observed in the parameter space which is deemed stable by the normal-mode theory. Using our model we have derived the discrete spectrum non-modal stability equations for three classical examples of shear instabilities: Rayleigh/Kelvin–Helmholtz, Holmboe and Taylor–Caulfield. We have shown that the N&S condition provides a range of unstable wavenumbers for each instability type, and this range matches the predictions of the normal-mode theory.
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Cao, M., K. W. Wang, L. DeVries, Y. Fujii ,, W. E. Tobler ,, G. M. Pietron ,, T. Tibbles ,, and J. McCallum. "Steady State Hydraulic Valve Fluid Field Estimator Based on Non-Dimensional Artificial Neural Network (NDANN)." Journal of Computing and Information Science in Engineering 4, no. 3 (September 1, 2004): 257–70. http://dx.doi.org/10.1115/1.1765119.
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An automatic transmission (AT) hydraulic control system includes many spool-type valves that have highly asymmetric flow geometry. A simplified flow field model based on a lumped geometry is computationally efficient. However, it often fails to account for asymmetric flow characteristics, leading to an inaccurate analysis. An accurate analysis of their flow fields typically requires using the computational fluid dynamics (CFD) technique, which is numerically inefficient and time consuming. In this paper, a new hydraulic valve fluid field model is developed based on non-dimensional artificial neural networks (NDANNs) to provide an accurate and numerically efficient tool in AT control system design applications. A grow-and-trim procedure is proposed to identify critical non-dimensional inputs and optimize the network architecture. A hydraulic valve testing bench is designed and built to provide data for neural network model development. NDANN-based fluid force and flow rate estimators are established based on the experimental data. The NDANN models provide more accurate predictions of flow force and flow rates under broad operating conditions (such as different pressure drops and valve openings) compared with conventional lumped flow field models. Because of its non-dimensional characteristic, the NDANN fluid field estimator also exhibits good input-output scalability, which allows the NDANN model to estimate the fluid force and flow rate even when the operating condition parameter or design geometry parameters are outside the range of the training data. That is, although the operating/geometry parameter values are outside the range of the training sets, the non-dimensional values of the specific operating/geometry parameters are still within the training range. This feature makes the new model a potential candidate as a system design tool.
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Soni, Sandeep, and DP Vakharia. "A steady-state performance analysis of a non-circular cylindrical floating ring journal bearing." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 231, no. 1 (November 12, 2016): 41–56. http://dx.doi.org/10.1177/1350650116645027.
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This paper analyses the steady-state performance behaviour of a new type of journal bearing, i.e. the non-circular cylindrical floating ring journal bearing. It consists of a floating ring in between the shaft and the upper and lower lobes of a two-lobe bearing. The journal and the inner surface of the ring are cylindrical while bearing surfaces are non-circular. The classical Navier–Stokes equations in the modified form together with the continuity equation are being solved by the finite element method. The cylindrical coordinates form of the Navier–Stokes equation and continuity equation are used in the present analysis to compute the important proposed bearing characteristics. In this analytical study, the finite bearing approximation ( L/ D=1) with a C2/ C1 value of 0.70 and 1.30 are being used to simulate the behaviour of non-circular cylindrical floating ring journal bearing. The Reynold’s boundary condition is used to enumerate the performance of the proposed bearing. In the present analysis, the steady-state parameters in terms of an inner and outer film eccentricity ratio, a speed ratio, attitude angle, load capacity, friction coefficient parameter, axial oil flow and rise in temperature variable are determined. The results reveal that the steady-state performance of the non-circular floating ring journal bearing is superior to a plain cylindrical floating ring journal bearing.
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Tri Atmaja, Sigit, and Abdul Halim. "Steady State Modification Method Based On Backpropagation Neural Network For Non-Intrusive Load Monitoring (NILM)." MATEC Web of Conferences 218 (2018): 02013. http://dx.doi.org/10.1051/matecconf/201821802013.
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Household electric power sector is highlighted as one of significant contributors to national energy consumption. To reduce electric energy usage in this sector, a technique called Non-Intrusive Load Monitoring (NILM) has been developed recently. NILM is a load disaggregating and monitoring tool that can be used to identify the daily usage behavior of individual electric appliance. Different to conventional method, NILM promises the reduction of sensor deployment significantly. NILM commonly uses either transient or steady state signal. Based on load/appliance signal condition, many NILM’s research results have been published. In this paper, steady state modification method of backpropagation neural network (NN) is applied for developing NILM. We use steady state signal to disaggregate the sum of load power signal. In the proposed method, NN is explored for feature extraction of electric power consumption of individual appliance. The presented method is powerful for load power signal which has almost same value. To verify the effectiveness of proposed method, data provided by tracebase.org has been used. The presented method can be applied for local data. It is obvious from simulation results that the proposed method could improve the recognition rate of appliances until 100 %.
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Hamadeh, Mazen J., and L. John Hoffer. "Tracer methods underestimate short-term variations in urea production in humans." American Journal of Physiology-Endocrinology and Metabolism 274, no. 3 (March 1, 1998): E547—E553. http://dx.doi.org/10.1152/ajpendo.1998.274.3.e547.
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Urea production rate (Ra) is commonly measured using a primed continuous tracer urea infusion, but the accuracy of this method has not been clearly established in humans. We used intravenous infusions of unlabeled urea to assess the accuracy of this technique in normal, postabsorptive men under the following four different conditions: 1) tracer [13C]urea was infused under basal conditions for 12 h (control); 2) tracer [13C]urea was infused for 12 h, and unlabeled urea was infused from hours 4 to 12 at a rate twofold greater than the endogenous Ra (“step” infusion); 3) tracer [13C]urea was infused for 12 h, and unlabeled urea was infused from hours 4 to 8 (“pulse” infusion); and 4) tracer [13C]urea was infused for 9 h, and unlabeled alanine was infused at a rate of 120 mg ⋅ kg−1 ⋅ h−1(1.35 mmol ⋅ kg−1 ⋅ h−1) from hours 4 to 9. Urea Ra was calculated using the isotopic steady-state equation (tracer infusion rate/tracer-to-tracee ratio), Steele’s non-steady-state equation, and urinary urea excretion corrected for changes in total body urea. For each subject, endogenous urea Ra was measured at hour 4 of the basal condition, and the sum of this rate plus exogenous urea input was considered as “true urea input.” Under control conditions, urea Ra at hour 4 was similar to that measured at hour 12. After 8-h step and 4-h pulse unlabeled urea infusions, Steele’s non-steady-state equation underestimated true urea input by 22% (step) and 33% (pulse), whereas the nonisotopic method underestimated true urea input by 28% (step) and 10% (pulse). Similar conclusions were derived from the alanine infusion. These results indicate that, although Steele’s non-steady-state equation and the nontracer method more accurately predict total urea Ra than the steady-state equation, they nevertheless seriously underestimate total urea Ra for as long as 8 h after a change in true urea Ra.
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Seki, Akira, Kotarou Hayashi, Takafumi Amino, Genichi Shigesato, Takayuki Nozaki, Masafumi Azuma, and Masayoshi Suehiro. "A Non-steady State Model for the Austenite-to-ferrite Transformation Kinetics under the Non-partition Condition in Fe–C–Mn Alloys." ISIJ International 59, no. 12 (December 15, 2019): 2311–18. http://dx.doi.org/10.2355/isijinternational.isijint-2019-216.
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Fomin, Sergei. "Three Regimes of Non-Newtonian Rimming Flow." Journal of Fluids Engineering 128, no. 1 (July 4, 2005): 107–12. http://dx.doi.org/10.1115/1.2137342.
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The present study is related to the rimming flow of non-Newtonian fluid on the inner surface of a horizontal rotating cylinder. Using a scale analysis, the main characteristic scales and nondimensional parameters, which describe the principal features of the process, are found. Exploiting the fact that one of the parameters is very small, an approximate asymptotic mathematical model of the process is developed and justified. For a wide range of fluids, a general constitutive law can be presented by a single function relating shear stress and shear rate that corresponds to a generalized Newtonian model. For this case, the run-off condition for rimming flow is derived. Provided the run-off condition is satisfied, the existence of a steady-state solution is proved. Within the bounds stipulated by this condition, film thickness admits a continuous solution, which corresponds to subcritical and critical flow regimes. It is proved that for the critical regime the solution has a corner on the rising wall of the cylinder. In the supercritical flow regime, a discontinuous solution is possible and a hydraulic jump may occur. It is shown that straightforward leading order steady-state theory can work well to study the shock location and height. For the particular case of a power-law model, the analytical solution of a steady-state equation for the fluid film thickness is found in explicit form. More complex rheological models, which show linear Newtonian behavior at low shear rates with transition to power law at moderate shear rates, are also considered. In particular, numerical computations were carried out for the Ellis model. For this model, some analytical asymptotic solutions have also been obtained in explicit form and compared with the results of numerical computations. Based on these solutions, the optimal values of parameters, which should be used in the Ellis equation for the correct simulation of the coating flows, are determined; the criteria that guarantee the steady-state continuous solutions are defined; and the size and location of the stationary hydraulic jumps, which form when the flow is in the supercritical state, are obtained for the different flow parameters.
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GRAFOV, BORIS M. "LANGEVIN'S APPROACH TO NON-GAUSSIAN INTERNAL NOISE DESCRIPTION." Fluctuation and Noise Letters 04, no. 04 (December 2004): L617—L622. http://dx.doi.org/10.1142/s0219477504002245.
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The dual Langevin stochastic equations for non-Gaussian internal noise that are consistent with Nyquist's fluctuation-dissipation theorem are derived. It results in the fact that the equilibrium current-voltage cumulant spectra possess the invariance property. The possibility to use the dual Langevin stochastic equations under the steady-state electrical current condition and in the quantum frequency range is discussed.
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Norton-Ford, Jessamy Sara, Siyi Deng, Ramesh Srinivasan, and Mary Louise Kean. "Sensitivity of the gamma band auditory steady state response to linguistic features of a stimulus." LSA Annual Meeting Extended Abstracts 1 (May 2, 2010): 40. http://dx.doi.org/10.3765/exabs.v0i0.519.
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Recent work has found differences in lateralization of gamma band auditory steady state response power (?-aSSR) in temporo-parietal areas to speech vs. non-speech stim- uli, based on differences in “meaningfulness” (Deng & Srinivasan, 2009). To investigate sensitivity of ?-aSSR to linguistic features of a stimulus, EEG data was collected from six participants in response to 40Hz amplitude-modulated speech, jabberwocky, reversed speech and spectrally-rotated (“unintelligible”) speech. Significance tests were conducted for the four conditions, within and across-hemisphere. Additionally, correlational analysis of stimulus speech envelope and EEG output will be conducted. Initial results indicate overall right-lateralization, and additional left-hemisphere distinction by condition.
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Agrisuelas, J., J. J. García-Jareño, C. Moreno, and F. Vicente. "Correction of mass drift in ac-electrogravimetry of Prussian Yellow films. Mass impedance under apparently non-steady state condition." Electrochimica Acta 138 (August 2014): 200–209. http://dx.doi.org/10.1016/j.electacta.2014.06.102.
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Deng, Wen Jun, C. Li, Wei Xia, and X. Z. Wei. "Finite Element Modeling of Burr Formation in Orthogonal Metal Cutting." Advanced Materials Research 53-54 (July 2008): 71–76. http://dx.doi.org/10.4028/www.scientific.net/amr.53-54.71.
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A coupled thermo-mechanical model of plane-strain orthogonal metal cutting including burr formation is presented using the commercial finite element code. A simulation procedure based on Normalized Cockroft-Latham damage criterion is proposed for the purpose of better understanding the burr formation mechanism and obtaining a quantitative analysis of burrs at exit. The cutting process is simulated from the transient initial chip formation state to the steady-state of cutting, and then to tool exit transient chip flow, by incrementally advancing the cutting tool. The effects of cutting condition on the non-steady-state chip flow while tool exit can be investigated using the developed finite element model.
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CONSIGLIERI, LUISA. "STEADY-STATE FLOWS OF THERMAL VISCOUS INCOMPRESSIBLE FLUIDS WITH CONVECTIVE-RADIATION EFFECTS." Mathematical Models and Methods in Applied Sciences 16, no. 12 (December 2006): 2013–27. http://dx.doi.org/10.1142/s0218202506001790.
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The work deals with the coupled system constituted by the equations of motion and energy with nonlinear and nonlocal boundary conditions in order to describe the thermal flow motion of a class of non-Newtonian fluids and the convective-radiation balance, respectively. For the constitutive laws in an n-dimensional space (n = 2,3), the stress tensor and the heat flux are considered related with the (p,q) coercivity parameters for p > 2n/(n + 1) and q > np/(p(n + 1) - n), respectively. The radiation character on the boundary condition presents an additional difficulty to the problem which already includes energy-dependent viscosity and conductivity behaviors. In the framework of nonstandard Sobolev spaces we prove the existence of steady-state solutions applying a fixed point argument. We also study the existence of a solution to a coupled system motivated by the buoyancy driven flows from geophysical and astrophysical models.
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Gouzé, Jean-Luc. "Positive and Negative Circuits in Dynamical Systems." Journal of Biological Systems 06, no. 01 (March 1998): 11–15. http://dx.doi.org/10.1142/s0218339098000054.
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We state precisely and demonstrate two conjectures of R. Thomas following which (a) the existence of a positive circuit in the oriented interaction graph of a differential system is a necessary condition for the existence of several steady states, and (b) the existence of a negative non-oriented circuit of length at least two is a necessary condition for the existence of a stable periodic orbit.
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Yu, Cheng-Wei, Frank Liu, and Ben R. Hodges. "Consistent initial conditions for the Saint-Venant equations in river network modeling." Hydrology and Earth System Sciences 21, no. 9 (September 29, 2017): 4959–72. http://dx.doi.org/10.5194/hess-21-4959-2017.
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Abstract. Initial conditions for flows and depths (cross-sectional areas) throughout a river network are required for any time-marching (unsteady) solution of the one-dimensional (1-D) hydrodynamic Saint-Venant equations. For a river network modeled with several Strahler orders of tributaries, comprehensive and consistent synoptic data are typically lacking and synthetic starting conditions are needed. Because of underlying nonlinearity, poorly defined or inconsistent initial conditions can lead to convergence problems and long spin-up times in an unsteady solver. Two new approaches are defined and demonstrated herein for computing flows and cross-sectional areas (or depths). These methods can produce an initial condition data set that is consistent with modeled landscape runoff and river geometry boundary conditions at the initial time. These new methods are (1) the pseudo time-marching method (PTM) that iterates toward a steady-state initial condition using an unsteady Saint-Venant solver and (2) the steady-solution method (SSM) that makes use of graph theory for initial flow rates and solution of a steady-state 1-D momentum equation for the channel cross-sectional areas. The PTM is shown to be adequate for short river reaches but is significantly slower and has occasional non-convergent behavior for large river networks. The SSM approach is shown to provide a rapid solution of consistent initial conditions for both small and large networks, albeit with the requirement that additional code must be written rather than applying an existing unsteady Saint-Venant solver.
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Anderson, D., J. Jarzynski, and R. F. Salant. "Condition monitoring of mechanical seals: Detection of film collapse using reflected ultrasonic waves." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 9 (September 1, 2000): 1187–94. http://dx.doi.org/10.1177/095440620021400901.
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A method for detecting the collapse of the lubricating film in a mechanical seal has been developed. A piezoelectric transducer is placed behind the non-rotating seal face and is used to generate ultrasonic waves, which propagate towards the interface between the two seal faces. The same transducer is used to detect the reflected waves, whose amplitude is a measure of the degree of contact between the faces. The results of bench tests, steady-state tests and transient tests show that the method is effective.
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Kovač, Žarko, Trevor Platt, and Shubha Sathyendranath. "Stability and resilience in a nutrient-phytoplankton marine ecosystem model." ICES Journal of Marine Science 77, no. 4 (June 29, 2020): 1556–72. http://dx.doi.org/10.1093/icesjms/fsaa067.
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Abstract We seek to understand, in mathematical terms, the causes of stability in marine phytoplankton biomass. The stability of a simple, mixed-layer-phytoplankton-nutrient model is analysed. Primary production is modelled as a non-linear function of nutrient concentration and light. The steady state of the model system is demonstrated to be stable with a linear relation between steady state biomass and nutrients. The causes of stability are shown to be shading and nutrient limitation. When only light limitation and shading are taken into account, the steady state is a sink node. However, when nutrient limitation is taken into account, without shading, the steady state can be either a sink node or a spiral sink. The transition from a sink node to a spiral sink occurs when normalized mixed layer production becomes larger than the equivalent influx rate of nutrients into the mixed layer, demonstrating that nutrient limitation of production is a necessary, but not a sufficient condition for oscillatory solutions. In both cases, the characteristic return times are derived explicitly. The effect of shading is found to cause the depression of the steady state towards lower biomass than would otherwise be attainable. The influence of mixed-layer depth variation on stability is also analysed.
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Mao, X., H. M. Blackburn, and S. J. Sherwin. "Optimal inflow boundary condition perturbations in steady stenotic flow." Journal of Fluid Mechanics 705 (March 1, 2012): 306–21. http://dx.doi.org/10.1017/jfm.2012.58.
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AbstractWe determine optimal inflow boundary perturbations to steady flow through a straight inflexible tube with a smooth axisymmetric stenosis at a bulk-flow Reynolds number $\mathit{Re}= 400$, for which the flow is asymptotically stable. The perturbations computed produce an optimal gain, i.e. kinetic energy in the domain at a given time horizon normalized by a measure of time-integrated energy on the inflow boundary segment. We demonstrate that similarly to the optimal initial condition problem, the gain can be interpreted as the leading singular value of the forward linearized operator that evolves the boundary conditions to the final state at a fixed time. In this investigation we restrict our attention to problems where the temporal profile of the perturbations examined is a product of a Gaussian bell and a sinusoid, whose frequency is selected to excite axial wavelengths similar to those of the optimal initial perturbations in the same geometry. Comparison of the final state induced by the optimal boundary perturbation with that induced by the optimal initial condition demonstrates a close agreement for the selected problem. Previous works dealing with optimal boundary perturbation considered a prescribed spatial structure and computed an optimal temporal variation of a wall-normal velocity component, whereas in this paper we consider the problem of a prescribed temporal structure and compute the optimal spatial variation of velocity boundary conditions over a one-dimensional inflow boundary segment. The methodology is capable of optimizing boundary perturbations in general non-parallel two- and three-dimensional flows.
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Yi, Taishan, and Xingfu Zou. "Map dynamics versus dynamics of associated delay reaction–diffusion equations with a Neumann condition." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466, no. 2122 (April 29, 2010): 2955–73. http://dx.doi.org/10.1098/rspa.2009.0650.
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In this paper, we consider a class of delay reaction–diffusion equations (DRDEs) with a parameter ε >0. A homogeneous Neumann boundary condition and non-negative initial functions are posed to the equation. By letting , such an equation is formally reduced to a scalar difference equation (or map dynamical system). The main concern is the relation of the absolute (or delay-independent) global stability of a steady state of the equation and the dynamics of the nonlinear map in the equation. By employing the idea of attracting intervals for solution semiflows of the DRDEs, we prove that the globally stable dynamics of the map indeed ensures the delay-independent global stability of a constant steady state of the DRDEs. We also give a counterexample to show that the delay-independent global stability of DRDEs cannot guarantee the globally stable dynamics of the map. Finally, we apply the abstract results to the diffusive delay Nicholson blowfly equation and the diffusive Mackey–Glass haematopoiesis equation. The resulting criteria for both model equations are amazingly simple and are optimal in some sense (although there is no existing result to compare with for the latter).
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WHITE, BRIAN L., and KARL R. HELFRICH. "Gravity currents and internal waves in a stratified fluid." Journal of Fluid Mechanics 616 (December 10, 2008): 327–56. http://dx.doi.org/10.1017/s0022112008003984.
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A steady theory is presented for gravity currents propagating with constant speed into a stratified fluid with a general density profile. Solution curves for front speed versus height have an energy-conserving upper bound (the conjugate state) and a lower bound marked by the onset of upstream influence. The conjugate state is the largest-amplitude nonlinear internal wave supported by the ambient stratification, and in the limit of weak stratification approaches Benjamin's energy-conserving gravity current solution. When the front speed becomes critical with respect to linear long waves generated above the current, steady solutions cannot be calculated, implying upstream influence. For non-uniform stratification, the critical long-wave speed exceeds the ambient long-wave speed, and the critical-Froude-number condition appropriate for uniform stratification must be generalized. The theoretical results demonstrate a clear connection between internal waves and gravity currents. The steady theory is also compared with non-hydrostatic numerical solutions of the full lock release initial-value problem. Some solutions resemble classic gravity currents with no upstream disturbance, but others show long internal waves propagating ahead of the gravity current. Wave generation generally occurs when the stratification and current speed are such that the steady gravity current theory fails. Thus the steady theory is consistent with the occurrence of either wave-generating or steady gravity solutions to the dam-break problem. When the available potential energy of the dam is large enough, the numerical simulations approach the energy-conserving conjugate state. Existing laboratory experiments for intrusions and gravity currents produced by full-depth lock exchange flows over a range of stratification profiles show excellent agreement with the conjugate state solutions.
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Pumo, D., F. Viola, and L. V. Noto. "Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations." Hydrology and Earth System Sciences Discussions 4, no. 5 (September 4, 2007): 2769–809. http://dx.doi.org/10.5194/hessd-4-2769-2007.
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Abstract. The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from the soil water balance, a stochastic differential equation where the unknown quantity is the function of the soil moisture, depending both on spaces and time. Most of existing solutions 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 problem by subtracting generalities from it. The steady-state hypothesis, used in many ecohydrological works, 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, thus recharging the soil moisture. This initial condition, especially for deep rooted vegetation, has a great importance by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during its first period. The aim of this paper is to investigate the soil moisture dynamics using a simple non-steady numerical ecohydrological model. The numerical model is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climate and soil conditions in steady state conditions. The proposed model gives both the soil moisture time-profile and the vegetation static water stress time-profile. From the former it is possible to extract the probability density function of soil-moisture during the whole growing season, while the latter allows the estimation of the vegetation response to the water stress. Here the differences between the analytical and the numerical probability density functions are presented, showing how the numerical model is able to capture the effects of winter recharge on the soil moisture. The dynamic water stress is numerically evaluated, implicitly taking into account the soil moisture condition at the beginning of the growing season. The model proposed here is applied in the forested river basin of the Eleuterio in Sicily (Italy).
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Muramatsu, Mayu, Keiji Yashiro, Tatsuya Kawada, and Kenjiro Tarada. "Numerical simulations of non-stationary distributions of electrochemical potentials in SOFC." Engineering Computations 34, no. 6 (August 7, 2017): 1956–88. http://dx.doi.org/10.1108/ec-08-2016-0311.
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Purpose The purpose of this study is to develop a simulation method to calculate non-stationary distributions of the chemical potential of oxygen in a solid oxide fuel cell (SOFC) under operation. Design/methodology/approach The initial-boundary value problem was appropriately formulated and the appropriate boundary conditions were implemented so that the problem of non-stationary behavior of SOFC can be solved in accordance with actual operational and typical experimental conditions. The dependencies of the material properties on the temperature and partial pressure of oxygen were also elaborately introduced to realize actual material responses. The capability of the proposed simulation method was demonstrated under arbitrary operating conditions. Findings The steady state calculated with the open circuit voltage condition was conformable with the analytical solution. In addition, the transient states of the spatial distributions of potentials and currents under the voltage- and current-controlled conditions were successfully differentiated, even though they eventually became the same steady state. Furthermore, the effects of dense materials assumed for interconnects and current collectors were found to not be influential. It is thus safe to conclude that the proposed method enables us to simulate any type of transient simulations regardless of controlling conditions. Practical implications Although only uniaxial models were tested in the numerical examples in this paper, the proposed method is applicable for arbitrary shapes of SOFC cells. Originality/value The value of this paper is that adequate numerical simulations by the proposed method properly captured the electrochemical transient transport phenomena in SOFC under various operational conditions, and that the applicability was confirmed by some numerical examples.
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Liu, Xiao Ling, Da Tong Song, and Pei Ran Yang. "On Transient EHL of a Skew Roller Subjected to a Load Impact in Rolling Bearings." Key Engineering Materials 739 (June 2017): 108–19. http://dx.doi.org/10.4028/www.scientific.net/kem.739.108.
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Based on the non-steady state operating condition in machine elements, numerical analysis of a transient elastohydrodynamic lubrication (EHL) finite line contact between a skewed roller and an outer race in cylindrical roller bearings was carried out, and a complete numerical solution of skewed roller pairs EHL under the transient condition was obtained. The effects of the load impact, together with the skewing angle impulses on the lubricating performance of skew roller pairs were discussed. Results show that, different from the steady state, the transient effect of the skew roller lubrication is mainly governed by the skew angle impulse, and the load impact. The film dimple is generated during the load impact, or the skewing angle impulse due to the normal approach velocity of the film. Compared to that of the ideal roller, the minimum film thickness decreases due to the roller skew when the transient load happens. Variation in the skewing angle leads to contrary distribution of the film thickness at the two half parts of the roller. Meanwhile, it can decrease the minimum film thickness and be harmful to the lubrication compared to the steady state. Consequently, the transient effect in the process of lubrication of skew roller pairs should not be neglected.
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Xiong, Shunhe, and Richard F. Salant. "A Dynamic Model of a Contacting Mechanical Seal for Down-Hole Tools." Journal of Tribology 125, no. 2 (March 19, 2003): 391–402. http://dx.doi.org/10.1115/1.1501085.
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A dynamic model of a contacting mechanical seal for down-hole tools, operating in the mixed lubrication regime, has been constructed. Two dynamic cases are examined: the behavior of the seal after it is subjected to a non-equilibrium initial condition and the behavior of the seal as it tracks axial runout of the rotating face. In both cases the seal experiences much larger leakage and inflow (incursion) rates than under steady-state conditions, although in the former case the duration of the increased rates is very short.
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Lawlor, Kelly, and Yunliang Meng. "The changing trend in songbirds’ abundance, variety and physical condition in Connecticut’s forestry habitat." Forestry Studies 70, no. 1 (June 1, 2019): 17–30. http://dx.doi.org/10.2478/fsmu-2019-0002.
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Abstract Songbirds are facing rapid population declines in Connecticut due to habitat loss. Man-made habitats such as powerline corridors are one of the few remaining ideal habitats for songbirds in the state. This study aims to determine if the abundance and variety of song-birds in four selected forests (i.e. Naugatuck State Forest, Sharon Audubon Society, Miles Wildlife Sanctuary, and Great Mountain Forest Species Variety) in Connecticut show patterns of decline from 2005 to 2014. This study also compares the physical condition of songbirds captured along a powerline corridor in the Naugatuck State Forest with those captured in the rest three non-fragmented forests in Northwestern Connecticut using Mann-Whitney U tests. Weight and wingspan are used as indicators of bird physical condition. The results demonstrate that the three non-fragmented forests experienced a steady decline in the variety of songbirds between 2005 and 2014. In addition, songbirds’ abundance decreased steadily during the same period, except that of the ovenbird (Seiurus aurocapilla) and wood thrush (Hylocichla mustelina) in Miles Wildlife Sanctuary. The results from the Mann-Whitney U test have shown that after sex- and age-controlled features, the physical conditions of the three selective songbirds – veery (Catharus fuscescens), ovenbird, and wood thrush – tend to be better in the Naugatuck State Forest than in the three non-fragmented forests – Sharon Audubon Society, Miles Wildlife Sanctuary, and Great Mountain Forest Species Variety. Given are recommendations on how to protect the shrubland habitat along powerline corridors and how to create the shrubland habitat in non-fragmented forests.
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Cao, Maojun, Hong Xiao, and Caizhi Wang. "Productivity-Index Behavior for a Horizontal Well Intercepted by Multiple Finite-Conductivity Fractures Considering Nonlinear Flow Mechanisms under Steady-State Condition." Energies 13, no. 8 (April 17, 2020): 2015. http://dx.doi.org/10.3390/en13082015.
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In this paper, a mathematical model is proposed to investigate the effect of nonlinear flow mechanisms on productivity-index (PI) behavior in hydraulically fractured reservoirs during steady-state condition. This approach focuses on the fact that PI approaches a constant value at a certain time, indicating the beginning of steady state. In this model, the reservoirs are considered as an elliptical-shaped drainage with constant-pressure boundary, which is depleted by a multiple-fractured horizontal well (MFHW), and various nonlinear flow mechanisms, such as the non-Darcy flow effect and pressure-dependency effect, control flow patterns in the hydraulic fractures. Then, an exact algorithm of solving the resulting nonlinear equations is developed to obtain the PI of MFHW using a semi-analytical approach. Next, type curves are generated to investigate the influences of flow mechanisms and fracture properties on PI. The most interesting points in this study are the following: (1) PI is determined by the properties of MHFW (i.e., dimensions and configuration), the reservoir geometry, and flow mechanism; (2) PI is deteriorated by non-Darcy flow caused by inertial forces; and (3) PI is reduced under the influence of pressure sensitivity caused by the degradation of dynamic conductivity. Generally, this study provides a significant insight into understanding the factors affecting the productivity of a MFHW with nonlinear flow mechanisms.
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Saood, Ahmad, Zain A. Khan, Mohd T. Parvez, and Arshad H. Khan. "On the Large Amplitude Forced Vibration Analysis of Composite Sectorial Plates." Journal of Composites Science 5, no. 3 (March 15, 2021): 83. http://dx.doi.org/10.3390/jcs5030083.
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The nonlinear steady state large amplitude forced vibration response of a laminated composite annular sector plate is presented. The nonlinear governing equation of motion of the laminated composite annular sector plate has been obtained using kinematics of first-order shear deformation theory (FSDT) and employing Hamilton’s principle. The governing equations of motion have been solved in a time domain using a modified shooting method and arc-length/pseudo-arc length continuation technique. The influence of the boundary condition, sector angle, and annularity ratio on the linear as well as nonlinear steady state forced vibration response has been investigated. The strain/stress variation across the thickness of the annular sector plate is presented to explain the reason for a decrease/increase in hardening nonlinear behaviour. The periodic variation of the non-linear steady state stress has also been obtained to throw light into the factors influencing the unequal stress half cycles and multiple cyclic stress reversals, which is detrimental to the fatigue design of laminated composite annular sectorial plates. The frequency spectra of the steady state stress reveals large even and odd higher harmonic contributions for different cases due to changes in the restoring force dynamics. The modal interaction/exchange during a cycle is demonstrated using a deformed configuration of the laminated annular sector plate.
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Xie, Nan, Yihai He, Ming Yao, and Changwei Jiang. "Lattice Boltzmann simulation of transient natural convection of air in square cavity under a magnetic quadrupole field." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 8 (November 7, 2016): 2441–61. http://dx.doi.org/10.1108/hff-07-2015-0277.
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Purpose The purpose of this paper is to apply the lattice Boltzmann method (LBM) with multiple distribution functions model, to simulate transient natural convection of air in a two-dimensional square cavity in the presence of a magnetic quadrupole field, under non-gravitational as well as gravitational conditions. Design/methodology/approach The density-temperature double distribution functions and D2Q9 model of LBM for the momentum and temperature equations are currently employed. Detailed transient structures of the flow and isotherms at unsteady state are obtained and compared for a range of magnetic force numbers from 1 to 100. Characteristics of the natural convection at initial moment, quasi-steady state and steady state are presented in present work. Findings At initial time, effects of the magnetic field and gravity are both relatively limited, but the effects become efficient as time evolves. Bi-cellular flow structures are obtained under non-gravitational condition, while the flow presents a single vortex structure at first under gravitational condition, and then emerges a bi-cellular structure with the increase of magnetic field force number. The average Nusselt number generally increases with the augment of magnetic field intensity. Practical implications This paper will be useful in the researches on crystal material and protein growth, oxygen concentration sensor, enhancement or suppression of the heat transfer in micro-electronics and micro-processing technology, etc. Originality/value The current study extended the application of LBM on the transient natural convective problem of paramagnetic fluids in the presence of an inhomogeneous magnetic field.
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Wu, Xue Li, Zi Zhong Tan, and Liang Gao. "A New Variable Step Size LMS Adaptive Filtering Algorithm and its Simulations." Applied Mechanics and Materials 513-517 (February 2014): 3736–39. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.3736.
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. Aiming at the disadvantage of the variable step size LMS adaptive filtering algorithms' convergence speed contradicting its steady-state error, a novel non-liner functional relationship between μ (n) and error signal e (n) was established. On the basis of the functional relationship, a new algorithm of variable step size LMS adaptive filtering was presented. The step size factor of the new algorithm is adjusted by the absolute value of the product of the current and former errors. It also uses the absolute estimation error compensation terms disturbance to speed up the convergence of adaptive filter tap weight vector. At the same time, the algorithm considers the relationship between step length of the last iteration and the former M error signal. As a result the algorithm has higher convergence characteristic and small steady state error. The theoretical analysis and simulation results show that the new algorithm has faster convergence speed, lower steady state error and better performance of noise suppression, also show the overall performance of this algorithm exceeds some others condition.
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RamReddy, Ch, P. Naveen, and D. Srinivasacharya. "Influence of Non-linear Boussinesq Approximation on Natural Convective Flow of a Power-Law Fluid along an Inclined Plate under Convective Thermal Boundary Condition." Nonlinear Engineering 8, no. 1 (January 28, 2019): 94–106. http://dx.doi.org/10.1515/nleng-2017-0138.
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Abstract In the present investigation, a problem of natural convective flow of a non-Newtonian power-law fluid over an inclined plate saturated in a non-Darcy porous medium is considered. Also, the nonlinear Boussinesq approximation and convective thermal boundary condition are taken into account to address heat and mass transfer phenomena of thermal systems which are operated at moderate and very high temperatures. The steady-state boundary layer equations are non-dimensionalized into non-similar form and then solved numerically by the local non-similarity method with successive linearisation method (SLM). The effects of various physical parameters on the fluid flow, heat and mass transfer characteristics are depicted graphically and analysed in detail.
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Zuo, Z., and J. Oerlemans. "Numerical modelling of the historic front variation and the future behaviour of the Pasterze glacier, Austria." Annals of Glaciology 24 (1997): 234–41. http://dx.doi.org/10.1017/s0260305500012234.
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An ice-flow model is used to simulate the front variations of the Pasterze glacier, Austria. The model deals explicitly with the ice flux from sub-streams and tributaries to the main ice stream. The dynamic calibration method adopted successfully calibrates the ice-flow model under a non-steady-state condition. Despite the complexity of the glacier geometry, the ice dynamics of the Pasterze are adequately simulated. Results of the sensitivity experiments suggest that the Pasterze glacier has been in a non-steady state most of the time and has a response time of 34–50 years. Projections of the behaviour of the Pasterze in the next 100 years are made under various climate scenarios. Results suggest that the Pasterze will undergo a substantial retreat if there is future warming. The glacier is likely to retreat 2–5 km by the year 2100. The ice volume could be reduced by 24–63% by the end of the 21st century.