Search results for "Stationary state"
showing 10 items of 40 documents
New Approach of Controlling Cardiac Alternans
2018
The alternans of the cardiac action potential duration is a pathological rhythm. It is considered to be relating to the onset of ventricular fibrillation and sudden cardiac death. It is well known that, the predictive control is among the control methods that use the chaos to stabilize the unstable fixed point. Firstly, we show that alternans (or period-2 orbit) can be suppressed temporally by the predictive control of the periodic state of the system. Secondly, we determine an estimation of the size of a restricted attraction's basin of the unstable equilibrium point representing the unstable regular rhythm stabilized by the control. This result allows the application of predictive control…
2015
Abstract. Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules …
Generalization of Vinen’s equation including transition to superfluid turbulence
2005
A phenomenological generalization of the well known Vinen equation for the evolution of vortex line density in superfluid counterflow turbulence is proposed. This generalization includes nonlinear production terms in the counterflow velocity and corrections depending on the diameter of the tube. The equation provides a unified framework for the various phenomena (stationary states and transitions) present in counterflow superfluid turbulence: in fact, it is able to describe the laminar regime, the first-order transition from laminar to turbulent TI state, the two turbulent states, the transition from TI to TII turbulent states, and it yields a slower decay of the counterflow turbulence than…
Stationary states in quantum walk search
2016
When classically searching a database, having additional correct answers makes the search easier. For a discrete-time quantum walk searching a graph for a marked vertex, however, additional marked vertices can make the search harder by causing the system to approximately begin in a stationary state, so the system fails to evolve. In this paper, we completely characterize the stationary states, or 1-eigenvectors, of the quantum walk search operator for general graphs and configurations of marked vertices by decomposing their amplitudes into uniform and flip states. This infinitely expands the number of known stationary states and gives an optimization procedure to find the stationary state c…
Adjacent Vertices Can Be Hard to Find by Quantum Walks
2017
Quantum walks have been useful for designing quantum algorithms that outperform their classical versions for a variety of search problems. Most of the papers, however, consider a search space containing a single marked element only. We show that if the search space contains more than one marked element, their placement may drastically affect the performance of the search. More specifically, we study search by quantum walks on general graphs and show a wide class of configurations of marked vertices, for which search by quantum walk needs \(\varOmega (N)\) steps, that is, it has no speed-up over the classical exhaustive search. The demonstrated configurations occur for certain placements of …
An Ecology and Economy Coupling Model. A global stationary state model for a sustainable economy in the Hamiltonian formalism
2020
Abstract The severity of the two deeply correlated crises, the environmental and the economic ones, needs to be faced also in theoretical terms; thus, the authors propose a model yielding a global “stationary state”, following the idea of a “steady-state economics” by Georgescu-Rogen and Herman Daly, by constructing only one dynamical system of ecological and economic coupled variables. This is possible resorting to the generalized Volterra model, that, translated in the Hamiltonian formalism and its Hamilton equations, makes possible to “conjugate” every pair of variables, one economic, the other one ecological, in describing the behavior in time of a unique dynamical system. Applying the …
Upperbounds on the probability of finding marked connected components using quantum walks
2019
Quantum walk search may exhibit phenomena beyond the intuition from a conventional random walk theory. One of such examples is exceptional configuration phenomenon -- it appears that it may be much harder to find any of two or more marked vertices, that if only one of them is marked. In this paper, we analyze the probability of finding any of marked vertices in such scenarios and prove upper bounds for various sets of marked vertices. We apply the upper bounds to large collection of graphs and show that the quantum search may be slow even when taking real-world networks.
Dependence of two-proton radioactivity on nuclear pairing models
2017
Sensitivity of two-proton emitting decay to nuclear pairing correlation is discussed within a time-dependent three-body model. We focus on the $^6$Be nucleus assuming $\alpha + p + p$ configuration, and its decay process is described as a time-evolution of the three-body resonance state. For a proton-proton subsystem, a schematic density-dependent contact (SDDC) pairing model is employed. From the time-dependent calculation, we observed the exponential decay rule of a two-proton emission. It is shown that the density dependence does not play a major role in determining the decay width, which can be controlled only by the asymptotic strength of the pairing interaction. This asymptotic pairin…
From stationary state to endogenous growth: International trade in the mathematical formulation of the Ricardian system
2015
In his 1814–15 correspondence with Malthus and in his Essay on Profits, Ricardo championed the free importation of wage goods as a highly effective growth-enhancing policy. In order to capture this aspect in the mathematical formulation of the Ricardian system first introduced by Pasinetti in 1960 in the context of a closed economy, we produce a variant of that model where the economy is a small open one. We show that this economy is characterised by endogenous growth since the growth rate is bounded from below and we locate two thresholds concerning the allocation of labour among the two sectors of the economy and the pattern of international trade.
From endogenous growth to stationary state: The world economy in the mathematical formulation of the Ricardian system
2016
AbstractWe analyse international trade in a Pasinetti–Ricardo growth model in the world economy scenario in which several small trading countries coexist and international commodity prices are determined by the interplay of supply and demand amongst them. We demonstrate that all the trading countries eventually reach the stationary state, though this process is not monotonic and the dynamics of capital and population may actually push some countries towards the stationary state and others away from it. We also use our model to assess an argument which Malthus employed in the second edition of An Essay on the Principle of Population (1803) to support a policy of agricultural protectionism.