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## Bang-Bang Control of Feeding: Role of Hypothalamic and Satiety Signals

Zanutto, B. Silvano; Staddon, John E. R
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
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Rats, people, and many other omnivores eat in meals rather than continuously. We show by experimental test that eating in meals is regulated by a simple bang-bang control system, an idea foreshadowed by Le Magnen and many others, shown by us to account for a wide range of behavioral data, but never explicitly tested or tied to neurophysiological facts. The hypothesis is simply that the tendency to eat rises with time at a rate determined by satiety signals. When these signals fall below a set point, eating begins, in on–off fashion. The delayed sequelae of eating increment the satiety signals, which eventually turn eating off. Thus, under free conditions, the organism eats in bouts separated by noneating activities. We report an experiment with rats to test novel predictions about meal patterns that are not explained by existing homeostatic approaches. Access to food was systematically but unpredictably interrupted just as the animal tried to start a new meal. A simple bang-bang model fits the resulting meal-pattern data well, and its elements can be identified with neurophysiological processes. Hypothalamic inputs can provide the set point for longer-term regulation carried out by a comparator in the hindbrain. Delayed gustatory and gastrointestinal aftereffects of eating act via the nucleus of the solitary tract and other hindbrain regions as neural feedback governing short-term regulation. In this way...

## Bang-bang Model for Regulation of Local Blood Flow

Golub, Aleksander S.; Pittman, Roland N.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The classical model of metabolic regulation of blood flow in muscle tissue implies the maintenance of basal tone in arterioles of resting muscle and their dilation in response to exercise and/or tissue hypoxia via the evoked production of vasodilator metabolites by myocytes. A century-long effort to identify specific metabolites responsible for explaining active and reactive hyperemia has not been successful. Furthermore, the metabolic theory is not compatible with new knowledge on the role of physiological radicals (e.g., nitric oxide, NO, and superoxide anion, O2−) in the regulation of microvascular tone. We propose a model of regulation in which muscle contraction and active hyperemia are considered the physiologically normal state. We employ the “bang-bang” or “on/off” regulatory model which makes use of a threshold and hysteresis; a float valve to control the water level in a tank is a common example of this type of regulation. Active bang-bang regulation comes into effect when the supply of oxygen and glucose exceeds the demand, leading to activation of membrane NADPH oxidase, release of O2− into the interstitial space and subsequent neutralization of the interstitial NO. Switching arterioles on/off when local blood flow crosses the threshold is realized by a local cell circuit with the properties of a bang-bang controller...

## Towards qubit noise spectroscopy by quantum bang-bang control

Chen, Zilong, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 91 p.; 4403746 bytes; 4408015 bytes; application/pdf; application/pdf
ENG
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Quantum bang-bang control is a method of suppressing decoherence in qubits [VKL99, VL98]. To date, mathematically rigorous treatments of quantum bang-bang control offered little intuition. To complement existing approaches and to seek better understanding, I present intuitive pictures to think about quantum bang-bang control. In addition, I develop a formalism for treating phase noise moments of a qubit under quantum bang-bang control. Although the desired purpose of quantum bang-bang control is to remove noise, it is conceivable that it can be used to infer information about the noise process and coupling on a qubit. By using a simple random rotation model of single qubit dephasing, I demonstrate how quantum bang-bang control can distinguish between dephasing under different stochastic processes. I also show how quantum bang-bang control can determine noise coupling in a toy model where noise couples to the qubit via a fixed noise axis. These two demonstrations indicate the potential of quantum bang-bang control as a tool for qubit noise spectroscopy.; by Zilong Chen.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, June 2004.; Includes bibliographical references (p. 89-91).

## Second order analysis for bang-bang control problems of PDEs

Casas Rentería, Eduardo
Fonte: Society for Industrial and Applied Mathematics Publicador: Society for Industrial and Applied Mathematics
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
Relevância na Pesquisa
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In this paper, we derive some suﬃcient second order optimality conditions for control problems of partial diﬀerential equations (PDEs) when the cost functional does not involve the usual quadratic term for the control or higher nonlinearities for it. Though not always, in this situation the optimal control is typically bang-bang. Two diﬀerent control problems are studied. The second diﬀers from the ﬁrst in the presence of the L1 norm of the control. This term leads to optimal controls that are sparse and usually take only three diﬀerent values (we call them bang-bang-bang controls). Though the proofs are detailed in the case of a semilinear elliptic state equation, the approach can be extended to parabolic control problems. Some hints are provided in the last section to extend the results.

## Optimal reinsurance under risk and uncertainty

Balbás, Alejandro; Balbás, Beatriz; Balbás, Raquel; Heras, Antonio
Tipo: info:eu-repo/semantics/draft; info:eu-repo/semantics/workingPaper
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This paper deals with the optimal reinsurance problem if both insurer and reinsurer are facing risk and uncertainty, though the classical uncertainty free case is also included. The insurer and reinsurer degrees of uncertainty do not have to be identical. The decision variable is not the retained (or ceded) risk, but its sensitivity with respect to the total claims. Thus, if one imposes strictly positive lower bounds for this variable, the reinsurer moral hazard is totally eliminated. Three main contributions seem to be reached. Firstly, necessary and sufficient opti- mality conditions are given. Secondly, the optimal contract is often a bang-bang solution, i:e:, the sensitivity between the retained risk and the total claims saturates the imposed constraints. For some special cases the optimal contract might not be bang-bang, but there is always a bang-bang contract as close as desired to the optimal one. Thirdly, the optimal reinsurance problem is equivalent to other linear programming problem, despite the fact that risk, uncertainty, and many premium principles are not linear. This may be impor- tant because linear problems are easy to solve in practice, since there are very efficient algorithms.

## Indirect Optimization of Bang-Bang Control Problems and Applications to Formation Flying Missions

ZAVOLI, ALESSANDRO
EN
Relevância na Pesquisa
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This thesis is focused on indirect optimization methods for the design of space missions, and, in particular, to a specific class of optimal control problems whose solution exhibits a discontinuous control law: the so called bang-bang optimal control. Any attempt to solving such problems by using an indirect method without any specific treatment of the bang-bang control inevitably results into a failure, except for trivial problems. The thesis compares two techniques, conceptually quite different, that aim to handle (or just to reduce) issues related to the discontinuous profile of the optimal control: the Multi-Bound Approach and the Continuation-Smoothing Technique. These two approaches are first tried out/tested on a very simple case (the rocket-sled problem) and then applied to obtain the solution of two rather complex problems: the cooperative rendezvous and the deployment of a two-spacecraft formation that flies in a High Eccentricity Orbit (referring to the Simbol-X project). The general philosophy that stands behind either approach is outlined, as well as relative strength and weakness. Range of applicability, effort required to the user, computational time, and convergence radius are analyzed and discussed.; This work was supported by the Centre National d’Etudes Spatiales (CNES)...

## Regularization and Bang-bang conjugate times in optimal control; Regularização e pontos conjugados Bang-bang no controlo óptimo

Silva, Cristiana João Soares da
ENG
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57.16%
Consideramos o problema de controlo óptimo de tempo mínimo para sistemas de controlo mono-entrada e controlo afim num espaço de dimensão finita com condições inicial e final fixas, onde o controlo escalar toma valores num intervalo fechado. Quando aplicamos o método de tiro a este problema, vários obstáculos podem surgir uma vez que a função de tiro não é diferenciável quando o controlo é bang-bang. No caso bang-bang os tempos conjugados são teoricamente bem definidos para este tipo de sistemas de controlo, contudo os algoritmos computacionais directos disponíveis são de difícil aplicação. Por outro lado, no caso suave o conceito teórico e prático de tempos conjugados é bem conhecido, e ferramentas computacionais eficazes estão disponíveis. Propomos um procedimento de regularização para o qual as soluções do problema de tempo mínimo correspondente dependem de um parâmetro real positivo suficientemente pequeno e são definidas por funções suaves em relação à variável tempo, facilitando a aplicação do método de tiro simples. Provamos, sob hipóteses convenientes, a convergência forte das soluções do problema regularizado para a solução do problema inicial, quando o parâmetro real tende para zero. A determinação de tempos conjugados das trajectórias localmente óptimas do problema regularizado enquadra-se na teoria suave conhecida. Provamos...

## Suppression of polarization decoherence for traveling light pulses via bang-bang dynamical decoupling

Lucamarini, M.; Di Giuseppe, G.; Damodarakurup, S.; Vitali, D.; Tombesi, P.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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In the propagation of optical pulses through dispersive media, the frequency degree of freedom acts as an effective decohering environment on the polarization state of the pulse. Here we discuss the application of open-loop dynamical-decoupling techniques for suppressing such a polarization decoherence in one-way communication channels. We describe in detail the experimental proof of principle of the "bang-bang" protection technique recently applied to flying qubits in [Damodarakurup et al., Phys. Rev. Lett. 103, 040502]. Bang-bang operations are implemented through appropriately oriented waveplates and dynamical decoupling is shown to be potentially useful to contrast a generic decoherence acting on polarization qubits propagating in dispersive media like, e.g., optical fibers.; Comment: 14 pages, 15 figures

## Fast transitionless expansions of Gaussian anharmonic traps for cold atoms: bang-singular-bang control

Lu, Xiao-Jing; Chen, Xi; Alonso, J.; Muga, J. G.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Combining invariant-based inverse engineering, perturbation theory, and Optimal Control Theory, we design fast, transitionless expansions of cold neutral atoms or ions in Gaussian anharmonic traps. Bounding the possible trap frequencies and using a "bang-singular-bang" control we find fast processes for a continuum of durations up to a minimum time that corresponds to a purely bang-bang (stepwise frequency constant) control.; Comment: 7 pages, 6 figures

## Enhancement of quantum correlations for the system of cavity QED by applying bang-bang pulses

Xu, Hang-Shi; Xu, Jing-Bo
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We propose a scheme of increasing quantum correlations for the cavity quantum electrodynamics system consisting of two noninteracting two-level atoms each locally interacting with its own quantized field mode by bang-bang pulses. We investigate the influence of the bang-bang pulses on the dynamics of quantum discord, entanglement, quantum mutual information and classical correlation between the two atoms. It is shown that the amount of quantum discord and entanglement of the two atoms can be improved by applying the bang-bang pulses.; Comment: 6 pages, 5 figures

## Empirical Determination of Bang-Bang Operations

Byrd, Mark S.; Lidar, Daniel A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.74%
Strong and fast "bang-bang" (BB) pulses have been recently proposed as a means for reducing decoherence in a quantum system. So far theoretical analysis of the BB technique relied on model Hamiltonians. Here we introduce a method for empirically determining the set of required BB pulses, that relies on quantum process tomography. In this manner an experimenter may tailor his or her BB pulses to the quantum system at hand, without having to assume a model Hamiltonian.; Comment: 14 pages, 2 eps figures, ReVTeX4 two-column

## Attainable subspaces and the bang-bang property of time optimal controls for heat equations

Wang, Gengsheng; Xu, Yashan; Zhang, Yubiao
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.97%
In this paper, we study two subjects on internally controlled heat equations with time varying potentials: the attainable subspaces and the bang-bang property for some time optimal control problems. We present some equivalent characterizations on the attainable subspaces, and provide a sufficient conditions to ensure the bang-bang property. Both the above-mentioned characterizations and the sufficient condition are closely related to some function spaces consisting of some solutions to the adjoint equations. It seems for us that the existing ways to derive the bang-bang property for heat equations with time-invariant potentials (see, for instance, [4],[7],[16],[26]) do not work for the case where the potentials are time-varying. We provide another way to approach it in the current paper.; Comment: 33pages

## Control of spin current in a Bose gas by bang-bang pulses

Eto, Yujiro; Sadgrove, Mark; Hasegawa, Sho; Saito, Hiroki; Hirano, Takuya
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.74%
We generate spin currents in an $^{87}$Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin coherence, as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic $\pi$ pulses (bang-bang control), producing longer spin coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.; Comment: 5 pages, 4 figures

## The existence of optimal bang-bang controls for GMxB contracts

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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A large collection of financial contracts offering guaranteed minimum benefits are often posed as control problems, in which at any point in the solution domain, a control is able to take any one of an uncountable number of values from the admissible set. Often, such contracts specify that the holder exert control at a finite number of deterministic times. The existence of an optimal bang-bang control, an optimal control taking on only a finite subset of values from the admissible set, is a common assumption in the literature. In this case, the numerical complexity of searching for an optimal control is considerably reduced. However, no rigorous treatment as to when an optimal bang-bang control exists is present in the literature. We provide the reader with a bang-bang principle from which the existence of such a control can be established for contracts satisfying some simple conditions. The bang-bang principle relies on the convexity and monotonicity of the solution and is developed using basic results in convex analysis and parabolic partial differential equations. We show that a guaranteed lifelong withdrawal benefit (GLWB) contract admits an optimal bang-bang control. In particular, we find that the holder of a GLWB can maximize a writer's losses by only ever performing nonwithdrawal...

## Compensation of decoherence from telegraph noise by means of bang-bang control

Gutmann, H.; Wilhelm, F. K.; Kaminsky, W. M.; Lloyd, S.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.08%
With the growing efforts in isolating solid-state qubits from external decoherence sources, the origins of noise inherent to the material start to play a relevant role. One representative example are charged impurities in the device material or substrate, which typically produce telegraph noise and can hence be modelled as bistable fluctuators. In order to demonstrate the possibility of the active suppression of the disturbance from a {\em single} fluctuator, we theoretically implement an elementary bang-bang control protocol. We numerically simulate the random walk of the qubit state on the Bloch sphere with and without bang-bang compensation by means of the stochastic Schr\"odinger equation and compare it with an analytical saddle point solution of the corresponding Langevin equation in the long-time limit. We find that the deviation with respect to the noiseless case is significantly reduced when bang-bang pulses are applied, being scaled down approximately by the ratio of the bang-bang period and the typical flipping time of the bistable fluctuation. Our analysis gives not only the effect of bang-bang control on the variance of these deviations, but also their entire distribution. As a result, we expect that bang-bang control works as a high-pass filter on the spectrum of noise sources. This indicates how the influence of $1/f$-noise ubiquitous to the solid state world can be reduced.; Comment: 4 pages...

## A Dynamical Mechanism for the Big Bang and Non-Regularizability for $w=1$

Belbruno, Edward
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.97%
We consider a contracting universe and its transition to expansion through the big bang singularity with a time varying equation of state $w$, where $w$ approaches $1$ as the universe contracts to the big bang. We show that this singularity is non-regularizable. That is, there is no unique extension of the physical quantities after the transition, but rather infinitely many. This is entirely different from the case of $w > 1$ studied in \cite{Xue:2014}, where $w$ approaches a constant value $w_c > 1$ as the universe contracts. In that case a continuous transition through the big bang to yield a unique extension was possible only for a discrete set of $w_c$ satisfying coprime conditions. We also show that there exists another time variable, $N$, at the big bang singularity itself, at $t=0$, where $w$, varies as a function of $N$. This defines an {\em extended big bang state}. Within it, $H$ is infinity. In the extended state, $w$ varies from a universe dominated by the cosmological constant to $1$. After $w$ reaches $1$ then the big bang occurs and time $t >0$ resumes. This gives a dynamical mechanism for the big bang that is mathematically complete as a function of $N$. Dynamical systems methods are used with classical modeling.; Comment: arXiv admin note: text overlap with arXiv:1403.2122

## Rapid Lyapunov control of finite-dimensional quantum systems

Kuang, Sen; Dong, Daoyi; Petersen, Ian R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.97%
Rapid state control of quantum systems is significant in reducing the influence of relaxation or decoherence caused by the environment and enhancing the capability in dealing with uncertainties in the model and control process. Bang-bang Lyapunov control can speed up the control process, but cannot guarantee convergence to a target state. This paper proposes two classes of new Lyapunov control methods that can achieve rapidly convergent control for quantum states. One class is switching Lyapunov control where the control law is designed by switching between bang-bang Lyapunov control and standard Lyapunov control. The other class is approximate bang-bang Lyapunov control where we propose two special control functions which are continuously differentiable and yet have a bang-bang type property. Related stability results are given and a construction method for the degrees of freedom in the Lyapunov function is presented to guarantee rapid convergence to a target eigenstate being isolated in the invariant set. Several numerical examples demonstrate that the proposed methods can achieve improved performance for rapid state control of quantum systems.; Comment: 15 pages, 5 figures

## La Teoría del Big bang y la doctrina de Nagarjuna el vacío o sunyata como síntesis ontológica de todo cuanto existe /

Fonte: Bellaterra : Universitat Autònoma de Barcelona, Publicador: Bellaterra : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis Formato: application/pdf
Relevância na Pesquisa
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Consultable des del TDX; Títol obtingut de la portada digitalitzada; Mi tesis doctoral investiga la Teoría del Big Bang sobre el origen del universo y su relación con la doctrina del sabio filósofo budista, Nagarjuna (India s.II-III), fundador de la Vía Media o Camino Medio del budismo, según su obra genuina titulada Mûla-mâdhyamaka-kârik_, un texto decididamente auténtico, opus magna de este autor conforme la tradición india, china y tibetana, prueba indiscutible de la historicidad de su figura. Nagarjuna, uno de los cuatro soles que iluminan al mundo desde sus cuatro direcciones, maestro espiritual de Oriente y Occidente, fue el creador de la escuela budista Mâdhyamaka viva en la India desde el siglo II al VI. La teoría científica de la Gran Explosión Universal o Big Bang concluye que el «vacío» es la fuente energética de donde surge el Cosmos: nuestro origen. La Doctrina de Nagarjuna prueba que el «vacío» es la esencia más profunda de la Realidad; un sistema filosófico consistente con las descripciones físicas contemporáneas acerca del campo de fuerza que da principio al Cosmos. De ahí que esta Tesis Doctoral se intitule: La Teoría del Big Bang y la Doctrina de Nagarjuna: el vacío o s_nyat_ como síntesis de todo cuanto existe. Una construcción teórica fundamentada en el principio según el cual filosofía y ciencia tienen un carácter universal y no están basadas únicamente en la cultura...

## STOP-BANG questionnaire as a screening tool for diagnosis of obstructive sleep apnea by unattended portable monitoring sleep study

Doshi, Viral; Walia, Reuben; Jones, Kellie; Aston, Christopher E.; Awab, Ahmed
Fonte: Springer International Publishing Publicador: Springer International Publishing
Tipo: Text