Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 19 of 19 for “"random perturbations"”.
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Random perturbations of delay differential equations at the verge of instability and periodically driven nonlinear oscillators
… (chapters 1-5) studies the effect of small noise perturbations on delay differential equations (DDE) whose fixed point is on the verge of instability. With appropriate scaling of coordinates, the dynamics close to the fixed point can be cast in the form of a linear DDE perturbed by small noise and …
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The Exit Time Distribution for Small Random Perturbations of Dynamical Systems with a Repulsive Type Stationary Point
We consider a stochastic differential equation on a domain D in n-dimensional real space, where the associated dynamical system is linear, and D contains a repulsive type stationary point at the origin O. We obtain an exit law for the first exit time of the solution process from a ball of arbitrary …
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New results in stochastic moving boundary problems
… moving boundary problems. In addition, random perturbations of partial differential equations (e.g. stochastic heat equations) have been studied extensively. However, there has not been much attention paid to random perturbations of moving boundary problems. In this thesis, we consider …
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Optimizing Integrated Airport Surface and Terminal Airspace Operations under Uncertainty
… and the terminal airspace are often altered by random perturbations, the consideration of uncertainty in flight schedules is crucial to improve the design of robust flight schedules. Previous research mainly focused on independently solving arrival scheduling problems, departure scheduling …
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A Numerical Study of the Structure and Vertical Transport Properties of A Tropical Convective System
… In order to initiate clouds, small amplitude random perturbations in the form of temperature fluctuations are also fed into the model at low level. The model allows clouds with various sizes to develop simultaneously inside the model domain. After run, horizontal and time averages of various …
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Perturbation studies of excitable media
… itself into a critical state as a response to random perturbations. Periodic forcing gives rise to waves being sustained in a subexcitable medium by imposing periodic perturbations above and below the excitability limit.
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Impact of geometric variability on compressor repeating-stage performance
… is then introduced probabilistically through random perturbations to tip clearances, profile losses and turning. For the variation input, at design incidence, the mean efficiency is found to decrease by 1%, mostly due to the mean shift in profile losses, and the mean pressure rise is reduced …
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Weighted arrays for modal isolation and active control of complex structures
… a function of the array size, the sensitivity to random perturbations, and the effects of transducer failure are explored.
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The effect of pre-processing techniques and optimal parameters on BPNN for data classification
… modify the learning model in order to add a random factor to the model which can help to overcome the tendency to sink into local minima. However, the random perturbations of the search direction and various kinds of stochastic adjustment to the current set of weights are not effective in …
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Modelling the human cochlea
… the calculation of linear instabilities given random perturbations in the cochlea which are predicted to produce spontaneous OAEs. The averaged stability results of an ensemble of randomly perturbed models have been published in [(2008) ‘Statistics of instabilities in a state space model of the …
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Velocity analysis in the presence of uncertainty
… using ideas on time reversal and imaging in randomly inhomogeneous media developed by Borcea and colleagues, in combination with velocity estimation methods of differential semblance type. The main result of this thesis is that the noise in seismic reflection data associated with the middle …
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Accuracy-aware privacy mechanisms for distributed computation
… Sharing strategy that involves using correlated random functions to obfuscate private objective functions followed by using a standard distributed optimization algorithm. We characterize a tight graph connectivity condition for proving privacy via non-identifiability of local objective functions. …
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Toward a unified view of complex multiscale stochastic systems: A generalized theory of interactions and its computational infrastructure for their universal and efficient investigation
… action, driven to a large extent by intrinsic random perturbations that cannot be removed without losing critical information for their scientific understanding. Systems that match this signature are ubiquitous across a large number of knowledge domains, yet no unified model explaining all …
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Theoretical and Computational Analyses on Transition and Turbulence in Purely Oscillating Pipe Flow
… as a disturbed laminar flow after imposing small random perturbations as initial conditions, qualitatively agrees with that estimated by the quasi-steady theory. The later transition stage at which the turbulence and relaminarization phenomena first emerge is detected from the high-amplitude …
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Microscopic Chaos, Fractals, and Transport in Nonequilibrium Steady States. - (Die Veröffentlichung einer ergänzten und überarbeiteten Version bei "World Scientific Publishing" ist für 2005/06 geplant.)
… one-dimensional maps generalizing a simple random walk on the line up to particle billiards that should be directly accessible in experiments. In all cases, the resulting transport coefficients turn out to be either strictly fractal, or at least to be profoundly irregular. The impact of …
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An architecture for network path selection
… a multipath routing technique, which uses random perturbations from the shortest path to create exponentially large number of paths with only a linear increase in state in a network. We also develop a simple interface to enable end systems to make path selection decisions. We present …
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Dynamically orthogonal field equations for stochastic fluid flows and particle dynamics
… laws. In all of the above cases the existence of random perturbations, combined with the complex dynamical mechanisms of the system often leads to their rapid growth which causes distribution of energy to a broadband spectrum of scales both in space and time, making the system state particularly …
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Accurate and Trustworthy Recommender Systems: Algorithms and Findings
… of existing recommender systems against input perturbations and devise a solution to enhance the robustness of the recommenders. Deep learning-based recommender systems have shown sensitivity to arbitrary and adversarial input perturbations, resulting in drastic alterations of recommendation …
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Uncertainty Quantification in Earth System Models Using Polynomial Chaos Expansions
… of various earth system models to different random sources, using polynomial chaos (PC) approaches. The following earth systems are considered, namely the HYbrid Coordinate Ocean Model (HYCOM, an ocean general circulation model (OGCM)) for the study of ocean circulation in the Gulf of Mexico …