488 research outputs found
Critical Transitions In a Model of a Genetic Regulatory System
We consider a model for substrate-depletion oscillations in genetic systems,
based on a stochastic differential equation with a slowly evolving external
signal. We show the existence of critical transitions in the system. We apply
two methods to numerically test the synthetic time series generated by the
system for early indicators of critical transitions: a detrended fluctuation
analysis method, and a novel method based on topological data analysis
(persistence diagrams).Comment: 19 pages, 8 figure
Non-global parameter estimation using local ensemble Kalman filtering
We study parameter estimation for non-global parameters in a low-dimensional
chaotic model using the local ensemble transform Kalman filter (LETKF). By
modifying existing techniques for using observational data to estimate global
parameters, we present a methodology whereby spatially-varying parameters can
be estimated using observations only within a localized region of space. Taking
a low-dimensional nonlinear chaotic conceptual model for atmospheric dynamics
as our numerical testbed, we show that this parameter estimation methodology
accurately estimates parameters which vary in both space and time, as well as
parameters representing physics absent from the model
Design of a Particle Beam Satellite System for Lunar Prospecting
One potential use for neutral particle beam (NPB) technology is as an active orbital probe to investigate the composition of selected locations on the lunar surface. Because the beam is narrow and can be precisely directed, the NPB probe offers possibilities for high resolution experiments that cannot be accomplished using passive techniques. Rather, the combination of both passive and active techniques can be used to provide both full-coverage mapping (passively) at low resolution (tens of kilometers) and high-resolution information for discrete locations of special interest. A preliminary study of NPB applicability for this dual-use application was recently conducted. The study was completed in Feb. 1993. A novel feature was the consideration of the use of a Russian launch vehicle (e.g., the Proton). The use of other Russian space hardware and capabilities was also encouraged. This paper describes the lunar prospector system design. Other researchers discuss the issues and opportunities involving lunar scientific experimentation using an NPB. The NPB lunar prospector utilizes a modified design of the Far Field Optics Experiment (FOX). Like the Earth-orbiting FOX, the core capability of the NPB lunar prospector will be a pulsed RF LINAC that produces a 5-MeV proton beam that is projected to the target with a 30-micro-r beam divergence and a 10-micro-r beam-pointing accuracy. Upon striking the lunar surface, the proton beam will excite characteristic radiation (e.g., X-rays) that can be sensed by one or more detectors on the NPB platform or on a separate detector satellite
Autumn Fancies : Etude
https://digitalcommons.library.umaine.edu/mmb-ps/2836/thumbnail.jp
THE POTENTIAL OF DAIRY FUTURES CONTRACTS AS RISK MANAGEMENT TOOLS
We examine the young dairy futures market as a risk management tool. Using New York Board of Trade (NYBOT) data, we find that the BFP futures market is efficient and may potentially be a useful hedging tool. However, we also find that competition from Chicago Mercantile Exchange (CME) contracts has significant detrimental effects on the NYBOT dairy futures contracts. As a result NYBOT dairy futures contracts are likely to dry up.Financial Economics, Livestock Production/Industries,
Using machine learning to predict catastrophes in dynamical systems
Nonlinear dynamical systems, which include models of the Earth\u27s climate, financial markets and complex ecosystems, often undergo abrupt transitions that lead to radically different behavior. The ability to predict such qualitative and potentially disruptive changes is an important problem with far-reaching implications. Even with robust mathematical models, predicting such critical transitions prior to their occurrence is extremely difficult. In this work, we propose a machine learning method to study the parameter space of a complex system, where the dynamics is coarsely characterized using topological invariants. We show that by using a nearest neighbor algorithm to sample the parameter space in a specific manner, we are able to predict with high accuracy the locations of critical transitions in parameter space. (C) 2011 Elsevier B.V. All rights reserved
Zeno-effect Computation: Opportunities and Challenges
Adiabatic quantum computing has demonstrated how quantum Zeno can be used to
construct quantum optimisers. However, much less work has been done to
understand how more general Zeno effects could be used in a similar setting. We
use a construction based on three state systems rather than directly in qubits,
so that a qubit can remain after projecting out one of the states. We find that
our model of computing is able to recover the dynamics of a transverse field
Ising model, several generalisations are possible, but our methods allow for
constraints to be implemented non-perturbatively and does not need tunable
couplers, unlike simple transverse field implementations. We further discuss
how to implement the protocol physically using methods building on STIRAP
protocols for state transfer. We find a substantial challenge, that settings
defined exclusively by measurement or dissipative Zeno effects do not allow for
frustration, and in these settings pathological spectral features arise leading
to unfavorable runtime scaling. We discuss methods to overcome this challenge
for example including gain as well as loss as is often done in optical Ising
machines
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