12,163 research outputs found
New advances in H∞ control and filtering for nonlinear systems
The main objective of this special issue is to
summarise recent advances in H∞ control and filtering
for nonlinear systems, including time-delay, hybrid and
stochastic systems. The published papers provide new
ideas and approaches, clearly indicating the advances
made in problem statements, methodologies or applications
with respect to the existing results. The special
issue also includes papers focusing on advanced and
non-traditional methods and presenting considerable
novelties in theoretical background or experimental
setup. Some papers present applications to newly
emerging fields, such as network-based control and
estimation
Expectations for the Difference Between Local and Global Measurements of the Hubble Constant
There are irreducible differences between the Hubble constant measured
locally and the global value. They are due to density perturbations and finite
sample volume (cosmic variance) and finite number of objects in the sample
(sampling variance). We quantify these differences for a suite of
COBE-normalized CDM models that are consistent with the observed large-scale
structure. For small samples of objects that only extend out to 10,000 km/sec,
the variance can approach 4%. For the largest samples of Type Ia supernovae
(SNeIa), which include about 40 objects and extend out to almost 40,000 km/sec,
the variance is 1-2% and is dominated by sampling variance. Sampling and cosmic
variance may be an important consideration in comparing local determinations of
the Hubble constant with precision determinations of the global value that will
be made from high-resolution maps of CBR anisotropy.Comment: 10 pages, Latex, 2 figures, version accepted for Ap.
Structural transformation and localization during simulated nanoindentation of a non-crystalline metal film
A simulation study demonstrates that localization can arise as the result of
the breakdown of stable quasi-crystal-like atomic configurations. Samples
produced at elevated quench rates and via more energetic processes contain a
lower fraction of such configurations and exhibit significantly less pronounced
localization and shorter spacing between bands. In the samples produced by the
lowest quench rates localization is accompanied by the amorphization of
material with initially quasi-crystal-like medium range order. This result is
of particular significance in light of recent experimental evidence of local
quasi-crystal order in the most stable of the bulk metallic glasses.Comment: 13 pages, 3 figure
Estimation Schemes for Networked Control Systems Using UDP-Like Communication
In this work we consider a class of networked control systems (NCS) when the control signal is sent to the plant via a UDP-like communication protocol, the controller sends a communication packet to the plant across a lossy network but the controller does not receive any acknowledgement signal indicating the status of reception/delivery of the control packet. Standard observer based estimators assume the estimator has knowledge of what control signal is applied to the plant, but under the UDP-like communication scheme the estimator does not know what control is applied. Continuing previous work, we present a simple estimation algorithm consisting of a state estimator and mode observer. For single input systems we can add an extra control signal that guarantees recovery of the fate of the control packet. Using a modified state feedback with the added input we can guarantee the estimation error is bounded as is the expected value of the state. This extra input is removed and sufficient conditions on the system properties are given to assure the estimation remain bounded. Comparisons are made between the algorithm presented and the method of unknown input observer. Simulations are provided to demonstrate the algorithm
Kalman Filtering Over A Packet Dropping Network: A Probabilistic Approach
We consider the problem of state estimation of a discrete time process over a packet dropping network. Previous pioneering work on Kalman filtering with intermittent observations is concerned with the asymptotic behavior of E[P_k], i.e., the expected value of the error covariance, for a given packet arrival rate. We consider a different performance metric, Pr[P_k ≤ M], i.e., the probability that P_k is bounded by a given M, and we derive lower and upper bounds on Pr[P_k ≤ M]. We are also able to recover the results in the literature when using Pr[P_k ≤ M] as a metric for scalar systems. Examples are provided to illustrate the theory developed in the paper
Vehicle currency
While in principle, international payments could be carried out using any currency or set of currencies, in practice, the U.S. dollar is predominant in international trade and financial flows. The dollar acts as a "vehicle currency" in the sense that agents in nondollar economies will generally engage in currency trade indirectly using the U.S. dollar rather than using direct bilateral trade among their own currencies. Indirect trade is desirable when there are transactions costs of exchange.> ; This paper constructs a dynamic general equilibrium model of a vehicle currency. We explore the nature of the efficiency gains arising from a vehicle currency, and show how this depends on the total number of currencies in existence, the size of the vehicle currency economy, and the monetary policy followed by the vehicle currency's government. We find that there can be very large welfare gains to a vehicle currency in a system of many independent currencies. But these gains are asymmetry weighted towards the residents of the vehicle currency country. The survival of a vehicle currency places natural limits on the monetary policy of the vehicle country.International trade ; Dollar, American ; Equilibrium (Economics) - Mathematical models ; Monetary policy
Vehicle Currency
While in principle, international payments could be carried out using any currency or set of currencies, in practice, the US dollar is predominant in international trade and financial flows. The dollar acts as a `vehicle currency' in the sense that agents in non-dollar economies will generally engage in currency trade indirectly using the US dollar rather than using direct bilateral trade among their own currencies. Indirect trade is desirable when there are transactions costs of exchange. This paper constructs a dynamic general equilibrium model of a vehicle currency. We explore the nature of the efficiency gains arising from a vehicle currency, and show how this depends on the total number of currencies in existence, the size of the vehicle currency economy, and the monetary policy followed by the vehicle currency's government. We find that there can be very large welfare gains to a vehicle currency in a system of many independent currencies. But these gains are asymmetrically weighted towards the residents of the vehicle currency country. The survival of a vehicle currency places natural limits on the monetary policy of the vehicle country.Vehicle currency; Transactions cost; Welfare gains
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