4,313 research outputs found
Stabilization of Cascaded Two-Port Networked Systems Against Nonlinear Perturbations
A networked control system (NCS) consisting of cascaded two-port
communication channels between the plant and controller is modeled and
analyzed. Towards this end, the robust stability of a standard closed-loop
system in the presence of conelike perturbations on the system graphs is
investigated. The underlying geometric insights are then exploited to analyze
the two-port NCS. It is shown that the robust stability of the two-port NCS can
be guaranteed when the nonlinear uncertainties in the transmission matrices are
sufficiently small in norm. The stability condition, given in the form of
"arcsin" of the uncertainty bounds, is both necessary and sufficient.Comment: 8 pages, in preparation for journal submissio
Electromagnetic counterparts of high-frequency gravitational waves having additional polarization states: distinguishing and probing tensor-mode, vector-mode and scalar-mode gravitons
GWs from extra dimensions, very early universe, and some high-energy
astrophysical process, might have at most six polarizations: plus- and
cross-type (tensor-mode gravitons), x-, y-type (vector-mode), and b-, l-type
(scalar-mode). Peak or partial peak regions of some of such GWs are just
distributed in GHz or higher frequency band, which would be optimal band for
electromagnetic(EM) response. In this paper we investigate EM response to such
high-frequency GWs(HFGWs) having additional polarizations. For the first time
we address:(1)concrete forms of analytic solutions for perturbed EM fields
caused by HFGWs having all six possible polarizations in background stable EM
fields; (2)perturbed EM signals of HFGWs with additional polarizations in
three-dimensional-synchro-resonance-system(3DSR system) and in
galactic-extragalactic background EM fields. These perturbative EM fields are
actually EM counterparts of HFGWs, and such results provide a novel way to
simultaneously distinguish and display all possible six polarizations. It is
also shown: (i)In EM response, pure cross-, x-type and pure y-type
polarizations can independently generate perturbative photon fluxes(PPFs,
signals), while plus-, b- and l-type polarizations produce PPFs in different
combination states. (ii) All such six polarizations have separability and
detectability. (iii)In EM response to HFGWs from extra-dimensions,
distinguishing and displaying different polarizations would be quite possible
due to their very high frequencies, large energy densities and special
properties of spectrum. (iv)Detection band(10^8 to 10^12 Hz or higher) of PPFs
by 3DSR and observation range(7*10^7 to 3*10^9 Hz) of PPFs by FAST
(Five-hundred-meter-Aperture-Spherical Telescope, China), have a certain
overlapping property, so their coincidence experiments will have high
complementarity.Comment: 27 pages, 16 figure
On the exponential convergence of input-output signals of nonlinear feedback systems
We show that the integral-constraint-based robust feedback stability theorem
for certain Lurye systems exhibits the property that the endogenous
input-output signals enjoy an exponential convergence rate for all initial
conditions of the linear time-invariant subsystem. More generally, we provide
conditions under which a feedback interconnection of possibly open-loop
unbounded subsystems to admit such an exponential convergence property, using
perturbation analysis and a combination of tools including integral quadratic
constraints, directed gap measure, and exponential weightings. As an
application, we apply the result to first-order convex optimisation methods. In
particular, by making use of the Zames-Falb multipliers, we state conditions
for these methods to converge exponentially when applied to strongly convex
functions with Lipschitz gradients.Comment: This paper has been submitted to Automatic
Converse negative imaginary theorems
Converse negative imaginary theorems for linear time-invariant systems are
derived. In particular, we provide necessary and sufficient conditions for a
feedback system to be robustly stable against various types of negative
imaginary (NI) uncertainty. Both marginally stable and exponentially stable
uncertain NI systems with restrictions on their static or instantaneous gains
are considered. It is shown that robust stability against the former class
entails the well-known strict NI property, whereas the latter class entails a
new type of output strict NI property that is hitherto unexplored. We also
establish a non-existence result that no stable system can robustly stabilise
all marginally stable NI uncertainty, thereby showing that the uncertainty
class of NI systems is too large as far as robust feedback stability is
concerned, thus justifying the consideration of subclasses of NI systems with
constrained static or instantaneous gains.Comment: This paper has been submitted for possible publication at Automatic
A Study on Trust of E-commerce Market Based on Multi-agents Model
The process of the trust production and transfer is both stochastic and rational. In this article, we analyze the characters of this process in consumer’s social networks, by dividing consumers and merchants into two types: Risk-aversion type and Risk-neutral type for consumers, high-grade and low-grade for merchants respectively. Based on multi-agent NETLogo system, three kinds of virtual social networks are constructed, which are the risk-neutral without institution, risk-aversion without institution, risk-aversion but with good institution. The rules of the production and transfer of trust in consumer-to-consumer and merchant-to-consumers are defined. Based on a series of computational experiments and statistical comparison, we draw a conclusion that the characters of consumers do not change the trend of e-business market scale, but only change the equilibrium value. On the other hand, a risk-aversion with good institutional society can boost market to have a highly upward trend and be self-stable. Consequentially, this article indirectly proved of the essentials for establishing the institution-based trust
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