4,336 research outputs found
Distributed Algorithms for Stochastic Source Seeking With Mobile Robot Networks
Autonomous robot networks are an effective tool for monitoring large-scale environmental fields. This paper proposes distributed control strategies for localizing the source of a noisy signal, which could represent a physical quantity of interest such as magnetic force, heat, radio signal, or chemical concentration. We develop algorithms specific to two scenarios: one in which the sensors have a precise model of the signal formation process and one in which a signal model is not available. In the model-free scenario, a team of sensors is used to follow a stochastic gradient of the signal field. Our approach is distributed, robust to deformations in the group geometry, does not necessitate global localization, and is guaranteed to lead the sensors to a neighborhood of a local maximum of the field. In the model-based scenario, the sensors follow a stochastic gradient of the mutual information (MI) between their expected measurements and the expected source location in a distributed manner. The performance is demonstrated in simulation using a robot sensor network to localize the source of a wireless radio signal
Revising the multipole moments of numerical spacetimes, and its consequences
Identifying the relativistic multipole moments of a spacetime of an
astrophysical object that has been constructed numerically is of major
interest, both because the multipole moments are intimately related to the
internal structure of the object, and because the construction of a suitable
analytic metric that mimics a numerical metric should be based on the multipole
moments of the latter one, in order to yield a reliable representation. In this
note we show that there has been a widespread delusion in the way the multipole
moments of a numerical metric are read from the asymptotic expansion of the
metric functions. We show how one should read correctly the first few multipole
moments (starting from the quadrupole mass-moment), and how these corrected
moments improve the efficiency of describing the metric functions with analytic
metrics that have already been used in the literature, as well as other
consequences of using the correct moments.Comment: article + supplemental materia
Observation of B_s Production at the Y(5S) Resonance
Using the CLEO detector at the Cornell Electron Storage Ring, we have observed the B_s meson in e^+e^- annihilation at the Υ(5S) resonance. We find 14 candidates consistent with B_s decays into final states with a J/ψ or a D_s^((*)-). The probability that we have observed a background fluctuation is less than 8×10^(-10). We have established that at the energy of the Υ(5S) resonance B_s production proceeds predominantly through the creation of B_s^*B̅ _s^* pairs. We find σ(e^+e^-→B^s^*B̅ ^*)=[0.11_(-0.03)^(+0.04)(stat)±0.02(syst)]  nb, and set the following limits: σ(e^+e^-→B_sB̅ _s)/σ(e^+e^-→B_s^*B̅ _s^*)<0.16 and [σ(e^+e^-→B_sB̅ _s^*)+σ(e^+e^-→B_s*B̅ _s)]/σ(e^+e^-→B_s*B̅ _s^*)<0.16 (90% C.L.). The mass of the B_s^* meson is measured to be M_(B_s^*=[5.414±0.001(stat)±0.003(syst)]  GeV/c^2
Two-photon width of the charmonium state X_(c2)
The two-photon width of X_(c2)^3P_2 state of charmonium has been measured using 14.4 fb^(-1) of e^+e^-data taken at √s
=9.46–11.30 GeV with the CLEO III detector. The yy-fusion reaction studied is e^+e^- → e^+e^-yy, → yy X_(c2) → yJ/Ψ → ye^+e^-(µ^+µ^-). We measure Г_(yy) (X_(c2))B(X_(c2)) → y
J/Ψ)B(J/Ψ → e^+e^- + µ^+µ^-)= 13.2 ± 1.4(stat)± 1.1(syst) eV, and obtain Г yy(Xc2)= 559 ± 57(stat) ± 48(syst) ± 36(br) eV. This result is in excellent agreement with the result of -fusion measurement by Belle and is consistent with that of the pp → X_(c2) → yy measurement, when they are both reevaluated using the recent CLEO result for the radiative decay X_(c2) → J/Ψ
Static Output Feedback: On Essential Feasible Information Patterns
In this paper, for linear time-invariant plants, where a collection of
possible inputs and outputs are known a priori, we address the problem of
determining the communication between outputs and inputs, i.e., information
patterns, such that desired control objectives of the closed-loop system (for
instance, stabilizability) through static output feedback may be ensured.
We address this problem in the structural system theoretic context. To this
end, given a specified structural pattern (locations of zeros/non-zeros) of the
plant matrices, we introduce the concept of essential information patterns,
i.e., communication patterns between outputs and inputs that satisfy the
following conditions: (i) ensure arbitrary spectrum assignment of the
closed-loop system, using static output feedback constrained to the information
pattern, for almost all possible plant instances with the specified structural
pattern; and (ii) any communication failure precludes the resulting information
pattern from attaining the pole placement objective in (i).
Subsequently, we study the problem of determining essential information
patterns. First, we provide several necessary and sufficient conditions to
verify whether a specified information pattern is essential or not. Further, we
show that such conditions can be verified by resorting to algorithms with
polynomial complexity (in the dimensions of the state, input and output).
Although such verification can be performed efficiently, it is shown that the
problem of determining essential information patterns is in general NP-hard.
The main results of the paper are illustrated through examples
Thin film dielectric microstrip kinetic inductance detectors
Microwave Kinetic Inductance Detectors, or MKIDs, are a type of low
temperature detector that exhibit intrinsic frequency domain multiplexing at
microwave frequencies. We present the first theory and measurements on a MKID
based on a microstrip transmission line resonator. A complete characterization
of the dielectric loss and noise properties of these resonators is performed,
and agrees well with the derived theory. A competitive noise equivalent power
of 5 W Hz at 1 Hz has been demonstrated. The
resonators exhibit the highest quality factors known in a microstrip resonator
with a deposited thin film dielectric.Comment: 10 pages, 4 figures, APL accepte
Cloud-based Quadratic Optimization with Partially Homomorphic Encryption
The development of large-scale distributed control systems has led to the
outsourcing of costly computations to cloud-computing platforms, as well as to
concerns about privacy of the collected sensitive data. This paper develops a
cloud-based protocol for a quadratic optimization problem involving multiple
parties, each holding information it seeks to maintain private. The protocol is
based on the projected gradient ascent on the Lagrange dual problem and
exploits partially homomorphic encryption and secure multi-party computation
techniques. Using formal cryptographic definitions of indistinguishability, the
protocol is shown to achieve computational privacy, i.e., there is no
computationally efficient algorithm that any involved party can employ to
obtain private information beyond what can be inferred from the party's inputs
and outputs only. In order to reduce the communication complexity of the
proposed protocol, we introduced a variant that achieves this objective at the
expense of weaker privacy guarantees. We discuss in detail the computational
and communication complexity properties of both algorithms theoretically and
also through implementations. We conclude the paper with a discussion on
computational privacy and other notions of privacy such as the non-unique
retrieval of the private information from the protocol outputs
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