100,670 research outputs found
Know Your Enemy: Stealth Configuration-Information Gathering in SDN
Software Defined Networking (SDN) is a network architecture that aims at
providing high flexibility through the separation of the network logic from the
forwarding functions. The industry has already widely adopted SDN and
researchers thoroughly analyzed its vulnerabilities, proposing solutions to
improve its security. However, we believe important security aspects of SDN are
still left uninvestigated. In this paper, we raise the concern of the
possibility for an attacker to obtain knowledge about an SDN network. In
particular, we introduce a novel attack, named Know Your Enemy (KYE), by means
of which an attacker can gather vital information about the configuration of
the network. This information ranges from the configuration of security tools,
such as attack detection thresholds for network scanning, to general network
policies like QoS and network virtualization. Additionally, we show that an
attacker can perform a KYE attack in a stealthy fashion, i.e., without the risk
of being detected. We underline that the vulnerability exploited by the KYE
attack is proper of SDN and is not present in legacy networks. To address the
KYE attack, we also propose an active defense countermeasure based on network
flows obfuscation, which considerably increases the complexity for a successful
attack. Our solution offers provable security guarantees that can be tailored
to the needs of the specific network under consideratio
Monostability and multistability of genetic regulatory networks with different types of regulation functions
The official published version of the article can be found at the link below.Monostability and multistability are proven to be two important topics in synthesis biology and system biology. In this paper, both monostability and multistability are analyzed in a unified framework by applying control theory and mathematical tools. The genetic regulatory networks (GRNs) with multiple time-varying delays and different types of regulation functions are considered. By putting forward a general sector-like regulation function and utilizing up-to-date techniques, a novel Lyapunov–Krasovskii functional is introduced for achieving delay dependence to ensure less conservatism. A new condition is then proposed for the general stability of a GRN in the form of linear matrix inequalities (LMIs) that are dependent on the upper and lower bounds of the delays. Our general stability conditions are applicable to several frequently used regulation functions. It is shown that the existing results for monostability of GRNs are special cases of our main results. Five examples are employed to illustrate the applicability and usefulness of the developed theoretical results.This work was supported in part by the Biotechnology and Biological Sciences Research Council (BBSRC) of the U.K. under Grant BB/C506264/1, the Royal Society of the U.K., the National Natural Science Foundation of China under Grants 60504008 and 60804028, the Program for New Century Excellent Talents in Universities of China, and the Alexander von Humboldt Foundation of Germany
Magnetic-Visual Sensor Fusion-based Dense 3D Reconstruction and Localization for Endoscopic Capsule Robots
Reliable and real-time 3D reconstruction and localization functionality is a
crucial prerequisite for the navigation of actively controlled capsule
endoscopic robots as an emerging, minimally invasive diagnostic and therapeutic
technology for use in the gastrointestinal (GI) tract. In this study, we
propose a fully dense, non-rigidly deformable, strictly real-time,
intraoperative map fusion approach for actively controlled endoscopic capsule
robot applications which combines magnetic and vision-based localization, with
non-rigid deformations based frame-to-model map fusion. The performance of the
proposed method is demonstrated using four different ex-vivo porcine stomach
models. Across different trajectories of varying speed and complexity, and four
different endoscopic cameras, the root mean square surface reconstruction
errors 1.58 to 2.17 cm.Comment: submitted to IROS 201
State estimation of a solar direct steam generation mono-tube cavity receiver using a modified Extended Kalman Filtering scheme
State estimation plays a key role in the development of advanced control strategies for Concentrating Solar Thermal Power (CSP)
systems, by providing an estimate of process variables that are otherwise infeasible to measure. The present study proposes a state estimation
scheme for a once-through direct steam generation plant, the SG4 steam generation system at the Australian National University.
The state estimation scheme is a modified Extended Kalman Filter that computes an estimate of the internal variables of the mono-tube
cavity receiver in the SG4 system, from a dynamic non-linear model of the receiver. The proposed scheme augments the capabilities of a
Continuous-Direct Extended Kalman Filter to deal with the switched nature of the receiver, in order to produce estimates during system
start-up, cloud transients and operation of the plant. The estimation process runs at regular sample intervals and happens in two stages, a
prediction and a correction stage. The prediction stage uses the receiver model to calculate the evolution of the system and the correction
stage modifies the predicted estimate from measurements of the SG4 system. The resulting estimate is a set of internal variables describing
the current state of the receiver, termed the state vector. This paper presents a description of the modified Extended Kalman Filter
and an evaluation of the scheme using computer simulations and experimental runs in the SG4 system. Simulations and experimental
results in this paper show that the filtering scheme improves a receiver state vector estimation purely based on the receiver model
and provides estimates of a quality sufficient for closed loop control.This work has been supported by the Australian
Renewable Energy Agency (ARENA)
Abrupt turn-on and hysteresis in a VCSEL with frequency-selective optical feedback
The emission characteristics of a vertical-cavity surface-emitting laser (VCSEL) operated in a single-transverse mode and coupled to an external cavity with a diffraction grating as a frequency-selective element are analyzed experimentally, numerically and analytically. The experiments yield a rather abrupt turn-on of the VCSEL to a high-amplitude emission state and hysteresis phenomena. The experimental results are explained by numerical simulations and analytical calculations demonstrating the possibility of bistability between lasing and non-lasing states close to threshold. Hence, the scheme might be useful in all-optical photonic switching applications. A detailed bifurcation analysis near threshold is given by superimposing the numerical results with analytical steady-state curves. The mode selection and switching behavior obtained in the simulations can be interpreted from the point of view of the preference of states with the minimal total losses
Executive stock option exercise with full and partial information on a drift change point
We analyse the optimal exercise of an executive stock option (ESO) written on
a stock whose drift parameter falls to a lower value at a change point, an
exponentially distributed random time independent of the Brownian motion
driving the stock. Two agents, who do not trade the stock, have differing
information on the change point, and seek to optimally exercise the option by
maximising its discounted payoff under the physical measure. The first agent
has full information, and observes the change point. The second agent has
partial information and filters the change point from price observations. This
scenario is designed to mimic the positions of two employees of varying
seniority, a fully informed executive and a partially informed less senior
employee, each of whom receives an ESO. The partial information scenario yields
a model under the observation filtration in which the
stock drift becomes a diffusion driven by the innovations process, an
-Brownian motion also driving the stock under
, and the partial information optimal stopping value
function has two spatial dimensions. We rigorously characterise the free
boundary PDEs for both agents, establish shape and regularity properties of the
associated optimal exercise boundaries, and prove the smooth pasting property
in both information scenarios, exploiting some stochastic flow ideas to do so
in the partial information case. We develop finite difference algorithms to
numerically solve both agents' exercise and valuation problems and illustrate
that the additional information of the fully informed agent can result in
exercise patterns which exploit the information on the change point, lending
credence to empirical studies which suggest that privileged information of bad
news is a factor leading to early exercise of ESOs prior to poor stock price
performance.Comment: 48 pages, final version, accepted for publication in SIAM Journal on
Financial Mathematic
Active Temporal Multiplexing of Photons
Photonic qubits constitute a leading platform to disruptive quantum
technologies due to their unique low-noise properties. The cost of the photonic
approach is the non-deterministic nature of many of the processes, including
single-photon generation, which arises from parametric sources and negligible
interaction between photons. Active temporal multiplexing - repeating a
generation process in time and rerouting to single modes using an optical
switching network - is a promising approach to overcome this challenge and will
likely be essential for large-scale applications with greatly reduced resource
complexity and system sizes. Requirements include the precise synchronization
of a system of low-loss switches, delay lines, fast photon detectors, and
feed-forward. Here we demonstrate temporal multiplexing of 8 'bins' from a
double-passed heralded photon source and observe an increase in the heralding
and heralded photon rates. This system points the way to harnessing temporal
multiplexing in quantum technologies, from single-photon sources to large-scale
computation.Comment: Minor revision
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