218,600 research outputs found
Langevin simulations of the out-of-equilibrium dynamics of the vortex glass in high-temperature superconductors
We study the relaxation dynamics of flux lines in dirty high-temperature
superconductors using numerical simulations of a London-Langevin model of the
interacting vortex lines. By analysing the equilibrium dynamics in the vortex
liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We
then focus on the out-of-equilibrium dynamics of the vortex glass phase using
tools that are common in the study of other glassy systems. By monitoring the
two-times roughness and dynamic wandering we identify and characterize
finite-size effects that are similar, though more complex, than the ones found
in the stationary roughness of clean interface dynamics. The two-times
density-density correlation and mean-squared-displacement correlation age and
their temporal scaling follows a multiplicative law similar to the one found at
criticality. The linear responses also age and the comparison with their
associated correlations shows that the equilibrium fluctuation-dissipation
relation is modified in a simple manner that allows for the identification of
an effective temperature characterizing the dynamics of the slow modes. The
effective temperature is closely related to the vortex liquid-vortex glass
crossover temperature. Interestingly enough, our study demonstrates that the
glassy dynamics in the vortex glass is basically identical to the one of a
single elastic line in a disordered environment (with the same type of scaling
though with different parameters). Possible extensions and the experimental
relevance of these results are also discussed.Comment: 22 pages, 29 figure
Ensuring Cyber-Security in Smart Railway Surveillance with SHIELD
Modern railways feature increasingly complex embedded computing systems for surveillance, that are moving towards fully wireless smart-sensors. Those systems are aimed at monitoring system status from a physical-security viewpoint, in order to detect intrusions and other environmental anomalies. However, the same systems used for physical-security surveillance are vulnerable to cyber-security threats, since they feature distributed hardware and software architectures often interconnected by âopen networksâ, like wireless channels and the Internet. In this paper, we show how the integrated approach to Security, Privacy and Dependability (SPD) in embedded systems provided by the SHIELD framework (developed within the EU funded pSHIELD and nSHIELD research projects) can be applied to railway surveillance systems in order to measure and improve their SPD level. SHIELD implements a layered architecture (node, network, middleware and overlay) and orchestrates SPD mechanisms based on ontology models, appropriate metrics and composability. The results of prototypical application to a real-world demonstrator show the effectiveness of SHIELD and justify its practical applicability in industrial settings
Large-scale Complex IT Systems
This paper explores the issues around the construction of large-scale complex
systems which are built as 'systems of systems' and suggests that there are
fundamental reasons, derived from the inherent complexity in these systems, why
our current software engineering methods and techniques cannot be scaled up to
cope with the engineering challenges of constructing such systems. It then goes
on to propose a research and education agenda for software engineering that
identifies the major challenges and issues in the development of large-scale
complex, software-intensive systems. Central to this is the notion that we
cannot separate software from the socio-technical environment in which it is
used.Comment: 12 pages, 2 figure
Why (and How) Networks Should Run Themselves
The proliferation of networked devices, systems, and applications that we
depend on every day makes managing networks more important than ever. The
increasing security, availability, and performance demands of these
applications suggest that these increasingly difficult network management
problems be solved in real time, across a complex web of interacting protocols
and systems. Alas, just as the importance of network management has increased,
the network has grown so complex that it is seemingly unmanageable. In this new
era, network management requires a fundamentally new approach. Instead of
optimizations based on closed-form analysis of individual protocols, network
operators need data-driven, machine-learning-based models of end-to-end and
application performance based on high-level policy goals and a holistic view of
the underlying components. Instead of anomaly detection algorithms that operate
on offline analysis of network traces, operators need classification and
detection algorithms that can make real-time, closed-loop decisions. Networks
should learn to drive themselves. This paper explores this concept, discussing
how we might attain this ambitious goal by more closely coupling measurement
with real-time control and by relying on learning for inference and prediction
about a networked application or system, as opposed to closed-form analysis of
individual protocols
Correct and Control Complex IoT Systems: Evaluation of a Classification for System Anomalies
In practice there are deficiencies in precise interteam communications about
system anomalies to perform troubleshooting and postmortem analysis along
different teams operating complex IoT systems. We evaluate the quality in use
of an adaptation of IEEE Std. 1044-2009 with the objective to differentiate the
handling of fault detection and fault reaction from handling of defect and its
options for defect correction. We extended the scope of IEEE Std. 1044-2009
from anomalies related to software only to anomalies related to complex IoT
systems. To evaluate the quality in use of our classification a study was
conducted at Robert Bosch GmbH. We applied our adaptation to a postmortem
analysis of an IoT solution and evaluated the quality in use by conducting
interviews with three stakeholders. Our adaptation was effectively applied and
interteam communications as well as iterative and inductive learning for
product improvement were enhanced. Further training and practice are required.Comment: Submitted to QRS 2020 (IEEE Conference on Software Quality,
Reliability and Security
Attack-Surface Metrics, OSSTMM and Common Criteria Based Approach to âComposable Securityâ in Complex Systems
In recent studies on Complex Systems and Systems-of-Systems theory, a huge effort has been put to cope with behavioral problems, i.e. the possibility of controlling a desired overall or end-to-end behavior by acting on the individual elements that constitute the system itself. This problem is particularly important in the âSMARTâ environments, where the huge number of devices, their significant computational capabilities as well as their tight interconnection produce a complex architecture for which it is difficult to predict (and control) a desired behavior; furthermore, if the scenario is allowed to dynamically evolve through the modification of both topology and subsystems composition, then the control problem becomes a real challenge. In this perspective, the purpose of this paper is to cope with a specific class of control problems in complex systems, the âcomposability of security functionalitiesâ, recently introduced by the European Funded research through the pSHIELD and nSHIELD projects (ARTEMIS-JU programme). In a nutshell, the objective of this research is to define a control framework that, given a target security level for a specific application scenario, is able to i) discover the system elements, ii) quantify the security level of each element as well as its contribution to the security of the overall system, and iii) compute the control action to be applied on such elements to reach the security target. The main innovations proposed by the authors are: i) the definition of a comprehensive methodology to quantify the security of a generic system independently from the technology and the environment and ii) the integration of the derived metrics into a closed-loop scheme that allows real-time control of the system. The solution described in this work moves from the proof-of-concepts performed in the early phase of the pSHIELD research and enrich es it through an innovative metric with a sound foundation, able to potentially cope with any kind of pplication scenarios (railways, automotive, manufacturing, ...)
- âŠ