A study on LQG/LTR control for damping inter-area oscillations in power systems

Published versio

The web of federal crimes in Brazil: topology, weaknesses, and control

Law enforcement and intelligence agencies worldwide struggle to find effective ways to fight and control organized crime. However, illegal networks operate outside the law and much of the data collected is classified. Therefore, little is known about criminal networks structure, topological weaknesses, and control. In this contribution we present a unique criminal network of federal crimes in Brazil. We study its structure, its response to different attack strategies, and its controllability. Surprisingly, the network composed of multiple crimes of federal jurisdiction has a giant component, enclosing more than a half of all its edges. This component shows some typical social network characteristics, such as small-worldness and high clustering coefficient, however it is much "darker" than common social networks, having low levels of edge density and network efficiency. On the other side, it has a very high modularity value, $Q=0.96$. Comparing multiple attack strategies, we show that it is possible to disrupt the giant component of the network by removing only $2\%$ of its edges or nodes, according to a module-based prescription, precisely due to its high modularity. Finally, we show that the component is controllable, in the sense of the exact network control theory, by getting access to $20\%$ of the driver nodes.Comment: 9 pages, 5 figure

HybMT: Hybrid Meta-Predictor based ML Algorithm for Fast Test Vector Generation

Testing an integrated circuit (IC) is a highly compute-intensive process. For today's complex designs, tests for many hard-to-detect faults are typically generated using deterministic test generation (DTG) algorithms. Machine Learning (ML) is being increasingly used to increase the test coverage and decrease the overall testing time. Such proposals primarily reduce the wasted work in the classic Path Oriented Decision Making (PODEM) algorithm without compromising on the test quality. With variants of PODEM, many times there is a need to backtrack because further progress cannot be made. There is thus a need to predict the best strategy at different points in the execution of the algorithm. The novel contribution of this paper is a 2-level predictor: the top level is a meta predictor that chooses one of several predictors at the lower level. We choose the best predictor given a circuit and a target net. The accuracy of the top-level meta predictor was found to be 99\%. This leads to a significantly reduced number of backtracking decisions compared to state-of-the-art ML-based and conventional solutions. As compared to a popular, state-of-the-art commercial ATPG tool, our 2-level predictor (HybMT) shows an overall reduction of 32.6\% in the CPU time without compromising on the fault coverage for the EPFL benchmark circuits. HybMT also shows a speedup of 24.4\% and 95.5\% over the existing state-of-the-art (the baseline) while obtaining equal or better fault coverage for the ISCAS'85 and EPFL benchmark circuits, respectively.Comment: 9 pages, 7 figures and 7 tables. Changes from the previous version: We performed more experiments with different regressor models and also proposed a new neural network model, HybNN. We report the results for the EPFL benchmark circuits (most recent and large) and compare our results against a popular commercial ATPG too

Correctness of services and their composition

We study correctness of services and their composition and investigate how the design of correct service compositions can be systematically supported. We thereby focus on the communication protocol of the service and approach these questions using formal methods and make contributions to three scenarios of SOC.Wir studieren die Korrektheit von Services und Servicekompositionen und untersuchen, wie der Entwurf von korrekten Servicekompositionen systematisch unterstützt werden kann. Wir legen dabei den Fokus auf das Kommunikationsprotokoll der Services. Mithilfe von formalen Methoden tragen wir zu drei Szenarien von SOC bei

Stealthy Sensor Attacks for Plants Modeled by Labeled Petri Nets

The problem of stealthy sensor attacks for labeled Petri nets is considered. An operator observes the plant to establish if a set of critical markings has been reached. The attacker can corrupt the sensor channels that transmit the sensor readings, making the operator incapable to establish when a critical marking is reached. We first construct the stealthy attack Petri net that keeps into account the real plant evolutions observed by the attacker and the corrupted plant evolutions observed by the operator. Starting from the reachability graph of the stealthy attack Petri net, an attack structure is defined: it describes all possible attacks. The supremal stealthy attack substructure can be obtained by appropriately trimming the attack structure. An attack function is effective if the supremal stealthy attack substructure contains a state whose first element is a critical marking and the second element is a noncritical marking

A branch and bound approach for the design of decentralized supervisors in Petri net models

The paper addresses the design of compact and maximally permissive decentralized supervisors for Petri nets, based on generalized mutual exclusion constraints. Decentralization constraints are formulated with respect to the net transitions, instructing each local supervisor to detect and disable transitions of its own control site only. A solution is characterized in terms of the states it allows and its feasibility is assessed by means of two separate tests, one checking the required behavioral properties (e.g., liveness, reversibility and controllability) of the induced reachability subgraph and the other ensuring the existence of a decentralized supervisor enforcing exactly the considered set of allowed states. The second test employs an integer linear programming formulation. Maximal permissivity is ensured by efficiently exploring the solution space using a branch and bound method that operates on the reachable states. Particular emphasis is posed on the obtainment of the controllability property, both in the structural and the behavioral interpretation