Sufficient Conditions For Detectability Research Articles

Almost sure detection of the presence of malicious components in cyber–physical systems

This article studies a fundamental problem of security of cyber–physical systems (CPSs): that of detecting, almost surely, the presence of malicious components in the CPS. We assume that some of the actuators may be malicious while all sensors are honest. We introduce a novel idea of separability of state trajectories generated by CPSs in two situations: those under the nominal no-attack situation and those under the influence of an attacker. We establish its connection to the security of CPSs, particularly in detecting the presence of malicious actuators (if any) in them. As primary contributions, we establish necessary and sufficient conditions for the aforementioned detection in CPSs modeled as Markov decision processes (MDPs). Moreover, we focus on the mechanism of perturbing the pre-determined control policies of the honest agents in CPSs modeled as stochastic linear systems, by injecting a certain class of random process called private excitation; sufficient conditions for detectability and non-detectability of the presence of malicious actuators, assuming that the policies are randomized history-dependent and randomized Markovian, are established. Several technical aspects of our results are discussed extensively.

Pareto–Koopmans efficiency in two‐stage network data envelopment analysis in the presence of undesirable intermediate products and nondiscretionary factors

AbstractMany studies have recently been conducted on the evaluation of system performance with a two‐stage network structure in data envelopment analysis (DEA) literature. One of the topics of interest to researchers has been the mitigation of undesirable products or nondiscretionary factors into their corresponding possible production set (PPS) and their impact on overall efficiency calculations. Determination of decision‐making units (DMUs) with Pareto–Koopmans efficiency status is decisive in identifying benchmark units. The calculated overall efficiency status is compromised when both undesirable products and nondiscretionary factors are present. This work utilizes an axiomatic approach. A novel PPS for a two‐stage network in presence of undesirable intermediate products and nondiscretionary exogenous inputs is introduced. Based on this PPS and by focusing on the principle of mathematical dominance, new models for evaluating overall and divisional efficiencies are presented. In addition, by proposing a two‐step network DEA approach, a necessary and sufficient condition for detection of DMUs with Pareto–Koopmans efficiency status is provided. And by introducing a two‐step algorithm, a novel technique for determining overall efficiency conditions is produced. Finally, the proposed technology is applied to a practical example, and outcomes are discussed.

Observability analysis and observer design for a class of cell population balance models

Abstract The observability and detectability of a class of population balance models described by a partial integro-differential equation coupled with an ordinary differential equation is characterized for a simple two-species bioreactor model. By a direct calculation of the indistinguishable trajectories and employing the direct method of Lyapunov sufficient conditions for detectability are derived in terms of the cell division characteristic distributions. The cases of monotonic and non-monotonic growth rate functions are considered and the corresponding differences highlighted. An observer is designed with ensured convergence rate in the first moment of the distribution. Numerical simulation results illustrate the theoretical assessments.

Detecting Topology Variations in Networks of Linear Dynamical Systems

In this paper, we consider the problem of detecting topology variations in networks of linear dynamical systems. We study the problem of finding conditions under which one can detect node or link disconnections from prior knowledge of the nominal network behavior and online measurements taken from the entire set or a fraction of network nodes. Necessary and sufficient conditions for detectability are given. Examples are discussed to substantiate the analysis. The considered approach makes use of analysis tools from switching systems theory.

Corruption and its detection: a graph-theoretic approach

We consider a corruption network where agents, both internal or external to the network, use connections and bribes to obtain goods or services outside the formal procedures. We develop a graph-theoretic model for the system and present sufficient conditions for detectability of the corruption status of at least one agent. Where detectability is not possible, we determine the topology of the network and all the possible corruption statuses of the agents. Further we provide, if we have information on the corruption status of a single agent, an algorithm that identifies the corruption status of every other agent in the network. Our results provide tools for detecting corrupt agents in organizations such as revenue authorities, municipalities, police, vehicle inspection departments, financial institutions and firms, while allowing the system to operate in normal mode.

Detecting 3-D Mirror Symmetry in a 2-D Camera Image for 3-D Shape Recovery

In this paper, we take up the long-standing problem of how to recover 3-D shapes represented by a 2-D image, such as the image on the retina of the eye, or in a video camera. Our approach is biologically grounded in a theory of how the human visual system solves this problem, focusing on shapes that are mirror symmetrical in 3-D. A 3-D mirror-symmetrical shape can be recovered from a single 2-D orthographic or perspective image by applying several a priori constraints: 3-D mirror symmetry, 3-D compactness, and planarity of contours. From the computational point of view, the application of a 3-D symmetry constraint is challenging because it requires establishing 3-D symmetry correspondence among features of a 2-D image, which itself is asymmetrical for almost all viewing directions relative to the 3-D symmetrical shape. We describe new invariants of a 3-D to 2-D projection for the case of a pair of mirror-symmetrical planar contours, and we formally state and prove the necessary and sufficient conditions for detection of this type of symmetry in a single orthographic and perspective image.

Statistical significance in high-dimensional linear models

We propose a method for constructing $p$-values for general hypotheses in a high-dimensional linear model. The hypotheses can be local for testing a single regression parameter or they may be more global involving several up to all parameters. Furthermore, when considering many hypotheses, we show how to adjust for multiple testing taking dependence among the $p$-values into account. Our technique is based on Ridge estimation with an additional correction term due to a substantial projection bias in high dimensions. We prove strong error control for our $p$-values and provide sufficient conditions for detection: for the former, we do not make any assumption on the size of the true underlying regression coefficients while regarding the latter, our procedure might not be optimal in terms of power. We demonstrate the method in simulated examples and a real data application.

Sensor Fault Detection, Diagnosis and Validation - A Survey

This paper provides an overview and analysis of data-driven sensor fault detection, diagnosis and validation from the application viewpoint. The typical sensor fault detection indices in the literature and the fundamental issues of necessary and sufficient conditions for detectability, reconstructability, identifiability and isolatability are analyzed. The main objective is to study the essential and important algorithms and techniques for single or multiple sensor fault diagnosis and validation. The issues of optimal principal components, sensor validity index, maximized sensitivity, as well as robust sensor fault diagnosis, etc. are discussed. Additional focuses are summarized at the end of the paper for future investigation.

Simple search games on an infinite circular cylinder

Differential search games with simple motions of objects on an infinite circular cylinder are approached geometrically, using sets whose structure depends on time. Sufficient conditions for detection with the corresponding strategies are given. New kinds of problems are proposed, their connections with the initial parameters are investigated.

Detecting optimal and non-optimal actions in average-cost Markov decision processes

We present two sufficient conditions for detection of optimal and non-optimal actions in (ergodic) average-cost MDPs. They are easily interpreted and can be implemented as detection tests in both policy iteration and linear programming methods. An efficient implementation of a recent new policy iteration scheme is discussed.

Detecting optimal and non-optimal actions in average-cost Markov decision processes

We present two sufficient conditions for detection of optimal and non-optimal actions in (ergodic) average-cost MDPs. They are easily interpreted and can be implemented as detection tests in both policy iteration and linear programming methods. An efficient implementation of a recent new policy iteration scheme is discussed.

Interferon-Related Leukocyte Inclusions in Acquired Immune Deficiency Syndrome: Localization in T Cells

Blood samples from a series of 12 patients with Kaposi's sarcoma or infectious complications of the acquired immunodeficiency syndrome (AIDS) and from 18 homosexual contacts of AIDS patients were screened for interferon-related tubuloreticular inclusions (TRI) in circulating leukocytes. In the AIDS patients, TRI were detected by transmission electron microscopy in 1.5 to 10% of mononuclear cell sections. They were most frequent in patients with a decreased fraction of T helper cells and T4/T8 ratios less than 0.2. Only rare TRI-positive sections were found in 3/12 homosexual contacts with lymphadenopathy and 1/6 asymptomatic contacts. Serum interferon was found to be elevated in each AIDS case tested, but was not a sufficient condition for detection of TRI in homosexual contacts. Active DNA virus infections, including cytomegalovirus, were common to the AIDS cases and possibly contributed to the TRI pathogenesis. Localization of TRI in T suppressor/cytotoxic cells was demonstrated with monoclonal anti-Leu 2a antibodies. The pathophysiologic significance of interferon stimulation with formation of TRI in immunocompetent cells requires further investigation.

Interferon-related leukocyte inclusions in acquired immune deficiency syndrome: localization in T cells.

Blood samples from a series of 12 patients with Kaposi's sarcoma or infectious complications of the acquired immunodeficiency syndrome (AIDS) and from 18 homosexual contacts of AIDS patients were screened for interferon-related tubuloreticular inclusions (TRI) in circulating leukocytes. In the AIDS patients, TRI were detected by transmission electron microscopy in 1.5 to 10% of mononuclear cell sections. They were most frequent in patients with a decreased fraction of T helper cells and T4/T8 ratios less than 0.2. Only rare TRI-positive sections were found in 3/12 homosexual contacts with lymphadenopathy and 1/6 asymptomatic contacts. Serum interferon was found to be elevated in each AIDS case tested, but was not a sufficient condition for detection of TRI in homosexual contacts. Active DNA virus infections, including cytomegalovirus, were common to the AIDS cases and possibly contributed to the TRI pathogenesis. Localization of TRI in T suppressor/cytotoxic cells was demonstrated with monoclonal anti-Leu 2a antibodies. The pathophysiologic significance of interferon stimulation with formation of TRI in immunocompetent cells requires further investigation.

Necessary and sufficient conditions for detectability of jumps in linear systems

Necessary and sufficient conditions for detectability of abrupt changes of unknown magnitude in inputs, outputs, and states of linear systems are derived. Results indicate the minimum number of sensors necessary for detection of different types of hypothesized jumps.

Fault Detection in Iterative Logic Arrays

Kautz has studied the problem of testing one-and two-dimensional arrays of combinational cells under the assumptions that all cell inputs must be applied to a cell to test it completely and that a fault in a cell may cause any arbitrary change in its outputs. In this paper we study the same problem under a more restricted set of assumptions: 1) all faults in a cell can be detected by a known set of inputs (usually smaller than the set of all inputs); and 2) each fault will affect the cell outputs in a known manner. Necessary and sufficient conditions for detection of faults in one-dimensional arrays are obtained. A procedure for deriving efficient tests for one-dimensional arrays is presented. Sufficient conditions for the testability of two-dimensional arrays and procedures for constructing tests for some arrays are obtained.