Hoda Mehrpouyan

Resiliency analysis for complex engineered system design

Abstract Resilience is a key driver in the design of systems that must operate in an uncertain operating environment, and it is a key metric to assess the capacity for systems to perform within the specified performance envelop despite disturbances to their operating environment. This paper describes a graph spectral approach to calculate the resilience of complex engineered systems. The resilience of the design architecture of complex engineered systems is deduced from graph spectra. This is calculated from adjacency matrix representations of the physical connections between components in complex engineered systems. Furthermore, we propose a new method to identify the most vulnerable components in the design and design architectures that are robust to transmission of failures. Nonlinear dynamical system and epidemic spreading models are used to compare the failure propagation mean time transformation. Using these metrics, we present a case study based on the Advanced Diagnostics and Prognostics Testbed, which is an electrical power system developed at NASA Ames as a subsystem for the ramp system of an infantry fighting vehicle.

Resilient Design of Complex Engineered Systems

This paper presents a complex network and graph spectral approach to calculate the resiliency of complex engineered systems. Resiliency is a key driver in how systems are developed to operate in an unexpected operating environment, and how systems change and respond to the environments in which they operate. This paper deduces resiliency properties of complex engineered systems based on graph spectra calculated from their adjacency matrix representations, which describes the physical connections between components in a complex engineered systems. In conjunction with the adjacency matrix, the degree and Laplacian matrices also have eigenvalue and eigenspectrum properties that can be used to calculate the resiliency of the complex engineered system. One such property of the Laplacian matrix is the algebraic connectivity. The algebraic connectivity is defined as the second smallest eigenvalue of the Laplacian matrix and is proven to be directly related to the resiliency of a complex network. Our motivation in the present work is to calculate the algebraic connectivity and other graph spectra properties to predict the resiliency of the system under design.Copyright

Exploring author gender in book rating and recommendation.

Collaborative filtering algorithms find useful patterns in rating and consumption data and exploit these patterns to guide users to good items. Many of the patterns in rating datasets reflect important real-world differences between the various users and items in the data; other patterns may be irrelevant or possibly undesirable for social or ethical reasons, particularly if they reflect undesired discrimination, such as gender or ethnic discrimination in publishing. In this work, we examine the response of collaborative filtering recommender algorithms to the distribution of their input data with respect to a dimension of social concern, namely content creator gender. Using publicly-available book ratings data, we measure the distribution of the genders of the authors of books in user rating profiles and recommendation lists produced from this data. We find that common collaborative filtering algorithms differ in the gender distribution of their recommendation lists, and in the relationship of that output distribution to user profile distribution.

Model Checking of Security Properties in Industrial Control Systems (ICS)

With the increasing inter-connection of operation technology to the IT network, the security threat to the Industrial Control System (ICS) is increasing daily. Therefore, it is critical to utilize formal verification technique such as model checking to mathematically prove the correctness of security and safety requirements in the controller logic before it is deployed on the field. However, model checking requires considerable effort for regular ICS users and control technician to verify properties. This paper, provides a simpler approach to the model checking of temperature process control system by first starting with the control module design without formal verification. Second, identifying possible vulnerabilities in such design. Third, verifying the safety and security properties with a formal method.

Misusing Sensory Channel to Attack Industrial Control Systems

Industrial control systems (ICS) are used to control and manage critical infrastructures and protecting these complex system and their interfaces, which can be exploited by internal and external attackers, are a vital security task. Sensors, as an interface device, are used by ICS to collect information about the physical environment and should be guarded against cyber attacks. This paper investigates how sensors can be used as a communication channel by hackers to send a malicious command and control into the ICS. Further, we examine how abusing sensory channel would lead to a data pattern, which can be detected by a proper signature-based intrusion detection system (IDS).

Combination of Compositional Verification and Model Checking for Safety Assessment of Complex Engineered Systems

This paper presents a novel safety specification and verification approach based on the compositional reasoning and model checking algorithms. The behavioral specification of each component and subsystem is modeled to describe the overall structure of the design. Then, these specifications are analyzed to determine the least number of component redundancies that are required to tolerate and prevent catastrophic system failure. The framework utilizes Labelled Transition Systems (LTS) formalism to model the behavior of components and subsystems. Furthermore, compositional analysis is used to reason about the components’ constraints (or assumptions) on their environments and the properties (or guarantees) of their output. This identification of local safety properties of components and subsystems leads to satisfaction of the desired safety requirements for the global system. A model of quad-redundant Electro-Mechanical Actuator (EMA) is constructed and, in an iterative approach, its safety properties are analyzed. Experimental results confirm the feasibility of the proposed approach for verifying the safety issues associated with complex systems in the early stages of the design process.Copyright

Resilient Design of Complex Engineered Systems Against Cascading Failure

This paper describes an approach commonly used with complex networks to study the failure propagation in an engineered system design. The goal of the research is to synthesize and illustrate system design characteristics that results from possible impact of the underlying design methodology based on cascading failures. Further, identifying the most vulnerable component in the design or system design architectures that are resilient to such dissemination of failures provide additional property improvement for resilient design. The paper presents a case study based on the ADAPT (Electrical Power System) EPS testbed at NASA Ames as a subsystem for the Ramp System of an Infantry Fighting Vehicle (IFV). A popular methodology based on the adjacency matrix, which is commonly used to represent edge connections between nodes in complex networks, has inspired interest in the use of similar methods to represent complex engineered systems. This is made possible, by defining the connections between components as a flow of energy, signal, and material and constraining physical connection between compatible components within complex engineered systems. Non-linear dynamical system (NLDS) and epidemic spreading models are used to compare the failure propagation mean time transformation. The results show that coupling, modularity, and module complexity all play an important part in the design of robust large complex engineered systems.Copyright

Complex System Design Verification Using Assumption Generation

In the era of large complex systems with continuous and discrete event components, it is critical to establish a complete design verification strategy to determine whether a system satisfies certain safety properties. However, traditional approaches for the verification of such a complex system lack the ability to take into account all possible system states, efficiently model all component interactions, and accurately quantify the risks and uncertainties. This paper presents a methodology for system-level design of complex systems verification based on compositional model checking. This methodology relies on assumption generation and on the domain independent compositional rules for correctness proof of the design of physical systems. The objective is to present a case study for applying the existing automated compositional verification techniques and observing the characteristics of the verification model. The main advantage of this method is that it enables the designer to verify the safety properties of the system without requiring the detail knowledge of the internal actions of the system. The under-approximate context model of the system design is constructed and, in an iterative approach, its safety properties are analyzed until a violation of a property is found and an execution trace called a counter example is produced. In the case of safety requirements violation, the early generation of counter examples leads to faster design verification.© 2013 ASME

A Model-Based Failure Identification and Propagation Framework for Conceptual Design of Complex Systems

In this paper, a model-based failure identification and propagation (MFIP) framework is introduced for early identification of potential safety issues caused by environmental disturbances and subsystem failures within a complex avionic system. The MFIP framework maps hazards and vulnerability modes to specific components in the system and analyzes failure propagation paths. Block definition diagrams (BDD) are used to represent system functional requirements in the form of demonstrating the relationships between various requirements, their associations, generalizations, as well as dependencies. These concept models help to identify hazardous factors and the relationships through which their detrimental effects are transferred through-out the proposed system architecture. As such, the approach provides the opportunity to reduce costs associated with redesign and provide important information on design viability. Using this technique, designers can examine the impacts of environmental and subsystem risks on the overall system during the early stages of design and develop hazard mitigation strategies.Copyright