147 research outputs found

    Reliability Analysis of a Multi-State Truly-Threshold System Using a Multi-Valued Karnaugh Map

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    This paper deals with the Boolean-based analysis of a prominent class of non-repairable coherent multistate systems with independent nonidentical multistate components. This class of systems is represented by a multistate coherent truly threshold system of several states, which is not necessarily binary-imaged. The paper represents such a system via Boolean expressions of system success or system failure at each non-zero level, which are in the form of minimal sop formulas, or disjoint sop formulas. These are expressions that are directly convertible to expected values. Several map representations are also offered, including a single multi-value Karnaugh map.Comment: 42 pages, 11 figures, 5 table

    Improving resilience to cyber-attacks by analysing system output impacts and costs

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    Cyber-attacks cost businesses millions of dollars every year, a key component of which is the cost of business disruption from system downtime. As cyber-attacks cannot all be prevented, there is a need to consider the cyber resilience of systems, i.e. the ability to withstand cyber-attacks and recover from them. Previous works discussing system cyber resilience typically either offer generic high-level guidance on best practices, provide limited attack modelling, or apply to systems with special characteristics. There is a lack of an approach to system cyber resilience evaluation that is generally applicable yet provides a detailed consideration for the system-level impacts of cyber-attacks and defences. We propose a methodology for evaluating the effectiveness of actions intended to improve resilience to cyber-attacks, considering their impacts on system output performance, and monetary costs. It is intended for analysing attacks that can disrupt the system function, and involves modelling attack progression, system output production, response to attacks, and costs from cyber-attacks and defensive actions. Studies of three use cases demonstrate the implementation and usefulness of our methodology. First, in our redundancy planning study, we considered the effect of redundancy additions on mitigating the impacts of cyber-attacks on system output performance. We found that redundancy with diversity can be effective in increasing resilience, although the reduction in attack-related costs must be balanced against added maintenance costs. Second, our work on attack countermeasure selection shows that by considering system output impacts across the duration of an attack, one can find more cost-effective attack responses than without such considerations. Third, we propose an approach to mission viability analysis for multi-UAV deployments facing cyber-attacks, which can aid resource planning and determining if the mission can conclude successfully despite an attack. We provide different implementations of our model components, based on use case requirements.Open Acces

    Confronting the Global Plastics Problem Threatening the Marine Environment – A Framework and Elements of an International Legal Response

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    At present, international law does not contain any one instrument that would have been designed to target the global plastics problem as a whole. Existing efforts remain fragmented and fail to establish a coherent legal regime, yet a globally recognized need to construct a coordinated and comprehensive international legal response exists. The problem and related regulatory challenges are tremendously complex and multifaceted. The aim of this dissertation is to understand the science and root causes behind the problem and the role of international law and States in contributing to solutions. Unlike earlier legal research, this study approaches the global plastics problem threatening the marine environment as a continuum of three sub-problems comprising extensive plastics wastes generation, plastics leakage to the oceans, and accumulating marine plastics pollution (MPP). It argues that each sub-problem has their distinctive features that require their own set of legal measures. This approach unfolds a problem-based doctrinal and interdisciplinary assessment of international law. While respecting the intricacies of the problem, the study offers a three-fold framework to examine the global plastics problem and elements of international law. An international legal response to the global plastics problem arises from a mix of diverse measures coming together

    An Integrated Framework to Evaluate Off-Nominal Requirements and Reliability of Novel Aircraft Architectures in Early Design

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    One of the barriers to the development of novel aircraft architectures and technologies is the uncertainty related to their reliability and the safety risk they pose. In the conceptual and preliminary design stages, traditional system safety techniques rely on heuristics, experience, and historical data to assess these requirements. The limitations and off-nominal operational considerations generally postulated during traditional safety analysis may not be complete or correct for new concepts. Additionally, dearth of available reliability data results in poor treatments of epistemic and aleatory uncertainty for novel aircraft architectures. Two performance-based methods are demonstrated to solve the problem of improving the identification and characterization of safety related off-nominal requirements in early design. The problem of allocating requirements to the unit level is solved using a network-based bottom-up analysis algorithm combined with the Critical Flow Method. A Bayesian probability approach is utilized to better deal with epistemic and aleatory uncertainty while assessing unit level failure rates. When combined with a Bayesian decision theoretic approach, it provides a mathematically backed framework for compliance finding under uncertainty. To estimate multi-state reliability of complex systems, this dissertation contributes a modified Monte-Carlo algorithm that uses the Bayesian failure rate posteriors previously generated. Finally, multi-state importance measures are introduced to determine the sensitivity of different hazard severity to unit reliability. The developed tools, techniques, and methods of this dissertation are combined into an integrated framework with the capability to perform trade-studies informed by safety and reliability considerations for novel aircraft architectures in early preliminary design. A test distributed electric propulsion (T-DEP) aircraft inspired by the X-57 is utilized as a test problem to demonstrate this frameworkPh.D

    Circular Economy and Industrial Packaging Material Waste in EU: Case Study

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    Current linear economy is based on take-make-use-dispose model which is damaging the environment with unsustainable resource use and generated waste. Sustainable alternative to current linear model is circular economy (CE), which integrates the economic activities and wellbeing with efficient resource use. The purpose of this thesis is to examine the impacts of CE to the consumption of industrial packaging material and waste management in international manufacturing industry. The study focuses primarily on environmental demands that EU is increasingly setting for multinational companies (MNCs) and how they impact on CE transition. Implementing circular business model within the organization may enable diverse benefits, e.g. potential to save considerable resources, gain competitive advantage and create value from economic, social and environmental perspective. Thus, the contribution of CE in gaining competitive advantage and creating value in global business context is observed in this study from resourcebased view (RBV). Furthermore, waste management is closely interconnected with CE and developing functioning waste management system is crucial for effective resource use, as well as packaging waste treatment. This thesis includes a qualitative case study, which examines the research topic by conducting interviews for external and internal stakeholders of a case company operating in global manufacturing industry. The research investigated the background of the demands for packaging material in EU, as well as identified the possibilities and challenges in terms of packaging material.It also mapped the current state of industrial packaging material waste treatment, monitoring and reporting. Current EU legislation and demands are not forcing companies to shift towards CE but are currently making the unsustainable actions and operations continuously more expensive and difficult. Reporting the inbound and outbound packaging material is mandatory for multinational companies in EU and currently very challenging. More reliable reporting would require extensive improvement in system data, requirements for suppliers about the packaging material, as well as more standardized packaging for products. CE can enable various possibilities for companies by turning the inefficiencies of linear economy model into business value. However, various factors are hindering the transition towards circular model, such as legislation, complex global supply chains, challenging packaging materials, as well as missing system for circulating material. In order to overcome these challenges, comprehensive cooperation within the organization and throughout the global value chains is mandatory. Certain requirements for stakeholders are necessary for developing more circular processes and ensure that supply chain partners are willing to operate in more sustainable way. Furthermore, there is an urgent need for developing waste treatment methods and new systems for circulating packaging. The waste should be seen as a resource but current challenges in recycling and reusing the materials are decelerating companies to do any actual actions

    Stochastic Activity Networks Templates: Supporting Variability in Performability Models

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    Model-based evaluation is extensively used to estimate performance and reliability of dependable systems. Traditionally, those systems were small and self-contained, and the main challenge for model-based evaluation has been the efficiency of the solution process. Recently, the problem of specifying and maintaining complex models has increasingly gained attention, as modern systems are characterized by many components and complex interactions. Components share similarities, but also exhibit variations in their behavior due to different configurations or roles in the system. From the modeling perspective, variations lead to replicating and altering a small set of base models multiple times. Variability is taken into account only informally, by defining a sample model and explaining its possible variations. In this paper we address the problem of including variability in performability models, focusing on Stochastic Activity Networks (SANs). We introduce the formal definition of Stochastic Activity Networks Templates (SAN-T), a formalism based on SANs with the addition of variability aspects. Differently from other approaches, parameters can also affect the structure of the model, like the number of cases of activities. We apply the SAN-T formalism to the modeling of the backbone network of an environmental monitoring infrastructure. In particular, we show how existing SAN models from the literature can be generalized using the newly introduced formalism

    A Probabilistic Model for Evaluating the Operational Cost of PKI-based Financial Transactions

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    Abstract. The use of PKI in large scale environments suffers some inherent problems concerning the options to adopt for the optimal cost-centered operation of the system. In this paper a Markov based probability model has been applied and a performability indicator has been introduced for assisting the evaluation of the operational cost of the system in a decision support process. Considering the unavailability of the Certification Authority server, three different strategies have been evaluated for determining the optimal one
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