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Interrupts
Published in Syed R. Rizvi, Microcontroller Programming, 2016
Embedded systems are generally reactive systems. A reactive system is a system whose role is to maintain an ongoing interaction with its environment rather than produce some final value upon termination. An air traffic control system and programs controlling mechanical devices such as a train, a plane, or ongoing processes such as a nuclear reactor are some of the typical examples of reactive systems. In many applications they must be viewed as real-time systems. Real-time systems are called real-time because they are subject to operational deadlines from event to system response. By contrast, a non-real-time system is one for which there is no deadline, even if fast response or high performance is desired or preferred. Thus, the success of a real-time system greatly depends upon the time in which its functions are performed. A real-time system may be one where its application can be considered to be mission critical. Mission critical refers to any factor that is essential to the core function of a system, and whose failure or disruption will result in the failure of the system. For example, the antilock brakes on a car are an example of a real-time system. Here, the deadline or real-time constraint is the short time in which the brakes must be activated to prevent the wheel from locking. Real-time systems can be considered to have failed if they do not respond before their deadline, where their deadline is relative to an event.
Insight into User Acceptance and Adoption of Autonomous Systems in Mission Critical Environments
Published in International Journal of Human–Computer Interaction, 2023
Kristin Weger, Lisa Matsuyama, Rileigh Zimmermann, Bryan Mesmer, Douglas Van Bossuyt, Robert Semmens, Casey Eaton
In civilian applications, a mission critical system can refer to a system that is essential to the survival of an organization and will adversely affect society when it fails (Hinchey & Coyle, 2010). Within the U.S. military, mission critical refers to any job functions that are identified as critical to the performance of the agency (Meyer, 2020). An example of a mission critical system in a military context is the navigational system for a spacecraft. If the navigational system were to fail, the spacecraft would either have degraded performance or could be lost entirely. Many mission critical systems can have major adverse impacts with the possibilities of loss of life, serious injury and/or financial loss if they fail especially in unanticipated ways. Within systems, specific components or subsystems can be mission critical where a failure of the component or subsystem causes the system to no longer function as anticipated which can cause hardware failure, software failure, or a loss of trust in the system by the user. Hence, the acceptance and adoption of mission critical autonomous systems is essential to improve military efficiency and safety because of an increase in system and mission complexity as well as a decrease in overall manpower in the military (Barrett-Pink et al., 2019; Benaskeur et al., 2011).
Performance-based maintenance contract for mission-critical equipment considering spare parts inventory cost-sharing and suppliers' risk attitudes
Published in International Journal of Production Research, 2022
Min Zhang, Keke Wei, Shuguang He, Zhen He, Wei Yan
In a PBC for maintenance service, one of the key performance indicators is the availability of mission-critical equipment (Kim, Cohen, and Netessin 2007; Qin, Shao, and Jiang 2020). The mission-critical equipment generally consists of some highly valuable and costly major components (e.g. engines in aircraft). The major components are often repaired offline when they fail. For example, if an engine in the aircraft fails and needs maintenance, it is substituted by a stored component (also known as a spare part) (Mirzahosseinian and Piplani 2011). These spare parts help to improve maintenance speed, efficiency, and mission-critical equipment availability (Wong, Van Oudheusden, and Cattrysse 2007; Qin et al. 2021). There are a lot of factors that affect the availability of the mission-critical equipment, such as spare parts inventory level, maintenance quality, failure rate, and so on. For the mission-critical equipment, the spare parts inventory level is considered as the most important factor to reduce the downtime (Kleindorfer and Saad 2005), and guarantee the equipment availability (Kim and Tomlin 2013). Thus, spare parts inventory decisions are important for operators and service suppliers.
Nuclear Power Concepts and Development Strategies for High-Power Electric Propulsion Missions to Mars
Published in Nuclear Technology, 2022
Lee Mason, Steve Oleson, David Jacobson, Paul Schmitz, Lou Qualls, Michael Smith, Brian Ade, Jorge Navarro
The DDT&E phase of the NEP power plan starts with the mission System Requirements Review (SRR) in year 2. The design of full-scale engineering model (EM) subsystems will occur in parallel and be informed by the TDU testing. The plan is to build multiple full-scale EMs that would be used to support various test objectives. A complete full-scale power string will be assembled with a high-fidelity reactor simulator, single Brayton unit, heat rejection loop, and PMAD power channel for an integrated 1000-h nonnuclear system test, most likely at the Space Power Facility at the GRC Neil A. Armstrong Test Facility. A second set of EM units will be subjected to launch vibration environments and placed on long-duration tests to evaluate performance relative to the mission design life, currently estimated at about 27 000 h for the power system and 23 000 h for the EP system. A third Brayton unit will be supplied to the DOE reactor team for use in a full-scale 100-h reactor prototype test to demonstrate nuclear performance. Candidate nuclear facilities to accommodate the reactor prototype test include the INL Experimental Breeder Reactor II facility and the Nevada National Security Site, U1A facility. Similar testing will be performed on full-scale EM thrusters, DDUs, and XFCs, culminating in an end-to-end performance verification test at GRC VF5. The three separate integrated tests of full-scale EM test articles (i.e., nonnuclear power string, reactor prototype, and EP string) combined with the subsystem launch vibration tests would provide critical data to support the mission Critical Design Review (CDR) and establish TRL 6 for the key NEP elements by year 6.