Critical Systems Research Articles

A full-scale experimental investigation of natural gas explosion in a 710-m long utility tunnel with multiple pipelines

Natural gas poses significant risks to the safe operation of utility tunnels, which house multiple critical infrastructure systems, including natural gas pipelines. To date, no full-scale gas explosion tests in utility tunnels have been published, and there is ongoing debate about whether pipelines can withstand such explosions. This study presents the first-ever 1:1-scale experiments conducted in a 710-meter-long tunnel with cross-sectional dimensions of 3.2 m × 2.6 m. Three pipelines, each approximately 25 m in length and constructed to industrial standards, were used to investigate potential damage. The experiments comprehensively captured the development of flow fields, including flame images, flame signals, temperature, and overpressure, as well as pipeline responses. Results revealed that variations in overpressure within the combustion region were driven by both positive and negative feedback loops. A significant pressure drop was also observed as airflow passed through a local expansion. The experiments further demonstrated that while pipelines within utility tunnels are unlikely to be directly damaged by gas explosions, accessories such as racks are at high risk of severe destruction. These findings offer essential insights for improving the safety design, construct, and operation of tunnel-like spaces involving flammable gases.

Remaining Useful Life prediction based on physics-informed data augmentation

Current approaches for monitoring machine health (SOH) and effective prognostics depend on the extensive use of complete degradation data trajectories, implying the reliance on data generation techniques that involve functional degradation of the real system until the failure state is reached. These commonly adopted approaches that depend on labeled target data remain operationally and economically nonviable for most industries and safety critical systems. This paper presents novel approaches that alleviate the existing dependence of most prognostics procedures on Remaining Useful Life (RUL) labeled data for training. To this end, firstly, a hybrid data augmentation procedure is proposed that enables the integration of system knowledge available a priori as well as physics of failure, within the training data. Secondly, an unsupervised Health Index (HI) extraction approach is developed, followed by a long-term prediction of this same HI, that leads to an efficient prediction of RUL without labeled data. Finally, a reliability-based assessment is performed to validate the proposed approach. This comprehensive approach (i.e. integrating all the various stages involved in achieving a RUL prediction based on unlabeled data) is tested on a real industrial aircraft system demonstrating the effectiveness of the proposed approach in real industrial context.

A method for evaluating safety reliability of descend/ascend drop-weight system and mission abort decision for deep-ocean scientific human submersibles

Descend and ascend of deep-water human-occupied submersibles based on buoyancy changes are enabled using a denomination of dispensable drop-weights, and loss of buoyancy are managed using emergency drop-weights and jettisoning identified systems. Failing to release the drop weights or jettison results in submersible stranding on the sea floor, leads to emergency recovery, and hence the drop-weight configuration has to be highly reliable. The paper, for the first time, based on hydrostatic stability, descend/ascend velocity needs, ocean salinity profile and loss-of-buoyancy situations, proposes a novel on-demand reliability based methodology for determining the safe drop-weight configuration and degradation-based mission abort strategy for deep-ocean human submersibles. Probabilistic on-demand reliability analysis based on IEC61508 standards for safety–critical systems using component field-failure data is carried out and the drop-weight configuration essential to meet the human-rated safety integrity level 3 during all stages of the subsea mission is identified for the deep-ocean human scientific submersible Matsya6000, based on which a mission abort protocol is evolved.

Using environmental flows to inform integrated water resource management in critically water scarce regions

AbstractEnvironmental flows (e‐flows) assessments are a powerful mechanism for enhancing and conserving the ecosystem goods and services rivers provide while allocating water to essential human use. There is a paucity of e‐flows assessments and implementation in water scarce regions such as the Middle East, where limited freshwater resources are under extreme pressure. We conducted a first e‐flows assessment of the Mujib River, a vitally important freshwater resource for biodiversity and people in Jordan. We employed a holistic approach based on the building block method (BBM), using expert knowledge, assessment and integration of the hydrology, hydraulics, fish, macroinvertebrates, vegetation, habitat integrity and benthic diatoms of the Mujib River to perform an e‐flows determination. Several significant threats to its ecology and fresh water supply were identified. The most significant was the absence of flooding and abstraction associated with upstream impoundments, as well as reliance on over‐exploited and severely pressured groundwater‐maintained flows. Overall, this paper presents the first e‐flows assessment for the Mujib River in Jordan, a vital step towards improved water resource monitoring and management in water scarce regions, and serves to highlight the urgent global need for e‐flows to preserve our critical freshwater systems.

Enriching systems practice with African perspectives

AbstractThis paper follows an autoethnographic approach that seeks to give a practitioner's reflection by exploring the intersection between African philosophies, particularly the concepts of Ubuntu and Ukama, and the practice of systems thinking. It raises concern about the absence of an African perspective in the discourse on mainstream systems thinking approaches. It argues that African philosophies, with their emphasis on relationality, community and humanness, can contribute to and enrich the discourse on developing systems thinking approaches. The main author's positionality, including his struggles with his identity as an African, his personal experiences growing up in a rural African village and being exposed to traditional African storytelling and community‐based practices, is used to illustrate the connections between African philosophies and systems thinking. As an example of this linkage and how an African perspective can enrich the practice of systems thinking, the paper applies an African worldview to Critical Systems Heuristics.

Code Generation for Neural Networks Based on Fixed-point Arithmetic

Over the past few years, neural networks have started penetrating safety critical systems to make decisions as, for example, in robots, rockets, and autonomous driving cars. Neural networks based on floating-point arithmetic are very time and memory consuming, which are not compatible with embedded systems known to have limited resources. They are also very sensitive to the precision in which they have been trained, so changing this precision generally degrades the quality of their answers. To deal with that, we introduce a new technique to generate a fixed-point code for a trained neural network. This technique is based on fixed-point arithmetic with mixed-precision. This arithmetic is based on integer operations only, which are compatible with small memory devices. The obtained neural network has the same behavior as the initial one (based on the floating-point arithmetic) up to an error threshold defined by the user. The experimental results show the efficiency of our tool SyFix in terms of memory saved and the accuracy of the computations.

A critical systems approach to conference organisation: Hosting an international conference in South Africa

AbstractAnnual meetings have the potential to be used to promote the objectives of a society in a unique setting. A carefully selected venue will not only enhance the experience but also promote the very essence of the society. However, conference organisation can also be a minefield of unexpected problems caused by the involvement of diverse service providers. The cost to members can easily exceed the benefits they experience.Critical systems thinking provides a framework of understanding for promoting holistic thinking and sensitivity to underlying assumptions, guiding the organiser to include multiple perspectives. In this paper, the systems approach, along with elements of critical systems heuristics, Ubuntu, and servant‐leadership, are used to reflect on the organisation of the annual meeting of an international systems organisation. The choice of venue provided both opportunities and challenges.The reflection on the process focuses on the fluidity of boundaries and the interplay between systemic planning and systematic implementation.

Numerical investigation of particle behavior and erosion wear in a centrifugal pump using coarse-grained Discrete Element Method

Erosion wear presents a significant challenge in the operation of hydrodynamic systems, particularly in centrifugal pumps. To address this issue, this study employs the coarse-grained Discrete Element Method (CGDEM) coupled with Computational Fluid Dynamics (CFD) to predict erosion wear areas and elucidate particle behavior dynamics. The simulation considers spherical solid particles (brown corundum) with diameters ranging from 0.3 mm to 1 mm and volume fractions of 15% and 5%. The flow field is calculated using the Navier-Stokes equations and the shear-stress-transport (SST) k-ω model. Particle movement is tracked using Newton’s second law, considering drag and gravitational forces. Results indicate that the highest turbulent kinetic energy (TKE) occurs at a flow rate of Q = 15 m3/h. Moreover, the pressure reduces slightly when the flow rate increases, although flow velocity might increase with volumetric discharge. Additionally, increased particle diameter leads to greater erosion wear, particularly on blade leading edges, the volute tongue area, and the volute casing belly region. As particle mass concentration intensifies, wear rates on the volute wall and inner hub edge also increase. The study’s robustness is demonstrated through alignment between experimental and numerical data. This investigation offers valuable insights into erosion dynamics in centrifugal pumps, crucial for enhancing operational efficiency and mitigating erosion-induced challenges in these critical systems.

Comparing the effects of various fluid resuscitative strategies on Glycocalyx damage in a canine hemorrhage model

Hemorrhagic shock and subsequent resuscitation can cause significant dysregulation of critical systems, including the vascular endothelium. Following hemorrhage, the endothelial lining (glycocalyx) can shed, causing release of glycocalyx components, endothelial activation, and systemic inflammation. A canine model of hemorrhagic shock was used to evaluate five resuscitation fluids, including Lactated Ringers+Hetastarch, Whole Blood (WB), Fresh Frozen Plasma+packed Red Blood Cells (FFP+pRBC), and two hemoglobin-based oxygen carrier (HBOC) fluids, for their impact on glycocalyx shedding. Under anesthesia, purpose-bred adult canines were instrumented and subjected to a controlled hemorrhage with blood being drawn until a mean arterial pressure of <50 mmHg was reached or 40 % of the estimated blood volume was removed. Canines were left in shock for 45 mins before being resuscitated with one of the resuscitation fluids over 30 mins. Following resuscitation, the dogs were monitored up to 2 weeks. Following an additional 3–4 weeks for washout, the canines repeated the protocol, undergoing each resuscitation fluid individually. Blood samples were collected during each round at various timepoints for serum isolation, which was used for detection of glycocalyx biomarker. Comparison of baseline and post-hemorrhage alone showed a significant reduction in serum protein (p<0.0001), heparan sulfate (p<0.001), and syndecan-1 (p<0.0001) concentrations, and a significant increase in hyaluronan (p<0.0001) concentration. Intercomparisons of resuscitation fluids indicated minimal differences in glycocalyx markers over time. Comparisons within each fluid showed dynamic responses in glycocalyx biomarkers over time. Relative to individual baselines, syndecan-1 was significantly reduced after resuscitation in most cases (p<0.0001), excluding WB and FFP+pRBC. In all cases, VE-cadherin was significantly elevated at 24 hr compared to baseline (p<0.001). Hyaluronan was significantly elevated by 3 hr in all cases (p<0.01), except for HBOC fluids. Total glycosaminoglycans were significantly reduced only at 3 hr (p<0.001) for non-HBOC fluids. Similarly, heparan sulfate was significantly reduced with all fluids between resuscitation and 24 hr (p<0.01), except WB. The temporal changes in canine glycocalyx biomarkers were atypical of hemorrhage response in other species. This suggests that the hemorrhage lacked severity and/or typical glycocalyx biomarkers do not reflect the canine endothelium compared to other species. Further research is needed to characterize the canine endothelium and the response to resuscitation fluids.

Quantifying nonuniversal corner free-energy contributions in weakly anisotropic two-dimensional critical systems.

We derive an exact formula for the corner free-energy contribution of weakly anisotropic two-dimensional critical systems in the Ising universality class on rectangular domains, expressed in terms of quantities that specify the anisotropic fluctuations. The resulting expression agrees with numerical exact calculations that we perform for the anisotropic triangular Ising model and quantifies the nonuniversality of the corner term for anisotropic critical two-dimensional systems. Our generic formula is expected to apply also to other weakly-anisotropic critical two-dimensional systems that allow for a conformal field theory description in the isotropic limit. We consider the three-states and four-states Potts models as further specific examples.

Digital twin technology training and research in health higher education: a review

Healthcare strives to ensure overall physical, mental, and emotional well-being for individuals while managing limited resources efficiently. Digital technologies can offer cost reduction, improved user experience, and expanded capacity. In addition, modern automation technologies, which were implemented in industrial control systems or industrial automation control systems, are essential for ensuring the availability of societies’ critical cyber-physical systems (CPSs) and the services they provide, such as healthcare. This narrative literature review produces information that can be applied when planning and implementing an interdisciplinary biomedical and health informatics (BMHI) master’s education focused on the challenges of digitalization in the health sector. The review results that virtual human twins (VHTs) are revolutionizing healthcare by addressing people’s complex medical problems with real-time monitoring and precision care while digital twin (DT) technology can make the hospital’s operational processes resilient and efficient. Thus, future BMHI education must address these technologies with a multidisciplinary approach, including computer science, information science, engineering, basic sciences, health sciences, socio-behavioral sciences, and ethical, legal, and policy aspects. Collected and cumulative data is essential for cognitive DTs. A prerequisite for this data is information sharing between different CPSs. Better information sharing and the development of scalable cognitive DTs and VHTs, the provision of critical services, quality, and cost-effectiveness, as well as health, safety, and resilience, will improve. Similarities between peoples’ health information exchange and information needed for ensuring the resilience of CPSs exist. Since humans are in many ways more complex than CPSs, security engineers have a lot to learn from VHTs in maintaining the resilience of CPSs. Cross-sectoral research and cooperation with different disciplines are essential for the progress of both human health and the resilience of CPSs. Along with interdisciplinary research cooperation, educational cooperation should also be intensified.

Maintenance cost optimisation in critical single-component systems: A technician’s training approach based on a joint learning–forgetting and fuzzy maintenance quality model

Effective maintenance in critical systems is crucial to ensure their operability and safety. Maintenance technicians play an important role in achieving the safety and reliability objectives of critical system components. However, the role of the technical team in maintenance quality is often overlooked. Our study addresses this knowledge gap by developing a methodology to optimise the training scheduling of maintenance technicians in single-component systems, focusing on a learn-and-forget approach. Our main objective is to improve maintenance efficiency by mitigating the negative impact of technician expertise level. To this end, we implemented a simulation-based optimisation, modelling the evolution of technician experience and its influence on maintenance costs. As a case study, we used an urban aerial passenger ropeway system, demonstrating that proper training of technical staff can significantly reduce both corrective and preventive maintenance costs. Our methodology identified three strategic areas for training technical staff throughout the system lifecycle. The results highlight the importance of investing in the training scheduling of technical equipment in critical systems and suggest that an appropriate training strategy can improve operational efficiency and reduce maintenance costs. In conclusion, our research underlines the need to actively consider the human factor in the maintenance of critical systems to ensure their optimal performance and long-term safety.

Jürgen Habermas revisited via Tim Cook's Wikipedia biography: A hermeneutic approach to critical Information Systems research

Critical Information Systems (IS) research is sometimes appreciated for the shades of gray it adds to sunny portraits of technology's emancipatory potential. In this article, we revisit a theory about Wikipedia’s putative freedom from the authority of corporate media's editors and authors. We present the curious example of Tim Cook's Wikipedia biography and its history of crowd-sourced editorial decisions, published on Wikipedia's talk pages. We use a hermeneutic method to subject the theory about Wikipedia's “rational discourse” and “emancipatory potential” to a soft, empirical test. When we examined Cook's Wikipedia biography and its editorial decisions, what we found pertained to authoritative discourse – the opposite of “rational discourse” – as well as Jürgen Habermas's concept of dramaturgical action. Our discussion aims to change how critical scholars think about IS's Habermasian theories and emancipatory technology. Our contribution – a critical intervention – is a clear alternative to mainstream IS research's moral prescriptions and mechanistic causes.

Criticality assessment and cascading effects: impacts of COVID-19 disruptions in public transport on marginalized groups in Dortmund, Germany, São Paulo, Brazil, and Cape Town, South Africa

The COVID-19 pandemic has underscored the interconnectedness of critical infrastructure systems and their profound impact on marginalized communities. This study investigates the cascading effects of reduced mobility and infrastructure disruptions caused by COVID-19 response strategies on marginalized households across three diverse urban settings: Dortmund, São Paulo, and Cape Town. Employing a criticality assessment, we examine disruptions in healthcare, food and nutrition, social work, education, and childcare sectors, highlighting interdependencies and their implications for marginalized communities. Our findings reveal that disruptions in one sector, such as public transportation, can trigger adverse consequences across interconnected systems, amplifying vulnerabilities and exacerbating social inequalities. Furthermore, limited digital accessibility compounds these challenges, particularly for marginalized groups who may lack access to necessary technologies or digital literacy skills. Addressing these disparities in digital access is crucial for ensuring equitable access to essential services and support networks, especially in times of crisis. The study underscores the importance of mobility and accessibility in addressing systemic vulnerabilities and advocates for comprehensive resilience strategies that prioritize the needs of marginalized communities. Recommendations for policymakers, urban planners, and community stakeholders are provided to enhance infrastructure resilience and mitigate the indirect effects of disruptions on marginalized groups. The study contributes to a deeper understanding of cascading effects within critical infrastructure networks and informs future research and policy initiatives aimed at building resilient communities in an interconnected world.

An Architecture of Enhanced Profiling Assurance for IoT Networks

Attacks launched from IoT networks can cause significant damage to critical network systems and services. IoT networks may contain a large volume of devices. Protecting these devices from being abused to launch traffic amplification attacks is critical. The manufacturer usage description (MUD) architecture uses pre-defined stateless access control rules to allow or block specific network traffic without stateful communication inspection. This can lead to false negative filtering of malicious traffic, as the MUD architecture does not include the monitoring of communication states to determine which connections to allow through. This study presents a novel solution, the enhanced profiling assurance (EPA) architecture. It incorporates both stateless and stateful communication inspection, a unique approach that enhances the detection effectiveness of the MUD architecture. EPA contains layered intrusion detection and prevention systems to monitor stateful and stateless communication. It adopts three-way decision theory with three outcomes: allow, deny, and uncertain. Packets that are marked as uncertain must be continuously monitored to determine access permission. Our analysis, conducted with two network scenarios, demonstrates the superiority of the EPA over the MUD architecture in detecting malicious activities.

“They just forget about the students”: Growing resilient urban farmers with a research practice partnership

A sustainable transdisciplinary research network was established through a research practice partnership (RPP) between an urban farm, faculty and staff from a Historically Black College (HBC), and researchers at a medium-sized private university. We investigate student-worker resilience at this urban farm situated on the HBC campus, drawing on literature that explores tensions between informal learning environments and formal spaces, equitable food systems and farming systems, as well as the resilience of farm work, and which is grounded critical food systems education theory. Utilizing a participatory design approach, we conducted semi-structured interviews and deductively analyzed the data. The research questions guiding this paper are: (1) What topics of discussion are most important to the student-workers and staff working on an urban farm, (2) How do student-workers and college staff members perceive and experience resilience on an urban farm? We found that what participants on an urban farm discuss, relating to their experiences, include (1) how participants were eager to engage with the local community, (2) how participants demonstrated resilience while working on the urban farm, (3) how power dynamics played a pivotal role informing the direction of the urban farm, (4) how participants consider community access to healthy foods an important mission for the farm, (5) how the college acted as a power wielding entity, perpetuating its privilege over the farmers and the farm operations. These findings have the potential to enable community organizing spaces to promote resilience for their volunteers and workers, and for urban farms top partner with their community to promote the mission of increasing access to healthy and affordable food options.

Review of chaos in hair-cell dynamics.

The remarkable signal-detection capabilities of the auditory and vestibular systems have been studied for decades. Much of the conceptual framework that arose from this research has suggested that these sensory systems rest on the verge of instability, near a Hopf bifurcation, in order to explain the detection specifications. However, this paradigm contains several unresolved issues. Critical systems are not robust to stochastic fluctuations or imprecise tuning of the system parameters. Further, a system poised at criticality exhibits a phenomenon known in dynamical systems theory as critical slowing down, where the response time diverges as the system approaches the critical point. An alternative description of these sensory systems is based on the notion of chaotic dynamics, where the instabilities inherent to the dynamics produce high temporal acuity and sensitivity to weak signals, even in the presence of noise. This alternative description resolves the issues that arise in the criticality picture. We review the conceptual framework and experimental evidence that supports the use of chaos for signal detection by these systems, and propose future validation experiments.

Security Control for a Fuzzy System under Dynamic Protocols and Cyber-Attacks with Engineering Applications

The objective of this study is to design a security control for ensuring the stability of systems, maintaining their state within bounded limits and securing operations. Thus, we enhance the reliability and resilience in control systems for critical infrastructure such as manufacturing, network bandwidth constraints, power grids, and transportation amid increasing cyber-threats. These systems operate as singularly perturbed structures with variables changing at different time scales, leading to complexities such as stiffness and parasitic parameters. To manage these complexities, we integrate type-2 fuzzy logic with Markov jumps in dynamic event-triggered protocols. These protocols handle communications, optimizing network resources and improving security by adjusting triggering thresholds in real-time based on system operational states. Incorporating fractional calculus into control algorithms enhances the modeling of memory properties in physical systems. Numerical studies validate the effectiveness of our proposal, demonstrating a 20% reduction in network load and enhanced stochastic stability under varying conditions and cyber-threats. This innovative proposal enables real-time adaptation to changing conditions and robust handling of uncertainties, setting it apart from traditional control strategies by offering a higher level of reliability and resilience. Our methodology shows potential for broader application in improving critical infrastructure systems.

Collaboration Practices for the Cybersecurity of Supply Chains to Critical Infrastructure

This work describes the collaboration practices of a community of interest in the UK that brings together cybersecurity professionals with a shared interest in improving supply chain cybersecurity for Operational Technology (OT) environments. This research emphasizes the need for collective responsibility between organizations and provides a set of principles for adopting a code of practice and partnership approach to supply chain cybersecurity. This work has enabled cybersecurity experience from several critical infrastructure sectors, including energy, rail, aviation, water, health, and food, to analyze the uptake and practical use of existing supply chain guidance, identifying gaps and challenges. The community has examined touch points with the supply chain and identified improvements related to the communication of cybersecurity requirements, technical and commercial engagement between customers and suppliers, and in the tailoring of implementations towards operational technology contexts. Communicating the context of securing cyber-physical systems is an essential perspective for this community. This work exemplifies a partnership framework and is translating experiences into useful guidance, particularly for OT systems, to improve cybersecurity levels across multiple contributors to critical infrastructure systems.

Understanding the impact of climate change on critical infrastructure through nlp analysis of scientific literature

ABSTRACT Climate change is intensifying natural hazards, putting critical infrastructure systems at risk. The effects of climate change on critical infrastructure can be significant, and communities need to consider these risks when planning and designing infrastructure systems for the future. To that end, natural language processing (NLP) is a promising approach for analyzing large volumes of climate change and infrastructure-related scientific literature. To train a supervised model using NLP techniques, a significant subset of the corpus must be labeled into categories based on user-defined criteria, which is a time-consuming process. To expedite this process, we developed a weak supervision-based approach that leverages semantic similarity between categories and documents to generate category labels for the domain-specific corpus. In comparison with a months-long process of subject-matter expert labeling, we assign category labels to the whole corpus using weak supervision and supervised learning in 13 hours.