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An alternative perspective on the classical solution to an optimal stopping problem with a spectrally negative Levy process
No full textTiN, CrN and TiCrN coating architectures on M2 steel: consequences for wear and micro-impact resistance
No full textCutting and forming tools operating under high load conditions often suffer from premature wear. Applying hard, wear-resistant coatings particularly multilayer coatings can significantly enhance their functional properties. In this study, three multilayered coatings were deposited on hardened M2 steel bars using arc-evaporation: (1) TiN/TiCrN/TiN, (2) TiN/TiCrN/(TiN/CrN)10/TiN system and (3) (Cr/CrN)25. Mechanical (nanoindentation), tribological (cylinder on cylinder reciprocating tests) behavior of the coatings was investigated along with micro-impact tests. SEM/TEM analysis of the coatings revealed dense and fine-grained columnar structure in the direction of growth. All multilayer coatings showed enhanced wear resistance compared to the TiN monolayer. The TiN/TiCrN/TiN system exhibited the highest hardness (30.6 GPa) and best wear resistance against Al₂O₃, with an 88 % reduction in volume loss compared to TiN. This performance is consistent with its high load-bearing capacity (H3/E2 = 0.107 GPa), moderate H/E (0.059) and the lowest friction coefficient (<0.2). On the other hand, the (Cr/CrN)₂₅ coating demonstrated the best impact performance — with no chipping at 500 mN over 500 cycles and minimal damage at 1500 mN. This is attributed to its high H/E (0.074) and H3/E2 (0.126 GPa) ratios, along with a relatively low modulus (310 GPa), much more closely matched (Ec/Es ∼ 1.5) to the substrate than the other coatings
Root cause analysis of a hydrogen storage explosion: A combined BowTie-Tripod approach applied to the Gangneung incident
No full textHydrogen storage is critical to the low-carbon transition, yet it introduces distinctive hazards associated with high-pressure vessels, cryogenic media and material degradation. This paper demonstrates a transparent application of an integrated BowTie–Tripod Beta framework, utilising the BowTieXP suite, to translate publicly available incident evidence into structured barrier-based and organisational learning. The 2019 Gangneung buffer-tank explosion was selected as a representative case from the Hydrogen Incident and Accident Database (HIAD). A BowTie diagram was first used to map the complete picture of the incident, highlighting six broad safety barriers that had failed, including the inadequacy or lack of evidence for detecting oxygen (O2) in H2, removal of O2, static controls, and the earthing and bonding system. Tripod Beta then traced each failed barrier back through its immediate causes, preconditions, and underlying causes, revealing systemic weaknesses in design verification, barrier maintenance, and process safety culture. Corrective and Preventive Actions (CAPAs) were formulated to address weaknesses identified in design reviews, barrier integrity monitoring, and competency management, through enhanced training and strict adherence to safety standards. In view of the exclusive reliance on secondary sources, the analysis explicitly grades the evidence strength for each barrier. It frames higher-level organisational contributors as plausible inferences rather than definitive findings. Although conclusions from this single case are not generalisable, the study provides a replicable reporting workflow and traceable CAPA development approach that can be adapted for other high-hazard hydrogen applications. Given the reliance on publicly available secondary sources, evidence-strength tags are used to communicate confidence and to frame the findings as structured hypotheses for verification and barrier design
Coupled mechanical-magnetic analysis of cut-edge damage in thin sheet electrical steels
No full textThin electrical steel sheets are extensively used in electric machine cores owing to their high magnetic permeability and low core losses. Blanking is the predominant manufacturing process for laminations in high-volume applications due to its efficiency and well-controlled parameters; however, localised deformation at the cut edge can adversely affect the magnetic performance. This study systematically examines the influence of blanking on the magnetic behaviour of a non-grain-oriented 3.2% Si electrical steel. The effects of sheet thickness, shear localisation, and fracture mechanisms are investigated through combined experimental and numerical approaches. A novel finite element model is developed for this class of material to directly correlate mechanical deformation with magnetic response, considering blanking-induced strain, strain-rate, and geometric dislocations attributed to non-local effects. A new formulation is introduced to correlate the magnetic permeability with the deformation-induced microstructural changes. In-situ blanking trials with digital image correlation, nano-indentation, and microstructural characterisation were used to validate the model. Magnetic hysteresis and magnetisation measurements using a single-sheet tester reveal that tensile residual stresses markedly reduce permeability, while both tensile and compressive stresses increase magnetic losses through inhibited domain mobility and grain-boundary pinning. The proposed model achieves an over 90% predictive accuracy with experimental measurements, providing a predictive tool for optimising blanking parameters and enhancing electromagnetic efficiency in advanced energy systems
A Nonparametric Approach to Practical Identifiability of Nonlinear Mixed Effects Models
Get PDFMathematical modelling is a widely used approach to understand and interpret clinical trial data. This modelling typically involves fitting mechanistic mathematical models to data from individual trial participants. Despite the widespread adoption of this individual-based fitting, it is becoming increasingly common to take a hierarchical approach to parameter estimation, where modellers characterize the population parameter distributions, rather than considering each individual independently. This hierarchical parameter estimation is standard in pharmacometric modelling. However, many of the existing techniques for parameter identifiability do not immediately translate from the individual-based fitting to the hierarchical setting. In this work, we propose a nonparametric approach to study practical identifiability within a hierarchical parameter estimation framework. We focus on the commonly used nonlinear mixed effects framework and investigate two well-studied examples from the pharmacometrics and viral dynamics literature to illustrate the potential utility of our approach
Racial injustice and the global crisis of state violence
No full textRacial injustice is not a local aberration or a historical footnote. It is a global, systemic crisis rooted in the very formation of the modern world. Across continents, societies are grappling with the enduring legacies of colonization, the relentless violence of the state, and the persistent inequalities produced and sustained by racism and classism. The twenty-first century, far from marking the end of these injustices, has seen their intensification under new guises and through new technologies of control. In this context, criminological inquiry, especially of a radical and global character, becomes not just important but imperative (Agozino, 2003; Smith, 2012; Saleh-Hanna et al., 2023; Cook et al., 2023; Williams & Battle, 2017)
Exploring the Intensity and Continuity of Hospital Care for Patients With Long Covid: Evidence From an English Urban Healthcare System
Get PDFBackground
Long Covid (LC) is a multisystem condition leading to a wide range of symptoms and often requiring treatment by several different clinical specialties. Patients with LC have reported difficulties in accessing care and a lack of coordination of their care, particularly in a hospital setting.
Objective
To determine the extent to which the intensity and continuity of hospital care changes for patients after they receive an LC diagnosis.
Design
Retrospective observational cohort study using a linked primary and secondary care dataset.
Setting and Participants
Routine healthcare data from North West London Integrated Care System of patients with a recorded diagnosis of LC who had attended a secondary care hospital Trust from 1 January 2019 to 30 September 2023.
Main Variables Studied
The intensity of utilisation of secondary care was calculated, and the continuity of care with respect to hospitals and specialties was computed using the sequential continuity score (SeCon) before the Covid-19 pandemic, before and after an LC diagnosis.
Results
5611 out of 6270 (90.1%) patients diagnosed with LC had a recorded secondary care interaction in the study period. Intensity of secondary care utilisation increased markedly in outpatient, inpatient and Emergency Department pathways after a diagnosis of LC but peaked in the week of diagnosis. Average hospital SeCon fell significantly after an LC diagnosis from 1.00 to 0.83, while specialty SeCon remained unchanged from after diagnosis (0.40) and before the pandemic (0.44). A notable shift in specialty activity was observed with a focus on respiratory medicine as a major hub in a densely connected patient-sharing network with cardiology and other medical and surgical specialties.
Discussion
A recorded LC diagnosis was associated with increases in the intensity of hospital activity and a reduction in hospital-level care continuity, but no change in specialty continuity, which remains low.
Conclusion
Collectively, this indicates a significant need to support LC patients as they navigate fragmented secondary care pathways.
Patient and Public Contribution
This study was co-designed with, conducted with and written in conjunction with people with long Covid
Double-checking in the safe administration of medicines: Policy and practice in English hospitals
Get PDFObjectives Double-checking medication administrations is one of the most frequently used strategies to prevent errors and associated harm. This practice is time-consuming, introduces repeated interruptions into the care process and lacks evidence of effectiveness. Double-checking is widespread in hospitals worldwide. In England, double-checking happens despite there being no regulatory requirement except for intravenous drugs and medicines that require complex calculations. Many hospital Trusts have assimilated double-checking over the past 25–30 years in response to recommendations from the investigation of medication administration errors. There is currently no national picture in England of the extent to which organisational policies stipulate double-checking, the variation in double-checking policy or how closely double-checking is perceived to be conducted in accordance with policies. This study set out to address these gaps in our understanding. Methods An online survey was distributed to a network of Medication Safety Officers (MSOs) and Freedom of Information requests were sent to 118 English NHS acute hospital Trusts for policies underpinning medicines administration. Data were analysed to address the research questions. Results Policies were received from 94 acute NHS Trusts (80% response rate) and 48 MSOs submitted a survey response (39% response rate). Double-checking policies vary considerably between Trusts. MSOs perceived that it is common in practice for double-checking not to be conducted in accordance with policy. All reviewed Trust policies required double-checking for controlled drugs. Further to this, many required double-checking for specific medicines or in particular circumstances. Most commonly, these were intravenous medicines, medicines administered to children, medicines requiring complex calculations and cytotoxic or chemotherapeutic medicines. However, policies varied considerably around administration of injectable medicines and insulin to adults. A minority of policies specified that ‘intravenous fluids’ needed to be double-checked. Most policies neither emphasised nor explained the importance of the independent nature of double-checking. There was also a great deal of variation between Trust policies in the medicines exempt from double-checking requirements. Conclusions The variation between policies identified by the present study might reflect a lack of robust evidence underpinning the practice of double-checking. Research is needed to understand if double-checking is effective at preventing medication errors and, if it is, the exact circumstances in which it is effective, to facilitate the standardisation of double-checking policies. Identifying circumstances in which double-checking is ineffective may justify the removal of some existing policies and could reduce nurse workload to free up time for patient-focused care
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