John Andrews
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View article: D2T2 Analysis of a Loss of Main Feed Water Accident
D2T2 Analysis of a Loss of Main Feed Water Accident Open
The availability of accurate models capturing the realistic behaviour of complex systems is critical for the safe operation and optimal management of nuclear installations. However, the dynamic nature of such systems and the resulting dens…
View article: Modelling complexity in system safety: generalizing the D2T2 methodology
Modelling complexity in system safety: generalizing the D2T2 methodology Open
Although Fault Tree and Event Tree analysis are still today the standard approach to system safety analysis for many engineering sectors, these techniques lack the capabilities of fully capturing the realistic, dynamic behaviour of complex…
View article: A Petri Net approach to predict the lifespan of a railway track asset
A Petri Net approach to predict the lifespan of a railway track asset Open
View article: Extending the dynamic and dependent tree theory (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mrow><mml:msup><mml:mi mathvariant="bold-italic">D</mml:mi><mml:mn mathvariant="bold">2</mml:mn></mml:msup><mml:msup><mml:mi mathvariant="bold-italic">T</mml:mi><mml:mn mathvariant="bold">2</mml:mn></mml:msup></mml:mrow></mml:math>) to safety barriers: An application to an offshore fire deluge system
Extending the dynamic and dependent tree theory () to safety barriers: An application to an offshore fire deluge system Open
Fault Tree (FT) Analysis is still one of the most common approaches for conducting reliability analysis of complex systems. However, it conceals several limitations such as the assumption of independent events and inability to model modern…
View article: Calibration free approaches for rapid polymorph discrimination <i>via</i> low frequency (THz) Raman spectroscopy
Calibration free approaches for rapid polymorph discrimination <i>via</i> low frequency (THz) Raman spectroscopy Open
Use of low frequency Raman spectroscopy in conjunction with multivariate curve resolution has significant advantages over powder X-ray diffraction, enabling rapid in situ analysis of solid form with no sample preparation required.
View article: An integrated Petri net-pseudo bond graph model for nuclear hazard assessment
An integrated Petri net-pseudo bond graph model for nuclear hazard assessment Open
A pseudo-bond graph is presented to model the heat transferred from the fuel rods to the coolant via its cladding in a generic nuclear reactor case study. Simulations performed using this model are used to explore the temperatures of the c…
View article: Calculation of the System Unavailability Measures of Component Importance Using the D2T2 Methodology of Fault Tree Analysis
Calculation of the System Unavailability Measures of Component Importance Using the D2T2 Methodology of Fault Tree Analysis Open
A recent development in Fault Tree Analysis (FTA), known as Dynamic and Dependent Tree Theory (D2T2), accounts for dependencies between the basic events, making FTA more powerful. The method uses an integrated combination of Binary Decisio…
View article: Extending the Dynamic and Dependent Tree Theory (D2t2) to Safety Barriers: An Application to an Offshore Fire Deluge System
Extending the Dynamic and Dependent Tree Theory (D2t2) to Safety Barriers: An Application to an Offshore Fire Deluge System Open
View article: Rapid determination of levels of the main constituents in e-liquids by near infrared spectroscopy
Rapid determination of levels of the main constituents in e-liquids by near infrared spectroscopy Open
Use of e-cigarettes is increasing, alongside an expanding variety of devices and e-liquids. To match this growth and in line with the expanding legal and regulatory requirements applicable to manufacturers of e-cigarettes (e.g. disclosure …
View article: Analysing the impact of local factors on the life-cycle of metallic bridge girders
Analysing the impact of local factors on the life-cycle of metallic bridge girders Open
A fundamental component of a life cycle analysis of a bridge is the modelling of asset condition post-construction. To enhance the accuracy of bridge deterioration models, several studies have calibrated models based on cohorts that incorp…
View article: Fault Tree Analysis Including Component Dependencies
Fault Tree Analysis Including Component Dependencies Open
Fault Tree analysis is not only the most common technique used in engineering practice for the estimation of system reliability, but is also a key tool shared between designers, analysts and regulators for safe operation and licensing purp…
View article: The Extension of Commonly used Measures of Importance for Dynamic and Dependent Tree Theory (DT)
The Extension of Commonly used Measures of Importance for Dynamic and Dependent Tree Theory (DT) Open
Traditional Fault Tree Analysis (FTA), known as Kinetic Tree Theory (KTT), was derived by Vesely et al (1970) to model and analyse engineering systems.The tree structure provides a clear visual representation of the causes of system failur…
View article: Extension of Common Measures of Importance for Dynamic and Dependent Tree Theory (D2T2)
Extension of Common Measures of Importance for Dynamic and Dependent Tree Theory (D2T2) Open
Traditional Fault Tree Analysis (FTA), known Kinetic Tree Theory (KTT), was derived by Vesely [1] in the 1970s to model and analyse engineering systems.The tree provides a clear visual representation of the causes of system failure in term…
View article: A Nested Petri Net -- Fault Tree Approach for System Dependency Modelling
A Nested Petri Net -- Fault Tree Approach for System Dependency Modelling Open
The Dynamic and Dependent Tree Theory (D 2 T 2 ) provides a safety analysis framework able to model complex features of engineering systems, such as dynamic behaviour, complex maintenance strategies or components dependencies which cannot …
View article: A nested Petri Net – Fault Tree approach for modelling complex failure behavior in engineering systems
A nested Petri Net – Fault Tree approach for modelling complex failure behavior in engineering systems Open
The Dynamic and Dependent Tree Theory (D 2 T 2 ) was developed in order to tackle the limitations of traditional Fault Tree approaches, providing tools for modelling realistic features, such as complex maintenance strategies and component …
View article: A Petri net model-based resilience analysis of nuclear power plants under the threat of natural hazards
A Petri net model-based resilience analysis of nuclear power plants under the threat of natural hazards Open
View article: Dynamic and dependent tree theory (D2T2): A framework for the analysis of fault trees with dependent basic events
Dynamic and dependent tree theory (D2T2): A framework for the analysis of fault trees with dependent basic events Open
View article: Temperature Correction of Spectra to Improve Solute Concentration Monitoring by In Situ Ultraviolet and Mid-Infrared Spectrometries toward Isothermal Local Model Performance
Temperature Correction of Spectra to Improve Solute Concentration Monitoring by In Situ Ultraviolet and Mid-Infrared Spectrometries toward Isothermal Local Model Performance Open
Changes in temperature can significantly affect spectroscopic-based methods for in situ monitoring of processes. As varying temperature is inherent to many processes, associated temperature effects on spectra are unavoidable, which can hin…
View article: Optimisation of nuclear reactor primary coolant design and maintenance parameters
Optimisation of nuclear reactor primary coolant design and maintenance parameters Open
An optimisation methodology is presented using the primary coolant circulation system of a nuclear reactor as its case study, the purpose of which is to find combinations of selected design and maintenance parameters to maximise the reacto…
View article: An integrated modelling framework for complex systems safety analysis
An integrated modelling framework for complex systems safety analysis Open
The ever‐increasing complexity of engineering systems has fuelled the need for novel and efficient computational tools able to enhance the accuracy of current modelling strategies for industrial systems. Indeed, traditional Fault and Event…
View article: A Petri net asset management framework for railway switches and crossings
A Petri net asset management framework for railway switches and crossings Open
Switches and Crossings (S&C) are a fundamental part of any railway network, they allow trains to switch between tracks and to cross over other tracks. They consist of various electrical and mechanical components to which there is a substan…
View article: A reliability study of railway switch and crossing components
A reliability study of railway switch and crossing components Open
Within any railway network Switches and Crossings (S&C) are essential. They allow trains to change tracks, allowing different routes to be selected. Despite their necessity, they generally have a lower reliability than plain line track and…
View article: Reduction of Petri net maintenance modeling complexity via Approximate Bayesian Computation
Reduction of Petri net maintenance modeling complexity via Approximate Bayesian Computation Open
View article: Railway track availability modelling with opportunistic maintenance practice
Railway track availability modelling with opportunistic maintenance practice Open
The geometry of railway track must be maintained within certain standards in order to provide a highly available network, as well as good ride comfort and safety for all rail users. Modelling is well utilised as part of asset management to…
View article: Risk modelling of ageing nuclear reactor systems
Risk modelling of ageing nuclear reactor systems Open
A nuclear reactor is expected to function for extensive periods, during which, coolant circulation and core reactivity must always be maintained safely. Understanding the risks associated with the operation of such systems requires proper …
View article: Incorporating defect specific condition indicators in a bridge life cycle analysis
Incorporating defect specific condition indicators in a bridge life cycle analysis Open
View article: A mathematical programming model to select maintenance strategies in railway networks
A mathematical programming model to select maintenance strategies in railway networks Open
View article: Modelling cycle for simulation digital twins
Modelling cycle for simulation digital twins Open
Digital twins (DT) form part of the Industry 4.0 revolution within manufacturing and related industries. A DT is a digital model (DM) of a real system that features continuous and automated synchronisation and feedback of optimisations bet…
View article: An Alternative Approach to Railway RAMS: Development of an Extended RAMS Framework
An Alternative Approach to Railway RAMS: Development of an Extended RAMS Framework Open
The management of a diverse asset portfolio is a demanding task for railway asset managers. They must ensure that the network delivers a high level of performance for customers and adheres to safety limits. Reliability, availability, maint…
View article: An alternative approach to railway asset management value analysis: application to a UK railway corridor
An alternative approach to railway asset management value analysis: application to a UK railway corridor Open
Railway networks are complex systems, and the management of such systems is a challenging task for railway asset managers. It is their responsibility to ensure that the network delivers the highest level of performance for all stakeholders…