Dr. Christos Ellinas

Dr. Christos Ellinas

Bristol, England, United Kingdom
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About

I lead teams of stellar engineers and scientists towards developing tech that improves…

Articles by Dr. Christos

Activity

Experience

  • Nodes & Links Graphic

    Nodes & Links

    London, United Kingdom

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    Oxford, England, United Kingdom

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    Bristol, United Kingdom

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    London, United Kingdom

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    Bristol, United Kingdom

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    Bristol, United Kingdom

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Education

  • University of Bristol Graphic

    University of Bristol

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    Title: An examination of inter-connectivity within organisational activity using complex networks : a risk perspective

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    Dissertation Topic: Managing Risk: Exploring the contrasting approaches of FIDIC 1999 and NEC3

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    Activities and Societies: School Football Team, Member of Physics Society, Member of the School Board, Member of the Prefect Team

    GCE A Levels:
    Mathematics - Grade A
    Further Pure Mathematics - Grade A
    Physics - Grade A
    Chemistry - Grade B
    Modern Greek - Grade A

Publications

  • Modelling indirect interactions during failure spreading in a project activity network

    Nature Scientific Reports

    Spreading broadly refers to the notion of an entity propagating throughout a networked system via its interacting components. Evidence of its ubiquity and severity can be seen in a range of phenomena, from disease epidemics to financial systemic risk. In order to understand the dynamics of these critical phenomena, computational models map the probability of propagation as a function of direct exposure, typically in the form of pairwise interactions between components. By doing so, the…

    Spreading broadly refers to the notion of an entity propagating throughout a networked system via its interacting components. Evidence of its ubiquity and severity can be seen in a range of phenomena, from disease epidemics to financial systemic risk. In order to understand the dynamics of these critical phenomena, computational models map the probability of propagation as a function of direct exposure, typically in the form of pairwise interactions between components. By doing so, the important role of indirect interactions remains unexplored. In response, we develop a simple model that accounts for the effect of both direct and subsequent exposure, which we deploy in the novel context of failure propagation within a real-world engineering project. We show that subsequent exposure has a significant effect in key aspects, including the: (a) final spreading event size, (b) propagation rate, and (c) spreading event structure. In addition, we demonstrate the existence of ‘hidden influentials’ in large-scale spreading events, and evaluate the role of direct and subsequent exposure in their emergence. Given the evidence of the importance of subsequent exposure, our findings offer new insight on particular aspects that need to be included when modelling network dynamics in general, and spreading processes specifically.

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  • Evaluating the role of risk networks on risk identification, classification and emergence

    Journal of Network Theory in Finance

    Modern society heavily relies on strongly connected socio-technical systems. As a result, distinct risks threatening the operation of individual systems can no longer be treated in isolation. Risk experts are actively seeking ways to relax the risk independence assumption that undermines typical risk management models. Prominent work has advocated the use of risk networks as a way forward. However, the inevitable biases introduced during the generation of these survey-based risk networks limit…

    Modern society heavily relies on strongly connected socio-technical systems. As a result, distinct risks threatening the operation of individual systems can no longer be treated in isolation. Risk experts are actively seeking ways to relax the risk independence assumption that undermines typical risk management models. Prominent work has advocated the use of risk networks as a way forward. However, the inevitable biases introduced during the generation of these survey-based risk networks limit our ability to examine their topology and in turn challenge the utility of the very notion of a risk network. To alleviate these concerns, we propose an alternative methodology for generating weighted risk networks. We subsequently apply this methodology to an empirical data set of financial data. This paper reports our findings on the study of the topology of the resulting risk network. We observe a modular topology and reason on its use as a robust risk classification framework. Using these modules, we highlight a tendency of specialization during the risk identification process, with some firms being solely focused on a subset of the available risk classes. Finally, we consider the independent and systemic impact of some risks and attribute possible mismatches to their emerging nature.

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  • Dynamics of organizational culture: Individual beliefs vs. social conformity

    PLoS ONE

    The complex nature of organizational culture challenges our ability to infer its underlying dynamics from observational studies. Recent computational studies have adopted a distinctly different view, where plausible mechanisms are proposed to describe a wide range of social phenomena, including the onset and evolution of organizational culture. In this spirit, this work introduces an empirically-grounded, agent-based model which relaxes a set of assumptions that describes past work–(a)…

    The complex nature of organizational culture challenges our ability to infer its underlying dynamics from observational studies. Recent computational studies have adopted a distinctly different view, where plausible mechanisms are proposed to describe a wide range of social phenomena, including the onset and evolution of organizational culture. In this spirit, this work introduces an empirically-grounded, agent-based model which relaxes a set of assumptions that describes past work–(a) omittance of an individual’s strive for achieving cognitive coherence; (b) limited integration of important contextual factors—by utilizing networks of beliefs and incorporating social rank into the dynamics. As a result, we illustrate that: (i) an organization may appear to be increasingly coherent in terms of its organizational culture, yet be composed of individuals with reduced levels of coherence; (ii) the components of social conformity—peer-pressure and social rank—are influential at different aggregation levels.

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  • Project Systemic Risk: Application Examples of a Network Model

    International Journal of Production Economics

    Projects are increasingly perceived as complex systems, yet little work has been done in developing methodologies that are theoretically grounded on complex systems theory. In response, this article argues the practical utility of a recently introduced model that draws on notions from Network Science (NS) – a prominent domain in the study of complexity. Its utility is exemplified in the context of Project Management (PM), tackling two specific challenges: risk and conflict management. In the…

    Projects are increasingly perceived as complex systems, yet little work has been done in developing methodologies that are theoretically grounded on complex systems theory. In response, this article argues the practical utility of a recently introduced model that draws on notions from Network Science (NS) – a prominent domain in the study of complexity. Its utility is exemplified in the context of Project Management (PM), tackling two specific challenges: risk and conflict management. In the case of the former (risk), shifts in the susceptibility of a project to systemic risk (in the form of inter-linked failures) are identified. In the case of the latter (conflict), the effect of (sub) contractor activity – in terms of variance and activity pattern – to project systemic risk is assessed. To do so, numerical methods are developed and applied on an empirical dataset of widely-captured data (Gantt charts). In the context of the two challenges proposed, it is shown that: (a) the exposure of a project to systemic risk varies in a non-trivial manner as it evolves, at both micro and macro level; (b) (sub) contractor activity substantially impacts the emergence of locally important tasks (i.e. tasks able to disrupt the operation of a (sub) contractor). From a theoretical perspective, this work initiates a dialogue between the two domains (PM and NS), potentially opening new ways of tackling long-lasting challenges of PM.

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  • Exploring Structural Patterns Across Evolved and Designed Systems: A Network Perspective

    Systems Engineering

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  • Toward Project Complexity Evaluation: A Structural Perspective

    IEEE Systems Journal

    Complexity is often quoted as an independent variable that challenges the utility of traditional project management tools and techniques. A large body of work has been devoted in exposing its numerous aspects, yet means for quantitatively assessing it have been scarce. Part of the challenge lies in the absence of hard evidence supporting the hypothesis that projects can be considered as complex systems, where techniques for measuring such complexity are better established. In response, this…

    Complexity is often quoted as an independent variable that challenges the utility of traditional project management tools and techniques. A large body of work has been devoted in exposing its numerous aspects, yet means for quantitatively assessing it have been scarce. Part of the challenge lies in the absence of hard evidence supporting the hypothesis that projects can be considered as complex systems, where techniques for measuring such complexity are better established. In response, this study uses empirical activity networks to account for the technological aspect of five projects. By doing so, the contribution of this study is twofold. First, a procedure for the quantitative assessment of an aspect of project complexity is presented; namely, structural complexity. Second, results of the analysis are used to highlight qualitatively similar behavior with a well-known complex system, the Internet. As such, it suggests a transition from the current, metaphorical view of projects being complex systems to a literal one.From a practical point of view, this study uses readily captured and widely used data, enabling practitioners to evaluate the structural complexity of their projects to explore system pathologies and, hence, improve the decision-making process around project bidding, resource allocation, and risk management.

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  • How Robust Is Your Project? From Local Failures to Global Catastrophes: A Complex Networks Approach to Project Systemic Risk

    PLOS ONE

    Current societal requirements necessitate the effective delivery of complex projects that can do more while using less. Yet, recent large-scale project failures suggest that our ability to successfully deliver them is still at its infancy. Such failures can be seen to arise through various failure mechanisms; this work focuses on one such mechanism. Specifically, it examines the likelihood of a project sustaining a large-scale catastrophe, as triggered by single task failure and delivered via a…

    Current societal requirements necessitate the effective delivery of complex projects that can do more while using less. Yet, recent large-scale project failures suggest that our ability to successfully deliver them is still at its infancy. Such failures can be seen to arise through various failure mechanisms; this work focuses on one such mechanism. Specifically, it examines the likelihood of a project sustaining a large-scale catastrophe, as triggered by single task failure and delivered via a cascading process. To do so, an analytical model was developed and tested on an empirical dataset by the means of numerical simulation. This paper makes three main contributions. First, it provides a methodology to identify the tasks most capable of impacting a project. In doing so, it is noted that a significant number of tasks induce no cascades, while a handful are capable of triggering surprisingly large ones. Secondly, it illustrates that crude task characteristics cannot aid in identifying them, highlighting the complexity of the underlying process and the utility of this approach. Thirdly, it draws parallels with systems encountered within the natural sciences by noting the emergence of self-organised criticality, commonly found within natural systems. These findings strengthen the need to account for structural intricacies of a project’s underlying task precedence structure as they can provide the conditions upon which large-scale catastrophes materialise.

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  • Structural Patterns in Complex Systems: A network perspective

    4th International Engineering Systems Symposium (CESUN 2014)

    Our desire to deliver increased functionality while setting tighter operational and regulative boundaries has fueled a recent influx of highly-coupled systems. Alas, our current capacity to successfully deliver them is, evidently, still in its infancy [1-5]. Understanding how such systems are structured, along with how they compare with their natural counterparts, can play an important role in bettering our capacity to do so. The following article will be grounded upon the principles of network…

    Our desire to deliver increased functionality while setting tighter operational and regulative boundaries has fueled a recent influx of highly-coupled systems. Alas, our current capacity to successfully deliver them is, evidently, still in its infancy [1-5]. Understanding how such systems are structured, along with how they compare with their natural counterparts, can play an important role in bettering our capacity to do so. The following article will be grounded upon the principles of network science in order to contrast such naturally evolved systems with systems that we purposefully engineer. Assuming that the underlying structural variety of such systems fuels design uncertainty, and by adopting an evidence-based methodology, systems of the latter class will be compared in terms of their adherence to statistical normality.

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  • Design through Failure: A Network Perspective

    14th International Design Conference (DEIGN 2014)

    Sociotechnical systems are central in the way our modern society is structured. Thus, understanding their global reaction to local failures is of great importance. Within the context of cyber-security, a worst case scenario of random and targeted attacks is numerically simulated in order to evaluate the resilience of three distinct system architectures. Of special interest is the capacity to provide early -warning signs and the trade-off between resilience and efficiency, in terms of the…

    Sociotechnical systems are central in the way our modern society is structured. Thus, understanding their global reaction to local failures is of great importance. Within the context of cyber-security, a worst case scenario of random and targeted attacks is numerically simulated in order to evaluate the resilience of three distinct system architectures. Of special interest is the capacity to provide early -warning signs and the trade-off between resilience and efficiency, in terms of the underlying architecture. The paper concludes with design implications based on the evidence provided

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  • How resilient is your organisation? From local failures to systemic risk

    ERM Symposium 2015

    Empirical evidence of reported losses suggests that insurance firms are interconnected in a non-trivial way. As a result, systemic risk is a real possibility, where the failure of a single firm can have a disproportionate effect to the market by affecting firms connected to it. Systemic risk can be viewed as the result of a cascading process, as it unravels throughout a network structure. In response, this work presents a simple analytical model that can simulate this process. The model is…

    Empirical evidence of reported losses suggests that insurance firms are interconnected in a non-trivial way. As a result, systemic risk is a real possibility, where the failure of a single firm can have a disproportionate effect to the market by affecting firms connected to it. Systemic risk can be viewed as the result of a cascading process, as it unravels throughout a network structure. In response, this work presents a simple analytical model that can simulate this process. The model is subsequently tested upon an empirical dataset via the means of numerical simulations. Consequently, the systemic role of individual firms, both in terms of triggering a cascade or being affect by one, is established based on two novel indices; the Criticality IDX and Sensitivity IDX respectively. This article makes three main contributions. First, it provides a novel methodology for quantitatively and objectively assessing the systemic role of individual firms within the insurance domain. Second, it exemplifies the inability of traditional, firm-based information in serving as proxies for mapping these systemic effects. Thirdly, it provides a practical example where network-based information (e.g. Criticality IDX, Sensitivity IDX) can outperform firm-based information (e.g. Admissible Assets, Excess Capital) resulting to an increased efficiency in the decision making process. These findings strengthen the need to account for the interconnected nature of the domain while showcasing some of the potential benefits that can be harvested by doing so.

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Projects

  • Developing methods for project resilience against failure cascades

    The aim of this EPSRC-funded research project is to: (a) identify the factors that affect project exposure to failure cascades, and (b) Develop mitigation scheme(s) that actively contribute to increased resilience

    Other creators

  • Engineering YES

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    Engineering Young Entrepreneurs Scheme is a competition for postgraduate students and post-doctoral researchers to present a business plan for an imaginary start-up company to a group of shrewd investors and industry experts. The programme covers all aspects of the commercialisation of new product and service development from discovery, to the first sales.

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Honors & Awards

  • Keynote Presenter at the 2nd Governance, Risk and Compliance Conference 2016

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    My talk was entitled: " A Hitchhiker’s Guide to Complexity: How connectivity affects your enterprise". The talk was supported by delivering a workshop entitled “Mapping the Extended Enterprise” during a panel expert session.

  • ERM Research Excellence Award in Memory of Hubert Mueller for Best Overall Paper 2015

    The Actuarial Foundation

    For paper "How resilient is your organisation? From local failures to systemic risk"

  • Guest Panelist in "Extended Enterprise 2014" conference

    Institute of Risk Management

    Guest panelist at the "Analyzing and Modelling your Commercial Network" at the "Extended Enterprise 2014" ran by the Institute of Risk Management at Cass Business School

  • Finalist on Frazer-Nash Consultancy best paper 2014

    Frazer-Nash Consultancy

    For paper "Structural Patterns in Complex Systems: A network perspective"

  • Guest Presenter at "TopoNets 2014"

    Clark Kerr Campus of the University of California

    Guest Presenter at "TopoNets 2014", a satellite meeting of NetSci 2014, presented "Comparing Topological Patterns between Engineered and Evolved Systems"

  • Guest Presenter at CESUN 2014

    Stevens Institute of Technology

    Guest Presenter in session "Complex Networks and Engineering Systems" where work from "Structural Patterns in Complex Systems: A network perspective" was presented

  • Finalist on Engineering Research Writer of the Year 2013

    Association of Engineering Doctorates

Languages

  • English

    Full professional proficiency

  • Greek

    Native or bilingual proficiency

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