Tag Archives: simulation

Digital twins could put at risk what it means to be human

Detail from abstract by Zahrah ReshI have written in the past about my research on the development and use of digital twins.  A digital twin is a functional representation in a virtual world of a real world entity that is continually updated with data from the real world [see ‘Fourth industrial revolution’ on July 4th, 2018 and also a short video at https://www.youtube.com/watch?v=iVS-AuSjpOQ].  I am working with others on developing an integrated digital nuclear environment from which digital twins of individual power stations could be spawned in parallel with the manufacture of their physical counterparts [see ‘Enabling or disruptive technology for nuclear engineering’ on January 1st, 2015 and ‘Digitally-enabled regulatory environment for fusion power-plants’ on March 20th, 2019].  A couple of months ago, I wrote about the difficulty of capturing tacit knowledge in digital twins, which is knowledge that is generally not expressed but is retained in the minds of experts and is often essential to developing and operating complex engineering systems [see ‘Tacit hurdle to digital twins’ on August 26th, 2020].  The concept of tapping into someone’s mind to extract tacit knowledge brings us close to thinking about human digital twins which so far have been restricted to computational models of various parts of human anatomy and physiology.  The idea of a digital twin of someone’s mind raises a myriad of philosophical and ethical issues.  Whilst the purpose of a digital twin of the mind of an operator of a complex system might be to better predict and understand human-machine interactions, the opportunity to use the digital twin to advance techniques of personalisation will likely be too tempting to ignore.  Personalisation is the tailoring of the digital world to respond to our personal needs, for instance using predictive algorithms to recommend what book you should read next or to suggest purchases to you.  At the moment, personalisation is driven by data derived from the tracks you make in the digital world as you surf the internet, watch videos and make purchases.  However, in the future, those predictive algorithms could be based on reading your mind, or at least its digital twin.  We worry about loss of privacy at the moment, by which we probably mean the collation of vast amounts of data about our lives by unaccountable organisations, and it worries us because of the potential for manipulation of our lives without us being aware it is happening.  Our free will is endangered by such manipulation but it might be lost entirely to a digital twin of our mind.  To quote the philosopher Michael Lynch, you would be handing over ‘privileged access to your mental states’ and to some extent you would no longer be a unique being.  We are long way from possessing the technology to realise a digital twin of human mind but the possibility is on the horizon.

Source: Richard Waters, They’re watching you, FT Weekend, 24/25 October 2020.

Image: Extract from abstract by Zahrah Resh.

35 years later and still working on a PhD thesis

It is about 35 years since I graduated with my PhD.  It was not ground-breaking although, together with my supervisor, I did publish about half a dozen technical papers based on it and some of those papers are still being cited, including one this month which surprises me.  I performed experiments and computer modelling on the load and stress distribution in threaded fasteners, or nuts and bolts.  There were no digital cameras and no computer tomography; so, the experiments involved making and sectioning models of nuts and bolts in transparent plastic using three-dimensional photoelasticity [see ‘Art and Experimental Mechanics‘ on July 17th, 2012].  I took hundreds of photographs of the sections and scanned the negatives in a microdensitometer.  The computer modelling was equally slow and laborious because there were no graphical user interfaces (GUI); instead, I had to type strings of numbers into a terminal, wait overnight while the calculations were performed, and then study reams of numbers printed out on long rolls of paper.  The tedium of the experimental work inspired me to work on utilising digital technology to revolutionise the field of experimental mechanics over the following 15 to 20 years.  In the past 15 to 20 years, I have moved back towards computer modelling and focused on transforming the way in which measurement data are used to improve the fidelity of computer models and to establish confidence in their predictions [see ‘Establishing fidelity and credibility in tests and simulations‘ on July 25th, 2018].  Since completing my PhD, I have supervised 32 students to successful completion of their PhDs.  You might think that was a straightforward process of an initial three years for the first one to complete their research and write their thesis, followed by one graduating every year.  But that is not how it worked out, instead I have had fallow years as well as productive years.  At the moment, I am in a productive period, having graduated two PhD students per year since 2017 – that’s a lot of reading and I have spent much of the last two weekends reviewing a thesis which is why PhD theses are the topic of this post!

Footnote: the most cited paper from my thesis is ‘Kenny B, Patterson EA. Load and stress distribution in screw threads. Experimental Mechanics. 1985 Sep 1;25(3):208-13‘ and this month it was cited by ‘Zhang D, Wang G, Huang F, Zhang K. Load-transferring mechanism and calculation theory along engaged threads of high-strength bolts under axial tension. Journal of Constructional Steel Research. 2020 Sep 1;172:106153‘.

Tacit hurdle to digital twins

Tacit knowledge is traditionally defined as knowledge that is not explicit or that is difficult to express or transfer from someone else.  This description of what it is not makes the definition itself tacit knowledge which is not very helpful.  Management guides resolve this by giving examples, such as aesthetic sense, or innovation and leadership skills which are elusive skills that are hard to explain [see ‘Innovation out of chaos‘ on June 29th 2016 and  ‘Clueless on leadership style‘ on June 14th, 2017].  In engineering, there are a series of skills that are hard to explain or teach, including creative problem-solving [see ‘Learning problem-solving skills‘  on October 24th, 2018], artful design [see ‘Skilled in ingenuity‘ on August 19th, 2015] and elegant modelling [see ‘Credibility is in the eye of the beholder‘ on April 20th, 2016].  In a university course we attempt to lay the foundations for this tacit engineering knowledge; however, much of it is gained in work through experience and becomes regarded by organisations as part of their intellectual assets – the core of their competitiveness and source of their sustainable technology advantage.  In our work on integrated nuclear digital environments, from which digital twins can be spawned, we would like to capture both explicit and tacit knowledge about complex systems throughout their life cycle which will extend beyond the working lives of their designers, builders and operators.  One of the potential advantages of digital twins is as a knowledge management system by duplicating the life of the physical system and thus allowing its safer and cheaper operation in the long-term as well as its eventual decommissioning.   However, besides the very nature of tacit knowledge that makes its capture difficult, we are finding that its perceived value as an intellectual asset renders stakeholders reluctant to discuss it with us; never mind consider how it might be preserved as part of a digital twin.  Research has shown that tacit knowledge sharing is influenced by environmental factors including national culture, leadership characteristics and social networks [Cai et al, 2020].  I suspect that all of these factors were present in the heyday of the UK civil nuclear power industry when it worked together to construct advanced and complex systems; however, it has not built a power station since 1995 and, at the moment, new power stations are cancelled more often than built, which has almost certainly depressed all of these factors.  So, perhaps we should not be surprised by the difficulties encountered in establishing an integrated nuclear digital environment despite its importance for the future of the industry.

Reference: Cai, Y., Song, Y., Xiao, X. and Shi, W., 2020. The Effect of Social Capital on Tacit Knowledge-Sharing Intention: The Mediating Role of Employee Vigor. SAGE Open, 10(3), p.2158244020945722.

Physical actions to inhibit COVID-19 infection

Figure 4 from Ai & Melikov, 2017

Politicians in many countries are fond of claiming that they are following scientific advice when telling us what we can or cannot do in an effort to prevent the spread of the coronavirus, COVID-19.  However, neither they nor the journalists who report their statements tell us what scientists have actually established.  So, I have been reading some of the literature.

A paper by Leung et al [1] published this month in Nature Medicine reports that surgical face masks could prevent transmission of human coronavirus and influenza viruses from symptomatic individuals.  Their conclusions were based on a study of 246 individuals ranging in age from 11 to more than 65 years old of which 59% were female.  Sande et al [2] in 2008, found that any type of general mask is likely to decrease viral exposure and infection risk on a population level; with surgical masks being more effective than home-made masks and children being less well protected.  The relative ineffectiveness of fabrics used in home-made masks, including sweatshirts, T-shirts, towels and scarfs, was demonstrated in 2010 by Rengasamy et al [3], who found that these fabrics had 40-97% instantaneous penetration for monodisperse aerosol particles in the 20 to 1000 nm range.  While in the same year, Cowling et al [4] conducted a systematic review of the subject and concluded there was some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help reduce influenza virus transmission.  There were fewer data to support the use of masks or respirators to prevent becoming infected.  So, the rational conclusion appears to be that we should wear face masks to protect society as a whole and remember they do not necessarily protect us as individuals.

The emphasis on social distancing is causing widespread economic distress and also appears to be causing a decrease in mental health.  It perhaps should be called physical distancing because that is what we asked to do – to keep 2 m apart or 1.5 m in some places.  In 2017, a team of engineers from the University of Hong Kong and Aalborg University in Denmark [5], concluded that a threshold distance of 1.5 m distinguished between two basic transmission processes of droplets, i.e. a short-range mode and a long-range airborne route.  They reviewed the literature, conducted experiments and performed computational simulations before concluding the risk of infection arising from person-to-person interactions was significantly reduced when people were more than 1.5 m apart because droplets greater than 60 microns in diameter are not transmitted further than 1.5 m; however, smaller droplets are carried further.  In the same year, Ai & Melikov [6] reviewed the airborne spread of expiratory droplets in indoors environments; they found inconsistent results due to different boundary conditions used in computer models and the available instrumentation being too slow to provide accurate time-dependent measurements.  However, it would appear, based on several investigations, that the risk of cross-infection is decreased sharply at distances of 0.8 to 1.5 m (see graphic).  Indoors, the flow interactions in the human microenvironment dominate airborne transmission over short distances (<0.5 m) while the general ventilation flow is more important over longer distances.  Hence, at short distances, the posture and orientation of individuals is important; while at longer distances, if the rate of change of air in the room is high enough then the risk of cross-infection is low.

These findings would seem to suggest that there is some scope to balance restarting social and economic activity with protecting people from the coronavirus by relaxing ‘social’ distancing from 2 m to 1.5 m unless you are  wearing a mask.  After all, we would simply following the example of Taiwan where there are almost no new cases.


[1] Leung NH, Chu DK, Shiu EY, Chan KH, McDevitt JJ, Hau BJ, Yen HL, Li Y, Ip DK, Peiris JM, Seto WH. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine. 2020 Apr 3:1-5.

[2] van der Sande M, Teunis P, Sabel R. Professional and home-made face masks reduce exposure to respiratory infections among the general population. PLoS One. 2008;3(7).

[3] Rengasamy S, Eimer B, Shaffer RE. Simple respiratory protection—evaluation of the filtration performance of cloth masks and common fabric materials against 20–1000 nm size particles. Annals of occupational hygiene. 2010 Oct 1;54(7):789-98.

[4] Cowling BJ, Zhou YD, Ip DK, Leung GM, Aiello AE. Face masks to prevent transmission of influenza virus: a systematic review. Epidemiology & Infection. 2010 Apr;138(4):449-56.

[5] Liu L, Li Y, Nielsen PV, Wei J, Jensen RL. Short‐range airborne transmission of expiratory droplets between two people. Indoor Air. 2017 Mar;27(2):452-62.

[6] Ai ZT, Melikov AK. Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review. Indoor air. 2018 Jul;28(4):500-24.