Category Archives: Engineering

Are we in a simulation?

Decorative photograph of trains at terminusThe concept of digital twins is gaining acceptance and our ability to generate them is advancing [see ‘Digital twins that thrive in the real-world’ on June 9th, 2021].  It is conceivable that we will be able to simulate many real-world systems in the not-too-distant future.  Perhaps not in my life-time but possibly in this century we will be able to connect these simulations together to create a computer-generated world.  This raises the possibility that other forms of life might have already reached this stage of technology development and that we are living in one of their simulations.  We cannot know for certain that we are not in a simulation but equally we cannot know for certain that we are in a simulation.  If some other life form had reached the stage of being able to simulate the universe then there is a possibility that they would do it for entertainment, so we might exist inside the equivalent of a teenager’s smart phone, or for scientific exploration in which case we might be inside one of thousands of simulations being performed simultaneously in a lab computer to gather statistical evidence on the development of universes.  It seems probable that there would be many more simulations performed for scientific research than for entertainment, so if we are in a simulation then it is more likely that the creator of the simulation is a scientist who is uninterested in this particular one in which we exist.  Of course, an alternative scenario is that humans become extinct before reaching the stage of being able to simulate the world or the universe.  If extinction occurs as a result of our inability to manage the technological advances, which would allow us to simulate the world, then it seems less likely that other life forms would have avoided this fate and so the probability that we are in a simulation should be reduced.  You could also question whether other life forms would have the same motivations or desires to create computer simulations of evolutionary history.  There are lots of reasons for doubting that we are in a computer simulation but it does not seem possible to be certain about it.

David J Chalmers explains the probability that we are in a simulation much more elegantly and comprehensively than me in his book Reality+; virtual worlds and the problems of philosophy, published by Penguin in 2022.

Tears in the heart

Figure 7 from Chew et al 1999A couple of weeks ago I wrote about speaking to a workshop on the aorta and reminisced about research on cardiac dynamics from about 15 years ago.  It triggered another memory of research we did more than 20 years ago on the tearing of the leaflets of artificial heart valves made from biological tissue.  We developed a computational model of the stresses associated with a tear developing in a porcine bioprosthetic heart valve.  The black and white images show snapshots of the predicted motion during the cardiac cycle of a damaged valve with a tear at about 11.30 along the edge of the top right leaflet.  The valve was simulated as being implanted to replace the aortic valve and the view is from the aorta, i.e., looking in the opposite direction to the blood flow out of the heart.  The tear causes part of the leaflet to flap outwards as can be seen in the middle snapshots.  The colour image shows the distribution of stress in the leaflet corresponding to the last snapshot of the motion and the concentration of stress around the tip of the tear can be seen which will tend to cause the leaflet to tear further leading to a bigger flap, more regurgitation of blood.  We were really excited about this research when we published it in 1999 but it has attracted relatively little attention in the last 23 years.  I would like to think that we were far ahead of our times but that’s unlikely and probably it was not as exciting as we thought, maybe because it lacked clinical relevance, our model lacked credibility or not many people have found our paper.

Source: Chew GG, Howard IC & Patterson EA, Simulation of damage in a porcine prosthetic heart valve, J. Medical Engineering & Technology, 23(5):178-189, 1999.

 

Horsepower driving ambition

A photograph of 'Physical Energy' in Kensington Gardens - a sculpture of a man on a horseWalking across Kensington Gardens in London last week, on my way to attend a conference on Carbon, I came across the sculpture in the picture.  It is ‘Physical Energy’ by George Frederick Watts (1817 – 1904), which really confused me because I automatically started thinking about the sort of energy that is associated with horsepower.  Horsepower is a unit of power (energy per unit time) developed by James Watt (1736 – 1819) to evaluate the output of his steam engines.  The plaque below the sculpture calls it a ‘sculptural masterpiece; a universal embodiment of the dynamic force of ambition’ and states that the artist described it as a ‘symbol of that restless physical impulse to seek the still unachieved in the domain of physical things.’  So, while the connections seemed obvious to me, it would appear that Watts was not inspired by Watt.

The conference was interesting too.  There were delegates from all over the world presenting research on a wide range of topics from new designs of batteries to using carbon as an sorbent for toxins, carbon-based composites and self-assembly of metal-organic meso-crystals.  Two students that I have supervised were presenting their research on establishing credibility for models of the graphite core in nuclear power plants and on algorithms for identifying the surface morphology in samples of graphite.

Aorta: structure to rupture

Decorative image from a video showing predicted flow through aortic valve and resultant stress in leaflets of valveRegular readers have probably already realised that I have very broad interests in engineering from aircraft and power stations [see ‘Conversations about engineering over dinner and haircut‘ on February 16th, 2022] to nanoparticles interacting with cells [see ‘Fancy a pint of science‘ on April 27th, 2022].  So, it will come as no surprise to hear that I gave a welcome address to a workshop on ‘Aorta: Structure to Rupture‘ last week.  The workshop was organised in Liverpool by one of my colleagues, with sponsorship from the British Heart Foundation, and I was invited to welcome delegates in my capacity as Dean of the School of Engineering.  It was exciting on two levels: speaking, for the first time in more than two years, to an audience who had travelled from around the world to discuss research. And because the topic was closely associated with cardiac dynamics, which is a field that I worked in for nearly twenty years until around 2006.  I was part of an interdisciplinary team modelling the fluid-structure interaction in the aortic valve as it opens when blood is pumped through it by the heart and then closes to prevent back flow into the heart.  The team dispersed after I moved to the USA in 2004.  So speaking to the workshop last week was something of a trip down memory lane for me and led me to look up our last publication in the field.  I was surprised to find it was cited seven times last year.

The image in the thumbnail is a snapshot from a video showing the predicted time-varying distribution of blood flow through the aortic valve and the resultant distribution of stress in the leaflets of the valve during a heart beat.  The simultation is described in our last publication in cardiac dynamics: Carmody, C. J., Burriesci, G., Howard, I. C., & Patterson, E. A.,  An approach to the simulation of fluid–structure interaction in the aortic valve. J. Biomechanics, 39(1), 158-169, 2006.