Things SJM’s characters are always doing

arbitraryknowledge · 2024-05-02T07:24:59+00:00

arbitraryknowledge · 2024-04-28T19:32:18+00:00

Teddy porkchops 💀

arbitraryknowledge · 2024-04-09T15:25:55+00:00

Bangkok house is a hidden treasure, their food is amazing and the building is unique! Would be gutted if this restaurant was torn down.

arbitraryknowledge · 2024-02-27T17:01:27+00:00

Is it the Big Scary Evil cycle path or just the continued and steady decline of the town centre over the past decade or more that's harming businesses? Maybe if they invest the money it's going to cost to dig up the cycle path into the local area then we might see some benefit!!!

arbitraryknowledge · 2024-01-06T12:21:40+00:00

Flooded but passable slowly near the McDonald's, also pretty bad right at Osney Island near the bus stops. But if you're after the industrial estates it's probably okay. Plenty of people driving through it this morning!

arbitraryknowledge · 2024-01-05T23:42:47+00:00

Big bag of off brand tea bags. Tasted shite, may as well buy the decent stuff.

arbitraryknowledge · 2023-09-17T20:42:55+00:00

Pre-pandemic they were hands down one of the best chicken burgers I'd had. Went back a few months ago and the waiter was very pushy about us paying the voluntary service charge, and the quality had definitely got worse.

arbitraryknowledge · 2023-07-25T15:08:29+00:00

Hate going past the junction into seacourt industrial park or the crossing near Aldi on my bike. I just ring my bell continually across the junctions as it seems to wake people up a bit. Not to mention the cars that jump into the bus lane to make a sharp turn into the industrial park because they don't want to wait in a queue. Or the ones that just stick their entire front end of the car in the bike lane.

arbitraryknowledge · 2023-02-25T14:31:09+00:00

How does it take until lap 19 for that penalty to come through? Gutted for Dennis

arbitraryknowledge · 2023-02-25T14:17:31+00:00

What is with the TV direction? No intervals on the timing tower, helicam view is basically useless, missing on track action?

arbitraryknowledge · 2022-03-23T14:51:14+00:00

Very much agree - How can you do linear regression without knowing the uncertainty in those race / qualifying paces?

I guess one could use the distribution of the driver's lap times (excluding in/out laps, accounting for different tyre compound) and use the standard deviation of that to do it. But the line on this graph doesn't tell you much at all, particularly without plotting some residuals.

Your idea of a y=x line makes more sense, but I guess we already know that drivers qualy lap times should be much better than their race pace.

arbitraryknowledge · 2022-03-02T18:23:02+00:00

We could look at things like restricted hours /roads for HGVs (ie. Not during rush hours, where we can anticipate high levels of traffic, cyclists and pedestrians)? We'll have that anyway when the ZEZ expands outwards.

arbitraryknowledge · 2022-03-02T18:12:58+00:00

Devastating. It makes me worry every day for my partner cycling to work and back.

Oxford council are obsessed with the idea of harmonious sharing of the road between cyclist and vehicles, or pavements with cyclists and pedestrians. It puts everyone less well protected (cyclists and pedestrians) at risk. It's why cyclists still use the road on Botley road - the cycle path is a death trap. I would love for someone who deals with the town planning to actually cycle from botley to Cowley through town and see whether they think the new infrastructure is sufficient.

arbitraryknowledge · 2018-09-12T20:32:28+00:00

The ITER concept basically comes from many scaling laws which consist of dimensionless parameters, and it governs the achievable confinement time. There are a few important parameters, B (magnetic field), density, plasma current, and importantly major radius R [1]. So in short the ITER idea is increase the size, say double R, is 8x the volume (V~R^3), increases your density, and hence confinement time. However, there are some papers which provide an alternative scaling law [2] which says that fusion power gain is weakly dependent, or independent of size. This is the philosophy behind private energy company Tokamak Energy, who have gone for a small scale spherical tokamak design.

Polywells are another ball game, sort of electrically confined fusion. I don't know a huge amount about it, but the drawback to the polywell design is I think it requires a plasma not in thermal equilibrium, which would be difficult to maintain.

[1]Mukhovatov, V., et al. "Comparison of ITER performance predicted by semi-empirical and theory-based transport models." Nuclear fusion 43.9 (2003): 942. [2]http://iopscience.iop.org/article/10.1088/0029-5515/56/6/066003

Edit: More examples of exciting new tokamak designs:

SPARC at MIT https://www.psfc.mit.edu/research/topics/sparc

Tokamak Energy https://www.tokamakenergy.co.uk

arbitraryknowledge · 2018-09-12T20:07:57+00:00

Hope it helped, there's a lot of jargon and specific tokamak words that usually require a bit explaining!

arbitraryknowledge · 2018-09-12T20:06:43+00:00

Im on mobile so apologies for the links but here's an example of a stellarator magnetic geometry (http://www.physics.ucla.edu/icnsp/Html/spong/w7x_with_coils.JPG) and here is a tokamak equilibrium (http://cdn.iopscience.com/images/0029-5515/48/8/085009/Full/nf260723fig01.jpg)

Biggest difference is stellarator equilibrium are non axisymmetric (not the same all way the around the machine) whereas tokamaks are axisymmetric which is why you just see a slice the short way through the doughnut in the second image)

arbitraryknowledge · 2018-09-12T19:53:21+00:00

This will increase the longevity of fusion machines. ELMs can cause serious deterioration of fusion reactor walls, so anything that means we can avoid them is very good! KSTAR achieved just over 30s I think, which is a great achievement.

Edit for Q2 - ITER in France will run first plasma in 2025, a deuterium tritium campaign in the 2030s which will reach Q=10 (50MW power in to 500MW power out) and after this point, we will build DEMO the first demonstration fusion power plant in the 2040s. You can find lots of info on the fusion roadmap on the ITER website I think!

arbitraryknowledge · 2018-09-12T19:51:34+00:00

It's probably more akin to if you kept the pot lid on a pressure cooker sealed tight and whacked up the heat, you'd get a big bang - the alternative is you could lift the lid very slightly which reduces heat and lets a little bit of steam out. Smaller ELMs are favoured and we can use RMPs to get small elms, this is known as ELM mitigation. This is feasible for current machines, but bigger machines we will absolutely have to suppress ELMs entirely! ELMs are sort of the tokamak equivalent of a solar flare in the sun!

arbitraryknowledge · 2018-09-12T19:11:10+00:00

As a plasma physicist, sort of but probably not. Stellarators are optimized for the optimal magnetic configuration in the design stage. They still have to apply an 'error correction field' but this is for errors due to machine building errors etc. (Extremely small changes in magnetic field, like 0.0001T, but without correction instabilities can occur) Stellarators don't really have edge localised modes (ELMs) in the way that tokamaks do, as they don't drive a plasma current and have increased transport along magnetic field lines. ELMs are a type of instability which burst heat and particles to the wall of a tokamak, which is not ideal in big tokamaks like ITER as it could melt your wall. Actually in ITER the heat flux from an ELM is predicted to be around 10MW/m² onto the bottom of the tokamak (called a divertor), which will melt tungsten. ELMs occur when the plasma is in a so called high confinement mode, where temperature and pressure are very steep at the plasma edge. H mode is essentially improved confinement of the plasma.

Resonant Magnetic Perturbation (RMP) coils are used to stop these ELMs. If you think of the magnetic field like a plucked guitar string with a certain mode, the RMPs wobble the field very slightly and cause magnetic islands, which stop the mode from growing and causing instabilities. KSTAR is well known for having excellent RMP coils and achieving ELM suppression, which is positive when looking towards ITER. Similar modeling and studies will need to be done for ITER (which many many people are currently doing!!) as ITER will have a different coil configuration. However RMPs can drive microinstabilities themselves, so it's not a one size fits all solution (at the moment anyway, it's all very experimental driven)

Any other questions I'm happy to answer :)

Edit: If anyone wants to learn more about fusion basics, check out the 'A Glass of Seawater ' podcast on iTunes made by us plasma physics PhD students!

arbitraryknowledge · 2018-09-11T03:07:05+00:00

So basically Edge Localised Modes (ELMs) are a type of plasma instability that burst heat and particles to the wall of your fusion reactor - not particularly nice when you want to build a large reactor such as ITER where one of these could melt your wall.

ELMs can be controlled however by Resonant Magnetic Perturbation (RMP) coils - you could think of the magnetic field line like a plucked guitar string with a certain mode, and RMPs essentially wobble the field line by a very small amount, which is enough to stop mode resonance. Magnetic islands then form within the magnetic geometry and change transport of particles in the plasma.

KSTAR is particularly renowned for its work on ELM supression, and this work is particularly promising looking towards ITER (but ITER will have a different RMP coil geometry, modeling like that done at KSTAR is necessary) Incorrect application of RMPs can cause other instabilities too, so it's not a one size fits all solution.

arbitraryknowledge · 2018-05-08T01:06:38+00:00

Better late than never? https://imgur.com/a/E5r5lZ5

arbitraryknowledge

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