I was recently involved in a large server purchase for work, where we wanted 72 hard drives of 24TB each for a server. They were available last year, but last month the largest we could get were 20TB drives.
Braking distance and following distance are two distinct things.
Following distance is the rule that you should leave a 2 second gap in front of you. That is often less distance than the braking distance.
You should be always able to see that your braking distance is or will be clear, and that sets the maximum speed you should drive at as you approach areas with reduced visibility, like corners or the brow of a hill. You must learn braking distances for the driving test.
This assumes that a 2 second interval is appropriate for all travelling speeds.
This assumption is untrue at very low speeds, particularly when it takes longer than 2 seconds for a car to pass a point. For instance if we assume cars are 4m long, then with an interval of 2 seconds the cars would be touching at 4.47mph
The assumption is also untrue at very high speeds. You'll want a larger gap. That's partly because at such high speeds the ability of a vehicle to decelerate differs - if a vehicle with good brakes does an emergency stop and the car behind it has a respectable 2 second gap but has worse brakes then they can end up colliding. It's also partly because a 2 second gap at very high speeds means the car in front is further away, and that can cause a greater delay before the driver realises what is happening. As a third reason a greater margin needs to be used at very high speeds simply because the consequences of a crash are that much greater and should therefore be avoided even more than at lower speeds.
Therefore there is a kind of U-shaped curve in the "safe" following interval, and consequently a speed at which safe throughput is maximised.
That's why variable speed limits have been introduced in various places. For instance, in the UK which normally has a 70mph speed limit on motorways, in very high traffic conditions this can be lowered using electronic signs to increase the safe throughput of the road. It's commonly reduced to 50mph, though it does get lowered further in sections approaching a queue of vehicles that has actually stopped.
There's also the issue of speed oscillations. With a high speed limit and vehicles following too closely, a little variation in speed in one vehicle can turn into a larger variation in the following vehicles, causing a backwards-travelling wave of braking (sometimes to an absolute halt) and speeding up again. Lowering the speed limit reduces this.
By 2 sec following distance I am referring to their back bumper to your front bumper. So cars "overlapping" in your example is not possible
If you want 4 sec gap at higher speeds that's fine, the formula is speed-independent for throughput, not speed-independent for following distance. If you want 4 seconds at high speed then use 4 sec instead of 2 sec (i.e. 1 car/ 4 sec)
>There's also the issue of speed oscillations. With a high speed limit and vehicles following too closely, a little variation in speed in one vehicle can turn into a larger variation in the following vehicles, causing a backwards-travelling wave of braking (sometimes to an absolute halt) and speeding up again. Lowering the speed limit reduces this.
"Lowering the speed limit reduces oscillations." Exactly, that is my whole point, that (again, locally analyzed) you can ignore the waves, and instead look only at the following distance of the slowest car in the lane, to determine throughput of the road behind that car. Your idea of "lowering the speed limit" to eliminate waves is the same net effect on throughput as observing that the throughput cannot exceed that given by the longest-following car on the road.
A niggle - if you are referring to a 2 second gap between the back bumper and the following front bumper, then the formula is no longer speed independent, as you need to add the small overhead to account for the time taken for the length of the vehicle to pass as well. This will be small enough to be mostly negligible except at low speeds.
Carnot efficiency is 1 - Tc/Th, where Th is the hot side temperature and Tc is the cold side temperature. Tc is set by the surrounding environment, probably in the vicinity of 300K. If you have a hot side temperature around 1,000,000K then the theoretical maximum efficiency is very good. If that heat has to be stepped down by separating it from materials that would melt and you can only sustain a hot side temperature of 1200K, then your theoretical maximum efficiency drops to 75%. Obviously the real life efficiency will be a bit less than that, but the principle shows that the "lucky to get 1% efficiency" bit is nonsense - you're not actually losing that much after all.
This is all about getting energy out of a very hot heat source. Theoretical efficiency is ~1, and a ~40% practical efficiency also doesn't seem to be hard: let something heat up to 1000C, and don't let much of the energy escape to the environment.
Also deuterium-tritium reactors get energy out of the plasma via capturing high energy neutrons, very similarly to nuclear power plants.
DF gets all the news (rightfully so, it's an epic game that I've dumped a ton of hours into) but if you haven't already, consider checking out Songs of Syx. It's like DF but multiplied by 100. You can have tens of thousands of citizens, doing most of the things they do in Dwarf Fortress, and a lot more, including waging huge wars against the neighbors. The limits of DF kinda made me sad, actually, that you are limited to so few Dwarves (and don't say it's because you want to know the story of all of them, because after 30 or so you lose track of who is who anyways, so might as well up the limit from 100 to 50K, or more? ;) Songs of Syx has also routinely been getting massive updates since 2020 and I have a feeling the code is a bit cleaner so the solo dev can add features faster (unlike DF's code base which is, according to one of the new devs a nightmare to work with). It's a game that is never talked about but deserves a whole lot more love from gamers.
I don't mean to cast shade on DF, I really do love it, and am happy for its existence, I just think that DF fans should also look into Songs of Syx.
The defining difference for me are the generated stories in DF, which often are a lot of random trash but still give a feeling of a deeper meaning.
For me, it actually seems fairly plausible. I was a fairly untrained 70kg forty-something when I went to the gym and very quickly found that as I did a bit of hiking, I could max out the standing calf raise machine at 155kg. This involves having a very padded 155kg on your shoulders while in a standing position. It felt to me like that was the most my shoulders and back could cope with, and it's more than double body weight.
It’s a huge difference having a loaded barbell which can move in every dimension on your shoulders versus a calf raise machine which is fixed in place and cannot move around!
I’ve squatted barbells since roughly 2006 and the feeling of having more than 100kg on your shoulders is very intense, even if you’ve trained up to it. It feels like it’s crushing your whole body and even breathing is hard.
The idea that an untrained person could put a 180kg barbell on their shoulders and be comfortable AND move around is laughable, they would collapse very quickly.
They wouldn't be able to unrack and stand there either. Just standing with a very heavy barbell is extremely difficult (assuming an untrained person).
Seriously, go and try it, load up 100KG or roughly 225lbs on a barbell and just stand there with it. If you're already a big/heavy/trained guy, put 180KG or 400lbs.
It will probably be quite a surprising experience for you.
And I will say, that even when I was training for heavy squatting, standing there with a very heavy barbell on your back isn't fun at all, you have to have a very tight core, tensed muscles, breathing is much harder. i.e. just standing there is hard work and you want to get your 5 squats done asap. Also, it just plain hurts your back as the metal bar on your spine is painful!
Agreed. Most of the time the cost of driving out of your way exceeds the saving you would make. However, there's a fuel station near me that is 19.8% cheaper than one only 1.6 miles away from it, and that's a thing that is worth knowing.
However this is only really good for slow connections. If your connection is faster than about 50MB/s then the delta calculation mechanism becomes the bottleneck. On fast connections you should use the -W option for rsync which switches the delta algorithm off.
Saving on transmitted bandwidth costs is more important to me than speed of transmission for my use cases which I feel are likely to be common use cases.
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