When I return something, I feel I'm contributing to the tragedy of the commons - I know I'm still paying for this return, it's just baked into the price. I wish I could get 8% off or something if I promised I wouldn't return it just because I didn't want it.
If it helps you feel better, the "tragedy of the commons" isn't a natural law, it's a highly debated topic that was somewhat re-invented by an economist and then coined in the modern era by an ecologist discussing the pamphlet by the economist, in which it's argued that unfettered access to "the commons" will lead to the common being destroyed.
What's missing from the regular usage of the term is the fact the pamphlet was written immediately the enclosure movement had subdivided the literal Commons - common land - that had functioned perfectly fine for centuries without over exploitation... until the enclosure movement subdivided them and landowners began over-exploiting them.
The lesson isn't that people can't be entrusted with unfettered access to common goods, it's that giving decision making power over the distribution of a common good to an owner (capitalist) will result in over-exploitation. In the case of returns, the price of the good has way more to do with the seller just getting the price up as high as they can get it and still profit, and far less to do with labor costs, manufacturing costs, shipping costs etc. A simple question: if they could sell it for more and make more money, why wouldn't they? If they could sell it for less and make less money, why would they? Hence why the cost of goods stayed up after the chip crisis despite the chip crisis ending.
One of my favorite sci-fi authors wrote Lady of Mazes, which in part explores what a "finished" tech tree looks like, and how societies might explicitly reject parts of it as part of their values. It explores multiple societies physically overlaid but invisible to each other because their technological values are incompatible. (The titular lady possesses a rare ability to step through to different societies.)
It really ought to lead with the license of each library. I was considering dietlibc until I got to the bottom - GPLv2. I am a GPL apologist and even I can appreciate that this is a nonstarter; even GNU's libc is only LGPL!
Note that dietlibc is the project of a sole coder in the CCC sphere from Berlin (Fefe). His main objective was to learn how low level infra is implemented and started using it in some of his other projects after realizing that there is a lot of bloat he can skip with just implementing the bare essentials. Musl has a different set of objectives.
> e-graphs-based compilers like Cranelift maintain an equivalence graph that represents all possible lowerings, and after the whole graph is built, an algorithm finds a single optimal lowering
Do you have a good entrypoint reference for learning about how this works? This (and the associated mention in the article) is the first time I've heard of this approach.
OBS Ford F-150s do this and it's not common knowledge even among enthusiasts. The back 4 pins work the door, the front 6 or so pins work the ignition. A common problem is that the ignition barrel keyswitch dies and you have to replace it, but then you have separate keys for the door and ignition. I took the new ignition key to a locksmith and had him copy the 4 back pins from the factory key, and I was back to a single key!
Impulse response is sort of overkill here. If you design a filter bank in the first place, you can just implement that filter bank much cheaper than doing even an FFT-based convolution. Convolution is useful when you don't know the underlying filter transfer function.
It really depends on what your filter bank looks like. If it's a 4-band parametric EQ, then sure, you can have four biquad IIR filters and that's it. But if you've measured an impulse response and want its inverse (e.g. through a Wiener filter), that's not what you have; you simply have another impulse response (effectively closer to a N-band graphical EQ where N >= 100), not a parametric EQ.
As a nitpick: You always know the filter transfer function, it's the DFT of the impulse response (and without the impulse response, you obviously cannot convolve).
There are a few procedures that convert an impulse response to an approximating IIR filter:
1. Hartmut Brandenstein and Rolf Unbehauen, "Weighted Least-Squares Approximation of FIR by IIR Digital Filters", IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL. 49, NO. 3, MARCH 2001
2. Hon Keung Kwan and Aimin Jiang, "Recent Advances in FIR Approximation by IIR Digital Filters", 2006 International Conference on Communications, Circuits and Systems
3. Ngai Wong and Chi-Un Lei, "FIR Filter Approximation by IIR Filters Based on
Discrete-Time Vector Fitting", 2007 IEEE International Symposium on Circuits and Systems (ISCAS)
The third one is approachable by anyone who has studied linear algebra at the level usually taught for physics students and knows NumPy. No special DSP course is required. My implementation takes approximately 200 lines of Python code.
The article contains a deterministic algorithm that takes a guess on the pole positions in the complex plane and returns a better guess. The idea is to start with a random guess with the correct symmetry and apply the algorithm iteratively.
The only two tricks to be aware of are: 1) their reformulation of everything in section III.B in terms of real numbers (instead of complex numbers) is not making anything simpler and should be ignored, and 2) explicitly symmetrize matrices that are supposed to be symmetrical, it order to avoid accumulation of numerical errors.
Still, it is not something that I would be willing to fully automate: for good results, one has to add a small delay or chop off a few initial near-zero samples, and guessing the delay correctly is what separates an easy-to-approximate filter from a bad one.
> generating a filter curve for a 300Hz slope, both channels were divided (A/B) against that curve
as defining a parametric EQ band. If you just generally want to invert a measured impulse response, then yeah, you don't know the underlying transfer function.
Well, immediately after that, they say they inverted the entire curve (through a naïve 1/|X| and then un-FFT, presumably) and saved it as an impulse response. I think the 300Hz slope is to _keep_ the rolloff in that area, so that the system doesn't try to boost bass by 40 dB and just end up clipping madly.
Since these operations sort-of commute, it is easier to understand if you invert the order of operations:
1. Invert the spectrum (ideally through something less sensitive to noise than what's done here). Now you have an impulse response that will, in theory, give you a perfectly flat frequency response.
2. Apply a 300 Hz slope. Now you gave up some of that flatness, but you have something that's physically realizable without murdering your speakers.
Exactly correct, that was my thought process while doing it.
I tried it without that 300 Hz slope first of course, but that did try to murder my speakers. :)
I'm not sure I understand. How would you apply your FIR filter? Are you suggesting there is a different way than to either do convolution in the time domain or a multiplication in the frequency domain?
REW can generate a set of peaking/shelf equalizer filters, but why would I want to do that instead of just applying the inverse impulse response instead?
It's just more work for a less perfect solution/result...
This depends entirely on the length of the impulse response, doesn't it? A very short time domain convolution isn't actually more computationally expensive than a bank of crossover filters.
The equivalent wattage of a gas pump is something like 1-2 megawatts, based on energy transfer per time. (Internalizing this fact is important for understanding why gasoline is hard to displace!)
"EVs convert over 77% of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12%–30% of the energy stored in gasoline to power at the wheels."
Things look even more dire for gas when you consider the entire supply chain. Remember that you burn gas as terrible efficiency to transport it to gas station.
it is even more dire - transport of gas - imagine hurricane, tornado damages, pipelines, electric supply for gas pump pumps... good luck with pumping gas without electricity, or i remember 8 hour queue before hurricane in front of gas station for some reason...
with PV on roof you do not need to transport anything from anywhere, charge and be functional. not even talking about house comfort while literally everyone around you is panicking, because of lack of electricity. ( you can connect 200watt inverter to your outlet to help "pace" ongrid inverter to work in offrgid situation, so yes all PV can do offgrid for 30 bucks on top)
yes generators are a thing until russia knocks on US sovereignty and US does nothing about it - Colonial Pipeline ransomware attack ...
Did you really think 10-20% loss would erase 50-60% more efficiency when you asked that question? Did you also ask the same question about gasoline energy efficiency and whether it included the significantly higher amount of energy required to move that oil/gasoline all over, multiple times, before it ends up in a tank?
You’re missing a state of change.
California uses coal, natural gas, and nuclear primarily.
Nuclear efficiency is low at 33%.
Best case you‘re charging your car from a new natural gas plant that is a combined cycle design which can potentially have up to 60% efficacy.
So 60% efficiency, minus 9.2% transmission loss, Minus charging losses and then electric motor efficiency loses… verses directly consuming fuel and putting the power to the wheels.
Electric cars are much less efficient if you consider the entire stream. If you want to use the argument that the gasoline needs to be refined and transported. Well so does natural gas. Or coal, or nuclear fuel rods, or bio mass, etc etc.
I’m not saying electric cars aren’t good. But we should really force people to charge them with solar if we want peak efficiency to save the planet.
I’m not missing anything. You’re being extremely selective in your argument by excluding all of the processes that extracted, transported, and converted, transported again, and again, and then again before ending up in a tank, and ignoring all those same processes required and used recursively for each of those processes, including the coal, natural gas, etc burned to power all those processes, etc etc to the same level of insane detail that you want to pick electric apart.
But then, starting from the position that 10% loss on a 60% directly efficient ‘fuel’ is worse than a minimum 83% loss of efficiency on another fuel isn’t much of a genuine position in the first place.
you forgot to calculate how much of cost of nuclear energy(sic) is going towards removing all CO2, NOx it is generating....
so if you are calculating efficiency of one power plant calculate this into price of another power plant too.
we can build utility PV + 12 hour battery with LCOE lower than nuclear... PV + battery price is for already deployed system. nuclear price is prediction of price of new plant...
Nuclear is dead in the water. And it is not pacific ocean water.
On the other hand, a significant number of trips will begin their trip with a full "tank" (battery) and will therefore not even need to stop to refill.
The median distance travelled on long-distance trips is less than 200 miles in the US, which is clearly within the limit of a normal BEV battery.
The GP's point about the energy density of gasoline and how quickly it can be transferred is not refuted by this irrelevant statistic; indeed, reading the same statistic with a pessimistic interpretation makes my point: if the median trip distance is 200 miles, about half of trips are longer than an EV battery charge, requiring a long refuel stop.
Half is a lot of trips to give up by switching to an EV!
> how quickly it can be transferred is not refuted by this irrelevant statistic
Of course it is refuted. No need to transfer is without a doubt faster than a transfer taking a few minutes.
> if the median trip distance is 200 miles half of trips are longer than an EV battery charge
The median LONG distance trip. The trip which only happens a few times per yer. That trip. There are about 2.6 billion long distance trips, and 411 billion daily trips. So this means that just over 0.5% of all trips in a year is a long-distance trip, and therefore significantly less than half of those again can be completed without a refill.
0.25% of 365 = 0.9125
So one, probably two, long distance trips in USA per year on average need a refill on the way, when adjusted for all trips in the nation.
I was the person who brought up the number originally as a way to illustrate that the he median _LONG_ distance trip is that distance. Those trips accounts for less than 1% of all travel by personal vehicle. Maybe it was unclear.
> BYD will soon start deploying its 1000 kW ultrafast charging stations in China. The first batch of 500 chargers will begin operating in early April
> ZEEKR unveiled a 1.2 Megawatt EV charger
So it's possible. Hard to do though, 1-10MW of available capacity is hard to come by, infrastructure is not ready. Well, gas station infrastructure was built over more than a century of gas domination
To further expand on this with some back-of-the-envelope calculation, I've heard EVs are on the order of 30-40 kWh. Say the power storage of the gas tank in an ICE car and the battery storage of an EV are commensurate. Conservatively, say refueling your ICE car takes about 1 min, so 30,000 Wh / ((1/60)h) ~ 1.8 MW.
for home charging, figures are exact opposite - when i come home it "costs me" 3 seconds to plug it in, then i do literally literally nothing ( or something else rather), then it "costs me" another 3 seconds to unplug it in morning,
so for 100kwh it is essentially 6 seconds. so electric car wastes 1/10 of my time compared to gasoline one.
im good mathematician, but i like engineering more, because it has to take into account external factors, not "just" numbers.
(intentionally not calculating travel time to and from gas station, queue, noise, smell of a gas station etc )
The way you've described it, charging at your home takes 8+ hours. You can do other tasks in parallel, so the effective cost to you is 6 seconds but that doesn't change how long it takes to charge your vehicle.
There are many use cases where charging at home is not an option, in which case understanding charging time becomes an important factor.
I like mathematics and engineering, which is why I like to understand basic facts to better address an issue rather than contort facts to dismiss an issue.
you phone literally knows when you're going to sleep, when on toilet, what cake did you have on your birthday. so you can ask it to tell you exact trips you took, and you can calculate when and how you can charge and for how long, from that data.
I just don’t buy this argument as a reason people don’t want EVs. The primary benefit of an EV is that you ~never need to stop and “refuel” it unless you’re making a long road trip. You can install a charger at home, even a very slow one that doesn’t need a special circuit, and always have a full battery in the morning. When you do need to stop on a road trip, you can use fast charging, which is ~250 kW, so somewhere around a quarter of the gas pump’s “wattage.” You’ll probably want to use the bathroom/buy a drink anyway, so charging taking four-ish times as long as pumping isn’t really a big deal.
> You can install a charger at home, even a very slow one that doesn’t need a special circuit
Lots of people rent, and might not have a parking space with charging available.
That said, battery and charging technology is evolving, so it might be a solved problem 10 years from now - especially as Toyota and Idemetsu Kosan are on track for mass producing Solid State EV batteries by 2028 [0]
Yeah, of course. I’m a renter, I understand. Some states [1] have laws allowing tenants to install chargers, although obviously not all renters have designated parking spaces. Where I live (NYC), most people rent and the idea of a “tenant parking space” is fairly foreign, but there are a decent number of EV chargers on the street in my neighborhood, so people make it work.
> You’ll probably want to use the bathroom/buy a drink anyway, so charging taking four-ish times as long as pumping isn’t really a big deal.
That doesn't take nearly as long as charging, nor do I need to do it as frequently as I would need to charge. And even if it did, the places where you can do that, and the places with chargers, aren't the same.
Maybe the US will get there in a decade (or two at current rates), but for now a PHEV seems like the best of both worlds.
For the routes I take on road trips, this is already the way. Lots of nice rest stops with lots of EV charging. Some restaurants, clean bathrooms, convenience stores to buy whatever snacks, etc.
I stop, go to the bathroom, grab a beverage, and by the time I'm back to the car I've got more than enough charge to hit the next stop. Coupled with Blue Cruise and road trips have never been so smooth and easy.
And I'm in Texas, a place you wouldn't expect to be some EV mecca.
> The primary benefit of an EV is that you ~never need to stop and “refuel” it unless you’re making a long road trip.
Maybe for some people. I bought an electric car in 2018 because I think over the long haul that, first, they'll be better for the environment and second, disentangle my country from foreign energy producers. Note: I'm not saying EVs or current battery tech are perfect in these ways now, just that I think they have better long-term potential, which will only be realized if people buy imperfect EVs today to justify investment in making them better tomorrow.
All that said, while my family has never had a problem with charging on long-ish road trips (we like to take a break and get out and walk around,) I don't expect everyone to have the same attitude. Some people really don't like the idea of a 20-minute "fill up".
What I'd really like to see - what I hope gets developed long term - is a fast-battery-pack swapping system. Bonus points for a standardized form factor from SAE or some similar standards body. This could solve a few problems:
* Faster recharges on trips - potentially faster than filling up a gasoline or diesel vehicle.
* Optimized energy use, at least to a certain extent. Battery packs could be charged off-hours to reduce load on the grid.
* As part of the cost of swapping the pack, the charging station could take on responsibility for repairing the battery packs.
Battery packs are the most expensive single component in most EVs, and I think some people do have anxiety on getting stuck with a five-figure repair bill if their battery pack goes bad.
Obviously there's a lot to work out, both technologically, and vis-a-vis the business model of a battery swapping network.
The problem with battery packs is that batteries age. It's not like returning a propane tank and getting a full one. If you just bought your car and you go to refuel and they swap your once used battery pack with one that's seen ten thousand charge cycles you aren't getting a fair deal.
I totally get where you're going with this, but propane tanks also age. One time I swapped the tank, and when I got around to replacing it less than a year later it was past it's certification time and they wouldn't take it unless I paid to get it recertified someplace else.
Much less of an issue than getting a bad battery though.
Why do you care if your interest in the battery pack is that it lasts 200 - 300 miles? The only way this model would work is if maintenance/replacement of the batteries is the charging network's problem.
The weight is the most trivial problem to solve in this whole problem chain. A hydraulic lifting apparatus capable of moving a ton that fits under a passenger car is something that exists today.
Getting automakers to agree to a standardized form factor (and to not put non-battery components in their battery packs ala Tesla,) automatically locating and removing whatever retentioning mechanism is used, having a large enough stock of batteries at each “filling station”, etc. are more difficult problems.
But, as I said, I hope this does happen in the future.
Presumably the battery network would have insurance and would factor that into the cost.
(I’d expect that all-in, this gets a lot closer to the cost of a gasoline fill-up. My current charging costs are far lower than the equivalent cost to fill up with gasoline, but my primary interest in this is environmental. I’ll take the lower cost while I can get it, but I don’t expect it to last forever.)
This is especially true, given that advances in battery tech, and fast charging are going to eliminate the need. Recharging as fast a petro fuel filling have already been demo'd.
Of course, here in the US we don't need any of that commonist technology. We're all so great, we're gonna say "Please, Please, don't make me any greater!". Can't wait 8-/
So, qualify what I wrote before with: _in_China_ they'll be able to charge as fast as a refuel.
I bought a used 2023 Nissan Leaf for $15K. It had 18K miles on it, 150 miles of range on a full charge, and still 5 years on the battery warranty, and 2 years on the bumper to bumper warranty. I did admittedly find a good deal, but this is not unobtainium
A friend wanted one of those licensed electric golf carts to drive around town, it cost more than my car.
With off-peak charging, (and the cost of gasoline in San Diego) I expect the car to pay for itself in fuel savings in ~5 years.
How many years will it take an inexpensive gasoline car to pay for itself?
Yes, about 2 years worth at my 300 mile/week usage and San Diego $5/gal gas price.
After which, the gas car continues to use gas, and I continue to save $3000/year by not buying gas...
But your comparison is valid. You could also compare the saving of the small, gas efficient, car to the choice of buying giant, low milage truck or SUV.
BTW, this good deal was not a once in a lifetime thing. I see EVs in this price range on craigslist routinely...
> I just don’t buy this argument as a reason people don’t want EVs.
These descriptions are unrealistic to our experience. We're on our third EV, so plenty of experience with this. It's always a pain to go anywhere outside a small area. Just this week my partner needed to go to a nearby city 2hrs away. Round trip too long for the EV. Luckily my office is halway there and has chargers, so stopped by for 2.5hrs to top up the batteries. That's a longer refueling stop than the whole trip. Faster chargers exist but they are few and far between, usually broken or taken, so finding one is an exercise in frustration.
> You can install a charger at home, even a very slow one that doesn’t need a special circuit, and always have a full battery in the morning.
It takes us three days to fill up the car at home if it gets really low, not having a special circuit. So if the car was used yesterday it won't be full this morning.
The only way this works at all is because my partner normally only needs to commute about 30 minutes and only twice a week.
'The primary benefit of an EV is that you ~never need to stop and “refuel”'
I beg to differ: The primary benefit of an EV is that I am not handing over my hard-earned post-tax income for oil to countries that loath my way of life and my values.
Some decisions in life should transcend economics.
If you’re in the US, most oil is domestic, but obviously that doesn’t make it much better. (If you’re not, sorry - “my way of life and my values” is very US-coded language.)
I just got a RAV4 Prime (a “plugin hybrid” or PHEV).
In EV mode, it has 40 or so miles of range. That’s high enough that I never need to use gas during the week, unless I go to the next city over. It’s also low enough that it can always fully charge overnight without a special circuit.
If I need to go further, it just becomes a RAV4 Hybrid (with better performance - aka HV mode). No long waits or searching for chargers needed.
Generally I put in maybe a half tank of gas ($15) once a month. Especially in the US, I really think PHEVs make much more sense than EVs. BYD seems to make some really nice ones, but we’re sadly hostile to them.
No, I’ve road tripped around the country with both types of vehicles. It’s delusional. And I’m not anti-EV by any means, I like them, but when you do need to use public charging, it sucks.
The charger may be right on the on your route, which is nice, but it often isn’t. If it’s five minutes out of the way, that’s an extra 10 minutes on my trip +20 minutes of charging. That’s a half hour where a gas station would’ve been three minutes. There are a good amount of times when it is more than five minutes away.
That’s extremely common and even supposes the chargers are available, I remembered to pre-condition the battery, etc. all of those are not given.
And for preservation of battery life you’re really operating with 60% of the stated capacity because you’re keeping it between 20 and 80 all the time. So a 250 mile range is really 150. I have had it happen where I drive two hours, spend a half hour charging, rinse, repeat on a road trip.
> When you do need to stop on a road trip, you can use fast charging, which is ~250 kW, so somewhere around a quarter of the gas pump’s “wattage.” You’ll probably want to use the bathroom/buy a drink anyway, so charging taking four-ish times as long as pumping isn’t really a big deal.
Yeah, no.
My gasoline car gets ~400 miles to a tank. Well, more than that: 400 miles is effectively the "no matter the circumstances [that cause gas mileage to be sapped], I can always guarantee making it at least that," not like EVs where the range number tends to be more of an aspiration than a reality. Admittedly, I have a small sedan which gets ~40mpg on the highway, but it takes less than 2 minutes to fill it up at the gas pump (about 100s IIRC, I did actually time it). Even derating for less fuel-efficient cars, you're comfortably extending your range by > 100 miles/minute of charging.
The EV charging, by contrast, is going to run something like 200 miles/20 minutes. That's a multiplier closer to 10×, not 4×; it makes the time you need to stop to charge it much more considerable.
But the range issue means I now have to slot an extra major stop. Sure, I can fill up during lunch. But that isn't enough to get me to my destination--I still have 5-6 hours of driving after lunch (sometimes more, since I like to take early lunches to avoid crowds). That extra stop takes longer than all of my bathroom breaks on the trip, combined. That's a not-insignificant amount of extra time on my trip.
The other consideration is that, if you're trying to tell people to overlap charging with lunch, well have you seen how crowded the travel plazas get on a busy travel day? They can get so packed that every parking space is taken up. The fill-up-while-you-eat rule suggests that pretty much every single one of those parking spaces needs a charger, most of which don't have the room for a charger as it stands.
Took a trip to Canada with my brother in his new EV. Trying to get an EV spot at the hotel was a nightmare and when one finally opened up, the charger was incompatible. Most charging stations weren't in convenient locations and the ones that were, were slow and required you to pay through an app. I'm not anti EV at all, but the experience of dealing with charging issues outside of the day to day routine was pure shite.
By this do you mean that Chinese automakers are getting close to a charging rate that would be equivalent to the time it takes to pump gasoline for the equivalent energy? If so, do you have any sources on that?
I was surprised, but at the same time not at all surprised, to find out that they not only reinvent Android UI libraries yearly, but also much lower level parts of their software.
(I build Android apps since 2011. I stopped following their updates since around 10 years ago. I still write Java, albeit modern versions, and use XML views. My apps are tiny and launch instantly. I'm also very controversial among the Android developer community.)
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