I actually like the google podcasts app. It's simple, it works, no ads, does everything I need it to do. Sigh. RIP.
3,693 karma · joined November 10, 2007
Hiring: JS/React and PHP (7.4+) engineers. Both full-stack and client services engineering.
We've been around for 12 years and quietly power various types of digital brand-meet-people interactions: on the surface, it's an "influencer marketing platform" (competitive with CreatorIQ et al), but we also power employee education portals, user generated content sites, and entire digital agencies with our technology.
We're a very small company that does high quality work and no overtime. You will be mentored, not micromanaged, but you must also be a self-starter and consistent.
Salary range $140k-$180k.
Email cto@tid.al with your resume and any other details you feel are relevant.
Have you ever tried reading perl code?
If so, it existed for a while but shut down years ago.
This shouldn't make you scratch your head though... other people value different things than you do, and each person has their own personalized formula for whether a Mac is worth it or not. still_grokking's value judgement is not canonical for anyone other than still_grokking.
I love linux, have used 4 different distros as my daily driver for the last 15-20 years or so. Yet still my linux-using friends and I have this joke: 'but will it hibernate?'
And to answer your question directly:
> Why are people using obviously extremely broken stuff
a) it's not obvious and b) it's not extreme. Apple products work smoothly for most people most of the time. We're on hacker news where the entire point of this forum is the selection bias around tech stories like this.
The authors of that paper did not intend to mislead -- this paper was published in 2011, likely written in 2010, only a handful of years after Michelin's unveiling of their gen 1 tweel design. To me, having been in the authors' position, I can easily tell what the true purpose of the paper actually was (the analytical procedure). But the authors had a secondary purpose driven by 'hype', almost, you could even call it click-bait: they wanted to make the tweel exciting so that other researchers would get interested in it and continue the work. One way to do that is by showing, from a materials perspective, that it is theoretically possible to design a tweel with a low rolling resistance, and given that, it's possible that tweels will be better for the environment over the full-lifecycle, including manufacturing and materials. And sure, this absolutely did/does deserve more research. However, the other issues with tweels, like NVH/comfort/etc, were 'out-of-scope' for that paper, and so they ignored those. Solving for those issues is what makes that 5.5 kg/T figure difficult/possibly impossible to attain.
When these papers are confined to academia, it all works out, because most of the people who read your paper are other people who are writing papers, and they get it. But once these types of papers are picked up by the press/media/general populous, they can be very quickly misinterpreted!
(To be clear, you didn't do anything wrong here, I'm just griping a bit about academia and pretending like I'm 'adding context' ;)
The money shot is here. Note that '5.5 kg/ton' refers to the rolling resistance of the tire.
> At this point the 5.5 kg/ton value is still only a design target, and this study serves mainly to confirm the environmental value of achieving that target.
Essentially, this conclusion is tautological. "If there were a tweel that had better rolling resistance than the best pneumatic tire on the market, then it will have a better fuel economy and environmental impact." Obviously!
I seriously doubt Michelin's tweel is anywhere close to that 5.5 kg/T mark. It's more likely something like 12 kg/T.
The purpose of this particular paper is not to show that tweels are better environmentally, it is to show an analytical framework for calculating the full-lifecycle environmental impact of tweels vs tires. Sort of like a "here are the equations, plug in real numbers later" kind of thing.
Not at all naive, because it is addressed with shock absorbers in the seats; that is one of the very many tools NVH engineers use. :) But they're not 'shock absorbers' in the way you're thinking; the actual foams used in the car seats are specifically designed and selected to dampen certain frequencies. But, kind of like a speaker or headphones or even ear plugs, the dampening happens over a spectrum, and in general our organs resonate at lower frequencies, which are harder for foamlike materials to dampen.
NVH engineers view the entire road-vehicle-driver system as a huge, complex, spring-mass-damper system, and do a whole ton of partial differential equations to solve for the outputs.
Edit to add: so why not use traditional 'shock absorbers', the spring-damper kind that you're used to seeing? For passenger vehicles the answer is weight and complexity. But many trucks and tractors and so on do in fact have these.
First, permeation decreases with pressure, at different rates for the two gases. If you consider only this fact you will find that the partial pressures of O2 and N2 asymptotically approach homeostasis, rather than simply all the O2 leaving and all the N2 remaining.
Second, permeability changes with temperature, so the ratio of O2 and N2 exfiltration rate changes seasonally, as each gas has a different permeability-vs-temperature curve. Third, the ideal gas law causes pressure changes seasonally which will also decrease exfiltration in winter, and once again, each gas will have its own permeability-vs-pressure curve, so these become very confounding factors.
All in all, the reality of the situation is that filling up your tires with atmospheric air will probably settle on partial pressure ratios of, say, 85/15 rather than 100/0. The deflation that you get comes from only about 5% of the O2 leaving the tire; and of course you get another big deflation when the weather first turns cold.
I don't know the exact numbers because I've frankly never thought to look into this before. So like I said, it was a clever thought! But it needed to be taken a few steps further.
One easy way to picture this is: recall your last long road trip, or airplane flight, anything more than 3 hours or so. You get so tired after those, especially considering that you've only just sat still for a few hours. But in actuality your body is making hundreds of tiny corrections to posture each minute, in response to the vibrations of the vehicle, and that literally exhausts your muscles and nervous system. Now imagine that you make that car "5% more harsh" and redo the road trip; you will feel the compound effects of that additional harshness. Auto manufacturers take NVH very seriously, because it turns out to be a pretty big deal.
My point is that even if NVH comes back OK in the lab, they still will need a good deal of real world data with test subjects representative of the 'average driver' before they can make a determination.
Edit to add: I know of at least one case where the entire drivetrain of a vehicle was redesigned due to NVH.
That said, tweels are typically designed to be much thinner and have much less interior volume than air-filled, in order to close the gap in rolling resistance. So you'd really need to compare a specific model tire against another specific model tweel in tests to know. But my intuition tells me that the rolling resistance will still be worse almost no-matter-what with today's tech.
So that's partly the reason they target lighter vehicles, and that's partly the reason they seem to be marketing around EVs specifically. That extra rolling resistance may be worth a few $s in gas each month vs only a few cents in electricity for the same driving conditions.