Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror

Comment Re:Yawn. (Score 1) 69

Supercharger V2, of which there are thousands deployed and thousands more in construction (with a minimum of two chargers per site), are 145kW. Without any problem to the grid. Supercharger V3 is going to be over 350kW (exact power has not been announced yet). In order to move to the higher capacity, V3 chargers will have a battery buffer, and thus stress the grid less than V2. That is to say, they'll trickle charge from the grid (and their solar awnings, which Tesla is looking to make standard), then surge charge EVs.

Battery swap is a total non-starter for about fifty reasons that aren't worth reiterating yet again here. Every major corporate proponent has either given up on them or gone bankrupt. Including, by the way, Tesla, who was demonstrating their automated swapping system a couple years ago, but has since cancelled it. It's technologically possible, but grossly economically impractical (due to stockpiling requirements, made worse by the unavoidable necessity for widely varying battery profiles and performance characteristics, as well as the ever-changing technological baseline) and gets poor consumer acceptance in practice (as there's widespread opposition to giving up your good new battery pack for someone else's old degraded battery pack). There's also concerns about durability when you're replacing such a large structural element in the vehicle with HV connectors, although this issue comes in a distant third.

Comment Shining some light (Score 5, Informative) 134

I'm a biologist, I don't understand P values [...]

Here's some light for that subject.

Suppose you make 20 measurements of rats in a maze and discover that 15 out of the 20 times they turn left on their first corridor junction. Is that significant?

We know that if the decisions were random we'd expect 10 out of 20, but we also know that there is variation in that number. 10 out of 20 is the highest probability of individual outcome, but it's even *more* probable that something other than 10 out of 20 will occur.

So to see if the 15 out of 20 is significant, we can compare this outcome to random chance.

We can simulate 20 coin flips in a computer and then write down the number of heads versus tails. Then we do it again and write down the new results, and then do it again and again for a million rounds.

Tallying the results, we can then find the *probability* that 20 random coin tosses will equal 15 or more heads, and this will give us a way to compare the rat data with random chance. What percent of random tosses yield 15 or more heads?

This is the P-value in a nutshell: it's the probability that your measurements could be the result of chance.

Note that we can never be *certain* that the results are significant, only that there is a *probability* that the results are significant. The probability of significance is chosen by convention depending on the outcome risks. For normal scientific studies, it's 5% (P < 0.05). If you're studying a new medicine, you might want to bump that up to 1% (P < 0.01) for safety. If you're exploring subatomic physics, and the experiments are very difficult to reproduce, you might want that to be P < .00001% to be relatively certain.

The conventional value of 5% is often incorrectly attributed to Pearson. He said the 5% value makes the results worthy of more study, not that 5% value makes the results significant.

Also of note, if everyone makes studies to P 5%, then on average 1 out of 20 studies *will* be due to random chance, which means that fully 5% of all scientific studies are reporting random events.

And of course, if your degree requires you to publish, or your tenure is based on your publishing history, there are ways to adjust the results to make the significance more likely.

(For example, you can record 8 different measurements of your rats. There are 8*7 = 76 possible pairs of measurements, so on average about 3 of those pairs will correlate to within 5%. If you want to publish a paper, this is one way to do it.)

Very, very few recent scientific papers have ever been verified (by reproducing), and when later examined were found to be unreproducible.

This is leading people to lose faith in the scientific method.

Comment Re:Clever Politicking (Score 1) 403

Still, you're talking about minor variations in configuration. A completely different drive system is a whole nother kettle of fish. And you'll be amortizing the costs of producing ICE's and transmissions over far fewer units, which means costs will be higher.

It's basically the mirror image of what we have today, where the number of electric drives sold is relatively small. If as many electric cars were sold as ICE cars, the cost would plummet.

Comment Re:Illegal Immigration? (Score 3, Interesting) 318

The numbers really don't support the idea that illegal immigration is a significant driver here. While it's always *possible* for someone to bring in measles, measles has an incubation period of about 10-12 days, so you only have to worry about the number of people who crossed the border illegally in the last week or so.

The total number of undocumented in the US is estimated to be around 11 million (useful fact to keep in mind in the immigration debate), two thirds of whom have lived here for a decade or more. By DHS's internal estimates, about 170,000 - 200,000 people annually cross the border illegally who are not caught.

Compare that to the number of Americans who travel abroad. Last year, that hit a record sixty-six million, twenty five million to Mexico alone. Since the vaccine has about a 2% failure rate, that means about 1.3 million non-immune Americans cross the US border legally every year, almost 10x the number of illegal immigrants. What's more Americans overwhelmingly fly in, which is significant given the incubation time of the virus. About 40% of illegal immigrants arrive by air, and these are overwhelmingly "overstays", people who enter the US illegally but overstay their visa. They are not "illegals" during the period they would be contagious.

Comment Re:People Don't Remember (Score 2) 318

It involves you even if you got your kids vaccinated.

No medication is 100% effective. About 2% of recipients fail to develop resistance -- more for patients using "alternative" vaccination schedules. Also for a significant number (about 5%) of patients immunity wanes after about ten years.

What this means is that everybody depends on herd immunity. Unless you've had wild measles, that includes you as an adult who received the vaccination decades ago.

Comment Re:Correlation is not causation (Score 4, Insightful) 293

You are operating under the assumption that people (or even a subset of people) are rational. Here's a simple test: does "gut" instinct play any part at all in your decision making processes? If so, you are at least to some degree irrational. Don't feel bad, you have lots of company: the rest of the human race.

If you look at the historical efforts of venture capitalists, you have to conclude that they're as irrational as anyone else. What injects realism into the process is failure. The thing is, having a bias against female team members doesn't necessarily result in failure. It results in narrowed opportunity for success, but if the rational aspects of the VCs decision processes bias those decisions enough to success, he'll still make money, and he'll feel completely vindicated in his mistaken belief in his rationality.

It's a case of the dog that didn't bark -- in this case the investment that you didn't take that would have made you a ton of money. However, now that this is out, it's possible that some smart VCs will start looking for undervalued opportunities. It will only be a matter of time before we have our first female rock star tech entrepreneur, and that will change things.

Comment Re: It makes sense (Score 1) 879

The medically accepted definition of schizophrenia implies specific things that would interfere with performing certain job duties. If you extend the definition of schizophrenia to include stuff outside those criteria like gender identification, then the use of the label to determine fitness for some particular job logically would have to change from "schizophrenics should not perform this job" to "some kinds of schizophrenics should not perform this job." Because you're no longer talking about the same thing.

There is an ongoing effort in psychology to improve definitions, and it constantly wrestles with the conflicting needs of having to assign a label to every patetient's condition, and knowing what to do when that label applies to someone. Having broad labels makes applying the label easier but it also makes knowing what to do harder. That's why the APA is constantly introducing new conditions nobody has ever heard of, like "dysthymia". Formerly that condition would have been considered "depression", but it turned out the conditions people had that used to be labelled "depression", while in a certain sense analogous, had different implications and had to be approached differently.

Transgender people used to be given a diagnostic label "schizophrenia", but if you are familiar with abnormal psychology you'll know that that label was hopelessly vague; it threw in people who "felt" an affinity for a different gender with people who heard voices telling them to do things. These are entirely different things, which is why we now have "Gender Dysphoria".

At one time homosexuality was commonly lumped in with hearing voices as "schizophrenia"; this largely predates DSM-1, which thoughtfully (for the time) gave homosexuality its own disease category. Now that a lot more gay people are out, they seem self-evidently normal, except for their sexual preference.

Comment A political issue (Score 2, Interesting) 318

Medically - politically - I have to look at the calendar everyday because it feels like I'm in a time warp and it's really 1917.

We, the USA, are getting dumber.

One thing you have to realize is that political issues are never black-and-white, but there are shades of grey. Issues have both positive *and* negative aspects, and it is up to us to assign an inherent value to the plusses and minuses in each case.

Vaccination in the US is all tangled up with immigration and foreign culture.

Measles is brought in by travellers from foreign countries and spurred mostly by immigration - going to visit relatives back in the home country, or having relatives come to visit. Neither of which is a problem, but it adds a small negative value to unrestricted immigration.

A couple of years ago I read about some Islamic groups in Pakistan who intentionally avoided the (freely offered) polio vaccine, and also avoided having polio-laden children *treated*, thinking that if they could somehow get the children into the US they could attack us that way(*).

A few years earlier I read about a California school system with 7,000 students and only enough money for 5,000 vaccinations, but of those 7,000 students 1,500 were illegals. The controversy was about "who gets the vaccinations", and whether we should put tax-paying citizens at a disadvantage by vaccinating foreign nationals for free.

You could definitely say that people are stupid for not getting vaccinated, but you could also say that curbing immigration would help, immigration adds a burden of cost to our society, and that sometimes other cultures and practices will get in the way.

The stupid answer is to have unlimited immigration and also insufficient funds for vaccination. If we have unlimited immigration, we should absolutely be willing to bear the increased medical costs simply for the protection of our own people.

Whether unlimited immigration is worth the increased costs is now a political issue that you can judge for yourself, and perhaps we should poll the population for consensus. Take all the positives and their inherent value, and compare to the negatives and *those* values.

Vaccination is the correct choice, but it's become partly a political issue.

(*) And it didn't help that the CIA used foreign vaxxing programs as a way to locate and register persons of interest.

Comment Re:Sample bias (Score 2) 211

While this is true, 87 of 91 is an astonishingly high proportion.

Under the "no effect/sampling bias" hypothesis, the brains donated for NFL players would be reflective of the general population of people who suffer from dementia. That would mean that Alzheimer's and vascular dementia would account for the vast majority of cases. The chances of a random sampling of 91 dementia brains turning up 87 cases of traumatic injury is vanishingly small, meaning that it is quite reasonable to conclude that playing football professionally had something to do with the rate of CTE in this sample. So given that these results hold up, the next logical question is whether the difference in this sample are due to the obvious hypothesis -- that they resulted from playing football -- or some confounding factor as yet unidentified.

Real-life data is never perfect, which is why we do laboratory experiments -- where such experiments are feasible and ethical. But "imperfect" is far from useless, and if this study holds up, then I'd say the burden of proof is on the hypothesis that there was some kind of confounding factor.

That really is the essence of science; it's not about establishing truth, it's about establishing burden of proof.

Comment Re:Biggest question completely ignored (Score 1) 69

Biggest problem is having like 2 chargers for every 1,000 or 10,000 cars.

What are you talking about? Tesla's supercharger map alone has 909 supercharger stations with 6118 superchargers, over half of which are operational. That's one supercharger per 60 cars sold, not "2 chargers for every 1000 or 10000 cars". And given that EVs spend the vast majority of their time charging at home, that's actually a huge ratio of chargers to cars.

As for costs: supercharger stations cost roughly the same to build as gas stations. They cycle vehicles much more slowly through, but their profit margins are much higher, as their operating costs are much smaller. They buy power at industrial rates (say, 6 cents per kWh) and sell it for $0.20/kWh or so and require no overhead for arranging deliveries or the like.

Your comment about 400V three-phase power makes little sense. If you're talking AC then you're talking onboard chargers, which don't use three-phase, are not 400V, and are limited in capacity. Are you meaning to talk about AC charging or DC?

Are you even talking about fast charging or slow? Adding slow chargers is an easy "loss leader" for businesses, in that the power costs so little, you earn goodwill, and if anyone actually wants to draw a meaningful amount of power then they're going to be spending long periods of time at your store. Charging can be as simple as an outdoor 120V (US) / 220V (Europe) outlet, although you'd usually prefer something like a J1772 connector.

EVs spontaneously bursting into flames is not exactly a common occurrence. EV fires have occurred during charging, but it's been very rare, and is a sign of manufacturing defects, generally in the charger (not the battery pack). Most EV fires have been in severe car accidents; however, the rate per mile seems to be significantly lower than gasoline car fires.

As for the amount of power needed, that depends on whether you're talking unbuffered chargers or battery-buffered chargers, and what rate charging you're discussing. Unbuffered chargers require lines with a high peak capacity, but rarely make use of that full capacity. They're cheaper to buy, but mean you pay for higher rates for having the connection. Buffered chargers are more expensive to buy, but can be installed on any line so long as the average draw can be provided for by the line. E.g. if you put a buffered supercharger out in the middle of Canyonlands and it was visited by only one EV per week (needing say 50kWh of power), you could power it for decades on end with nothing more than 7 square meters of solar panels costing $2k and making a couple hundred watts of power. Now, even an unbuffered supercharger will cost you in the upper 5 figures, so it's probably not worth it to stick a supercharger out in the middle of Canyonlands, but just saying... ;) For infrequently visited sites, having a solar awning over the charger can provide most to all of the power.

(The lower the peak power, the cheaper a charger is - and AC chargers are cheaper than DC, but limited to whatever the EV's onboard charger can handle. Little AC chargers directly wired into the wall and delivering 5-20kW generally cost only $500 or so, plus installation costs)

Comment Re:Biggest question completely ignored (Score 3, Interesting) 69

Even Tesla's super-charger takes at least an hour to fully charge the small capacity batteries.

1) Tesla's batteries are "small capacity"? 4-5 hours highway driving time per charge is "small capacity"?

2) Actually, it takes 125 minutes to fully charge a Tesla pack. But it takes only 30 minutes to charge one to 80%. There's a taper over the course of a charge, so the higher you want the percentage, the slower it gets.**

3) Supercharger V2 is 120kW per vehicle / 145kW shared, but the upcoming V3 is going to be "over 350kW". That could potentially up the speed in the first ~50% or so of a charge, although more dramatic improvements will also require battery pack improvements.

** - Basically, early in the charge, almost all of the energy you pump in becomes stored as fast as you can get, with only a tiny fraction converted to heat. As cells begin to fill up (unevenly), however, the incoming power is increasingly turned into heat. The charge rate must consequently be reduced to avoid excessive cell heat during charging, which is one of the biggest contributors to reducing cell lifespans.

Slashdot Top Deals

Money isn't everything -- but it's a long way ahead of what comes next. -- Sir Edmond Stockdale

Working...