koblenski

Thanks, for another good introduction to DSP, there's this excellent website: http://jackschaedler.github.io/circles-sines-signals/index.h.... It also has good animations, and some are more interactive than mine. It takes a bit of a different path through DSP concepts, and focuses on the relationship between circles, trigonometric functions, and signal analysis.

For a more in depth study of DSP, I would recommend this book: http://www.amazon.com/Understanding-Digital-Signal-Processin.... It's quite readable for a textbook, and from my experience with linear algebra and signals and systems texts (they're all related), it's more understandable.

It would be nice to have a full online, animated DSP book, as that's a natural fit for DSP, but I'm not aware of something like that, yet. Maybe these posts could be the beginning of something like that.

(edit: Amazon link)

That's a good point. I couldn't stand the lectures in the few edX courses I took, but the slides and notes could be more beneficial. Although, I tend to prefer the better continuity of books when reading, and there are tons of great books out there. Of course, getting through books takes a lot of intrinsic motivation while Coursera or edX courses may provide the extra motivation that will help more people get through the whole course.

Yeah, I thought about that one, too. I felt like he covered a lot of the same stuff in other posts I included, but that was definitely a good one. It would have made the list a nice even 2^4.

I think another aspect of improving the problem of ugly comments is figuring out more ways to encourage insightful, constructive comments while making it worthless to post hateful things. HN seems to have figured out how to do this reasonably well, but it's somewhat specific to the community that has grown up around it and that community has shown a willingness to defend itself. How can a similar system work for more general audiences at news sites and forums, much less sites like YouTube where the comments are almost universally horrible?

I think making incivility even worse than worthless would be a start. Make it a waste of the poster's time. Make it so the ugliness can be completely ignored, taking away the influence and attention that the poster seeks. Make it reflect badly on the poster somehow so they will have an incentive to not post their hate.

I always thought these kinds of policies would have to come from the community, but the idea of AI doing some of the work is intriguing. It may seem far-fetched now, but like so many things, starting the work and making progress will probably lead to great advances.

Maybe things like Discourse will make progress here, and I know Jeff Atwood believes just as passionately about civility on the internet as Eric Sink expresses in his post. But those kinds of systems would have to be adopted more universally to make that big of a difference. I sincerely hope that happens.

That's a really good point. I didn't want to get into nonlinear solvers for this post, but I should have mentioned the considerations, at least.

I should have noted that and said polynomial regression is linear regression of nonlinear data. Thanks for the correction.

Yes, there was plenty of abuse going on, and the I.F. thought that abuse was necessary for survival. They never stopped to think if there was possibly another explanation for the first two wars with the buggers and the following calm. They relentlessly pursued extermination of another intelligent life-form at the hands of an innocent minor. In the end it was far from clear whether any of that was necessary, and that is where the biggest uncertainty lies.

It sucks that that was the path they chose, but I can't say that it's something humanity isn't or wouldn't be capable of.

Thanks for the tip on the Reasoned Schemer. It was on my book list, so I'll have to bump it up to the top. Sounds like I'll enjoy it.

Battery energy density is improving at about 7% per year. (http://www.greencarreports.com/news/1074183_how-much-and-how...). After 10 years, that's a 97% improvement. If one of the new battery technologies becomes feasible with all of the new investment in battery research, there could be a much bigger jump in energy density before then.

Many of the arguments claiming that Moore's law would end were based on the physical properties of light in lithography and the material characteristics of silicon substrate and gate oxide interactions. These are issues that people thought were physical limitations, but we found ways around them.

Theoretical max efficiency of PV also relies on assumptions about the physical properties of light in absorption and the materials being used. I'm not saying we know how to get around these limitations right now. I'm saying that we can't predict future innovations that will make the impossible possible.

Summer peak sun hours will be much more than the annual average, when road trips are normally taken. Admittedly, it's not 12 hours, probably closer to 7-8 hours.

Theoretical max efficiency still uses a number of assumptions to get to 40%. If we learned anything from the path of semiconductors, it's that we shouldn't try to predict what's impossible. According to these 10-year predictions, current microprocessors are impossible to manufacture. And so were last year's, and the year before, going all the way back to the 1980s.

I'm not going to accept that infinite range cars are an impossibility. They may be impossible with today's technology, but what about the technology we have 30 years from now? Maybe solar charging is not the way we will do it, but I'm sure we will see it happen.

The Leaf is the first mass-produced EV for sale that consumers can actually buy and own. The EV1 could only be leased.

I admit that the idea of driving on solar panel energy was more of a pie-in-the-sky idea, but it's not as bad as you're making it out to be. The Leaf's cross section is about 8 m^2. If we assume 5 m^2 can be covered with 50% efficiency solar panels and using an Earth's surface solar constant of 400 W/m^2, that would give 2 kWh of energy to the motor/batteries. If the car can be driven at 5 miles/kWh efficiency (already possible and improvements will make it more common), that adds 10 miles of range per hour of solar charging. If you drive 600 miles in 12 hours (including breaks where the solar panels are still charging), then the battery only needs to supply about 500 miles of that to drive all day.

It's a range extension idea, not a battery replacement idea.

I would say that the advice in The Pragmatic Programmer is timeless, much like The Mythical Man Month. A lot of the ideas presented there were later formalized into agile principles and practices, and are still quite relevant today.

Code Complete, on the other hand, is a little more hit-or-miss. Some parts of it are still very relevant, like how to write clear, readable code. But other parts have been supplanted by better practices. The book tends to lean more towards waterfall development approaches.

There's a fascinating discussion of this on stackoverflow: http://stackoverflow.com/questions/1525521/nth-fibonacci-num...

If you want an exact value for a particular Fibonacci number, it will take at least O(n) time regardless of the algorithm used because a Fibonacci number 'n' has O(n) digits, and it will take O(n) time to clear and set the memory for that number. In any case, there is no O(1) algorithm. There is an O(ln n) algorithm for small 'n' for which the result will fit within the processor's native data types.

I had not thought that Fibonacci numbers increased quite that rapidly, but after thinking about it, it makes sense.

That is a closed form expression, but it is not O(1) unless the processor can raise a number (an inexact floating point number, no less) to a power in constant time. The closed form expression is still O(n) because of multiplication, and the result isn't an exact number unless the constants are run out to enough precision for the value of n that is being computed.

I'm having difficulty finding articles specific to the Leaf's motor, but there's a nice explanation for EV motors in general here:

http://www.diyelectriccar.com/forums/showthread.php/why-do-e...

Basically, the motor controller limits the current below its maximum so the amount of torque output will remain constant until it drops below the current limit. There's an explanation of different current limiting methods here:

http://homepage.cs.uiowa.edu/~jones/step/current.html

The Leaf's controller likely uses an active current limiting method, and there's a lot of advances in this technology right now. That's where a lot of the motor efficiency improvements are coming from.

Surprisingly, I can't find much good info on Wikipedia, but I'm probably not using the right search terms.

What I meant was that in both cases there is essentially one gear, but I see you're point. CVT can be thought of as infinitely many gear ratios and the Leaf's is only one. I updated the article, so hopefully it's more clear.

The on-board charger is that smart. If you're charging off of a 440V quick charger and the battery gets too hot, it will shut off, and the car will send you an email telling you what happened if you've added an email address in the car's settings.

In other cases with a 110V or 220V charger, it's highly unlikely that the battery will ever be too hot to charge unless it's 120F outside and you've been pushing the car hard.

Look, it really is a minor issue that never crossed my mind until I came across the recommendation in the manual recently. It probably will impact the battery's life only slightly, but it's easy to change the timer and start charging a bit later. It's certainly true that any heat a battery sees will contribute to its degradation, especially while charging because that also generates heat. I figured I'd pass along the recommendation as an additional way to take good care of the very expensive battery.

They produce their max torque at 0 rpm and it decreases from there.

That's true in an unregulated motor, but Nissan electronically regulates the motor so the torque isn't ridiculous at 0rpm. The torque curve ends up being flat over most of the range, and it seems to start falling off around 50mph. I haven't seen a plot, so that's just my impression. I can see how the wording is incorrect, so I modified it to refer specifically to the Leaf's motor.

No documentation I have found states it has a CVT.

You're right. Fixed.

The guy that I mentioned in the article that put 78,000 miles on his Leaf has a 65-mile each way commute, and that was in Washington state with cold winters. You might be able to do it, but you'll probably need a 220V charger at your destination to charge up completely for the drive home. The 2013 Leaf is more efficient so it would do better than my 2012, but it really depends on the climate and geography in your area and how fast you drive. You'll lose charge faster at 65+mph freeway speeds because of drag.

I'm willing to bet you've never driven a Leaf, and/or you're comparing it to all-out sports cars. You can get the Leaf S for US$21,300 after the federal rebate, and you'd be hard-pressed to find a higher performance car at that price.

No, you can set the battery charge timer that's part of the car UI so that it charges at a specific time after you know it will be cool. Having said that, I used to charge immediately after driving, and it didn't cause any problems. Nissan just recommends it if you want to marginally improve your battery life, so I set my timer a half hour later.

Nissan calls it a single-speed reduction gear, and it's standard on all Leafs. I guess it's not technically a CVT, but the concept is similar.

I imagine it's the tree game. The Leaf builds a pine tree next to the speedometer, and you can complete up to 5 trees by driving as eco-friendly as possible. Then you can upload the trees you build through the car's internet connection to compete on a leaderboard with other Leaf owners.

I don't participate. I figure I'm already doing my part to save the environment, and the measly extra kWh I'd save in a month by driving like that isn't worth it. I'd rather have some fun. I do drive 55 on the beltline, but that's the speed limit. I'd only get to my destination a minute faster by going 60.

There's nothing about the car itself that limits driving normally. Even in ECO mode all of the acceleration is there. It's just farther up the accelerator.

Well, that's 1-2 miles per minute if you don't run the A/C continuously. If you were to keep the cabin at a climate controlled temperature, the Leaf normally estimates ~10% reduction in range. I'm not sure how true that is because I've never needed to do it. A couple 1-minute blasts is plenty to get me home comfortably.

I do agree that the Leaf could benefit from more range, of course. Although it should be able to handle your commute in the summer without an extra charge. In the winter it would be a stretch, especially with the heater running.

The Tesla is an awesome car, if you can afford it.

Sorry for the confusing code. I took a look back at it after reading some of the comments here, and I found that I or Blogger had mangled the post. Almost half of it was missing right out of the middle. It's updated now, so hopefully it makes more sense.

Yes, that's true. Multiple tools does pose that problem. It's a tough choice between separate tools that are just good enough and one tool that tries to do everything. Everyone probably has a slightly different way of attacking this eternal problem. It seems that we all need a personal assistant as a second brain with a perfect memory and can anticipate our needs. Wouldn't that be nice if task management software could eventually do that?

I've got a DX for reading technical books. It's great for that. If you intend on reading tech books on a Kindle, definitely get the DX or the big Fire HD! The little paper whites aren't going to cut it.

I calculated that a Leaf should break even with a Prius at about 120k miles as well. Of course, that was the 2012 Leaf, which was $4,000 more than it is now, and less efficient. Now you can get a 2013 Leaf S for $21k after government rebate, which is less than you can get a Prius II for, so you break even immediately.

Anyway, it's true that it would take me ~20 years to break even with the 2012 Leaf, but I wasn't optimizing for economy. I was optimizing for the environment.