Recently in Misc Category


July 19, 2012

The other day I went to Home Depot to buy some party supplies (incidentally, check out the party invitation here and the bonus Web site here. It's some of my better work.). One of the things I wanted was a set of rope lights. I eventually picked up three sets of 48' lights for $36.48. However, when I went to ring them up (you know Home Depot is almost all self-check, right?) two rang up at $62.48.

Looking closely, what happened is that the lights were packaged in clear plastic clamshell packaging with two paper labels, one in the front and one in the back. The paper label in the front showed the 48' lights listed above. The back label (the one with the bar code) showed 27' LED lights (LEDs are cooler and cool == expensive). It took a while for Home Depot to sort the problem out. Customer service's initial reaction was that someone had returned a set of the cheap lights but swapped the back labels so that they could get a larger refund. But then they had some more lights pulled off the shelf and they were mismatched as well, so things started to look a bit confused. Eventually, they just pulled the back pages out of the package (I guess to make it hard for me to do a return) and sent me on my way.

Here's the screwed up thing: nobody in this entire transaction was sure which set of actual lights I had in my hand. The matching package (the one which had rung up as expected) looked a lot like the other two packages, but really these things look pretty similar and after all we didn't know that any of the packages was right. I offered to take them out and measure them for length, but nobody seemed interested. So, at the time I walked out the door it seemed quite possible that Home Depot had sold me $188 worth of lights for $109. Of course, I assured them that I would bring them back if they turned out to be the LED lights, but they had no way of knowing I actually would (or of verifying if I did or not). I actually tried to explain this several times, but nobody seemed to care and eventually I gave up and left.

Turns out that they were the right lights after all, though.


February 25, 2012

Disclaimer: I am not a car guy. Read the following with that in mind.

As long-time EG readers will know, I've complained in the past that my Prius has a feeble starter/electronics battery which is easy to run down even by leaving the interior lights on. This despite the fact that the Prius has a huge battery running the hybrid system to draw on. But I certainly didn't want this. Michael DeGusta reports that if you leave your Tesla parked for a long time (like months), then the car bleeds enough power off of the battery to run the auxilary vehicle systems [parasitic load] to drain it down into deep discharge (and hance damage to the battery) territory:

A Tesla Roadster that is simply parked without being plugged in will eventually become a "brick". The parasitic load from the car's always-on subsystems continually drains the battery and if the battery's charge is ever totally depleted, it is essentially destroyed. Complete discharge can happen even when the car is plugged in if it isn't receiving sufficient current to charge, which can be caused by something as simple as using an extension cord. After battery death, the car is completely inoperable. At least in the case of the Tesla Roadster, it's not even possible to enable tow mode, meaning the wheels will not turn and the vehicle cannot be pushed nor transported to a repair facility by traditional means.

The amount of time it takes an unplugged Tesla to die varies. Tesla's Roadster Owners Manual [Full Zipped PDF] states that the battery should take approximately 11 weeks of inactivity to completely discharge [Page 5-2, Column 3: PDF]. However, that is from a full 100% charge. If the car has been driven first, say to be parked at an airport for a long trip, that time can be substantially reduced. If the car is driven to nearly its maximum range and then left unplugged, it could potentially "brick" in about one week.1 Many other scenarios are possible: for example, the car becomes unplugged by accident, or is unwittingly plugged into an extension cord that is defective or too long.

When a Tesla battery does reach total discharge, it cannot be recovered and must be entirely replaced. Unlike a normal car battery, the best-case replacement cost of the Tesla battery is currently at least $32,000, not including labor and taxes that can add thousands more to the cost.

There's been a lot of controversy about this report (see, for instance, this defense), but Tesla's response seems to by consistent with DeGusta's basic argument, as does the letter that Jalopnik reproduces above:

All automobiles require some level of owner care. For example, combustion vehicles require regular oil changes or the engine will be destroyed. Electric vehicles should be plugged in and charging when not in use for maximum performance. All batteries are subject to damage if the charge is kept at zero for long periods of time. However, Tesla avoids this problem in virtually all instances with numerous counter-measures. Tesla batteries can remain unplugged for weeks (even months), without reaching zero state of charge. Owners of Roadster 2.0 and all subsequent Tesla products can request that their vehicle alert Tesla if SOC falls to a low level. All Tesla vehicles emit various visual and audible warnings if the battery pack falls below 5 percent SOC. Tesla provides extensive maintenance recommendations as part of the customer experience.

At present, then, the agreed upon facts seem to be that:

  1. If you leave the Tesla's batteries at zero charge, battery damage occurs.
  2. If you leave a Tesla unplugged for long enough, even with a charged battery, parasitic load from the vehicle systems will eventually consume the battery's charge, leaving you in state (1) above. [Note that this appears to exceed the Lithium-Ion self-discharge rate, so it likely is parasitic load.]

The controversy really seems to be about who's fault this is, namely whether the customer should have known better, whether Tesla notified them correctly, etc. I don't have a Tesla so I don't care about that. I'm much more interested in the engineering question of what's going on and what, if anything, can be done about it.

The parasitic load thing isn't totally unfamiliar territory, of course. Any modern vehicle has electronics and those need power, which they get from the battery. Some do a better job than others. My BMW R1200GS motorcycle, for instance, has this problem and the manual explicitly tells you to connect it to a trickle charger (an expensive BMW model, of course, though you can use a standard one if you're willing to do a tiny bit of work) if you're not going to drive it for a while, and I duly plug it into the wall whenever I get home. If you don't do that, however, the worst you're going to be out is new lead-acid battery, which depending on what vehicle you have, leaves you out something like $50-$200, not $40,000.

However, the level of load we're talking about here seems awful high. Remember that we're talking about a battery capable of powering your car for 200 miles or so on a single charge (53 kWh). In order to deplete the battery in 11 weeks (~2000 hrs) you would need continuous battery consumption of around 30 W. For comparison, a Macbook Air has a 50Wh battery and gets something like 5 hours on a charge, so it's like the Tesla is running 5 Airs at once 24x7. It's natural to ask where all that power is going, since you don't need anywhere near that much to keep a vehicle on standby. One likely source seems to be the battery cooling system, of which Wikipedia says "Coolant is pumped continuously through the ESS both when the car is running and when the car is turned off if the pack retains more than a 90% charge. The coolant pump draws 146 watts." [Original reference and long discussion here. Note that this post is due to Martin Eberhard, one of the Tesla Founders but apparently no longer with the company at the time he wrote it. Thanks Wayback Machine for preserving this!].

Obviously, if you have a load this high, then you're going to deplete the battery. The question then becomes whether there is some way of avoiding permanent battery damage as the depletion gets to dangerous levels. The natural thing to do is install some sort of cutoff that turns off all power drain once you get close to that level. This may end up blowing away a bunch of the car's configuration (though really, it's not that hard to store that stuff in flash memory, even though historically manufacturers have tended not to), but surely it's cheaper to reboot your car than replace the entire battery pack. However, if the power is going to the cooling system and the cooling system is doing something important, like keeping the battery from being damaged by excessive heat, then this may not help.

Oh, one more thing. DeGusta claims that Tesla has the capability to remotely monitor the battery and locate the car, and has sent people out to fix it:

In at least one case, Tesla went even further. The Tesla service manager admitted that, unable to contact an owner by phone, Tesla remotely activated a dying vehicle's GPS to determine its location and then dispatched Tesla staff to go there. It is not clear if Tesla had obtained this owner's consent to allow this tracking5, or if the owner is even aware that his vehicle had been tracked. Further, the service manager acknowledged that this use of tracking was not something they generally tell customers about.

If true, that would be... interesting.


January 22, 2012

On my way to Red Rock today to do some work, I looked in my wallet to see if I had enough money to afford my hot chocolate (paying for a $3.50 drink with a credit card is a pretty lame move). Here's what I found:

After some sorting, it comes out as follows...

Currency Count Value (nominal) Value (USD)
USD 3 3 3
CAD 7 100 98.55
CZK 2 2100 106.40
GBP 1 10 15.55
EUR 1 20 25.79
INR 1 100 1.99
RUB 9 1570 49.97
Total 24 - 301.25

In other words, out of 24 total pieces of paper valued at over $300, I had three spendable pieces of paper valued at $3. Oh, and a couple of United beverage vouchers which expire in 9 days. I ended up going to the ATM.


January 11, 2012

In Dahlia Lithwick's report on FCC v. Fox (about the FCC's TV indecency policy), she writes:
Justice Stephen Breyer raises a question about why the ABC ass case is being heard together with the fleeting-expletives case. Justice Ginsburg asks whether Hair could be broadcast on network television (Verrilli: "Serious questions") and then whether the opera Metropolis could be broadcast (Verrilli: "Context-based approach"). Then Justice Anthony Kennedy interrupts the parade of naked horrible to clarify: "What you're saying is that there is a public value in having a particular segment of the media with different standards than other segments." Verrilli replies that, yes, this is about preserving "a safe haven where if parents want to put their kids down in front of the television at 8:00 p.m. they're not going to have to worry about whether the kids are going to get bombarded with curse words or nudity."

Because if you want that, you can find it in the back seat of my car, at rush hour when we're late for Kung Fu. Just ask my children.

Kennedy replies that the V-chip is available and that "you ask your 15-year-old, or your 10-year-old, how to turn off the chip. They're the only ones that know how to do it."

I'm not saying this isn't true--though I rather suspect it's more likely that parents don't know how to turn on the V-chip [explanation here, in case you don't know] than that they don't know how to turn it off. However, I think discussion illustrates pretty clearly the confusion over the problem that people are trying to solve. (The terminology "threat model" as applied to children probably sounds funny to non-parents.) In any case, there are two different things one might be trying to accomplish with respect to potentially objectionable content:

  • Prevent children from inadvertantly accessing objectionable content.
  • Prevent children from intentionally accessing objectionable content.

If your objective is the former, then the V-chip works fine (except for the horrible UI); you just configure your device to suppress objectionable content. The sort of content-based regulation the FCC is engaging in works as well, assuming you don't let your kids watch TV except in the "safe" period, but it's a very inefficient mechanism compared to the V-chip, being both overbroad (affecting everyone, including people who don't have children) and not very effective, as it applies only to broadcast TV.

On the other hand, if your model is to prevent children from intentionally accessing objectionable content, and you further expect them to attempt to bypass content controls, then restrictions on broadcast TV don't do very much given that (a) if you have cable your kids can just tune to unrestricted channels and (b) large number of other sources of such content exist on the Internet. Blocking the tiny sliver of such content you still get through broadcast TV mostly looks silly and anachronistic. Though I guess it's less silly if you get hit with a huge fine for breaching the rather unclear rules.


October 2, 2011

As veteran Star Trek viewers know, Starfleet cadets take the Kobayashi Maru test. The details of the test don't matter; what matters is that it's a simulation exercise designed so that there is no way to win, and either the cadet in command lets a bunch of innocent people die or their ship gets destroyed. As Spock puts it in the 2009 Star Trek reboot, the purpose of the test is "The purpose is to experience fear. Fear in the face of certain death. To accept that fear, and maintain control of oneself and one's crew. This is a quality expected in every Starfleet captain."

I don't really see how it does this, though, because everyone knows that the test is unwinnable and that everyone dies. This makes it pretty hard to obtain the requisite level of immersivity; as games designers know well, getting people to immerse themselves in your simulation game isn't just a matter of having realistic graphics, but also of having there be just the right balance of control and uncertainty. Games which are too easy (e.g., playing in god mode) or too hard (where you clearly can't survive at all), are very hard for people to take seriously, which would seem to be a critical element if you want people to "experience fear".


August 30, 2011

Mrs. G and I watched Watchmen last night. I don't think this is a film I would have really wanted to see without having read the graphic novel, but it's interesting to see how they've adapted it. Like many of the recent films based on comic book graphic novel "classics" (and indeed director Zack Snyder's previous 300) it is visually and thematically a reasonably faithful adaptation. Mostly, it works less well in this format: elements that in the novel are like woah heavy feel more like heavy-handed when transferred to film. The one big exception here is Rorschach's journal: the same inner dialogue that feels gritty when printed on the page comes off totally differently when turned into a pompous Blade Runner-style voiceover that really hammers home what a complete psycho Rorschach is.

Spoilers below. Though, really, if you haven't read Watchmen yet, you're probably not going to and so they're not much in the way of spoilers.


August 22, 2011

The process of turning raw wool into fabric by hand is extremely time consuming. Prior to the Industrial Revolution, the production process operated in a pyramid, with a large number of carders supported a smaller number of spinners, supporting an even smaller number of weavers [Note: weaving is much faster than the other two major technqiues for turning yarn into cloth: knitting and crocheting]. I've heard varying numbers, but Wikipedia claims that the ratio was around 9:3:1.

Isn't it interesting, then, that when you look at the list of common American surnames, which are often associated with occupations, that "Weaver" appears at position 190 (.05% of the population) but "Spinner" appears at 1/50th the rate, at position 7393 (.001%). Carder is at 4255 (.003%); Carter is, I would assume, a different profession. [The first 10 names, btw are: Smith, Johnson, Williams, Jones, Brown, Davis, Miller, Wilson, Moore, Taylor].

I'm not attempting to claim that there's some direct relationship between last name frequency and historical occupation rates, but it's still entertaining to speculate on the cause. My initial suggestion was that carding and spinning were more likely to be women's work and of course in the West women's surnames don't get propagated. Mrs. Guesswork suggests that spinning and carding weren't professionalized the way that weaving was [prior to the invention of the spinning wheel, spinning technology was extremely low-tech], so you might spin or card in your spare time, but weaving requires enough capital equipment that you would expect it to be done professionally and thus be more likely to get a surname attached to it.

Equally likely, of course, is that it's just coincidence, but what fun would that be?


June 23, 2011

Today's XKCD quite correctly points out that if you're unfamiliar with some aesthetic experience (his example is wine), you're willing to tolerate any cheap crap, but once you have some experience, you tend to develop some taste. Inevitably, you find yourself preferring some varieties of that experience more than others.

Arguably, developing taste is a good thing, since, as Munroe has his character suggests, it opens up whole new vistas to you—albeit at the risk of turning you into an annoying snob.

There's another downside too, though: it tends to be expensive. This isn't inevitable, of course: after sampling a whole bunch of whiskeys you might find that you prefer Jack Daniels ($16.99/750) to Macallan 25 ($649.99), but assuming your neural architecture isn't too different from the rest of humanity—and perhaps you take your cues from your peers—it seems likely you're going to find that your tastes line up with others. And as things which are in demand naturally tend to be more expensive, you're suddenly going to be expending a lot more money on the same general class of experience. [I don't think the market's natural response to produce more of a desirable product helps out here, since you can almost always invest more and more input into some product (use the best grapes, age it longer, etc.), in the interest of creating an ever more exclusive and allegedly better version.]

Of course, the mere fact that you're shelling out more money doesn't necessarily mean you're worse off, since the counter-argument would go that you're getting more hedonic value out of the better product. I'm not sure that's true, though, since you habituate so fast. When I first started eating sushi, I was happy to eat the cheap stuff, but now that I've had reasonably good sushi, I'm not prepared to go back. Seems like a good reason to stay away from Masa.


May 28, 2011

I've been listening to Gregory Clark's World Economic History -- Pre-Hsitory to the Industrial Revolution class on iTunes U. The class, taught out of Clark's popular A Farewell To Alms, is devoted to Clark's thesis that prior to the Industrial Revolution all humans mostly lived on the Malthusian frontier [*]. That is to say that the population level is maintained in equilibrium between population and resource levels/income. Anything that adjusts these factors temporarily removes the system from equilibrium, but homeostasis quickly reasserts itself. So, for instance, if there is some new technology that increases crop yields, people respond by having more children or by living longer (whether consciously or because being better fed makes you more fertile and live longer) and thus population increases with little or no likely impact on overall standard of living. Thus (Clark argues) there was nearly no net improvement in standard of living from the Neolithic to the Industrial Revolution.

As I understand it, Clark argues that two factors acted to change this state of affairs. First, technological change accelerated to the point where the the amount of resources that could be exploited was changing faster than the time scale on which birth and death rates responded, keeping the system permanently out of equilibrium. Second, people started practicing real fertility control, which acts to damp the population response to higher income levels (and of course there are natural limits on how much lifespan can increase solely on the basis of income.) [There's also a whole bunch of stuff about how these changes are due to cultural and biological evolution as a result of differential reproduction between the rich and the poor, but I don't want to talk about that just yet.]

Much of the first half of the course is devoted to explicating the model, and in classic counterintuitive economist style, Clark makes a big point about how in the Malthusian world, things that you ordinarily think of as good are bad, and vice versa. To take on example, if a horrible disease gets introduced into your society so that it increases the death rate by 10%, that leaves more resources for everyone else with the result that the people who don't die of plague have a higher overall standard of living. Here's Clark's Table 2.2 (page 37 of "A Farewall to Alms"):

Malthusian "Virtues" and "Vices"
Fertility limitationFecundity
Bad sanitationCleanliness
Harvest failuresPublic granaries
InfanticideParental solicitude
Income inequalityIncome equality
IndolenceHard work

Note the scare quotes around virtues and vices. Clark sort of equivocates between the view that societies with short life spans and high material standards of living are really better and the view that income levels are just one instrument. For instance, on page 36 he writes:

In summary table 2.2 shows Malthusian "virtues" and "vices." But virtue and vice here are measured with reference only to whether actions raised or lowered material income per person.

This sort of supports the "it's just an instrument" view but then on page 38 Clark writes:

The failure of settled agriculture to improve living conditions, and the possibility that living conditions fell with the arrival of agricultire, have led some economists, anthropologists, and archaeologists to puzzle over why mankind abandoned the superior hunter-gatherer lifestyle for inferior agrarian societies.

This argument isn't a new one. In fact, this specific form of the argument was famously made by Diamond's The Worst Mistake in the History of the Human Race. Clark comes back to the more general theme repeatedly, and suggests in a number of places during the class that people in fact would prefer to live in societies with a lot of disease and violence but correspondingly higher material living standards (though again, there is some ambiguity about the level to which he is actually endorsing this view.)

It seems to me that one ought to raise at least two objections to this general line of argument. First, it's not at all obvious that it's that useful to assess people's welfare by their income level (or as I once heard it put more crudely, by the number of calories they are able to consume per day.) [I wish I could remember where I read this.] First, to a great degree human sense of how happy they are is positional, so if everyone in society gets 100% richer, that doesn't make everyone 100% happier, it's just that instead of being jealous of the guy next to me at the stop light in his Audi RS4, I'm now jealous that he has a 911 Turbo; not much of a net win. Second, in the Malthusian model a lot of the "virtues" that result in a higher standard of living are things people find really unpleasant. In particular, random violence, crop failures, and disease (and uncertainty in general) is incredibly stressful (see Sapolsky's Why Zebras Don't Get Ulcers for a good primer on this.) It's not clear at all that people in general would rather trade much higher rates of catastrophic events for a somewhat higher level of expected welfare if you survive. Clark does offer some arguments that people make choices along these lines, for instance that people voluntarily joined the East India Company even though the risks were very high, but it's not clear that it's really that useful to use the risk/reward behaviors of 20-year old male adventure seekers as a stand-in for the entire society.

Even if we are to concede that people are individually happier in societies with high violence and disease rates (and hence lower populations) but high standards of living than they would be in societies with lower violence and disease rates (and hence higher populations) but correspondingly lower standards of living, that does not mean that those societies are truly more desirable. (See, for instance Parfit's "Only France Survives" in Reasons and Persons). Surely, most people in societies with a low standard of living would nevertheless prefer to be alive than dead, even if dead would mean that other people would live better, so it's difficult to say that the society with the lower population is better, especially when that equilibrium is obtained by high death rates (i.e., the killing of people who exist and have their own interests) rather than low birth rates (i.e., the nonexistence of people who might otherwise exist.)


May 9, 2011

MSNBC (from Reuters) reports that Sen. Charles Schumer wants Amtrak to create a "no-ride" list for trains (þ Volokh):
Schumer, citing U.S. intelligence analysts, said attacks were also considered on Christmas and New Year's Day and following the president's State of the Union address.

He called on the U.S. Department of Homeland Security to expand the Secure Flight monitoring program, which cross-checks air travelers with the terror watch list in an attempt to prevent anyone on the "no-fly list" from boarding, for use on Amtrak.

Such a procedure would create an Amtrak "no-ride list" to keep suspected terrorists off the U.S. rail system, he said.

This is one of those situations where reasoning by analogy can lead you seriously astray. Airplanes are an unusual case not so much because they are uniquely vulnerable, but because they are uniquely secure. It's true that planes are relatively fragile in that a small amount of explosive can kill a lot of people, and that even small accidends tend to kill everyone. [This is only a partially unique property, though, so a full account of why planes are such an attractive target surely needs to involve some social and psychological factors.] However, they are also ordinarily well protected, so it's hard to get access to them to do damage. At least in theory planes are kept in secure conditions on the ground so it's hard to place a bomb, and obviously once they're in the air it takes something like a surface-to-air missile (or least good luck with a gun) to cause catastrophic damage. This means that if you want to attack a plane, it's very convenient to actually be on it, so it's at least arguably useful to keep suspected terrorists off the plane.

But this doesn't apply to trains, which are (a) not particularly well secured and (b) easily accessible when they are in transit, which means you need to secure hundreds of miles of track. This means that if you want to attack a train, you don't need to be on it, you just need to get access to the track and damage it at the right time. (See here for a list of train accidents). It's like these guys have never seen Bridge on the River Kwai.

Even if that weren't true, it's important to remember that while planes are already a limited-access type thing, trains often are not. Amtrak may do some kind of passenger identification there are lots of commuter trains (e.g., Caltrain) where that not only aren't passengers identified, you can get on the train without a ticket. Instead, the conductors just come by periodically and audit. Converting to a system where you actually checked ID for each passenger before they got on (and remember that something like 50-100 people might get on in 2 minutes on an open platform) seems like it would be prohibitively expensive. These trains don't carry as many people as some Amtrak trains, but they certainly have enough passengers that if you could kill a significant fraction of them it would be bad. And this doesn't even get into the question of subways. In general, train security is set at a level designed to deter fare evasion, not to protect the train itself.

Even if you think that airplane security is set at an appropriate level (which IMHO it probably isn't) this seems like a security measure which comes at a huge amount of cost and very little benefit.