Technology and Science Links – May The Fourth Be With You Edition

I’m in Hawaii on vacation, but I still wanted you all to have something.

Aerospace

One of these days, I am going to read up on exactly why co-axial helicopters did not dominate the design of helicopters early on, because the tail rotor always struck me as a weak point in the design.  Also, I think co-axial designs are just sexy,

Good news for the new MST3K, there are real planets made of styrofoam in space!  Fine, they are as dense as styrofoam, not made of styrofoam.  Everyone is so pedantic…

Yes, NASA, those are all great uses for your new, 3D printed fabric, but what everyone wants to know is when will it be available for people to use at the next RenFair/LARP/SCA convention?

That’s impressive, and by the time she leaves, it’ll be even more so.

SABRE engines, coming to a spaceplane near you!  (Hopefully…)

Cassini is getting in the ring.

Bio

So the artificial womb is now a thing.  Granted, this isn’t a full Uterine Replicator, but it’s a step in that direction.  It will also open up some interesting questions, like how early is too early for fetal viability, which should add a fresh wrinkle to the abortion debate. – Will linked to this last week, Sc3

There is an XPrize to develop a Star Trek Medical Tricoder, and it has some finalists.

Scientist asks someone to hold his beer, licks a frog, discovers the frog slime kills flu viruses.  OK, maybe it didn’t happen exactly like that…

Because “What The Bleep Do We Know?” wasn’t bad enough.

Cockroaches, feminist icons.

Microscopes looking at tissues blow past the 4-bit color barrier!

The Doctors of WHO are about to field test the first malaria vaccine.  This is really good news.

Well this has my attention.

An exercise pill?  Cool, but oh man, I can hear the moralizing already…

Computing

Steve Ballmer is using the power of computers to shine a light our national financial and other statistical data.

Speaking of leveraging heat for computing, we now have thermal diodes, which could pave the way for computers that can’t overheat until the parts start to melt.

Energy

A handheld turbine for use in the wind, or in water, and for not a lot of money.

It’ll dry your clothes in minutes, and drive all the dogs in the neighborhood nuts.

Using titanium to improve artificial photosynthesis (producing fuel and removing CO2 from the air).

Legal

When ridiculous professional licensing hits home.

Materials

Another plastic munching critter.

Printing glass.  Seems overly complicated, but for specific applications, it would have considerable utility.

You can also create some pretty amazing things with a boss laser engraver, that let you make interesting designs and create stuff.

I found this while looking at something else.  Interesting ideas on upcycling trash.

Robotics

Because when SkyNet comes online, we want the robots to be able to chase us down like the predators of old.

A cable driven 3D printer that keeps an eye on what it’s doing.  It not only watches what it’s laying down, but also what it’s laying it down on, to make sure the foundational surface is ready.

Rapid Liquid Printing.  Instead of printing an object in the air, with throw away support structures, print it in a vat of gel that acts to support the structure as it cures, then pull it out and hose it off.

I’m willing to grant the robot the ability to make site specific design changes, but I doubt it will be doing any actual ‘design’ beyond that.  Also, site location requires more than just a flat spot.

Simulation

This one is a pure plug for the kind of work I do.  In this case, it’s talking about maritime propulsion design.  Hrmm, I should poke around our press releases, so if there is anything else interesting.

Transportation

A bicycle tweel!  As long as I can mount an electric motor on it, I’m sold (I hate having to keep tires inflated, and I hate spokes).

Ford is making car parts out of bamboo.  Luckily, it won’t look like something The Professor put together so he could take Mary-Ann for a ride to the far side of the lagoon.

Much like the train I mentioned last time, big rigs are another ideal platform for debugging hydrogen fuel cells.

X-raying the remains of a crash test, to look for hidden damage.

Wacky And Fun

How not to design and bring to market a product, AKA what happens when engineering and marketing not only get along, but have too much budget.  Also, the Bolt blog is a lot of fun.

Modern treehouses. More, with pics.  Less Endor, more Lothlorien.

This is smart, especially given how a lot of performance bikes seem to be in a race to mount the smallest damn brake light and rear turn indicators they can on that waspy back fairing.  It’s a motorcycle, fro crying out loud, visibility is a perennial issue.  Cycles should be lit up like a damn carnival.

Down with the abominable tyranny of Base 10! – via Aaron W

Image by p_a_h


Staff Writer

A Navy Turbine Tech who learned to spin wrenches on old cars, Oscar has since been trained as an Engineer & Software Developer & now writes tools for other engineers. When not in his shop or at work, he can be found spending time with his family, gardening, hiking, kayaking, gaming, or whatever strikes his fancy & fits in the budget. ...more →

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82 thoughts on “Technology and Science Links – May The Fourth Be With You Edition

  1. The problem with anything other than a decimal system is that the names of our numbers (at least in english, tamil and mandarin*) are in base 10. That is, there is a nice regularity between what we call a given quantity (except for 11 and twelve in english. The connection between symbol and name is is more regular in tamil) and the symbols we use to represent those quantities. The reason for that is that in order to read off the number 521 in the decimal system you know that 5 is in the hundreds place, 2 in the tens and 1 in the ones places. You can therefore read it off as five hundred and twenty one. If you were asked to represent five hundred and twenty one in numerals in the decimal system, you could do that relatively straightforwardly.

    But, representing five hundred and twenty one in a dozenal system would be much harder. For us, we have to do repeated divisions over 12 just to get the representation right. The answer if my calculaitons are accurate is 375. You just cannot mechanically read off 375 as five hundred and twenty one. In order for a dozenal system to work, you would need to invent a whole new set of names for the same quantities. So we might call it something like three squazen and sevenze five. And while 100 is squazen (squared dozen) and 1000 is cuzen (cubed dozen) we start running into problems in naming 10^6, 10^9 etc.

    Not being able to mechanically read off a quantity from its numerical representation and not being able to mechanically represent a quantity in numerals is a huge defect of a numeral system. In order to mechanically read off anything other than a decimal system you would have to change the language. That is an extremely tall order. And, if you want this to go into scientific journals, you are going to have to change every major language. Practically every major world language will have to be revised. This is an impossible task. There is no way in which it is either feasible or desirable to change one, let alone every language in order to concisely represent 1/3 as 0.25 in duodecimal.

    This is the same kind of bullshit that gets people to come up with esperanto. Also, no one uses the imperial system except for americans and brits. Hell, even the supermarkets in england price fruits and vegetables on the kg. Milk is the only thing that is sold in pints and that is usually for the house brands. The only real holdover of the imperial system is for distance, which is still in miles. If you go to the doctors office, they will measure your height and weight in metric units. Why? so that they can calculate your BMI. Speedometers in cars nowadays tend to come with both mph and kph because people do drive to europe, which has adopted the metric system. While it is not strictly necessary for either the US or the UK to change, if anybody has to change it is easier to implement a metric system in the US and the UK than to implement a non-decimal system world wide.

    * For those who are familiar with french, spanish, german or italian, you can probably confirm that quantites are named decimally. I can confirm that this is the case for practically every language in south and southeast asia as well as every chinese dialect I am aware of. I doubt other east asian languages are any different. People who know russian and swahili will have to confirm whether this is the same for them as well.

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    • If you look at computers internally for integers they use a base 16 system. So I doubt anyone would use base 12 if started today. If you ever read core dumps then you get used to base 16, just like in the old days when computers (at least CDC computers) used base 8. Now for real numbers there is floating point but that takes 1/2 of a book by Knuth to explain.

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      • Yeah, French seems to have some weird old remnants of what was maybe once a base-4 system or something. (There was a joke making the rounds on the Internet a while back:)
        Ten
        Twenty
        Thirty
        Forty
        Fifty
        Sixty
        Sixtyten
        “What?”
        Four twenties
        “France, stop it.”
        Four twenties and ten
        “France you’re drunk.”

        Someone also tells me that Belgian French has some different terms for 70 and 90 as well.

        What I know of German numbers, it’s like English, but the numbers get really long and tedious once you get past thirty or so.

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          • It is the power of underlying assumptions about how things work.

            I am currently working on a piece about how bases on balls were scored in early baseball. The mental framework was that if a guy got on base there were two possible ways to account for it: either he got a hit or a fielder made an error. There were no other possibilities. So bases on balls were scored as errors by the pitcher. But this didn’t really work for purposes of batting average of ERA. They circled around this for about two decades, never being able to quite figure it out. Eventually they backed into the idea that there could be more ways to get on base besides hits and errors. This also let them finally figure out the fielder’s choice.

            The confusion seems strange today. Neither category of “hit” or “error” works? Then clearly this is another category. What’s the problem? It is totally obvious in retrospect. I imagine that the concept of zero was like this.

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              • Heh. Maybe that’s why they tell kids about irrational numbers so early; like the K9 Corps in Starship Troopers, the only way to handle it is exposure during early brain formation. Adult non-sensitized brains, when they internalize the information, go into a nonrecoverable psychosis pattern.

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        • Yeah, German decimal names are similar to English. The only odd part is after twenty, the single units precede the tens:

          one-and-twenty, two-and-twenty, etc.

          Then when we reach one-hundred, it reverses:

          hundred-one, hundred-two, etc.

          Then reverses again:

          hundred-one-and-twenty, hundred-two-and-twenty, etc.

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          • IIRC English used to do this to but switched at some point. If you look at old literature a 21 year old would say they were “one and twenty”. I think you can find examples of this in Victorian literature, maybe later stuff. It might also be one of the linguistic splits between English English and Americanized English.

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            • Could be, I see different examples by looking at the original King James Version of the Bible:

              “And Eber liued foure and thirty yeeres, and begate Peleg.” (Genesis 11:16)

              “And the dayes that Dauid raigned ouer Israel, were fourty yeeres: seuen yeeres raigned hee in Hebron, and thirty and three yeeres raigned hee in Ierusalem.” (1 King 2:11)

              Spelling conventions were emergent in 1611, and it would appear that numbering order was too.

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        • I could be totally wrong about this – it was probably something I misread on the internet – but French students are marginally slower at mathematics than average because they use a (slightly) base-20 system, and the calculations take longer. Chinese has a different word for each number, and Chinese students are the fastest at mathematics.

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    • As a teenager I was very impressed by Asimov essays on this kind of stuff: number systems using a more efficient base, improved calendar design, and so forth. As abstract mental exercises they are fine, but they don’t hold up to even modest scrutiny as practical proposals.

      Come to think of it, as a teenager I was very impressed by Asimov generally. A few years back I re-read his autobiography and realized that he was an insufferable dick: probably fun to hang out with at the occasional con, but not someone I would want to be around regularly.

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      • I dunno about “improving” existing systems. I always look at the clusterfish that was the French Republican (post-Revolution) calendar where they tried to decimalize it.

        I have a colleague who has an odd love for this calendar and is always telling me what month it “should” be. Yeah, fine, great, but how will you know how your business dealing with Belgium or Italy are going if you’re not lining up with them in terms of calendar?

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      • I feel the same way about Asimov, ditto Sagan.

        It’s got me thinking that it’s not that the current day popular science folks are any different, but that the media ecosystem around it has changed (plus the lived experience of WW2 and the Cold War)

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        • I don’t have nearly so strong an impression of any sort about Sagan, but it wouldn’t surprise me if, were I have look into it, I would have the same reaction.

          In the case of Asimov, it is his public persona shtick of the absurdly overdone raging egomania done with a wink, giving him the appearance of being a modest fellow with a comedy routine. In my maturity, it is obvious that the “modest fellow” persona is in turn a layer above a raging egomaniac, which in turn is a layer over a core bundle of insecurities seeking validation. In my teens and twenties I was a devoted Asimov fan. Now, in my extremely advanced twenties, I look back at Young Me and shake my head in despair.

          Also, it is obvious that Asimov was a terrible husband, at least to his first wife. We need not read too far between the lines to realize that he treated conventions as traveling harems.

          In related news, in my teens and twenties I also adored Heinlein. It was something of a shock to pick up one of his beloved books a few years after last looking at it, and realizing that this stuff is awful, ranging from merely unreadable to go-take-a-shower-afterwards creepy. I gather that this is a common enough phenomenon that there is a name for it: GOOH (Grew Out of Heinlein).

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    • Yes, Russian and the Slavic languages generally are 10-based — in fact , they even have non-exceptional 10-based words for 11 & 12 (one-on-ten, two-on-ten). The only exception is the word for “forty” in Russian — while the usual “four tens” was also used historically, what ended up being the official term started out as a special word for a bundle of 40 pelts.

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    • How do you write ten dollars in the Canadian monetary system? $10. Its value happens to be about $7.3 in the US monetary system right now, but we understand Canadians don’t say “seven dollars thirty cents” and write “$10”

      “Five hundred and twenty one” in a dozenal system would be written 521. Its value in decimal would be 745. But if you’re using dozenal, you use dozenal.

      Also, why do computer scientists get Halloween and Christmas confused?

      Because 31 oct is 25 dec.

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      • “Five hundred and twenty one” in a dozenal system would be written 521. Its value in decimal would be 745. But if you’re using dozenal, you use dozenal.

        It doesnt work like that, not unless you expressly change the meanings of “hundred” and “twenty”.

        Consider “four” is written as 100 in the binary system. When we look at the numerals 101 in binary, we don’t say hundred and one, we say 5. There is no reason to think that 101 in dozenal is hundred and one any more than it is in binary.

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        • I guess we’re agreeing and disagreeing at once? I agree switching arithmetic bases would have to be a total switch – linguistic, numeric, the whole bit. Switching it for numeric representations but not the words for those numbers would make no sense at all, and wouldn’t take.

          I understand that there are some indications a dozenal system may have been in place in some places and times:

          – medieval documents with things like “Duke such-and-such brought seven hundred archers, and Baron so-and-so brought five hundred pikemen, making an army of a thousand.”

          – TIL that the Romans used a decimal system for whole numbers but a dozenal system for fractions. The basic unit for fractions was the ‘uncia’ or twelfth – related to the ‘inch’ and ‘ounce’ (Troy, specifically). Also see the division of the day, the English shilling, etc.

          – along with having words for eleven and twelve that don’t fit the “-teen” pattern, we have “dozen”, “gross”, and “great gross”.

          So, we have words for the two necessary extra digits of a dozenal system, and we have words for the first three orders of magnitude in a dozenal system. They didn’t come out of nowhere. Someone somewhere was doing their arithmetic in dozenal.

          So I guess going back to your top-of-thread post:

          “Five hundred twenty one” is how you say ‘521 dec’
          “Three gross seven dozen five” is how you say ‘375 doz’
          Those happen to be the same number.

          Similar to how “one foot two and three quarter inches” and “thirty seven and a half centimetres” happen to be the same length.

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  2. Enjoy Hawaii. Its supposed to be one of the most benign places on earth from a climate and weather perspective for humans so I heard and it seems to be gorgeous.

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    • It’s rare to have air- conditioning on Oahu, mostly just high rises and ritzier leeward side homes had it for the most part (it might be more common with new construction since 2000, and with Kapolei and that area being more dense now)

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      • Yeah, the open architecture is really interesting to experience… when we were there I think it was 76 every day; one day the sun got frisky and it might have worked itself to 78, but quickly returned to its senses. Even the rain is good natured enough to only bother part of the island.

        The waves, though, are angry waves; my wife and I witnessed what we’re pretty sure was the end of a marriage when a husband convinced his bride to go paddle boarding… what could go wrong with that? The inland surf, that’s what. Basically you had three zones… the calm peaceful beach (where they sell you the paddle board stuff), the deep slowly ululating ocean (where you paddle), and the 50 feet of surf where angry waves ambush you as if they have an insatiable hunger for sunglasses, hats, and bikini tops – which 1000 years from now will be archeological clues of what our culture valued. By now you can probably guess what happened. Husband and guide managed to time the surf and get to the launch point; the wife? Ambushed by a frothy azure wave…I believe the locals have a name for just this sort of wave, but I didn’t catch it. Ass over beachcomber hat; she popped out of the surf absent protection for her eyes, breasts and head – with (in other circumstances) beautiful volcanic sand in her (now wildly disheveled) hair. Now the wave had spun her completely around so that the Beach was in front of her and closer than the anticipatory fun of a paddle board… she took this as a sign and continued in that direction never breaking stride until she could grab a towel and remedy some of the missing sun protection.

        Veterans of Marriage and Football will recognize this as what we call, “a broken play.” In my mind, I’m thinking, “just fall on the ball, just fall on the ball.” He did not fall on the ball… and, well this is already dragging on, so we’ll just wrap it up with the observation that he must have had more invested in the paddle excursion than the marriage because that’s what he elected to do.

        If you happen to be on Maui, take a trip to Mama’s Fishouse… its something of a mid-century institution and the food is still decent.

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  3. Oregon’s illicit engineer: I very much doubt that this fine would hold up to constitutional scrutiny. I expect that he could even find a lawyer to take this on for free–if not the ACLU, then someone who either is offended by the whole thing, or wants the publicity, or both.

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        • Many years ago, the NJ legislature introduced a bill that made computer programming a subset of engineering, and would have required programmers to get a professional engineer’s license in order to practice. I was really tempted to take a day off and go to Trenton when they were holding the committee meetings for the public to make comments. The heads of both Bell Labs and Sarnoff Labs were there, and flatly stated that the day NJ passed such a law was the day that they relocated all of their people to another state.

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          • what’s oregon’s angle in all this? local gov’t gone a bit bonkers to avoid criticism? or is there some kind of long game here (presumably involving taxes, fees, or revenue of some kind?)

            hopefully they kinda slapp streisand’d their way into losing this one.

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    • As with most things, There’s More Going On Here.

      The issue is about Professional Engineers, those persons whose job is to sign off on buildings and bridges and HVAC or plumbing or electrical installations. The idea is that the lifetimes and usage of infrastructure and construction projects are such that a certain level of certification and oversight is appropriate, and that if someone describes themselves as An Engineer and makes statements about the fitness of a building design then they should both know what they’re talking about and be reachable in case the thing burns down, falls over, and sinks into the swamp.

      So. If someone claims that they are An Engineer and that they are therefore qualified to make statements about infrastructure installations like a traffic light, then it’s not out of the question to interpret them as claiming expertise and training in the area of civil engineering. And the state, with its duty towards the care and safety of the people, has a vested interested in ensuring that any random Joe Schmoe not advertise themselves as An Engineer without verifying that Joe knows what he’s talking about and won’t design bad buildings that burn down, fall over, etcetera.

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      • I’ve always understood the term of art “professional engineer” covers this case. Certainly I’m not a PE. Thus I would never describe myself as such. That said, my job title is “SWE,” short for “software engineer.” So there is certainly a sense that I am recognized in industry as (some kind of) “engineer.”

        In any case, this is all pretty silly. Words don’t work like this.

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      • Yah, and you seemed to miss some of it…

        “He has a degree in electrical engineering from Sweden, and he’s worked in a range of technical fields for decades” Assuming his work in technical fields has anything to do with his degree (likely) calling him an “engineer” seems correct. If you pass the state’s CPA exam folk tend to call you a CPA (cause you are), but that doesn’t mean you have to become licensed by the state and PRACTICE as a CPA for folks to call me a CPA.

        “They launched a full-blown investigation, alleging that he’d engaged in the unlicensed “practice of engineering.” No, he was acting in his capacity as a citczen, questioning things, pointing out facts any reasonably smart technical person would ask. The state just didn’t like it that he was asking those questions.

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        • This. He engaged in constitutionally protected speech. That the topic at hand relates to engineering does not change this, and the idea that license laws can be used to restrict political speech is absurd. If the courts there have any sense, this won’t get past summary judgment.

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          • I guess I mostly agree w/ DensityDuck here, though the article does not give a lot of meaningful details. The default order claims he advised the County Sheriff as to the correct algorithm for traffic signal timing. I don’t see the letter, but it sounds as if he was trying to encourage the timing to be changed, or maybe even get some business.

            The stuff about communicating with the oversight board (to complain that local traffic engineers are misapplying the traffic signal formula) and to the inventor of the formula seem to be overkill.

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          • I’m trying to figure out if there are analogies to other professions. If you go to law school and get your JD but never sit for an exam, are you “practicing law” if you opine on legal matters and mention that you’re a trained lawyer?

            I thought the litmus test here was, “Did you take on a client and represent yourself as a licensed professional?”

            On the engineering side it’s even crazier. The majority of people who get accredited engineering degrees never get a PE certification (not to mention titles that include “engineer” in them that don’t even require an engineering degree). There’s a small set of superpowers that PEs have in their fields that non-PEs don’t get to exercise, but it seems to me that as long as you’re not trying to exercise those powers, you’re not doing anything remotely wrong. It’s not like the guy tried to put his signature on a truss design.

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            • “I’m trying to figure out if there are analogies to other professions.”

              Easy. It’s like saying that a PhD in Chemistry makes you competent to perform surgery because people address you as “Doctor”.

              “There’s a small set of superpowers that PEs have in their fields that non-PEs don’t get to exercise, but it seems to me that as long as you’re not trying to exercise those powers, you’re not doing anything remotely wrong.”

              Oh, absolutely! This is a bullshit charge that’s clearly being brought because some bro in the administration got mad. But that’s different from “he’s an engineer so how could anyone ever say he can’t call himself an engineer”, and there actually are reasons why that makes sense.

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              • There’s a very real difference between an engineer & a Professional Engineer. A person with a degree can call themselves an engineer, but only a person who has passed the PE exam gets to put the PE after their name.

                Where this gets sticky is when a person does engineering as a profession. I am an engineering professional, but not a Professional Engineer. A person who did not get their degree in the US might fail to note the difference and think that engineering professional == professional engineer. As long as he did not make the mistake of putting PE after his name on official work documents, he’s fine, and since he doesn’t work for the government, he can’t produce official work products.

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                • I have a friend who is a forensic engineer, who testifies as an expert witness in court cases about why particular devices failed. He says that he might be able to convince people that he was qualified based on his resume, but that once he says “PE, Mechanical Engineering and Materials” everyone is willing to accept that he’s an expert.

                  I know lots of people who do sophisticated software work (including myself, at times). The only person I know with a PE in software engineering is a woman who also did forensic work and testified as an expert witness.

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                  • That bit about everyone accepting that he is an expert is really about shortening the discussion. If he is called to testify as an expert, the other side can challenge his qualification, not merely with regard to the credibility of his testimony but whether or not he is allowed to testify. Having the magic words “PE, Mechanical Engineering and Materials” tells the other side not to bother, thereby saving everyone’s time. Without those magic words there might have to be an extended conclave in the judge’s chambers, even if it arrives at the same place in the end.

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          • Well, there’s a gray area. IIRC, you work in the legal field but aren’t a lawyer that’s passed the bar. There’s stuff that is clearly just your comments on a legal topic covered by free speech. There’s also you opening up a store front and selling legal advice, even if you don’t claim to be a lawyer. In between, there’s stuff that’s less clear. In Oregon, depending on phrasing, exactly what offers might have been made (eg, “I’ll be happy to sit down with you and go over the details of why the standards are wrong”), and what the state statute and case law are, there’s stuff that might be interpreted as soliciting business as if he were a practicing civil engineer. Certainly courts have made weirder decisions than that.

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      • It’s obvious that any software engineer should probably be versed enough in civil and mechanical engineering to be a PE. I mean, suppose you’re writing to a file. The file gets written to your hard drive by a read/write head that’s on an arm that’s constructed as a cantilever beam. Then you start wondering about the mechanical resonance of the arm, the rotational inertia of the seek motor, and how that all might conspire to delay the sector write by enough microseconds to slow your program down by enough cumulative milliseconds so that the user gets bored and goes over and clicks on a game of Freecell.

        Similarly, when a run across a structural engineer designing something like a steel mezzanine that’s going to hold a multi-million dollar, multi-ton slat sorter, I quiz him on his familiarity with Dijkstra’s thoughts on program correctness.

        I recall one time when I was shoveling snow with an Amtrak engineer to get my fellow passengers off the train (which was stuck behind a freight train whose crew had hit their daily limit of hours). I asked him how he came to be an engineer. He said he had a degree in wildlife biology and heard Amtrak had finally started hiring new engineers (they had to wait until the old ones retired out). I asked him if his biology degree was useful as an engineer, and he replied that it allowed him to easily identify almost anything he hit.

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        • “It’s obvious that any software engineer should probably be versed enough in civil and mechanical engineering to be a PE.”

          Sure! Did they take the test? No? Not a PE, then.

          People have the idea that I’m defending this. What I’m doing is describing how someone could get into a place where a reasonable and rational thing to do is censure an engineer for describing himself as an engineer.

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  4. What the literature will tell you about co-axial rotors is that the mechanism is complex, this has always had effects on reliability, and that under high-stress maneuvers there’s a chance that the rotors will strike each other.

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  5. I have a naval propulsion question.

    Instead of an adjustable pitch propeller, what about a shrouded, fixed-pitch propeller with adjustable entrance-and exit areas for the shroud?

    So the propeller runs inside a cylinder with slightly tapered ends. At those ends sits something akin to a large football, similar to the hydraulically adjustable inlet cone on the J58 engine on an SR-71. There’s a similar football shaped cone at the shroud’s exit. That lets you decouple the thruster’s inlet and outlet areas, and since these areas are smaller than the internal area of the propeller disk, the flow speed past the propeller will be slower than the hull speed through the water.

    Inside the shroud, between the propeller and the exit cone, you could add fixed “stators” to untwist the trailing vortex, and you could make the propeller shroud as a two-piece structure with lots of sound dampening, and given what you could do with the inlet and exit cones, you could probably dampen the sound emitted ahead and astern.

    But the main point is that the ability to dynamically adjust the ratio of inlet area to propeller area lets you set an upper limit on the flow rate past the propeller, and thus allow the vessel to efficiently travel faster than the propeller’s cavitation speed. But of course it adds a lot of other losses due to wetted area.

    Also, why do ships use conventional Brayton cycle gas turbines instead of much more efficient approximated Ericsson cycle turbines, where the air is cooled in between compressor stages, run through a reheater prior to combustion, and then combusted with reheating (extra fuel shot in) between turbine stages? The true Ericsson cycle uses isothermal compression and expansion, but Ericsson (who designed the Monitor) couldn’t figure out how to build such a piston engine in the cramped machinery spaces of a ship. An approximated Ericsson cycle turbine, according to a 1970’s RAND report, should run at better than 60% efficiency, much better than a Brayton cycle turbine.

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    • First the steam turbine was not invented till the 1880s by Charles Parsons. All Erickson had during the civil war was the old fashioned reciprocating steam engine. Once the steam turbine was applied to ships in 1897 it easily outran the steam powered naval ships. The gas turbine was invented after WWI and was first used in airplanes. The propeller itself was also invented by Ericsson and first used in the 1840s. Since cavitation requires high speeds and high power it was not a problem on reciprocating engine powered ships. Cavitation was only discovered in 1895 by Froude.

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      • Ericsson developed all sorts of interesting engine cycles prior to the Civil War, including the Brayton Cycle, oddly enough. But he was stuck with using pistons and his more advanced cycle with isothermal compression and expansion, along with a recuperator for heat exchange, wasn’t feasible in a ship at that time.

        But now we have gas turbines, and with some modifications they can approximate an Ericsson cycle to produce much higher efficiencies.

        1979 RAND report on approximated Ericsson cycle engines for the US power grid.

        That report uses 1970’s material limits with a 1500 F turbine inlet temperature, but should still exceed 50% efficiency. And also, the main post mentions the SABRE engine and its revolutionary heat transfer material. That would be ideal for use between each compressor stage on an Ericsson engine, keeping the air from heating up from stage to stage, thus better approximating the ideal isothermal compression by having the number of heat exchangers equal to the number of compressor rows. The RAND report just looked at 3-stage and 5-stage compression cycles, which is to say three or five heat exchangers to keep the air from getting very hot. Instead of a big triangle on the PV diagram, these split it up into three or five smaller triangles, thus encompassing more area on the chart. The finer you divide up the triangles, the less chart area they waste.

        For a fixed power plant, where you have acres to work with, you could just skip the turbine compressor, get really crude (water cylinders, brickwork recuperators, split cycle compression, molten salt expansion pistons), and run the efficiency much higher.

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        • For Navy tin cans, the setup sounds rather complex, and tin cans are not fans of further propulsion complexity. Right now, a main gas turbine sits in an eclosure that can be disconnected & pulled out of the hull via the stack in about 12 hours, even at sea.

          Also, that’s a lot of heat exchangers (IIRC an LM2500 has 16 stage compressor), and the ship has to do something with that heat that preferably doesn’t produce even more of a thermal bloom for IR to see.

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          • The idea with the isothermal compression is that you never really get much above ambient throughout the whole compression phase because you’re cooling the air between each stage. If the SABRE type heat exchangers are small and efficient enough, they’d just be a unit behind each stator section, circulating a fluid that dumps the low temperature heat to sea water. That could probably be done with just one additional external pipe. But the compressor section would probably be at least twice as long.

            The RAND study assumed a multi-shaft compressor, with each separate section feeding through a heat exchanger to another separate section. Back then a heat exchanger probably would have been stainless steel tubes.

            Hopefully the SABRE technology would also allow the recuperator to be equally small, because that has to move heat from the exhaust section to the compressor exit. Then the combustion section would be broken up so that there’s a bit of combustion in between each set of turbines, and you might want to add more turbine stages, each drawing a little less energy than current designs.

            The RAND study predicted 50% efficiency with a turbine inlet temperature of 1500F, but modern TIT’s of around 2,500 F should boost the efficiency well up into the 60’s.

            Of course the problem would be coughing up a couple billion for GE and Pratt and Whitney to look into it.

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            • Well an increase in length would require a redesign of the engine room & stacks, which means new ship class.

              My question would be, given that the cycle is so efficient, what kind of performance does it get, because a modern destroyer has to be able to go from zero to flank in about RIGHT FECKING NOW! IIRC, an LM2500 with a properly trained crew can go from cold zero to flank speed in about 120 seconds.

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              • I don’t think the spool up time would be effected, and may be a little shorter because the cooler air compresses with less work, one of the reasons the engine is more efficient.

                There’s no way around the increased length or the need for a new ship class. But if such an engine offered $X in fuel savings for the Navy, they’d probably go for it, because fuel is such a big part of their budget. The savings would also of course translate into either increased range or increased payload.

                What the Ericsson cycle lacks is sufficient supporters, much like the liquid flourine thorium fuel cycle, which is simple enough to use for nuclear powered destroyers. If the Ericsson cycle could result in an turbine that’s not much heavier than exiting turbines, only about 15 feet longer than the LM2500, but 50 to 60% efficient instead of 37 to 39% efficient, I think they’d jump at it, perhaps after coughing at what GE is going to ask to look at the design.
                .
                I highly recommend looking at the RAND study linked above. It was quite interesting, and mentions that after someone showed the math that a turbofan would be vastly more fuel efficient than a pure turbojet, it took a couple of decades or so before aerospace engineers said, “Hey, we should make a turbofan to save fuel.” I have no idea why they didn’t immediately jump to high bypass turbofans, especially since the early jets were subsonic, but they didn’t even consider it for decades.

                Perhaps engineers have some little mental flaw similar to perfectly-efficient-market economists. Two of those were at a conference in New York and as they were walking down the sidewalk to lunch they saw a $100 bill on the sidewalk. They walked on past and one asked “Why didn’t you pick up the $100 bill?” The other replied “If it was a real $100 bill someone would have already picked it up.”

                The approximated Ericsson cycle is like free money that’s been laying on the sidewalk since 1979. Perhaps somebody should pick it up.

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                • I can’t visualize all of what your saying, but have a couple questions about it.

                  What is happening with your delta T?

                  Is the volume that the delta T occurs allowing more entropy than what the current configuration produces?

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                  • Sheesh turbine guys.
                    Where is the heat from the intercoolers going?

                    I see the value of that regenerator now.

                    Most of the fuel in the late stage turbines will be starved for available oxygen, they readily admit it.

                    The delta T kind of sucks 70F-1800F?
                    (somebody wake me up when we they get to 2800F, yes I gots material issues, ever see an engine run glowing white?)

                    The volume of turbine stages is elongated do to multiple burners. Be interesting to see if there is much entropy loss beyond the regular units.

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    • “Instead of an adjustable pitch propeller, what about a shrouded, fixed-pitch propeller with adjustable entrance-and exit areas for the shroud?”

      I think you’re describing a decelerating shroud, which is a thing that ships already use (it’s to reduce cavitation, exactly as you suggest.) There are also accelerating shrouds, which act to increase the speed of flow (and improve the power output of propellers acting at low vessel speeds, such as maneuvering thrusters or the primary drives of tugboats.)

      This is achieved by proper shaping of the shroud, though, rather than by changing the inlet area. One could conceivably develop a variable-geometry shroud that could produce an acceleration at low speeds and a deceleration at high speeds, but that doesn’t seem any less complicated than a variable-pitch propeller.

      Also, the SR-71 inlets don’t slow the flow down by changing inlet area; they slow the flow by inducing a compression shock wave in the supersonic airstream ahead of the inlet. This wouldn’t work for water, which is incompressible; reducing the shroud area would increase the speed of the water entering it.

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      • The change in inlet (capture) area is just a small part of what the SR-71 does by moving the inlet cone forward or back, as that also changes the positions of the pattern of reflected shock waves and the internal throat area.

        But I’m going for something simpler, which is just to use a hydraulic system to move the “football” axially into the tapering inlet. Fully retracted, the whole inlet area is open and the water just flows around the football, perhaps with a constant cross sectional area. As the nosecone moves forward, the open area at the front decreases, and if moved all the way forward the football simply plugs the inlet closed (which might be good for reducing drag on an idled prop). The football at the back acts similarly, preventing flow separation and raising exit speed above the local flow velocity, so as to produce thrust instead of drag. Internally, there’s just the fairly small diameter propeller shaft and large diameter propeller.

        If the inlet and exit cones are nearly closed, for high speed operation, the flow past the propeller is still quite low because the thruster’s internal cross sectional area is much larger than the inlet area, so the propeller can run at much lower RPM’s, much further from cavitation, and thus hopefully produce a much smaller acoustic signature, on top of any sound dampening built into the shroud and cones, perhaps allowing for something like a quieter high speed torpedo.

        But I was mainly looking at the way it could use just two simple hydraulic rams and a fixed pitch prop to possibly compete in efficiency with a variable pitch prop, which are quite difficult to engineer given the stresses on the blade mechanisms. (The first attempts at variable pitch props on our destroyers ended with snapped blades.)

        It’s certainly a rather bulky solution, but I thought it might be interesting to investigate.

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        • I’m think I know what you are describing, but if you want to sketch it up and mail it to me (madrocketsci at gmail), I can offer a more definitive answer, and if I can’t, I’ll see if I can push it through the CFD solver and get you some pretty pictures.

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          • You’re idea of what I’m describing is probably as accurate as what I’m describing. Some little sliding footballs in the ends of a roughly submarine or dirigible shaped pod, truncated front and back, with a big fixed pitch propeller in the middle.

            I imagine that the trick is to avoid flow separation in the inlet, especially along the back of the inlet cone where the flow slows down. The back end could instead use the variable area tail-feather arrangement of modern fighters, but the football (or finely tapering like the exhaust of Princess Amidala’s fighter that blew up in Episode I) is going to be smoother and have only one moving part.

            I’m confident it will work, but I don’t know how efficient it would be, how useful it would be, or if it would have some advantage in a particular application that would make it useful to pursue, from acoustic signature reduction to blast hardening if you had a really tough shroud.
            .

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  6. On number bases we actually use several in everyday life, 10, 12/24 (clocks some english measurements) 60 (clocks) 360(degrees in a circle) apparently a lot of the non base 10 systems come from Babylon. I suspect in the future bases will be based on some power of 2.
    Likley 16 as introduced with the IBM 360 system, and now on PCs, since that is the definition of a byte. 2**8.

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