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From Scientific American August 2009 "Swimming in SpaceTime" in curved space the notion of center of mass is not so simple. As a result upon certain repetitive changes in one's geometry/shape the center of mass can translate across said curved surface w/o need of pushing against it and w/o need of propellant. Imagine e.g. whilst upon a friction free curved ice pond flailing one's arms and legs in a certain manner one finds oneself gliding in some direction. It must be stressed a curved surface is required also it must be stressed no new physics here it is rather a matter of Newton's laws in simple/usual/conventional form assume flat space but can not be interpreted in the usual way in curved space instead require more care. To elaborate in Newtonian Physics the curved surface is a constraint on the system which is of course a collection of forces therefor if one ignores these one obtains a wrong answer. These constraining forces are of a kind which do no work so it is possible to treat them as geometry instead of the usual F = ma. For General Relativity and its curved spacetime I am not certain the notion of constraint still applies. -Cheerio
modified 11-Aug-22 8:40am.
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PaltryProgrammer wrote: it must be stressed no new physics here it is rather a matter of Newton's laws in simple/usual/conventional form
I'm impressed. Happy to see that you understand it. Looks like you fully understand it too!  I was beginning to wonder if I should post a cat example[^] to illustrate the concept! 
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Thank You for the kind words. May I say I do not understand why the cat example is often presented as as near as I can discern the phenomena of nonholonomic rotation can be demonstrated in flat spacetime while the effect of swimming requires curved. Perhaps more importantly the cat does not return to its' original shape/geometry so as near as I can discern it is not a matter of nonholonomic rotation but rather simply conservation of angular momentum but of course I must be incorrect as the example is cited by those much more knowledgeable than myself. I consider myself falling and merely extend my little finger and bingo presto my moment of inertia has changed so has presumably my geometry perhaps to one which I favor e.g. with legs below me. As for Hannay’s hoop as near as I can discern it not only requires a curved space but also a rotation of same also the mass in question does not seem to change its' geometry/shape. -Best
modified 11-Aug-22 2:44am.
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Hmmm,
I don't really know why cats are always used as an example. Looks like it's really common:
Cats nonholonomic[^]
If you read the paper you can see that he makes the comparison in the first paragraph:
At low Reynolds number, the effects of
inertia are negligible and, in the absence of
external forces, bodies are at rest. Nevertheless,
as a body changes its shape, its location and
orientation generally change. A cyclic change in
the shape of a body can lead to a net translation
or rotation. The net translation or rotation does
not depend on the speed with which the shape
changes are carried out; it is a consequence of
the geometry of the sequence of shapes,
a classical example of geometric phase. It's possible that you missed this part, for some reason he uses the QM terminology[^] here. The author is referring to a Nonholonomic system[^] in that statement.
Swimming in Spacetime: Motion by Cyclic Changes in Body Shape[^]
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I was lost at "Reynolds number". Upon reflection re/ cat presumably it is in fact nonholonomic rotation. So I am left w/ question can one change one's orientation via change of moment of inertia. 
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Isn’t this how all of the tic tac UFOs propel themselves?
Someone has it figured out.
Duck!
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I thought the standard explanation was they create a gravitational field in front of the tic-tac so they fall forward into it thus permitting infinite acceleration w/o harm to occupants. Quarck 
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(nobody actually said that. probably ever)
Looping MIDI performances creates a number of interesting challenges. For starters, you have to count the number of times note offs and note ons happen so that the note offs you've captured in a loop do not cut the notes you're actively playing short.
Secondly, you have to insert note offs for any note that's currently being held down when the loop is finalized *but* you avoid sending the actual note offs, you just insert them at the end of the loop for the next time around.
Finally, you have to quantize the loop lengths so you don't have to have the timing of a 12-year old gamer to actually play the thing.
And and there's gotchas, like not capturing MIDI reset messages, or pitch bend messages.
All that is ignoring the user interface, where you have to set up which midi signals you use to indicate the start and stop of a loop, and how to navigate multiple loops. It gets hairy fast.
It's an interesting challenge though - one I solved ages ago purely in software as a VST plugin but I've long since lost that code.
To err is human. Fortune favors the monsters.
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You need to return to the software side of things to establish the rules of play.
Laws before enforcement (hardware).
"A little time, a little trouble, your better day"
Badfinger
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She's been having issues with low blood pressure causing fainting, and last night she started having chest pain. Took her to the hospital around 2:30 PM, and went home an hour or so later to let the dog out. I got a call from her a bit ago, and she's been admitted for monitoring overnight due to damage on her heart and elevated cardiac enzymes (at 58, normal is < 10). The doctor is going to do a cardiac catheterization in the morning, and go from there.
What do you get when you cross a joke with a rhetorical question?
The metaphorical solid rear-end expulsions have impacted the metaphorical motorized bladed rotating air movement mechanism.
Do questions with multiple question marks annoy you???
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![Rose | [Rose]](https://www.codeproject.com/script/Forums/Images/rose.gif) I wish her (and you) well. Elevated enzymes are usually a signal of a recent infarction. Good that she's getting immediate intervention.
A few weeks ago one of my crew (female, 70s) at the Fire Control Centre said quietly "Peter, I'm not feeling well." Did the obvious checks, called an ambulance. Paramedics did an ECG, nothing obvious. BP all over the place. Took her to the local hospital for further tests. Wound up staying for 3 nights until they could get meds sorted to manage her BP.
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
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That doesn't sound good. I hope she comes through OK.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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At least she's in the right place, and it sound like at the right time as well.
I hope she recovers well, but there is no good reason why she shouldn't!
If it helps, my younger brother has had four cardiac stents fitted a decade or so ago, and is fine.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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 Hoping for the best
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Really hope all works out well for her.
Thinking of you.
"Rock journalism is people who can't write interviewing people who can't talk for people who can't read." Frank Zappa 1980
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I recently bought a new 14TB disk drive to put in my new 4-disk enclosure (no raid or anything special, just a simple enclosure to save power strips) connected to my file server via 6gb eSATA.
I liked the way it performed so went back to buy another one only to find it was out of stock but they offered a "renewed" version of the same disk for $10 less. I decided against this as disk life seemed important and I don't care how much they polished the case, the disk itself had obviously done some amount of spinning before it was "renewed".
Anyone got any definite knowledge or even vague opinions about this?
- I would love to change the world, but they won’t give me the source code.
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Use the renewed one as a backup / for backups of the new one (or vise versa).
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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Gerry Schmitz wrote: Use the renewed one as a backup / for backups of the new one
Backups are for for cowards. Live dangerously!
Nothing succeeds like a budgie without teeth.
To err is human, to arr is pirate.
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$10 off on a $300 dollar HDD to get a used drive? I'll give it a miss. 
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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But think of all the pron "important work documents" you could recover if they haven't wiped it properly!
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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HDDs are assembled in a clean room (How it's made - Western Digital Hard Disk Drives - YouTube), because even dust particles can cause damage to the platters or R/W heads. There is no guarantee that the "renewal" work was performed to the same standard.
Note that some HDD manufacturers will sell refurbished drives. These are typically repaired drives that have been tested by the manufacturer to meet the same standards as new drives, and are typically sold at a significant discount. Going to Western Digital's website, a MyCloud Home 8TB lists for US $299, while a refurbished device lists for US $199.
Personally, given the relatively low price/TB of new HDDs, I would not risk my data on a drive that has already failed once.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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Daniel Pfeffer wrote: a drive that has already failed once
^ This.
Why else does anyone return a drive?
It's a ticking timebomb. I would not use a drive for anything important. That includes using it as a backup drive, as someone above suggested. Why would you back up anything on a drive you'd have less trust in than a drive for your "live" data??
Unless it's purely as an additional backup set.
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dandy72 wrote: Why else does anyone return a drive?
I had to search on "renewed", as I had no idea what the term means:
4. Renewed
In general, refurbished and renewed refer to the same thing. But Amazon's renewed means more things. It not only includes refurbished products, but also pre-owned and open-box products.
Pre-owned: Products that are likely used, but were in better condition when returned than a refurbished product may have been.
Open-box: Products whose packaging was opened but the actual product was not used.
A large percentage of refurbished products are open box, e.g., the box was opened but the product never used. It's possible that the item was non-functional and has been repaired, but in the case of HD, that is highly unlikely due to the conditions necessary for repair.
All refurbished items have been inspected, in contrast to production items where it's typically 1 in 10,000, so refurbs can be a good choice.
However, for $10 off a $300 item? I'd buy new. If it was 1/3 off, I'd think about it.
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OP said it was "the only one available". Everybody ignores that point.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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I still wouldn't buy the refurbished disk. It's not as if new disks are not being made, so in the worst case he can buy new from another seller.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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