Amiga.org
Coffee House => Coffee House Boards => CH / Science and Technology => Topic started by: KennyR on November 25, 2004, 10:27:36 PM
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My indice algebra is rusty, but I can't find my old maths books. And google isn't helping.
Basically, I want to solve C=(1-D)^T for T. (^T means to the power of T). I just can't remember what law to use to get that T down from there. Anyone?
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Laws of logs apply here don't they?
log (x^y) = y.log x
C=(1-D)^T
ln (C) = T ln (1-D)
T = ln(C)/ln(1-D)
I would think
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Aha, thanks Karlos! :-D I remember now.
It just went totally out of my head there, and nothing I could do would remind me...it's amazing how quickly you forget the things. :-(
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KennyR wrote:
it's amazing how quickly you forget the things. :-(
What things?
Who are you and what have you done to my cuppa?
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Karlos wrote:
What things?
Well, I really meant bizarre abstract rules and laws governing algebra, but since it's obviously the flavour of the month here in Amiga.org, my answer is: socks.
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KennyR wrote:
but since it's obviously the flavour of the month here in Amiga.org, my answer is: socks.
Ick. I hadn't realised people had stooped so low as to be chewing on the things now...
Still, can only be as bad as aloe vera ;-)
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Which reminds me, I was supposed to be making some tea :lol:
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So what are you graphing/solving anyway? Whenever I see T I instinctively think of absolute temperature...
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But I'm damned if I can think of anything that has a direct power dependency on temperature ;-)
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Oh, something incredibly trivial. I was trying to work what battery manufacturers call "shelf life". They say that the shelf life of batteries is how long they take to get to 85% of original charge, just sitting there and not being used.
T=time, in years
D=discharge (per year)
C=charge level (1 being full, 0 being empty)
I worked out that C=(1-D)^T, but got stuck trying to get it for T. But with your help:
T = ln(C)/ln(1-D)
Cheap alkaline or zinc chloride batteries, for instance, have a self-discharge rate of 4% per year, therefore:
T = ln(0.85)/ln(1-0.04)
= 3.98
So it works out as a shelf life of 4 years. Which is exactly what they are advertised as having.
I needed to get this for other kinds of battery. It may be pointless, but it beats chewing a sock, even if I do need the fibre. :)
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KennyR wrote:
Oh, something incredibly trivial. I was trying to work what battery manufacturers call "shelf life". They say that the shelf life of batteries is how long they take to get to 85% of original charge, just sitting there and not being used.
Ah, I see.
I needed to get this for other kinds of battery. It may be pointless, but it beats chewing a sock, even if I do need the fibre. :)
Combustarse say: "man who eat vindaloo has no need of fibre"
I think you'd get more semi decomposed protein and sugar and amines than you would fibre from chewing "The Sock" ;-)
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Karlos wrote:
I think you'd get more semi decomposed protein and sugar and amines than you would fibre from chewing "The Sock" ;-)
Especially bloodline's socks ;)
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KennyR wrote:
Karlos wrote:
I think you'd get more semi decomposed protein and sugar and amines than you would fibre from chewing "The Sock" ;-)
Especially bloodline's socks ;)
That *is* "The Sock" :-)
Hmm, now you have me wondering. Are there any other serial sox offenders here that we don't know about?
Name and shame! :lol:
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None must resign themselves to the dubious pleasures of forbidden laundry now we've armed ourselves with the knowledge of batteries. What woman could resist pick-up lines like "Wow, do you know that NiMH batteries, once fully charged, will self-discharge while unused to 85% of capacity in only SEVEN DAYS!?!"
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I can just hear the enthusiastic feminine chorus of "Get your coat, you've pulled!" :-D
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Something tells me the catchy title of this thread is keeping people at bay :-D
Either that or they've actually read it :lol:
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Karlos wrote:
Something tells me the catchy title of this thread is keeping people at bay :-D
I only read it cos I thought it might have been about the guy that could get the 13th root of a 100 digit number in under 30 secs..
Wonder if he`s any more successful in pulling the girlies with that trick, compared to the battery trivia chatup line?
I know what you mean about forgetting the basics of maths, the other day at work it took me a while to work out what 2.5% of 100g was !! standing there talking to myself.. "10% is 10g,half it so 5% is 5g, half it again so 2.5% is..DOH " :-x
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@kenny
ok you said...
T=time, in years
D=discharge (per year)
C=charge level (1 being full, 0 being empty)
I worked out that C=(1-D)^T, but got stuck trying to get it for T. But with your help:
T = ln(C)/ln(1-D)
Cheap alkaline or zinc chloride batteries, for instance, have a self-discharge rate of 4% per year, therefore:
T = ln(0.85)/ln(1-0.04)
= 3.98
So where did you get the value D from....???
It`S a bit like saying D= 1 x (D x 1)
:-)
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That's the formula for cumulative percentages, blob. It's (1+D) for additive, such as when working our interest on an account, (1-D) for subtractive. D is the percentage you lose or gain every iteration.
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Ah,
you mean:
first year = 96% charge ( d=4%)
second year = 92.16 (96 - 3.84 , d=4%)
third year = 88.4736 (92.16 - 3.6864, d=4%)
forth year = 88.4736 - (88.4736 x 0.04 = 3.538944) = 84.934656%
:-)
(rather than the rough method of 15 / 4 = 3.75)
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It's basically an exponential decay curve, just like any other proportional (as in the current absolute rate is always dependent on the current amount) decay.
The manufacturers could have chosen the half life of the cell to make it more obvious, but I doubt that a cell at 50% charge is not much use so they picked the 85% threshold instead.
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Karlos wrote:
The manufacturers could have chosen the half life of the cell to make it more obvious, but I doubt that a cell at 50% charge is not much use so they picked the 85% threshold instead.
Right. It's a matter of internal resistance. Most cell chemistries gain internal resistance as they lose capacity, decreasing the output voltage of the cell. At 50% capacity, your average alkaline battery would have an output of only 1.1-1.2 volts rather than the advertised 1.5, which is actually just not enough for some stuff. Their performance gets worse as they drain.
Incidentally, NiCd and NiMH don't have this effect (low internal resistance), which is why I like them. Pity they only have 1.2V even when fully charged, and they lose charge like fiends. And even worse, shops only sell padded crap like 2300 mAh NiMH D batteries (the theoretical capacity of an alkaline D battery is around 18,000 mAh, which should mean NimH D should be around 9000 mAh. These do exist, but they can only be bought specially and cost about £12 each!!).
Someone should do the world a favour and invent rechargeable batteries with 1.5V, low self-discharge and low internal resistance, but which aren't full of explosive ether like Li-Ion are. They'd be a rich man/woman! ;)
Until consumer fuel cells came out that is... :-P
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You sure are into cells dude :-)
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That said, I can think of worse cells to be in of a Saturday night ;-)
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Electrochemistry is my forte. ;) I didn't want it to be, that's just how it ended up. I'd rather have specialised in nerve agents or explosives, but unbelievably they wouldn't let me at uni, and gave an oscilloscope and some electrodes instead. Now I'm cursed with being specialised in perhaps the most horribly boring of all the sectors of chemistry.
Still, given today's choice between researching mind-numbingly mundane battery facts and anthropod/sock interaction, I made my choice and I'm sticking to it. It's better than getting drawn into the bickering on the front page, for sure.
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You'd find it easier to stick to the sock, er...
As for explosives, I do recall some very interesting reactions I had to set up when I embarked on my PhD.
I needed to prepare isopropyl 1-napthyl sulfoxide (and also the sulfone) in order to ascertain the barrier to rotation (if any).
The first stage was to prepare the thioether and then oxidise it up. I ended up having to perform a reflux of neat propene at -6 C directly on napthan-1-thiol with an acid resin catalyst.
I had a dry ice cold finger and gently passing dry propene direct from a gas bottle, diluted with nitrogen to be on the safe side.
I went away for lunch, came back and found someone had been in my fume hood to get something and had knocked the assembly, pulling out the N2 line. They'd reattached the wrong one and were now diluting the propene with compressed air.
Good job nothing sparked in there!
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Still, can only be as bad as aloe vera
Your comparing a crusty old sock to Aloe Vera??? Thats a bit of an understatment I would say, crusty old socks have far more appeal than a hearty glass of Aloe Vera juice anyday :-P
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@ Karlos
@ kenny
You may be interested in this article I found, er, in Platinum Today (http://www.platinum.matthey.com/media_room/1101466804.html)...
“Scientists in the US have succeeded in breaking through the "oxo-wall" to forge multiple stable chemical bonds between oxygen and platinum.
The breakthrough is being widely hailed as a significant achievement because the process was previously thought to be impossible because oxygen is extremely unstable when combined with certain metals”
I wonder what the properties that would have,
Ect…
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Are they talking about multiple bond order between oxygen and platinum?
If they are talking about oxoplatinate species, my first guess would be that they are good oxidising agents ;-)
Mind you, nothing beats perxennate as a source of reactive oxygen...
/gets coat :lol:
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Conincidentally, I was just thinking about using one of the platinum group in an oxygen related reaction.
I was actually wondering if we could trap platinum ions in a heme and make biomechanical blood cells. Synthetic pink blood that gives human beings superhuman capabilities! Yay!
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Is the power of a human limited to the transport of oxygen to his cells then? You'd think that there are other limitations too in ATP, ion and CO2 transport.
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Yes, there's more to it than oxygen transport :-)
However, if someone did improve upon haemoglobin, it would effectively improve the aerobic fitness of the individual, giving them better endurance before they get lactic acid build up and so on...
Of course, platinum, like most heavy metal elements is toxic as hell - a slight oversight perhaps should any of these biomechanical corpuscles break down ;-)
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adz wrote:
Still, can only be as bad as aloe vera
Your comparing a crusty old sock to Aloe Vera??? Thats a bit of an understatment I would say, crusty old socks have far more appeal than a hearty glass of Aloe Vera juice anyday :-P
What, even with the septic cat juice chaser?
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Karlos wrote:
What, even with the septic cat juice chaser?
Yes, even with a septic cat juice/ear wax cocktail...hmmm, what could we call that and would you frost the glass with sugar or salt??? Thinking caps peoples :-D
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adz wrote:
Karlos wrote:
What, even with the septic cat juice chaser?
Yes, even with a septic cat juice/ear wax cocktail...hmmm, what could we call that and would you frost the glass with sugar or salt??? Thinking caps peoples :-D
Might as well float a couple of veggie-mince derived turd nuggets in there too
blurrrrrgggggh!
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Karlos wrote:
Might as well float a couple of veggie-mince derived turd nuggets in there too
blurrrrrgggggh!
An ideal substitute for ice cubes??? :lol:
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Only if they're fresh....and only if you need the cocktail warmed up a bit....
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odin wrote:
Only if they're fresh....and only if you need the cocktail warmed up a bit....
"This coffee tastes like sh*t!"
"It is sh*t, Austin..."
"Ah, I thought it was just me..."
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odin wrote:
Only if they're fresh....and only if you need the cocktail warmed up a bit....
Or you could freeze 'em :lol:
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Karlos wrote:
"This coffee tastes like sh*t!"
"It is sh*t, Austin..."
"Ah, I thought it was just me..."
:lol: :lol: :lol:
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So to recap:
Not even a tall glass of fresh septic cat pus, blended with earwax and with chilled veggie mince turd nuggets bobbing about in it, quaffed whilst eating some of bloodline's vintage extra crisp sock-crackers is enough to overpower the taste of aloe vera?
There's no hope then.
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So anyway, what was this thread about again? :lol:
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They don't half serve some exotic {bleep}tails in this Coffehouse . :lol:
{Edit}
I can't believe the word C_ocktail is censored yet the word sock is allowed.
Oh yeah... the thread ..erm I can't really say I know what it's about :lol:
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Yeah.... Mouthwatering, I'm sure :pint:
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@Gadget
To uncensor the word so that you can post cocktail, you have to insert some tags into it to stop the parser from getting "offended" :-)
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Karlos wrote:
So to recap:
Not even a tall glass of fresh septic cat pus, blended with earwax and with chilled veggie mince turd nuggets bobbing about in it, quaffed whilst eating some of bloodline's vintage extra crisp sock-crackers is enough to overpower the taste of aloe vera?
There's no hope then.
Now hang on, where did I mention anything about bloodline's vintage extra crisp sock-crackers??? You need Aloe Vera to wash down the crackers, followed by a septic cat cocktail to overpower the Aloe Vera :lol:
BTW, I'm kinda used to the Aloe Vera now, and I've only got another two shots of it left :-D
BTW Mark II, hows the sock avatar going Karlos?? :-P
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Karlos wrote:
So anyway, what was this thread about again? :lol:
Yet another tag team thread hijack :lol:
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*raise*
Blimey, it is all still here, after all this time :-o
Who could have thought that a simple question of logarithms could devolve into this?
Well, we could have for starters ;-)