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Unread postAuthor: Zeus » Mon Dec 17, 2012 2:30 pm

I just got onto Fringe myself, can't stand 24, and Homeland went to crap after season one.

I really wish someone had told me to watch Fringe, I gave my mate a hard drive to fill up, and it xame back with 400gb of films and TV shows, and 40gb of metal in .flac.

On another note, thanks to a clerical error, I had to do 12 essays in 4 hours for my lab course. Turns out I work well under stress.
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Unread postAuthor: mobile chernobyl » Mon Dec 17, 2012 4:35 pm

Zeus wrote:On another note, thanks to a clerical error, I had to do 12 essays in 4 hours for my lab course. Turns out I work well under stress.


12 essays in 4 hours?? That's 3 per hour - one every 20 minutes!!

How long were these essays?? Lab reports usually require extensive data analysis that can take many times as long as the words that come after it!


I also tend to work well under stress though. My test's usually go something like this:
60% done in 90% of the time given, the last 40% done in - 10% of the time lol.
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Unread postAuthor: MrCrowley » Mon Dec 17, 2012 4:55 pm

mobile chernobyl wrote:How long were these essays?? Lab reports usually require extensive data analysis that can take many times as long as the words that come after it!
I don't think I could even complete the literature review for one essay in only 4 hours :D

Though if you're getting assigned 12 essays at the same time (more than I would write in two semesters excluding tests and exams) I imagine they're not quite what me and MC are thinking about :P

I downloaded Mendeley over the weekend (it's free) to sort all the journal articles on my computer and I can highly recommend it to anyone else. Its interface is almost addictive because it's so easy to record notes, highlight text, attach annotations, and organise papers in to different categories. I find myself downloading a dozen or so new articles each day :)
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Unread postAuthor: dewey-1 » Mon Dec 17, 2012 6:52 pm

mobile chernobyl wrote:
I also tend to work well under stress though. My test's usually go something like this:
60% done in 90% of the time given, the last 40% done in - 10% of the time lol.


That is the famous 90/10 rule that states:

"The first 90% of any task takes 10% of your time while the last 10% of that task takes 90% of your time."
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2012 1:34 am

Doesn't work for me, actually getting round to starting the first 10% takes 90% of the allotted time :roll:

Image

Per la serie "cazzo tecnologia, mi fai paura!":

[youtube]http://www.youtube.com/watch?v=Jplh7uatr-E[/youtube]

[youtube]http://www.youtube.com/watch?v=20JCGDwBt7A[/youtube]

[youtube]http://www.youtube.com/watch?v=msHJLwYWX30[/youtube]

:shock:
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Unread postAuthor: al-xg » Tue Dec 18, 2012 8:10 am

Ah, they used that same crappy paintball pistol as me :D
It really isn't that difficult to mount the marker on gimbals in order to actually be able to aim. Flight control boards with position hold, and way-point navigation are quite cheap now. I'm using one for my dissertation project this year.

Flight time is still quite a limitation for rotary wing UAVs, but that will change if things like lithium-air, micro-generators, etc... provide better energy density than the current batteries.

That said, just with small improvements in efficiency (rotors, motors, air frame geometry) I seem to have managed to improve the flight time by at least 60%
With a battery payload just for extended flight time, hour flights seem very plausible. Using fancy batteries, quite a bit more.
For hover flying only, I reckon some high energy density Li-ion cells could work pretty well, but not for heavy payloads as they have a limited discharge current capacity.
Some guy in Russia has posted a video of his multi-rotor flying for over two hours (discarding spent batteries), but I have the feeling this still hasn't been verified.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2012 8:26 am

Something like the Parrot drone stripped down can easily carry 20 or so grams of magic powder in a fragmenting case, this would have a couple of metres lethal radius (with the parts of the drone becoming potentially lethal fragments in their own right).

Something like that being flown to a precise location - possibly from a hidden location with a delay time giving the perpetrator more than enough time to disappear - is a very scary prospect indeed as these things get more capable.
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Unread postAuthor: al-xg » Tue Dec 18, 2012 8:52 am

Well in that case, my dissertation project can carry up to 1.5kg to a location pointed out on google maps within a 2km range, whilst avoiding obstacles along the way :roll:

If you can live with 10-20g payload (depending on what flight times are acceptable) you can get mini quad rotors for $40 delivered and all set up.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2012 9:24 am

al-xg wrote:Well in that case, my dissertation project can carry up to 1.5kg to a location pointed out on google maps within a 2km range, whilst avoiding obstacles along the way :roll:


Hope that doesn't put you on a watch list ;)

If you can live with 10-20g payload (depending on what flight times are acceptable) you can get mini quad rotors for $40 delivered and all set up.


Something like this?

Still just an RC helicopter though, not something you're going to program in any special way or provide video footage etc.
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Unread postAuthor: POLAND_SPUD » Tue Dec 18, 2012 10:05 am

this would have a couple of metres lethal radius (with the parts of the drone becoming potentially lethal fragments in their own right).
Says a guy warning others about watchlists :D

Flight time is still quite a limitation for rotary wing UAVs, but that will change if things like lithium-air, micro-generators, etc... provide better energy density than the current batteries.
With a battery payload just for extended flight time, hour flights seem very plausible. Using fancy batteries, quite a bit more.

Small IC engines could provide both the propulsion and electricity

The only problem is that they aren't as easy to control as electric motors so they don't work well for quatrocopters...
though they are certainly a viable option for fixed wing aircraft thx to energy density of fuel


UAVs are indeed very impressive/scary... I don't think I recall seeing a spudgun that reached more than 700meters....
yet with a UAV one could get 5 or 10km range and pretty good accuracy easily
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Unread postAuthor: al-xg » Tue Dec 18, 2012 11:22 am

The only problem is that they aren't as easy to control as electric motors so they don't work well for quatrocopters...

Variable pitch propellers fix this. A single engine can be used this way and it actually enables inverted flying. There aren't many about but they do work.
You could even run a gas turbine one and abduct people :D

But small hobby grade ICEs aren't very efficient and are pretty noisy.
As far as micro generators, something along these lines would be interesting.
http://www.dtic.mil/cgi-bin/GetTRDoc?Lo ... =ADA504220

Still, even with today's batteries -Edit: actually, there may be a better battery combination for this, I'll try and work it out later on, off to use the laser cutter, they're so cool :lol:-(for example a pack (20cells) made from these: http://www.aliexpress.com/item/20pcs-lo ... 80884.html), can keep a small quad rotor in the air for 1h with a live feed onboard camera. This is based on my own quad's thrust efficiency, and it fits in my backpack.
By adding motors and therefore the payload capacity this could be greatly increased but it would also be bulky.
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Unread postAuthor: POLAND_SPUD » Tue Dec 18, 2012 11:29 am

But small hobby grade ICEs aren't very efficient and are pretty noisy.
still the Spirit of Butts Farm had and ICE ;-) so I guess even a slightly inefficient ICE + fuel tank beats any brushless motor + battery pack by an order of magnitude


Energy density (MJ per liter)

gasoline -> ~36
Lithium-ion battery -> 0.9-2.23

so even if you take into consideration inefficiency of an ICE gasoline still beats lithium-ion batteries when volume is considered
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Last edited by POLAND_SPUD on Tue Dec 18, 2012 11:38 am, edited 1 time in total.
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Unread postAuthor: al-xg » Tue Dec 18, 2012 11:33 am

That's still a lot bigger than what you could put on a small multirotor. For large stuff it's fine.

Just rearanging the above specs in terms of specific energy:
36MJ/l is 46.8MJ/kg so 13kWh/kg not sure what the efficiency of a small hobby ICE is but I can't see it being more than 20% so lets say ~2.6kWh/kg assuming the small ICE is engineered in a similar way the latest car engines ~4.6kWh/kg

Best consumer Li-ion so far 0.265kWh/kg, that's pretty near the limit for this technology I believe, 80% efficient? > 0.212kWh/kg
Current lithium-air prototypes 0.7kWh/kg > 0.56kWh/kg
Lithium-air max density ~10kWh/kg > 8kWh/kg


Something like this?
Still just an RC helicopter though, not something you're going to program in any special way or provide video footage etc.

Yeah, you can get 6 axis gyro+acc stabilised ones though.
They'd be for line of sight only, but then so is the ARdrone really.
Home built/modified solutions are still best in that respect if you want actual autonomous flight.

On a separate note, I was quite surprised to find out that the ARdrone actually runs a Linux OS to handle the video streaming, optical flow position hold and smartphone interfacing.

Hope that doesn't put you on a watch list

I'm taking a plane tomorrow, so we'll (well, at least, I'll) soon find out :D
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Unread postAuthor: POLAND_SPUD » Tue Dec 18, 2012 12:48 pm

well don't forget that you have to take into consideration efficiencies of all teh parts -> batteries, motors and ESCs

TAM 5 flew for +38 hours on 0.9 L of fuel that's f###### impressive
http://en.wikipedia.org/wiki/The_Spirit_of_Butts_Farm

ohh and guess what... I've just found out that they use an alternator to power the electronics on board
Most of the electrical energy for long duration flights is produced by a three-phase alternator driven by the engine. A small battery supplies energy for the descent and landing after the engine is stopped.

from http://tam.plannet21.com/FAQs.htm#energy



ohh and JSR...
[youtube]http://www.youtube.com/watch?v=R7ezXBEBE6U[/youtube]
...if that thing come by my house I kill it :D
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2012 1:12 pm

POLAND_SPUD wrote:Says a guy warning others about watchlists :D


Just warning about the future ;)

As far as micro generators, something along these lines would be interesting.
http://www.dtic.mil/cgi-bin/GetTRDoc?Lo ... c.pdf&AD=A DA504220


Fascinating :)

...if that thing come by my house I kill it


This thing could obliterate your house before you even knew it was there ;)

Image

... and they're going to be close to home too!

http://www.tvn24.pl/mon-powaznie-rozwaz ... 903,s.html
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