| View previous topic :: View next topic |
| Author |
Message |
Sara Delan
Sage
Joined: 08 Jan 2008
Posts: 579
|
 Posted: Tue Aug 25, 2009 1:00 am Post subject: Account Filter? |
 |
With those spambot things? I thought you needed to get your account, like, approved before you could do stuff? Maybe I'm just wrong and fabricating memories again, but I remember having to get approval before I could post stuff.
If I'm wrong, could/should that be set up? I mean, there's almost always a moderater of some level logged on at any one point anyway, wouldn't be THAT much a deterrant from posting nearly right away.
I guess it's not that big a deal, in the long run... just throwing that out there.
_________________
I have no idea what you are talking about.
Sig curtisy of Yasamin
|
|
| Back to top |
|
 |
Halister Marner
Site Programmer
Joined: 05 Oct 2006
Posts: 2217
|
| Posted: Tue Aug 25, 2009 1:15 am Post subject: |
|
That was only the second one in the past few months, it's either a human registering for spam purposes, or we are just getting way more hits from spambots and the 6 picture CAPTCHA is being randomly broken, since with enough registration requests, 6 check boxes would eventually let the odd bot through.
If it keeps up, I'll just change the images from 6 to 8, or from 6 to 10 to reduce that chance.
If it ends up being human registrations, and they get worse, we'll probably have to set registration to admin approval. However there's always creative ways around that, I have lots of interesting methods for any bot situation.
_________________
"There are those who dream to escape reality, and there are those who dream to change it." |
|
| Back to top |
|
|
Cal Hurst
Atlantic Legend
Joined: 29 Dec 2003
Posts: 8025
Location: Massachusetts
|
| Posted: Tue Aug 25, 2009 1:20 am Post subject: |
|
Put up a picture and ask what animal it is or something. Or the picture of someone and ask what their last name is. couple options. Could also have some fun with this...
_________________
 |
|
| Back to top |
|
|
Sara Delan
Sage
Joined: 08 Jan 2008
Posts: 579
|
| Posted: Tue Aug 25, 2009 1:22 am Post subject: |
|
Ask really biased questions
"Which is better? Ham or Turkey?"
_________________
I have no idea what you are talking about.
Sig curtisy of Yasamin
|
|
| Back to top |
|
|
Halister Marner
Site Programmer
Joined: 05 Oct 2006
Posts: 2217
|
| Posted: Tue Aug 25, 2009 1:26 am Post subject: |
|
How about, "What is the air speed velocity of an unladen swallow?"
_________________
"There are those who dream to escape reality, and there are those who dream to change it." |
|
| Back to top |
|
|
Lord Aragothias
Journeyman
Joined: 06 Aug 2004
Posts: 191
|
| Posted: Tue Aug 25, 2009 2:27 am Post subject: |
|
| Halister Marner wrote: | | How about, "What is the air speed velocity of an unladen swallow?" |
What do you mean, an African or European Swallow?
To begin with, I needed basic kinematic data on African and European swallow species.
South African Swallow
(Hirundo spilodera) European Swallow
(Hirundo rustica)
Although 47 of the 74 worldwide swallow species are found in Africa,1 only two species are named after the continent: the West African Swallow (Hirundo domicella) and the South African Swallow (Hirundo spilodera), also known as the South African Cave Swallow.
Since the range of the South African Swallow extends only as far north as Zaire,2 I felt fairly confident that this was the non-migratory African species referred to in previous discussions of the comparative and cooperative weight-bearing capabilities of African and European swallows.3
Kinematic data for both African species was difficult to find, but the Barn or European Swallow (Hirundo rustica) has been studied intensively, and kinematic data for that species was readily available.
It’s a simple question of weight ratios
A 54-year survey of 26,285 European Swallows captured and released by the Avian Demography Unit of the University of Capetown finds that the average adult European swallow has a wing length of 12.2 cm and a body mass of 20.3 grams.4
Because wing beat frequency and wing amplitude both scale with body mass,5 and flight kinematic data is available for at least 22 other bird species,6 it should be possible to estimate the frequency (f ) and amplitude (A) of the European Swallow by a comparison with similar species. With those two numbers, it will be possible to estimate airspeed (U).
In order to maintain airspeed velocity, a swallow needs to beat its wings forty-three times every second, right?
Actually, wrong. By comparing the European Swallow with bird species of similar body mass, we can estimate that the swallow beats its wings 18 times a second with an amplitude of 18 cm:
Species Body mass Frequency Amplitude
Zebra Finch 13 g 27 Hz 11 cm
European Swallow 20 g ≈ 18 Hz? ≈ 18 cm?
Downy Woodpecker 27 g 14 Hz 29 cm
Budgerigar 34 g 14 Hz 15 cm
Note that even the tiny Zebra Finch flaps its wings no more than 27 times a second while cruising.
If we ignore body mass and look only at bird species with a similar wingspan, we can estimate an average frequency of 14 beats per second and an amplitude of 23 cm:
Species Wingspan Frequency Amplitude
Budgerigar 27 cm 14 Hz 15 cm
European Swallow ≈ 28–30 cm ≈ 14 Hz? ≈ 23 cm?
Downy Woodpecker 31 cm 14 Hz 29 cm
European Starling 35 cm 14 Hz 26 cm
By averaging all 6 values, we can estimate that an average European Swallow flies at cruising speed with a frequency of roughly 15 beats per second, and an amplitude of roughly 22 cm.
Skip a bit, Brother
Last month’s article on The Strouhal Number in Cruising Flight showed how simplified flight waveforms that graph amplitude versus wavelength can be useful for visualizing the Strouhal ratio (fA/U), a dimensionless parameter that tends to fall in the range of 0.2–0.4 during efficient cruising flight.
For a European Swallow flying with our estimated wingbeat amplitude of 24 cm, the predicted pattern of cruising flight ranges from a Strouhal number (St) of 0.2:
... to a less efficient 0.4:
If the first diagram (St = 0.2) is accurate, then the cruising speed of the European Swallow would be roughly 16 meters per second (15 beats per second * 1.1 meters per beat). If the second diagram (St = 0.4) is accurate, then the cruising speed of the European Swallow would be closer to 8 meters per second (15 beats per second * 0.55 meters per beat).
If we settle on an intermediate Strouhal value of 0.3:
We can estimate the airspeed of the European Swallow to be roughly 11 meters per second (15 beats per second * 0.73 meters per beat).
Three shall be the number thou shalt count
Airspeed can also be predicted using a published formula. By inverting this midpoint Strouhal ratio of 0.3 (fA/U ≈ 0.3), Graham K. Taylor et al. show that as a rule of thumb, the speed of a flying animal is roughly 3 times frequency times amplitude (U ≈ 3fA).5
We now need only plug in the numbers:
U ≈ 3fA
f ≈ 15 (beats per second)
A ≈ 0.22 (meters per beat)
U ≈ 3*15*0.22 ≈ 9.9
... to estimate that the airspeed velocity of an unladen European Swallow is 10 meters per second.
Oh, yeah, I agree with that
With some further study, it became clear that these estimates are accurate, though perhaps coincidental.
An actual study of two European Swallows flying in a low-turbulence wind tunnel in Lund, Sweden, shows that swallows flap their wings much slower than my estimate, at only 7–9 beats per second:
“Compared with other species of similar size, the swallow has quite low wingbeat frequency and relatively long wings.” 7
The maximum speed the birds could maintain was 13–14 meters per second, and although the Lund study does not discuss cruising flight in particular, the most efficient flapping (7 beats per second) occurred at an airspeed in the range of 8–11 meters per second, with an amplitude of 90–100° (17–19 cm).
And there was much rejoicing
Averaging the above numbers and plugging them in to the Strouhal equation for cruising flight (fA/U = 7 beats per second * 0.18 meters per beat / 9.5 meters per second) yields a Strouhal number of roughly 0.13:
... indicating a surprisingly efficient flight pattern falling well below the expected range of 0.2–0.4.
Although a definitive answer would of course require further measurements, published species-wide averages of wing length and body mass, initial Strouhal estimates based on those averages and cross-species comparisons, the Lund wind tunnel study of birds flying at a range of speeds, and revised Strouhal numbers based on that study all lead me to estimate that the average cruising airspeed velocity of an unladen European Swallow is roughly 11 meters per second, or 24 miles an hour. |
|
| Back to top |
|
|
Cal Hurst
Atlantic Legend
Joined: 29 Dec 2003
Posts: 8025
Location: Massachusetts
|
| Posted: Tue Aug 25, 2009 2:43 am Post subject: |
|
That'd be a good one. They should be required to type in all of the above.
_________________
|
|
| Back to top |
|
|
Yasamin
Lore Master
Joined: 25 Jul 2007
Posts: 1221
Location: Behind the laughter that lays within the shadows
|
| Posted: Tue Aug 25, 2009 2:50 am Post subject: |
|
*blinks* Tell me that's all made up, or in an article somewhere and you didn't actually care enough to figure that out? Please?
_________________
(4:45:41 PM) Jarem: It becomes increasingly difficult to feel noble in my causes when my cause is to defend my charge from her own violent tendencies. |
|
| Back to top |
|
|
Davaran Skyfire
Sage
Joined: 10 Feb 2008
Posts: 679
Location: Sanctus, The Kingdom Of
|
| Posted: Tue Aug 25, 2009 3:05 am Post subject: |
|
 |
|
| Back to top |
|
|
Arakad
Lore Keeper
Joined: 02 Jan 2005
Posts: 940
|
| Posted: Tue Aug 25, 2009 3:40 am Post subject: |
|
| Yasamin wrote: | | *blinks* Tell me that's all made up, or in an article somewhere and you didn't actually care enough to figure that out? Please? |
Monty Python *chuckles* |
|
| Back to top |
|
|
Ceinwyn ab'Arawn
Transcendent Spammer
Joined: 13 Dec 2004
Posts: 5017
|
| Posted: Tue Aug 25, 2009 7:57 am Post subject: |
|
| Yasamin wrote: | | *blinks* Tell me that's all made up, or in an article somewhere and you didn't actually care enough to figure that out? Please? |
Yasa, you have to go watch that, NOW. Homework assignment. >< |
|
| Back to top |
|
|
Edda
Certifiable
Joined: 20 Jan 2009
Posts: 1586
Location: US
|
| Posted: Tue Aug 25, 2009 7:58 am Post subject: |
|
HAAHAHHAHAHAHAHAHHAHAHAHAHAHA
I love random references to that movie
Right , Ken? |
|
| Back to top |
|
|
Yasamin
Lore Master
Joined: 25 Jul 2007
Posts: 1221
Location: Behind the laughter that lays within the shadows
|
| Posted: Tue Aug 25, 2009 1:04 pm Post subject: |
|
UGH Monty Python seriously? *bangs head*
_________________
(4:45:41 PM) Jarem: It becomes increasingly difficult to feel noble in my causes when my cause is to defend my charge from her own violent tendencies. |
|
| Back to top |
|
|
Cal Hurst
Atlantic Legend
Joined: 29 Dec 2003
Posts: 8025
Location: Massachusetts
|
| Posted: Tue Aug 25, 2009 2:21 pm Post subject: |
|
Bring out your dead!
In fact, what if you typed out a long-winded paragraph about the community at the authorization screen. And then stated something like "The fourth word in the fifth sentence followed by the number combination 246 is the password to authorize your account" or something like that. it's a little elaborate, yeah, but I bet it'd do away with the spambots, and even some of those people who manually register.
_________________
|
|
| Back to top |
|
|
Molly
Moderator
Joined: 29 Dec 2003
Posts: 3627
Location: The ARPC Boards or Sanctus, Luna, Malas (VA USA)
|
| Posted: Sun Aug 30, 2009 12:07 pm Post subject: |
|
I fart in your general direction!
_________________
Grand Duchess Molly Kaldhel
Oracle of Truth
The House Gauntlet
Sanctus, Luna, Malas
https://www.youtube.com/watch?v=xXoGDbJ5nLU
_______________________
"In politics, if you want anything said, ask a man. If you want anything done, ask a woman."
-Margaret Thatcher- |
|
| Back to top |
|
|
|
FAQ
Search
Calendar
Links
Wiki
Register
Usergroups
RSS Feed
Portal
Profile
