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Jun 23, 2017, 02:51 PM
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Discussion

"Alternative facts"-- oddball theory of dynamic soaring


(EDIT 8-4-2018 -- I am going to close this thread soon, simply to preserve a record of the conversation without risk of future edits. Feel free to continue the conversation here -- https://www.rcgroups.com/forums/show...soaring-part-2)

(EDIT 5-11-2018-- this thread has gone on for a long time now, through many twists and turns. Of course it's obvious from first principles that the ideas in Colin Taylor's "Dynamic Soaring For Birds" website don't hold water. But if you are interested in learning about some of the specific errors that Mr Taylor has made in developing his theories, you may want to look at post #36, and then skip ahead to posts #215, 216, 220, and 221 https://www.rcgroups.com/forums/show...soaring/page15 . These later posts get into specifics about what exactly is wrong with Mr Taylor's approach at least as it appeared on his website at the time they were written. Note that some of the content regarding kinetic energy and potential energy referenced in the early posts in this thread has now been removed from Colin Taylor's website.

In short, Colin's theories can be best described as errors piled on top of errors. At the root of it all is a basic lack of understanding of how to deal with vector components representing velocity, force, and acceleration operating in two or more dimensions. It's rather amazing that Colin has persisted so long with these theories that are so completely incongruent with what we actually observe when we fly.

Sincerely, Steve Seibel

-- end edit.)

(EDIT 6-15-2018 -- it appears that within the last several months, Colin Taylor's "Dynamic Soaring For Birds" website http://www.dynamic-soaring-for-birds.co.uk has evolved to highlight an alleged "propulsive" effect generated by turning in the downwind direction. See for example the content under the heading "The Leeward Turn" on the home page. This alleged effect is examined and debunked in post #215 https://www.rcgroups.com/forums/show...&postcount=215 in this thread, in the paragraph about in the middle of the (long) post, beginning "(Look-- in fact we find reference to this alleged "propulsive" effect right on the home page of Mr. Taylor's website..", and also in the preceding paragraph.

-- end edit.)

Wow, this guy has put together a whole website to argue essentially that the albatross doesn't really need the wind gradient, he just needs to make a slow turn to windward followed by a fast turn to leeward, repeated over and over.

(Which is why you find sailplane pilots the world over using this excellent technique thousands of feet above the earth's surface, right?)

You don't need to read very far before you'll start encountering things like this:

"The Downwind Turn

If a glider is heading into wind it has low ground-speed and low kinetic energy. As it turns downwind ground-speed and kinetic energy increase. Where does the energy come from? The glider is propelled by gravity and the energy comes from an increased expenditure of potential energy, that is to say height. In other words an increased rate of descent. "

and

"In turning downwind, the glider is not propelled by the wind, at constant airspeed it is diving to gain ground-speed to keep up with the wind."

and

" What I am bringing to this subject is over 40 years and 16000 hours of flying experience on over 30 different types, including gliders. If there is one thing I have learned, it is that nothing good ever comes from a wind gradient or a wind shear. "

Steve

(search keywords albatross dynamic soaring Colin Taylor )
Last edited by aeronaut999; Aug 04, 2018 at 09:26 AM. Reason: Content added at beginning of post
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Jun 23, 2017, 03:14 PM
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You may have found something posted on the internet that's wrong!
Jun 23, 2017, 04:08 PM
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Oh good gosh. Now I see he's also got oddball theories about lee-side dynamic soaring, as practiced by rc gliders--

http://www.dynamic-soaring-for-birds...e_soaring.html

"As explained elsewhere, potential energy is gained in a windward turn but in this case the ‘windward’ turn is made in still air so there is no gain of energy. Energy is lost in a downwind turn, in this case in a strong wind!"

Uh- oh-- sounds like things aren't adding up-- but never mind there's always an explanation to be found:

"I do not think this is either wind-gradient or windward turn dynamic soaring. I think it is more like a kind of auto-rotation, the kind of thing that keeps the rotor of an auto-gyro or the vanes of a vertical-axis windmill turning."

" It is similar to a kind of vertical axis wind turbine. Like a cup anemometer, it has a vertical axis and three arms, but with a vertical airfoil blade at the end of each arm instead of the cup. Like the cup anemometer, this device will also rotate regardless of the wind direction. Just imagine instead of three arms, a single arm and single airfoil and there is your glider in a steep turn sipping at the wind at the upwind peak of the orbit."

"Also, although these glider models are achieving very high ground-speeds, recorded by radar speed guns, it may be that they are generating and flying within, a rotating vortex in the otherwise stationary air in the lee of the hill. This would mean that the airspeed and (G loading) are not as high as the ground speed. "
Jun 23, 2017, 04:26 PM
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It would help if you included a link to an explanation you deem to be true. I remember trying to understand albatross soaring a few years ago and none of it made sense (I'm pretty sure that was one of the websites I was looking at though so maybe that's why.)
Jun 23, 2017, 04:39 PM
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Well basically you gain free energy whenever you climb nose-to-wind in a wind gradient, and also whenever you descend tail-to-the-wind in a wind gradient. The airspeed tends to increase in both cases, or if the airspeed is held constant, you get a free climb in the upwind case, and a flatter-than-usual glide in the downwind case. Going sideways to the wind the gradient has no effect. So you can climb nose-to-wind, then turn 90 degrees and run sideways in a long flat glide, then turn nose to wind and climb again, all with a constant airspeed. Sorry that's just a really rough overview, there are all kinds of nuances to add, is the bird getting significant ridge lift off the waves, is the airspeed varying rather than constant, and on and on.

Some links are given near the top of this web page. It's been a long time since I've looked at them so don't remember which to recommend above others--

http://www.aeroexperiments.org/links.shtml
Jun 23, 2017, 06:09 PM
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Did this guy fall for it too? (full scale soaring)


Skip to 2:22-- it's not obvious why there would be much of a wind gradient here. I guess you can see he is near the same altitude as a distant ridgetop-- but seems to me he'd have to be a lot closer to the ridgeline to really get a strong gradient effect-- especially on a convective day with lots of mixing--

Dynamic Soaring USAF (4 min 16 sec)


also that Turkey Vulture's u-turn at 0:30 doesn't seem to have much altitude change involved-- so no benefit from gradient / actual increase in airspeed--
Last edited by aeronaut999; Jun 24, 2017 at 11:06 PM.
Jun 23, 2017, 07:50 PM
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ON THE HEADWIND:
Is there some transient only effect going on? Because the steady state condition is if you keep nosing into the wind for long enough won't you eventually start moving backwards relative to the ground and moving at zero speed relative to the wind (i.e. being carried along with the wind)?

Maybe it's the case that when nosed into the fast wind, you gain potential energy in the form of altitude as long as as your airspeed is greater than zero (as long as your plane is not yet just being blown along with the wind). I guess it must needs to be such that it is a net increase and not just trading your initial kinetic energy (airspeed) for potential energy (more altitude).

I am having trouble visualizing if the headwind would give a greater altitude gain than without one because it provides an increase in airspeed for the same AOA (which I assume remains fixed the entire time so that you aren't actually using more elevator to climb into the headwind) which would produces more drag, which would slow down the plane to the zero airspeed threshold faster than gliding in still air. But I guess the time taken until airspeed is reduced to zero doesn't actually matter as long as you gain altitude at a faster rate (than pulling up on the climbing with the elevator in still air until you stall) such that the altitude gained is greater than that obtained if you climbed with the elevator in still air.
---
ON THE TAILWIND:
Then, whenever you do decide to turn around in order to traverse from the wind gradient while riding the tailwind. You surely are converting some potential energy into kinetic energy...but I am unable to clearly visualize if you actually gain kinetic energy from that tailwind. It definitely speeds you up relative to the ground more than if you were just descending in still air so I guess it must? Something feels not entirely clear though...Is it that the kinetic energy gained from the tailwind is an increase in ground speed but not airspeed, and therefore you must drop out of the fast wind into the slower wind to exploit it for the purposes of flight (since flight only depends on airspeed and not at all on ground speed?)

I feel like I'm getting into the weird conundrum of kinetic energy being associated with velocity, except velocity is measured with respect to something and I'm not sure if the reference is supposed to be the wind or the ground. Sort of like how trying to figure out the gravitational potential energy of something in space but not sure what gravity well you're supposed to be using. Perhaps it's that kinetic energy is measured with respect to groundspeed (since airspeeds are also measured with respect to the ground) but for the purposes of flight it's airspeed that matters so there's a weird back and forth happening between the two.
------
I mean, so far it seems less intuitive but more logically clear when I work through it how you gain energy from the tailwind phase. But the headwind phase seems more intuitive but less logically clear as to how the net energy is gained.
Last edited by DKNguyen; Jun 23, 2017 at 08:35 PM.
Jun 23, 2017, 08:53 PM
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Hmmm...having trouble following what his website is trying to say. I think I sort of get the gist of it. It sounds like he's weighed all the factors a bit differently so they balance out for an easier net-gain in energy so that you don't need the gradient and he spends a lot of time talking about the turns because that's where most of the energy is supposed to be lost or gained by messing with the relative wind.

I dunno...it doesn't seem that crazy to me?
Last edited by DKNguyen; Jun 23, 2017 at 09:17 PM.
Jun 24, 2017, 04:50 AM
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"the answer my friend, is blowing in the wind"


It's all about transient effects

Forgetting the exact technique used by the albatross (remember this is a fairly low altitude thing, higher up we get into "normal" soaring with normal lift sources, including very high altitude "ridge-soaring" at the intersection of diff-velocity wind layers), imagine an albatross sized/mass/wingloading/airspeed MODEL aircraft with a huge velocity-changing fan in front of it:

1. If the wind speed suddenly (as in instantaneously!) increases, the albatross/model/plane will MOMENTARILY climb ... then descend below the starting altitude before the wind-velocity change (Entropy loss because the plane will slow down at the top of its brief climb, then speed up as it descends, having reached the same airspeed as before, the true velocity change w.r.t. the Earth Inertial Reference Frame losing energy due to Entropy, like a bike coasting down and then up another hill can never reach the same height just using stored momentum)

2. The reverse happens if the wind /fan suddenly decreases: model will drop, speed up then climb but to a height lower than the start of the wind-speed change.

All of this is calculable using the model's mass, L/D, wind-speed change, etc.

The point is it takes the model or albatross a small amount of time to react to a change in the AIRSPEED to which it has been self-stabilized [trimmed]. The effect is not essentially different as when releasing a flat piece of paper or foam into the wind at a positive AoA: the paper/foam will climb for a bit and as it reaches the wind's speed then fall at a distance LESS than the time it was in the air multiplied by the wind-speed (loss described as being due to Entropy).

The entire process is reverse-analogous to "pumping up" a kite, with height-changing energy inputted via the kite-line, and in this way getting the kite itself into higher, faster moving air. whereas the albatross needs to stay low to be in the greatest velocity gradient (as opposed to a featherweight kite the birds weigh around 20 lb/ 9 kg)


Since the living albatross is gaining/using energy from the velocity gradient (due to the ocean surface slowing down the wind passing over it), the albatrosses' action in turn eventually slows the Earth. Given the impossibility of exact calculations as to how much (imagine many albatrosses in diff parts of the Pacific flying in diff directions at the same time), the energy gained can be considered inconsequential w.r.t. changing the Earth's rotational momentum. Free (enough) Energy (not really if there were as many albatrosses as humans) ....
Last edited by xlcrlee; Jun 24, 2017 at 05:43 PM.
Jun 24, 2017, 05:52 AM
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re: Post #9 >

An interesting use of the same inertia vs. flight velocity VECTOR change can be noted in the situation of a falcon trying to snag a Budgie in a flock:

Apparently these small parrots are the only birds the Australian falcons can NOT catch! The Budgie and falcon have similar wingform (planform) and can fly at about the same speed in level flight. The two species have comparable intelligence, the falcon specializing in hunting strategy (knowing which way a certain species is likely to use to avoid capture and quick death) while the Budgie is highly social. These parrots are always aware of each other, visually, sound-wise and by telepathy, a kind of radio-like connection confirmed by US and RU spy agencies ["Distant Viewing"] and by Boeing for years working on pilot thought-control of aircraft as depicted in the "Firefox" film.

Another most important feature of the Budgies is the strong use of random thought and decisions. This is similar to the random action in the knee ganglia of being-chased rabbits: the rabbits do NOT know exactly which way their next escaping spring will take them ... so the hunting animal also does not know and must wait, giving the rabbit a bit of extra time. Of course sometimes a tree gets in the way ....

Falcons soon learn that the Budgie species have no set escape plan and she must WAIT to see which way to go to instead of being able to instantly head off the Budgie with the shortest attack path ("head 'em off at the pass, cowboy"). With similar flying speed, this eliminates the falcon's main advantage over other animals.

The Budgies behind the falcon can see which way her head is pointed, can tell who is her present target, and the ENTIRE flock is now aware of the falcon's position and target. The "connected" flock (visually, etc.), including the target, now has the same information as the falcon, maybe more. They can watch her head, wings and tail-feathers to intelligently predict her next move or next target, if that has suddenly changed.

NOW the connection to Dynamic Soaring ....

It takes a tiny moment from when the falcon changes her flying surfaces and head to when the actual flight vector changes. This very brief moment, a long time for a bird whose brain operates up to 20x faster than ours, allows the hunted Budgie to make a sudden random change while the falcon is still stuck with her "old" plan!

The momentum VECTOR and the time required to change it is a fact with which we must all deal ... and the Budgie flies off in some unexpected manner. I watched a docu showing an Australian watering-hole at which a large flock of thirsty Budgies were drinking and getting wet (Outback is a desert). One poor Budgie had a hawk at his 6, above him and getting ready to grab. Just above the water, in an unpracticed but clever move, the Budgie withdrew his wings and dropped into the water. The hungry raptor continued with the Budgie well behind, having merely bounced into and back out of the water again, quickly back in the air again at high speed in a direction away from attack.

MOMENTUM is a vector quantity
Jun 24, 2017, 06:01 AM
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re: "radio-like" connection

addendum factoid: I can often be typing (mobile or computer) something while smart talkative Budgie Kiki (he started speaking & understanding English at ONE month old) is across the room and unable to see what I am typing. More than a few times if I type (and thus think! ) a word like "food" ... from across the room Kiki will at the same time SAY "eat" (one of his favorite activities).

Only one of many daily-occurring examples

honest ....
Jun 24, 2017, 11:54 AM
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There has to be a wind gradient, or a transient change in wind speed, involved in dynamic soaring. (As is well known and has apparently been well understood since at least 1883-- see http://www.dynamic-soaring-for-birds.co.uk/index.html.) You can't formulate a theory that allows you to do a certain series of maneuvers and gain altitude in a completely uniform, horizontal windfield. Otherwise, a sailplane pilot at high altitude (far from the effect of the ground) could pick any arbitrary reference frame-- say a truck driving 100 mph on a straight highway below-- and say "I define that to be the ground, and therefore I define this uniform airmass I'm flying in to be in motion at 100 mph wind speed." Even if it is in fact completely calm. He could then proceed to do a series of maneuvers, correctly oriented in relation to this arbitrary "ground" reference frame, and gain more altitude as a result. It doesn't work this way in reality!

I posed this issue to the author of the website and he replied that it would not work unless there was really an actual wind, but in that case it would work-- we should be able to go dynamic soaring albatross-style at any arbitrary altitude-- so long as we are efficient enough not to need the assistance of ground effect, (emphasis that's ground effect, not wind gradient) and so long as we have adequate roll rate capability and such.

One fundamental flaw at the bottom of this house of cards is the idea that as an aircraft turns downwind, inertia tends to make it lose airspeed and/ or altitude. And the opposite while turning upwind. From the airmass reference frame it's obvious why this isn't true. From the ground reference frame it's less obvious until we realize the sideways lift vector from the banked wing is not purely centripetal in the ground reference frame, and automatically provides the increase/ decrease in groundspeed that is required to hold the airspeed constant. "Inertia" just means that when there is an acceleration, there must be a force causing the acceleration, and now we understand what that force is. The sideways force from the banked wing.

The other fundamental flaw at the bottom of this house of cards, is the failure to appreciate that the ground is not some special, privileged reference frame, as compared to any other valid inertial reference frame, such as an airmass in uniform motion.

Don't let the pages of math fool you-- this website is riddled with really fundamental errors.

Ouch I don't want to get started too far these rabbit holes today!

Steve
Last edited by aeronaut999; Jun 24, 2017 at 09:17 PM.
Jun 24, 2017, 05:20 PM
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The arguments given on the website are so imprecise and inconsistent that it's hard to tell if the author thinks it's the turn-to-downwind, or the turn-to-upwind, that pumps energy into the bird/ aircraft, even under simple conditions of no elaborate maneuvers. With various elaborate maneuvers he seems to be arguing that in some cases BOTH the turn-to-downwind and the turn-to-upwind can pump energy into the bird/ aircraft. And remember, all of this is supposedly NOT dependent on the wind gradient or on gusts etc.

Puzzling over lee-side dynamic soaring, he says "As explained elsewhere, potential energy is gained in a windward turn but in this case the ‘windward’ turn is made in still air so there is no gain of energy. Energy is lost in a downwind turn, in this case in a strong wind!" So basically it seems he thinks a turn-into-wind is generally favorable and a turn-away-from-the-wind is generally unfavorable.

Yet in another place, discussing turns-to-downwind, he says

"The Leeward Turn

The albatross gains momentum in the leeward turn using a component of aerodynamic force to act as a propulsive force. It provides the acceleration which is seen as an increase in ground-speed rather than airspeed. Thus it gains horizontal momentum and kinetic energy without losing potential energy other than a small drag loss during the turn reversals."

Sounds like magic to me!

Again remember all this is supposedly NOT dependent on the wind gradient

Actually the above leeward turn description is indeed accurate if we are measuring momentum and kinetic energy relative to the ground-based reference frame rather than the airmass-based reference frame-- which is a totally legitimate approach. The force from the banked wing does include a component that drives the increase in groundspeed. The catch is, as soon as the bird begins to turn upwind all this extra momentum/ kinetic energy will start to disappear--again due to the action of the force from the banked wing-- and there will be no altitude pay-off, just as there was no altitude cost to the downwind acceleration.

In an email to me, he said an aircraft would tend to lose energy (apparently speaking in relation to the airmass reference frame) while turning to upwind, because the groundspeed would slow, and due to inertia this would involve some increase in airspeed, which would cause some extra drag. OK, so now an airspeed gain has an unfavorable energetic effect, and it's the downwind turn that is favorable, and the upwind turn that is unfavorable, in terms of energy gain/ loss? But shouldn't an increase in airspeed also lead to a temporary tendency to gain altitude?

(Brief edit 7/24-- the idea that inertia causes some delay in an aircraft's adjustment to the increasing headwind component experienced while turning in the upwind direction, is a core element of Mr. Taylor's theories and is explicitly addressed on his website: see the page http://www.dynamic-soaring-for-birds...rn_theory.html : "For example, if the headwind increases, airspeed increases slightly, drag increases, ground-speed and airspeed reduce and a new state of equilibrium is reached with the original airspeed but with reduced ground-speed. In other words, while inertia resists changes to ground-speed, the changing wind components affect the airspeed. Those changing wind-components can be due to changing wind-velocity or changing aircraft-velocity relative to the wind, eg. changing wind-angle."

Clearly, Mr. Taylor's conception of an increase in headwind is not limited to an actual increase in windspeed, but also includes an increase in headwind component due to a turn (change in heading). End brief edit 7/24.)

*** The above line of argument seems to view "inertia" as some sort of time lag between certain events and other related events. Basically we are claiming that the groundspeed can't actually decrease fast enough to keep the airspeed constant as we turn nose-to-wind. But why should this be so? In reality, inertia is simply the fact that when a force acts on an object, the object does not accelerate at an infinite rate, but rather accelerates at a rate that is proportional to the force acting on the object, and inversely proportional to the mass of the object. And guess what--that's exactly the sort of acceleration/ deceleration (change in groundspeed) that we need to see in response to the sideways force from the banked wing, in order to keep the airspeed exactly constant as we turn nose-to wind. There is no valid inertia-based argument that the airspeed should tend to increase, due to some sort of lag in the decrease in groundspeed or some other related effect, as we turn nose-to-wind. IF we expected the decrease in groundspeed to be somehow driven by the aircraft's inherent pitch stabliity dynamics, acting to try to hold the airspeed constant in the face of some external disturbance, rather than driven purely by the sideways force from the banked wing, THEN we could make an argument for a temporary "overshoot" or "undershoot" in both groundspeed and airspeed. But that's not what's going on here. ***

(Back to the website now-- ) Lots of vague arguments about kinetic energy, potential energy, and momentum, but a complete lack of accurate force vector diagrams showing the aerodynamic forces actually acting on the bird/ aircraft at any point in time

Here he's claiming that simply by turning to face into the wind, while holding airspeed constant, you get a free gain of potential energy (altitude) equal to the loss of kinetic energy as seen in the ground-based reference frame (i.e. groundspeed)-- sounds awesome! --

"Airspeed is constant in the windward turn, but kinetic energy at the beginning of the turn is proportional to airspeed plus tailwind component (squared) and at the end of the turn is proportional to airspeed minus headwind component (squared). The law of conservation of energy means that energy is not lost but can be converted to another form of energy. The change of kinetic energy (KE) is equivalent to a change of potential energy (PE) which, in turn, is equivalent to drag losses. When the wind is strong enough, the gain of potential energy from KE is greater than the losses due to drag and the bird can maintain or gain height."

As already noted above, it doesn't work this way. The related thread I recently started helps us understand why the law of conservation of energy can NOT be applied in this way--"Thought experiment puzzle-- pertains to upwind/ downwind"-- http://www.rcgroups.com/forums/showt...pwind-downwind . Energy is not conserved because we are not accounting for the energy transferred from the bird or aircraft to the airmass-- which is not transferred at a constant rate throughout the course of the turn or circle, from the standpoint of the ground-based reference frame. Thus we can't make an argument for some tendency to gain altitude and potential energy as we turn upwind while holding the airspeed constant, despite the fact that we're losing groundspeed and ground-referenced kinetic energy.

Everything on this website is hopelessly jumbled up-- I hate to see that someone put so much work into something that is so far off the mark.

And it all looks so "science-y"-- see the "data" page-- http://www.dynamic-soaring-for-birds...html/data.html -- I hope no one doing serious work on these topics is sucked in to spending their time giving serious consideration to this line of argument--

Steve
Last edited by aeronaut999; Jul 24, 2017 at 06:40 PM.
Jun 24, 2017, 09:28 PM
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Guess what, no one else is falling for it-- (though the argument has made it as far as the web page of an ornithological society-- )

Scroll down to "comments" section here

(thread from three years ago)

http://www.bou.org.uk/dynamic-soaring/

key search terms: british ornithologist's union albatross dynamic soaring Colin Taylor

oh dear-- see also http://talkrational.org/archive/show...&postcount=217

PS here's another article on the bou website that is a response to Colin Taylor's ideas--

http://www.bou.org.uk/birds-and-dynamic-soaring/
Last edited by aeronaut999; May 19, 2018 at 09:41 AM. Reason: added another link
Jun 27, 2017, 01:36 PM
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(accidental double post)


Sorry for double post, was hidden on the previous page of my browser window
Last edited by aeronaut999; Jun 27, 2017 at 02:01 PM.


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