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Archive for January, 2009

I came across a report on the new year eve of an old problem concerning the fantastic pattern formation and columnar jointing in nature  resolved. This particular problem  has been close to my heart as I elaborate in the paragraph below hence it was fun to read about it.

A Childhood Story: When I was in grade 2, my pappa got me a set of Childcraft Worldbook. It had some very interesting pictures. I was too young to understand the text completely but I used to love looking at the pictures. There was a very nice picture and a short accompanying article on the Giant’s Causeway in Volume 6 – Our World, on page 31 . However, I enjoyed reading this particular article as it had a story of the kind that kids are attracted to. It said that a lot of people before the turn of the century thought it was made by a giant, Fionn Mac Cumhail, to travel from Ireland to Scotland, and that this explained why the mostly regular hexagonal blocks that made up the Giant’s Causeway were so huge. I was fascinated by the story, but there was a short note at the end – It is believed that these columns were made by volcanic activity. I think fascination is fundamental to most science and art, when talking of science it has to be coupled with its seemingly opposite characteristic – skepticism. I think the line on volcanic activity making the structure did just that. Over the years whenever I saw a picture of the Causeway, I used to wonder how it (specifically the shapes) might have formed. And a PhD student has answered that question now!

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The Giant’s Causeway: On the coast of northern Ireland, there is an area of about 40,000 interlocking basalt columns extending into the sea. Most of the columns are hexagonal and fit very neatly, the neatness of this structure inspired a number of legends of an “intelligent designer”.

giantscauseway_1[A view of the Giant’s Causeway on the northern Irish Coast : Image Source]

Click to Enlarge

giants_causeway[A view of the Basalt Columns on the Causeway: Image Source -BBC]

A structure similar somewhat to the Giant’s Causeway is the Devil’s Postpile in California.

What is known is that in the Paleogene period, there was intense volcanic activity in the region (Antrim), and that it is what formed the structures. However, what was not known was how was it that such specific forms, shapes were formed.

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Research: PhD student Lucas Goehring and his adviser Dr Stephen Morris of the department of Physics  of the University of Toronto have been working on the problem above. They found out that the size of the columns that varies from one site to another varies as according to the speed of cooling of the lava from an eruption/flow. Using a combination (as required for such a task) of solid mathematical theory provided by Harvard Prof L Mahadevan, good experimentation and field work at the actual sites the researchers solved the problem of what determines the size of the columns.The field work involved making measurements in-situ i.e on the columns to determine at what rate had the lava cooled to form them.

The key to understanding and confirming their ideas was reproducing the phenomenon in the lab, that they did using simple materials. The idea was to use water and corn- starch, which cracks when dried and forms very similar columns as the ones talked about. Controlling the drying rate, a relationship between the size of the columns and the cooling rate was worked out.

starch_expt[Image Source – Reference 1]

The above is the experimental setup for the one just described above. According to Goehring : “The columns are formed as a sharp front of cooling moves into the lava flow, assisted by the boiling of groundwater, As the front advances, it leaves behind a crack network which evolves into an almost hexagonal arrangement. This network carves out the columns.”. They found out that the slower the cooling the much larger the columns.

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For more detailed information on the research carried out in this regard, I’d direct you to pages from Goehring’s website.

>> Experiments

>> Field Work

>> Models

>> Extensions

He in the above pages gives a quite accessible picture of their findings and their work. Perfect, especially for somebody like me who is not trained in the field in which this research has been carried out, but are very interested in how it was done.

The findings of this work appeared in the December issue of the proceedings of the national academy of sciences.

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Quick Links:

1. Order and Disorder in Columnar Joints

2. Workshop on Emergent Pattern Formation

3. U-Toronto Press Release

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Today this blog completes one year. I started it last year as a part of a resolution with a number of aims in mind. I am not sure if they have been met at all. So I am kind of disappointed. But then I can give a good fresh try this year (maybe the use of “year” is only figuratively speaking, I know everyday can be a “new year”).

64076main_earth_orbit_330

In one year the blog received 33909 hits. Well, just about okay I guess.

Suggestions are most welcome in the comments or through email if you have something in mind. If some of you are willing to write a guest post on an idea/topic of your choice then you can e-mail me for the same. We can work things out.

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Please Note: I might not be as regular with the blog for the first 4 months of this year for a multiplicity of reasons. Probably they are too private to be discussed here. However I will try to post once in a while. And I will try to stick to the mean number of posts for the previous year.

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Here are some posts from last year that might be looked at in case you missed them (In order of posting):

Note: I am only including posts that can be of general interest.

1. The Working of a Bird Swarm.

2. Adaptive Routing taking Cues from Stigmergy in Ants.

3. Problems with Orion like Projects.

4. Altruism in Animals.

5. Swarm Paintings: Non-Human Art.

6. The Need for Heretics in the Society.

7. REAL Viruses of the Mind.

8. Kafka to Red Ant: A strange Metamorphosis.

9. Peace.

10. The Radical Ideas of Thomas Gold.

11. Smart Man, Wise Man, Feynman!

12. American Prometheus.

13. What makes Terrorists?

14. Voronoi Art.

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I came across a very cool video today morning and that gives this post its name. Before I get into that, I think it would be much desirable to give an introduction to Ornithopters in general and talk about some robotic ornithopters. For those interested solely in the video, well it is at the end of the post (second last video).

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Introduction

An Ornithopter basically means an aircraft (even a robot) that can fly by flapping its wings. Though the word might sound complicated initially (Although the prefix Ornith- is well known). All of us at some point in time (whether as a childhood fantasy or as a serious hobby or professional work) have wanted Ornithopters. Ornithopters have been a fantasy since very ancient times, and it is obvious to have been as birds have always fascinated and amazed humans. There have been many reported Ornithopters in Hindu mythology. Also the legend of Daedalus and Icarus is well known, in which Daedalus designed feathered wings to fly out of the island of Crete on to which he was imprisoned.

The legendary Leonardo Da Vinci – A genius  imprisoned in a time where his ideas just could not have been realized, made some designs of Ornithopters and other glider type flying machines (but let’s avoid machines that do not have any moving wings in this post, though some are very cool). Some of which were very good engineering designs.

design_for_a_flying_machine

Click to Enlarge

Though we tend to regard the idea of wing powered machines as failed because of the success of modern day style aircraft there have been many successful flights. The first reported to have flown successfully was made in 1929 by Alexander Lippisch, it flew about 300 meters before the flight was terminated due to the obvious limitations of human muscle power. A number of motorized ornithopters have been made since then. A number of people take  Ornithopters as a serious hobby.

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Modern Ornithopters

These days though, the interest has been more in ornithopters that resemble insects, such as bees, both as toys and sophisticated autonomous flying spy robots. The size of such Miniature Aerial Vehicles would ensure they are impossible to detect and hence are perfect for spying missions. Especially in the case of urban warfare when the opposing party might be holed up in a building. Thus, needless to say these can be very helpful in counter-terror operations. The aim in making such bots would be to make them very low cost with flight times as high as 5-6 hours. Let me cite some examples of some cool miniature aerial vehicles of the ornithopter category.

After some early feasibility studies done at the Lincoln laboratories at the MIT, DARPA in 1997 began a multi-million dollar program to make some sophisticated Miniature Aerial Vehicles (MAVs), some of the designs and projects also included ornithopters.

One such ornithopter was the MicroBat ornithopter developed at the California Institute of Technology along with AeroVironment and UCLA.

microbat

[The MicroBat Ornithopter, Image Source]

This paper reports the making  of the MicroBat Ornithopter. The excerpt to the paper:

This paper reports the successful development of “Microbat,” the first electrically powered palm-sized ornithopter. This first prototype was flown for 9 seconds in October 1998. It was powered by two 1-farad super capacitors. Due to the rapid discharge of the capacitor power source, the flight duration was limited. To achieve a longer flight, a rechargeable battery as a power source is preferred. The second prototype houses a small 3-gram rechargeable Ni-Cad battery. The best flight performance for this prototype lasted 22 seconds. The latest and current prototype is radio-controlled and is capable of turning left or right, pitching up or down. It weighs approximately 12.5 grams. So far, the best flight duration achieved is 42 seconds. The paper also discusses the study of flapping-wing flight in the wind tunnel using wings developed by MEMS technology. This enables a better understanding the key elements in developing efficient wings to achieve aerodynamic advantage in flapping-wing flight.

Another research group led by Robert C. Michelson made another Ornithopter called the Entomopter. This went one step ahead and can be called a milestone in MAV ornithopter development. The aim was to closely mimick the flight of birds and thus totally eliminate the usage of gears and motors. The entomopter is driven by wings that are driven by a reciprocating chemical muscle.

yellow_sla_entomopter

Click to Enlarge

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Ornithopter Toys

There are now a number of companies that offer ornithopter toys. One of the most well known probably is the FlyTech Dragonfly from WowWee, It is a remote controlled wireless ornithopter. It seems like a pretty fun toy. You can see a video on this toy here >>

800px-flytech_dragonfly_blue_1200px [FlyTech DragonFly Ornithopter]

A number of people take making ornithopters as a very serious hobby. If you wish to make one, then I would direct you to this page.

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Butterfly Ornithopter

Finally I come to the part that gave this blog post its title. ;-)

In a paper at IROS 2008, researchers from the Shimoyama – Matsumoto Lab at the university of Tokyo presented their work on an extremely light butterfly ornithopter.

butterfly_ornithopter_univ_tokyo

[Butterfly Ornithopter: Image Source]

The artificial butterfly wing consists of a thin polymer membrane which is supported by viens of plastic having rectangular cross section. The purpose of this paper was to study the effect of veins on the performance of flight. The parameters for this “butterfly” are more or less comparable to that of an actual butterfly.The weight of the ornithopter including the wings is just about 0.39 gms and the flapping frequency 10 Hz.

Here is a fantastic video of the Ornithopter depicted in the figure above:

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Some more work on Ornithopters at Shimoyama – Matsumoto Lab:

Since I have just mentioned the work on the Butterfly Ornithopter, there is some cool work going at the Shimoyama – Matsumoto Lab on ornithopters.

>> Dragonfly Type of Ornithopters

>> Butterfly Type of Ornithopters

>> Hovering Flight of Ornithopters

taji1

[Hovering Type Ornithopter: Image Source]

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Bio-Inspired Flying Robots

Finally before ending, I would like to post a bonus video ;-)

This video was the winner at the AAAI – 08 video contest. Like the video on Morphogenesis (Swarm Intelligence) which I posted about 10 months back, which was also a winner in the same contest, this video too is excellent.

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Quick Links:

1. MAVSTAR – Micro Aerial Vehicles for Search Tracking and Reconnaissance.

2. A Reciprocating Chemical Muscle for Micro Air Vehicle “Entomopter” Flight – GTRI

3. Nano Air Vehicle – DARPA

4. Ornithopter Zone – Excellent site for the hobbyist.

5.  Project Ornithopter – Project on making Ornithopters on a much larger scale than those discussed in this post.

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