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07/01/2017

Researchers Find a Way to Tap into Long-Lived Sound Waves in Glass

A newly published study from Yale scientists reveals how to enhance the lifetime of sound waves traveling through glass — the material at the heart of fiber optic technologies.

Everyday experience tells us that glass (silica) is highly transparent. In fact, silica is one of the most transparent materials on earth. Light can propagate for tens of kilometers in silica before it experiences any appreciable weakening. This transparency, combined with glass’ formability and low cost, is why glass is used in so many of the fiber-optic technologies that shape the information age.

Yet silica also has a mysterious side. At room temperature, silica is an excellent acoustic material. You can demonstrate this by tapping a wine glass with a fork and listening to it ring for several seconds. However, in sharp contrast with most materials, this resonance is quickly muted when the glass is cooled to cryogenic temperatures.

These peculiar acoustic properties are at the heart of long-standing mysteries in glass physics. In the 1960s scientists discovered many perplexing properties of glass: It conducted heat much less efficiently than expected, and it heated up much more slowly than anticipated. These puzzling discoveries were ultimately explained by localized absorbers within glass that interact with sound waves in the same manner that atoms interact with light. To this day however, the true nature of these “acoustic atoms” is not fully understood.

In addition, absorption by these “acoustic atoms” has another consequence that intrigues scientists. At low temperatures the amplitude of a sound wave affects how long it will ring. Roughly speaking, this means you can make your wine glass ring longer by turning on your stereo, which causes the glass to vibrate at altogether different frequencies. Moreover, the duration of the ringing increases as the stereo volume is turned up.

Yale scientists have used this concept to control the lifetime of sound within glass. By shining laser light into fiber optic waveguides made of glass, they were able to probe and generate acoustic waves in the fiber core. By generating an intense acoustic wave at one frequency (i.e. “turning on the stereo”) and probing at another (“tapping a wine glass”), the researchers were able to extend the lifetime of a sound wave.

The researchers said that because glass is the backbone of a range of cutting-edge technologies, the findings open the possibility of new forms of high-precision sensing and information processing.

“Our work takes an important step toward engineered sound dynamics in glass,” said Peter Rakich, assistant professor of applied physics and physics at Yale and principal investigator of the study.

First author Ryan Behunin, an associate research scientist in Rakich’s lab, said, “Our results demonstrate a new paradigm for achieving higher performance in optomechanical systems.”

The discovery is described in the January edition of the journal Nature Materials.

Co-authors of the study were Yale graduate student Prashanta Kharel and associate research scientist William Renninger.

Publication: R. O. Behunin, et al., “Engineering dissipation with phononic spectral hole burning,” Nature Materials (2016) doi:10.1038/nmat4819

Source: Jim Shelton, Yale University

07/01/2017

26/11/2015

Simply Copying Nature is No Way to Succeed at Inventing – Just Ask Leonardo da Vinci (Op-Ed)

Where do inventions come from? There’s no magic formula, but there are ways to improve your creativity. One method is to look at nature. Some call this activity bionics, others call it biomimetics. Whatever you call it, it is big business: in recent years we have seen the rise of university courses, institutes and learned journals in the subject. The term I prefer is bio-inspired design, and here’s why.

If it hadn’t been for birds, I doubt if anyone would have even thought that it might be possible for something heavier than air to get airborne. With his flying machine, Leonardo da Vinci had a detailed design that looks, on paper, very impressive. But it doesn’t work.

Several centuries passed before we realised why. The bird’s wing performs two separate tasks, both of which are essential. By its shape, it provides lift when air passes over it. And by its movements it provides power. The crucial step to making aircraft was to separate these two functions, leaving the wing to do the lifting but transferring the power function to an engine and propeller, something no bird ever possessed.

There is an important lesson here. The first step is to imitate nature, and the second step is to abandon nature’s ways. At some point you have to give up the love affair, dump nature and move on. The problem is that simply copying nature doesn’t work.

Here is an example from my field – structural materials. Bones are an excellent material, providing support and strength. Currently we can’t make materials that reproduce a bone’s internal structure. But even if we could, we wouldn’t be able to use it in engineering structures for many reasons.

First, nature can live with failure, but we can’t. When we design a component for a car or aircraft, we need to ensure that the probability of failure of that part per year is something like one in a million. Because a vehicle has thousands of parts and is supposed to last for tens of years without catastrophic failure.

But nature is happy to work with much higher failure rates: the chance of breaking a bone if you are a monkey in the wild is about 2% per bone per year. If engineers worked to that standard they would soon be looking for another job. The reason for this difference is that for nature the failure of an individual is of no consequence. What matters is the survival of the species. So nature is wasteful of individual lives, in a way which we risk-averse humans can’t tolerate.

In a recent paper, published in the Journal of Mechanical Engineering Science, I consider several bio-inspired concepts. One is the work of the German engineering Claus Mattheck. His book Design in Nature: Learning from Trees is a classic on biomimetics. Mattheck’s lifelong love affair with trees has led to many important innovations in engineering design.

One of these considers the junction where the branch of a tree meets the trunk. Mattheck said the curvature around this junction was very cleverly designed to minimise the concentration of stress that occurs when engineers try to design the same shape. He suggested that the tree was sensitive to stress and so, as it grew, would deliberately place material in such a way as to minimise stress. He developed a computer programme to simulate tree growth, and the result was a fantastic reduction in stress concentration, allowing for more slender components. This is important, because shaving a few percent off the weight of a component in a car means lower material costs, less fuel usage, less CO2 emissions and so on.

But when I go and actually look at trees, I don’t think Mattheck is right. I don’t think trees are doing what he thinks they are doing, and proving it would be quite difficult. But of course it doesn’t matter if you remember that nature was only the starting point, not the objective of the exercise.

Another example is the recent news that scientists have discovered an animal that runs faster than any other – and it’s a mite. The story – no doubt distorting the original science – was that this mite runs faster than a cheetah if you measure speed in terms of how many body lengths it covers per second.

The report predicted that this fascinating result will be used by bioengineers to improve engineering design. Well, perhaps it will, but if so the inspiration will be the opposite of what it seems. It is well known that smaller animals can run faster when measured by body size – even the humble cockroach beats the cheetah on that measure. But a simple biomechanical model, applying the appropriate scaling laws, would suggest that all animals should be able to run at the same absolute speed, not the same relative speed. So the inspiration here will come from asking “why are the little guys so slow?”.

Nature can be a wonderful muse, an excellent starting point in the development of a new engineering device or material, but don’t make the mistake of thinking that nature has already solved your problems for you.

David Taylor does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

26/11/2015

What is Li-Fi and how is it 100 times faster than Wi-Fi?
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Just as you thought 4G or 5G LTE would finish off Wi-Fi once and for all, Li-Fi appears on the scene to rock its status.
Wi-Fi has been great but it's already being outdone in 5G tests and now on a more local scale Li-Fi is 100 times faster, and more secure.
Li-Fi uses light to transmit data rather than Wi-Fi's radiowaves. Although this was still in the testing phases not long ago it's already set to reach the public.
So how can Li-Fi be so fast and is it really the death of Wi-Fi?
PureLiFi
li-fi
Li-Fi uses light for faster transmission
By using visible light to transmit data Li-Fi is able to increase bandwidth by 100 times. This equates to downloading 18 movies at 1.5GB each, in a single second.
Lab tests revealed that the Li-Fi connection could transmit up to 224 gigbits per second. Now in real world use scientists have reportedly managed to hit a whopping 1GB per second of data transmission.
This was first discovered in 2011 at the University of Edinburgh by Harold Haas. He showed that flickering the light from an LED could transmit more data than a cellular tower.
The current iteration uses Visible Light Communication (VLC) which is light between 400 and 800 terahertz. It's a bit like switching a light on and off for Morse code, or more accurately, to send the ones and zeros of binary bits.
Boston University
lifi_environment
Li-Fi should appear alongside Wi-Fi
It looks like Wi-Fi may not be endangered after all. Li-Fi's creators admit that with Wi-Fi so deeply built into society, replacing it would be unrealistic. Instead they're working on ways to retrofit it to current systems.
So it's likely that in the future we could jump between mobile network data connection, Wi-Fi and Li-Fi seamlessly from our smartphones, for example.
Haas and his team have launched a brand called PureLiFi which offers plug and play access currently limited to 11.5MB per second.
The point of Li-Fi right now is that light is unable to pass through walls. Rather than this being a range disadvantage it's being touted as a positive for security. For this reason companies are looking into implementing Li-Fi in offices. Another reason is that Li-Fi should also suffer far less than Wi-Fi from interference of multiple devices on the same network.
French company Oledcomm is installing its own Li-Fi technology in local hospitals.
The future is bright for Li-Fi
The world of tomorrow may be one where light and internet access are provided from the same point.
Haas said: "In the future we will not only have 14 billion light bulbs, we may have 14 billion LiFis deployed worldwide for a cleaner, greener, and even brighter future."

21/01/2015

Material Science Madness: Crazy Metal Melts in Your Hand...!!
There is an incredible metal that shatters like glass, melts in a human hand, attacks other metals but is non-toxic to humans, and acts like an alien life form when exposed to sulfuric acid and dichromate solution. It sounds too amazing to be true, but gallium is an absolutely real chemical element that’s found in some of the gadgets we use every day.

But perhaps more interestingly, there are a ton of insane experiments scientists like to do with gallium. Thanks to its odd properties and behavior, gallium can do some pretty strange things in the lab. The above video shows what happens when gallium “attacks” aluminum.

The “gallium beating heart” experiment is a popular one that shows how gallium can act like a living thing when submerged in sulfuric acid and a dichromate solution. By altering the surface tension of the gallium, the scientists are able to make the metal look like an organic beating heart.

The melting gallium spoon is a fun demonstration that makes good use of gallium’s 85 degree (F) melting point. A gallium spoon stirs hot water and immediately melts into a puddle on the bottom of the mug. The video above warns against using it for pranks, but we have to admit it would be really, really hard to resist.

15/01/2014

10/12/2013

Ideas & Inspiration...

Webhub Science Alert

10/12/2013

Finding Good Ideas for the Science Fair Projects...!!

10/12/2013

Instrument-Builders...!!

10/12/2013

Science & Technology; "One Million New Scientists. One Million New Ideas."