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Quiet cuttlefish robot dives through underwater forest

“A four-finned robot ripples through the water, taking inspiration from the movement of cuttlefish.

Although the animal is better known for its powers of disguise and stunning communication skills, its undulating swimming motion is also noteworthy, allowing for efficient and agile motion.

Created by Pascal Buholzer and fellow students from the Swiss Federal Institute of Technology in Zürich, the copycat robot, named Sepios, demonstrates that its finned design can be an environmentally friendly alternative to propellers.”

See the full video at New Scientist: http://goo.gl/o3p0dN
Learn more about the project at their website: http://sepios.org/
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Apparently +NASA​ is working on a 4-legged spider-like robot that can assemble lightweight structures in #space like a spider spins a web. This project is loosely #biomimetic, I suppose. It certainly is the kind of project that gives you the feeling of the #technology promised by science fiction. So, in that regard, this is an exciting development.

[ #news #tech #technews #NASA #SpiderFab ]
It's SpiderFab, a tech that could change how we build & deploy spacecraft: http://www.nasa.gov/content/spiderfab ‪#‎321TechOff‬
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This Ingenious Augmented Reality Mirror will Take Telepresence to A New Level

We all know that the conventional mirror being the most reliable way of actually viewing oneself. A camera image is nowhere close to that.

A group of American and Japanese inventors claim to have invented a way of actually being able to achieve a feat of capturing the perfect image and When the image stream from the camera is displayed on the screen, it appears to mimic a reflection in a mirror, rather than a recorded video stream.

How the Tech Behind this AR Mirror Works -

The camera(s) will generate a stream of images of the user and send it across to a processor. The processor employed here detects the presence of the user and applies adaptive transformation mapping to the stream of images generated.

What is Adaptive Transformation Mapping – This is image transformation technique that is a combination of at least two of the followings transformation–  Vertical flip, projection transformation, rotation resize, 2D offset, optic distortion correction etc.
 
The adaptive transformation uses the stream of images to generate virtual reality in real time. The original images from the camera are discarded, and instead the virtual world is presented on the monitor.

What you can do with this -
1. The telepresence will be very close to meeting in reality.
2. Doctors can do patient monitoring and diagnosis from miles away.
3. It will provide a robust security system where a mirror will authenticate a person.
4. By using augmented reality and adaptive image transformation you can change your appearance like color of your shirt, tie or pant    before a video chat.


Have a look - http://greybmusings.wordpress.com/2014/10/09/augmented-reality-mirror-utilising-adaptive-image-transformation/

  #augmentedrealityandtelepresence #telepresence #augmentedreality #adaptiveimagetransformation

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Why did the scramjet not take off? : Its been a long haul for the scramjet. The technology has existed since the 1950s, but since Budget cuts and politics (and rocket tech) came along, scramjets were relegated to a 'also ran' program. Why is it an idea one would want? The cost per launch using a railgun cum scramjet or air to air launch would be many orders of magnitude less than conventional rocket technology. Unfortunately, the testing of these has been dogged by failure and budget cuts...

Disappointment : Until the last few years, the scramjet had an unbroken history of disappointment. Budget cuts killed the program in 1993. Its shape, however, lived on in two small test vehicles, the NASA X-43 and U.S. Air Force X-51, which have managed a few seconds of scramjet flight.

Sweet spot : “If you fly too low, there’s a lot of air density friction and the aircraft gets too hot,” said Goyne. “Too high, you start to run out of oxygen. The sweet spot altitude is 100,000 ft. or so.” Goyne says one of the key advantages of a scramjet over a rocket engine is that the scramjet gets the oxidizer to combust its fuel from the air it is flying through, whereas a rocket engine needs to carry liquid oxygen to burn its liquid hydrogen fuel.

Foray into railgun cum scramjets : In April, President Obama urged NASA to come up with, among other things, a less expensive method than conventional rocketry for launching spacecraft. By September, the agency’s engineers floated a plan that would save millions of dollars in propellant, improve astronaut safety, and allow for more frequent flights. All it will take is two miles of train track, an airplane that can fly at 10 times the speed of sound, and a jolt of electricity big enough to light a small town. The system calls for a two-mile long rail gun that will launch a scramjet, which will then fly to 200,000 feet. The scramjet will then fire a payload into orbit and return to Earth. The process is more complex than a rocket launch, but engineers say it’s also more flexible. With it, NASA could orbit a 10,000-pound satellite one day and send a manned ship toward the moon the next, on a fraction of the propellant used by today’s rockets.

Politics : So what really happened to ramjets? Sputnik and Robert McNamara. The space race diverted U.S. space science into rocketry, and President John Kennedy’s defense secretary and his whiz-kid advisors backed intercontinental ballistic missiles over air-breathers, expecting the latter to be easily shot down by bigger enemy missiles.

Article source: http://www.airspacemag.com/flight-today/ramjet-and-rocket-180950239/?no-ist=&page=1

Additional source on railgun cum scramjet: http://wordlesstech.com/2010/12/22/nasa-proposes-a-rail-gun-and-a-scramjet-to-fire-spacecraft-into-orbit/

Source for history: http://www.forbes.com/sites/brucedorminey/2014/08/22/hypersonic-scramjets-still-key-to-future-of-aerospace/

The screaming X-51A Hypersonic Waverider scramjet rides shockwaves : http://goo.gl/vbBjHi (earlier post)

Combining a Railgun and a Scramjet : http://goo.gl/CnDxAj (earlier post)

Rail-launched scramjet : http://goo.gl/RAOJU6 (earlier post)

Wikipedia link: http://en.wikipedia.org/wiki/Scramjet

NASA factsheet: http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-040-DFRC.html#.VBvnZBZkmwQ

+NASA mission: http://www.nasa.gov/missions/research/x43-image-feature.html

Pics courtesy: http://goo.gl/jKNaqB, NASA and http://goo.gl/y2eosk

#scramjet #ramjet #space  
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New Thermoplastic Composite Bolts Stronger than Steel

In this post I discuss the newest thermoplastic composite injection molded bolts designed for high performance use.  

I also have included some basic information about polymers and references to different polymers.

More than you probably wanted to know about plastic bolts. 
Injection-Moldable Thermoplastic Bolts, Stronger Than Steel

Another interesting Materials Engineering article from Design News discusses injection moldable thermoplastic composites that are being developed for the use in high performance bolts.  

First a bit of background, generally polymers (long-chain molecules) or plastics come in two varieties; thermoset - those that when heated become solid, and thermoplastic - those that soften or melt upon heating.  
Examples of a common thermoset polymer are epoxy resins (which harden by chemical reaction), and vulcanized rubber (which hardens by chemical reaction and heat).  Examples of thermoplastic polymers are nylon, polyethylene, or polypropylene which all soften when heated.

Composite polymers are plastics that are made from two or more materials and the end product can be stronger that the individual materials.  Composites can be thermoset or thermoplastic, in this case we are discussing thermoplastic composites.

A new thermoplastic composite for high-speed, high-volume injection molding has tensile strength that's close to, and sometimes better than, either lay-up composites or metals.  ⓐ

Kyron MAX is a new line of injection-moldable composites, with both glass and carbon fiber versions, from Piper Plastics. The material comes in three performance levels. Depending on the combination of polymer type and fillers, tensile strength can reach from up to 50,000 psi (345 MPa) to as high as 120,000 psi (827 MPa). That last figure puts it above steel, Dave Wilkinson, materials engineering manager for Piper Plastics, told Design News. Tensile modulus ranges from up to 5 million psi (35 GPa) to as high as 12 million psi (83 GPa).  ⓐ

The composites are almost 75% lighter than steel and about 60% lighter than titanium. Polymers include PEEK, PPS, PEI, PPA, and PA. "The strength of any fiber-filled polymer is the strength of that fiber combined with the strength of the fiber's adhesion to the polymer," Wilkinson told us. "So we've developed a stronger fiber and a new sizing technology to adhere the fiber to the polymer. Depending on the application's mechanical strength needs, we use either short or long fibers."  ⓐ

Since filler loadings can be lower than in traditional thermoplastic compounds, the material has greater elongation at yield, so parts made with the composite can yield more without fracturing. Lower filler loadings also reduce processing windows and make the material lighter. Industries targeted by the new composite material include aerospace, defense, medical, automotive, oil & gas, electronics, and industrial companies that need high-precision, high-strength, structural polymer machined parts.  ⓐ

As I suggested on my last Design News related post, I recommend that you go and have a look at the article with emphasis on the comments.  These are engineers commenting and answering questions from other engineers.  The comments are an excellent resource.

These new polymer thermoplastic composite bolts are lighter, stronger, more wear resistant, and more corrosion resistant than some metal bolts, including titanium bolts.  This material is also being used as a bearing material in some new Formula 1 race cars.

I have included a list of references for all the different polymers used in the manufacture of these bolts, as well as the manufacturer of these new bolts.

ⓐ  Design News 
Injection-Moldable Composite Beats Metal Specs
http://www.designnews.com/author.asp?section_id=1392&doc_id=274376

Piper Plastics, Inc.
http://www.piperplastics.com/HTML/Featured_Material.html

Wiki Thermoplastic
http://en.wikipedia.org/w/index.php?title=Thermoplastic&oldid=623573464

Wiki Thermosetting polymer
http://en.wikipedia.org/w/index.php?title=Thermosetting_polymer&oldid=621279177

THERMOSET VS. THERMOPLASTIC MATERIALS
http://www.rlhudson.com/publications/techfiles/thermo.htm

Wiki Composite Material
http://en.wikipedia.org/w/index.php?title=Composite_material&oldid=623696004 

Polyether ether ketone (PEEK)
http://en.wikipedia.org/w/index.php?title=PEEK&oldid=608098079

Polyphenylene sulfide (PPS) is an organic polymer consisting of aromatic rings linked with sulfides.
http://en.wikipedia.org/w/index.php?title=Poly(p-phenylene_sulfide)&oldid=610150127

Polyetherimide (PEI) is an amorphous, amber-to-transparent thermoplastic with characteristics similar to the related plastic PEEK.
http://en.wikipedia.org/w/index.php?title=Polyetherimide&oldid=613598520

Polyphthalamide (aka. PPA, High Performance Polyamide) is a thermoplastic synthetic resin of the polyamide (nylon) family.
http://en.wikipedia.org/w/index.php?title=Polyphthalamide&oldid=623698337

PA  A polyamide is a macromolecule with repeating units linked by amide bonds. 
http://en.wikipedia.org/w/index.php?title=Polyamide&oldid=615137168


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Piper Plastics used one of the highest-performing XS series Kyron MAX polymer grades to mold a standard #10-32 bolt for replacing titanium aerospace bolts. The part exceeds target minimum tensile load at 741 lb and double shear strength at 1,890 lb.  
Source, Piper Plastics
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The Epic Fail. Why Traditional Teachings of Rock Blasting Are Unfit For Purpose.

In this post I explore anti-science in the mining industry and I ask whether operating outside of the modern science is inherently unsafe.

When blasting engineers say to me “its not an exact science” this sets alarm bells ringing.
The actual problem is that rock blasting, in its current form, is exactly not science.


The modern vs traditional theories of rock fragmentation are quite different as exemplified in these two papers:
www.rockgeotech.org/qikan/manage/wenzhang/20090001.pdf
http://sem-proceedings.com/09s/sem.org-SEM-2009-Ann-Conf-s039p04-Plate-Impact-Experiments-Investigate-Shock-induced-Inelasticity.pdf
and this recent research project:
http://www.memin.de/results-tp-7.html
- that the rock blasting side of the mining industry has not even informed itself of these scientific advances is apparent. In fact the textbooks have barely changed in decades.

Here I show how the traditional theory of rock mechanics simply fails the reality check. Here I will focus specifically on the traditional teachings as they pertain to rock blasting with explosives.
In this post, I will seek to demonstrate clearly why these traditional teachings have totally failed the industry that they are meant to serve and why, therefore, they are not fit-for-purpose.

1. The Danger Signs
“If you can’t explain it you don’t understand it yourself” – Einstein.
Unfortunately, I can not even begin to write down the traditional explanation of how rock blasting works. There is simply not enough space. A good example of why is this student thesis from 2004, which provides a summary of the traditional teachings in a chapter called "The Explosive-Rock interaction: General Blasting Mechanisms":
oa.upm.es/365/1/Pablo_Segarra_Catasus.pdf
It takes the student nearly five pages with diagrams just to summarize the explanation of the basic mechanisms.
Another good source is an article entitled "Back to Basics: The Fundamentals of Blast Design".
http://www.iseegoldenwest.org/Back%20to%20Basics.pdf
Even in this "Back to Basics" description, it takes the author 3 pages with diagrams to explain the basics of the Physics of Energy Release and Rock Breaking.

To be clear, it is not the authors who are at fault - these are two of the best attempts ever to write down the traditional descriptions. Both articles are necessarily tortuous, baroque descriptions which only leave the reader confused and bemused, because they are indeed the embodiments of the traditional teachings.

Neither of these brave attempts provide the reader with any definite answers,they describe the debates and the doubts, the questions marks over each of the fundamental tenets.Even after pages of text and diagrams, the reader is still left to interpret for themselves.

At the outset, therefore, it is clear something is deeply amiss. Any description of a physical process which requires pages of text and diagrams is necessarily the wrong one. Any explanation which leaves the reader bamboozled or confused is necessarily not the scientific one.

I do not understand these two written explanations myself, not at all. I doubt that any one does.

2. Failing the Reality Check

As shown in my related posts on my google+ page, the traditional teachings actually fail at the first hurdle. They simply do not, in any part or as whole, meet the reality test of direct comparison with the field data or the observational evidence. The traditional teachings neither explain nor predict reality. They violate the fundamental principles of physics. They neglect physical processes which are clearly observable as critical - such as my running example of the clear primary role of stemming. Indeed, when 30% of a blast hole filling, by volume, is stemming and well over 50% by mass, not accounting properly for its primary role is, in itself, a failure of the most basic of reality checks.

3. The Signs of the Cult

These traditional teachings have failed the industry. After decades of existence, they have brought us little closer to either the answers or to robust solutions to any of the perennial questions which plague the industry.
The blasting industry currently operates on bootstraps and sticking plaster workarounds, empirical fixes without understanding . When things inevitably go wrong the suppliers, consultants , drillers, blasters and miners blame each other.But no-one ever thinks to blame the textbooks, which is where the real problem lies.
As demonstrated by the two reference works above, the traditional teachings are clearly in the realm of the arcane. As engineering theory they are moribund. It is simply not possible to even express the traditional explanations in terms of mathematical formulae. The traditional picture cannot be reduced to the language of engineering, when it cannot even be expressed clearly and succinctly in words.

The industry is reliant on a cult of consultancy. These "priest-consultants" move around the industry using their own mystic understandings of the arcane teachings to problem solve.But ask five blasting consultants the same question and you will usually get five different answers, or the same answers but with five different explanations. The client does not understand these answers and is left none-the-wiser of how translate them into practice. The client is reliant on the priest-consultant to come again the next time there is a problem. Usually the same problem recurring.

One only has to read through the discussion threads in any of the LinkedIn blasting group to verify these statements for themselves.

4. The Traditional Teachings as Religion

The traditional teachings have, in fact, now become a cult of indoctrination. Simply put, they have not evolved, changed or grown in decades. Like religious texts they are set in stone. For this reason alone, we know they simply cannot be the correct engineering or science basis for rock blasting. No proper engineering theory or practice has ever stood the test of time, certainly not over three or four decades. It evolves and adapts to new knowledge and data.

These teachings have also become sacrosanct and inviolate. They are not to be questioned. Questioning them or challenging them invokes anger and worse. Postulating engineering alternatives makes one a heretic. This is not the hallmark of science, but of religion.

The standard response when one points out its inconsistencies and fallacies is “but we have nothing to replace it with”. The industry cannot move forward or away from the traditional teachings until something else comes fully formed to replace it. Again this is not the way science or engineering works. We test hypothesis and when they fail we do more research and ask different questions. We often need to this urgently for safety reasons when flaws in thinking or the theory become apparent.

Yet the industry is locked in to the traditional teachings even when the risks are clear. It has become, truly, indoctrinated. The textbooks have become dogma.

5. The Solution

The solution is clear. It is simple. The traditional teachings must now be questioned at every level. They must not only be challenged, they must, right now, become completely and freely challengeable. In every part and as a whole. Whenever and wherever they are found wanting, we must seek the answers elsewhere. At times we will need to do this as a matter of urgency and at costs, if identified systematic failures of the system have associated identifiable risks.

In short we must turn away from the traditional and instead embrace a standard engineering approach. We must look towards modern science.

Wikipedia defines engineering as
"Engineering (from Latin ingenium, meaning "cleverness" and ingeniare, meaning "to contrive, devise") is the application of scientific, economic, social, and practical knowledge in order to invent, design, build, maintain, and improve structures, machines, devices, systems, materials and processes. The discipline of engineering is extremely broad, and encompasses a range of more specialized fields of engineering, each with a more specific emphasis on particular areas of applied science, technology and types of application."

And so it is. The traditional teachings bear no resemblance to this.
This is why they are unfit for our industry. They must be abandoned.
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This is how a Spiral Bevel Gear Works.

The teeth in the image are concave on root and convex on the tip. 
Oddly enough this gear was being developed in somewhat similar way to this image at MIL Helicopter from 1986-1992. More or less a spiral bevel gear is actually a bevel gear with helical (having the shape or form of a helix) teeth. Typically a spiral bevel gear is mounted on shafts spaced 90 degrees apart. However,  it is possible for them to be designed to work at other angles too. 

Here are some resources regarding this: 
1. http://science.howstuffworks.com/transport/engines-equipment/gear4.htm
2. http://spiralbevel.com/

#science   #technology  

(image via zakgear.com)
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The #SilkLeafProject was created by a student from the Royal College of Art and the Tufts University Silk Lab to produce artificial leaves in order to supply oxygen to astronauts on longer space journeys.

The leaves are made from tough silk proteins, which directly extract chloroplasts from real leaves and suspend them in a silk matrix.

Julian Melchiorri, the student who created the leaves, says "*NASA is researching different ways to produce oxygen for long-distance space journeys to let us live in space. This material could allow us to explore space much further than we can now.*"

Click here to watch the interview video of Julian Melchiorri: http://goo.gl/qnd0kk 

Although the efficiency of the photosynthesis process has yet to be tested, the scientists are hopeful that the leaves could be applied in all manner of futuristic architectural projects for better use.

Check out the full article here: http://goo.gl/YZ5KLA
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DARPA has tapped the Lawrence Livermore National Laboratory to develop an implantable neural device with the ability to record and stimulate neurons within the brain using electrical and chemical signals to help restore memory function for those with traumatic brain injuries.

The research builds on the understanding that memory is a process in which neurons in certain regions of the brain encode information, store it and retrieve it. Certain types of illnesses and injuries, including Traumatic Brain Injury (TBI), Alzheimer's disease and epilepsy, disrupt this process and cause memory loss. TBI, in particular, has affected 270,000 military service members since 2000.

The goal of LLNL's work -- driven by LLNL's Neural Technology group and undertaken in collaboration with the University of California, Los Angeles (UCLA) and Medtronic -- is to develop a device that uses real-time recording and closed-loop stimulation of neural tissues to bridge gaps in the injured brain and restore individuals' ability to form new memories and access previously formed ones.

Specifically, the Neural Technology group will seek to develop a neuromodulation system -- a sophisticated electronics system to modulate neurons -- that will investigate areas of the brain associated with memory to understand how new memories are formed. The device will be developed at LLNL's Center for Bioengineering....

Read more: http://1.usa.gov/1qVzqrd Animation: http://bit.ly/TTGqpO

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The Boolean Circuit and Electronic Logic, Part 2
The Boolean Circuit and Electronic Logic, Part 2

This is the fourth part in my multi-part series on how computers work. If you like, you can read the post in blog form here: http://www.thephysicsmill.com/2014/06/29/boolean-circuit-electronic-logic-part-2/

Computers are thinking machines, but they can’t do this on their own. We need to teach them how to think. And for this, we need a language of logic. In the first part of the series, I introduced this language of logic, Boolean algebra. In the second part, I described how to formulate complex logical statements using Boolean algebra. In the third part, I described how some of the electronics in old-school computers worked.

Here are the previous three parts:
1http://www.thephysicsmill.com/2014/06/08/george-boole-language-logic/

2. http://www.thephysicsmill.com/2014/06/14/george-bool-language-logic-2/

3. http://www.thephysicsmill.com/2014/06/22/boolean-cirucit-logic/

This time, I finally get to the meat of things. I describe how you can use the circuits described in part 3 to actually implement Boolean logic electronically.

Voltages

The following discussion is going to depend heavily on an understanding of the triode vacuum tubes [1] that I discussed last time. So if you haven’t already, you probably want to last week’s article before you read this one.

That said, some review is probably in order. First let’s review electric voltage. The salient points are this. Electrons want to flow from places in a circuit that are at low voltage to places that are at high voltage.  Voltage is measured in volts. We want to use voltage as a stand-in for the truth values described in parts one and two of my series on how computers work.

There are a number of ways we can use voltage to represent truth values. But let’s pick the most common way. Let’s say we have a circuit. We’ll connect a voltage-measuring device to a spot on our circuit—perhaps where two wires intersect—and say that, if it reads any voltage higher than +5 volts, then our circuit represents true at that spot. If it reads any lower, then our circuit represents false there.

(There’s an important detail I’m skipping here. Voltages are not absolute numbers. We know that electrons flow from low voltage to high voltage. But we need a baseline for what “zero volts” means. In every circuit, this “zero volts” value might be different, but we always have to set it and choose a value. We usually call “zero volts” ground.)

Vacuum Review

 Now let’s review the basics of a triode. As the name suggests, a triode is a circuit component with three terminals, called the cathode, anode, and filament, as shown in figure 2. There’s another piece called the called the heating element that we won’t discuss in much detail.

I discuss the triode in great detail in last week’s article.  But for now, here’s what you need to know. The filament controls the flow of electrons from the cathode to the anode. Suppose that I hook up the triode in a circuit so that the anode is at a high voltage, and the cathode is at a low voltage. Then if the filament is at a low voltage like the cathode, then no current will flow. If the filament is at a high voltage like the anode, then current will flow.

Fiddly Names

It’s worth noting that the pieces of a triode can have other names. The cathode is often called the plate and the filament is often called the grid. In this naming scheme, confusingly, the heating element is often called the filament.

It’s also worth noting that these days triodes have been almost completely replaced by transistors.But transistors have different names for these parts. In a transistor, the cathode is called the source, the anode is called the drain, and the filament (or grid) is called the gate. A transistor does not have a heating element. To avoid confusion, I’ll use vacuum tubes instead of transistors. And I’ll use the names in my diagram.

Boolean Circuity

Now let’s implement Boolean logic! To do this, let’s chain some triodes together, as shown in figure 3.

Here we keep the anodes at a very high voltage, much higher than the cathodes could possibly be at. We then connect both cathodes to a terminal that we call C. We name the filament terminals A and B respectively.

Now let’s manipulate the terminals A and B and see what terminal &C& does. If both A and B are at a low voltage (i.e., false), then current won’t flow through either triode. The result is that C stays at a low voltage, which we’ll call false. But now let’s put terminal A at a higher voltage, say true. (For now we’ll leave B as false.) Then current will flow through the left-most triode and raise the voltage at terminal C so that it becomes true. 

Similarly, if we keep A at a low voltage (i.e., false) but raise the voltage at B so that it becomes true, then current will flow through the right-most triode. This too will raise the voltage at terminal C and make it true. And of course, if both A and B are true, then current will flow and raise the voltage at C, making it true.

So if both A and B are false, then C is false. But if either A or B or both A and B are true, then C is true too. The astute among you might recognize C as the result of the logical operation A or B. We've just made the logical or work electronically! The circuit we just constructed is called an or gate.

More Gates

Can we do the same thing to make a logical and? Let’s try. We’ll still use two triodes. But now let’s connect them in a different way, as shown in figure 4. We put the anode of the first triode at a very high voltage. But we connect its cathode to the anode of the second triode. We label the filaments A and B respectively and the cathode of the second triode C.

Now current will be unable to flow unless both terminals A and B are at a high voltage. In other words, C will be true only if both A and B are true. You might then recognize C as the output of the logical A and B, which we've now implemented electronically! This circuit is called an and gate.

Gates in Practice

I showed you how to electronically implement the boolean operations and and or described in George Boole and the Language of Logic, Part 1 (see: http://www.thephysicsmill.com/2014/06/08/george-boole-language-logic/). If we wanted to make composite statements as we did in part 2 (see: http://www.thephysicsmill.com/2014/06/14/george-bool-language-logic-2/), then we’d also need the not operator. But that’s actually a bit trickier (though not impossible) to make electronically. So I won’t describe it.

Usually, in practice, people use nand and nor gates as opposed to and, or, and not. These are harder to make, however, so I won’t describe them. Hopefully the gates I did describe, however, give you a feel for how this works.

Electronic Caveats

In my description of the and and or gates, I claimed that when current flowed through a triode, the voltage at the cathode changed. In practice things are a lot more complicated. Voltage and current are related. In simple cases, the relationship is given by Ohm’s law [2], which many of you are probably familiar with. In more complicated cases, where the current changes quickly, you need to take more things into account, like the travel time of electrical signals.

That said, the description I gave gets the basic idea across and, if we added more circuit components (such as capacitors [3], inductors [4], and resistors [5]), the gates I described would work.

References
[1] https://en.wikipedia.org/wiki/Triode
[2] https://en.wikipedia.org/wiki/Ohms_law
[3] https://en.wikipedia.org/wiki/Capacitor
[4] https://en.wikipedia.org/wiki/Inductor
[5] https://en.wikipedia.org/wiki/Resistor

Next Time

Performing a logical calculation is useless unless you can record your findings. Next time, I’ll describe how to use logic gates to teach computers how to remember.

Further Reading

If you want to know more, here are some resources on how logic gates are implemented.

1. +Ólafur Jens Sigurðsson ointed me to this absolutely amazing MIT course that walks the student through the creation of a simple computer, from the hardware to the operating system to the program: http://www.nand2tetris.org/

2. HowStuffWorks has a nice article on how boolean logic works inside a computer, starting from the very beginning. You can find it here: http://computer.howstuffworks.com/boolean.htm

3. This slideshow gently introduces how to build logic gates from transistors: This slideshow gently introduces how to build logic gates from transistors: http://www.csd.uwo.ca/~lila/logic/minimization.pdf

Related Reading

If you liked this article, you might also like the following articles I’ve written.

I am currently in the middle of a series on how computers work, from the ground up. Here are the previous articles:

1. In this article, I describe the basics of Boolean logic, starting with truth tables: http://www.thephysicsmill.com/2014/06/08/george-boole-language-logic/

2. In this article, I describe how to make composite logical statements using Boolean logic: http://www.thephysicsmill.com/2014/06/14/george-bool-language-logic-2/

3. In this article, I introduce the triode vacuum tube and describe how it works: http://www.thephysicsmill.com/2014/06/22/boolean-cirucit-logic/

And if you like articles on how things work. Here are some other articles I’ve written in the same vein.

1. In this article, I describe one way to make a transistor: http://www.thephysicsmill.com/2013/03/15/field-effect-transistor/

2. In this article, I describe how lasers work: In this article, I describe how lasers work: http://www.thephysicsmill.com/2013/11/17/things-work-lasers/

3. In this article, I describe how to make a pulsed laser: http://www.thephysicsmill.com/2014/04/27/mode-locked-lasers-beating-pulse-metrology/

#science   #electronics   #logic   #logicgates   #binary   #booleanalgebra   #sciencesunday   #scienceeveryday  
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2014-06-29
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