nhaliday + ieee   39

Is the human brain analog or digital? - Quora
The brain is neither analog nor digital, but works using a signal processing paradigm that has some properties in common with both.
Unlike a digital computer, the brain does not use binary logic or binary addressable memory, and it does not perform binary arithmetic. Information in the brain is represented in terms of statistical approximations and estimations rather than exact values. The brain is also non-deterministic and cannot replay instruction sequences with error-free precision. So in all these ways, the brain is definitely not "digital".
At the same time, the signals sent around the brain are "either-or" states that are similar to binary. A neuron fires or it does not. These all-or-nothing pulses are the basic language of the brain. So in this sense, the brain is computing using something like binary signals. Instead of 1s and 0s, or "on" and "off", the brain uses "spike" or "no spike" (referring to the firing of a neuron).
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april 2018 by nhaliday
Static electricity - Wikipedia
Electrons can be exchanged between materials on contact; materials with weakly bound electrons tend to lose them while materials with sparsely filled outer shells tend to gain them. This is known as the triboelectric effect and results in one material becoming positively charged and the other negatively charged. The polarity and strength of the charge on a material once they are separated depends on their relative positions in the triboelectric series. The triboelectric effect is the main cause of static electricity as observed in everyday life, and in common high-school science demonstrations involving rubbing different materials together (e.g., fur against an acrylic rod). Contact-induced charge separation causes your hair to stand up and causes "static cling" (for example, a balloon rubbed against the hair becomes negatively charged; when near a wall, the charged balloon is attracted to positively charged particles in the wall, and can "cling" to it, appearing to be suspended against gravity).
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november 2017 by nhaliday
What are the Laws of Biology?
The core finding of systems biology is that only a very small subset of possible network motifs is actually used and that these motifs recur in all kinds of different systems, from transcriptional to biochemical to neural networks. This is because only those arrangements of interactions effectively perform some useful operation, which underlies some necessary function at a cellular or organismal level. There are different arrangements for input summation, input comparison, integration over time, high-pass or low-pass filtering, negative auto-regulation, coincidence detection, periodic oscillation, bistability, rapid onset response, rapid offset response, turning a graded signal into a sharp pulse or boundary, and so on, and so on.

These are all familiar concepts and designs in engineering and computing, with well-known properties. In living organisms there is one other general property that the designs must satisfy: robustness. They have to work with noisy components, at a scale that’s highly susceptible to thermal noise and environmental perturbations. Of the subset of designs that perform some operation, only a much smaller subset will do it robustly enough to be useful in a living organism. That is, they can still perform their particular functions in the face of noisy or fluctuating inputs or variation in the number of components constituting the elements of the network itself.
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november 2017 by nhaliday
What kills, current or voltage? - Quora
Its an oversimplification to say that voltage kills or current kills and the cause of much misunderstanding.
You cannot have one without the other, therefore one could claim that answering one or the other is correct.
However, it is the current THROUGH key parts of the body that can be lethal. BUT even a lot of Current in a wire won't harm you if the current is constrained to the wire..
Specifically in order for you to be electrocuted, the voltage must be high enough to drive a lethal amount of current through your body over coming body resistance, the voltage must be applied in the right places so that the current path is through your (usually) heart muscle, and it must be long enough duration to stop the heart muscle due to fibrillation.

another good answer:
As I write this note, I’m looking at the textbook Basic Engineering Circuit Analysis by Irwin and Nelms (ISBN 0-471-48728-7). On page 449 the authors reference the work of Dr. John G. Webster who suggests the body resistance values that I have taken the liberty to sketch into this poor character.
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september 2017 by nhaliday
electricity - Why is AC more "dangerous" than DC? - Physics Stack Exchange
One of the reasons that AC might be considered more dangerous is that it arguably has more ways of getting into your body. Since the voltage alternates, it can cause current to enter and exit your body even without a closed loop, since your body (and what ground it's attached to) has capacitance. DC cannot do that. Also, AC is quite easily stepped up to higher voltages using transformers, while with DC that requires some relatively elaborate electronics. Finally, while your skin has a fairly high resistance to protect you, and the air is also a terrific insulator as long as you're not touching any wires, sometimes the inductance of AC transformers can cause high-voltage sparks that break down the air and I imagine can get through your skin a bit as well.

Also, like you mentioned, the heart is controlled by electric pulses and repeated pulses of electricity can throw this off quite a bit and cause a heart attack. However, I don't think that this is unique to alternating current. I read once about an unfortunate young man that was learning about electricity and wanted to measure the resistance of his own body. He took a multimeter and set a lead to each thumb. By accident or by stupidity, he punctured both thumbs with the leads, and the small (I imagine it to be 9 V) battery in the multimeter caused a current in his bloodstream, and he died on the spot. So maybe ignorance is more dangerous than either AC or DC.
nibble  q-n-a  overflow  physics  electromag  dirty-hands  embodied  safety  short-circuit  IEEE  death 
september 2017 by nhaliday
Battle for the Planet of Low-Hanging Fruit | West Hunter
Peter Chamberlen the elder [1560-1631] was the son of a Huguenot surgeon who had left France in 1576. He invented obstetric forceps , a surgical instrument similar to a pair of tongs, useful in extracting the baby in a  difficult birth.   He, his brother, and  his brother’s descendants preserved and prospered from their private technology for 125 years. They  went to a fair amount of effort to preserve the secret: the pregnant patient was blindfolded, and all others had to leave the room.  The Chamberlens specialized in difficult births  among the rich and famous.
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may 2017 by nhaliday
Convex Optimization Applications
there was a problem in ACM113 related to this (the portfolio optimization SDP stuff)
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december 2016 by nhaliday

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