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Nick Gall's Weblog
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Wednesday, May 12, 2004 |
Signal Processing is the Science of Finding Patterns.I saw this quote in an interview with Teresa Meng (founder of Atheros) in ACM Queue regarding Signal Processing:
RB: How would you advise someone who wants to get involved with digital signal processing and new applications?
TM: You will have to master a few areas. You cannot just learn math and ignore the silicon, especially in signal processing where the algorithms really mean nothing unless you have an interesting, efficient way of implementing them. Then you immerse yourself in the application domain of your interest.
RB: Do you have any ideas on what you might do after the neural area?
TM: Probably something bio-related. I do feel that signal processing is the basic tool that can be applied to many different areas. We have applied it to low-power circuit designs, video processing, and, most recently, wireless communication. I think in the next several decades signal processing will be widely used in the bio field—for example, genome analysis or diagnostics. Signal processing is after all a science for optimal detection. I think there might be some interesting developments in those areas. [emphasis added]
I've never heard anyone describe signal processing this way. I interpret her as saying that signal processing is the science of finding patterns.
Also, given the broad definition of signal ("A signal is an abstract element of information"), signal seems synonymous with datum/data. Thus information processing seems synonymous with signal processing. A pattern is just a relationship, which is what a signal is.
Furthermore, in a later article in the ACM Queue issue on DSP, it is observed that DSP systems must optimize three concerns: speed, precision, and power. I would add a forth: adaptability (aka programmability). The three concerns are equivalent to my three concerns for liquidity: timeliness, value, and efficiency.
Finally, perhaps Signal Processing is the Science of Finding and Generating Patterns. Thus evolution (which finds and generates patterns) is a form of signal processing.
5:00:23 PM 
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Monday, May 10, 2004 |
Crack's in the Second Law of Thermodynamics?Just came across this fascinating issue of the open access online journal Entropy: Quantum Limits to the Second Law of Thermodynamics. Not sure what to believe here, but my gut tells me that the Second Law is on a shaky foundation. Here is a quote from the opening of the overview article: The Second Law Mystique:
Over fifty years ago Arthur Eddington wrote [1]: "The second law of thermodynamics holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation, well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation".
Although this is perhaps the most famous endorsement of the second law, it is certainly not the only one; in the works of Einstein, Planck, Maxwell, and other luminaries one can find similarly strong imprimaturs. Common to them is an almost mystical faith in the law's inviolability. Aside perhaps from the standard conservation laws, no physical axiom engenders more support from the scientific community. The reasons are not hard to list. No experimental violation of the second law has been recognized by the scientific community in over 150 years; meanwhile, it has been confirmed in countless experiments and natural phenomena. Absolute inviolability is intellectually satisfying. One should also not discount the power of peer pressure; like most paradigms, the second law is understood deeply by few and taken on faith by most. Such faith is cemented by many famous endorsements and is so deeply rooted in a century and a half of cultural legacy that it has put the second law nearly beyond the reach of serious scientific discussion. Taken together, these constitute what may be called the second law mystique.
Despite the deeply rooted belief in its absolute status, the second law has always had surprisingly shallow roots. Despite vaunted claims to the contrary, it does not have a fully satisfactory theoretical proof; therefore, its absolute status has always been questionable and contingent and, like all good laws, it is falsifiable in the Popperian sense. Second, since its discovery, physics has undergone multiple paradigm shifts - e.g., quantum mechanics, relativity, chaos - that have revolutionized our view of reality, and yet the second law has emerged essentially unchanged from its classical roots and has been inadequatedly tested in many new experimental regimes where it should apply. Lacking full theoretical or experimental support, it is epistemologically unsound to presume it at the level to which the scientific community has become accustomed. Third, there are more than a half dozen common statements of it - dating back to Clausius and Thomson and, in spirit, to Carnot 180 years ago - not all of which are equivalent. As quipped by Clifford Truesdell, "Every physicist knows exactly what the first and second law mean, but it's my experience that no two physicists agree on them". From a purely logical standpoint, this Babel-like understanding is intolerable - but this situation has not only been tolerated by the scientific community, it has been embraced. Sensing some of these difficulties, there have been some serious attempts to render the second law axiomatic in recent years [2,3].
8:29:55 PM
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