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From: Jon Kirwan on 16 Feb 2010 21:38 On Tue, 16 Feb 2010 16:43:55 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jon Kirwan wrote: >> On Tue, 16 Feb 2010 09:10:06 -0800, Joerg >> <invalid(a)invalid.invalid> wrote: >> >>> Jon Kirwan wrote: >>>> On Mon, 15 Feb 2010 13:29:30 -0800, Joerg >>>> <invalid(a)invalid.invalid> wrote: >>>> >>>>> <snip> >>>>> It's much more important to >>>>> experiment, experiment, experiment, get a "feel" for what works, _then_ >>>>> dive into the theory. Not the other way around. Just my 2 cents. >>>> It's hard for most of us to get a feel for what works without >>>> first having some idea of what to expect. Theory is primary >>>> to interpreting and understanding experimental result. >>>> >>>> What isn't known through theory defines the word 'random.' >>> That would be the professor's thought process. To us back then things we >>> didn't understand were not random at all. For example, you simply "knew" >>> that the Q of a power matching network had to be at least 10 or you'd >>> get into EMI troubles. Or that grid-bias tube stages were way more >>> stable by nature. Or that certain modes of operation in a transistor >>> could lead to a phssst ... *BANG* (later I learned about the concept of >>> a SOA), and so on. >> >> I think you missed my meaning. It's not that theory must >> exist for the observation itself. It's that theory is >> primary to interpreting and understanding experimental >> results. >> >> I've used the concept of a small-angle pendulum swing here, >> before. I added then the point about "observing"; that the >> period itself, when better timing becomes available to notice >> (itself, depending upon prior theory), is not well-enough >> predicted. That's an example of interpreting and >> understanding experimental results. >> >> What remains (let's say, the idea that the diameter of the >> hole and the different diameter of the pin must be accounted >> in some way) is consistent -- at that moment -- with the idea >> of 'random.' The values may then be subjected to _other_ >> theory, the idea of Poisson events and its integral (Gaussian >> distribution) to see if the distribution has a skew to it for >> which some rule of thumb might then be applied, though >> otherwise ignorantly until better theory is developed. No >> one is prevented by what I wrote from accounting for an issue >> by making up rules that "seem to work until something better >> comes along." A bias, or skew, or some other element can >> certainly be found. >> >> But take note, using _other_ theory to do so and inform that >> choice. >> > >Ok, but: Lets say the guy with the pendulum never really had a chance to >visit a school, very common in medieval days. But he wants to make >clocks. Good clocks. So he might decide to conduct numerous long term >experiments to see which pendulum works best without actually fully >understanding why it does. IOW, not having a grasp on the theory does >not preclude him from making clocks of superb quality and consequently a >nice chunk of money. > > >> Your example takes place amidst a great deal of existing >> theory of one kind or another, as well. All of which helps >> to inform some rule of thumb, as well. Which makes the point >> well. >> >> To strip away all of the veneer of cultural training, imagine >> a neanderthal posed along a mountain ridge, looking into the >> distance at a slightly curving horizon. Without any concept >> of "sphere" in mind. With that theory firmly held, _we_ are >> _able_ to "observe" that curve and adduce it to a spherical >> Earth 'theory.' We can "see" it. However, the neanderthal >> probably wouldn't have any way of even noticing the effect. >> > >Or he does notice, starts walking up to the curved horizon and the dang >thang keeps moving away from him. Hence, the horizon must be afraid of >him :-) > > >> I might argue that theory not only informs observation, in >> many regards the lack of it prevents such observation from >> even taking place. >> > >True. > > >> Now, let's add a "theory of a flat world surface" to this >> neanderthal's mind. Now, the neanderthal _can_ observe the >> curve, because it _differs_ from existing theory. And might >> even be able to formulate some rule of thumb about the >> deviation observed vs relative height on a mountain, perhaps. >> >> But again, observation through theory. >> > >Or he might decide "Ah, what the heck, let's get something to eat" :-) > > >>> If it was all random we'd have had much more failing parts and homebrew >>> devices, but we didn't. >> >> Well, I hope the point I was making is clearer. Or not. ;) >> > >There are two ways to arrive at good product. Theoretical and empirical, >or a combination thereof. I've heard many old masters respond to >questions "Well, that's just how it is" and these guys were real masters >in their profession. > >I grew up in medical ultrasound. Back in the 80's a lot of stuff around >PZT-based transducers was not understood. Yet the front end parts and >transducers of the old machines are not that much different in >performance from the ones today, where we have oodles of computer >horsepower to simulate and calculate just about anything. If we had said >"Oh shoot, we don't understand the theory so let's not build but keep >studying until we do" a lot of people in hospitals would have needlessly >died. Understood and point taken, as well. Life goes on. People could float on a board in the water before they had much more than a vague idea about it -- drawn from some collected observations. .... This moves now into a protracted discussion, which I'd better not enter deeply here. But ad hoc rules, regardless of apparent value, are rarely any more than the vague appearance of a common "rule" from specific, repeated observation. Not a very good foundation, as ideas go, to build upon. As such things doesn't extrapolate very well to areas we haven't yet trod. (More on this in a moment.) One can succeed with induction like this, almost as well with Tarot cards, as necromancy, as pretty much any idea that "seems to work" for some point in time and understanding. Some are okay as far as they go, of course. But it is very much like unearthing stones (fragments of utility) to make a farm wall. Each bit of this kind of inductive knowledge exists by itself and is barely connected to any other bit. Works great so long as you don't go outside the experience which created it. Still, a farm wall is useful and may keep the cows in. No arguing with that. If you blow a hole in one part of it, the rest stays, too. That is it's power, in a way. A rock over on this part of the wall does NOT much depend upon a rock over 'there' for its strength. But at the same time, that's also its weakness. Structures formed like this cannot be efficiently used to carry extremely heavy loads, since almost none of it builds upon the strengths of other parts. They must be in close proximity to cooperate. Science, of late, has focused upon deductive theory -- preferring to test and falsify based up deduction of general theory predicted into specific cases, given the particulars. It yields knowledge structures that are quite different. Induction still plays a role, but not nearly as important as before. In science knowledge, the parts are highly unified. So in keeping with the above 'farm wall' concept, I'd now introduce the archway concept. Stones in science are shaped and fashioned so that they cooperate with each other, like stones in a grand, curving archway; with each piece lending strength to other pieces. The result is a structure that _can_ carry a heavy load. Of course, if you blow a huge hole in it, the whole thing falls down. ;) Same nuggets of stone, two different structures resulting. In fact, what separates science from other forms of knowledge isn't that science is "true" and the others less so. It's the unifying nature of the resulting body. It's no more "true" than anything else. But it is MUCH more unified. I like to think of science knowledge as being "Borg." You can easily tell just how Borg some bit of knowledge is by how well connected it happens to be with "the collective." If it isn't connected into the collective, it's not Borg. And it's not science. Doesn't mean it is wrong. Doesn't mean it is useless. Just means it's not Borg/science. Jon P.S. There is a great book on knowledge; IMHO very easily grasped and extremely very well argued in six separate lectures. The author is Jacob Bronowski and the book is called, "The Origins of Knowledge and Imagination," 1979. Copies are available for very little money (only a few dollars) via abebooks or alibris. I consider it to be an excellent primer, enjoyably told, and I gladly recommend it to anyone. No matter how you come down on anything I write, I think you'll enjoy his lectures -- they were given to very young students and are very easy to follow, while simultaneously engaging, too.
From: Bill Bowden on 17 Feb 2010 00:50 On Feb 16, 12:27 am, "Joel Koltner" <zapwireDASHgro...(a)yahoo.com> wrote: > "Bill Bowden" <wrongaddr...(a)att.net> wrote in message > > news:b13fe59a-8f59-4458-8b6f-a49f1e118e7f(a)p13g2000pre.googlegroups.com... > > > What did I do wrong? > > You never substituted your equation for V2 into the preceeding equation > (V1-V2=R1*...) -- you just took your equation for V2 and shuffled both sides > around until you got 0=0! (Effectively you had one equation but two unknowns > still -- V2 and V3 -- so the "0=0" tells you that there are infinitely many > values of V2 and V3 that satisfy the equation. You need the additional > constraint of the other equation to obtain a unique solution.) > > ---Joel Yes, I found it. (V1-V2)/R1 = (V2-V3/R2) - .005 8.4 = R1*(V2-V3/R2) -1.2 +V2 8.4 +1.2 -V2 = (R1V2 -R1V3)/R2 R2(9.6 -V2) = R1V2 -R1V3 570(9.6 -V2) = 240V2 - 240V3 5472 - 570V2 = 240V2 - 240V3 5472 = 810V2 - 240V3 240V3 = 810V2 - 5472 810V2 = 240V3 + 5472 V2 = ( 240V3 + 5472) /810 V2 = .296V3 + 6.76 (V2-V3)/R2 = V3/R3 - .005 Substituting V2 from previous ((.296V3 + 6.76) -V3)/570 = V3/100 -.005 .296V3 +6.76 -V3 = 5.7V3 - 2.85 .296V3 +6.76 = 6.7V3 - 2.85 9.6 = 6.4V3 V3 = 9.6 / 6.4 = 1.5 V -Bill
From: Ban on 17 Feb 2010 02:18 Joerg wrote: > > I grew up in medical ultrasound. Back in the 80's a lot of stuff > around PZT-based transducers was not understood. Yet the front end > parts and transducers of the old machines are not that much different > in performance from the ones today, where we have oodles of computer > horsepower to simulate and calculate just about anything. If we had > said "Oh shoot, we don't understand the theory so let's not build but > keep studying until we do" a lot of people in hospitals would have > needlessly died. What a pathetic story. But as always just your limited experience. I also worked for a company(Krautkraemer) in the 80s and those guys from the transducer department were called "the Phds" in the company. They knew what they were doing. The whole principle of operation was actually found/invented by 2 brother professors in the 40s who later founded the company, hardly any "Neandertals". ciao Ban
From: Bitrex on 17 Feb 2010 07:11 > Bitrex, > Do you have a degree presently? Did you get another degree back in > the deeps of time? If so, then go for a masters in EE. Easier, and > more fun! > > Charlie No such luck I'm afraid, Charlie. I did several semesters of college as a Comp Sci major, back in the late 90s, but I made a poor choice of school and things didn't work out. I was searching for somewhere to transfer to when I fell ill the first time. After recovering from that I had to give up my educational aspirations in favor of making a living, at least until I fell seriously ill the second time...Go on like that for a while and suddenly a decade has passed. I do have a lot of "gen ed" prerequisite courses for transfer credit under my belt, I did them here and there at various community colleges (and Harvard's adult education program) over the years with the hope that someday I'd have the chance to enroll in a full degree program. Circumstances have granted me that opportunity now, and I feel this is probably my last chance.
From: Charlie E. on 17 Feb 2010 11:25
On Wed, 17 Feb 2010 07:11:28 -0500, Bitrex <bitrex(a)de.lete.earthlink.net> wrote: > >> Bitrex, >> Do you have a degree presently? Did you get another degree back in >> the deeps of time? If so, then go for a masters in EE. Easier, and >> more fun! >> >> Charlie > >No such luck I'm afraid, Charlie. I did several semesters of college as >a Comp Sci major, back in the late 90s, but I made a poor choice of >school and things didn't work out. I was searching for somewhere to >transfer to when I fell ill the first time. After recovering from that >I had to give up my educational aspirations in favor of making a living, >at least until I fell seriously ill the second time...Go on like that >for a while and suddenly a decade has passed. > >I do have a lot of "gen ed" prerequisite courses for transfer credit >under my belt, I did them here and there at various community colleges >(and Harvard's adult education program) over the years with the hope >that someday I'd have the chance to enroll in a full degree program. >Circumstances have granted me that opportunity now, and I feel this is >probably my last chance. then, your greatest problem might be just getting accepted into a program. Many EE programs are 'impacted', i.e. they have many more applicants than they have slots for students, so they become very selective. I know that twenty years ago, when I decided to go back and get an EE degree, I ended up moving out of state to get accepted to a program. Later, I found that I could get a masters in EE, even with my bachelors in psychology, and so was able to move back... Charlie |