Cool scientific Java applets

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Every once in a while you run across something that reaffirms what a good resource the web is. If you have a bent for physics/science, you should find the following site fun/interesting:
http://www.phy.ntnu.edu.tw/ntnujava /
Just as an example, for those woodworkers who need a refresher on how to read/interpolate the vernier scale on a set of calipers or a ruler with decimal place/fractional accuracy, check out the Misc section for java script exercises.
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Last update: 10/22/08
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On Sun, 20 Dec 2009 16:55:22 -0600, the infamous Swingman

Does it have refresher courses on trig, perchance?
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Larry Jaques wrote:

Just for those who need a refresher:
http://www.iedu.com/DeSoto/Projects/CNC/trig.html
If I missed any favorite formulas, let me know so I can add 'em...
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On Mon, 21 Dec 2009 02:50:43 -0600, the infamous Morris Dovey

Thanks. But no comment on my requesting math questions from a physics site? <evil grinne>
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wrote:

Why would that raise any eyebrows? First day in Physics 101 was spent teaching students how to do integral calculus with definite integrals in order to permit teaching the equations of motion. Definite integral calculus was a topic by the way, that wasn't covered in Calculus 101 (a co- requisite with Physics 101) until the final week of the semester.

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Mark & Juanita wrote: ...

Why virtually every engineering curriculum I'm aware of teaches subject-specific math classes outside the mathematics department...several departments went so far at my undergraduate uni as to remove the four-semester calculus/analytic geometry course sequence from their curriculum in favor of doing it themselves in order to at least coordinate the subjects taught and sequence in order to provide the necessary background in time...
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Somebody wrote: ====================================First day in Physics 101 was spent teaching students how to do integral calculus with definite integrals in order to permit teaching the equations of motion. ==================================My Physics 101 prof was very straight forward on the first day of class.
He stated that periodically he would give "snap" quizes, but not to worry, the answer would always be "1".
Our job was to define the "units" associated with that "1".
Lew
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dpb wrote:

This was an engineering curriculum. Calculus was taught through the applied math department of the engineering college rather that the math department of arts & sciences
I do understand what you are saying here though. Our circuit analysis course spent the first several weeks covering linear algebra & differential equations with s-transform theory. By the time I got to the Linear Algebra & Differential Equations math course TWO semesters later; there wasn't a whole lot of surprise in that course content.

Whatta concept. During my entire undergraduate career, I always had the impression that the PRE-requisite for just about any engineering course I was taking was a full working knowledge of all the material to be covered during the course.

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scrawled the following:

Ouch, I think.

That makes sense.
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Larry Jaques wrote:

IANAP. The web site has a lot more to do with staying warm and comfortable without being dependent on the energy/fuel sellers.
I've added a few pages for folks wanting to have water to drink, for sanitation, and for agriculture on that same basis.
All the rest is fluff. :)
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Morris Dovey wrote: ...

Morris, a wondering/question mixing the two? You ever tried/considered solar stock tank heater in IA winter? Is it even on the cusp of practical???
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dpb wrote:

I was considering a solar stock tank heater until I looked at these passive geothermal heaters on the Winebrenner farm down in E. Peru, IA:
http://www.cobett.com /
and talked to one of their customers. They're reliable, much more simple, and less expensive than anything I could come up with. The customer with whom I spoke buried a run of drain pipe to increase the amount of heat available and said he'd had no freeze problems since installation.
That's at least a good indicator of practicality. :)
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Morris Dovey wrote:

Thanks for the link...
Looked at it; they only keep the valves from freezing by burying them deeply; water surface still freezes w/o external heat source. Could live w/ that I guess, but the real kicker is they're "large" model is sized for 2-3 head at a time which wouldn't cut it for us w/o a large number of them. We're running 12-1500 head over winter, typically w/ none anywhere during cold weather except on pasture; we sell as feeders to the lots in spring w/ a small feeder operation here while then farm during summer months as have virtually no permanent grass (40A, only, roughly).
So the problem is for the tanks on winter pasture where have no power and are temporary so burial that Cobett uses is out. It's a real difficult chore to keep any propane/gas design have found so far lit in the high W KS wind consistently. Alternatively, chopping ice every morning is _not_ my idea of fun and it takes quite a lot of time not to mention the waste of (albeit solid) water which isn't cheap to pump nor haul the first time what more the multiple the multiple time(s) to replace it. Many days if any bad weather and given short daylight hours the entire day is nothing but hauling water from shortly after dawn to dark... :(
My guess is there's not enough solar heat density to make it practical in size anyway, just wondered if you'd looked into it.
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dpb wrote:

I have, but not for a while - because (in my ignorance) I thought it a solved problem.
The approach I had been working on involved using a solar-powered pump to pump solar-heated _air_ through an immersed tube in an insulated stock tank.
I think it can be made workable, so if you have a little time to collaborate, you're invited to e-mail me directly...
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Morris Dovey wrote:

OK, later on I may do that. Will have to guesstimate what heat load would have to be to have a relatively low level of icing given a tank size. You have any idea what kind of power level you might be talking?
Meanwhile, today I've got to get stuff tied down ahead of the blizzard warnings for tomorrow/next day. We may get somewhat shorted on the snow they say but the wind is certainly coming it appears and if they're only off by a few miles on the snow track might be pretty nasty couple of days. 40+ mph doesn't take a lot of snow to be a pitproverbialappenage. Looks like the brunt may be back towards your area again...
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dpb wrote:

It's fairly difficult for me to do much estimating without a handle on your weather conditions and some info on tank/stock dimensions - for example, I don't have any idea how far a steer can (or is willing to) "reach" for a drink, and that'll be a determining factor for the thickness of insulation that can be used around the tank.
The way to approach his kind of problem is to assume that all the power needed is available, and then design to use it as efficiently as possible - and size the collector to capture whatever turns out to be needed.

Here's hoping you miss the worst of the snow. Our local forecasters are guessing that we'll see more rain than snow in this area, which may make for interesting road conditions.
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Morris Dovey wrote:

Well, they'll reach as far as they can if thirsty, just like they reach under a fence for that delectable blade of grass... :)
About 3-ft is probably practical limit--but you have to count for the water level dropping as they slurp it down, too. Even in cold weather they'll average 3-5 gal/day/head. So far all we've used are the round metal tanks--typically 12-ft diam are convenient to handle/haul and one or two are enough for each location.
Not sure the best estimates for weather to try to use as I think of this more. The problem as I see it on further consideration is that the coldest weather is when the pita factor kicks in the most as that's when if the heaters go out the tanks freeze fastest and thickest so both longer time w/o water and more waste and more trouble. Yet to design for the 0F/30-mph condition would probably be way over what could be practical. I'll have to think some more, Morris and take this offline...
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dpb wrote:

Ok, 12-feet it is. How tall are the tanks, and to how far from the top do you fill 'em? Next time you're out, please take a tape rule and your digital camera. I've already started on drawings, but have /zip/ experience with cattle operations.

I have historical weather data from NREL (National Renewable Energy Labs, www.nrel.gov), but need to know more about less scientific stuff like portability and what would make for ease of deployment and how to build something that won't be done in by curious/bored critters. :)
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dpb wrote:
.... snip

Best of luck to you. That's not a pleasant task, especially if you are fighting the wind while doing it.
Been windy as all get out here in AZ today also. Rain just started a little while ago -- cold rain.

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Mark & Juanita wrote:

afternoon after the switch from NW a little after noon and the pressure began to drop and the dewpoint obviously rising. About 36-38F mid-afternoon; last heard windchill was in low 20s. Only foggy so far (<1/2-mi which is nearest neighbor and can't see a glimmer of their yardlights)...looks on radar as though enough to begin to show up out on the mesa in W OK panhandle/NE NM--that's a few hours away yet...
Blizzard watch posted for tomorrow night thru Thursday altho predicted winds only 30-35/gusts 40. That's not messy but not anything truly drastic unless it really snows hard w/ it. Not like "the big-un" of '57 that blew 50-70mph from Sat noon thru the weekend until following Monday noon, roughly. That buried a 20-ft light pole in the yard but for the top couple of feet...we ended up w/ cattle drifted with it as far as 50 miles away. One ended up at a sale barn in August over 100 miles away after a TX ranch roundup--we figure she probably was gathered up w/ others and missed getting cut out rather than actually walked all that far but don't know for sure.
I've done all I can do but wait and watch...
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