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.

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

Larry Jaques wrote:

Does it have refresher courses on trig, perchance?

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...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Larry Jaques wrote:

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

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.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Mark & Juanita 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.
....

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...

--

Morris Dovey 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.

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???

--

dpb wrote:
Morris Dovey 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.

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???

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.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

dpb wrote:

Mark & Juanita 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.
...

Why virtually every engineering curriculum I'm aware of teaches
subject-specific math classes outside the mathematics
department...

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.

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...

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.


--

--

There is never a situation where having more rounds is a disadvantage

Rob Leatham

On Mon, 21 Dec 2009 14:01:39 -0600, the infamous dpb
scrawled the following:

Mark & Juanita 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.
...

Ouch, I think.


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...

That makes sense.

--
REMEMBER: The sooner you fall behind,
the more time you'll have to catch up!

Morris Dovey wrote:
dpb wrote:
Morris Dovey 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.

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???

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.

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.

--

dpb wrote:

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.

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...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Morris Dovey wrote:
dpb wrote:

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.

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...

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...

--

dpb wrote:
Morris Dovey wrote:
dpb wrote:

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.

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...

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?

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.

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...

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.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

dpb wrote:

..... snip

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...


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.



--

--

There is never a situation where having more rounds is a disadvantage

Rob Leatham

Mark & Juanita wrote:
dpb wrote:

.... snip
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...


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.

Pretty gentle by our standards today -- about 15-20 from NE this
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...

--

Morris Dovey wrote:
dpb wrote:
Morris Dovey wrote:
dpb wrote:

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.

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...

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?

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.

....

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...

--

Mark & Juanita wrote:
....

Been windy as all get out here in AZ today also. Rain just started a
little while ago -- cold rain.
....

I had gotten so involved in the "gettin' ready" process had slipped my
mind--I had seen the sandstorm on TWC.

It's been a major change here the last 30 years w/ the advent of low-
and no-till cultivation, more irrigation and the large acreages back
into native grass thru the Conservation Reserve (CRP) that we've not had
widescale blowing dirt on the scale I recall in the previous drought
cycles (early 50s, in particular; I'm too young for the Dirty 30's)
altho there were areas in W OK/N TX panhandles SE CO/NE NM this year
that got bad for a while it was much more local than years ago...

It looks like they got shorts all in a wad for nothing over this 'un
here, though...we got a dusting this AM but they now have down to 20%
chances for anything at all else and no accumulation forecast. Have
even backed off on the wind levels as the low just never deepened and is
farther north and has a splitoff to the south that prevented the
frontogenesis they were so concerned over earlier.

Looks like from Chicago back thru Ioway is where it's all headed...

Sorry for those who do get hit; there's a lot of corn and beans still in
the fields back there but can't say I'm at all sorry to miss the
blizzard conditions here altho could have stood a few inches of nice,
wet snow if it would've stayed on the wheat...

MC, all...

--

dpb 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.

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.

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...

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.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/