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#### EVDL List

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I believe you can get one of these from KTA and or Electro Automotive.

---- dave cover <[email protected]> wrote:
> Along the same vein, I picked up a shunt for the motor side of my
> controller, 50mv/1000Amps. I wanted to measure the current my controller
> could handle and came across a shunt first. I had been watching for a lon g
> time before this option came along. The problem I'm finding is no one makes
> a meter to match the shunt.
>
> I've been watching eBay as well as the usual sources; DigiKey, Mouser,
> SurplusStore, etc. I just can't find a compatible meter. I'd even go with a
> 50mv/100A meter, but haven't seen one. It seems all the meters in my range
> work at 75mv for the top end.
>
> Since you already have a meter, you know what shunt you need. My problem is
> I can't find a meter to match my shunt. Go figure. If I'd have known how
> incompatible these can be I wouldn't have jumped on it so quickly.
>
> Dave Cover
>
>
Zeke Yewdall <[email protected]> wrote:
>
> > I've only seen ones that are 50mV/500A and 100mV/100A (Occasionally
> > 100mV/150A or 50mV/100A). I suppose you could use two of the
> > 50mV/500A shunts in series, then put a 3:4 voltage divider on the
> > signal to generate the 75mV/500A signal.... sort of clunky though...
> >
> > Z
> >
> > On Mon, Apr 28, 2008 at 5:39 AM, vehiculeselectriques.free.fr
> > <[email protected]> wrote:
> > > Mine is more like this one, though for a 75mV/500A,
> > > If your customer is in a hurry, i'm willing to sell it as i never
> > ordered
> > > the Emeter to use it with, contact me off list
> > >
> > >
> > http://cgi.ebay.com/Blue-Sea-9229-Analog-Meter-Shunt-75A-50mV_W0QQitemZ120231828390QQihZ002QQcategoryZ58049QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
> > >
> > >
> > > philippe
> > >
> > > 2008/4/28, Ian Hooper <[email protected]>:
> > > >
> > >
> > >
> > > > Yeah that's the exact sort he's not happy with - apparently they are
> > > > too big, too ugly (roughly finished), and too hard to mount (no
> > > > insulating base). He's actually not the first of my customers to
> > > > complain about these shunts either, oh well..
> > > >
> > > > -Ian
> > > >
> > > > On 28/04/2008, at 6:04 PM, [email protected] wrote:
> > > >
> > > > >> they appears on Ebay often, i have purchased mine from here
> > > > >>
> > > > >> Philippe
> > > > >
> > > > > If he has one like this:
> > > > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250241133623
> > > > > they look neat enough. Would be nice to have a non-conductive block
> > > > > attached at the bottom for mounting, or how about a clear tube
> > > > > (http://electroauto.com/catalog/elec.shtml#fuselink) to protect
> > from
> > > > > contact?
> > > > >
> > > > > _______________________________________________
> > > > > For subscription options, see
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> > > > >
> > > >
> > > > _______________________________________________
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> > > >
> > > _______________________________________________
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> > >
> >
> > _______________________________________________
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> >
> _______________________________________________
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Ah, I didn't even consider the possibility of it being an analog
meter. I just assumed it was an e-meter/link10 type device. Ooops.

I don't think the resistor bridge will work to increase the voltage --
if we wanted a lower signal voltage than what the shunt is giving, we
could use it to decrease the voltage though. Any other EE's want to
weigh in on this?

Z

Mark Grasser <[email protected]> wrote:
> I think if it is analog Lee 1s correct, 1/3 the resistance of the meter in
> series will the meter should do it. It's volts at this point not amps, the
> current will be very low. If it is a digital meter then a resistor bridge of
> two resistors will do. Something like 100 ohms and 33 ohms in series across
> the shunt and then the meter across the 100 ohm resistor.
>
> Mark Grasser
>
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf
> Of Zeke Yewdall
> Sent: Monday, April 28, 2008 11:49 AM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Shunts
>
> >
> > The easiest solution is to get a 100mv shunt, and connect a resistor in
> > series with the meter to drop the extra 25mv (so he gets 75mv at the
> meter).
> >
>
> That's pretty tricky, since you'd have to know exactly how much
> current the meter was drawing. I'm not familiar with the particular
> one he has, but the ones I've used are very low current -- like
> microamps, on the sense inputs. If the meter doesn't have seperate
> sense and power inputs, the current draw could be up in the mA range,
> but could also vary depending on how many digits of the display are
> lit up, which won't work.
>
>
>
> _______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev
>
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Zeke Yewdall <[email protected]> wrote:
> Ah, I didn't even consider the possibility of it being an analog
> meter. I just assumed it was an e-meter/link10 type device. Ooops.
>
> I don't think the resistor bridge will work to increase the voltage --
> if we wanted a lower signal voltage than what the shunt is giving, we
> could use it to decrease the voltage though. Any other EE's want to
> weigh in on this?

I guess this also depends on which question we are answering... there
are now two of them running through this thread.

>
> Z
>
>
>
> On Mon, Apr 28, 2008 at 10:22 AM, Mark Grasser <[email protected]> wrote:
> > I think if it is analog Lee 1s correct, 1/3 the resistance of the meter in
> > series will the meter should do it. It's volts at this point not amps, the
> > current will be very low. If it is a digital meter then a resistor bridge of
> > two resistors will do. Something like 100 ohms and 33 ohms in series across
> > the shunt and then the meter across the 100 ohm resistor.
> >
> > Mark Grasser
> >
> >
> >
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On Behalf
> > Of Zeke Yewdall
> > Sent: Monday, April 28, 2008 11:49 AM
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Shunts
> >
> > >
> > > The easiest solution is to get a 100mv shunt, and connect a resistor in
> > > series with the meter to drop the extra 25mv (so he gets 75mv at the
> > meter).
> > >
> >
> > That's pretty tricky, since you'd have to know exactly how much
> > current the meter was drawing. I'm not familiar with the particular
> > one he has, but the ones I've used are very low current -- like
> > microamps, on the sense inputs. If the meter doesn't have seperate
> > sense and power inputs, the current draw could be up in the mA range,
> > but could also vary depending on how many digits of the display are
> > lit up, which won't work.
> >
> >
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>

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#### EVDL List

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Discussion Starter · ·
I was responding to the question of how to use a 100mv shunt with a 75mv
meter. Either resistor method should work. The only way to use the 50mv
shunt would be to use some type of amplifier circuit. Incidentally, 1000amps
= a .1volt drop across the 100mvshunt. That 100 watts of heat. You will need
to be moving some air if you are going to do it very often.

Mark Grasser

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Zeke Yewdall
Sent: Monday, April 28, 2008 1:01 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Shunts

Zeke Yewdall <[email protected]> wrote:
> Ah, I didn't even consider the possibility of it being an analog
> meter. I just assumed it was an e-meter/link10 type device. Ooops.
>
> I don't think the resistor bridge will work to increase the voltage --
> if we wanted a lower signal voltage than what the shunt is giving, we
> could use it to decrease the voltage though. Any other EE's want to
> weigh in on this?

I guess this also depends on which question we are answering... there
are now two of them running through this thread.

>
> Z
>
>
>
> On Mon, Apr 28, 2008 at 10:22 AM, Mark Grasser <[email protected]>
wrote:
> > I think if it is analog Lee 1s correct, 1/3 the resistance of the meter
in
> > series will the meter should do it. It's volts at this point not amps,
the
> > current will be very low. If it is a digital meter then a resistor
bridge of
> > two resistors will do. Something like 100 ohms and 33 ohms in series
across
> > the shunt and then the meter across the 100 ohm resistor.
> >
> > Mark Grasser
> >
> >
> >
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On
Behalf
> > Of Zeke Yewdall
> > Sent: Monday, April 28, 2008 11:49 AM
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Shunts
> >
> > >
> > > The easiest solution is to get a 100mv shunt, and connect a
resistor in
> > > series with the meter to drop the extra 25mv (so he gets 75mv at
the
> > meter).
> > >
> >
> > That's pretty tricky, since you'd have to know exactly how much
> > current the meter was drawing. I'm not familiar with the particular
> > one he has, but the ones I've used are very low current -- like
> > microamps, on the sense inputs. If the meter doesn't have seperate
> > sense and power inputs, the current draw could be up in the mA range,
> > but could also vary depending on how many digits of the display are
> > lit up, which won't work.
> >
> >
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>

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#### EVDL List

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Discussion Starter · ·
Okay. We agree I thought you were referring to the 50mV shunt.

yeah... that's alot of heat for a little shunt to dissipate. I've
never actually seen a shunt rated at any more than 500 amps, and those
are 50mV ones, so only 25 wattts there. But, apparently there are
bigger ones out there.

Z

Mark Grasser <[email protected]> wrote:
> I was responding to the question of how to use a 100mv shunt with a 75mv
> meter. Either resistor method should work. The only way to use the 50mv
> shunt would be to use some type of amplifier circuit. Incidentally, 1000amps
> = a .1volt drop across the 100mvshunt. That 100 watts of heat. You will need
> to be moving some air if you are going to do it very often.
>
>
> Mark Grasser
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf
> Of Zeke Yewdall
>
>
> Sent: Monday, April 28, 2008 1:01 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Shunts
>
> On Mon, Apr 28, 2008 at 10:59 AM, Zeke Yewdall <[email protected]> wrote:
> > Ah, I didn't even consider the possibility of it being an analog
> > meter. I just assumed it was an e-meter/link10 type device. Ooops.
> >
> > I don't think the resistor bridge will work to increase the voltage --
> > if we wanted a lower signal voltage than what the shunt is giving, we
> > could use it to decrease the voltage though. Any other EE's want to
> > weigh in on this?
>
> I guess this also depends on which question we are answering... there
> are now two of them running through this thread.
>
> >
> > Z
> >
> >
> >
> > On Mon, Apr 28, 2008 at 10:22 AM, Mark Grasser <[email protected]>
> wrote:
> > > I think if it is analog Lee 1s correct, 1/3 the resistance of the meter
> in
> > > series will the meter should do it. It's volts at this point not amps,
> the
> > > current will be very low. If it is a digital meter then a resistor
> bridge of
> > > two resistors will do. Something like 100 ohms and 33 ohms in series
> across
> > > the shunt and then the meter across the 100 ohm resistor.
> > >
> > > Mark Grasser
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: [email protected] [mailto:[email protected]] On
> Behalf
> > > Of Zeke Yewdall
> > > Sent: Monday, April 28, 2008 11:49 AM
> > > To: Electric Vehicle Discussion List
> > > Subject: Re: [EVDL] Shunts
> > >
> > > >
> > > > The easiest solution is to get a 100mv shunt, and connect a
> resistor in
> > > > series with the meter to drop the extra 25mv (so he gets 75mv at
> the
> > > meter).
> > > >
> > >
> > > That's pretty tricky, since you'd have to know exactly how much
> > > current the meter was drawing. I'm not familiar with the particular
> > > one he has, but the ones I've used are very low current -- like
> > > microamps, on the sense inputs. If the meter doesn't have seperate
> > > sense and power inputs, the current draw could be up in the mA range,
> > > but could also vary depending on how many digits of the display are
> > > lit up, which won't work.
> > >
> > >
> > >
> > > _______________________________________________
> > > For subscription options, see
> > > http://lists.sjsu.edu/mailman/listinfo/ev
> > >
> > > _______________________________________________
> > > For subscription options, see
> > > http://lists.sjsu.edu/mailman/listinfo/ev
> > >
> >
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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#### EVDL List

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Discussion Starter · ·
I talked to a representative of a shunt company, and he said that the
rating listed on the shunt is the *continuous* rating, and they should
be able to handle much more peak current.

-Morgan LaMoore

Zeke Yewdall <[email protected]> wrote:
> Okay. We agree I thought you were referring to the 50mV shunt.
>
> yeah... that's alot of heat for a little shunt to dissipate. I've
> never actually seen a shunt rated at any more than 500 amps, and those
> are 50mV ones, so only 25 wattts there. But, apparently there are
> bigger ones out there.
>
> Z
>
>
>
> On Mon, Apr 28, 2008 at 11:40 AM, Mark Grasser <[email protected]> wrote:
> > I was responding to the question of how to use a 100mv shunt with a 75mv
> > meter. Either resistor method should work. The only way to use the 50mv
> > shunt would be to use some type of amplifier circuit. Incidentally, 1000amps
> > = a .1volt drop across the 100mvshunt. That 100 watts of heat. You will need
> > to be moving some air if you are going to do it very often.
> >
> >
> > Mark Grasser
> >
> >
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On Behalf
> > Of Zeke Yewdall
> >
> >
> > Sent: Monday, April 28, 2008 1:01 PM
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Shunts
> >
> > On Mon, Apr 28, 2008 at 10:59 AM, Zeke Yewdall <[email protected]> wrote:
> > > Ah, I didn't even consider the possibility of it being an analog
> > > meter. I just assumed it was an e-meter/link10 type device. Ooops.
> > >
> > > I don't think the resistor bridge will work to increase the voltage --
> > > if we wanted a lower signal voltage than what the shunt is giving, we
> > > could use it to decrease the voltage though. Any other EE's want to
> > > weigh in on this?
> >
> > I guess this also depends on which question we are answering... there
> > are now two of them running through this thread.
> >
> > >
> > > Z
> > >
> > >
> > >
> > > On Mon, Apr 28, 2008 at 10:22 AM, Mark Grasser <[email protected]>
> > wrote:
> > > > I think if it is analog Lee 1s correct, 1/3 the resistance of the meter
> > in
> > > > series will the meter should do it. It's volts at this point not amps,
> > the
> > > > current will be very low. If it is a digital meter then a resistor
> > bridge of
> > > > two resistors will do. Something like 100 ohms and 33 ohms in series
> > across
> > > > the shunt and then the meter across the 100 ohm resistor.
> > > >
> > > > Mark Grasser
> > > >
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: [email protected] [mailto:[email protected]] On
> > Behalf
> > > > Of Zeke Yewdall
> > > > Sent: Monday, April 28, 2008 11:49 AM
> > > > To: Electric Vehicle Discussion List
> > > > Subject: Re: [EVDL] Shunts
> > > >
> > > > >
> > > > > The easiest solution is to get a 100mv shunt, and connect a
> > resistor in
> > > > > series with the meter to drop the extra 25mv (so he gets 75mv at
> > the
> > > > meter).
> > > > >
> > > >
> > > > That's pretty tricky, since you'd have to know exactly how much
> > > > current the meter was drawing. I'm not familiar with the particular
> > > > one he has, but the ones I've used are very low current -- like
> > > > microamps, on the sense inputs. If the meter doesn't have seperate
> > > > sense and power inputs, the current draw could be up in the mA range,
> > > > but could also vary depending on how many digits of the display are
> > > > lit up, which won't work.
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > For subscription options, see
> > > > http://lists.sjsu.edu/mailman/listinfo/ev
> > > >
> > > > _______________________________________________
> > > > For subscription options, see
> > > > http://lists.sjsu.edu/mailman/listinfo/ev
> > > >
> > >
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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#### EVDL List

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Discussion Starter · ·
Maybe his shunts, depends how they rate them. I have melted the solder out
of shunts, turned them blue, even made them blister, never more than 25%
over the rating. Of course the ones I used came from "that place".

Mark Grasser
Balyntec
Marine Products, LLC
828-581-4601
[email protected]

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Morgan LaMoore
Sent: Monday, April 28, 2008 2:11 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Shunts

I talked to a representative of a shunt company, and he said that the
rating listed on the shunt is the *continuous* rating, and they should
be able to handle much more peak current.

-Morgan LaMoore

Zeke Yewdall <[email protected]> wrote:
> Okay. We agree I thought you were referring to the 50mV shunt.
>
> yeah... that's alot of heat for a little shunt to dissipate. I've
> never actually seen a shunt rated at any more than 500 amps, and those
> are 50mV ones, so only 25 wattts there. But, apparently there are
> bigger ones out there.
>
> Z
>
>
>
> On Mon, Apr 28, 2008 at 11:40 AM, Mark Grasser <[email protected]>
wrote:
> > I was responding to the question of how to use a 100mv shunt with a
75mv
> > meter. Either resistor method should work. The only way to use the
50mv
> > shunt would be to use some type of amplifier circuit. Incidentally,
1000amps
> > = a .1volt drop across the 100mvshunt. That 100 watts of heat. You
will need
> > to be moving some air if you are going to do it very often.
> >
> >
> > Mark Grasser
> >
> >
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On
Behalf
> > Of Zeke Yewdall
> >
> >
> > Sent: Monday, April 28, 2008 1:01 PM
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Shunts
> >
> > On Mon, Apr 28, 2008 at 10:59 AM, Zeke Yewdall <[email protected]>
wrote:
> > > Ah, I didn't even consider the possibility of it being an analog
> > > meter. I just assumed it was an e-meter/link10 type device.
Ooops.
> > >
> > > I don't think the resistor bridge will work to increase the voltage
--
> > > if we wanted a lower signal voltage than what the shunt is giving,
we
> > > could use it to decrease the voltage though. Any other EE's want
to
> > > weigh in on this?
> >
> > I guess this also depends on which question we are answering... there
> > are now two of them running through this thread.
> >
> > >
> > > Z
> > >
> > >
> > >
> > > On Mon, Apr 28, 2008 at 10:22 AM, Mark Grasser
<[email protected]>
> > wrote:
> > > > I think if it is analog Lee 1s correct, 1/3 the resistance of the
meter
> > in
> > > > series will the meter should do it. It's volts at this point not
amps,
> > the
> > > > current will be very low. If it is a digital meter then a
resistor
> > bridge of
> > > > two resistors will do. Something like 100 ohms and 33 ohms in
series
> > across
> > > > the shunt and then the meter across the 100 ohm resistor.
> > > >
> > > > Mark Grasser
> > > >
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: [email protected]
[mailto:[email protected]] On
> > Behalf
> > > > Of Zeke Yewdall
> > > > Sent: Monday, April 28, 2008 11:49 AM
> > > > To: Electric Vehicle Discussion List
> > > > Subject: Re: [EVDL] Shunts
> > > >
> > > > >
> > > > > The easiest solution is to get a 100mv shunt, and connect a
> > resistor in
> > > > > series with the meter to drop the extra 25mv (so he gets 75mv
at
> > the
> > > > meter).
> > > > >
> > > >
> > > > That's pretty tricky, since you'd have to know exactly how much
> > > > current the meter was drawing. I'm not familiar with the
particular
> > > > one he has, but the ones I've used are very low current -- like
> > > > microamps, on the sense inputs. If the meter doesn't have
seperate
> > > > sense and power inputs, the current draw could be up in the mA
range,
> > > > but could also vary depending on how many digits of the display
are
> > > > lit up, which won't work.
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > For subscription options, see
> > > > http://lists.sjsu.edu/mailman/listinfo/ev
> > > >
> > > > _______________________________________________
> > > > For subscription options, see
> > > > http://lists.sjsu.edu/mailman/listinfo/ev
> > > >
> > >
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
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#### EVDL List

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70 Posts
Discussion Starter · ·
Take a look at this 100A meter (you have to multiply by 10):

http://www.allelectronics.com/cgi-bin/item/PMD-100A/385/100_AMP_DC_PANEL_METER_.html

They don't say how many mV it is, but they also sell a 100A 50mV shunt,
so my guess is...

- SteveS

Zeke Yewdall wrote:
> You could always use a standard 50mV/500A meter, and remember that
> it's only reading half of the actual amperage......
>
> Z
>
>
dave cover <[email protected]> wrote:
>
>> Along the same vein, I picked up a shunt for the motor side of my
>> controller, 50mv/1000Amps. I wanted to measure the current my controller
>> could handle and came across a shunt first. I had been watching for a lon g
>> time before this option came along. The problem I'm finding is no one makes
>> a meter to match the shunt.
>>
>> I've been watching eBay as well as the usual sources; DigiKey, Mouser,
>> SurplusStore, etc. I just can't find a compatible meter. I'd even go with a
>> 50mv/100A meter, but haven't seen one. It seems all the meters in my range
>> work at 75mv for the top end.
>>
>> Since you already have a meter, you know what shunt you need. My problem is
>> I can't find a meter to match my shunt. Go figure. If I'd have known how
>> incompatible these can be I wouldn't have jumped on it so quickly.
>>
>> Dave Cover
>>
>>
>>
>> On Mon, Apr 28, 2008 at 9:18 AM, Zeke Yewdall <[email protected]> wrote:
>>
>> > I've only seen ones that are 50mV/500A and 100mV/100A (Occasionally
>> > 100mV/150A or 50mV/100A). I suppose you could use two of the
>> > 50mV/500A shunts in series, then put a 3:4 voltage divider on the
>> > signal to generate the 75mV/500A signal.... sort of clunky though...
>> >
>> > Z
>> >
>> > On Mon, Apr 28, 2008 at 5:39 AM, vehiculeselectriques.free.fr
>> > <[email protected]> wrote:
>> > > Mine is more like this one, though for a 75mV/500A,
>> > > If your customer is in a hurry, i'm willing to sell it as i never
>> > ordered
>> > > the Emeter to use it with, contact me off list
>> > >
>> > >
>> > http://cgi.ebay.com/Blue-Sea-9229-Analog-Meter-Shunt-75A-50mV_W0QQitemZ120231828390QQihZ002QQcategoryZ58049QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
>> > >
>> > >
>> > > philippe
>> > >
>> > > 2008/4/28, Ian Hooper <[email protected]>:
>> > > >
>> > >
>> > >
>> > > > Yeah that's the exact sort he's not happy with - apparently they are
>> > > > too big, too ugly (roughly finished), and too hard to mount (no
>> > > > insulating base). He's actually not the first of my customers to
>> > > > complain about these shunts either, oh well..
>> > > >
>> > > > -Ian
>> > > >
>> > > > On 28/04/2008, at 6:04 PM, [email protected] wrote:
>> > > >
>> > > > >> they appears on Ebay often, i have purchased mine from here
>> > > > >>
>> > > > >> Philippe
>> > > > >
>> > > > > If he has one like this:
>> > > > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250241133623
>> > > > > they look neat enough. Would be nice to have a non-conductive block
>> > > > > attached at the bottom for mounting, or how about a clear tube
>> > > > > (http://electroauto.com/catalog/elec.shtml#fuselink) to protect
>> > from
>> > > > > contact?
>>
>
>

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##### Registered
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70 Posts
Discussion Starter · ·
dave cover wrote:
> Along the same vein, I picked up a shunt for the motor side of my
> controller, 50mv/1000Amps. I wanted to measure the current my controller
> could handle and came across a shunt first. I had been watching for a lon g
> time before this option came along. The problem I'm finding is no one makes
> a meter to match the shunt.
>
> I've been watching eBay as well as the usual sources; DigiKey, Mouser,
> SurplusStore, etc. I just can't find a compatible meter. I'd even go with a
> 50mv/100A meter, but haven't seen one. It seems all the meters in my range
> work at 75mv for the top end.
>
> Since you already have a meter, you know what shunt you need. My problem is
> I can't find a meter to match my shunt. Go figure. If I'd have known how
> incompatible these can be I wouldn't have jumped on it so quickly.

50mv is a common standard shunt values. You know, you can just *buy* a
meter to match, without getting it surplus or used. Digikey and Mouser
specialize in electronics, not electrics like meters, so they aren't a
preferres source.

Try Simpson Electric Co. at http://www.simpsonelectric.com/ and look at
their analog panel meters.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Discussion Starter · ·
>> The easiest solution is to get a 100mv shunt, and connect a
>> resistor in series with the meter to drop the extra 25mv (so he
>> gets 75mv at the meter).

Zeke Yewdall wrote:
> That's pretty tricky, since you'd have to know exactly how much
> current the meter was drawing.

Analog ammeters are just a simple resistor electrically. Often, their
resistance is printed right on them. An analog ammeter marked (say) "100
amps" will in fact be a 50 millivolt full-scale meter that draws between
1 ma and 100 ma. For example, I have one with a "50 amp" scale; it's
actually 50mv full-scale and measures 18 ohms (2.77ma full scale). To
use it with a 75mv shunt, add a 9 ohm precision resistor in series.

Digital meters often have a very high input impedance (1 megohm or
more). For example, the common E-meter / Link-10 is 2 megohms input
impedance. So a simple voltage divider will work fine.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Discussion Starter · ·
Morgan LaMoore wrote:

> I talked to a representative of a shunt company, and he said
> that the rating listed on the shunt is the *continuous*
> rating, and they should be able to handle much more peak current.

Be aware that this will apparently depend on whose shunt you are using (and=
perhaps even on the technical knowledge of the representative you speak wi=
th ;^). Deltec shunts, for instance are not to be used at more than 2/3 of=
the rated current continuously. Fromt the Deltec website (<http://www.del=
tecco.com/>):

"Shunt Operation
For continuous operation, it is recommended that shunts are not used at mor=
e than 2/3 of the rated current under normal operation conditions. Shunts s=
hould be located in an area where freely circulating air is available. If t=
his is not possible adequate forced ventilation should be provided to keep =
the shunt operating temperature at 40=B0 - 60=B0C. Shunt temperature must b=
e maintained under 145=B0 C or a permanent change in resistance will occur."

Deltec shunts are the ones commonly used with E-meters/Link-10s. Bear in m=
ind, however, that the Deltec shunts are calibrated for +/-0.25% accuracy a=
nd it is quite possible that the permanent change in resistance that may oc=
cur due to running them at higher than intended currents may be significant=
to someone requiring the +/-0.25% accuracy and completely irrelevant for E=
Vers.

Cheers,

Roger.

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21 - 31 of 31 Posts


text:
LieBracket - Maple Help

# Online Help

###### All Products    Maple    MapleSim

LieBracket

calculate the Lie bracket of two VectorField objects

Commutator

a synonym for LieBracket

 Calling Sequence LieBracket (X, Y) Commutator (X, Y)

Parameters

 X - a VectorField object Y - a VectorField object on the same space as X

Description

 • The Lie bracket of two vector fields $X$, $Y$, defined on the same space, is the vector field $Z$ such that $Z\left(f\right)=X\left(Y\left(f\right)\right)-Y\left(X\left(f\right)\right)$ where $f$ is a real-valued function on the same space as $X$ and $Y$. The standard notation is $Z=\left[X,Y\right]$.
 • The LieBracket(X,Y) method returns a VectorField object on the same space as $X$ and $Y$.
 • The Commutator method is provided as an alias.
 • This method is associated with the VectorField object. For more detail, see Overview of the VectorField object.

Examples

 > $\mathrm{with}\left(\mathrm{LieAlgebrasOfVectorFields}\right):$
 > $U≔\mathrm{VectorField}\left(x\mathrm{D}\left[x\right]+y\mathrm{D}\left[y\right],\mathrm{space}=\left[x,y\right]\right)$
 ${U}{≔}{x}{}\frac{{\partial }}{{\partial }{x}}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}{+}{y}{}\frac{{\partial }}{{\partial }{y}}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}$ (1)

 > $\mathrm{Tx}≔\mathrm{VectorField}\left(\mathrm{D}\left[x\right],\mathrm{space}=\left[x,y\right]\right)$
 ${\mathrm{Tx}}{≔}\frac{{\partial }}{{\partial }{x}}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}$ (2)

 > $\mathrm{LieBracket}\left(U,\mathrm{Tx}\right)$
 ${-}\frac{{\partial }}{{\partial }{x}}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}$ (3)

which is the same as

 > $\mathrm{Commutator}\left(U,\mathrm{Tx}\right)$
 ${-}\frac{{\partial }}{{\partial }{x}}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}$ (4)

Compatibility

 • The LieBracket and Commutator commands were introduced in Maple 2020.
 • For more information on Maple 2020 changes, see Updates in Maple 2020.

 See Also

format: plain


text:
• anonymous
powerseries Lifesaver (1 fan)Become a fan You're a fanNot a fan Surface area of a torus which has radius r which is generated by the circle centered at (R,0) with radius r. And assume R>r. So the equation of the circle is (x-R)^2 +y^2 = r^2. FOr some reason my integral does not work. i have integral 2pi y dS, where y = sqrt [r^2 - (x-R)^2], and ds = sqrt ( 1 + dy/dx ^2). dy/dx = -2(x-R)/ (2sqrt(r^2 - (x-R)^2)). anyways, integration limits , the lower limit is R-r, and upper R+r
Physics

Looking for something else?

Not the answer you are looking for? Search for more explanations.


text:
# Circular Data Analysis: Calculating Sample Circular Dispersion

Using Fisher (1993) Statistical analysis of circular data (p30-35), I calculated the sample circular dispersion of some timestamp data. However, I got circular dispersion greater than $1,000$. Is this possible? Does a circular dispersion of, for example, $361$ equivalent to a circular dispersion of $1$? Or did I do some massive calculation error?

Just as a reference, I also followed this post. Thus, quoting Kees Mulder:

1. Denote the data by $\boldsymbol\theta = \{\theta_1, \dots, \theta_n\}.$ An estimate of the mean $\bar\theta$ can be calculated with

2. Calculate $\bar{R} = \frac{\sqrt{S^2 + C^2}}{n}$

3. Calculate the dispersion as suggested by whuber. I'm not sure why, but Wikipedia's definition seems to differ slightly from Fisher. I will use Fisher's:

• $\hat\delta = \frac{1 - \left[ (1/n) \sum_{i=1}^{n} \cos 2 (\theta_i - \hat\mu) \right]}{2\bar{R}^2}$
4. Then, choose some constant $c$ (1 is probably fine, but you may fine-tune). Then, the interval is given by

• $\left[\hat\mu - c \hat\delta, \hat\mu + c \hat\delta \right]$

Also, unfortunately, I cannot post my data.

Given the questions and comments below, I just want to clarify what I am looking for. I am primarily interested in whether the circular dispersion has an upper bound and how to interpret large circular dispersions. I am actually fairly confident that my calculations are correct, as long as the notes that I posted are correct.

• What is your mean resultant length and sample size, in this case? – Kees Mulder Nov 21 '16 at 19:15
• Could you add a fuller reference/citation than "Fisher (1995)", as you would in a paper or dissertation? – Silverfish Nov 21 '16 at 19:52
• To make this self-contained, please define circular dispersion and give a small dataset with puzzling result sufficient to replicate (or correct) what you find. – Nick Cox Nov 21 '16 at 19:54
• If you want to know for sure whether you made a calculation error, I can't see an alternative to you posting your data! Or are you just interested in whether the circular dispersion has an upper bound? – Silverfish Nov 21 '16 at 19:58
• You are making a calculation error. You don't have to reproduce your actual data: make a very small dataset with similar characteristics and see whether the problem recurs with it. Then you can post that dataset. – whuber Nov 22 '16 at 16:25


text:
Basic plotting

library(bayesplay)

The bayesplay package includes functionality for basic plotting of prior and likelihood objects. These plots are all generated with the generic plot() function. The plot() function returns a ggplot2 object. These plots are styled with sensible defaults; however, they can be further styled using standard ggplot2 syntax.

Examples

Plotting likelihoods

To plot a likelihood, you first need to define a likelihood using the standard syntax (see basic usage).

In the example below, we define normal likelihood with a mean of 5.5 and a standard error of 32.35.

norm_mod <- likelihood(family = "normal", mean = 5.5, sd = 32.35)
norm_mod
#> Likelihood
#>   Family
#>     normal
#>   Parameters
#>     mean: 5.5
#>     sd: 32.35
#>

To plot this object we just use it as the input to the plot() function.

plot(norm_mod)

As shown above, default axis labels are applied to the x and y axis. The x-axis limits are also automatically set to so that the full shape of the likelihood is visible.

An identical approach can also be used for plotting t likelihoods. First we define the likelihood.

t_mod <- likelihood(family = "student_t", mean = 10, sd = 5, df = 15)
t_mod
#> Likelihood
#>   Family
#>     student_t
#>   Parameters
#>     mean: 10
#>     sd: 5
#>     df: 15
#>

We can then plot the likelihood using the plot() function.

plot(t_mod)

Plotting priors

The process for plotting priors is identical to plotting likelihoods. First we define the prior, and then we plot it. Sensible axis labels are applied to plots of priors.

For example, we can plot a point prior, typically used for a null model.

point_prior <- prior(family = "point", point = 0)
plot(point_prior)

We can also plot a uniform prior.

uniform_prior <- prior(family = "uniform", min = 10, max = 20)
plot(uniform_prior)

Or a normal prior.

normal_prior <- prior(family = "normal", mean = 10, sd = 10)
plot(normal_prior)

The plot() function also behaves sensibly with, for example, half-normal priors. The height of the plot is scaled appropriately, and the plot is only show over the appropriate parameter range.

half_normal_prior <- prior(family = "normal", mean = 10, sd = 10, range = c(10, Inf))
plot(half_normal_prior)

Styling plots

The plots produced by the plot() function are standard ggplot2 objects and, therefore, they can be styled using the standard ggplot2 syntax.

First, we load the ggplot2 package to gain access to it’s styling functions.

library(ggplot2)

The functions than then we used to modify the output for the plot() function. For example, axis labels can be changed with ggplot2::labs()

plot(t_mod) + labs(x = "data", y = "likelihood", title = "t likelihood")

or axis limits can be changed using, for example, ggplot2::xlim(). Note that because scales have already been set by the plot() function, a warning message will be produced. This however, this message can be suppressed using standard R methods.

plot(uniform_prior) + xlim(-100,100)
#> Scale for 'x' is already present. Adding another scale for 'x', which will
#> replace the existing scale.

Or the plot can be themed using ggplot2 themes such as ggplot2::theme_linedraw()

plot(norm_mod) +
labs(title  = "normal likelihood") +
theme_linedraw()

For the advanced plot types like the prior and posterior plots and the visual comparison (see Advanced usage) it is also possible to change the colours and the linetypes.

For example, the default colours for these plots are blue and red solid lines.

data_model <- likelihood("noncentral_d", d = 0, n = 20)

d_model1 <- extract_predictions(data_model * prior("cauchy", 0, .707))
d_model2 <- extract_predictions(data_model * prior("point", 0))
visual_compare(d_model1, d_model2)

plot(extract_posterior(data_model * prior("cauchy", 0, .707)), add_prior = TRUE)

However, it is possible to change this with ggplot2::scale_colour_manual()

visual_compare(d_model1, d_model2) +
scale_colour_manual(values = c("green", "blue"),
labels = c("d_model1", "d_model2"), name = "Model")
#> Scale for 'colour' is already present. Adding another scale for 'colour',
#> which will replace the existing scale.

plot(extract_posterior(data_model * prior("cauchy", 0, .707)), add_prior = TRUE) +
scale_colour_manual(values = c("green", "blue"),
labels = c("posterior", "prior"), name = NULL)
#> Scale for 'colour' is already present. Adding another scale for 'colour',
#> which will replace the existing scale.

It is also possible to change the linetype with ggplo2::scale_linetype_manual(),

visual_compare(d_model1, d_model2) +
scale_linetype_manual(values = c(1, 2),
labels = c("d_model1", "d_model2"), name = "Model")
#> Scale for 'linetype' is already present. Adding another scale for 'linetype',
#> which will replace the existing scale.

plot(extract_posterior(data_model * prior("cauchy", 0, .707)), add_prior = TRUE) +
scale_linetype_manual(values = c(1, 2),
labels = c("posterior", "prior"), name = NULL)
#> Scale for 'linetype' is already present. Adding another scale for 'linetype',
#> which will replace the existing scale.

or to change both the colour and the linetype.

visual_compare(d_model1, d_model2) +
scale_linetype_manual(values = c(1, 2),
labels = c("d_model1", "d_model2"), name = NULL) +
scale_colour_manual(values = c("grey", "black"),
labels = c("d_model1", "d_model2"), name = NULL)
#> Scale for 'linetype' is already present. Adding another scale for 'linetype',
#> which will replace the existing scale.
#> Scale for 'colour' is already present. Adding another scale for 'colour',
#> which will replace the existing scale.

plot(extract_posterior(data_model * prior("cauchy", 0, .707)), add_prior = TRUE) +
scale_linetype_manual(values = c(1, 2),
labels = c("posterior", "prior"), name = NULL) +
scale_colour_manual(values = c("black", "black"),
labels = c("posterior", "prior"), name = NULL)
#> Scale for 'linetype' is already present. Adding another scale for 'linetype',
#> which will replace the existing scale.
#> Scale for 'colour' is already present. Adding another scale for 'colour',
#> which will replace the existing scale.


text:
WeBWorK Main Forum

Re: WeBWorK Problem Authoring - Summer Online Workshop

by John Travis -
Number of replies: 0
We are looking forward to a great online workshop starting in a couple of weeks. Registration has been good thus far (almost 30 participants) but we can take a few more if you are interested in joining us.

Regular rates and now in effect but still a great deal at $200 for a primary participant and$75 for a secondary colleague. If interested, send an email to drjt07@gmail.com soon.

Also, a Workshop 0 covering the features of WeBWorK (designed for newbies) will be held on Monday, June 5 starting at 2pm Central time.


text:
# Why will Wolfram CountryData not give population data after 2014 (e.g. for the US)?

CountryData[ "UnitedStates", {"Population", 2014} ]

322 422 965 people

CountryData[ "UnitedStates", {"Population", 2015} ]

Missing[ "NotAvailable" ]

How can I update it? I am new to Mathematica.

• Both statistics and its implementation in Mathematica are slow. Lags usually equal few years. WolframAlpha in my Mma through ==Population of United States in 2015 answers 320 million people (2015 estimate). – user64494 Jan 17 '19 at 15:55
• Also WA in my Mma answers 327 million people (world rank: 3^(rd)) (2018 estimate) – user64494 Jan 17 '19 at 16:35
• @user64494 That is interesting, WolframAlpha[ "Population of the United States"] for me returns 324 million people (2017 estimate). Seems like there are different data bases queried? – gwr Jan 17 '19 at 17:04
• @gwr: Your question should be addressed to Wolfram developers, not to me. Try WolframAlpha["Population of the United States in 2018"]. Good luck! – user64494 Jan 17 '19 at 17:12
• @user64494 But you indeed have given the answer! Specifically asking for the population in 2018 will give the value you have given. It simply will not appear just asking for population for some reason. :) – gwr Jan 17 '19 at 17:15

CountryData does appear to be out of date, and that is a shame. Many of the XXXData functions now act as wrappers to call EntityValue. Run TracePrint[PlanetData["Venus", "AngularDiameterFromEarth"],_EntityValue] to see that this is true.

But CountryData has not been updated to work this way. So we can call EntityValue directly for the data. To find out what the right syntax would be I will use Ctrl=:

becomes

which is a formatted form of

Entity["Country", "UnitedStates"][
EntityProperty["Country", "Population", {"Date" -> DateObject[{1978}]}]
]

I can query for a date range as well. Using Ctrl= on "US population 2000 through 2018" returns this input expression:

Entity["Country", "UnitedStates"][
EntityProperty["Country",
"Population",
{"Date" -> Interval[{DateObject[{2000}], DateObject @ {2018}}]}
]
]

which returns a TimeSeries object suitable for further computation or visualization.

You should report to WRI. As a workaround you may use the entity functions instead; it is a bit verbose.

First you can get a list of qualifier values of an EntityProperty by

EntityValue[EntityProperty["Country", "Population"], "QualifierValues"]

{Age->{Adult,MiddleAge,PreSchool,SchoolAge,Senior,Young,YoungAdult},
CitizenshipStatus->{BornInPuertoRico,BornInUS,BornToAmericanParents,NaturalizedCitizen,NotCitizen,TotalCitizens},
Date->{},
Gender->{Female,Male},
MarginOfError->{MarginOfError,StandardError},
Percent->{Main},
Race->{AmericanIndian,Asian,Black,NativeHawaiian,Other,TwoOrMore,White,{All,Hispanic}},
TwoOrMore->{ThreeOrMore,TwoIncludingOther},
UrbanRural->{Rural,Urban}}

"Date" is a qualifier. This post gives details on how to specify a "Date" qualifier (156014); an area where the docs can improve.

EntityValue[
Entity["Country", "UnitedStates"],
EntityProperty["Country", "Population", {"Date" -> DateObject[{2015}]}]
]

319,929,162 people

However, you do have a bit more flexibility with this syntax.

EntityValue[
Entity["Country", "UnitedStates"],
EntityProperty["Country",
"Population", {"Date" -> Interval[{DateObject[{2015}], DateObject[{2019}]}]}]
]

and

EntityValue[
Entity["Country", "UnitedStates"],
EntityProperty["Country", "Population", {"Date" -> All}]
]

Hope this helps.


text:
• B A Dasannacharya

Articles written in Pramana – Journal of Physics

• Dynamics of liquid ammonia from cold neutron scattering

The scattering of 4.1 Å neutrons by liquid ammonia has been measured at 218 K in the angular range of 30–90° using the Trombay rotating crystal spectrometer. The experimental data, after correcting for multiple scattering, have been compared with model calculations, and it is shown that it is possible to get detailed information about the rotational correlation function on the basis of neutron experiments alone. The model assumes Langevin diffusion for translational motions. Rotational motions are described by means of an orientational correlation function which has a gaseous behaviour for times up toτ0 and then changes over to a diffusive character with a rotational diffusion constantDr. Within the framework of the model the correlation function can be described withDr=0.28×1013sec−1 andτ0=0.57×10−18sec. Corrections for multiple scattering and their dependence on model parameters are discussed.

• Lattice dynamics of beryllium

Phonon frequencies in beryllium along the principal symmetry directions have been determined by means of the slow neutron inelastic scattering technique. The data are analysed in terms of a six-neighbour force constant model and the force constants are evaluated. It is concluded that strong tensor forces are present in beryllium and the importance of this finding to basic theories of lattice dynamics is pointed out.

• Normalisation and assessment of neutron diffraction data from liquids

A couple of normalisation criteria have been proposed to assess liquid structure data over the past decade. In this paper, a critical examination of these and other plausible criteria is made. Neutron diffraction data from liquid krypton measured by Clayton and Heaton is used to study these criteria. It is shown that if the structure factorS (Q)=1+γ (Q) satisfies the Krogh-Moe relation, namely$$\rho _{0 = \frac{1}{{2\pi ^2 }}} {\text{ }}\mathop \smallint \limits_{\text{0}}^\infty {\text{ }}Q^{\text{2}} {\text{ }}\gamma {\text{ (}}Q{\text{) }}dQ$$ whereQ is the wavevector transfer andρ0 the mean atomic number density,S (Q) is properly normalised. Subjecting such data to the other criteria would reveal, however, the quality of data in so far as systematic errors and/or termination errors are concerned. If the data is measured with reasonable accuracy to sufficiently large values of the wavevector transfer all these criteria would assess the quality of the data to almost the same extent. This is established in this paper by improving and extending the liquid krypton data by procedures similar to that of Kaplow, Strong and Averbach and subjecting this revised data to the various criteria. It is concluded, thereby, that (i) one can study the neutron diffraction data from liquids using any of the criteria mentioned in the paper to improve the quality of the data and (ii) for normalisation purposes the simple relation {ie328-2} would suffice.

• Dynamics of liquid silane

Neutron scattering of cold neutrons from liquid silane at 137° K and 98°K is explained on the basis of a simple model. The rotational diffusion constant,Dr, and the delay time,τ0, after which rotational diffusion may be said to occur are derived on the basis of this model. At 137° K we getDr=0.22×1013 sec−1 andτ0=0.68×10−13 sec. At 98°KDr (=0.06×1013 sec−1) is down by a factor of more than three butτ0=(0.54×10−13 sec) shows only a small change. By comparison with data on liquid CH4 it is concluded that the law of corresponding states is not applicable for describing rotational dynamics of CH4 and SiH4. Rotational motions in SiH4 are more hindered than in CH4 at the same reduced temperature.

• High resolution measurement of bragg cut-off in beryllium

Bragg cut-off for$$(10\bar 10)$$ plane of polycrystalline beryllium of various lengths of 300 and 116 K has been measured with an energy resolution of 5 μeV. The natural width of the cut-off is 12.5±1.5 μeV, independent of temperature and length of beryllium and also of physical characteristics and certain metallurgical treatments of the powder. Such blocks of beryllium would be suitable for designing a ΔT-window spectrometer with resolution ⩾20 μeV. Bragg cut-offs corresponding to (0002) and$$(10\bar 11)$$ planes of beryllium have been separated for the first time. These can also be used for producing additional energy windows in a ΔT-window spectrometer, thus increasing its efficiency.

• ΔT-window neutron spectrometer

A high resolution neutron spectrometer making use of a ΔT-window filter for the analyser and time-of-flight technique for analysing incident neutron energy has been designed. The spectrometer will provide a continuously variable energy resolution ΔE from 40–50µeV at ∼ 5230µeV. The range of energy transfer allowed is −1450µeV to +2950µeV and the range of wavevector transferQ allowed is 0·82–3·06 Å−1. Depending on the resolution used, the counting rates are expected to vary from 28–60 × 103 counts/hr if one assumes 10% isotropic elastic scattering from the sample.

• Magnetic field dependence of critical current density in YBa2Cu3O7

We have measured the transport critical current densityJcof sintered YBa2Cu3O7, in various applied fields up to 185 Oe at 77 K. We find a sharp decay ofJcwith magnetic field. We show that this sharp decay is consistent with the low field hysteresis results of Groveret al. We argue that the observed field dependence is not caused by intragranular weak links.

• Field and temperature dependence of intergranular hysteresis in YBa2Cu3O7

We have studied the variation of low field magnetization hysteresis in YBa2Cu3O7 as a function of the maximum magnetic field applied during a hysteresis cycle (1 G<Hmax<7.3 G) and also as a function of temperature (77 K<T<95 K). The remnant magnetization is studied as a function ofHmax andT and the measured dependences are explained using the extended critical state model. The potential of this technique as a contactless method of probing the temperature dependence ofJc is discussed.

• Form-factors for different aggregation models of micelles

Spherical micelles in ionic micellar solutions, often aggregate to form spherical, cylindrical or chain-like aggregates on addition of salt to the solution. It is known that the technique of small angle neutron scattering (SANS) can be used to distinguish spherical and cylindrical aggregates. To examine if SANS can be used to distinguish the latter two aggregation processes, we have calculated the angular distribution of scattered neutrons from 0.002 M CTAB solutions. These calculations show that aggregation of CTAB micelles results in large changes in SANS spectra. The shapes of SANS spectra are different for the above three types of aggregates, suggesting that technique of SANS can indeed be used to distinguish the three aggregation processes. The size of the aggregate can also be obtained from such studies.

• Small angle neutron scattering from micellar solutions of triton X-100

Micellar solutions of non-ionic surfactant triton X-100 (8% by weight) show phase separation at cloud pointTcp ∼ 335 K. This paper reports results of small angle neutron scattering (SANS) experiments from this solution as a function of temperature between 298 and 332 K. The range of wave-vector transferQ, covered in these experiments is from 0.02 to 0.15 Å−1. It is seen that as one approachesTcp, the neutron scattering cross section diverges in the region of lowQ (<0.06 Å−1) while it is independent of temperature in region of largeQ(>0.06 Å−1). We believe that the divergence of scattering at lowQ with an increase in temperature is because of changes in the structure factorS(Q) of the solution. The measured distributions have been analyzed using four different models for inter-micellar potential. The models used to calculate the structure factorS(Q) are (1) mean spherical approximation (MSA) with Yukawa tail for attractive potential, (2) MSA with an attractive square well potential, (3) random phase approximation (RPA) with an attractive square-well potential and (4) Sticky hard sphere model (attractive square-well potential with Percus-Yevick approximation). The strengths of the attractive potential required to fit the SANS data are (−6.6 to − 14.4)/kt for model (1), (− 6.6 to − 15.0)/kt for model (2), (− 3.8 to − 7.3)/kB T for model (3) and (−2 to −2.7)/kt for model (4). On the basis of reasonableness of the derived strength of the potential near the phase separation temperature and its relative temperature dependence, it is concluded that present data favour the Sticky hard sphere model.

• Raman study of phase transition in ferroelectric Ba0.95Ca0.05TiO3

Raman scattering investigation of phase transition in the ferroelectric Ba0.95Ca0.05TiO3 is reported. The results suggest onset of significant dynamic disorder at 105°C. This corroborates findings of recent structural study regarding large positional disorder associated with Ti and O1 atoms well below the tetragonal to cubic transition temperature (∼150°C).

• Pramana – Journal of Physics

Volume 96, 2022
All articles
Continuous Article Publishing mode

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019


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# Fractions

## Objective

Place any fraction on a number line with endpoints 0 and 1.

## Common Core Standards

### Core Standards

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• 3.NF.A.2 — Understand a fraction as a number on the number line; represent fractions on a number line diagram.

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• 2.MD.B.6

## Criteria for Success

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1. Plot a given fraction on a number line by partitioning a whole on the number line into fractional units and counting by unit fractions to locate the relevant point (MP.5).
2. Determine the value of a plotted point by determining the fractional unit and counting them from 0.
3. Plot a given fraction or determine the value of a plotted point in special cases, including number lines where more intervals beyond one whole are shown (e.g., 6 intervals of 1 fourth are shown with 1 whole labeled) or the whole is already partitioned into related fractions (e.g., the number line is partitioned into halves and needs to be partitioned into fourths).
4. Determine the distance between two points on a number line. (Optional)

#### Fishtank Plus

• Problem Set
• Student Handout Editor
• Vocabulary Package

?

### Problem 1

Mark and label a point for each fraction below on the number line to its right.

 a. $\frac{3}{4}$ b. $\frac{5}{6}$

#### References

EngageNY Mathematics Grade 3 Mathematics > Module 5 > Topic D > Lesson 15Concept Development

Grade 3 Mathematics > Module 5 > Topic D > Lesson 15 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by The Match Foundation, Inc.

### Problem 2

Determine the location of each of the following points.

 a. b.

### Problem 3

Erin walked 1 mile from her house to the library. Along the way, she passed several places shown on the number line below.

1. Which place is $\frac{4}{8}$mile from Erin’s house?
2. Erin also passed the fire station, which is $\frac{1}{8}$ mile from Erin’s house. Plot the location of the fire station on the number line above.
3. What is the distance, in miles, between the park and the market?

#### References

Question #9

From EngageNY.org of the New York State Education Department. New York State Testing Program Grade 3 Common Core Mathematics Test Released Questions June 2017. Internet. Available from https://www.engageny.org/resource/released-2017-3-8-ela-and-mathematics-state-test-questions/file/150251; accessed Sept. 25, 2018, 4:32 p.m..

Modified by The Match Foundation, Inc.

## Problem Set & Homework

#### Discussion of Problem Set

• What is the distance from 0 to each of the fractions you plotted in #2? What is the distance from each of the fractions you plotted in #2 to 1? How are these pairs of fractions related to our work with shaded and unshaded portions of a whole?
• How did you determine what fraction Point Q represented in #3? Why is it located at the same point as 1?
• How did you determine what fraction Point B represented in #5?
• What mistake did Shawn make in #6? How did you correct his mistake?
• I think the Point P represents $\frac{1}{6}$ in #7. What mistake did I make?
• How far does Barney live from the post office in #8? Is this the same or a different value than it would be if you were just labeled the value of that point? Why?
• What made #9 more challenging than many of the previous problems?

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### Problem 1

1. Identify the labeled points on the number line below.

A = ______

B = ______

1. Explain how you figured out what fraction point B represents.

#### References

Achievement First Grade 3, Unit 5, Lesson 11Exit Ticket

Grade 3, Unit 5, Lesson 11 is made available by Achievement First as a part of their Open Source web portal under a CC BY 4.0 license. Copyright © 1999-2017 Achievement First. Accessed March 8, 2019, 3:58 p.m..

Modified by The Match Foundation, Inc.

### Problem 2

Mary is running a marathon. The number line below represents the whole route. Mary stops after running $\frac{1}{6}$ mile to drink some water, and she stops after $\frac{3}{6}$ mile to tie her shoe. Place a W above where she stops to drink water and an S above where she stops to tie her shoe on the number line below.

#### References

Achievement First Grade 3, Unit 5, Lesson 11Exit Ticket

Grade 3, Unit 5, Lesson 11 is made available by Achievement First as a part of their Open Source web portal under a CC BY 4.0 license. Copyright © 1999-2017 Achievement First. Accessed March 8, 2019, 3:58 p.m..

Modified by The Match Foundation, Inc.

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# LatexToLyx

Categories: tex2lyx
<< | Page list | >>

## This page is obsolete, tex2lyx is part of regular LyX releases now.

 ' Converting *.tex to *.lyx ' The LyX Team July 2005

We all know that LyX produces LaTeX files, but often it's necessary to go the other way and convert a LaTeX file to LyX. Two tools are available to help:

1. the traditional (but unmaintained) reLyX Perl script and
2. the brand new and shiny tex2lyx C++ code.

tex2lyx is part of the 1.4 release of LyX. This page describes its use with older LyXes (such as LyX 1.3.x) and provides some ready-to-use packages.

Note that the command line syntax has been changed (25 July 2005) in order to be compatible with reLyX. See the usage example below.

## Pre-built packages

tex2lyx has not yet been released formally. Nonetheless, it is in a useable state now and is far more powerful than the old reLyX. Here, therefore, are some snapshots for various platforms. Feel free to upload one compiled on your own OS. (Recipes to create such a package are provided below.) Remember, however, that this is pre-release software. Always back up your files. Caveat emptor.

## Package Contents

The package will expand to a directory tree:

  LyX/
bin/
reLyX
tex2lyx.exe
Resources/
lyx/
lyx2lyx/
lyx2lyx

(LyX is packaged slightly differently on different OSes. The tree above is that of the Windows package. In the Unix package the Resources directory is named share.) Here, I installed the package as J:\Programs\LyX. It'd be interesting to hear if all works as expected if it's installed as C:\Program Files\LyX.

The tree above highlights the three tools that are bundled in the package:

• reLyX is the old, deprecated Perl script to convert a LaTeX file to LyX. It's unmaintained but it might just work for you.
• tex2lyx.exe is the replacement for reLyX. It's written in C++, so must be compiled for your particular OS. It is based on a formally-correct TeX parser and so should be able to handle almost any LaTeX file that's thrown at it. Those LaTeX constructs that it does not know about or which LyX does not support natively will become ERT insets in the LyX file. I.e., nothing will be lost but LyX will display the raw LaTeX.
• lyx2lyx is a Python script to convert a LyX file in one format to a LyX file in another format. The LyX file format evolves from one release to the next, so this tool enables the LyX executable that you're using to read the LyX file that you've produced. tex2lyx produces a LyX file in a format understandable to LyX 1.4.0. The lyx2lyx script packaged here (unlike the version packaged with LyX 1.3.x) is able to revert this to a format understandable to LyX 1.3.x because it refers to *.py files shipped with LyX 1.4.

OBS!

• You may safely copy the *.py files located in share/lyx/lyx2lyx {Resources/LyX/lyx2lyx} (but NOT the lyx2lyx script istelf) in your 1.3.x (for x >= 6) share/lyx/lyx2lyx {Resources/lyx/lyx2lyx} directory: if you have multipart documents, you should do it to reread the lyx files without using the lyx-1.4 lyx2lyx script on each files created.
• You should not mix the other files coming with this package (e.g. layouts) with the files already present in your LyX installation.

## Usage

These tools have no graphical interface and so must be invoked from the command line (alternatively, you can invoke tex2lyx directly from LyX as explained in Tex2Lyx invoked from Lyx). In the example below I assume that the name of the LyX 1.3.x expectable is lyx-13x and that it, python and tex2lyx are in the PATH. The location of the lyx2lyx script is dependent on how the package above was installed. Change to suit, but you will not need to run it on the imported files if you have patched the LyX-1.4/share|resources/lyx/lyx2lyx/*.py files in the lyx|LyX/share|resources/lyx2lyx directory.

The prefix $ indicates a command input at the command line whilst the prefix # indicates a comment.  # Export the LyX User Guide in LyX 1.3.x format (format number 221) to LaTeX. # This will create a file UserGuide_13x.tex.$ lyx-13x --export latex UserGuide_13x.lyx

# Convert this LaTeX file back to LyX using tex2lyx.  # This creates a file UserGuide_14x.lyx in a format  # understandable to LyX 1.4.0 but not to LyX 1.3.x.  $tex2lyx UserGuide_13x.tex UserGuide_14x.lyx # Note that tex2lyx versions older than 2005-07-25 wrote the file # to standard output, and therefore needed the following command line: # tex2lyx UserGuide_13x.tex > UserGuide_14x.lyx # Convert this LyX file to one understandable to LyX 1.3.x.$ python J:/Programs/LyX/Resources/lyx/lyx2lyx/lyx2lyx \
--to 221 --output UserGuide_13x_2.lyx UserGuide_14x.lyx

The resulting LyX file UserGuide_13x_2.lyx is clearly different to the original UserGuide_13x.lyx. Much of this difference is simply formatting, however. Loading and saving the file with lyx-13x will remove the noise leaving only substantive changes. These changes can be classified in four groups:

• Default values for fields which need not be stored in the LyX file. The converted file does not contain these.
• Constructs that are not exported by LyX to LaTeX. That's the contents of any Note insets.
• LaTeX constructs that are not (yet) recognized by tex2lyx as translatable to an appropriate LyX inset. Until 2005-03-05 the footnote inset in the Author field at the top of the User Guide fell into this category. The footnote inset became an ERT inset in UserGuide_13x_2.lyx containing the raw LaTeX.
• Things that have been translated incorrectly. The test for this is a comparison of the .dvi files generated from the two LyX files.

At the time of writing, the two .dvi files are almost, but not quite, identical:

  $ls -l *.dvi -rw-rw-r-- 1 angus angus 496736 Feb 15 22:33 UserGuide_13x.dvi -rw-rw-r-- 1 angus angus 496940 Feb 15 22:33 UserGuide_13x_2.dvi  Preliminary investigations suggest that the primary problem here lies with the \includegraphics LaTeX construct. If the .eps files are not found (as was the case here), then LyX exports a LaTeX file containing the pretty-printing output 'mobius.eps not found!'. tex2lyx imports this back as the file mobius.eps not found!! ## How to make it better The best way to make the code better is to use it and to report any problems that it has to the LyX developers mailing list. Please report the problem using bugzilla if you are familiar with it. Please included a minimal LaTeX file that exhibits the problem. Examples in decreasing order of severity might be: • Translation to a mal-formed LyX file (one that cannot be loaded by LyX); • Translation to a valid LyX file but one which outputs different LaTeX to the original. The real test is presumably a difference in the content of the generated .dvi files; • A special case of the previous one are constructs that are translated to native LyX formatting but which are only partially supported in LyX. One example is the environment thebibliography, which takes one parameter. This parameter is computed automatically in LyX, so tex2lyx discards it on translation. • Translation to a formally-correct LyX file but one which contains ERT insets of things that should be supported natively by LyX. ## Known issues The following shortcomings of tex2lyx are known, so please don't report them again: • minipages and parboxes may be converted incorrectly. This depends on the options. • A \bibliographystyle command may be converted to ERT and native LyX format. LaTeX will not run in this case. Simply remove the generated ERT to make it work. • tables may be imported incorrectly. Until 2005-03-10 the set of supported column specifications was rather limited. Convert all columns to c if you have a tex2lyx from that date or older and the columns are recognized incorrectly. Then you can set the column style from LyX. • longtables may be imported incorrectly. • Nested tables make tex2lyx versions before 2005-03-14 crash • \vspace between paragraphs is sometimes not recognized as paragraph skip but converted to ERT. • Many fancy preamble constructs are not supported, and can confuse tex2lyx, so that it creates a broken .lyx file. If you have a complex preamble, move its contents to a file (say preamble.tex) and include it in the preamble of your main document with \input{preamble}. tex2lyx will then leave the file preamble.tex alone. You should however leave all \usepackage commands in the main document, since tex2lyx recognizes many of them and converts them to suitable LyX document settings. ## Creating your own package It's possible that the packages attached above won't run on your platform or that they have become out of date. Remember, we're talking about pre-release software here, so things evolve. In either case, you should consider building your own package. That's probably quite easy for Linux users, used to having a functional compiler environment on their machines, but also something that sounds quite scary to most Windows bods. Don't worry: the process of setting up the environment is mechanical, although it also requires some stamina. Thereafter, building the package itself takes only a few minutes. If you do build a package, then please upload it to this page. ### Setting up the build environment on a Windows machine ### Setting up the build environment on an Linux distribution You should be fine, if you have chosen "Development" or something similar in the Task selection on installing your system. • You need a new automake (and dependencies). Debian/testing defaults to automake 1.4 which is too old. The package automake1.7 works fine, however. ### Grabbing the sources from the CVS repository See the LyX Developer Page for instructions on how to get hold of the LyX sources. Using a command-line interface, it should be as simple as:  # You'll be prompted for a password. It is lyx.$ cvs -d:pserver:anoncvs@anoncvs.us.lyx.org:/var/cvs/lyx login
# Install the LyX sources in a directory devel.
$cvs -d:pserver:anoncvs@anoncvs.us.lyx.org:/var/cvs/lyx checkout -d devel lyx-devel  Thereafter, you'll be able to keep your sources up to date by typing: $ cvs update -dP

from the devel directory. You won't need to specify the anoncvs.us.lyx.org server anymore; that information is stored safely in the CVS/Root file.

Windows users tend to use a GUI tool such as TortoiseCVS. Use is straightforward.

### Building the package

Having set up the build environment and grabbed the LyX 1.4.x sources from the CVS repository, building the tex2lyx distribution is as simple as using the make_tex2lyx_dist shell script from the top level of the LyX source distribution:

  \$ sh make_tex2lyx_dist.sh .

Thereafter, it takes 3:30 minutes on a 2.8GHz machine running Fedora Core 3 and somewhat longer (10 minutes) on the same machine running Windows XP. The result of these builds were files tex2lyx_win32_15Feb05.zip and tex2lyx_linux_16Feb05.tar.gz. This latter was renamed as tex2lyx_FC3_16Feb05.tar.gz before it was uploaded to enable other Linux distributions to be uploaded and retrieved also.


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# Normal subgroup and Lie algebra

I have an exercise of Lie group as follows: "Let $G,H$ be closed connected subgroup of $GL_n(\mathbb{R})$, and $H$ be subgoup of $G$. Suppose that $Lie(H)$ is an ideal of $Lie(G)$. Prove that $H$ is a normal subgroup of $G$." I get stuck to solve this problem. Also I have no idea to use the connectedness of $G$ and $H$. Some one can help me? Thanks a lot!

-

Let $G$ be a Lie group with Lie algebra $\mathfrak{g}$. Suppose that $\mathfrak{h}$ is a Lie subalgebra of $\mathfrak{g}$. Then there is a unique connected immersed Lie subgroup $H\subseteq G$ whose Lie algebra corresponds to $\mathfrak{h}$.
You are given $H$ a closed connected Lie subgroup of the Lie group $G$. Choose $g\in G$, and let $H' = gHg^{-1}$. Then $H'$ is a Lie group with corresponding Lie algebra $Lie(H')\subseteq Lie(G)$. However, the assumption that $Lie(H)$ is an ideal of $Lie(G)$ says exactly that $Lie(H') = Lie(H)$. You then have that $H$ and $H'$ are two connected Lie subgroups of $G$ with the same Lie algebra. By the uniqueness in the above theorem, it follows that $H = H'$, and hence that $H$ is normal.
Thank you so much. But I don't know about the theorem you said. Can you tell me the name of the theorem? By chance, if the Lie group $G$ is linear, i.e a closed subgroup of $GL_n{\mathbb{R}}$, do we have simple proof for this theorem? –  mapping Nov 3 '12 at 15:11
@mapping: I don't know if the theorem has a name. It is essentially the Frobenius Theorem. The idea is as follows. Take a basis $X_1,\ldots, X_r$ for $\mathfrak{h}$. These are invariant vector fields. Since $\mathfrak{h}$ is a subalgebra, these vector fields involutive. Frobenius' Theorem says there is a unique connected integral submanifold $H\subseteq G$ through the identity element. This is the subgroup $H$. Of course, you have to prove it is a Lie subgroup. –  froggie Nov 3 '12 at 16:44
Thanks a lot! I will try to prove by this way. However I have trouble to prove $Lie(H')=Lie(H)$: If I take $X\in Lie{H'}$ then we have $\exp(tX)\in H'\forall t$. Then I can deduce that $g^{-1}Xg=Z\in Lie(H)$. So I need to prove $gZg^{-1}\in Lie(H)$. Using the condition $Lie(H)$ is an ideal of $Lie(G)$, we obtain $gZ-Zg\in Lie(H)$, hence $[gZ-Zg,g^{-1}]\in Lie(H)$. Finally I get $gZg^{-1}+g^{-1}Zg\in Lie(H)$. Until here, I don't know how to continue. Can you help me? –  mapping Nov 3 '12 at 17:53


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## A cone has a volume of 4000cm3 . Determine the height of the cone if the diameter of the cone is 30 cm.

Question

A cone has a volume of 4000cm3

. Determine the height of the cone if the diameter of the cone

is 30 cm.

in progress 0
2 weeks 2021-07-19T23:03:33+00:00 1 Answers 2 views 0

17cm

Step-by-step explanation:

Given that the Volume of a cone is 4,000 cm³. And we need to determine the height of the cone , if the diameter is 30cm .

Diagram :

Step 1: Using the formula of cone :

The volume of cone is ,

Step 2: Substitute the respective value :

As Radius is half of diameter , therefore here r = 30cm/2 = 15cm .

Step 3: Simplify the RHS :

Step 4: Move all the constant nos. to one side

Hence the height of the cone is 17cm .


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# Linear Approximation and Linear Probability of Camellia Sbox

In this article,Analysis of Camellia (para 2. Differential and linear cryptanalysis, page 3), it says

The maximum bias of a linear approximation through one S-box is $2^{-4}$ , which gives a linear probability of $2^{-6}$

what does this mean? isn't the linear approximation probability $2^{-4}$?

See This Question Too

• Can you specify the exact location of your quote? – kodlu Nov 21 '16 at 21:47
• check the referenced paper – abraza Nov 22 '16 at 5:36

Let $LP$ be the linear probability (also called "correlation potential"), $Cor$ be the correlation coefficient and $\epsilon$ be the bias of a linear approximation. Then

$LP = Cor^2 = (2\times \epsilon)^2$.

So, if $\epsilon=2^{-4}$, then $LP = ({2\times 2^{-4}})^2=2^{-6}$.

[1] Daemen, J., Rijmen, V.: Probability distributions of correlation and differentials in block ciphers. J. Mathematical Cryptology 1(3), 221–242 (2007). DOI 10.1515/JMC.2007.011. URL http://jda.noekeon.org/JDA_VRI_Stat_2007.pdf


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시간 제한 메모리 제한 제출 정답 맞은 사람 정답 비율
1 초 256 MB 1 1 1 100.000%

## 문제

The Urdu language is written in the Nastaleeq or Naskh writing styles. It is written from right to left and top to bottom. The particularity of these writing styles is that the form of a particular letter depends on its place in the word.

For example, the Urdu word for “picture”, transliterated into roman is “tasviir”. Here, reading from right to left, we see the component letters in their detached form (ta s v ii r) and how they are put together as a word:

This example illustrates that each letter has a detached form (on the right), as well as up to three more forms: initial, medial and final. For example, the first letter, “ta” has an initial form that we see at the start of the word. For the next letter, as it is placed between two consonants, its medial form needs to be used. Similar logic applies to the third letter in the word. The medial form of this letter, “vaow”, is used. The fourth letter, “yay” is preceded by one of the two special vowels in Urdu, “alif” and “vaow”. These letters are special in the sense that the following letter must appear in its initial form (rather than its medial or final form). Hence, the fourth letter, “cchoTi yay” appears in its initial form despite the fact that it is not the first letter of the word. The fifth letter, “ray”, being the last letter in the word, appears in its final form:

The following table illustrates all the forms of the first letter in our word:

Your task is to validate a sequence of Urdu letters, each in a certain form, and indicatewhether the word is correctly written.

For use in this problem, the 38 letters of the alphabet have been coded from 1 through to 38, so that the first letter is represented by 1, the second by 2 and so on through to the last letter represented by 38. Similarly, the four possible forms of a letter, detached, initial, medial and final are encoded as detached – 0, initial – 1, medial – 2, final – 3. To represent a letter in a particular form we will multiply the letter code by 4 and add the form code to it.

Here is a summary of the validation rules.

The first letter of a word, as well as the first letter after special vowel (letter codes 1 and 33 in any form) should always be in the initial form.
If a letter is followed by another (and as long as it is not preceded by the special vowels – see rule #1), it should be in medial form.
The last letter should be in the final form, unless the preceding letter is a special vowel. In that case, last letter should be in detached form.

## 입력

The input consists of multiple test cases. The first line of input is the number of test cases N (1≤N≤100). Each of the following N lines contains an integer M (1≤M≤20) followed by M encoded Urdu letters of a single Urdu word according to the encoding given above.

## 출력

For each test case, print a single line that says "Case #n: " where n is the test case number followed by a space and the word “Yes” if correct letter forms have been used and the word “No” if incorrect letter forms have been used.

## 예제 입력 1

3
5 17 82 134 150 59
3 13 6 114
4 13 6 121 115

## 예제 출력 1

Case #1: No
Case #2: No
Case #3: Yes


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# Comma separated images for .gif creation

I recently created a key frame animation using Mandelbulber 2.18-1. Each .png image was placed in a folder with known location. I then dragged all the images and dropped them into a Mathematica notebook.

The images were separated by a space only. I manually placed the images between curly braces and put a comma between each pair and assigned them to the name "images". The following code generated an animated .gif exactly as intended:

Export["Madelbulb.gif", images,"AnimationRepetitions" -> \[Infinity]]

However, I can envision a much larger project and am wondering if there is a way to import the images as a comma separated list automatically? This was 300 images. Already quite mind numbing with the commas.

imagePaths = FileNames["path/to/images/*.png"];


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# Thread: Triganomic Ratios

1. ## Triganomic Ratios

Find sec(theta) if tan(theta)=sqrt(3)/3, and sin(theta)<0.

2. Originally Posted by Chinnie15
Find sec(theta) if tan(theta)=sqrt(3)/3, and sin(theta)<0.
use the identity ...

$sec^2{t} = 1 + \tan^2{t}$

3. Thanks!

4. Originally Posted by Chinnie15
Thanks!

I'm not sure how to find t? I've been trying all day to learn this stuff, and it's just not clicking.
$\sec^2{t} = 1 + \left(\frac{\sqrt{3}}{3}\right)^2$

solve for $\sec{t}$ ... mind your signs.

5. Ok, I understand the rest now, but what is the sin<theta? What does that have to do with the problem?

I took the root of both sides and have ended up with sqrt(3)+1/3. Is this correct?

6. Originally Posted by Chinnie15
Ok, I understand the rest now, but what is the sin<theta? What does that have to do with the problem?
you were given $\tan{t} = \frac{\sqrt{3}}{3}$ ... a (+) value

you were also told $\sin{\theta} < 0$ ... a (-) value

those two pieces of information tell you what quadrant $\theta$ is in ... so you can determine the correct sign for $\sec{\theta}$

7. Ok, thanks!

I have 2/sq(3)=secΘ

8. Find sec(theta) if tan(theta)=sqrt(3)/3, and sin(theta)<0.

tan is + and sin is < 0, that is - ; that is in the 3rd quadrant.

But in the 3rd quadrant only tan and cot are positive, the rest negative.

, from this we have,
sec = -(2/3)(sqrt 3)

the negative sign ( - ) is introduced since it is in the 3rd quadtant


text:
×

a continuous function

Given a comtnuous function from F:[0,1]→[0,∞) that satisfy the follow:

$$f\left( \frac{1}{2}x+\frac{1}{2} \right)=f\left( x \right)+1$$

$$f\left( 1-x \right)=\dfrac{1}{f\left( x \right)}$$

for all $$x\in (0,1)$$

Determine value of $$\int\limits_{0}^{1}{f\left( x \right)dx}$$

Note by Idham Muqoddas
4 years, 2 months ago

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You need to clarify your definitions a bit. If $$f$$ is continuous on $$[0,1]$$ (including $$0$$ and $$1$$) and $f\big(\tfrac12x+\tfrac12\big) = f(x) + 1 \qquad 0 < x < 1$ then this identity is also true when $$x=0,1$$, since both sides of this identity are continuous functions on $$[0,1]$$. In particular, putting $$x=1$$, $$f(1) = f(1) + 1$$, which is not possible.

Do you mean that $$f$$ is only to be defined and continuous on $$(0,1)$$? Then $$f$$ must be unbounded, tending to $$\infty$$ as $$x\to\infty$$, so we are looking at either an improper Riemann or a Lebesgue integral.

- 4 years, 2 months ago


text:
# What does it mean to be “closed” under beta reduction?

I am reading the paper Compiling with Continuations, Continued, and in section 2.4, Comparison with ANF, the author draws attention to the fact that ANF is not closed under beta reduction. The snippet of text in question follows:

As Flanagan et al. (1993) suggest, the “back end of an A-normal form compiler can employ the same code generation techniques that a CPS compiler uses”. However, as we mentioned in the Introduction, it is not so apparent whether ANF is ideally suited to optimization. After all, it is not even closed under the usual rule for β reduction (λx.A) v → A[v/x].

What does the author mean by this last sentence? (My guess is that he means ANF beta reduction can introduce new, unbound variables into the reduced term. If that is the case, I am having a hard time visualizing when this would occur and would appreciate outside confirmation that my interpretation is correct.)

The claim is that after applying β-reduction to an expression in A-normal form you can be left with an expression no longer in A-normal form.

The only explicit definition I can find of A-normal form is not consistent with the definition Kennedy seems to be (implicitly) using in this paper. Wikipedia defines A-normal form as the subset of lambda calculus expressions where only constants, $\lambda$-terms, and variables can be arguments of function applications, and then (vaguely) says that results of non-trivial expressions must be captured by let-bound variables.

That is: f(g(x)) is not in A-normal form because the argument to the application of f is another application (g(x)) rather than a constant, $\lambda$-term, or variable. This expression in A-normal form would be something like let y=g(x) in f(y).

Kennedy uses the vague "definition"

a let construct assigns names to every intermediate computation. (Section 1.1.ANF).

But then in Section 1.2 he gives an example of an A-normal form not being preserved under β-reduction

Consider the ANF term let x = (λy.let z = a b in c) d in e. Now naïve β-reduction produces let x = (let z = a b in c) in e which is not in normal form. The ‘fix’ is to define a more complex notion of β-reduction that re-normalizes let constructs (Sabry and Wadler 1997), in this case producing the normal form let z = a b in (let x = c in e).

So apparently Kennedy's variant of A-normal form places some kind of restriction on what can be in the assignment part of a let clause, but I can't figure out what (or why) that restriction is. In addition to Kennedy's paper you linked, I looked in several of his references:

Amr Sabry; Philip Wadler: A reflection on call-by-value. ACM T. Prog. Lang. and Sys. (TOPLAS), 19(6):916-941, 1997.

Amr Sabry; Matthias Felleisen: Reasoning about Programs in Continuation-Passing Style. Lisp and Symbolic Computation 6(3-4):289-360, 1993.

Flanagan, Cormac; Sabry, Amr; Duba, Bruce F.; Felleisen, Matthias: The Essence of Compiling with Continuations. Proc. ACM SIGPLAN Conf. on Programming Language Design and Implementation, (PLDI):237-247, 1993.

• Thank you for you response and for reframing the statement I was confused about back into the examples given earlier in the paper! – bronxbomber92 Apr 6 '15 at 5:54
• (Whoops, didn't mean to press enter).... I believe I can also help you understand the restrictions on ANF. ANF aims to both name and sequence all "computations." If nested lets were admitted by ANF, then sequential ordering would not be respected -- the binder for the computation that must occur 1st (from the inner let) would syntactically appear later than the binder (of the outer let) for the dependent computation. If allowed, this presumably would complicate compiler analyses' implementations – bronxbomber92 Apr 6 '15 at 6:09

A set $S$ is closed under an operation $f$ if, whenever $x\in S$, $f(x)\in S$ also.

• I am aware of that definition but it is unclear to me how to apply this definition to the usage at hand. Would it mean that beta reduction of an A-normal form term would yield a term that is not in A-normal form? – bronxbomber92 Apr 5 '15 at 18:43
• Yes, the set is not closed if there is at least one $x\in S$ such that $f(x)\notin S$. – David Richerby Apr 5 '15 at 19:10

An example:

(let (x (f v))
(g x))

is in ANF. But beta reduction of the x would yield

(g (f v))

which is not.