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# nLab math blogs

### Context

#### Mathematics

This page lists links to blogs, and online mathematical communities like forums and wikis. For links to main repositories of free books, lectures, videos, reviews and math papers see math archives and for a list of societies and institutions see math institutions. A higher level branch page is math resources. Math is here just a mnemo, this page partains also to the related areas of interest for $n$Lab like LaTeX, physics, philosophy, theoretical computer science etc.

For a quick introduction to math blogging, see

• add information to links on what kind of activity tends to go on at the sites being linked to.

Note: To maintain the quality and relevance of this list, any new links not containing a brief description may be removed.

# Math blogs and wikis

## Mathematics

### Older Blogs (last is entry over a year old)

• Delta Epsilons A group blog focusing on algebra, representation theory, and Olympiad-style problem-solving –last update August 2010

• Embûches tissues (computational algebraic geometry, commutative algebra) – last update March 2010

• Geometric Group Theory (structured text with theorems, proofs and exercises in GGT) – last updated August 2009

• Konrad Volkel blog (cohomology, geometry, topology); has also nice math resource list

• Mathematics and Physics (Richard Borcherds – last update January 2008)

• Mathematics Expressions (Colin Tan: complex geometry – last update April 2010)

• mathlight (by an $n$lab regular–last update December 2010)

• Noncommutative geometry with point, by a grad student at Kansas–last updated September 2010

• The Rising Sea (Daniel Murfet on algebraic geometry, triangulated categories, sheaves…; lots of neat LaTeX notes–last updated December 2009)

• Vivatsgasse 7 (Max Planck Bonn graduate students– last update November 2007)


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group(deprecated)/inter - Maple Help

group(deprecated)

 inter
 find the intersection of two permutation groups

 Calling Sequence inter(pg1, pg2)

Parameters

 pg1, pg2 - two permgroups of the same degree

Description

 • Important: The group package has been deprecated. Use the superseding command GroupTheory[Intersection] instead.
 • The intersection of two permutation groups is computed, and returned in the form of a permgroup.
 • The command with(group,inter) allows the use of the abbreviated form of this command.

Examples

Important: The group package has been deprecated. Use the superseding command GroupTheory[Intersection] instead.

 > $\mathrm{with}\left(\mathrm{group}\right):$
 > $\mathrm{pg1}≔\mathrm{permgroup}\left(7,\left\{\left[\left[2,3,4\right]\right],\left[\left[3,4,5,6,7\right]\right]\right\}\right):$
 > $\mathrm{pg2}≔\mathrm{permgroup}\left(7,\left\{\left[\left[1,2\right]\right],\left[\left[1,2,3,4,5,6\right]\right]\right\}\right):$
 > $\mathrm{inter}\left(\mathrm{pg1},\mathrm{pg2}\right)$
 ${\mathrm{permgroup}}{}\left({7}{,}\left\{\left[\left[{2}{,}{4}{,}{3}\right]\right]{,}\left[\left[{2}{,}{4}{,}{5}\right]\right]{,}\left[\left[{2}{,}{4}{,}{6}\right]\right]\right\}\right)$ (1)

format: plain


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# Monthly Archives: August 2014

## Ulnar Nerve Entrapment

Ulnar Nerve Entrapment occurs when the nerve is compressed on its path from the cervical spine down to the hand.  Although ulnar nerve entrapment can occur anywhere along its path, the most common site of compression is at the elbow.  As the ulnar nerve travels on its way down to the hand, it passes through […]

## Deltoid Ligament

The deltoid ligament is a strong band of tissue on the inside of the ankle.  This ligament has several parts which joint the tibia (leg bone) to the bones of the foot.  The function of the deltoid ligament is to provide stability to the ankle.  A sprain occurs when this band of tissue is injured during […]

## Posterior Tarsal Tunnel Syndrome

Posterior Tarsal Tunnel Syndrome is a painful problem in the foot that occurs due to compression of the tibial nerve.  The tibial nerve travels down the back of the leg and through the posterior tarsal tunnel.  The posterior tarsal tunnel is a space that lies on the inside of the ankle.  The bones at that […]

## Baker’s Cyst

Baker’s Cyst is a fluid filled sac that develops behind the knee.  The fluid originates from the synovial joint of the knee.  Often the cyst will arise after trauma to the knee and may go unnoticed for some time.  Patients with Baker’s Cyst often have swelling and pain behind the knee.  The cyst will become […]


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# In the rectangular coordinate system, are the points (a,

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In the rectangular coordinate system, are the points (a, [#permalink]  02 Jun 2009, 03:05
1
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In the rectangular coordinate system, are the points $$(a, b)$$ and $$(c, d)$$ equidistant from the origin?

(1) $$\frac{a}{b} =\frac{c}{d}$$

(2) $$\sqrt{a^2} + \sqrt{b^2} = \sqrt{c^2} + \sqrt{d^2}$$
[Reveal] Spoiler: OA

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Last edited by Bunuel on 28 Apr 2015, 03:31, edited 1 time in total.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  02 Jun 2009, 06:44
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mbaMission wrote:
In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d
(2) (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2)

(1) If a/b = c/d, a and b could be 100 and c and d could be 1 or a, b, c and d could be 1. NSF.

(2) If (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2), then a+b = c+d. In this case, if a = 9 and b = 1, and c =d=5, a+b = c+d is true. but they have different distance.NSF.

From 1 and 2, a must be equal to c and b must be equal to d. So Suff.

Thats C.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  02 Jun 2009, 11:13
In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d

This singnifies that the sign combination on both sides of = is the same.
i.e. if one of the numbers on LHS is -ve , one of the numbers on RHS has to -ve as well.
However since a,b / c,d can take any value , INSUFFICIENT.

(2) (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2)
Since we do not know anything about signs of a,b / c,d - INSUFFICIENT.

Using 1 and 2 together ,
using (1) the second statement drills down to
a+b=c+d (the sign combination on both sides of = is the same.)

Since a/b=c/d and a+b=c+d , (a, b) and (c, d) equidistant from the origin and infact represent the same point.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  02 Jun 2009, 17:23
amolsk11 wrote:
In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d

This singnifies that the sign combination on both sides of = is the same.
i.e. if one of the numbers on LHS is -ve , one of the numbers on RHS has to -ve as well.
However since a,b / c,d can take any value , INSUFFICIENT.

(2) (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2)
Since we do not know anything about signs of a,b / c,d - INSUFFICIENT.

Using 1 and 2 together ,
using (1) the second statement drills down to
a+b=c+d (the sign combination on both sides of = is the same.)

Since a/b=c/d and a+b=c+d , (a, b) and (c, d) equidistant from the origin and infact represent the same point.

Is there a way we can derive, using these two equations, that the two points are equidistant ?
Manager
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Kudos [?]: 40 [4] , given: 2

Re: In the rectangular coordinate system, are the points (a, [#permalink]  02 Jun 2009, 20:44
4
KUDOS
goldeneagle94 wrote:
amolsk11 wrote:
In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d

This singnifies that the sign combination on both sides of = is the same.
i.e. if one of the numbers on LHS is -ve , one of the numbers on RHS has to -ve as well.
However since a,b / c,d can take any value , INSUFFICIENT.

(2) (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2)
Since we do not know anything about signs of a,b / c,d - INSUFFICIENT.

Using 1 and 2 together ,
using (1) the second statement drills down to
a+b=c+d (the sign combination on both sides of = is the same.)

Since a/b=c/d and a+b=c+d , (a, b) and (c, d) equidistant from the origin and infact represent the same point.

Is there a way we can derive, using these two equations, that the two points are equidistant ?

For the derivation part:

a^2 + b^2 = c^2 + d^2

b^2[(a^2/b^2) + 1] = d^2[(c^2/d^2 +1)] --------> 1

from I

a/b = c/d
squaring both sides
a^2/b^2 = c^2/d^2
putting above in 1 and simplifying

b^2[(c^2/d^2) + 1] = d^2[(c^2/d^2 +1)]
simplifying

b^2 = d^2
or |b| = |d|
=> |a| = |c|

therefore points are equidistant from (0,0) or Origin.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  03 Jun 2009, 06:24
1
KUDOS
in order for the points to be equidistant

a2 + b2 = c2+ d2 -----> eq X

1--> insufficent (has already been discussed)
2--> insufficent (has already been discussed)

combining both,
equation 2 can be written as a+b = c+d

eq1 a/b = c/d
a+b/b = c+d/d, from eq 1 from b=d ----3

similarly, b/a = d/c, a+b/a = d+c/c from eq 1 a = c ----4

plug in values of a, b in eq X... it satifies.

Hence points are equidistant. Answer is C
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  08 Jun 2009, 22:29
GMAT TIGER wrote:
mbaMission wrote:
In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

(1) a/b = c/d
(2) (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2)

(1) If a/b = c/d, a and b could be 100 and c and d could be 1 or a, b, c and d could be 1. NSF.

(2) If (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2), then a+b = c+d. In this case, if a = 9 and b = 1, and c =d=5, a+b = c+d is true. but they have different distance.NSF.

From 1 and 2, a must be equal to c and b must be equal to d. So Suff.

Thats C.

why from a^2 + b^2= c^2 + d^2 => a+b=c+d ?
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  19 Aug 2009, 18:29
ngoctraiden1905 wrote:
why from a^2 + b^2= c^2 + d^2 => a+b=c+d ?

That is not so.

What other posters said is that from (a^2)^(1/2) + (b^2)^(1/2) = (c^2)^(1/2) + (d^2)^(1/2) => a+b=c+d

That is actually incorrect. Should be |a|+|b|=|c|+|d|.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 11:45
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 12:06
3
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1
This post was
BOOKMARKED
tinki wrote:
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses

a/b=c/d <---- Equation 1

|a|+|b|=|c|+|d|

Add 1 to both sides of Equation 1

(a+b)/b=(c+d)/d

Now a+b=c+d => 1/b=1/d

Thus, b=d
Similarly,
b/a=d/c
Adding 1 to both sides of above equation:
(b+a)/a=(d+c)/c
a+b=d+c => 1/a=1/c
Therefore a=c
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 12:53
16
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Expert's post
1
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tinki wrote:
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses

In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

Distance between the point A (x,y) and the origin can be found by the formula: $$D=\sqrt{x^2+y^2}$$.

So we are asked whether $$\sqrt{a^2+b^2}=\sqrt{c^2+d^2}$$? Or whether $$a^2+b^2=c^2+d^2$$?

(1) $$\frac{a}{b}=\frac{c}{d}$$ --> $$a=cx$$ and $$b=dx$$, for some non-zero $$x$$. Not sufficient.

(2) $$\sqrt{a^2}+\sqrt{b^2}=\sqrt{c^2} +\sqrt{d^2}$$ --> $$|a|+|b|=|c|+|d|$$. Not sufficient.

(1)+(2) From (1) $$a=cx$$ and $$b=dx$$, substitute this in (2): $$|cx|+|dx|=|c|+|d|$$ --> $$|x|(|c|+|d|)=|c|+|d|$$ --> $$|x|=1$$ (another solution $$|c|+|d|=0$$ is not possible as $$d$$ in (1) given in denominator and can not be zero, so $$d\neq{0}$$ --> $$|c|+|d|>0$$) --> now, as $$|x|=1$$ and $$a=cx$$ and $$b=dx$$, then $$|a|=|c|$$ and $$|b|=|d|$$ --> square this equations: $$a^2=c^2$$ and $$b^2=d^2$$ --> add them: $$a^2+b^2=c^2+d^2$$. Sufficient.

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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 13:27
1
KUDOS
Bunuel wrote:
tinki wrote:
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses

In the rectangular coordinate system, are the points (a, b) and (c, d) equidistant from the origin?

Distance between the point A (x,y) and the origin can be found by the formula: $$D=\sqrt{x^2+y^2}$$.

So we are asked whether $$\sqrt{a^2+b^2}=\sqrt{c^2+d^2}$$? Or whether $$a^2+b^2=c^2+d^2$$?

(1) $$\frac{a}{b}=\frac{c}{d}$$ --> $$a=cx$$ and $$b=dx$$, for some non-zero $$x$$. Not sufficient.

(2) $$\sqrt{a^2}+\sqrt{b^2}=\sqrt{c^2} +\sqrt{d^2}$$ --> $$|a|+|b|=|c|+|d|$$. Not sufficient.

(1)+(2) From (1) $$a=cx$$ and $$b=dx$$, substitute this in (2): $$|cx|+|dx|=|c|+|d|$$ --> $$|x|(|c|+|d|)=|c|+|d|$$ --> $$|x|=1$$ (another solution $$|c|+|d|=0$$ is not possible as $$d$$ in (1) given in denominator and can not be zero, so $$d\neq{0}$$ --> $$|c|+|d|>0$$) --> now, as $$|x|=1$$ and $$a=cx$$ and $$b=dx$$, then $$|a|=|c|$$ and $$|b|=|d|$$ --> square this equations: $$a^2=c^2$$ and $$b^2=d^2$$ --> add them: $$a^2+b^2=c^2+d^2$$. Sufficient.

your explanation is great as always ! thaaanks
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 13:32
Expert's post
AmrithS wrote:
tinki wrote:
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses

a/b=c/d <---- Equation 1

|a|+|b|=|c|+|d|

Add 1 to both sides of Equation 1

(a+b)/b=(c+d)/d

Now a+b=c+d => 1/b=1/d

Thus, b=d
Similarly,
b/a=d/c
Adding 1 to both sides of above equation:
(b+a)/a=(d+c)/c
a+b=d+c => 1/a=1/c
Therefore a=c

No that's not correct.

|a|+|b|=|c|+|d| doesn't mean that a+b=c+d (consider a=b=1 and c=d=-1). So from |a|+|b|=|c|+|d| and a/b=c/d we can not derive that a=c and b=d. What we can derive is that |a|=|c| and |b|=|d|. Refer to my post above for complete solution.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  05 Feb 2011, 19:36
Bunuel is right! Thanks for the explanation man....
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  19 Feb 2011, 18:12
Entwistle wrote:
tinki wrote:
Official explanation says:
"If we know the proportion of a to b is the same as c to d and that |a| + |b| = |c| + |d|, then it must be the case that |a| = |c| and |b| = |d| ?

could someone elaborate how we are supposed to know |a| = |c| and |b| = |d|? a bit vague statement for me

thanks for responses

a/b=c/d <---- Equation 1

|a|+|b|=|c|+|d|

Add 1 to both sides of Equation 1

(a+b)/b=(c+d)/d

Now a+b=c+d => 1/b=1/d

Thus, b=d
Similarly,
b/a=d/c
Adding 1 to both sides of above equation:
(b+a)/a=(d+c)/c
a+b=d+c => 1/a=1/c
Therefore a=c

I liked your explanation, of course Bunuel was as helpful as ever too.
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  21 Dec 2011, 09:34
1
KUDOS
Here's a simpler solution......

We need to prove a^2 + d^2 = c^2 + b^2

Simpler way is to rearrange statement 2 viz. |a| + |b| = |c| + |d| as
1. |a| - |d| = |c| - |b| and then square both sides. We get -
2. a^2 + d^2 - 2*|a|*|d| = c^2 + b^2 - 2*|c|*|b|.

Since ad = bc as per statement 1,

3. |ad| = |bc| => |a|.|d| = |b|.|c| (Rule -> Abs of Product = Product of Abs)

So we can cancel the third term out from both sides of equation 2. to get the desired equation

HTH
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  27 Jul 2012, 20:49
Hi there, i was just wondering if the way i do it is correct!

Statement 1: insuff
Statement 2 : |a|+|b|=|c|+|d|

Our goal is to prove that a^2 + b^2 = c^2 + d^2

(1+2)

Square both sides in stmt 2.

We have a^2 + b^2 + 2|a||b| = c^2 + d^2 + 2|c||d| ----------- *
From one we know that a/b=c/d, therefore their LHS=RHS and therefore, this condition would allow us to cancel out 2|a||b| from LHS and 2|c||d| from equation *.

Please tell me that i am correct! =)

Reagan
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  08 Aug 2012, 02:22
1
KUDOS
reagan wrote:
Hi there, i was just wondering if the way i do it is correct!

Statement 1: insuff
Statement 2 : |a|+|b|=|c|+|d|

Our goal is to prove that a^2 + b^2 = c^2 + d^2

(1+2)

Square both sides in stmt 2.

We have a^2 + b^2 + 2|a||b| = c^2 + d^2 + 2|c||d| ----------- *
From one we know that a/b=c/d, therefore their LHS=RHS and therefore, this condition would allow us to cancel out 2|a||b| from LHS and 2|c||d| from equation *.

Please tell me that i am correct! =)

Reagan

Absolutely, I found this approach much better. Infact I am wondering why we are targetting absolute values in the equation.

(a+b)^2 = a^2+b^2+2ab [no absolute |a|, |b| needed]

From
1) we know ab = cd
2) we know a + b = c + d. and hence (a+b)^2 = (c+d)^2

Combining 1) & 2) we can very well see that a^2+b^2 = c^2+d^2
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Re: In the rectangular coordinate system, are the points (a, [#permalink]  01 Nov 2013, 03:40
Hello from the GMAT Club BumpBot!

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Re: In the rectangular coordinate system, are the points (a, [#permalink]  25 May 2014, 07:13
Awesome discussion and solution analysis.

Thank you all!
Re: In the rectangular coordinate system, are the points (a,   [#permalink] 25 May 2014, 07:13

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WP34S: Reset when printing statistical registers?
07-03-2014, 02:45 PM
Post: #21
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 11:56 AM)Marcus von Cube Wrote:  Here is a short summary of the possible startup messages:
...
Memory seems to be intact: "Reset"

That's not what you wanted to tell us, is it? When I start my WP 34S and "Memory seems to be intact" it will display the last content of X. It does so consistently.

(07-03-2014 11:56 AM)Marcus von Cube Wrote:  "Reset" is an indication that the processor failed for some reason, be it a programming error (illegal instruction, stack corruption, etc.) or some physical condition (power too low for the selected processor speed).

Hmmh, now we're almost as informed as before, aren't we?

d:-?
07-03-2014, 09:53 PM
Post: #22
 Paul Dale Senior Member Posts: 1,378 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 02:45 PM)walter b Wrote:  That's not what you wanted to tell us, is it? When I start my WP 34S and "Memory seems to be intact" it will display the last content of X. It does so consistently.

Pressing the on button doesn't actually start the device. It was already running. Start up in this context is the CPU's initial boot process.

Yes, the nomenclature is ambiguous

- Pauli
07-03-2014, 10:13 PM
Post: #23
 jebem Senior Member Posts: 1,260 Joined: Feb 2014
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 10:39 AM)rkf Wrote:
(07-03-2014 10:30 AM)Paul Dale Wrote:  ... Most likely, we're drawing too much current from the coin cells and their voltage is dropping because of this. I've seen this too from time to time and sometimes the low battery indicator comes on briefly. ...

What a pity, just set ()DLAY to 0 again to provoke the Reset message, and watched closely the LCD panel while doing a print summation registers, trying to glimpse the Low Batt annunciator. Unfortunately, this time neither a Reset shows up, nor a broken I/O character is printed - no matter how often I try.

?!?

Kind regards, Ralf.

Interesting subject. A couple of questions...
- How far can the calculator be from the printer and still get a good connection?

IMHO the IR LED current should not be too high when compared with what the calculator processor can consume.
I would say that the HP-30B can consume as much as 20mA in many situations, and the IR LED should only add a few mA more, maybe 2 to 4mA in a proper implementation and using one adequate and efficient IR LED type (however with that current values I would expect the working distance range to be small, like 30cm or about 1 foot at maximum).

But the real IR LED current consumption can be higher, depending on the circuit used to drive it. If the IR LED series current limiter is absent or is of a very low value (below 330 ohm), it can deplete the batteries in shorter time than normal, but you should be able to communicate at larger distances in this case!

From your description, the probable cause seems to be a voltage drop condition from the batteries you are using.
Sometimes the batteries recovers by themselves, yes, but in the end it will happen again soon.
And not all the battery brands are created equal...

I would try a new set of battery cells and see.
I get my batteries from China in the TAS for peanuts and the quality is more than acceptable for the asking price and free delivery.

As a final note, if you enjoy a little diy and have a multimeter, you may use an external 3Volt power supply (two AA batteries in series will do), a couple of cable clips to connect it to your calculator and measure the current consumption when printing to find out more about your calculator current consumption.

Jose Mesquita

07-03-2014, 10:15 PM (This post was last modified: 07-04-2014 03:33 AM by pito.)
Post: #24
 pito Member Posts: 127 Joined: Jun 2014
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 09:29 AM)walter b Wrote:
(07-03-2014 09:24 AM)pito Wrote:  Do we measure the battery voltage (BATT) under full load??
When not, the BATT does not show the proper numbers..

Do you want to switch the WP 34S to full load just for measuring the voltage by BATT?

d:-?

Of course YES! When you measure the wp34s current in the key_scanning_mode it takes maybe 150uA current, when you switch to let say 30MHz it takes for example 40mA current. Provided the internal resistance of the CR2032 is 10-1000 ohm (based on its capacity consumed, up to 100ohm at 60% used) you may easily calculate the difference between the measurements.. (done for you - see below for a single CR2032 cell, for 2 in parallel half the Rin).
PS: try to measure your car battery after a year of having it resting on the shelf in your garage - you will measure 14V when not loaded happily, but your car will definitely not start

Attached File(s) Thumbnail(s)

07-04-2014, 04:37 AM
Post: #25
 rkf Member Posts: 52 Joined: Apr 2014
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 11:08 AM)walter b Wrote:  ... Anyway, Ralf, if you can reproduce it once again, please SAVE your data before. I'd be interested in whether "Restored" will show up instead of "Reset" then. ...

Today I tried hard to reproduce it. First I interchanged some times the batteries of my both WP34S. Both have pairs of 3.02V each, with BATT displaying 3.0, but no way to reproduce the discussed behaviour.

Then I took the batteries of my PR Error HP15C LE. Those batteries had both 2.91V, and a BATT value of 2.8 - and voilá! The printer managed to print only the first line, and even did not accomplish printing the broken I/O symbol, because of a shutdown/restart of the WP34S - which ended in "Restored".

I hope this helps, Walter.
Kind regards,
Ralf.
07-04-2014, 05:15 AM
Post: #26
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 04:37 AM)rkf Wrote:  I hope this helps, Walter.

Thank you very much, Ralf.

d:-)
07-04-2014, 05:31 AM (This post was last modified: 07-04-2014 06:14 AM by rkf.)
Post: #27
 rkf Member Posts: 52 Joined: Apr 2014
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 10:13 PM)jebem Wrote:  ... A couple of questions...
- How far can the calculator be from the printer and still get a good connection?
...

- I tried to measure this as exactly as possible. The maximum working distance I reached was 150 mm (for our U.S. readers: 5 29/32 inches, Happy Independence Day, BTW!)

Edit: Just tested my HP42S with respect to Infrared Printing. The maximum working distance of my 1991 model is 1100 mm, thus a good deal further.

Kind regards, Ralf.
07-04-2014, 07:49 AM
Post: #28
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
Thank you for the calculations. We shouldn't forget that the WP 34S switches off for voltages <2.1V.

d:-)
07-04-2014, 08:03 AM
Post: #29
 jebem Senior Member Posts: 1,260 Joined: Feb 2014
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 05:31 AM)rkf Wrote:
(07-03-2014 10:13 PM)jebem Wrote:  ... A couple of questions...
- How far can the calculator be from the printer and still get a good connection?
...

- I tried to measure this as exactly as possible. The maximum working distance I reached was 150 mm (for our U.S. readers: 5 29/32 inches, Happy Independence Day, BTW!)

Edit: Just tested my HP42S with respect to Infrared Printing. The maximum working distance of my 1991 model is 1100 mm, thus a good deal further.

Kind regards, Ralf.

Somehow I have similar experience here.

I don't have a printer but I'm using my own IR receiver for testing purposes, and it seems I need to find a more efficient IR LED circuit for my 34S when I have the time and the mood for that.

I have one "as-new-in-the-box" HP-42S got the previous week, and it can reach larger distances than my 34S. But there are several possible reasons for this different behavior to be investigated if and when time and mood allows it.

Jose Mesquita

07-04-2014, 11:12 AM (This post was last modified: 07-04-2014 11:22 AM by pito.)
Post: #30
 pito Member Posts: 127 Joined: Jun 2014
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 07:49 AM)walter b Wrote:  Thank you for the calculations. We shouldn't forget that the WP 34S switches off for voltages <2.1V.
d:-)

I've taken a fresh CR2032 (Vinnic?) from my stock:

Code:
1. Voltage without a load (actually 10Mohm, I = ~332nA) = 3.32V 2. Voltage with 200ohm load = 2.89V 3. Internal resistance of the battery is  Rint = dV@Rint/dI@Rint = (3.32V - 2.89V)/(2.89V/200ohm - 332nA) = 29.75 ohm

So my above estimation was rather optimistic. Both batteries in parallel will have ~15ohm Rint when fresh. The load of ~15mA will create a ~0.22V drop with two fresh batteries in parallel.

When measuring with BATT not loaded with the "nominal load", you will measure ~3.3V, what is of course a "Hausnummer"

When 50-60% capacity consumed, a 10mA load (a calculation for example) will drop BATT below 2V (but the BATT will show you 3V).
07-04-2014, 06:51 PM
Post: #31
 Marcus von Cube Senior Member Posts: 754 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 09:24 AM)pito Wrote:  Do we measure the battery voltage (BATT) under full load??
When not, the BATT does not show the proper numbers..

I agree on your conclusion but I can't help it. The battery monitor is more software than hardware. The brown out detection circuit is programmed to a threshold and signals if the current supply voltage is below or above the programmed value. To detect the actual voltage the software updates the threshold in regular intervals and monitors the result bit. The main problem is the time the circuit takes to stabilize after a change to the threshold. So the algorithm is:

1. Get the current bit value
2. Is the supply voltage below the threshold? If yes decrease the value, otherwise increase it.
3. Wait for the next interrupt to repeat the cycle.

The time between interrupts is needed for the output to stabilize. If I want to measure under load I'd need to switch to high speed whenever I adjust the threshold value, i. e. all the time. This would deplete the batteries unnecessarily.

You can measure the voltage under load by executing BATT in a programmed loop and let it run for a while. A running program is executed at full speed unless you set SLOW mode which roughly halves the speed.

Marcus von Cube
Wehrheim, Germany
http://www.mvcsys.de
http://wp34s.sf.net
http://mvcsys.de/doc/basic-compare.html
07-04-2014, 07:29 PM (This post was last modified: 07-04-2014 07:41 PM by pito.)
Post: #32
 pito Member Posts: 127 Joined: Jun 2014
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 06:51 PM)Marcus von Cube Wrote:
(07-03-2014 09:24 AM)pito Wrote:  Do we measure the battery voltage (BATT) under full load??
When not, the BATT does not show the proper numbers..
..
I agree on your conclusion but I can't help it.

You do measure the battery with BOD regularly _after_ this chunk:

Code:
 ..if ( GoFast ) {                 /*                  *  We are doing serious work                  */                 if ( ++GoFast == 5 ) {                         speed = SPEED_HALF;                 }                 else if ( GoFast == 10 ) {                         speed = SPEED_HIGH;                         GoFast = 0;                 }         }     >>>>>>>>>>>>>>HERE YOU MEASURE BATT..

As we know quite well how a CR2032 behaves, you can predict the switching into SPEED_HALF (20mA) or SPEED_HIGH (40mA) will trigger the reset. So you may not to allow to switch into SPEED_HALF or SPEED_HIGH modi (based on the previous BATT values). That is maybe a small mod to the above code.. Just an idea..
07-04-2014, 07:54 PM (This post was last modified: 07-04-2014 07:56 PM by Marcus von Cube.)
Post: #33
 Marcus von Cube Senior Member Posts: 754 Joined: Dec 2013
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 07:29 PM)pito Wrote:  As we know quite well how a CR2032 behaves, you can predict the switching into SPEED_HALF (20mA) or SPEED_HIGH (40mA) will trigger the reset. So you may not to allow to switch into SPEED_HALF or SPEED_HIGH modi (based on the previous BATT values). That is maybe a small mod to the above code.. Just an idea..

The speed switch itself is smart enough and does not allow SPEED_HIGH if the battery voltage is below a certain value. SPEED_HIGH is then treated the same as SPEED_HALF. The battery measurement algorithm is so slow that a single interrupt cycle makes no noticeable difference.

Disallowing SPEED_HALF isn't an option in my view. This is a situation were a shutdown makes more sense.

Marcus von Cube
Wehrheim, Germany
http://www.mvcsys.de
http://wp34s.sf.net
http://mvcsys.de/doc/basic-compare.html
07-04-2014, 08:34 PM
Post: #34
 pito Member Posts: 127 Joined: Jun 2014
RE: WP34S: Reset when printing statistical registers?
(07-04-2014 07:54 PM)Marcus von Cube Wrote:  Disallowing SPEED_HALF isn't an option in my view. This is a situation were a shutdown makes more sense.
Another idea - maybe a quick BATT measurement "under full load" upon switching the calculator "on" may provide an info on the "real" battery status. When it shuts down during that measurement the user knows what is going on.. When the value will be at the edge you may slow down and indicate..
02-13-2015, 04:06 AM
Post: #35
 matthiaspaul Senior Member Posts: 385 Joined: Jan 2015
RE: WP34S: Reset when printing statistical registers?
For easier cross-reference a similar thread can be found here:

Greetings,

Matthias

--
"Programs are poems for computers."
02-13-2015, 01:00 PM
Post: #36
 ElectroDuende Member Posts: 139 Joined: Jul 2014
RE: WP34S: Reset when printing statistical registers?
(07-03-2014 10:13 PM)jebem Wrote:  I get my batteries from China in the TAS for peanuts and the quality is more than acceptable for the asking price and free delivery.

It's a long time since this post, I was reviewing HP34S issues and went along it, and I though it may be interesting to know this.

Last year I got a pack of 20 CR2032 cells from a chinese auctioner, its expiration date is mid 2017. Some days ago one of my daugther toys with one of them in stopped working, and after opening I saw the battery had leaked (fortunately the toy was ok).

When I opened my spare baterries box, I saw that some of the unused chinese CR2032, had also leaked in the package!

So for future... no cheap chinese batteries in my calculators.
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text:
# Input processing/state machine function

I'm making a Mario clone in pygame and I have just wrote a function proccesses inputs and acts as a state machine for Mario. Everything is working just as I want it, but I was wondering if you can think of any more efficient way to write this code.

A note that these methods are all a part of a class called mario.

def __init__(self):
#The inputs currently binded to each of marios actions.
self.keybinds = {
'right': K_RIGHT,
'left' : K_LEFT,
'jump' : K_z,
'spd'  : K_LSHIFT
}

# The current state mario is in.
# Valid states: 'stand', 'air', 'death'.
self.state = 'stand'

# The current action mario is doing.
# Valid actions: 'none', 'walk', 'run', 'jump'.
self.action = 'none'

# The current direction mario is facing.
# Valid values: 'r', 'l'.
self.faceDir = 'r'

# The direction that the user wants mario to be moving in
self.des_dir = 'n'

# The current speed mario is moving at.
# Valid speeds: 'norm', 'fast'.
self.spd = 'norm'

# A boolean based on whether a character instance can jump.
self.canJump = True

self.crnt_mdx = 2.7 # The current max x velocity mario can move at.

self.slow_dx = 2.7 # The max x velocity mario can move at when he is walking.
self.fast_dx = 4.7 # The max x velocity mario can move at when he is running.

def processInput(self, keys, keyup):
#keys = a list of all keybord keys currently being pressed.
#I have imported a module that has a bunch of variables that represent each key.
#keyup = the current key that was just released, if any.

if keyup == self.keybinds['jump']:
self.canJump = True

if self.state == 'stand' or self.state == 'air':
if keys[self.keybinds['right']]:
self.moveHorz('r')
self.accelerate('r')
self.set_crnt_acc('r')
self.faceDir = 'r'
self.des_dir = 'r'
elif keys[self.keybinds['left']]:
self.moveHorz('l')
self.accelerate('l')
self.set_crnt_acc('l')
self.faceDir = 'l'
self.des_dir = 'l'
else:
if self.state == 'stand' and self.horzDir != 'n':
self.slowDown()
self.des_dir = 'n'

if self.state == 'stand':
if keys[self.keybinds['spd']]:
self.crnt_mdx = self.fast_dx
else:
self.crnt_mdx = self.slow_dx

if keys[K_z] and self.canJump:
self.canJump = False
self.action = 'jump'
else:
pass

# Style

The style for naming in Python is as follows.

• Variables should be in snake_case.
• Constant variables should be in UPPER_SNAKE_CASE.
• Functions should also be in snake_case.
• Classes should be in PascalCase.

You should also replace comments in functions like this:

#keys = a list of all keybord keys currently being pressed.
#I have imported a module that has a bunch of variables that represent each key.
#keyup = the current key that was just released, if any.

To docstrings, like this:

"""Brief description of the function/class.

More detailed description of function/class.

Keyword Arguments:
argument -- Argument description.
...
"""

# Design

There's not much about your design that I can nitpick, the only thing I'd really suggest is shortening these two blocks of code:

self.moveHorz('r')
self.accelerate('r')
self.set_crnt_acc('r')
self.faceDir = 'r'
self.des_dir = 'r'

And:

self.moveHorz('l')
self.accelerate('l')
self.set_crnt_acc('l')
self.faceDir = 'l'
self.des_dir = 'l'

To a shortened method, like this:

def change_direction(self, direction):
if direction == "l" or direction == "r":
self.moveHorz(direction)
self.accelerate(direction)
self.set_crnt_acc(direction)
self.faceDir = direction
self.des_dir = direction
else:
print("Direction must either be \"l\" or \"r\"")

This is especially useful if you need to repeat this code in many places.

On a side note, you should get rid of the magic values 'l' and 'r' and do something like this:

LEFT = 'l'
RIGHT = 'r'

You could also use integers to represent this as well:

LEFT = 0
RIGHT = 1

Or if you're feeling really adventurous, you can use an Enum, like this:

class Directions(Enum):
LEFT = 0
RIGHT = 1

• Yes you are right about the style and I can't believe I didn't think of putting that part into a function :p. – Robbie Jul 29 '15 at 0:28


text:
## Conservation of energy using orientation

1. The problem statement, all variables and given/known data
a hockey player of mass 80 kg was skating at a velocity of 7.5 m/s [E 20 S] when he accidentally hit a linesman who was just standing on the ice. The mass of the linesman is 90 kg and his velocity after the collision was 3 m/s [ N 30 E]. Find the velocity of the hockey player after the collision and the kinetic energy lost during the collision in percentage?

2. Relevant equations
I would be using the kinetic energy equation which is
1/2mv^2=1/2mv1+1/2mv2

3. The attempt at a solution
The problem i have is that how would i get started i mean they are standing on the incline and i do not understand why the linesman's collision orientaion N 30 E. isn't that almost verticle?

 PhysOrg.com science news on PhysOrg.com >> Heat-related deaths in Manhattan projected to rise>> Dire outlook despite global warming 'pause': study>> Sea level influenced tropical climate during the last ice age
 Mentor Blog Entries: 1 Kinetic energy is not conserved. (They even ask how much is lost.) But what is conserved?

 Quote by Doc Al Kinetic energy is not conserved. (They even ask how much is lost.) But what is conserved?
well the conservation of momentum is conserved...

Mentor
Blog Entries: 1

## Conservation of energy using orientation

 Quote by Lolagoeslala well the conservation of momentum is conserved...
Yes, momentum is conserved. Use that to figure out the velocity of the first guy after the collision.

 Quote by Doc Al Yes, momentum is conserved. Use that to figure out the velocity of the first guy after the collision.
so...

m1v1 + m2v2 = m1v1 + m2v2
(80 kg)(7.5 m/s [E20S] = (80kg)(V1) + (90 kg)(3 m/s[N30E])
600 kgm/s [E20S] = (80kg)(V1) + 270 kgm/s [N30E]
600 kgm/s [E20S] - 270 kgm/s [N30E]
563.8155 kgm/s[E]+205.212086 kgm/s[S]+233.826 kgm/s[S]+135 kgm/s[W] = (80kg)(V1)
428.8155 kgm/s[E] + 439.038086 kgm/s[S] = (80kg)(V1)
613.44 kgm/s [S44.3E] = (80kg)(V1)
7.668 m/s [S44.3E]

But why can't i just simple use this equation
1/2m1v1^2 = 1/2m1v1^2 + 1/2m2v2^2
This way i don't have to use the orientation since its scaler

Mentor
Blog Entries: 1
 Quote by Lolagoeslala But why can't i just simple use this equation 1/2m1v1^2 = 1/2m1v1^2 + 1/2m2v2^2 This way i don't have to use the orientation since its scaler
You can't use it because it's not true. In general, kinetic energy is not conserved in a collision. (When it is conserved, it's called a perfectly elastic collision.) But momentum is always conserved.

 Quote by Doc Al You can't use it because it's not true. In general, kinetic energy is not conserved in a collision. (When it is conserved, it's called a perfectly elastic collision.) But momentum is always conserved.
Im confused..... so for the kinetic energy it is the work being done...
after the collision wouldn't the work be transferred into some other energy???

Mentor
Blog Entries: 1
 Quote by Lolagoeslala Im confused..... so for the kinetic energy it is the work being done... after the collision wouldn't the work be transferred into some other energy???
The kinetic energy 'lost' in the collision is transformed to other forms of energy, such as 'heat'.

 Quote by Doc Al The kinetic energy 'lost' in the collision is transformed to other forms of energy, such as 'heat'.
yes.... so
why can't i use the equation for kinetic energy
is it because some of the energy has been used for other energies???

Mentor
Blog Entries: 1
 Quote by Lolagoeslala yes.... so why can't i use the equation for kinetic energy
Because kinetic energy is not conserved. (Total energy including everything is always conserved, but you have no way of using that fact.)
 is it because some of the energy has been used for other energies???
That's right.

 Quote by Doc Al Because kinetic energy is not conserved. (Total energy including everything is always conserved, but you have no way of using that fact.) That's right.
oh ok ... thanks :D

 Quote by Doc Al Because kinetic energy is not conserved. (Total energy including everything is always conserved, but you have no way of using that fact.) That's right.
Umm how would i find the kinetic lost during the collision in percentage?

Mentor
Blog Entries: 1
 Quote by Lolagoeslala Umm how would i find the kinetic lost during the collision in percentage?
Calculate the total kinetic energy before and after the collision. Subtract to find the change.

 Quote by Doc Al Calculate the total kinetic energy before and after the collision. Subtract to find the change.
so...

Ek1 = 1/2m1v1
Ek2 = 1/2m1v1^2 + 1/2m2v2^2

Ek1= 1/2(80kg)(7.5m/s)^2
Ek1= 2250 J

Ek2= 1/2m1v1^2 + 1/2m2v2`^2
Ek2= 1/2(80kg)(7.668 m/s)^2 + 1/2(90kg)(3 m/s)^2
EK2= 2351.92896 J + 405 J
Ek2= 2756.92896 J

Ek2 - Ek1
506.929 J

But this does not seem right..
and how would i get this into percentage?

 Mentor Blog Entries: 1 I suspect that your calculation of the velocity is wrong. Redo your conservation of momentum work. I suggest that you write separate equations for North and East components of momentum.

 Quote by Doc Al I suspect that your calculation of the velocity is wrong. Redo your conservation of momentum work. I suggest that you write separate equations for North and East components of momentum.
I am still getting the same answer...... i mean what do you mean by separate components i do break them apart.. as i did in the calculation above .....

Mentor
Blog Entries: 1
 Quote by Lolagoeslala I am still getting the same answer...... i mean what do you mean by separate components i do break them apart.. as i did in the calculation above .....
I did not quite follow the calculation you did in post #5.

Here's what I would do. Map things onto an x-y axis, where east is in the positive x direction and north is in the positive y direction. Then set up two momentum conservation equations, one for the x components and one for the y components. Then you can solve for the components of the velocity of the first hockey player.


text:
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# Noncrystalline Chromium, Molybdenum and Tungsten Phosphate Films Prepared by Metal Organic-Chemical Vapor-Deposition

Watson, Ian, Connor, Joseph A., Whyman, R. (1991) Noncrystalline Chromium, Molybdenum and Tungsten Phosphate Films Prepared by Metal Organic-Chemical Vapor-Deposition. Thin Solid Films, 201 (2). pp. 337-349. ISSN 0040-6090. (doi:10.1016/0040-6090(91)90122-E) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:22786)

 The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. Official URLhttp://dx.doi.org/10.1016/0040-6090(91)90122-E

## Abstract

Novel, glass-like transition metal phosphate films between 0.5 and 0.03-mu-m thick were prepared by metal organic chemical vapour deposition. The films were deposited at 250-262-degrees-C, using Cr(CO)5(PH3), Mo(CO)5(PH3) or W(CO)5(PH3) as the precursor compound. They were characterized by techniques including X-ray diffraction, secondary ion mass spectrometry, Rutherford backscattering, and X-ray photoelectron spectroscopy. The chromium phosphate films resemble crystalline beta-CrPO4 in terms of their composition and properties, but are not readily converted into crystalline material. The P:Mo ratio in the molybdenum phosphate films is approximately 0.83, and the average molybdenum oxidation state is near +5. Bulk molybdenum phosphate glasses with similar compositions and properties are known. The P:W ratio in the tungsten phosphate films is comparatively small, being approximately 0.12, and the average tungsten oxidation state is slightly lower than +6. Non-crystalline chromium phosphate films were also obtained in initial experiments investigating the effects of higher deposition temperatures. Molybdenum and tungsten phosphate films of the type described are potentially useful in solid state electrochemical devices.

Item Type: Article 10.1016/0040-6090(91)90122-E Q Science > Q Science (General) Divisions > Division of Natural Sciences > Biosciences P. Ogbuji 04 Oct 2009 19:31 UTC 16 Nov 2021 10:01 UTC https://kar.kent.ac.uk/id/eprint/22786 (The current URI for this page, for reference purposes)
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text:
Automatic alignment in tabulars

I am trying to make a table with both left and right alignments. Now I can get the view like this

The first problem is with the left alignment - there is a space between left side and tabular with two items.

The second problem is that I have to set width of parboxes manually. Isn't the way to automate that by the width of title? Maybe parboxes is not the best way for wrapping lines in tables?

My code:

\documentclass{article}

\usepackage{multicol}
\usepackage{makecell}
\usepackage{pbox}
\usepackage{array}
\usepackage{amsmath}

\begin{document}

\begin{tabular}{l}

{\Huge Some title text is written here...} \\
\Xhline{1.5mm}
\parbox{11.1cm}{
\begin{multicols}{2}
\renewcommand{\arraystretch}{2}
\begin{tabular}{|c|c|}
\hline
$\boldsymbol{\bigotimes}$  & {\large this is an example} \\
\hline
\end{tabular} \\
Lorem ipsum dolor sit amet, consectetur adipisicing elit
\end{multicols}
} \\

\renewcommand{\arraystretch}{2}
\begin{tabular}{|c|cll|}
\hline
$\bigcirc$ & 1 & First item &
\pbox{7.3cm}{Sed ut perspiciatis unde
omnis iste natus error sit voluptatem
accusantium doloremque laudantium} \\
\hline
$\bigcirc$ & 2 & Second item & Some definition. \\
\hline
\end{tabular}
\end{tabular}
\end{document}

-

The multiple nested tabulars and parboxes complicate the input, I think you can use a much simpler scheme, something like this:

\documentclass{article}

\usepackage{tabularx}
\usepackage{amsmath}

\setlength\extrarowheight{3pt}

\begin{document}

\noindent

{\Huge \strut Some title text is written here...\par}
\hrule height 3pt

\smallskip

\noindent
\begin{tabularx}{\textwidth}{|l|l|X}
\cline{1-2}
$\boldsymbol{\bigotimes}$  &
\large this is an example &
Lorem ipsum dolor sit amet, consectetur adipisicing elit\\
\cline{1-2}
\end{tabularx}
\smallskip

\noindent
\begin{tabularx}{\textwidth}{|l|llX|}
\hline
$\bigcirc$ & 1 & First item &
Sed ut perspiciatis unde
omnis iste natus error sit voluptatem
accusantium doloremque laudantium \\
\hline
$\bigcirc$ & 2 & Second item & Some definition. \\
\hline
\end{tabularx}
\end{document}

-


text:
# God (programmer)

Programmer God simulation hypothesis modelling

The simulation hypothesis or simulation theory is the proposal that all of reality, including the Earth and the rest of the universe, could in fact be an artificial simulation, such as a computer simulation. Neil deGrasse Tyson put the odds at 50-50 that our entire existence is a program on someone else’s hard drive [1]. David Chalmers noted “We in this universe can create simulated worlds and there’s nothing remotely spooky about that. Our creator isn’t especially spooky, it’s just some teenage hacker in the next universe up. Turn the tables, and we are essentially gods over our own computer creations [2] [3] [4].

The commonly postulated ancestor simulation approach, which Nick Bostrom called "the simulation argument", argues for "high-fidelity" simulations of ancestral life that would be indistinguishable from reality to the simulated ancestor. However this simulation variant can be traced back to an 'organic base reality' (the original programmer ancestors). The Programmer God hypothesis conversely states that the simulation began with the big bang and was programmed by an external intelligence (external to the physical universe), the Programmer by definition a God in the creator of the universe context [5].

## Discussion

The Mathematical universe hypothesis states that Our external physical reality is a mathematical structure.[6] That is, the physical universe is not merely described by mathematics, but is mathematics (specifically, a mathematical structure).

The principle constraints to any mathematical universe simulation hypothesis are;

1. the computational resources required. The ancestor simulation can resolve this by adapting from the virtual reality approach where only the visible region is simulated and only to the degree required, and

2. that any 'self-aware structures' (humans for example) within the simulation will "subjectively perceive themselves as existing in a physically 'real' world".[7].

## Planck scale

The Planck scale refers to the magnitudes of space, time, energy and other units, below which (or beyond which) the predictions of the Standard Model, quantum field theory and general relativity are no longer reconcilable, and quantum effects of gravity are expected to dominate (quantum gravitational effects only appear at length scales near the Planck scale). Consequently any study of a deep universe simulation must consider (if not begin at) the Planck scale [8].

### Dimensioned quantities

A fundamental physical constant is a physical quantity that is generally believed to be both universal in nature and have a constant value in time. These can be divided into dimension-ed (with units kg, m, s ... ; speed of light c, gravitational constant G, Planck constant h ...) and dimension-less (units = 1, such as the fine structure constant α). There are also dimension-less mathematical constants such as pi.

The SI units mksa units are; meter (length), kilogram (mass), second (time), ampere (electric current). The corresponding mksa Planck units are Planck length, Planck mass, Planck time, Planck charge.

Physicist Lev Okun noted "Theoretical equations describing the physical world deal with dimensionless quantities and their solutions depend on dimensionless fundamental parameters. But experiments, from which these theories are extracted and by which they could be tested, involve measurements, i.e. comparisons with standard dimensionful scales. Without standard dimensionful units and hence without certain conventions physics is unthinkable. [9].

Successful implementation of a Planck scale simulation would therefore require that the programmed (dimension-less) mathematical structures for mass, space and time be indistinguishable from the (dimensioned) 'physical' units for mass, space and time as observed from within the simulation.

## Programming structure

“God vs. science debates tend to be restricted to the premise that a God does not rely on science and that science does not need a God. As science and God are thus seen as mutually exclusive there are few, if any, serious attempts to construct mathematical models of a universe whose principle axiom does require a God. However, if there is an Intelligence responsible for the 14 billion year old universe of modern physics, being the universe of Einstein and Dirac, and beginning with the big bang as the act of 'creation', then we must ask how it might be done? What construction technique could have been used to set the laws of physics in motion?” [10]

### Numbering systems

As well as our decimal system, computers apply binary and hexadecimal numbering systems. In particular the decimal and hexadecimal are of terrestrial origin and may not be considered 'universal'. Furthermore numbering systems measure only the frequency of an event and contain no information as to the event itself. The number 299 792 458 could refer to the speed of light (299 792 458 m/s) or could equally be referring to the number of apples in a container (299 792 458 apples). As such numbers require a 'descriptive', whether m/s or apples. Numbers also do not include their history, was 299 792 458 for example a derivation of base numbers?

Present universe simulations use the laws of physics and the physical constants are built in, however both these laws and the physical constants are known only to a limited precision, and so a simulation with 1062 iterations (the present age of the universe in units of Planck time) will accumulate errors. Number based computing may be sufficient for ancestor-simulation models but has inherent limitations for deep universe simulations. The actual computational requirements for a Planck scale universe simulation based on a numbering system with the laws of physics embedded would be an unknown and consequently lead to an 'untestable' hypothesis. This is a commonly applied reasoning for rejecting the deep universe simulation.

### Geometrical objects

A number such as π refers to a geometrical construct rather than any numbering system and so may be considered universal and defined as a constant. Likewise, by assigning geometrical objects instead of numbers to the Planck units, the problems with a numbering system could be resolved. These objects would however have to fulfill the following conditions, for example the object for length must;

1. embed the function of length such that a descriptive (km, mile ... ) is not required

Electron wavelength would then be measurable in terms of the length object, as such the length object must be embedded within the electron. Although the mass object would incorporate the function mass, the time object the function time ..., it is not necessary that there be an individual physical mass or physical length or physical time ..., but only that in relation to the other units, that object must express that function (i.e.: the mass object has the function of mass when in the presence of the objects for space and time). The electron would then be a complex event constructed by combining the objects for mass, length, time and charge into 1 event, and thus electron charge, wavelength, frequency and mass would be different aspects of that 1 geometry (the electron event) and not independent parameters (independent of each other).

The objects for mass, length, time and charge must therefore be

2. be able to combine with other objects (for mass, time, charge ...) to form more complex objects (events) such as particles and apples whilst still retaining the underlying information (the individual objects that combined to form that event)

3. combine in such a ratio that they cancel whereby the sum universe itself (being a mathematical universe) is unit-less. While internally the universe has measurable units, externally (seen from outside the simulation) the universe has no physical structure.

Not only must these objects be able to form complex events such as particles, but these events themselves are geometrical objects and so must likewise function according to their geometries. Electrons would orbit protons according to their respective electron and proton geometries, these orbits the result of geometrical imperatives and not due to any built-in laws of physics. As orbits follow regular and repeating patterns, they can be described using mathematical formulas. As the events grow in complexity (from atoms to molecules to planets), so too will the patterns (and so the formulas then used to describe them). Consequently the laws of physics would then become mathematical descriptions of the underlying geometrically imposed patterns. The computational problem could thus be resolved by instituting a geometrically autonomous universe.

Furthermore, as the sum universe is unit-less, there is no limit to the number of objects (size, mass, age ... and so the information content that can be stored and manipulated). If the 'Programmer' can determine appropriate geometrical objects that satisfy the above and also include a mechanism for the addition of further objects, then a universe could 'grow' accordingly.

There is a caveat; self aware structures within the simulation will perceive a physical mass, space and time as forming their physical reality, these mathematical objects must therefore be indistinguishable from any observed physical reality.

## Planck universe

The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve.

The following describes how a geometrical approach to a Planck scale deep universe simulation could be implemented [12].

### Simulation clock-rate

The simulation clock-rate would be defined as the minimum 'time' age increment to the simulation. It may be that Gods use analog computers, but as an example;

 'begin simulation
FOR age = 1 TO the_end                       'big bang = 1
conduct certain processes ........
NEXT age
'end simulation

Quantum spacetime and Quantum gravity models refer to Planck time as the smallest discrete unit of time and so the incrementing variable age could be used to generate units of Planck time (and other Planck units), for example;

 FOR age = 1 TO the_end                       'age is a dimensionless variable
generate 1 time object T             'T is a dimensioned unit of time
generate 1 mass object M             'M is a dimensioned unit of mass
generate 1 length object L           'L is a dimensioned unit of length
........
NEXT age

The variable age is the simulation clock-rate (the universe age). If age is the origin of Planck time (the time object T) then age = 1062, the present age of the universe measured in units of Planck time.

For each age, certain operations are performed, only after they are finished does age increment. As such, age is a (discrete) incremental variable and not a time dimension, for there is no 'time' interval between increments. Although those operations may be extensive, self-aware structures from within the simulation would have no means to determine this, they could only perceive themselves as being in a real-time. Their dimension of time would be a measure of relative motion and so although ultimately deriving from the variable age, it would not be the same as age. If there were no motion, if all particles and photons were still (no change of state), then the observed dimension time could not update, age however would continue to increment. The analogy being pressing the pause button on a movie, this would not affect the computer clock-rate itself.

### Expanding universe

By adding mass, space and time objects with each increment to the simulation age, the universe would grow in size and mass accordingly resembling a black hole (black hole cosmology), thus dispensing with the requirement for a 'dark energy'. As the universe scaffolding includes objects for mass M, 'dark matter' could correspond to the underlying fabric of the universe itself (a vacuum may indicate an absence of particle matter but not an absence of universe).

As the universe expands in size per increment to age, this expansion could also be used to 'pull' particles with it. Thus this expansion could serve the purpose of introducing momentum into the simulation, the expansion being the origin of particle motion (this would restrict the permitted topologies of the simulation). The expansion of the particle universe would not be the same as this expansion, although it would be driven by this expansion.

The velocity of expansion would be the maximum attainable velocity and so the origin of the speed of light c (to go faster than this velocity would mean leaving the simulation itself). thus both the velocity of expansion (and so c) and the incrementing variable age (and so Planck time) are constants.

The forward increment to age would constitute the arrow of time. Reversing this would reverse the arrow of time, the universe would likewise shrink in size and mass accordingly (a white hole is the (time) reverse of a black hole).

 FOR age = the_end TO 1 STEP -1
delete 1 time object T
delete 1 mass object M
delete 1 length object L
........
NEXT age

### Universe time-line

As the universe expands and if the data storage capacity expands proportionately, then the 'past' could be retained.

 FOR age = 1 TO the_end
........
FOR n = 1 TO total_number_of_particles
SAVE particle_details{age, particle(n)}
NEXT n
NEXT age

Because particles are pulled along by this expansion, previous information is not over-written by new information. The analogy would be the storing of every keystroke. This also forms a universe time-line against which previous information can be compared with new information (a 'memory' of events).

#### Time travel

As the simulation data is stored in entirety (a Planck scale version of the Akashic records), the simulation can be replayed. We could even speculate that if mankind made a bad 'move', such as initiating a nuclear war, it may be possible to rewind the simulation clock back to a period prior to that move and reset the simulation. All future events from that point in time would then be over-written. Time-travel (travelling backwards in time) for an individual may not be possible but for the entire universe it is.

### Mass, length, time, charge

Here geometrical objects are assigned to units mass M, length L, time T, ampere A. For a simulated universe to be unit-less, the units must be able to cancel within a certain ratio such that in sum total there is no physical universe (when seen from outside the simulation, the universe is merely a data set on a celestial hard-drive). In the following table are illustrated objects MTLA in terms of 2 dimensionless physical constants; the fine structure constant α and Omega Ω, and to fulfill the above condition, the mathematical relationships (un) between them [13]. These objects correspond to the Planck units.

Geometrical units
Attribute Geometrical object Relationship
mass ${\displaystyle M=1}$ ${\displaystyle unit=u^{15}}$
time ${\displaystyle T=2\pi }$ ${\displaystyle unit=u^{-30}}$
length ${\displaystyle L=2\pi ^{2}\Omega ^{2}}$ ${\displaystyle unit=u^{-13}}$
velocity ${\displaystyle V=2\pi \Omega ^{2}}$ ${\displaystyle unit=u^{17}}$
ampere ${\displaystyle A={\frac {2^{6}\pi ^{3}\Omega ^{3}}{\alpha }}}$ ${\displaystyle unit=u^{3}}$

The unit relationships show how these units interrelate to each other. In a particular ratio they will overlap and cancel, for example, if the universe 'scaffolding' is a construct of (AL)3 and T then the sum universe is unit-less (there is no physical universe).

${\displaystyle {\frac {{u^{3}}^{3}{u^{-13}}^{3}}{u^{-30}}}\;({\frac {ampere^{3}\;length^{3}}{time}})={\frac {{u^{-13}}^{15}}{{u^{15}}^{9}{u^{-30}}^{11}}}({\frac {length^{15}}{mass^{9}\;time^{11}}})=1}$

Embedded within the electron are these objects for mass, length, time, charge MLTA hence we can measure the parameters of the electron; electron mass, wavelength, frequency and charge, however the electron itself reduces to the following formula fe, it has no measurable units (they overlap and cancel) and so the electron itself it does not exist in any physical dimension, yet the physical universe is seemingly a construct of electrons. What actually defines our physical universe are those parameters, the electron itself (this mathematical formula fe) dictates how the MLTA objects are arranged into those parameters.

${\displaystyle f_{e}=4\pi ^{2}(2^{6}3\pi ^{2}\alpha \Omega ^{5})^{3}=.23895453...x10^{23},\;units=1}$

By this artifice, although the 'physical' universe is constructed from particles (particle matter), particles themselves are not physical, they are mathematical.

### Null universe

If the universe expands per increment of age by adding units of mass, space and time, and if these units overlap and cancel, then the sum universe is unit-less. This also means that to make time (which adds object time T) we must also make an equivalent of MLA to balance this ratio, and so to create time, the time required to read this sentence for example, the universe had to grow larger (add space) and more massive (add mass). Likewise, if time went backward the universe would have to shrink in size and mass. But regardless of the age of the universe, if we combine all the mass, space and time within, the universe would disappear (units = 1). Seen from the outside, there is no universe.

### Relativistic universe

The mathematics of perspective is a technique used to project a 3-D image onto a 2-D screen (i.e.: a photograph or a landscape painting), using the same approach here would implement a 4-axis hypersphere universe structure in which 3-D space is the projection [14].

The expanding universe approach can also be used as a method to replace independent particle motion with motion as a function of the expansion itself, this expansion generating the universe time-line. In the mass point-state the particle would have defined co-ordinates and so all particles simultaneously in the point-state per unit of age may be measured relative to each other. As photons (electromagnetic spectrum) have no mass state, they cannot be pulled along by the universe expansion (they are date stamped, as it takes 8 minutes for a photon from the sun to reach us, that photon is 8 minutes old) and so photons would have a lateral motion within the hyper-sphere. Visible 3-D space then becomes a projected image from the 4-axis hyper-sphere, the relativity formulas are used to translate between the hyper-sphere co-ordinates and 3-D space co-ordinates [15].

In hyper-sphere co-ordinate terms; age (the simulation clock-rate), and velocity (the velocity of expansion as the origin of c) would be constants and thus all particles and objects would travel at, and only at, V = c, however in 3-D space co-ordinate terms, time and motion would be relative to the observer. The time dimension of the observer measures the change in state = change of information = change in relative position of particles in respect to each other and thus derives from, but is not the same as, the expansion clock-rate age or object time T, for in the absence of motion there is no means for the observer to measure either, age however would continue to increment (the universe hyper-sphere would continue to expand at the speed of light).

### Gravity

8-body (8 mass points, 28 orbitals) orbit

All particles simultaneously in the point-state at any unit of age form gravitational orbital pairs with each other [16]. These orbital pairs then rotate by a specific angle depending on the radius of the orbital. Furthermore the orbital plane also rotates. The results are then summed and averaged and so the entire universe can be updated in real time (before the next increment to age). The observed gravitational orbits of planets are the sum of these individual orbital pairs averaged over time. Thus it is in principle not necessary to have direct information regarding the orbiting objects in order to calculate their respective orbits.

Orbits, being also driven by the universe expansion, occur at the speed of light, however the orbit along the expansion time-line is not noted by the observer and so the orbital period is measured using only 3D space co-ordinates.

### Singularity

In a simulation, the data (software) requires a storage device that is ultimately hardware (RAM, HD ...). In a data world of 1's and 0's such as a computer game, characters within that game may analyze other parts of their 1's and 0's game, but they have no means to analyze the hard disk upon which they (and their game) are stored, for the hard disk is an electro- mechanical device, is not part of their 1's and 0's world, it is a part of the 'real world', the world of the Programmer. Furthermore the rules programmed into their game would constitute for them the laws of physics (the laws by which their game operates), but these may or may not resemble the Laws that operate in the 'real world', assuming there even exist such laws. Thus any region where the laws of physics (the laws of the game world) break down would be significant. A singularity inside a black hole is such a region.

For the black-hole electron, the mass point-state would then be analogous to a storage address on a hard disk, the interface between the simulation world and the real world, a massive black-hole as a data sector.

The surface of the black-hole would then be of the simulation world, the size of the black hole surface reflecting the stored information, the interior of the black-hole however would be the interface between the data world and the real world, and so would not exist in any 'physical' terms. Thus we may discuss the 3D surface area of a black-hole but not its volume (interior).

## Laws of Physics

The scientific method is built upon testable hypothesis and reproducible results. Water has always boiled, under identical conditions, at 100°C. In a geometrical universe particles behave according to geometrical imperatives, the geometry of the electron and proton ensuring that electrons will orbit nuclei in repeating and predictable patterns. The laws of physics would then be a set of mathematical formulas that describe these patterns, the more complex the orbits, the more complex the formulas required to describe them and so forth. If there is a source code from which these geometrical conditions were programmed there there may be non-repeating events, back-doors built into the code, these by definition would lie outside the laws of physics and so be labelled as miracles, yet they would be no less valid.

## Purpose

Any simulated universe, whether a simple computer game or NASA program, may presume a 'purpose', that the simulation, being the result of an 'intelligent design', is intended for an 'intelligent reason'. We cannot judge the motives of the Programmer God, however in theological texts we do find a common thread and that is the battle between Good and Evil and so this may be taken as a metaphor.

Zoroastrianism is one of the world's oldest continuously practiced religions. It is a multi-faceted faith centered on a dualistic cosmology of good and evil and an eschatology predicting the ultimate conquest of evil. The opening chapters of the Book of Genesis provide a mythic history of the infiltration of evil into the world. God places the first man and woman (Adam and Eve) in his Garden of Eden, from whence they are expelled.

As noted above, embedded within the electron are the objects for mass, length, time, charge MLTA hence we can measure the parameters of the electron; electron mass, wavelength, frequency and charge, however the electron itself has no measurable units, it does not exist in any physical dimension. We may draw an analogy with Evil, whose parameters are the emotions it generates [17].

### Determinism

An animation of the figure-8 solution to the three-body problem over a single period T ≃ 6.3259.[18]

Particles form more complex structures such as atoms and molecules via a system of orbitals; nuclear, atomic and gravitational. The 3-body problem is the problem of taking the initial positions and velocities (or momenta |momentum|momenta) of three or more point masses and solving for their subsequent motion according to Newton's laws of motion and Newton's law of universal gravitation.[19]. Simply put, this means that although a simulation using gravitational orbitals of similar mass may have a pre-determined outcome, it seems that for God's and men alike the only way to know what that outcome will be is to run the simulation itself.


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# Simulation of boost converter using SiC MOSFET in LTspice

I am trying to simulate boost converter using SiC MOSFET (MOSFET MODEL = G2R1000MT17D). The boost converter specifications are:

1. Vin = 200 V
2. Vout = 400 V
3. Fsw = 150 kHz

When simulating the above converter my simulation is not running. Kindly help me to figure out where I am going wrong[![LTspice schematic][2]][2]

• Where is your V(out) node? Sep 14, 2021 at 7:04
• Hi andy thanks for asking The Vout node is across the resistor 320 ohm. Sep 14, 2021 at 10:21
• I think you would change ... .options abstol=0.1 (? absolute tolerance on voltage = 0.1 V) ... .IC v(vout)=400 (ok) ... and add .IC i(L1)=2.5 ... .tran 0 5m -- proceed by little step time (5 ms, max internal step 1ns) save intermediary results and continue simulation ... it works for me with microcap v12. Sep 14, 2021 at 12:41
• Sure Antonio i will try and let you know Sep 14, 2021 at 14:51
• @Vengatesh The reason Andy asked about V(out) is because you have an .IC condition for a node named OUT, but there's no such label attached, anywhere. Therefore your .IC has no effect. Try ading ic=380 to the capacitor, maybe also rser=10m. It might help to add rser=10m rpar=10k to the inductor, rser=10m cpar=1m to the voltage source, add a capacitor across the SiC with 100p rser=100. There's not much else to do since the library that I have (from genesicsemi.com, Cree needs registration) is encrypted. Sep 14, 2021 at 15:36

## 1 Answer

Here are my simulations about "starting" behavior.

UJ3C120080K3S for SiC (1200V 8A) and 6EWH06FN-E (600V 6A) for diode (should be changed). I will update ... diode voltage too low. Changed for a 1200 V. Peaks are same.

You can see that there is (ok, there are short ... but not negligible when choosing devices ...) important peaks of voltage of capacitor and current of inductor. (Can be "avoided" or "admissible" by an "intelligent starting" phase, duty cycle = ~ 5%, then increased progressively until what is needed)

NB : Simulation done at 200 kHz (duty cycle = 50 %)

For stationary picture, add : .ic v(Vc) 400 and .ic i(L1) 2.5 ...