# Math / Science

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The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.

Proper AWG for low voltage application.

I want to run some wire for a low voltage lighting.  The transformer supply will be about 6 -8 feet from the LED lights.  Transformer max output is rated at 36 watts.
36w / 12v = 3Amps.  (max)

Question: What would be safe wire gage to use ?  Was considering using 16AWG lamp cord ?   Most of the documentation and/or charts that I can find online shows 16AWG would be sufficient.  See Attached.
WireSelectionChart.png
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Do I need a water-water heat exchanger to run a shower off an Antminer S9-Aqua?

My hovel is currently heated by several crypto-miners but they all blow hot air out and do not provide hot water. If I get a water-cooled mining rig can I connect it directly to my hot water tank or do I need a heat exchanger?

I live in a hard water area. there is a lot of chalk in the tap water which makes it taste nice but tends to clog the pipes.
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Please help me to identify the correct type or find a replacement alternative to the broken mini push button used in GPS Prestigio Geovision 5055 as seen in the photos from attached pdf file.

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How do i get the attached data "normalised" -- made into normal distribution ?

Worksheet "Data" = Full Data
"Filtered 25-65" = data with 25-65 s filtered by "Data" and copied in this worksheet.

If i use 25-65, it has the best result - ie, less skewness but stil not into normal distribution.

Any idea to use that range such that the data plotted is normal distribution  ?
Data-25-65--Check-Normal--EE.xlsx
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I'm exploring the use of drones to do delivery (for items that weigh up to 20kg
ie about 44 lbs) of dimensions up to 2ft long x 2ft wide x 10 inches thick.

Once local authority approves it, thought of sourcing/purchasing some of these
drones but will need to look into the cost effectiveness (ie its  gasoline/petrol
costs, maintenance/repair) or is there any that uses rechargeable powerbanks?

Has Amazon or any country done it & what's the safety & regulatory requirements?
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Hi,
I would like to prepare data for regression analysis.
I can prepare data in two forms.
a) values
b) rankings.
example:
values  60,30,25,90
rankings 2,3,4,1
Which format would be most suitable or does it not matter ?
many thanks
Ian
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We need an MBR, but it needs to be returned as a 5 point polygon.

Test sample :

with OrientedPoint as
(
SELECT 1 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(1,11,0,1,0,0))  AS geom FROM dual union all
SELECT 2 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(2,12,0,1,0,0))  AS geom FROM dual union all
SELECT 3 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(3,13,0,1,0,0))  AS geom FROM dual union all
SELECT 4 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(4,14,0,1,0,0))  AS geom FROM dual union all
SELECT 5 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(5,15,0,1,0,0))  AS geom FROM dual union all
SELECT 6 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(11,21,0,1,0,0)) AS geom FROM dual union all
SELECT 7 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(11,31,0,1,0,0)) AS geom FROM dual union all
SELECT 8 AS OrientedPoint, sdo_geometry(3001,31370,NULL,sdo_elem_info_array(1,1,1,4,1,0),sdo_ordinate_array(15,21,0,1,0,0)) AS geom FROM dual union all
SELECT 9 AS OrientedPoint, …
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The question is from Physics book titled "Physics for Scientists and Engineers" by Randall D. Knight.  Attached is part of chapter 10.1.

"Objects A and B are oblivious to our choice of system, so change in total kinetic energy for system 2 is exactly the same as for system 1."

How is that possible?  System 1 has kinetic energy because there are external forces but System 2 doesn't have external forces.
interactive_system.PNG
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I drive a Toyota Sienta Hybrid, 2017 make.

Regular mechanic told me the engine / motor oil (he used synthetic type)
for hybrid is different from non-hybrid cars.

Q1:
What about spark plugs (I'm looking at iridium) : is it different from non-
hybrid cars'  iridium spark plugs?

Q2:
Can point me to an ebay, Amazon or Aliexpress link that sell Sienta
Hybrid's iridium spark plugs?
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Following is a sentence about telescope from HowStuffWorks.com

"For example, a small 6-inch (15 centimeter) scope lets you read the writing on a dime from 150 feet (55 meters) away!"

Is 6-inch diameter of objective lens ?

Attached is image of telescope.
Telescope_Parts.PNG
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I've been using the Azure ML Studio and it is great.

I get the basics of what ML is and what it does. But now I'd like to learn it in more detail - understand the deeper issues, the math behind it, what the different algorithms do and so on.

But I don't know where to go for this. Most of the introductions to ML use Python and TensorFlow. Ideally I'd like to stick to Azure ML Studio but I just can't find anything that tells me about the theory of ML rather than how to use Azure ML Studio.

I'm talking about books or courses - I think ideally a book but either would be fine.

This book might be promising:

Predictive Analytics with Microsoft Azure Machine Learning 2nd Edition Paperback – 19 Aug 2015
by Valentine Fontama (Author), Roger Barga (Contributor), Wee Hyong Tok (Contributor)

But I'm concerned it doesn't give the background - the reviews seem to indicate this.

Let me know if you have read a good book or completed a good course that explains the math of ML and would be something I could use with the Azure ML Studio.

Thanks!
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Math Formula to determine Network/Host subnet

Let's say I have a subnet  192.168.10.0/24 , if I need to have 400 Hosts in the network , I can just change the subnet to 192.16.10.0/23.. this can stem from the formula (2^9) -2=510 ,this will be the correct  one that covers 400 Hosts , because if I use (2^8)-2=254  , it will be less than 400
***2^9 means I already have 8 bits for the Host in the /24 and will just borrow 1 bit from the Network portion and will be /23

Sometimes the request is much more complex, for instance when they ask for 1113 hosts, then I will have to use the calculator and start from 2^1 and add  each time 1 to the power to get  closer to the desired number , ex: 2^10,2^11,etc.....

I wonder if there is a formula, like (2^x)-2= "a number close to 1113", and then I will just determine the value of x.

Thank you
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Why don’t all the bugs look alike?
What could have done differently so that the two drawings  would look more alike?
Was it hard not to ask questions?

BUG 1

http://ge.tt/7SyQToq2

BUG 2
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What is the next number in the series : 1,2,4,8 ...
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Hi,
I was thinking of some good biological videos which shows exactly what happens when u eat oily food inside your body.
what happens when one eats chicken/rice/ other common food items.
Any good video or article which has this details.
Although i see many when searched on google..But cannot be sure about the credibility.
Or anything on similar lines if not exactly the above...backed by scientific evidence
Wonder if someone has taken a video of inside of stomach with some instrument to see what happens
Thanks
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Dear experts,

The below url shows the compound interest calculations - discrete and continuous.

In the video between time lines 6.45 minutes - 7.05 minutes, it shows log 2/0.05 = 11.55 yrs

If log 2 to the base 10 gives 0.3010. Then 0.3010/.06 = c5.016. How is the number 11.55 arrived?

Is it considering log 2 to the base 'e'?

then in which cases do we calculate log use base 'e'?

Thank you

Kindly help.
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Dear experts

I am reading a book on Derivatives.

In this i have come across continuous compounding of interest rates. The author has applied log in the equation. This is where i am stuck.

Can anyone kindly look at the attached document and point me to a youtube video which will explain these steps.

In the recent past I have raised a question on 'e'. I have got responses. I will be honest i have gone through those videos in detail, yet. I will watch those videos tomorrow.

But any help in the meantime is always welcome.

Thank you
Continuous-compounding-Logarithm.docx
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All, I am preparing for MFE (financial engineering). I could not thin of any other forum where i could seek help for clearing my doubts on financial products.

Dear experts, is my below understanding correct?

Is  r>-1  coming from this statement?

&&&1 + r&&&

if 1+r>0, then r>-1
*****

Extract from Stochastic Calculus for Finance 1

We introduce also an interest rate 1^n. One dollar invested in the money

market at time zero will yield 1 + r dollars at time one. Conversely, one dollar

borrowed from the money market at time zero will result in a debt of &&&1 + r&&&

at time one. In particular, the interest rate for borrowing is the same as the

interest rate for investing. It is almost always true that r >= 0, and this is

the case to keep in mind. However, the mathematics we develop requires only

that r > -1.

Kindly guide
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Dear experts,

I have been a member in this group for the last 13 years and it has been a amazing journey for me.

Now i have resigned from my job and doing mathematics to pursue Financial Engineering.

I have done CFA but my experience has not been in and around Treasury /Risk management.

Now my question to the experts is, can anyone suggest me a forum where i can post questions on both derivatives (financial products) and math relevant for Financial Engineering.

My observation is this forum has address my math questions till now.

But i am looking for a nich forum. I am happy to join even if it is a paid one.

I want my questions to be answered within reasonable turn-around-time.

Kindly suggest

Thank you
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measurements

is it customary to list width before height?

Use Electric shower curtains or just regular shower curtains as an example.

A followup question will add depth and length.
I just thought a shower curtain was a good example because it is height is clear (and there is no depth).

Dont use a door because there is depth and that would confuse me because there is no such thing as a flat door. But there is a flat shower curtain.
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Dear experts,

I am preparing for Financial Engineering.

Can any of the experts recommend a book on Probability theory which will support the understanding required for stochastic calculus.

Thank you
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The last 1 year, I've got 7 burnt LED drivers  (4W-24W) from unbranded (made in
China) & one even cause total power trip in the house : url above is one of them.

So far the LED lights are Ok, it's only the drivers.  A contractor recommends
OSRAM.  Would the following driver support all my drivers (that ranges from
4-24W) as it states 2-30W : I plan to replace all of them with reliable one:

https://www.ebay.com/itm/OSRAM-ET-LED-2W-30W-12V-electronic-transformer-ballast-driver-220-240V-LED/362358629177?hash=item545e41e339%3Am%3Amey_87LTajrRQpyEOy0LA2A&var=631552817451

Have also seen cases the LED light flickers or dimmed to a quarter of the brightness
& replacing the driver helped always.
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A lawyer advised me and my spouse to write separate wills :
as the will is charged at a fee per will, I'm trying to establish if this is a general
practice out there & the reasons for it : if it's one joint will, it will be charged
for one will's fee.

Reason was the lawyer wants to customize it to meet our special-needs
(intellectually disabled who can't live on his own) kid but by making the
wills separate, I'm curious how this helps
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Which industries use the "end of period" and "beginning of period" options in the PMT, FV, PV and other financial functions.
When I've taken out a personal loan at the bank, I was never asked "Would you like to pay at the end of the month? or would you like to pay at the beginning of the month?"

Which types of transactions?  Is it non-USA entities?  Is it real estate? Asset-based loans?
Can anyone point to an article, blog post, or video that discusses who uses the last option in these financial functions.
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# Math / Science

9K

Solutions

6K

Contributors

The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.