Math / Science

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If we slide a 1/2 inside diameter pipe into a 3/4 inside diameter pipe how much watch pressure do we lose. Would that cause an issue when the house was sold and the buyer inspector noticed the weaker water pressure. They don't find everything because my inspector failed to find a gas leak as well as the fact that the roof had been in a fire years before. The water heater had propane fittings when the gas was natural gas and required natural gas fittings and the inspector missed that. Maybe they and the buyer think the water pressure through half inch pipe is normal.
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Learn about longtime user Rowby Goren and his great contributions to the site. We explore his method for posing questions that are likely to yield a solution, and take a look at how his career transformed from a Hollywood writer to a website entrepreneur.

First at all sorry for my bad English.
I would like to create a kind of lock with no internet connexion and a RTC inside.
The lock will open with a code 8 chars long. The chars can be from 0 to 9 and from A to D. (I use a 16 key keypad)
The main idea is to have a code generator that encrypt with this 14 chars (0-9 and A-D) a code that says to the lock : you will have to open from this date until this date. And because i want the code to work only with the serial of one lock the code have to be compatible only with the lock I create the code for.

So to resume :
I have a lock with a 16 keys that are 0-9 and A-D the last two are R for reset and V like run :)
The lock have a serial number could be 000 to 999
When I create the code the code have to contain on max 8 chars : the start date, end date and the serial of the lock.

I've tried some ideas like work with a base 14 or something like. Use a kind of offset from the a defined date that is the same on the lock and the generator and then use the difference from this date to create the start date. Use the serial of the lock to do a CRC so when the lock check the code if the CRC is not ok then it won't open.

Well as you see I'm getting lost so if you have a simple idea please help

Thanks a lot
U = {digits}
E = {-3, -2, -1, 0, ...}

What are digits?

What is E intersection U
What can you tell me about Expert Systems?

I work for a technology company where there are hundreds of very smart engineers such as Electrical Engineers, Chemical Engineers and Manufacturing engineers.

They are all very smart and skilled. But the downside of every one is they are human.

I look at Supercomputers, like Summit, by IBM (200 Trillion computations per second), as well as Watson, which I know very little about, and I worry that Watson could wipe out small businesses like the one I work for.

How close are Expert Systems like Watson from performing completed designs, automatically? Let's say, for example, an integrated circuit.

I am curious to hear what a company that sees Watson as their true competition can do on a shoestring budget to harness their own engineers knowledge in a form that can be coalesced into a internal use only decision support system.

The sky's the limit on your theories...This is a wide open question, meant to tickle the mind.

The distance from the far wall to the back of the closed door = 11 feet. I was hoping for 12 feet (144 inches). Actually we need 140 inches.

The width of the upright dresser is 36 inches and the bed 74 inches and the fully opened door of 30 inches = 140,

If the dresser is turned to the side and open fully the left door of the dresser it's 28 inches so 8 inches gained. The bed is 74 inches. I assume the door is a standard 30 inches wide. If we put the back of the dresser against the far wall and open the door fully then we have then used 28 of the 132 inches (11 feet). Then the bed which adds 74 inches. So at this point the dresser doors and drawers will open as desired and the bed in place and we have used 28+74 inches = 102.

If the door is 30 inches wide then it appears the door can be opened fully and we are using 132 inches which is the full 11 feet but it could be tight if the home owner measured the 11 feet correctly. Since nothing much is gained by opening the door fully (since all that will be there is the foot of the bed) we can gain some inches by only opening the door by "x" number of degrees. I took geometry and so forth but I do not recall the formulas.

With the door fully opened it's 90 degrees from the door frame. If we open the door 45 degrees from fully opened or even 60 degrees, how many inches would we gain so the bed and dresser are not having to touch each other but still the door can be opened far enough to enter the room. The only reason a …
Is this Statistical Question as simple as i hope it is...

If I have a 5 Minute Time Bar for measuring trade volume within a Stock Symbol (any symbol)

Which is 300 seconds in total (5 x 60 seconds in a minute = 300)  

and i divide the 300 seconds into 10 equal segments of time -- 30 seconds each

and i measure the buying volume that took place from trades during EACH of the 10 segments --- HOW DO I MEASURE THE RATE OF BUYING PER SEGMENT IN RELATION TO THE 10 SEGMENTS to quantify how smooth was the trading done... Measure the Variance ? How do i measure the consistency of the buying ?

For example:

If each of the 10 segments of 30 seconds had 1000 shares traded then the rate of trade volume consistency of trading per each segment would be exact or the same rate flow of volume

1000  - 1st segment
1000 - 10th segment

But in the real world you get more inconsistent flow something like this... and i would like to understand how to measure the variance here ?

1250 - 1st segment
1500 - 10th segment
My bathroom tends to develop dark patches/spots of mildews/fungus
on the edges, toothbrushes, towels (that are hang in the bathroom),
shampoo caps,  practically anywhere in the bathroom.

I've thought of mopping the room dry but it's frequently used so this
is not practical.

These dark patches can't be scrubbed off & will need fungus gels to
be applied (& after a few hours, they can be removed).  They can
form in a matter of a day or two on towels.

Would a ventilator help?

Is there any chemical or how can I identify the source of the issue?
My old house's bathroom didn't have this issue.

What  else can I do to minimize these fungal formations?
Kite flying for the kids at church. If it is too windy it won't work well. Trying to catch a slightly windy day and access to kids will be a very hit and miss. So, on a non windy day, I know from my younger years that the air flow and movement of air is above the ground. If you can run with the kite string until you get the kite high enough it will progress higher.
So on a non windy day how many feet high would the kite need to be before the air flow takes the kite to higher levels. I once had a kite so high you could barely see it with the naked eye.

I need your help to find the name of statistical test. I used Welch t-test to find the variance between classes. I used Welch t-test as the size of the classes was different. However, I now need to find within class similarity. Appreciate, if you could please advise on the name of the test.

We have an Igloo cooler and dispute over the size. The interior measurements are 34 inches long, 11 inches deep, 14 inches wide. We need that calculated to quarts.
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Hey Experts!  Fully admit that I am working on something that is slightly outside my realm but I'm very interested in learning how to make this work so your help is greatly appreciated.

For software being developed, I'm trying to build a formula to calculate the success of an event (build a wooden crate) based on factors like character's smarts (+10% increase in success), speed (+5% increase in success) and ability (+15% increase in success).  

I've been looking all over the internet for how to build this equation or how to determine success/failure.  I've written formulas for Excel but not something like this so I appreciate your help and time.
Any idea how to do the attached question ?  I have left this question in my assignment and I don't have any idea on it ?

Any idea how find the partial fraction decomposition ?

Hello and Good Afternoon Everyone,

           This question is similar but not exactly like the one I have currently open.  Basically, I wish to know how to convert a number to a percentage.  The number of interest is total deductions.   To simplify my question here is a condensed hypothetical overview.  Gross Amount: $1,924.70   Total Personal Deductions: $424.05  Net Amount:  $1,500.65.

           If more information is needed, please feel free to let me know and it will be given.

           Thank you


So I must disclaim that I know that this is not an idea solution, however wanted to get some science and technical terms correct for running two networks off one NIC card as a work around to having VLAN and/or second router.  Again, this is NOT how I would do things, but for some home user wanting to run lets say a network off of another network for testing that it can be done this way because of how layer 2 works.  The layer 2 part is what I am most interested in, but wanted to get some expert opinions and why it works.

So a home user has a PC that is hooked into a dumb switch.  The dumb switch then goes to a normal home router, however one port goes to a switch to a garage for instance.  The home network is and the garage is that runs some devices that do not need internet.  Just needs to be able to send and receive data, and those devices might have another device down the line like a switch with more devices.  Now I know that you can set the NIC card on the computer to be the main IPv4 of etc on the main page and on the advanced tab you can add a secondary IP of no gateway and it will route the traffic to that network with zero issues and normal LAN traffic will go out the other direction.

I guess call it a proof of concept, but it allows this happen because it is only doing layer 2 and switched go off of MAC addresses so that traffic will never hit the router for this …
Hello and Good Afternoon Everyone,

            I wish to help a friend with a percentage question as it relates to his payroll check.  Basically, he wishes to know the percentage of deduction for a bonus in the amount of $1,000.   In other words, he wishes to know how much of the $1,000 he keeps.  To aid in the computation, here is a brief summary of details:  Gross Amount:
 $2, 891.84.... Net Amount:  $1,933.81..... Total Personal Deductions: $958.03.  The bonus of $1,000 was combined with his regular pay to make one check as opposed to it being a separate payout.  

            If more information is needed in computing the percentage of deduction for the bonus, please let me know and it will be provided upon request.  That said, I look forward to hearing back from everyone regarding this question.

            Thank you

I have a cash projection model in Excel.
I have around 10 years of monthly data.
There are around 10 sources of cash and around 10 uses of cash.
I have determined the type of distribution which best fits each of the 20 series.
I have calculated the pertinent statistical parameters of each of the 20 series (e.g. mean or mode, standard deviation, etc.)
I have fitted the selected distributions with their respective parameters.
Some of the series have a normal distribution around a relatively high mean value.
Some of the series have a more Rayleigh or Weibull distribution - always positive but not symmetrical.

The purpose of the model is to predict the cash position over each of the next 12 months.
In some cases, a series has a growth factor to be included.

Each month, for each series, the current actual value is appended resulting in a new series of actual values.

Then an expected value is calculated for each of the next 12 months.

The question is:
Given a random series with known distribution parameters, what is a good way of generating expected value predictions?

In some cases, it appears that the best prediction is the current value.
However, if there's an outlier in the current value, this doesn't work well.
Determine the roots in the following case :
 i. Square roots of i
ii. Square roots of (1+i)
iii. Square roots of 1+sqrt(3) i

Total no hints on how to solve the problem. ANy idea ?
I need to use compression to change bit depth of a video signal.  

Our Focal Plane Array(FPA) is Vanadium Oxide(VOx) Resistive Microbolometers Uncooled Thermal Infrared Detector.  The output of this image sensor is 14-bit, Wide Dynamic Range(WDR), raw, monochrome, 640 x 480 resolution.  The pixels of this video signal will be processed by Image Signal Processor(ISP).  ISP input is 12-bits.  Therefore, I need to compress FPA output to 12 bits and then input into ISP.

How to perform global tone mapping using two methods, PWL and LUT (curve defined by lut) based mapping.  I need to tone map 14 bit data to 12 bit.  What does PWL stand for?  Please provide sufficient information so I can achieve this.  It's suppose to be similar to gamma compression.  I can do gamma correction in matlab.  Can this tone mapping also be done in matlab?  If yes, please provide some examples.
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Please explain Gamma Compression algorithms. How to write Gamma Compression algorithms for typical video and image processing system?  Please provide some detailed examples.  How to gain sufficient understanding to be able to write Gamma Compression in 'C' or MATLAB?
I was asked last night about performing maths with quadratic equations and I could show how to solve most problems but there was one that has left me completely baffled.  After about 45 minutes last night I had to give up.  (Probably missed something obvious and was making life way to complex for myself.)

Given the following quadratic equation:
4x.x - 35x + q = 0
what is the value of q.  One is also told the raltionship between two values of x which solve the equation.  Call those solution n and m then n = m squared (n = m.m).

I can use formulae from vieta to obtain things like m + n = 35/4 and m.n = q/4 and the formula for solving the quadratic but I then just get a horrendous mess with quadratic or higher equations when trying to simplify things.

Can someone point me in the right direction please.
There are 39 numbered ping pong balls. The people who control the handling of the balls have a very complex way of making the draws 100% random.
The cash rewards are for 2-3-4 or 5 numbers.

The chances of one of our 5 numbers drawn in the first draw is 5 in 39 or 12.82% = ?
Then the chances of one of our other 4 numbers being drawn in round two would be 4/38 = 10.52% = ?

Their site says the chances for match 2 is 9.2%
3 = 1 in 95
4 = 1 in 3042
5 = 1 in 501.942

If four of our numbers have been drawn there are only 35 numbers left to be drawn. Why isn't the chance on the 5th number 1/35?
Hi friends,

I have some visualisation project where textual info is displayed on a colored background (that is not disputable). The background color is meant to give a mental shortcut to the value, and it could be basically any color in the 3 byte RGB space. Nevertheless the textual info needs to be easily readable against the background.

I've found some algorithms to generate contrasting colors from background color by inverting (XOR with #FF) the R, G and B bytes of the background color, some with improvements for R/G/B values near 128. Unfortunately these algorithms generate some color combinations which are (to be very, very euphemistic) more insulting to the eye than mere unergonomic .

What I need is some algorithm that produces contrasting, but eye-friendly companion foreground colors out of the values of the background color values. (I'd take ready-to-use code, too ;-)

Any idea ?
How do I go about this?

5 liters but they come in 4 packages --> $11.95 - $2.49 to give me 4 packages out of 5 .. not sure if I'm on the right track

I've bought a sample test to practice my upcoming interviews.

I don't know how to go about this one. Any help would be great.