Wikipedia:Reference desk/Archives/Computing/2015 January 24

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January 24

FOSS for electromagnetic FEA simulations

Are there any open source software out there that can perform electromagnetic FEA simulations? List of finite element software packages contains a bunch of candidates but it doesn't say anything about the capabilities of any of them. WinterWall (talk) 05:32, 24 January 2015 (UTC)

GNU Octave may be the most versatile general-purpose tool for you. What are you trying to model? Electromagnetic simulation is a very broad area. When I studied RF in school, we got Puff (pun intended). It is free and open-source software! But it needs a very old DOS compiler to work. Despite its horrible interface, I found it to be more accurate than Cadence for my UHF amplifiers - but sometimes accuracy is less important than ease of use and feature-completeness.

Here's the textbook listing for Numerical Electromagnetics. When I studied that, the assumption was implicitly that if we could understand the math, it would be trivial to write our own software to implement it. A lot of the books contain source listings in FORTRAN or MATLAB.

It will really help if you narrow what you're trying to model. Do you want to model waves in nonlinear media? Do you want to study antenna coupling? Are you interested in waveform accuracy? Time or frequency doman? ...And so on.

Out in the real world, people who do RF simulations often write their own code in MATLAB (or Octave); or they use fancy expensive commercial tools like the stuff that's built into test-equipment. Scour the websites of Agilent or Rohde & Schwartz or other vendors to see the software they sell that pairs with their RF equipment.

Nimur (talk) 17:50, 24 January 2015 (UTC)

Thank you for the help. It's nothing complicated like RF, I'm just trying to model a solenoid with a moving magnet inside. Basically a miniature shake flashlight. I'm using COMSOL Multiphysics right now, but my currently workflow is atrocious:

1. Change a parameter

2. Run simulation (which takes 5 minutes)

3. See if the results are better

I'm basically trying to select the right size for the magnet and the coil, but this will take forever if each iteration takes at least 5 minutes. So I'm trying to look for an open source solution where I can use a script to tell it: "try magnet diameters from 6mm to 20 mm at 2 mm increments and coil lengths from 30 mm to 50 mm at 1 mm increments" and then leave it to run over the weekend. WinterWall (talk) 20:23, 24 January 2015 (UTC)

COMSOL has batch jobs; it may be worth checking out. Also if you have Matlab, there looks to be a basic binding there. --Mark viking (talk) 20:32, 24 January 2015 (UTC)

If you're just trying to pick solenoid size, you need to ask and answer this truthfully: why do you think a highly parameterized numerical simulation will be more accurate than just using simple analytical methods applied to the basic solenoid equation? Nimur (talk) 15:39, 25 January 2015 (UTC)

I'm looking for a shoe

Hi there,
I have been trying to find a shoe which its model is: A960314WR of Asics in the web.
I haven't found it in Amazon.
Can anyone help me? — Preceding unsigned comment added by 77.126.167.131 (talk) 15:45, 24 January 2015 (UTC)

I searched their own web site, and found nothing: [1]. This suggests the model number is wrong. That might be a retailer's stock number or something else. The model numbers I saw were shorter, like "T3N2N". StuRat (talk) 16:30, 24 January 2015 (UTC)

As StuRat says, it might be a retailer's number, so the best call might be to run the number by them and see what the shoe is called. Then contact Asics direct to find out who their retailers are... or just order from their site. I tried googling that number and all that comes up is this thread. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 5 Shevat 5775 05:40, 25 January 2015 (UTC) Edit: Actually, I see from your IP address that you're in Israel, and so this might be a bit trickier. If Amazon has the shoe then order through them, otherwise check to see which other online providers have it that might ship to you, or if Asics can ship to Israel. Then of course pray that Doar Israel doesn't lose the package.... Sir William Matthew Flinders Petrie | ^{Say Shalom!} 5 Shevat 5775 05:44, 25 January 2015 (UTC)

That looks like an Amazon product code. You can search Amazon by order code (it's the bit after the "dp/" in the URLs), but A960314WR is drawing a blank. LongHairedFop (talk) 13:28, 25 January 2015 (UTC)

If you can't find a shoe online, you might need to reboot. :-) StuRat (talk) 16:30, 24 January 2015 (UTC)

Such pedestrian humor.—Noah 02:26, 25 January 2015 (UTC)

I'm looking for a shoe, too. And I can't go anywhere until I find it. ―Mandruss ☎ 02:35, 25 January 2015 (UTC)

Never criticize a man until you've walked a mile in his shoes, as he will then be a mile away, and without shoes, making it much harder for him to beat the crap out of you. StuRat (talk) 05:33, 25 January 2015 (UTC)

Can your friends tell when you've logged into Facebook?

I have a Facebook account I have not been active on in a long time.

Every now and then I log in to look at the activity feed of my Friends, but I never open their messages.

I get email notifications when I receive a message; these include the opening text (the first line or two) of the message.

Today after logging on to the account for the first time in month, I got an email notification of a message that said "why are you ignoring me?"

If I haven't posted, liked, shared etc. anything on the account, is there any way my Friends would know I had logged into the account?

Thank you for your time. I googled extensively but was unable to find an answer. 91.142.106.73 (talk) 21:27, 24 January 2015 (UTC)

P.S. My chat function is always set to "Off" 91.142.106.73 (talk) 21:29, 24 January 2015 (UTC)

Unless you actually open a message, turn on chat, or do anything you know makes your presence known, then no. Your friend may just be trying to get a response out of you and should try phoning or texting IMO. To the rest of the world however, you're basically one of those people too cool to check your FB and they don't know you're on.... Sir William Matthew Flinders Petrie | ^{Say Shalom!} 5 Shevat 5775 05:47, 25 January 2015 (UTC). FB also notifies your friend when you read their chat.

Facebook chat is turned on by default; As you interact with FB all your friends can see that you are available for chat, and how long ago you were last on chat. On the desktop, to hide yourself from chat for all your friends, click on the gear on the bottom of that chat side bar, and select "Turn off chat". To hide from one friend, click on that friend, and at the top of their chat, click on the gear, and select "hide chat for <friends name>". You used to be able to hide chat for your friends-groups, that seems to have been removed.

However, on the FB ticker your friends will still get notification of your activity on your wall, mutual friends' walls, all public groups/pages, and private group/pages that your are both members off. They can also look at your wall to see if you've posted/shared anything there. LongHairedFop (talk) 13:20, 25 January 2015 (UTC)

I think the OP said in his/her P.S. that their chat is turned off. They also implied they're not doing any of those things that would show up in your news feed or ticker. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 5 Shevat 5775 17:48, 25 January 2015 (UTC)

Guys, thank you so much for your detailed and helpful answers, I really appreciate it. 91.142.106.73 (talk) 22:23, 27 January 2015 (UTC)

You're welcome! Sir William Matthew Flinders Petrie | ^{Say Shalom!} 7 Shevat 5775 22:31, 27 January 2015 (UTC)

Headphones plugged into notebook or tablet

Why is it that I seem to get a higher quality playing the same file and using the same headphone when I plug it into a notebook conpared to an iPad? Is this to do with the sound card? 194.66.246.27 (talk) 21:54, 24 January 2015 (UTC)

Yes. Laptops and desktops generally have better sound card quality than tablets because they don't have to squeeze it into a tiny space. KonveyorBelt 22:31, 24 January 2015 (UTC)

But is that the only reason? Is it to do with software too? — Preceding unsigned comment added by 194.66.246.27 (talk) 22:32, 24 January 2015 (UTC)

Check your sync settings in iTunes. Look for the one that saves your songs at a lower bit rate (e.g. 128kbps vs 256kbps) when copied to your iPad. There is a trade off here, of course, as you will use up more space on your iPad if the songs are copied over at their full size. Another possibility that may cause you to notice changes in sound quaility is that you may have your notebooks levels (aka equalization) set in a manner that appeals to you but your iPad is using defaults that are unappealing to you. —Noah 02:30, 25 January 2015 (UTC)

Well the OP said the same file. If the OP really is using the same file, rather than simply the same song from the same source, than the bit rate issue is irrelevant. (The bit rate may affect the quality of the images, but there's no reason why an iPad would be worse at lower bitrates files.) Nil Einne (talk) 14:02, 25 January 2015 (UTC)