How can I transfer money between investment accounts without being taxed?

Question: I currently have money in the Acorns investment app and would like to withdraw it all to invest using TD Ameritrade. I'm worried that I will withdraw it, reinvest it using TD Ameritrade, then be charged tax on money that's still sitting in an investment account. Is it possible to transfer my money without being charged a capital gains tax since it's not income yet?
Comment: Is it a tax-advantaged account like an IRA? Is the "money" invested in securities you'll have to sell before you can withdraw it, or is it already uninvested cash? Looking for the reason you think there would be a taxable event, if all you want to do is move cash out of one account into another.
Comment: What type of investments do you have in Acorn?  And what type of account? If TD Ameritrade has the same funds you should be able to transfer your account. Acorn will likely charge a fee. If you sell an investment you will have to pay taxes on any gains whether or not you move it to a new broker. Unless it is a tax-advantaged account. There are some restrictions on cashing out a tax-advantaged account even when you are moving it to a new broker. So be sure to keep that in mind.
Comment: If you withdraw money from a tax advantaged account, you realize the gains.  Transfers are different and most  can be done without penalty (IRA accounts, annuities, etc.).   I don't know what an Acorns investment app is so I wouldn't offer an opinion on that. Contact Acorn and TD Ameritrade and find out what the process is for transfer.  Ask if fees are involved (likely that Acorn will have one).
Answer: Yes, you can 100% transfer your assets between custodians without creating a taxable event.  I've done this twice over the last few years.  You are best served by contacting your new custodian, TD Ameritrade, to request the transfer paperwork.  Typically, the outgoing custodian will charge a transfer fee and, depending on the custodian and generally the value of your assets, the new custodian will reimburse that fee.  I've also had a fair amount of success getting the new custodian to "buy" my account with things like X free trades or something like that.  To my knowledge you can't transfer your unit(s)/share(s) of traditional mutual funds (I've never tried), but your regular common stock and most other assets are transferable without selling or creating a tax event; in fact your cost basis data will be transferred too.
I don't know if Acorn (or Robinhood or any other investment "apps") wrap your assets in some strange thing to facilitate the low dollar trades and prevent the very normal transfer process, but TD will know what's possible.
Answer: Contact TDA. If you can, try to go to one of their physical sites. If you have an account with TDA you have a rep that does not work on commission. Call the rep. If you are transferring you may be able to make a direct in kind transfer.


Will all Windows 7 applications run on Windows 8?

Question: Most software are not mentioning if they are compatible with Windows 8 or not right now on their specifications. So I will like to know if its safe to upgrade to Windows 8 completely assuming all Windows 7 applications will be supported on it.
Answer: You should try to download windows upgrade assistant - it will tell you if the programs you have installed are supported.
In general all windows 7 applications should work, but there isn't a comprehensive list.
Comment: I had trouble with one program that needed .net 2.005.  Then I saw that all I had to do was Turn on Feature, .net 3.5 and older versions.
Comment: It should be noted that for a Windows 8 "RT" tablet **none** of your existing apps will work because of the new architecture (without being re-compiled) **AND** there is a limit to the number of concurrent apps you can run at once.
Comment: @scunliffe - Windows 7 and Windows 8 desktop applications cannot run on Windows RT even if they are recompiled.  You cannot install desktop applications on Windows RT.
Answer: Windows 7 and 8 are pretty much identical as far as I can tell and Windows 8 (in my experience) runs anything that works in Windows 7
I have even had a number of older apps that were a pain to get working initially in Windows 7 work in Windows 8, using the same compatibility settings between the two Operating Systems.
Note, this isn't the case with Windows RT. Also, be aware of complications that may arise if switching from 32 bit to 64 bit, some of our apps refuse to work on 64 bit machines (they are very specialized software, but it is something to be aware of.)
Answer: Poke around on this page, people vote on what works and what does not.
.
Answer: Most programs designed for Windows 7 (programmed for it, not just compatible with win XP) will work just fine in Windows 8.
I use "Most" because There is no way to give a blanket "yes" to this answer.
Answer: Some 3rd party's SDKs and printer drivers do not work, as we have found out to our cost.
Certain Brother Printers (the TD range) have Windows 8 drivers, but their SDKs do not yet work in Windows 8. This means that if you rely on the SDK for automatic printing you are stuck. the workaround we had to do was to run a VM hosting an older OS (XP in our case as we had a spare license for it) and map the USB port through to it.
It won't be ideal for some people, but it's a workround until they update their SDK.
Comment: The author asked about applications not drivers.  One shouldn't expect Windows 7 drivers to work since the drive model was updated with Windows 8.  They can work but its not guaranteed.


S Bracket Transistors and Reverse Breakdown diodes in Texas Instrument 74LS32 DataSheet?

Question:
Hi, I have included the image of the schematic of the Texas Instrument 74LS32. Basically the chip consists of 4 OR gates and the schematic shows the logic how 1 of those gates is set up on the chip. In the figure shown on the LS32 version (the RHS schematic) is a transistor made up of a squiggly S on the body of it where the straight line would normally be, compared to the normal illustration of a transistor illustrated in the 32 schematic(LHS schematic). The same thing again with the diodes the ones on the right have squiggles and the ones on the left don't. I think I remember that this is a reverse breakdown diode? (but would like confirmation) I have a theory that this is illustrating a PNP transistor? But am not sure. Also I was wondering what is that italicized upside down pitchfork thingy right before GND sink? Insights would be appreciated.
Comment: The word you're looking for is "Schottky". The "LS" in 74LS32 stands for Low power Schottky. (and the pitchfork is a GND symbol)
 https://electronics.stackexchange.com/questions/55073/schottky-transistor-not-sure-i-understand-it/55090#55090
Comment: thank you appreciate
Answer: That is an NPN transistor with integrated Baker Clamp. It can be known as a Shottky Transistor Wikipedia.

It is equivalent to this:

The diode between the collector and base prevents the transistor from saturating - if the collector attempts to go less than ~0.5V it will divert charge away from the base.
By preventing saturation the transistor can turn off more quickly because there will be less stored charge in the base region.
The diodes shown with the similar embellishment to the symbol are Shottky diodes. They are not to be confused with a zener diode that usually only have the bracket on one side, a backward diode that have them pointing the same way outwards or a tunnel diode where they both turn inwards.
Shottky diodes are diodes where one of the electrodes is a metal, rather than both being semiconductor. The turn-on voltage is significantly less and they have essentially zero stored charge so they are very fast.
The three pronged symbol is a connection to ground or in the case of an IC it is to the substrate. It also often means the connection to chassis in equipment or old schematics.
Comment: Wow thank you this is very insightful :) Do you know about the upside-down pitchfork thingy too?
Comment: @Klever5548: the pitchfork thingy is one of several commonly-used Ground symbols.
Comment: Some people use "baker clamp" to refer specifically to the kind that uses two standard pn diodes; it might be worth mentioning that the schottky transistor symbol does specifically mean the type with a single schottky diode.
Comment: ok thank you Peter and Hearth


How to explain the increase in current with the increase in the concentration of responsible ions?

Question: I have conducted an experiment wherein I have used different concentrations of $\ce{H2SO4}$, $\ce{HNO3}$ and $\ce{H3PO4}$ as the electrolytes. I filled the acid in glass tube and used a 9V battery, wires and two graphite electrodes to complete the circuit. I also attached an ammeter to check the current variation during a time period of 1 minute. I observed that the current was higher with more concentrated solutions, although my query is that when I add more of these acids, the concentration of the $\ce{OH-}$ ions reduces; it is the $\ce{OH-}$ ions and the $\ce{H+}$ ions that dissociate. How exactly do I explain the increase in current due to increase in concentration?
Answer: The electrical current is carried by all ions in the solution, including the $\ce{SO_4^{2-}}$/ $\ce{HSO_4^-}$, $\ce{NO_3^-}$, and $\ce{PO_4^{3-}}$/ $\ce{HPO_4^{2-}}$/ $\ce{H_2PO_4^-}$ ions, and not just by $\ce{H+}$ and $\ce{OH-}$.  So, even though the $\ce{OH-}$ concentration is decreasing with increasing acid concentration, like you say, it's much more than made up for by the increased concentration of the anions from the acids.
EDIT (in response to a comment): The contribution of ions that don't participate in the electrochemistry differs depending on the system.  For example, in $\ce{NaOH}$ the $\ce{Na+}$ effectively just distributes to balance the charge from the concentration gradient in $\ce{OH-}$:

$\ce{H2O}$ is reduced to $\ce{H2}$ and $\ce{OH-}$ at the cathode, increasing the $\ce{OH-}$ concentration there
$\ce{OH-}$ is oxidized to $\ce{O2}$ and $\ce{H+}$ at the anode, decreasing the $\ce{OH-}$ concentration there
Thus, $[\ce{OH-}]$ changes from high at the cathode to low at the anode
In order for the solution to maintain electroneutrality, something has to balance the higher concentration of negative charge at the cathode, and in this system $\ce{Na+}$ is the major contributor.  (Water self-ionization can't provide enough $\ce{H+}$ to maintain the charge balance.)

In other systems such as $\ce{H3PO4}$, the acid-base equilibration behavior of an electrochemically inert species can contribute to the charge carrying function:

Adjusted to pH 7 with, say, NaOH, phosphoric acid exists mainly as $\ce{H2PO4-}$ and $\ce{HPO4^{2-}}$
Water is oxidized at the anode, producing $\ce{H+}$, which reacts with $\ce{HPO4^{2-}}$ to form $\ce{H2PO4-}$
Water is reduced at the cathode, producing $\ce{OH-}$, which reacts with $\ce{H2PO4^{-}}$ to form $\ce{HPO4^{2-}}$ and $\ce{H2O}$
So, $\ce{HPO4^{2-}}$ has a higher concentration around the cathode than the anode, and $\ce{H2PO4^{-}}$ has a higher concentration around the anode than the cathode.  These concentration differences result in a net transfer of charge between the two electrodes.
All of the negatively charged phosphate ions are balanced out by a corresponding distribution of positively-charged $\ce{Na+}$, similar to the $\ce{NaOH}$ case.
Comment: @nick yes. current is the rate of flow of charge. whether the charge comes from a salt or from and acid is irrelevant
Comment: thank you! but say i did not use acids and used salts instead, could the same explanation be used?
Comment: thank you! but at the end only particular ions go through the redox reactions at the electrodes. so how do the other ions that do not go through the redox reactions at the elctrodes contribute?


Personal Hotspot feature on IPad 2

Question: I am not able to set-up Personal Hotspot in my IPad 2. I have read somewhere that, if my carrier allows me to enable Hotspot, then the IPad also will allow me to enable Hotspot, as Apple has no correspondence with the Hotspot. But, when I connect the same SIM card to my IPhone, the hotspot works. So, is there any way I can enable Hotspot in my IPad?
Answer: According to this Apple Support document the personal hotspot feature is only available from the third generation iPad upwards.

Learn how to share your cellular data connection using Personal Hotspot, the Internet-sharing feature on iPhone, iPad (3rd generation) Wi-Fi + Cellular or later, and iPad mini Wi-Fi + Cellular.

Personal Hotspot feature on IPad 2


Experience with anti-keyloggers?

Question: Does anyone have any experiences with anti-keyloggers?  I have been looking at Zemana and it looks good to me.
Comment: A quick look at the page makes no mention of hardware keyloggers... do they make you type one real & then one fake keystroke, all the time?
Answer: The fact that they say block all unknown threats makes me believe they are a load of bull. Pardon my American. I would say just run any good program like Malwarebytes and just do the standard safety stuff like don't load attachments that are fishy. If you are so worried about keyloggers load up a linux livecd and use that.
Answer: The simple answer would be not enter sensitive information (like logging into your bank account) when you aren't on a trusted computer. Library's, friends computers, public terminals, etc. Those would be the most vulnerable.

Experience with anti-keyloggers?


Admob Live Wallpaper on Display?

Question: Is there a way to display an admob ad every hour or so right on the live wallpaper?
Comment: This is diabolical. Pure evil, sir.
Answer: I'm assuming you mean a general live wallpaper rather than your own.
I don't think it is possible but even if it is technically possible, you would have to figure out how to display it. For example, consider an animated live wallpaper which repaints itself completely for each frame.
I recommand using the notification (or if you must the Toast) mechanism since it is much less intrusive and you can use it regardless of the current live wallpaper.

Admob Live Wallpaper on Display?


Displaying rows for this week only in PHP

Question: I have two dates stored in my database as columns dtp_s and dtp_e (start, end). These derive from a populated form which the user is made to select a start and end date.
I want to display records from Monday - Sunday of the current week, but my current solution is showing dates from 7 Days before - Today.
SELECT id
FROM _records
WHERE
    dtp_s > unix_timestamp(now() - interval 1 week)
    AND userid = ?
ORDER BY dtp_s DESC
LIMIT 5

I have tried to change now() to be the value of strtotime( 'sunday' ) but this then shows no records when one does exist.
Any ideas on how I only show data based on ones that start the same week (Mon - Sun) ?
Answer: To get the Monday of the current week you could use:-
select date(curdate() - interval weekday(curdate()) day)

To add this into your code:-
SELECT id FROM _records
WHERE dtp_s > date(curdate() - interval weekday(curdate()) day) AND userid = ?
ORDER BY dtp_s DESC
LIMIT 5

Answer: After looking at other questions from SO, this can be achieved in SQL rather than mixing PHP strtotime values that could be in different timezones if not configured correctly.
SELECT id FROM _records
WHERE dtp_s > unix_timestamp(date(now() + interval 6 - weekday(now()) DAY) - interval 1 week)
AND userid = ?
ORDER BY dtp_s DESC
LIMIT 5

I am getting only the records for this week displayed.


AttributeError: 'NoneType' object has no attribute 'replace'

Question: right sorry that I'm not all good at python
but my problem is that i need to replace a character
here is the thing i am trying to change all i need to change is # to an A for all of the lines
def puzzle():
print ("#+/084&;")
print ("#3*#%#+")
print ("8%203:")
print (",1$&")
print ("!-*%")
print (".#7&33&")
print ("#*#71%")
print ("&-&641'2")
print ("#))85")
print ("9&330*;")

so here is what i attempted to do(it was in another py file)
from original_puzzle import puzzle

puzzle()

result = puzzle()

question = input("first letter ")

for letter in question:
    if letter == "a":
        result = result.replace("#","A")
        print (result)

here is what it gives me
 Traceback (most recent call last):
  File "N:\AQA 4512;1-practical programming\code\game.py", line 36, in <module>
    result = result.replace("#","A")
AttributeError: 'NoneType' object has no attribute 'replace'

it would help if somebody told me a different way around it aswell
thanks for the help and sorry again that i'm bad at python
Comment: Have a look at what `puzzle()` returns.
Comment: See also http://stackoverflow.com/questions/21471876/python-function-returning-none
Answer: if you don't explicitly return something from a python function, python returns None.
>>> def puzzle():
...   print 'hi'
...
>>>
>>> puzzle() is None
hi
True
>>> def puzzle():
...   print 'hi'
...   return None
...
>>> puzzle() is None
hi
True
>>> def puzzle():
...   return 'hi'
...
>>> puzzle()
'hi'
>>> puzzle() is None
False
>>>

Answer: The puzzle() function does not return anything. That's why you get this error.


Is there a connection between פסח (Pesach) and פה (peh / mouth)?

Question: Is there a connection between פסח (Pesach) and פה (peh / mouth)?  They sound similar.  Plus, we are commanded to do lots of symbolic eating on the holiday.  Has it been written about or discussed?  Thank you.
Answer: The Arizal (Pri Eitz Chaim, Shaar Mikrah Kodesh, ch. 4) related it to the idea "Peh sach" - "a mouth converses" (as noted by sam in a comment). This can also be connected to the mitzvah of magid.
See also: http://www.hebrewbooks.org/pagefeed/hebrewbooks_org_52839_131.pdf :

The Arizal taught that the word "Pesach" is composed of the words
  peh sach, which means "speaking mouth." When Bnei Yisrael
  sacrificed the Korban Pesach, they sacrificed their speech to
  Hashem - by refraining from uttering forbidden words of lashon
  hara, anger and contention. Accordingly, the Korban Pesach was an
  essential catalyst of the Exodus from Egypt. By sacrificing their peh
  sach, their "speaking mouths", they proved their greatness and their
  worthiness to be redeemed.
Comment: (I haven't heard it connected to the eating we do. We Jews tend to eat at every festivity;)
Comment: On second thought, this site throws it in, albeit parenthetically: "...the Arizal writes is all about "peh sach," when the mouth does a lot of talking- when speech, sippur, and hallel (and eating, of course) are the order of the day..." http://www.jemsem.org/index.php?option=com_content&view=article&id=346&Itemid=54
Comment: It should be noted, although it really goes without saying, that this obviously contradicts the various views of he Rishonim regarding the etymology of Pesach. (And is difficult to fit with the psukim). I imagine he probably meant that there is a homiletical, rather than etymological connection. If so, consider editing "the word "Pesach" is composed" to something such as "the word Pesach can be interpreted as"
Comment: @mevaqesh That was a direct quote from the reference. But yes I think it goes without saying that it is intended as a derash. I assumed that was all the OP wanted.
Answer: Nesivos Shalom comments that Sichon (from the word siach, as in speech) is melech haEmoree, as in amira, speaking. Sichon is spelled
סחון
Talmud Brachos uses sach with a samech ches to mean speak
תלמוד בבלי מסכת ברכות דף נא/א
אמר רבי ישמעאל בן אלישע שלשה דברים סח לי סוריאל שר הפנים
Also see drushei tzlach shabbos hagadol os daled where he says same as arizal


How to create a running process graph in Linux

Question: Basically, I need to draw a graph over all running Linux Processes.
I followed below step's but looking out some best solution for this work.
Using Top command get all running process and redirect to a file, next then extract input from given file and draw Graph using some programming API.
This step's seem to be very tedious, Is there any other way to do this work in Linux itself. Please give a suggestion.
Comment: You mean like the `pstree` command does?
Comment: Can you please describe your graph? What do you have on the X and Y axis?
Comment: See below relevant link : http://stackoverflow.com/questions/7998302/graphing-a-processs-memory-usage
Answer: You should investigate the <code>/proc</code> filesystem, it has the information you need in a matter that is easily accessible to a perl script.
There is some documentation available at http://www.tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
Of special interest to you is the "children" meta file, there is some documentation at https://lwn.net/Articles/475688/


How to share a fan robot with LEGO?

Question: I've made a really awesome robot with LEGO Mindstorms EV3 (and I'd like not to say what it is here). I've seen fan robots on the LEGO site, and I wonder whether they could add mine on the site. I've seen a site for uploading ideas for LEGO kits, but I can't find anywhere to upload robots. Can anyone please help?
Comment: Not really. Imagine the amount of MOCs posted worldwide would also be sent to TLG. LEGO Ideas is the place you can submit your idea. And if you get enough likes from community it might be considered by TLG for production. However it is dedicated for something entirely new - old ideas, alternate models or something with licenses that TLG has agreement with most likely will be denied.
Comment: Hmmm... so we can't send it directly to LEGO?
Comment: Ok, thanks a lot!
Answer: It looks like you don't quite understand how those robots became supported by Lego.
You see, EV3 was released in 2013, and they've supported only 12 fan robots. That's not a lot, and if they were still accepting fan robots for years they definitely would've had more robots on their site. I have an unofficial book by Laurens Valk about EV3 programming, in this book he has instructions for about 3 more of his robots. Yet none of them are on the site.
Why am I even mentioning a Lego fan and his book? Because this page says that the race truck was designed by him. That's the only model he made that's on their site, but there are some people who have had multiple models of theirs accepted by Lego. They are Martyn Boogaarts and Kenneth Madsen. And I could've sworn that I saw a video(s) somewhere where they were interviewing the designers of these robots.
Looks like they were only accepting fan robots from skilled EV3 users.
Comment: Great answer! Wasn't aware of the actual "Fan robots" stuff. Do you happen to know the URL for these "Fan models"?
Comment: @Alex I'm sorry, I dont remember the link for the videos. Once again, I couldve sworn i saw them but I dont have time to look. If you want the general page about them, it's the hyperlink in my answer.
Comment: Is [this](https://www.lego.com/en-gb/themes/mindstorms/buildarobot) the page? I can count 12 models you've mentioned here.
Comment: @Alex yes, thats the one.
Comment: Thanks a lot for the info, @mindstormsboi, and thanks particularly for the **skilled** comment.

How to share a fan robot with LEGO?


marshmallow trouble with internal storage

Question: i have galaxy on5 device. its updated to marshmallow on last week but after update it start performing some error. biggest problem is with storage. in internal storage it showing 7.3 gb used but actually it used only 5.4gb. because of showing 7.3 gb used out of 8gb i uninstall some big apps but still it showing 7.3gb used only. actually i having same problem with my sd card but i just unmount my sd card and again mount it, then it shows the correct space used.
kindly tell me how to troubleshoot this problem.
email: email@example.com
Answer: Did you try cleaning the cache? There might be junk folders and files you can delete also. Don't forget moving all movable apps in the SD Card. I would recommend you install ES File Explorer on Google play to clean your storage.


How to change the theme of a program

Question: I have a piece of software, a winform program developed in c#, that has several different themes. But if one of my team members wants to change the theme they have to ask me, then i have to change it, recompile and send it. Instead I wish for them to be able to freely change the theme. It is like changing the theme in Firefox, etc. Any ideas on how to begin coding such a piece of software?
Answer: This seems like a good thing to put into your config file.  Have a method that checks the config file for a theme setting.  And change the theme based on that.  I would also recommend having a default theme in case the config file fails to specify one.
Alternatively, this could go into the admin / settings / options portion of the application.  Where you could save it with your other settings.  In the registry, or app settings folder, etc.

How to change the theme of a program


How to create realistic animal hair and fur?

Question: I am trying to make hair in blender for 15 days, but can't get a better result. i,m beginner not  more know about blender. I wanna to create every type of animal hair and fur.

Here is my blend file
Answer: You probably need to work at least 3 things:

The color of your hair, you can use an Input > Hair Info (Intercept output) as node in your material to create a gradient:

Make the base of the hair thicker and the end thinner with the Hair Shape values:

Give your hair system some Children > type > Simple and play with the Clumping, Roughness and Kink parameters to make the hair mor realistic:

Result (needs more work of course):


My theme not supporting Page Builder by SiteOrigin

Question: Recently i converted a HTML template to WP theme. It functioning good but the  Page Builder by SiteOrigin plugin is not functioning i mean stylish etc.
How can i make my theme to support this plugin ?
Is these bootstrap themes support this plugin ?
please help me.
Answer: Most page builder plugins operate by taking over the_content() function in WordPress. Is your theme utilizing that function on your single post/page templates?
While I can't help with SiteOrigin's page builder, I am on a team that released the FastLine Page Builder. If you're not able to get SiteOrigin's builder working, give ours a try. We would be more than happy to continue helping you troubleshoot!


What component does the 'coupon' label refer to in terms of PCBs?

Question: I was looking at a motherboard recently and I found a couple interestingly labelled component footprints. They're two through-hole mounted components right next to the CPU, and they seem to be called COUPON1 and COUPON2. The problem is, the two components were never put into the board, so I have no way of knowing what the holes are really for. I did some Google searching, but all I could find were links to cheap motherboards and PCB.
Comment: I have heard of using coupons to validate trace impedance. As I understand it, you include unused traces on the board which have the same geometry as the trace whose impedance you want to verify. You measure the impedance of the coupon traces as a form of quality control.
http://www.polarinstruments.com/support/cits/AP8502.html
Comment: those holes look like they'd take a 2x2 2.54mm pin header, possibly for the test @mkeith describes.
Comment: mkeith is right. There's a previous detailed answer from a PCB design pov that touches on impedance test coupons [here](http://electronics.stackexchange.com/questions/208856/how-do-i-lay-out-pcb-traces-for-a-given-differential-impedance). There are other ways to instrument a PCB design to prove various things such as [stacking strips](http://electronics.stackexchange.com/questions/208856/how-do-i-lay-out-pcb-traces-for-a-given-differential-impedance) which help verify the stackup is right.
Answer: Most of us think of a coupon as a small tear out thing in a magazine or sales mailer that is used to save money when you buy something. In the PC board world these were generally added to the periphery of a PCB layout (or at the periphery of a matrix of boards when a batch are step and repeated on a panel). The design would be that these would be scored for breakaway or routed with snap off tabs so that they could be removed before deploying the actual circuit board. It is likely this removal nature where the usage of the coupon terminology came into play. Note that coupons need not be manufactured as a break away part of the circuit board and may in fact be designed as a separate small circuit board that is placed on the same panel as the circuit boards.
These periphery areas of the board are used for a number of things such as:

Contain traces with known length and spacing so that they can be measured to see if the produced circuit board meets the intended impedance characteristics. These traces can be single ended or dual traces operating as a differential pair. Holes at the end of the traces accommodate test probes for the measurement process.
Sometimes pads are placed on the coupon for placement of components by the pick and place machine. High usage components on the BOM such as the 0.1uF and 0.01uF capacitors are included on the pads of the coupon. Other critical components are included as well. The idea is that these components can be probed by automatic test equipment after board assembly to check their values to ensure that the feeder reels in the pick and place machine were loaded with the proper components. The coupon components generally have no other circuit connections other than test points so it is easy to measure their values accurately.
Another use for coupons is to use them for cross sectioning to validate that the board stack-up was done correctly with the proper thickness of copper and insulator layers between copper layers. The coupon permits the tests without having to sacrifice a whole circuit board.

It is my experience that the inclusion of "coupon" usage directly into the PC board design itself is an unusual extrapolation of the terminology. That said I fully agree that in the example board that you showed they are almost assuredly used for trace impedance measurements.
Answer: Their placement next to the CPU would likely signify it's a jumper for a selectable option. They would have a standard 0.1" jumper or dip switch. If you had mentioned the board manufacturer or part number, or the intended CPU type, we could confirm.


How does the thickness of a string affect the frequency?

Question: I've notice that thicker strings have lower frequencies, but is there a specific relationship between theses two?
Answer: A vibrating string is governed by the wave equation:
$$\frac{\partial^2y}{\partial t^2}=c^2\frac{\partial^2y}{\partial x^2}$$
Where $y$ is a function $y(x,t)$, $T$ is the string tension and $\rho$ the linear density ($\mathrm{kg/m}$) of the string, and:
$$c=\sqrt{\frac{T}{\rho}}$$
Solved, this equation yields:
$$y(x,t)=\displaystyle\sum_{n=1}^{\infty}A_n\cos\Big(\frac{n\pi ct}{L}\Big)\sin\Big(\frac{n\pi x}{L}\Big)$$
For $n=1,2,3,4...$ and with $L$ the string's length.
(the $A_n$ are coefficients yet to be determined from the initial condition (state) of the string)
(My full derivation of the solution can be found here)
Now let $\cos\Big(\frac{n\pi ct}{L}\Big)=\cos\omega t$
with $\omega=2\pi f=\frac{n\pi c}{L}$
For $n=1$, i.e. 'the fundamental' frequency:
$$\boxed{f_1=\frac{1}{2\pi L}\sqrt{\frac{T}{\rho}}}$$
It now becomes apparent that the frequency (pitch) of the fundamental is:
1) inversely proportional to the string's length.
2) proportional to the square root of the tension.
3) inversely proportional to the square root of the string's density.
$$All other things being equal, heavier strings will produce lower pitched notes.**
This is somewhat analogous to the simpler mass-spring system, where higher $m$ also leads to smaller $f$.
$$f=\frac{1}{2\pi }\sqrt{\frac{k}{m}}$$
Comment: I believe you have an extra $pi$ in your $f_1$ relation.  Also, $\rho$ has a standard use as a volume density, so seeing it in this relation could be confusing.
Comment: @BillN  *Also, ρ has a standard use as a volume density, so seeing it in this relation could be confusing.* Nope. The symbol $\rho$ is well defined in the text.
Comment: @BillN the usual derivation uses the *linear density* (mass per unit length) as in this answer. Your answer using the volume density makes the arbitrary assumptions that the cross section of the string is circular, and that the two strings have the same volume density That is not true for many stringed musical instruments, for example, where different strings may be made from different materials. For example "thin" piano "strings" are steel wire, but the thicker strings are a steel core surrounded by coiled copper, with different numbers of coiled layers for different groups of strings.
Comment: @alephzero I understand all that. I am simply leveling the "playing field" to explain the OP question.  What you have pointed out simply means that I can have a thick, low density string with the same fundamental as a thin high density string for a given tension and length.  And yes, linear density *is* the usual presentation. How would you *isolate* the idea of thick versus thin? My answer points out specifically that thickness is not the only factor, but proceeds to a perspective in which it *could* be the only factor.  Consider two solid steel strings, one 0.014" and another 0.028".
Answer: It's a bit more complicated than "thicker" or "thinner," but if you specify that the strings your are comparing have the same length ($L$), have the same volume density ($\rho$), and have the same tension ($T$), then a thicker string will have a lower fundamental frequency than a thinner one.
Now let's look at this with some mathematical tools:
The fundamental frequency of an ideal string (the real stiffness of a string can affect the frequency slightly) fixed at both ends is
$$f_1=\frac{1}{2L}\sqrt{\frac{T}{\rho A}}$$
where $A$ is the cross-sectional area of the string of radius $R$:
$$A=\pi R^2.$$
If we put this area in the fundamental frequency relation we get
$$f_1=\frac{1}{2LR}\sqrt{\frac{T}{\rho \pi}}.$$
This shows us that for strings of same length of the same density experiencing the same tension, the thicker string will have the lower fundamental (and consequently a lower pitch).


How do I find out which Contrib module is compatible with PHP 7?

Question: Drupal.org misses a PHP version field. As far as I can see, I have to go through the issue queue or .info file for every third-party module to find out which PHP version is supported. Is that correct?
Answer: Sort of.
The PHP version isn't a required key for module .info files, and it's a minimum version of compatibility anyway. So a module could declare itself as requiring PHP5.6, but still work absolutely fine under PHP7. Or it could not declare a minimum version of PHP at all, and still work under PHP7. Or it could declare PHP5.6 as minimum, but not work at all in PHP7. You get the idea.
So yes, you need to check on a case-by-case basis to find out which will work under a specific version of PHP.
Answer: Yes, this is (still) correct.
If you just want to know if your existing Installation and modules are ready for a new PHP-Version, you can try to use PHP_CodeSniffer.
This tool scans your directory to detect violations of a defined coding standard.
Depending on how you installed your website you can use composer for that. It could look something like that:
composer require --dev phpcompatibility/php-compatibility
cd [folder_of_your_drupal_composer_file]
vendor/bin/phpcs --config-set installed_paths vendor/phpcompatibility/php-compatibility/PHPCompatibility
vendor/bin/phpcs -p [folder_to_scan] --standard=PHPCompatibility --extensions=[extensions_to_check] --runtime-set testVersion [PHP-Version_to_check]

To check all your modules for compatibility for PHP8.0 and save the log to the file "compatibility_php80.txt", the last line could look something like that:
vendor/bin/phpcs -p web/modules --standard=PHPCompatibility --extensions=module/php,inc/php,install/php,php/php --runtime-set testVersion 8.0 --report-full=compatibility_php80.txt

You can find a quite similar approach on the drupal handbook page "Drupal - PHP version compatibility check"


Is an integral in the complex plane an integral over a single number?

Question: A recent question from Juan Saloman reminded me of something that has nagged me for years, and I have never understood and never heard explained.  (or maybe I just don't remember, but anyway ...)  In the complex plane, can an integral of the general form $\int dz f(z)$ over the complex plane be treated as a straightforward 1-D integral if no path in the complex plane is specified?  I have been in classes where the professors seemed to do just that.  But, I mean, $z$ has two independent parts, right?  In other words, it's the complex plane, not the complex line.  I have seen these kinds of integrals before and sort learned to deal with them in a monkey-see-monkey-do fashion, but never really understood what was going on to my own satisfaction.  Thanks.
Comment: I don't understand the title.
Answer: In the complex plane $\Bbb C$ certain functions $z\mapsto f(z)$ are distinguished as being holomorphic. Any such function comes with a domain $\Omega\subset\Bbb C$, which by definition is an open and connected set.
Given such an $f$ and a curve
$$\gamma:\ [a,b]\to\Omega, \quad t\mapsto z(t)\tag{1}$$
one can consider the integral
$$\int_\gamma f(z)\ dz:=\int_a^b f\bigl(z(t)\bigr)\ z'(t)\ dt\ ,$$
whose value depends on $f$ as well as on $\gamma$.
When $f$ happens to be the derivative of some other analytic function $F:\ \Omega\to\Bbb C$, as $\ \cos\ $ is the derivative of $\ \sin$, and if $(1)$ is an arbitrary curve in $\Omega$ connecting the point $\gamma(a)=z_1\in\Omega$ with the point $\gamma(b)=z_2\in\Omega$ then
$$\int_\gamma f(z)\ dz= F(z_2)-F(z_1)\ .\tag{2}$$
In order to prove $(2)$ consider  the auxiliary function
$$\phi(t):=F\bigl(z(t)\bigr)\qquad(a\leq t\leq b)$$
and rewrite the formula  $\int_a^b \phi'(t)\ dt=\phi(b)-\phi(a)$ in terms of $f$ and $F$.
In this light the formula $\int_a^b f(x)\ dx=F(b)-F(a)$ from ordinary calculus can  be considered as the special case where $\gamma$ is the directed segment $[a,b]\subset\Bbb C$.
Comment: It should be added that, on a **simply-connected** domain, every holomorphic function has an antiderivative.
Comment: Much obliged.  Just to make sure I understand, any two paths give the same integral as long as the two paths together don't encircle any singularities.  Right?
Comment: @bob.sacamento: Yes.
Answer: You need to integrate over a curve, but if $f(z)$ has an antiderivative, it won't matter which curve you integrate over, as long as the curve is contained in an open set on which $f$ has an antiderivative. (Only the endpoints of the curve matter.)


How to delete sections of path in GIMP?

Question: I have a path in GIMP, imported from an SVG created in Inkscape. The path consists of multiple letters converted from text, so there are multiple unconnected sections of the path. I want to delete all of the letters except for one. What is the best way to do this? Thank you.
Answer: If the text is all one combined path, you can delete nodes using the Paths Tool by holding down Ctrl+Shift+click to delete them. Continue deleting until the letter is completely gone. You can also delete line segments using the same method by doing this on a line rather than a node, but the nodes will be left behind.
If the paths for each letter are separate, you can delete a path in the Paths panel. Simply select the Path in the panel by highlighting it, and hit the X at the bottom of the palette to Delete This Path.
In the long run it might be easier to just edit the SVG in Inkscape, select all the paths you don't want, delete them, then save a new SVG and import that into GIMP.  Remember that GIMP isn't a vector image editor and only has very basic vector path support.
Answer: Using the ofn-path-edit script, several ways:

#1: Make a selection (Freehand, rectangle...) around the characters you want to delete (or keep) and use the Delete Stroke/Extract strokes function.
#2: Use the Break text path apart function, that will create a new path per character (or diacritic mark). Keep the one you need.

How to delete sections of path in GIMP?


Can i use the same name for a spell in my game that already exists in another game

Question: what does trademarks and copyrights contain.
how similar can a name be to a name that already exists.
Comment: Hi user138617, this may not be the best place for this type of question. This site has mostly game developers, so it will be difficult to get answers about legal matters.
Answer: Unfortunately your question is too vague to answer in depth.  Trademarks are governed based on laws that originate from countries, so what is legal in one country may not be legal in another.  As a general rule, Trademarks cannot be copied. So if you want to name your game "Star Trek 2" for example, you will probably get a lawsuit.  If you want to name an object in your game "Shields" then you are safe, even though Star Trek uses the same name, because "Shields" is a description based name and cannot be copyrighted, for the most part. To share an example, I use a Music Creation Utility Called "FL Studios".  Before they changed their name, it used to be called "Fruity Loops".  They were sued by Kellogg's because their cereal "Fruit Loops" is trade marked, and so they had to change the name to FL Studios.
Another example would be "Levi's" and "Wrangler". Both companies produce "Jeans" and both companies can use the term "Jeans" to describe their product, because it is a descriptive term that cannot be copyrighted.  So if your spell is named "Fire Ball" or "Lightning Strike" multiple people can use it because it is description based.  But if it is a specific name and not descriptive, you could be liable for using it.
Answer: we may not be the most suitable to answer. It would be best to go to a lawyer whose specialty is copyright.
But I will try to contribute my 2 cents to the subject, remembering how little I have been taught about Legislation, and Computer Legislation at the University.
Technically the copyright falls on the name of a trademark. And for this, they must be duly registered in the patent and / or copyright office that legislates and controls in each country. One can register any name as a trademark, as long as he can demonstrate that he will make an onerous use of it.
Now, going specifically in the area of computing and software, where things are abstract, there are certain things to consider.
What one registers is the manifestation of an idea. And not the idea itself.
It is true that there are places in the world where one can patent an idea. In fact, I would almost dare say that the USA is the only one.
The USA patent and copyright and trademark system is one of the most disastrous and contrary to common sense. Examples of the ridiculous things you will find in the fight for the one who invented round edges on cell phones.
Pointing out in your case, and considering the legislative aspects of the USA, your concern is totally valid. But it is highly unlikely that a video game company will register the name of one of their spells to screw around and prevent others from using them.
Using Derrick's example, how is the company in question going to demonstrate that they were the inventors of the name for their spells? What other ways could a fireball be called? You cannot limit the action of an idea!
If you want to put a fireball spell and other games do it too, that's fine. That some company appears now pretending to prevent others from using fireballs because they already have them ... it is nonsense.
Now, if it turns out that the spell's name properly has a highly distinguishable name, and that it is fully assimilated as part of the game's name trademark, the thing may have some legal complication.
Take as a case the "Windarmium Leviosá", from the world of Harry Potter. Take this spell outside, if it can conflict. Makes the entire package "Harry Poter"! And if you try to use it somewhere else, other than "Harry Poter something" it is quite likely that you will be accused of plagiarism.
On the other hand there are expressions that are already as common and current as "focus focus", or "Abra Cadabra" which do not fit copyrights.
Mainly for 2 reasons:
1. are current expressions and that were acquired by popular use and custom.
2. The possible rights that may have been applied to it expired long ago.
One possibility you can evaluate is to consult the developers or the company, and they give you their permission. But first: consult a lawyer who works on the subject.
Comment: "Trade Dress" might be another relevant area of intellectual property law here. The Final Fantasy series has established the Fire/Fira/Firaga sequence as a signature element of their magic systems, so an argument could be made that another game using the -a/-aga suffixes is imitating these signature elements of their brand to imply a relationship with this game series or its creators, without any actual endorsement.
Comment: I don't know the expression "Trade Dress" I'm afraid to misinterpret the term, so I wouldn't know how to say something about it. On the other hand, what you say about the Final Fantasy example, I acknowledge that it could lead to some legal conflict, albeit minor (some warning or sanction). Intellectual property laws require that the act be shown it was in bad faith to act against someone. And if in truth there is no bad faith or intent to confuse, pretend to deceive, and / or impersonate or replace the original then you can use the same name or one based on / inspired by the original.
Comment: Now, following the example that he quotes from Final Fantasy, if I stole his entire spell system, their names, colors, shapes, etc. and put it in another context I am afraid that it would be evident that one has acted with ill will. It is similar to what I gave as an example of "Harry Potter". If you take "everything" as the hallmark and take it out of context for other purposes, chances are good that you're in trouble.


Converting multipatch layer into polygon layer using ArcMap

Question: I have a shapefile which reads its geometry type as "multipatch". I tried to perform the clip function using this layer and it does not work.
How can I convert this multipatch layer into a polygon shapefile?
I am using ArcMap 10.3.
Answer: If you have a 3D Analyst license, there is a tool in the 3D Analyst Toolbox called "Multipatch Footprint".  Using this tool will

Create polygon footprints representing the two-dimensional area occupied by a multipatch feature class

See tool help at Multipatch Footprint - ArcGIS Desktop Help
You can find the Multipatch Footprint tool in ArcToolbox > 3D Analyst > Conversion > From Feature Class > MultiPatch Footprint

You just point to your Multipatch file as in put and specify an output to save the polygons to.
Answer: For those who don't have 3D Analyst, here is the python code I'm using as a workaround.
<code># Initialize the variables (choose your folder and names)
out_path = arcpy.env.workspace
out_name = 'new_layer'
multipatch_layer = <insert_layer_name>

# Select all fields to be present in the output layer as well
# (except FID [created automatically] and Shape [we are constructing it])
fields = [f.name for f in arcpy.ListFields(multipatch_layer) if f.type != 'OID' and f.type != 'Geometry']

# Read the data with a search cursor
data = []
for row in arcpy.da.SearchCursor(multipatch_layer, ['SHAPE@'] + fields):
    for arr in row[0]:
        # At least one element has to be non-vertical for the results to be correct (i.e. conversion to polygon yieds a partCount > 0)
        # If all elements are vertical, arcpy somehow returns the bounding box -> don't add these elements
        if arcpy.Polygon(arr).partCount > 0:

            # Option 1: Union the multipatch with an empty polygon -> converts it to polygon
            poly = row[0].union(arcpy.Polygon(arcpy.Array(None)))

            # Option 2: Take the difference of multipatch with empty polygon -> converts it to polygon
            poly = row[0].difference(arcpy.Polygon(arcpy.Array(None)))

            data.append([poly] + list(row[1:]))
            break

# Create the output feature class (fields copied from the multipatch_layer)
arcpy.CreateFeatureclass_management(out_path, out_name, 'POLYGON', multipatch_layer)

# Insert the data into the output layer
ic = arcpy.da.InsertCursor(out_name, ['SHAPE@'] + fields)
for row in data:
    ic.insertRow(row)
del ic

</code>
Unfortunately, since there is no arcpy documentation for multipatch objects I don't know if it always works; but it did in the cases I was testing. Additionally, I have to say that I'm using ArcGIS pro 2.3 and can only hope that it works in other versions as well.


Downloading and installing programs in Ubuntu 14.04 LTS

Question: It's the first time I use Ubuntu and I don't have a clue how to download and install programs. Can anyone help?
Comment: https://help.ubuntu.com/14.04/ubuntu-help/addremove-install.html
Answer: Ubuntu has pre-installed Software center where you can download software. Otherwise you can get your program from command line with this command:
sudo apt-get install program

Answer: There are a lot of ways using which you can download programs, packages and applications in Ubuntu. Most common of them are :-

Installing Graphically

Ubuntu Software Center/Software Center (For Ubuntu 15.10 and prior versions)
Ubuntu Software/GNOME Software (For Ubuntu 16.04 and later versions)
Synaptic Package Manager
Synaptic doesn't come pre-installed in Ubuntu. So you have to install it first. You can install it either by using Ubuntu Software Center/Ubuntu Software or by typing sudo apt-get install synaptic in the terminal. Once installed, you can open it, and search for the application that you want to install, and just mark it for installation.
GDebi Package Installer
gdebi is a simple tool to install .deb files.
It lets you install local deb packages resolving and installing
its dependencies. It has a graphical user interface but can also be used in your terminal. apt does the same, but only for remote (http, ftp) located package repositories. GDebi doesn't come pre-installed in Ubuntu. So you have to install it first. You can install it either by using Ubuntu Software Center/Ubuntu Software or by typing sudo apt-get install gdebi in the terminal.
NOTE: Manually downloaded .deb file can also be installed by opening it in the Ubuntu Software Center/Ubuntu Software by double-clicking it and then installing it from the Ubuntu Software Center/Ubuntu Software !

Installing via Terminal

Using APT(Advanced Packaging Tool)
(i) Open Terminal by typing Ctrl+Alt+T or by going in your Dashboard and searching for Terminal.
(ii) Then type the following command in it :- sudo apt-get install package (Replace "package" with the name of the package in the given command.
(iii) Sometimes you have to add repositories or PPAs before installing packages. You can do so by typing the commands given below in the terminal :-
sudo add-apt-repository repository_name
sudo apt-get update
sudo apt-get install application_name
Replace repository_name and application_name with the name of repository and application respectively.
Manually downloaded .deb file can also be installed using Terminal. Press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, type the following commands in it :-
sudo dpkg -i /path/to/deb/file
sudo apt-get install -f
You can also install applications from .tar.gz or .tar.bz2 files by taking a look at one of the links given below :-
(i) How do I install a .tar.gz (or .tar.bz2) file?
(ii) http://www.howtogeek.com/105413/how-to-compile-and-install-from-source-on-ubuntu/


Getting differences between WVGA800 and WVGA854 in Android Emulator

Question: So far I just have one XML layout file, and one drawable directory, drawable-hdpi.
I first want to target the high density screens.
I added a bunch of imagebuttons to a relativelayout and everything looks perfect in the WVGA800 emulator. The problem arises when I view it in the WVGA854 emulator. Not only do the imagebuttons not position the same, but the images are blurry. I used dip for the layout margins on the imagebuttons even though it shouldn't matter in this case because WVGA800 and 854 are both high density. What is the problem? Why would it look totally different on emulators that have the same density and almost have the same exact screen dimensions?
Thanks!
Comment: That sounds odd. Screenshots / XML might help.
Answer: For some reason, closing/restarting Eclipse and the Emulator worked. Sorry for the stupid question.


Difference between "delete" and "remove"

Question: I am writing a mobile application that will, as a part of its functionality, display a list of recorded thoughts. Now I am deciding the textual content of the menus and that left me thinking whether there is a logical difference between words remove and delete. Which one is more appropriate when speaking about taking an item off the list? I guess remove is, but why?
Comment: General reference works are often poor at helping readers distinguish between fine shades of meaning. In addition, the number of upvotes indicates that this question holds clear value for the community. It should be reopened.
Answer: Delete and remove are defined quite similarly, but the main difference between them is that delete means erase (i.e. rendered nonexistent or nonrecoverable), while remove connotes take away and set aside (but kept in existence).
In your example, if the item is existent after the removal, just say remove, but if it ceases to exist, say delete.
As a side note: delete is sometimes used of computer files to mean move to trash/recycle bin (hence it is still recoverable), but that's not a standard meaning outside of that context.
Comment: I use the excellent [foobar2000](http://www.foobar2000.org/download) to look after my pc-based music library. Mostly because of its almost limitless configurability, but a major pluspoint is Foobar lets me have lots of customised "playlists". Any given track only "physically?" exists in one location on my hard drives, but it may appear in several playlists. Foobar has a "File operations" submenu where you can "really, permanently" **Delete** a track, but if you change your mind about having it in a particular playlist, that option is called **Remove**. That makes a lot of sense to me.
Comment: Thank you. Since I am removing item for good, I am going to use delete as a menu item word.
Comment: I had it kind of backwards considering that in computing, there is a notion of *undelete*
 but no *unremove*, i.e. **deletion** *can be undone* but **removal** *cannot*. To me, *remove* meant to *physically* move sth. away from access (make it eventually inaccessible) and *delete* would mean to make sth.logically inaccessible. OTOH, removing could be undone, like removing a plate from a table. Guess it's ambiguous like *synchronous* (1. concurrent or 2. serial execution, respectively) & *asynchronous* in computing ? Synchronous: 1) at the same time, in parallel; 2) synchronized, serialized.
Comment: The first sentence of this post is essentially identical to the one at https://www.labor.ny.gov/ux/design-remove-vs-delete.html. I trust you have authored the text at ny.gov, and that it isn't a case of plagiarism?
Comment: I think the "delete" operation of modern OSes is a historical reason before the "trash" thing. i.e MS-DOS didn't have this 2-step" remove->deletion of files. it was only delete from the FAT, but it was possibly undelete because the raw data on the disk were not already overwritten (it's still true today with modern OSes).
In modern OSes now is just a 2-phase "delete", 1.remove (move to trash/ prepare for deletion); 2. physically delete from the file system. It's still valid the undelete operation until the physical sector of disk are not overwritten.
Answer: They are very similar, but the way I would make the distinction here is based on what the action does, and on the item being removed/deleted from the list.
If the item will continue to exist outside the list, I would recommend "remove", as it is being removed from the list, but the item itself is not deleted.
If the item will no longer exist, then "remove" and "delete" are essentially equivalent, although "delete" may be a bit clearer, since the user is deleting the item.
Answer: You can remove something from a collection (eg a file from a project, a folder from a library) without deleting it. If the item in question has no life outside your collection (eg a paragraph from a word document) then there's no difference between remove and delete. But if it has such a life (eg an image file in an HTML page) then remove and delete could be different. Delete is stronger - not only stop including it in my collection to it, linking to it, whatever, but also delete it from wherever it lives.
Comment: +1 Just what I was getting at, but better said.


Can I use walletnotify or blocknotify remotely with a NodeJS application?

Question: I'd like to get information from my bitcoin node running on a cloud server to be used to make changes in my NodeJS app running on my computer. So, in the bitcoin.conf file, should I have something like walletnotify=curl http://My.IP.Address:PortAppUses/walletnotify.js?tx=%s? If that's right, what do I write in the walletnotify.js file to simply save the incoming transaction id as a variable?
Answer: In your example you are telling it to place the transaction id as a GET request in the URI under the tx parameter.
walletnotify=curl http://My.IP.Address:PortAppUses/walletnotify.js?tx=%s

All you would need to do inside of walletnotify.js is pull the tx GET, in nodejs express that would be something like:
const express = require("express");
const app = express();
const request = require("request");

app.get("/", function(req, res){

    let transactionId = req.query.tx;

    //do whatever with transactionId

});

Comment: I already got it, but I appreciate it! Love your YouTube, by the way!


Is there an efficient way to manage references in answers?

Question: I just re-read this answer of mine and noticed I'd made some claims without proper references. I will edit this if I find time, but it will require a bit (not that much of course) of work because I wrote all references as plain text. Is there a way to make references enumerate themselves automatically here as in LaTeX?
Comment: What did you try? (works even on meta, wow)
Comment: @draks I'm sure what I could try. All I did was search meta for "references" and "bibliography", finding nothing relevant. And what works even on meta?
Comment: The WDYT-question! :-)
Comment: @draks Ah, OK. I don't know whether it works or not.
Comment: Me neither, sorry...
Answer: Short answer: not something built-in.
Longer answer: for a work around, you can use-and-abuse the hyperlink function of the MarkDown syntax. In particular, instead of
<code>[Displayed Text](Hyper link address)
</code>
you can use
<code>[Displayed Text][linkname]
</code>
(note the square brackets!) with linkname defined at the end of the post
<code>[linkname]: hyperlink address
</code>
So for your references 1 and 2 in your post, I would write, for example (using the AMS style Author-Year labels)
<code>See references [GI84] and [GI84a]. Yada yada.
This other thing is also proven in [GI84a].
</code>
(when the link name is the same as the displayed text, you can omit one set of the brackets) and link to the mathscinet portal
<code>[GI84]: http://www.ams.org/mathscinet-getitem?mr=729648
[GI84a]: http://www.ams.org/mathscinet-getitem?mr=729652
</code>
Here's what the above snips would look like:

See references GI84 and GI84a. Yada yada. This other thing is also proven in GI84a.
Comment: Very nice, thank you!


Lightweight tool to create video montages?

Question: Do you know a tool to create video collages? I made the one below with After Effects, but I'm looking for something lightweight.
https://twitter.com/Szili/status/839510854496370688
Answer: You can do lots of effects like that with MoviePy which has the following prerequisites:

Python Obviously
Numpy, imageio, Decorator, tqdm and FFMPEG (All automatically installed)
Imagemagick Optional
PyGame - For previews
PIL or Pillow Advanced Use
Scipy Advanced Use
Scikit Image Advanced Use
OpenCV >= 2.4.6 Advanced Use

You can inset one or more videos on top of another as shown here.
You can join movies together on the screen in an uneven manner using masks.
Even place different movies in various shapes

You can even use it, with video grep, to select clips based on the subtitles and paste them together.
All of the software mentioned above is:

Free, Gratis & Open Source
Cross Platform Win/OS-X/Linux
Small and compact, (by modern standards).

Download of the Python installer is ~30 MB,
FFMPEG < 50 MB,
OpenCV (if required) is quite large at 120 MB,
SciPy+Numpy is about 62 MB,
imagemagick about 20 MB and those are the biggest downloads.


Why does bash print the debug trap after edit-and-execute-command

Question: I've found a behavior in bash (or is it readline?) that I cannot explain. After invoking the edit-and-execute-command Readline command, the debug trap's command is printed prior to execution. Is this a bug?
Here's how to reproduce the issue with a default bash install (no dotfiles besides those in /etc, and it happens on Linux and macOS with all the versionf of bash I could find):
bash-5.0$ trap date DEBUG
bash-5.0$ echo hi
Fri May  1 23:07:38 PDT 2020
hi
bash-5.0$ echo hi

At this point, type Control-X Control-E. The editor opens. Exit the editor. This is what you see next:
echo hi
date
Fri May  1 23:07:47 PDT 2020
hi
bash-5.0$ echo hi

My question is if there's any good reason for the shell to print date after exiting the editor.
The reason this is a problem for me is that I use the debug trap to run a command after the user enters a command but before it runs for iTerm2's shell integration using https://github.com/rcaloras/bash-preexec. AFAIK there is no other way to do this in bash (though I'm open to alternatives!)
For context, it originally came up here: https://gitlab.com/gnachman/iterm2/-/issues/8808#note_331367916
Answer: I got lucky and found an almost satisfying answer in the bash source code. It's detailed here: https://gitlab.com/gnachman/iterm2/-/issues/8808#note_335276685


How to import users from a different domain in User Profile service application?

Question: The sharepoint server is setup in the public domain and all service accounts used for installation and configuration are based off of the same(public)domain as well. The server is meant to host the extranet and hence I need the user profiles from the local domain as well. I used the publicDomain\spfarm to obtain all user profiles from the public domain.
Now how would I go about doing the same for the  users from the local domain? What account would I need to use?Do I need to create a new one?
Please note that there is a two way trust between the domains.
Thanks
Answer: If there is a two way trust in place, simply map a connection to that second domain into UPS. In the scenario where there is a two way trust, you don't have to do anything special, simply tell UPS to also synchronize against that second domain. I did have one client that had a two way trust in place, but there was some issue with the Replicating Director Changes role where one of the domains wasn't honoring the trust that our sync account should have that role, and we had to manually grant Replicating Directory Changes on the other domain as well. That said, it was an environment that had many AD issues, that's not a normal requirement. If your sync account has Replicating Directory Changes on one domain, and there's a full trust in place, it should honor it. Note that if you want extranet users to see only extranet profiles then you will want to create a second UPS Service Application that's restricted to only the extranet web application so you can isolate them.
As you have a two way trust, you won't need to do anything special for the people picker either. I'll offer this (Microsoft document) only for future reference. If you have a situation where there's a one way trust, you have to configure the people picker with an account that has the necessary query permissions on that other domain in order for the people picker to be able to search and return users in that domain. Again, only applicable in a one way trust scenario. I also have a blog post that covers some similar people picker issues.
Comment: Thanks for the input. I ran the sync using my publicDomain\spfarm account that does have replicate directory changes but when I go back in and check (post sync) by entering my Company.local domain It does not return all user profiles and i also did get a lot of "no start credentials" (and an equal amount of succeeds) error while monitoring it on Synchronization service manager. I have appended a picture to my original Question for reference. It would be really heloful if you can suggest me an alternative. Thanks again
Comment: Are they two separate synchronization connections, or somehow combined into a single one? Typically you'd just select the applicable OU(s) from each domain, as opposed to syncing the entire thing.
Comment: It is one User Profile Service App with two connections. One to sync user profiles from the local domain and the other to pull user profiles from the public domain.


Difference between slow system calls and fast system calls

Question: What's the difference between slow system calls and fast system calls? I have learned that slow system call can block if the process catches some signals, because the caught signals may wake up the blocked system call, but I can't exactly understand this mechanism. Any examples would be appreciated.
Answer: There are in fact three gradations in system calls.

Some system calls return immediately. "Immediately" means that the only thing they need is a little processor time. There's no hard limit to how long they can take (except in real-time systems), but these calls return as soon as they've been scheduled for long enough.
These calls are usually called non-blocking. Examples of non-blocking calls are calls that just read a bit of system state, or make a simple change to system state, such as getpid, gettimeofday, getuid or setuid. Some system calls can be blocking or non-blocking depending on the circumstances; for example read never blocks if the file is a pipe or other type that supports non-blocking reads and the O_NONBLOCK flag is set.
A few system calls can take a while to complete, but not forever. A typical example is sleep.
Some system calls will not return until some external event happens. These calls are said to be blocking. For example, read called on a blocking file descriptor is blocking, and so is wait.

The distinction between "fast" and "slow" system calls is close to non-blocking vs. blocking, but this time from the point of view of the kernel implementer. A fast syscall is one that is known to be able to complete without blocking or waiting. When the kernel encounters a fast syscall, it knows it can execute the syscall immediately and keep the same process scheduled. (In some operating systems with non-preemptive multitasking, fast syscalls may be non-preemptive; this is not the case in normal unix systems.) On the other hand, a slow syscall potentially requires waiting for another task to complete, so the kernel must prepare to pause the calling process and run another task.
Some cases are a bit of a gray area. For example a disk read (read from a regular file) is normally considered non-blocking, because it's not waiting for another process; it's only waiting for the disk, which normally takes only a little time to answer, but won't take forever (so that's case 2 above). But from the kernel's perspective, the process has to wait for the disk driver to complete, so it's definitely a slow syscall.
Comment: thanks a great! but if the file is a pipe, is reading file non-blocking? see that http://www2.hawaii.edu/~esb/2007spring.ics612/apr10.html
Comment: it denotes "slow reads/writes (e.g. on a pipe or a terminal) "
Comment: @KayKay: For a pipe, you can have both, depending on the state of the `O_NONBLOCK` flag. If the flag is set, the syscall can complete without waiting on anything else, so it's non-blocking, and the kernel can treat it as a fast syscall.
Comment: you mean it depends on O_NONBLOCK flag!
Answer: A slow system call is something like a TCP socket read() - if you don't have O_ASYNC (or whatever) set, it can wait for ever.
A fast system call is something like gettimeofday() or getpid(), both of which return information to the process that the kernel has immediately available.
Disk reads fall in the category of slow system calls.  If a process does a read() on a true disk file, file descriptor, the kernel may have to read in one or more disk blocks to satisfy the read.  Depending on the underlying file system's on-disk structure, this may mean reading the on-disk-inode to get the disk block number of an "indirect block", reading the indirect block to get the data block and then reading the data block itself. Quite time consuming, at least in terms of CPU cycles per disk access, probably worse today than it was in the Good Old Days.
I haven't seen this in ages, but the "bottom half" of old Unix disk drive device driver code would block signals/interrupts so that it was easier to maintain on-disk filesystem integrity.  Occasionally, a buggy driver or failing disk would never deliver the disk block a process had asked for, and the process slept forever. Even a kill -9 did nothing to it.


how this Grant Access Using Hierarchies works?

Question: How this Grant Access Using Hierarchies works. Please explain I am getting confused. Please explain me how this Grant Access Using Hierarchies works in OWD setting, groups etc. Does its use changes at different places. Please explain when record is access to Hierarchies users and when it restricted, when object is made private.
Answer: When Grant Access using Hierarchy is checked for custom object(For standard objects this is always checked) even if the record is private ,users higher in the role than the owner of the record still gets access to the records .
A simple example can be assume opportunity is private OWD and you are Sales Rep owning an opportunity record ,you have your manager who is higher in the role hierarchy than you ,even though opportunity is private he will still get access to your records .
Technically a for every user who has access there will be a share record in the Share table of the Object.
Comment: I am getting confused with this statement when compare with yours. " if the Grant Access Using Hierarchies option is disabled for a custom object, only the record owner and users granted access by the organization-wide defaults receive access to the object's records." this in from role doc by salesforce : https://help.salesforce.com/HTViewHelpDoc?id=admin_roles.htm&language=en_US can you please check this.
Comment: Ok so that statement means if grant access using hierarchy is not checked users will have access only if there is a sharing rule providing access to other users .Hope thats clear


Could I 3D print an airbrush?

Question: Could I 3D model and print a working airbrush in
PLA?
Comment: Im not sure but there might be a .STL for one of those hand  airbrushes, where you blow into it with a paint bowl on to wich pushes out the paint. Not sure if this would be an ideal solution but its an option.
Comment: Dear Dylan Rollins Garfield, welcome to our 3D Printing SE site. Please be so kind to review our tour to make sure that your questions willl lead to answers that are beneficial for a wider group of people. What are your idead and where are your problems? From there we can take it to a fruitful discussion https://3dprinting.stackexchange.com/tour
Answer: The problem with this I see is that the PLA takes and holds paint super well. I have painted it with acrylic a lot and it works great for models you want painted after printing.
I know next to nothing about airbrushing, but it seems to me like keeping a printed airbrush clean for re-use would be a big pain. It looks like they make the pro airbrushes with some kind of stainless steel most likely for the non-sticking purposes of re-use, which PLA just won't have.
That being said, don't be afraid to model it and try! I would make a suggestion that you switch to ABS and then do a vapor bath on the result to smooth out the material and possibly make it easier to clean excess paint out of.

Could I 3D print an airbrush?


Can a wife force her husband to have sex in islam?

Question: Is it allowed for a woman to force her husband to have sex with her in islam?
Answer: Allah said (Translation):

And women shall have rights similar to the rights against them,
according to what is equitable, but men have a degree (of advantage) over them.

Accordingly, fulfilling the need of each other is required and it is one of the purposes of marriage in Islam.
Yet, no one can force the other, especially if they are ill or unable to do it (e.g. the wife during the period).
Allah said (Translation):

On the contrary live with them on a footing of kindness and equity

Nevertheless, there is an authentic hadith that if the wife does not obey her husband in bed in doing what is Halal, without any reasonable cause, such as being sick or something like the period...etc, she will be cursed by angels.
Although I don't know a similar rule if it is vice versa, a woman can ask for a divorce if the husband is sexually faulty/blameworthy, if she wills.


Can you grow mushrooms from other mushrooms?

Question: I saw a video of someone growing mushrooms from burying another mushroom in dirt. However, most other videos show only show that you can grow mushrooms from spawn or spores from a company. Can you actually just bury a mushroom and grow your own? If not is there any way to pull the spore yourself and grow mushrooms? I want to grow mushrooms year after year without buying new spawn every time it runs out.
Comment: Heh heh. I'm flashing on the Leslie Nielson character in "Men With Brooms." https://www.imdb.com/title/tt0263734/
Answer: Depending on what you mean by "mushroom", some are not difficult to propagate , many are difficult to propagate. They have specific environmental needs . I have started cominus comatus -shaggy manes -a few places ; they are tolerant of location. I have just tossed the mature mushrooms onto lawns. I have read that shitake grow fairly well on oak wood ( cut branches and trunks). The common ( in US grocery stores) agaricus compestry is grown on artificial manure in caves or dark warehouses.
Comment: So you don't actually need spawn?
Comment: The mushroom itself is the "fruiting body" , it contains spoors that ,under the right conditions ,grow and produce mushrooms.
Answer: In fact you only need to buy mushroom culture once. Then you have so many options to multiply your mycelium and save this culture for years!
If you have:

Mushroom Spores -> you can make unlimited liquid culture (it can be stored for 6-12 month)
Liquid Culture (LC) in syringe or Spore syringe -> you can prepare sterile liquid medium and share 1 syringe among 3-5 jars 300-500ml each, so that you'll get minimum 1 Quart of LC. LC can be stored 6-12 month.
Spawn -> you can make Grain to Grain transfer (G2G) and create more spawn jars/bags. Usually 1 spawn jar/bag turn into 5-10 spawn jars/bags. Spawn can be stored for 3-4 month.
You can gather spores from mushrooms and make a spore print (for basidiomycetes) and store them up to 5 years !
Working with sterile agar media in Petri dishes:

spores on agar
spawn samples on agar
mycelium on agar to agar (A2A transfer)
cloning (you've asked about) placing a piece of mushroom tissue on agar medium in order to obtain growing mycelium. This is not strictly related to the colloquial notion of cloning, and is simply a manipulation of the natural asexual reproduction system of fungi.
Mycelium on agar can be stored in refrigerator ~12 month and even longer.

Then you can use mycelium for mushroom growing any time, any season!
Unfortunately, such method as 'growing mushrooms from burying another mushroom in dirt' usually don't work due to high risks of contamination (bacteria and molds) or work with extremely resistant species. However burying mycelium (or even wasted mushroom blocks) works much better;)
Actually a lot of nuances depend on the mushroom species and cultivation tek, but basic principles are the same :)
Cheers,
Shroomok


Thus vs thusly for mathematicians

Question: My expertise is in math & science, not grammar.  For mathematicians, 'thus' is generally seen as a synonym for 'therefore'.  If I were to write, "The equation should be written thus:", most would tend to interpret this as "The equation should be written therefore:". On the other hand, if I were to write, "The equation should be written thusly:", this would be interpreted as "The equation should be written as follows:".  In this case, is 'thus' still considered preferable to 'thusly'?  This is now just a matter of curiosity since I think I've already decided to replace 'thusly' with 'as follows'.
Comment: Possible duplicate of ["Thus" vs. "Thusly"](http://english.stackexchange.com/questions/91269/thus-vs-thusly) Also [Shall I use 'thus' or 'thusly'?](http://english.stackexchange.com/questions/152342/)
Comment: Use of *thusly* is a blasphemy against the Holy Spirit which will earn the sinner an eternity proofreading MBA theses.
Comment: Actually, both terms are a bit archaic, but *thusly* more than *thus*.
Answer:
thus
  adverb  literary or formal

As a result or consequence of this; therefore:
'Burke knocked out Byrne, thus becoming champion'
  Synonyms: consequently, as a consequence, in consequence, thereby, so, that being so, therefore, ergo, accordingly, hence, as a result, for that reason, ipso facto, because of that, on that account
In the manner now being indicated or exemplified; in this way:
'she phoned Susan, and while she was thus engaged, Charles summoned the doctor'
  Synonyms: like that, in that way, so, like so
[as submodifier] To this point; so:
'the website has been cracked three times thus far'
  Synonyms: so far, until now, up until now, up to now, up to this point, hitherto

thusly
  adverb  informal

Another term for thus (sense 2).
'the review was conducted thusly'

The definitions quoted above indicate that:

thusly is a synoym of only one meaning/usage of the word thus, namely the meaning "In the manner now being indicated or exemplified; in this way" (sense 2).  This would seem to equate to your desired meaning of "as follows".
thusly is not a synoym of thus when used to mean "therefore" (sense 1).

So, yes, you could use thusly to mean "as follows", but — as you suggest — in your particular situation, it is probably better to use an alternative expression.
Personally, I would say that thusly is obscure and rarely used (at least in British English) these days.
Answer: "thus" has various meanings, one of which is synonymous with "therefore", and another meaning "like this" or "in this way".
http://www.thefreedictionary.com/thus

In this manner: Lay the pieces out thus. See Usage Note at thusly.
To a stated degree or extent; so.
Therefore; consequently: Thus it was necessary for me to resign.
For example: Few of the nation's largest cities are state capitals; thus neither New York nor Chicago is the seat of its state's government.

"The equation should be written thus" is an example of the "in this way" meaning, not "therefore", and we can see this in your example sentence, which is plainly wrong:  we would not write "The equation should be written therefore:"
thusly is a colloquial usage of "thus" without any additional meaning, and should be avoided unless you deliberately want it to look like it was written hundreds of years ago.
EDIT:  with reference to your last point, about using "as follows" instead of "thus":  Personally I think that "as follows" is clearer.
Answer: From looking at the Oxford English Dictionary entries for "thus" and "thusly"—which are behind a paywall, as is the entire online OED—I can tell you the following. The first documented usage of "thusly" occurs in 1865 in the New York-based Harper's Magazine. "Thusly", like "thus", is an adverb, and a synonym for one of the older documented usages of "thus", "In this way, like this," but not for "In accordance with this; accordingly, and so; consequently; therefore."
So, while you're correct in saying that "thusly" isn't synonymous with "therefore," "thus" already can mean "In the following manner; as follows; in these words." Moreover, since "thusly" was first constructed by adding the adverbial "-ly" suffix to "thus," this, I want to speculate, probably happened as a form of hypercorrection, as a way of making the adverb "thus" appear even more like an adverb. So stay away from "thusly," not because it's too florid or non-standard, but because compared to "thus" it's grammatically redundant.
Comment: The other answers here indicate that *thus* and *thusly* do **not** "both mean the same thing" in all cases; although they do have the meaning
"as follows" or "in this way" in common.
Comment: Thanks, it seems you're right. I've rewritten my entire answer to make that clear.

Thus vs thusly for mathematicians


Pseudotensors for describing physical quantities

Question: I have been reading about tensors from Mathematical methods for Physics and Engineering, by K.F. Riley, M.P. Hobson and S.J. Bence.
And there are a couple of things i am not getting. On page 949 (section 26.10, chapter 26), its stated
 "Vectors can be divided into two categories: polar vectors(position, velocity), which reverse direction under an active inversion of physical system through the origin, and axial vectors(such as angular momentum), which remain unchanged. It should be emphasized that at no point in this discussion have we used the concept of a pseudovector to describe a real physical quantity."
Now, according to pseudovectors pseudovectors and axial vectors are equivalent terms. So, i am pretty confused to the statement made in the book.
Also, in the next section (page 949, section 26.11), its stated that
"Although pseudotensors are not themselves appropriate for the description of physical phenomenon, they are sometimes needed"
But Magnetic field is a pseudotensor. I am relatively new to these topics. So can someone clear it up for me?
Here is a link to the statements from the book(page 798 in this link) :Riley Hobson
Answer: The claim you quote is utter nonsense.
Pseudotensors (in the sense of quantities that do not change sign under reflection like ordinary tensors of the same rank, not in the sense of the pseudotensors in General Relativity) are perfectly appropriate for the description of physical phenomena. Some quantities genuinely are pseudotensors, such as e.g. angular momentum and the magnetic field, see also this answer of mine for a general explanation of pseudotensors and this answer for a closer look on angular momentum and magnetic fields.
Comment: Riley Hobson is often regarded as a standard textbook for mathematical physics so i never thought a claim made in the book will be utter nonsense.
Comment: @HarshdeepSingh I second his comment. That claim does not make much sense --pseudotensors are quite useful when it comes to describing many types of physical phenomena.


What's the simplest way to implement multisig ownership in Solidity?

Question: I have a list of owners in a smart contract and would like to require a minimum number of their approvals in order to execute some administrative functions. What's the simplest way to implement it? I am between using Gnosis Safe + Ownable but I would rather find a simpler and cheaper (in terms of gas costs) solution (preferable already audited). Do you know of any examples? Thanks!
Answer: For the problem given, a simple governance contract would be the best, where there should be a function to propose (only by owners), vote (only by owners), and execute/cancel (only by owners).
Execution of proposal itself should be very simple, checking if proposal is already executed, and execution of submitted target, value, method signature, and calldata.
For reference check:

Hord protocol implementation of a simple multisig: HordCongress.sol contract https://github.com/hord/smart-contracts/blob/master/contracts/governance/HordCongress.sol

Compound protocol implementation of governance contract: GovernorAlpha.sol contract https://github.com/compound-finance/compound-protocol/blob/master/contracts/Governance/GovernorAlpha.sol
Comment: First link returns 404?
Answer:
Gnosis Safe + Ownable

This is the easiest and most robust way. The fees on Gnosis Safe 2.0 are not that massive, as you pay only once at the transaction execution.
Gas fees as what they are and they are outside of your control.
Comment: Thanks! Could you link a simple example of this implementation?
Comment: https://github.com/dawn-Protocol/dawn-erc20-erc777
Comment: I see it uses Ownable and that the owner can be a multisig, but coudln't find where it is actually deploying the multisig or any examples of that. Do you know if I can use GnosisSafe without their UI and in Ropsten? And if there is any documentation of a simple example of how to use it, sign messages, etc? Thanks!
Comment: You can deploy a new contract from Gnosis Safe UI itself. If not then you deploy the contract by hand or in a test suite as well. They might not support Ropsten, but they supported some test networks in the past.
Comment: Using the Gnosis Safe is so simple that it does not need documentation.


Is it possible to write a story where every character has the same name?

Question: I know this is probably going to get me a down vote, but I've had this idea for a while. I wanted to know if it would work or if it would be an awful failure. Every character is the same person from alternate universes; they are brought together to fight some unknown evil. I'm currently working on other things, so I haven't had much time to think about a plot.
Comment: At least one such novel exists: https://en.wikipedia.org/wiki/Yawning_Heights - in Russian, translated to several laguages. A satire on socialistic USSR. Every character there has the name Iban Ibanovich Ibanov and they are distinguished for reader only by nicknames, occupations etc.
Comment: It has already been done, at least in film.
Comment: Technically, all stories with only one character also satisfy the criterion :P -- It's a bit easier in film and comics, because alternate-universe versions can at least be visually distinct. But if you can't/don't distinguish the different copies then it's really just one character.
Comment: thats what i figured the answer would be.
Comment: David Gerrold did something similar with *The Man Who Folded HImself* but his was time travel.
Comment: I remember seeing an example or responding to something involving with that title.
Comment: Don't do this. Just don't.
Answer: It's certainly possible! In visual media (films, TV, comics) this is made significantly easier than text as you can have visual differentiators to help the audience keep track.
Regardless of your intended medium you're going to have to work out a streamlined way of keeping the different versions distinct that the characters can use to refer to each other - having half the room turn around when someone says the character's name is great for an occasional comedic moment but it's going to get really tedious really fast if it's happening all the time. Ideally you'll want your "naming convention" to be no more cumbersome than referring to someone by an name - a good example of this is in Rick & Morty where the various dimension's Ricks and Mortys are referred to by a short code representing their origin universe e.g. "Rick C137", "Rick J22", or by a short descriptor (usually to tie in to the appearance of the character) e.g. "Cool Rick", "Lizard Morty" etc. This helps keep dialog from being bogged down by delineations between the different versions while keeping it clear to whom the characters are referring.
The best bit is because this is going to be a "problem" that needs solving in the story as well as out of it you can make coming up with the naming convention part of the story:

Steve:  Hey Steve!
[CHORUS] "Yeah?"
Steve: Oh man, this is going to get real confusing, real quick! Ok - you're "Big Steve", you're "Little Steve", and you're "Scar Steve"
Little Steve: Hey! Why am I "Little Steve"?!
Big Steve: Are you calling me fat?
Answer: We get a lot of these "is it possible to write a story where ..." questions. I can't imagine someone seriously saying, "No, that's impossible". Like, what, you're going to be arrested by the Novel Police?
The serious question is, How do you make it work?
There's the rather obvious problem that the reader won't know who is doing what. If you just say, "Then Bob said ... and Bob replied ... Bob ran out of the room, leaving Bob alone" etc., the story is going to be very confusing. There might be times when such confusion is the point of the story. Like, "Nancy was sitting alone when Bob walked into the room ...", and she has no way to know which Bob, maybe she doesn't even know that there are multiple Bobs. But if there are multiple Bobs in a room talking, presumably they know which of them it is who is speaking or doing whatever at any moment.
I think it likely you would have to distinguish them. Maybe that just means saying "Bob #1", "Bob #2", etc. Or "Short Bob" and "Tall Bob" and "Red-haired Bob" etc.
I've read time travel stories where a person goes back in time and meets himself. Usually the writers solution is to just call them "Old Bob" and "Young Bob" or some such. Similarly for parallel dimensions stories.
Comment: I think I wrote it the way I did to make me feel like I can really start working on that and feel confident I can do it.
Answer:
Novelty is not a reason to justify bad design.

-Mark Rosewater, head designer of Magic: the Gathering

Just because you can do something doesn't mean you should.
It is possible to write a good and/or successful novel using anything as a premise.  But some restrictions make such an endeavor significantly harder than others.  This is one of them.  And writing a good novel is hard enough to start with - you don't need to make it harder on yourself.
The only reason for giving all your characters the same name that I would consider valid is if you absolutely cannot tell the story you want to tell without it - that it is so integral to the story's premise that without it you have a different story.  If that's the case then go for it - but novelty for novelty's sake is paid at the expense of quality.
Comment: +10 for the lead-in quote. I've read many posts on writers' forums where someone talks about doing something weird just for the sake of doing something weird. Like, "Wouldn't it be cool to write a story where the hero's shoe size keeps turning out to be important" or "Wouldn't it be cool to write a story where every sentence is exactly 10 words long". Such gimmicks are no doubt challenging to write and therefore fun, but they rarely make good stories. Note not to be confused with, I am trying to achieve this interesting result, and oh, I could accomplish that by doing this weird thing.
Comment: Or as a writing exercise.  That is also a good reason to justify random writing restrictions.
Comment: I feel this is the best way to tell the story for reasons relating to something I will not explain here, but I know it'll be a challenge. If I really want to make a sure path for a writing career, then I feel I need a challenge. Also, I will have few characters with different names.
Comment: @Jay it's a good quote. Novelty isn't bad it is just frequently used to justify decisions which would otherwise be obviously terrible
Comment: @ArcanistLupus Like many things in writing, when someone asks "could I write a good story that does X", that answer is routinely, "Sure ... if you do it well." Almost anything you try to do in a story can be done well or can be done poorly. If you try to do something unusual just for the sake of doing something unusual, you are probably making things more difficult for yourself. There's usually a reason why most writers don't do that. If it was easy to make it work, lots of writers would do it.
Answer: A very interesting concept. How about this: you number them. You have Bob 1, Bob 2, Bob 3, and so forth. Bob 1 is the main character, or the first one introduced, and every time you add another Bob, you add another number.
If you don't want to do it like that, you can give each alternate universe a number (how you would do that is beyond me). Bob 872 comes from Universe 872, Bob 245 comes from Universe 245, and so forth.
If you don't number them, it will be exceedingly tricky for your reader to keep track of who's who--unless you don't care, and all actions are done by a collective group of Bobs. In that case, numbers and personal identification don't matter, and you can blur them all together.


what are the proof-theoretic ordinals of second-order arithmetic and ZFC?

Question: are they still smaller than omega-1-CK?what are the notations of them?
Answer: The proof-theoretic ordinal of any theory is less than $\omega_1^{CK}$.  No notations are known for second-order arithmetic, let alone ZFC.
Comment: Henry, could you elaborate with further explanation of your first sentence? For example, what exactly would it mean to have the proof-theoretic ordinal of ZFC? (And by the way, thanks again for your talk at CUNY last week.)
Comment: Is the notion of $\omega_1^{CK}$ absolute? I mean, it's a fairly small ordinal (as countable ordinals go), so certainly it is less than the least height of a transitive model of $\sf ZFC$. But given two transitive models of $\sf ZFC$ (regardless to their size), do they have to agree [with $V$] on $\omega_1^{CK}$? (@Joel, you might know the answer to that as well, so I'm pinging you too.)
Comment: For transitive models, yes, it is absolute, since transitive models have all the same TM programs and they agree on whether a given relation on the natural numbers is well-founded or not. Meanwhile, there are models of ZFC with the same $\mathbb{N}$ that disagree on $\omega_1^{CK}$; this is proved in my recent paper http://jdh.hamkins.org/satisfaction-is-not-absolute/.
Comment: @JoelDavidHamkins: The proof-theoretic ordinal of a theory T is usually defined to be the smallest ordinal $\alpha$ such that there is no computable (equivalently: primitive recursive) representation of $\alpha$ as an ordering of $\mathbb{N}$ such that T proves the well-foundedness of this ordering.  Such an ordinal exists and is less than $\omega_1^{CK}$ because $\omega_1^{CK}$ is, by definition, larger than any ordinal with a computable representation.
Comment: Roughly what I was saying at the start of that talk was that usually when we talk about a proof-theoretic ordinal, we expect it to have various other properties as well, and sometimes people take one of those to be the definition.  But for ZFC (as a "reasonable" theory), they're probably equivalent anyway.


What does it mean that stepwise, backward and forward selection methods are "path dependent"?

Question: In many papers I read that stepwise, backward and forward selection methods are "path dependent". What does it mean? Could anyone give me some practical example to understand the underlying concept? It is related to the fact that these methods are local search techniques?
Answer: Forward stepwise selection begins with a model containing no predictors, and then adds predictors to the model, one-at-a-time, until all of the predictors are in the model.
In particular, at each step the variable that gives the greatest additional improvement to the fit is added to the model.
In detail:

Let $\mathcal{M}_0$ denote the null model, which contains no predictors.
For $k = 0, \dots, p - 1:$ Consider all $p - k$ models that augment the predictors in $\mathcal{M}_k$ with one additional predictor. Choose the best among these $p - k$ models, and call it $\mathcal{M}_{k + 1}$. Here best is defined as having the smallest $RSS$, or equivalently largest $R^2$.
Select a single best model from among $\mathcal{M}_0, \dots, \mathcal{M}_p$ using cross-validated prediction error, $AIC$, $BIC$, or adjusted $R^2$.

It is not guaranteed to find the best possible model out of all $2^p$ models containing subsets of the $p$ predictors. This is because the variable that has been selected in round 1 (i.e., for $k=0$) will definitely be in the final model, even if it occurred at a later stage that, when considering the best $k$-dimensional model, $k>1$, does not need that particular variable.
In slightly different words, it might happen that a variable gives the largest reduction in $RSS$ relative the null model, but that, when also considering combinations of, say, three variables, that some combination of three predictors makes the variable chosen in round 1 redundant.
Comment: sure, try the function step in R with the argument direction="both".
Comment: The basic logic is still the same. Since only one regressor is added at a time, pairs or larger groups of variables that are relevant only together but not separately may be skipped in stepwise selection even though they might belong to the best model if all possible subsets are considered.
Comment: Thanks christoph, your answer is really clear. Could you explain me why this path dependence occurs also for stepwise selection? Because, it will start with an arbitrary subset of the full model (the subset is chosen by the user) and then it is not true (in this case) that the variables selected in round 1 (for k=0) will definitely be in the final model: at each step I can add variables but I can also eliminate the variables that already are in the model. If you can explain that I will accept your answer because I think is really clear and useful.
Comment: Could you provide a link where that flavor of stepwise is explained in more detail? I am not sure I understand it correctly.
Comment: http://stats.stackexchange.com/questions/4640/interpreting-the-step-output-in-r
Comment: in the link that I added there are some examples of the step function, if you write direction="both" you run the classical stepwise regression, with AIC as statistical criterion for adding/remove variables