Are SharkBite plumbing connectors as reliable as soldered connectors?

Question: Are SharkBite plumbing connectors as reliable as soldered connectors?
Comment: Using a propane torch is more fun though.
Comment: See also http://diy.stackexchange.com/questions/207/what-are-the-advantages-and-disadvantage-of-using-pushfit-pipe-fittings.
Answer: So far they seem to be just as reliable, although given that they've only been on the market for a few years they don't have the same history as soldered connections. Here in the UK almost all new-build houses use push-fit connectors for concealed work as it's much quicker and easier.
You most likely do need to take extra care that the tube is perfectly round for an inch or so at the end, and that there's no bits of swarf, paint or other dirt there. Solder is good at filling in little gaps which push-fit connectors won't seal. On the other hand it's very easy to not heat a solder joint up enough to melt the solder properly, especially in confined spaces.
Obviously, make sure you push them in firmly.
Finally you don't really want to use them for exposed pipes, soldered joints are much neater.
Answer: I've not used Shark Bite, but I have used other push fit connectors and as long as you make sure that you push the pipes firmly into the connectors they do the job they're intended for.
I haven't had any leaks or other problems with them.
Another advantage is that you can rotate the pipes and fittings once they're in place so if you have a tight or awkward space to work in you're less restricted.
If you're not confident about your soldering skills then using compression or push fit connectors is probably a better idea as you can sort them out after the water's turned back on without necessarily having to drain the system again.
Answer: I've had a few SharkBite connectors installed for a couple years without any leaks. They are pricey but save a lot of time when trying to make repairs or otherwise plumb in tight spaces. In fact, I've seen more leaks from improper solders that then have to be re-soldered than I have from SharkBites, primarily because tight spaces can inhibit applying the torch/flame correctly.
Answer: I've had Sharkbites both to Pex and copper in our house for about 8 years including on our boiler copper and Pex O2. Haven't had any leaks so far. Cleaned all the copper with steel wool so it was shiny with no imperfections and de-burred and made sure the Pex was good as well with no scratches and that both copper and Pex were cut straight and fully seated. I think these things are key to them lasting with no leaks. Even a little off in the cut may be why some leak or if you don't clean the copper or it is not round or has imperfections at the point of contact. Just my opinion as I'm not a plumber but a 40 plus year general contractor/carpenter contractor. I only do minor plumbing and electrical, nothing major. I use the pros when I need them which is 95% of the time. I had one leak right after putting it on but it was a pin hole you couldn't see in the brass elbow. Put a new one in and took the old back and got a new one in it's place. I know a lot of plumbers don't like them and are using press fittings. There's good and bad in everything and most of the time it boils down to correct installation and taking time to do it right.
Comment: Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know the details of contributing here.
Answer: The previous cheapy shut off valve to my toilet had seized. There was no way I could solder a new pipe because whoever installed the pipe didn't leave much room.  I replaced it with a shark bite 4 years ago and it has not yet leaked. What I don't know is will be ok in 10 years. Like you car rubber seals dry up and there is a rubber o-ring that provides the tight seal. You would think that whoever designed these fittings would provide a wider rubber seal and perhaps a longer sleeve for the pipe to fit in....right now the sleeve is less than 1"....imagine if it was say 1.5"and there was more rubber seal for it to grip on.
That being said, my father redid all the plumbing in his house back in 1972.....when I sold the house after he died not one pipe was leaking....all the pipes were solder and amazingly he had installed some compression shut off valves which did not leak or show signs of fatigue. They've be known to fail. I just don't know how the shark bit value will fare out.
The way I look at it is if I have to replace it every 5 years even at $15 its cheaper than a plumber.....but I am also concerned about the plastic collar they use....plastic as we all know gets brittle over time.....if it ever cracked on its own you'd have one hell of a leak. I guess we are all going to have to wait say 10 years to see what the failure rate is on these push on fittings. There is no way I would trust them in a concealed area....image the mess to cut through drywall to fix a leak.
Comment: It shouldn't be a rubber seal.  Probably nylon, silicon, or some other modern material.
Answer: I think any connection will eventually fail. Shark Bite fittings have been slowly taking over in my 35 year old plumbing system and working just fine on hot and cold water.  Expensive, simple, fast and you can put them on with water running out the end. Try that with a soldered joint. Time will tell.
Answer: I have only one experience with the push on fittings, on a refrigerator water/icemaker connection.  Connected a valve to copper stub which failed although the stub was cleaned well.  I went back and soldered the connection--no problems.  I am converting to Pex and crimps--not clamps-would not trust them.
Comment: Hello, and welcome to Home Improvement. Thanks for the answer, but it isn't clear; are you saying some types of SharkBite are good and some are bad? Would you clarify which? And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to contribute here.
Comment: I like the pex and crimp connectors not the push on which are expensive and in my experience are not reliable on copper,  they may do better with the pex tubing.
Comment: Thanks. Would you edit this into your answer? Comments aren't meant to be part of a good answer.
Answer: For emergencies only lol. Also depends. A real plumber would use it but in certain situations. also upscale the proper fix.  Now The industrial sharkbites were u need to use the crimp tool hand or pneumatic is A ok depending on preassure rating I'd say and overall use any wheres.
Comment: Hello, and welcome to Home Improvement. It's really hard to see how this answers the original question; would you edit it a bit to make it clearer? And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to contribute here.


Using SageTeX within Windows

Question: Sage 5.5 was just released. It is a Linux native, is there a way to use it within windows with minimal constraints?
Answer: After experimenting, I suggest the following method. It is based on MikTex 2.9, TeXnicCenter, VMWare player (this one is free for home use), Linux Mint 14 with Cinnamon and of course Sage 5.5. It should be similar if you use VirtualBox. The goal was to use windows as most as possible and linux as little as possible, there is no need here to install TexLive in the virtual machine and to coordinate it with MikTeX.
The big picture is this one, it should be enough for a windows geek, it is followed by a more detailed explanantion.
INSTALLATION

Install a virtualization software (VMWare, Virtual Box, Windows
Virtual PC)
Install a Debian Linux distribution (Mint 14 Cinnamon recommended as closest to the Windows look and feel)
Share your TeX document directory between the host and the guest operating system with R/W rights
Download and expand the latest sage package (Ubuntu 32 bit)
"Install" sage in any user directory, sage being "portable", in windows parlance it is just a move of the directory
Transfer the sage tex directory to the host operating system
Make sage "known" to MikTeX, like any other new style or package

UTILIZATION

"Miktexify" your *.tex file using the sagetex package with pdflatex,
this generate a new *.sagetex.sage in your TeX directory and some warnings
Open the guest operating system and start sage in a terminal
Using a DOS, Linux command cd (change directory) at the sage prompt place the sage program in the shared Host/Guest Tex directory
load (execute) sage your *.sagetex.sage file,
this will generate two new files *.sagetex.scmd and *.sagetex.sout in your tx directory
"Miktexify" your *.tex file again, the result of the sage computation will be written to your pdf output.

The result is just great, really worth the installation effort, it will improve the quality of your document avoiding typos in long expressions.
In the following modus operandi, the places where the Sage documentation is insufficient or not up to date are more detailed

Install VMWare player from https://my.vmware.com/web/vmware/free#desktop_end_user_computing/vmware_player/5_0
Install your favorite Linux distro (but if you read this, you are obviously not a
Linux fan so use Linux Mint 14 with Cinnamon, the closest to windows
so far). http://www.linuxmint.com/edition.php?id=117
Install VMWare tools

Let suppose that your windows working Tex directory is C:\Documents\Maths and your name is usrx
Within VMWare Virtual Machine Settings, tab Options Enable Shared Folders, always enable, uncheck the read only case in properties (the default is RW so it should not be necessary). In the Hardware tab for network adapter use NAT.
Download the package "sage-5.5-linux-32bit-ubuntu_12.04.1_lts-i86-Linux.tar.lzma" from
http://www.sagemath.org/download.html
 and expand it (as a you would do in windows..) in your user directory /home/usrx, rename the directory to sage55 to make it short.
You now have sage installed in the directory /home/usrx/sage55, test it by double clicking the sage icon, choosing run in a terminal (let the directory update run its course)
When you get the sage: prompt, test it with your favorite instruction, 2+2 may be, if you get 4 you are good to go.

Now, using Nemo, (here Windows users can read Explorer, the file icon at the bottom of the screen) open the directories /home/usrx/sage55/local/share/texmf where you get a directory tex, right click and copy it.
From the same nemo double click File System then the icon mnt (mount) and then hgfs. If everything went OK, you should find there your windows directory, Maths shared between the host (Windows) and the guest (Mint 14).
In this directory you paste the tex directory copied from /home/usrx/sage55/local/share/texmf
Now, we get back to windows but do not close the virtual machine, neither the sage terminal, you will use it for sagetex.
Using Administrator rights copy again this directory to your MikTeX installation with your other particular styles for example (I use one called modified  C:\Program Files\MiKTeX 2.9\tex\latex\modified , e.g.) so that you now have C:\Program Files\MiKTeX 2.9\tex\latex\modified\tex).
Update MikTex from the program menu, with the Maintenance (Admin) Setting(admin) Refresh FNDB button as usual.

Now we can try to use sagetex.
From TeXnicCenter, create a sample tex file, such as this one
\documentclass{article}
\usepackage{sagetex}
\begin{document}
 Factoring $x^{12}-y^{12}$.
      With Sage, for the rationals, we find
   \begin{sageblock}
   L.<x,y>=LaurentPolynomialRing(QQ)
   f=x^(12)-y^(12)
   \end{sageblock}
  \[\sage{f.factor()}\]
In the real domain we find
\[x^{12}-y^{12}=(x+y)(x-y)\left(x^2+y^2\right)\left(x^2+y^2+xy\right)\left(x^2+y^2-   xy\right)\left(x^2+x y \sqrt{3}+y^2\right)\left(x^2-x y \sqrt{3}+y^2\right).\]
\end{document}

call it SageX.tex, e.g.
Build and view your file once. You will have warnings about unreferenced sage items

and in your /mnt/hgfs/Maths directory, you will find a new file called SageX.sagetex.sage (NOT SageX.sage). The pdf file will have ?? where the answer to the factorization should be.

Go back to the virtual machine, to the sage terminal and sage prompt (sage:)
There you need to type a linux instruction followed by return, (Here the sage manual says that a linux instruction should be typed !cd but this does not work)

sage: cd /mnt/hgfs/Maths

(change to the share windowslinux directory), you should see this answer
    /mnt/hgfs/Maths
Now type the instruction
    sage: load SageX.sagetex.sage
If all went well you will get the answer
sage: load SageX.sagetex.sage
Processing Sage code for SageX.tex...
Code block begin...end
Inline formula 0
Sage processing complete. Run LaTeX on SageX.tex again.

Back to Windows. In C:\Documents\Maths, you have two new files SageX.sagetex.scmd and SageX.sagetex.sout. Run TeXnicCenter again, you should have no more warnings and the factorization of the polynomial in the rationals, computed by sage, will have replaced the ??.

Note that as long as you do not modify the sage instruction, you don't need to run sage again, you can modify your text or add new LaTeX code within windows as long as you don't add (or modify) new sage code (or as long as you delete the three *.sage, *.scmd and *.sout files).
Sagetex is a great product so my hope is that some windows users will try the process and be convinced by the product (and also help in improving this text)...
Comment: `sagetex` can be installed with the package manager in MiKTeX. I cannot judge, though, whether this is the recent version; otherwise regarding "transfer sage directory and make sage known to MiKTeX" I want to point to [Create a local texmf tree in MiKTeX](http://tex.stackexchange.com/questions/69483/create-a-local-texmf-tree-in-miktex). And: [For Sage there exists a Windows binary](http://www.sagemath.org/doc/installation/index.html), what actually is a VirtualBox image, as written by you.
Comment: I would like to add that this wasn't sufficient for me to work. Sage could not compile  plots. Running " sudo apt-get install python-numpy " in the terminal got me what was missing and now it works. But thanks for the step by step tutorial.
Comment: No need for adding WSL overheads nor a VM if you simply use the latest 8.6 Cygwin combined SageMath package and run it from inside your choice of windows editor.
Answer: There is a way to use sagetex on windows:
Step 1: Install miktex 2.9 64-bit, full install.
Step 2: Install Texniccenter 2.02 64-bit (I think another program like texworks, texmaker, winedt, etc will work).
Step 3: Install Sagemath 8.6 64-bit or better.
Step 4: Sagetex version in miktex is different to sagetex version in Sagemath 8.6. Then you should install in miktex same version of sagetex as you have in Sagemath.
This can be done copying al files in
c:\Program Files\SageMath 8.6\runtime\opt\sagemath-8.6\local\share\texmf\tex\latex\sagetex\

into
c:\Program Files\MiKTeX 2.9\tex\latex\sagetex\

Now using sagetex on windows is possible according this:

Use texniccenter to compile your .tex document. Remember you have to load sagetex package: \usepackage{sagetex}
Sagemath installation on windows has 3 shotcurts. You should open Sagemath 8.6, not Sagemath 8.6 Shell or Sagemat 8.6 Notebook. Remember, Sagemath 8.6. After that a shell is opened and when we see sage:, sagemath is ready.
Navigate to folder where our files are using "cd" command, like cd documents. Is important, if your folder's name has spaces placing it between ' ', i.e. cd 'folder 1'
When you are into your destination folder, you can see its contents with "ls". There should be your sagetex.sage file. To process the file you have to write load('file.sagetex.sage') (file is the name of your .tex file) and the procces will start when you press enter.
Finaly, use texniccenter to compile again the .tex file.

When you need to use again sage, you don't need to write the command, because using up arrow on your keyboard will apear the command and you only have to press enter.
I think will be possible automatize 3 steps using postprocessor on texniccenter, but I don't know how to do it right now.
Comment: You should not corrupt MiKTeX by copying the files to c:\Program Files\MiKTeX 2.9\tex\latex\sagetex\ the official instructions give three alternative safe ways to place the SageTeX file in the texmf search path 1)your work folder 2) you add the sage folder to TEXINPUTS 3) The recommended way is you add it to your personal texmf folder (that is NOT a MiKTeX one where it will corrupt the filename database)
Comment: Thanks for your advice. In fact, I tried those 3 ways, but I don't know why them didn't work for me. Then I forced the situation and it worked!.

Using SageTeX within Windows


galaxy s5 says battery temperature too high too low!

Question: help me please. my galaxy s5 won't charge it says the battery temperature is too high or too low. i used to change my battery but when the new battery runs out of life and when i try to charge it, the same problem exist. what can I do? any helps or suggestion please. thank you.
Comment: I posted my answer over there too in case it's duplicate. There was hardly any useful info over there for how many views it has.
Answer: I have an S5 also, I haven't had this problem. I have extra batteries along with an external wall charger.
I use the wall charger to avoid charging my phone. It was $15 on ebay, and it may be a viable workaround and/or solution outside of replacing the motherboard.
These wall chargers will charge your battery no matter what, you can confirm this by looking at the pins on the image below. If the third pin not present, the charger does not check battery stats before charging.

(I consider this a solution, because we'll be taking advantage of the removable battery feature, and the chargers come in packs of three batteries so you'll never be stuck to an outlet again. I recommend labeling each battery with lines around the curved edges.)
Anyway, hope this helps.


Is the $E=E(k)$ dispersion relation periodic across Brillouin zones?

Question: I am quite confused by the Brillouin zones. I know there is a dispersion relation $E=E(k)$ for the first Brillouin zone. But is this dispersion relation periodic across different Brillouin zones? Thinking in one way that larger $k$ should give rise to larger energy tends me to think that in higher-order Brillouin zones the energy is larger, but the Bloch theorem seems to hint a periodic structure. I also found references that seemed to give contradictory answers. For example, page 13 in this document seems to indicate energy is larger in higher-order zones, but page 4 in this other document seems to indicate energy is periodic across different Brillouin zones. I need some really good explanations.
Answer: Basically, there are several ways to describe how your energy eigenvalues depend on the wavevector, in so-called zone-scheme representations:

An extended zone-scheme, like the one displayed on page 13 of your first reference and Fig. 2a of the second one, is useful to compare the energy dispersion of a crystalline electron compared to the parabolic one of a free electron.
However, since all lattice points are equivalent by translational symmetry, the choice of the origin in momentum space is completely arbitrary. As a consequence, in a repeated zone-scheme, the same dispersion relation is repeated all over $k$-space, at each reciprocal lattice point. An example of a repeated zone-scheme is Fig. 2b in your second reference. This scheme is useful to visualize the periodicity of the dispersion relation in momentum space $E(k)=E(k+G)$.
Still, the repeated zone-scheme is clearly redundant, as all contributions from all reciprocal lattice points to the first Brillouin zone, i.e. in $-\frac{\pi}{a}\leq k \leq\frac{\pi}{a}$, correspond to all contributions from all reciprocal lattice points to each Brillouin zone. So we are free to pick one Brillouin zone and we choose to restrict to the first. This results in a reduced zone-scheme, as displayed in Fig. 2c in your second reference.


Where did the term "Your Obedient Servant" originate?

Question: In political letters throughout history, the closing "Your Obedient Servant" appears many times (For example, president Lincoln uses it in all of his letters). Where and how did this phrase originate and how did its usage develop?
Comment: @tchrist  Really?  Did Cicero use it?  Or a Borgia?
Comment: Why would so common a formulation have some discrete origin? It happens in countless languages.
Comment: See [The King's English](http://www.history.org/history/teaching/enewsletter/june03/english.cfm) for how, by whom and to whom, the phrase was used in the 18th century. This source is from a publication of the Department of Historical Research, Colonial Williamsburg.  It does not give the origin of the phrase.  It's too late in my time zone to develop this into an answer -- anyone can build on this, but this source does not by itself answer the OP's question.
Comment: In its listing for this, the *Oxford English Dictionary* has quotes back to 1543
Comment: You find the likes of "By your most simple servant," from 1443 in the 15th-century [Paston letters](https://books.google.co.uk/books?id=22UDAAAAMAAJ&lpg=RA3-PA51&ots=4qaBK6wk94) (spelling modernised). But if you are someone's servant, or want to show obedience to someone whose aid you are requesting, it is a very logical thing to say.
Comment: It was probably from Latin, as originally, literate people in Europe studied Latin,
Answer: Early specimens of 'your obedient servant'
The earliest Google Books match for "your obedient servant" at the close of a letter is from a letter from an Englishman (from York) contained in George Smith, The Compleat English Grammar (1758), as part of a somewhat more elaborate leave-taking:

Sir your friend
your obedient Servant
and Unfeigned friend.
JOHN THOUGHTS

The same Google Books search finds a match from The Gentleman's Magazine, or Monthly Intelligencer (June 1742), involving an interview with "Landois the Second," a courtier, originally published in Common Sense. In this instance, the phrase comes at the close of the interview:

A, Sir, I thank you. We are the Chancellor of the Exchequer's most humble Servant,———by his good conduct we have gain'd Part of your Trade, and humbled our Enemies upon the Continent———long, very long may he rule over you for our Sakes; but if he was our Chancellor of the Exchequer, we should serve him a Trick that I do not much care to tell;———however, I am obliged to you for your Information, and am your obedient Servant, &c.

And a translation (from Spanish) of the closing to a brief letter from General Wall to the Spanish ambassador on reprinted in Papers Relative to the Rupture with Spain (1762) ends with this:

Most Excellent Lord, I kiss your Excellency's Hands,
Your obedient Servant,
Don RICARDO WALL

But the Google Books search's earliest formal and succinct "your humble servant" in English-language letter closures are from the 1770s. The first appears in a letter from Walter Shirley to John Fletcher, reprinted in John Fletcher, A Vindication of the Rev. Mr. Wesley's Last Minutes (1771):

I am SIR, Your obedient Servant, WALTER SHIRLEY.

Then from William Tryon to Jonathan Trumbull written on April 17, 1778, and reproduced in The Town and Country (July 1778):

I am, Sir, your obedient servant, W. TRYON.

(In his letter of response to Tryon, Governor Turnbull used the equally polite wording "I am, Sir, your humble servant," leaving us to decide whether a humble servant or an obedient one is the more conformable to one's will.)
And the other in a letter from George Johnstone to Robert Morris, written on June 16, 1778, and reproduced in The Edinburgh Magazine, and Literary Miscellany (October 1778):

I am, with affection and esteem, dear Sir, your obedient servant, Geo. Johnstone.

The Shirley letter was written and published in England, but both of the 1778 instances involve American correspondents—and indeed there appears to have been a vogue of this usage in the United States in the late 1700s.
The wording "Your obedient servant" was fairly common in both the United States and Great Britain by 1800.

Early specimens of 'obliged and obedient' (and often humble) servants
The lengthier sign-offs of the "obliged and obedient" school are spread across the late 1600s and much of the 1700s. I will try to provide a representative selection of these florid farewells, both with regard to year of writing and mode of expression. First, from William Temple to the King, written on December 4, 1674, published in Letters to the King, the Prince of Orange, the Chief Ministers of State, and Other Persons, volume 3 (1703):

The Knowledge of all worth your Majesty's Trouble from hence, will, I know, be transmitted from my Lord Chamberlain, and leave me no other Part than that of my Humble Acknowledgments upon the Confidence your Majesty has been pleased to express of me in so great Occasions, and the plain Offers of that very Sincere Devotion, wherewith I am, and shall ever be,
Your Majesty's most Loyal
Subject, and most Obedient
Humble Servant.

From a letter from F.E. to "your grace" written some time in 1688 and reprinted in The State Letters of Henry, Earl of Clarendon, Lord Lieutenant of Ireland During the Reign of K. James the Second (1763):

God send your grace a good night, and a happy morning. I am
your obliged and obedient servant,
F. E———.

From a supposed letter from Lady Lizard to the author, in Addison & Steele's The Guardian (April 30, 1713):

I am
Your most Obliged,
and Obedient Humble Servant,
MARY LIZARD.

From a letter from Richard Steele to the clergy of the Church of England, in The Political State of Great Britain (January 1714):

And as there are no Instruments under Heaven so capable of this great Work, that God would make you such to this divided Nation, is the hearty Prayer of, GENTLEMEN, Your most dutiful, and most obedient Humble Servant, RICHARD STEELE.

From the epistle dedicatory to the second edition of William Petty, The Political Anatomy of Ireland, 1672 (1719):

I am,
May it please your Lordship,
Your Lordship's,
Most obliged, and most
Obedient, Humble Servant

From a letter from A, Ramsay to Jonathan Swift, written on August 1, 1727, in Letters Written By The Late Jonathan Swift, D. D. Dean of St. Patrick's, Dublin; and Several of His Friends, volume 2 (1768):

I am with the utmost regard and esteem, reverend Sir, your most humble, and most obliged, obedient servant,
A. RAMSAY.

From a letter from B. Motte to Jonathan Swift, written on October 4, 1735, and reprinted in Letters Written By The Late Jonathan Swift, D. D. Dean of St. Patrick's, Dublin; and Several of His Friends, volume 4 (1766):

I have been so particular (I fear even to tediousness) in that letter, that I have nothing to add, but a repetition of the sincere profession I there made, that I am, with all possible gratitude, truth, and sincerity, Sir, your obliged and obedient humble servant,
B. MOTTE

From an epistle dedicatory to the commissioners of the Royal Hospital at Chelsea in John Woodman, The Rat-catcher at Chelsea College: A Tale (1740):

...that every one on this Board may so encourage and promote a Design, propos'd entirely for Good and Use of the Publick, that he may say with more Justice than Horace did, "Exegi Monumentum ære perennius," is the ardent Prayer and Expectation of,
My LORDS,
Your LORDSHIPS
Most obedient humble Servant,
J. WOODMAN

From a letter written by John Spencer to the citizens of Bristol, England, reprinted in The Whitehall Evening Post Or London Intelligencer (1756):

...and assure you, I shall always continue to wish the utmost Prosperity to the City of Bristol, and am,
GENTLEMEN,
Your obliged and obedient humble Servant,
JOHN SPENCER.

Then, from a letter from Richard Grindall to William Watson, written on December 7, 1857, and reprinted in The Universal Magazine (1758):

I am, with respect,
Your obliged and obedient Servant,
Richard Grindall.

In a letter from John Morgan to the Sheriff of Herfordshire, written on June 10, 1763, and published in The London Magazine; Or, Gentleman's Monthly Intelligencer (1763):

I am, Mr. Sheriff,
Your obliged and obedient
Humble servant,
JOHN MORGAN.

And in a letter from George Washington to John Jay, written April 14, 1779, and reprinted in The Life of John Jay: With Selections from His Correspondence and Miscellaneous Papers, volume 2 (1833):

With the truest esteem and personal regard,
I am, dear sir,
Your obliged and obedient servant,
Geo. Washington.

Conclusion
Today, "Your obedient servant" may sound extravagant and highly ornamental; but in the second half of the eighteenth century, when it first became popular, it must have sounded almost brusque, arriving as it did after many decades of truly elaborate declarations of loyal and grateful servitude.
The short answer to the question "Where did 'Your obedient servant' originate?" is "In abject expressions of admiration of and devotion to powerful people by letter writers, book writers, and other supplicants seeking patronage, ingratiation, and in some cases forgiveness." The form later carried over to exchanges between equals, just because it seemed respectful and polite, and at some point received a pairing down to "Your humble servant"—and from there, perhaps, to the even more abrupt "Yours truly," "Sincerely yours," or just "Yours."

Update (October 12, 2019): 'Your obedient servant' in letter closes before 1750
I checked the Hathi Trust database for of publications and found several instances of "Your obedient servant" at the close of letters published before 1742. Following are some examples.
From a letter of Secretary Windebank, clerk, to Viscount Conway (May 7, 1640), reprinted in Calendar of State Papers, Domestic Seriesof the Reign of Charles I, 1640 (1880):

... The intelligence which your Lordship has been pleased thus freely to begin I beseech you to continue, and if you will make it a step to render me of more use and consideration to you, I shall hold that a great ad to the honour and happiness of your obedient servant.

From a letter from the Earl of Thomond to H. Cromwell (February 18, 1658) in A Collection of the State Papers of John Thurloe, volume 7 (1742):

...I shall only add, that my head, being ill, was  was made better by writing, and my hear=t much cordialed to apprehend, that my lines may be received with that welcome, as my exact obedience presentes them with my lowest reverence to yourselfe and worthy lady : my lord, now and ever to my power,
Your obedient servant,
THOMOND

From a letter from Richard Watts to Joseph Williamson (June 12, 1667), in Calendar of State Papers, Domestic series, of the Reign of Charles II, 1667 (1866)

... I am commanded by you to show you the opinion and report of the country, But if I should write all, I should first request for a pardon, for mouths are now very loose.
But Sir, I am,
Your obedient Servant,
RI. WATTS.

From the Epistle Dedicatory to the Lord Mayor and aldermen of London, in John Goodman, The Leaven of Pharisaism and Sadducism Purged Out : A Sermon Preached December 16, 1688 (1689):

And may all you the Worthy Magistrates of this Great and Famous City, live to see Jerusalem in its Glory ; ... so that You in your Stations may be instrumental in so Glorious a Work, shall be the Hearty Prayer of
(My Lord and Gentlemen)
Your Obedient Servant
J. GOODMAN

From a letter from Elihu Yale to Captain James Perriman (January 20, 1689), in Records of Fort St. George: Letters from Fort St. George, 1689 (1916):

... I have also forbade of Cheife att Conomeer to entertain any of yor : soldiers who writes me there is none in their service but passible they may be in the Duans as many of ours and & out of my reach but be assur'd I shall protect none of them from you being
Honored Sr:
Your obedient servant
ELIHU YALE.

From a letter from Captain Peter Wall to Abraham Anselm (May 26, 1693), in The Manuscripts of the House of Lords, 1693–1695 (1900):

... I have no more to add, but I am your obedient servant at command. Signed, Peter Wall.

From a letter from Charles Brooke in answer to a paper by William Penn (~April 1697) in The Manuscripts of the House of Lords, 1695–1697 (1903):

All which is humbly submitted by your obedient servant—
CHAS. BROOKE.

From The Compleat Mendicant : or, Unhappy Beggar (1699):

'Tis true, 'tis a violent necessity that has urg'd me upon this ungrateful expedient, and that I hope, in Conjunction with your own Charity and Compassion, will interpose a little for this unfortunate dtranger, that with all the distance and submission that can be, Subscribes himself, your Obedient Servant,
PEREGRINE

From a letter from Matthew Birche to the government of Pennsylvania (August 17, 1699), in The Manuscripts of the House of Lords, 1699–1702 (1908):

... But I have given your Honours such large accounts of these things that this may be tautology. I wait your commands and am
Your obedient servant,
MATH. BIRCHE.

From a letter from James Hamilton to Brigadier General Maitland (July 23, 1703), in Journals of the House of Lords, volume 17 (1701–1704):

...If it be a Match at Hunting only, I know not ; but I think it my Duty to acquaint you, whatever may fall out, of any such Body of Men in Arms, particularly in our Northern Parts. My humble Duty to your Lady. I am,
Right Honourable,
Your obedient Servant,
JAMES HAMILTON

From a letter from Sir George Rooke to the Governor of Gibralter (July 22, 1704), in The Manuscripts of the House of Lords, 1704–1706 (1912):

... But, if you think fit to refuse this offer [of terms for surrender], we will this night storm the town and put every soul to the sword, so that, for the effusion of the blood that shall be shed on this occasion, it will be charged on your own madness and not on the inclinations of, Sir, your obedient servant, G. Rooke.

From a letter from John Gyles to Alderman M____ (February 16, 1709) in The Present State of Europe for the Month of March 1709 (1709):

SIR, After You and the Clergy, and your other Friends, have perused the Book I have left with your servant, please let it be sent to Parker's Coffee-House, there to remain for the Perusal of the Clergy, and others, in order to publish the Message to the Learned and Knowing of this City. I am
Your obedient servant,
John Gyles.

From The Tatler, No. 78 (October 8, 1709):

'SIR, I am just recovering out of a languishing sickness by the care of Hippocrates, who visited me throughout my whole illness, ... I know no method of thanking him, but recommending it to you to celebrate so great humanity in the manner you think fit, and to do it with the spirit and sentiments of a man just relieved from grief, misery, and pain, to joy, satisfaction, and ease : in which you will represent the grateful sense of your obedient servant, T. B.'

From The Spectator, No. 398 (June 6, 1712):

'MADAM,—I have that prejudice in favour of all you do, that it is not  possible for you to determine upon what will not be very pleasing to your obedient servant, CYNTHIO.'

From The Spectator, No. 432 (July 16, 1712):

Reflections of this nature have expunged all prejudices out of my heart; insomuch, that though I am a firm Protestant, I hope to see the pope and cardinals without violent emotions; and though I am naturally grave, I expect to meet good company at Paris.
I am, Sir, your obedient Servant.

From a letter by Thomas Cooke to Nathaniel Elwick (February 1, 1722), in Records of Fort St. George: Diary and Consultation Book of 1722 (1930):

... I can give your Hon. &ca. no further Accot. of it being with Respect.
Honble. Sr. &ca.
Your obedient servant
Thomas Cooke.

From a letter from the Duke of Montagu to the Duke of Newcastle (January 1728), in Calendar of State Papers, Colonial Series, America and West Indies, 1728–1729 (1937):

I depend upon you to be my friend and advocate, and I intend to waite on you Wednesday morning to know my fate, for i hope by that tyme you will have settled it with your brother Ministers, and not only till then but for ever, I am and shall be your obedient servant, Signed, Montagu.

From a letter from Joshua Ward to the editor of The Political State, in The Political State of Great Britain for January 1735 (1735):

Wherefore, as I have the Lord Chief Baron's Leave, I beg you will insert the inclosed Letter and Case in your next Paper, and you will very much oblige,
SIR,
Your obedient Servant,
JOSHUA WARD.

From a letter from Y. Z. to the author of The Political State  in The Political State of Great Britain for April 1739 (1739):

I am, SIR,
Your obedient Servant,
Y. Z.

These numerous examples indicate that use of "Your obedient servant" as part of a polite sign-off to a letter goes back to at least 1640, and had become fairly common in some formal settings by the final decade of the seventeenth century.
Comment: This answer does not demonstrate that the phrase "first became popular" in "the second half of the eighteenth century." Scholarly research is not  accomplished by 'seeing what Google books has to offer'. This is a crude and tool dependent methodology
Comment: Maybe the conclusion should have been toned down somewhat to be less assertive, but in my (limited) experience, Google Books often provides a *larger* selection of relevant historical documents than many university libraries can offer, so short of putting in an effort befitting a master's thesis, I doubt a much better answer could be crafted.
Comment: Even though the OP has accepted this answer, and even though it is very illuminating indeed, it does not quite answer the question as formulated: where did the term **originate**? The answer provides numerous 'early specimens' of the term's use, but what these 'specimens' show is only that, at their respective times, the term was **already** in use and readily understood, which implies that its origin is still earlier. The question of where the term originated is probably unanswerable, as was pointed out by @tchrist within minutes of its being posted.
Comment: See also "[The Authors Epistle Dedicatory to the Lady Ann of Rohan, Sister to the Duke of Rohan](https://quod.lib.umich.edu/e/eebo2/A20946.0001.001/1:3?ALLSELECTED=1;amt2=40;amt3=40;c=eebo;c=eebo2;g=eebogroup;rgn=div1;singlegenre=All;sort=datea;subview=detail;type=proximity;view=fulltext;xc=1;q1=your;op2=near;q2=obedient;op3=near;q3=servant)," in _Heraclitus, or, Meditations vpon the vanity & misery of humane life first written in French by that excellent scholler & admirable divine Peter Du Moulin minister of the sacred word in the Reformed Church of Paris_ (1609):
Comment: "But seeing that it must now trauerse abroad by your commandement, my desire is that it may be receiued as frō the hand of him, which prayeth to God for the prosperity of your most Noble family, which God hath honoured with his holy and diuine alliance, & who hath noe other ambition thē to obey you, and remaine all his life | **Your Ladyships most humble and obedient servant, PETER du MOVLIN."** The French original was translated into English by "R.S. gentleman," suggesting that the form may have been imported into English from French at an early date.
Answer: See this 1633 example from Galileo Galilei (1564-1642). Used in his 1633 Trial by the Inquisition.

              The valediction:
         Humiliso et Obdns Sevs
             which is in Latin:
   Humilus et Oboedens Servus
                           or
  Humble and Obedient Servant
(Source)
Answer: How I see this phrase is that it could perhaps be an English version of the common greeting or concluding saying "Servus" which is common more often now in eastern European countries but was a derivative of the Latin saying "Servus humillimus sum, O domine spectabilis" which means "I am [your] humble servant, O noble lord". (https://en.wikipedia.org/wiki/Servus)
This saying was quite popular in medieval times, especially for those educated in Latin, so it would make sense that during the Enlightenment period, a point at which Latin was most widely taught and held one of its highest estimations throughout the world, that this saying would be adopted not only in Latin, but in its translated English variation by whosoever was educated enough in both languages and adopted the ancient saying. And especially since those most of who knew how to write well and whose letters we have extant were usually also educated in Latin (as was tradition for most education), it makes quite a lot of sense then that the letters would have been concluded in that "O so notably Roman" fashion.
There may very well be other causes for the existence of this saying, whereof I remain presently and unfortunately unaware, but this seems to make the greatest sense to myself. It is only a theory in the end tho', and I am personally not educated sufficiently in the historical happenings of the 17th and 18th century to pronounce any conclusive reasoning whether this or some other theory is true.
Answer: I am surprised that no one has offered the opinion that the use of this phrase may have originated in the fact that Jesus is represented in the gospel of Mark as teaching that his followers are never to seek to domineer or rule one another, but are to be servants and even slaves of one another because, he says, even "the Son of Man came not to be served, but to serve, and to give his life as a ransom for many" (Mark 10:43-45).
Such an admonition to practice loving, freely given servanthood toward others (not to be confused with enforced, compelled servitude) may have caused people to think they should at least pay lip service to that ideal in the way they signed their correspondence. (I feel compelled to add that I believe there were instances in which someone would write a letter scathingly critical of and even insulting to the recipient, yet still sign it, "your humble and obedient servant."
--James Boswell, author of The Dead Sea Gospel
Comment: This would benefit from a citation with the specific phrase from the question.
Comment: And I'm surprised you got just one upvote! I upvoted you. Can you please elaborate your answer? For instance, can you please explain (Mark 10:43-45) in Simple English? Please just edit your answer, rather than answering as a comment.
Answer: The phrase "your  servant" is first recorded in English in the 15th century:
OED

P2. your servant.
a. Used formulaically when ending a formal letter, to refer to oneself as the author when addressing a patron in the dedication of a book, etc.  Also frequently with modifying adjective, as your humble, obedient, etc., servant; in this form later also used more generally in other contexts, as an elaborate or self-deprecating way to refer to oneself.
1438   in O. T. Bruce Liber Cartarum Prioratus St. Andree (1841) 430   Rycht worschipfull lord and derast maistir Jamys of Kyninmond of that ilke yhoure humble seruand rycht mekly besekis yhoure hee lordschip that [etc.].
?1444   J. Gresham in Paston Lett. & Papers (2004) II. 14   Wretyn right simply... By your most symple seruaunt Jamys Gresham.
1474   W. Caxton tr. Game & Playe of Chesse (1883) Ded. 1   Your most humble servant william Caxton amonge other of your seruantes sendes unto yow peas.

Why this form was adopted seems to be lost in the mists of time, but it could simply be a fashion.


Can a Gnosis Safe Wallet be Owner of Another Gnosis Safe Wallet?

Question: In a Gnosis Safe Wallet setup, can one of the keys be another gnosis safe multisig? Such that in 1/2 setup, the second multisig wallet is able to initiate transactions  on behalf of the first multisig
Answer: To answer the question literally, then the answer is Yes BUT No ... (seriously)
You can add any address as an owner, even non-existent or contracts, but it will not work.
You need to log in with a wallet to approve and sign transactions using your private key.
Contracts don't have private keys. Gnosis Safe Wallet is a contract.
Answer: There are 2 types of accounts on Ethereum:

Externally Owned Accounts (EOA): can initiate transactions
Contract Account (CA): can contain logic

A Gnosis Safe Multisig is a smart contract and by design it does not have the ability to sign messages even if you setup your main safe with that secondary safe as an owner, so the answer to your question is no.
However you could adapt the Gnosis Safe Multisig for ERC-1271 and allow signatures on behalf of the secondary safe, but the contract account per se still can not sign messages itself.
Answer: Smart contracts cannot produce cryptographic signatures without exposing the underlying keys to generate those signatures to all network participants, however ERC-1271 enables pseudo-signing of data by a smart contract.
The most recent Gnosis Safe contract has built in support for ERC-1271, so Safes can be signers for other safes.
See gnosis safe code here: https://github.com/safe-global/safe-contracts/blob/main/contracts/Safe.sol#L334-L347
Maybe earlier versions did not have this support, but the latest Safe version does.
You'll have to use wallet connect to propose these and sign from the multisig signer, but it is possible and does not require modifying existing code.
I've personally seen multiple projects have multisigs with signers being other multisigs.


current loop transmitter with higher regulated voltage

Question: I have a xtr115 in my circuit that is used for 4-20mA current transmitter, the regulated voltage of xtr115 is +5V, but I need +12V and -12V in my circuit, is it possible to connect an external Regulator to XTR115 to build +12V without dependent on the output current?
Comment: Yes, you could do that with a switching supply, but the amount of available current will be very low and your supply must have exceptionally low quiescent current (not to mention your actual loads) so that you don't exceed the few mW available.
Answer: If you are asking if you can run the XTR115 from your +12 volt supply the answer is yes since it will work with 7.5 volts up to 24 volts (recommended maximum).
If you are asking can you generate a 12 volt supply from the internal 5 volt regulator of the XTR115, that would not be the best choice due to current limitations. You would be better to add a buck/boost regulator off of whatever is the voltage supply to the XTR115.


Can't cast an instant after my opponent declares attackers in Arena

Question: If I have an instant that gives a creature +1/+7 (Aegis of the Heavens) until end of turn, I should be able to cast this after my opponent declares their attackers, right? Because the game hasn't been giving me the opportunity.
Comment: Are you sure that you had enough untapped lands in the right colors to cast the spell at that time? Arena will skip opportunities to cast spells like that if you are not actually capable of casting anything.
Comment: Sometimes switching to full-control mode is necessary, have you had it enabled?
Comment: @murgatroid99 That is not universally true. There are bugs in the autotap algorithms that make the game skip opportunities that you actually have. Example from reddit, submitted by me: https://www.reddit.com/r/MagicArena/comments/9abyhg/ai_does_not_understand_unclaimed_territory/
Comment: @Marcus I did not, but that's besides the point, the behaviour was clearly a bug in an important feature. Full control would have been one workaround, as would have been manually tapping before casting, but you can't reasonably expect such behaviour, so there was no reason use those workarounds before you knew about the issue.
Comment: @ TeaNTea Welcome to the site! In the future it may be helpful to take a screenshot of the board state so answers have more information to figure out what might have happened. In arena you should have had two opportunities to cast your pump spell (after declare attacks, and after declare blocks) without having to go to full control.
Comment: @Hackworth I never claimed that being unable to cast the spell was the only possible explanation. But it is one possible explanation.
Answer: Yes, declaring attackers happens during the Declare Attackers step (rule 508). After declaring attackers (508.1), the active player (your opponent) gets priority (508.2) but you'll get priority thereafter and should be able to cast an instant.
Unless there are other effects in place barring you from casting spells, it seems to be an Arena bug.


Disabling roaming profiles on a single server in a network

Question: I want to disable the roaming profiles on a single server which is used as a terminal and RemoteApp server. This option should be applied to all users in the active directory.
Answer: I've found it in the GPO under Administrative Templates > User Profiles. There are two options you have to enable.
Answer:
Open GPEDIT.MSC
Go to Computer Configuration\Administrative Templates\System\User Profiles
Enable both the

Prevent Roaming Profile changes from propagating to the server
Only allow local user profiles

This will disable the roaming profiles.


What is the minimum number of co-ordinates used to perfectly describe the shape,orientation and position of an n-dimensional object?

Question: What is the minimum number of co-ordinates used to perfectly describe the shape,orientation and position of a n-dimensional object? How do I make an approach to this problem? I am confused with the shape and orientation. How many dimensions do we need to measure even common 3-d objects?
Comment: Is this question intended as stated? Leaving out the description of the shape would render an answerable question: *"What is the minimum number of parameters required to perfectly describe the position and orientation of an arbitrary object in n-dimensional space?"*
Comment: Notice that every object which is indeed describable will be describable on a one dimensional string. You can e.g. tape a video where you explain exactly how the object looks like and where the points are etc. and then take an Edding marker and paint that files data on a long thread, e.g. in Morse code.
Comment: If you remove shape, this has an answer--- it's N position variables plus N(N-1)/2 orientation variables. Why are you asking about shape?
Comment: if the shape is (piecewise) smooth, then countable infinity, I believe.
Answer: The question is ill posed. A point can exist in an n-dimensional space. You need n coordinates to specify its position, but it has neither shape nor orientation. A piece with some arbitrary fractal surface as a shape would need infinitely many. The next step up from a point would be a sphere. It is a truly n-dimensional object wich can be specified with n+1 coordinates (for example the radius).  The person who posed that question probably had the answer (n+1)*n in mind. This is the number of coordinates necessary to define a simplex -- the smallest polytope that is truly n-dimensional. It does have a completely defined orientation, and because the person who posed the question wanted to prevent something like the sphere as a solution he threw "shape" in there as well, making it quite ill posed.
Answer: The minimum pieces of information required also depends on where, what dimensional space it is placed, and not only on what dimensional the object is. For example, you place a point on itself, you need nothing. You place it on a line, you need one co-ordinate. You keep it in space, you need three.
And for determining shape, orientation etc.,consider this: Suppose you want to do it for a sphere whose radius you know. You can know about it's orientation and shape (but which you obviously still know) completely with four pieces of information: The three space co-ordinates of it's centre and it's radius. But this would not have been possible if you did not know that it were a sphere. Then you would probably be getting millions of co-ordinates and still knowing almost nothing.
One does not worry much about this because most of the time, you can do pretty well physics treating your object as point like.


Is it healthy to drink 1.5L of milk a day?

Question: I drink 1.5 to 2 liters of milk a day. Is it healthy?
Comment: Why you think it's not? It really depends on what kind of milk you drink.
Answer: There are several risks related to excessive consumption of milk. A 12 years prospective study run on around 78000 women showed that high consumption of milk (2-3 glasses per day) increased the risk of fracture when compared to people who used to drink one glass or less per week. (1) Similar results were found in other studies like, for example: 2.
The amount that you say, 1.5 L, contains about 1800 mg of calcium, that must be sum to other daily dietary sources (as dairy, green leaves, sesam seeds, water). A study showed that dietary intakes of calcium greater than 1400 were associated with higher death rates from all causes, cardiovascular disease and ischaemic heart disease (3).
Finally, high intakes of calcium can interfere with iron absorption and lead to iron deficiency (4, 5).
Comment: +1 for references.
Comment: That increase in fracture risk in the first study you cite was *not significant*, though, the 95 percent confidence interval includes 1, so you really can't say it was increased.
Answer: Consuming anything in excessive amounts for a long period of time is not good for your health. There are two main problems. One is that the stomach  will get upset and other is that you can have allergies. The other problems depend on the elements that the food or drink contain most. Generally high amounts of milk are taken for protein and calcium. Such amounts are generally taken by body builders and athletes, but not for a long time. They start to take it several months before their competition, usually three or four months. Sometimes, for people with some medical conditions, consumption of high amounts of milk is suggested but not as high as 1.5 or 2 liters.
Before I answer your question some important things need to know are why you are drinking such a high amount of milk, how long will you be doing this, have you done this before, and what kind of the milk will it be (ie: cow, goat, soybean etc.). I am assuming that you want to drink cow's milk. The best way to get answer this question is google just type "side effect of take excessive amount of milk". you will get many result. Here I have given some link generally i use these links...

Are There Any Side-Effects From Drinking Too Much Milk
Risk of Dietary Toxicity
Food Sensitivities
Milk and Food Allergy/Intolerance
Cow's milk, grass-fed
calcium
Foods List
Wikipedia - Milk


How many cores does my Mac have?

Question: I am confused, because when I see my mac about window, I see

That I have 1 Processor and 4 cores. But when I run htop, I see 8 cores

What am I missing?
Answer: From a terminal you can see the difference between the number of physical processors and logical processors using sysctl:
$ sysctl hw.physicalcpu hw.logicalcpu
hw.physicalcpu: 4
hw.logicalcpu: 8

Comment: Why was this downvoted ? This command works (at least on El Capitan).
Comment: It's working on Big Sur...
Comment: works in mojave too
Comment: Still works in Catalina as well. Upvoted.
Comment: Worked for me on Monterey.
Answer:
What am I missing?

Hyperthreading. You have 4 physical cores, but 8 logical ones.

For each processor core that is physically present, the operating system addresses two virtual (logical) cores and shares the workload between them when possible.

See also the Intel data on your processor, the i7 4870HQ:

# of Cores   4
Cores is a hardware term that describes the number of independent central processing units in a single computing component (die or chip).
# of Threads     8
A Thread, or thread of execution, is a software term for the basic ordered sequence of instructions that can be passed through or processed by a single CPU core.
Answer: What you see are so called hyperthreaded cores.
For each physical core there are two hyperthreaded (or logical) cores, you can read up more about hyperthreading here
Answer: your CPU is an i7, so it has Hyperthreading, which presents itself to system monitoring applications by doubling the number of cores, since each  can process two threads semi-simultaneously.
Answer: It has 4 physical cores and 4 logical cores giving you the total of 8 cores.
This is called Hyper-threading
Comment: This is wrong. There are 4 physical cores, and each physical core has two logical cores. So there are 8 logical cores.
Answer: While most of the answers here are providing the link to Wikipedia (which is correct!), I just want to list a paragraph from the same article which helped me understand how can the logical processor work.

Hyper-threading works by duplicating certain sections of the processor—those that store the architectural state—but not duplicating the main execution resources. This allows a hyper-threading processor to appear as the usual "physical" processor and an extra "logical" processor to the host operating system (HTT-unaware operating systems see two "physical" processors), allowing the operating system to schedule two threads or processes simultaneously and appropriately. When execution resources would not be used by the current task in a processor without hyper-threading, and especially when the processor is stalled, a hyper-threading equipped processor can use those execution resources to execute another scheduled task. (The processor may stall due to a cache miss, branch misprediction, or data dependency.)

Source: can you guess?

How many cores does my Mac have?


PSR12, Drupal or DrupalPractice?

Question: I want to respect coding standard in my new Drupal projects (for Drupal 8 and Drupal 9).
Using phpcs and phpcbf, I am wondering if I should use PSR12, Drupal, or DrupalPractice coding standards. Do you have any advice?
Answer: Drupal / DrupalPractice are the Drupal coding standards, which is probably why your question got downvoted.
The Drupal coding standards are pretty well documented.
Drupalize.me also has a tutorial about how to set up your local dev environment.
There are also a variety of tools that automatically apply the coding standards such as the Drupal Code Quality Checker.
Comment: Yes i know that, i was just wondering myself why the don't adopt PSR12.
Comment: @Ichabrand Given the size of the Drupal ecosystem, it would be an enormous amount of work to change standards.  Maybe they will eventually, but Drupal is historically pretty slow to adopt other standards, and it tends to hold on to what it's got.  (For example, jQuery is still in core even though it's no longer a hot technology and there are many other js libraries that are much "cooler".)

PSR12, Drupal or DrupalPractice?


Suppress default CRM.alert in hook_postProcess

Question: Trying to figure out an answer to this question, have tried to just disable a default CRM.alert using CRM_Core_Session::setStatus(null, false);  in hook_postProcess (defined in a drupal module), but alert still pops up (not a problem generally, it pops up in a default style, would like to use  CRM.status  instead, which works perfectly even outside of CiviCRM, while CRM.alert doesn't).
Any advice, please!
Answer: To clear all status messages and prevent them from being shown to the user, you can do:
CRM_Core_Session::getStatus(TRUE);

Comment: you are my hero, thanks!!  For those, who've been asking for exact code example, here is it:
  **(new CRM_Core_Session)->getStatus(TRUE);**


Omni Channel - Set different capacity per user

Question: I would like to assign cases to agents via Omni Channel, but I've seen capacity is set at Presence Configuration, and it's classified by profile, or user by user. Isn't there any way to do it by another object or without creating a lot of presence configurations? Because I would like to make it easy to manage.
I was thinking about a new field at Users object, setting current capacity for each of them, and call thar info from apex, but I'm actually searching if it is possible. My last option was setting presence status for each user.
Answer: At the end, we classified users into categories according experience: Level 01, Level 02 and Level 03, using those categories as Presence Configurations and assigning users to these ones.
Answer: To achieve this by creating multiple presence configurations, you will need to create PresenceUserConfigUser record.
DML operation not allowed on this object through APEX. So, you need to use screen flow.
Answer: I try to use flow to create PresenceUserConfigUser record, but flow will throw error too .. :D
flow error : The flow failed to access the value for UserPresenceRecord.UserId because it hasn't been set or assigned.
Comment: This does not really answer the question. If you have a different question, you can ask it by clicking [Ask Question](https://salesforce.stackexchange.com/questions/ask). To get notified when this question gets new answers, you can [follow this question](https://meta.stackexchange.com/q/345661). Once you have enough [reputation](https://salesforce.stackexchange.com/help/whats-reputation), you can also [add a bounty](https://salesforce.stackexchange.com/help/privileges/set-bounties) to draw more attention to this question. - [From Review](/review/late-answers/193950)
Comment: thanks for your suggestion.


Duplicate meta descriptions & title tags

Question:
    I have website and have some issue with duplicate description and title. Can any body help me to solve this error in easy and simple words?
Comment: You have 4 pages with duplicate description meta-tags and 2 pages with duplicate title tags- this means that these tags are the same across a few pages. In the most ideal case, each page would have a unique title and description. It depends on how your website is built on how to change these. It can be as simple as editing HTML files or updating a post in your CMS or blogging software. You would also need to figure out what pages are the same. We can help you with this, but you will need to tell us more about how your site is made. Editing out the link so that the question does not get closed.
Comment: It looks like you only have 4 pages so there is no problem figuring out which ones should be changed. What are you using to create your site??
Comment: just find the pages which had duplicate titles and descriptions and edit meta Page title and description tags between head head tags manually with your choice of text.
Answer: I'm gonna attempt to go simple as the OP requests.
Each webpage with a title and meta description will contain source code with these lines in it near the beginning of the code:
<title>insert title here</title>

<meta name="description" content="insert description here">

...Except that "insert title here" is meant to be the actual title and "insert description here" is meant to be the actual description.
What google is telling you is that these two values need to be different for every page on your website. You can't use the same title on two pages nor can you use the same description on two pages.
If by chance you're doing a site involving multiple pages that people can look through, then consider adding "page 1" to the title and "page 1" to the description for the first page of the document, then increment where appropriate.
Here's what I mean. Say I wrote a 3 page article on apples. On page one, I'll have code that includes the following:
<title>Apples Page 1</title>

<meta name="description" content="All about Apples. Page number 1">

Then on the second page, I would have:
<title>Apples Page 2</title>

<meta name="description" content="All about Apples. Page number 2">

Then on the third page, I would have:
<title>Apples Page 3</title>

<meta name="description" content="All about Apples. Page number 3">

Next, if you can change your pages into categories or section names, then that's a bonus since the names are more creative.
Answer: The meta-description should be a natural language, brief summary of the page while the meta-keywords should be a concise list of highly relevant keywords in a comma delimited list that are related to concepts, terms or branding elements of the page. Be mindful of your use of trademarked terms in your keywords and branding.
The keywords are NOT a repeat of the description.
Also descriptions and keywords should be specific to the page. Ultimately you want little to no duplication of keywords across pages because you want them seen as unique for the specific topic of that page.
Answer: Create UNIQUE title and meta descriptions for each page.
<title>Unique Title Here</title>
<meta name="description" content="Unique Meta Description">


Logos with avatars (mascots) vs anything else

Question: Has anyone seen a study on how users react to logos that contain alive things like birds vs just geometric shapes or really anything else? I assume everyone will grow to love a mascot more then just a circle, but I need evidence.
Comment: Exhibit A to the contrary: Microsoft's Clippy. *Everyone* hates Clippy.
Comment: @LaurenIpsum I used to love Clippy and his interchangeable buddies. Granted though I ***never*** used him for anything work-related. Mostly Right-Click > Animate =).
Comment: "Annoy me with that freaking paper clip every 30 seconds?" yes/no
Comment: All depends on how it's executed
Comment: Though this does not entirely answer your question [this paper](http://personal.stevens.edu/~rchen/creativity/colors%20in%20brand%20perception.pdf) offers some insight in color and brand logo effectiveness.
Comment: Oh, and that yellow dog that appeared in the Explorer search (Rover from Microsoft Bob), a repeating WTF-moment on its own...
Answer: I don't think you can assert a matter of perception as a "law" which applies to everyone.  I personally like shapes and symbols better than personifying everything - it gets a little cheesy after awhile. I think it is all about preference and execution.  If you have a crappy mascot, it won't fly.  If you have a crappy geometric logo, it won't fly either; but either one is just as viable when executed correctly.
Answer: Personally, I think it is hugely dependent on your audience.
Children for example love characters, cartoons, animations, smiles and general rainbows, sunshine and happiness. (or at least that's what we condition them to like/like to think they like). So responsive characters and smiley faces are rampant in logos aimed at children. E.g CBeebies this is their logo
now the clever thing is that though their logo is lacking in a mascot, they have these little guys who are consistently shown along side the logo, or bouncing on screen right before or after the logo shows up. As a result their logo is associated with a super happy character/mascot who has a design that iterates that of their logo.

This paper explores 'BRANDS, MASCOTS AND CHILDREN: A QUALITATIVE APPROACH' basically it shows that;

As far as mascots perception is
  concerned, children's answers show that they are an important way to develop the
  relationships between children and brands

Personally I feel that mascots can help a brand to a variety of audiences, for example the minions of Despicable Me have become notoriously loved as mascots for the movie. So much so that they trump the logo, for example a google search of Despicable Me images returns the minion characters before the logo for the movie.
I think the defining catch is that if you have a mascot in a logo you need to be able to give it character. Naturally with video it is much easier to give a mascot character as there is more media to play with to help identify that individual and create a relationship between it and an audience member, thus creating a relationship between a consumer and a brand.
That said, specific to graphic design and logos I have taken some research based on consumerism and interpreted a little 'companies need to be able to communicate a meaning' (see this paper for more) If this meaning is communicated more effectively through the use of a mascot in a logo/product well then it can contribute to the meaning the appearance of a product communicates which in turn helps consumers to assess the product on functional, aesthetic, symbolic or ergonomic motives. These motives play a role in the overall product appraisal (same paper) or in the case of a logo the appraisal of the brand.
So in short, yeah if your logo has a mascot that contributes to the communication of a specific meaning, then people should like it.
Long story, we could open the can of worms of visual response and the uniqueness of the context of each audience member and therefore there perception - this is talked about in relation to persuasive imagery here - I think it would be a bit of a tangent for me to ramble about it!
Hope I've helped!
Answer: I don't have any studies, but years ago I came across a website called Suicide Food. I don't advocate the viewpoint, but I think it is relevant to your question.
Once you see what they are talking about it is hard not to see it in logos etc. everywhere. My personal reaction is humor and laughter, but I suspect the people who run/ran that blog are earnest about their outrage.
A secondary problem related to animal mascots is that they are often anthropomorphised, and the choices you make as a designer to give character can easily be seen as racist.
Now, you can easily brush this off as people being easily offended, but the point is that you are asking about a logo. If offending people is part of the company culture, then it is probably OK.
Then again, even Tinky-Winky managed to offended some people.
Comment: I think it is interesting: meat rarely have a picture of the actual animal on the packet. And _if_ they do it, it is anthropomorphised, cartoonish; rendered inoffensive and "humorous". I think however what the OP might want to know, are more in the vein of company logos where technically the company has nothing to do with pandas/tigers/flamingos or other high-profile animals.
Comment: I agree. I don't have any studies unfortunately. I am sure there is a difference in response to, say, a Porky Pig type character than the Lufthansa logo, and I am interested to read anything anyone might come up with.
Comment: Same here, absolutely interesting. And what - if - the difference between the stylised thing, such as Lufthansa, and the more realistic ones, and wether the company is in any way related to animals/biology.


Is the MCMC simply a probabilistic gradient descent?

Question: I'm learning about Markov Chain Monte Carlo methods, and to my undifferentiated mind, they basically resemble gradient descent with a stochastic component replacing the gradient computation. Is this a correct understanding. If not what key difference am I missing?
Comment: Although it's been a long while since the question was asked, I would like to point to [Max Welling and Yee Whye Teh, _"Bayesian Learning via Stochastic Gradient Langevin Dynamics"_ , ICML 2011](https://www.ics.uci.edu/~welling/publications/papers/stoclangevin_v6.pdf) which explains "seamless transition between optimization and Bayesian posterior sampling".
Answer: The key difference is that we are not attempting to optimize anything.  Instead, we are attempting to estimate a density function - but not by estimating in some optimal manner a small number of parameters, instead by generating a lot of random numbers from the density function and going from there.  So MCMC is really a random number generation technique, not an optimization technique.
To see what a gradient descent-like algorithm with a stochastic component looks like, check out stochastic approximation.  The simultaneous perturbation variant is quite effective and accessible.
Comment: I see your point, but somewhat disagree.  With cost minimization, we know the cost function, and we are trying to find the peak.  The stochastic gradient techniques pick a random direction (guided by history) with that objective.  With MCMC, we don't try to reach the peak.  With an independence sampler, we aren't even selecting the next proposal with any reference to our current location (so this would analogize to trying to min. a function by just randomly selecting inputs.)  The only real similarity I see is solving a problem via random proposals with an acceptance step.
Comment: Thanks! I get that, but to me this is a difference of intent rather than technique. To me the density function in MCMC takes the place of the cost function in optimization. True, in the case of MCMC we don't stop when we reach the peak of the density but keep exploring, visiting each neighborhood proportional to the density landscape, but it looks remarkably similar.
Comment: The Metropolis algorithm that we statisticians use to get samples from posterior distributions can also be used to optimize functions (that's what simulated annealing is), but it's still not stochastic gradient descent.
Comment: Good! I wasn't seeing ghosts completely :) I realize MCMC is not gradient descent, but there are similarities, especially since the acceptance step compares the value of the new and old densities and effectively tries to climb up hill (with a little slip, if you will)
Answer: I know this question has been answered, but if anyone is interested in learning more on on jbowman's suggestion of random proposals with an acceptance step see Simulated Annealing:
http://en.wikipedia.org/wiki/Simulated_annealing
Excerpt:

"The method is an adaptation of the Metropolis-Hastings algorithm, a
  Monte Carlo method to generate sample states of a thermodynamic
  system..."

Typically slower then SGD, it's a good MC-based method for seeking global minima.
Java implementation for reference: https://github.com/wlmiller/BKTSimulatedAnnealing
Answer: While the accepted answer here is true, it is a bit misleading in light of recent theoretical work.
When you are doing gradient descent, you are trying to find the maximum a posterior (MAP) - aka the mode of your posterior distribution.  While stochastic gradient descent (SGD) will only give you a point estimate, it will give you a trajectory that will allow you to explore the posterior density around your MAP estimate.
There is a ton of emerging literature around this, starting with Neal 2012 / Welling 2011 with Langevin dynamics and later Mandt 2017, Maddox 2019 and Zhang 2021. At this point, it is safe to say that SGD will generate a single MCMC draw from your posterior distribution.


How do I explain the below phenomenon I am seeing along the edges of my eyeglass lenses?

Question: I am near-sighted. Here is the phenomenon: I stand in front of a light source that is situated on the ceiling so that it reflects off my eyeglass lenses and appears circular. It is a white light source but appears shifted a blue-green in the reflection. When I tilt my head so the reflection is in the very corner of the lens, the circle becomes dramatically oval-shaped and the color has shifted. On the side closest the edge it is red and on the more medial side, blue. First, why is the reflected image (no head tilt) green? Second, why does the image shift in color when situated on the edges? I am guessing the thickness of the lens has a role to play, being thicker on the edges but I don't know how to explain all of it. I'm am guessing also as I tilt my head the angle may hit a critical point where it acts like a prism where you can get all the colors out. Again just speculating here though
Comment: I think that oval shaped circle is due to the change in curvature of the lens. Also, the changes in the spectral colours observed may be due to the changes in the relative refractive indices of different parts of the lens.
Answer: Probably the colors are due to an antireflection coating or UV rejection coating on your lenses.  Those  shift color with the angle of reflection.
You are right that the oval shape of the reflected image of a circle is due to curvature of the lens.  If you look at the reflections in, e.g., a christmas tree ball or fishbowl, you wiĺl see a similar effect ( though not the color shift).  To see a similar color shift, you could look at reflections in good quality camera lenses or binocular lenses.
Comment: Yes, except that the color would not change with angle.  However, if the color is due to multilayer interference (as in the case of oil on water or thin coatings on glass) the reflected color is a function of angle.
Comment: I guess in a christamas tree ball (red one for example) there'd be a drastic color 'shift' ? ;)
Answer: It might even be due to spherochromatism, coupled with barrel distortion?
White light is polychromatic in nature.
Spherochromatism (also called chromatic aberration) is a phenomenon where light rays of different wavelengths (as seen in the composition of white light) are deviated to different angles within the lens, such that they all do not converge at the same focus. This causes "coloured fringes" to manifest at the edges of images.
It's mainly because of an irregular curvature or refractive index in the bulk of the lens.
This might be why your images have blue or green on the edges.

And the reason the fringe colours change while you move your head must most likely be because of your eye's accomodation. As you look at things of different distances from your eye, to focus that light and view objects clearly, the human eye changes the focal length of its lens which is termed accomodation of far and close objects. By changing this focal length, out of the various colours refracted, only one colour must be reaching your retina at a time, most likely causing the colours to change as you move your head.
"Barrel distortion" most likely is the reason for the ovoid shape which you talked about. This is also called a fishbowl effect, and is extremely common in the concave lenses used to treat myopia; which you must be using, since you mentioned that you are near-sighted.
Its because of a changing curvature of these concave lenses at the edges by which image magnification decreases at their peripheries, causing an enlarged image in the centre with lesser-magnified images at the fringes giving an ovoid, fishbowl effect.
The opposite is observed in convex lenses, where the peripheries are magnified more than the central regions, causing "pincushion distortion", as shown in the figures I've attached below.


Calculate cost of predefined path

Question: I am trying to calculate the cost of walking a predefined path. The path can be a line or a number of points along that line. I have a DEM and derived it's slope, which I will use as a friction map. I want to know the cost of getting from point A to point B using the line/points as a path, not the least cost path.
Answer: Using GRASS GIS, you could convert the path to a raster, then extract the slope values from all slope pixels along the path raster, and sum them up. So:
<code># Assuming a line vector named "path" and cost raster named "slope"
v.to.rast input=path output=path type=line use=val value=1
r.mapcalc "path_cost = if (path=1, slope, null())"
# The sum of the pixels will be the total cost based on slope of all pixels "under" the path
r.univar path_cost # Check value of "sum"
</code>

Calculate cost of predefined path


How does a hole do impact ionization?

Question: Impact ionization is said to be generation of electron-hole pairs with help of free electrons and holes. I have the intuition on how a free electron would be able to generate electron hole pair. I can't understand how a hole can do so.Please help.
Answer: A hole is just a low energy location in the valence band, where electrons tend to jump.
A hole could be a vacancy left behind by an electron jumping to the conduction band or to another hole or it could be a low energy orbital of an acceptor atom imbedded, via a p-type doping, into semiconductor to promote conductivity in the valence band.
When, under the influence of an electric field, a valence electron jumps to a hole and leaves another hole behind, another electron could jump into that new hole, setting off a chain of jumps and thus creating a current. This could make an impression that a hole itself is moving, giving a rise to the concept of a hole current, which flows in the direction opposite to the direction of the electron current.
In fact, of course, we still have moving electrons, and, similar to free electrons in the conduction band, they could hit neutral atoms and, given a strong enough field, generate new electron-hole pairs.
Comment: What you are talking about is annihilation of a hole to produce another hole  whereas impact ionization means creation of another electron hole pair by a free electron or a hole without either getting annihilated.
Comment: @Rohan I am talking about annihilation of a hole by an electron jumping into a hole just to explain that the hole current is, in fact, the current of electrons, which, unlike holes, are  real physical particles that carry energy and, therefore, while they move from one hole to another, can hit neutral atoms and ionize them, thus producing new electron-hole pairs.  The hole current is just a convention, introduced to differentiate current made up by free electrons in conduction band and bound electrons in valence band. Semi. currents could be described without ever mentioning holes.

How does a hole do impact ionization?


Do particles always flow from high to low pressure?

Question: In a recent question, it was stated that

particles in high pressure air always flow to lower pressure.

In a pipe with a constriction, fluid flows from from low to high pressure after the constriction. (From here.)
How are these concepts related?
Answer: Particle do NOT always move from high pressure to low pressure. They can move from a low pressure region to high pressure region and experience a decrease in speed.
The question is analogous to asking if objects always move in the direction of the net force on them. They don't, but they do always accelerate in the direction of the net force on them. If an object has a velocity in a direction opposite the net force on it, the object will slow down.
Consider a small parcel of fluid at a particular location. The pressure gradient at that location (plus the weight of the parcel) is the net force on a parcel of fluid there. This determines the direction the parcel accelerates, which could be different that its velocity.
Comment: Discussing the acceleration of the fluid in terms of the pressure gradient and weight per unit volume is equivalent to discussing the Bernoulli equation. I don't understand what it is that you are claiming is untrue about my answer.
Comment: I'm sorry. I read your last paragraph incorrectly. I'll delete the earlier comment. You were correct to say that particles would be decelerating (on average) as they moved out of the venturi.
Comment: At the orifices at the outlet end of a venturi there are exchanges of energy between kinetic and potential forms where the pressure gradient will not explain the flow. Its essentially like a pendulum on the upswing where kinetic energy is being continuously converted into potential energy.
Answer: Particles do not always flow from high pressure to low pressure, but there is a good reason why they claim so.
First order of business, particles move in a quasi-random manner.  Sometimes they go one direction, sometimes they go another.  On average they flow in a direction.  However, I don't believe that is exactly what you are asking about.
The claim that particles always flow from high pressure to low pressure is only true as long as the particle velocities are low.  If you have high velocity (such as in the middle of a venturi), that momentum can drive particles from lower pressure to higher pressure.  This is seen in the graph.
The claim is useful because there are many situations where velocity can be ignored.  For example, if you have a tank of compressed air and let it decompress into the air through a nozzle, there may be many pressure variations inside the tube, but the general airflow will be from high pressure standing still (inside the tank) to low pressure standing still(outside air).
The other way that claim is useful is if you use what is known as "static pressure" rather than the usual dynamic pressure.  If, instead of taking the pressure from the sides of the walls, your example had a pitot tube like device which sampled from the middle of the tube, pointing towards the tank, you'd see a different distribution of pressures.  In the middle of the Venturi, you would have a lot of particles "piling up" to get into the pitot tube, slowing down as they do.  This piling up would drive the apparent pressure (when measured) higher... to its "static pressure."
Answer: Flow of a fluid is from high pressure to low pressure.
This is explained in the first link of your question.
In the second link, the author is describing the fact that fluid pressure in a pipe is reduced at a point where the pipe diameter is reduced ('constricted', sometimes called a 'venturi'). This is explained using the Bernoulli principle. In the static case, there is no flow, since the pressure on either side of the venturi is the same. In the case of a fluid flowing through a venturi, the fluid pressure drops in the venturi. Flow is still from high to low pressure. As the fluid flows out of the venturi, its velocity decreases and pressure increases (Bernoulli principle). This time however, there is a pressure differential across the venturi. That is, the pressure on the 'inlet' side is higher than the pressure on the 'outlet' side, so flow is still from high pressure to low pressure side.
Comment: Not so. The flow is from low pressure to high pressure. Pressure is just a measure of one local form of energy gradient.
Answer: The determinants of the net velocity of particles is a combination of the kinetic energy and the potential energy. In a venturi the kinetic energy is higher than on either the inlet side or the outlet side. At the outlet side the kinetic energy will be decreasing as the particles exit the pipe into the high pressure "reservoir." They are essentially giving up their kinetic energy to increase the pressure (and potential energy) on the other side.
Bernoulli's Eqn which is really a restatement of conservation of energy for incompressible fluids says that along streamlines:
<code> {v^2/2} + gz + {p/rho} = {constant}
</code>
where :
<code>    v is velocity

    g is gravitational acceleration , z is height above reference level

    p is pressure and rho is density
</code>
So pressure is just one contribution to the relevant conservation principle, and  thinking of both kinetic and potential energy is a more comprehensive viewpoint. In the more realistic situation there are dissipative forces where energy is being lost to heat and sound, but this equation will remain an excellent approximation.
Answer: Flow always flows from high total pressure to low total pressure. And if its gets obstruction at any point then static pressure at that point gets high
Comment: Hello, and welcome to Stack Exchange. This does not answer the original question; you may want to edit it so that it addresses the question.
Answer: The statement "fluid flows from region of high pressure to region of low pressure" in the original question may be corrected as "velocity of fluid increases from region of high pressure to region of pressure and decreases from region of low pressure to region of high pressure." Comments solicited.
Comment: This doesn't really answer the question, it recommends a change to the verbiage used.
Comment: I don't see how this improves on or clarifies any other answers here.  It seems like a less detailed version of most of the other answers.
Comment: If the initial velocity of the particle is zero, it will flow from high pressure air region to lower pressure region.
Answer: The net movement of particles is from high to low pressure however individual particles may not move this way.
Let us assume that the particles have negligible inter-molecular forces - ideal gas assumption but probably appropriate in most fluids.  This would imply that a particle wouldn't 'know' if it was in a high or a low pressure region, it would just whizz along as would either way.
However, in a high pressure region there are more, faster, particles.  If you had 2 regions, one with high pressure and one with low pressure, connected by a pipe, particles would move both ways.  However, just out of statistics, more particles would move from high pressure to low pressure.
There is no extra force on the high pressure area, just more particles flowing.
Granted, for highly viscous fluids the inter-molecular forces will play a larger role and cannot be neglected like this.
Answer: It doesn't necessarily flow from higher pressure to lower, but from higher energy to lower energy, as per Bernoulli's theorem. That's the answer you want here when you are pertaining to the venturimeter.
Bernoulli's theorem states that total energy remains same between any two points. Total energy includes pressure energy plus kinetic energy and potential energy (datum head). So to maintain equilibrium if pressure reduces at any point, then kinetic energy has to increase, which means velocity increases.
$$\text{total energy}=\text{pressure energy}+\text{kinetic energy}+\text{datum energy}$$
Note that fluid flows from region of higher energy to lower energy. And not from higher pressure to lower pressure, which is a very common myth. Let's see the proof.
Let's look at venturimeter. Let section 1 be normal area section at starting point. Let section 2 be throat section. Let section 3 be the normal section after throat.
First half has converging section. Area reduces and therefore velocity increases to maintain equal discharge between two section to obey continuity ($\text{discharge}=\text{vel}\times\text{area}$). Now as the velocity increases its pressure has to decrease to maintain total energy equilibrium by Bernoulli equation.
$$\text{result: velocity 2 > velocity 1 and pressure 1 > pressure 2.}$$
So yes: fluid just flowed from higher pressure region to lower. The next half is more important than first half. Let's see what does it have.
In the second half the area increases which implies the velocity reduces in diverging section to satisfy continuity equation. Which means pressure energy has to increase to satisfy Bernoulli equation has to increase.
$$\text{result : velocity 2 > velocity 3 and therefore pressure 2 < pressure at 3.}$$
So fluid still flowed from lower to higher pressure region, which is against the myth of fluid only flows from higher pressure to lower pressure.


How can I reopen chrome window?

Question: Unfortunately, I closed my chrome window which contains more than 20 tabs. Few of them have good information. Search for again all those pages it will take much time, few I forgot where I got those pages also.
Answer: <code> To reopen recently closed chrome tabs/windows:
 Press Ctrl (Command for mac users) + Shift + T
 Note: It can reopen not only tabs, it can reopen recently closed windows also.
</code>

How can I reopen chrome window?


Variable length variable output encryption with out any padding?

Question: I would like to know if there is any encryption algorithm with variable input variable output with out any padding? For example if I give 16(17,18,67,117,..any size) bit plaintext, my ciphertext is also 16(17,18,67,117,..any size) bits.
Comment: Look for format preserving encryption. But if you can afford it, you should use an IV and a MAC, even if they cost a couple of bytes.
Comment: stream ciphers?
Answer: It is important to understand that secure encryption - by the standard notion of security - must be probabilistic. This is so that the same value encrypted twice will look completely different. Otherwise, it is possible to compute statistics and learn a lot of information. The easy fact based on this is that secure encryption must increase the size (the ciphertext has to be bigger than the plaintext).
It is possible to also assume state. For example, if the encryptor and decryptor can keep track of a unique nonce (e.g., a counter), then it is possible to still get secure encryption. (For example, use CTR mode.)
If you don't have either of these, then you are in trouble. This doesn't mean that you can't do anything reasonable, but we don't have enough information about your application to help. Just encrypting using format-preserving encryption can be very problematic, depending on what you want to do. I refer to a recent paper by Seny Kamara and others that will appear at ACM CCS 2015 that presents attacks on databases encrypted using deterministic encryption.


Why is /var/log/auth.log.1 smaller than auth.log

Question: I know there's a cronjob that rotates the auth.log files every set amount of time but I have noticed that the auth.log.1 is small compared to the actual auth.log. Doesn't auth.log get renamed to auth.log.1 and a new auth.log created?
Comment: Yes, that's how it works.
Answer: Yes and no:

Yes, auth.log gets renamed to auth.log.1
No, auth.log.1 is not necessarily smaller than auth.log as it depends on the usage of the machine.

E.G.: On my machine:
ll /var/log/auth*
-rw-r----- 1 syslog adm 209K Nov 30 17:55 /var/log/auth.log
-rw-r----- 1 syslog adm 304K Nov 25 17:08 /var/log/auth.log.1
-rw-r----- 1 syslog adm  27K Nov 18 09:20 /var/log/auth.log.2.gz
-rw-r----- 1 syslog adm  16K Nov 11 07:35 /var/log/auth.log.3.gz
-rw-r----- 1 syslog adm  19K Nov  5 07:35 /var/log/auth.log.4.gz

However, the other (older) logs get compressed so they're indeed smaller.
Comment: "as it depends on the usage of the machine." And also depends on whether or not the machine is exposed to the internet, where there's consistent attacks from botnet mafia to break into port 22 or other services, and that can fill up the log really fast into gigabyte size.  Also depends on the logging level, [see the post on topic](https://serverfault.com/a/454746/363611)
Answer: Log rotation is managed by logrotate package, which was designed for the task.
From man logrotate
NAME
       logrotate ‐ rotates, compresses, and mails system logs

SYNOPSIS
       logrotate [-dv] [-f|--force] [-s|--state file] config_file ..

DESCRIPTION
       logrotate  is  designed to ease administration of systems that generate large numbers of log files.  It allows automatic rotation, compression, removal, and mailing of
       log files.  Each log file may be handled daily, weekly, monthly, or when it grows too large.

       Normally, logrotate is run as a daily cron job.  It will not modify a log more than once in one day unless the criterion for that log is based on the  log's  size  and
       logrotate is being run more than once each day, or unless the -f or --force option is used.

       Any  number  of  config files may be given on the command line. Later config files may override the options given in earlier files, so the order in which the logrotate
       config files are listed is important.  Normally, a single config file which includes any other config files which are needed should be used.  See below for more infor‐
       mation on how to use the include directive to accomplish this.  If a directory is given on the command line, every file in that directory is used as a config file.

       If  no  command line arguments are given, logrotate will print version and copyright information, along with a short usage summary.  If any errors occur while rotating
       logs, logrotate will exit with non-zero status.

Comment: *Facepalm!*  Not `cron`!  `logrotate`!!!  **+1**