How to test the connection speed of a server?

Question: What are the techniques to test the connection speed of a server (in my case, virtual Ubuntu server @ Slicehost)? Bonus points for one liner bash command.
Comment: What exactly are we testing? Are we testing website requests per second or what. Are we testing a single connection or multiple connections simultanious? Just saw it was asked 7 years ago, ok nvm.
Answer: One of the better command line tools for checking bandwidth available is iperf. However you need another box on an known fast connection to run the test against. I'm not aware of any public iperf servers.
Answer: Run netserver on one computer and netperf -h other.server.com -l 30 on another; see the official Netperf site for more details, source, and a Windows binary (most *nix port/package systems have netperf in them). Note: the results will be limited by the slowest connection between the two and port 12865 must be open on the server side.
Answer: Take a look at this question for a technique to use dd over netcat and make note of the discovery that disk I/O was the limiting factor over a local network with the particular hardware involved. Over the internet and with faster hardware, your mileage may vary. By using /dev/zero as the source and /dev/null as the destination, the disk I/O factor will be eliminated as noted in the comments.

target system:
      nc -l -p 9000 | pv | dd of=/dev/null
source system:
      dd if=/dev/zero | pv | nc 9000 -q 10
Comment: +1 for the use of pv. You can also replace /dev/hda by /dev/null and /dev/random for network testing without beeing limited by disk i/o.
Comment: Uh, excuse me, `dd of=/dev/hda`? Won't that overwrite the contents of first disk? The thread you linked to is about cloning a machine over the network... OP beware :)
Comment: /dev/zero would be a good source for this - /dev/hda will be limited by disk I/O - and you'd want to set the "of" to /dev/null - OTHERWISE YOU'LL GET DATA LOSS.
Comment: Yes, I meant to change that. I'll do it now.
Answer: This is my own one-linner to get the time of th emost basic HTTP 1/1 request on my servers.
Change www.foo.com by the ServerName and 192.168.1.15by the HTTP server IP (use the IP, as with the real name you would have the DNS search time added).
time printf 'GET / HTTP/1.1\nHost:www.foo.com\n\n' |nc -w 10 -q 10 192.168.1.15 80 1>/dev/null

I usually do it on a very simple default Virtualhost with a static HTML page, to get the base response time (no cgi or php things, not even session, mod_rewrite or auth managment.
For the real time tracking I use Nagios plugins, apache status results (very usefull on bash one linners as well wityh q=auto), and sometime autobench (based on httperf).
Answer: I think the simplest is to use iftop.
On the server @ slicehost run

sudo iftop

Then start downloading a large file with wget in another SSH window.
From the iftop man page:

The main part of the display lists,
  for each pair of hosts, the rate at
  which data has been sent and received
  over the preceding 2, 10 and 40 second
  intervals. The direction of data flow
  is indicated by arrows, <= and =>. For
  instance,

   foo.example.com  =>  bar.example.com      1Kb  500b   100b
                    <=                       2Mb    2Mb    2Mb

etc...


Remove password protection from an outlook .pst file programmatically

Question: I am working on a project which involves reading through a lot of Outlook.pst files.
These files are all password protected but I have the password in question. The problem is that it's very tedious process opening each file in Outlook and enter in the password in order to read the data.
Now I'm thinking if there is any way to create a script which opens each .pst file for me automatically, enters in the password and saves the file again without the password.
I've been googling around and don't seem to find any solution to my problem, looks like the MAPI outlook.application interface is poorly documented. So far I've seen a PowerShell script doing this with an Excel application from technet
<code>$comments = @'
Script name: Remove-Password.ps1
Created on: Tuesday, July 03, 2007
Author: Kent Finkle
Purpose: How can I use Windows Powershell to
Remove the Password When Opening an Excel Spreadsheet?
'@
#-----------------------------------------------------
function Release-Ref ($ref) {
([System.Runtime.InteropServices.Marshal]::ReleaseComObject(
[System.__ComObject]$ref) -gt 0)
[System.GC]::Collect()
[System.GC]::WaitForPendingFinalizers()
}
#-----------------------------------------------------
$xl = new-object -comobject excel.application
$xl.Visible = $True
$xl.DisplayAlerts = $False
$wb = $xl.Workbooks.Open("C:\Scripts\Test.xls",0,$False,1,"%reTG54w")
$wb.Password = ""
$a = $wb.SaveAs( "C:\Scripts\Test.xls")
$a = Release-Ref($wb)
$a = Release-Ref($xl)
</code>
Possibly I could apply this to MAPI with something similar to this
<code>$outlook = new-object -com outlook.application;
$ns = $outlook.GetNameSpace("MAPI");
$fSaveMe = $ns.GetDefaultFolder($olFolderInbox).Folders.Item("Save Me")
$fSaveMe.Items | foreach { [void]$_.Move($ns.Folders.Item("Legal")) }
</code>
Is there anyone that has had a similar problem ? The potential solution doesn't have to be in PowerShell, it can be in Python, Perl, Java, C# or just about anything as long as it gets the job done :)
Answer: It can be done with extended mapi which is only possible with c(++) or delphi. Alternative (and much easier) is Redemption which wraps extended mapi in a com object. More specifically, see the AddPstStoreWithPassword method of RDOStores


Can I apply a WP theme to a specific custom page template?

Question: One section of my website is going to be completely different visually than the rest of the pages, is there a way to apply a WP Theme to specific page templates ?
Answer: In fact there is, using template_redirect, which you would put in the functions.php file - Here's what I use:
function uniquename_default_template() {
    if(get_post_type() == 'posttype') : /* You could use is_single() instead of get_post_type() == '' or any type of conditional tag) */
    include(TEMPLATEDIR . 'path/to/theme/file.php'); /* You could use TEMPLATEDIR to get a file from a template folder, or PLUGINDIR to get a file from the plugins directory - doesn't support HTTP requests */
    exit; endif;
}
add_action('template_redirect', 'uniquename_default_template');

The above code checks for a post_type called posttype, if it is, it will include the PHP file specified in the include statement by redirecting the template using the template_redirect function.
Comment: @mike23 - that's just example code, jared suggested to have some template inside a plugin but you can naturally use some template from within another theme and then use TEMPLATEDIR to point to the right file.
Comment: Ok so I put this function into the functions.php of my main theme. Then I have a second theme that I want to apply only to a specific page template. I can test this condition on the first line of your function with `if(is_page_template('template_special_area.php') )`. Then I have to include this said template, how do I do that? Doesn't TEMPLATEDIR point to the main theme fodler?
Comment: @mike23 - hakre is right, you would need to use `TEMPLATEDIR` (which points to `/public_html/wp-content/themes/`) if the file is in your themes folder. But my code may be a little buggy, I haven't tested it much but it might just work for what you need. Either way, the function you're looking for to use is `template_redirect` - I wouldn't count on my code above to work 100%.
Comment: @mike23 - I revised my code a bit, it is in the proper format now and above is how it should be used.


How are they/How were they?

Question:
I saw my children two days ago.
How are they?/How were they?

Are both of these natural in the given context or only one of them?
Answer: There is no clear dividing line between how your children still are and how they were when you saw them. There's a grey area between the present and the past.
If someone asks you are how your parents are, and they were fine last time you saw them, you are likely to answer  They're fine unless you have reason to believe otherwise. It doesn't really matter whether you saw them yesterday or last week.
And the same applies to your question. If your children were healthy and happy two days ago, and the questioner is merely being polite, s/he is likely to ask how are they.
If the questioner is aware that they had been ill or involved in a minor accident, the natural question would be how were they (when you saw them).
As so often, it's the context rather than the time elapsed that dictates the tense of the question and the answer.

How are they/How were they?


What exactly is Microsoft Expression Studio and how does it integrate with Visual Studio?

Question: My university is part of MSDNAA, so I downloaded it a while back, but I just got around to installing it. I guess part of it replaces FrontPage for web editing, and there appears to be a video editor and a vector graphics editor, but I don't think I've even scratched the surface of what it is and what it can do. Could someone enlighten me, especially since I haven't found an "Expression Studio for Dummies" type website.
Answer: Expression Studio is basically a design studio. It consists of a bunch of design software that Microsoft has bought for the most part. The audience is designers, not developers. The gist of the software is that Expression Blend enables designers and programmers to work seamlessly together in letting the designer create the graphical user interface.
In a normal workflow, the designer would deliver a mockup which the developer would have to implement. Using Expression Blend in combination with WPF, this is no longer necessary. The graphical UI made by the designer is functional. All the developer has to do is write the code for the function behind the design.
This in itself is great because developers invariably fail to implement the design as thought out by the designer. Technical limitations, lack of communication … whatever the reason. UIs never look like them mockup done up front.
Expression Design is basically a vector drawing program that can be used to design smaller components that are then used within Expression Blend as parts of the UI. For example, graphical buttons could be designed that way. It can also be used as a vanilla drawing program. I did the graphics in my thesis using Expression Design.
Answer: The idea is that designers will work in Expression Design (to design vector artwork) and Expression Blend (to build and style XAML interactions, as well as to define timeline based animations and interactions).
Developers will work on the application in Visual Studio. Visual Studio includes very basic XAML editing capabilities, so developers would only be making minor edits and would mostly be focusing on the code-behind.
That's the theory / product strategy side of it. In reality, if you're performing both roles, you'll end up having your project open in both Expression Blend and Visual Studio, switching back and forth between them depending on whether you're doing "designer tasks" or "developer tasks". Fortunately, Expression Blend and Visual Studio use the same project files.
Answer: From Wikipedia:
Microsoft Expression Studio is a suite of design and media applications from Microsoft aimed at developers and designers. It consists of:

Microsoft Expression Web (code-named Quartz) - WYSIWYG website designer and HTML editor.
Microsoft Expression Blend (code-named Sparkle) - Visual user interface builder for Windows Presentation Foundation and Silverlight applications.
Microsoft Expression Design (code-named Acrylic) - Raster and vector graphics editor.
Microsoft Expression Media - Digital asset and media manager.
Microsoft Expression Encoder - VC-1 content professional encoder.

For web development Expression Web is useful. For XAML development, Blend and Design are useful.
Answer: EDIT: Okay, I type too slow so most of what I had to say was already mentioned, so I'll strip it out except for...
The BIG thing to take note of is that the WSYWIG designer they used in Expression Web made it's way into Visual Studio 2008, which is a VERY GOOD thing. There is now EXCELLENT support for CSS, a better editing interface, and you can even go into a split edit mode to see the code and the content while editing.
For the longest time I was using Expression Web to do all my initial layout and then loading that into Visual Studio 2005. With Visual Studio 2008, there is no need to do it.
Answer: The Expression site is the first place to start. These are tools that bridge the developer/designer gap for building rich internet applications with Silverlight and WPF. They compete with Adobe Studio products.
Whilst Visual Studio is good for working with code, it has some weaknesses when it comes to dealing with XAML. In many cases a designer will build something visually different from a Windows application and Expression Blend allows them this freedom. It ties in Visual Studio for the C#/VB coding and debugging part of development.
Answer: Expression Studio is targeted more at designers.  It integrates with Visual Studio in that Expression Studio uses solution and project files, just like Visual Studio.  Which makes collaborating with designer easier.  The developer and the designer open up the same project.  The developer sets up the initial page with all the binding and the designer takes that page and makes it look pretty.
Answer: Please check for XAML .NET development, most of the tutorials makes use of many Expression tools.


Filter Views in Drupal - select nodes from taxonomy with children

Question: I'm using drupal 7 with views 3. I added some filters to the page and one filter is taxonomy. This taxonomy has a tree structure. Filter is exposed, so the user can change it. Everything works fine but there is one major bug.
Example structure:

Parent 1

Child 1
Child 2

Subchild 1

Parent 2
...

When I select for example Child 1 I can see all the nodes from the child 1 - that's ok. But for example when I choose Child 2 I can't see nodes from Subchild 1. Same situation if I choose Parent 1 - i see only nodes exactly from Parent 1 - Child 1,2 and Subchild 1 are not displayed.
Is it possible to show all children with parent with views? Or maybe I should do something like extract all the children manualy from code, than alter the query and make WHERE IN condition?
All help will be appreciated:)
Answer: Use the filter 'Has taxonomy terms (with depth)'


ER diagram to Relational Schema (Many to Many relationship)

Question:
In this ER diagram, can anyone explain how we should convert the many to many relationships ('view', 'update' and 'diagnose') to Relational Schema and then SQL? What I think is that there shouldn't be any relational table for 'view', 'update' and 'diagnose' for all many to many relationships. Instead, what I think is that we just grant permission to the specific users on whether they can 'view', 'update' or 'diagnose'. Can anyone make it clear or show me how to do it?
Comment: I think you are confusing permissions and relationships, they are not the same.
Answer: Let's start from a point that your ER diagram should not include possible user roles or actions such as view or update. You have to clearly specify your entities(objects for which you want to create separate tables) and connections between them which are not actions like you specified in your example, instead they show the relations between entities.
After creating your ER diagram you can change many-to-many relationships into relational schema by creating 3 corresponding tables; 2 tables for entities themselves and one which connects them by showing their relation, like for example User, Role and UserRole to specify the role for the users. After that you can give permissions to users from your application or from your dbms if they are database users, to filter and specify who can see what.


Single word for staying late at the office

Question: I've heard a lot of single words meaning "staying late at the office", but I'm not able to recall them at the moment. What word can I use to describe this?
Answer: The best (and only) one word description I can think of is working overtime.

Lisa was out sick yesterday, so the boss had me take her place and work overtime.


Dandruff with male cat

Question: My male cat has horrible dandruff. What can I do?
Answer: Dandruff can be caused by a few things such as:
1) Low quality diet
2) Improper grooming
3) Dry air (think of winter and the type of heating you use).
If he is obese or a geriatric (arthritis) cat they typically have a difficult time grooming themselves and will need assistance from you by brushing and bathing (preferably a dry bath). CEVA has some really nice sprays and dry baths designed for different skin issues - the product that is recommended for dry skin is Douxo Care or Douxo Calm. These are sold in veterinary hospitals, the staff at your regular vet can help you with your selection. For a brush I really love the Furminator, it really gets that undercoat - does absolute wonders in appearance if he has fur that he cant groom out himself.
Another product you can try is Dermoscent, it's a monthly topical that's pretty cheap that will help with overall skin and coat health. Good option for dry winter air.
If you cannot afford higher end foods, adding Omega 6 to his diet will help with skin and coat. When it comes to supplementing I advise you get directions from your veterinarian, they will know what supplement brands in your area are of good quality and can properly dose him from his weight and health status. Human grade supplements are not regulated (least in Canada) so you won't get what it says on the bottle (I.E 100mg tablet of B12 actually contains 2mg) there are some codes to look for to ensure quality (I forget at this time but will update once I ask the vets).
Comment: Thank you! He's already on a special diet for struvite crystals and he has to stay on it. I'll look into the other options you've provided for me.
Comment: fish oil might also help(not cod liver oil)all vets sell it,ask your vet about the dosage and if it might help your cat.feed it once a week for atleast one month,to see if it might help your cat.

Dandruff with male cat


How do I buy a PSN gift card for a friend in another continent?

Question: I don't have a PS4 console or PSN account but since you can't gift games directly I want to gift my friend a gift card. They live in Asia and I live in North America. Would I have to make an Asian PSN account or a NA one? I want to make sure the gift works for them so can someone please explain to me the logistics of it?
Answer:
How do I buy a PSN gift card for a friend in another continent?

You just buy codes from online retailers from a different country. For example, at least in Singapore, it's Lazada, SEAGM, eClubStore to name a few. These retailers typically charge about 5-10% above retail value (at exchange rates), but they stock codes from many other regions.

What are the logistics?

You pay, they take a code from a list of codes that they have (and obviously have not used, because their aim is to sell them legitimately, not scam you). After that, they or their servers give you a code that they have and you use it.
They usually buy codes off many sources, which includes directly from Valve.

What about scam?

There's nothing stopping them from giving you a fraudalent code, so you have to do your research and see who is credible. You can try a proper store, or find an individual seller.
General rule is: If it's below market price (and after exchange rates), it's likely to be a scam. The stores I've listed above have worked for me, and have assisted in times when my codes do not work.
Comment: Really, if its not to be a surprise, I would say ask your friend or someone who lives there where they would buy the card from. You'll get what is a true shop overthere and what is just a site trying to scam you (i'd guess a true, brick and mortar store will not scam your ass.)
Comment: Thanks can you link some of the stores you buy from? And the code how do I know that it will work in their regional account?


How likely are caverns inside the mantle?

Question: Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum?
Comment: As likely as carvens inside the mantle are
Answer: It is extremely unlikely that any hollow volumes exist in the mantle.
The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.
Answer: mantle isn't liquid, it is a thixotropic substance that flows when pressure decreases and fluids can flow. If there's huge mineral deposits with high melting points there may be pockets. But caverns need a "Floor".
Comment: The floor would be towards where the gravity acts. 1g gravity remains similar until the outer core from where it decreases until 0 at the center of Earth.


If I doubled my RAM, would my memory usage go down?

Question: My PC currently only has 1GB of RAM, and I am currently using 86% of that. With 2GB of RAM, would I be using 43% right now?
Comment: @David Schwartz I posted this 3 years ago, now I can tell you right now with everything running and 12gb of RAM my system does use a lot more resources, I generally run around 80-95% in use, A huge chunk of that seems to be 1 of Google Chromes extensions which I think is the Flash extension as it just grows untilI run out of RAM, I then close Flash and my RAM free's up almost 50% of it...seems to be a HUGE memory leak in Chrome/Flash
Comment: No, quite the reverse. Under the same load, the system should need about the same amount of free memory to handle it. With twice as much memory, the same amount free would mean 93% in use. (What would be the point of adding another GB of RAM just to have it not be used?! If the system was that stupid, why bother adding RAM? It won't run any faster, it'd just waste more memory.) Modern operating systems only need free memory to handle certain specific unusual cases. The rest of the memory, they are able to use.
Answer: Yes, your math is correct, to some extent.
However, note that modern operating systems use excess memory for caching. This article does a good job of explaining how OS memory management works (written for Windows Vista, but generally relevant for all operating systems); basically, it tries to use up your free (idle) memory for its cache, and when needed by another program, that memory is released again.
So the OS might appear to be taking up more memory, but it is only for caching purposes and can be freed at any time.
Comment: Even XP and earlier versions of windows used free memory as disk cache; this isn't new to Vista.
Comment: XP and earlier versions of Windows were based on the design assumption that memory was scarce and couldn't use significant amounts of memory as a disk cache. Vista and later take the more modern approach of trying to keep as much memory in use as possible.
Comment: thanks, I'm using windows 7 so it's probably similar to vista
Answer: Not necessarily, most operating systems use extra memory as a buffer.
Answer: vista used to occupy about 50% of my RAM when i had 2GB of RAM,idle
Answer: My company recently upgraded their XP laptops from 1 GB to 2 GB and my machine is currently using 1 GB of RAM, so XP probably uses more, too.
It's not like your memory is only RAM. There is also the pagefile, which is basically used for the same data. Just think of RAM as the faster part of your system memory. If the OS notices there is more RAM available, it will use more of it to store data that would normally reside in the pagefile. But if needed, the memory can be released quickly again, so that's nothing to worry about.
Comment: This is really totally incorrect. Windows will use very, very little pagefile unless it is under memory pressure. It the OS notices there is more RAM available, it will use more of it to store data that would it would normally read from the filesystems.
Answer: No, you'd probably be using less than 86% of that. It's like the way a family lives in a house. If you have 10% of the house empty and you move into a house twice the size, you eventually wind up with the new house about 90% full as well. Managing space is an active process, and more space means you can keep more stuff. There's no point in having more space just to keep more of it empty.
Free memory is just a cushion, a necessary evil in case the system needs space faster than it can free it. Otherwise, the system does its best to use all available memory. That tends to result in the least disk I/O and the most responsive system.
Answer: No you would most probably not be using 43% of your RAM if you upgrade to 2GB. Some programs utilize RAM in a logarithmic manner - more RAM detected, they will attempt to use more then.
Answer: No.
Having recently upgraded my RAM, I know that XP will use more for buffering and caching purposes when it has more to mess with.  With 768mb RAM simple services in Windows like spoolsv.exe (printer related) would use about 1 to 1.5mb of RAM.  With an upgrade to 2.5gb of RAM spoolsv.exe is now hogging 4mb, as are many other services that previously used around 1mb.
Answer: It is important to understand that memory usage in Windows is highly dynamic. Memory usage is dependent on system workload and how much memory is available. When more memory is available the system will enlarge the system cache and process working sets. When memory is short then working sets will be trimmed back. Physical memory usage is controlled almost entirely by the system with applications having only limited influence.


Need to Decryptor tool the Ransomware .Vesad extension

Question: Need  Decryptor tool for my encrypted jpeg files which was infected by Ransomware .Vesad extension.please help me on this.
Comment: The only reliable thing after a virus attack is restore from a safe backup. And no matter what you do, remember to reformat the affected compuuter as soon as possible.
Answer: The STOPDecrypter does support some of the .vesad version of this ransomware.
For the software and instructions/details check out the support topic over at Bleeping Computers: https://www.bleepingcomputer.com/forums/t/671473/stop-ransomware-stop-puma-djvu-promo-drume-help-support-topic/


undoing armature skinning?

Question: I want to undo armature skinning I pressed ctrl z but didnt work since the file was saved and opened again so I think I lost the reversing by ctrl z function
Answer: To remove all armature influence, you will need to remove the parent and remove the armature modifier from the mesh.
Select the mesh object and press ALT-P -> Clear Parent to remove parenting. Go to the modifier properties and remove all armature modifiers with the X on the right. Do not apply the modifier nor apply it as a shapekey.

undoing armature skinning?


Why do square shaped cups spill easier than round cups?

Question: I've noticed that when I use a cup that is square shaped with convex sides, it spills more easily than a circular cup. Why does this happen? What is the most spill-prone cup shape? What is the most spill-resistant basic cup shape?
Answer: When a square cup is displaced slightly from its position, the water inside it moves to a diagonal corner of the cup. If we look at the direction of motion of the fluid then we will see that the fluid moves from lower corner to upper diagonal corner. You can imagine your room as the cup and consider water in it. Suppose the room is slightly disturbed. The water will move towards a corner (visualize it in your room). The fluid hitting the sides of the walls get reflected(actually they experience a normal force) and add up to the velocity of the fluid in the diagonal direction. Again as the fluid moves towards the corner, the cross sectional area perpendicular to the diagonal goes on decreasing(imagine the diagonal of your room and visualize its perpendicular planes) However your cup has no such ceiling to bind the fluid. So the fluid moves over the top of the cup and is spilled.
The more closer the cup shape is to a sphere, the more spill resistant it is.(As then it will not have corners in any direction and the rate of decrease of perpendicular plane's cross sectional area will be the least)
Comment: Wonderful easy-to-understand explanation. Thank you.
Answer: Look at the bottom of a round cup.  The distance from the center of mass,
is the same in all directions from a point that is the center of the
circle that forms the bottom of the cup.  Thus when a force is applied
to tip over the cup, the direction that the force is applied is
unimportant because the distance from the center of the bottom of the
cup is identical in all directions to the outer edge of the bottom of
the cup.
The same is not true of a square bottomed cup.  On a square bottomed cup,
there are four points where the distance is a maximum, and four sides
where the distance is a minimum.  It is the minimum distance, less than
that of a circle that make the square bottomed cup less stable than
a round bottomed cup.
To maximize a cups stability, it needs to be short in height, and
great in diameter of a circle at the base.  There is a " spill proof "
coffee cup that is basically a truncated cone ( point up ) with an open
cylinder attached.
To think about bases, the least stable base is a triangle, and the most
stable base is a circle.  Stability increases as the number of sides
at the base increases.
A square is more stable than a triangle.   A five sided base is more stable than
a four sided base.  Etc.  Also short and wide is more stable than
tall and skinny.
Answer: It is the corners where the liquid molecules collect (for a very short time), collide and some of them tend to go upwards because that is the only available direction to move freely. The smaller is the angle between two sides, the greater the chance that liquid will spill from that corner (given that the motion of molecules inside the cup is random). A star shaped cup with narrow angles will be most prone to spilling. The next spill-friendly shape is an equilateral triangle.
A circular cup is most prone resistant because there are no corners where molecules can collect and bounce. That is, there is no barrier in the path of molecules where they collide with the walls and rise upwards. If you shape your cup a bit like a cone (the upper side being the narrow side), it will be maximum spill resistant when the contents are shaken.


Grobner basis for an ideal in $\mathbb{Z}[x_1,\dots,x_n]$

Question: In an article I'm reading the author says that a certain set of polynomials is a basis for an ideal $I\subset \Bbb Z[x_1,\dots,x_n]$. However, I have only ever seen Groebner basis in the context of polynomial rings over a field. I also cannot find any sources discussing groebner bases over general rings, or even PIDs. Does anyone know of such a source? Or does anyone know if there are important differences between the characteristics of Groebner bases over PIDs vs Groebner bases over a field?
Comment: @Mark I'm not sure that works... For example if we have $I=\langle 2x \rangle\subset \Bbb Z[x]$, then in $\Bbb Q[x]$ we have that $I=\langle x\rangle$, and this is a Groebner basis. However, $x\not\in I\subset \Bbb Z[x]$
Comment: Can't you compute the grobner basis over $\mathbb Q$ and then clear the (finitely many) denominators?
Answer: The book Gröbner bases by Thomas Becker and Volker Weispfenning (on springer) has a chapter on Gröbner bases over other kinds of rings in the end.
But yeah, as mentioned in the comments, $\mathbb Z$ is a subring of $\mathbb Q$ so it could probably be much easier than that.
Abstract:

The material in this section is not needed for the remaining sections
  of this chapter. Here, we will generalize the theory of Gröbner bases
  to polynomial rings over principal ideal domains. We will show that
  for every given finite subset F of such a polynomial ring, the
  equivalence problem for the ideal Id(F) is solvable by means of a
  Gröbner basis construction. The reduction relation will not in general
  allow the computation of unique normal forms, but it will be such that
  f ∈ Id(F) iff every normal form of f equals 0. This is good enough for
  the solution of the equivalence problem (cf. Theorem 5.55). For
  Euclidean domains that allow the computation of unique remainders, we
  will even obtain a reduction relation with unique normal forms.

Edit:
Bernard beat me to it, but the book by Adams and Lostaunau (published by the AMS) has a chapter on it as well. That book is in general far more readable than the B&W book in my opinion! I couldn't remember the authors so I was looking through the bib file I used when I referenced it, but then Bernard reminded me. It is better recommendation I think!
Answer: You also can take a look at chapter 4 of An Introduction to Gröbner Bases, by William W. Adams & Philippe Loustounau, Graduate Studies in Mathematics, vol. 1 (AMS Publications).
Comment: Haha, was just about to edit my post to include that book...
Comment: Thank you for your suggestion too


I tightened a Titus Minifix Cam too hard and now I have to take it apart. Is that OK?

Question: I put together this TV stand, and used a cam/bolt dowel for the first time when I got to the step of attaching the top of the TV stand (A) to the two stand panels (E). Since I assumed the cam had to be as tight as possible and it was fastened by a screwdriver, the first one I fastened I tightened way too hard and it messed the hole up a little bit. It was still tight, but it was a little angular and ugly, but that's fine because it was sturdy as hell. Once I realized not to do that I didn't do it again, but fast forward all the way to the final step of attaching the bottom/base and when I tilted the stand to its upright position and everything looks great except the top is backwards. Now I have to take everything apart, but I'm worried that since I've screwed everything in so tight, including the cam/bolt dowel, that when I put it back together it won't be as sturdy. Is there anything I can do to fix this situation? I'm an idiot.
Comment: Step 1) disassemble top. Step 2) reassemble top in proper orientation. Step 3) check to see if you have a problem. **IF** you have a problem, Step 4) [edit] your post to describe the actual problem. Seriously... You _may_ have damaged the particle board too much to make a secure connection, you may not have. The only way to know for sure it to try it out.
Comment: Thanks, I'm new to this board so forgive me if I didn't get to my point quick enough. I am at work but stressing to go home and potentially break my new furniture.
Comment: It's not about you being new, it's about not stressing over something that might not be a problem at all. Give it a try - either you'll be able to reassemble it without issue or you'll have a bit of a problem. Until you figure out which it is, don't worry! I'd venture that since you say it was "sturdy as hell" you haven't done any significant damage and you'll be able to reassemble with no/minimal problem.
Comment: Did you ever get this resolved? If so, please give a check-mark to the answer or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
Answer: It is understandable to be stressed about not breaking your furniture.
These cam locks can be loosened and tightened more than once.  The cam can only turn so far with pin inserted into it. Just turn them all 1/4 turn counter clockwise to unlock them from the pin, then you may need to tap lightly from under the top at each of the points where there is a cam lock or dowel. Use a rubber mallet or something that will not dent or leave marks, if you only have a regulare hammer then use a piece of scrap wood to protect the furniture.
When reinstalling the top do the opposite (tap in down). Then turn each cam 1/4 turn clockwise. When you get to the cam that is questionable do not try to take it out as the wood is particle board and you may end up doing more harm then good. Just use the screwdriver to push in as you turn, the pin will prevent the cam from turning to far so snug it up tight but no need to be Hercules just snug to tight not super tight.
What you do not want to do is unnecessarily turn the cams or turn them more then 1/4 turn when the pin is not in them as that may cause excessive wear on the particle board. The hole is sized to fit the cam. Nothing holds the cam in the hole except for the pressure created by the cam's internal machining rotating against the pin.


Unable to boot windows 10 or Ubuntu in dual OS installation

Question: I installed ubuntu in my lenovo notebook already running Windows 10. Followed the instructions given in the website https://www.tecmint.com/install-ubuntu-16-04-alongside-with-windows-10-or-8-in-dual-boot/comment-page-14/#comments. After installing I am unable to boot into both Windows 10 and Ubuntu. I don't get the boot options screen. Only the error message "Unable to boot Ubuntu". I tried boot-repair tool and obtained the following diagnosis report http://paste.ubuntu.com/p/wrZyxsG9zW/.
I am able to run live-ubuntu from installation disc.
Appreciate any help.
Comment: I think what you want to do is access the boot menu, so you can choose to boot into Windows before GRUB is loaded. It's possible you need to turn off Fast Boot in order to do this. The keys you need to press to access the Boot Menu (or BIOS, in order to disable Fast Boot) are different from manufacturer to  manufacturer, and sometimes even from model to model so look up instructions based on your computer. It may be useful to edit your answer to include this information (what computer you have)
Comment: On a side note, it looks like Ubuntu can't mount the NTFS partitions where Windows is installed...this is something you can fix with chkdisk once you figure out how to boot into Windows.
Answer: Windows is BIOS/MBR and it looks like you forced an UEFI install of Ubuntu on a MBR(msdos) partitioned drive. Normally UEFI uses gpt partitioning. But  Windows in BIOS boot mode must be MBR and boot flag must then be on the NTFS partition with Windows boot files or your sda1.
You show errors on NTFS sda2, not sure if just Windows 10 hibernation or it needs chkdsk which you can only run from Windows or Windows repair disk or installer with repair console. Use gparted and move boot flag back to sda1, see if Windows boots or if f8 takes you to repair console.
First fix Windows, chkdsk and turn off fast start up, You need to make Windows repair flash drive as you will need both Boot-Repair/Ubuntu live and Windows repair flash drives with BIOS/MBR.
Then use Boot-Repair from Ubuntu live installer booted in BIOS/Legacy/CSM boot mode and in advanced mode do a full reinstall of grub2, so it is the BIOS boot version of grub. You do not need to reinstall Ubuntu, just grub2.
Windows 10 works better dual booting in UEFI mode. Windows will, with updates, turn fast start up back on. Then grub will not boot it and you only can then directly boot using Windows boot loader. With UEFI, you can choose that from UEFI boot menu. But with BIOS, you only have one MBR and then have to temporarily restore Windows boot loader, fix Windows & then restore grub to MBR.
Since you have newer UEFI hardware, the other option to to reinstall Windows in UEFI boot mode. But that will erase system, and you need good backups of all your data & configuration. How you boot install media UEFI or BIOS, is then how it installs for both Windows & Ubuntu.


Honda Civic 2002 remote central locking and key stopped working

Question: I have an issue with my car not starting. The car drove fine never causing any issues. Overnight it developed the following fault.
In the morning I could not open the car with remote central locking. I used the key on the driver's side (it opened the driver's door only). I inserted the key into the ignition and all control lamps lit as usual. I turned my key and the starter motor kicked in and tried to start the engine. Strater motor made "normal" sound like it is engaged with the engine rather than spinning on its own.
Engin did not start and the green "key" lamp started flashing. I tried few times with no effect. I checked the remote for central locking that built-in red led flashes when I press the lock/unlock button. I changed the remote central locking battery regardless, still does not open/close the car. Both faults develop at the same time.
Please advise if you encountered the same problem or have a potential solution.
Answer: The fault was due to a faulty MICU replacing the MICU resolved the issue.
Answer: Do you have the owner's manual to review the factory antitheft system? If not, this link might help; https://www.youtube.com/watch?v=RzM2wPNzZWE. Finding Honda Civic forums is another alternative to ask Civic owners about factory immobilizer systems, resetting, etc. This presumes the factory immobilizer is enabled and actively disabling all or part of the EFI system.  If you have an aftermarket alarm system and its faulty, you may have to find instructions on it when it fails. Be sure to check for blown fuses. If this isn't an issue with the theft system and/or fuses then it may be an EFI issue, usually a fuel or spark problem. If both are faulty then a possible crank sensor failure may be preventing the EFI system from running.
Comment: Thank you for your comment. I have checked all the fuses and they are ok. I believe my alarm system is factory fitted cannot know for sure. I will try to find my owners manual and look for any useful information.
Comment: Additionally, I tested my central locking remote with an oscilloscope. When the lock/unlock button is pressed I can measure modulated signal produced by the remote. The puzzling part is that unlocking the car with the key does not open all the doors only driver side door. Also, cannot open the trunk with the key.


How to get subarray from array?

Question: I have var ar = [1, 2, 3, 4, 5] and want some function getSubarray(array, fromIndex, toIndex), that result of call getSubarray(ar, 1, 3) is new array [2, 3, 4].
Comment: Have you tried [slice](http://www.w3schools.com/jsref/jsref_slice_array.asp)?
Answer: Take a look at Array.slice(begin, end)

const ar  = [1, 2, 3, 4, 5];

// slice from 1..3 - add 1 as the end index is not included

const ar2 = ar.slice(1, 3 + 1);

console.log(ar2);
Comment: It's probably worth explicitly mentioning here that the original `ar` is unmodified.

`console.log(ar);`

`// -> [1, 2, 3, 4, 5]`
Comment: Also, don't make the mistake of confusing the `slice()` method with `splice()`: `splice()` changes the original array while `slice()` doesn't.
Comment: @Igor No, slice does not raise an exception.  If the `end`  is greater than the length of the sequence, slice extracts through to the end of the sequence (`arr.length`). https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice
Comment: I'm sorry, but what if I try to slice using parameters, that'd raise some sort of "index out of bounds" error? In the example imagine I'd go with `ar.slice(4, 4);`? I guess I should try out :x..
Comment: I want to add another note that `slice` does not raise exceptions for any type of input (string, undefined, object whatever). If `start` is out of range (negative or greater than the length), it just returns an empty array.
Answer: For a simple use of slice, use my extension to Array Class:
Array.prototype.subarray = function(start, end) {
    if (!end) { end = -1; }
    return this.slice(start, this.length + 1 - (end * -1));
};

Then:
var bigArr = ["a", "b", "c", "fd", "ze"];

Test1:
bigArr.subarray(1, -1);

< ["b", "c", "fd", "ze"]
Test2:
bigArr.subarray(2, -2);

< ["c", "fd"]
Test3:
bigArr.subarray(2);

< ["c", "fd","ze"]
Might be easier for developers coming from another language (i.e. Groovy).
Comment: [Don't modify objects you don't own](https://www.nczonline.net/blog/2010/03/02/maintainable-javascript-dont-modify-objects-you-down-own/)
Comment: What K_7 said; most especially, monkey-patching the Builtins (Object, Array, Promise, etc) is *very* naughty. See the famous example of [MooTools forcing a rename](https://github.com/tc39/Array.prototype.includes/commit/4b6b9534582cb7991daea3980c26a34af0e76c6c) of the proposed native `Array.prototype.contains` to `Array.prototype.includes`.
Comment: Not to mention, your `subarray` method delivers unexpected results. `bigArr.slice(1,-1)` returns `['b','c','fd']`, which you would expect (the -1 knocks one element off the end of the new array). But `bigArr.subarray(1,-1)` returns the same as `bigArr.subarray(1)`, which is to say *everything* from position 1 to the end of `bigArr`. You're also forcing users to always give negative numbers as the `end` parameter. Any `end >= -1` gives the same result as when `end === undefined`. On the other hand, `bigArr.slice(1,3)` returns `['b','c']`, which again is expected.
Answer:

const array_one = [11, 22, 33, 44, 55];
const start = 1;
const end = array_one.length - 1;
const array_2 = array_one.slice(start, end);
console.log(array_2);
Comment: it does not compile here the correction : var array_one = [11, 22, 33, 44,55];
var ar2 = array_one.slice(0, array_one.length-1);
console.log(ar2)
Answer:
I have var ar = [1, 2, 3, 4, 5] and want some function
getSubarray(array, fromIndex, toIndex), that result of call
getSubarray(ar, 1, 3) is new array [2, 3, 4].

Exact Solution
function getSubarray(array, fromIndex, toIndex) {
    return array.slice(fromIndex, toIndex+1);
}

Let's Test the Solution
let ar = [1, 2, 3, 4, 5]
getSubarray(ar, 1, 3)

// result: [2,3,4]

Array.prototype.slice()

The slice() method returns a shallow copy of a portion of an array
into a new array object selected from start to end (end not included)
where start and end represent the index of items in that array. The
original array will not be modified.

Basically, slice lets you select a subarray from an array.
For example, let's take this array:
const animals = ['ant', 'bison', 'camel', 'duck', 'elephant'];
Doing this:
console.log(animals.slice(2, 4));
Will give us this output:
// result: ["camel", "duck"]
Syntax:
slice() // creates a shallow copy of the array
slice(start) // shows only starting point and returns all values after start index
slice(start, end) // slices from start index to end index

See shallow copy reference
Answer: The question is actually asking for a New array, so I believe a better solution would be to combine Abdennour TOUMI's answer with a clone function:

function clone(obj) {
  if (null == obj || "object" != typeof obj) return obj;
  const copy = obj.constructor();
  for (const attr in obj) {
    if (obj.hasOwnProperty(attr)) copy[attr] = obj[attr];
  }
  return copy;
}

// With the `clone()` function, you can now do the following:

Array.prototype.subarray = function(start, end) {
  if (!end) {
    end = this.length;
  }
  const newArray = clone(this);
  return newArray.slice(start, end);
};

// Without a copy you will lose your original array.

// **Example:**

const array = [1, 2, 3, 4, 5];
console.log(array.subarray(2)); // print the subarray [3, 4, 5, subarray: function]

console.log(array); // print the original array [1, 2, 3, 4, 5, subarray: function]

[http://stackoverflow.com/questions/728360/most-elegant-way-to-clone-a-javascript-object]
Comment: `Array.prototype.slice` returns a copy already. `Array.prototype.splice` modifies the original array.
Comment: I dont think that slice will change the original array.
Comment: The slice() method returns a shallow copy of a portion of an array into a new array object. See [Mozilla Developer Network](https://developer.mozilla.org/en-S/docs/Web/JavaScript/Reference/Global_Objects/Array/slice). Downvoted.
Comment: As others have said, `slice` already returns a shallow copy, making this `subarray` implementation unnecessary. But it's also worth mentioning you've monkey-patched a builtin object, which is a big no-no. See the comments on [Abdennour TOUMI's answer](https://stackoverflow.com/a/18359274/2211532).

How to get subarray from array?


What adhesive would mate PLA and PVC?

Question: I have two fixtures, a PVC pipe and a (3D Printed) socket made out of PLA that I would like to mate. I made a trip to the hardware store and was intimidated by the selection the fact that most cautioned against using on plastics. What kind of adhesive (and I'm not picky to glue, putty, epoxy or cement etc) do I specifically need?
Comment: What are the requirements for the "mating"?  Do they need to be air/water tight, etc?
Comment: Just stick together mechanically.
Answer: Beware that if in a use that is subject to plumbing code, your 3D printed item almost certainly will be a code violation.
The probable best bet (and I'm not guaranteeing success) would be a "Multipurpose plastic pipe glue" - go to the plumbing section, find the PVC pipe cement, don't buy that - look for the somewhat smaller stock of pipe cement that claims to work on PVC, ABS, and perhaps a few other variants of plastics - try that. Use PVC pipe cleaner and primer on the PVC side of the joint. Make some test joints and try to tear them apart after they have had a day or two to cure.
If, as I vaguely gather, PLA is essentially the most common form of hot glue, then judicious and careful use of a hot glue gun would be the other option that might work.
Comment: Forget plumbing code.  PLA is used in certain human implants, because it breaks down to lactic acid in as little as 6 months.   It wouldn't be suitable in any permanent plumbing application.
Answer: I've had success gluing a printed PLA part to PVC using a glue from Selleys called All Plastic Fix. It's a two step procedure where you use a priming pen/marker on both areas to be joined then simply apply the cyanoacrylate glue to one side and hold pressure on the join for around 30 secs.
The resulting bond is very strong and unless you're using it for a mechanical component where it would have to endure high levels of shear stress at the join it should be fine.

What adhesive would mate PLA and PVC?


OneDrive error: Uploading is paused, Sign in to continue

Question: Why do I encounter an error, "Uploading is paused, Sign in to continue" after uploading a large file (~100MB) to onedrive?
Comment: Have you been moving about, weakening your signal? Loss of signal? If this is wifi, have you moved into another wifi range?
Answer: I have found the solution from here. Apparently, you should not allow your phone to lock when uploading.

the app must be running in the background for the upload to continuously take place, which is why the uploading is paused when the mobile device is locked.


How to build Arena-ish level using grid tiles?

Question: I had an idea of procedurally generating arena-type levels in which the player would either fight hordes of enemies, or another skilled opponent. The level would be built at the very start of the layout, and will have a layout similar to those in Quake Live; Pickups, enemy spawners, etc. What would be the best way to achieve this?
Comment: What's your specific problem? As it stands this is a pretty broad question.
Comment: Well, I guess I just wish to know any good algorithms to use for making the Top-Down arenas. Like, would Perlin Noise work, or point-midplacement, for this situation? What would be best to use and where could I find an example to get me started?
Answer: Algorithms are specific solutions for specific problems, for level generation you don't need algorithms, just logic.
First of all you need a specific idea how the maps should look like, then you need a few abstract data types which describes the features of the map, in this case those could be: player start point, platforms, pathways.
Now you have set those you need to distribute them: where should platforms be placed and where the player start point? Also how many platforms? When you have done that you can connect the Platforms by Pathways.
Having that basic structure set up you then can place game play details: you could connect a few platforms by jumpers and put item spawns on others.
Short example pseudo code:
<code>func generateMap(int width, int height)
{
  struct Point{ int x, y; };
  struct Connection{ Point start, end; };
  list<Point> platforms;
  list<Connection> pathways;
  Point player;

  // Set Player point somewhere on the left side in the middle:
  player = { width/4+Random(-100, 100), height/2 };
  platforms.append(player);

  // Now distribute a few more platforms:
  int numPlatforms = (width*height)/300+Random(-2, 2);
  for(i=0; i < numPlatforms; i++)
  {
    /* Insert code here to generate random coordinates which are not too near to the already existing platforms*/
    platforms.append({x, y});
  };

  // Make connections (for simplicity sake here just randomly, this doesn't really work well obviously.)
  foreach(Point platform in platforms) pathways.append( {platform, platforms[Random(platforms.length)]} );

  // Quake style arenas are symmetrical so just mirror what you already have here.
  [...]

  // Now do stuff like generating a Tile map from that data, depends a lot on the underlying engine.
  [...]
}
</code>
Answer: You're unlikely to find a standard algorithm for doing that. Also, I'm not sure you'd get the structural aspects you want from using pure noise. I'd look into how procedural cities or building are generated, then apply those to making your own algorithm. There's a Survey of Procedural City Generation (pdf). Then over at the Procedural Content Generation Wiki, there's a good list of links related to dungeon generation. Hopefully this is enough to get you started.


Why if you remove a regular fee from the list on an event does it not get removed from the price set in the database?

Question: If I set up an event and use the regular fees section rather than setting up a price set then it stores this information in a price set.

If I remove a value from this table then it stays in the database. If I know the price set id then I can find these fields via the UI

Why does the system keep this other value?
Having these other fields causes confusion when creating views because as far as a basic user can tell there is only one fee and there is no reason for them to expect there to be other ones hiding.
Answer: Disabling of price field is actually helpful in case you need it in future and it is not shown anywhere else except price field browse page.
Eg:

Configure an event with regular priceset(is_quick_config = 1) with three field options.
Remove two of them (backend - civi disables it).
Now, a user creates a new priceset from Manage Price Set page and configure on this event. At this point, your regular priceset is not lost. Its value of is_quick_config is changed to zero, hence it will be now shown on the list of PriceSet page.

So, it provides a flexibility of again choosing the original priceset for your event. You can also delete unwanted field options of it from civicrm/admin/price/field/option?action=browse&reset=1&sid={set_id}&fid={field_id} just like normal pricesets, if it is not used by any other event.
Comment: what about if a user has already registered using the now disabled amount, would that be another reason to keep the value in the db?
Comment: Yea, agree to that. as it isn't allowed to delete priceset/field if it is being used by any contribution row as per https://civicrm.stackexchange.com/questions/19721/unable-to-delete-price-field-from-price-set-used-for-contributions/19722#19722


Tips for getting a 2m dipole higher while out in the field

Question: I want to start operating the 2m band while camping, but with my current setup, my antenna would be very close to the ground and ineffective. So I'm wondering, does anyone have tips for constructing some sort of tower to get the antenna higher?
Comment: not sure my idea of camping cooperates very well with the idea of carrying a stiff 10m pole, @MikeWaters, but I think camping styles might be different. I_like_python: you say "your current setup": could you tell us what that is, so that we can work off something?
Comment: @MarcusMüller That's what I did at Field Day around 1980. That was camping. :-) Three or four 10' long Rohn TV masts. 11 element beam on top, and rotatable from the ground.
Comment: How high do you want it? If less than 30 feet or so, then you can use a guyed pole support instead.
Answer: Use a cheap quad-copter, or bow and arrow, to put fishing line over a tree branch, and then pull paracord back, and finally, hoist the antenna with the paracord.  I do this in my backyard but I go from 15lbs. test monofilament to 50lbs. test, to paracord, then finally, for a semi-permanent installation, I end up with 1/2" rope with flexible tubing on the branch end so the branch doesn't cut through my rope.
I have as many stages as I do because I first need a light weight line for the quad-copter to lift, and then with some of my attempts going over multiple tree branches, and rough bark of the trees I use, I need something stronger than 15 lbs. test to even get the paracord over the tree limbs, and even 50lbs. test may not be able to get 1/2" rope, with all of its weight  at 70' of elevation, and high resistance over rough bark; so I drag progressively stronger cords back and forth over the tree.
Also, unless you have to be horizontally polarized, just build a 1/4 wave ground plane antenna for hoisting, it will be a lot easier than finding two trees, or a pair of branches to put up a dipole.
Answer: I just bought an MFJ-1910 33 foot pushup tower and I will be using it for my OCF 40m with tuner. It seemed the cheapest way to go for now, but I can take it to Feild or... All I need to be ready is a tri-pod. At home there is a hole in the cement right where the pole will go. I haven't measured as I just got the pole via UPS, and it's lunch time, but I have used to have a j-pole in that hole.
Answer: If you want to do 2m while backpacking, your best bet might be a ladder line J-pole.  This is light weight, and can roll up into a very small package when not in use.
To get elevation, throw it in a tree.   Options include arborist's bean bag on a rope, sling shot and fishing line, or what works best for me, fishing line on a fishing pole....  (fishing in trees! Fun!)
You probably don't want to hang the antenna from fishing line, but it works quite well to get the fishing line up, and then tie a rope to the end, and pull the rope up by reeling in the fishing line.
But all this is only necessary if you can't get enough distance from a hand held antenna.  Sometimes just a taller antenna on the HT is good enough.  A large (1/4wl or 3/8wl) whip might work well, or you can get a half wave telescoping antenna (but beware that he extra weight can break the HT antenna connector, so use this carefully and sparingly -- you don't want to be walking around with a large stiff heavy antenna directly connected to the radio).  For a few extra feet of height, use a speaker mic and hold the HT up.
Comment: The J-pole is a great balanced solution since the overall lowest height can be higher.  The aperture is not as large as a full dipole, but the additional height compensates for semi-line of sight signals.
Comment: Actually, a J-pole is an end fed half wave, so it is a full dipole.
Comment: Electrically, yes it is a full dipole. But to be more accurate the J indicates a fold back on itself.  This fold increases the characteristic impedance requiring matchng. It is not as efficient as a a dipole, only close.One definition of aperture size is the length of the span of the wires;  the J-pole falls short. However, another equally true definition requires the wavefront to fully illuminate the aperture. The height of the bottom of the J pole and the matching section will get collect more energy than a dipole from a distant or occluded source than lost by the matching network.


Modify exposure of a specific part of an image using rawtherapee or gimp (ufraw)

Question: Is there a way to modify the exposure on a specific part of an image using rawtherapee, Gimp's ufraw, or any other free/open source tool?
Comment: @AkramMellice Neither ufraw or rawtherapee have brush or gradient tools.
Comment: what it's the problem of using a brush and paint the parts that you want to modify? Also using gradient tool could do it
Comment: @AkramMellice would you be able to provide a more detailed answer?
Comment: @ElendilTheTall yeah I'm not knowledgeable in both so I was suggesting to look for them but wasn't sure if they exist or not so I didn't post an answer, thanks for the info
Answer: I'm doing it my way in GIMP - I take "Free select tool", select the part I want to modify.  Then I feather the edges of the selection by 30-100px depending on the size of selection (most often I go for 50px), then I copy the feathered selection and past it as a new layer. This way I can do any adjustments to this particular bit and the rest of the image will remain untouched.
It takes time to post process an image this way, but it allows me to achieve desired results, so I like to work like this.
Answer: You can do this in Darktable using the 'Zone System' plugin, shown below. I'm making the assumption that the part of your image you want to modify would be automatically selected by the plugin for adjustment (shown in yellow highlighting in my screenshot).
Comment: It should be noted that Darktable is essentially a Linux-only raw processor. There is an OSX version but it is somewhat buggy.


How to import a .mhx file into blender using a python script

Question: I need to write a python script in order to import .mhx file and management it. I don't if it is possible to do that or no? Any help?
Comment: Make human comes with a script to import MHX files into blender. there are tutorials at the main website http://www.makehuman.org/documentation
Comment: If this is a question about python you may better ask it on the main SO. Maybe you should edit your question to "how can I export MakeHuman files to Blender"
Answer:
Download the make human blender tools from the make human website.
Open the zip. It will create a "blendertools" folder where you opened it.
Install the make human scene importer script:
blendertools\mhx_importer\import_scene_mhx.py
Once the plugin is installed, this command will become available to you via python:
bpy.ops.import_scene.makehuman_mhx(filter_glob="*.mhx", filepath="", scale=1, advanced=False, enforce=True, mesh=True, proxy=True, cage=False, clothes=True, shapekeys=True, drivers=False, diamond=False, rigify=True)
Comment: Thanks. I guess not all of these parameters are needed? Some of them must be set by default
Comment: Sure, every param there has a default value, though I'd make sure to provide a value for the filepath param :)
Answer: Have you had a look at the blender-addons repository?
There are quite a few resources available for you to dive in, like this one for example:
io_import_scene_mhx.py
The ImportMhx class at line 2958 gives you a good starting point.
Answer: For some reasons the newer version of MakeHuman (1.1.x) have removed the .mhx export option! Somebody has developed the MHX2 plugin which you can download from here or from the BitBucket repo. Then following the instructions on the README file:

copy the 9_export_mhx2 folder to the MakeHuman plugins folder. For example on macOS it is in /Applications/MakeHuman.app/Contents/Resources/plugins
copy the import_runtime_mhx2 folder to the Blender addons folder. On my macOS it is on /Users/userName/Library/Application Support/Blender/2.79/scripts/addons
The you may follow these instructions to activate the plugin on Blender

After that you can export as mhx2 and then directly import in Blender.


Browsers (IE and Firefox) freeze when copying large amount of text

Question: I have a web application - a Java servlet - that delivers data to users in the form of a text printout in a browser (text marked up with HTML in order to display in the browser as we want it to).  The text does display in different colors, though most of it is black.  One typical mode of operation is this:
1. User submits a form to request data.
2. Servlet delivers HTML file to browser.
3. User does CTRL+A to select all the text.
4. User does CTRL+C to copy all the text.
5. User goes to a text editor and does CTRL+V to paste the text.
In the testing where I'm having this problem, step #2 successfully loads all the data - we wait for that to complete.  We can scroll down to the end of what the browser loaded and see the end of the data.  However, the browser freezes on step #3 (Firefox) or on step #4 (IE).  Because step #2 finishes, I think it is a browser/memory issue, and not an issue with the web application.
If I run queries to deliver smaller amounts of data (but after several queries we get the same data we would have above in one query) and copy/paste this text, the file I save it into ends up being about 8 MB.  If I save the browser's displayed HTML to a file on my computer via File-Save As from the browser menu, it works fine and the file is about 22 MB.
We've tried this on 2 different computers at work (both running Windows XP, with at least 2 GB of RAM and many GB of free disk space), using Firefox and IE.  We also tried it on a home computer from a home network outside of work (thinking it might be our IT security software causing the problem), running Windows 7 using IE, and still had the problem.  When I've done this, I can see whatever browser I'm using utilizing the CPU at 50%.  Firefox's memory usage grows to about 1 GB; IE's stays in the several hundred MBs.  We once let this run for half an hour, and it did not complete.
I'm most likely going to modify the web app to have an option of delivering a plain text file for download, and I imagine that will get the users what they need.  But for the mean time, and because I'm curious - and I don't like my application freezing people's browsers, does anyone have any ideas about the browser freezing?  I understand that sometimes you just reach your memory limit, but 22 MB sounds to me like an amount I should be able to copy to the clipboard.
Answer: Why not just do a File -> Save Page As
Comment: Even if I do that and save it as a text file, there is HTML formatting in the file.  My goal is to give the users a text file with just the numbers and no markup.


How can I change the plugin update server for specific plugins?

Question: There are specific plugins that I want to use my own repo for for updating my sites. How can I identify the plugin to target and what server they should be looking at?
Comment: since this question was asked, WP 5.8 added an official method of doing this via filters and the plugins header
Answer: this can be done with the filter plugins_api :
https://developer.wordpress.org/reference/hooks/plugins_api/
try this code :
add_filter("plugins_api", function ($plugins_api, $action, $args) {

    if ("plugin_information" !== $action) {
        return $plugins_api;
    }

    $pluginSlug = $args->slug;

    if (... update available ...) {

        $plugins_api = new \stdClass();
        $plugins_api->name = $pluginSlug;
        $plugins_api->version = "5"; // new version
        $plugins_api->download_link = "https://server/directory/newVersion.zip";

        $plugins_api->slug = $pluginSlug;
        $plugins_api->sections = []; // sections of "view details" of update page when update is available

    }

    return $plugins_api;

}, 10, 3);

Comment: Is specifying a version necessary and the "slug" is that the plugin's handle that needs to be updated? And do you have an example of specifying if the update is available?
Comment: Maybe I should specify - I'm trying to change the location of the update for an already existing plugin. I think the code and below's answer are for my own plugins.
Answer: There is also this solution, which is a bit more work to set up, but allows you to get updates from your own GitHub or private repository.  I use it for my own private plugin that contains my personal settings for all web sites I develop.
https://github.com/YahnisElsts/plugin-update-checker#github-integration
Comment: You have to adjust that require for the location of the functions.php. The process is built for a theme/plugin to look for updates in a non-WP repository; perhaps your own Github repository, or a spot on your domain. And the zip has to contain a folder that is the same name as the theme/plugin, then the plugin/theme files are in that subfolder. Carefully read/follow the instructions; it can be a bit tricky.
Comment: Is there a way to use this outside of a plugin or theme's folder? I tried this in `functions.php` but it crashes `require '../../plugins/plugin-update-checker/plugin-update-checker.php';`


Martian space elevator from the vulcano Olympus Mon to the moon Phobos?

Question: In my fascinating imagination, I am seeing a space elevator from the vulcano Olympus Mon to the moon Phobos. Phobos also seems to keep spaceships - while a smaller shuttle attaches itself to the elevator and travels down- they can also travel inside Olympus Mon. I was wondering if this is mathematical possible and it seems, it is.
Comment: Probably worth mentioning that Kim Stanley Robinson in his Mars trilogy [SPOILERS] decided to position the space elevator between Pavonis Mons (which is very close to the equator) and a smaller asteroid captured for the sole purpose of this enterprise. Phobos and Deimos are larger, and were more suited for other needs (for example military)
Comment: You would have to put Phobos into a much higher orbit, first and even then Olympus Mons is not located on the equator of Mars, so you can't put an object into a stationary orbit right above that place. To compensate for that, you would need, at least, a second elevator cable. It doesn't sound like it's worth doing either, especially since escaping Mars gravity with a rocket is so much easier than launching on Earth. The problem with the space elevator is that where it would be needed, the concept is tough to implement, and where it's easy to implement, one does not really need it.
Comment: The close votes are a bit harsh. The question is whether a space elevator could be built from Olympus Mons to Phobos. This is a perfectly reasonable question, and the answer is *no* for the physical reasons explained by CuriousOne. @CuriousOne: do you fancy turning your comment into an answer?
Comment: @JohnRennie: If you don't mind. I agree that there is a non-trivial question in there.
Comment: Related: http://physics.stackexchange.com/q/33547/2451
Comment: http://physics.stackexchange.com/questions/277688/space-elevator-solved
Answer: The space elevator probably deserves an entire series of questions (and I am sure there have been plenty of posts), but if we stick to this particular version, there are a couple of problems with it.
First of all, a space elevator needs a counterweight in an orbit that is higher than the areostationary orbit (the Martian equivalent of Earth's geostationary orbit). In case of Mars that orbit lies approx. 17,000km (11,000 miles) above the planet's equator.  Phobos is in an orbit with a semi-major axis of just 9376km (5826m miles). It orbits the planet every 7 hour 39 minutes with an orbital velocity of 2.138 km/s, while even an areostationary orbit would require an orbital speed of a mere 1.45km/s. We are therefor tasked to give a large object (the mass of Phobos is 1e16kg) a delta-v on the order of at least 1km/s to get it into place. That requires a lot of energy (and propellant mass), which one could use to launch a lot of payload with conventional rockets, instead!
Anchoring the space elevator over Olympus Mons is also not an easy option. This spot lies at 18.65 degrees North of the equator. Since our counterweight has to be above the equator, we would need a second cable located 18.65 degrees South. Now we have two elevators, but they are both under a slight angle, which doesn't make the design any easier.
If we let go of the particular location and we place a conventional design between a spot on the equator and a smaller counterweight above, we are certainly going to make our lives a little bit easier.
Deimos, on the other hand, is almost in the right place for a counterweight, it seems. With an orbital period of approx. 30 hours and a mass of 1.4e15kg it's a lot closer to what we need than Phobos... except, of course, that we still have to watch out for Phobos cutting our cable every eight hours, which means that we have either to deploy a movable cable (which is not particularly hard compared to the extreme engineering that we already had to do) or we have to use two cables separated by a few degrees, again, so that Phobos can just slip trough our sky-hook!


What is the proper way to deal self plagiarism?

Question: Couple of months ago i've checked plagiarism of one of my research work in turnitin.
I've reused the same research work in order enhancement it. When i checked new assignment again in turnitin with different class ID it shows similarity index from old one. I've changed my university and as per its rule it can not accept new assignment with such similarity index.
How can i deal with this issue?
Comment: I'm confused. You're saying that you submitted an assignment in a class, and now you want to submit what is substantially the same work in a different class? Does the professor in the new class permit re-using assignments in this manner?
Comment: Actually i am reusing research work. No i'm not submitting same thing twice. I did further enhancement in it.
Answer: I'll assume you're wondering why your similarity level is still high.
With most courses, it is up to the professor. You might have a professor that would allow you to do something like this, but it's incredibly unlikely.
When assignments are submitted to TurnItIn, they are stored in an external database that your school unlikely has access to. This is something maintained by the company. This is why your originality checks appeared to remain the same despite transferring institutions. You might have some benefit to this, as your professor's "common sense" is pretty important when using something like TurnItIn; they'll basically have to review it and talk to you about it. However, if it's not random bits and bobs like citations and bibliographies, you might not be in such good graces.
As for what you can do about this, very little. Talk to your professor about re-using the old assignment. They're going to need to know about it regardless. However, my two-cents are that you shouldn't have bothered reusing an old assignment; most professors simply do not accept work that was done for a different course, regardless if it was your work or not. None of mine ever have, from recent memory.


When would it be practical to have a library with one-book electronic tablets in place of physical books?

Question: I'm trying to create a 'futuristic library' in a 1st-world country set in the 21st century. I'm imagining a library where for each book, there is instead an electronic tablet to hold the same text. Each electronic tablet only holds one text and serves the same purpose as a book. In what context would such a the creation of a library system with electronic tablets be practical or preferred to physical books?
Comment: Archive.org [lending library](https://archive.org/details/lendinglibrary). (The entire idea behind electronic book readers is that they can hold *any* text. Therefore, the practical arrangement is for the library to have a database of electronic texts, and only sufficient tablets for their population of readers, which is always very much smaller than the number of texts in the library. Then when a reader borrows a book, the library will download it to a tablet and hand it over to the reader.)
Comment: Libraries are already lending e-books. It may not take many decades for them to (mostly) replace paper books. But then there will be no need for a physical library, as you can borrow books online and use your own reader. The question is rather, if all books were electronic, why would people still go to a library?
Comment: Digital Rights Management. The books can not be copied. For specialty non-fiction books only where the information is highly valuable..
Comment: Electronic, individual e-paper shelf price tags in supermarkets are already a reality in some parts of the world...
Comment: Welcome to the world's largest library; https://external-preview.redd.it/se2xhaQ2BKQEln3PXTNwkvufmArGYYdtbwvFlcx_3pI.png?auto=webp&s=293e31ea6066d851531255ac5ddd1c2f1f1088a9
Comment: Paywalled archives like JSTOR and ordinary desktop PCs currently serve this role at modern universities.
Comment: Two ideas: A single text is loaded on the Reader's ROM at creation (so it works OOB).  Rare minerals to make the connection _or something_ 'tween cartridge and Reader has been sequestered for more important uses (defence?).  Readers don't use this mineral.  *Assumes books come in cartridges.  Or:  they killed the internet.  Physical deliveries (of Readers) are still possible, but downloading new content either doesn't happen, or relies on mass [sneakernet](https://en.wikipedia.org/wiki/Sneakernet) arrangements whenever the regional 'internet provider' is in town. *Assumes books are electronic.
Comment: not gonna lie though, on an electronic device, you have the option to place as much bookmarks as you want, to zoom, to read it in the dark because of backlights, whereas you can't read a physical book in the dark
Comment: You do know that we can borrow e-book from a library from our own computer at home, right?
Answer: Realistically, never.
Books just aren't that much raw data. A one-book tablet would consist of a very small ROM chip with the book and a lot more chips controlling the screen, input/output, and other functions (to say nothing of the expense and bulk of the screen itself, or the casing, or the battery, etc).
No matter how much you can slash the price of each of those components, there's no getting around the fact that it would be more practical to have many books' worth of data for each physical tablet - this requires far less material and storage space, and hardly impacts usability since the vast majority of library books spend most of their time on the shelf.
What would be even more practical is to separate the two parts. Keep a huge vault full of ROM chips, and a smaller number of tablets to slot them into. In this sense, the vault of memory chips is much like a microfilm repository, except that the reader is small enough to be portable and lent out to library-goers.
Comment: "a huge vault full of ROM chips" -> This is pretty much the architecture of 1980's video game consoles.
Comment: e-ink readers are now sufficiently cheap that they can be used as magazine covers; https://www.youtube.com/watch?v=8xW9wanzQXA
Comment: @Richard A quick search turns up a [rather scathing Wired article](https://www.wired.com/2008/09/esquires-first/) pointing out that it cost an extra $2 per copy for the e-ink cover, on top of whatever Ford paid to sponsor it; and the result didn't display any text or graphics itself, just switched monochrome overlays on and off over various parts of the printed cover. Granted, things might have improved further since, but it's not a great comparison.
Comment: @IMSoP - I'm assuming there would also be substantial cost reductions for scale.
Comment: @
IMSoP
 Methinks that Wired article is nothing but sour grapes over a competitor's scoop. Wired is supposed to be the forefront tech leader, not Esquire, yet Ford picked Esquire to do the initial rollout. I am sure Wired would have a completely different perspective if Ford had chosen Wired for the initial offering.
Comment: @JustinThymetheSecond Hah, true. It does show the limitations of the technology at the time, though; it was a long way from being a complete e-book at that price.
Comment: @
IMSoP
 The first mass-produced 'recorded sound' devices were wax cylinders, and each one had to be produced from an original sound source.  Very  limited technology, but it was a commercial success nevertheless. The monetary return provided the impetus to continue to develop the technology.
Comment: I really like this idea in conjuction with the top-secret motive mentioned in the comment by  Jeremy.
Answer: When the information in the books is top secret.
The problem with distributing information electronically (e.g. downloading to regular eBooks) is that digital information is easy to copy and share, and therefore likely to be copied and shared.  Normally that's a good thing, but if the information in your library is highly sensitive/classified (nuclear codes?  DNA source code for killer viruses?  Black magic spellbooks?  Level 35 Scientology texts?  etc), then you want a way to keep the information secure and share it with only the few people who you trust to see that information.
One way to do that would be to keep the information on old-fashioned paper books, but those are subject to mildew, aging, etc, so instead you fashion hermetically sealed tamper-proof eBooks, each with a hard-coded encrypted ROM containing the sensitive info, plus maybe some other security devices like a retina scanner, a self-destruct, geofencing alarm system, photocopy-resistant display, and so on.  Now if anyone tries to make off with a book to steal its secrets, the book will fight back!  :)
Comment: This is the first answer that explains why a library would actually have individual ebooks instead of individual paper books and not use the possibilities of easy copying of digital data.
Answer: When paper started to become mass produced, libraries and libraries were reluctant to adopt it as replacement for parchment, because there were concerns that paper was less resistant to time and less versatile whenever there were needs for "corrections".
In your case, tablets might be ok-ish, as long as the electronic is reliable. I recently had to buy a new laptop because the other one had a sudden failure of the motherboard, resulting in its irreversible death. While it was disappointing for me, I can imagine that no library would appreciate losing content due to random failures which, with big numbers, are bound to happen.
Therefore having what you describe would be viable only when and if the underlying electronics had become massively reliable or, even better, capable of self repair.
Answer: Cheaper to Produce
In the real world it is cheaper to make a paper book than an electronic one. In your world it must be cheaper to make the electronic one.
Perhaps we have chopped down most of the trees in the world and not found a good alternative for slices of pulped dried wood. Paper is a luxury item.
One top of that, the electronic books are small to lower material costs. Each book is just a data chip that contains the text. It either (a) projects the text onto a surface to read or (b) gets inserted into a tablet-shaped reader.
The library has tablets you can use inside the library. They have a few hundred tablets but millions of book chips. You can also bring your own reader, or use a reader app on your smart device. If you rent the book you can insert into a reader at home.
Comment: @JustinThymetheSecond --- How does that prevent optical copying?
Comment: @JustinThymetheSecond Anything you can see can be copied *somehow*, otherwise you wouldn't be able to see it.
Comment: This chain of comments has little to do with my answer.
Comment: Digital Rights Management. Each data chip has an encryption system that prevents the 'book' from being copied. The data chip reader has the decryption algorithm, so the data chip can only be 'read' on compatible readers. This protects copywrite.
Comment: @elemtilas
 Polarized filters.
Comment: @Michael
 I can see hallucinations. Can they be copied?
Comment: @JustinThymetheSecond -- Only useful if you borrow the library's tablet. BYOT means whatever's on the tablet can be easily copied.
Comment: @elemtilas
  Have you seen those flat 3D pictures that seem to be meaningless, but if you stare at them the right way, a 3D image pops up? That is all in your mind. Eventually, I suspect that the image on the DRM tablet will look like random noise, and will copy as random noise, but only if the right time-sensitive encryption is sent over the net,  will the noise become meaningful. The book/tablet and your own personalized polarizing/decrypting  filters will have to be synched in a public-key private-key system. Truly a 'for your eyes only' system.
Comment: Because your answer does not cover downloading from the Internet. That is the cheapest solution of all. That is the way music went. Records to tapes to CD's to downloading. How do you propose to stop the downloading of the books on the chips?
Comment: @JustinThymetheSecond The internet was not mentioned on the question.
Comment: That's our point.
Answer: Practicality or preference might not matter. Product doesn't have to be better if it can be sold in right-way to right audience that is those who decide to buy the books.
Whole thing could be type of pork project or indirect subsidy to local manufacturing economy.  Readers would be produced by local company with connections to government. Giving money directly would go against regulations or trade rules. But buying tens of thousand of devices would be no problem. Hand crafting all of those devices would generate jobs.
Also it could be marketed as being at the bleeding edge of technology. Getting rid of old dusty books and replacing them with modern technology. Look you can even change the font size for single book stored in the device.
Answer: The library has a diverse audience (in terms of language, eyesight, reading ability, etc.)  The electronic books automatically adjust to the reader's preferred format.  They have:

Auto-translation into many languages
Automatic font scaling for people who need large print
Text-to-speech abilities for illiterate or distracted readers.
Bookmarking functions, so dog-earing is obsolete
Automatic search and indexing, to easily find topics in the book
Comment: That is an argument for having one tablet per user. Not one tablet per text.
Comment: @MartinGrey -- It is an argument for electronic text(s) instead of paper texts.  It says nothing about number of tablets per user or number of tablets per text.
Answer: The supreme court ruled that piracy is in fact not a theft so people can copy and share any digital material without breaking the law. To counter that Publishers decided to implement DRM protection so strong you cannot buy an e-book file without authorizing it with hardware chip found in the reader. After years of this practice they notice that pirating a paper copy is a lot easier because of scanners and they can control companies licensed to make DRM chip-enabled devices so they stop printing. Since electronics are extremely cheap and cutting trees a taboo, libraries concluded it's better to have one reader per book than multiple readers authorized to open thousands of book files they own.
Comment: Interesting factoids, going back to the original Apple II and the clone Orange. Lawsuits flew between them for breach of IP rights. Orange argued you can not copywrite digital binary code, it is not human readable. Apple found programmers that could indeed read pure binary and explain what the machine code did, so binary machine code was a human-readable language. Apple put a copywrite on the circuit boards and argued that any board that copied the same connections between chips was breaking copywrite. Orange re-arranged the chips, but Apple argued rearranging chips is like paraphrasing.
Answer: In your world, engineers haven't invented dense electronic storage or WiFi (or these are prohibitively expensive), but space is still at a premium (like in a very large city). This leads to a strange balance where one tablet can just barely hold one book (especially with illustrations), but it's still cheaper to make a library of thin tablets than to buy a larger space to house the same number of books.
Alternatively, people in your world just prefer things this way. No messy menus, no search functions, no page turning. Just one book per tablet, plain and simple. And if tech is cheap enough to provide this luxury, why not?
Answer: There are no cows or trees
In the late 21st, due to runaway emissions, humanity has killed inadvertently killed off all plant life. All animal life, therefore, also went extinct, except for those pets which eat the same artificial food that people eat. People live in climate-controlled biospheres, and there are a few trees to maintain oxygen and to add a bit of color. Meat is an expensive luxury, affordable only to the ultra-wealthy, and the mass-production of paper or parchment is unfeasible. Electronic components, such as tablets, become the literary medium of choice, by default. Tablets are still expensive, so lending-libraries with many tablets to borrow is still more budget-friendly than buying one's own.
Comment: It would be several times cheaper to have one one tablet per library user, not one tablet per text.
Answer: Physical and digital books can be copied. For a truly 'digits rights management' system, there has to be some form of encryption.
Recall those flat 2D images that look like nonsense, but if you stare at them in the right way, they become a 3D image? The image is all in your head, not on the paper.
I can foresee a system wherein the tablet has encryption technology for the data on it, and your eyes have some form of contact lens that decrypts the signal. Perhaps some form of polarizing filter that only lets select pixels through, based on some encryption algorithm. Without the decryption, the image from the tablet is just random noise, that even if copied, produces even worse non-encrypted random noise. Totally meaningless, with absolutely no meaning in the data stream.
The tablet and your personalized eye filter would have to be synched, at the point of transaction, in a private-key public-key quantum encryption system. Only then will your filter be able to 'read' the content of the tablet. The image will be 'all in your head'. Only you, and your mind, will be able to extract any data from it. Your personalized serial number in your filter has to match the personalized serial number of the book and of the library to unlock the data. The public-key private-key synch will be a time-sensitive, one-time-only interaction controlled by quantum entanglement computing. And since quantum entanglement is a one-off system that is 'localized' to a specific 'entanglement event', each entangled tablet would be unique in its quantum entanglement. No possibility of duplicating the tablet with the data on it, since the original entanglement 'pair' would also have to be duplicated. The data would only be in useable form on that tablet only.
Thus, very high-end 'professional' books and manuals, containing very expensive data that the authors wish to be protected, would be stored on their own limited-edition tablets, keyed/encrypted only for that data, to ensure their limited distribution. These would be kept in 'libraries', where the data was not able to be transmitted over any form of 'net'. One would have to personally have the tablet in order to have access to the data.
And since the entire process could be made time-limited, much like a library has a 'due back by' date, when the borrowing time was up, the encryption key is no longer valid, and the tablet just displays noise to the viewer again. The tablet would be only so much useless technology, unless returned to the library and re-activated. The data on it would otherwise be lost forever.
Being able to download the information onto the tablet would defeat the purpose, as there is now a copy in a 'downloadable' format in existence, that can be hacked by others at the distributed source (library, book store, or other). To be a truly 'limited edition' format, the original work would have to be stored in a controlled facility where the tablets were produced, and not further distributed or made available. Thus, one tablet, one iteration of the data. The number of tablets with that data on it could be strictly controlled. If the tablet is destroyed, the data on it is permanently 'out of circulation'.
I suppose a human  could be the intermediary to copy the data from the encrypted form to another form, much like someone reading a book into a recording device, but the public-key private-key would be controlled as to who has access to it. Also, I can not envision how pictures, images, and graphs could be transcribed.
I doubt if the system would be used for mass-market pulp-fiction and such, as the circulation would not be great enough to make each novel profitable, and these mass-market books have a short best-before date. However, for really good works of literature, limited edition works, and for books that contain highly valuable information that one does NOT want in mass circulation, I suspect there would be a limited market for select libraries in select places, like universities and such. Collectors, as well, might have access to the synch technology that would allow them to provide access to the tablet for others to enjoy, allowing them to pass on the public key to others, but the original tablet would still have to be physically present to view it. One tablet, one copy of the works on it.
Think perhaps along the lines of great artistic creations, works of literary and digital art much like the 'one-off' works of the physical art masters. Art galleries would evolve into 'tablet galleries', viewable only to those who's personalized eye filters were quantum entangled/synched/encrypted to the tablet.
Addendum
Even a 'block chain' technology, such as is used for cryptocurrency, can be 'split' and then each copy placed on a completely separate 'net', each 'net' now a copy of the original cryptocurrency, that can be circulated within its own system. The block chain cryptocurrency only has protection and value within its own distribution net, its own contiguous block chain. Only a 'physical hard copy', suitably encrypted and uniquely serialized, can ensure that the works are kept original and 'limited edition'.
Answer: the tablets while only containing 1 book at a time can be downloaded with any book in the library's digital archive every book can be any book this means that books don't have to be sorted or rearranged and new books can be added more easily. As to why each tablet can only hold one book I don't really have an idea for that but it could work as an incentive to return the tablets in order to have a new book stored on them.


Negative sign of acceleration

Question: This is the problem from our Physics textbook :

A player throws a ball upwards with an initial speed of 29.4 m s–1.
  (a) Choose the x = 0 m and t = 0 s to be the location and time of the ball at its highest point, vertically downward direction to be the positive direction of
  x-axis, and give the signs of position, velocity and acceleration of the ball
  during its upward, and downward motion.

Answer is :

x > 0 (upward and downward motion); v < 0 (upward), v > 0 (downward), a > 0
  throughout;

a > 0 is what is bothering me and I have done hours of searching and trying to understand.
Kindly explain all the parts of the answer.
Thanks in advance.
Comment: We don't do particular instance of homework questions. There is [a meta thread](http://meta.physics.stackexchange.com/questions/714/how-do-i-ask-homework-questions-on-physics-stack-exchange) that explains how to ask basic  questions in a way that we *will* answer.
Answer: The acceleration is a vector $\mathbf{g}$ throughout the motion, and $\mathbf{g}$ is always pointing downward. Since you choose positive $x$ to be vertically downward, so $\mathbf{g}$ is along positive $x$ if we draw out the Cartesian coordinate, then $\mathbf{g}$ must have positive value, $\mathbf{g}=g\,\hat{\mathbf{x}}$. If you choose vertically upward to be $x>0$, then acceleration $\mathbf{g}$ has negative sign, $\mathbf{g}=-g\,\hat{\mathbf{x}}$. It's just the matter how you choose the $x>0,y>0$ directions. Draw a diagram of $v$, $g$, force on the ball with $(x,y)$ coordinates.
Comment: Since top is x=0, so position remains positive through out, and why velocity sign is - when going up and + when going down, as object never enters negative territory which is beyond x=0, so entire action takes place in the plus zone.
Answer:
a > 0 is what is bothering me

The only acceleration in the problem is the acceleration of gravity, correct?
If you agree with that, then I think you'll agree that the acceleration is always pointing downward towards the Earth and thus, the acceleration does not change sign for this problem.
Now, from the problem statement:

vertically downward direction to be the positive direction

So, what is the sign of the acceleration?

Negative sign of acceleration


How can I uniformly apply an image as a texture to an object?

Question: I'm trying to make an icosphere with a hexagonal pattern applied to it, but the image I'm using ends up getting completely warped and ripped along the faces. I don't know how to fix this, so please help.
Comment: I'm not attempting to answer your question: I just wanted to make you aware about some issues with [balls and hexagons](https://www.youtube.com/watch?v=btPqKAGyajM)
Answer: You might want to try the node setup shown below. Change the parameters in the mapping node to move the image around. This might not work, as it is possible that the problem is in the UV projection, but I've already solved problems like this using this node setup.
I hope this helps.
Comment: can you [edit] to explain why this might not work?
Answer: There are two ways to approach this problem.
1) UV Unwrapping
There is a major problem with texturing a 3D sphere.
It is mathematically impossible to map a 2D texture onto a 3D sphere without distortion.
Here is a great Stack Exchange thread where such situation and possible solutions are discussed in detail.

2) Procedural textures
If your texture is simple, you might want to use procedural texturing, instead of an image.
This way you can get a seamless pattern without any distortion.
Here is an official Blender video about procedural textures.
Good luck.
If you'll need any clarification, let me know.