If engines are closer to the wing (or in the wing) does it increase efficiency

Question: If you were to make an engine in the wing or at least closer to it in commercial airliners such as the 747, 737 and A380 etc. Would it increase efficiency?
Answer: Yes, mounting jet engines in the wing root increases aerodynamic efficiency due to:

No drag from engine pods
Smaller yawing moment upon engine fail, and resulting smaller vertical tail.

But that is about it. There is a host of disadvantages to mounting the engines in the wing root, one of them being that high lift devices cannot be used and the wing is bigger, causing more drag.
Three huge advantages of mounting the engines in pods, underneath the wing, in front of the aeroelasitc axes are:

High bypass engines can be mounted, vastly improving fuel efficiency.
The engines are within easy reach for maintenance.
The weight of the engines provides both bending relief, and reduces structural weight to prevent flutter.

Also see this question.
Comment: Why do some commercial airplanes not implement it? Like the b2.


Orange Geo Map does not show background map

Question: We are running Orange with our students and most of them are having problems with running the Geo Map widget. It does not show any background map. In the bottom an error message is displayed: <code>"Cannot fetch map from the Internet. Displaying only cached parts."</code>
I have found this Github page, but it does not explain how to update or add any JSON files that might be missing:
https://github.com/biolab/orange3-geo/blob/master/CONTRIBUTING.md
What do we have to do to get the background maps to appear again in the Geo Map widget?
Answer: The issue with the Geo Map widget has been solved in a new release of Orange3. The Geo Map widget now works correctly again in Orange3 version 3.23.1 and Geo Add-on version 0.26. Great!


Best way to add a second server to existing site in case of downtime?

Question: Well my $379 dedicated sever just went cold again for the second time this month. I need to find a way to get another server going at a different provider that I can just flip on in case this happens again. What is the best way to deal with this type of situation?
Answer: Replacing the broken server.
Seriously - adding a second server works. but it is not that easy espeically when databases get involved. YOu need after all to real time replicate stuff.
If a server crashess twice per month, there are two things possible:

Admin is incompetent (totally borked drivers etc.) or
Broken Hardware
(* well, or hardware not supported by the os).

In all cases I would tackle it on that end. Basically - server broken, please replace on warranty. Twice per month is too much.
Answer: finding a solid provider with a decent uptime SLA would be the start, I guess.
in terms of your question - how to get some form of redundancy going should you have a second server at a separate location - requires some knowledge of what you are doing on the server in the first place (hosting web sites? email? some other service?)
A standard LAMP setup can be made relatively redundant using rsync to synchronise files to a standby machine, and DNS (essentially setting up the relavant A records with low TTL values) to allow switching between the two active sites.
downsides: it's a slow and clumsy way of doing it, requires manual intervention and will require DNS that isn't handled by either of the two boxes (not a problem if you're using an outside DNS provider).
The biggest issue in this type of solution is the database: basic replication of a database is fairly easy (well, relatively) but being able to seamlessly switch back once the outage is over is not. Also, running a system dependent on a remote commit could slow everything down significantly. The scenario is also complicated by having two machines at two providers - a traditional load balancer would be difficult to implement as the networks are physically separate and the work required for something like haproxy or a general shared storage solution is on the other side of a diminishing returns curve.
you will spend more time trying to figure out how to deal with the switching (and then the monitoring and management thereof) than actually running a decent service.
So I guess the answer is as mentioned already: to build something that allows you to just flip over from one machine to the other depends on what you are doing, but is almost guaranteed to be more costly and complicated than simply getting a solid, SLA backed hosting arrangement with a well organised provider. do that first, then worry about load balancing and redundancy.
Answer: I think your plan is sound. It's clear something is awry with your current provider and your confidence in their ability to provide reliable service is waning. I'd wander over to the dedicated server forum on Web Hosting Talk and see what people are saying about the providers in your price range.
Answer: I would suggest you get a backup dedicated server, obviously it doesn't need to be nearly as beefy as your present server since it will only be used for backup purposes. I would suggest these guys www.smarterdedicatedserver.com since they are really cheap and offer good uptime protection at their datacenter. In terms of setting up the failover or even load balancing you can use this company http://www.autofailover.com/ or something similar. You'll also need to keep the two servers synced, I would either write a script to do this nightly and use something like database mirroring (SQL Server) to keep the databases synced up in real time or some other replication strategy. Its definately going to be extra work but the uptime will be much better. No service can possibly be 100% uptime so if that is important I would setup a second dedicated server.
Answer: This is a very broad subject area without more details. Specifically we need to know whether the failures you've had are due to comms link or hardware.
If the former, look at getting co-located or hosted in a secondary datacentre with real-time replication.
If the latter, we need to know how quickly you need to get back online after a failure. This will determine whether we're looking at real-time replication (in the same or another datacenter) or recovery from disk/tape-based backup.
If you want specific details of anything, we need to know what application(s) you're running that need to be highly available.
Comment: More specifically, it crashes from an out-of-memory error when OOM Killer comes in and kills access to everything.


Running Drag Resistance Parachute and Agility Ladder

Question: Do people use running Parachute and Agility Ladder for martial arts training or it is not something useful?
Comment: For the agility ladder, see http://martialarts.stackexchange.com/questions/2257/drills-for-training-agility-cross-art
Answer: Martial arts drills involve a large set of aspects of a human body. It may be difficult to find all the ways that can help your body to adapt to these drills.
Anything and everything that tests your endurance, strength and agility will be useful for the training.
However,

Agility laders, although can be used, will not be of any much utility. This is because the drills and work outs of a martial artist test, increase and build up your body for further adaptation at every stage. However, the effectiveness of agility ladders can be easily forgotten in this case; Since there are other more fruitful ways of building up agility and endurance.
Running parachutes are definitely used in all sorts of sports today including martial arts (Of course depends on what art you are learning). That being said, it again may not be as useful as some other drills.

Certain points to be noted :

Some martial arts like Muay Thai, where stamina plays an exceptional role, are definitely an exception.
These tools do provide a healthy amount of utility but at a marginal expense of a lot of time that could be invested in better ways of improvisation.
This answer is completely based on my experience in Krav Maga and Kung Fu.

Hope this helps! :)
Answer: I use an agility ladder for general fitness (great for calf strength) and footwork speed. I have seen people who incorporate kicks into their drills with ladders as well. Not sure if it is the best training method out there but I think it has to help a little and I enjoy it.


How to disable/enable cache of all views programmatically?

Question: Case: I have over 50 views in my site and for performance improvement all were enabled to cache data during their implementation.
Now I want to disable cache for all views at once for some reason (make it more realtime).
Please help.
Answer: You could switch them all off with features and a bit of hacking. Also, as this involves changing lots of things in mass, make sure you back up your work before doing it and make sure you test it out on a dev server first.
With features, you can create a feature containing just your views. You can then download this feature, which will give you something that looks a lot like a module file.
One of the files in this module will be a file called your_feature.views_default.inc, which will contain a bunch of code that will look ALOT like a view export script (because that's exactly what it is.)
If you look at the lines of code, they each represent a configuration in your views, you should be have a bunch of lines that looks like:
  $handler->display->display_options['cache']['type'] = 'time';
  $handler->display->display_options['cache']['results_lifespan'] = '3600';
  $handler->display->display_options['cache']['results_lifespan_custom'] = '0';
  $handler->display->display_options['cache']['output_lifespan'] = '3600';
  $handler->display->display_options['cache']['output_lifespan_custom'] = '0';

depending how you set your caching. Regardless, if you want to shut off caching on all your views, all of those lines need to become:
$handler->display->display_options['cache']['type'] = 'none';

One your edits are done, save the file and upload the feature module back up to your site in your sites/all/modules folder.
Once it's uploaded, head back to your site, and head to the features admin at admin/structure/features, you should see your feature hanging out there, and it's state should be "Overridden." Click on "Overridden," and you see the overview of your feature, along with a handy-dandy button on the lower right hand of the screen that says "revert components." Click the checkbox next to the views list (to tell features what you want reverted), and then click on the revert components to revert the views to what is stored in code.
Now, there is a down side to using this method. The way features works is it actually takes your view and stores it in code, not the DB. So removing your feature would actually remove you views as well. This will be true until you edit your view, in which case it would go back in the database (just that one view though, not all of them).
Answer: If you are looking for a permanent solution. I would suggest doing it in an update hook. Create an array of the views or views/displays you want to affect, and then do something like the following
<?php
$views = array(
  'view1' => array(),
  'view1' => array('master', 'display_1'),
);

foreach ($views as $view_name => $displays) {
  $view = views_get_view($view_name);
  foreach($view->display as &$display) {
    if (empty($displays) || isset($view->display[$display]) {
      $display->display_options['cache']['type'] = 'none';
    }
  }
  $view->save();
}

If you are looking for a temporary solution (as in for development/testing purposes), consider setting $conf['views_skip_cache'] = TRUE; in your settings.php or local.settings.php file. This will turn off caching completely for Views. See views_cache_get().
Answer: I don't think it's possible as Views are saved in the database as a PHP array.
However, there are 2 cache tables cache_views and cache_views_data which contain the various cached items, if you emptied the contents of these tables it would have the same effect as turning off caching apart from you'd need to empty these tables on every request.
Answer: Think you're looking for this module https://www.drupal.org/project/views_cache_bully
It's listed in the speaker notes of slide 26 from the DIY Drupal 7 performance presentation
Looking at how the module works you'd want to implement hook_views_pre_view(). Here's where the magic happens in the module
/**
 * Implements hook_views_pre_view().
 */
function views_cache_bully_views_pre_build(&$view) {
  // Run if this view does not have a cache.
  if ($view->display_handler->get_plugin('cache')->plugin_name == 'none') {
    // Make views_cache_bully_view_is_exempt() available.
    module_load_include('inc', 'views_cache_bully');
    if (!views_cache_bully_view_is_exempt($view)) {
      // Enable the view cache.
      $view->display_handler->override_option('cache', array(
        'type' => 'time',
        'results_lifespan' => variable_get('views_cache_bully_results_lifespan', 3600),
        'output_lifespan' => variable_get('views_cache_bully_output_lifespan', 3600),
      ));
    }
  }
}

So in your case I would change it to this
/**
 * Implements hook_views_pre_view().
 */
function mymodule_views_pre_build(&$view) {
  // Run if this variable is enabled.
  if (variable_get('mymodule_no_views_cache', TRUE)) {
    // Disable the view cache.
    $view->display_handler->override_option('cache', array(
      'type' => 'none',
    ));
  }
}


Do wood cuts matter for wands?

Question: I am having a wand made, and I wondered if wood cuts mattered.  I heard rift sawn wood is the best for strength in boards, but they only receive pressure from the surface.  A wand would only receive pressure on the long part and not the ends, but it would receive pressure from all around.  Is rift sawn still the strongest cut?  Does it matter?  Money is not an issue.  I care only about strength and durability over time.
Comment: If it was my goal to have maximum strength in a stick, I'd be sure to have it riven. (Or at least I hope that's the past tense of riving.) Anyway, riving is the process of splitting the wood naturally along the grain, so you have long strands of wood fibers.
Answer: Warning: Depending who you mean by rift-sawn it can also mean quarter-sawn. In this question it was understood that modern quarter-sawn wood is what you are describing. I am going to refer to quarter-sawn from here.
Unless your wood stock is from a twig I would guess that the wood you end up with will have the grain of Quarter-Sawn anyway because of its size. This is of course assuming the length of the wand is perpendicular to the grain.... which you would want (I refer you to Graphus' answer for a visual representation of my meaning). This type of wood is favoured by furniture makers as it is less likely to warp.
For a wood to be Quarter-Sawn it has to average 60 degree to 90 degree in grain direction. With a wood diameter that small you should get that (Again I refer you to Graphus' answer for a visual representation).
We have not discussed wood selection yet and that is harder to answer since I do not know your location but oak, hickory, elm and white ash would be good choices to consider. They are primary choices for tool handles and I think would fit well here.
Another question here covers some simple methods in making wands if you were so inclined. Part of me feels you are having it made for you but good information none the less.
Wood features to avoid
The two most important things I would avoid when choosing wood, especially for this project, is avoid the pith and, in general, knotting wood. Using either is asking for a premature break. Like if the knot was to cross the entire diameter of the wand.
Comment: Although it's a good general caution, knots need not be an inherent weakness if the form of the piece allows them to be incorporated properly, e.g. as in longbows made from knotty yew.
Answer: As long as the grain goes in the same direction as the long dimension of the wand you are good.  If the grain goes across the length of the wand it will be much weaker and easily break.
Answer:
I am having a wand made, and I wondered if wood cuts mattered.

Basically no it shouldn't. Assuming I am imagining the form of the wand correctly, the grain will run across the cross-section in nearly exactly the same way irrespective of the cut of the original piece of wood:

Grain orientation in the other direction on the other hand might contribute greatly to whether you end up with a stronger or weaker piece. If the wand is straight (somewhat like a drumstick or a conductor's baton) then straight grain that runs the full length will give the strongest result, but if there is what is called grain run-out (second image below) it will be more prone to failure if subjected to sideways forces:

Note this is only relatively weak, very strong woods like oak and hickory can be very resilient even if the grain is less than ideal (as is the case on many modern axe and hammer handles for example).

I heard rift sawn wood is the best for strength in boards, but they only receive pressure from the surface.

Other things being equal quarter-sawn should be the strongest, and most stable (in addition to having the visual characteristics that it is often valued for). As Matt's answer already covers, some rift-sawn planks will effectively be quarter-sawn wood, but not all. So strength (and stability) of rift-sawn wood can be highly variable.
Answer: To answer your title question Does the cut of wood matter?, unless the wand is going to be used by the 2- to 4-year-old set to beat on everything in sight, I don't think that the strength or cut of wood is going to matter in the least so long as you go beyond small twig size in diameter. If this is being made as a keepsake for someone it will, most likely, sit on a shelf and be played with on occasion.
My daughter has several manufactured (plastic/resin) "Harry Potter" wands which sit in their closed boxes, and she'll get them out once or twice a year to fiddle with them for a few minutes. Granted, she's 18 now, so not quite as fanatical as when she was 12, but even when she was younger, the handling was gentle, as she viewed them more as a collector's item/keepsake than an actual toy.
Even if it's being made for LARP use, that would likely involve older people (beyond the 2- to 4-year-old set) who would likely take care in the use of the wand, and wouldn't throw it, beat on people, rocks, or trees, with it, etc.
I'm posting as an answer to this question in particular, but I feel it applies to all of your I'm having a wand made questions.

Do wood cuts matter for wands?


If the pilots used the brakes upon landing, would the force essentially slam the front wheel down?

Question: So if the pilots braked immediately, with only the back wheels down, and nose wheel still up, would the force from braking cause the front wheel to come slamming down?
Comment: Not in most aircraft.  For the braking force to be high, there needs to be a substantial load on the mains, so the nosewheel is close to settling.  Also, generally technique on mid to small sized aircraft is to hold the nose off until the speed is lower, where it will more naturally drop.  For max braking, many aircraft will use the technique of copious rear elevator (nose up pitch) which transfers weight to the mains.  Different aircraft have different design trades, different tail clearances, and different operational recommendations.
Comment: If you're a reasonably skilled pilot, you adjust your braking effort and elevator so that that doesn't happen.  Same as you generally don't slam on the brakes when you're driving a car.
Comment: It would be nice if an answer addressed the general case, rather than transport aircraft.  There are lots of utility aircraft, and light aircraft and even military and cargo aircraft with different brakes, different aerodynamics, different braking systems, and of course different recommended techniques.  Having answers which are focused on transport aircraft with highly specialized systems to manage secondary effects tends to obscure the underlying understanding of how the brakes, the aircraft mass distribution and the underlying issues the OP appears to be seeking to address.
Answer: If you get on the brakes hard after main touchdown, once the anti-skid is active following wheel spin-up (you can't land with brakes applied on any airliner with anti-skid - brakes are depressurized until after the main wheels start to spin and/or you are weight-on-wheels for a minimum time) and don't apply any additional compensating elevator, the nose will come down faster than if just hold the existing elevator input, and will contact a bit harder, but "slamming down" would be a bit extreme unless you also relieved some of the control back pressure as you did so. Then it would be a bit firm and if you were reckless enough you might blow the nose tires, and somebody would have a chat with you.
In practice though, on most jets you land the mains, then the nose in two separate actions and during that "second phase" you are applying elevator to modulate the sink rate of the nose to make it touch down reasonably gently for that "2nd landing".  If you were on the brakes hard at that point you would normally just compensate instinctively with extra elevator input to get a gentle landing of the nose.
You would certainly have enough tail power available to counteract the nose down torque of the braking at high speed.  But you would probably get scolded for getting on the brakes before nose wheel contact anyway, and a lot of pilots will keep their feet low on the pedals to avoid applying brake, then move them up once the nose wheel is down.
Answer: Yes. Hammering on the brakes right at touchdown will apply a torque to the airplane which will tend to rotate the fuselage "nose down".
Answer: Yes, it would. In the case of the A320, you would actually put the nose down smoothly (fly it down). If you hold the nose up and apply harsh brakes (or have Med autobrake set), then the nose wheel will slam down eventually.


Is asynchronous perfect forward secrecy possible?

Question: DH key agreement protocols require the participation of both parties, so are only suitable for synchronous connections.  Is it possible to implement PFS in a fashion usable for asynchronous protocols, like e-mail, or storage?  I'm intuitively thinking not, but I haven't be able to find conclusive proof one way or the other.
Comment: @RickyDemer Pointing to a search engine like Google is not really useful, as the results are changing. Could you select some relevant papers and add them? Or even better, write an answer with the key points of some of these papers?
Comment: http://google.com/#output=search&q=forward-secure+PKE $\;$
Answer: Asynchronous forward secure encryption is possible if you allow users to have synchronous clocks. It seems impossible without that or a third party, though I am aware of no formal result.
A trivial(and hence awful) solution is to generate N key pairs  and use one for each interval, discarding them as we go. A somewhat more efficient solution is to use Identity Based Encryption(IBE) to have one public key and N private keys.
The most efficient scheme I know of  is due to  Canetti, Halevi, and Katz  in this paper. It provides for constant size public keys and $O(log(N))$ private keys where N is the number of time intervals. As far as I know, no paper has improved on that bound, though several have achieved that bound with more efficient techniques.
The gist of the design is you have a tree of keys where there is one root public key and messages can be encrypted to any node in the tree with the root public key and the index identifying the node. (So far, this is just an IBE scheme). Unlike IBE, the decryption key for a given node can be computed from it's parent key.
We now map time intervals to nodes using a pre order traversal (i.e. the root is interval one, the left child interval 2, the left left grandchild of root is interval 3 ...). So once time interval 1 is up, we derive the keys for both the left and right nodes and then delete the root key. Now messages encrypted to interval one are safe, but we can still decrypt everything targeted at the remaining N-1 intervals.
Comment: Your suggested traversal will eventually require storing $\:\Omega(N)\:$ private keys. $\;\;\;$
Comment: @RickyDemer I don't see how. Call the node you had for the previous interval node X. You will have node X's right child key(if X is an internal node) and the left child key of every node between X and Root inclusive. Since the tree is of height $log(N)$ this gives you at most N keys at any given time.
Comment: Ah, I see that I misunderstood what the pre-order traversal is. $\:$ (However, the last sentence of your comment would be compatible with my previous comment.) $\;\;\;$
Comment: @Yes, I should have said you end up with $log(N)$ keys.
Answer: There's been some interesting research published since @imichaelmiers's answer. It looks like asynchronous messaging / 0-RTT / store-and-forward isn't quite as incompatible with practical perfect forward secrecy as was once thought!

Green & Miers, 2015, 'Forward Secure Asynchronous Messaging from Puncturable Encryption' provides a couple of primitives that can be put together with the ideas from Canetti et al to get something that might be workable.
Günther et al, 2017, '0-RTT Key Exchange with Full Forward Secrecy' take a slightly different tack in assembling various pieces into something that resembles a proper cryptosystem.
Derler et al, 2018, 'Bloom Filter Encryption and Applications to Efficient Forward-Secret 0-RTT Key Exchange' is a refinement that (claims to) make Günther et al's proposal actually practical.

I don't think any of these actually have production-ready implementations yet - especially not the first two, which are too slow for practical use - and of course you want cryptographers to beat them up and see if any problems shake out.


How to calculate the data rate in 802.11g?

Question: I know this is not the community to discuss my homework problem but I cam confused because I cannot find a formula that can find data rate for 802.11g standard given modulation, coding rate and transport layer protocol. And how does transport layer affect the data rate of 802.11g?
Comment: To answer your question, consider the difference between TCP and UDP.
Comment: Unfortunately, all "_education, certification, or homework_" questions are explicitly off-topic here. There are hundreds of webs sites catering to these types of questions.
Answer: The transport layer does not affect the data rate of 802.11 networks.
The data rate is the the rate at which the AP and client modulate frames.  This is based on the signal-to-noise ratio (SNR) between the AP and the wireless client. This is highly variable based on many conditions, including RF interference, distance, device drivers, etc. and often fluctuates over time.
Throughput is what we can measure within the TCP/IP stack, which is where our transport layer comes into play. This is also highly variable depending on quite a few factors, such as:

application protocol
backhaul (how the AP is connected to the wired network)
wireless data rate
other wireless clients in the cell
RF interference

You can make educated guesses by taking the data rate (say, 54Mbps) and dividing it by two (because Wi-Fi is a half-duplex medium), then using that as a line rate for further calculations that take into account the overhead of your protocol.
For 802.11g data rates, I would refer to this article:
https://en.wikipedia.org/wiki/IEEE_802.11g-2003#Technical_description
Modern wireless protocols (802.11n and newer) use Modulation Coding Scheme (MCS) to determine the data rate. There's a great table at http://mcsindex.com that shows all the data rate combinations for MCS.


Limit on Push Notifications

Question: We are configuring the push notifications for our hybrid app at the moment and we ran into one of the governor limits.
This is the error we are getting:

System.LimitException: Too many Mobile Apex push calls: 11

The error matches the governor limit mentioned in the Developer's guide:

Maximum number of push notification method calls allowed per Apex
  transaction   10

If you look at the trigger example in the implementation guide for the push notifications, you will notice the "send" method could be called for each record in the trigger. Since a trigger processes the records in batches of 200, the "send" method for the push notifications could be called 200 times potentially. The governor limit indicates you can only call the "send" method 10 times though.
Has anyone encountered the same issue before and what is a possible solution for this?
Many thanks in advance.
Answer: In the current project I am working on, we have 3 native apps. We also send push notifications to many users and because the maximum limit is 10, we use an external feature to send the notifications. That external feature is pushwoosh (https://www.pushwoosh.com/). They have an api which you can use in an apex class.
I hope this can help you.

Limit on Push Notifications


Guitar intonations sounds a bit off?

Question: So I've got this Les Paul Custom a couple of weeks ago and it feels and plays great. I intonated it perfectly when I first got it too. So today I wanted to test how is intonation holding up and did some tests with perfect 5th. I played 6th fret on low E and compared it to 11th on B. I then played 6th on B and compared it to 11th on G but it sounded sharp in comparison. Basically 6th on B sounds the same as 10th on G whereas it should be sounding the same on 11th.I tried to move a screw a bit on my tune o matic but it just doesn't bulge anymore due to lack of space. What should I do?
Comment: A simple way to test intonation is to compare the fretted note and harmonic at the 12th fret; they should be the same.
Comment: I think you may be confused, or have mistyped your question.  In standard tuning,  the 6th fret of the B string is F and the 10th fret of the G string is F.  The 11th fret of the G string would be F#.
Answer: Just to expand on jonrsharpe's comment a little, you need to tune your guitar up and fret the note at the 12th fret so it's perfectly in tune. Then play the harmonic at the 12th fret and whether it's sharp or flat will tell you if you need to change the intonation.
However, since you've probably adjusted the intonation already, what you should do is;

loosen the strings
make sure the intonation screws are centered, so you have the maximum possible range of making it sharp or flat
tune your guitar like normal
check the intonation and adjust, as mentioned earlier.

EDIT;
Just to mention as well, remember the intonation will change as the neck moves and also if you change string gauges or tuning. It doesn't take a lot to mess the intonation around, but it all depends on the guitar and how well it's built as well!

Guitar intonations sounds a bit off?


OBIEE 11g - Copy MDS and BIPLATFORM schemas for new OBI install

Question: I had OBIEE 126.96.36.199.4 installed on a windows 7 server.  The app installation was corrupted and I had to re-install.  Well, I re-installed OBIEE 126.96.36.199.12 (only install files I have).  I want to use the same MDS and BIPLATFORM repositories as before, however; I do not have the schema passwords for the MDS and BIPLATFORM schemas.  To get around this, I copied the database and gave new passwords.
When I attempt to hook the OBIEE 126.96.36.199.12 installation up to the copied database, OBIEE config says the BIPLATFORM and MDS schemas cannot be found.  Does anyone know if this can be a version issue?  The copied database was from a 220.127.116.11.4 install and the app is now 126.96.36.199.12.  Is this the problem?
Any thoughts?
Answer: I found the answer and wanted to post it for others.  There is a table in the repository called dbo.schema_version_registry$.  If you change the schema prefix in the copied database (required if using the same DB), then you will need to manually edit this table to reflect the new prefix!
Took me days to track down but it's just a simple update against the table.  Hope this helps someone.
Comment: On Oracle (I'm guessing you've using SQL Server), there is also a system view that you may need SYSTEM.SCHEMA_VERSION_REGISTRY. Without this I can image uninstall/reinstalls might fail.


Checking if user authored an entry in another channel while in loop, N+1 problem

Question: I have 2 channels set up: Channel A and Channel B.  I also have public registration so users can log in and fill out two forms (Form A and Form B), each form creating an entry in their respective channel with the user as the author.  The user can only create an entry in Channel B if they already have an entry in Channel A.
To get all the users who have an entry in Channel A but not in Channel B, I tried writing something like this in my class:
public function getUsersWithoutChannelBEntry()
{
    $channel_A_entries = Entry::find()
        ->sectionId(1)
        ->all();

    $userIds = [];
    foreach ($channel_A_entries as $entry) {

        $channel_B_entry_exists = Entry::find()
            ->sectionId(2)
            ->authorId($entry->authorId)
            ->exists();

        if (! $channel_B_entry_exists) {
            $userIds[] = $entry->authorId;
        }

    }

    return User::find()
        ->id($userIds)
        ->all();
}

However, this creates an N+1 problem. I have roughly 200 users, so potentially 200 entries in either channel, and thus a lot of db queries and a substantially larger load time.
As an alternative approach, I've also tried looping through Channel A, adding each author ID into an array (Array A), then doing the same with Channel B making Array B.  Then I use array_diff() to extract the author IDs that are in Array A but not in Array B.  However, this still causes a bit of long load time.
I've looked into eager loading, but that seems to only apply to related fields.
Is there a more efficient way to get all users who authored a Channel A entry but not Channel B entry?
Answer: There's one bit missing in the constrains you explain above, do users end up with 1 entry only per channel so a total of 2 posts max?
If so, we know that:

each users can have a max of 2 posts
a user cannot post in B is they haven't completed their post in A

So assuming this first condition is also true (2 entries/user) you could just loop through users post count looking for those with less than 2 posts and they would automatically be the users who haven't posted in B..? Just a shot in the dark :)


How to cluster two Ubuntu Linux Desktops to run a program?

Question: Background: For some friends in a local academic institution, I wrote a Java program that simulates the growth of the crystal in a microcellular matrix as a concurrent program that implements 100,000 MonteCarlo iterations, each iteration comprises of 14,240^2 steps. First implemented in 2-dimensions, its able to support up to 14,240x14,240 size matrix, each cell is a byte, and associated data structures to support algorithms to compute areas of the grains etc.
The program has been written as 4 concurrent threads that use the quad core CPU (100%) with each thread executing 1/4th the number of steps, and the threads "recombine" at end of the 14,240^2/4 trials, and start the next iteration, where I fork new threads. The access to the common matrix etc. is controlled by using synchronize keyword, and 4 threads are controlled to close by using a semaphore.
Also, I built the hardware for them – Intel Core i5 2500K processor, with 16GB RAM, dual partitioned into Windows (for their use) and Linux – for my testing.
Problem: These friends now want me to try and help write a 3-Dimensional version and are willing to concede to a size of 10,000x10,000x10,000 matrix.
My idea: Clearly one single machine will not be able to handle this. Is it possible to use a cluster of two-three such machines? If so, can anyone please guide me to a open source, free, metaware or a Java implementation that can execute JVM(s) on these nodes, and then run this program ?
On one single machine I am able to touch up to a 400x400x400 matrix only. I am willing to rewrite the code so that each quadrant of the matrix is processed on different cluster, with each quadrant trials but need to know how to execute the program concurrently in different machines and how do I synch the computations.
I remain grateful for any suggestion or idea.
Answer: MPI is probably where you should start.  The Message Passing Interface is very common when trying to build clusters.


90s Prostitute reference in Law & Order: SVU

Question: Episode 4 in season 1 of Law & Order: SVU is about a policeman that kills prostitutes, and one night he killed a woman that was in good health and had good nutrition, and the mortician referred to her as a prostitute from the 90's. Why?
Comment: Possibly because it was the 90's?
Comment: Someone that commits sexual acts for money may be considered a prostitute. The health and nutrition of such a person is irrelevant. In fact, I've heard of prostitutes that make more money than I do by a large margin, and I'm at least upper middle class.
Comment: Could be **Manhattan streets numbered 90-99**, especially if he said "*East* 90s" or "*West* 90s". These are parts of the Upper East Side and Upper West Side areas (East and West of Central Park), which are as Wikipedia puts it "affluent" and "[primarily] residential".
Answer:
The M.E.: "Stomach contents include soybeans; vegetables; whole grains. A health conscious hooker."
Olivia: "How 90's."

Saying that a health conscious hooker is so 90's in the 1990's would be like saying, "How millennial." in 2010. I'm not sure what it is now. The year isn't important; it's just a saying. Every decade has had its health kicks; coffee and eggs seem to have been continually debated throughout the last 100 years. Renewable energy? How 70's.
The 90's were a strange convergence of opportunity and availability, and could leave you with a feeling of we can do anything and we can do better. See The Dot Com Bubble to learn how that ended. AFAIK, the 90's were also the first decade in America that the trend to become health conscious became trendy.
So, how 90's of that hooker it was to be concerned with their food choices, while they subjected their bodies to prostitution.
In retrospect, I can't rule out the chance that Olivia might have meant something more along the lines of, "Kids these days...", but I still think the comment is more about a sign of the times.
Comment: Wow, Mezuraa, thank you!! I didnt know, very good analogy, so 80s was sex, drugs and rnr? :D


What does pH of NH3 solution refers to?

Question: I was introduced with an exercise which asks to find $K_\mathrm{b}$ of $\ce{NH3}$ when the $\mathrm{pH}$ of $\ce{NH3}$ solution with concentration $M_1$. Well, in order to solve it, I used the fact that $\mathrm{pOH} = 14 - \mathrm{pH}$ and the dissociation $\ce{NH3 + H2O <=> NH4+ + OH-}$ to compute $\ce{[OH-]}$ and then $K_\mathrm{b}$. However I don't fully understand what does $\mathrm{pH}$ mean, since in this dissociation there aren't any $\ce{H3O+}$ molecules. I think it relates to the conjugate dissociation of the $\ce{NH4+}$, i.e.: $\ce{NH4+ + H2O <=> NH3 + H3O+}$, so the $\mathrm{pH}$ of the $\ce{NH3}$ solution is in fact related to the concentration of $\ce{H3O+}$ which is formed from the $\ce{NH4+}$ dissociation. Is it indeed the case? I would really appreciate any explanation.
Comment: pH means the same as always. See, _pure water_ also has pH, hence it must have some H3O+. How so? Well, just like that.
Comment: For that you need to understand where the H3O+ comes from in pure H2O.
Comment: Yes, but I try to understand where the $H_3O^+$ come from since the $NH_3$ forms $NH_4^+ + OH^-$  when reacting with water and not $H_3O^+$. I'll try to emphasize my question with another example - taking $NH_4Cl$ which dissociate to $NH_4^+ + Cl^- $ , how should I understand (or maybe view would be a better term) the $pH$ and the $pOH$ of $NH_4Cl$ solution?  @IvanNeretin
Answer: As Ivan Neretin said in the comments, $\ce{H3O+}$ is already there, via the autodissociation of water:
$$\ce{2H2O <=> H3O+ + OH-}\tag{1}$$
Now water reacts with the ammonia that you add, according to the equilibrium reaction you provided:
$$\ce{NH3 + H2O <=> NH4+ + OH-}\tag{2}$$
This increases the hydroxide concentration further, so the first reaction is out of equilibrium, and consumes some hydronium and hydroxide by going in the net reverse direction, increasing the pH.
Alternatively, you can combine the two reactions to show that adding ammonia will lower the hydronium concentration:
$$\ce{NH3 + H3O+ <=> NH4+ + H2O}\tag{3}$$
All three reaction and the reverse reactions will occur simultaneously.

However I don't fully understand what does pH mean, since in this dissociation there aren't any H3O+ molecules.

For basic solutions, the hydronium ion is a minor species. For acidic solutions, the hydroxide ion is a minor species. Sometimes in calculations, we get away with ignoring a minor species for a while, but they are still there.

What does pH of NH3 solution refers to?


Correlation coefficient for categorical data resulting from multiple judges

Question: I have data resulting from 3 (fixed) judges observing 15 medical students performing physical exam maneuvers. I'm trying to decide the correct correlation statistic to use. The results can be: done and done correctly (1), attempted (2), or did not attempt (3). I initially thought to use ICC, but I got really screwy results when there was perfect or almost perfect agreement. I think because the data are not normal. Incidentally I am using Stata.
Comment: Agreement is not the same as correlation. It looks like you need measures of agreement, not measures of correlation
Comment: I may be incorrect, but I thought one could only use Kappa if there were 2 judges, not more.
Answer: The appropriate measure here is a measure of agreement since the rating is a categorical variable. For three raters the usual technique was discussed by Fleiss in a paper entitled "Measuring nominal scale agreement among many raters" available here. The method is quite general and does not assume the same raters throughout.
The issue of what to do when there is near perfect agreement is complex as it depends on the exact data-set but if the problem is that the raters tend to only use one category it is useful to report percent agreement alngside kappa.
Answer: I understand that your goal is to compute correlation between different judges to measure how consistent are results.
The first point should be decide what kind of data you have:

Categorical data, if there is not an order in your 3 results (correctly is better than attempted, but is attempted better than not attempted?).
Ordered data: correctly better than attempted better than not attempted.
Quantitative data: Although your data is not actually quantitative, it could be treated as quantitative if there were and order and the "distance" between correctly and attempted were the same as between attempted and not attempted.

I don't know a usual measure of correlation for categorical data in 3 levels, although for 2 levels there is odds ratio and related statistics.
For ordered data - which seems likely - you can use a non parametric measure of rank correlation as Spearman's rank correlation coefficient.
If your data can be seen as quantitative Spearman's would be also fine, but it's more common to use Pearson's correlation coefficient.
Beware that correlation coefficients are computed on pairs of variables; therefore, you will have a correlation coefficient for each pair of judges - most statistical packages have an order to compute it for all pairs in a group and present them as a correlation matrix. ICC does work with several groups at once, although I doubt if it actually can fit your needs.
Furthermore, if you want to test effect of judge and student in results you could use Kruskal Wallis test, although it needs that your data can be seen as quantitative.
Comment: You really need a measure of **Agreement**, not of correlation. See the answer by @mdewey.


If several people use the same username, how do you ping just one of them?

Question: I want to get someone's attention by using the @username feature. But I noticed that several people use the same username. So how does that work?
Comment: See [Agent Smith Calling Agent Smith](http://meta.math.stackexchange.com/questions/4801/agent-smith-calling-agent-smith)
Answer: If they have all recently been in the chatroom you are in, or participating in the same comment thread, then there is no way to differentiate them. If you ping one, you will ping them all.
user147263 points out that Rule 4 says that in comments, the user chosen is the user

who matches the name supplied
who has participated in the comments on or edited the particular question or answer
who has acted most recently (editing, commneting, etc)

However, I have been the "victim" of misdirected pings to <code>@rob</code> in chatrooms, so, unless the code has changed recently, I am pretty sure that chat pings any match. Further evidence that the chat code is different: multiple people can be notified in a single chat message.
Comment: @user147263 What if the person hasn't participated in the thread other than setting up a bounty?
Comment: I don't go in the general Mathematics room much precisely because I get hit with all @alex pings.
Comment: minor point, I've noticed, if I am the first and only comment on a question and the OP writes a comment without any @ field, often i get pinged anyway. Probably not every time; in any case, if I remain interested, i go back and check my own activity for comments without @ fields...


How do I find my base attack bonus?

Question: I just started Pathfinder RPG and I'm designing a level 1 character. How do I find my base attack bonus? I have the core rulebook but I'm quite confused.
 Stats:
Str 16       Dex 15         Con 15        Int 12         Wis 12         Cha 13
Half-Orc Fighter with Battle Axe, short bow, and great club. Feats are Dodge(combat), Point-Blank shot, and lightning reflexes.
Please help and thank you so much!
Comment: you may want to specify if you intended to start at level 1 or 2.
Comment: Welcome to the site, CornDawg! It's good to see questions from a new player's perspective. When you get the chance take a [tour](https://rpg.stackexchange.com/tour) of this site; there's good information about what questions work or don't work here (and you get a 'medal'... kind of like achievements). When someone gives an answer you feel fits well and helped you resolve the question, don't forget to click the check mark near the vote up/vote down buttons to 'accept' it.
Answer: Every class has a table, showing the Base Attack Bonus (or BAB), Base Saves, and special abilities gained at each class level. So, assuming you only have levels in one class, you look at the BAB value on that table. For instance, Fighter 5 gets a BAB value of +5, and Cleric 4 gets +3. Most classes will gain either +1 or +0 BAB at first level.
If you have levels in multiple classes or racial hit dice for some reason, the process is slightly more complicated - you look up the BAB amount for each of the class levels and hit dice you have, and then total them together for your total BAB. For instance, if you are a Fighter 5/Cleric 4, your total BAB will be +8.
To calculate your actual attack bonus for a specific attack type, you then add any other modifiers involved to the BAB, such as for the stat involved (Str for melee or Dex for missile, generally).
In your specific case, assuming you are level 1, your BAB will be +1. Your attack bonus with the melee weapons (Axe and Great Club) will be your BAB of +1 plus your Strength modifier of +3, for a total of +4. Your attack bonus with the missile weapon (short bow) will be BAB +1 plus Dex +2, for a total of +3. At 30' or less, Point Blank Shot will add an extra +1 attack bonus with the bow, for a total of +4. Your GM may apply various other specific modifiers during combat (one likely to come up is a -4 penalty for shooting into melee, which Precise Shot can remove).
Comment: Lol, never say never. Maybe a Prestige class will come along with +2 BAB at first level, or even -1 BAB...
Comment: Are there any classes that *don't* have a BAB of either 1 or 0 at level one?  That'd be pretty crazy!
Comment: Not that I know of, but I thought I should add the usual caveat, just in case :)
Comment: It may be worth mentioning (knowing the class) that if they only ever put levels in Fighter, their BAB will equal their level (which is then modified by Abilities like STR or DEX) instead of assuming 1st level (he has 3 Feats as a non-human).
Comment: There is no official class with anything but BAB +0 or BAB +1 at 1st level, and there almost-certainly never will be. There are only three BAB progressions in the game, and one starts at +1 and the others at +0. And values less than 0 or above 1 would be completely absurd.
Answer: your base attack bonus is not the same as your attack bonus. Think of it like a base military soldier's paycheck. They always get that much money a month, but if they get assigned special training, they get paid bonuses, so their income goes up in certain circumstances.
As a Fighter, your base attack bonus is always your level for the first attack, and your level -5 for the second attack, level -10 for the third attack, and so on. While your strength gives you a +3 bonus to the level 2's +2, totaling +5, your base attack would still be a +2. You must be level 6 before you get a second attack. You do not use your strength bonus for calculating how many attacks per round you get.
A starting (level 1) Fighter gets 1 extra feat, Dodge,
a level 1 gets 1 extra feat, Point Blank Shot
a level 2 (Fighter only) gets 1 extra feat, Lightning Reflexes
if you are not level 2, that you are a Half Orc implies you did not get a third feat and must remove one, as only humans get a bonus feat.
Comment: Your discussion of iteratives is not actually correct - a character's base attack bonus does not vary by the attacks he makes. The total attack bonus for an iterative attack might, but not the bab.
Comment: Also, your discussion of feats is wrong-- there are several ways this level one non-human fighter might have three feats; I would guess that the most probable of which would be their being an Antihero.
Comment: Actually I'm not an Antihero. It says in the core rulebook that half-orcs "count as both humans and orcs for any effect related to race". It says the same for half-elfs. Does that not apply to feats?
Comment: That's a separate question - but heh heh no.

How do I find my base attack bonus?


How can I disable the "Make your voice heard. Take the 2019 Developer Survey now"-banner

Question: This banner pops up every day I open Stack Overflow. I participated in the survey, yet it still asks me again. When I click it even told me to go away because I already did it.
Comment: Are you allowing cookies on SO? I dismissed it and it's never come back.
Comment: It literally told you to go away? That is not very welcoming.
Comment: Yes. I did that yesterday, after it told me to go away. Today it appeared again. If it is so smart to notice that I already did it, why is it even displaying it.
Comment: Have you clicked the "X" on the right hand side to close the notice?
Comment: I'd suggest testing on a different (up-to-date) browser with cookies enabled. I have never had problems with that banner.
Comment: seems like a fair question.  why is it down voted so much?  I agree that this is  a quality of service bug to reprompt for a completed task.
Answer: As said by TheWanderer, this is not a bug but has something to do with the cookies in your browser.
When you click on the X at the right side of the banner, there's a cookie being set in your browser with the name: ds-notice. Which will remember whether you closed it or not.
When viewing the cookies in edge, it looks like this:

Enabling cookies will most likely solve your issue and remember to keep the banner hidden when you close it.
Enabling cookies in Edge.
Enabling cookies in Chrome.
Enabling cookies in Firefox


Why do we wear green on St. Patrick's Day and get pinched if we don't?

Question: Wearing green on St. Patrick's Day is a tradition. No questions asked, just do it, kinda thing. So, as I'm running away to ask this, in my green shirt (it says "WORLD'S TALLEST LEPRECHAUN), I came to wonder why we do it. Why do we wear green on St. Patrick's Day and get pinched if we don't?
Comment: That's two questions :-)
Comment: It is 2 in one.
Comment: No problem, now @yannis has edited the title to make that clear.
Comment: I have never heard the "pinched" part of this, and anyone who tried to assault me over my sartorial choices would be sporting a whole lot of self-sourced red. I assumed people *chose* to wear green because it's the color associated with Ireland, and Patrick is an Irish saint. Why else would people do it?
Comment: Saint Patrick's Days falls close to the equinox, on March 17, and is thus closely linked to the blossoming vegetation brought on by the coming spring.
Answer: I can remember several years ago, a friend of mine got pinched on St. Patrick's Day in Wagner, Oklahoma of all places.
So why do we wear green on St. Patrick's Day and get pinched if we do not?
To be honest the answer has to do several items:

St. Patrick
The Color Green
The Irish Potato Famine
Leprechauns

Why do people wear green on St. Patrick's Day?

As to how that became the day we love/fear, March 17 is the day on which St. Patrick is thought to have died, and a Feast Day was instituted to commemorate his life and accomplishments. As Irish immigrants celebrated it across the pond in America in the early 18th Century, the feast became a bigger and bigger deal to the Irish community. This led to the first-ever St. Patrick's Day parade in Boston in 1737, and by 1903 the Feast Day was  a National Holiday back in Ireland.
The link between green and Irish pride originated in the Irish Rebellion of 1798. As the Irish rebelled against the British soldiers, who wore red, they wore green uniforms. There's a famous ballad about this called "The Wearing of the Green," which is guaranteed to make you feel somber and proud even though you have no connection to those events. As a sign of solidarity with the rebellion, people began wearing green as an expression of Irish pride. Since St. Patrick's Day was the official day to express that pride, the two became linked. - The Questions You're Too Afraid to Ask About St. Patrick's Day Answered

How does the Irish Potato Famine fit in to this in America?

The Irish Famine caused the first mass migration of Irish people to the United States. The effects of the Irish Potato Famine continued to spur on Irish immigration well into the 20th century after the devastating fungus that destroyed Ireland's prized potato crops died out in 1850.
Starvation and diseased claimed around a million lives during 1845-1850, which lead to almost twice that number to emigrate to other countries, including a majority into the United States. The lack of industry and overall poverty that remained constant in the region brought many impoverished Catholic farmers and laborers into the U.S. - Irish Immigrants to the United States

So we can see that the Irish during the 1800s came to the United States in large numbers and brought their Irish heritage with them.
Now for the color green. There are several points to be made here.
Green is a liturgical color to Irish Catholics that symbolizes hope. Hope in a new country and a new way of life in the US.
Green, not purple was the original Episcopal color and St. Patrick was a Catholic Bishop.
And again there is The Wearing of the Green.

"The Wearing of the Green" is an Irish street ballad lamenting the repression of supporters of the Irish Rebellion of 1798. It is to an old Irish air, and many versions of the lyric exist, the best-known being by Dion Boucicault.1 The song proclaims that "they are hanging men and women for the wearing of the green".

The revolutionary Society of United Irishmen adopted green as its colour, and supporters wore green-coloured garments, ribbons, or cockades. In some versions, the "green" being worn is shamrock rather than fabric. - The Wearing of the Green
Let us not forget the legend of St. Patrick and the shamrock. The shamrock is green too.

Traditionally, shamrock is said to have been used by Saint Patrick to illustrate the Christian doctrine of the Holy Trinity when Christianizing Ireland in the 5th century. The first evidence of a link between St Patrick and the shamrock appears in 1675 on the St Patrick's Coppers or Halpennies. These appear to show a figure of St Patrick preaching to a crowd while holding a shamrock, presumably to explain the doctrine of the Holy Trinity. In pagan Ireland, three was a significant number and the Irish had many triple deities, which could have aided St Patrick in his evangelization efforts. Patricia Monaghan states that "There is no evidence that the clover or wood sorrel (both of which are called shamrocks) were sacred to the Celts". However, Jack Santino speculates that "The shamrock was probably associated with the earth and assumed by the druids to be symbolic of the regenerative powers of nature ... Nevertheless, the shamrock, whatever its history as a folk symbol, today has its meaning in a Christian context. Pictures of Saint Patrick depict him driving the snakes out of Ireland with a cross in one hand and a sprig of shamrocks in the other."

And finally the Leprechauns:

And this is why the pinching on St. Patrick's Day happens.
The pinching on St. Patrick's Day is connected to another of the holiday's staples: the leprechaun. Superstitions claimed that wearing the color green made you "invisible" to these magical creatures, who went around violating people's personal space and pinching everyone they could see. The reason behind this inconsiderate behavior? They're just mischievous.
But this quickly devolved into people taking matters into their own hands, quite literally, and pinching those around them on St. Patrick's Day who weren't wearing green — as a reminder that leprechauns might pinch them. So there's really no escaping the pinch. - Here's the real deal with the pinching on St. Patrick's Day


What's inside a proton?

Question: What constitutes protons? When I see pictures, I can't understand. Protons are made of quarks, but some say that they are made of 99% empty space. Also, in this illustration from Wikipedia, what's between the quarks?
Comment: Note that "empty space" is just a philosophical abstraction. Ultimately, space is the name we give to that handy utility which prevents everything from occupying the same spot. How much space is between two particles depends on how fat you consider them to be: where is the boundary between what is in the particle and what is outside. This is complicated by the boundary being fuzzy: just a sort of density function, which is not even time-invariant.
Comment: We think that they might be point-like, but we're not really sure about that.
Comment: @DavidZ Because due to surpassing some hotness threshold or whatever, it has appeared in the stackexchange-network-wide list of hot questions, which creates a positive feedback loop of upvoting.
Comment: Although even that explanation is undersimplified; all we _really_ know is that these models we've come up with (which include things like 'atoms', 'molecules', and 'cells') do a pretty good job of explaining certain observations, and even at predicting what we will observe if we change things in certain ways. (To a certain extent, that is even true of even more basic things, like 'gravity', 'physical objects', etc.) The lesson here though is that the point isn't that everything makes sense, but that it makes enough sense that we can use it to predict things.
Comment: I would presume that since 3 quarks make a proton, that the grey blob probably represents the proton size. Definitely not to scale though, given that we don't really know how big the quarks are (just a *large* range, from $10^{-35}$ m up to $10^{-15}$ m).
Comment: Actually, _atoms_ aren't even as point like as most people would like to think. They are not little marbles made of smaller marbles; they are little fuzzy blobs. All we know is that occasionally, when you hit the fuzzy blob with another fuzzy blob, a piece of one of the blobs splits off, but always in one of certain particular ways. Depending on what happens when that new blob interacts with other blobs, we give it different names, and came up with a theory that these blobs are made up of certain 'primal elements', which appears to be consistent with our observations.
Comment: Quarks are point like particles, they have no volume.
Comment: Related to the previous comment: http://physics.stackexchange.com/questions/32476/quark-radius-upper-bound?rq=1
Comment: @Kaz I've won a prize? (I like cookies)
Comment: @Kaz Note that "space" and "time" are just philosophical abstractions. It is extremely likely that our space and time do not exist outside of our universe.
Answer: Ah, I know this one!
What's in a proton?
A proton is really made of excitations in quantum fields (kind of like localized waves). Remember that. Any time you hear any other description of the composition of a proton, it's just some approximation of the behavior of quantum fields in terms of something people are likely to be more familiar with. We need to do this because quantum fields behave in very nonintuitive ways, so if you're not working with the full mathematical machinery of QCD (which is hard), you have to make some kind of simplified model to use as an analogy.
One of the more confusing things about quantum field excitations is that they react differently depending on how they are observed. More specifically, the only way to measure the properties of an excitation in a quantum field is to make it interact with another excitation and see how the excitations affect each other. Or in particle language, you have to hit the particle with another particle (the "probe") and see what comes out. Depending on the charge, energy, momentum and other properties of the probe, you can get various results.
People have been doing this for decades, and they've compiled the results into a few general conclusions. For example, in a slow collision, with very little energy involved, a proton acts like a single point particle. If we give the particles slightly more energy, the proton looks more like a blob with three points in it --- this is part of why it's often said that the proton consists of three quarks. (Incidentally, the reason you see images like the one you found on Wikipedia is that for a long time, people were colliding protons at the intermediate energies where they appear to behave as a group of three quarks.) If we give the colliding particles even more and more energy, the proton will appear to be an ever-more-dense amalgamation of all sorts of particles: quarks, antiquarks, gluons, photons, electrons, and everything else. We call these particle partons (because they're part of the proton).
The following diagram shows representative examples of the effective composition of the proton in different kinds of collisions. The vertical axis basically corresponds to collision energy, and the horizontal axis corresponds to the "resolving power" of the incident ("probe") particle. (Resolving power is basically transverse momentum, but I can't explain how that connection works without getting into more detail of quantum mechanics than I think is necessary.) The contents of each circle represents, roughly, a sample "snapshot" of how the proton behaves in a collision at the corresponding energy and resolving power. The exact numbers, locations, and colors of the dots aren't significant (except sort of in the bottom left), just note how they get larger or smaller and more or less numerous as you move around the plot.

So for example, if you hit a proton with a beam of high-energy probes (top) that have weak resolving power (left), it behaves like a dense cluster of partons (quarks and gluons etc.), each of which is fairly large. Or if you hit the proton with a beam of low-energy probes (bottom) with high resolving power (right), it behaves like a sparse cluster of partons, each of which is small. If you hit it with a beam of low-energy (bottom), low-resolving-power (left) probes, it behaves like a collection of three particles.
Physicists describe this apparently-changing composition using parton distribution functions (PDFs), often denoted $f(x, Q^2)$. Under certain not-too-crazy assumptions, $f(x, Q^2)$ can be interpreted as the probability density of the probe interacting with a particular type of parton with a particular amount of momentum. Visually, $f(x, Q^2)$ is related to the number of particles in the circle at the corresponding $(x,Q)$ point on the plot (though again, the exact numbers are not chosen to exactly reflect reality). For more information on parton distributions, I would refer you to this answer of mine and the resources named therein, as well as this one.
What's the gray region?
In the preceding image, I displayed each snapshot of the proton as a set of partons (quarks and gluons etc.) uniformly distributed within a circle, as if the proton has a definite edge and there is nothing outside that edge. But in reality, that's not the case. The quantum fields that make up a proton gradually fade away to zero as you move further away from the center, giving the proton a fuzzy edge. So a (somewhat) more accurate sample snapshot would look something like this:

Notice that there are more dots near the center of the proton, and progressively fewer as you move toward the edge; this represents the fact that a probe which hits a proton dead-center is more likely to interact than a probe which hits it near the edge.
The ordinary parton distributions that I mentioned above, $f(x, Q^2)$, are part of a simplified model in which we ignore this fact and pretend that partons are distributed uniformly throughout space. But we can make a more complicated model that does take into account the fact that partons are clumped up toward the center of the proton. In such a model, instead of regular parton distributions, you get more complicated functions, called impact parameter-dependent parton distributions, and denoted $f(x, Q^2, b)$, where $b$ is the radial distance from the center at which the probe hits - the impact parameter.
There have been some theoretical studies showing that these impact parameter-dependent parton distributions trail off gradually as you go to large radii. For example, see figure 5 of this paper (arXiv) or figure 7 in this one (arXiv):

Here $N(y)$ is a quantity related to the parton distributions (specifically, it's the color dipole scattering amplitude), which kind of "condenses" the many different parton distributions into one quantity. (Huge oversimplification, but it's good enough for this.) You can then define the spatial extent of the proton as the region in which $N(y)$ is above, say, 5% of its maximum value. Or 10%. Or 50%. The exact number is somewhat arbitrary, but the point is, whatever number you pick, you'll wind up with a circle that encompasses the region in which the parton distribution function is large, kind of like this:

This is roughly what the gray circle in the image from Wikipedia represents. It's a region with a size on the order of $1\text{ fm}$ (that's about $5\text{ GeV}^{-1}$ in natural units), where the chance of an incident particle (a probe) scattering off the proton is relatively significant. Equivalently, it's the region in which the parton distributions are large, and also the region in which the quantum fields that constitute the proton are much different from zero.
As you can guess, all this is pretty imprecise. You can make a more rigorous definition of the size of a proton by using the scattering cross section. You can also get a definition without using scattering, using the charge radius, which can be measured or calculated using various other methods. I won't go into those, as the details would be material for a whole separate question, but the results of all these methods come out to a radius a little less than $1\text{ fm}$.

Incidentally, this claim of a proton being 99% empty space is probably false using any reasonable definition. You might be thinking of atoms, where the volume in which the electron's quantum field has an appreciable value is much larger than the size of the electron itself, whatever it may be. People sometimes simplify that to say that the atom consists of a large fraction of empty space. But you can't really do the same with a proton, given the large number of particles in it and the strength of their interactions.
Comment: +1: This is an excellent example of how "what the insides look like" is more nuanced when *the energy needed to "see" the insides approaches the mass of the insides*. Needless to say the macroscopic world isn't this way. Not even electrons around atoms (except the 1s orbitals in heavy elements) nor protons and neutrons within a nucleus are this way. But quarks are.
Answer: The illustration doesn't show the underlined physical reality. A proton is made up of 3 quarks, namely $uud$, but it is also constituted, as jinawee pointed out, of virtual quarks and antiquarks who are constantly being created and annihilated via strong force which is mediated by gluons, described by Quantum Chromodynamics (QCD).
The grey sphere in Wikipedia's site, shows the region where quarks make the proton, in other terms, if the wave-function shows the probability of finding a particle in a region of space, then this sphere shows the probability where you can find the essential quarks making up a proton.
Comment: This answer is vastly incomplete as it doesn't even mention gluons.
Comment: @Wedge I mentioned the strong force, should I edit the post to incorporate 'gluons' to explain a bit more the strong force?
Comment: @dj_mummy Thank you for your proposal. But I was more talking of a low energetic proton and I don't want to repeat or extend what *David Z* eloquently explained, only if you insist or if the OP finds it useful.
Answer: You can't consider a proton just as three quarks (called valence quarks, because they determine the quantum numbers) because virtual quarks and antiquarks are constantly being created and anhilated via strong force. So a proton is more like a quark sea. In fact, this process gives most part of the proton's mass (the valence quarks are just the 2% of the mass).
It's something like this:

The lines that connect quarks are gluons (the force carrier particles of the strong interaction).
Comment: I'm asking about the orange thing in your schema;
Comment: If you mean the circle of the background, it's nothing physical.  Only what you would observe as the proton's approximate radius.
Comment: @MyFavouritePhysicistIsNewtax In analogy with an hydrogen atom:how would you draw it? One proton and one electron or a sphere with a core? Both ways are correct. The interpretation of the last drawing should be like a long exposure photo, where the sphere is the zone where the electron can be.
Comment: @MyFavouritePhysicistIsNewtax schemata can be false only if one thinks they represent reality factually. The schema is a representation of the current model of the proton. The background is a conceptual help to localize the interactions  within a radius.
Comment: And note that the proton's radius is about $10^{-15}$ m and the quark is smaller than $10^{-19}$ m (at least 10000 times smaller).
Comment: If 3 quarks are *confined* to make a proton, then it is reasonable to think that these colored regions are (effectively) the proton size (and, again, without regard to scales).
Comment: So that schema is false let alone the scales.
Comment: Yes, it is schematic, not a mathematical representation. One can imagine the number of constituents going to very large numbers
Comment: @annav Isn't my picture incomplete, since a proton would be represented by infinite Feynman diagrams.
Comment: And what are the squiggly lines here?
Comment: @ja72 That are the the gluons which mediate the strong interaction.
Answer: The question you are asking has been answered in terms of popularized description.
The real physics picture is not simple and depends a lot on a number of experimental measurements by many experiments. If you look at figure 9.18 of the link you will see that the composition of the proton changes according to the momentum transfer from the probing particle.

Contrary to the statement that it is mainly empty space, it is not. Particles probing the proton do not sail through unscathed, they interact with the quarks and gluons that compose it and thus we get the parton functions in the figure. The reason it is not mostly empty is because Quantum Chromodynamics, contrary to the other forces does not diminish with distance, but increases, thus the constituents are tightly bound.
So the answer to "whats inside the proton" is "it depends on the way you look inside it". From outside, it has the quantum numbers assigned to it by the three valence quarks.
Answer: The real problem here is that when things get really, really small, they don't behave like the world we see around us. That can make a lot of what goes on in that weird world quite hard to grasp.
The diagram is misleading. Protons aren't really round, grey blobs, and quarks aren't really little spheres that sit inside them. Down at the subatomic level, Quantum Mechanics rules.
One of the weird upshots of Quantum Mechanics is that really tiny things don't actually occupy a single space. Take a look at your hand. It's there, right? In one, single place. If you curl it into a fist, it takes up less space, and if you stretch it out, it takes up more. But it's always in one place.
Really tiny things don't work like this. Instead, they occupy many points in space at the same time. We usually draw diagrams where the actual positions of tiny things are represented like clouds: they're in lots of places, all at once.
Quarks are like this, too. They're held together by incredibly strong forces, but they're trying to get away from one another, too. Like when you're in a car with your parents on a long drive. What do I do on a long drive with my parents? I fidget. I couldn't tell you where I'll be - front seat, back seat - because I'm constantly moving around. But you know I'm somewhere inside the car, even if you can't tell me exactly where.
And so with quarks, with one twist: they really are in many different places at the same time. What we do know is that they're most likely stay within a boundary: in this case, the grey circle of the proton.
As for the 99% of empty space, the actual figure is much higher than that. Very little is actually 'made up' of matter (we usually call matter-like particles 'hadrons'). So why don't we fall through things all the time? Why doesn't my laptop slip through my desk, if it's mostly nothing? Well, because the forces between these tiny particles are tremendous, compared to their size (and, more importantly, compared to their mass). That allows them to stay a balanced distance from each other, and stops anything else from coming too close to them, or falling 'in between' the particles. When you catch a ball, the particles in your hand and the particles in the ball never even come close to 'touching', because the forces between particles are so strong. Instead, the ball is 'repulsed' from your hand. This repulsion balances against the ball's force due to gravity, so the ball stays where it is.
TL;DR: The diagram does the best it can at explaining how things work on the very very small-scale. Unfortunately, it's very misleading. The 'space between' particles is a) not really space, but 'point clouds' of possible particle positions (there's a mouthful), and b) it's forces between particles, rather than the particles themselves, that stop the 'empty space' in the proton from being something you could actually go through.
Comment: Morg - no. This is not how Science works. What you are quoting is empirical realism, which was a very popular philosophical movement in the 30s but died out shortly after Karl Popper's introduction of falsification. The modern scientific method uses a Hypothetico-Deductive method: a hypothesis is deduced from existing research, asserted and tested. There is no 'right' or 'wrong' about it, merely *self-consistent* or *inconsistent*. Modern Science makes no claims about the nature of reality, rather offers an occasionally unusual, abstract or counterintuitive *self-consistent theoretical model*.
Comment: +1, but just wanted to nitpick that, technically, your stretched-out hand and your curled-up hand take up the same amount of space and displace the same volume of air. :)
Comment: Actually, this is a very wrong and dangerous explanation. Every Physics theory is a failed attempt at explaining how the universe works. Every new theory is a better attempt, but it is critically important to remember that it is WRONG as long as it does not explain everything. It is instead VERY likely that quantum theory is only a statistical approximation of reality and that our understanding is strongly biased by our limited senses and sensors.
Comment: Jeff - you're absolutely right, of course. I was using an analogy that would help differentiate between two concepts: *extended* spacial occupation (macroscopic, non-point objects) and *distributed* spacial occupation (quantum-mechanical objects). I hoped the question 'does a hand really take up more space when you stretch it out?' might have led to the question 'does a quantum-mechanical system *really* take up 'more space' when left to evolve unobserved?'. Of course, the answer comes down to a definition of 'space' and 'place', which both need to be treated differently at the quantum level.
Answer: As some of the answers have pointed out, the "gray ball" shown in the picture is not really a physical entity in itself. It has to do more with the classical view that we have of subatomic particles as being a solid object, when in fact they are not. It's a representation of the average radius of the particle.
When you perform an experiment to detect the proton, you have a certain probability to find it inside the gray area, but also a small one of finding it outside. So a better way to show it would be to represent the ball with a lighter shade of gray as you are moving away from the centre of the particle. This would give a better notion of the fact that the particle is not a solid with defined edges. As you move away from the expected position (the centre of the gray zone), it is less and less probable to detect the proton.
Answer: The point is, that is not a picture of a proton; it's a schematic representation.  You can see it as a Euler diagram that says that in the proton you have 3 valence quarks and some gluons.
By the way the exact constituents of a proton is still an open question.

What's inside a proton?


how do i publish a chart built in bis to another sharepoint site

Question: I have been playing around with creating dashboards and charts using Performance Point services in the Dashboard Designer. I got the documentation on how to create them and built a couple in my BI SharePoint site. Now I would like to know what are my next steps to display one of my charts or dashboards in one of my other non-business intelligence centre SharePoint sites.
Answer: Use Chart WebPart and configure it's data source as explained in this MSDN article.
Create a chart by using the Chart Web Part
e.g. You can connect this webpart to a Business Data Catalog

What kinds of data sources can be used with the Chart Web Part?
A
  Chart Web Part can use one of the following data sources:
Another Web Part. You can connect the Chart Web Part to another Web
  Part that is capable of sending data. Examples of such Web Parts
  include a Document Library or a Contacts list.
A SharePoint List. You
  can connect the Chart Web Part to a SharePoint list that is located in
  the same site collection.
A Business Connectivity Services component.
  You can connect the Chart Web Part to a BCS component to display
  external or line of business data.
An Excel Services file. You can
  connect the Chart Web Part to an Excel workbook that has been
  published to Excel Services.
Comment: Unfortunately I'm using SharePoint 2013 and the Chart web part is not available anymore. I have created my charts in Dashboard designer under PerformancePoint
Comment: @PieterDuToit check if this helps you http://office.microsoft.com/en-gb/performancepoint-server/link-a-scorecard-kpi-to-an-analytic-chart-or-grid-using-dashboard-designer-HA010252493.aspx


Moderators why is this question acceptable but this one gets the "not a real question" moniker?

Question: Why is it that Can there be too much uniformity in coding standards? gets challenged by a mod as "not a real question" but yet this Easter eggs, good or bad? is just fine and is determined a "real question".  I'm really getting confused as the point of this site.
Comment: @Josh K thanks for improving my links I should have been more complete.
Comment: No problem.
Comment: You'll want to look at this question that I posted as well: http://meta.programmers.stackexchange.com/questions/877/do-we-need-a-definition-and-policy-on-what-would-be-considered-overly-broad-que. I think some of the closing guidelines are just too blunt of an instrument and left open to interpretation if not open to abuse by those who are zealous about questions meeting varied criteria.
Comment: And then there is this one: http://meta.programmers.stackexchange.com/questions/1050/voting-to-close-vs-flagging. It just seems to me the fundamental issue of what is an acceptable question here ought to be revisited.
Answer: Part of the reason will be that the different moderators will have different interpretations of the guidelines. We're not identical so this is inevitable. Personally I think your question is OK - but perhaps you should have brought out the style over substance aspect a little more clearly - and with the accepted answer it has I think it is a useful question.
Try not to take the criticism personally (I know it's hard). As to what you can do, well you've brought this to our attention so we can have a discussion and hopefully reach a better consensus of what's OK and what's not OK.
The other thing you can do is to look at your question as though it were written by someone else. Does it give enough information? Is the intention clear? The question isn't just for you - if it's a good question it needs to be beneficial to the wider community.
Comment: I don't take it personally.  I don't mind criticism in the least.  What I find frustrating is the aggressive closing of questions.  There is very little consistency.  If a moderator thinks a questions is borderline how about letting it go and see what the community thinks.  Go close the questions that clearly don't meet the requirements  instead of the borderline cases.
Comment: I would understand that completely however as I pointed out in the comments of my question there was only one other question on the front page with more votes.  At the time my question had 5.  That was the point I was trying to make exactly, that others felt differently than the moderator.
Comment: +1, also there is a reasonable chance that all moderators won't be looking at all the same questions.
Comment: @Gratzy - not an excuse, but an explanation (of sorts) - with questions moving off the home page relatively quickly there aren't enough non moderator eyes on the questions with a few votes so the mods have to step in. There are only 5 other 10K+ users who have access to the "tools" to see the lists of questions pending closure. As more people hit 10K there'll be less need for the mods to step in. On a personal note I try to leave a comment on dubious questions to start the ball rolling and only come back and cast my vote after it has 2 or 3 non-mod votes.
Answer: That's fine -- this is the very purpose of meta, so we can have these discussions in a constructive way and learn how to make these decisions better in the future.
In these specific cases, I support both questions with the edits they had to make them more constructive.
So the guidance is

yes, ask on meta! That's great! I mentally add 5 airquote upvotes to any person smart enough to come to meta and make a reasonable, non-argumentative statement in support of their questions!
always be open to editing questions to make them more clear and more constructive
Answer: One thing that is important to remember is that it's been well agreed upon by moderators and the site owners that upvotes are not an indicator that a question should remain open.
However, I don't think this is very well communicated to users who haven't being reading meta or the comments of many closed questions.
To those users, it's natural to think that upvotes indicate a good question.  What it indicates is that it's a popular question.  If you read http://meta.stackoverflow.com and http://blog.stackoverflow.com, you'll realize this has been addressed many times - even popular questions can have a long term negative effect on keeping the site in line with it's purpose.
There are a number of topics that would likely receive a high net score, but yet be closed as not aligned with the site's purpose.  Just search through the questions sorted by votes and you'll find several, including two of the first four.
That being said, I didn't see anything wrong with your question, and I felt like the upvotes were also well deserved.  As others have pointed out, sometimes the wording of a question can simply feel like a "discussion topic" to a moderator rather than an answerable question, but I didn't see yours that way (which is why I answered it!)
Comment: I don't quite agree with "upvotes are not an indicator that a question should remain open". I don't mean popular=good, I mean that popular questions should be harder to close. You point to meta and to blog. Meta is a whole site, so the premise "if you read it" is always false. On blog I see nothing about closing questions. So I'm missing your argument "why".
Comment: "upvotes are not an indicator that a question should remain open." I'm sorry, but then what is the point of upvoting a question if the moderators can simply take it down if they don't agree with the community? I've upvoted questions that have not met all (or any) of the requirements of a good question, but have yielded good answers regardless. It seems to me the merit of a question needs to take into consideration the answers it yields as well, if it gets that far. I appreciate that most mods are offering chances to edit questions to raise the quality, but upvotes really ought to be respected.
Comment: We should rename the badges then
Comment: @maaartinus if you are going to take my points so literally then I can't help you.  I mean that by browsing meta and SO blog then you see comments about this problem being addressed.  I don't have links simply because it's so large, but it's been said - many times.  My point is that it *should* be addressed in a place where more users, and especially new users, learn this concept.


Strong companions in Skyrim

Question: I've had a few companions who have died.
What are the best companions from a health perspective? And from a damage perspective?
Comment: The dog companion, "Barbas" from Clavicus Vile's quest, is badass. He took out several enemies that would have been quite a challenge for me to kill. My only previous companion, my Housekarl, died during the first battle we fought.
Answer: As explained here, companians usually don't die.
Additionally, it seems that every companions does have the same stats. They also can use very different weapons and armory, you just have to give them a better weapon and they'll use it.
Answer: I have tried a few of them, and I really don't see the big difference - they might as well be the same.
A good tip would be too take all their stuff. Replace it with a bow and some better armor, this will make them not run in to the battle and get hit by accident when in 'wounded' mode. Then they will die very rarely, but they will not make a good Tank this way.
It is quite useful if you use spells or a bow yourself.
Comment: I'm marking your answer as correct because the advice sounds best... a bow - smart
Comment: I would also recommend carrying around a healing spell to heal them, this is also a good way of raising your restoration skill. I would also focus on a warrior companion that can wear heavy armor.
Answer: Marcurio is amazing, I have played with him over 24 hours and hasn't died yet, I could even lay down and let him kill dragons.

Marcurio is a male Imperial that lives in Riften. He can be found in
  the Bee and Barb and can be hired as a companion for 500 .
He is a great follower using mainly destruction spells and can kill
  most things with ease. However beware having him near friendly NPC's
  because he mainly uses chainlighting and this has been known to jump
  to them and cause a fight/bounty.

Source:
http://elderscrolls.wikia.com/wiki/Marcurio
Answer: Barbas cannot die and tanks like a boss.  Once you get the quest to retrieve an axe for his master, use him as your companion and never complete the quest.
Comment: Barbas is the MOST annoying companion - He's always walking into me. I found myself walking up to a cliff and Barbas pushed me! I couldn't wait to finish that quest and kill him.
Answer: The best companions to have are the members of the Companions.
The reason is that all regular companions in the game are at least 6 levels under your own level, but not the Companions. You can get them to follow you if you are their leader, after destroying Kordlaks beast spirit.
And remember, the Companions are not only good followers, they are also trainers.

Farkas is the companion with the most dmg in the game, if you get him the right weapon. Trains for heavy armor.
Aela is a ranged who wont stand in you way all the time and can sneak very well. Trains for Archery.
Vilkas also has great damage, but is not as tanky as Farkas is. Trains for Two-Handed weapons.
Answer: Complete all the Dark Brotherhood quests and get Cicero. When you get a choice to kill him or keep alive, keep him alive for a companion. He's a super strong assassin.
Answer: To find the right companions use your judgement. If you want a tanky companion look for a beefy guy with a shield and an axe. Want a mage? Look for a scrawny guy in a robe. There is a companion in every main city (they are mercenaries and cost 500g). Try looking in the Inns for these companions.
Another thing to note is that their base equipment is pretty bad, so if you can afford it or make it give them some upgrades. They will use the best base damage/ armor in their inventories, so make sure that the weapon/ armor you want them to use is the best one they have.
Answer: I went with Mjoll the Lioness, as she's a quest NPC she can't actually die. She just goes into a downed state and then gets back up after the right. Pretty much making her invincible, which is a shame really as sometimes it'd be nice if she shutup.
Comment: Can't she be dismissed like others?
Answer: As far as I'm concerned, at some point out in front of Windhelm some of the cat traders should be camping out. I believe one gives you a side quest where you must retrieve his "Moon Amulet" from some bandits. I believe the quest givers name is Kharjo. He becomes available as a follower shortly afterwards and has a tendency to kill everything that comes your way. I stood and watched as he slayed and elder dragon in front of my face, all ebony gear.
Answer: From what I remember companions' stats are based on your level when you acquire them.
That's why Lydia is often considered the weakest; because she is usually acquired very early game when you are low level. I never had that problem with her, because I wait until I am much higher level before getting her and then she can tank alongside me against almost any foe.
It does help to give them buffed (enchanted) armor, of course!
Answer: The main determinant of a companion's power level is their actual level.
Before patch 1.6, followers would get a level when they first spawned, based on the Dragonborn's level, and then stay there. This meant that the later you met a follower, the stronger they were.
This was fixed, and they now level with the Dragonborn, up to a cap. This cap varies depending on the companion. The Elder Scrolls Wiki section on Followers' Leveling says that:

Followers will match the current level of one's character, up to a certain level cap that varies from follower to follower. The vast majority of followers cap at level thirty. Roggi Knot-Beard and Sven notably cap at level twenty.
All recruitable members of The Companions who are not part of the Circle, as well as Adelaisa Vendicci, cap at level twenty-five. Mjoll the Lioness, Illia, and all hireable Mercenaries (including Erik the Slayer) cap at level forty. Also, in the Dawnguard add-on, Beleval and Agmaer cap at twenty-five.
Erandur, the members of the Circle (Aela, Farkas, and Vilkas), and all Housecarls cap at level 50. In Dawnguard, Serana caps at level 50.

However, there are some companions who don't have a cap. If you are a higher-level dragonborn, then clearly these are the strongest followers:

The followers who, before patch 1.9, would level with the Dragonborn to 81, after the patch have no level cap and will continue to level with the player. They include J'zargo and the Dark Brotherhood Initiate, and with Dawnguard and Dragonborn, the followers Celann, Ingjard, and Durak, along with Frea, are added, respectively, with no level cap.
Answer: Shadowmere is the best companion in Skyrim, you can either mount it or let it tank for you.

Strong companions in Skyrim