How long would it take to raise a Wyvern?

Question: In the monster manual, it states that if you get it as a hatchling, you can raise a wyvern much easier but how long would that take? It doesn't state how old they can live and how long it takes an egg to hatch, so is there any obscure rule or something on the age of Wyverns? It seems like a pretty big oversight to mention you should get hatchlings but not mention how long it takes for them to mature. I'm not really using it, but I was just wondering if there was something somewhere on this topic.
Answer: This is one of those things on which D&D bows to the DM's authority over their world. D&D has provided the creature, but not all the details of its life cycle, ecology, mating habits, regional variations, history, origin, etc. ad nauseum. Different editions have given more or less detail on these aspects of creatures, and this is the level of detail 5e has settled on.
So, in a phrase, "ask your DM," since it will vary according to what the DM wants for their setting. In one setting wyverns might be like reptilian mayflies who live only a year and die every winter, while in another setting they can live thousands of years, and in a third setting they have a lifespan similar to cats, etc.
Answer: First, a Wyvern has dragonsblood but are not what the MM deems a true dragon.  Be that as it may, it seems true dragons live to 800 years old or more.  Let's say we cut that in half for a Wyvern and make it 400 (Speculation).  Now you have a measurement of time.

Wyrmling: 5 years old or less
Young: 6 - 100 years
Adult: 101-800 Years
Ancient: 801 +

Second, as to the finding of an egg, hatching and raising of a hatchling Wyvern, and then taming it.  The MM says it is a Difficult and Deadly Challenge (Which actually gives you challenge/Difficulty ratings for attempting to do exactly that using dice roll...which you would use multiple dice roll over the course of weeks/months to maintain a success rate.)
PHB pg 187:

Downtime Activies: : "...Between adventures, the DM might ask you what your character is doing during his/her downtime.  Periods vary in duration, but each downtime activity requires a certain number of days to complete before you gain any benefit, and at least 8 hours of each day must be spent on the chosen activity.  The days do not need to be consecutive..."

It goes on to say that if there is something you'd like your character to be doing (Such as raising a Wyvern egg.) you may discuss it with your DM.  He or She will tell you what an appropriate amount of time to be spending doing said activity would be.  These lengths of time are extensive however.  Training in the use of a set of tools takes 250 days.  Smithing a suit of armor is 5GP per day of smithing towards the market price of any craftable metallic object.  (A 1,500 suit of plate armor would take 300 days: 1500 / 5 = 300) .  Hatching a Wyvern egg and the subsequent training/raising of the baby Wyvern into a creature of a proper companion size would take equal time.
The above is, of course, my interpretation and decision on how I would run that sort of downtime activity.  I would say to expect to spend a lot of time caring for a Wyvern egg and probably a year (365 days) raising it into a creature that can begin to learn orders and commands and not just want to eat meat and sleep....
Comment: Like most of the non quoted parts of my post, that's a matter of both interpretation and speculation.  If you are the DM, YOU tell ME how long it takes for a dragon to mature.  If you are not the DM, then ask him to tell you how long he feels is a reasonable amount of time.  I can't find any quotes that say how long that takes.  One can only speculate.  I'll edit relative information into my above post though that may help such speculation.
Comment: How long until a dragon is considered "mature"? Basically, when can they fly and support riders?
Answer: Most animals in the wild grow the most in their youth. It's a survival trait of almost all life to grow as fast as you can to 1) survive and 2) produce offspring.
Those two things (survive and make more) are the prime directives of all life.
Using the dragon table kindly provided in another answer and understanding that a wyvern is not really a true dragon but a smaller cousin and combining that with an extrapolation of riding animals in general (horses, camels, oxen, elephants, etc). Where they can be trained and ridden as young as 1 to 2 years old. It would be easy to speculate that a wyvern could also be trained and ridden while young. Therefore I place the age of rideable size at 2 1/2 to 5 years years based on the dragon age table saying young age begins at 5 and that wyvern a are smaller cousins of dragons and that smaller varieties of life forms mature and age faster than larger varieties.
Comment: Where does it says that the life span of a wyvern is half of a dragon's?
Comment: I took that directly from Airatome's answer, now of course looking back I see he just speculated that. However it still changes not so much, the extrapolation still rings true, we could just say 5 years then, which I will change in my answer.
Answer: Let us confirm at least a few separate assumed truths in a fantasy setting.
a) Wyverns are beasts, but aren't magical beasts.
b) Wyverns are reptiles, but what type of reptiles is the question.
1)Extant archosaurs (we'll assume Wyverns are) are  in the real world, and phylo-genetically they are the descendants of dinosaurs which are represented by birds and crocodilians.
c) Accepting above , we must make th decision if wyverns are more like crocodilians for their maturation rates, or more like that of birds.
1) Either way, the larger a verterbrate organisms adult size is, the longer their maturation rate.
d) If we assume that wyverns are more avian than croc, then their maturation rate would increase quite a bit.
1) The maturation rate of the largest crocodilians is years. In fact longer than humans. Even with an optimal environment with limitless caloric intake.
<code>2) Wild ostriches have a maturation rate close to one year, whereas domestic ostriches are closer to half a year.
</code>
e) Taking all this into account, one might assume that wild wyverns are more likely to mature at the rate of an enormous bird, but perhaps we should multiply that growth for size, and perhaps slow it down a bit towards the crocodilian side of things.
Given all of the above we can say that wyvern eggs probably hatch, under optimal conditions, quite quickly. As do both reptile and bird eggs. Lets say two months at most.
Given a wild environment, a wyvern likely won't start flying on its own for about a year. AT which time they  might start bravely leaving the nest, and becoming independent by year two..at which point they aren't fully grown, and are basically subadults, but like crocodilians, are capable of surviving on their own.
Now, lets assume that their's a market for domesticated wyverns. Entrepreneurial thieves that have made a living stealing wyvern eggs until they could find a tameable mating pair.
So , a wyvern probably could be a rideable mount for a human until it's around at least 7 years old. Unless it was a domesticated wyvern, which might be 5ish.
Needless to say. You're better off spening the 50000 gps to buy an adult that's been trained already.
Comment: This is speculation without any basis in the game's mechanics.
Comment: Everything is speculation and subjective.  We'e talking fantasy RPG here. How have RPG's evolved? Certainly not by strictly adhering to game mechanics.
Comment: Unfortunately, this stack exchange is pretty much all about rules and the interpretation thereof.


Difference between "on the fringe" and "on the fringes"

Question: The Longman Dictionary seems to suggest that on the fringes can be used either literally or figuratively, while on the fringe refers to something actually physically away from the center.

on the fringes (of something)
a) not completely belonging to or accepted by a group of people who share the same job, activities etc
a small group on the fringes of the art world
b) (also on the fringe) at the part of something that is farthest from the centre SYN on the edge of something
Nina remained on the fringe of the crowd.

The Free Dictionary, on the other hand, seems to only have an entry for on the fringe and defines it both in literal and figurative usages.

on the fringe

Lit. at the outer boundary or edge of something. He doesn't live in the city, just on the fringe.
Fig. at the extremes of something, typically political thought. He is way out. His political ideas are really on the fringe.

Any differences? Or is it something that has not reached an orthographic consensus?
Answer: They are almost the same but on the fringes only makes sense used figuratively.  While on the fringe makes sense both literally and figuratively.
From your example, one could physically be on the fringe of a crowd, or they could be socially on the fringe of a crowd (just barely a part of that group of people).  But to say one was on the fringes of a crowd could only mean the latter.


Does using an app send my IP address and device identification info to the app maker?

Question: if I use an app, would I be giving info like my IP address and device identification like the MAC address to the app developer/owner?
Comment: It certainly could be the case. It depends on the app and if they collect such information. Your IP is public, so unless you use a Proxy server anyone can see it.
Comment: Are You asking about iOS or OS X?
Comment: It indeed entirely depends on the app developer. Apple automatically sends reports to help with bug fixes. Also, when apps crash, you have a choice to send report to apple.
Comment: Also indicate which version of OS you are asking about. For example, early versions of iOS did allow access to MAC address, but the more recent versions including iOS 8 do not. IP address is always potentially available to any OS X or iOS app - most apps do use the internet and as a natural consequence of that communication, your IP address is known at the remote server.
Answer: This completely depends on the app. There's nothing that by default sends identifying in formation about your system to the App developers, the App would have to have been written in order to have this behavior. Depending on the app, however, it's possible that some might.
You didn't mention if you're on iOS or Mac OS. If you're on Mac OS, and you're concerned, or curious, you should consider installing an outgoing firewall like Little Snitch. What this will do is show an alert message asking for permission every time any app tries to send data to the Internet. You can use the Little Snitch network monitor to identify what data is being sent, to determine if your privacy is being violated. You can also prevent the app from sending data at all.
If you wanted to do the same for iOS you could use software on your router, but this is an advanced topic and beyond the scope of this answer.


Encrypting table in SQL Server

Question: I'm a .NET guy that is trying to start using table encryption on some of my Users tables but I could do with some questions being answered first. I don't want just anyone to be able to see these tables.
When should you start encrypting your tables in SQL server, should I encrypt all tables?
How to avoid going to far?
The steps required to encrypt a table?
Answer: Encryption is a huge topic. There are lots of caveats, and most of those are about business requirements, not about technology.
Start by taking a step back and look at the big picture. Pop the why? stack until the business requirements are clear. Then start formulating requirements about what data needs to be protected and what kind of attacks are expected. Only after then start exploring what encryption would be suitable and what wouldn't.
Who or what would attack the database? Rogue admin? Oops, data-at-rest encryption doesn't help much. Network sniffer? Hope you are using TLS between application and SQL Server. SQL injection? Something else?
What would happen in case of data breach? Vandalism? Lawsuits? Loss of reputation? Heist of Bitcoins? Authoritarian government hangs dissidents?
Some domains, like health care and banking, often have strict laws about data protection. US, EU and rest of the world have their own quirks.
As practical issues, key management is among the most complex one. Do you have a key management process? Without one, managing certificates and encryption keys is going to be painful. Restoring old backups and server migrations are suddenly extra complex, as backup itself isn't enough.
If working on Enterprise Edition or Developer Edition, TDE is relatively simple to set up.
Column encryption is suitable for hiding a subset of data. An example about securing national id numbers.
Always Encrypted moves the crypto to application layer. Good solution for some cases, abysmal for the rest.
Dynamic data masking isn't actually encryption, but suitable for many cases in which confidential data must be partly exposed.

Encrypting table in SQL Server


How do I restore a SQL Server backup to a different server that will synchronize the users correctly?

Question: The issue I am having is I have 2 servers A and B.  On A I have a dB, say it's called "MyDB"...  On server B there are 2 dBs called "MyDB_Dev" and "MyDB_Test".  These all were set up upon my arrival to the client. On server A and B there are Users, Rolls and schemas set up using the same name (e.g., User1, User2, User3, etc.) The issue is that the client wants to stand up a new dB on server B called "MyDB_Stage". What I did was run a backup of the production db and then restored it to server B. The issue is that the user rights will not allow them to log into the staging dB using their user id. What I don't understand is if I open the server user login list the login is not associated to the staging dB - seems fine because I should be able to simply add a check to the new dB, however, when I try it tells me the dB already is assigned that user. I then tried to delete the user from the dB but I get an error that the schema is being used by another login.  For this system there are a lot of users, rolls, and schemas and I would hate to have to remove everything and have to put them back.  Any advice?
Comment: Duplicate: [How do I create logins for all database users in a database that was just restored for a different server?](https://dba.stackexchange.com/questions/16730/how-do-i-create-logins-for-all-database-users-in-a-database-that-was-just-restor)
Answer: When you create users on server A and B manually, they will have another SID (Security Identifier). In this case, I think it would be better to copy the users from server A to server B, with keeping the original SID in place. In the user database, the SID is used.
To copy the users you can make use of the sp_help_revlogin stored procedure. See link.
https://learn.microsoft.com/en-us/troubleshoot/sql/database-engine/security/transfer-logins-passwords-between-instances
Comment: Also see this for fixing orphaned users: https://learn.microsoft.com/en-us/sql/sql-server/failover-clusters/troubleshoot-orphaned-users-sql-server?view=sql-server-ver16


How to Open Windows Painted Shut

Question: We just bought a house and it turns out one of the windows seems to be painted shut. It's a reasonably recent double paned wooden double hung window (say around 15 years old). The house was painted for the showing and while most of it is surprisingly good the painters got a little sloppy on this one. Could someone recommend how to get it unstuck.
Comment: Check all your electric receptacles, light switches, etc. - very often painted over instead of removing the cover plates for painting.
Answer: I don't think I'd use a knife. It's very easy for the blade tip to grab the wood grain and climb out of the groove. Now you have a slice where you don't want a slice.
I don't think I'd use an oscillating tool. It seems much too coarse for this job. You'll end up with a fairly ratty edge on both the sash and the jamb or sill, especially if clearances were tight to begin with or you don't have the blade at the right angle with respect to the joint.
I do think I'd take a putty knife and a hammer and gently tap the knife into the crease, just through the paint thickness, working along the entire width. Keep the knife flat against the sash to prevent damage. The reason this works well is because it cuts and wedges at the same time, resulting in minimal damage before the paint pops loose.
I'd then use a foam sanding block or similar to ease the edge that remains on the sash and the jamb and/or sill.
Comment: Actually this answer is better than mine.  I suggested a putty knife "after" a utility knife.  I've removed that part.   If you angle the putty knife well, as this answer suggests the sash frame will guide it nicely where you want it to go.  If you additionally angle it slightly upwards or downwards, so that it's only cutting in one place and not across the entire width of the blade, it should cut through easily with light hammering and you don't need to start with a sharp knife.  This is MUCH safer for the wood and for you.
Answer: Yes, I have always had success by running a sharp knife - stanley or box cutter around the joints that have been sealed by paint.
Warning make sure your fingers are clear and go slow - slipping can leave lots of damage.
Answer: Another tip:
[edit: removed suggestion to use putty knife after box knife.  Putty knife alone is better]
If the window doesn't have a handle, don't use the top rail to push violently upward.  You can cause damage to the window by pulling up too hard on the middle of the top rail.   Instead, screw a couple of metal handles diagonally across the bottom of the sash, with screws in both the vertical and bottom rail on both sides.  Use the handles to manipulate the window until it moves freely.
Answer:
Score as deeply as you can with a utility knife.   The problem is here, they are not flat.   Your standard box cutters will nut cut a straight parallel line because of their housing.    So don't go to deep or the angle may cut into some of the wood.

There are many things you can use but I often use a reciprocating saw blade - just the blade.   These are usually thin enough to get into the crack your created when you scored.  I have seen guys use drywall knife and other types of knives (long steak knives - you use what you have).
Answer: I've had luck with a "multi-tool" like this Dremel. Just run the blade carefully along the painted over bits between the window and the jamb.  Some sanding and touch up may be required.  It's a pretty safe tool to use. Like Solar Mike said, slipping with a knife could cause an injury which could cost way more than a Dremel tool!
Comment: I would have thought this tool can do a lot of undesired damage.  But come to think of it, I've done a lot of undesired damage with a utility knife freeing painted-up windows. So I'm intrigued ... I might give this a go!!

How to Open Windows Painted Shut


C# listview paging question

Question: In Listview, if I want to use the paging feature, how can i increase the amount of rows shown for each page? I would like to increase the current rows form say 10 to 35.
Comment: perhaps the other answers will help you out http://stackoverflow.com/questions/597384/paging-in-asp-net-listview-control
Comment: paging feature? Are you taking about using a `DataPager` in ASP.Net?
Comment: In listview there is not such a property with which you set the Page Size. Page Size property is available in GridView. For ListView you can use the DataPager Control with the ListView.
Answer: Use the PageSize property as in:
<asp:GridView runat="server" AllowPaging="True" PageSize="25">

EDIT
I just saw that you're talking about ListView. In that case, here is an article that describes paging for ListViews.
Basically you add a DataPager, which again has a PageSize property. It is well described in the linked article.
Comment: He asked for listview not grid view.
Answer: if you are talking about ASP.net you could use a DataPager control that allows you to set up all the common Paging properties(PageSize,etc)
http://thibautvs.com/blog/?p=718
https://web.archive.org/web/20210125144848/http://www.4guysfromrolla.com/articles/021308-1.aspx

C# listview paging question


How do I tell sIFR 3 to use different fonts for bold, italic, etc?

Question: I've done some research, and it seems that if you're using a different font for the bold and italic variants of your sIFR font (as opposed to letting Flash fake it with the B and I buttons) then you have to include the fonts in your SWF, and then write code like this:
sIFR.replace(sentinel, {
  selector: '.intro p',
  css: [
    '.sIFR-root { font-family: "Sentinel-Medium"; }',
    'strong { font-family: "Sentinel-Bold"; }',
    'em { font-family: Sentinel-MediumItalic; }',
    'a { color: #0000ff; }',
    'a:hover { color: #ff0000; }'
  ]
});
When I do that, the flash movie comes up empty. I'm guessing this is just a syntax problem with my code. Any suggestions?
Update: I managed to get this mostly working (demo page) using the following code, but I can't get the nested styles to work properly. For example, I turned em text red and strong text blue -- but then if I try to set em text inside a strong to purple, it changes ALL ems to purple.
sIFR.replace(sentinel, {
  selector: '.sifr-test',
  css: [
    '.sIFR-root { font-family: "Sentinel Medium"; }',
    'strong { font-family: "Sentinel Bold"; font-weight: normal; color: #6666ff; }',
    'em { font-family: Sentinel Medium Italic; font-style: normal; color: #ff6666; }',
    'strong em { font-family: Sentinel Semibold Italic; font-weight: normal; font-style: normal; color: #ff66ff; }',
    'a { color: #0000ff; }',
    'a:hover { color: #ff0000; }'
  ]
});
Answer: Not sure if you can do that, the CSS support in Flash isn't very advanced.


Should the log-likelihood value be reported?

Question: Just a quick question.
I have used maximum likelihood estimation to find the best-fit parameters of a model. In doing so I get a log likelihood value, which obviously is the highest log likelihood value of all parameter sets. However, when reporting these parameters in a paper, should the log likelihood value of that set be reported as well, or does that not have any significant value on its own?
Comment: If you do report it, it's essential you provide a formula, because many algorithms and software packages do not actually compute the log likelihood: they compute a value that will differ from the true log likelihood by some (uncomputed) constant.
Answer: Many papers report the output chart of the optimization, especially those using Matlab or other softwares that have a standard output table when the optimization is completed.. So if you have time you could replicate one of those with all the info reported. However, the value of the loglik does not say much if taken alone in the context of a MLE: it becomes relevant instead when you want to compare multiple models. So it depends on what your final purpose is: if you just wish to draw a MLE estimate, then the value of the function at the optimum does not say much and, for brevity, you can skip it with no theoretical damage to the paper. On the contrary, if  you have a model comparison of any kind (AIC, BIC, LR tests,...), it is recommendable to report it because it will be used within the comparison for the calculation of the above mentioned statistics (AIC, BIC,...). Also in that case however you can just report the different AICs/BICs derivated from the loglik
Comment: It is also adequate to report a pseudo $R^2$ that is derived simply from the model likelihood ratio $\chi^2$ statistic (and for some indexes the maximum attainable log likelihood).
Comment: Thanks for the answer, this is not a model comparison, but parameter estimations of different models, so I don't think the AIC/BIC is necessary.
@FrankHarrell would that count as the goodness of fit for this model, or am I missing something?
Comment: @DenverDang ok in that case
Comment: None of this has directly to do with goodness of fit.  For that I'd do directed assessments, e.g., related to linearity and additivity.


Story Identification: Fantasy, magic system involves holding contradictory thoughts

Question: I have vague recollections of a fantasy novel (or series) where the training for the magic system requires holding as many contradictory thoughts as possible at once. If I remember correctly, this correlates to how many magic spells the protagonist can cast at once.
Comment: Could it be Patrick Rothfuss, [The Kingkiller Chronicle](http://en.wikipedia.org/wiki/The_Kingkiller_Chronicle)? IIRC, this was one of Kvothe's early training exercises while he was still with the troupe of Edema Ruh.
Comment: @NiallC. I definitely read them, and the system of magic looks right. Feel free to add an answer and unless something else comes up that fits my memory better I'll accept it shortly.
Answer: This sounds like the 'Sympathy' magic system which exists in Patrick Rothfuss' The Kingkiller Chronicle, which involves Alar, described here as

to believe something so strongly as to give it the force of reality.

Once Kvothe had mastered believing one thing enough to perform Sympathy with it, one of his training exercises was to believe two or more things, again with the goal of being able to perform Sympathy.
Comment: I'll search for and add some corroborating quotations from the books later. I have the dead tree editions though, so it might take me a little while.
Comment: The opening bit where Abenthy trains him in this technique is good.  "I want you to believe that the rock will fall up."  It bent my brain just listening to it.
Comment: He teaches him to keep believing the rock won't fall when he lets it go.  When he finally manages to keep believing it even though he just watched the rock fall, the teacher smirks at him at says "Now, I want you to believe both that the rock *will* and *will not* fall"...  I stared at that line for a few minutes before I found my jaw and moved on :D


Number of distinct surjective functions

Question: Consider two sets A and B each with "n" elements. How many distinct surjective (onto) functions from A to B are possible?
Comment: Isn't it $n!$, the number of all permutations of the set $\{1,2,\dots,n\}$? You need to cover every element of $B$ (there are $n$ of them), plus since $A$ has $n$ elements, only such functions are permutations.
Answer: Note that a surjective function from $A$ to $B$, both having the same cardinality is an injection. (Hence, a bijection).
The first element of $A$ has $n$ options for B.
The second element of $A$ has $n-1$ options, avoiding the selected element, otherwise, it will not be a surjection.
The $i$-th element has $n-(i-1)$ options.
Multiplying them up, we have $n!$ such choices.
Alternatively,
you can also go through the first element of $B$ and let it choose its preimage. It has $n$ options.
Now choose the preimage for the second element of $B$, it can't choose the same element as the first as that would violate the definition of a function.
Repeat the argument and you will get $n!$.
Comment: This relies on the alluded-to fact that injection = surjection for finite sets of the same cardinality; it might be good to state that explicitly.
Comment: I agree, thanks for the feedback.

Number of distinct surjective functions


Left out of team Lunch; how to handle this professionally?

Question: My boss, for whom I have worked for a long time, invited all managers to lunch for their Christmas present at her expense (she says it is a work development tool) but tells me the email invite I got was sent as a mistake, I feel hurt by this but am to humiliated to say anything. I feel ashamed to be so petty but it really hurts.
Comment: Hello rick, so what is your question? Are you also a manager?
Comment: Are you a manager?
Comment: And, are you still celebrating Christmas?
Answer: You may not be being petty
Are you a manager? If you are, you have a problem. You did not say whether or not you were a manager, but if you are and you were not invited to this, then you are clearly not one of the team members designated to be professionally developed. You should be examining your career options as you are evidently not one of the valued ones.
If you are in a different job/at a lower rank, then you should never have gotten an invite and yes, you are being petty.
Comment: Good answer. If OP is not manager then this is not a hill to die on... now if OP is a manager... things are different like you said.
Answer:
I feel ashamed to be so petty but it really hurts.

I am sorry you feel this way. I understand that receiving an invitation and then it being withdrawn can feel uncomfortable.
Now, the professional course of action I suggest is that you let it go, and move on.
Your boss already excused herself and said it was a mistake; that should be sufficient excuse for an email mixup.
Try not to take it personally. The lunch would probably have taken place even if you didn't received the invitation, so no need to over-analyze the situation.
Not being invited to a single lunch is no reason for you to scratch the trust and relationship you have with your boss.
Answer: If there's a pattern with the other people invited - they're managers (and you're not), they're department heads (and you're not), they're from specific parts of the organisation (and you're not) - there's no need to feel hurt by this.
You could even reframe it. Your boss made a list of the people she wanted to invite - people she regarded as important - and automatically or subconsciously included you. That she reconsidered later could be a lot less significant than your original inclusion.


Transistor simulation not working properly in Proteus

Question: I'm recently working with Proteus. So I created a simple schematic for a transistor to work as a switch. But when I simulate it, it doesn't work as it should. In the picture below you can see that the resistor is not receiving current at the base, however the led is lighted up as if it were. I've even tried to remove everything from the base of the transistor and even then somehow the led still lights up. So I suppose it's a problem with the software. But maybe there's a setting missconfigured that I don't know of. Have anyone had this problem or any idea on what could be a solution? Thanks.
PD. I've already tried to reinstall the software and it didn't work.
Comment: Thanks. I tried that but that was not the problem. I fixed it changing the "model type" of the led from "digital" to "analog".
Comment: Try a pull down resistor on the base to ground.
Comment: A good news story.
Answer: I fixed it. First I switched the "model type" of the Led from "digital" to "analog". Then I changed the transistor to a 2N2222. And I also fixed a design problem by adding a resistor that goes from the base to ground, to avoid any charge in the environment from turning on the transistor.


How to post on the wall of a person who is not your friend facebook?

Question: My goal is to post on the wall of several persons (whether or not my friends) from my application in facebook (made in php) after an event has taken place by a button.
The "Facebook User ID" (FBUID) I get them and I have heard that I can post by the graph api if users gives me permission "publish_stream".
I tried to do with the graph api, using "feed" as follows:
<code>$ fbuid = array (0 => 'first_fbuid', 1 => 'second_fbuid', ......) / / These are ID's that are and are not my friends.

foreach ($ fbuid as fb) {
$ facebook-> api ("/ $ fb / feed ',' post ', array (
         'message' => some_message,
         'name' => 'My application name',
         'description' => 'description goes here',
         'picture' => $ imageurl));
}
</code>
But when I try to post to people who are NOT my friends gives me an error. Only does the posting on the wall of people who are my friends.
Is there a way to do otherwise by POST to those people? Or can not by restrictions on facebook? Is there another way?
Note: For comments on the website, it says that my own application without problems can post on the wall of people getting the access_token. Can you do that?

UPDATE: If the post to anyone is not possible, so.. Can I send a request to anyone? I think is posible because games like FarmVille do that.
The request can be automatically? Without dialog?
Or if posible to send a Notification to anyone user?.. In the api I see a function called send.Notification.
Comment: I'd imagine that restrictions by Facebook wouldn't make this possible...probably for a good reason, too.
Comment: Reason of Error could be the User Privacy Settings and Application Access you might wanna checkout that thing...!!
Comment: Uuhhmm,I think that games like farmville can do that. They can send notifications to anyone, friend or not.
Answer: Think of it this way.  The API reflects what a normal Facebook user can reasonably do within the terms of the site, and with respect to the other party's privacy wishes.  If you can't post on their wall without being their friend as a human being, why would Facebook want to allow someone to do that through an API?
I would say that this is impossible to do within the usage rules of the API.
Not to mention all of the drama Facebook has with privacy issues.
Answer: are you talking about posting on the user wall like this app for example? http://applionaire.me/supporters/
If that's the case, then you don't really need access token to do that.
You would need an access token if you wanted to post on the user wall whether they are logged in to facebook or not.


use of the definite article ' the'

Question: When we talk about a noun in general it is not preceded by the definite article "the". As-

Indian food is very delicious.

But in another sentence it is -

The food of India is very delicious.

Why has here the definite article "the" been used before the noun "food", while here also the noun "food" has been used in general.
Should this sentence be -

Food of India is very delicious.
Answer: Food is a poor choice of noun to use for your example, it has two very different meanings:
When you say "The food of India" you refer to the specific current cuisine (the method of cooking) of India. You can use a definite article.
However when you say "Indian food" you're qualifying food as a noun meaning actual meals that people eat. So you can say "The Indian food is delicious." but it would mean at a meal where there was Indian food and Japanese food, that you were referring to the specific Indian food at that meal.
Without the article, "Indian food is delicious", you're not referring to any particular meal, and you are making a general statement about food (all the meals) which is(are) Indian.
Comment: *The X* refers to an instance of X.  Plain *X* refers to a type of X.

use of the definite article ' the'


Hecke operators on modular forms

Question: Would you please explain the importance of Hecke operators on modular forms?  I am studying modular forms mostly on my own and I have a pretty good understanding up to Hecke operators.  So, I just wonder why we care about them.
Answer: This is a layman answer. Hecke operators commute and are self-adjoint, hence the modular forms which are eigenvectors wrt. all Hecke operators form a basis of the space of all modular forms (and the same for cusp forms). If $f$ is such an eigenvector then the L-series corresponding to $f$ has multiplicative coefficients, i.e. it can be represented by an Euler product (over all primes). So AFAIK, Hecke operators are important for connections of modular forms with number theory.
Comment: Can you repeat for a layman's layman?
Answer: Here are a couple of reasons:

Abstractly the space of modular forms (of a given weight and level) is just a vector space (finite dimensional). Hecke operators give you a very concrete set of (commuting) operators on this vector space and hence you can get some control on this spaces purely in terms of linear algebra.
The coefficients of cusp forms (a very important subset) of modular forms contain arithmetic information. Historically there were many remarkable conjectures about them. The introduction of Hecke operator demystifies them and many of these conjectures become simple.
one can study modular forms from the perspective of representation theory and geometry and in both these case Hecke operators arise as rather natural operations on this space. This suggests that Hecke operators are intimately connected to study of modular forms.
Answer: As a very specific example, we can use Hecke operators and the theory of modular forms to quickly get Jacobi's Four Squares Formula.
Comment: You'll need the [dimension formulas](http://www.paris8.free.fr/Fred%20Diamond%20Jerry%20Shurman%20A%20First%20Course%20in%20Modular%20Forms.pdf) (chapter 3), not so easy

Hecke operators on modular forms


Opening/moving focus to layout in ArcGIS Pro using ArcPy

Question: I have an ArcGIS Pro project which contains multiple layouts.  I've got a Python toolbox with a script which, among other things, chooses which of the layouts is appropriate for a specific map.  At the end of the script, I would like the selected layout to open (if it isn't already), and have ArcGIS Pro move the 'focus' to the chosen layout. (i.e. if the layout is open but in a tab which is not in the front, I would like it to move to the front. 'Focus' might not be the right word to describe this.)  I've looked through the ArcGIS Project object, and the layout object, without finding anything which will do this.
Answer: This is not possible with arcpy.mp. You will need to use the ArcGIS Pro SDK (.NET).
The snippets on this page should give you a starting point (relevant excerpts quoted below)
Activate an already open layout view
<code>//Activate an already open layout view.
//A layout view may be open but it may not be active.

//Find the pane that references the layout and activate it.
//Note - there can be multiple panes referencing the same layout.
foreach (var pane in ProApp.Panes)
{
  var layoutPane = pane as ILayoutPane;
  if (layoutPane == null)  //if not a layout view, continue to the next pane
    continue;
  if (layoutPane.LayoutView.Layout == layout) //if there is a match, activate the view
  {
    (layoutPane as Pane).Activate();
    return;
  }
}
</code>
Open a layout project item in a new view
<code>//Open a layout project item in a new view.
//A layout project item may exist but it may not be open in a view.

//Reference a layout project item by name
LayoutProjectItem someLytItem = Project.Current.GetItems<LayoutProjectItem>().FirstOrDefault(item => item.Name.Equals("MyLayout"));

//Get the layout associated with the layout project item
Layout layout = await QueuedTask.Run(() => someLytItem.GetLayout());  //Worker thread

//Create the new pane
ILayoutPane iNewLayoutPane = await ProApp.Panes.CreateLayoutPaneAsync(layout); //GUI thread
</code>
Since you already have your Python tool set up, you could just make a tool in .NET that calls this Python tool, and then when finished uses the .NET code to do what you need to the layouts.
Comment: Thank you; I feared this might be the case.


Does current have a physical effect on wire?

Question: Does current have an effect on the wire it moves through? I think I heard somewhere that over time small wires in CPUs can move because of the current going through them. If it is a thing what's the technical term for it?
Comment: Like melting..?
Comment: As far as I understand it... The power dissipated by the heat produced affects it but not in a permanent way unless you get very hot. The magnetic field it creates in the wire could cause motion of the wire. In a straight wire I'd expect that to be tiny/nothing against the stiffness of the wire. But both of these are secondary effects, not change because of the passage of electrons through the material.
Comment: Link to what you heard/read/imagined please. So go googling and find an article then, if the article isn't clear come back and ask a sensible question. If the answer is clear then job done, come back and delete your question.
Answer: Yes, at the nano-meter scale you always run into an issue titled Electromigration.
At the nano scale a conductor has to not only be rated for voltage drop but also for current density. To achieve sufficient reliability due to deterioration from electromigration.
Comment: Yes, I recall this phenomenon being described to me by an IC engineer at RCA in 1972.  The effect, within an IC, is something like the flow of water in a river causing an "oxbow" or "meander" -- the metal comprising a turn in the wiring would migrate to the outside of the turn, until either the wire got too thin to carry the current, or until it migrated into an adjacent wire.  Obviously, component failure was the result.  (No doubt the phenomenon had other effects as well.)
Answer: The vast majority of the time, the physical effect of a current through a wire is negligible.
High current densities can physically effect a wire in 4 very different ways:

The electromigration effect ( as mentioned by sstobbe ) is the gradual movement of ions along the length of a conductor due to the momentum transfer of electrons moving in a wire. At high current density, eventually enough ions of the metal wire get pushed out of where they were originally placed to leave a gap (an open circuit) in that wire, or build up enough displaced ions to bridge the gap between that wire and some adjacent wire (a short circuit). This can cause long-term reliability issues -- when people design things to run right on the edge or slightly past manufacturer's recommendations, this effect allows the device to seem to work fine for a while, but lead to early failure.
The resistive heating of wires, also known as Joule heating or "I squared R heating", is proportional to the square of the current through the wire. When an integrated circuit is stressed by voltages far beyond the manufacturer's recommendations, this effect often melts or vaporizes one or all of the small wires of the IC.
The magnetostriction effect causes some materials to change shape when magnetized. This effect is the most common cause of transformer hum. (The current through the coils of the transformer creates a strong magnetic field, which leads to magnetostriction in those wires or in the ferrite core or both).
In a strong magnetic field, the wire is physically shoved sideways by a force proportional to the current and to the magnetic field -- that force is sometimes called the Laplace force, but more often calculated as part of the Lorentz force (as alluded to by Uwe ). This effect also causes transformer hum.
Answer: If strong currents flow in two parallel conductors, the magnetic fields cause a force between the conductors, see https://en.wikipedia.org/wiki/Amp%C3%A8re%27s_force_law. But the currents flowing through small wires in a CPU are too small for movement.
Comment: _"But the currents flowing through small wires in a CPU are too small for movement."_ - Are they though? Modern CPUs can pull something like 75A. Now that current is not running through a single bond wire, but still, several hundred mA through a single bond wire wouldn't surprise me. And they're small so they need less force to move.
Comment: The bond wires are too short for a substantial force.


How to highlight a user in a table?

Question: I'm creating a data table and I would like to highlight the user, so they know it's them on the table when they view it. What would be the best way to do it? Adding '(you)' after the name, or just changing the color of the row is enough?
Comment: Welcome to UX StackExchange. Can you share screenshots of what you are attempting?
Comment: Hi, I have added a screenshot!
Comment: How does this table work? Do other rows get highlighted when the cursor hovers over it, or does it stay static? Can you place the user (you) at the top on default, or is the order important?
Answer: It depends but I would say that just highlighting the row often isn't enough because tables generally have a number of select and hover over states that will highlight rows or columns, and it would be easier to use other indicators.
Some common choices are to use text (as you have shown) or provide a specific icon or symbol. However, I suspect that from the example that you are showing, each row should have a unique key or combination of fields that can be used to identify people with the same name (e.g. user id, birthdate, address, etc.).
Answer: Like Michael said, it would depend on what other interaction states you have for the rows. For example, it might be confusing to highlight your row background in conjunction with a mouse hover state highlight.
The "you" solution might be enough if the table is short, allowing the user to scan and find the label. However, it can be problematic if your table has tens or hundreds of rows. It would be much more difficult to look for the "you" label.
Another solution could be bolding the name. It would make it noticeable enough while scanning, while not overriding hover states, etc. If your table is extensive, adding a shortcut button to jump to your row might also be useful. Similar to the "Today" button in calendars.
Additional thought with the "you": Would a user not know their name indicates themselves? Or are they given a name they are unfamiliar with? Or is it common to have repeated full names?
Answer: Changing colour to convey a state is not enough, you need to add words or an icon, or change some other form factor.
Adding "(You)" is a great way to achieve that, why not along with a highlight colour.
A considerable amount of humans (8 % of men, 0.5 % of women) have some form of color vision deficiency (CVD), aka color blindness. Add to this users with glaring screens that reflect light, or the sun shining on a display.
Therefore, the most basic level of the Web Accessibility Guidelines, which are the basis for many legal accessibility requirements, require the following:

Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

From Understanding Success Criterion 1.4.1:Use of Color (Level A)

How to highlight a user in a table?


Thermal expansion for two objects

Question: Among two bodies of same mass, specific heat capacity but different coefficients of linear expansion which would require more heat for same change in temperature considering concepts of thermal expansion?
Comment: I actually wanted to ask that if two bodies identical in all ways except their coefficients of thermal expansion which would      have more specific heat capacity
Answer: So long as the specific heat capacity of the two materials remain the same, it will take the same amount of energy to increase the temperature in both materials.  That is because the heat required is defined through $Q = m C \Delta T$. By definition they will require the same amount of heat to change the temperature.
I understand your question as "doesn't some of the energy go into changing the materials properties?", and the answer is that if it does, this will be factored into the definition of $C$.
Comment: I actually wanted to ask that if two bodies identical in all ways except their coefficients of thermal expansion which would      have more specific heat capacity
Answer: To me your question implies that you are asking about solids but even so the specific capacity will depend on not only the material but also the temperature and the expansion or otherwise of the material.
Because of this dependence of the specific heat capacity on a number of variables it is usual to quote the value of specific heat capacity for a material at a given temperature and then quote values when the material is not allowed to expand which is called the specific heat capacity at constant volume $C_V$ and when the material is allowed to expand at constant external pressure $C_P$.
The difference between these two so called principal specific heat capacities is significant for gases but very much less so for liquids and solids primarily because for gases their volume changes much more than liquids and solids for a given temperature change.
So if it is $C_V$ which you are making equal then that does not include the work which must be done (extra heat added) when a material expands.
In that case $C_P$ will be larger for the material which has the larger coefficient of thermal expansion.
On the other hand if it is $C_P$ that you have assumed to be equal then that already includes the heat input which has to be added to expand the material.
If you look at tables of specific heat capacities (e.g. Kaye and Laby) you will note that both $C_V$ and $C_P$ (or their ratio) are listed for gases whereas only $C_P$ is listed for liquids and solids because for most purposes when their temperature changes liquid and solids can be assumed not to change their volume by very much and the specific heat capacity is measured at constant pressure.
Answer: While expansion, more coefficient of linear expansion implies more kinetic energy, thus more heat is required.
Comment: You can edit your previous post to add to it, or you can comment on it.  Answers are for answers.
Comment: This post has formatting problems that make it very difficult to read.

Thermal expansion for two objects


What type of artisan's tools would a tailor use?

Question: I'm creating a character with a Guild Artisan background as a tailor, but I'm not sure what tool would be good to get proficiency in.
Answer: Weaver's Tools
Building on LyreCode's suggestion, the weaver's tools would be the best choice for a tailor's artisan's tool. In fact, I have semi-recently (as DM) helped one of my players create a PC who was previously a tailor before they become an adventurer, and we settled on choosing these tools for the reasons below.
There is information on the weaver's tools in XGtE, p. 85. In particular, the opening sentence says:

Weaver's tools allow you to create cloth and tailor it into articles of clothing.

Ok, so the word tailor here is used as verb rather than a noun, but this description still describes a tailor pretty well (certainly more so than any of the descriptions for the other artisan's tools).
Furthermore, that page contains a few sub-headings under Weaver's Tools, including the following:

that the tools themselves include thread, needles and cloth, as well as the fact that you know how to work a loom;
that you can inspect and determine attributes about various cloth objects, including tapestries or clothing;
that you can repair clothing, and that you can create items of clothing.

I'm not going to quote all of that here, but it's all very indicative of what a tailor's profession would likely entail.
Answer: Weaver's tools would probably be best.
Comment: Welcome to RPG.SE! Take the [tour] if you haven't already, and check out the [help] for more guidance. We expect answers to be supported by citations; could you include some evidence or experience to support your answer? (For instance, Xanathar's Guide to Everything lists the contents of each type of artisan's tools, suggesting certain skill checks that proficiency might give advantage on, listing a special action a proficient character might be able to take with it, and providing sample DCs for common uses.) You should elaborate on your answer instead of simply asserting it to be true.


Fixing tear in vinyl floor

Question:
My dog locked herself in the bathroom while I was gone & tore up a gap in the vinyl on the floor. This is a rental so I want to repair it if possible. Any tips? I have the ripped pieces in tact.
Answer: There is no way to fix that.  Just replace the bathroom flooring.  A small area won't be expensive if you DIY.
Maybe wait until you are ready to move if the dog could repeat this.  It wouldn't hurt to talk to the landlord.  If the flooring needs to be replaced, they might prefer something different, in which case they might agree to just taking an amount you would have spent on the repair (without you having to be responsible for the work).
Answer: That is terrible flooring. I would replace it with LVP, rated for bathrooms. Do not buy lvp less than 6 mm thick, seriously, every time I went even to 5 mm, something went wrong, it's too brittle or something. That tear isn't repairable and, the landlord would do well to put better stuff in there. Maybe work out a deal with him. The LVP is really easy to install.
Comment: This does not provide an answer to the question. Once you have sufficient [reputation](https://diy.stackexchange.com/help/whats-reputation) you will be able to [comment on any post](https://diy.stackexchange.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/175188)

Fixing tear in vinyl floor


Free online image libraries of trachoma

Question: I'm looking for an online source with images of the eye disease trachoma. I'm looking preferably for resources from a credible source that have images from each stage of the disease.
Answer: According to wikipedia there are two different way to distinguish stage of the disease. One is from McCallan and one from the World health organisation (WHO). For the second one, on WHO website, you can find their grading card with eyes images. You can download it with also a little description.
Hope it helps.

Free online image libraries of trachoma


How to list sample of files from a directory

Question: I have a directory that contains hundred thousands of files.
I need to list sample of these files (example 10 files), without processing all the files found in the directory which will take too much processing time.
Comment: However you throw it, you're going to have to interrogate the inode structure. You could use a file indexer to query instead, note that will require an initial directory scan too. see [man locate](http://unixhelp.ed.ac.uk/CGI/man-cgi?locate+1)
Comment: It appears the answer you want is [described over here](http://stackoverflow.com/q/414164/114147), assuming you use bash or similar variants.
Comment: @invert actually, sorting a list of hundred thousands of files is probably not such a good idea. Maybe use `ls -f| tail -n 1000` instead of just `ls` for the answer in the link
Comment: `tail` is aweful in this case, since it will wait for `ls` to finish its work! `head` would terminate it after reading the 1000 lines it needs.
Answer: I don't think you can sample from the whole file list without reading them all in some way or the other, even on the filesystem level.
Unless their names follow a pattern that is (eg. fileXXXXXXX), in which case you could pregenerate a random list of names before accessing the files. For such a large amount of files it would be odd if their names were random.
But let's assume you're not that lucky. Using find is prefered over ls, since it can escape output with null, making it immune to nonstandard characters in filenames. If we don't want to read all the files, it is the fastest to use the ones at the start of the listing. To get a better sample, I would use a bigger sample first ($oversamplesize below) and then do a random subselection of size $samplesize from there. I didn't manage to make sort -R or shuf work well with null separators, so the shuffling and final selection is done by awk:
 find ~ -type f -print0 |
 grep --null --null-data -m ${oversamplesize:-100} . |
 awk -v samplesize=${oversamplesize:-11} -vRS='\0' -vORS='\0' \
   '{ a[NR]=$0 } END {srand(); while (i<samplesize) { b=(int(rand()*10000)%samplesize); if (b in c) {continue;} else {c[b]=a[b]; print a[b]; i++;} }; }' |
 xargs -0 echo # echo here being just a dummy

Two notes here. For some reason, it often also prints an empty filename, so I increased the sample size just in case. The trivial note is not to forget to change the search path (~ here) and the final command.


Block user from accessing "sudo su -"

Question: How can I block a user not to use "sudo su -" command ? Because that will give him root access anyway. I want to limit him to read only permission for all files apart from what ever I give write access.
Comment: Standard users won't have permission unless you add permission in sudoers file.
Answer: If you want a user to have sudo  permission for other commands, but not to be able to log in as root, you need to edit the visudo file and specify the access you want the user to have.
sudo visudo

Then inside that file you would define the user and give permissions based on what you want that user to be able to do, for example
test    ALL=(ALL:`/home/test/) /home/test/, /usr/bin/vi, !/usr/bin/su

The above states that user test is allowed to access their home directory, run vim with sudo (as root) but nothing else. I am also explicitly telling the sudoers file to not allow the user to run su.
You should take a moment and read the sudoers manual, it explains everything.
Comment: Using '!' on a command spec is a VERY risky thing, since it's so easy to work around.  I'd recommend a classic 'mostly closed' setup, and never allowing anything in the list of tools that would also allow privilege escalation.

(vi is in that list.  Consider something newer)
Comment: "for all you haters out there, I do not have the reputation to comment yet" Haters? We have rules for a reason, you only need 50 rep to comment, earn it. Do you really think insulting the community will get you votes?
Comment: !/usr/bin/su entry in visudo answered my query. yes, I wanted to block the user from accessing root. Thanks for your help.  Will go through Sudoers manual to check further.
Comment: Can you mark it as correct?

Block user from accessing "sudo su -"


What is the port for a hostname query?

Question: I want to query an IP to get its hostname. What is the standard port for this ? Could it be port 101 listed under "hostnames" in /etc/services ?
Answer: Most of the "well known ports" found in /etc/services are remnants of historic implementations -- implementations of these "historic protocols" are no longer in use.
The port 101 you found is commented "NIC Host Name Server".  I found that RFC 811 and RFC953 describe the protocol served on port 101.  Most interesting to note is that the only implementation at the time of RFC 811 (1982) was running on a particular machine at SRI International.  The "port 101 protocol" is not a service that you will find on the Internet in the modern time.
The only service I can think of which is designed to provide information like you need is SNMP, and there is no guarantee you will either find an SNMP service running or that you will know the access keyword required ("community name") to see the remote hostname via the SNMP service.
Many specific implementations of services respond with the hostname, for example:
telnet alias.machine.net 25
220 realname.machine.net ESMTP Postfix (Debian/GNU)

Edit: A few other answers are suggesting you look into the DNS port.  DNS (Domain Name System) is not really what you asked for.  If you do want to use a DNS lookup, however, check into the gethostbyaddr() function available from C under Windows, MacBSD and Linux.
Answer: UDP port 101 used to provide the 'hostname' service, but the original RFC (RFC811) is obsoleted by RFC953, and RFC953 is marked 'historic'.
These days, you would consult the DNS (Domain Name System), which has many other relevant RFCs listed as updating it.  And you would normally use the appropriate library functions for the language you are using to consult the DNS (one issue being what is the IP address of the DNS server you should consult).
In both these cases (hostname and DNS), you consulted a machine other than the one with the specific IP address you are interested in.  It is not clear from your question whether you expect to ask the host with the interesting IP address what its name is, or whether you are expecting to ask another machine the question.  In practice, you will end up asking other machines - the DNS server(s).
Answer: well dns runs on port 53

What is the port for a hostname query?


ADFS 2.0 CRM Dynamics and SharePoint 2013

Question: Our current setup:
ADFS 2.0 with rules for CRM Dynamics (works fine), and rules for SharePoint (created from using instructions here
ADFS 2.0 is on the same server as the CRM Dynamics web application - no rewrites or redirects required
SharePoint 2013 is on its own back-end server accessible with appropriate urls defined in DNS. On the ADFS 2.0/CRM Dynamics WFE server, at server-level in IIS, a rewrite rule exists.

Requested URL Matches the Pattern, using Wildcards. Pattern: *
Conditions: {HOST_HEADER} Matches the pattern: sharepoint.macreportmedia.com
Action: Rewrite url: <'url to the sharepoint server'> and append query string

We've also tried rewrites with {REQUEST_URI} appended along with append query string option checked/unchecked

It's set to NOT stop processing

Our issue:

Navigating to our sharepoint URL returns the ADFS 2.0 login page as expected
Credentials are authenticated (I can verify this by immediately going to our CRM url and am able to enter the site without authenticating again)
Instead of being directed to the sharepoint website, it puts us back to the ADFS 2.0 login page.

If I need to give more information, let me know. We just really need help figuring out WHY we can't get into our Sharepoint page.
Thanks!
Answer: I assume that you experience kind of a redirect loop and that you are using IE.
This is usually happening when the participating sites are not in the same security zone of IE. Therefore they are not able to share the cookies. ADFS sees that your are authenticated and redirects to SharePoint. SharePoint does not receive the tokens and redirects back to ADFS.


Blender to Unity, Specular Hardness/Smoothness Texture

Question: In Unity there's a parameter for specularity (both modes) - Smoothness... I don't know what it corresponds to in Blender. You can bake two specularity maps: color and intensity, and at first I naively thought it to be intensity, but the result in Unity doesn't look quite right (beside the fact that it doesn't actually make sense). So I've decided that it's Hardness, but there's no baking option for Hardness in Blender, and I don't know what I'm supposed to do. I guess I could edit the alpha of the specular color texture down to prevent the object from looking like it's made from wet glass (although just the color is going to help there, I think), but maybe I'm missing something.
Answer: It doesn't really correspond to anything in Blender, unless you remake Unity's Standard Shader using Blender's Cycles.
The basic materials in Blender use relatively simply models, whereas Unity's Standard Shader is based on PBR and global illumination - where specular is much more complicated and interacts with a fresnel effect, in addition to receiving some light reflected by nearby surfaces. The Standard Shader material charts demonstrates what the different parameters mean. You may be able to get a better idea of how to accomplish what you're after by looking at those.
If after reviewing everything you're not actually interested in using full physically based rendering - which can be rather complex to bake for - you can simply switch the material to one of the Legacy Shaders in Unity.
See also:

Filmic Games: Everything is shiny
Filmic Games: Everything has Fresnel
Comment: Well, that's quite an eye-opener when I study it closely. I thought Blender's diffuse and spec color corresponded quite well to Unity's albedo and spec RGB, but actually it's quite a mess, and I'm essentially never going to know what my model looks like if I texture it in the default Blender shader... So are people using different programs for this?
Comment: Well, at least one person created [a Cycle node](http://blenderartists.org/forum/showthread.php?374544-Shader-Pack-Unity-standard-shader-in-blender-cycles) to be able to preview things in Blender. Would make it a lot easier to bake that way.


How to execute an equivalent function of Xcode's Instruments > "File Activity" in shell?

Question: I need to be able to show and capture the same output that Xcode.app/Contents/Applications/Instruments.app captures while in Terminal.app (in the shell).  Is there a dtrace function / script, or some such equivalent, that can be run in order to capture this data directly?
Answer: Have you tried fs_usage with -f filesys or diskio options?

The fs_usage utility presents an ongoing display of system call usage information pertaining to filesystem activity.  It requires root privileges due to the kernel tracing facility it uses to operate.  By default, the activity monitored includes all system processes except the running fs_usage process, Terminal, telnetd, telnet, sshd, rlogind, tcsh, csh, sh, and zsh.  These defaults can be overridden such that output is limited to include or exclude a list of processes specified by the user.


Is there a way to train Doc2Vec on a corpus of docs and be able to take a novel doc and see how similar it is to the trained corpus?

Question: I have a project idea, where I train a bunch of documents on Doc2Vec and then take a novel, input doc, and ideally be able to be told how similar it is to the docs supplied for training as a whole or how well it "fits" with the training docs. Is there a way to do this?
Answer: There are many possible approaches:

using simple similarity measures (e.g. cosine) to compare the new document against every training document.
train a binary classifier to distinguish the reference documents from "anything else". Requires negative examples, it's usually difficult to have a representative sample.
Use one-class classification, i.e. train a model using only the reference documents. The model tries to represent this class of documents and considers anything else as negative.
Could even consider it as a regression problem, i.e. score documents by how similar they are from the reference documents.


How to connect FPGA to Xbee?

Question: How can I connect an Xbee to FPGA to transmit data.
Comment: Do you have a soft core processor in there, or are you planning to do it all with a state machine?  Can you load custom code into the module for a web page or TCP-serial interface, or do you have to implement a network server on your FPGA board?
Answer: The correct answer is, of course, "with wires".
I assume you've read the WiFi module's datasheet? A quick look at the XBee website shows that their WiFi module communicates over either UART or SPI.
Implementing a UART or SPI master on an FPGA is (relatively) simple and, if you've never done much FPGA work before, a good learning experience. If you don't want to go down that route then you can either explore the IP provided by Actel or have a look for something open source.
Actel have something called "CoreUART" which would probably provide a robust UART implementation, and something called "CoreSPI" which does the same for SPI. If you don't have licenses for them, opencores probably have what you need. There's a few UART and SPI projects listed there, although I can't give any testament to their functionality.
These cores would just give the core protocol - a method of writing or reading bytes to the device. Depending on the WiFi device, you may need to implement a lot of further logic to send and receive commands, or it may do it all for you (acting as an "invisible" serial port between your FPGA and your computer). All that would be revealed in the documentation.
As Chris Stratton said, If you're using a soft-core processor then the answer will be very different. Is the FPGA part of a larger robotics platform, or is it just an FPGA development board?

How to connect FPGA to Xbee?


Enable disable masks in Sculpt mode

Question: How to disable the paint mask in sculpt mode without removing it (Alt +  M). Because in some case i may need it later so i don't have to redraw it again.
Answer: In the Face sets menu you can create a Face set from masked.
Then the Auto masking menu lets you turn on and off the face set limits for every brush, or every single brush can be limited in its action on the face sets using the brush menu.
Anyway you will loose the softness of the edges (a face in the face set is on or off).

Enable disable masks in Sculpt mode


Why do protons stay together in nucleus even though they are like charges?

Question: As per Coulomb's law positive charges must repel but in the the nucleus of an atom positively charged protons stay together, why is this so?
Comment: https://physics.stackexchange.com/a/268834/156748
Answer: Short answer :
Within the range of 2 fermi $(1\space fm=10^{-15}m)$, strong nuclear attractive forces overcome the relatively weaker repulsive forces of protons.
These nuclear forces are attractive in nature and independent of the charge of the particles. Neutrons attract neutrons, neutrons attract protons and protons attract protons.
If this force was absent, stable nuclei wouldn't exist.
Answer: The picture bellow schematically shows the Coulomb repulsion by a dashed blue line.
The sum of Coulomb and nuclear force is in solid blue.
If you manage to get the nuclei close enough, they interact via the strong force and can overcome the Coulomb barrier.
Sometimes, in some configurations, the nuclear force is not able to create a bound system (it is energetically more favored to go away) - so you will not find bi-proton. And you also cannot find bi-neutron, despite there is not charge messing.
Comment: The last I heard the possible existence of a bi-neutron remains undecided.
Comment: Thanks for the comment. From the perspective of isospin triplet, it is usually taught (I was) that it is unbound, as well as T=1 $p-n$ system.  I see, the experiment could be difficult on this. Anyway, if there is a virtual state, is that an existence?
Comment: Assume you mean resonance by virtual state.  No, this would not count. The di-neutron probably has no bound state. The Deuter on is barely bound by nuclear standards.


What is the origin and thought process behind the tradition of hats?

Question: Winter Bash is always a lot of fun and makes people trek across sites and participate in communities they are not usually a part of, but how did they originate? What was the thought process behind introducing this tradition?
Comment: [Team Fortress 2](http://meta.stackexchange.com/q/159184/162704)
Comment: I recall reading that Winter Bash served to get people on SE during the holiday period, when there is traditionally less activity on the site. Not sure if that's true, and  can't find it back :-(
Comment: And no, I am not after the Sun Wukong hat (already have it), I would just like an as official as possible answer as to why they decided to implement hats.
Answer: It started out in 2011 on the Gaming Stack Exchange under the name "Hat Dash", a fun event for that site's community and also a nod to the game Team Fortress 2.
The users loved it, and so in 2012 it was revived on the whole network and with the name "Winter Bash", and has been a thing ever since.
Comment: Yeah, the definition of the hats is a lot of discussion every year. It's more lighthearted than, say, badges, but you still don't want to encourage really bad behavior (like, at hat for defacing twenty questions quickly enough before getting suspended). It's always a mixture of encouraging nice (or at least interesting) things, sometimes even trying out ideas for new badges, and plain ol' fun.
Comment: Thank you, that makes sense. What were some of the things that were considered though? Were effects on the community thought about, etc?


Running DUB wide crank with 52mm chainline

Question: I have a set of sram xx1 carbon cranks that are DUB wide.  My bike (2023 Specialized Epic Evo) is DUB crank 52mm chainline.  If I add BB spacers to the DUB wide crank and use a 6mm offset chainring will this achieve the original 52mm chainline?  Also, would this cause any issues or downgrades to performance?
Comment: What exact cranks do you have, as in the model printed on the inside of the arm? FC-XX-1-C2?
Answer: Presuming you have FC-XX-1-C2/00.6118.608.001 it shouldn't be a problem to do this with a 6mm offset ring. I believe that is the only permutation of XX1 DUB Wide, but SRAM often makes it difficult to corroborate that kind of thing. Specifically, if an 8-bolt DM variant exists now or later, you'd need an 8-bolt 6mm offset ring for it, and that doesn't exist at present AFAIK.
Spacer configuration with DUB Wide cranks is a function of the shell type, presence or absence of a chain guide, and nothing else. Target chainline is immaterial and is configured only by the ring offset. If the cranks came from somewhere else and you want to make sure you have the right spacers, look it up in the SRAM DUB Cranksets and Bottom Brackets User Manual.


At which part of your design process do you refer to an existing user journey map

Question: When designing a feature, an improvement, or a product i'm curious at what point would you refer to the user journey map? Why would you refer to it? and what information or insights would hope to gain?
Answer: Depends
It's crucial to user Journey?
You could use Agile UX and document lightly, if the new feature impact the user journey, or delivery a big value you should consider update your journey map.
When a crucial information in the Journey Map, you can remember, discuss, thinking, together with your team, understading how to improve this feature, how the user feel in this point.


Why is energy released during fission reactions?

Question: If the energy released during a fission reaction is the binding energy then what energy is left to bind the nucleons together? I'm very confused if there's a better explanation on fission I'd appreciate that.
Answer: This is the curve of binding energy per nucleon for the list of nuclei, versus the number of nucleons in a nucleus.

Up to iron Fe, which has 56 nucleons the more nucleons the higher average binding energy per nucleon This means if one can fuse  two nuclei below 56  energy may be released energy.
after that, the more nucleons, the less binding energy per nucleon. This means that a break up of a high nucleon content nucleus may release energy, because the fragments will be more bound than the original .
Not all heavy nuclei will break conveniently, releasing energy, because this is a quantum mechanical scattering process and quantum numbers have to be conserved as well as energy. For example uraneum-235 can be broken ( is fissile) into pieces  by a neutron scattering, that will release energy.
Answer: The total rest masses of the fission products is less then the original fuel nucleus. The excess mass is the invariant mass of the energy that is released as gamma rays, and kinetic energy of the fission fragments.
You are asking whether if all the binding energy is released then what binds the fragments (after fission) together. Now not all binding energy is released. Typically, when a nucleus fissions into two daughter nuclei fragments, only 0,1 % of the original mass of the nucleus is released fission energy. Most of this fission energy comes in the kinetic energy of the daughter nuclei which fly apart at 3% of the speed of light.
If you look at a nucleus, 99% of its rest mass comes from binding energy and only 1% is the rest mass of its constituents. Now if only 0.1% of the mass is released as fission energy, that will mean that the daughter nuclei will have less rest mass, by 0.1% then the original nucleus. But 99% of that rest mass (of the original nucleus) was binding energy, and 1% was rest mass of the constituents. Only 0.1% of that 99% binding energy is released as fission energy (and only 0.1% of the 1% rest mass of the constituents), so most of the binding energy is still going to be there that will hold the daughter nuclei in one piece.
What you are missing is that the binding energy is not only between neutrons and protons. If you look at a neutron, 99% of its rest mass comes from binding energy between (color force) the quarks that make up the neutron, and only 1% of its rest mass comes from the rest mass of the quarks themselves.
So when there is nuclear fission, and a nucleus (made of protons and neutrons) fissions into daughter nuclei, that themselves have protons and neutrons, there is still binding energy that holds the daughter nuclei in one piece, binding energy between the dughter nucleus's neutrons and protons, and between the quarks that make up the neutrons and protons. Only 0.1% of that binding energy is released as fission energy.
Comment: There's a lot of overlap between the flaws in this answer and in [this similar answer by you today](https://physics.stackexchange.com/a/471201/44126).


In the movie In Bruges, which is the clock tower

Question: In the mvoie in bruges they visit a specific tower a few times. Where is that clock tower in real life? I just visited the clock tower in the city Bruges and it looks nothing like the movie version. Did they actually film in the interior of The Belfort? If so did they make any changes for better scenes?
Answer: It's The Belfort that's seen in the movie.
Also,
According to IMDB, "the scene in which Ray and Ken visit the Basilica of the Holy Blood is in fact filmed in the Jerusalem Church, Bruges" IMDB filming
If one inputs either location in Google Earth "Search" one can compare the two locations from street level.  They aren't that far from each other.
Comment: I am talking about the clock tower from which Ken jumped off. Tjat is the basilica?
Comment: I 'fixed' my answer as you were typing your comment. lol.
Comment: But I just came from belfort. It's not the same as in the movie. The stairs and the bell etc
Comment: I've not been within Belfort.  You do mention "in the real tower" but I would edit the question to state, "interior", as in "Was the interior of The Belfort used for filming....?"  This would emphasize what you're question is really about.
Comment: Edited my question


How to choose the default (or any) CKEditor toolbar?

Question: OK, I'm obviously missing something.  I've installed CKEditor into a D7 site, and all's well.  The only problem is I can't figure out how to specify the toolbar that will come up by default in CKEditor-enabled fields.  I've defined a new toolbar in .../ckeditor/ckeditor/ckeditor.config.js, but I haven't found any place in the site's config options (or the code, for that matter) that let me say that I want CKEditor to put up this particular toolbar.  For that matter, I don't see any way to be able to choose the other toolbars in ckeditor.config.js (like DrupalAdvanced and DrupalFull).  Any clarification out there?  Thanks!
Answer: I finally figured this out: See http://drupal.org/node/1434814#comment-5583354 for the solution.  The most important bits are:

If you're just using the basic CKEditor module, ckeditor.config.js is completely irrelevant to getting your toolbar set up. Ignore it.
CKEditor toolbars are associated with text formats, like "Filtered HTML" or "Full HTML" (or, presumably, other text formats you might define). Each text format can be connected to exactly one toolbar; when a textbox with that text format appears, its toolbar will be presented.


calculating sinewave frequency for a low pass filter with only cutoff frequency, input sinewave amplitude and output sinewave amplitude?

Question: I have the input and output sinwave amplitudes as well as the cut off frequency how do I use that to calculate the sinewave frequency(Hz) for a low pass filter. I'm unsure of what I need to be a looking for to calculate it.
Comment: Dave dont be that way.  From any filter design you can work out any unknown given all the other. DOH. If you cannot make a suggest to improve dont be that way (-1) If you dont understand how to design a filter or compute f from this understanding. Dont delete without  warning... again./
Comment: @Andy Aka I think he wants to calculate the frequency for which he knows the input/output amplitude ratio, and not the -3dB frequency, which he already knows.@Apple You need the transfer function, which is defined as H(s) = 1/(1+sT) for a first order low pass filter.
Comment: @Bart you may well be correct.
Comment: You will need the frequencies of the input and output signals at the known amplitudes. But that is not how it normally works. Analog filters go in steps of -6db/octave per stage. From that you have to determine how many stages you need to meet or exceed your requirements.
Answer: Assumptions:
There are many traditional and fundamental ways to go about this in which you could use various filter equations and sampling techniques to fine tune a result that would give you the wide band operation of your filter. I propose the below solution with the assumption of a relatively ideal low pas filter and simple hand-calculated method given that your filter behaves as a simple low-pass filter. In reality you would use much more complicated filter assumptions to estimate the filter as mentioned in other comments.
Background
We essentially need to solve the low pass filter response, as @Bart mentioned.
$$H(s) = {{1} \over 1 + (sT)} $$
Where s is a frequency Laplace variable and T is the time constant.
In this example it is enough to just do magnitude of this equation. We can also replace s with jw in this case so that we can look into the specific frequency response.
$$|H(jw)| = {{1} \over \sqrt{1 + (wT)^2}} $$
Knowns:
$$Ain, Ao, fc$$
Where Ao is the output amplitude you know, Ain is the input amplitude you know and fc is the cut off frequency.
Solution:
First we find T using the cut off frequency. We know that at cut off the amplitude is -3db. To get dB from the |H(jw)| we must square it and take the log and then multiply by 10.
$$10\log{|H(jw)|^2} = 10 \log{ {{1} \over \sqrt{1 + (wT)^2}^2} \ }$$
$$-3 = {10 \log{1} - 10 \log{( 1 + (wT)^2 )} \ }$$
$$-3 = - 10*\log{(1 + (wT)^2)}$$
$$0.3 =\log{(1 + (wT)^2)}$$
$$1 + (wT)^2 = 2$$
$$T = \sqrt{{1} \over 2 \pi fc} $$
Now that you have T, simply plug it back into your magnitude equation and solve for fc.
$$|H(jw)| = {{1} \over \sqrt{1 + (2 \pi fc T)^2}} $$
$${{Ao} \over {Ain}} = {{1} \over \sqrt{1 + (2 \pi fc T)^2}} $$
I'm not going to go through this part with variables since actual numbers will make it a lot faster, but I hope you get the picture.
Answer: LP Filters must be defined as follows
Pass f-3db.
Stop band f and attenuation -x dB.
This defines the breakpoint and order of filter which is -6dB per octave (2xf)
Eg if you have a 1st order LP filter with -6dB per octave given attenuation -X dB at some f1, and breakpoint fo Then what f1?
If attenuation X is 20 log fo/f1 then \$f1 = 10^{X/20} * fo\$. ( using X=+)
Answer: Take the example of a simple 1 kohm and 10 nF low pass filter. It has a cut-off frequency of 15.915 kHz. This is the frequency where the output voltage has dropped to 0.7071 of the input voltage. If you plotted a few points: -

100 Hz, Vout/Vin = 0.99998
1000 Hz, Vout/Vin = 0.998

You will notice that there is barely a change between 100 Hz and 1000 Hz so if you have a ratio that is approximately 1 then you cannot hope to pin-point the frequency with any degree of accuracy. However, from 1 kHz onwards it gets easier: -

2000 Hz, Vout/Vin = 0.992 and possibly discernible from 1000 Hz
5000 Hz, Vout/Vin = 0.954 and this should be easily pin-pointed to a fairly precise point in the spectrum.

However, knowing the cut-off point doesn't tell you anything about the filter order and it's shape. Here is a picture of a 2nd order filter with different damping ratios and notice how there can be two points on the response that have the same transfer function magnitude: -

So, if you have a slight peak in the response you cannot say for sure what the point on the spectrum is by knowing only the ratio of output to input levels. The problem compounds when taking higher order filter shapes into account: -

Above picture taken from wiki.


How do I deal with Cloakers?

Question: I'm getting very consistently demolished by charging Cloakers. As they are designed, I never really see them coming, and on the occasions that I do see them, I tend to panic and miss a lot of my shots. How can I keep myself (and my teammates) from getting charged at and destroyed by a Cloaker? Is there any way to tell where they are coming from without having to rely on spotting them?
Comment: They look like Blue Swat members, but have darker clothes and have night vision goggles.
Comment: Played Payday 2 for ages, but I have no idea what these "Cloakers" are!
Comment: @peper757 They were added relatively recently. They are designed to take the player by surprise, attacking the team from unexpected angles (air vents, etc) and pick people off one by one. And it's terrifying on so many levels.
Comment: Doesn't really sound as if they fit in. What do they look like?
Answer: Cloakers make a high pitched screeching sound when they are nearby. This is most likely your first line of information that lets you know that a cloaker is close. Unfortunately cloakers like to camp and stay hidden until an opportunity presents itself, so its advisable to travel in a group.
Cloakers can also spawn from vents or manholes so be they can seemingly appear out of nowhere. Again the best advice is to move as a group to reduce the risk of being downed alone.
The biggest threat a cloaker poses is its melee attack that downs the player in 1 hit. So when engaging a cloaker always maintain range. When someone is downed by a cloaker, the cloaker will stick around and camp near the victim. So it is adviseable to prioritize killing the cloaker over reviving your teammate. And if you're ever downed by a cloaker try to point them and let your teammates know so they can react accordingly.
Comment: They can also hide under cars in the street.
Answer: Cloaker spawn locations
Each level has a place where cloakers regularly spawn or camp. Remember where the cloaker spawn or camp locations are. If it's a manhole cover or air vent, it is most likely a cloaker spawn location. Avoid standing below air vents.
Detecting cloakers
If you're using trip mines as an equipment, put them at or near cloaker spawn / camp locations like air vents or manhole covers and set them to sensor mode, so they will highlight cloakers.
Also, try to always point at or highlight cloakers (F by default, in the PC) to make it easier to see where they are.
Avoiding cloaker downs
Cloakers have two types of attacks that can down you: the "drop-kick" and the "charge" attack.  Cloakers need a straight path (no obstacles that are jumpable over) to you before they can drop-kick you. If you see one nearby, try to retreat to a position behind a non-jumpable obstacle, or behind a wall or obstacle edge to lessen the chances of them downing you. Avoid positions where there is a clear path or jumpable obstacle to you.
Cloakers are fast and can catch you if you are running directly backwards. Move sideways when retreating from them to avoid them connecting the drop-kick.
Drop-kicks can also be dodged fairly consistently by walking to the side in the last moment. However, the charge attack always connects. If you have light armor, no heavier than an HBV, you actually have enough speed to outrun a cloaker, and buy yourself enough time to shoot them before they reach you.1
Counter-Strike Ace skill
The Fugitive skill tree's "Counter-Strike Ace" skill will allow you to counter-attack cloakers.2

Basic: When charging your melee weapon you will counterattack
enemies that try to strike you, knocking them down. The knockdown does
not deal any damage.
Ace: You can now counterattack Cloakers.

Sources:
1 Reddit /r/paydaytheheist posts by users, SgtTittyfist, laagone and Kazzei
2 PayDay wiki. Thanks to MadMAxJr for mentioning the skill in his comment.
Comment: I thought getting behind obstacles is bad because they can acrobatics over objects, then be at point blank range.
Comment: @ShadowZorgon I should have clarified that one should hide behind obstacles that are high enough (not jumpable over) or try to shoot while hiding behind wall/obstacle edges.
Comment: With the addition of the Old Hoxton update and the Vigilante skill tree, you can now take a perk to knock down a charging cloaker while holding a charged melee weapon.
Comment: Since this has already been marked correct, please include the info about the high pitched screeching sound that wr4ith described. I never get surprised by cloakers because of that.
Answer: Another thing no one's mentioned - Cloaker's take 4x damage to the head, so always aim for the head if possible.
Comment: [*All* enemies take increased damage to the head.](http://gaming.stackexchange.com/q/149968/4797) In most cases, one should always aim for an enemy's head.

How do I deal with Cloakers?


Why do long results from Git commands kill my PowerShell prompt?

Question: I am using Git Shell (the  module for PowerShell) on Windows. It's the one that got installed when I installed Git for Windows. When I run a command that results in a  lot of text such as git log I get a page of results and then a ":" at the bottom of the screen. I guess it's a continuation prompt because I press ENTER and get another screen of data. I can't usually recover to a normal prompt after this happens though. I get the text (END) at the bottom of the shell and it looks like it's masking the first few characters of whatever command I try to type and it even seems to act a little sporadic. I can't seem to figure it out. Any ideas?
Comment: Press the `Q` key for Quit. You can do this when at the END or when you see the `:`.
Comment: Incidentally you might be interested in [posh-git (PowerShell Git)](https://github.com/dahlbyk/posh-git)
Comment: @vcsjones, thank you.  I was having to close my powershell console.
Comment: Sometimes `q` just doesn't work in PowerShell for unexplained (as of yet) reasons.
Answer: Several of the git commands use a pager to allow you to view one screen full of information at a time.  The one that come with git is usually less (more info).  You can visit the link for common commands, but as you've found the most important is q to quit to get back to the command prompt.  The next most useful one I've found is space to move to the next screen full.
You can change the pager used if you like in the git config file's core.pager field.
Comment: You can also limit the results you get from git log by using the { git log --pretty=oneline } command
Answer: Just to add to the existing answers, the normal "windows" pager is more.com, which is usually referenced from cmd as simply more, but hidden by the function more with similar functionality in PowerShell. If you set
git config --global core.pager more.com

your problems should go away (although at the cost of features that exist in less but not more).
Answer: This is an old question, but I thought I would mention that git also provides a --no-pager option for you to leverage as well.
git --no-pager log

Hope that helps someone.
Comment: That's new to me and I appreciate it.


Why does Guan Yin ride a dragon?

Question:
Someone had once asked here "Why is Kwan Yin riding a sea turtle?", but what I'm more curious about is why is she seen on a dragon? There are many images or the Bodhisattva riding a dragon, one I posted being but one example. But who/what is the dragon? Is there a story behind it? I've heard the dragon is a symbol of wisdom and purity, others have suggested the dragon represents a wrathful force subdued by Guan Yin underfoot, but really what's the case here? Is it merely symbolic or is the dragon a literal entity (sentient or otherwise)? Any information would be appreciated (not modern "New Age").
Comment: I don't know about the dragon, but the in some pictures she's depicted pouring water from a vessel (such as the one she holds upright here) onto the world, the water symbolising the peace of meditation soothing the suffering of the world.
Answer: Wikipedia says that she is "protector of fishermen, sailors, and generally people who are out at sea".
A Chinese dragon is esteemed (a symbol of the emperor), and "traditionally symbolize potent and auspicious powers, particularly control over water, rainfall, typhoons, and floods", also prosperity and good luck and so on, rulers of weather and water.
So I assume that riding a dragon like that symbolizes control over the sea (part of being "protector of fishermen and sailors").
Answer: I believe there are many metaphors and intrinsic meanings in this Avalokiteshvara Riding Dragon image. I would provide one of the many aspects, that the dragon is symbolic of Rage/Anger/Jealousy (嗔), riding the dragon is symbolizing conquered of Anger. Greed (貪), anger (嗔) and delusion (癡) are the Three Afflictions  of the mind. Avalokiteshvara is respected as the Great Compassionate Bodhisattva (大悲菩薩). Compassion (大悲) termed 同體大悲, means "all differences but are one". The Chinese Character of 悲 graphically depicted the meaning, the upper is 非, means "not", "difference", the left and right are the reflection as if looking into a mirror, means all appeared different but in fact are reflections of the other. The lower is 心, a heart. A great heart will uphold all differences together, that's the meaning of compassion 悲. Now, rage, anger and jealousy are the greatest enemy to compassion. The extreme of rage and anger is hatred then escalated to war, then killing... By subduing the Dragon of Rage - a Chinese phrase 嗔心如毒龍 - heart full of rage is like a poisonous dragon - great compassion is achieved. Dragon is also symbol for energy, rage is a kind of energy but in bad use, if one could conquer it, one is able to turn the energy to great use, i.e., the reflection of rage is compassion, like the opposite of love is hate. ;)
P.S. Please be careful of modern rendering of the Buddha and Bodhisattva images, some of them are illegitimate. There are strict proportions and rules to abide when rendering these images, recorded in, such as 《佛說造像量度經》. These modern artists in this time of the world using their own habits and imaginations to freely draw these sacred images are full of blemishes. One should avoid but to find the good one if possible.
Answer: I to have this question. What I would like to share is that through my experience of studying the symbolism of dragons you need to carefully find the origin of the the dragon depicted because depending on the person, culture and/or artist that created the image the symbolism changes. Because the dragon symbolizes different things in different cultures there is confusion of what the dragon symbolizes. If you want the original meaning find the beginning of who Kwan Yin is. Then which ever culture first put her on a dragon will give you what it means for her to be riding the dragon.
Some facts from my research

Original name: Avalokitasvara
The original form Avalokitasvara appears in Sanskrit fragments of the fifth century.
Refers to the Mahāyāna bodhisattva of the same name.
Because this bodhisattva is considered the personification of compassion and kindness, a mother goddess and patron of mothers and seamen, the representation in China was further interpreted in an all-female form around the 12th century. In the modern period, Guanyin is most often represented as a beautiful, white-robed woman, a depiction which derives from the earlier Pandaravasini form.
In Chinese art, Guanyin is often depicted standing atop a dragon.
For the most part, no theme would be accepted in traditional Chinese art that was not inspiring, noble (either elevating or admonitory), refreshing to the spirit, or at least charming.
All traditional Chinese art is symbolic, for everything that is painted reflects some aspect of a totality of which the artist is intuitively aware
In Chinese mythology there are nine classical types of dragons.
A turquoise dragons can symbolized the benevolent but potentially dangerous emperor
Of the nine dragons the horned dragon is the giver of rain. (I chose this because the dragon in the picture is a horned dragon.)

Still with this information the dragon could mean different things. So who is the artist and why did he paint this.
Answer: Generally speaking Mahayana Buddhism employs skillful means to cleverly convey the message of Buddhism, and metaphors and symbolism are frequently used. The Avalokiteshvara represents the embodiment of the Dharma, and devotion to him is the central focus in the Universal Gate Chapter of the Lotus Sutra. In the Chapter he is described as having 33 transformations including that of Buddha, Pratyekabuddha etc. Whatever form as needed to teach sentient beings. The Dharma being present in all beings. This is also associated with 33 forms of Guanyin. I am uncertain of the origins of these forms but they are available in the following:
http://big5.xuefo.net/nr/article3/34985.html
The second form is the 龍頭觀音 the Dragon riding Guanyin described. This is also the form associated with the Pratyekabuddha transformation body. The Pratyekabuddha in Mahayana Buddhism is also associated with self realization.
So based on these facts we can probably guess at the meanings of the iconic picture. The Dragon is the Chinese translation of the serpentine Naga, which is a powerful often destructive beast that has the form that twists and turns symbolizing impermanence. So the image of Guanyin on the head of a Dragon represents transcending and utilization of the impermanence by the Dharma.
Comment: Thank you, this answer is helpful. And the link was good too, helping me find English blogs as well. Hope to find an English site with that legend of the sea dragon as translation of that link was a little scratchy. Open to more answers if anyone else reads this
Comment: The first two characters 龍頭 may provide some clue to the painting. According to wiktionary, the meaning of the two characters together is beginning, leader etc. Looked at separately, 龍 means dragon but is used figuratively for emperor/king and 頭 means head in its literal and figurative senses (like Hebrew ראש). "King of kings" perhaps? The remaining two characters of the four translate Avalokiteśvara. [source: Wiktionary]

Why does Guan Yin ride a dragon?